THE
PHYSICAL GEOGRAIHY
OF
TIE SEA,
AND
ITS METEOROLOGY.
BY M, FA MAURY, LL,AD  UASN9
SUPERINTENDENT OF THE NATIONAL'OSEZVATORY.
THE EIGHTH EDITION, REVISED AND GREATLY ENLARGED.
NEW YORK:
HARPER & BROTHERS, PUBLISHERS,
FRANKLIN SQUAAE.
LONDON:
SAMPSON LOW, SON & CO.
1861.
[The right of Translation is reserved.]




Entered, according to Act of Congress, in the year one thousand eight hundred
and sixty, by
H ARPER  &  BROTHERS,
In the Clerk's Office of the District Court of the Southern District of New York.




TO
WM. C. HASBROUCK,
OF NEWBURGH, NEW YORK,
"Ihit bolume is  narriber,
A TOKEN OF THE FRIENDSHIP AND ESTEEM, FROME BOYHOOD TILL NOW, OF H/IS
FORMER PUPIL,
THE AUTHOR.
28th Nov., 1860.








INTRODUCTION  TO  THE  EIGHTH  EDITION.
THE great activity in our field of research, the increasing number of laborers in it, and the rich gleanings from it, have made
necessary a recast of this work. With new lights and better materials, I have not hesitated to tear down and build up anew whenever they seemed to require it. The results that are embodied in
Plate I. alone of this edition would, had the data for it been collected by a force specially employed for the purpose, have demanded constant occupation from a fleet of ten sail for more than
one hundred years. The co-ordinating of these observations after
they were made, and the bringing of them to the present condensed form, has involved a vast amount of additional labor. Officers here have been engaged upon the work for many years.
This patient labor has been rewarded with the. discovery of laws
and the development of truths of great value in navigation and
very precious to science.
It would be presumptuous to claim freedom from error for a
work like this: true progress consists in the discovery of error
as well as of truth. But I may be pardoned for saying that the
present edition of this work will be found to contain more of truth
and less of error than any of its predecessors, simply because it is
founded on wider research, and based on the results of more abundant observations than they. Indeed, it could not, or, rather, it
should not be otherwise; for, as long as we are making progress
in any field of physical research, so long must the results continue
to increase in value; and just so long must what at first was conjecture grow and gain as truth, or fade and fall as error.
How much more valuable the sum total of the contribution now
offered to the stock of human knowledge concerning the physics
of sea and air than were the offerings of previous editions, is for
the reader, not for the writer, to decide. The fact seems now to
be clearly established that the atmosphere is very unequally di



iv                   INTRODUCTION.
vided on opposite sides of the equator, and that there is a mild
climate in the unknown regions of the antarctic circle. Over the
extra-tropical regions of our planet, the atmosphere on the polar
side of 40~ N. and 40~ S. is so unequally divided as to produce
an average pressure, parallel for parallel, of 50 lbs. less upon the
square foot of sea surface in southern than upon the square foot
of sea surface in northern latitudes. These, and many other developments not less interesting, seemed to call for a recast of the
work. Indeed, though something has been done by this system
of research for the sea, much, very much yet remains to be done.
There is, in particular, one field which is exceedingly inviting,
but in which laborers are wanting, and into which only a few are
preparing to enter. The seventh edition of Sailing Directions,
published in 1855, contains a fac-simile of the log of the American
ship Garrick, Captain R. W. Foster, from New York to Liverpool
and back, in 1854. Captain Foster is accustomed, in his leisure
hours at sea, to amuse himself by hauling up buckets of water
from alongside, that he may, with a common magnifier of his sextant, examine the animalcule in it. Their multitudes, their diversity of forms, their variety of color, afforded him sources of
never-ceasing wonder and astonishment. His abstract log was
embellished with pen-and-ink sketches of some of the most curious of these as they appeared under his lens. These were reproduced in the lithographic plates of his log,* not because they possessed any value in the estimation of the naturalist, for they did
not, but simply with the hope that they might provoke more skillful eyes and hands to the work, and ultimately tempt experts to
enter this field and undertake the " insects of the sea" in'a regular way.
This hope soon met with encouragement. The fac-simile of
Foster's log fell into the hands of Captain Henry Toynbee, of the
English East Indiaman the Gloriana, then on a v.oyage from England to India, with a regiment of British soldiers on board. Mr.
Welsh, the surgeon, had a microscope; and Mrs. Toynbee, among
her many and elegant accomplishments, could draw and sketch
most beautifully. Whenever the ship was becalmed, or had but
little wind, they threw out their net for " insects," and became
deeply interested, but only as amateurs, in delineating many of
* See Maury's Sailing Directions, 1855.




INTRODUCTION.                      v
the strange marine forms as they appeared under the microscope.
These drawings, though not calculated to satisfy the wants of naturalists, were nevertheless considered by me in thelight of another great step gained like that of Captain Foster; and with the
hope of still farther provoking laborers, whom the naturalists
might in time regard as experts, to enter this field, fac-similes of
the Toynbee insects, some of which are colored to nature, were
published in the eighth edition of Sailing Directions, 1859.
When it is considered that the sea was commanded to bring
forth abundantly; that its waters more teem with organisms
than the air does with insect life; that it has been explored but
sparingly for its animalcule; and that in the corps of observers
who co-operate with me there are those who are daily becoming
more and more interested in the oceanic economy, the importance
of tempting them into this field becomes obvious.
It is not expected that the hands which haul up the deep-sea
line with the sounding-rod loaded with "bottom" should furnish
a description of the organisms thus recovered, neither is it to be
demanded that the sailor who tows the insect-net in the water
shall furnish us with drawings, secundum artem, of the little prisoners he may capture in it. All that I venture to ask is, that
such treasures may be sought for in the sea by my fellow-laborers; that, when found, they may be properly labeled and carefully
preserved, so that they may reach the hands of experts at home
in a condition suitable for study under the microscope.
Brooke's sounding-rod has opened a new field for study at the
bottom of the ocean; so may the bucket of Foster and the net of
Toynbee enlarge that at the surface.
The Toynbees have succeeded in preserving many specimens,
and getting them to England in excellent condition for the microscope. The following extract of a letter from Captain Toynbee, dated May 21st, 1860, becomes of special interest in this connection:
"We have published a paper or two in the Nautical Magazine
on the' Minute Inhabitants of the Surface Waters of the Deep
Sea.' Mr. Lubbock, a son of Sir John, has taken up the subject
of the Crustaceans, and seems to be the best authority in England
respecting these little creatures. The millions of minute shells




vi                   INTRODUCTION.
found in the surface waters do not seem to be well understood
by any body. You will, I hope, soon receive specimens of them.
Some few resemble the Globigerinae brought up by the Atlantic
soundings; but how it is that the soundings for the electric telegraph brought up little else than Globigerinae is very remarkable.
July 14th, 1858, in lat. 400 46' N., long. 310 05' W., current S. 61~
E. 7a miles, specific gravity 1.028, we found the surface water
abounding with a small bivalve, which seemed full, but there were
no signs of life. With this shell, which was Very abundant, there
were some spiked balls, but no other shells. My idea is, that if
a net, lined with bunting, were carefully towed across the Atlantic, about where the soundings were taken, Globigerinse would
be found on the surface as abundant as they are at the bottom.
We have had two or three instances of different parts of the sea
having their particular inhabitants. In towing for these Globigerinae, or, in fact, for any other minute shells, the net should be
turned inside out and washed in a bucket of clean water, the bucket painted white inside; then, by stirring the water quickly round,
the shells may be picked from the centre by means of a glass tube.
The net should be towed in calms, or when the ship is moving
slowly through the water. I suppose you communicate with many
commanders who are constantly crossing the Atlantic. I used to
allow the net to be washed a dozen times or more before I examined the bucket, so that it contained the result of two or three
hours towing."
Several new chapters have been added to this edition, and
many new subjects have been treated of in it. New views also
have been presented, and the errors of former views corrected
wherever in them farther research has pointed out error. These
researches have grown so wide that they comprehend not only
the physics of the sea, but they relate extensively to its meteorology also; hence the present title, THE PHYSICAL GEOGRAPHY
OF THE SEA, AND ITS METEOROLOGY.
NATIONAL OBSERVATORY, WASHINGTON, November, 1860.




INTRODUCTION TO THE FIRST EDITION —1855.
THE primary object of "The Wind and Current Charts," out
of which has grown this Treatise on the Physical Geography of
the Sea, was to collect the experience of every navigator as to
the winds and currents of the ocean, to discuss his observations
upon them, and then to present the world with the results on
charts for the improvement of commerce and navigation.
By putting down on a chart the tracks of many vessels on the
same voyage, but at different times, in different years, and during
all seasons, and by projecting along each track the winds and currents daily encountered, it was plain that navigators hereafter, by
consulting this chart, would have for their guide the results of
the combined experience of all whose tracks were thus pointed out.
Perhaps it might be the first voyage of a young navigator to
the given port, when his own personal experience of the winds to
be expected, the currents to be encountered by the way, would itself be blank. If so, there would be the wind and current chart.
It would spread out before him the tracks of a thousand vessels
that had preceded him on the same voyage, wherever it might be,
and that, too, at the same season of the year. Such a chart, it
was held, would show him not only the tracks of the vessels, but
the experience also of each master as to the winds and currents
by the way, the temperature of the ocean, and the variation of the
needle. All this could be taken in at a glance, and thus the
young mariner, instead of groping his way along until the lights
of experience should come to him by the slow teachings of the
dearest of all schools, would here find, at once, that he had already
the experience of a thousand navigators to guide him on his voyage. He might, therefore, set out upon his first voyage with as
much confidence in his knowledge as to the winds and' currents
he might expect to meet with, as though he himself had already
been that way a thousand times before.
Such a chart could not fail to commend itself to intelligent ship



viii                       INTRODUCTION.
masters, and such a chart was constructed for them.  They took
it to sea, they tried it, and to their surprise and delight they found
that, with the knowledge it afforded, the remote corners of the
earth were brought closer together, in some instances, by many
days' sail. The passage hence to the equator alone was shortened
ten days.  Before the commencement of this undertaking, the
average passage to California was 183 days; but with these charts
for their guide, navigators have reduced that average, and brought
it down to 135 days.
Between England and Australia, the average time going, without these charts, is ascertained to be 124 days, and coming, about
the same; making the round voyage one of about 250 days on
the average.
These charts, and the system  of research to which they have
given rise, bid fair to bring that colony and the mother country
nearer by many days, reducing, in no small measure, the average
duration of the round voyage.*
At the meeting of the British Association of 1853, it was stated
by a distinguished member-and the statement was again repeated at its meeting in 1854 —that in Bombay, whence he came, it
was estimated that this system  of research, if extended to the Indian Ocean, and embodied in a set of charts for that sea, such as
I have been describing, would produce an annual saving to British commerce, in those waters alone, of one or two millions of dollars;t and in all seas, of ten millions.4
* The outward passage, it has since been ascertained, has been reduced to 97
days on the average, and the homeward passage has been made in 63.
t See Inaugural Address of the Earl of Harrowby, President of the British Association at its twenty-fourth meeting. Liverpool, 1854..... "Now let us make a calculation of the annual saving to the commerce of
the United States effected by those charts and sailing directions. According to Mr.
Maury, the average freight from the United States to Rio Janeiro is 17.7 cts. per ton
per day; to Australia, 20 cts.; to California, also, about 20 cts. The mean of this
is a little over 19 cts. per ton per day; but to be within the mark, we will take it at
15, and include all the ports of South America, China, and the East Indies.
" The sailing directions have shortened the passages to California 30 days, to Australia 20, to Rio Janeiro 10. The mean of this is 20, but we will take it at 15, and
also include the above-named ports of South America, China, and the East Indies.
"Ve estimate the tonnage of the United States engaged in trade with these places
at 1,000,000 tons per annum.
"WVith these data, we see that there has been effected a saving for each one of:these,tons of 15 cents per day for.a period of 15 days, which will give an aggregate




INTRODUCTION.                          ix
A system of philosophical research which is so rich with fruits
and abundant with promise could not fail to attract the attention
and commend itself to the consideration of the seafaring community of the whole civilized world.  It was founded on observation; it was the result of the experience of many observant men,
now brought together for the first time and patiently discussed.
The results tended to increase human knowledge with regard to
the sea and its wonders, and therefore the system of research
could not be wanting in attractions to right-minded men.
The results of the first chart, however, though meagre and unsatisfactory, were brought to the notice of navigators; their attention was called to the blank spaces, and the importance of
more and better observations than the old sea-logs generally contained was urged upon them.
They were told that if each one would agree to co-operate in a
general plan of observations at sea, and would send regularly, at
the end of every cruise, an abstract log of their voyage to the National Observatory at WVashington, he should, for so doing, be furiished, free of cost, with a copy of the charts and sailing directions that might be founded upon those observations.
The quick, practical mind of the American ship-master took
hold of the proposition at once. To him the field was inviting,
for he saw in it the promise of a rich harvest and of many useful
results.
So, in a little while, there were more than a thousand navigators engaged day and night, and in all parts of the ocean, in making and recording observations according to a uniform plan, and
in furthering this attempt to increase our knowledge as to the
winds and currents of the sea, and other phenomena that relate to
its safe navigation and physical geography.
To enlist the service of such a large corps of observers, and to
have the attention of so many clever and observant men directed
to the same subject, was a great point gained: it was a giant
of $2,250,000 saved per annum. This is on the outward voyage alone, and the tonnage trading with all other parts of the world is also left out of the calculation.
Take these into consideration, and also the fact that there is a vast amount of foreign tonnage trading between these places and the United States, and it will be seen
that the annual sum saved will swell to an enormous amount. "-Extractfrom lunt's
A-iIerchant's lIayaazine, Illay, 1854.




X                    INTRODUCTION.
stride in the advancement of knowledge, and a great step toward
its spread upon the waters.
Important results soon followed, and great discoveries were
made. These attracted the attention of the commercial world,
and did not escape the notice of philosophers every where.
The field was immense, the harvest was plenteous, and there
was both need and room for more laborers. Whatever the reapers should gather, or the merest gleaner collect, was to inure to
the benefit of commerce and navigation-the increase of knowledge-the good of all.
Therefore, all who use the sea were equally interested in the
undertaking. The government of,the United States, so considering the matter, proposed a uniform system of observations at sea,
and invited all the maritime states of Christendom to a conference
upon the subject.
This conference, consisting of representatives from France, England, and Russia, from Sweden and Norway, Holland, Denmark,
Belgium, Portugal, and the United States, met in Brussels, August
23, 1853, and recommended a plan of observations which should
be followed on board the vessels of all friendly nations, and especially of those there present in the persons of their representatives.
Prussia, Spain, Sardinia, the Holy See, the free city of Hamburg, the republics of B3remen and Chili, and the empires of Austria and Brazil, have since offered their co-operation also in the
same plan.
Thus the sea has been brought regularly within the domains
of philosophical research, and crowded with observers.
In peace and in war these observations are to be carried on,
and, in case any of the vessels on board of which they are conducted may be captured, the abstract log —as the journal which
contains these observations is called-is to be held sacred.
Baron Humboldt is of opinion that the results already obtained
from this system of research are sufficient to give rise to a new
department of science, which he has called the PHYSICAL GEOGRAPHY OF THE SEA. If so much have already been accomplished by one nation, what may we not expect in the course of a few
years from the joint co-operation of so many?
Rarely before has there been such a sublime spectacle presented to the scientific world: all nations agreeing to unite and co



INTRODUCTION.                     xi
operate in carrying out one system of philosophical research with
regard to the sea. Though they may be enemies in all else, here
they are to be friends. Every ship that navigates the high seas
with these charts and blank abstract logs on board may henceforth be regarded as a floating observatory, a temple of science.
The instruments used by every co-operating vessel are to be compared with standards that are common to all; so that an observation that is made any where and in any ship may be referred to
and compared with all similar observations by all other ships in
all parts of the world.
But these meteorological observations which this extensive and
admirable system includes will relate only to the sea. This is not
enough. The plan should include the land also, and be universal. Other great interests of society are to be benefited by such
extension no less than commerce and navigation have been. A
series of systematic observations, directed over large districts of
country, nay, over continents, to the improvement of agricultural
and sanitary meteorology, would, I have no doubt, tend to a development of many interesting, important, and valuable results.
With proper encouragement, this plan of research is capable
of great expansion. With the aid of the magnetic telegraph, and
by simply a properly devised system of daily reports through it,
sentinels upon the weather may be so posted that we may have
warning in advance of every storm that traverses the'country.
The agricultural societies of many states of the Union have addressed memorials to the American Congress, asking for such extension; and it is hoped that that enlightened body will not fail
favorably to respond.
This plan contemplates the co-operation of all the states of
Christendom, at least so far as the form, method, subjects of observations, time of making them, and the interchange of results
are concerned. I hope that my fellow-citizens will not fail to
second and co-operate in such a humane, wise, and noble scheme.
The Secretary of the Navy, taking the enlarged and enlightened
views which do honor to great statesmen, has officially recommended the adoption of such a systemn, and the President has asked the favorable consideration thereof by Congress. These researches for the land look not only to the advancement of the
great interests of sanitary and agricultural meteorology, but they




Bxii                    INTRODUCTION.
involve also a study of the laws which regulate the atmosphere,
and a careful investigation of all its phenomena.
Another beautiful feature in this system is, that it costs nothing additional. The instruments that these observations at sea
call for are such as are already in use on board of every well-conditioned ship, and the observations that are required are precisely
those which are necessary for her safe and proper navigation.
As great as is the value attached to what has been accomplished by these researches in the way of shortening passages and less.
ening the dangers of the sea, a good of higher value is, in the
opinion of many seamen, yet to come out of the moral, the educational influence which they are calculated to exert upon the seafaring community of the world.  A very clever English ship-master, speaking recently of the advantages of educational influences
among those who intend to follow the sea, remarks:
" To the cultivated lad there is a new world spread out when
he enters on his first voyage. As his education has fitted, so will
he perceive, year by year, that his profession makes him acquainted with things new and instructive.  His intelligence will enable
him to appreciate the contrasts of each country in its general aspect, manners, and productions, and in modes of navigation adapted to the character of coast, climate, and rivers. He will dwell
with interest on the phases of the ocean, the storm, the calm, and
the breeze, and will look for traces of the laws which regulate
them.  All this will induce a serious earnestness in his work, and
teach him to view lightly those irksome and often offensive duties
incident to the beginner."*
And that these researches do have such an effect many noblehearted mariners have testified. Captain Phinney, of the American ship Gertrude, writing from  Callao, January, 1855, thus expresses himself:
"Having to proceed from this to the Chincha Islands and remain three months, I avail myself of the present opportunity to
forward to you abstracts of my two passages over your southern
* " THE LoG OF A MERCHANT OFFICER; viewed with reference to the Education
of young Officers and the Youth of the Merchant Service. By ROBERT METHREN,
commander in the Peninsular and Oriential Company, and author of the'Narrative
of the Blenheim Hurricane of 1851."' London: John Weale, 59 High Holborn;
Smith, Elder & Co., Cornhill; Ackerman & Co., Strand. 1854.




INTRODUCTION.                   xiii
routes, although not required to do so until my own return to the
United Statcs next summer; knowing that you are less amply
supplied with abstracts of voyages over these regions than of
many other parts of the ocean, and, such as it is, I am happy to
contribute my mite toward furnishing you with material to work
out still farther toward perfection your great and glorious task,
not only of pointing out the most speedy routes for ships to follow over the ocean, but also of teaching us sailors to look about
us, and see by what wonderful manifestations of the wisdom and
goodness of the great God we are continually surrounded.
" For myself, I am free to confess that for many years I commanded a ship, and, although never insensible to the beauties of
nature upon the sea or land, I yet feel that, until I took up your
work, I had been traversing the ocean blindfolded. I did not
think; I did not know the amazing and beautiful combination of
all the works of Him whom you so beautifully term' the Great
First Thought.'
"I feel that, aside from any pecuniary profit to myself from
your labors, you have done me good as a man. You have taught
me to look above, around, and beneath me, and recognize God's
hand in every element by which I am surrounded. I am grateful for this personal benefit. Your remarks on this subject, so
frequently made in your work, cause in me feelings of the greatest
admiration, although my capacity to comprehend your beautiful
theory is very limited.
"The man of such sentiments as you express will not be displeased with, or, at least, will know how to excuse, so much of
what (in a letter of this kind) might be termed irrelevant matter.
I have therefore spoken as I feel, and with sentiments of the greatest respect."  Sentiments like these can not fail to meet with a
hearty response from all good men, whether ashore or afloat.
Never before has such a corps of observers been enlisted in the
cause of any department of physical science as is that which is
now about to be engaged in advancing our knowledge of the
Physical Geography of the Sea, and never before have men felt
such an interest with regard to this knowledge.
Under this term will be included a philosophical account of the
winds and currents of the sea; of the circulation of the atmosphere
and ocean; of the temperature and depth of the sea; of the won



xiv                          INTRODUCTION.
ders that lie hidden in its depths; and of the phenomena that display themselves at its surface.  In short, I shall treat of the economy of the sea and its adaptations-of its salts, its waters, its climates, and its inhabitants, and of whatever there may be of general interest in its commercial uses or industrial pursuits, for all
such things pertain to its PHYSICAL GEOGRAPHY.
The object of this little book, moreover, is to show the present
state, and, from time to time, the progress of this new and beautiful
system  of research, as well as of this interesting department of science; and the aim of the author is to present the gleanings from
this new field in a manner that may be interesting and instructive
to all, whether old or young, ashore or afloat, who desire a closer
look into "the wonders of the great deep," or a better knowledge
as to its winds, its adaptations, or its Physical Geography.*
* There is an old and very rare book which treats upon some of the subjects to
which this little work relates. It is by Count L. F. MARSIGLI, an Italian, and is
called NATURAL DESCRIPTION OF THE SEAS. The copy to which I refer was translated into Dutch by Boerhaave in 1786.
The learned count made his observations along the coast of Provence and Languedoc. The description only relates to that part of the Mediterranean.  The book is
divided into four chapters: the first, on the bottom and shape of the sea; the second,
of sea water; the third, on the movements of sea water; and the fourth, of sea plants.
He divides sea water into surface and deep-sea water; because, when he makes salt
from surface water (not more than half a foot below the upper strata), this salt will
give a red color to blue paper; whereas the salt from deep-sea water will not alter
the colors at all.  The blue paper can only change its color by the action of an acid.
The reason why this acid (iodine?) is found in surface and not in deep-sea water is,
it is derived from the air; but hbe supposes that the saltpetre that is found in sea water, by the action of the sun's rays and the motion of the waves, is deprived of its
coarse parts, and, by evaporation, embodied in the air, to be conveyed to beasts or
plants for their existence, or deposited upon the earth's crust, as it occurs on the
plains of Hungary, where the earth absorbs so much of this saltpetre vapor.
Donati, also, was a valuable laborer in this field. His inquiries enabled Mr. Trembley' to conclude that there are, " at the bottom of the water, mountains, plains, valleys, and caverns, just as upon the land."
But by far the most interesting and valuable book touching the physical geography
of the Mediterranean is Admiral Smyth's last work, entitled " THE MEDITERRANEAN;
A MEMOIR, PHYSICAL, HISTORICAL, AND NAUTICAL.  By Rear-admiral WILLIAM
I-IEERY S.IYTII, K.S.F., D.C.L.," &c. London: John W. Parker and Son. 1854.
Philosophical Transactions.




INTRODUCTION TO THE REVISED EDITION. —1856.
THE department of the Physical Geography of the Sea is a new
field of research; there is great activity in it, and it is the aim of
the author of this work to keep its readers posted up with the improvements, the developments, and the contributions that are made
in this interesting field from time to time.
The present edition contains much that is new; for the fifth
edition has been most carefully revised, much of it has been recast, and some parts omitted.
The desire is, that this work shall keep pace with the progress
of research. As it may be supposed, facts are sometimes misinterpreted or not understood when first developed. Whenever subsequent research shows such to have been the case, I have not
hesitated to tear down whatever of conjecture or theory may have
been built on unstable foundations, and to reconstruct according
to the best lights.
It is proper to say that, in accounting for the various phenomena that present themselves, I am wedded to no theories, and do not
advocate the doctrines of any particular school. Truth is my object. Therefore, when the explanation which I may have at any
time offered touching any facts fails to satisfy farther developments,
it is given up the moment one is suggested which will account for
the new, and equally as well for the old system of facts. In every
instance that theory is preferred which is reconcilable with the
greatest number of known facts. The chapter of the Gulf Stream
has been enriched with the results of recent investigation, and the
theory of it farther developed. So also that on the Salts of the
Sea; the Open Sea in the Arctic Ocean; the Basin of the Atlantic, and several others, but these especially have been greatly improved.
A separate chapter is now devoted to the Land and Sea Breezes,




xvi                   INTRODUCTION.
and extensive contributions have been made to that on Monsoons,
Trade Winds, and Cyclones. Lieutenant Jansen, of the Dutch
Navy, has helped me to enrich these with his fine thoughts. The
reader will, I am sure, feel, as I do, deeply indebted to him for so
much instructive matter, set forth in his very delightful and pleasing manner.
NATIONAL OBSERVATORY, WASHINGTON, April, 1856.




CONTENT So
CHAPTER I.
THE SEA AND THE ATMOSPHERE.
The two Oceans of Air and Water, ~ 1.-Their Meeting, 2.-Their Depth, 3.-The
Weight of the Atmosphere, 4.-Three fourths below the Mountain-tops, 5.-Its
Height, 6.-Data conjectural, 7. - Analysis of Air, 8. - Information respecting
the Depth of the Ocean, 9.-Its probable Depth, 10.-Relation between the Depth
and the Waves of the Sea, 11.-Airy's Tables, 12.-The Earthquake of Simoda,
13.-The Propagation of its Waves, 14.-Their Breadth and Velocity, 15.-Average Depth of the North Pacific, 16.-Specific Gravity of Sea-water, 17.-Ditto
of Air, 18.-Unequal Distribution of Light and Heat, of Air, Water, and Land,
19.- The Sun longer in northern Declination, 20.- England about the Pole of
the Hemisphere with most Land, 21.-Effects in the terrestrial Economy of Inequality in the Distribution of Land and Water, 22.-Quantity of fresh Water in
American Lakes, 23.-The southern Seas likened to the Boiler, northern Lands
to the Condenser of a Steam-engine, 24.-Offices of the Atmosphere multitudinous, 25.-Dr. Buist, 26.-The Sea and the Atmosphere contrasted, 27.-Influence of the Sun, 28.-Of diurnal Rotation, 29.-Currents, 30.-Icebergs, 310Mountain Ranges, 32.-Water, 33.-Latent Heat, 34.-Effects of, upon the Earth,
35.-The Tides, 36.-Hurricanes, 37. - Powers of the Air, 38.- Its Functions,
39 —The Operations of Water, 40.-Its marvelous Powers, 41.-It caters on the
Land for the Insects of the Sea, 42. - Leaching, 43. - Solid Ingredients, 44. -
Quantity of Silver in the Sea, 45.-Its Inhabitants, their Offices, 46.-Monuments
of their Industry, 47.-Analysis of Sea-water, 48.-Proportion of Water to the
Mass of the Earth, 49. -The three great Oceans, 50. - The Atlantic, 51.- Its
Tides, 52.-Its Depths, 53.-Contrasted with the Pacific, 54.-The Telegraphic
Plateau, 55................................................................ Page 1
CHAPTER II.
THE GULF STREAM.
Its Color, ~ 70.-How caused, 71.-Speculations concerning the Gulf Stream, 72.Agencies concerned, 73.-Early Writers, 74.-Objection to the fresh-water Theory, 75. —Livingston's Hypothesis, 76.-Franklin's Theory, 77.-Objections to it,
78.-Herschel's Explanation, 79.-Objections to it, 80.-The Supremacy of the
Winds disputed, 81.-The Bonifaccio Current, 82.-The Bed of the Gulf Stream
an ascending Plane, 83.-The Niagara, 84.-A  Current counter to the Gulf
Stream, 85.-Bottle Chart, 86.i Their Drift, 87.-The Sargasso Sea, 88.-A
Bifurcation, 89.-Winds exercise but little Influence upon constant Currents, 90.Effects of diurnal Rotation upon the Gulf Stream, 91.-The Gulf Stream can not
be accounted for by a higher Level, 92.-Nor by the trade-wind Theory, 93.-Illustration, 94.-The Gulf Stream the Effect of some constantly operating Power,
2




xviii                          CONTENTS.
95. —The Production of Currents without WVind, 96.-WVarm Currents flow toward
the Pole, cold toward the Equator, 97.-The Edges of the Gulf Stream a striking
Feature, 98.-Illustrations, 99.-How the Water of the Gulf Stream differs from
the littoral Waters, 100.-Action on Copper, 101. —Saltness of the Gulf Stream,
102.-Agents concerned, 103.-Evaporation and Precipitation, 104.-Current
into the Caribbean Sea, 105.-Amount of Salt, left by Evaporation, 106. —Currents created by Storms, 107.-The dynamical Force that calls forth the Gulf
Stream to be found in the Difference as to Specific Gravity of intertropical and
polar Waters, 108.-Winter Temperature of the Gulf Stream, 109.-The Top of
the Gulf Stream roof-shaped, 110.-Drift Matter sloughed off to the right, 11 1.Why so sloughed off, 112.-Illustration, 113.-Drift-wood on the Mississippi, 114.
-Effect of diurnal Rotation upon, 115. —Formation of the Grand Banks, 116.Deep Water near, 117.-The Gulf Stream describes in its Course the Path of a
Trajectory, 118.-Its Path from Bemini to Ireland, 119.-The Tendency of all
Currents, both in the Sea and Air, to move in Great Circles a physical Law, 120.This Law recognized by the Gulf Stream, 121.-The Shoals of Nantucket do not
control its Course, 122.-Herschel's Theory not consistent with known Facts, 123.
-The Channel of the Gulf Stream shifts with the Season, 124.-The Phenomenon thermal in its Character, 125.-Limits of the Gulf Stream in March and September, 126. —Reluctance of Layers or Patches to mingle, 127.-Streaks of warm
and cool, 128.-Waters of the Ocean kept in Motion by thermo-dynamical Means,
129.-Fig. A, Plate VI., 130.-The high Temperature and Drift in the western
Half of the North Atlantic and Pacific Oceans, 131.-A Gulf Stream in each, 132.
-Their Connection with the Arctic Ocean, 133.-The Sargassos show the feeble
Power of the Trade-winds upon Currents, 134.-The drift Matter confined to Sargassos by Currents, 135.-Theory'as to the Formation of Sargassos, 136.-Sargassos of southern Seas to the left of the southern, to the right of the great polar and
equatorial Flow and Reflow, 137.-Their Position conforms to the Theory, 138.The Discovery of a new Sargasso, 139. —One in the South Atlantic, 140.-The
large Volume of warm Water outside of the Gulf:Stream, 141.-The Resemblance
between the Currents in the North Atlantic and tlie North Pacific, 142.-A Cushion of cool Water protects the Bottom of the deep Sea from' Abrasion by its Currents, 143.................................................................................. Page  19
CHAPTER III.
INFLUENCE OF TIIE GULF STREAM UPON CLIMATES AND COIMMERCE.
How the Washington Observatory is warmed, ~ 150.-An Analogy showing how the
Gulf Stream raises Temperature in Europe, 151.-Depth and Temperature, 152.
-Contrasts of Climates in the same Latitudes, 153.-Mildness of an Orkney Winter, 154.-Amount of Heat daily escaping through the Gulf Stream, 155.-Its benign Influences, 156.-Cold Water at the Bottom of the Gulf Stream, 157. —Fish
and Currents, 158.-A Shoal of Sea-nettles, 159. —Food for Whales, 160.-Piazzi
Smith's Description, 161.-The VWaters of the Sea bring forth-oh how abundantly! 162.-Contrasts between the Climates of Land and Sea, 163.-Order and Design, 164.-Terrestrial Adaptations, 165.-Meteorology of the Sea: the Gulf Stream
the Weather-breeder-its Storms-the great Hurricane of 1780, 166.-Inquiries instituted by the Admiralty, 167.-The most stormy Sea, 168. —Northern Seas more
boisterous than southern, 169.-Storms in the North Atlantic and Pacific, 170.Storms along their western Shores, 171.-Position of the Poles of maximum Cold,




CONTENTS.                              xix
and their Influence upon the Meteorology of these two Oceans, 172.-Climates of
England and Silver Fogs of Newfoundland, 173.-Influences upon Storms, 174.
-More Observations in and about the Gulf Stream a Desideratum, 175.-Certain
Storms make for it and follow it, 176.-How aqueous Vapor assists in producing
Winds, 177.-Storms in the Interior attracted by the Gulf Stream, 178.-Storms
of, dreaded by Seamen, 179.-Routes formerly governed by the Gulf'Stream, 180.
-Difficulties with early Navigators,  181.-Finding Longitude by the Gulf Stream,
182. —Folger's Chart, 183.-Using the Gulf Stream in Winter, 184. —Running
south to spend the Winter, 185.-Thermal Navigation, 186.-Commodore Truxton, 187.-The Discovery of the high Temperature of the Gulf Stream followed by
a Decline in Southern Commerce, 188. —Statistics, 189. —The Shortening of Voyages, 190. —The Scope of these Researches, 191............................... Page 49
CHAPTER IV.
TIE ATMOSPIERE.
Likened to a Machine, ~ 200. —The Air and the Ocean governed by stable Laws, 201.
-Importance of observing the Works of Nature, 202.-Materials for this Chapter,
203.-Different Belts of Winds, 204.-The trade-wind Belts, 205.-The return
Current, 206.-The Effect of diurnal Rotation on the Course of the Trade-winds,
207.-Two grand Systems of Currents, 208.-From the Pole to 35~-30~, 209.The "Horse Latitudes," 210. —The Barometer there, 211.-The equatorial calm
Belt, 212.-The calm Belt of Capricorn, 213.-The polar Calms and the return
Current, 214.-Diagram of the Winds-Plate I., 215. —As our Knowledge of the
Laws of Nature has increased, so have our Readings of the Bible improved, 216.
-Sloughing off from the counter Trades, 217.-The Air which supplies the southeast Trade-wind in the Band 50 does not cross the Band 25~, 218.-Winds with
Northing and Winds with Southing in them contrasted, 219.-Southeast Tradewinds stronger near the equatorial Limits, 220.-Speed of Vessels through the
Trade-winds, 221.-The Question, Whence are the southeast Trade-winds supplied
with Air? answered, 222.-Whither it goes, 223.-How it is drawn down from
above, 224.-Velocity of southeast shown to be greater than northeast Tradewinds, 225.-The Air sloughed off from the counter Trades moist Air, 226.The Air sloughed off from the upper trade Current dry, 227. —The meteorological
Influences of ascending Columns of moist Air, 228. —Supposing the Air visible,
the Spectacle that would be presented between the upper and lower Currents, 229.
-The Importance of atmospherical Circulation, 230.-Its vertical Movements,
how produced, 231.-Vertical and horizontal Movements in the Air Consequents
of, and dependent upon each other, 232.-Cold Belts, 233. —The upper Currents,
their Numbers and Offices, 234.-Tendency of Air when put in Motion to move
in the Plane of a Great Circle, 235.-The Results upon its Circulation of this
Tendency, 236.-Experiments by the French Academy, 237.-How Supplies of
fresh Air are brought down from the upper Sky, 238.-Beautiful and benign Arrangements, 239.-Their Influences upon the Mind, 240.-The Effect of downward Currents in producing Cold, 241. —The Winter Northers of Texas, 242.Their severe Cold, 243.-The Wind in his Circuits, 244.-Forces which propel
the Wind, 245. —Effect of the direct Heat of the Sun upon the Trade-winds, 246.
-The two Systems of Trade-winds unequal both in Force, Duration, and Stability, 247.-Effects of Heat and Vapor, 248.-Hurricanes not due to direct Heat
of the Sun, 249.-The Influence of other Agents required, 250.-Where found,




xx                            CONTENTS.
251.-Vapor as one of the Causes of the Trade-winds, 252.-Black's Law, 253.The latent Heat transported in Vapor, 254.-The Effect of the Deserts upon the
Trade-winds, 255.-Indications of a Crossing at the calm Belts, 256.-The counter Trades-they approach the Pole in Spirals, 257.-They turn with the Hands
of a Watch about the south Pole, against them about the north, 258.-The Arrows
in the Diagram of the Winds, 259. —The Offices of Sea and Air in the physical
Economy, 260.-Powerful Machinery, 261...................................... Page 71
CHAPTER V.
RAINS AND RIVERS.
Rivers considered as Rain-gatges-the ten largest, ~ 270.-Heat required to lift Vapor for these Rivers, 271.-Rain-fall in the Mississippi Valley, 272.-Its Area,
and the latent Heat liberated during the Processes of Condensation there, 273. —
Annual Discharge of the Mississippi River, 274.-Physical Adaptations, 275.Whence come the Rains for the Mississippi, 276.-The northeast Trades of the
Atlantic supply Rains only for the Rivers of Central and South America, 277.The calm Belt of Cancer furnishes little or no Rain, 278. —The North Atlantic
insufficient to supply Rain for so large a Portion of the Earth as one sixth of all
the Land, 279.-Daily Rate of Evaporation at Sea less than on Land-Observations wanted, 280.-Rivers are Gauges for the Amount of effective Evaporation,
281.-Importance of Rain and River Gauges, 282.-Hypsometry in the North Atlantic peculiar, 283.-Limited Capacity of Winds to take up and transport, for
the Rivers of Europe and America, Vapor from the North Atlantic, 284.-The
Vapor-springs for all these Rivers not in the Atlantic Ocean, 285.-The Places in
the Sea whence come the Rivers of the North, discovered-proves the Crossing at
the calm Belts, 286.-Spirit in which the Search for Truth should be conducted,
287.-The Number of known Facts that are reconciled by the Theory of a Crossing at the calm Belts, 288.-The Atmosphere to be studied, like any other Machinery, by its Operations, 289.-Arguments furnished by the Rivers, 290.-More
Rain in the northern than in the southern Hemisphere, 291.-The Trade-winds
the evaporating Winds, 292.-The saltest Part of the Sea, 293.-Seeing that the
southern Hemisphere affords the largest evaporating Surface, how, unless there be
a Crossing, could we have most Rain and the great Rivers in the northern? 294.
-The rainy Seasons, 295.-The rainy Seasons of California and Panama, 296.The rainless Regions, 297.-The rainy Side of li~ountains, 298. —The Regions of
greatest Precipitation, Cherraponjie and Patagonia, 299.-Amount of Evaporation
greatest from the Indian Ocean, 300.-The Rivers of India, and the Measure of
the effective Evaporation from that Ocean, 301.-Physical Adjustments, 302.Adaptations, their Beauties and sublimity, 303......................................... 99
CHAPTER VI.
RED FOGS AND SEA BREEZES.
The Alternations of Land and Sea Breezes, ~ 311.-The Sea Breeze at Valparaiso,
312.-The Contrast, 313.-Land and Sea Breezes along the Shores of intertropical Countries, 314.-Cause of Land and Sea Breezes, 315.-Lieutenant Jansen
on the Land and Sea Breezes in the Indian Archipelago, 316.-Sanitary Influences of Land and Sea Breezes, 317.-Influences which regulate their Strength,
318.-Land Breezes from the west Coast of Africa scorching hot, 319.-Land
Breeze in Brazil and Cuba, 320.-Night Scenes when sailing with the Land




CONTENTS.                                xi
Breeze, 321.-Red Fogs in the Mediterranean, 322.-Red Fogs near the Equator,
323.-Putting Tallies on the Wind, 324.-They tell of a Crossing at the calm
Belts, 325.-Humboldt's Description of the Dust-whirlwinds of the Orinoco, 326.
-Are the great Deserts Centres of Circulation? 327.-The Color of "Sea-dust,"
328.-A Clew leading into the Chambers of the South, 329.-Red Fogs do not
always occur at the same Place, but they occur on a northeast and southwest
Range, 330.-Conditions requisite to the Production of a Sea Fog, 331.-What
is the Agent that guides the Air across the calm Belts? 332................ Page 127
CHAPTER VII.
TEIHE EASTING OF THE TRADE-WINDS, THE CROSSING AT THE CALM BELTS, AND THE
MAGNETISM OF THE ATMOSPHERE.
Halley's Theory not fully confirmed by Observations, ~ 341.-Observed Course of
the Trade-winds, 342.-Velocities of the Trade-winds, 343.-Difference between
Observation and Theory, 344.-Faraday's Discovery of Magnetism in the Air,
345.-Lines of magnetic Force, 346.-The magnetic Influences of the Oxygen of
the Air and of the Spots on the Sun, 347.-The Needle in its diurnal Variations,
the Barometer in its Readings, and the Atmosphere in its electrical Tension, all
have the same Hours for their Maxima and Minima, 348.-The Question raised
by modern Researches, 349.-Wet and dry Air of the calm Belts, 350.-Principles according to which the physical Machinery of our Planet should be studied,
351.-Division into Wind-bands, 352.-The medial Bands, 353.-The rainless
Regions and the calm Belts, 354.-The Theory of the Crossings restated, and the
Facts reconciled by it, 355.-The Question, How can two Currents of Air cross?
answered, 356.-The Rain Winds in the Mississippi Valley, 357.-Ehrenberg and
his Microscope, 358.-Quetelet's Observations, 359.-At Sea in the southern
Hemisphere we have the Rule, on Land in the northern the Exception, as to the
general Circulation of the Atmosphere, 360.-The magnetic Poles, the Poles of
the Wind and of Cold coincident, 361.-The Barometer in the Wind Bands,
362.-More Atmosphere in the northern than in the southern Hemisphere, 363.
-A Standard of Comparison for the Barometer at Sea, 364.-Southeast Tradewinds having no Moisture traced over into rainless Regions of the northern Hemisphere, 365.-Each Hemisphere receives from the Sun the same Amount of
Heat, 366.-The northern radiates most, 367.-Another Proof of the Crossings
at the calm Belts, 368-Facts and Pearls, 369................................. 148
CHAPTER VIII.
CURRENTS OF THE SEA.
Obedient to Order, ~ 370.-The Fauna and Flora of the Sea, 371.-Those of southern unlike those of northern Seas, 372.-The Capacity of Water to convey Heat,
373.-Currents of the Sea to be considered in Pairs, 374.-Marine Currents do
not, like those on Land, run of Necessity from higher to lower Levels, 375.-The
Red Sea Current, 376.-Upper and under Currents through Straits explained,
377.-The Mediterranean Current, 378. —The Suez Canal, 379.-Hydrometrical
Observations at Sea wanted, 380.-Specific Gravity of Red Sea Water, 381.Evaporation friom, 382.-The Mediterranean Currents, 383.-The "Drift" of the
Phoenix, 384.-Saltness of the Mediterranean, 385.-The Escape of salt and
heavy Water by under Currents, 386.-Vertical Circulation in the Sea a physical Necessity, 387.-The Bars at the Mouths of the Mississippi an Illustration,




XXii                            CONTENTS.
388.-Views of Admiral Smyth and Sir C. Lyell, 389.-Currents of the Indian
Ocean, 390.-The Black Stream of the Pacific contrasted with the Gulf Stream
of the Atlantic, 391.-The Lagulhas Current and the Storms of the Cape, 392.The Currents and Drift of the Indian Ocean, 393.-The ice-bearing Currents
from the antarctic Regions, 394.-The Currents of the Pacific-Drift-wood, 395.
-The Black Current of the Pacific, like the Gulf Stream, salter than the adjacent Waters, 396.-The Current of Okotsk, 397. —Iumboldt's Current, 398.The "' desolate" Region, 399.-Polynesian Drift, 400.-Equatorial Currents, 401.
-The Influence of Rains and Evaporation upon Currents, 402.-Under Currents
-Parker's deep-sea Sounding, 403.-The Compressibility of Water-Effect of, in
the oceanic Circulation, 404.-Assisted by its Salts, 405.-The Origin of Currents, 406.-Currents of the Atlantic, 407.-The St. Roque Current, 408.-The
Greenland Current, 409........................................................... Page 175
CHAPTER IX.
THE SPECIFIC GRAVITY OF THE SEA, AND THE OPEN WATER IN THE ARCTIC OCEAN.
Interesting physical Inquiries, ~ 420.-Voyages of Discovery to the North Pole, 421.
-The first Suggestions of an open Sea in the Arctic Ocean, 422.-HIlarpoonsHabits of the Whales, 423.-The under Current into the Arctic Ocean-its Influences, 424.-Indications of a milder Climate, 425. —How the littoral Waters, by
being diluted from the Rivers and the Rains, serve as a Mantle for the salter and
warmer Sea Water below, 426.-An under Current of warm but salt and heavy
Water, 427.-De Haven's water Sky, 428.-Dr. Kane, 429. —Under Currents
change Temperature slowly, 430.-Solid Matter annually drifted out of the polar
Basin, 431.-Volume of Water kept in Motion by the arctic Flow and Reflow,
432.-The Hydrometer at Sea, 433.-Specific Gravity of average Sea Water, 434.
-An Anomaly, 435.-Influence of the Trade-winds upon the specific Gravity of
Sea Water, 436. - Compensating Influences, 437. — Nicely adjusted, 438.-A.
thermal Tide, 439.-The isothermal Floor of the Ocean, 440.-Thermal Dilatation of the Water, 441.-Experiments on the freezing Point, 442.-Sea Water at
summer more expansible than Sea Water at winter Temperature, 443.-Data for
Plate X., 444.-A thermal Tide: it ebbs and flows once a Year, 445.-Sea Water of the southern cooler and heavier, Parallel for Parallel, than Sea Water of
the northern Hemisphere, 446.-Testimony of the Hydrometer in favor of the
Air Crossings at the calm Belts, 447.-Amount of Salt in, and mean specific
Gravity of Sea Water, 448.-Light cast by Plate X. on the open Sea in the Arctic Ocean, 449.-The heaviest Water, 450.-Chapman's Experiments, 451.The Hydrometer indicates the rainy Latitudes at Sea, 452.-Astronomical View,
453.-The latent Heat of Vapor, 454.-Its Influence upon Climates, 455.-The
Results of the marine Hydrometer, 456.-BarometricIndications of an open Sea,
457.-Polar Rarefaction, 458.-The middle Ice, 459.-Position of the open Sea,
460............................................................................................... 203
CHAPTER X.
TIIE SALTS OF THE SEA.
The Brine of the Ocean, ~ 461. —T ere the Sea of fresh Water-  462.-Uniform
Character of Sea Water, 463.-Hypothesis, 464.-Arguments afforded by Corallines in favor of, 465.-Ditto by the Red Sea, 466.-A general System of Circulation required for the Ocean, 467.-Dynamical Agents, 468.-Currents without




CONTENTS.                            xxiii
Wind, 469.-Influence of Salts and Evaporation, 470.-The under Currents
owing entirely to the Salts of Sea-water, 471.-A Property peculiar to Seas of
salt Water, 472.-Quantity of Salt in the Sea, 473.-Deductions, 474.-Drift of
the Resolute, 475.-De Haven's Drift, 476.-An anti-polynian View, 477.-The
Drift explained, 478.-Thickness of a Winter's Ice, 479.-Layers of Water of
different Temperature in the Arctic Ocean, 480.-The ice-bearing Drift from
the Arctic like the ordinary Drift from the Baltic, 481.-Icebergs drifting north,
482.-Temperature of the under Current, 483.-It comes to the Surface, 484.Sea-shells-their Influence upon Currents, 485.-Solid Matter secreted by them,
486. —Dynamical Force derived firom, 487.-Their physical Relations, 488.-The
Regulators of the Sea, 489.-Whence does the Sea derive its Salts? 490.-Their
Antiquity, 491.-Insects of the Sea-their Abundance, 492.-I)itto, calcareous
in the Pacific, silicious in the Atlantic, 493.-The Records of the Sea and of
Revelation agree, 494.-Cubic Miles of Sea-salt, 495.-The Salthess of Water
retards Evaporation, 496. —The Harmonies of the Ocean, 497. —The Microscope and the Telescope, 498.-Sea-shells and Animalculm in a new Light,
4 99..................................................................................... Page     234
CHAPTER XI.
THE CLOUD REGION, THE EQUATORIAL CLOUD-RING, AND SEA FOGS.
Cloud Region-highest in the calm  Belts, ~ 501.-Fogless Regions, 502.-The
most stormy Latitudes, 503.-Influences of the Gulf Stream and the ice-bearing
Currents of the South, 504.-Sea Fogs rare within 20~ of the Equator-Red
Fogs, 505.-Cloudless Regions and Height of Clouds at Sea, 506.-Height and
Velocity of Waves-Plan for determining, 507.-Determining the Height of
Clouds at Sea, 508.-Cloud Regions at Sea in the Shape of a double-inclined
Plane, 509.-Fogs in the Harbor of Callao, 510.-The cloudy Latitudes, 511.Why there should be less Atmosphere in the southern than in the northern Hemisphere, 512.-Influence of antarctic Icebergs in expelling the Air from austral
Regions, 513.-The Horse Latitudes-the Doldrums, 514.-A Frigate under the
Cloud-ring, 515.-Subjects which at Sea present themselves for Contemplation,
516.-The Barometer under the Cloud-ring, 517.-Its Motions, 518.-Meteorological Processes, 5 19. —Snow-line mounts up as it crosses the Equatorial calm
Belt, 520.-Offices of the Cloud-ring, 521.-It acts as a Regulator, 522.-The
latent Heat liberated in the Processes of Condensation from and under the Cloudring, true Cause of the Trade-winds, 523.-Imagined Appearance of the Cloudring to a distant Observer, 524.-Thunder, 525.-Exceeding Interest attached to
physical Research at Sea, 526......................................................   270
CHAPTER XII.
THEI GEOLOGICAL AGENCY OF THE WINDS.
The Sea and Air regarded as 1arts of the same Machine, ~ 531.-The Level of the
Dead Sea, 532.-An ancient River from it, 533.-Precipitation and Evaporation
in the Dead Sea Valley, 534.-Whence come its Rains? 535.-The Influence
of mountain Ranges, 536.-How the Level of Caspians is reduced, 537.-The
Formation of inland Basins-a third Process, 538.-Examples, 539.-The Influence of the South American Continent upon the Climate of the Dead Sea, 540.The Path of the S.E. Trade-winds over into the northern Hemisphere, 541.-Relays for supplying them with Vapor by the way, 542.-Adjustments in this HIy



xxiv                           CONTENTS.
grometry of Caspians, 543.-Countries in the temperate Zone of this Hemisphere
that are under the Lee of Land in the trade-wind Regions of the other are dry
Countries, 544.-Their Situation, and the Range of dry Winds, 545.-The Mediterranean within it, 546.-Heavy Evaporation, 547.-The Winds that give Rains
to Siberian Rivers have to cross the Steppes of Asia, 548.-How Climates in one
Hemisphere depend upon the Arrangement of Land in the other, and upon the
Course of the Winds, 549.-Terrestrial Adaptations, 550.-The Red Sea and its
Vapors, 551.-Certain Seas and Deserts considered as Counterpoises in the Terrestrial Machinery, 55B2.-Hypothesis supported by Facts, 553.-How, by the
Winds, the Age of certain geological Phenomena in our Hemisphere may be
compared with the Age of those in the other, 554.-The Andes older than the
Dead Sea as an inland Water, 555.............................................. Page 285
CHAPTER XIII.
THE DEPTHS OF THE OCEAN.
Submarine Scenery, ~ 560.-Ignorance concerning the Depth of "Blue Water," 561.
-Early Attempts at deep-sea Soundings-unworthy of Reliance, 562.-Various
Methods tried or proposed, 563.-Physical Problems more difficult than that of
measuring the Depth of the Sea have been accomplished, 564.-The deep-sea
sounding Apparatus of Peter the Great, 565.-A Plan of deep-sea Sounding devised for the American Navy, 566.-The great Depths and Failures of the first
Attempts, 567.-The Plan finally adopted, 568.-Discovery of Currents in the
Depths of the Sea, 569.-Evidence in favor of a regular System of oceanic Circulation, 570. —Methocl of making a deep-sea Sounding, 571.-The Law of the
Plummet's Descent, 572.-Brooke's sounding Apparatus, 573.-The deepest Part
of the Atlantic Ocean, 574.-Deep-sea Soundings by the English Navy, 575. 304
CHAPTER XIV.
THE BASIN AND BED OF THE ATLANTIC.
The Wonders of the Sea, ~ 580.-Its Bottom  and Chimborazo, 581.-An orographic View, 582.-Plate XI., 583.-" What's the Use" of deep-sea Soundings?
584.-The telegraphic Plateau, 585.-The first Specimens of deep-sea Soundings,
586.-Bailey's Letter, 587.-Specimens from the coral Sea, 588.-They belong
to the Animal, not to the Vegetable or Mineral Kingdom, 589.-Quiet reigns in
the Depths of the Sea, 590.-Is there Life- in them? 591.-The Ocean in a new
Light, 592.-Leveling Agencies, 593.-The Offices of Animalcule, 594.-The
Study of them profitable, 595.-The Abrasion of Currents, 596.-Their Pressure
on the Bottom, 597.-Why they can not chafe it, 598. —What it consists of, 599.
— The Causes that produce Currents in the Sea reside near its Surface, 600.Their Depth, 601.-The Cushion of still Water-its Thickness, 602.-The Conservators of the Sea, 603.-The anti-biotic View the most natural, 604.-The
Question stated, 605.-The Arguments of the Biotics, 606. —Ehrenberg's Statement of them, 607.-The anti-biotic View, 608.-Their Arguments based on the
Tides, 609.-On the antiseptic Properties of Sea-water, 610.-On Pressure, 611.
-Arguments from the Bible, 612.-A Plan for solving the Question, 613.-An
unexpected Solution afforded, 614.-A Discovery suggested by it, 615.-Specimens from the three Oceans all tell the same Story, 616.-Their Suggestions,
617.-The work of Readaptation, how carried on, 618.......................... 315




CONTENTS.                              XXV
CHAPTER XV.
SEA ROUTES, CALM BELTS, AND VARIABLE WINDS.
Practical Results of physical Researches at Sea, ~ 621.-Time-tables, 622.-Close
Running, 623.-A Desideratum on Shipboard, 624.-How Passages have been
shortened, 625. —Fast Sailing, 626.-The longest Voyage, 627.-Obstructions to
the Navigator, 628. —Plate VIII., 629.-Deserts, 630.-Diurnal Rotation, 631.
-The Land in the northern Hemisphere, 632.-Why the southeast Trades are
the stronger, 633.-Their Uniformity of Temperature, 634.-The mean Place of
the equatorial calm Belt, 635.-Never at rest, 636.-The calm Belts occupy medial Positions, 637.-Strength of the Trade-winds varies with the Seasons, 638.Sailing through them in Fall and Winter, 639.-A thermal Adjustment, 640.The Barometer in the Trade-winds and equatorial Calms, 641.-Experiments in
the French Navy, 642.-Difference in Tons of the barometric Pressure upon the
northeast and southeast Trade-winds, 643. —Why the Barometer should stand
higher in the southeast than in the northeast Trade-winds; 644.-Cataclysms,
645.-Are the Climates of the Earth changing? 646.-Temperature of the Tradewinds and calm Belts, 647.-The thermal Equator, 648. —A natural Actinometer
in the Trade-winds, 649. —Heat daily received by the southeast Trade-winds, 650.
-Equatorial calm Belt never stationary, 651.-It varies with the Strength of the
Trade-winds, 652.-Precipitation in it, 653.-The Appearance of the calm Belts
from  a distant Planet, 654.-Rainy Seasons of the tropical calm Belts, 655.Their Position, 656.-A meteorological Law, 657.-The Barometer in the calm
Belts, 65S.-Winds with Northiag and Winds with Sonthiazg in them, 659.-The
barometric Ridges, 660.-They make a Depression in the Atmosphere, 661.-The
upper Surface of the Atmosphere, 662.-Winds in the southern stronger than
Winds in the northern Hemisphere, 663. —The Waves and Gales off the Cape of
Good Hope, 664. -Winds blow from a high to a low Barometer, 665. -Polar
Rarefaction, 666.-The tropical calm Belts caused by the polar and equatorial
Calms, 667.-The meteorological Power of latent Heat, 668.-The low Barometer off Cape Horn, 669.-Barometric Table, 670.-Barometer at the Poles, 671.
-The " brave west Winds"-their barometric Descent, 672.-Study of the Monsoons affords farther Information touching the calm Belts, 673.-The southwest
Winds of the Atlantic, 674. —Sailing through the Trade-wind, 675.-The Influence of the Land upon the Winds at Sea, 676.-A "Gulf Stream" in the Air,
677.-Counterpoises, 678.-Normal State of the Atmosphere, 679.-Rain-winds,
680..........................................    Page  334
CHAPTER XVI.
MONSOONS.
The Cause of, ~ 681.-The Region of, 682.-A low Barometer in Northern India,
683.-The S.W. Monsoons "backing down," 684.-How they begin, 685.-The
Sun assisted by the latent Heat of Vapor, 686.-The Rain-fall in India, 687.Its Influences upon the Monsoons, 688.-The March of the Monsoons, 689.Their Conflict-it begins at the north, 690.-The barometric Descent of the Monsoons, 691.-The Summer Rains of Cherraponjie, 692.-Dovre and the Monsoons,
693.-The southeast Trades passing into southwest Monsoons, 694.-Lieutenant
Jansen, 695.- Monsoons in the Pacific, 696. -Influence of Coral Reefs upon
Winds, 697.-Monsoons in Miniature, 698.-The Changing of the Monsoons, 699.




xxvi                            CONTENTS.
- H-ow the calm Belt of Cancer is pushed to the north, 700. —The curved
Form of the equatorial calm Belt in the Indian Ocean, 701.-The Winter Monsoons, 702.-The Monsoons of Australasia, 703.-Thunder and Lightning, 704.
- Water-spouts, 705. — The cast Monsoon in the Java Sea, 706. - Currents,
707. - Marking the Seasons, 708. - Conflicts in the Air, 709. -Passing of the
calm Belts, 710.-Where they are, there the Changing of the Monsoons is going
on, 711...e............................. Page 364
CHAPTER XVII.
THE CLIMATES OF THE SEA.
A "Milky Way" in the Ocean, ~ 720. —The Vibrations of the Gulf Stream, 721.Sea and Land Climates contrasted, 722.-Plate IV., 723.-The Effects of Night
and Day upon the Temperature of Sea Water, 724.-A Belt of uniform Temperature at Sea, 725.-The western Half of the Atlantic warmer than the eastern,
726. — The warmest Sides of Oceans and the coldest Shores of Continents in
Juxtaposition, 727. - The Climates of Europe influenced by tile Shore-lines of
Brazil, 728. - The Gulf of Guinea and the Climate of Patagonia, 729. - Shorelines, 730.-Sudden Changes in the WVater Thermometer, 731.-The Fogs of
Newfoundland, 732.-Aqueous isothermal Lines, 733.-The Meeting of cool and
warm Waters, 734.-The Direction of Aqueous Isotherms on opposite Sides of
tilhe Sea, 735......................................................................... 81.....     1
CHAPTER XVIII.
TIDE-RIPS AND SEA DRIFT.
Tile Glories of the Sea, ~ 740.-Drift described, 741.-Plate IX., 742.-The great
Bend in the Gulf Stream, 743.-The Horse-shoe in the Japan Current, 744.The Animalculme of the Sea, 745.-Colored Patches, 746.-Whence the Red Sea
derives its Name, 747. —The Escape of warm Waters from the Pacific, 748.Ditto from the Indian Ocean, 749.-A wide Current, 750.-Commotions in the
Sea, 751.-Humboldt's Description of Tide-rips, 752. —Horsburgh's, 753.-Tiderips in the Atlantic, 754.-Mock Vigias, 755.-Bores, Eagres, and the Earthquake Wave of Lisbon, 756. - Rains at Sea, and their Effect upon its Equilibrium, 757.-Ditto of Cloud and Sunshine, 758.-Day and Night, 759.-Logs
overhauled for Kelp and Ice, 760.-A Sargasso in the South Pacific, 761. —Seaweed about the Falkland Islands, 762.-The African Sargasso, 763.-Icebergs,
764.-The largest drift farthest, 765. —The Line of Antarctic Drift, 766.-Necessity for and Advantages of an Antarctic Expedition, 767.-Commercial Considerations, 768.-Value of the Fisheries, 769.-Sperm Whales, 770.-A  Sea of
Fire to the, 771.-Right Whales, 772.......................................  395
CHAPTER XIX.
STORMS, HURRICANES, AND TYPHOONS.
Plate V., ~ 781.-Typhoons, 782.-The Mauritius Hurricanes, 783.-The West India Hurricanes, 784. -The Cyclone Theory, 785. - Puzzling Questions, 786.Espy's Theory, 787.-Dovd's Law, 788. —Bernouilli's Formula, 789.-Predicting
Storms, 790.-The Changing of the Wind in a Cyclone, 791.-The Wind stronger on one Side than the other, 792.-The rainy Quadrant of a Cyclone, 793. —Erroneous Theories, 794.-The WVind in a true Cyclone blows in Spirals, 795.-An
Illustration, 796.-Dust W~hirlwinds and Water-spouts, 797.-A vera Causa, 798.




CONTENTS.                           xxvii
-Objections to the Theory, 799.-The three Forces, 800. —The Effect of each,
801.-A Storm within a Storm, 802.-The Black Sea Storm of 1854, 803.-Cyclones of the North Atlantic, 804.-The Hurricane Season, 805.-Cyclones in the
Mississippi Valley, 806.-Extra-tropical Gales, 807.-Storm and Rain Charts,
808.................................g............................. Page 413
CHAPTER XX.
THE WINDS OF THE SOUTHERN IIEMISPIHERE.
Repetition often necessary, ~ 811. —The S.E. and N.E. Trade-winds put in a Balance, 812.-Observations by 2235 Vessels, 813.-Ships used as Anemometers,
814.-Velocity of the Trade-winds, 815.-Ditto of the Counter-trades, 816.The Waves they get up, 817.-A meteorological Corollary, 818.-Facts established, 819.-Atmospherical Circulation more active in the southern than in the
northern Hemisphere, 820.-Gales in the two 1Hemispheres, 821.-Ditto Calms,
822. —The propelling Power of the Winds, 823. —Lt. Van Gogh's Storm and Rain
Charts, 824.-The "brave west Winds" caused by Rarefaction in the Antarctic
Regions, 825.-Reclative Frequency of Rains and Gales at Sea, 826.-The Rainfall of Cape Horn and Cherraponjie, 827.-Influence of Highlands upon Precipitation, 828.-The latent Heat of Vapor, 829.-The Cause of the boisterous Weather off Cape Horn, 830.-Offices of Icebergs in the meteorological Machinery, 831.
-The Antarctic calm Place a Region of constant Precipitation, 832.-Also of a
low Barometer, 833.-Aqueous Vapor the Cause of both, 834.-The topographical Features of Antarctic Lands, 835.-A  perpetual Cyclone, 836.-Discovery
of Design in the meteorological Machinery, 837.-Indications which the Winds
afford concerning the unexplored Regions of the South, 838.-Their Extent;
Plate XV., 839.-A physical Law concerning the Distribution of Land and Water, 840.-Dr. Jilek, 841.-Antarctic Expeditions, 842................... 433
CHAPTER XXI.
THE ANTARCTIC REGIONS AIND THEIR CLIMATOLOGY.
Indications of a mild Climate about the. South Pole, ~ 850. -The Story of the
Winds, 851.-The null Belts, 852.-Extent of the polar Indraught, 853.-The
Rarefaction of the Air over polar Regions, 854.-Barometrical Observations, 855.
-The low austral Barometer, 856. —Discussion of Observations, 857.-Barometric Curve at Sea, 858.-Ditto over the Land, 859.-Agreement of Observations
at Sea, 860.-The Question why the Barometer should stand lower about the
South than the North Pole considered, 861.-Psychrometry of polar Winds, 862.
-Aerial Rarefaction about the North Pole, 863. —Ditto about the South Pole, 864.
-Influences favorable to heavy Precipitation, 865.-The Climates of corresponding Shores and Latitudes north and south, 866.-Thermal Difference between
Arctic and Antarctic Climates, 867.-How the Temperature of Air may be raised
by crossing Mountains, 868.-Aurora Australis, 869.-An erroneous Opinion,
870.-Tropical Regions of the southern Hemisphere cooler, extra-tropical warmer, than those of the northern, 871. -Formation of southern Icebergs, 872. -
Mild Climate in 63~ S., 873.-Antarctic Ice-drift, 874.-Antarctic Currents, 875.
-Antarctic Explorations demanded, 876.-Former Expeditions, 877.-An Appeal for others, 878.......................................................  453




xxviii                          CONTENTS.
CHAPTER XXII.
THE ACTINOMIETRY OF THE SEA.
A new Field, ~ 879.-The warmest Waters in the Sea-where are they? at or below
the Surface? 880. —The annual Supply of solar Heat uniform, 881.-Quantity
of Heat daily impressed upon the Earth, 882.-How far below the Surface does
the Heat of the Sun penetrate? 883.-The Stratum of warmest Water, 884.-Its
Position, S85. —The different Subjects for Observation, 886.-Expected Discoveries, 887.-Actinic Processes, 888.-The Reservoirs of Heat, 889. —The radiating
Powers of Earth, Air, and Water compared, 890.-An Office for Waves in the
Sea, 891.-A Reflection concerning Heat, 892. —Probable Relation between the
Actinometry of the Sea and its Depth, 893........................P............. Page 469




EXPLANATION OF THE PLATESo
PLATE I. —This plate combines in its construction the results of 1,159,353 separate
observations on the force and direction of the wind, and a little upward of 100,000
observations on the height of the barometer at sea. The wind observations embrace
a period of eight hours each, or three during the twenty-four hours. Each one of
the barometric observations expresses the mean height of the barometer for the day;
therefore each one of the 100, 000 may itself be the mean of many, or it may be only
one. Suffice it to say, that 83,334 of them were obtained by Lieutenant Andranl
from the logs of Dutch ships during their voyages to and fro between the parallels
of 500 N. and 36~ S.; that nearly 6000 of them were made south of the parallel of
36~ S., and obtained from the log-books at the Observatory in Washington; that for
the others at sea I am indebted to the observations of Captain Wilkes, of the Exploring Expedition, of Sir James Clark Ross, on board the I "Erebuzs" and " Terror," in
high southern latitudes, and of Dr. Kane in the Arctic Ocean. Besides these, others
made near the sea have been used, as those at Greenwich, St. Petersburg, Hobart
Town, etc., making upward of 100,000 in all. This profile shows how unequally
the atmosphere is divided by the equator.
The arrows within the circle fly with the wind. They represent its mean annual
direction from each quarter, and by bands 50 of latitude in breadth, and according
to actual observation at sea. They show by their length the annual duration of the
wind in months. They are on a scale of one twentieth of an inch per month, except the half-bearded arrows, which are on a scale twice as great, or one tenth of an
inch to the month. It will thus be perceived at a glance that the winds of the longest duration are the S.E. trades, between the parallels of 5~ and 10~ south, where
the long feathered arrows represent an annual average of ten months.
The most prevalent winds in each band are represented by full-feathered arrows;
the next by half-feathered, except between the parallels of 30~ and 350 N.. where the
N.E. and S.W. winds, and between the parallels of 350 and 400, where the N.W. and
S.W. winds contend for the mastery as to average annual duration.
The rows of arrows on each side of the axis, and nearest to it, are projected with
the utmost care as to direction, and length or duration.
The feathered arrows in the shading around the circle represent the crossing at
the calm belts, and the great equatorial and, polar movements by upper and lower
currents of air in its general system of atmospherical circulation.
The small featherless and curved arrows, n, q, r, s, on the shading around the circle, are intended to suggest how the trade-winds, as they cross parallels of larger and
larger circumference on their way to the equator, act as an undertow, and draw supplies of pure air down from the counter-current above; which supplies are required
to satisfy the increasing demands of these winds; for, as they near the equator, they
not only cross parallels of larger circumference, but, as actual observations show, they
also greatly increase both their duration and velocity. In like manner, the countertrades, as they approach the poles, are going from latitudes where the parallels are




XXX                EXPLANATION OF THE PLATES.
larger to latitudes where the parallels are smaller.  In other words, they diminish, as
they approach the poles, the area of their vertical section; consequently there is a
crowding out-a sloughing off from the lower current, and a joining and a turning
back with the upper current. This phenomenon is represented by the small featherless and curved arrows in the periphery on the polar side of the calm belts of Cancer
and Capricorn.
This dotted or shaded periphery is intended to represent a profile view of the atmosphere as suggested by the readings of the barometer at sea.  This method of
delineating the atmosphere is resorted to in order to show the unequal distribution
of the atmosphere, particularly on the polar side of lat. 400 S.; also the piling up
over the calm belts, and the depression —balrometrical - over the equatorial calms
and cloud ring.
The engirdling seas of the extra-tropical south suggest at once the cause of this
inequality in the arrangement over them of the airy covering of our planet.  Excepting a small portion of South America, the belt between the parallels of 40~ and 65~
or 70~ south may be considered to consist entirely of sea. This immense area of
water surface keeps the atmosphere continually saturated with vapor. The specific
gravity of common atmospheric air being taken as unity, that of aqueous vapor is
about 0.6; consequently the atmosphere is expelled thence by the steam, if, for the
sake of explanation, we may so call the vapor which is continually rising up from
this immense boiler. This vapor displaces a certain portion of air, occupies its place,
and, being one third lighter, also makes lighter the barometric column.  Moreover,
being lighter, it mounts up into the cloud region, where it is condensed either into
clouds or rain, and the latent heat that is set free in the process assists still farther to
lessen the barometric column; for the heat thus liberated warms and expands the
upper air, causing it to swell out above its proper level, and so flow back toward the
equator with the upper current of these regions.
Thus, though the barometer stands so low as to show that there is less atmosphere
over high southern latitudes than there is in corresponding latitudes north, yet, if it
were visible and we could see it, we should discover, owing to the effect of this vapor
and the liberation of its latent heat, and the resulting intumescence of the lighter air
over the austral regions, the actual height of this invisible covering to be higher there
than it is in the boreal regions.
Taking the mean height of the barometer for the northern hemisphere to be 30
inches, and taking the 100,000 barometric observations used as data for the construction of this diagram to be correct, we have facts for the assertion that in the
austral regions the quantity of air that this vapor permanently expels thence is from
one twelfth to one fifteenth of the whole quantity that belongs to corresponding latitudes north-a curious, most interesting, and suggestive physical revelation.
PLATES II. and III. are drawings of Brooke's Deep-sea Sounding Apparatus for
bringing up specimens of the bottom (~ 573).
PLATE IV. (~ 723) is intended to illustrate the extreme movements of the isotherms
50~, 60~, 70~, etc., in the Atlantic Ocean during the year. The connection between
the law of this motion and the climates of the sea is exceedingly interesting.
PLATE V. (~ 781) is a section taken from one of the manuscript charts at the Observatory. It illustrates the method adopted there for co-ordinating for the Pilot
Charts the winds as reported in the abstract logs. For this purpose the ocean is divided into convenient sections, usually five degrees of latitude by five degrees of
longitude. These parallelograms are then subdivided into a system of engraved




EXPLANATION OF THE PLATES.                           xxx
squares, the months of the year being the ordinates, and the points of the compass
being the abscissa. As the wind is reported by a vessel that passes through any
part of the parallelogram, so is it assumed to have been at that time all over the parallelogram. From such investigations as this the Pilot Charts are constructed.
PLATE VI. illustrates the position of the channel of the Gulf Stream (Chap. lI.) for
summer and winter. The diagram A shows a thermometrical profile presented by
cross-sections of the Gulf Stream, according to observations made by the hydrographicalparties of the United States Coast Survey.  The elements for this diagram were
kindly furnished me by the superintendent of that work. They are from a paper on
the Gulf Stream, read by him before the American Association for the Advancemlent
of Science at its meeting in Washington, 1854. Imagine a vessel to sail from the
Capes of Virginia straight out to sea, crossing the Gulf Stream at right angles, and
taking the temperature of its waters at the surface and at various depths.  The diagram shows the elevation and depression of the thermometer across this section as
they were actually observed by such a vessel.
The black lines x, y, z, in the Gulf Stream, show the course which those threads
of warm waters take (~ 130).  The lines a, b show the computed drift route that the
unfortunate steamer San Francisco would take after her terrible disaster in December, 1853.
PLATE VII. is intended to show how the winds may become geological agents. It
shows where the winds that, in the general system of atmospherical circulation, blow
over the deserts and thirsty lands in Asia and Africa (where the annual amount of
precipitation is small) are supposed to get their vapors from; where, as surface winds,
they are supposed to condense portions of it; and whither they are supposed to transport the residue thereof through the upper regions, retaining it until they again become surface rinds.
PLATE VIII. shows the prevailing direction of the wind during the year in all parts
of the ocean.  It also shows the principal routes across the seas to various places.
Where the cross-lines representing the yards are oblique to the keel of the vessel,
they indicate that the winds are, for the most part, ahead; when perpendicular or
square, that the winds are, for the most part, fair.  The figures on or near the diagrams representing the vessels show the average length of the passage in days.
The arrows denote the prevailing direction of the wind; they are supposed to fly
with it; so that the wind is going as the arrows point. The half-bearded and halffeathered arrows represent monsoons (~ 630), and the stippled or shaded belts the
calm zones.
In the regions on the polar side of the calms of Capricorn and of Cancer, where
the arrows ale flying both from the northwest and the southwest, the idea intended
to be conveyed is, that the prevailing direction of the wind is between the northwest
and the southwest, and that their frequency is from these two quarters in proportion
to the number of arrows.
PLATE IX. is intended to show the present state of our knowledge with regard to
the drift of the ocean, or, more properly, with regard to the great flow of polar and
equatorial waters, and their channels of circulation as indicated by the thermometer
(~ 742). Farther researches will enable us to improve this chart. The sargasso seas
and the most favorite places of resort for the whale-right in cold, and sperm in
warm water-are also exhibited on this chart.
PLATE X. (p. 214) represents the curves of specific gravity and temperature of the
surface waters of the ocean, as observed by Captain John Rodgers in the U. S. ship




xxxii              EXPLANATION OF THE PLATES.
Vincennes, on a voyage from Behring's Strait via California and Cape Horn to New
York.
PLATES XI. and XII. speak for themselves, They are orographic for the North
Atlantic Ocean, and exhibit completely the present state of our knowledge with regard to the elevations and depressions in the bed of that sea as derived from the deepsea soundings taken by the American and English navies from the commencement
of the system to Dayman's soundings in the Bay of Biscay, 1859; Plate XII. exhibiting a vertical section of the Atlantic, and showing the contrasts of its bottom with
the sea-level in a line from Mexico across Yucatan, Cuba, San Domingo, and the
Cape de Verds, to the coast of Africa, marked A on Plate XI.
PLATE X11I.-The data for this Plate are furnished by Maury's Storm and Rain
Charts, including observations for 107,277 days in the North Atlantic, and 158,025
in the South; collated by Lieutenant J. J. Guthrie, at the Washington Observatory,
in 1855.
The heavy vertical lines, 50, 10~, 15~, etc., represent parallels of latitude; the other
vertical lines, months; and the horizontal lines, per cents., or the number of days in
a hundred.
The continuous curve line stands for phenomena in the North, and the broken
curve line for phenomena in the South Atlantic.  Thus the Gales' Curve shows that
in every hundred days, and on the average, in the month of January of different
years, there have been observed, in the northern hemisphere, 36 gales (36 per cent.)
between the parallels of 500 and 550; whereas during the same time and between
the same parallels in the southern hemisphere, only 10 gales on the average (10 per
cent.) have been reported.
The fact is here developed that the atmosphere is in a -more unstable condition in
the North than in the South Atlantic; that we have more calms, more rains, more
fogs, more gales, and more thunder in the northern than in the southern hemisphere,
particularly between the equator and the 55th parallel. Beyond that the influence
of Cape Horn becomes manifest.
PLATE XIV. (~ 838) shows the limits of the unexplored area about the south pole.
PLATE XV. shows the average number of days annually, and for every degree of
latitude between the parallels of 60~ north and 60~ south that the winds have northing in them on one hand, and southing in them on the other; also, the proportion
of calm days, vide p. 156.




THE
PHYSICAL GEOGRAPHY OF THE SEA,
AND ITS METEOROLOGY,
CHAPTER I.
~ 1-55.-THE SEA AND THE ATMOSPHERE.
~ 1. OUR planet is invested with two great oceans; one visiThe two oceans of ble, the other invisible; one underfoot, the oth.er
air and water. overhead; one entirely envelops it, the other covers about two thirds of its surface. All the water of the one
weighs about 400 times as much as all the air of the other.
2. It is at the bottom of this lighter ocean where the forces
Their meeting. which we are about to study are brought into play;
to treat of the Physical Geography of the Sea, we must necessarily refer to the phenomena which are displayed at the meeting
of these two oceans. Let us, therefore, before entering either of
these fields for study, proceed first to consider each one in some
of its most striking characteristics. They are both in a state of
what is called unstable equilibriuml; hence the currents of one
and the winds of the other.
3. As to their depth, we know very little more of the one than
Their depth.  of the other; but the conjecture that the average
depth of the sea does not much exceed four miles is probably
as near the truth as is the commonly received opinion that the
height of the atmosphere does not exceed 50 miles. If the air
were, like water, non-elastic, and not more compressible than this
non-elastic fluid, we could sound out the atmospherical ocean withthe barometer and gauge it by its pressure. The mean height
of the barometer in the torrid and temperate zones, at the level
of the sea, is about 30 inches-rather under than over. Now, it
A




2         THE PHYSICAL GEOGRAPHY OF THE SEA.
has been ascertained that, if we place a barometer 87 feet above
the level of the sea, its average height will be reduced from 30.00
in. to 29.90 in.; that is, it will be diminished one tenth of an inch,
or the three hundredth part of the whole; consequently, by going
up 300 x 87(=26,100) feet, the barometer, were the air non-elastic,
would stand at 0. It would then be at the top of the atmosphere.
The height of 26,100 feet is just five miles lacking 300 feet.
4. But the air is elastic, and very unlike water. That at the
Weight of the at- bottom is weighed down by the superincumbent
mosphere.    air with the force of about 15 pounds to the square
inch, while that at the top is inconceivably light.  If we imagine
the lightest down, in layers of equal weight and ten feet thick,
to be carded into a pit several miles deep, we can readily imagine
that the bottom layer, though it might have been ten feet thick
when it first fell, yet with the weight of the accumulated and superincumbent mass, it might now, the pit being full, be compressed
into a layer of only a few inches in thickness, while the top layer
of all, being uncompressed, would be exceedingly light, and still
ten feet thick; so that a person ascending from the bottom of the
pit would find the layers of equal weight thicker and thicker until he reached the top. So it is with the barometer and the atmosphere; when it is carried up in the air through several strata
of 87 feet, the observer does not find that it falls a tenth of an
inch for every successive 87 feet upward through which he may
carry it. To get it to fall a tenth of an inch, he must carry it
highe-r and higher for every successive layer.
5. More than three fourths of the entire atmosphere is below
Three fourths below the level of the highest mountains; the other fourth
themountain tops. is rarefied and expanded in consequence of the diminished pressure, until the height of many miles be attained.
From the reflection of the sun's rays after he has set, or before he
rises above the horizon, it is calculated that this upper fourth part
must extend at least forty or forty-five miles higher.
6. At the height of 26,000 miles from the earth, the centrifugal
Its height. force would counteract gravity; consequently, all
ponderable matter that the earth carries with it in its diurnal
revolution must be within that distance, and consequently the atmosphere can not extend beyond that. This limit, however, has
been greatly reduced, for Sir John Herschel has shown, by bal



~ 7-10.        THE SEA AND THE ATMOSPHERE.                       3
loon observations,* that at the height of 80 or 90 miles there is a
vacuum far more complete than any which we can produce by any
air-pump. In 1783 a large meteor, computed to be half a mile
in diameter and fifty miles from the earth, was heard to explode.
As sound can not travel through vacuum, it was inferred that the
explosion took place within the limits of the atmosphere. IIerschel concludes that the aerial ocean is at least 50 miles deep.
7. The data from which we deduce our estimate, both as to the
Data conjectural. mean height of the atmosphere and average depth
of the ocean, are, to some extent, conjectural; consequently, the
estimates themselves must be regarded as approximations, but sufficiently close, nevertheless, for the present purposes of this work.
8. Chemists who have made the analysis tell us that, out of
Analysis of air. 100 parts of atmospheric air, 99.5 consist of oxygen
and nitrogen, mixed in the proportion of 21 of oxygen to 79 of nitrogen by volume, and of 23 to 77 by weight. The remaining half
of a part consists of.05 of carbonic acid and.45 of aqueous vapor.
9. The average depth of the ocean has been variously comInformationrespect- puted by astronomers, from such arguments as the
ing the depth of the
ocean.        science affords, to be from 26 to 11 miles.  About
ten years ago I was permitted to organize and set on foot in the
navy a plan for " sounding out" the ocean with the plummet.t
Other navies, especially the English, have dofe not a little in
furtherance of that object.  Suffice it to say that, within this brief
period, though the undertaking has been by no means completed
-no, not even to the tenth part —yet more knowledge has been
gained concerning the depths and bottom of the dee2p sea, than all
the world had before acquired in all previous time.
10. The system of deep-sea soundings thus inaugurated does
Its probable depth. not thus far authorize the conclusion that the average depth of ocean water is more than three or four miles (~ 3),
nor have any reliable soundings yet been made in water over five
miles deep.
* Those of Mr. Welsh, in his ascent from Kew.
t And be it Jiltlier enacted, That the Secretary of the Navy be directed to detail
three suitable vessels of the navy in testing new routes and perfecting the discoveries
made by Lieut. Maury in the course of his investigations of the winds and currents
of the ocean; and to cause the vessels of the navy to co-operate in procuring materials for such investigations, in so.far as said co-operation may not be incompatible
with the public interests."-From Naval Appropriation Bill, approved March 3, 1849.




4           THE PHYSICAL GEOGRAPHY OF THE SEA.
11. In very shallow pools, where the water is not more than a
Relation between its few inches deep, the ripples or waves, as all of us,
depth and the waves
of the sea.    when children, have observed, are small; their motion, also, is slow. But when the water is deep, the waves are
larger and more rapid in their progress, thus indicating the existence of a numerical relation between their breadth and their velocity, and the depth of the water. It may be inferred, therefore,
that if we knew the size and velocity of certain waves, we could
compute the depth of the ocean.
12. Such a computation has been made, and we have the auAiry's tables. thority of Mr. Airy,* the Astronomer Royal of England, that waves of given breadths will travel in water of certain
depths with the velocities as per table:
Depth of                    Breadth of the Wave in Feet.
the Water
in Feet.    1    10    100 j 1000  10,000 100,000 1,000, 000 10,000, 000
Corresponding Velocity of Wave per Hour in Miles.
1  1.54  3.81   3.86   3.8 6          3.86      3.86      3. 86
10  1.54  4.87  11.51  12.21   12.22   12.22    12.22     12.22
100  1.54  4.87  15.18  36.40   38.64-  38.66    38.66     38.66
1,000  1.54  4.87  15.18  48.77  115.11  122. 18    122.27    122.27
10,000  1.54  4.87  15.18  48.77  154.25  364.02    386.40    386.66
100,000  1.54  4.87  15.18  48.77  154.25  487.79   1151.11   1222.70
13. Accident has afforded us an opportunity of giving a quasi
The earthquake of practical application to Mr. Airy's formuhs.  On
Simoda.       the 23d of December, 1854, at 9.45 A.M.,t the first
shocks of an earthquake were felt on board the Russian frigate
"Diana," as she lay at anchor in the harbor of Simoda, not far
from Jeddo, in Japan.  In fifteen minutes afterward (10 o'clock),
a large wave was observed rolling into the harbor, and the water
on the beach to be rapidly rising. The town, as seen from the
friigate, appeared to be sinking.  This wave was followed by another, and when the two receded —which was at 10h. 15m.-there
was not a house, save an unfinished temple, left standing in the
village. These waves continued to come and go until 2.30 P.M.,
during which time the frigate was thrown on her beam ends five
times.  A  piece of her keel 81 feet long was torn off, holes were
* Encyclop. Metropol.
t Notes of a Russian Officer, p. 97, No. 2 (Feb. 1856), vol. xxv., Nauztical ]3fagazine, London.




~ 14-18.      THE SEA AND THE ATMOSPHERE.                    5
knocked in her by striking on the bottom, and she was reduced
to a wreck. Illn the course of five minutes the water in the harbor
fell, it it said, from 23 to 3 feet, and the anchors of the ship were
laid bare. There was a great loss of life; many houses were
washed into the sea, and many junks carried up-one two miles
-and dashed to pieces on the'shore.  The day was beautifully
fine, and no warning was given of the approaching convulsion;
the barometer standing at 29.87 in., thermometer 58~; the sea
perfectly smooth when its surface was broken by the first wave.
It was calm in the morning, and the wind continued light all
day.
14. In a few hours afterward, at San Francisco and San Diego,
The propagation of the tidle-gauges showed that several well-marked
its waves.   and extraordinary waves had arrived off the coast
of California.*  The origin of these waves,'and those which destroyed the town of Simoda, in Japan, and wrecked the Diana,
was doubtless the same.  But where was their birthplace?  Supposing it to be near the coasts of Japan, we may, with the tidegauge observations in California and Mr. Airy's formule, calculate the average depth of the sea along the path of the wave from
Simoda to both San Francisco and San Diego.
15. Supposing the waves to have taken up their line of march
Their breadth and from some point along the coast of Japan, the San
velocity.   PFrancisco wave, having a breadth of 256 miles, had
a velocity of 438 miles an hour; while the breadth of the San
Diego wave was 221 miles, and its rate of travel 427 miles an hour.
16. Admitting these premises —which are partly assumed-to
Average depth ofthe be correct, then, according to Airy's formule, the
North Pacific.    average depth of the North Pacific between Japan
and California is, by the path of the San Francisco wave, 2149
fathoms, by the San Diego, 2034 (say 2- miles).
17. At the temperature of 600, the, specific gravity of average
Specific gravity of sea-water is 1.0272,ft and the weight of a cubic foot
sea-water.   is 64.003 lbs.
18. With the barometer at 30 in. and the thermometer at 32~,
Of air.   the weight of a cubic foot of dry atmospheric air is
* Ex. Doc. No. 22, Senate, 1st sess. 34th Congress, p. 342.' Maury's Sailing Directions, vol. i. Sir John Herschel quotes it at 1.0275 for
620~.




G         THE JPHYSICAL GEOGRAPHY OF THE SEA.
1.291 oz., and its specific gravity.00129. Such is the difference
in weight between the two elements, the phenomena of which
give the physical geography of the sea its charms as a study.
19. There is in the northern hemisphere more land, less sea,
Unequaidistribution more fresh water, and more atmospheric air, than
of light, etc.    there is in the southern.
20. The sun dispenses light and heat unequally also between
The sun longer in them. In his,annual round he tarries a week (7,
northern declination.        days) longer on the north than he does on the south
side of the equator, and consequently the antarctic night and its
winter are both longer, and should, if there were no interferences,
be more intense than the polar winter and night of the arctic regions. The southern hemisphere is said also to be cooler, and
this is true to a certain degree. In the summer of the southern
hemisphere, the sun is in perigee, and during the course of a diurnal revolution there the southern half of our planet receives
more heat than the northern half during the same period of our
summer. This difference, Sir John Herschel thinks, is compensated by the longer duration of the northern summer. Admitting this to be so-and it is susceptible of mathematical demonstration-there remains outstanding the longer winter for the
southern hemisphere, which may radiate more heat than the
northern hemisphere can do in its short winter. But the southern hemisphere is the cooler chiefly on account of the latent heat
which is brought thence by vapor, and set free here by condensation.
21. Within the torrid zone the land is nearly equally divided
England about the north and south of the equator, the proportion bepole of hemisphere
with most land.  ing as 5 to 4. In the temperate zones, however, the
north with its land is thirteen times in excess of the south. Indeed, such is the inequality in the distribution of land over the
surface of the globe that the world may be divided into hemispheres consisting, the one with almost all the land in it, except
Australia and a slip of America lying south of a line drawn from
the Desert of Atacama to Uruguay; England is the centre of this
hemisphere. The other, an aqueous hemisphere, contains all the
great waters except the Atlantic Ocean; New Zealand is the
nearest land to its centre.
22. This unequal distribution of land, air, and water is suggest



~ 23-27.      THE SEA AND THE ATMOSPHERE.                    7
Effects of inequality ive. To it we owe the different climates of the earth.
in distribution of
land and water.   Were it different, they would be different also;
were it not for the winds, the vapors that rise from the sea would
from the clouds be returned in showers back to the places in the
sea whence they came; we should have neither green pastures,
still waters, nor running brooks to beautify the landscape on an
earth where no winds blow. WVere there no currents in the sea,
the seasons might change, but climates would be a simple affair,
depending solely on the declination of the sun in the sky.
23. About two thirds of all the fresh water on the surface of
Quantity of fresh the earth is contained in the great American lakes;
water in American
lakes.       and though there be in the northern, as compared
with the southern hemisphere, so much less sea surface to yield
vapor, so much more land to swallow up rain, and so many more
plants to drink it in, yet the fresh-water courses are far more numerous and copious on the north than they are on the south side
of the equator.
24. These facts have suggested the comparison in which the
Southern seas the southern hemisphere has been likened to the boilboiler, and northern
landsthecondenser. er and the northern to the condenser of the steamengine. This vast amount of steam or vapor rising up in the
extra-tropical regions of the south, expels the air thence, causing
the barometer to show a much less weight of atmosphere on the
polar side of 40~ S. than we find in corresponding latitudes north.
25. The offices of the atmosphere are many, marvelous, and
Offices of the atmos- various.  Though many of them  are past finding
phere.       out, yet, beautiful to contemplate, they afford most
instructive and profitable themes for meditation.
26. When this system of research touching the physics of the
Dr. Buist.  sea first began-when friends were timid and co-laborers few, the learned Dr. Buist stood up as its friend and champion in India; and by the services he thus rendered entitled himself to the gratitude of all who with me take delight in the results which have been obtained.  The field which it was proposed to occupy-the firstlings of which were gathered in this
little book-was described by him in glowing terms, colored to
nature. They are apropos, and it is a pleasure to repeat them,
with such alterations only as experience shall approve —
27. " The weight of the atmosphere is equal to that of a solid




8         THE PHYSICAL GEOGRAPHY OF THE SEA.
The sea and the at- globe of lead sixty miles in diameter. Its principal
mosphere contrasted.          elements are oxygen and nitrogen gases, with a
vast quantity of water suspended in them in the shape of vapor,
and commingled with these a quantity of carbon in the shape of
fixed air, equal to restore from its mass many fold the coal that
now exists in the world. In common with all substances, the
ocean and the air are increased in bulk, and, consequently, diminishedl in weight, by heat; like all fluids, they are mobile, tending
to extend themselves equally in all directions, and to fill up depressions wherever vacant space will admit them; hence, in these
respects, the resemblance betwixt their movements.  Water is
not compressible or elastic, and it may be solidified into ice or vaporized into steam; the air is elastic; it may be condensed to any
extent by pressure, or expanded to an indefinite degree of tenuity
by pressure being removed from it; it is not liable to undergo
any change in its constitution beyond these, by any of the ordinary influences by which it is affected.
28. "These facts are few and simple enough; let us see what
Influence of the sun. results arise from them: As the constant exposure
of the equatorial regions of the earth to the sun must necessarily
there engender a vast amount of heat, and as his absence from
the polar regions must in like manner promote an infinite. accumulation of cold, to fit the entire earth for a habitation to similar
races of beings, a constant interchange and communion betwixt
the heat of the one and the cold of the other must be carried on.
The ease and simplicity with which this is effected surpass all description.  The air, heated near the equator by the overpowering
influences of the sun, is expanded and lightened; it ascends into
upper space, leaving a partial vacuum at the surface to be supplied from the regions adjoining. Two currents from the poles
toward the equator are thus established at the surface, while the
sublimated air, diffusing itself by its mobility, flows in the upper
regions of space from the equator toward the poles. Two vast
whirlpools are thus established, constantly carrying away the heat
from the torrid toward the icy regions, and, there becoming cold
by contact with the ice, they carry back their gelid freight to refresh the torrid zone.
29. "I Did the earth, as was long believed, stand still while the
Of diurnal rotation. sun circled around it, we should have had directly




~ 30, 31.     THE SEA AND THE ATMOSPHERE.                 9
from north and south two sets of meridional currents blowing at
the surface of the earth toward the equator; in the upper regions
we should have had them flowing back again to the place whence
they came. On the other hand, were the heating and cooling influences just referred to to cease, and the earth to fail in impressing its own motion on the atmosphere, we should have a furious
hurricane rushing round the globe at the rate of 1000 miles an
hour-tornadoes of ten times the speed of the most violent inow
known to us, sweeping every thing before them. A combination
of the two influences, modified by the friction of the earth, which
tends to draw the air after it, gives us the trade-winds, which, at
the speed of from ten to twenty miles an hour, sweep round the
equatorial region of the globe unceasingly.
30. " Impressed with the motion of the air, constantly sweeping
Currents.  its surface in one direction, and obeying the same
laws of motion, the great sea itself would be excited into currents
similar to those of the air, were it not walled in by continents
and subjected to other control. As it is, there are constant currents flowing from the torrid toward the frigid zone to supply the
vast amount of vapor there drained off, while other whirlpools
and currents, such as the' gigantic Gulf Stream, come to perform
their part in the same stupendous drama. The waters of this vast
ocean river are, to the north of the tropic, greatly warmer than
those around; the climate of every country it approaches is improved by it, and the Laplander is enabled by its means to live
and cultivate his barley in a latitude which, every where else
throughout the world, is condemned to perpetual sterility. There
are other laws which the great sea obeys which peculiarly adapt
it as the vehicle of interchange of heat and cold betwixt those
regions where either exists in excess.
31. " In obedience to these laws water warmer than ice attacks
Icebergs.  the basis and saps the foundations of the icebergs
-themselves gigantic glaciers, which have fallen from the mountains into the sea, or which have grown to their present size in
the shelter of bays and estuaries, and by accumulations from
above. Once forced from their anchorage, the first storm that
arises drifts them to sea, where the beautiful law which renders
ice lighter than the warmest water enables it to float, and drifts
southward a vast magazine of cold to cool the tepid water which




10        THE PHYSICAL GEOGR-APHY OF THE SEA.
bears it along-the evaporation at the equator causing a deficit,
the melting and accumulation of the ice in the frigid zone giving
rise to an excess of accumulation, which tends, along with the
action of the air and other causes, to institute and maintain the
transporting current. These stupendous masses, which have been
seen at sea in the form of church spires, and gothic towers, and
minarets, rising to the height of from 300 to' 600 feet, and extending over an area of not less than six square miles, the masses
above water being only'one tenth of the whole, are often to be
found within the tropics.
32. " But these, though among the most regular and magnifiMountain ranges. cent, are but a small number of the contrivances by
which the vast and beneficent ends of nature are brought about.
Ascent from the surface of the earth produces the same change,
in point of climate, as an approach to the poles; even under the
torrid zone mountains reach the line of perpetual congelation
at nearly a third less altitude than the extreme elevation which
they sometimes attain. At the poles snow is perpetual on the
ground, and at the different intervening latitudes reaches some
intermediate point of congelation betwixt one and 20,000 feet.
In America, from the line south to the tropics, as also, as there is
now every reason to believe, in Africa within similar latitudes,
vast ridges of mountains, covered with perpetual snow, run northward and southward in the line of the meridian right across the
path of the trade-winds. A similar ridge, though of less magnificent dimensions, traverses the peninsula of Hindoostan, increasing in altitude as it approaches the line, attaining an elevation of 8500 feet at Dodabetta, and above 6000 in Ceylon. The
Alps in Europe, and the gigantic chain of the Himalayas in Asia,
both far south in the temperate zone, stretch from east to west,
and intercept the aerial current from the north. Others of lesser
note, in the equatorial or meridional, or some intermediate direction, cross the paths of the atmospherical currents in every direction, imparting to them fresh supplies of cold, as they themselves
obtain from them warmth in exchange; in strictness the two operations. are the same.
33. "Magnificent and stupendous as are the effects and results
Water.   of the water and of air acting independently on
each other, in equalizing the temperature of the globe, they are




~ 34,35.      THE SEA AND THE ATMOSPHERE.                 1
still more so when combined. One cubic inch of water, when
invested with a sufficiency of heat, will form one cubic foot of
steam-the water before its evaporation, and the vapor which it
forms, being exactly of the same temperature; though in reality,
in the process of conversion, 1100 degrees of heat have been absorbed or carried away from the vicinage, and rendered latent or
imperceptible; this heat is returned in a sensible and perceptible
form the moment the vapor is converted once more into water.
The general fact is the same in the case of vapor carried off by
dry air at any temperature that may be imagined; for, down far
below the freezing point, evaporation proceeds uninterruptedly.
34. " The air, heated and dried as it sweeps over the arid surface
Latent heat.  of the soil, drinks up by clay myriads of tons of
moisture from the sea-as much, indeed, as would, were no moisture restored to it, depress its whole surface at the rate of eight or
ten feet annually.  The quantity of heat thus converted from a
sensible or perceptible to an insensible or latent state is almost incredible. The action equally goes on, and with the like results,
over the surface of the earth, where there is moisture to be withdrawn. But night and the seasons of the year come around, and
the surplus temperature, thus withdrawn and stored away at the
time it might have proved superfluous or inconvenient, is rendered back so soon as it is required; thus the cold of night and the
rigor of winter are modified by the heat given out at the point of
condensation by dew, rain, hail, and snow.
35. " The earth is a bad conductor of heat; the rays of the sun,
Effects upon the which enter its surface and raise the temperature
earth.      to 1000 or 150~, scarcely penetrate a foot into the
ground; a few feet down, the warmth of the ground is nearly the
same night and day. The moisture which is there preserved free
from the influence of currents of air is never raised into vapor;
so soon as the upper stratum of earth becomes thoroughly dried,
capillary action, by means of which all excess of water was withdrawn, ceases; so that, even under the heats of the tropics, the
soil two. feet down will be found, on the approach of the rains,
sufficiently moist for the nourishment of plants. The splendid
flowers and vigorous foliage which burst forth in May, when the
parched soil would lead us to look for nothing but sterility, need
in no way surprise us; fountains of water, boundless in extent




12        THE PHYSICAL GEOGRAPHY OF THE SEA.
and limited in depth only by the thickness of the soil which contains them, have been set aside and sealed up for their use, beyond the reach of those thirsty winds or burning rays which are
suffered to carry off only the water which is superfluous, and
would be pernicious. They remove it to other lands, -where its
agency is required, or treasure it up, as the material of clouds
and dew, in the crystal vault of the firmament, the source, when
the fitting season comes round again, of those deluges of rain
which provide for the wants of the year. Such are some of the
examples which may be supplied of general laws operating over
nearly the whole surface of the terraqueous globe. Among the
local provisions ancillary to these are the monsoons of India, and
the land and sea breezes prevalent throughout the tropical coasts.
36. " We have not noticed the tides, which, obedient to the sun
The tides. and moon, daily convey two vast masses of water
round the globe, and which twice a month, rising to an unusual
height, visit elevations which otherwise are dry. During one
half of the year the highest tides visit us by clay, the other half
by night; and at Bombay, at spring tide, the depths of the two
differ by two or three feet from each other. The tides simply
rise and fall, in the open ocean, to an elevation of two or three
feet in all; along our shores, and up gulfs and estuaries, they
sweep with the violence of a torrent, having a general range of
ten or twelve feet-sometimes, as at Fundy, in America, at Brest
and Milford Haven, in Europe, to a height of from forty to sixty
feet. The tides sweep our shores from filth, and purify our rivers and inlets, affording to the residents of our islands and continents the benefits of a bi-diurnal ablution, and giving a health,
and freshness, and purity wherever they appear. Obedient to the
influence of bodies many millions of miles removed from them,
their subjection is not the less complete; the vast volume of water, capable of crushing by its weight the most stupendous barriers that can be opposed to it, and bearing on its bosom the navies of the world, impetuously rushing against our shores, gently
stops at a given line, and flows back again to its place when the
word goes forth,'Thus far shalt thou go, and no farther;' and
that which no human power or contrivance could have repelled,
returns at its appointed time so regularly and surely that the hour
of its approach, and measure of its mass, may be predicted with
unerring certainty centuries beforehand.




~ 37, 38.     THE SEA AND THE ATMOSPHERE.                 13
37. "The hurricanes which whirl with such fearful violence
Hurricanes.  over the surface, raising the waters of the sea to
enormous elevations, and submerging coasts and islands, attended as they are by the fearful attributes of thunder and deluges
of rain, seem requisite to defiagrate the noxious gases which have
accumulated, to commingle in one healthful mass the polluted elements of the air, and restore it fitted for the ends designed for it.
WTe have hitherto dealt with the sea and air —the one the medium
through which the commerce of all nations is transported, the
other the means by which it is moved along-as themselves the
great vehicles of moisture, heat, and cold throughout the regions
of the world —the means of securing the interchange of these inestimable commodities, so that excess may be removed to where
deficiency exists, deficiency substituted for excess, to the unbounded advantage of all. This group of illustrations has been
selected because they are the most obvious, the most simple, and
the most intelligible and beautiful that could be chosen.
38. "We have already said that the atmosphere forms a spheriPowers of the air. cal shell, surrounding the earth to a depth which is
unknown to us, by reason of its growing tenuity, as it is released
from the pressure of its own superincumbent mass. Its upper
surface can not be nearer to us than fifty, and can scarcely be
more remote than five hundred miles. It surrounds us on all
sides, yet we see it not; it presses on us with a load of fifteen
pounds on every square inch of surface of our bodies, or' from
seventy to one hundred tons on us in all, yet we do not so much
as feel its weight.  Softer than the finest down, more impalpable
than the finest gossamer, it leaves the cobweb undisturbed, and
scarcely stirs the lightest flower that feeds on the dew it supplies;
yet it bears the fleets of nations on its wings around the world,
and crushes the most refractory substances with its weight. WVhen
inl motion, its force is sufficient to level with the earth the most
stately forests and stable buildings, to raise the waters of the ocean
into ridges like mountains, and dash the strongest ships to pieces
like toys. It warms and cools by turns the earth and the living
creatures that inhabit it. It draws up vapors from the sea and
land, retains them dissolved in itself or suspended in cisterns of
clouds, and throws them down again, as rain or dew, when they
arer equired. It bends the rays of the sun from their path to give




14        THE PHYSICAL GEOGRAPHY OF THE SEA.
us the aurora of the morning and twilight of evening; it disperses
and refracts their various tints to beautify the approach and the
retreat of the orb of day. But for the atmosphere, sunshine would
burst on us in a moment and fail us in the twinkling of an eye,
removing us in an instant from midnight darkness to the blaze
of noon. WVe should have no twilight to soften and beautify the
landscape, no clouds to shade us from the scorching heat; but the
bald earth, as it revolved on its axis, would turn its tanned and
weakened front to the full and unmitigated rays of the lord of
day.
39. " The atmosphere affords the gas which vivifies and warms
Its functions. our frames; it receives into itself that which has
been polluted by use, and is thrown off as noxious. It feeds the
flame of life exactly as it does that of the fire. It is in both cases
consumed, in both cases it affords the food of consumption, and
in both cases it becomes combined with charcoal, which requires
id for combustion, and which removes it when combustion is over.
It is the girdling encircling air that makes the whole world kin.
The carbonic acid with which to-day our breathing fills the air,
to-morrow seeks its way round the world. The date-trees that
grow round the falls of the Nile will drink it iii by their leaves;
the cedars of Lebanon will take of it to add to their stature; the
cocoa-nuts of Tahiti will grow rapidly upon it; and the palms
and bananas of Japan will change it into flowers. The oxygen
we are breathing was distilled for us some short time ago by the
magnolias of the Susquehanna and the great trees that skirt the
Orinoco and the Amazon; the giant rhododendrons of the Himalayas contributed to it, and the roses and myrtles of Cashmere,
the cinnamon-tree of Ceylon, and the forest, older than the flood,
that lies buried deep in the heart of Africa, far behind the Mountains of the Moon, gave it out. The rain we see descending was
thawed for us out of the icebergs which have watched the Polar
Star for ages, or it came from snows that rested on the summits
of the Alps, but which the lotus lilies have soaked up from the
Nile, and exhaled as vapor again into the ever-present air."
40. There are processes no less interesting going on in other
The operations of parts of this magnificent field of research. Water
water.      is nature's carrier. With its currents it conveys
heat away from the torrid zone and ice from the frigid; or, bot



~ 41-43.      THE SEA AND THE ATMOSPHERE.                   15
tling the caloric away in the vesicles of its vapor, it first makes
it impalpable, and then conveys it, by unknown paths, to the most
distant parts of the earth.  The materials of which the coral builds
the island, and the sea-conch its shell, are gathered by this restless leveler from mountains, rocks: and valleys in all latitudes.
Some it washes down from the Mountains of the Moon, or out of
the gold-fields of Australia, or from the mines of Potosi, others
from the battle-fields of Europe, or from the marble quarries of
ancient Greece and Rome.  These materials, thus collected and
carried over falls or down rapids, are transported from river to
sea, and delivered by the obedient waters to each insect and to
every plant in the ocean at the right time and temperature, in
proper form, and in due quantity.
41. Treating the rocks less gently, it grinds them into dust, or
Its marvelous pow- pounds them into sand, or rolls them  in pebbles,
e rs.        rubble, or boulders: the sand and shingle on the
sea-shore are monuments of the abrading, triturating power of
water. By water the soil has been brought down from the hills
and spread out into valleys, plains, and fields for man's use.
Saving the rocks on which the everlasting hills are established,
every thing on the surface of our planet seems to have been removed from  its original foundation and lodged in its present
place by water. Protean in shape, benignant in office, water,
whether fresh or salt, solid, fluid, or gaseous, is marvelous in its
powers.
42. It is one of the chief agents in the manifold workshops in
Itcatersonlandfor which and by which the earth has been made a
insects of the sea.  habitation fit for man.  Circulating in veins below
the surface, it pervades the solid crust of the earth in the fulfillment of its offices; passing under the mountains, it runs among
the hills and down through the valley in search of pabulum for
the moving creatures that have life in the sea.  In rivers and in
rain it gathers up by ceaseless lixiviation food for the creatures
that wait upon it. It carries off from the land whatever of solid
matter the sea in its economy requires.
43. The waters which dash against the shore, which the runLeaching.   ning streams pour into the flood, or with which the
tides and currents scour the bottom of their channel ways, have
soaked from the soil, or leached out of the disintegrated materials




16         THE PHYSICAL GEOGRAPHY OF THE SEA.
which strew the beach or line the shores, portions of every soluble ingredient known in nature.  Thus impregnated, the laughing, dancing waters come down from  the mountains, turning
wheels, driving machinery, and serving the manifold purposes
of man. At last they find their way into the sea, and so make
the lye of the earth brine for the ocean.
44. Iron, lime, silver, sulphur, and copper, silex, soda, magSoli ingredients. nesia, potash, chlorine, iodine, bromine, ammonia,
are all found in sea-water; some of them in quantities too minute
for the nicest appliances of the best chemists to detect, but which,
nevertheless, are elaborated therefrom by physical processes.
45. By examining the copper that had been a great while on
Quantity of silver in the bottom of a ship in Valparaiso, the presence of
the sea.     silver, which it obtained from the sea, was detected
in it. It was in such quantities as to form the basis of a calculation, by which it would appear that there is held in solution by
the sea a quantity of silver sufficient to weigh no less than two
hundred million tons, could it all, by any process, be precipitated
and collected into bars.
46. The salts of the sea, as its solid ingredients may be called,
Its inhabitants- can neither be precipitated on the bottom, nor taken
their offices. up by the vapors, nor returned again by the rains
to the land; and, but for the presence in the sea of certain agents
to which has been assigned the task of collecting these ingredients
again, in the sea they would have to remain.  There, accumulating in its waters, they would alter the quality of the brine, injure the health of its inhabitants, retard evaporation, change
climates, and work endless mischief upon the fauna and the flora
of both sea, earth, and air. But in the oceanic machinery all this
is prevented by compensations the most beautiful and adjustments
the most exquisite., As in the atmosphere the plants are charged
with the office of purifying the air by elaborating into vegetable
tissue and fibre the impurities which the animals are continually
casting into it, so also to the mollusks, to the madrepores, and
insects of the sea, has been assigned the office of taking out of its
waters and making solid again all this lixiviated matter as fast as
the dripping streams and searching rains discharge it into the
ocean.
47. As to the extent and magnitude of this endless task some




~ 48-51.         THE SEA AND THE ATMOSPHERE.                          17
Monuments of their idea may be formed from  the coral islands, the marl
industry.      beds, the shell banks, the chalk cliffs, and other
marine deposits which deck the sea or strew the land.
48. Fresh water is composed of oxygen and hydrogen gas in
Analysis of sea-wa- the proportion by weight of 1 to 8; and the printer.           cipal ingredients which chemists, by treating small
samples of sea-water in the laboratory, have found in a thousand
grains are,
Water.........................................................  962.0 grains
Chloride  of Sodium........................................   27.1  "
Chloride of Magnesium....................................4   "
Chloride of Potassium........................  0.4   "
Bromide of Magnesia.............................  0.1   "
Sulphate of Magnesia...............................  1.2
Sulphate of Lime...........................................  0.8
Carbonate of Lime........................................  0.1   "
Leaving a residuum of...................................  2.9   " -1000,
consisting of sulphureted hydrogen gas, hydrochlorat6 of ammonia, etc., etc., in various quantities and proportions, according to
the locality of the specimen.
49. If we imagine the whole mass of the earth to be divided
Proportion of water into 1786 equal parts by weight, then the weight
to the mass of the
earth.         of all the water in the sea would, according to an
estimate by Sir John Herschel, be equivalent to one of such parts.
Such is the quantity, and such some of the qualities of that delightful fluid to which, in the laboratories and workshops of nature, such mighty tasks, such important offices, such manifold
and multitudinous powers have been assigned.
50. This volume of water, that outweighs the atmosphere about
The three great 400 times, is divided into three great oceans, the
oceans.        Atlantic, the Pacific, and the Arctic; for in the
rapid survey which in this chapter we are taking of the field before us, the Indian and Pacific oceans may be regarded as one.
51. The Atlantic Ocean, with its arms, is supposed to extend
The Atlantic.  from  the Arctic to the Antarctic-perhaps from
pole to pole; but, measuring from  the icy barrier of the north to
that of the south, it is about 9000 miles in length, with a mean
breadth of 2700 miles. It covers an area of about 25,000,000
square miles.  It lies between the Old World and the New; passing beyond the " stormy capes," there is no longer any barrier, but
B




18        THE PHYSICAL GEOGRAPHY OF THE SEA.
only an imaginary line to separate its waters from that great
southern waste in which the tides are cradled.
52. The young tidal wave, rising in the circumpolar seas of
Its tides.  the south, rolls thence into the Atlantic, and in 12
hours after passing the parallel of Cape Horn, it is found pouring
its flood into the Bay of Fundy.
53. The Atlantic is a deep ocean, and the middle its deepest
Its depths.  part, therefore the more favorable (~ 13) to the
propagation of this wave.
54. The Atlantic Ocean contrasts very strikingly with the PaContrasted with the cific. The greatest length of one lies east and west;
Pacific.     of the other, north and south. The currents of the
Pacific are broad and sluggish, those of the Atlantic swift and
contracted. The Mozambique current, as it is called, has been
found by navigators in the South Pacific to be upward of 1600
miles wide-nearly as broad as the Gulf Stream is long.  The
principal currents in the Atlantic run to and fro between the
equator and the Northern Ocean. In the Pacific they run between the equator and the southern seas. In the Atlantic the
tides are high, in the Pacific they are low. The Pacific feeds the
clouds with vapors, and the rains feed the Atlantic with rivers.
If the volume of rain which is discharged into the Pacific and on
its slopes be represented by 1, that discharged upon the hydrographical basin of the Atlantic would be represented by 5. The
Atlantic is crossed daily by steamers, the Pacific not once a year.
The Atlantic washes the shores of the most powerful, intelligent,
and Christian nations; but a pagan or a heathen people in the
countries to which the Pacific gives drainage are like the sands
upon its shores for multitude. The Atlantic is the most stormy
sea in the world, the Pacific the most tranquil.
55. Among the many valuable discoveries to which these reTheTelegraphicPla- searches touching the physics of the sea have led,
teau.        none perhaps is more interesting than the Telegraphic Plateau of the Atlantic, and the fact that the bottom of
the deep sea is lined with its own dead, whose microscopic remains are protected from the abrading action of its currents and
the violence of its waves by cushions of still water.




~ 70, 71.           THE GULF STREAM.                       19
CHAPTER II.
~ 70-143. —THE GULF STREAM.
70. THERE is a river in the ocean: in the severest droughts
Its color. it never fails, and in the mightiest floods it never
overflows; its banks and its bottom  are of cold water, while its
current is of warm; the Gulf of Mexico is its fountain, and its
mouth is in the Arctic Seas. It is the Gulf Stream. There is in
the world no other such majestic flow of waters. Its current is
more rapid than the Mississippi or the Amazon, and its volume
more than a thousand times greater. Its waters, as far out from
the Gulf as the Carolina coasts, are of an indigo blue. They are
so distinctly marked that their line of junction with the common
sea-water may be traced by the eye. Often one half of the vessel may be perceived floating. in Gulf Stream water, while the
other half is in common water of the sea-so sharp is the line,
and such the want of affinity between those waters, and such, too,
the reluctance, so to speak, on the part of those of the Gulf Stream
to mingle with the littoral waters of the sea.
71. At the salt-works in France, and along the shores of the
How caused.  Adriatic, where the "salines" are carried on by the
process of solar evaporation, there is a series of vats or pools
through which the water is passed as it comes from the sea, and
is reduced to the briny state. The longer it is exposed to evaporation, the salter it grows, and the deeper is the hue of its blue,
until crystallization is about to commence, when the now deep
blue water puts on a reddish tint. Now the waters of the Gulf
Stream are salter (~ 102) than the littoral waters of the sea through
which they flow, and hence we can account for the deep indigo
blue which all navigators observe off the Carolina coasts. The
salt-makers are in the habit of judging of the richness of the seawater in salt by its color-the greener the hue, the fresher the
water. We have in this, perhaps, an explanation of the contrasts
which the waters of the Gulf Stream present with those of the
Atlantic, as well as of the light green of the North Sea and other




20         THE PHYSICAL GEOGRAPHY OF THE SEA.
Polar waters; also of the dark blue of the trade-wind regions, and
especially of the Indian Ocean, which poets have described as the
" black waters."
72. What is the cause of the Gulf Stream has always puzzled
Speculations  con- philosophers.  Many are the theories and numercerning the Gulf
Stream.      ous the speculations that have been advanced with
regard to it. Modern investigations and examinations are beginning to throw some light upon the subject, though all is not yet
entirely clear. But they seem to encourage the opinion that this
stream, as well as all the constant currents of the sea, is due mainly to the constant difference produced by temperature and saltness
in the specific gravity of water in certain parts of the ocean. Such
difference of specific gravity is inconsistent with aqueous equilibrium, and to maintain this equilibrium these great currents are
set in motion. The agents which derange equilibrium in the
waters of the sea, by altering specific gravity, reach from the
equator to the poles, and in their operations they are as ceaseless
as heat and cold, consequently they call for a system of perpetual
currents to undo their perpetual work.
73. These agents, however, are not the sole cause of currents.
Agencies concerned. The winds help to make currents by pressing upon
the waves and drifting before them the water of the sea; so do
the rains, by raising its level here and there; and so does the atmosphere, by pressing with more or less superincumbent force
upon different parts of the ocean at the same moment, and as indicated by the changes of the barometric column.  But when the
winds and the rains cease, and the barometer is stationary, the
currents that were the consequence also cease. The currents thus
created are therefore ephemeral. But the changes of temperature
and of saltness, and the work of other agents which affect the
specific gravity of sea-water and derange its equilibrium, are as
ceaseless in their operations as the sun in his course, and in their
effects they are as endless. Philosophy points to them as the chief
cause of the Gulf Stream and of all the constant currents of the sea.
74. Early writers, however, maintained that the Mississippi
Early writers.  River was the father of the Gulf Stream. Its floods,
they said, produce it, for the velocity of this river in the sea
might, it was held, be computed by the rate of the current of the
river on the land.




~ 75-78.            THE GULF STREAM.                     21
75. Captain Livingston overturned this hypothesis by showing
Objection to the that the volume of water which the Mississippi
fresh-water theory. River empties into the Gulf of Mexico is not equal
to the three thousandth part of that which escapes from it through
the Gulf Stream. Moreover, the water of the Gulf Stream is salt
-that of the Mississippi, fresh; and the advocates of this freshwater theory (~ 74) forgot that just as much salt as escapes from
the Gulf of Mexico through this stream, must enter the Gulf
through some other channel from the main ocean; for, if it did
not, the Gulf of Mexico, in process of time, unless it had a salt bed
at the bottom, or was fed with salt springs from below-neither
of which is probable-would become a fresh-water basin.
76. The above quoted argument of CaptainLivingston, however,
Livingston'shypoth- was held to be conclusive; and upon the remains
csis.       of the hypothesis which he had so completely overturned, he set up another, which, in turn, has also been upset. In
it he ascribed the velocity of the Gulf Stream as depending "on
the motion of the sun in the ecliptic, and the influence he has on
the waters of the Atlantic."
77. But the opinion that came to be most generally received
F:ranklin's theory. and deep-rooted in the mind of seafaring people was
the one repeated by Dr. Franklin, and which held that the Gulf
Stream is the escaping of the waters that have been forced into the
Caribbean Sea by the trade-winds, and that it is the pressure of
those winds upon the water which drives up into that sea a head,
as it were, for this stream.
78. We know of instances in which waters have been accuObjections to it. mulated on one side of a lake, or in one end of a
canal, at the expense of the other. The pressure of the tradewinds may assist to give the Gulf Stream its initial velocity, but
are they of themselves adequate to such an effect?  Examination shows that they are not. With the view of ascertaining the
average number of days during the year that the N.E. tradewinds of the Atlantic operate upon the currents between 25~ N.
and the equator, log-books containing no less than 380,284* observations on the force and direction of the wind in that ocean
were examined. The data thus afforded were carefully compared
and discussed. The results show that within those latitudes, and
* Nautical Monographs, Washington Observatory, No. 1.




22         THE PHYSICAL GEOGRAPHY OF THE SEA.
on the average, the wind from the N.E. quadrant is in excess of
the winds from the S.W. only 111 days out of the 365.  During
the rest of the year the S.W. counteract the effect of the N.E.
winds upon the currents.  Now can the N.E. trades, by blowing
for less than one third of the time, cause the Gulf Stream to run
all the time, and without varying its velocity either to their force
or their prevalence?
79. Sir John Herschel maintains* that they can; that the tradeHerschel's explana- winds are the sole causet of the Gulf Stream; not,
tion.         indeed, by causing " a head of water" in the West
Indian seas, but by rolling particles of water before them somewhat as billiard balls are rolled over the table.  He denies to
evaporation, temperature, salts, and sea-shells, any effective influence whatever upon the circulation of the waters in the ocean.
According to him, the winds are the supreme current-producing
power in the sea.4
80. This theory would require all the currents of the sea to set
Objections to it. with the winds, or, when deflected, to be deflected
from the shore, as billiard balls are from the cushions of the table,
making the littoral angles of incidence and reflection equal. Now,
so far from this being the case, not ONE of the constant currents of
the sea either makes such a rebound or sets with the winds. The
Gulf Stream sets, as it comes out of the Gulf of Mexico, and for
hundreds of miles after it enters the Atlantic, against the tradewinds; for a part of the way it runs right in the "wind's eye."
The Japan current, "s the Gulf Stream of the Pacific," does the
same.  The Mozambique current runs to the south, against the
S.E. trade-winds, and it changes not with the monsoons.  The
ice-bearing currents of the north oppose the winds in their course.
Humboldt's current has its genesis in the ex-tropical regions of the
south, where the "brave west winds" blow  with almost if not
with quite the regularity of the trades, but with double their
force.  And this current, instead of setting to the S.E. before
these winds, flows north in spite of them.  These are the main
* Article "Physical Geography," 8th edition Encyclopsedia Britannica.' " The dynamics of the Gulf Stream have of late, in the work of Lieut. Maury,
already mentioned, been made the subject of much (we can not but think misplaced)
wonder, as if there could be any possible ground for doubting that it owes its origin
entirely to the trade-winds. "-Art. 57, Phys. Geography, 8th edition Encyc. Brit.: Art. 65, Phys. Geography, Encyc. Brit.




~ 81, 82.              THE GULF STREAM.                          23
and constant currents of the sea-the great arteries and jugulars
through which its circulation is conducted. In every instance,
and regardless of winds, those currents that are warm flow toward
the poles, those that are cold set toward the equator.  And this
they do, not by the force of the winds, but in spite of them, and
by the force of those very agencies that make the winds to blow.
They flow thus by virtue of those efforts which the sea is continually making to restore that equilibrium to its waters which heat
and cold, the forces of evaporation, and the secretion of its inhabitants are everlastingly destroying.
81. If the winds make the upper, what makes the under and
The supremacy of counter currents? This question is of itself enough
the winds disputed. to impeach that supremacy of the winds upon the
currents, which the renowned philosopher, with whom  I am  so
unfortunate as to differ, traveled so far out of his way to vindicate.*
82. That the winds do make currents in the sea no one will
The Bonifaccio cur- have the hardihood to deny; but currents that are
rent.         born of the winds are as unstable as the winds; uncertain as to time, place, and direction, they are sporadic and
ephemeral; they are not the constant currents such as have been
already enumerated. Admiral Smyth, in his valuable memoir on
the Mediterranean (p. 162), m.entions that a continuance in the Sea
of Tuscany of "gusty gales" from the southwest has been known
to raise its surface no less than twelve feet above its ordinary
level.  This, he says, occasions a strong surface drift through the
Strait of Bonifaccio.  But in this we have nothing like the Gulf
Stream; no deep and narrow channel-way to conduct these waters
off like a miniature river even in that sea, but a mere surface
flow, such as usually follows the piling up of water in any pond
or gulf above the ordinary level. The Bonifaccio current does
not flow like a "river in the sea" across the Mediterranean, but it
spreads itself out as soon as it passes the Straits, and, like a circle
* "We have, perhaps, been more diffuse on the subject of oceanic currents than the
nature of this article may seem to justify; but some such detail seemed necessary to
vindicate to the winds their supremacy in the production of currents, without calling
in the feeble and ineffective aid of heated water, or the still more insignificant influence of insect secretion, which has been pressed into the service as a cause of buoyancy in the regions occupied by coral formations."-Art. 65, Phys. Geography,
Encyc. Brit.




24         THE PHYSICAL GEOGRAPHY OF THE SEA.
On the water, loses itself by broad spreading as soon as it finds
sea room. As soon as the force that begets it expends itself, the
current is done.
83. Supposing, with Franklin, and those of his school, that the
The bed of the Gulf pressure of the waters that are forced into the CarStream an ascending plane.   ibbean Sea by the trade-winds is the sole cause of
the Gulf Stream, that sea and the Mexican Gulf should have a
much higher level than the Atlantic. Accordingly, the advocates of this theory require for its support " a great degree of elevation."  Major Rennell likens the stream to " an immense river
descending from  a higher level into a plain."  Now we know
very nearly the average breadth and velocity of the Gulf Stream
in the Florida Pass.  We also know, with a like degree of approximation, the velocity and breadth of the same waters off Cape
Hatteras.  Their breadth here is about seventy-five miles against
thirty-two in the " Narrows" of the Straits, and their mean velocity is three knots off Hatteras against four in the "Narrows."
This being the case, it is easy to show that the depth of the Gulf
Stream off Hatteras is not so great as it is in the "Narrows" of
Bemini by nearly 50 per cent., and that, consequently, instead of
descending, its bed represents the surface of an inclined planeinclined from  the north toward the south-up which plane the
lower depths of the stream must ascend. If we assume its depth
off Bemini* to be two hundred fathoms, which are thought to be
within limits, the above rates of breadth and velocity will give
one hundred and fourteen fathoms for its depth off Hatteras.
The waters, therefore, which in the Straits are below the level of
the Hatteras depth, so far from descending, are actually forced up
an inclined plane, whose submarine ascent is not less than ten
inches to the mile.
84. The Niagara is an "immense river descending into a plain."
The Niagara.  But instead of preserving its character in Lake Ontario as a distinct and well-defined stream  for several hundred
miles, it spreads itself out, and its waters are immediately lost in
those of the lake.  Why should not the Gulf Stream  do the
same?  It gradually enlarges itself, it is true; but, instead of
* The superintendent reports that the officers of the Coast Survey have sounded
with the deep-sea lead, and ascertained its depth here to be 370 fathoms (Januaryv,
1856).




~ 85-87.            THE GULF STREAM.                     25
mingling with the ocean by broad spreading, as the "immense
rivers" descending into the northern lakes do, its waters, like a
stream of oil in the ocean, preserve a distinctive character for
more than three thousand miles.
85. Moreover, while the Gulf Stream is running to the north
A current counterto from its supposed elevated level at the south, there
the Gulf Stream. is a cold current coming down from the north;
meeting the warm waters of the Gulf midway the ocean, it divides
itself, and runs by the side of them right back into those very reservoirs at the south,'to which theory gives an elevation sufficient
to send out entirely across the Atlantic a jet of warm water said
to be more than three thousand times greater in volume than the
Mississippi River. This current from Baffin's Bay has not only
no trade-winds to give it a head, but the prevailing winds are unfavorable to it, and for a great part of the way it is below the surface, and far beyond the propelling reach of any wind. And
there is every reason to believe that this, with other polar currents, is quite equal in volume to the Gulf Stream. Are they not
the effects of like causes? If so, what have the trade-winds to do
with the one more than the other?
86. It is a custom often practiced by sea-faring people to throw
Bottle chart. a bottle overboard, with a paper, stating the time
and place at which it is done. In the absence of other information as to currents, that afforded by these mute little navigators is
of great value. They leave no tracks behind them, it is true, and
their routes can not be ascertained. But knowing where they
were cast, and seeing where they are found, some idea may be
formed as to their course. Straight lines may at least be drawn,
showing the shortest distance from the beginning to the end of
their voyage, with the time elapsed. Captain Becher, R. N., has
prepared a chart representing in this way the tracks of more than
one hundred bottles. From it it appears that the waters from
every quarter of the Atlantic tend toward the Gulf of Mexico and
its stream. Bottles cast into the sea midway between the Old
and the New Worlds, near the coasts of Europe, Africa, and America, at the extreme north or farthest south, have been found either
in the West Indies, on the British Isles, or within the well-known
range of Gulf Stream waters.
87. Of two cast out together in south latitude on the coast of




26        1THE PHYSICAL GEOGRAPHY OF THE SEA.
Their drift.  Africa, one was found on the island of Trinidad;
the other on Guernsey, in the English Channel. In the absence
of positive information on the subject, the circumstantial evidence
that the latter performed the tour of the Gulf is all but conclusive.
And there is reason to suppose that some of the bottles of the, gallant captain's chart have also performed the tour of the Gulf
Stream; then, without being cast ashore, have returned with the
drift along the coast of Africa into the intertropical region;
thence through the Caribbean Sea, and so on with the Gulf Stream
again. (Plate VI.) Another bottle, said to be thrown over off
Cape Horn by an American ship-master in 1837, was afterward
picked up on the coast of Ireland. An inspection of the chart,
and of the drift of the other bottles, seems toforce the conclusion
that this bottle too went even from that remote region to the socalled higher level of the Gulf Stream reservoir.
88. Midway the Atlantic, in the triangular space between the
The Sargasso Sea. Azores, Canaries, and the Cape de Verd Islands, is the
great Sargasso Sea. (Plate VI.) Covering an area equal in extent
to the Mississippi Valley, it is so thickly matted over with Gulf
weeds (fucus nactns) that the speed of vessels passing through it
is often much retarded. When the companions of Columbus saw
it, they thought it marked the limits of navigation, and became
alarmed. To the eye, at a little distance, it seems substantial
enough to walk upon. Patches of the weed are always to be seen
floating along the outer edge of the Gulf Stream. Now, if bits of
cork or chaff, or any floating substance, be put into a basin, and a
circular motion be given to the water, all the light substances will
be found crowding together near the centre of the pool, where
there is the least motion. Just such a basin is the Atlantic Ocean
to the Gulf Stream, and the Sargasso Sea is the centre of the
whirl.  Columbus first found this weedy sea in his voyage of discovery; there it has remained to this day, moving up and down,
and changing its position, like the calms of Cancer, according to
the seasons, the storms, and the winds. Exact observations as to
its limits and their range, extending back for fifty years, assure
us that its mean position has not been altered since that time.
This indication of a circular motion by the Gulf Stream is corroborated by the bottle chart, by Plate VI., and other sources of information. If, therefore, this be so, why give the endless current
a higher level in one part of its course than another?




~ 89-91.              THE GULF STREAM.                        27
89. Nay, more; at the very season of the year when the Gulf
A bifurcation. Stream is rushing in greatest volume through the
Straits of Florida, and hastening to the north with the greatest rapidity, there is a cold stream from Baffin's Bay, Labrador, and the
coasts of the north, running to the south with equal velocity.
Where is the trade-wind that gives the higher level to Baffin's
Bay, or that even presses upon, or assists to put this current in
motion? The agency of winds in producing currents in the deep
sea must be very partial. These two currents meet off the Grand
Banks, where the latter is divided.  One part of it underruns the
Gulf Stream, as is shown by the icebergs which are carried in a
direction tending across its course. The probability is, that this
"fork" flows on toward the south, and runs into the Caribbean
Sea, for the temperature of the water at a little depth there has
been found far below the mean temperature of the earth's crust,
and quite as cold as at a corresponding depth off the Arctic
shores of Spitzbergen.
90. More water call not run from the equator or the pole than
Winds exercise but to it.  If we make the trade-winds to cause the
little influence upon
constant currents.  Gulf Stream, we ought to have some other wind to
produce the Polar flow; but these currents, for the most part,
and for great distances, are submarine, and therefore beyond the
influence of winds. Hence it should appear that winds have little
to do with the general system of aqueous circulation in the ocean.
The other "fork" runs between our shores and the Gulf Stream
to the south, as already described.  As far as it has been traced,
it warrants the belief that it, too, runs up to seek the so-called
higher level of the Mexican Gulf.
91. The power necessary to overcome the resistance opposed
Effects of diurnal to such a body of water as that of the Gulf Stream,
rotation upon the
Gulf Stream.  running several thousand miles without any renewal of impulse from the forces of gravitation or any other known
cause, is truly surprising. It so happens that we have an argument for determining, with considerable accuracy, the resistance
which the waters of this stream meet with in their motion toward
the east. Owing to the diurnal rotation, they are carried around
with the earth on its axis toward the east with an hourly velocity
of one hundred and fifty-seven* miles greater when they enter
* In this calculation the earth is treated as a perfect sphere, with a diameter of
7925.56 miles.




28         THE PHYSICAL GEOGRAPHY OF THE SEA.
the Atlantic than when they arrive off the Banks of Newfoundland; for in consequence of the difference of latitude between the
parallels of these two places, their rate of motion around the axis
of the earth is reduced from  nine hundred and fifteen* to seven
hundred and fifty-eight miles the hour. Hence this immense volume of water would, if we suppose it to pass from the Bahamas
to the Grand Banks in an hour, meet with an opposing force in
the shape of resistance sufficient, in the aggregate, to retard it two
miles and a half the minute in its eastwardly rate.  If the actual
resistance be calculated according to received laws, it will be
found equal to several atmospheres. And by analogy, how inadequate must the pressure of the gentle trade-winds be to such resistance, and to the effect assigned them!
92. If, therefore, in the proposed inquiry, we search for a proThe Gulf Stream can pelling power nowhere but in the higher level of the
not be accounted for
by a higher level.  Gulf, or in the "billiard- ball" rebound from its
shores, we must admit, in the head of water there, the existence
of a force capable of putting in motion, and of driving over a
plain at the rate of four miles the hour, all the waters, as fast as
they can be brought down by three thousand (~ 75) such streams
as the Mississippi River-a power, at least, sufficient to overcome
the resistance required to reduce from two miles and a half to a
few feet per minute the velocity of a stream that keeps in perpetual motion one fourth of all the waters in the Atlantic Ocean.
93. The advocates of the trade-wind theory, whether, with
Nor by the trade- Franklin (~ 77), they make the propelling power to
wind theory.  be derived from a " head of water" in the Gulf, or,
with Herschel (~ 79), from the rebound, d la billiard-balls, against
its shores, require that the impulse then and there communicated
to the waters of the Gulf Stream should be sufficient to send them
entirely across the Ocean; for in neither case does their theory
provide for any renewal of the propelling power by the wayside.
Can this be? Can water flow on any more than cannon balls can
continue their flight after the propelling force has been expended?
94. When we inject water into a pool, be the force never so
Illustration.  great, the jet is soon overcome, broken up, and
* Or, 915.26 to 758.60. On the latter parallel the current has an east set of about
one and a half miles the hour, making the true velocity to the east, and on the axis
of the earth, about seven hundred and sixty miles an hour at the Grand Banks.




~ 95, 96.             THE GULF STREAM.                        29
made to disappear.  In this illustration the Gulf Stream may be
likened to the jet, and the Atlantic to the pool.  WVe remember to have observed as children how soon the mill-tail loses its
current in the pool below; or we may now see at any time, and
on a larger scale, how soon the Niagara, current and all, is swallowed up in the lake.
95. Nothing but a continually-acting power can keep currents
Gulf Stream the ef- in the sea, any more than cannon balls in the air or
fett of ompeat c- rivers on the land, in motion.  But for the forces
power.        of gravitation the waters of the Mississippi would
remain at its fountain, and but for difference of specific gravity the
waters of the Gulf Stream would remain in the caldron, as the
intertropical parts of the Atlantic Ocean may be called.
96. For the sake of further illustration, let us suppose a globe
The production of of the earth's size, and with a solid nucleus to be
currents  without
wind.        covered all over with water two hundred fathoms
deep, and that every source of heat and cause of radiation be removed, so that its fluid temperature becomes constant and uniform throughout.  On such a globe, the equilibrium  remaining
undisturbed, there would be neither wind nor current.  Let us
now suppose that all the water within the tropics, to the depth
of one hundred fathoms, suddenly becomes oil.  The aqueous
equilibrium of the planet would thereby be disturbed, and a general system of currents and counter currents would be immediately commenced-the oil, in an unbroken sheet on the surface,
running toward the poles, and the water, in an under current, toward the equator. The oil is supposed, as it reaches the polar
basin, to be reconverted into water, and the water to become oil
as it crosses Cancer and Capricorn, rising to the surface in the intertropical regions and returning as before.  Thus, without wind,
we should have a perpetual and uniform system  of tropical and
polar currents, though without wind, Sir John Herschel maintains,* we should have no currents whatever in the sea.  In consequence of the diurnal rotation of the planet on its axis, each particle
of oil, were resistance small, would approach the poles on a spiral
turning to the east with a relative velocity greater and greater,
* "If there were no atmosphere, there would be no Gulf Stream or any other
considerable oceanic current (as distinguished from a mere surface drift) whatever."
-Art. 37, Pkysical Geography, 8th ed. Encyclop. ]Brit.




30         THE PHYSICAL GEOGRAPHY OF THE SEA.
until, finally, it would reach the pole, and whirl about it at the
rate of nearly a thousand miles the hour. Becoming water and
losing its velocity, it would approach the tropics by a similar, but
reversed spiral, turning toward the west. Owing to the principle here alluded to, all currents from the equator to the poles
should have an eastward tendency, and all from the poles toward
the equator a westward. Let us now suppose the solid nucleus
of this hypothetical globe to assume the exact form and shape of
the bottom of our seas, and in all respects, as to figure and size,
to represent the shoals and islands of the sea, as well as the coast
lines and continents of the earth.  The uniform system of currents just described would now be interrupted by obstructions
and local causes of various kinds, such as unequal depth of water,
contour of shore lines, &c.; and we should have at certain places
currents greater in volume and velocity than at others. But still
there would be a system of currents and counter currents to and
from either pole and the equator. Now, do not the cold waters
of the north, and the warm waters of the Gulf, made specifically
lighter by tropical heat, and which we see aqtually preserving
such a system of counter currents, hold, at least in some degree,
the relation of the supposed water and oil?
97. In obedience to the laws here hinted at, there is a constant
Warm currentsflow tendency (Plate IX.) of polar waters toward the
toward the poIe cold
toward the equator. tropics and of tropical waters toward the poles.
Captain Wilkes, of the United States Exploring Expedition,
crossed one of these hyperborean under currents two hundred
miles in breadth at the equator.
98. No feature of the Gulf Stream excites remark among
Edges of the Gulf seamen more frequently than the sharpness of its
Stream a striking
feature.     edges, particularly along its inner borders.  There,
it is a streak on the water.' As high up as the Carolinas this
streak may be seen, like a greenish edging to a blue border-the
bright indigo of the tropical contrasting finely (~ 70) with the dirty
green of the littoral waters. It is this apparent reluctance of
the warm waters of the stream to mix with the cool of the ocean
that excites wonder and calls forth remark. But have we not, so
to speak, a similar reluctance manifested by all fluids, only upon
a smaller scale, or under circumstances less calculated to attract
attention or excite remark?




~ 99-102.            THE GULF STREAM.                       31
99. The water, hot and cold, as it is let into the tub for a warm
Illustrations. bath, generally arranges itself in layers or sections,
according to temperature; it requires violent stirring to break
them up, mix, and bring the whole to an even temperature.  The
jet of air from the blow-pipe, or of gas from the burner, presents the phenomenon still more familiarly; here we have, as
with the Gulf Stream, the dividing line between fluids in motion
and fluids at rest finely presented.  There is a like reluctance for
mixing between streams of clear and muddy water.  This is very
marked between the red waters of the Missouri and the inky
waters of the upper Mississippi; here the waters of each may be
distinguished for the distance of several miles after these two
rivers come together. It requires force to inject, as it were, the
particles of one of these waters among those of the other, for
mere vis inertia tends to maintain in their statu quo fluids that
have already arranged themselves in layers, streaks, or aggregations.
100. In the ocean we have the continual heaving of the sea and
Ilow the water of agitation of the waves to overcome this vis inertia,
the Gulf,Steam dif- and the marvel is, that they in their violence do,,aters.     not, by mingling the Gulf and littoral waters together (~ 70), sooner break up and obliterate all marks of a division between them. But the waters of the Gulf Stream differ
from the in-shore waters not only in color, transparency, and temperature, but in specific gravity, in saltness (~ 102), and in other
properties, I conjecture, also. Therefore they may have a peculiar
viscosity, or molecular arrangement of their own, which further
tends to prevent mixture, and so preserve their line of demarkation.
101. Observations made for the purpose in the navy show that
Actionon copper. ships cruising in the West Indies suffer in their
copper sheathing more than they do in any other seas. This
would indicate that the waters of the Caribbean Sea and Gulf
of Mexico, from which the Gulf Stream is fed, have some peculiar
property or other which makes them so destructive upon the copper of cruisers.
102. The story told by the copper and the blue color (~ 71) indiSaltness of the Gulf cates a higher point of saturation with salts than sea
Stream.      water generally has; and the salometer confirms it.




32         THE PHYSICAL GEOGRAPHY OF THE SEA.
Dr. Thomassy, a French savant, who has been extensively engaged
in the manufacture of salt by solar evaporation, informs me that on
his passage to the United States he tried the saltness of the water
with a most delicate instrument: he found it in the Bay of Biscay
to contain 31 per cent. of salt; in the trade-wind region, 4 4 per
cent.; and in the Gulf Stream, off Charleston, 4 per cent., notwithstanding the Amazon and the Mississippi, with all the intermediate rivers, and the clouds of the West Indies, had lent their
fresh water to dilute the saltness of this basin.
103. Now the question may be asked, What should make the
Agents concerned. waters of the Mexican Gulf and Caribbean Sea salter than the waters in those parts of the ocean through which the
Gulf Stream flows?  There are physical agents that are known
to be at work in different parts of the ocean, the tendency of
which is to make the waters in one part of the ocean salter and
heavier, and, in another part lighter and less salt than the average of sea water. These agents are those employed by sea-shells
in secreting solid matter for their structures; they are also heat*
and radiation, evaporation and precipitation. In the trade-wind
regions at sea (Plate VIII.), evaporation is generally in excess of
precipitation, while in the extra-tropical regions the reverse is
the case; that is, the clouds let down more water there than the
winds take up again; and these are the regions in which the Gulf
Stream enters the Atlantic. Along the shores of India, where
observations have been carefully made, the evaporation from the
sea is said to amount to three fourths of an inch daily. Suppose it in the trade-wind region of the Atlantic to amount to only
half an inch, that would give an annual evaporation of fifteen feet.
In the process of evaporation from the sea, fresh water only is
taken up; the salts are left behind. Now a layer of sea water
fifteen feet deep, and as broad as the trade-wind belts of the Atlantic, and reaching across the ocean, contains an immense amount
of salts.  The great equatorial current (Plate VI.) which often
sweeps from the shores of Africa across the Atlantic into the Caribbean Sea is a surface current; and may it not bear into that sea
a large portion of those waters that have satisfied the thirsty tradewinds with saltless vapor?  If so-and it probably does-have
* According to Dr. Marcet, sea water contracts down to 28~; my own to about
25.6.




~ 104, 105.           THE GULF STREAAM.                     33
we not detected here the foot-prints of an agent that does tend to
make the waters of the Caribbean Sea salter, and therefore heavier, than the average of sea water at a given temperature?
104. It is immaterial, so far as the correctness of the principle
Evaporationandpre- upon which this reasoning depends'is concerned,
cipitation.  whether the annual evaporation from  the tradewind regions of the Atlantic be fifteen, ten, or five feet. The
layer of water, whatever be its thickness, that is evaporated from
this part of the ocean, is not all poured back by the clouds upon
the same spot whence it came. But they take it and pour it down
in showers upon the extra-tropical regions of the earth-on the
land as well as in the sea-and on the land more water is let down
than is taken up into the clouds again.  The rest sinks down
through the soil to feed the springs, and return through the rivers to the sea. Suppose the. excess of precipitation in these extra-tropical regions of the sea to amount to but twelve inches, or
even to but two-it is twelve inches or two inches, as the case
may be, of fresh water added to the sea in those parts, and which
therefore tends to lessen the specific gravity of sea water there to
that extent, and to produce a double dynamical effect, for the
simple reason that what is taken from one scale, by being put into
the other, doubles the difference.
105. Now that we may form some idea as to the influence which
CufrtentintotheCar- the salts left by the vapor that the trade-winds,
ibbean Sea.  northeast and southeast, take up from sea water, is
calculated to exert in creating currents, let us make a partial calculation to show how much salt this vapor held in solution before
it was taken up, and, of course, while it was yet in the state of
sea water. The northeast trade-wind regions of the Atlantic embrace an area of at least three million square miles, and the yearly
evaporation from it is (~ 103), we will suppose, fifteen feet. The
salt that is contained in a mass of sea water covering to the depth
of fifteen feet an area of three million square miles in superficial
extent, would be sufficient to cover the British islands to the depth
of fourteen feet. As this water supplies the trade-winds with vapor, it therefore becomes salter, and as it becomes salter, the forces
of aggregation among its particles are increased, as we may infer
from the fact (~ 98) that the waters of the Gulf Stream are reluctant to mix with those of the ocean.
C




34         THE PHYSICAL GEOGRAPHY OF THE SEA.
106. Whatever be the cause that enables these trade-wind waAmount of salt left ters to remain on the surface, whether it be from the
by evaporation.   fact just stated, and in consequence of which the
waters of the Gulf Stream are held together in their channel; or
whether it be from the fact that the expansion from the heat of
the torrid zone is sufficient to compensate for this increased saltness; or whether it be from the low temperature and high saturation of the submarine waters of the intertropical ocean; or whether it be owing to all of these influences together that these waters
are kept on the surface, suffice it to say, we do know that they go
into the Caribbean Sea (~ 103) as a surface current. On their
passage to and through it, they intermingle with the fresh waters
that are emptied into the sea from the Amazon, the Orinoco, andt
the Mississippi, and from the clouds, and the rivers of the coasts
round about. An immense volume of fresh water is supplied
from these sources. It tends to make the sea water, that the
trade-winds have been playing upon and driving along, less briny,
warmer, and lighter; for the waters of these large intertropical
streams are warmer than sea water. This admixture of fresh water still leaves the Gulf Stream a brine stronger than that of the
extra-tropical sea generally, but not quite so strong (~ 102) as that
of the trade-wind regions.
107. The dynamics of the sea confess the power of the winds in
Currents created by those tremendous currents which storms are somestorms.     times known to create; and that even the gentle
trade-winds may have influence and effect upon the currents of the
sea has not been denied (~ 82). But the effect of moderate winds,
as the trades are, is to cause what may be called the drift of the
sea rather than a current.  Drift is confined to surface waters, and
the trade-winds of the Atlantic may assist in creating the Gulf
Stream by drifting the waters which have supplied them with vapor toward the Caribbean Sea. But admit never so much of the
water which the trade-winds have played upon to be drifted into
the Caribbean Sea, what should make it flow thence with the
Gulf Stream to the shores of Europe?  It is because of the difference in the specific gravity of sea water in an intertropical sea on
one side, as compared with the specific gravity of water in northern seas and frozen oceans on the other, that they so flow.
108. The dynamical forces which are expressed by the- Gulf




~ 109.                  THE GULF STREAM.                          35
Thedynamicalforce Stream may with as much propriety be said to rethatlf cll forth the side in those northern waters as in the West Infonced in thesp de  dia seas; for on one side we have the Caribbean
gravlity of int'rop-  Sea and Gulf of Mexico, with their waters of brine;
ters.          on the other, the great Polar basin, the Baltic, and
the North Sea, the two latter with waters that are but little more
than brackish.v In one set of these sea-basins the water is heavy;
in the other it is light.  Between them the ocean intervenes; but
water is bound to seek and to maintain its level; and here, therefore, we unmask one of the agents concerned in causing the Gulf
Stream. What is the power of this agent-is it greater than that of
other agents, and how much?  We can not say; we only know it
is one of the chief agents concerned.  Moreover, speculate as we
may as to all the agencies concerned in collecting these waters,
that have supplied the trade-winds with vapor, into the Caribbean
Sea, and then in driving them across the Atlantic —we are forced
to conclude that the salt which the trade-wind vapor leaves behind in the tropics has to be conveyed away from the trade-wind
region, to be mixed up again in due proportion with the other
water of the sea-the Baltic Sea and the Arctic Ocean includedand that these are some of the waters, at least, which we see running off through the Gulf Stream. To convey them away is
doubtless one of the offices which, in the economy of the ocean,
has been assigned to it.  But as for the seat of the forces which
put and keep the Gulf Stream in motion, theorists may place them
exclusive/y on one side of the ocean with as much philosophical
propriety as on the other. Its waters find their way into the
North Sea and the Arctic Ocean by virtue of their specific gravity, while water thence, to take their place, is, by virtue of its specific gravity and by counter currents, carried back into the Gulf.
The dynamical force which causes the Gulf Stream may therefore
be said to reside both in the polar and in the intertropical waters
of the Atlantic.
109. As to the temperature of the Gulf Stream, there is, in a
* The Polar basin has a known water area of 3,000,000 square miles, and an unexplored area, including land and water, of 1,500,000 square miles. Whether the
water in this basin be more or less salt than that of the intertropical seas, we know
it is quite different in temperature, and difference of temperature will beget currents
quite as readily as difference in saltness, for change in specific gravity follows either.




36       rTHE PHYSICAL GEOGRAPHY OF THE SEA.
WVinter temperature winter's day, off Hatteras, and even as high up as
of the Gulf Stream. the Grand Banks of Newfoundland in mid-ocean, a
difference between its waters and those of the ocean near by of 20~,
and even 30~. Water, we know, expands by heat, and here the
difference of temperature may more than compensate for the difference in saltness, and leave, therefore, the waters of the Gulf
Stream, though salter, yet lighter by reason of their warmth.
110. If they be lighter, they should therefore occupy a higher
Top of Gulf Stream level than those through which they flow. Assumroof-shaped.    ing the depth off Hatteras to be one hundred and
fourteen fathoms, and allowing the usual rates of expansion for
sea water, figures show that the middle or axis of the Gulf Stream
there should be nearly two feet higher than the contiguous waters
of the Atlantic. Hence the surface of the stream should present
a double inclined plane, from which the water would be running
down on either side as from the roof of a house. As this runs
off at the top, the same weight of colder water runs in at the bottomn, and so raises up the cold-water bed of the Gulf Stream, and
causes it to become shallower and shallower as it goes north. That
the Gulf Stream. is therefore roof-shaped, causing the waters on its
surface to flow off to either side from the middle, we have not
only circumstantial evidence to show, but observations to prove.
Navigators, while drifting along with the Gulf Stream, have lowered a boat to try the surface current. In such cases, the boat
would drift either to the east or to the west, as it happened to be
on one side or the other of the axis of the stream, while the vessel herself would drift along with the stream in the direction of
its course; thus showing the existence of a shallow roof-current
from the middle toward either edge, which would carry the boat
along, but which, being superficial, does not extend deep enough
to affect the drift of the vessel.
111. That such is the case (~ 110) is also indicated by the
Drift matter sIough- circumstance that the sea-weed and drift - wood
ed off to the right. which are found in such large quantities along the
outer edge of the Gulf Stream, are rarely, even with the prevalence of easterly winds, found along its inner edge-and for the
simple reason that to cross the Gulf Stream, and to pass over from
that side to this, they would have to drift up an inclined plane, as
it were; that is, they would have to stem this roof-current until




~ 112, 113.          THE GULF STREAM.                       37
they reached the middle of the stream. We rarely hear of planks,
or wrecks, or of any floating substance which is cast into the sea
on the other side of the Gulf Stream being found along the coast
of the United States. Drift-wood, trees, and seeds from the WVest
India islands, are often cast up on the shores of Europe, but rarely on the Atlantic shores of this country.
112. We are treating now of the effects of physical causes. The
Whysosloughedoff. question to which I ask attention is, Why does the
Gulf Stream. slough off and cast upon its outer edge, sea-weed,
drift-wood, and all other solid bodies that are found floating upon
it? One cause has been shown to be in its roof-shaped current;
but there is another which tends to produce the same effect; and
because it is a physical agent, it should not, in a treatise of this
kind, be overlooked, be its action never so slight. I allude now
to the effects produced upon the drift matter of the stream by the
diurnal rotation of the earth.
113. Take, for illustration, a railroad that lies north and south
Illusttion.  in our hemisphere. It is well known to engineers
that when the cars are going north on such a road, their tendency
is to run off olX the east side; but when the train is going south,
their tendency is to run off on the west side of the track —i. e.,
always on the right-hand side. Whether the road be one mile or
one hundred miles in length, the effect of diurnal rotation is the
same; and, whether the road be long or short, the tendency to
run off; as you cross a given parallel at a stated rate of speed, is
the same; for the tendency to fly off the track is in proportion to
the speed of the train, and not at all in proportion to the length
of the road. Now, vis inertice and velocity being taken into the
account, the tendency to obey the force of this diurnul rotation, and
to trend to the right, is proportionably as great in the case of a
patch of sea-weed as it drifts along the Gulf Stream, as it is in the
case of the train of cars as they speed to the north along the iron
track of the Hudson River railway, or any other railway that lies
north and south. The rails restrain the cars and prevent them
from flying off; but there are no rails to restrain the sea-weed,
and nothing to prevent the drift-matter of the Gulf Stream from
going off in obedience to this force. The slightest impulse tending to turn aside bodies moving freely in water is immediately
felt and implicitly obeyed.




38         THE PHYSICAL GEOGRAPHY OF THE SEA.
114. It is in consequence of this diurnal rotation that driftDrift-wood on the wood coming down the Mississippi is so very apt
Mississippi.  to be cast upon the west or right bank. This is the
reverse of what obtains upon the Gulf Stream, for it flows to the
north; it therefore sloughs off (~ 111) to the east.
115. The effect of diurnal rotation upon the winds and upon
Effect of diurnal ro- the currents of the sea is admitted by all-the tradetation upon.  winds derive their eastinyg from it-it must, therefore, extend to all the matter which these currents bear with them,
to the largest iceberg as well as to the smallest spire of grass that
floats upon the waters, or the minutest organism that the most
powerful microscope can detect among the impalpable particles
of sea-dust. This effect of diurnal rotation upon drift will be frequently alluded to in the pages of this work.
116. In its course to the north, the Gulf Stream gradually trends
Formation of the more and more to the eastward, until it arrives off
Grand Banks.    the Banks of Newfoundland, where its course becomes nearly due east. These banks, it has been thought, deflect
it from its proper course, and cause it to take this turn. Examination will prove, I think, that they are an effect, certainly not
the cause. It is here that the frigid current already spoken of
(~ 85), and its icebergs from the north, are met and melted by the
warm waters of the Gulf. Of course the loads of earth, stones,
and gravel brought down upon these bergs are here deposited.
Captain Scoresby, far away in the north, counted at one time five
hundred icebergs setting out from the same vicinity upon this
cold current for the south.  Many of them, loaded with earth,
have been seen aground on the Banks. This process of transferring deposits from the north for these shoals, and of snowing
down upon them the infusoria and the corpses of "living creatures" that are brought forth so abundantly in the warm waters of
the Gulf Stream, and delivered in myriads for burial where the
conflict between it and the great Polar current (~ 89) takes place,
is everlastingly going on. These agencies, with time, seem altogether adequate to the formation of extensive bars or banks.
117. The deep-sea soundings that have been made by vessels of
Deep water near. the navy (Plate XI.) tend to confirm this view as to
the formation of these Banks.  The greatest contrast in the bottom of the Atlantic is just to the south of these Banks. Nowhere




~ 118-120.            THE GULF STREAM.                       39
in the open sea has the water been found to deepen so suddenly
as here. Coming from the north, the bottom of the sea is shelving; but suddenly, after passing these Banks, it dips down by a
precipitous descent to unknown depths-thus indicating that the
debris which forms the Grand Banks comes from the north.
118. From the Straits of Bemini the course of the Gulf Stream
The Gulf Stream de- (Plate VI.) describes (as far as it can be traced over
ecribes in its course toward the British Islands which are in the midst
the path of a trajectory.          of its waters) the arc of a great circle nearly.  Such
a course as the Gulf Stream takes is very nearly the course that
a cannon ball, could it be shot from these straits to those islands,
would follow.
119. If it were possible to see Ireland from Bemini, and to get
Its path from Bemi a cannon that would reach that far, the person standini to Ireland.    ing on Bemini and taking aim, intending to shoot
at Ireland as a target, would, if the earth were at rest, sight direct, and make no allowance for difference of motion between
marksman and target. Its path would lie in the plane of a great
circle. But there is diurnal rotation; the earth does revolve on
its axis; and since Bemini is nearer to the equator -than Ireland
is, the gun would be moving in diurnal rotation (~ 91) faster than
the target, and therefore the marksman, taking aim point blank
at his target, would miss.  He would find, on examination, that
he had shot south-that is, to the right (~ 103) of his mark.  In
other words, that the path actually described by the ball would
be a resultant arising from this difference in the rate of rotation
and the trajectile force. Like a ray of light from the stars, the
ball would be affected by aberration. The ball so shot presents
the case of the passenger in the railroad car throwing an apple,
as the train sweeps by, to a boy standing by the way-side.  If he
throw straight at the boy, he will miss, for the apple, partaking
of the motion of the cars, will go ahead of the boy, and for the
very reason that the shot will pass in advance of the target, for
both the marksman and the passenger are going faster than the
object at which they aim.
120. Hence we may assume it as a law, that the natural tendTendencyof allcur- ency of all currents in the sea, like the natural
rents both in the sea
and air to move in tendency of all projectiles through the air, is to degreat circles a physical law.    scribe each its curve of flight very nearly in the




40        THE PHYSICAL GEOGRAPHY OF THE SEA.
plane of a great circle. The natural tendency of all matter, when
put in motion, is to go from point to point by the shortest distance, and it requires force to overcome this tendency. Light,
heat, and electricity, the howling wind, running water, and all
substances, whether ponderable or imponderable, seek, when in
motion, to obey this law. Electricity may be turned aside from
its course, and so may the cannon ball or running water; but remove every obstruction, and leave the current or the shot free to
continue on in the direction of the first impulse, or to turn aside
of its own volition, so to speak, and straight it will go, and continue to go-if on a plane, in a straight line; if about a sphere,
in the arc of a great circle-thus showing that it has no volition
except to obey impulse; and that impulse comes from the physical requirements upon it to take the shortest way to its point of
destination.
121. The waters of the Gulf Stream, as they escape from the
This law recognized Gulf, are bound for the British Islands, to the North
by theGulf Stream. Sea, and Frozen Ocean (Plate IX.).  Accordingly,
they take (~ 118), in obedience to this physical law, the most direct course by which nature will permit them to reach their destination. And this course, as already remarked, is nearly that
of the great circle, and of the supposed cannon ball.
122. Many philosophers have expressed the opinion-indeed,
Shoals of Nantucket the belief (~ 116) is common among mariners-that
do not control its
course.     the coasts of the United States and the Shoals of
Nantucket turn the Gulf Stream toward the east; but if the view
I have been endeavoring to make clear be correct, it would appear that the course of the Gulf Stream is fixed and prescribed by
exactly the same laws that require the planets to revolve in orbits,
the planes of which shall pass through the centre of the sun; and
that, were the Nantucket Shoals not in existence, the course of
the Gulf Stream, in the main, would be exactly as it is and where
it is. The Gulf Stream is bound over to the North Sea and Bay
of Biscay partly for the reason, perhaps, that the waters there are
lighter than those of the Mexican Gulf; and if the Shoals of Nantucket were not in existence, it could not pursue a more direct
route. The Grand Banks, however, are encroaching (~ 116), and
cold currents from the north come down upon it: they may, and
probably do, assist now and then to turn it aside.




~ 123-125.           THE GULF STREAM.                      41
123. Now if this explanation as to the course of the Gulf Stream
lIerschel's theory and its eastward tendency hold good, a current setnot consistent with
nown facts.   ting from the north toward the south should (~ 103)
have a westward tendency. It should also move in a circle of
trajection, or such as would be described by a trajectile moving
through the air without resistance and for a great distance. Accordingly, and in obedience to the propelling powers derived
from the rate at which different parallels are whirled around in
diurnal motion (~ 91), we find the current from the north, which
meets the Gulf Stream on the Grand Banks (Plate IX.), taking a
southwestwardly direction, as already described (~ 114). It runs
down to the tropics by the side of the Gulf Stream, and stretches
as far to the west as our own shores will allow. Yet, in the face
of these facts, and in spite of this force, both Major Rennell and
M. Arago would make the coasts of the United States and the
Shoals of Nantucket to turn the Gulf Stream toward the east;
and Sir John Herschel (~ 79) makes the trade-winds, which blow
from the eastward, drive the stream to the eastward!
124. But there are other forces operating upon the Gulf Stream.
The channel of the They are derived from the effect of changes in the
Gulf Stream shifts
with the season.  waters of the whole ocean, as produced by changes
in their temperature from time to time.  As the Gulf Stream
leaves the coasts of the United States, it begins to vary its position according to the seasons; the limit of its northern edge, as it
passes the meridian of Cape Race (Plate VI.), being in winter
about latitude 40-41~, and in September, when the sea is hottest,
about latitude 45-46~. The trough of the Gulf Stream, therefore,
may be supposed to waver about in the ocean not unlike a pennon in the breeze. Its head is confined between the shoals of the
Bahamas and the Carolinas; but that part of it which stretches
over toward the Grand Banks of Newfoundland is, as the temperature of the waters of the ocean changes, first pressed down toward the south, and then again up toward the north, according to
the season of the year.
125. To appreciate the extent of the force by which it is so
The phenomenon pressed, let us imagine the waters of the Gulf
thermal in its character.       Stream to extend all the way to the bottom of the
sea, so as completely to separate, by an impenetrable liquid wall,
if you please, the waters of the ocean on the right from the waters




42        THE PHYSICAL GEOGRAPHY OF THE SEA.
in the ocean on the left of the stream. It is the height of sunmmer: the waters of the sea on either hand are for the most part in
a liquid state, and the Gulf Stream, let it be supposed, has assumed a normal condition between the two divisions, adjusting itself to the pressure on either side so as to balance them exactly
and be in equilibrium.  Now, again, it is the dead of winter, and
the temperature of the waters over an area of millions of square
miles in the North Atlantic has been changed many degrees, and
this change of temperature has been followed likewise by a change
in volume of those waters, amounting, no doubt, in the aggregate,
to many hundred millions of tons, over the whole ocean; for sea
water, unlike fresh (~ 103), contracts to freezing, and below. Now
is it probable that, in passing from their summer to their winter
temperature, the sea waters to the right of the Gulf Stream should
change their specific gravity exactly as much in the aggregate as
do the waters in the whole ocean to the left of it?  If not, the
difference must be compensated by some means. Sparks are not.
more prone to fly upward, nor water to seek its level, than Nature is sure with her efforts to restore equilibrium in both sea and
air whenever, wherever, and by whatever it be disturbed. Theretore, though the waters of the Gulf Stream do not extend to the
bottom, and though they be not impenetrable to the waters on
either hand, yet, seeing that they have a waste of waters on the
right and a waste of waters on the left, to which (~ 70) they offer
a sort of resisting permeability, we are enabled to comprehend
how the waters on either hand, as their specific gravity is increased or diminished, will impart to the trough of this stream a
vibratory motion, pressing it now to the right, now to the left,
according to the seasons and the consequent changes of temperature in the sea.
126. Plate VI. shows the limits of the Gulf Stream for March
Limits of the Gulf and September. The reason for this change of poStream in March
and September.  sition is obvious. The banks of the Gulf Stream
(~ 70) are cold water. In winter the volume of cold water on the
American, or left side of the stream, is greatly increased. It must
have room, and gains it by pressing the warmer waters of the
stream farther to the south, or right. In September, the temperature of these cold waters is modified; there is not such an extent
of them, and then the warmer waters, in turn, press them back,
and so the pendulum-like motion is preserved.




~ 127-129.           THE GULF STREAM.                       43
127. In the offings of the Balize, sometimes as far out as a hundReluctance of layers red miles or more from the land, puddles or patches
orpatches tomingle. of Mississippi water may be observed on the surface of the sea with little or none of its brine mixed with it. This
anti-mixing property in water has already (~ 98) been remarked
upon. It may be observed, from the gutters in the street to the
rivers in the ocean, and every where, wherever two bodies of
water that differ in color are found in juxtaposition. The patches
of white, black, green, yellow, and reddish waters so often met
with at sea are striking and familiar examples. We have seen,
also, that a like proclivity exists (~ 99) between bodies or streams
of water that differ in temperature or velocity.  This peculiarity
is often so strikingly developed in the neighborhood of the Gulf
Stream  that persons have been led to suppose that the Gulf
Stream has forks in the sea, and that these are they.
128. Now, if any vessel will take up her position a little to the
Streaksof warmand northward of Bermuda, and steering thence for the
cool.        Capes of Virginia, will try the water-thermometer
all the way at short intervals, she will find its readings to be now
higher, now lower; and the observer will discover that he has
been crossing streak after streak of warm and cool water in regular alternations. He will then cease to regard them as bifurcations of the Gulf Stream, and view them rather in the light of
thermal streaks of water which have, in the plan of oceanic circulation and in the system of unequal heating and cooling, been
brought together.
129. The waters of the Gulf Stream form by no means the only
watersofthe ocean body of warm  water that the thermo-dynamical
kept in metion by forces of the ocean keep in motion. Nearly all
thermo- dynamical
means.       that portion of the Atlantic which lies between the
Gulf Stream  and the island of Bermuda has its surface covered
with water which a tropical sun and tropical winds have played
upon-with water, the specific gravity of which has been altered
by their action, and which is now drifting to more northern climes
in the endless search after lost equilibrium.  This water, moreover, as well as that of the Gulf Stream, cools unequally.  It
would be surprising if it did not; for by being spread out over
such a large area, and then drifting for so great a distance, and
through such a diversity of climates, it is not probable that all




44         THE PHYSICAL GEOGRAPHY OF THE SEA.
parts of it should have been exposed to like vicissitudes by the
way, or even to the same thermal conditions; therefore all of the
water over such a surface can not be heated alike; radiation here,
sunshine there; clouds and rain one day, and storms the next;
the unequal depths; the breaking up of the fountains below, and
the bringing their cooler waters to the surface by the violence
of the waves, may all be expected, and are well calculated to produce unequal heating in the torrid and unequal cooling in the
temperate zone; the natural result of which would be streaks and
patches of water differing in temperature. Hence it would be
surprising if, in crossing this drift and stream (Plate VI.) with the
water-thermometer, the observer should find the water all of one
temperature. By the time it has reached the parallel of Bermuda
or "the Capes" of the Chesapeake, some of this water has been
ten days, some ten weeks, and some perhaps longer on its way
from the " caldron" at the south. It has consequently had ample
time to arrange itself into those differently-tempered streaks and
layers (~ 127) which are so familiar to navigators, and which have
been mistaken for "forks of the Gulf Stream."
130. Curves showing some of these variations of temperature
rFig.A,PlateVI. have been projected by the Coast Survey on a
chart of engraved squares (Fig. A, Plate VI.). These curves show
how these waters have arranged themselves off the Capes of Virginia into a series of thermal elevations and depressions.
131. In studying the Gulf Stream, the high temperature and
The high tempera- drift of the waters to the east of it are worthy of
tnre and drift in the
westernhalfofNorth consideration.  The Japan current (~ 80) has a like
Atlantic and Pacific
Oceans.      drift Qf warm water to the east of it also (Plates VI.
and IX.). In the western half, reaching up from the equator to
the Gulf Stream, both of the North Atlantic and North Pacific,
the water is warmer, parallel for parallel, than it is in the eastern
half. On the west side, where the water is warm, the flow is to
the north; on the east side, where the temperature is lower, the
flow is to the south —making good the remark (~ 80) that, when
the waters of the sea meet in currents, the tendency of the warm
is to seek cooler latitudes, and of the cool, warmer.
132. The Gulf Stream of each has its genesis on the west side,
A Gulf Stream in and in its course skirts the coast along; leaving the
each.       coast, it strikes off to the eastward in each case,




~ 133-135.           THE GULF STREAM.                       45
losing velocity and spreading out.  Between each of these Gulf
Streams and its coasts there is a current of cool water setting to
the south. On the outside of each stream, and coming up from
the tropics, is a broad sheet of warm water; it covers an area of
thousands of square miles, and its drift is to the north. Between
the northern drift on the one side and the southern set on the
other, there is in each ocean a sargasso (~ 88), into which all drift
matter, such as wood and weeds, finds its way. In both oceans
the Gulf Streams sweep across to the eastern shores, and so,
bounding these seas, interpose a barrier between them and the
higher parallels of latitude, which this drift matter can not pass.
Such are the points of resemblance between the two oceans and
in the circulation of their waters.
133. A prominent point for contrast is afforded by the chanTheir connection nels or water-ways between the Arctic and these
with the Arctic
Ocean.       two oceans. With the Atlantic they are divers and
large; with the Pacific there is but one, and it is both narrow
and shallow. In comparison with that of the Atlantic, the Gulf
Stream of the Pacific is sluggish, ill defined, and irregular. Were
the water-ways between the Atlantic and the Arctic Ocean no
larger than Behring's Straits, our Gulf Stream would fall far below that of the Pacific in majesty and grandeur.
134. Here I am reminded to turn aside and call attention to anThe sargassos show other fact that militates against the vast current-bethe trle  Pindo np-f getting power that has been given by theory to the
on curents.  gentle trade-winds.  In both oceans these weedy
seas lie partly within the trade-wind region; but in neither do
these winds give rise to any current.  The weeds are partly out
of water, and the wind has therefore more power upon them than
it has upon the water itself; and if the supreme power over the
currents of the sea reside in the winds, as Sir John Herschel
would have it, then, of all places in the trade-wind region, we
should have here the strongest currents. Had there been currents here, these weeds would have been borne away long ago;
but, so far from it, we simply know that they have been in the
Sargasso Sea (~ 88) of the Atlantic since the first voyage of Columbus. But to take up the broken thread.
135. The water that is drifting north, on the outside of the Gulf
Stream, turns, with the Gulf Stream, to the east also. It can not




46         THE PHYSICAL GEOGRAPHY OF THE SEA.
Thedriftmattercon- reach the high latitudes (~ 80), for it can not cross
fined to sargassos by
currents.     the Gulf Stream.  Two streams of water can not
cross each other, unless one dip down and underrun the other;
and if this drift water do dclip down, as it may, it can not carry
with it its floating matter, which, like its weeds, is too light to
sink.  They, therefore, are cut off from  a passage into higher
latitudes.
136. According to this view, there ought to be a sargasso sea
Thleoryastothefor- somewhere in the sort of middle ground between
mionof sargassos. the grand equatorial flow and reflow which is performed by the waters of all the great oceans. The place where
the drift matter of each sea would naturally collect would be in
this sort of pool, into which every current, as it goes from the
equator, and again as it returns, would slough off its drift matter.
The forces of diurnal rotation would require this collection of
drift to be, in the northern hemisphere, on the'right-hand side of
the current, and, in the southern, to be on the left.  (See Chap.
XVIII. and Plate IX.)
137. Thus, with the Gulf Stream of the Atlantic, and the "Black
Sargassos of south- Stream" of the Pacific, their sargassos are on the
ef tseaso the~ left right, as they are also on the right of the returning
of the southern, to   h
the right ofthe great and cooler currents on the eastern side of each one
polar and equatorial
Sow and reflow. of those northern oceans. So, also, with the MIozambique current, which runs south along the east coast of Africa
from the Indian Ocean, and with the cooler current setting to the
north on the Australian side of the same sea.  Between these
there is a sargasso on the left.
138. Again, there is in the South Pacific a flow of equatorial
Their position con- waters to the Antarctic on the east of Australia,
forms to the theory. and of Antarctic waters (Humboldt's current) to the
north, along the western shores of South America; and, according
to this principle, there ought to be another sargasso somewhere
between New Zealand and the coast of Chili. (See Plate IX.)
139. To test the correctness of this view, I requested Lieut.
The discovery of a Warley to overhaul our sea-journals for notices of
new sargasso.    kelp and drift matter on the passage from Australia
to Cape Horn and the Chincha Islands.  He did so, and found it
abounding in small patches, with "many birds about," between
the parallels of 40~ and 500 south, the meridians of 140~ and 178~




~ 140-142.            THE GULF STREAM.                        47
west. This sargasso is directly south of the Georgian Islands,
and is, perhaps, less abundantly supplied with drift matter, less
distinct in outline, and less permanent in position than any one
of the others.
140. There is no warm  current, or if one, a very feeble one,
One in the South flowing out of the South Atlantic.  Most of the
Atlantic.     drift matter borne upon the ice-bearing current into
that sea finds its way to the equator, and then into the veins
which give volume to the Gulf Stream and supply the sargasso
of the North Atlantic with extra quantities of drift. The sargasso of the South Atlantic is therefore small. The formations
and physical relations of sargassos will be again alluded to in
Chapter XVIII.
141. Let us return (~ 129) to this great expanse of warm water
The large volume of which, coming from the torrid zone on the southwarm water outside
of the Gulf Stream. western side of the Atlantic, drifts along to the north
on the outside of the Gulf Stream. Its velocity is slow, not sufficient to give it the name of current; it is a drift, or what sailors
call a " set."  By the time this water reaches the parallel of 35~ or
40~ it has parted with a good deal of its intertropical heat; consequent upon this change in temperature is a change in specific
gravity also, and by reason of this change as well as by the difficulties of crossing the Gulf Stream, its progress to the north is arrested.  It now turns to the east with the Gulf Stream, and, yielding to the force of the westerly winds of this latitude, is by them
slowly driftecd along; losing temperature by the way, these waters
reach the southwardly flow on the east side with their specific
gravity so altered that, disregarding the gentle forces of the wind,
they heed the voice of the sea, and proceed to unite with this
cool flow, and to set south in obedience to those dynamical laws
that derive their force in the sea from differing specific gravity.
142. The Thermal Charts of the North Atlantic afford for these
The resemblancebe- views other illustrations which, when compared
tween the currents
in the NorthAtlan- with the charts of the North Pacific now in the
tic and the North
Pacific.     process of construction, will make still more striking the resemblance of the two oceans in the general features of
their systems of circulation. WVe see how, in accordance with
this principle (~ 132), the currents necessary for the formation
of thickly-set sargassos are generally wanting in southern oceans.




48        THE PHYSICAL GEOGRAPHY OF THE SEA.
How closely these two seas of the north resemble each other;
and how, on account of the large openings between the Atlantic
and the Frozen Oceans, the flow of warm waters to the north and
of cold waters to the south is so much more active in the Atlantic
than it is in the Pacific. Ought it not so to be?
143. As a rule, the hottest water of the Gulf Stream is at or
Acushion of cool wa- near the surface; and as the deep-sea thermometer
ter protects the bot —
tom of the deep sea is sent down, it shows that these waters, though
from abrasion by its
currents.    still far warmer than the water on either side at
corresponding depths, gradually become less and less warm until
the bottom of'the current is reached. There is reason to believe
that the warm waters of the Gulf Stream are nowhere permitted,
in the oceanic economy, to touch the bottom of the sea. There
is every where a cushion of cool water between them and the
solid parts of the earth's crust. This arrangement is suggestive,
and strikingly beautiful.  One of the benign offices of the Gulf
Stream is to convey heat from the Gulf of Mexico, where otherwise it would become excessive, and to dispense it in regions beyond the Atlantic for the amelioration of the climates of the
British Islands and of all Western Europe. Now cold water is
one of the best non-conductors of heat, and if the warm water
of the Gulf Stream was sent across the Atlantic in contact with
the solid crust of the earth-comparatively a good conductor of
heat —instead of being sent across, as it is, in contact with a cold,
non-conducting cushion of cool water to fend it from the bottom,
much of its heat would be lost in the first part of the way, and
the soft climates of both France and England would be, as that
of Labrador, severe in the extreme, ice-bound, and bitterly cold.




~ 150, 151. GULF STREAM, CLIMATES, AND COMMERCE.        49
CHAPTER III.
~ 150-191. —INFLUENCE OF THE GULF STREAM UPON CLIMATES
AND COMMERCE.
1[50. MODERN ingenuity has suggested a beautiful mode of
How the Washing- warming houses in winter. It is done by means
ton Observatory is
warmed.     of hot water. The furnace and the caldron are
sometimes placed at a distance from the apartments to be warmed.
It is so at the Observatory. In this case, pipes are used to conduct the heated water from the caldron under the superintendent's
dwelling over into one of the basement rooms of the Observatory,
a distance of one hundred feet. These pipes are then flared out
so as to present a large cooling surface; after which they are
united into one again, through which the water, being now cooled, returns of its own accord to the caldron. Thus cool water is
returning all the time and flowing in at the bottom of the caldron,
while hot water is continually flowing out at the top. The ventilation of the Observatory is so arranged that the circulation of
the atmosphere through it is led from this basement room, where
the pipes are, to all other parts of the building; and in the process
of this circulation, the warmth conveyed by the water to the basement is taken thence by the air and distributed over all the
rooms. Now, to compare small things with great, we have, in
the warm waters which are confined in the Gulf of Mexico, just
such a heating apparatus for Great Britain, the North Atlantic,
and Western Europe.
151. The furnace is the torrid zone; the Mexican Gulf and
Ananalogyshowing Caribbean Sea are the caldrons; the Gulf Stream
how the Gulf Stream is the conducting pipe. From the Grand Banks of
raises temperature
in Europe.  Newfoundland to the shores of Europe is the basement-the hot-air chamber —in which this pipe is flared out so as
to present a large cooling surface.' Here the circulation of the
atmosphere is arranged by nature; it is from west to east; consequently it is such that the warmth thus conveyed into this warmair chamber of mid-ocean is taken up by the genial west winds,
and dispensed, in the most benign manner, throughout Great
D




50        THE PHYSICAL GEOGRAPHY OF THE SEA.
Britain and the west of Europe. The mean temperature of the
water-heated air-chamber of the Observatory is about 90~. The
maximum temperature of the Gulf Stream is 86~, or about 90
above the ocean temperature due the latitude. Increasing its
latitude 10~, it loses but 2~ of temperature; and, after having run
three thousand miles toward the north, it still preserves, even in
winter, the heat of summer. With this temperature, it crosses
the 40th degree of north latitude, and there, overflowing its liquid
banks, it spreads itself out for thousands of square leagues over
the cold waters around, covering the ocean with a mantle of
warmth that serves so much to mitigate in Europe the rigors of
winter. Moving now more slowly, but dispensing its genial influences more freely, it finally meets the British Islands. By these
it is divided (Plate IX.), one part going into the polar basin of
Spitzbergen, the other entering the Bay of Biscay, but each with
a warmth considerably above the ocean temperature. Such an immense volume of heated water can not fail to carry with it beyond
the seas a mild and moist atmosphere. And this it is which so
much softens climate there.
152. We know not, except approximately in a few places,
Depth and temper- what the depth or the under temperature of the
Gulf Stream may be; but assuming the temperature
and velocity at the depth of two hundred fathoms to be those of
the surface, and taking the well-known difference between the
capacity of air and of water for specific heat as the argument, a
simple calculation will show that the quantity of heat discharged
over the Atlantic from the waters of the Gulf Stream in a winter's day would be sufficient to raise the whole column of atmosphere that rests upon France and the British Islands from the
freezing point to summer heat.
153. Every west wind that blows crosses the stream on its way
Contrasts of cli- to Europe, and carries with it a portion of this heat
mates in the same
latitudee.  to temper there the northern winds of winter. It
is the influence of this stream upon climate that makes Erin the
"Emerald Isle of the Sea," and that clothes the shores of Albion in evergreen robes; while in the same latitude, on this side,
the coasts of Labrador are fast bound in fetters of ice. In a valuable paper on currents,* Mr. Redfield states, that in 1831 the
* American Journal of Science, vol. xiv., p. 293.




~ 154, 155.  GULF STREAM, CLIMATES, AND COMMERCE.             51
harbor of St. John's, Newfoundland, was closed with ice as late
as the month of June; yet who ever heard of the port of Liverpool, on the other side, though 2~ farther north, being closed with
ice, even in the dead of winter?
154. The Thermal Chart (Plate IV.) shows this. The isotherMildness of an Ork- mal lines of 60~, 50~, etc., starting off from the parney winter.  allel of 40~ near the coasts of the United States, run
off in a northeastwardly direction, showing the same oceanic temperature on the European side of the Atlantic in latitude 55~ or
60~, that we have on the western side in latitude 40~.  Scott, in
one of his beautiful novels, tells us that the ponds in the Orkneys
(latitude near 60~) are not frozen in winter. The people there
owe their soft climate to this grand heating apparatus, for driftwood from the West Indies is occasionally cast ashore there by
the Gulf Stream.
155. Nor do the beneficial influences of this stream  upon cliAmount of heat dai- mate end here. The West Indian Archipelago is
ly escaping. through
the Gulf Stream.  encompassed on one side by its chain of islands,
and on the other by the Cordilleras of the Andes, contracting
with the Isthmus of Darien, and stretching themselves out over
the plains of Central America and Mexico.  Beginning on the
summit of this range, we leave the regions of perpetual snow, and
descend first into the tierra tzempladca, and then into the tierra
caliente, or burning land.  Descending still lower, we reach both
the level and the surface of the Mexican seas, where, were it not
for this beautiful and benign system of aqueous circulation, the
peculiar features of the surrounding country assure us we should
have the hottest, if not the most pestilential climate in the world.
As the waters in these two caldrons become heated, they are
borne off by the Gulf Stream, and are replaced by cooler currents
through the Caribbean Sea; the surface water, as it enters here,
being 30 or 40, and that in depth even 40~' cooler than when it
escapes from the Gulf. Taking only this difference in surface
temperature as an index of the heat accumulated there, a simple
calculation will show that the quantity of heat daily carried off
* Temperature of the Caribbean Sea (from the journals of Mr. Dunsterville):
Surface temperature: 830, September; 840, July; 830-S61~, Mosquito Coast.
Temperature in depth: 480, 240 fathoms; 430, 386 fathoms; 420, 450 fathoms;
430, 500 fathoms.




52        TI-HE PHYSICAL GEOGRAPHY OF THE SEA.
by the Gulf Stream from those regions, and discharged over the
Atlantic, is sufficient to raise mountains of iron from zero to the
melting point, and to keep in flow from them a molten stream of
metal greater in volume than the waters daily discharged from
the Mississippi River.
156. Who, therefore, can calculate the benign influence of this
Its benign influences. wonderful current upon the climate of the South?
In the pursuit of this subject, the mind is led from nature up to
the great Architect of nature; and what mind will the study of
this subject not fill with profitable emotions?  Unchanged and
unchanging alone, of all created things, the ocean is the great emblem of its everlasting Creator.  " He treadeth upon the waves
of the sea," and is seen in the wonders of the deep. Yea, " He
calleth for its waters, and poureth them out upon the face of the
earth." In obedience to this call, the aqueous portion of our
planet preserves its beautiful system of circulation. By it heat
and warmth are dispensed to the extra-tropical regions; clouds
and rain are sent to refresh the dry land; and by it cooling
streams are brought from Polar Seas to temper the heat of the
torrid zone. At the depth of two hundred and forty fathoms, the
temperature of the currents setting into the Caribbean Sea has
been found as low as 480, while that of the surface was 85~. Another cast with three hundred and eighty-six fathoms gave 430 below against 83~ at the surface. The hurricanes of those regions
agitate the sea to great depths; that of 1780 tore rocks up from the
bottom seven fathoms deep, and cast them ashore. They therefore can not fail to bring to the surface portions of the cooler water below.
157. At the very bottom of the Gulf Stream, when its surface
Cold water at the temperature was 80~, the deep-sea thermometer of,bottom  of the Gulf
Stream.     the Coast Survey has recorded a temperature as
low as 350 Fahrenheit. These cold waters doubtless come down
from the north to replace the warm water sent through the Gulf
Stream to moderate the cold of Spitzbergen; for within the Arctic Circle the temperature at corresponding depths off the shores
of that island is said to be only one degree colder than in the Caribbean Sea, while on the coasts of Labrador and in the Polar Seas
the temperature of the water beneath the ice was invariably found
by Lieutenant De Haven at 28~, or 4~ below the melting point of




~ 158.   GULF STREAM, CLIMATES, AND COMMERCE.            53
fresh-water ice. Captain Scoresby relates, that on the coast of
Greenland, in latitude 72~, the temperature of the air was 42~; of
the water, 340; and 290 at the depth of one hundred and eighteen
fathoms. lie there found a surface current setting to the south,
and bearing with it this extremely cold water, with vast numbers
of icebergs, whose centres, perhaps, were far below zero. It would
be curious to ascertain the routes of these under currents on their
way to the tropical regions, which. they are intended to cool. One
has been found at the equator (~ 97) two hundred miles broad and
23~ colder than the surface water. Unless the land or shoals intervene, it no doubt comes down in a spiral curve (~ 96), approaching in its course the great circle route.
158. Perhaps the best indication as to these cold currents may
Fish and currents. be derived from the fish of the sea. The whales,
by avoiding its warm waters, pointed out to the fisherman the existence of the Gulf Stream. Along our own coasts, all those delicate animals and marine productions which delight in warmer waters are wanting; thus indicating, by their absence, the prevalence
of the cold current from the north now known to exist there. In
the genial warmth of the sea about the Bermudas on one hand,
and Africa on the other, we find, in great abundance, those delicate shell-fish and coral formations whichare altogether wanting
in the same latitudes along the shores of South Carolina. The
same obtains in the west coast of South America; for there the
immense flow of polar waters known as Humboldt's Current almost reaches the line before the first sprig of coral is found to
grow. A few years ago, great numbers of bonita and albercoretropical fish-following the Gulf Stream, entered the English
Channel, and alarmed the fishermen of Cornwall and Devonshire
by the havoc which they created among the pilchards there. It
may well be questioned if our Atlantic cities and towns do not
owe their excellent fish-markets, as well as our watering-places
their refreshing sea-bathing in summer, to this littoral stream of
cold water. The temperature of the Mediterranean is 4~ or 5~
above the ocean temperature of the same latitude, and the fish
there are, for the most part, very indifferent.  On the other hand,
the temperature along our coast is several degrees below that of
the ocean, and from Maine to Florida our tables are supplied with
the most excellent of fish. The shcep's-head of this cold current,




54        THE PHYSICAL GEOGRAPHY OF THE SEA.
so much esteemed in Virginia and the Carolinas, loses its flavor,
and is held in no esteem, when taken on the warm coral banks of
the Bahamas. The same is the case with other fish: when taken
in the cold water of that coast, they have a delicious flavor and
are highly esteemed; but when taken in the warm water on the
other edge of the Gulf Stream, though but a few miles distant,
their flesh is soft and unfit for the table. The temperature of the
water at the Balize reaches 90~. The fish taken there are not to
be compared with those of the same latitude in this cold stream.
New Orleans, therefore, resorts to the cool waters on the Florida
coasts for her choicest fish. The same is the case in the Pacific.
A current of cold water (~ 398) from the south sweeps the shores
of Chili, Peru, and Columbia, and reaches the Gallipagos Islands
under the equator. Throughout this whole distance, the world
does not afford a more abundant or excellent supply of fish. Yet
out in the Pacific, at the Society Islands, where coral abounds, and
the water preserves a higher temperature, the fish, though they
vie in gorgeousness of coloring with the birds, and plants, and insects of the tropics, are held in no esteem as an article of food. I
have known sailors, even after long voyages, still to prefer their
salt beef and pork to a mess of fish taken there. The few facts
which we have bearing upon this subject seem to suggest it as a
point of the inquiry to be made, whether the habitat of certain
fish does not indicate the temperature of the water; and whether
these cold and warm currents of the ocean do not constitute the
great highways through which migratory fishes travel from one
region to another. Why should not fish be as much the creatures
of climate as plants, or as birds and other animals of land, sea, and
air? Indeed, we know that some kinds of fish are found only in
certain climates. In other words, they live where the temperature of the water ranges between certain degrees.
159. Navigators have often met with vast numbers of young
A shoal of sea-net- sea-nettles (medusce) drifting along with the Gulf
tles.        Stream. They are known to constitute the principal food for the whale; but whither bound by this route has
caused much curious speculation, for it is well known that the
habits of the right whale are averse to the warm waters of this
stream. An intelligent sea-captain informs me that, several years
ago, in the Gulf Stream off the coast of Florida, he fell in with




~ 160, 161. GULF STREAM, CLIMATES, AND COMMERCE.         55
such a " school of young sea-nettles as had never before been heard
of." The sea was covered with them for many leagues. He likened them, as they appeared on near inspection in the water, to
acorns floating on a stream; but they were so thick as to completely cover the sea, giving it the appearance, in the distance, of
a boundless meadow in the yellow leaf. He was bound to England, and was five or six days in sailing through them. In
about sixty days afterward, on his return, he fell in with the same
school off the Western Islands, and here he was three or four
days in passing them again. He recognized them as the same,
for he had never before seen any like them; and on both occasions he frequently hauled up buckets full and examined them.
160. Now the Western Islands is the great place of resort for
Food for whales whales; and at first there is something curious to
us in the idea that the Gulf of Mexico is the harvest field, and the
Gulf Stream the gleaner which collects the fruitage planted there,
and conveys it thousands of miles off to the hungry whale at sea.
But how perfectly in unison is it with the kind and providential
care of that great and good Being which caters for the sparrow,
and feeds the young ravens when they cry!
161. Piazzi Smyth, the Astronomer Royal of Edinburgh, when
Piazzi Smyth's d- bound to Teneriffe on his celebrated astronomical
scription.   expedition of 1856, fell in with the annual harvest
of these creatures. They were in the form of hollow gelatinous
lobes, arranged in groups of five or nine —each lobe having an
orange vein down the centre. Thus each animal was formed of
an aggregation of lobes, with an orange-colored vein, or stomach,
in every lobe. " Examining," says he, " in the microscope a portion of one of the orange veins, apparently the stomach of the
creature, it was found to be extraordinarily rich in diatomes, and
of the most bizarre forms, as stars, Maltese crosses, embossed circles, semicircles, and spirals. The whole stomach could hardly
have contained less than seven hundred thousand; and when we
multiply them by the number of lobes, and then by the number
of groups, we shall have some idea of the countless millions of
diatomes that go to make a feast for the meduse —some of the
softest things in the world thus confounding and devouring the
hardest-the flinty-shelled diatomace." Each of these "sea-nettles," as the sailors call them, had in his nine stomachs not less,




56         THE PHYSICAL GEOGRAPHY OF THE SEA.
according to this computation, than five or six millions of these
mites of flinty shells, the materials of which their inhabitants had
collected from the silicious matter which the rains washed out
from the valleys, and which the rivers are continually rolling
down to the sea.
162. The medusse have the power of sucking in the sea-water
The watersofthesea slowly, and of ejecting it again with more or less
bring forth —oh how
abundantly!    force. Thus they derive both food and the power
of locomotion, for, in the passage of the water, they strain it and
collect the little diatomes. Imagine, now, how many medussemouthfuls of water there must be in the sea, which, though loaded with diatomes, are never filtered through the stomachs of these
creatures; imagine how many medusse the whale must gulp down
with every mouthful; imagine how deep and thickly the bottom
of the sea must, during the process of ages, have become covered
with the flinty remains of these little organisms; now call to
mind the command which was given to the waters of the sea on
the fifth day of creation; and then the powers of the imagination
are silenced by the emotions of wonder, love, and praise.
163. The sea has its climates as well as the land. They both
Contrasts between change with the latitude; but one varies with the
tile climates of land
and sea.     elevation above, the other with the depression below the sea level. The climates in each are regulated by circulation; but the regulators are, on the one hand, winds; on the
other, currents.
164. The inhabitants of the ocean are as much the creatures
Order and design. of climate as are those of the dry land; for the
same Almighty hand which decked the lily and cares for the
sparrow, fashioned also the pearl and feeds the great whale; He
adapted each to the physical conditions by which his providence
has surrounded it. Whether of the land or the sea, the inhabitants are all his creatures, subjects of his laws, and agents in his
economy. The sea, therefore, we may safely infer, has its offices
and duties to perform; so, may we infer, have its currents, and so,
too, its inhabitants; consequently, he who undertakes to study
its phenomena must cease to regard it as a waste of waters. He
must look upon it as a part of that exquisite machinery by which
the harmonies of nature are preserved, and then he will begin to
perceive the developments of order and the evidences of design;




~ 165.   GULF STREAM, CLIMATES, AND COMMERCE.             57
viewed ill this light, it becomes a most beautiful and interesting
subject for contemplation.
165. To one who has never studied the mechanism of a watch,
Terrestrial aarpta- its main-spring or the balance-wheel is a mere piece
tions.       of metal. He may have looked at the face of the
watch, and, while he admires the motion of its hands, and the
time it keeps, or the tune it plays, he may have wondered in idle
amazement as to the character of the machinery which is concealed within. Take it to pieces, and show him each part separately;
he will recognize neither design, nor adaptation, nor relation between them; but put them together, set them to work, point out
the offices of each spring, wheel, and cog, explain their movements, and then show him the result; now he perceives that it is
all one design; that, notwithstanding the number of parts, their
diverse forms and various offices, and the agents concerned, the
whole piece is of one thought, the expression of one idea. He
now rightly concludes that when the main-spring was fashioned
and tempered, its relation to all the other parts must have been
considered; that the cogs on this wheel are cut and regulatedadccptec —to the rachets on that, &c.; and his final conclusion will
be, that such a piece of mechanism could not have been produced
by chance; for the adaptation of the parts is such as to show it
to be according to design, and obedient to the will of one intelligence. So, too, when one looks out upon the face of this beautiful world, he may admire its lovely scenery, but his admiration
can never grow into adoration unless he will take the trouble to
look behind and study, in some of its details at least, the exquisite
system of machinery by which such beautiful results are brought
about. To him who does this, the sea, with its physical geography, becomes as the main-spring of a watch; its waters, and its
currents, and its salts, and its inhabitants, with their adaptations,
as balance-wheels, cogs, and pinions, and jewels in the terrestrial
mechanism. *Thus he perceives that they too are according to
design-parts of the physical machinery that are the expression of
One Thought, a unity with harmonies which One Intelligence,
and One Intelligence alone, could utter. And when he has arrived at this point, then he feels that the study of the sea, in its
physical aspects, is truly sublime. It elevates the mind and ennobles the man. The Gulf Stream is now no longer, therefore,




58        TITHE PHYSICAL GEOGRAPHY OF THE SEA.
to be regarded by such an one merely as an immense current of
warm water running across the ocean, but as a balance-wheel-a
part of that grand machinery by which air and water are adapted
to each other, and by which this earth itself is adapted to the wellbeing of its inhabitants-of the flora which decks; and the fauna
which enlivens its surface.
166. Let us now consider the Influence of the Gulf Stream upon
METEOROLOGY OFTHE the Meteorology of the Ocean. To use a sailor exSmE: Gulf Stream
te wether-beam reeder pression, the Gulf Stream  is the great "weather-greits lstor the breeder" of the North Atlantic Ocean. The most
great hurricane  of
1T80.       furious gales of wind sweep along with it; and the
fogs of Newfoundland, which so much endanger navigation in
spring and summer, doubtless owe their existence to the presence,
in that cold sea, of immense volumes of warm water brought by
the Gulf Stream. Sir Philip Brooke found the air on each side
of it at the freezing point, while that of its waters was 80~. "The
heavy, warm, damp air over the current produced great irregularities in his chronometers." The excess of heat daily brought
into such a region by the waters of the Gulf Stream would, if
suddenly stricken from them, be sufficient to make the column
of superincumbent atmosphere hotter than melted iron. With
such an element of atmospherical disturbance in its bosom, we
might expect storms of the most violent kind to accompany it in
its course. Accordingly, the most terrific that rage on the ocean
have been known to spend their fury within or near its borders.
Of all storms, the hurricanes of the West Indies and the typhoons
of the China seas cause the most ships to founder. The stoutest
men-of-war go down before them, and seldom, indeed, is any one
of the crew left to tell the tale. Of this the Hornet, the Albany,
and the Grampus, armed cruisers in the American navy, all are
memorable and melancholy examples. Our nautical works tell
us of a West India hurricane so violent that it forced the Gulf
Stream back to its sources, and piled up the water in the Gulf to
the height of thirty feet. The Ledbury Snow attempted to ride
it out. When it abated, she found herself high up on the dry
land, and discovered that she had let go her anchor among the
tree-tops on Elliott's Key. The Florida Keys were inundated
many feet, and, it is said, the scene presented in the Gulf Stream
was never surpassed in awful sublimity on the ocean. The water




~ 167-169. GULF STREAM, CLIMATES, AND COMMERCE.           59
thus dammed up is said to have rushed out with frightful velocity against the fury of the gale, producing a sea that beggared
description. The "great hurricane" of 1780 commenced at Barbadoes. In it the bark.,was blown from the trees, and the fruits
of the earth destroyed; the very bottom and depths of the sea
were uprooted, and the waves rose to such a height that forts and
castles were washed away, and their great guns carried about in
the air like chaff; houses were razed, ships were wrecked, and
the bodies of men and beasts lifted up in the air and dashed to
pieces in the storm. At the different islands, not less than twenty
thousand persons lost their lives on shore, while farther to the
north, the "Sterling Castle" and the "Dover Castle," men-of-war,
went down at sea, and fifty sail were driven on shore at the Bermudas.
167. Several years ago the British Admiralty set on foot inInquirlies instituted quiries as to the cause of the storms in certain parts
by the Admiralty. of the Atlantic, which so often rage with disastrous
effects to navigation. The result may be summed up in the conclusion to which the investigation led: that they are occasioned
by the irregularity between the temperature of the Gulf Stream
and of the neighboring regions, both in the air and water.
168. The southern points of South America and Africa have
Themoststormy sea. won for themselves, among seamen, the name of
" the stormy capes;" but investigations carried on in that mine of
sea-lore contained in the log-books at the National Observatory
have shown that there is not a storm-fiend in the wide ocean can
out-top that which rages along the Atlantic coasts of North
America. The China seas and the North Pacific may vie in the
fury of their gales with this part of the Atlantic, but Cape Horn
and the Cape of Good Hope can not equal them, certainly, in frequency, nor do I believe in fury.
169. In the ex-tropical regions of the south we lack those conNorthlern seas more trasts which the mountains, the deserts, the plains,
boisterous than southeUn.         the continents, and the seas of the north afford for
the production of atmospherical disturbances.  Neither have we
in the southern seas such contrasts of hot and cold currents. The
flow of warm water toward the pole, and of polar water toward
the equator is as great-perhaps if measured according to volume,
is greater in the southern hemisphere. But in the southern hemi



60        THE PHYSICAL GEOGRAPHY OF THE SEA.
sphere the currents are broad and sluggish; in the northern,
narrow, sharp, and strong.  Then we have in the north other
climatic contrasts for which we may search southern seas in vain.
Hence, without further investigation, we may infer southern seas
to be less boisterous than northern.
170. By a like reasoning we may judge the North Pacific to.
Stormsin the North be less boisterous than the North Atlantic; for,
Atlantic andPacific. though we have continental climates on either side
of each, and a Gulf Stream in both, yet the Pacific is a very much
wider sea, and its Gulf Stream is (~ 54) not so warm, nor so sharp,
nor so rapid; therefore the broad Pacific does not, on the whole,
present the elements of atmospherical disturbance in that compactness which is so striking in the narrow North Atlantic.
171. Nevertheless, though thee North Pacific generally may not
Storms along their be so stormy as the North Atlantic, we have reason
western shores. to believe that meteorological agents of nearly equal
power are clustered along the western shores of each ocean.
Though the Gulf Stream of the Pacific is not so hot, nor the cool
littoral currents so cold as those of our ocean are, yet they lave
the shores of a broader continent, and hug them quite as closely
as ours do. Moreover, the Japan Current, with its neighboring
seas, is some 500 miles nearer to the pole of maximum cold than
the Gulf Stream of the Atlantic is.
172. Some philosophers hold that there are in the northern
Position of the poles hemisphere two poles of maximum cold: the Asind maximum colde, atic7 near the intersection of the parallel of 80~
upon the meteorolo- with the meridian of 120~ E., and the American,
gy of these two        mri         1    E,      t
oceans.      near lat. 790 and long. 100~ W.  The Asiatic pole
is the colder. The distance between it and the Japan Current is
about 1500 miles; the distance between the other pole and the
Gulf Stream  is about 2000 miles.  The bringing of the heat of
summer, as these twvo streams do, in such close juxtaposition
with the cold of winter, can not fail to produce violent commotions in the atmosphere. These commotions, as indicated by the
storms, are far more frequent and violent in winter, when the
contrasts between the warm and cool places are greater, than they
are in summer, when those contrasts are least.  Moreover, each
of these poles is to the northwest of its ocean, the quarter whence
come the most terrific gales of winter. Whatever be the exact




~ 173, 174. GULF STREAM, CLIMATES, AND COMMERCE.         61
degree of influence which future research may show to be exercised by these cool places, and the heat dispensed so near them
by these mighty streams of tepid water, there is reason to believe
that they do act and react upon each other with no inconsiderable meteorological power. In winter the Gulf Stream carries the
temperature of summer as far north as the Grand Banks of Newfoundland.
173. The habitual dampness of the climate of the British IslClimatesof England ands, as well as the occasional dampness of that
and silver fogs of
Newfoundland. along the Atlantic coasts of the United States
when easterly winds prevail, is attributable also to the Gulf
Stream. These winds come to us loaded with vapors gathered
from its warm and smoking waters. The Gulf Stream carries the
temperature of summer, even in the dead of winter, as far north
as the Grand Banks of Newfoundland, and there maintains it in
the midst of the severest frosts. It is the presence of this warm
water and a cold atmosphere in juxtaposition there which gives
rise to the " silver fogs" of Newfoundland, one of the most beautiful phenomena to be seen any where among the treasures of the
frost-king.
174. The Gulf Stream exercises a powerful influence upon
Influences  upon the storms of the North Atlantic, especially those
Storms.     which take their rise within the tropics, even as
far over as the coast of Africa, and also upon those which,
though not intertropical in their origin, are known to visit the
offings of our own coasts. These gales, in whatever part of the
ocean east of the Gulf Stream they take their rise, march to the
northwest until they join it, when they " recurvate," as the phrase
is, and take up their line of march to the northeast along with it.
Gales of wind have been traced from latitude 10~ N. on the other
side of the Atlantic to the Gulf Stream on this, and then with it
back again to the other side, off the shores of Europe. By examining the log-books of ships, the tracks of storms have been
traced out and followed for a week or ten days. Their path is
marked by wreck and disaster. At a meeting of the American
Association for the Advancement of Science, in 1854, Mr. Redfield mentioned one which he had traced out, and in which no
less than seventy odd vessels had been wrecked, dismasted, or
damaged.




62        THE PHYSICAL GEOGRAPHY OF THE SEA.
175. Now, what should attract these storms to the Gulf Stream,
More observationsin is a question which yet remains to be satisfactorily
and about the Gulf answered. A  good series of simultaneous baroStream a desideratum.         metric observations within and on either side of
the Gulf Stream is a great desideratum in the meteorology of
the Atlantic.  At the equator, where the trade-winds meet and
ascend, where the air is loaded with moisture, and the vapor from
the warm waters below condensed into the equatorial cloud-ring
above, we have a low barometer.
176. Itow is it with the Gulf Stream when these storms from
Certainstormsmake right and left burst in upon it, and, turning about,
forit and follow it. course along with it?  Its waters are warm; they
give off vapor rapidly; and, were this vapor visible to an observer in the moon, he no doubt would, on a winter's day especially, be able to trace out by the mist in the air the path of the
Gulf Streal-m through the sea.
177. Let us consider the effect of vapor upon winds, and then
Iow aqueous vapor the importance of the observations proposed (~ 175)
assists in producing
winds.       will perhaps be better appreciated. Aqueous vapor assists in at least five, perhaps six ways to put air in motion
and produce winds. (1.) By evaporation the air is cooled; by
cooling its specific gravity is changed, and, consequently, here is
one cause of movement in the air, as is manifest in the tendency
of the cooled air to flow off, and of warmer and lighter to take its
place. (2.) Excepting hydrogen and ammonia, there is no gas so
light as aqueous vapor, its weight being to common air in the
proportion of nearly 5 to 8; consequently, as soon as it is formed
it commences to rise; and, as each vesicle of vapor may be likened, in the movements which it produces in the air, to a balloon as
it rises, it will be readily perceived how these vaporous particles,
as they ascend, become entangled with those of the air, Fand so, carTying them along, upward currents are produced: thus the wind
is called on to rush in below, that the supply for the upward
movement may be kept up. (3.) The vapor, being lighter than air,
presses it out, and, as it were, takes its place, causing the barometer
to fall: thus again an in-rush or'wind is called for below. (4.) Arrived in the cloud-region, this vapor, being condensed, liberates
the latent heat which it borrowed from the air and water below;
which heat being now set free and made sensible, raises the tem



~ 178-181. GULF STREAM, CLIMATES, AND COMMERCE.             63
perature of the surrounding air, causing it to expand and ascend
still higher; and so winds are again called for. Ever ready, they
come; thus we have a fourth way. (5.) Innumerable rain-drops
now begin to fall, and in their descent, as in a heavy shower, they
displace and press the air out below with great force. To this
cause Espy ascribes the gusts of wind which are often found to
blow outward from the centre, as it were, of sudden and violent
thunder-showers. (6.) Probably, and especially in thunder-storms,
electricity may assist in creating movements in the atmosphere,
and so make claim to be regarded as a wind-producing agent.
But the winds are supposed to depend mainly on the power of
agents (2), (3), and (4) for their violence.
178. These agents, singly and together, produce rarefaction,
Storms in the inte- diminish pressure, and call for an inward rush of
rior attracted by the
Gulf Stream.  air from either side.  Mr. Espy asserts, and quotes
actual observation to sustain the assertion, that the storms of the
United States, even those which arise in the Mississippi Valley,
travel east, and often march out to sea, where they join the Gulf
Stream in its course.  That those which have their origin at sea,
on the other side of the Gulf Stream, do (~ 174) often make right
for it, is a fact well known to most observant sailors.  Hence the
interest that is attached to a proper series of observations on the
meteorology of the Gulf Stream.
179. Sailors dread its storms more than they do the storms in
Storms of-dreaded any other part of the ocean.  It is not the fury of
by seamen.   the storm alone that they dread, but it is the "ugly
sea" which these storms raise.  The current of the stream running in one direction, and the wind blowing in another, create a
sea that is often frightful.
180. The influence of the Gulf Stream:upon commerce and naviRoutes formerlygov- gation. Formerly the Gulf Stream controlled comerned by the Gulf
Stream.      merce across the Atlantic by governing vessels in
their routes through this ocean to a greater extent than it does
now, and simply for the reason that ships are faster, nautical instruments better, and navigators are more skillful now than formerly they were.
181. Up to the close of the last century, the navigator guessed
Difficulties with ear- as much as he calculated the place of his ship; vesl navigators.    sels from Europe to Boston frequently made New




64        THE PHYSICAL GEOGRAPHY OF THE SEA.
York, and thought the landfall by no means bad. Chronometers,
now so accurate, were then an experiment. The Nautical Ephemeris itself was faulty, and gave tables which involved errors of
thirty miles in the longitude. The instruments of navigation
erred by degrees quite as much as they now do by minutes; for
the rude " cross staff" and " back staff," the " sea-ring" and " mariner's bow," had not yet given place to the nicer sextant and circle of reflection of the present day. Instances are numerous of
vessels navigating the Atlantic in those times being 6~, 8%, and
even 10~ of longitude out of their reckoning in as many days from
port.
182. Though navigators had been in the habit of crossing and
Finding longitude recrossing the Gulf Stream almost daily for three
by the Gulf Stream. centuries, it never occurred to them to make use of
it as a means of giving them their longitude, and of warning them
of their approach to the shores of this continent. Dr. Franklin
was the first to suggest this use of it. The contrast afforded by
the temperature of its waters and that of the sea between the
Stream and the shores of America was striking. The dividing
line between the warm and the cool waters was sharp (~ 70); and
this dividing line, especially that on the western side of the stream,
seldom changed its position as much in longitude as mariners often erred in their reckoning.
183. When he was in London, in 1770, he happened to be conFolger's Chart. suited as to a memorial which the Board of Customs
at Boston sent to the Lords of the Treasury, stating that the Falmouth packets were generally a fortnight longer to Boston than
common traders were from London to Providence, Rhode Island.
They therefore asked that the Falmouth packets might be sent to
Providence instead of to Boston. This appeared strange to the doctor, for London was much farther than Falmouth, and from Falmouth the routes were the same, and the difference should have
been the other way. Hle, however, consulted Captain Folger, a
Nantucket whaler, who chanced to be in London also; the fisherman explained to the philosopher that the difference arose from the
circumstance that the Rhode Island captains were acquainted with
the Gulf Stream, while those of the English packets were not.
The latter kept in it, and were set back sixty or seventy miles a
day, while the former avoided it altogether. He had been made




~ 184.    GULF STREAM, CLIMATES, AND COMMERCE.           65
acquainted with it by the whales which were found on either side
of it, but never in it (~ 158). At the request of the doctor, he
then traced on a chart the course of this stream from the Straits
of Florida. The doctor had it engraved at Tower Hill, and sent
copies of it to the Falmouth captains, who paid no attention to it.
The course of the Gulf Stream, as laid down by that fisherman
from his general recollection of it, has been retained and quoted
on the charts for navigation, we may say, until the present day.
But the investigations of which we are treating are beginning to
throw more light upon this'subject; they are giving us more correct knowledge in every respect with regard to it, and to many
other new and striking features in the physical geography of the
sea.
184. No part of the world affords a more difficult or dangerous
Using the Gulf navigation than the approaches of our northern
Stream in winter. coast in winter. Before the warmth of the Gulf
Stream was known, a voyage at this season from Europe to New
England, New York, and even to the Capes of the Delaware or
Chesapeake, was many times more trying, difficult, and dangerous
than it now is. In making this part of the coast, vessels are frequently met by snow-storms and gales which mock the seaman's
strength and set at naught his skill. In a little while his bark
becomes a mass of ice; with her crew frosted and helpless, she
remains obedient only to her helm, and is kept away for the Gulf
Stream. After a few hours' run, she reaches its edge, and almost
at the next bound passes from the midst of winter into a sea at
summer heat. Now the ice disappears from her apparel; the
sailor bathes his stiffened limbs in tepid waters; feeling himself
invigorated and refreshed with the genial warmth about him, he
realizes, out there at sea, the fable of Antaeus and his mother
Earth. He rises up, and attempts to make his port again, and is
again, perhaps, as rudely met and beat back from the northwest;
but each time that he is driven off from the contest, he comes foyth
from this stream, like the ancient son of Neptune, stronger and
stronger, until, after many days, his freshened strength prevails,
and he at last triumphs, and enters his haven in safety, though in
this contest he sometimes falls to rise no more, for it is terrible.
Many ships annually founder in these gales; and I might name
instances, for they are not uncommon, in which vessels bound to
E




66        THE PHYSICAL GEOGRAPHY OF THE SEA.
Norfolk or Baltimore, with their crews enervated in tropical climates, have encountered, as far down as the Capes of Virginia,
snow-storms that have driven them back into the Gulf Stream
time and again, and have kept them out for forty, fifty, and even
for sixty days, trying to make an anchorage.
185. Nevertheless, the presence of the warm waters of the Gulf
Running south to Stream, with their summer heat in mid-winter, off
spend the winter. the shores of New England, is a great boon to navigation. At this season of the year especially, the gumber of
wrecks and the loss of life along the Atlantic sea-front are frightful. The month's average of wrecks has been as high as three a
day. How many escape by seeking refuge from the cold in the
warm waters of the Gulf Stream is matter of conjecture. Suffice
it to say, that before their temperature was known, vessels thus
distressed knew of no place of refuge short of the West Indies;
and the newspapers of that day-Franklin's Pennsylvania Gazette
among them —inform us that it was no uncommon occurrence for
vessels bound for the Capes of the Delaware in winter to be
blown off and to go to the West Indies, and there wait for the return of spring before they would attempt another approach to this
part of the coast.
186. Accordingly, Dr. Franklin's discovery with regard to the
Thermalnavigation. Gulf Stream temperature was looked upon as one
of great importance, not only on account of its affording to the
frosted mariner in winter a convenient refuge from the snow-storm,
but because of its serving the navigator with an excellent landmark or beacon for our coast in all weathers. And so viewing it,
the doctor, through political considerations, concealed his discovery for a while. The prize of ~20,000, which had been offered,
and partly paid, by the British government, to Harrison, the chronometer maker, for improving the means of finding longitude at
sea, was fresh in the minds of navigators.  And here it was
thought a solution of the grand problem- for longitude at sea
was a grand problem- had been stumbled upon by chance; for,
on approaching the coast, the current of warm water in the Gulf
Stream, and of cold water on this side of it, if tried with the thermometer, would enable the mariner to judge with great certainty,
and in the worst of weather, as to his position. Jonathan Williams afterward, in speaking of the importance which the thermal




~ 187, 188. GULF STREAM, CLIMATES, AND COMMERCE.         6'7
use of these warm and cold currents would prove to navigation,
pertinently asked the question, " If these stripes of water had been
distinguished by the colors of red, white, and blue, could they be
more distinctly discovered than they are by the constant use of
the thermometer?"  And he might have added, could they have
marked the position of the ship more clearly?
187. When his work on Thermometrical Navigation appeared,
CommodoreTruxton. Commodore Truxton wrote to him: "Your publication will be of:use to navigation by rendering sea voyages secure far beyond what even you yourself will immediately calculate, for I have proved the utility of the thermometer very often
since we sailed together. It will be found a most valuable instrument in the hands of mariners, and particularly as to those
who are unacquainted with astronomical observations; * * * *
these particularly stand in need of a simple method of ascertaining their approach to or distance from the coast, especially in the
winter season; for it is then that passages are often prolonged,
and ships blown off the coast by hard westerly winds, and vessels
get into the Gulf Stream without its being known; on which account they are often hove to by the captains' supposing themselves near the coast when they are very far off (having been
drifted by the currents). On the other hand, ships are often cast
on the coast by sailing in the eddy of the Stream, which causes
them to outrun their common reckoning. Every year produces
new proofs of these facts, and of the calamities incident thereto."
188. Though Dr. Franklin's discovery was made in 1775, yet,
Thediscovery of the for political reasons, it was not generally made
theGlfsteamfol- known till 1790. Its immediate effect in navigalowed by a decline in
Southern commerce. tion was to make the ports of the North as accessible in winter as in summer. What agency this circumstance
had in the decline of the direct trade of the South, which followed
this discovery, would be, at least to the political economist, a subject for much curious and interesting speculation. I have referred to the commercial tables of the time, and have compared
the trade of Charleston with that of the northern cities for several
years, both before and after the discovery of Dr. Franklin became
generally known to navigators. The comparison shows an immediate decline in the Southern trade and a wonderful increase
in that of the North. But whether this discovery in navigation




68                THE PHYSICAL GEOGRAPHY OF THE SEA.
and this revolution in trade stand in the relation of cause and
effect, or be merely a coincidence, let others judge.
189. In 1769 the commerce of the two Carolinas equaled that
statistics.    of all the New  England States together; it was
more than double that of New York, and exceeded that of Pennsylvania by one third.* In 1792, the exports from New York
amounted in value to two millions and a half; from Pennsylvania,
to $3,820,000; and from Charleston alone, to $3,834,000. But
in 1795-by which time the Gulf Stream began to be as well understood by navigators as it now is, and the average passages
from Europe to the North were shortened nearly one half, while
those to the South remained about the same-the customs at
Philadelphia alone amounted to $2,941,000,t or more than one
half of those collected in all the states together.
190. Nor did the effect of the doctor's discovery end here.
The shortening of Before it was made, the Gulf Stream was altogether
voyages.              insidious in its effects.  By it, vessels were often
drifted many miles out of their course without knowing it; and
in bad and cloudy weather, when many days would intervene
from  one observation to another, the set of the current, though
* From  M'Pherson's Annals of Commnerce.-Exports and Imports in 1769, valued in
Sterling MIoney.
EXPORTS.
To Gr. Britain. Sol. of Europe.   West Indies.  Africa.       Total... s.           ~ s.d.    ~ s.. s...   ~    s. d.           s. d.
New England...........-142,775 12 9  81,173 16  2 308,427  9  6 17,713  0  9 550,089 19  2
New York............... 113,382  8  8 50,885 13  0 66,324 1T.5   1,313  2  6 231,906  1  7
Pennsylvania........        28,112  6  9 203,762 11 11 178,331  7  8    560  9  9 410,756 16  1
North and South Carolina. 405,014 13  1 76,119 12 10  8T,758 19  3    691 12  1569,584 17  3
- IMPORTS,
New England............ 223,695 11 6  25,408 17  9 314,749 14  5    180  0  01564,034  3  8
New York...............75,930 19  7 14,927  7    897,420  4  0    697 10  0 188,976  1  3
Pennsylvania............204,979 17 4  14,249  8  4 180,591 12  4                      399,830 18  0
North and South Carolina. 327,084  8  6   7,099  510 76,269 17 11 137,620 10  9 535,714  2  3
t                                 Value of Exports in Dollars. 1
179         1792. 17.   1793.       1794.        1790.        1796.
Massachusetts......... 2,519,651   2,888,104   3,755,347  5,292,441    7,117,907    9,949,345
New York............. 2,505,465  2,535,790   2,932,370   5,442,000   10,304,000   12,208,027
Pennsylvania..........    3,436,000   3,820,000   6,958,000  6,643,000   11,518,000   17,513,866
South Carolina......... 69,000   2,428,000   3,191,000   3,868,000    5,998,009    7,620,000
D)uties on Imports in Dollars.
1791.       1792.       1793.       1794.       1795.       1796.       1833.
Massachusetts.  1,006,000       723,000  1,044,000  1,121,000  1,520,000   1,460,000   3,055,000
New York....   1,334,000   1,173,000  1,204,000   1,878,000  2,028,000   2,187,000 10,713,000
Pennsylvaniao..  1,466,000   1,100,000  1,823,000  1,498,000  2,300,000   2,050,000   2,207,000
South Carolina.   523,000       359,000    360,000    661,000    722,000         66,000    389,000
Doec. No. 330, H. R., 2d Session, 25th Congress.  Some of its statements do not agree with those
a:ken from McPherson and previously quoted.




~ 191.   GULF STREAM, CLIMATES, AND COMMERCE.            69
really felt but for a few hours during the interval, could only be
proportioned out equally among the whole number of days.
Therefore navigators could have only very vague ideas either as
to the strength or the actual limits of the Gulf Stream, until they
were marked out to the Nantucket fishermen by the whales, or
made known by Captain Folger to Dr. Franklin. The discovery,
therefore, of its high temperature assured the navigator of the
presence of a current of surprising velocity, and which, now turned to certain account, would hasten, as it had retarded his voyage
in a wonderful degree. Such, at the present day, is the degree
of perfection to which nautical tables and instruments have been
brought, that the navigator may now detect, and with great certainty, every current that thwarts his way. He makes great use
of them. Colonel Sabine, in his passage, a few years ago, from
Sierra Leone to New York, was drifted one thousand six hundred
miles of his way by the force of currents alone; and, since the
application of the thermometer to the Gulf Stream, the average
passage from England has been reduced from upward of eight
weeks to a little more than four. Some political economists of
America have ascribed the great decline of Southern commerce
which followed the adoption of the Constitution of the United
States to the protection given by legislation to Northern interests.
But I think these statements and figures show that this decline
was in no small degree owing to the Gulf Stream, the water-thermometer, and the improvements in navigation; for they changed
the relations of Charleston —the great Southern emporium of the
times-removing it from its position as a half-way house, and
placing it in the category of an outside station.
191. The plan of our work takes us necessarily into the air, for
The scope of these the sea derives from the winds some of the most
researches.  striking features in its physical geography. Without a knowledge of the winds, we can neither understand the
navigation of the ocean, nor make ourselves intelligently acquainted with the great highways across it. As with the land,
so with the sea; some parts of it are as untraveled and as unknown as the great Amazonian wilderness of Brazil, or the inland
basins of Central Africa. To the south of a line extending from
Cape Horn to the Cape of Good Hope (Plate VIII.) is an immense waste of waters. None of the commercial thoroughfares




70        THE PHYSICAL GEOGRAPHY OF THE SEA.
of the ocean lead through it; only the adventurous whaleman
finds his way there now and then in pursuit of his game; but for
all the purposes of science and navigation, it is a vast unknown
region. Now, were the prevailing winds of the South Atlantic
northerly or southerly, instead of easterly or westerly, this unplowed sea would be an oft-used thoroughfare. Nay, more, the
sea supplies the winds with food for the rain which these busy
messengers convey away from the ocean to "the springs in the
valleys which run among the hills." To the philosopher, the
places which supply the vapors are as suggestive and as interesting for the instruction they afford, as the places are upon which
the vapors are showered down. Therefore, as he who studies the
physical geography of the land is expected to make himself acquainted with the regions of precipitation, so he who looks into
the physical geography of the sea should search for the regions
of evaporation, and for those springs in the ocean which supply
the reservoirs among the mountains with water to feed the rivers; and, in order to conduct this search properly, he must consult the winds, and make himself acquainted with their " circuits."
Hence, in a work on the Physical Geography of the Sea and its
Meteorology, we treat also of the ATMOSPHERE.




~ 200, 201.         THE ATMOSPHERE.                     71
CHAPTER IV.
~ 200-261.-THE ATMOSPHERE.
200. THERE is no employment more ennobling to man and
Likened to a ma- his intellect than to trace the evidences of design
chine.      and purpose, which are visible in many parts of the
creation. Hence, to the right-minded mariner, and to him. who
studies the physical relations of earth, sea, and air, the atmosphere
is something more than a shoreless ocean, at the bottom of which
he creeps along. It is an envelope or covering for the dispersion
of light and heat over the surface of the earth; it is a sewer into
which, with every breath we draw, we cast vast quantities of
dead animal matter; it is a laboratory for purification, in which
that matter is recompounded, and wrought again into wholesome and healthful shapes; it is a machine (~ 191) for pumping up all the rivers from the sea, and for conveying the water
from the ocean to their sources in the mountains; it is an inexhaustible magazine, marvelously stored. Upon the proper working of this machine depends the well-being of every plant and
animal that inhabits the earth. How interesting, then, ought not
the study of it to be! An examination of the uses which plants
and animals make of the air is sufficient to satisfy any reasoning
mind in the conviction that when they were created, the necessity
of this adaptation was taken into account. The connection between any two parts of an artificial machine that work into each
other, does not render design in its construction more patent than
is the fact that the great atmospherical machine of our planet was
constructed by an Architect who designed it for certain purposes;
therefore the management of it, its movements, and the performance of its offices, can not be left to chance. They are, we may
rely upon it, guided by laws that make all parts, functions, and
movements of this machinery as obedient to order and as harmonious as are the planets in their orbits.
201. An examination into the economy of the universe will be
The air and the sufficient to satisfy the well-balanced minds of obocean governed by
stable laws.    servant men that the laws which govern the atmos



72        THE PHYSICAL GEOGRAPHY OF THE SEA.
phere and the laws which govern the ocean (~ 164) are laws which
were put in force by the Creator when the foundations of the
earth were laid, and that therefore they are laws of order; else,
why should the Gulf Stream, for instance, be always where it is,
and running from the Gulf of Mexico, and not somewhere else,
and sometimes running into it? Why should there be a perpetual drought in one part of the world, and continual showers in
another? Or why should the conscious winds ever heed the voice
of rebuke, or the " waves of the sea clap their hands with joy?"
202. To one who looks abroad to contemplate the agents of
Importance of ob- nature, as he sees them at work upon our planet,
serving the works of
nature.      no expression uttered or act performed by them is
without meaning. By such an one, the wind and rain, the vapor
and the cloud, the tide, the current, the saltness, and depth, and
warmth, and color of the sea, the shade of the sky, the temperature of the air, the tint and shape of the clouds, the height of the
tree on the shore, the size of its leaves, the brilliancy of its flowers-each and all may be regarded as the exponent of certain
physical combinations, and therefore as the expression in which
Nature chooses to announce her own doings, or, if we please, as
the language in which she writes down or elects to make known
her own laws. To understand that language and to interpret
aright those laws is the object of the undertaking which we now
have in hand. No fact gathered from such a volume as the one before us can therefore come amiss to those who tread the walks of
inductive philosophy; for, in the hand-book of nature, every such
fact is a syllable; and it is by patiently collecting fact after fact,
and by joining together syllable after syllable, that we may finally
seek to read aright from the great volume which the mariner at
sea as well as the philosopher on the mountain each sees spread
out before him.
203. There have been examined at the Observatory more than
Materials for this a million of observations on the force and direction
chapter.     of the winds at sea.*  The discussion of such a
mass of material has thrown much light upon the circulation of
the atmosphere; for, as in the ocean (~ 201), so in the air, there is
a regular system of circulation.
204. Before we proceed to describe this system, let us point out
* Nautical Monograph, No. 1, 1859.




~ 204.               THE ATMOSPHERE.                      73
Different belts of the principal belts or bands of wind that actual obwinds.       servation has shown to exist at sea, and which, with
more or less distinctness of outline, extend to the land also, and
thus encircle the earth. If we imagine a ship to take her departure from Greenland for the South Shetland Islands, she will, between the parallels of 60~ north and south, cross these several
bands or belts of winds and calms nearly at right angles, and in
the following order: (1.) At setting out she will find herself in
the region of southwest winds, or counter trades of the northcalled counter because they blow in the direction whence come
thee trade-winds of their hemisphere.  (2.) After crossing 50~,
and until reaching the parallel of 35~ N., she finds herself in the
belt of westerly winds, a region in which winds from the southwest and winds from the northwest contend for the mastery, and
with nearly equal persistency. (3.) Between 350 and 30~, she finds
herself in a region of variable winds and calms; the winds blowing all around the compass, and averaging about three months
from each quarter during the year. Our fancied ship is now in
the " horse latitudes."  Hitherto winds with westing in them have
been most prevalent; but, crossing the calm belt of Cancer, she
reaches latitudes where winds with easting become more prevalent. (4.) Crossing into these, she enters the region of northeast
trades, which now become the prevailing winds, until she reaches
the parallel of 10~ N., and enters the equatorial calm belt, which,
like all the other wind-bands, does not hold stationary limits.
(5.) Crossing the parallel of 5~ N., she enters where the southeast
trades are the prevailing winds, and so continue until the parallel
of 30~ S. is reached. (6.) Here is the calm belt of Capricorn,
where, as in that of Cancer (3), she again finds herself in a region
of shifting winds, light airs, and calms, and where the winds with
westing in them become the prevailing winds. (7.) Between the
parallels of 35~ and 40~ S., the northwest and southwest winds
contend with equal powers for the mastery. (8.) Crossing 40~,
the counter-trades (1)-the northwest winds of the southern hemisphere-become the prevailing winds, and so remain, as far toward the south pole as our observations at sea extend.
Such are the most striking movements of the winds at the surface of the sea. But, in order to treat of the general system of
atmospherical circulation, we should consider where those agents




74        THE PHYSICAL GEOGRAPHY OF THE SEA.
reside which impart to that system its dynamical force. They evidently reside near the equator on one side, and about the poles on
the other. Therefore, if, instead of confining our attention to the
winds at the surface, and their relative prevalence from each one
of the four quarters, we direct our attention to the upper and
lower currents, and to the general movements back and forth between the equator and the poles, we shall be enabled the better
to understand the general movements of this grand machine.
205. Thus treating the subject, observations show that from the
Thetrade-windbelts. parallel of about 30~ or 350 north and south to the
equator, we have, extending entirely around the earth, two zones
of perpetual winds, viz., the zone of northeast trades on this side,
and of southeast on that. With slight interruptions, these winds
blow perpetually, and are as steady and as constant as the currents of the Mississippi River, always moving in the same direction (Plate I.) except when they are turned aside by a desert here
and there to blow as monsoons, or as land and sea breezes. As
these two main currents of air are constantly flowing from the
poles toward the equator, we are safe in assuming that the air
which they keep in motion must return by some channel to the
place toward the poles whence it came in order to supply the
trades. If this were not so, these winds would soon exhaust the
polar regions of atmosphere, and pile it up about the equator, and
then cease to blow for the want of air to make more wind of.
206. This return current, therefore, must be in the upper reThe return current. gions of the atmosphere, at least until it passes over
those parallels between which the trade-winds are usually blowing on the surface. The return current must also move in the
direction opposite to that wind the place of which it is intended
to supply. These direct and counter currents are also made to
move in a sort of spiral or loxodromic curve, turning to the west
as they go from the poles to the equator, and in the opposite direction as they move from the equator toward the poles. This
turning is caused by the rotation of the earth on its axis.
207. The earth, we know, moves from west to east. Now if
Effect of diurnal ro- we imagine a particle of atmosphere at the north
tation on the course
of thetrade-winds. pole, where it is at rest, to be put in motion in a
straight line toward the equator, we can easily see how this particle of air, coming from the very axis of diurnal rotation, where




~ 208, 209.          THE ATMOSPHERE.                      75
it did not partake of the diurnal motion of the earth, would, in
consequence of its vis inertice, find, as it travels south, the earth
slipping from under it, as it were, and thus it would appear to be
coming from the northeast and going toward the southwest; in
other words, it would be a northeast wind. The better to explain, let us take a common terrestrial globe for the illustration.
Bring the island of Madeira, or any other place about the same
parallel, under the brazen meridian; put a finger of the left hand
on the place; then, moving the finger down along the meridian
to the south, to represent the particle of air, turn the globe on its
axis from west to east, to represent the diurnal rotation of the
earth, and when the finger reaches the equator, stop. It will now
be seen that the place on the globe under the finger is to the
southward and westward of the place from which the finger started; in other words, the track of the finger over the surface of
the globe, like the track of the particle of air upon the earth, has
beenfrom the northward and eastward. On the other hand, we
can perceive how a like particle of atmosphere that starts from
the equator, to. take the place of the other at the pole, would, as it
travels north, in consequence of its vis inertice, be going toward the
east faster than the earth. It would therefore appear to be blowing from the southwest, and going toward the northeast, and exactly in the opposite direction to the other. Writing south for
north, the same takes place between the south pole and the equator.
208. Such is the process which is actually going on in nature;
Two grand systems and if we take the motions of these two particles as
of currents.  the type of the motion of all, we shall have an illustration of the great currents in the air (~ 204), the equator being near
one of the nodes, and there being at least two systems of currents,
an upper and an under, between it and each pole. Halley, in his
theory of the trade-winds, pointed out the key to the explanation,
so far, of the atmospherical circulation; but, were the explanation
to rest here, a northeast trade-wind extending from the pole to the
equator would satisfy it; and were this so, we should have, on the
surface, no winds but the northeast trade-winds on this side, and
none but southeast trade-winds on the other side, of the equator.
209. Let us return now to our northern particle (~ 207), and
From the Pole to follow it in a round from the north pole across the
350-300.    equator to the south pole, and back again. Setting




76        THE PHYSICAL GEOGRAPHY OF THE SEA.
off from the polar regions, this particle of air, for some reason
which does not appear. to have been very satisfactorily explained
by philosophers, instead of traveling (~ 208) on the surface all the
way from the pole to the equator, travels in the upper regions of
the atmosphere until.it gets near the parallel of 300-35~. Here it
meets, also in the clouds, the hypothetical particle that is coming
from the south, and going north to take its place.
210. About this parallel of 300-35~ north, then, these two parThe "horse lati- tides press against each other with the whole amount
tudes."      of their motive power, and produce a calm and an
accumulation of atmosphere: this accumulation is sufficient to
balance the pressure of the two winds from the north and south.
From under this bank of calms, which seamen call the "horse latitudes," two surfacer currents of wind are ejected or drawn out;
one toward the equator, as the northeast trades, the other* toward the pole, as the southwest "passage-winds," or countertrades. These winds come out at the lower surface of the calm
region, and consequently the place of the air borne away in this
manner must be supplied, we may infer, by downward currents
from the superincumbent air of the calm region. Like the case
of a vessel of water which has two streams from opposite directions running in at the top, and two of equal capacity discharging
in opposite directions at the bottom, the motion of the water
would be downward; so is the motion of the air in this calm zone.
211. The barometer, in this calm region, stands higher than it
Thebarometerthere. does either to the north or to the south of it; and
this is another proof as to the accumulation of the atmosphere
here, and pressure from its downward motion. And because the
pressure under this calm belt is greater than it is on either side
of it, the tendency of the air will be to flow out on either side;
therefore, supposing we were untaught by observation, reason
would teach us to look for the prevailing winds on each side of
this calm belt to be from it.
212. Following our imaginary particle of air, however, from
The equatorial calm the north across this calm belt of Cancer, we now
belt.       feel it moving on the surface of the earth as the
northeast trade-wind; and as such it continues till it arrives near
the equator, where it meets a like hypothetical particle, which,
starting from the south at the same time the other started from




~ 213-215.           THE ATMOSPHERE.                      77
the north pole, has blown as the southeast trade-wind.  Here, at
this equatorial place of meeting, there is another conflict of winds
and.another calm region, for a northeast and southeast wind can
not blow at the same time in the same place.  The two particles
have been put in motion by the same power; they meet with equal
force; and, therefore, at their place of meeting, they are arrested
in their course. I Here, therefore, there is a calm belt, as well as
at Capricorn and Cancer. Warmed now by the heat of the sun,
and pressed on each side by the whole force of the northeast and
southeast trades, these two hypothetical particles, taken as the
type of the whole, cease to move onward and ascend. This operation is the reverse of that which took place at the meeting (~ 210)
near the parallel of 300-35~.
213. This imaginary particle then, having ascended to the upThe calm belt' of per regions of the atmosphere again, travels there
Capricorn.  counter to the southeast trades, until it meets, near
the calm belt of Capricorn, another particle from the south pole;
here there is a descent as before (~ 210); it then (~ 211) flows on
toward the south pole as a surface wind from the northwest.
214. Entering the polar regions obliquely, it is pressed upon
Thepolar calmsand by similar particles flowing in oblique currents
the return current. across every meridian; -and here again is a calm
place or node; for, as our imaginary particle approaches the parallels near the polar calms more and more obliquely, it, with all
the rest, is whirled about the pole in a continued circular gale;
finally, reaching the vortex or the calm place, it is carried upward to the regions of atmosphere above, whence it commences
again its reflow to the north as an upper current, as far as the
calm belt of Capricorn; here it encounters (~ 213) its fellow from
the north (~ 207); they stop, descend, and flow out as surface
currents (~ 210), the one with which the imagination is traveling,
to the equatorial calm as the southeast trade-wind; here (~ 212)
it ascends, traveling thence to the calm belt of Cancer as an upper
current counter to the northeast trades. Here (~ 210 and 209) it
ceases to be an upper current, but, descending (~ 210), travels on
with the southwest passage-winds toward the pole.
215. Now the course we have imagined an atom of air to
Diagram of the take, as illustrated by the " diagram of the winds,"
winds-PlateI.  is this: an ascent in a place of calms about the




'78       THE PHYSICAL GEOGRAPHY OF THE SEA.
north pole, as at V, P; an efflux thence as an upper current,
A, B, C, until it meets I, S (also an upper current) over the calms
of Cancer. Here there is supposed to be a descent, as shown by
the arrows C D, S T. This current, A, B, C, D, from the pole,
now becomes the northeast trade-wind, D, E, on the surface, until
it meets the southeast trades, 0, Q, in the equatorial calms, where
it ascends as E, F, and travels as F, G with the upper current to
the calms of Capricorn, thence as H, J, K, with the prevailing
northwest surface current to the south pole, thence up with the
arrow P, and around with the hands of a watch, and back, as indicated by the arrows along L, M, N, O, Q, R, S, T, U, V.
216. The Bible frequently makes allusion to the laws of naAs ourknowledge of ture, their operation and effects. But such alluthe laws of nature sions are often so wrapped in the folds of the
has   increased,  so
ofthve ou reading peculiar and graceful drapery with which its lanproved.      guage is occasionally clothed, that the meaning,
though peeping out from its thin covering all the while, yet lies
in some sense concealed, until the lights and revelations of science are thrown upon it; then it bursts out and strikes us with
exquisite force and beauty. As our knowledge of nature and
her laws has increased, so has our understanding of many passages
in the Bible been improved. The Psalmist called the earth'" the
round world;" yet for ages it was the most damnable heresy for
Christian men to say the world is round; and, finally, sailors circumnavigated the globe, proved the Bible to be right, and saved
Christian men of science from the stake.  " Canst thou bind the
sweet influences of Pleiades?"  Astronomers of the present day,
if they have not answered this question, have thrown so much
light upon it as to show that, if ever it be answered by man, he
must consult the science of astronomy. It has been recently all
but proved, that the earth and sun, with their splendid retinue
of comets, satellites, and planets, are all in motion around some
point or centre of attraction inconceivably remote, and that that
point is in the direction of the star Alcyon, one of the Pleiades! Who but the astronomer, then, could tell their "sweet influences?"  And as for the general system ofatmospherical circulation which I have been so long endeavoring to describe, the
Bible tells it all in a single sentence: "The wind goeth toward
the south, and turneth about unto the north; it whirleth about




~ 217, 218.           THE ATMOSPHERE.                        79
continually, and the wind returneth again according to his circuits."-Eccl., i., 6.
217. Of course, as the surface winds, XI, J, K and T, U, V, apSloughing off from proach the poles, there must be a sloughing off, if I
the counter trades. may be allowed the expression, of air from them, in
consequence of their approaching the poles.  For as they near the
poles, the parallels become smaller and smaller, and the surface
current must either extend much higher up, and blow with greater
rapidity, or else a part of it must be sloughed off above, and so
turn back before reaching the calms about the poles. The latter
is probably the case. Such was the conjecture. Subsequent investigations* have, by proving the converse, established its correctness, and in this way: they show that the southeast trade-winds,
as in the Atlantic, blow, on the average, during the year, 124 days
between the parallels of 25~ and 30~ S., and that as you approach
the equator their average annual duration increases until you
reach 5~ S. Here between 5~ and 10~ S. they blow on the average for 329 out of the 365 days.
218. Now the question may be asked, Where do the supplies
The air which sup- which furnish air for these winds for 329 days come
plies the southeast
trade-wind in the from?  The "trades" could not convey this fresh
band- 5~ does not
cross theband250. supply of air across the parallel of 250 S. during
the time annually allotted for them to blow in that latitude.
They can not for these reasons: (1.) Because the trade-winds in
lat. 5~ are stronger than they are in lat. 25~, and therefore, in
equal times, they waft larger volumes of air across 5~ than they
do across 25~. (2.) Because the girdle of the earth near the equator is larger than it is farther off, as at 25~; therefore, admitting
equal heights and velocities for the wind at the two parallels, it
would, in equal times, bear more air across the one of larger circumference.  Much less, therefore, can the air which crosses the
parallel of 25~ S. annually in the 124 trade-wind days of that
latitude be sufficient to supply the trade-winds with air for their
329 days in lat. 5~.  Whence comes the extra supply for them in
this latitude? (3.) Of all parts of the ocean the trade-winds obtain their best development between 5~ and 10~ S. in the Atlantic Ocean, for it is there only that they attain the unequaled annual average duration of 329 days. But referring now to the
* Nautical Monographs, No. 1, Observatory, Washington, October, 1859.




80         THE PHYSICAL GEOGRAPHY OF THE SEA.
average annual duration of the southeast trade-wind in all seas,
we may, for the sake of illustration, liken this belt of winds which
encircles the earth, say between the parallels of 5~ and 25~ S., to
the frustum of a hollow cone, with its base toward the equator.
219. Now, dividing the winds into only two classes, as winds
Winds with north- with northing and winds with sougthing in them, acting and winds wvith ual observations show, taking the world around,
southing in them                     tkn               aon
contrasted.  that winds having southing in them blow into the
southern or smaller end of this cone for 209 days annually, and
out of the northern and larger end for 286 days.?  They appear
(~ 221) to come out of the larger end with greater velocity than
they enter the smaller end. But we assume the velocity at going
in and at coming out to be the same, merely for illustration.
During the rest of the year, either winds with northirig in them
are blowing in at the big end, or out at the little end of the imaginary cone, or no wind is blowing at all: that is, it is calm. Now,
if we suppose, merely for the sake of assisting farther in the illustration, that these winds with northing and these winds with
southing move equal volumes of air in equal times, we may subtract the days of the one from the days of the other, and thus
ascertain how much more air comes out at one end than goes in
at the other of our frustum.  Winds with northing in them blow
in at the big end for 72 days, and out at the little end for 146 days
annually: Now, if we subtract the whole number of winds (146)
with northing in them  that blow out at the south or small end,
from the whole number (209) with southing in them that blow
in, we shall have for the quantity that is to pass through, or go
from the parallel of 25~ to 5~0, the value expressed by the transporting power of the southeast trade-winds at latitude 25~ for 63
days (209-146=63).  In like manner we obtain, in similar
terms, an expression for the volume which these winds bring out
at the large or equatorial end, and find it to be as much air as the
southeast trade-winds can transport across the parallel of 5~ S. in
214 days (286-72-214).  Again,
220. The southeast trade-winds, as they cross the parallel of
5~ and come out of this belt, appear to be strongert than they
* Nautical Monographs, No. 1, " The Winds of the Sea," Observatory, Washington, 1859.
t The force of the trade-winds, as determined by the average speed of 2235 vessels




~ 221-223.             THE ATMOSPHERE.                          81
Southeast trade- are when they enter it. But assuming the velocity
tinds st'onger'Iear at each parallel to be the same, we have (~ 219)
its.          just three times as much air with southing in it coming
out of this belt on the equatorial side as with southing in it we find
entering (~ 218) on the polar side.  From this it is made plain
that if all the air, whether from  the southward and eastward, or
from the southward and westward, which enters the southeast tradewind belt near its polar borders, were to come out at its equatorial
edge as southeast trade-winds, there would not be enough, by the
volume required to supply them for 151 days (214-63  151), to
keep up such a constant current of air as we find the southeast
trade-winds actually conveying across this parallel of 5~ S.
221. The average speed which vessels make in sailing through
Speed of vessels the trade-winds in different parts of the world has
through the tradewinds.        been laboriously investigated at the National Observatory.* By this it appears that their average speed through
the southeast trade-winds of the Atlantic is, between the parallels
of 5~ and 10~, 6.1 knots an hour, and 5.7 between 25~ and 30~.
222. All these facts being weighed, they indicate that the volThe qulestion,Whence ume of air which investigations show that the
aree the southeas southeast trade-winds of the world annually waft
trade-winds supplied
with air? answered.  across the parallels of 10~-5~ S. in 285t days-for
that is their average duration —is at least twice as great as the volume which they annually sweep across the parallel of 25~ in 139
days, which is their average here.  Hence the answer to the question (~ 218), Whence comes the excess? is, it can only come from
above, and in this way, viz.: the southeast trade-winds, as they
rush from 25~ S. toward the equator, act upon the upper air like
an under-tow. Crossing, as they approach the equator, parallels
of larger and larger circumference, they draw down and turn back
from the counter current above air enough to supply pabulum to
larger and larger, and to stronger and stronger currents of wind.
223. The air which the trade-winds pour into the equatorial
Whither it goes. calm belt (~ 213) rises up, and has to flow off as an
sailing through them, is greater between 5~ and 10~ S. than it is between 250 and
300 S. —lfaury's Sailing Directions, 1859.
* See "Average Force of the Trade-winds," p. 857, vol. ii., Sth ed., Maury's
Sailing Directions, 1859.
t Nautical Monographs, Plate I., No. 1, "The winds at sea."




82          THE PHYSICAL GEOGRAPHY OF THE SEA.
upper current, to make room for that which the trade-winds are
continually pouring in below. They bring it from toward the poles
— back, therefore, toward the poles the upper currents must carry
it. On their journey they cross parallel after parallel, each smaller than the other in circumference. There is, therefore, a constant
tendency with the air that these upper currents carry polarward
to be crowded out, so to speak-to slough off and turn back.
Thus the upper current is ever ready to supply the trade-winds,
as they approach the equator, with air exactly at the right place,
and in quantities just sufficient to satisfy the demand.
224. This upper air, having supplied the equatorial cloud-ring
How it is drawn (~ 514) with vapor for its clouds, and with moistdown from above.  ure for its rains, flows off polarward as comparatively dry air.  The dryest air is the heaviest.  This dry and
heavy air is therefore the air most likely to be turned back with
the trade-winds, imparting to them that elasticity, freshness, and
vigor for which they are so famous, and which help to make them
so grateful to man and beast in tropical climates. The curved
arrows, fg and f g', r s and r' s', are intended to represent, in the
a" diagram of the winds" (Plate I.), this sloughing off and turning
back of air from the upper currents to the trade-winds below.
225. According to investigations which are stated at length in
Velocity ofsoutheast Maury's Sailing Directions, on his Wind and Curshown to be greater rent Charts, and in the Monographs of the Observthan northeast tradewinds.        atory, the average strength and annual duration of
the southeast trade-winds of the Atlantic may be thus stated for
every band of 5~ of latitude in breadth, from 300 to the equator.
For the band between
Ann. duration.    Force.       No. of obs.
30~ and 250 S........... 124 days.  5.6 miles.*   19,817
250 and 20~.............. 157 "   5.7 "          20,762
200 and 150~.............. 244     5.9           17,844
15~ and 10 ~............... 295 "  6.3  "         14,422
100 and 50................ 329  "  6.1 "c         13,714
5~ and 00.................. 314  "  6.0  "         15,463
It thus appears that the southeast trade-winds of the Atlantic
blow with most regularity between 10~ and 50, and with most
force between 10~ and 15~.
226. On the polar side of 350-40~, and in the counter trades
* Distance per hour that vessels average while sailing through it.




~ 227-229.            THE ATMOSPHERE.                        83
The air sloughed off (~ 204 [7] ), a different process of sloughing off and
from the counter
trades,moistair.  turning back is going on.  Here the winds are
blowing toward the poles; they are going from parallels of large
to parallels of smaller circumference, while the upper return current is doing the reverse; it is widening out with the increasing
circumference of parallels, and creating room for more air, while
the narrowing current below is crowding out and sloughing off
air for its winds.
227. In the other case (~ 224), it was the heavy dry air that
The air sloughed off was sloughed off to join the winds below. In this
from the upper trade
current dry.  case it is the moist and lightest air that is crowded
out to join the current above.
228. This is particularly the case in the southern hemisphere,
Tie meteorological where, entirely around between the parallels of 40~
inufluences of ascend- and 60~ or 65~, all, or nearly all, is water.  In this
lug columns of moist
air.          great austral band the winds are in contact with
an evaporating surface all the time. Aqueous vapor is very much
lighter than atmospheric air; as this vapor rises, it becomes entangled with the particles of air, some of which it carries up with
it, thus producing, through the horizontal flow of air with the
winds, numerous little ascending columns. As these columns of
air and vapor go up, the superincumbent pressure decreases, the
air expands and cools, causing precipitation or condensation of
the vapor.  The heat that is set free during this process expands
the air still further, thus causing here and there in those regions,
and wherever it may chance to be raining, intumescenses, so to
speak, from the wind stratum below; the upper current, sweeping over these protuberances, bears them off in its course toward the equator, and thus we have another turning back-a constant mingling.  The curved arrows, hj k and h'j' c', are intendled, on the " diagram of the winds" (Plate I.), to represent this rising up from the counter trades and turning back with the upper
current.
229. Let us imagine the air to be visible, that we could see
Supposing the air these different strata of winds, and the air as it is
visible, the spectacle sloughedof from  one stratum  to join the other.
that would be pre-     o  f     o   sa                t 
sente~dt    r We can only liken  the spectacle that would be preupper and lower currents.       sented between the upper and the lower stratum of
these winds to the combing of a succession of long waves as




84          THE PHYSICAL GEOGRAPHY OF THE SEA.
they come rolling in from  sea, and, one after another, breaking
upon the beach. They curl over and are caught up, leaving foam
from their white caps behind, but nevertheless stirring up the sea
and mixing up its waters so as to keep them all alike.
230. If the ordinances of nature require a constant circulation
The importance of and continual mixing up of the water in the sea,
atmospherical circulation.        that it become not stagnant, and that it may be
kept in a wholesome state for its inhabitants, and subserve properly the various offices required of it in the terrestrial economy,
how much more imperative must they not be with the air?  It is
more liable to corruption than water; stagnation is ruinous to it.
It is both the sewer and the laboratory for the whole animal and
vegetable kingdoms.  Ceaseless motion has been givenlzto it; perpetual circulation and intermingling of its ingredients are required
of it. Personal experience teaches us this, as is manifest in the
recognized necessity of ventilation in our buildings-the wholesome influences of fresh air, and the noxious qualities of " an at-.rmosphere that has no circulation."  Hence, continual mixing up
of particles in the atmosphere being required of the winds in their
circuits, is it possible for the human mind to conceive of the appointment of "circuits" for them  (~ 216) which are so admirably
designed and exquisitely adapted for the purpose as are those
which this view suggests?
231. As a physical necessity, the vertical circulation of the air
Its vertical move- seems to be no less important than its horizontal
ments — howf produced.         movements, which we call wind.  One begets the
other.  The wind, when it blows across parallels of latitude-as
it always must, except at the equator, for it blows in arcs of great
circles, and not in small ones*-creates a vertical circulation
* The tendency of all bodies, when put in motion on the surface of the earth, is,
whether fluid, solid, or gaseous, to go from the point of departure to the point of destination by the shortest line possible; and this, when the motion is horizontal, is an
are of a great circle. If we imagine a partial vacuum to be formed at the north
pole, we can readily enough perceive that the wind for 50~, 100, 200 of polar distance,
all around, would tend to rush north and strive to get there along the meridiansarcs of great circles. This would be the case whether the earth be supposed to be
with or without diurnal rotation, or motion of any sort. Now suppose the place of
rarefaction to be any where away from the poles, then draw great circles to a point
in the middle of it, and the air all around would, in rushing into the vacuum, seek
to reach it by these great circles. Force may turn it aside, but such is the tendency (~ 120).




~ 232-234.           THE ATMOSPHERE.                        85
either by dragging down air from the upper regions (~ 224), or
by sloughing it off and forcing it up from the lower (~ 228), according as the wind is approaching the pole or the equator.
232. Indeed, the point may be well made whether the horizonVerticalandairizon- tal circulation of the air be not dependent upon
tal movements in the
air consequents of, and a consequent of its vertical circulation-so nearand dependent upon
eac.h other.    ly allied are the two motions in their relations as
cause and effect. Upward and downward movements in fluids
are consequent upon each other, and they involve lateral movements. The sea, with its vapor, is the great engine which gives
upward motion in the air (~ 227). As soon as aqueous vapor is
formed it rises; the air resists its ascent; but it is lighter than
the air, therefore it forces the resisting particles of air up along
with it, and so produces ascending columns in the atmosphere.
The juxta air comes in to occupy the space which that carried up
by the vapor left behind it, and so there is a wind produced.
The wind arising from this source alone is so slight generally, as
scarcely to be perceived. But when the ascending vapor is condensed, and its latent heat liberated and set free in the upper air,
we often have the most terrific storms.
233. Now suppose the surface from which this vapor rises, or
Cold belts.  on which it is condensed, be sufficiently large to
produce a rush of wind from afar; suppose it, moreover, to be an
oblong lying east and west somewhere, for example, in the temperate zone of the northern hemisphere. The wind, that comes
rushing in from  the south side will be in the category of the
counter trades of the southern hemisphere (~ 228), going from
larger to smaller parallels, and giving rise to ascending columns;
while that from the northern side, moving in the opposite direction, is, like the trade-winds (~ 223), bringing down air from
above.
234. By the motion of the clouds upper currents of wind are
The upper currents discerned in the sky.  They are arranged in layers
-their numbers and
offices.     or strata one above the other.  The clouds of each
stratum are carried by its winds in a direction and with a velocity
peculiar to their stratum.  HIow many of these superimposed currents of wind there may be between the top and bottom of the
atmosphere we know not.  As high up as the cloud-region several are often seen at the same time.  They are pinions and




86         THE PHYSICAL GEOGRAPHY OF THE SEA.
rachets in the atmospherical machinery. We have seen (~ 230)
some of their uses: let us examine them more in detail. Now,
as the tendency of air in motion is (~ 120) to move in arcs of
great circles, and as all great circles that can be drawn about the
earth must cross each other in two points, it is evident that the
particles of the atmosphere which are borne along as wind must
have their paths all in diverging or converging lines, and that consequently each wind must either be, like the trade-winds (~ 222),
drawing down and sucking in air from above, or, like the counter trades (~ 226), crowding out and forcing it off into the upper
currents.
235. This tendency to move in great circles is checked by the
Tendency of air forces of diurnal rotation, or by the pressure of the
ohen pu' in mtheplan wind when it blows toward a common centre as in
to move in the plane    c
of a great circle. a cyclone. In no case is it entirely overcome in its
tendency, but in all, it is diverted from the great circle path and
forced to take up its line of march either in spirals about a point
on the surface of the earth, or in loxodromics about its axis. In
either case the pushing up or pulling down of the combing, curdling air from layer to layer is going on.
236. Thus the laws of motion, the force of gravity, and the
The results upon its figure of the earth all unite in requiring every wind
circulation of this
tendency.    that blows either to force air up from the surface
into the regions above, or to draw it down to the earth from the
crystal vaults of the upper sky. Add to these the storm-kingtraversing the air, he thrusts in the whirlwind or sends forth the
cyclone, the tornado, and the hurricane to stir up and agitate, to
mix and mingle the whole in one homogeneous mass. By this
perpetual stirring up, this continual agitation, motion, mixing, and
circulation, the airy covering of the globe is kept in that state
which the well-being of the organic world requires. Every breath
we draw, every fire we kindle, every blade of grass that grows or
decays, every blaze that shines and burns adds something that is
noxious, or takes something that is healthful away from the surrounding air. Diligent, therefore, in their offices must the agents
be which have been appointed to maintain the chemical status of
the atmosphere, to preserve its proportions, to adjust its ingredients, and to keep them in that state of admixture best calculated
to fit it for its purposes.




~ 237, 238.          THE ATMOSPHERE.                      87
237. Several years ago the French Academy sent out bottles
Experiments by the and caused specimens of air from various parts of
French Academy. the world to be collected and brought home to be
analyzed. The nicest tests which the most skillful chemists could
apply were incapable of detecting any, the slightest, difference as
to ingredients in the specimens from either side of the equator;
so thorough.in the performance of their office are these agents.
Nevertheless, there are a great many more demands on the atmosphere by the organic world for pabtulunz in one hemisphere
than in the other; and consequently a great many more inequalities for these agents to restore in one than in the other. Of the
two, the land of our hemisphere most teems with life, and here
the atmosphere is most taxed. Here the hearth-stone of the human family has been laid. Here, with our fires in winter and our
crops in summer, with our work-shops, steam-engines, and fiery
furnaces going night and day-with the ceaseless and almost limitless demands which the animal and vegetable kingdoms are
making upon the air overhead, we can not detect the slightest
difference between atmospherical ingredients in different hemispheres; and yet, notwithstanding the compensations and adjustments between the two kingdoms of the organic world, there are
almost in every neighborhood causes at work which would produce a difference were it not for these ascending and descending
columns of air; for the obedient winds; for this benign system
of circulation; these little cogs and rachets which have been provided for its perfect working. The study of its mechanism is
good and wholesome in its influences, and the contemplation of
it well calculated to excite in the bosom of right-minded philosophers the deepest and the best of emotions.
238. Upon the proper adjustments of the dynamical forces
Iownsupplies offresh which keep up these ceaselesss movements the life of
air are brought down
from the upper sky. organic nature depends. If the air that is breathed
were not taken away and renewed, warm-blooded life would
cease; if carbon, and oxygen, and hydrogen, and water were not
in due quantities dispensed by the restless air to the flora of the
earth, all vegetation would perish for lack of food. That our
planet may be liable to no such calamity, power has been given
to the wayward wind, as it "bloweth where it listeth," to bring
down from the pure blue sky fresh supplies of life-giving air




88        THE PHYSICAL GEOGRAPHY OF THE SEA.
wherever it is wanted, and to catch up from the earth wherever
it may be found, that which has become stale; to force it up,
there to be deflagrated among the clouds, purified and renovated
by processes known only to Him whose ministers they are. The
slightest change in the purity of the atmosphere, though it may
be too slight for recognition by chemical analysis in the laboratory, is sure to be detected by its effects upon the nicer chemistry.
of the human system, for it is known to be productive of disease and death. No chemical tests are sensitive enough to tell us
what those changes are, but experience has taught us the necessity of ventilation in our buildings, of circulation through our
groves. The cry in cities for fresh air from the mountains or the
sea, reminds us continually of the life-giving virtues of circulation.
Experience teaches that all air when pent up and deprived of
circulation becomes impure and poisonous.
239. How  minute, then, pervading, and general, benignant,
Beautifulandbenign sure, and perfect must be that system of circulation
arrangements.    which invests the atmosphere and makes the " whole
world kin 1"  In the system of vertical circulation which I have
been endeavoring to describe, we see, as in a figure, the lither sky
filled with crystal vessels continually ascending and descending between the bottom and the top of the atmospherical ocean full of
life-giving air; these buckets are let down by invisible hands from
above, and, as they are taken up again, they carry off from the
surface, to be purified in the laboratory of the skies, phials of
mephitic vapors and noxious gases, with the dank and deadly
air of marshes, ponds, and rivers.
240. Whenever, by study and research, we succeed in gaining
Their influences up- an insight, though never so dim, into any one of
on the mind.    the offices for which any particular part of the
physical machinery of our planet was designed by the great Architect, the mind is enriched with the conviction that it has comprehended a thought that was entertained at the creation. For
this reason the beautiful compensations which philosophers have
discovered in terrestrial arrangements are sources of never-failing
wonder and delight. How often have we been called on to admire the beautiful provision by which fresh water is so constituted that it expands from a certain temperature down to freezing! We recognize in the formation of ice on the top instead of




~ 241-243.            THE ATMOSPHERE.                     89
at the bottom of freezing water, an arrangement which subserves,
in manifold ways, wise and beneficent purposes. So, too, when
we discern in the upper sky (~ 234) currents of wind arranged in
strata one above the other, and running hither and thither in different directions, may we not say that we can here recognize also
at least one of the foreordained offices of these upper winds?
That by sending down fresh air and taking up foul, they assist
in maintaining the world in that state in which it was made and
for which it is designed-" a habitation fit for man?"
241. The phenomenon of cold belts or bands is often observed
The effect of down- in the United States, and I suppose in other parts of
ward currents in 
producing cold.  the world also; and here in these downward currents we have the explanation and the cause of sudden and severe
local spells of cold. These belts generally lie east and west rather than north and south, and we have often much colder weather
in them than we have even several degrees to the north of them.
The conditions required for one of these "cold snaps" appear to
be a north or northwest wind of considerable breadth from west
to east. As it goes to the south, its tendency is, if it reach high
enough, to bring down cold air from above in the manner of the
trade-winds (~ 238); and when the air thus brought down
chances to be, as it often is, dry and cold, we have the phenomenon of a cold belt, with warmer weather both to the north and the
south of it. While I write the thermometer is -4~ in Mississippi, lat. 32~, and they are having colder weather there than we have
either in Washington or Cincinnati, 70 farther to the north.
242. The winter "northers" of Texas sometimes bring down the
The winter northers cold air there with terrific effect. These bitter cold
of Texas.    winds are very severe at Nueces, in the coast country, or the southwest corner of Texas bordering the Gulf of
Mexico, lat. 27~.5. They are often felt to the west in Mexico,
but rarely in eastern or northern Texas. The fact that they are
not known in northern Texas goes to show that the cold they
bring is not translated by the surface winds from the north.
243. A correspondent in Nueces, lat. 27~ 36' N., long. 970 27'
Their severe cold. W., has described these winds there during the winter of 1859-60. They prevail from November to March, and commence with the thermometer about 80~ or 85~. A calm ensues on
the coast; black clouds roll up from the north; the wind is heard




90          THE PHYSICAL GEOGRAPHY OF THE SEA.
several minutes before it is felt; the thermometer begins to fall;
the cold norther bursts upon the people, bringing the temperature
down to 28~, and sometimes even to 25~, before the inhabitants
have time to change clothing and make fires. So severe is the
cold, so dry the air, that men and cattle have been known to perish in them.*  These are the winds which, entering the Gulf and
sucking up heat and moisture therefrom, still retain enough of
strength to make themselves terrible to mariners-they are the
far-famed northers of Vera Cruz.
244. We now see the general course of the " wind in his cirThe wind in his cir- cuits," as we see the general course of the water in
cuits.         a river.  There are many abrading surfaces, irregularities, &c., which produce a thousand eddies in the main stream;
yet, nevertheless, the general direction of the whole is not disturbed nor affected by those counter currents; so with the atmosphere
and the variable winds which we find here in this latitude. Have
I not, therefore, very good grounds for the opinion (~ 200) that
the " wind in his circuits," though apparently to us never so wayward, is as obedient to law and as subservient to order as were
the morning stars when first they " sang together?"
245. There are at least two forces concerned in driving the
Forces which propel wind through its circuits.  We have seen (~ 207)
the wind.      whence that force is derived which gives easting to
the winds as they approach the equator, and westing as they approach the poles; and allusion, without explanation, has been
made (~ 212) to the source whence they derive their northing and
their southing. Philosophers formerly held that the trade-winds
are drawn toward the equator by the influence of the direct rays
of the sun upon the atmosphere there. They heated it, expanded
it, and produced rarefaction, thereby causing a rush of the wind
both from the north and the south; and as they played with
greatest effect at the equator, there the ascent of the air and the
meeting of the two winds would naturally be.  Such was the
doctrine.
* "Two men," says Mr. M. A. Taylor, in a letter dated January 11th, 1860, at
Nueces, Texas, "were actually frozen to death within a few miles of this place this
winter in a norther. Animals seem to tell by instinct when the norther is coming,
and make their way from the open prairies to timber and other shelter, starting often on a run when the heat is not oppressive. This is when the change is to be sudden and violent. Many cattle, horses, and sheep are frozen to death at such times."




~ 246-248.            THE ATMOSPHERE.                         91
246. But the direct rays of the sun, instead of being most powEffect of the direct erful upon the air at the equator, is most powerful
heat of the sun upon
the trade-winds. where the sun is vertical; and if the trade-winds
were produced by direct heat alone from the sun, the place of
meeting would follow the sun in declination much more regularly
than it does. But, instead of so following the sun, the usual place
of meeting between the trade-winds is neither at the equator nor
where the sun is vertical. It is at a mean between the parallels
of 5~ and 10~ or 120 N. It is in the northern hemisphere, notwithstanding the fact that in the southern summer, when the sun
is on the other side of the line, the earth is in perihelion, and the
amount of heat received from the vertical ray in a day there is
very much greater (-1-) than it is when she is in aphelion, as in
our midsummer.  For this reason the southern summer is really
hotter than the northern; yet, notwithstanding this, the southeast
trade-winds actually blow the air away from under this hot southern sun, and bring it over into the northern hemisphere. They
cross over into the northern hemisphere annually, and blow between 00 and 5~ N. for 193 days,* whereas the northeast trades
have rarely the force to reach the south side of the equator at all.
247. By examining the log-books of vessels while sailing
The two systems of through the northeast and southeast trade-wind
trade-winds unequal belts, and comparing their rate of sailing, it has
both in force, dura-r
tion, andstability. been ascertained that ships sail faster with the
southeast than they do with the northeast trade-winds, and that
the southeast blow more days during the year than do the northeast trades.t  The logs of vessels that spent no less than 166,000
days in sailing through these two belts of wind show that the average sailing speed through the southeast trade-wind belt, which lies
between the equator and 30~ S., is about eight miles an hour, and
the average number of uninterrupted southeast trade-wind days
in the year is 227. For the northeast it is 183 days, with strength
enough to give ships an average speed of only 5.6 miles an hour.
Hence it appears that the two systems of trade-winds are very
unequal both as to force and stability, the southeast surpassing in
both.
248. MiIoreover, the hottest place within the trade-wind regions
* "The Winds of the Sea," Maury's Nautical Monographs, No. 1.
t See Maury's WVind and Current Charts, vol. ii., 8th edition, Sailing Directions.




92        THE PHYSICAL GEOGRAPHY OF THE SEA.
Effects of heat and is not at the equator, it is where these two winds
vapor.       meet (~ 246). Lieutenant Warley has collated from
the abstract logs the observations on the temperature of the air
made by 100 vessels, indiscriminately taken, during their passage
across the trade-wind and equatorial calm belts of the Atlantic.
The observations were noted at each edge of the calm belt, in the
middle of it, and 50 from each edge in the trade-winds, with the
following averages: In the northeast trades, 5~ north of the north
edge of the equatorial calm belt, siay in latitude 14~ N., air 78~.69.
North edge calm belt, say 9~ N., air 80~.90.  Middle of calm belt,
say 40~ N., air 82~. South edge, say 0~, air 82~.30; and 5~ S. (in
southeast trades), air 810.14. These thermometers had not all been
compared with standards, but their differences are probably correct,
notwithstanding the means themselves may not be so. Hence
we infer the south edge of the calm belt is 1~.4 warmer than the
north.  The extreme difference between the annual isotherms
that lie between the parallels of 30~ N. and 30~ S.-between which
the trade-wind belts are included-does not probably exceed 12~.
According to the experiments of Gay-Lussac and Dalton, the dilatation of atmospheric air due a change of 120 in temperature is
2~ per cent.; that is, a column of atmosphere 100 feet high will,
after its temperature has been raised 12~, be 1021 feet high. However, only about one third of the direct heat of the sun is absorbed in its passage down through the atmosphere.  The other
two thirds are employed in lifting vapor up from the sea, or in
warming the crust of the earth, thence to be radiated off again, or
to raise the temperature of sea and air by conduction.  The air
at the surface of the earth receives most heat directly from the
sun; as you ascend, it receives less and less, and the consequent
temperature becomes more and more uniform; so that the height
within the tropics to which the direct rays of the sun is not, as
reason suggests, and as the snow-lines of Chimborazo and other
mountains show, very great or very variable.
249. Moreover, daily observations show most conclusively that
Ituriicanes not due the strong winds and the great winds, the burrito direct heat of the
sun.         canes and tornadoes, do not arise from the direct
heat of the sun, for they do not come in the hottest weather or in
the clearest skies.  On the contrary, winter is the stormy period
in the extra-tropical regions of the north;* and in the south, rains
* Gales of the Atlantic, Observatory, Washington, 1856.




~ 250-252.           THE ATMOSPHERE.                      93
and gales-not gales and sunshine — accompany each other. The
land and sea breezes express more than double the amount of
wind force which the direct heat of the sun is capable of exerting
upon the trade-winds. I say more than double, because in the
land and sea breezes the wind-producing power acts alternately on
the land and on the sea-in opposite scales of the balance; whereas in the trade-winds it acts all the time in one scale-in the sea
scale; and the thermal impression which the solar ray makes
through the land upon the air is much greater than that which it
makes by playing upon the water.
250. From these facts it is made obvious that other agents beThe influence of oth- sides the direct and reflected heat of the sun are
eraentsrequired. concerned in producing the trade-winds. Let us
inquire into the nature of these agents.
251. They are to be found in the unequal distribution of land
Where found. and sea, and rains, as between the two hemispheres.
They derive their power from heat, it is true, but it is chiefly
from the latent heat of vapor which is set free during the processes of precipitation.  The vapor itself, as it rises from the sea, is
(~ 232) no feeble agent in the production of wind, nor is it inconsiderable in its influence upon the trade-winds.
252. Let us consider this influence. A cubic foot of water, beVapor as one of the ing converted into vapor, occupies the space of 1800
causes of the tradewinds.       cubic feet.t  This vapor is also lighter than the
1800 cubic feet of air which it displaces.  Thus, if the displaced
air weigh 1000 ounces, the vapor will weigh 623; consequently,
when air is surcharged with vapor, the atmosphere is bulged out
above, and the barometric pressure is diminished in proportion to
the volume which flows off above in consequence of this bulging
out. Thus, if we imagine the air over the Atlantic Ocean to be
all in a state of rest, and that suddenly during this calm columns
of vapor were to commence rising from the middle of this ocean,
we can understand how the wind would commence to flow into
this central space from all around.  Now, if we imagine no other
disturbing cause to arise, but suppose the evaporation from this
central area to go on with ceaseless activity, we can see that there
would be a system of winds in the Atlantic as steady, but perhaps
not so strong as the trades, yet owing their existence, neverthe* Storm and Rain Charts.  f Black and Watt's Experiments on HIeat.




94         THE PHYSICAL GEOGRAPHY OF THE SEA.
less, merely to the formation of aqueous vapor. But this is not
all.
253. C" During the conversion of solids into liquids, or of liquids
Black's law.  into vapors, heat is absorbed, which is again given
out on their recondensation."' In the process of converting one
measure of water into vapor, heat enough is absorbed-i. e., rendered latent, without raising the temperature of the vapor in the
least-to raise the temperature of 1000 such measures of water
1~; when this vapor is condensed again into water, wherever the
place of recondensation may be, this heat is set free again. If it
be still further condensed, as into hail or snow, the latent heat
rendered sensible during the process of congelation would be sufficient to raise the temperature of 140 additional measures of water 1~.
254. In this heat rendered latent by the processes of evapoThelatent heat trans- ration, and transported hither and thither by the
ported in vapor.    winds, resides the chief source of the dynamical
power which gives them motion. In some aspects vapor is to
the winds what fuel is to the steam-engine: they carry it to the
equatorial calm belt; there it rises, entangling the air, and carrying it up along with it as it goes. As it ascends it expands, as it
expands it grows cool; and as it does this its vapor is condensed,
the latent heat of which is thus liberated; this raises the temperature of the upper air, causing it to be rarefied and to ascend still
higher. This increased rarefaction calls for increased velocity on
the part of the inpouring trade-winds below.
255. Thus the vapors uniting with the direct solar ray would,
The effect of the des- were there no counteracting influences, cause the
erts upon the tradewinds.       northeast and southeast trade-winds to rush in with
equal force. But there is on the polar side of the northeast tradewinds an immense area of arid plains for the heat of the solar
ray to beat down upon, also an area of immense precipitation.
These two sources of heat hold back the northeast trade-winds, as
it were, and, when the two are united, as they are in India, they
are sufficient not only to hold back the northeast trade-wind, but
to reverse it, causing the southwest monsoon to blow for half the
year instead of the northeast trade.
256. We have, in this difference as to strength and stability
* Black's law. It is an important one, and should be remembered.




~ 257, 258.          THE ATMOSPHERE,                      95
Indications of a (~ 247) between the northeast and southeast tradecrossing at the calm
belts.       winds, another link in the chain of facts tending to
show that there is a crossing of the winds at the calm belts. The
greatest amount of evaporation takes place in the southern hemisphere, which is known by the simple circumstance that there is
so much more sea-surface there. The greatest quantity of rain
falls in the northern hemisphere, as both the rain-gauge and the
rivers show. So likewise does the thermometer; for the vapor
which affords this excess of precipitation brings the heat-the
dynamical power —from the southern hemisphere; this vapor
transports the heat in the upper regions from the equatorial
cloud-ring to the calms of Cancer, on the polar side of which it
is liberated as the vapor is precipitated, thus assisting to make
the northern warmer than the southern hemisphere. In those
northern latitudes where the precipitation of vapor and liberation of heat take place, aerial rarefaction is produced, and the air
in the calm belt of Cancer, which is about to blow northeast trade,
is turned back and called in to supply the indraught toward the
north. Thus, the northeast trade-winds being checked, the southeast are called on to supply the largest portion of the air that is required to feed the ascending columns in the equatorial calm belt.
257. On the north side of the trade-wind belt in the northern,
The counter trades and on the south side in the southern hemisphere,
-they approach the
pole in spirals.the the prevailing direction of the winds is not toward
the equator, but exactly in the opposite direction. In the extratropical region of each hemisphere the prevailing winds blow
from the equator toward the poles. These are the counter-trades
(~ 204). The precipitation and congelation that go on about the
poles produce in the amount of heat set free, according to Black's
law (~ 253), a"rarefaction in the upper regions, and an ascent of
air about the poles similar to that about the equator, with this difference, however: the place of ascent over the equator is a line, or
band, or belt; about the poles it is a disc. The air rushing in from
all sides will give rise to a wind, which, being operated upon by
the forces of diurnal rotation as it flows north, for example, will
approach the north pole by a series of spirals from the southwest.
258. If we draw a circle about this pole on a common terrestrial globe, and intersect it by spirals to represent the direction
of the wind, we shall see that the wind enters all parts of this cir



96         THE PHYSICAL GEOGRAPHY OF THE SEA.
They turn scith the cle from the southwest, and that, consequently, there
hands of a watch
about the south pole, should be about the poles a disc or circular space
against them about
the north.   of calms, in which the air ceases to move forward
as wind, and ascends as in a calm; about this calm disc, therefore, there should be a whirl, in which the ascending column of
air revolves from right to left, or against the hands of a watch.
At the south pole the winds come from the northwest (~ 213),
and consequently there they revolve about it with the hands of a
watch.  That this should be so will be obvious to any one who
will look at the arrows on the polar sides of the calms of Cancer
and Capricorn (Plate I., ~ 215).  These arrows are intended to
represent the prevailing direction of the wind at the surface of
the earth on the polar side of these calms.
259. The arrows that are drawn about the axis of this diagram
The arrows in the di- are intended to represent, by Itheir flight, the mean
agram of the winds direction of the wind, and by their length and their
feathers the mean annual duration from each quadrant. Only
the arrows nearest to the axis in each belt of 5~ of latitude are
drawn with such nicety. The largest arrow indicates that the
wind in that belt blows annually, on the average, for ten months
as the arrow flies. The arrow from the next most prevalent
quarter is half-feathered, provided the average annual duration
of the wind represented is not less than four months.  The unfeathered arrows represent winds having an average duration of
less than three months.  The arrows are on the decimal scale;
the longest arrow-which is that representing the southeast tradewinds between 50 and 10~ S., where their average duration is
ten months-being half an inch. Winds that blow five months
are represented by an arrow half this length, and so on. The halfbearded arrows are on a scale of two for one. It appears, at first,
as a singular coincidence that the wind should whirl in these discs
about the poles as it does in cyclones, viz., against the hands of a
watch in the northern, with them in the southern hemisphere.
260. To act and react upon each other, to distribute moisture
The offices of sea and over the surface of the earth, and to temper the cliair in the physical
economy.     mate of different latitudes, it would seem, are two of
the many offices assigned by their Creator to the ocean and the air.
When the northeast and southeast trades meet and produce the
equatorial calms (~ 212), the air, by the time it reaches this calm




~ 260.               THE ATMOSPHERE.                     97
belt, is heavily laden with moisture, for in each hemisphere it has
traveled obliquely over a large space of the ocean. It has no
room for escape but in the upward direction (~ 223). It expands
as it ascends, and becomes cooler; a portion of its vapor is thus
condensed, and comes down in the shape of rain. Therefore it is
that, under these calms, we have a region of constant precipitation. Old sailors tell us of such dead calms of long continuance
here, of such heavy and constant" rains, that they have scooped
up fresh water from the sea to drink.  The conditions to which
this air is exposed here under the equator are probably not such
as to cause it to precipitate all the moisture that it has taken up
in its long sweep across the waters. Let us see what becomes of
the rest; for Nature, in her economy, permits nothing to be taken
away from the earth which is not to be restored to it again in
some form, and at some time or other. Consider the great rivers
-the Amazon and the Mississippi, for example. We see them
day after day, and year after year, discharging immense volumes
of water into the ocean. " All the rivers run into the sea, yet the
sea is not full."-Eccl., i., 7. Where do the waters so discharged
go, and where do they come from? They come from their sources,
you will say. But whence are their sources supplied? for, unless
what the fountain sends forth be returned to it again, it will fail
and be dry. We see simply, in the waters that are discharged by
these rivers, the amount by which the precipitation exceeds the
evaporation throughout the whole extent of valley drained by
them; and by precipitation I mean the total amount of water that
falls from, or is deposited by the atmosphere, whether as dew,
rain, hail, or snow. The springs of these rivers (~ 191) are supplied from the rains of heaven, and these rains are formed of vapors which are taken up from the sea, that "it be not full," and
carried up to the mountains through the air.  "Note the place
whence the rivers come, thither they return again." Behold now
the waters of the Amazon, of the Mississippi, the St. Lawrence,
and all the great rivers of America, Europe, and Asia, lifted up by
the atmosphere, and flowing in invisible streams back through the
air to their sources among the hills (~ 191), and that through channels so regular, certain, and well defined, that the quantity thus
conveyed one year with the other is nearly the same: for that is
the quantity which we see running down to the ocean through
G




98        THE PHYSICAL GEOGRAPHY OF THE SEA.
these rivers; and the quantity discharged annually by each river
is, as far we can judge, nearly a constant.
261. We now begin to conceive what a powerful machine the
rowerful machinery. atmosphere must be; and, though it is apparently
so capricious and wayward in its movements, here is evidence of
order and arrangement which we must admit, and proof which we
can not deny, that it performs this mighty office with regularity
and certainty, and is therefore as obedient to law as is the steamengine to the will of its builder. It, too, is an engine. The South
Seas themselves, in all their vast intertropical extent, are the
boiler for it, and the northern hemisphere is its condenser (~ 24).
The mechanical power exerted by the air and the sun in lifting
water from the earth, in transporting it from one place to another,
and in letting it down again, is inconceivably great. The utilitarian who compares the water-power that the Falls of Niagara
would afford if applied to machinery, is astonished at the number
of figures which are required to express its equivalent in horsepower. Yet what is the horse-power of the Niagara, falling a few
steps, in comparison with the horse-power that is required to lift
up as high as the clouds and Jet down again all the water that is
discharged into the sea, not only by this river, but by all the other
rivers in the world. The calculation has been made by engineers,
and, according to it, the force for making and lifting vapor from
each area of one acre that is included on the surface of the earth
is equal to the power of 30 horses.




~ 270.                   RAINS AND RIVERS.                             9
CHAPTER Y.
~ 270-303. —RAINS AND RIVERS.
270. RIvERS are the rain-gauges of nature.  The volume of
Rivers considered as water annually discharged by any river into the
rain-gauges-the ten
largest.       sea expresses the total amount by which the precipitation upon the valley drained by such river exceeds the evaporation from  the same valley during the year.  There are but ten
rivers that we shall treat as rain-gauges; and there are only ten
in the world whose valleys include an area of more than 500,000
square miles. They are:
Square miles.
The Amazon, including the Tocantines and Orinoco........ 2,048,000
Mississippi..............................................................  982,000
La Plata.880,00......................                  886,000
Yenisei.............................................   785, 000
Obi........................................................   725,000
Lena..........94,000...................................  594000
Amoor...................................................................  583,000
Yang-tse-kiang.............................................  548,000
Hoang-ho...............................................................  537,000
Nile............................   -......-...  520) 000
These areas are stated in round numbers, and according to the
best authorities. The basin of the Amazon is usually computed
at 1,512,000 square miles; but such computation excludes the
Tocantines, 204,000 square miles, which joins the Amazon near
its mouth, and the Orinoco, with a hydrographic area of 252,000
square miles, which, by means of the Casiquiare, is connected also
with the Amazon.  We think that these three rivers should all
be regarded as belonging to one hydrographic basin, for a canoe
may pass inland from  any one to either of the others without
portage.  Of these hydrographic basins, three, including an area
of 3,916,000 square miles, are American; six, which contain an
area of 3,772,000 square miles, belong to Asia, one to Africa, and
none to Europe. The three largest rivers of Asia, the Yenisei,
Obi, and Lena (2,104,000 square miles), discharge their waters
into the Arctic Ocean; their outlets are beyond the reach of the




100       THE PHYSICAL GEOGRAPHY OF THE SEA.
commercial world; consequently they do not possess the interest
which, in the minds of men generally, is attached to the rest. The
three others of Asia drain 1,668,000 square miles, and run into
the Pacific; while the whole American system feed with their
waters and their commerce the Atlantic Ocean. These rivers,
with their springs, give drink to man and beast, and nourish with
their waters plants and reptiles, with fish and fowl not a few.
The capacity of their basins for production and wealth is without
limits. These streams are the great arteries of inland commerce.
WVere they to dry up, political communities would be torn asunder, the harmonies of the earth would be destroyed, and that beautiful adaptation of physical forces to terrestrial machinery, by
which climates are regulated, would lose its adjustment and run
wild, like a watch without a balance.
271. We see these majestic streams pouring their waters into
Heat required tolift the sea, and from the sea we know those waters
vapor for these rivers.         must come again, else the sea would be full. We
know, also, that the sunbeam and the sea-breeze suck them up
again; and it is curious to fancy such volumes of water as this
mighty company of ten great rivers is continually discharging
into the sea, taken up by the winds and the sun, and borne away
through the invisible channels of the air to the springs among the
hills that are the source of all rivers. This operation is perpetually going on, yet we perceive it not. It is the work of that invisible, imponderable, omnipresent, and wonderful agent called
heat. This is the agent which controls both sea and air in their
movements and in many of their offices. The average amount of
heat daily dispensed to our planet from the source of light in the
heavens is enough to melt a coating of ice completely encasing
the earth with a film 11 in. in thickness.*  Heat is the agent that
distills for us fresh water from the sea. It pumps up out of the
ocean all the water for our lakes and rivers, and gives power to
the winds to transport it as vapor thence to the mountains. And
though this is but a part of the work which in the terrestrial
economy has been assigned to this mighty agent, we may acquire
much profitable knowledge by examining its operations here in various aspects. To assist in this undertaking I have appealed to
the ten greatest rivers for terms and measures in which some defi* Deduced from the experiments of Pouillet.




~ 272, 273.         RAINS AND RIVERS.                 101
nite idea may be conveyed as to the magnitude of the work and
the immense physico-mechanical power of this imponderable and
invisible agent called heat. Calculations have been made which
show that the great American lakes contain 11,000 cubic miles
of water. This, according to the best computation, is twice as
much as is contained in all the other fresh water lakes, and rivers,
and cisterns of the world. The Mississippi River does not, during
a hundred years, discharge into the sea so large a volume of water
as is at this moment contained in the great northern lakes of this
continent; and yet this agent, whose works we are about to study,
operating through the winds, has power annually to lift up from
the sea and pour down upon the earth in grateful showers fresh
water enough to fill the lakes at least twenty times over.
272. That we may be enabled the better to appreciate the powRain-fall in the Mis- er and the majesty of the thermal forces of the sun,
issippi Valley.   and comprehend in detail the magnitude and grandeur of their operations, let us inquire how much rain falls annually upon the water-sheds of one of these streams, as of the Mississippi; how much is carried off by the river; how much is taken
up by evaporation; and how much heat is evolved in hoisting up
and letting down all this water. In another chapter we shall inquire for the springs in the sea that feed the clouds with rain for
these rivers. If we had a pool of water one mile square and six
inches deep to be evaporated by artificial heat, and if we wished
to find out how much would be required for the purpose, we
should learn from Mr. Joule's experiments that it would require
about as much as is evolved in the combustion of 30,000 tons of
coal. Thus we obtain (~ 271) our unit of measure to help us in
the calculation; for if the number of square miles contained in
the Mississippi Valley, and the number of inches of rain that fall
upon it annually be given, then it will be easy to tell how many
of such huge measures of heat are set free during the annual operation of condensing the raini for our hydrographic basin. And
then, if we could tell how many inches of this rain-water are again
taken up by evaporation, we should have the data for determining the number of these monstrous measures of heat that are employed for that operation also.
273. The area of the Mississippi Valley is said by physical geographers to embrace 982,000 square miles; and upon every




102       THE PHYSICAL GEOGRAPHY OF THE SEA.
Its area, and the la- square mile there is an annual average rain-fall of 40
tent heat liberated
during the process- inches. Now if we multiply 982,000 by the numes of condensation
there.       ber of times 6 will go into 40, we shall have the number of our units of heat that are annually set free among the
clouds that give rain to the Mississippi Valley. Thus the imagination is startled, and the mind overwhelmed with the announcement that the quantity of heat evolved from the vapors as they
are condensed to supply the Mississippi Valley with water is as
much as would be set free by the combustion of 30,000 tons of
coal multiplied 6,540,000 times. MAr. Joule, of Manchester, is our
authority for the heating power of one pound of coal; the Army
Meteorological Register, compiled by Lorin Blodget, and published by the Surgeon General's Office in 1855, is the authority on
which we base our estimate as to the average annual fall of rain;
and the annals of the National Observatory show, according to
the observations made by Lieutenant Marr at Memphis, the annual
fall of rain there to be 49 inches, the annual evaporation 43, and
the quantity of water that annually passes by in the Mississippi
to be 93 cubic miles. The water required to cover to the depth
of 40 inches an area of 982,000 square miles would, if collected
together in one place, make a sea one mile deep, with a superficial
area of 620 square miles.
274. It is estimated that the tributaries which the Mississippi
Annual discharge of River receives below Memphis increase the volume
theMisissippiRiver. of its waters about one eighth, so that its annual
average discharge into the sea may be estimated to be about 107
cubic miles, or about one sixth of all the rain that falls upon its
water-shed. This would leave 513 cubic miles of water to be evaporated from this river-basin annually. All the coal that the present mining force of the country could raise from its coal measures
in a thousand years would not, during its combustion, give out
as much heat as is rendered latent annually in evaporating this
water. Utterly insignificant are the sources of man's mechanical
powers when compared with those employed by nature in moving
machinery which brings the seasons around and preserves the harmonies of creation!
275. The amount of heat required to reconvert these 513 cubic
Physical adaptations. miles of rain-water into vapor and bear it away,
had accumulated in the Mississippi Valley faster than the earth




~ 276, 277.         RAINS AND RIVERS.                    103
could throw it off by radiation. Its continuance there would have
been inconsistent with the terrestrial economy. From this standpoint we see how the rain-drop is made to preserve the harmonies
of nature, and how water from the sea is made to carry off by reevaporation from the plains and valleys of the earth their surplusage of heat, which could not otherwise be got rid of without first
disturbing the terrestrial arrangements, and producing on the land
desolation and a desert. Behold now the offices of clouds and
vapor —the adaptations of heat. Clouds and vapor do something
more than brew storms, fetch rain, and send down thunder-bolts.
The benignant vapors cool our climates in summer by rendering
latent the excessive heat of the noonday sun; and they temper
them in winter, by rendering sensible and restoring again to the
air the equivalent of that selfsame heat.
276. Whence came, and by what channels did they come, these
Whence come the cubic miles of water which the Mississippi River
rains for the Mississippi.       pours annually into the sea?  The wisest of men
has told us they come from the sea. Let us explore the sea for
their place and the air for their channel. The Gulf of Mexico
can not furnish rain for all the Mississippi Valley. The Gulf lies
within the region of the northeast trades, and these winds carry
its vapors off to the westward, and deliver them in rain to the
hills, and the valleys, and the rivers of Mexico and Central America. The winds that bring the rains for the upper Mississippi
Valley come not from the south; they come from the direction of
the Rocky Mountains, the Sierra Nevada, and the great chain that
skirts the Pacific coast. It is, therefore, needless to search in the
Gulf, for the rain that comes from it upon that valley is by no
means sufficient to feed one half of its springs. Let us next examine the Atlantic Ocean, and include its slopes also in the investigation.
277. The northeast trade-wind region of this ocean extends
The northeast trades (~ 210) from the parallel of 30~ to the equator. They
of the Atlantic supplyrainsonly forthe carry their vapor before them, and, meeting the
rivers of Central and
South America.  southeast trade-wind, the two form clouds which give
rain not only to Central America, but they drop down, also, water
in abundance for the Atrato, the Magdalena, the Orinoco, the Amazon, and all the great rivers of intertropical America; also for the
Senegal, the Niger, and the Congo of Africa. So completely is the




104        THE PHYSICAL GEOGRAPHY OF THE SEA.
rain wrung out of these winds for these American rivers by the
Andes, that they become dry and rainless after passing this barrier, and as such reach the western shores of the continent, producing there, as in Peru, a rainless region. The place in the sea
whence our rivers come, and whence Europe is supplied with
rains, is clearly not to be found in this part of the ocean.
278. Between the parallels of 30~ and 35~ N. lies the calm belt
The calm belt ofCan- of Cancer, a region where there is no prevailing
cer furnishes little or 
no rain.      wind (see Diagram of the Winds, Plate I.).  It is a
belt of light airs and calms-of airs so baffling that they are often
insufficient to carry off the "loom," or that stratum of air which,
being charged with vapor, covers calm seas as with a film, and as
if to prevent farther evaporation.  This band of the ocean can
scarcely be said to furnish any vapor to the land, for a rainless
country, both in Africa, and Asia, and America, lies within it.
279. All Europe is on the north side of this calm belt.  Let us
The North Atlantic extend our search, then, to that part of the Atlantic
insufficient to supply which lies between the parallels of 35~ and 600 N.,
rain for so large a
portion oifthe earth to see if we have water surface enough there to supas one sixth of all
the land.     ply rains for the 8- millions of square miles that
are embraced by the water-sheds under consideration. The area
of this part of the Atlantic is not quite 5 millions of square miles,
and it does not include more than one thirtieth of the entire sea
surface of our planet, while the water-sheds under consideration
contain one sixth part of its entire land surface. The natural proportion of land and water surface is nearly as 1 to 3. According
to this ratio, the extent of sea surface required to give rain for
these 8  millions of square miles would be a little over 25, instead
of a little less than 5 millions of square miles.
280. The state of our knowledge concerning the actual amount
Daily rate of evap- of evaporation that is daily going on at sea has, notoratison ata less withstanding the activity in the fields of physical
than on land — observations wanted. research, been but little improved.  Records as to
the amount of water daily evaporated from a plate or dish on
shore afford us no means of judging as to what is going on even
in the same latitude at sea. Sea-water is salt, and does not throw
off its vapor as freely as fresh-water.  Moreover, the wind that
blows over the evaporating dish on shore is often dry and fresh.
It comes from the mountains, or over the plains where it found




~ 281-283.           RAINS AND RIVERS.                     105
little or no water to drink up; therefore it reaches the observer's
dish as thirsty wind, and drinks up vapor from it greedily. Now
had the same dish been placed on the sea, the air would come to
it over the water, drinking as it comes, and arriving already quite
or nearly saturated with moisture; consequently, the observations
of the amount of evaporation on shore give no idea of it at sea.
281. There is no physical question of the day which is more
Riversaregaugesfor worthy of attention than the amount of effective
thle amount of effective evaporation. evaporation that is daily going on in the sea. By
effective I mean the amount of water that, in the shape of vapor, is
daily transferred from the sea to the land. The volume discharged
by the rivers into the sea expresses (~ 270) that quantity; and it
may be ascertained with considerable accuracy by gauging the
other great rivers as I procured the Mississippi to be gauged at
Memphis in 1849.
282. The monsoons supply rains to feed the rivers of India, as
Importance of rain the northeast and southeast trade-winds of the Atand river gauges.  lantic supply rains to feed the rivers of Central and
South America. Now rain-gauges which will give us the mean
annual rain-fall on these water-sheds, and river-gauges which
would give us the mean annual discharge of the principal watercourses, would afford data for an excellent determination as to the
amount of evaporation from some parts of the ocean at least, especially for the trade-wind belts of the Atlantic and the monsoon
region of the Indian Ocean.  All the rain which the monsoons
of India deliver to the land the rivers of India return to the sea.
And if, in measuring this for the whole of India, our gauges
should lead us into a probable error, amounting in volume to half
the discharge of the Mississippi River, it would not make a difference in the computed rate of the effective daily evaporation from
the North Indian Ocean exceeding the one two-thousandth part
of an inch (0.002 in.).
283. That part of the extra-tropical North Atlantic under contHypsometry in the sideration is peculiar as to its hypsometry. It is
North Atlantic peculiar.      traversed by large icebergs, which are more favorable to the recondensation of its vapors than so many islets would
be. Warm waters are in the middle of it, and both the east and
the west winds, which waft its vapors to the land, have, before
reaching the shores, to cross currents of cool waters, as the in



106       THE PHYSICAL GEOGRAPHY OF THE SEA.
shore current counter to the Gulf Stream on the western side, and
the cool drift from the north on the east side. In illustration of
this view, and of the influence of the icebergs and cold currents
of the Atlantic upon the hypsometry of that ocean, it is only necessary to refer to the North Pacific, where there are no icebergs
nor marked contrasts between the temperature of its currents.
Ireland and the Aleutian Islands are situated between the same
parallels.  On the Pacific islands there is an uninterrupted rainfall during the entire winter. At other seasons of the year sailors describe the weather, in their log-books, there as " raining
pretty much all the time." This is far from being the case even
on the western coasts of Ireland, where there is a rain-fall of only
47* inches-probably not more than a third of what Oonalaska
receives. And simply for this reason: the winds reach Ireland
after they have been robbed (partially) of the vapors by the cool
temperatures of the icebergs and cold currents which lie in their
way; whereas, such being absent from the North Pacific, they
arrive at the islands there literally reeking with moisture. Oregon in America, and France on the Bay of Biscay, are between the
same parallels of latitude; their situation with regard both to
wind and sea is the same, for each has an ocean to windward.
Yet their annual rain-fall is, for Oregon,t 65 inches, for France,
30. None of the islands which curtain the shores of Europe are
visited as abundantly by rains as are those in the same latitudes
which curtain our northwest coast.- The American water-shed
receives about twice as much rain as the European. How shall
we account for this difference except upon the supposition that
the winds from the Pacific carry more rain than the winds from
the Atlantic?  Why should they do this, except for the icebergs
and cool streaks already alluded to?:
284. It may well be doubted whether the southwesterly winds
Limited capacity of — which are the prevailing winds in this part of
winds to take up
and transport, for the Atlantic-carry into the interior of Europe
the rivers of Europe
and America, vapor much more moisture than they bring with them
from the North Atlantic.      into the Atlantic.  They enter it with a mean annual temperature of 60~, with anll average dew point of about 55~.
They leave it at a mean temperature varying from 60~ to 400, ac* Keith Johnston.            F Army Meteorological Register, 1855.
$ Keith Johnston, " Physical Atlas."




~ 285-287.           RAINS AND RIVERS.                    107
cording to the latitude in which they reach the shore, and consequently with an average dew-point not higher than the mean
temperature. Classifying the winds of this part of the ocean according to the halves of the horizon as east and west, the mean
of 44,999 observations in the log-books of the Observatory shows
that, on the average, the west winds blow annually 230 and the
east winds 122 days.
285. Taking all these facts and circumstances into consideraThe vapor-springsfor tion, and without pretending to determine how
all these rivers not in
the Atlantic Ocean. much of the water which the rivers of America and
Europe carry into this part of the ocean comes from it again, we
may with confidence assume that the winds do not get vapor
enough from this part of the ocean to give rain to Europe, to the
Mississippi Valley, to our Atlantic slopes, and the western half
of Asiatic Russia. We are authorized in this conclusion, just as
we have authority to say that the evaporation from the Mediterranean is greater in amount than the volume of water discharged
into it again by the rivers and the rains; only in this case the reverse takes place, for the rivers empty more water into the Atlantic than the winds carry from it. This fact also is confirmed by
the hydrometer, for it shows that the water of the North Atlantic
is, parallel for parallel, lighter than water in the Southern Ocean.
286. The inference, then, from all this is, that the place in the
The places in thesea sea (~ 276) whence come the waters of the Missiswhe of t her great rivers of the northern hemicovere              is t-proves the    ob  orn    oceans, and
crossing at the calm sphere is tbefu    in these southern oe,and
belts.       the channels by which they come are to be searched out aloft, in the upper currents of the air. Thus we bring evidence and facts which seem to call for a crossing of air at the calm
belts, as represented by the diagram of the winds, Plate I. It
remains for those who deny that there is any such crossing-who
also deny that extra-tropical rivers of the northern are fed by
rains condensed from vapors taken up in the southern hemisphere
-to show whence come the hundreds of cubic miles of water
which these rivers annually pour into the Atlantic and the Arctic Oceans. In finding the "place" of all this water, it is incumbent upon them to show us the winds which bring it also, and
point out its channels.
287. "In the greater number of physical investigations some




108          THE PHYSICAL GEOGRAPHY OF THE SEA.
Spirit in which the hypothesis is requisite, in the first'instance, to aid
search  for truth the imperfection of our senses; and when the pheshould be conducted.            nomena of nature accord with the assumption, we
are justified in believing it to be a general law."*
288. In this spirit this hypothesis has been made.  Without
Thenumberofknown any evidence bearing upon the subject, it would be
facts that are reconciled by the theory as philosophical to maintain that there is no crossof a crossing at the
calm belts.     ing at the calm  belts as it would be to hold that
there is; but nature suggests in several instances that there must
be a crossing. (1.) In the homogeneousness of the atmosphere
(~ 237).  The vegetable kingdom takes from it the impurities with
which respiration and combustion are continually loading it; and
in the winter, when the vegetable energies of the northern hemisphere are asleep, they are in full play in the southern hemisphere.
And is it consistent with the spirit of true philosophy to deny the
existence, because we may not comprehend the nature of a contrivance in the machinery of the universe which guides the impure
air that proceeds from our chimneys and the nostrils of all airbreathing creatures in our winter over into the other hemisphere
for re-elaboration, and which conducts across the calm places and
over into this that which has been, replenished from the plains and
sylvas of the south? (2.) Most rain, notwithstanding there is
most water in the southern hemisphere, falls in this.  How  can
vapor thence come to us except the winds bring it, and how can
the winds fetch it except by crossing the calm places? (3.) The
" sea-dust" of the southern hemisphere, as Ehrenberg calls the red
fogs of the Atlantic, has its locus on the other side of the equator,
but it is found in the winds of the North Atlantic Ocean. If this
be so, it must cross one or more of the calm belts.t (4.) Parallel
* Mrs. Somerville.
F After this had been written, I received from my colleague, Lieut. Andrau, an
account of the following little tell-tale upon this subject:
"I found a confirmation of your theory in a piece of vegetable substance caught in
a small sack (hoisted up above the tops) between 22 0-25~ lat. N., and 380-39~ ~ long.
W. This piece is of the following dimensions: 14 millim. long, 1 to 11 mm. large,
1 mm. thick, and weighing 1 milligrams. Our famous microscopist and naturalist,
Professor P. Harting, at Utrecht, told me, after an exact inquiry,' that this vegetable fragment issued from a leaf of the family Monocotyledon, probably not from a
palm-tree, but from a Pardanacese or Scitaminse'-consequently, from trees belonging to the tropical regions. Now I am sure it comes from the tropics. I am greatly
surprised to perceive that a piece of leaf of this dimension could run off a distance




~ 288.                    RAINS AND RIVERS.                            109
for parallel, from the equator to 40~ or 450 S., the southern hemisphere is the cooler. This fact is consistent with the supposition
that the heat which is rendered latent and- abstracted from  that
hemisphere by its vapors is set free by their condensation in this.
Upon no other hypothesis than by these supposed crossings can
this fact be reconciled, for the amount of heat annually received
from the sun by the two hemispheres is, as astronomers have
shown, precisely the same.* (5.) WVell-conducted observations
made with the hydrometert (~ 285) for every parallel of latitude
in the Atlantic Ocean from 40~ S. to 40~ N., show that, parallel
for parallel, and notwithstanding the difference of temperature,
the specific gravity of sea-water is greater in the southern than it
is in the northern hemisphere. This difference as to the average
condition of the sea on different sides of the line is reconciled by
the hypothesis which requires a crossing at the calm belts. The
vapor which conveys fresh water and caloric from the southern
hemisphere to the northern will in part account for this difference both of specific gravity and temperature, and no other hypothesis will.  This hydrometric difference indicates the amount
of fresh water which, as vapor in the air, as streams on the land,
of more than 1200 geographical miles in the upper regions of the atmosphere; for
the nearest coast-lines of the two continents, America and Africa, lay at the said
distance from the place where this vegetable fragment was caught, by the carefulness of
Capt. S. Stapert, one of our most zealous co-operators. There can be no doubt that it
comes from South America, because the direction of the trade-winds on the west coast
of Africa is too northerly to bring this fragment to the finding-place in 25~ N. and
38~ W." —Letterfone Lieut. Andrau, of the Dutch Navy, dated Utrecht, Jan. 2, 1860.
* The amount of solar heat annually impressed upon the two hemispheres is identically the same; yet within certain latitudes the southern hemisphere is, parallel for
parallel, the cooler. How does it become so?  If it be the cooler by radiation, then
it must be made so by radiating more heat than it receives; such a process would be
cumulative in its effects, and were it so, the southern hemisphere would be gradually
growing cooler. There is no evidence that it is so growing, and the inference that
it is'seems inadmissible. In fact, the southern hemisphere radiates less heat than the
northern, though it receives as much from the sun. And it radiates more for this
reason: there is more land in the northern-land is a better radiator than watertherefore the northern radiates more heat than the southern hemisphere; the southern has more water and more clouds-clouds prevent radiation-therefore the southern hemisphere radiates less heat than the northern; still it is the cooler. How is this
paradox to be reconciled but upon the supposition that the southern surplusage is
stowed away in vapors, transported thence across the calm belts by the winds, and
liberated by precipitation on our side of the equator?
t Rodgers, in the Vincennes.  Maury's Sailing Directions, 8th ed., vol. i., p. 235.




110        THE PHYSICAL GEOGRAPHY OF THE SEA.
and as currents in the sea,@ is constantly in transitu between the
two hemispheres.  All these facts are inconsistent with the supposition that there is no crossing at the calm belts, and consistent
with the hypothesis that there is. It is no argument against the
hypothesis that assumes a crossing, to urge our ignorance of any
agent with power to conduct the air across the calm belts.  It
would be as reasonable to deny the red to the rose or the blush
to the peach, because we do not comprehend the processes by
which the coloring matter is collected and given to the fruit or
flower, instead of the wood or leaves of the plant. To assume
that the direction of the air is, after it enters the calm belts, left to
chance, would be inconsistent with our notions of the attributes of
the great Architect. The planets have their orbits, the stars their
courses, and the wind "his circuits."  And in the construction
of our hypotheses, it is pleasant to build them up on the premiss
that He can and has contrived all the machinery necessary for
guiding every atom of air in the atmosphere through its channels
and according to its circuits, as truly and as surely as He has
contrived it for holding comets to their courses and binding the
stars in their places. These circumstances, and others favoring
this hypothesis as to these air-crossings, will be presented more in
detail.
289. In observing the workings and studying the offices of the
The atmosphere to various parts of the physical machinery which keeps
be studied like any the world in order, we should ever re1ember that
other machinery, by  o
its operations. it is all made for its purposes, that it was planned
according to design, and arranged so as to make the world as we
behold it-a place for the habitation of man. Upon no other hypothesis can the student expect to gain profitable knowledge concerning the physics of sea, earth, or air. Regarding these elements
of the old philosophers as parts only of the same piece of machinery, we are struck with the fact, and disposed to inquire why is it
that the proportion of land and water in the northern hemisphere
is very different from the proportion that obtains between them
in the southern?   In the northern hemisphere, the land and
water are nearly equally divided.  In the southern, there is several times more water than land. Is there no connection between' The water which the rivers empty into the North Atlantic has to find its way
south with the currents of the sea.




~ 290.               RAINS AND RIVERS.                    11l
the machinery of the two hemispheres? Are they not adapted to
each other? Or, in studying the physical geography of our planet,
shall we regard the two hemispheres as separated from each other?
Rather let us regard them as made for each other, as adapted to
each other, and the one as an essential to the other. So regarding them, we observe that all the great rivers in the world are in
the northern hemisphere, where there is less ocean to supply them.
Whence, then, are their sources replenished? Those of the Amazon are, as we have seen (~ 277), supplied with rain from the equatorial calms and trade-winds of the Atlantic. That river runs east,
its branches come from the north and south; it is always the rainy
season on one side or the other of it; consequently, it is a river
without periodic stages of a very marked character. It is always
near its high-water mark. For one half of the year its northern
tributaries are flooded, and its southern for the other half. It discharges under the line, and as its tributaries come from both hemispheres, it can not be said to belong exclusively to either. It is
supplied with water made of vapor that is taken up from the Atlantic Ocean. Taking the Amazon, therefore, out of the count,
the Rio de la Plata is the only great river of the southern hemisphere. There is no large river in New Holland. The South Sea
Islands give rise to none, nor is there one in South Africa entitled
to be called great that we know of.
290. The great rivers of North America and North Africa, and
Arguments furnished all the rivers of Europe and Asia, lie wholly within
by the rivers. the northern hemisphere. How is it, then, considering that the evaporating surface lies mainly in the southern hemisphere-how is it, I say, that we should have the evaporation to
take place in one hemisphere and the condensation in the other?
The total amount of rain which falls in the northern hemisphere
is much greater, meteorologists tell us, than that which falls in the
southern.  The annual amount of rain in the north temperate
zone is half as much again as that of the south temperate.  How
is it, then, that this vapor gets, as stated, from the southern into
the northern hemisphere, and comes with such regularity that our
rivers never go dry and our springs fail not? It is because of
these air-crossings-these beautiful operations, and the exquisite
compfensation of this grand machine, the atmosphere. It is exquisitely and wonderfully counterpoised. Late in the autumn of




112       THE PHYSICAL GEOGRAPHY OF THE SEA.
the north, throughout its winter, and in early spring, the sun is
pouring his rays with the greatest intensity down upon the seas
of the southern hemisphere, and this powerful engine which we
are contemplating is pumping up the water there (~ 261) with the
greatest activity, and sending it over here for our rivers. The
heat which this heavy evaporation absorbs becomes latent, and,
with the moisture, is carried through the upper regions of the atmosphere until it reaches our climates. Here the vapor is formed
into clouds, condensed, and precipitated. The heat which held
this water in the state of vapor is set free, it becomes sensible heat,
and it is that [ (4), ~ 288] which contributes so much to temper our
winter climate. It clouds up in winter, turns warm, and we say
we are going to have falling weather. That is because the process of condensation has already commenced, though no rain or
snow may have fallen: thus we feel this southern heat, that has
been collected from the rays of the sun by the sea, been bottled
away by the winds in the clouds of a southern summer, and set
free in the process of condensation in our northern winter. If
Plate I. fairly represent the course of the winds, the southeast
trade-winds would enter the northern hemisphere, and, as an upper current, bear into it all their moisture, except that which is
precipitated in the region of equatorial calms, and in the crossing
of high mountain ranges, as the Cordilleras of South America.
291. The South Seas, then, according to ~ 290, should supply
More rain in the mainly the water for this engine, while the northnorthern than = i ern hemisphere condenses it; we should, therefore,
the southern hemisphere.      have more rain in the northern hemisphere. The
rivers tell us that we have-the rain-gauge also.  The yearly
average of rain in the north temperate zone is, according to Johnston, thirty-seven inches. He gives but twenty-six in the south
temperate. The observations of mariners are also corroborative
of the same.  Log-books, containing altogether the records for
upward of 260,000 days in the Atlantic Ocean north and south
(Plate XIII.), have been carefully examined for the purpose of
ascertaining, for comparison, the number of calms, rains, and gales
therein recorded for each hemisphere. Proportionally the number of each is given as decidedly greater for the north than it is
for the south. The result of this examination is very instructive,
for it shows the status of the atmosphere to be much more unsta



~ 292, 293.          RAINS AND RIVERS.                    113
ble in the northern hemisphere, with its excess of land, than in the
southern, with its excess of water. Rains, and fogs, and thunder,
and calms, and storms, all occur much more frequently, and are
more irregular also as to the time and place of their occurrence on
this side, than they are on the other side of the equator.  Moisture is never extracted from the air by subjecting it from a low to
a higher temperature, but the reverse.  Thus all the air which
comes loaded with moisture from the other hemisphere, and is
borne into this with the southeast trade-winds, travels in the upper regions of the atmosphere (~ 213) until it reaches the calms
of Cancer; here it becomes the surface wind that prevails from
the southward and westward.  As it goes north it grows cooler,
and the process of condensation commences. We may now liken
it to the wet sponge, and the decrease of temperature to the hand
that squeezes that sponge. Finally reaching the cold latitudes,
all the moisture that a dew-point of zero, and even far below, can
extract, is wrung from it; and this air then commences " to return
according to his circuits" as dry atmosphere.  And here we can
quote Scripture again: " The north wind driveth away rain." This
is a meteorological fact of high authority, and one of great significance too.
292. By reasoning in this manner and from such facts, we are
The trade-winds the led to the conclusion that our rivers are supplied
evaporating winds. with their waters principally from the trade-wind
regions-the extra-tropical northern rivers from the southern
trades, and the extra-tropical southern rivers from the northern
trade-winds, for the trade-winds are the evaporating winds.
293. Taking for our guide such faint glimmerings of light as
The saltest part of we can catch from these facts, and supposing these
the sea.     views to be correct, then the saltest portion of the
sea should be in the trade-wind regions, where the water ior all
the rivers is evaporated; and there the saltest portions are found.
There, too, the rains fall less frequently (Plate XIII.). Dr. Ruschenberger, of the Navy, on his last voyage to India, was kind
enough to conduct a series of observations on the specific gravity
of sea water. In about the parallel of 17~ north and south —
midway of the trade-wind regions-he found the heaviest water.
Though so warm, the water there was heavier than the cold water to the south of the Cape of Good Hope. Lieutenant D. D.
H




114        THE PHYSICAL GEOGRAPHY OF THE SEA.
Porter, in the steam-ship Golden Age, found the heaviest water
about the parallels of 20~ north and 17~ south. Captain Rodgers,
in the United States ship Vincennes, found the heaviest water in
17~ N., and between 20~ and 25~ S.
294. In summing up the evidence in favor of this view of the
Seeingthat thesouth- general system of atmospherical circulation, it reern hemisphere affords the largest mains to be shown how it is, if the view be correct,
evaporating surface,
how, unless there be there should be smaller rivers and less rain in the
a crossing, could we
have most rain nd southern hemisphere.  The winds that are to blow
the great rivers in
the northern?  as the northeast trade-winds, returning from  the
polar regions, where the moisture (~ 292) has been compressed out
of them, remain, as we have seen, dry winds until they cross the
calm zone of Cancer, and are felt on the surface as the northeast
trades. About two thirds of them only can then blow over the
ocean; the rest blow over the land, over Asia, Africa, and North
America, where there is comparatively but a small portion of
evaporating surface exposed to their action. The zone of the
northeast trades extends, on an average, from about 29~ north to
7~ north. Now, if we examine the globe, to see how much of
this zone is land and how much water, we shall find, commencing
with China and coming over Asia, the broad part of Africa, and
so on, across the continent of America to the Pacific, land enough
to fill up, as nearly as may be, just one third of it.  This land, if
thrown into one body between these parallels, would make a belt
equal to 1200 of longitude by 22~ of latitude, and comprise an
area of about twelve and a half millions of square miles, thus
leaving an evaporating surface of about twenty-five millions of
square miles in the northern against about seventy-five millions
in the southern hemisphere. According to the hypothesis, illustrated by Plate I., as to the circulation of the atmosphere, it is
these northeast trade-winds that take up and carry over, after they
rise up in the belt of equatorial calms, the vapors which make
the rains that feed the rivers in the extra-tropical regions of the
southern hemisphere. Upon this supposition, then, two thirds
only of the northern trade-winds are fully charged with moisture,
and only two thirds of the amount of rain that falls in the northern hemisphere should fall in the southern; and this is just'about
the proportion (~ 292) that observation gives. In like manner,
the southeast trade-winds take up the vapors which make our




~ 295, 296.         RAINS AND RIVERS.                   115
rivers, and as they prevail to a much greater extent at sea, and
have exposed to their action about twice as much ocean as the
northeast trade-winds have, we might expect, according to this
hypothesis, more rains in the northern —and, consequently, more
and larger rivers-than ill the southern hemisphere. A glance at
Plate VIII. will show how very much larger that part of the ocean
over which the southeast trades prevail is than that where the
northeast trade-winds blow. This estimate as to the quantity of
rain in the two hemispheres is one which is not capable of verification by any more than the rudest approximations; for the greater extent of southeast trades on one side, and of high mountains
on the other, must each of necessity, and independent of other
agents, have their effects. Nevertheless, this estimate gives as
close an approximation as we can make out from our data.
295. The Rainy Seasons, hzow caused.-The calm and trade-wind
TE RAINY SEASONS. regions or belts move up and down the earth, annually, in latitude nearly a thousand miles. In July and August
the zone of equatorial calms is found between 7~ north and 12~
north; sometimes higher; in March and April, between latitude
5~ south and 2~ north.*  With this fact and these points of view
before us, it is easy to perceive why it is that we have a rainy
season in Oregon, a rainy and dry season in California, another at
Panama, two at Bo1gota, none in Peru, and one in Chili. In Oregon it rains every month, but about five times more in the winter
than in the summer months. The winter there is the summer of
the southern hemisphere, when this steam-engine (~ 24) is working with the greatest pressure. The vapor that is taken up by
the southeast trades is borne along over the region of northeast
trades to latitude 350 or 40~ north, where it descends and appears
on the surface with the southwest winds of those latitudes. Driving upon the highlands of the continent, this vapor is condensed
and precipitated, during this part of the year, almost in constant
showers, and to the depth of about thirty inches in three months.
296. In the winter the calm belt of Cancer approaches the equaThe rainy seasons of tor. This whole system of zones, viz., of trades,
California and Panama.         calms, and westerly winds, follows the sun; and
they of our hemisphere are nearer the equator in the winter and
spring months than at any other season. The southwest winds
* See the Trade-wind Chart.




116       THE PHYSICAL GEOGRAPHY OF THE SEA:
commence at this season to prevail as far down as the lower part
of California. In winter and spring the land in California is cooler than the sea air, and is quite cold enough to extract moisture
from it. But in summer and autumn the land is the warmer, and
can not condense the vapors of water held by the air. So the
same cause which made it rain in Oregon now makes it rain in
California. As the sun returns to the north, he brings the calm
belt of Cancer and the northeast trades along with him; and now,
at places where, six months before, the southwest winds were the
prevailing winds, the northeast trades are found to blow. This
is the case in the latitude of California. The prevailing winds,
then, instead of going from a warmer to a cooler climate, as before,
are going the opposite way. Consequently, if, under these circumstances, they have the moisture in them to make rains of, they
can not precipitate it. Proof, if proof were wanting that the prevailing winds in the latitude of California are from the westward,
is obvious to all who cross the Rocky Mountains or ascend the
Sierra Madre. In the pass south of the Great Salt Lake basin
those west winds have worn away the hills and polished the rock
by their ceaseless abrasion and the scouring effects of the driving
sand. Those who have crossed this pass are astonished at the
force of the wind and the marks there exhibited of its GEOLOGICAL
AGENCIES. Panama is in the region of equatorial calms. This
belt of calms travels during the year, back and forth, over about
17~ of latitude, coming farther north in the summer, where it tarries for several months, and then returning so as to reach its extreme southern latitude some time in March or April. Where
these calms are it is always raining, and the chart* shows that
they hang over the latitude of Panama from June to November;
consequently, from June to November is the rainy season at Panama. The rest of the year that place is in the region of the northeast trades, which, before they arrive there, have to cross the
mountains of the isthmus, on the cool tops of which they deposit
their moisture, and leave Panama rainless and pleasant until the
sun returns north with the belt of equatorial calms after him.
They then push the belt of northeast trades farther to the north,
occupy a part of the winter zone, and refresh that part of the
earth with summer rains. This belt of calms moves over more. Vide Trade-wind Chart (Maury's Wind and Current).




~ 297.              RAINS AND RIVERS.                  117
than double of its breadth, and nearly the entire motion from
south to north is accomplished generally in two months, May and
June. Take the parallel of 4~ north as an illustration: during
these two months the entire belt of calms crosses this parallel, and
then leaves it in the region of the southeast trades. During these
two months it was pouring down rain on that parallel. After the
calm belt passes it the rains cease, and the people in that latitude
have no more wet weather till the fall, when the belt of calms recrosses this parallel on its way to the south. By examining the
" Trade-wind Chart," it may be seen what the latitudes are that
have two rainy seasons, and that Bogota is within the bi-rainy
latitudes.
297. T~Ne Rainless Regions.-The coast of Peru is within the reT=E Rhl.ss RE- gion of perpetual southeast trade-winds. Though
GIONS.      the Peruvian shores are on the verge of the great
South Sea boiler, yet it never rains there. The reason is plain.
The southeast trade-winds in the Atlantic Ocean first strike the
water on the coast of Africa. Traveling to the northwest, they
blow obliquely across the ocean till they reach the coast of Brazil. By this time they are heavily laden with vapor, which they
continue to bear along across the continent, depositing it as they
go, and supplying with it the sources of the Rio de la Plata and
the southern tributaries of the Amazon. Finally they reach the
snow-capped Andes, and here is wrung from them the last particle of moisture that that very low temperature can extract. Reaching the summit of that range, they now tumble down as cool and
dry winds on the Pacific slopes beyond. Meeting with no evaporating surface, and with no temperature colder than that to which
they were subjected on the mountain-tops, they reach the ocean
before they again become charged with fresh vapor, and before,
therefore, they have any which the Peruvian climate can extract.
The last they had to spare was deposited as snow on the tops of
the Cordilleras, to feed mountain streams under the heat of the
sun, and irrigate the valleys on the western slopes. Thus we see
how the top of the Andes becomes the reservoir from which are
supplied the rivers of Chili and Peru. The other rainless or almost rainless regions are the western coasts of Mexico, the deserts
of Africa, Asia, North America, and Australia. Now study the
geographical features of the country surrounding those regions;




118       THE PHYSICAL GEOGRAPHY OF THE SEA.
see how the mountain ranges run; then turn to Plate VIII. to see
how the winds blow, and where the sources are (~ 276) which
supply them with vapors. This plate shows the prevailing direction of the wind only at sea; but, knowing it there, we may
infer what it is on the land. Supposing it to prevail on the land
as it generally does in corresponding latitudes at sea, then the
Plate will suggest readily enough how the winds that blow over
these deserts came to be robbed of their moisture, or, rather, to
have so much of it taken from them as to reduce their dew-point
below the Desert temperature; for the air can never deposit its
moisture when its temperature is higher than its dew-p2oint. We have
a rainless region about the Red Sea, because the Red Sea, for the
most part, lies within the northeast trade-wind region, and these
winds, when they reach that region, are dry winds, for they have
as yet, in their course, crossed no wide sheets of water from which
they could take up a supply of vapor. Most of New Holland lies
within the southeast trade-wind region; so does most of intertropical South America. But intertropical South America is the
land of showers. The largest rivers and most copiously watered
country in the world are to be found there, whereas almost exactly the reverse is the case in Australia. Whence this difference?
Examine the direction of the winds with regard to the shore-line
of these two regions, and the explanation will at once be suggested. In Australia-east coast-the shore-line is stretched out in
the direction of the trades; in South America-east coast-it is
perpendicular to their direction. In Australia they fringe this
shore only with their vapor; thus that thirsty land is so stinted
with showers that the trees can not afford to spread their leaves
out to the sun, for it evaporates all the moisture from them; their
vegetable instincts teach them to turn their edges to his rays. In
intertropical South America the trade-winds blow perpendicularly upon the shore, penetrating the very heart of the country
with their moisture.  Here the leaves, measuring many feet
square-as the plantain, &c.-turn their broad sides up to the
sun, and court his rays.
298. Why there is mnore rain on one side of a mountain than on
TnIE RAINY SIDE OF the other. We may now, from what has been said,
IOUNTAINS.   see why the Andes and all other mountains which
lie athwart the course of the winds have a dry and a rainy side,




~ 298.              RAINS AND RIVERS.                  119
and how the prevailing winds of the latitude determine which is
the rainy and which the dry side. Thus, let us take the southern
coast of Chili for illustration. In our summer time, when the sun
comes north, and drags after him the belts of perpetual winds and
calms, that coast is left within the regions of the northwest winds
-the winds that are counter to the southeast trades-which, cooled by the winter temperature of the highlands of Chili, deposit
their moisture copiously. During the rest of the year, the most
of Chili is in the region of the southeast trades, and the same
causes which operate in California to prevent rain there, operate
in Chili; only the dry season in one place is the rainy season of
the other. Hience we see that the weather side of all such mountains as the Andes is the wet side, and the lee side the dry. The
same phenomenon, from a like cause, is repeated in intertropical
India, only in that country each side of the mountain is made alternately the wet and the dry side by a change in the prevailing
direction of the wind. Plate VIII. shows India to be in one of
the monsoon regions: it is the most famous of them all. From
October to April the northeast trades prevail. They evaporate
from the Bay of Bengal water enough to feed with rains, during
this season, the western shores of this bay and the Ghauts range
of mountains. This range holds the relation to these winds that
the Andes of Peru (~ 297) hold to the southeast trades; it first
cools and then relieves them of their moisture, and they tumble
down on the western slopes of the Ghauts, Peruvian-like, cool,
rainless, and dry; wherefore that narrow strip of country between
the Ghauts and the Arabian Sea would, like that in Peru between
the Andes and the Pacific, remain without rain forever, were it
not for other agents which are at work about India and not about
Peru. The work of the agents to which I allude is felt in the
monsoons, and these prevail in India and not in Peru. After the
northeast trades have blown out their season, which in India ends
in April, the great arid plains of Central Asia, of Tartary, Thibet,
and Mongolia, become heated up; they rarefy the air of the
northeast trades, and cause it to ascend. This rarefaction and
ascent, by their demand for an indraught, are felt by the air
which the southeast trade-winds bring to the equatorial Doldrums
of the Indian Ocean: it rushes over into the northern hemisphere
to supply the upward draught from the heated plains as the south



120       THE PHYSICAL GEOGRAPHY OF THE SEA.
west monsoons. The forces of diurnal rotation assist (~ 113) to
give these winds their westing. Thus the southeast trades, in
certain parts of the Indian Ocean, are converted, during the summer and early autumn, into southwest monsoons. These then
come from the Indian Ocean and Sea of Arabia loaded with
moisture, and, striking with it perpendicularly upon the Ghauts,
precipitate upon that narrow strip of land between this range and
the Arabian Sea an amount of water that is truly astonishing.
Here, then, are not only the conditions for causing more rain,
now on the west, now on the east side of this mountain range, but
the conditions also for the most copious precipitation. Accordingly, when we come to consult rain gauges, and to ask meteorological observers in India about the fall of rain, they tell us that
on the western slopes of the Ghauts it sometimes reaches the enormous depth of twelve or fifteen inches in one day.*  Were the
Andes stretched along the eastern instead of the western coast of
America, we.should have an amount of precipitation on their
eastern slopes that would be truly astonishing; for the water
which the Amazon and the other majestic streams of South
America return to the ocean would still be precipitated between
the sea-shore and the crest of these mountains. These winds of
India then continue their course to the Himalaya range as dry
winds. In crossing this range, they are subjected to a lower temperature than that to which they were exposed in crossing the
Ghauts. Here they drop more of their moisture in the shape of
snow and rain, and then pass over into the thirsty lands beyond
with scarcely enough vapor in them to make even a cloud.
Thence they ascend into the upper air, there to become countercurrents in the general system of atmospherical circulation. By
studying Plate VIII., where the rainless regions and inland basins, as well as the course of the prevailing winds, are shown, these
facts will become obvious.
299. The Regions of Greatest Precip9itation.-We shall now be
Theregionsofgreat- enabled to determine, if the views which I have
est precipitation- been endeavoring to present be correct, what parts
Cherraponjie and
Patagonia.   of the earth are subject to the greatest fall of rain.
They should be on the slopes of those mountains which the tradewinds or monsoons first strike after having blown across the
* Ieith Johnston.




~ 299.              RAINS AND RIVERS.                   121
greatest tract of ocean. The more abrupt the elevation, and the
shorter the distance between the mountain top and the ocean
(~ 298), the greater the amount of precipitation. If, therefore, we
commence at the parallel of about 30~ north in the Pacific, where
the northeast trade-winds first strike that ocean, and trace them
through their circuits till they first meet high land, we ought to
find such a place of heavy rains. Commencing at this parallel
of 30~, therefore, in the North Pacific, and tracing thence the
course of the northeast trade-winds, we shall find that they blow
thence, and reach the region of equatorial calms near the Caroline
Islands. Here they rise up; but, instead of pursuing the same
course in the upper stratum of winds through the southern hemisphere, they, in consequence of the rotation of the earth (~ 207),
are made to take a southeast course. They keep in this upper
stratum  until they reach the calms of Capricorn, between the
parallels of 30~ and 40~, after which they become the prevailing
northwest winds of the southern hemisphere, which correspond to
the southwest of the northern.' Continuing on to the southeast,
they are now the surface winds; they are going from warmer to
cooler latitudes; they become as the wet sponge (~ 292), and are
abruptly intercepted by the Andes of Patagonia, whose cold summit compresses them, and with its low dew-point squeezes the
water out of them. Captain King found the astonishing fall of
water here of nearly thirteen feet (one hundred and fifty-one
inches) in forty-one days; and Mr. Darwin reports that the sea
water along this part of the South American coast is sometimes
quite fresh, from the vast quantity of rain that falls. A similar
rain-fall occurs on the sides of Cherraponjie, a mountain in India.
Colonel Sykes reports a fall there during the southwest monsoons
of 605T inches. This is at the rate of 86feet during the year; but
King's Patagonia rain-fall is at the rate of 114 feet during the
year. Cherraponjie is not so near the coast as the Patagonia
range, and the monsoons lose moisture before they reach it. We
ought to expect a corresponding rainy region to be found to
the north of Oregon; but there the mountains are not so high,
the obstruction to the southwest winds is not so abrupt, the highlands are farther from the coast, and the air which these winds
carry in their circulation to that part of the coast, though it be as
heavily charged with moisture as at Patagonia, has a greater ex



122        THE PHYSICAL GEOGRAPHY OF THE SEA.
tent of country over which to deposit its rain, and, consequently,
the fall to the square inch will not be as great. In like manner,
we should be enabled to say in what part of the world the most
equable climates are to be found. They are to be found in the
equatorial calms, where the northeast and southeast trades meet
fresh from the ocean, and keep the temperature uniform under a
canopy of perpetual clouds.
300. Amount of Evaporation.-The mean annual fall of rain on
AmOUNT OF EVAPO- the entire surface of the earth is estimated at about
RATION greatest from
the Indian Ocean. five feet. To evaporate water enough annually
from the ocean to cover the earth, on the average, five feet deep
with rain; to transport it from one zone to another; and to precipitate it in the right places, at suitable times, and in the proportions due, is one of the offices of the grand atmospherical machine.
This water is evaporated principally from the torrid zone. Supposing it all to come thence, we shall have, encircling the earth,
a belt of ocean three thousand miles in breadth, from which this
atmosphere evaporates a layer of water annually sixteen feet in
depth. And to hoist up as high as the clouds, and lower down
again all the water in a lake sixteen feet deep, and three thousand
miles broad, and twenty-four thousand long, is the yearly business
of this invisible machinery. WVhat a powerful engine is the atmosphere! and how nicely adjusted must be all the cogs, and
wheels, and springs, and com pensations of this exquisite piece of
machinery, that it never wears out nor breaks down, nor fails to
do its work at the right time and in the right way! The abstract
logs at the Observatory in Washington show that the water of
the Indian Ocean is warmer than that of any other sea; therefore it may be inferred that the evaporation from it is also greater.
The North Indian Ocean contains about 4,500,000 square miles,
while its Asiatic water-shed contains an area of 2,500,000. Supposing allthe rivers of this water-shed to discharge annually into the
sea four times as much water as the Mississippi (~ 274) discharges
into the Gulf, we shall have an average annual evaporation (~ 282)
from the North Indian Ocean of 6.0 inches, or 0.0165 per day.
301. The rivers of India are fed by the monsoons, which have
The rivers of India, to do their work of distributing their moisture in
and tihe meaure of about three months.  Thus we obtain 0.065 inch
the          as the  veratie evaporation from that ocean. as the average daily rate of effective (Q 282) evapo



~ 302.                  RAINS AND RIVERS.                         123
ration from the warm waters of this ocean.  If it were all rained
down upon India, it would give it a drainage which would require
rivers having sixteen times the capacity of the Mississippi to discharge.  Nevertheless, the evaporation from  the North Indian
Ocean required for such a flood is only one sixteenth of an inch
daily throughout the year.*  Availing myself of the best lights
-dim  at best-as to the total amount of evaporation that annually takes place in the trade-wind region generally at sea, I estimate that it does not exceedfourfeet.
302. We see the light beginning to break upon us, for we now
Physicaladjustments. begin to perceive why it is that the proportions between the land and water were made as we find them in nature.
If there had been more water and less land, we should have had
more rain, and vice versa; and then climates would have been
different from what they are now, and the inhabitants, animal or
vegetable, would not have been as they are. And as they are,
that wise Being who, in his kind providence, so watches over and
regards the things of this world that he takes notice of the sparrow's fall, and numbers the very hairs of our head, doubtless designed them to be. The mind is delighted, and the imagination
charmed, by contemplating the physical arrangements of the earth
from such points of view as this is which we now have before us;
from it the sea, and the air, and the land, appear each as a part of
that grand machinery upon which the well-being of all the inhabitants of earth, sea, and air depends; and which, in the beautiful
adaptations that we are pointing out, affords new and striking evidence that they all have their origin in ONE omniscient idea, just
as the different parts of a watch may be considered to have been
constructed and arranged according to one human design.  In
some parts of the earth the precipitation is greater than the evaporation; thus the amount of water borne down by every river that
* In his annual report to the Society (Transactions of the Bombay Geographical
Society from May, 1849, to August, 1850, vol. ix.), Dr. Buist, the secretary, states, on
the authority of Mr. Laidly, the evaporation at Calcutta to be " about fifteen feet annually; that between the Cape and Calcutta it averages, in October and November,
nearly three fourths of an inch daily; between 100 and 20~ in the Bay of Bengal, it
was found to exceed an inch daily. Supposing this to be double the average throughout the year, we should," continues the doctor, " have eighteen feet of evaporation
annually." All the heat received by the intertropical seas from the sun annually
would not be sufficient to convert into vapor a layer of water from them sixteen feet
deep. It is these observations as to the late of evaporation on shore that have led
(~ 280) to such extravagant estimates as to the rate at sea.




124       THE PHYSICAL GEOGRAPHY OF THE SEA.
runs into the sea (~ 270) may be considered as the excess of the
precipitation over the evaporation that takes place in the valley
drained by that river. In other parts of the earth the evaporation and precipitation are exactly equal, as in those inland basins
such as that in which the city of Mexico, Lake Titicaca, the Caspian Sea, etc., etc., are situated, which basins have no ocean drainage. If more rain fell in the valley of the Caspian Sea than is
evaporated from it, that sea would finally get full and overflow
the whole of that great basin. If less fell than is evaporated from
it again, then that sea, in the course of time, would dry up, and
plants and animals there would all perish for the want of water.
In the sheets of water which we find distributed over that and every other inhabitable inland basin, we see reservoirs or evaporating surfaces just sufficient for the supply of that degree of moisture which is best adapted to the well-being of the plants and animals that people such basins. In other parts of the, earth still,
we find places, as the Desert of Sahara, in which neither evaporation nor precipitation takes place, and in which we find neither
plant nor animal to fit the land for man's use.
303. ADAPTATIONS. —In contemplating the system of terresADAPTATIONS-their trial adaptations, these researches teach one to rebeauties and sublimity.      gard the mountain ranges and the great deserts of
the earth as the astronomer does the counterpoises to his telescope-though they be mere dead weights, they are, nevertheless,
necessary to make the balance complete, the adjustment of his
machine perfect. These counterpoises give ease to the motions,
stability to the performance, and accuracy to the workings of the
instrument. They are "compensations."  Whenever I turn to
contemplate the works of nature, I am struck with the admirable
system of compensation, with the beauty and nicety with which
every department is adjusted, adapted, and regulated according
to the others; things and principles are meted out in directions
apparently the most opposite, but in proportions so exactly balanced that results the most harmonions are produced. It is by
the action of opposite and compensating forces that the earth is
kept in its orbit, and the stars are held suspended in the azure
vault of heaven; and these forces are so exquisitely adjusted,
that, at the end of a thousand years, the earth, the sun, and moon,
and every star in the firmament, is found to come and twinkle in
its proper place at the proper moment. Nay, philosophy teaches




~ 303.              RAINS AND RIVERS.                   125
us that when the little snow-drop, which in our garden-walks
we see raising its head at " the singing of birds," to remind us
that "the winter is passed and gone," was created, the whole
mass of the earth, from pole to pole, and from circumference to
centre, must have been taken into account and weighed, in order
that the proper degree of strength might be given to its tiny
fibres. Botanists tell us that the constitution of this plant is
such as to require that, at a certain stage of its growth, the stalk
should bend, and the flower should bow its head, that an operation may take place which is necessary in order that the herb
should produce seed after its kind; and that, after this fecundation, its vegetable health requires that it should lift its head again
and stand erect. Now, if the mass of the earth had been greater
or less, the force of gravity would have been different; in that
case, the strength of fibre in the snow-drop, as it is, would have
been too much or too little; the plant could not bow or raise its
-head at the right time, fecundation could not take place, and its
family would have become extinct with the first individual that
was planted, because its " seed" would not have been " in itself,"
and therefore could not have reproduced itself; and its creation
would have been a failure. Now, if we see such a perfect adaptation, such exquisite adjustment in'the case of one of the smallest flowers of the field, how much more may we not expect " compensation" in the atmosphere and the ocean, upon the right adjustment and due performance of which depends not only the
life of that plant, but the well-being of every individual that is
found in the entire vegetable and animal kingdoms of the world?
When the east winds blow along the Atlantic coast for a little
while, they bring us air saturated with moisture from the Gulf
Stream, and we complain of the sultry, oppressive, heavy atmosphere; the invalid grows worse, and the well man feels ill, because, when he takes this atmosphere into his lungs, it is already
so charged with moisture that it can not take up anrid carry off
that which encumbers his lungs, and which nature has caused his
blood to bring and leave there, that respiration may take up and
carry off. At other times the air is dry and hot; he feels that it
is conveying off matter from the lungs too fast; he realizes the
idea that it is consuming him, and he calls the sensation burning.
Therefore, in considering the general laws which govern the
physical agents of the universe, and regulate them in the due




126       THE PIIYSICAL GEOGRAPHY OF THE SEA.
performance of their offices, I have felt myself constrained to set
out with the assumption that, if the atmosphere had had a greater
or less capacity for moisture, or if the proportion of land and water had been different-if the earth, air, and water had not been
in exact counterpoise —the whole arrangement of the animal and
vegetable kingdoms would have varied from their present state.
But God, for reasons which man may never know, chose to make
those kingdoms what they are; for this purpose it was necessary,
in his judgment, to establish the proportions between the land
and water, and the desert, just as they are, and to make the capacity of the air to circulate heat and moisture just what it is,
and to have it to do all its work in obedience to law and in subservience to order. If it were not so, why was power given to
the winds to lift up and transport moisture, and to feed the plants
with nourishment? or why was the property given to the sea by
which its waters may become first vapor, and then fruitful showers or gentle dews? If the proportions and properties of land,
sea, and air were not adjusted according to the reciprocal capacities of all to perform the functions required by each, why should
we be told that EE " measured the waters in the hollow of his
hand, and comprehended the dust in a measure, and weighed the
mountains in scales, and the hills in a balance?"  Why did he
span the heavens but that he might mete out the atmosphere in
-exact proportion to all the rest, and impart to it those properties
and powers which it was necessary for it to have, in order that
it might perform all those offices and duties for which he designed it? Harmonious in their action, the air and sea are obedient
to law and subject to order in all their movements; when we
consult them in the performance of their manifold and marvelous
offices, they teach us lessons concerning the wonders of the deep,
the mysteries of the sky, the greatness, and the wisdom, and goodness of the Creator, which make us wiser and better men. The
investigations into the broad-spreading circle of phenomena connected with the winds of heaven and the waves of the sea are
second to none for the good which they do and the lessons which
they teach. The astronomer is said to see the hand of God in
the sky; but does not the right-minded mariner, who looks aloft
as he ponders over these things, hear his voice in every wave of
the sea that "claps its hands," and feel his presence in every
breeze that blows?




~ 311-313.      RED FOGS AND SEA BREEZES.                  127
CHAPTER VI.
~ 311-332. —RED FOGS AND SEA BREEZES.
311. THE inhabitants of the sea-shore in tropical countries wait
The alternations of every morning with impatience the coming of the
landandseabreezes.'sea breeze. It usually sets in about ten o'clock.
Then the sultry heat of the oppressive morning is dissipated, and
there is a delightful freshness in the air which seems to give new
life to all for their daily labors. About sunset there is again another calm. The sea breeze is now done, and in a short time the
land breeze sets in. This alternation of the land and sea breeze
-a wind from the sea by day and from the land by night-is so
regular in intertropical countries, that they are looked for by the
people with as much confidence as the rising and setting of the sun.
312. In extra-tropical countries, especially those on the polar
The sea breeze at side of the trade-winds, this phenomenon is presentValparaiso. ed only in summer and fall, when the heat of the
sun is sufficiently intense to produce the requisite degree of atmospherical rarefaction over the land.  This depends in a measure,
also, upon the character of the land upon which the sea breeze
blows; for when the surface is arid and the soil barren, the heating power of the sun is exerted with most effect. In such cases
the sea breeze amounts to a gale of wind. In the summer of the
southern hemisphere the sea breeze is more powerfully developed
at Valparaiso than at any other place to which my services afloat
have led me. Here regularly in the afternoon, at this season, the
sea breeze blows furiously; pebbles are torn up from the walks
and whirled about the streets; people seek shelter; the Almendral is deserted, business interrupted, and all communication from
the shipping to the shore is cut off. Suddenly the winds and the
sea, as if they had again heard the voice of rebuke, are hushed,
and there is a great calm.
313. The lull that follows is delightful. The sky is without a
The contrast. cloud; the atmosphere is transparency itself; the
Andes seem to draw near; the climate, always mild and soft, be



128       THE PHYSICAL GEOGRAPHY OF THE SEA.
comes now doubly sweet by the contrast. The evening invites
abroad, and the population sally forth —the ladies in ball costume,
for now there is not wind enough to disarrange the lightest curl.
In the southern summer this change takes place day after day
with the utmost regularity, and yet the calm always seems to surprise, and to come before one has time to realize that the furious
sea-wind could so soon be hushed. Presently the stars begin to
peep out, timidly at first, as if to see whether the elements here
below had ceased their strife, and if the scene on earth be such as
they, from bright spheres aloft, may shed their sweet influences
upon. Sirius, or that blazing world n Argus, may be the first
watcher to send down'a feeble ray; then follow another and another, all smiling meekly; but presently, in the short twilight of
the latitude, the bright leaders of the starry host blaze forth in all
their glory, and the sky is decked and spangled with superb brilliants. In the twinkling of an eye, and faster than the admiring
gazer can tell, the stars seem to leap out from their hiding-places.
By invisible hands, and in quick succession, the constellations are
hung out; but first of all, and with dazzling glory, in the azure
depths of space appears the Great Southern Cross. That shining
symbol lends a holy grandeur to the scene, making it still more
impressive. Alone in the night-watch, after the sea breeze has
sunk to rest, I have stood on the deck under those beautiful skies
gazing, admiring, rapt. I have seen there, above the horizon at
once, and shining with a splendor unknown to these latitudes,
every star of the first magnitude-save only six-that is contained in the catalogue of the 100 principal fixed stars of astronomers.
There lies the city on the sea-shore, wrapped in sleep. The sky
looks solid, like a vault of steel set with diamonds. The stillness
below is in harmony with the silence above, and one almost fears
to speak, lest the harsh sound of the human voice, reverberating
through those vaulted "chambers of the south," should wake up
echo, and drown the music that fills the soul. On looking aloft,
the first emotion gives birth to a homeward thought: bright and
lovely as they are, those, to northern sons, are not the stars nor the
skies of fatherland. Alpha Lyrse, with his pure white light, has
gone fromn the zenith, and only appears for one short hour above
the top of the northern hills. Polaris and the Great Bear have
ceased to watch from their posts; they are away down below the




:~ 314, 315.    RED FOGS AND SEA BREEZES.                129
horizon. But, glancing the eye above and around, you are dazzled with the splendors of the firmament. The moon and the
planets stand out from it; they do not seem to touch the blue
vault in which the stars are set. The Southern Cross is just about
to culminate. Climbing up in the east are the Centaurs, Spica,
Bootes, and Antares, with his lovely little companion, which only
the best telescopes have power to unveil. These are all bright
particular stars, differing from one another in color as they do in
glory. At the same time, the western sky is glorious with its
brilliants too. Orion is there, just about to march down into the
sea; but Canopus and Sirius, with Castor and his twin brother,
and Procyon, n Argus, and Regulus-these are high up in their
course; they look down with great splendor, smiling peacefully
as they precede the Southern Cross on its western way. And
yonder, farther still, away to the south, float the Magellanic clouds,
and the "Coal Sacks"-those mysterious, dark spots in the sky,
which seem as though it had been rent, and these were holes in
the " azure robe of night," looking out into the starless, empty,
blackl abyss beyond. One who has never watched the southern sky
in the stillness of the night, after the sea breeze with its turmoil
is done, can have no idea of its grandeur, beauty, and loveliness.
314. Within the tropics, however, the land and sea breezes are
Landandseabreezes more gentle, and, though the night-scenes there are
altong the shore of not so suggestive as those just described, yet they
intertropical  countries.       are exceedingly delightful and altogether lovely.
The oppressive heat of the sun and the climate of the sea-shore is
mitigated and made both refreshing and healthful by the alternation of those winds which invariably come from the coolest place
-the sea, which is the cooler by day, and the land, which is the
cooler by night. About ten in the morning the heat of the sun
has played upon the land with sufficient intensity to raise its temporature above that of the water. A portion of this heat, being
imparted to the superincumbent air, causes it to rise, when the air,
first from the beach, then from the sea, to the distance of several
miles, begins to flow in with a most delightful and invigorating
freshness.
315. When a fire is kindled on the hearth, we may, if we will
Cause of land and observe the moats floating in the room, see that
sea breezes.    those nearest to the chimney are the first to feel
I




130         THE PHYSICAL GEOGRAPHY OF THE SEA.
the draught and to obey it-they are drawn into the blaze.  The
circle of infiowing air is gradually enlarged, until it is scarcely
perceived in the remote parts of the room.  Now the land is the
hearth, the rays of the sun the fire, and the sea, with its cool and
calm air, the room; and thus we have at our firesides the seabreeze in miniature. When the sun goes down the fire ceases;
then the dry land commences to give off its surplus heat by radiation, so that by dew-fall it and the air above it are cooled below
the sea temperature. The atmosphere on the land thus becomes
heavier than on the sea, and, consequently, there is a wind seaward which we call the land-breeze.
316. "A long residence in the Indian Archipelago, and, conseLieut. Jansen on the quently, in that part of the world where the invesland and sea breezes tigations of the Observatory at Washington have
in the Indian Archi-             O vty                          hv
pelago.        not extended, has given me," says Jansen,* in his
Appendix to the Physical Geography of the Sea, "the opportunity of studying the phenomena which there occur in the atmosphere, and to these phenomena my attention was, in the first
place, directed.  I was involuntarily led from one research to another, and it is the result of these investigations to which I would
modestly give a place at the conclusion of Maury's Physical Geography of the Sea, with the hope that these first-fruits of the logbooks of the Netherlands may be speedily followed by more and
better. Upon the northern coast of Java, the phencvnenon of
daily land and sea breezes is finely developed. There, as the
gorgeous'eye of day' rises almost perpendicularly from the sea
with fiery ardor, in a cloudless sky, it is greeted by the volcanoes
with a column of white smoke, which, ascending from the conical
summits high in the firmament above, forms a crown, or assumes
* I have been assisted in my investigations into these phenomena of the sea by
many thinking minds; among those whose debtor I am stands first and foremost the
clear head and warm heart of a foreign officer, Lieutenant Marin Jansen, of the
Dutch Navy, whom I am proud to call my friend. He has served many years in the
East Indies, and has enriched my humble contributions to the " Physical Geography
of the Sea" with contributions from the store-house of his knowledge, set off and presented in many fine pictures, and has appended them to a translation of the first
edition of this work in the Dutch language. He has added a chapter on the land
and sea breezes; another on the changing of the monsoons in the East Indian Archipelago: he has also extended his remarks to the northwest monsoon, to hurricanes, the southeast trades of the South Atlantic, and to winds and currents generally.




~ 316.           RED FOGS AND SEA BREEZES.                    131
the shape of an immense bouquet,* that they seem to offer to the
dawn; then the joyful land-breeze plays over the flood, which, in
the torrid zone, furnishes, with its fresh breath, so much enjoyment to the inhabitants of that sultry belt of the earth, for, by
means of it, every thing is refreshed and beautified.  Then, under
the influence of the glorious accompaniments of the break of day,
the silence of the night is awakened, and we hear commencing
every where the morning hymn of mute nature, whose gesticulation is so expressive and sublime. All that lives feels the necessity of pouring forth, each in its way, and in various tones and
accents, from the depths of inspiration, a song of praise. The
air, still filled with the freshness of the evening dew, bears aloft
the enraptured song, as, mingled with the jubilee tones which the
contemplation of nature every where forces from the soul, it
gushes forth in deep earnestness to convey the daily thank-offering over the sea, over hill and dale.t  As the sun ascends the
sky, the azure vault is bathed in dazzling light; now the landbreeze, wearied with play, goes to rest. Here and there it still
plays over the water, as if it could not sleep; but finally becoming exhausted, it sinks to repose in the stillness of the calm. But
not so with the atmosphere: it sparkles, and glitters, and twinkles,
becoming clear under the increasing heat, while the gentle swelling of the now polished waves reflects, like a thousand mirrors,
the rays of light which dance and leap to the tremulous but vertical movements of the atmosphere. Like pleasant visions of the
night, that pass before the mind in sleep, so do sweet phantoms
hover about the land-breeze as it slumbers upon the sea. The
shore seems to approach and to display all its charms to the mariner in the offing.  All objects become distinct and more clearly
delineated,: while, upon the sea, small fishing-boats loom up like
large vessels.  The seaman, drifting along the coast, and misled
by the increasing clearness and mirage, believes that he has been
* Upon the coast of Java I saw daily, during the east monsoon, such a column of
smoke ascending at sunrise from Bromo, Lamongan, and Smiro. Probably there is
then no wind above. —JANsEN.
t In the very fine mist of the morning, a noise-for example, the firing of cannon
-at a short distance is scarcely heard, while at midday, with the sea-breeze, it penetrates for miles with great distinctness.-JANSEN.
t The transparency of the atmosphere is so great that we can sometimes discover
Venus in the sky in the middle of the day.-JANSENo




132        THE PHYSICAL GEOGRAPHY OF THE SEA.
driven by a current toward the land; he casts the lead, and looks
anxiously out for the sea-breeze, in order to escape from what he
believes to be threatening danger.* The planks burn under his
feet; in vain he spreads the awning to shelter himself from the
broiling sun. Its rays are oppressive; repose does not refresh;
motion is not agreeable. The inhabitants of the deep, awakened
by the clear light of day, prepare themselves for labor. Corals,
and thousands of crustacea, await, perhaps impatiently, the coming of the sea-breeze, which shall cause evaporation to take place
more rapidly, and thus provide them with a bountiful store of
building material for their picturesque and artfully constructed
dwellings: these they know how to paint and to polish in the
depths of the sea more beautifully than can be accomplished by
any human art.  Like them, also, the plants of the sea are dependent upon the winds, upon the clouds, and upon the sunshine;
for upon these depend the vapor and the rains which feed the
streams that bring nourishment for them into the sea.t  When
the sun reaches the zenith, and his stern eye, with burning glare,
is turned more and more upon the Java Sea, the air seems to fall
into a magnetic sleep; yet, even as the magnetizer exercises his
will upon his subject, and the latter, with uncertain and changeable gestures, gradually puts himself in motion, and sleeping
obeys that will, so also we see the slow efforts of the sea-breeze to
repress the vertical movements of the air, and to obey the will
which calls it to the land.  This vertical movement appears to be
not easily overcome by the horizontal which we call wind. Yonder, far out upon the sea, arises and disappears alternately a darker tint upon the otherwise shining sea-carpet; finally, that tint
remains and approaches; that is the long-wished-for sea-breeze:
and yet it is sometimes one, yes, even two hours before the darker tint is permanent, before the sea-breeze has regularly set ill.
Now small white clouds begin to rise above the horizon; to the
experienced seaman they are a prelude to a fresh sea-breeze. We
welcome the first breath from  the sea; it is cooling, but it soon
* Especially in the rainy season the land looms very greatly; then we see mountains which are from 5000 to 6000 feet high at a distance of 80 or 100 English miles.
t The archipelago of coral islands on the north side of the Straits of Sunda is remarkable. Before the salt water flowed from the Straits it was deprived of the solid
matter of which the Thousand Islands are constructed. A similar group of islands
is found between the Straits of Macassar and Balie.-JANSEN.




~ 316.          RED FOGS AND SEA BREEZES.                  133
ceases; presently it is succeeded by other grateful puffs of air,
which continue longer; presently they settle down into the regular sea-breeze, with its cooling and refreshing breath. The sun
declines, and the sea-wind-that is, the common trade-wind or
monsoon which is drawn toward the land-is awakened. It
blows right, earnestly, as if it would perform its daily task with
the greatest possible ado. The air, itself refreshed upon the deep,
becomes gray from the vapor which envelops the promontories
in mist, and curtains the inland with dark clouds.  The land is
discernible only by the darker tint which it gives to the mist;
but the distance can not be estimated.  The sailor thinks himself
farther from shore than he really is, and steers on his course carelessly, while the capricious wind lashes the waters, and makes a
short and broken sea, from  the white caps of which light curls
are torn, with sportive hand, to float away like party-colored
streamers in the sunbeam. In the mean while clouds appear now
and then high in the air, yet it is too misty to see far.  The sun
approaches the horizon. Far over the land the clouds continue
to heap up; already the thunder is heard among the distant hills;
the thunder-bolts reverberate from  hill-side to hill-side, while
through the mist the sheets of lightning are seen.* Finally, the'king of day' sinks to rest; now the mist gradually disappears,
and as soon as the wind has laid down the lash, the sea, which,
chafing and fretting, had with curled mane resisted its violence,
begins to go down also. Presently both winds and waves are
hushed, and all is again still. Above the sea, the air is clearer or
slightly clouded; above the land, it is thick, dark, and swollen.
To the feelings, this stillness is pleasant. The sea-breeze, the
driving brine, that has made a.salt-pan of the face, the short, restless sea, the dampness-all have grown wearisome, and welcome
is the calm. There is, however, a somewhat of dimness in the
air, an uncertain but threatening appearance. Presently, from
the dark mass of clouds, which hastens the change of day into
night, the thunder-storm peals forth.  The rain falls in torrents in
the mountains, and the clouds gradually overspread the whole
sky. But for the wind, which again springs up, it would be
* At Buitenzorg, near Batavia, 40 English miles from the shore, five hundred feet
above the sea, with high hills around, these thunder-storms occur between 4 P.M.
and 8 P.M.




134       THE PHYSICAL GEOGRAPHY OF THE SEA.
alarming to the sailor, who is helpless in a calm. What change
will take place in the air?  The experienced seaman, who has to
work against the trade-wind or against the monsoon, is off the
coast, in order to take advantage of the land-breeze (the destroyer
of the trade) so soon as it shall come. He rejoices when the air
is released from the land and the breeze comes, at first feebly, but
afterward growing stronger, as usual, during the whole night. If
the land-breeze meets with a squall, then it is brief, and becomes
feeble and uncertain. We sometimes find then the permanent
sea-breeze close to the coast, which otherwise remains twenty or
more English miles from it. One is not always certain to get the
land-breeze at the fixed time. It sometimes suffers itself to be
waited for; sometimes it tarries the whole night long. During
the greatest part of the rainy season, the land-breeze in tha Java
Sea can not be depended upon. This is readily explained according to the theory which ascribes the origin of the sea and land
breezes to the heating of the soil by day, and the cooling by
means of radiation by night; for, during the rainy season, the
clouds extend over land and sea, interrupting the sun's rays by
day, and the radiation of heat by night, thus preventing the variations of temperature; and from these variations, according to
this theory, the land and sea breezes arise. Yet there are other
tropical regions where the land and sea breezes, even in the rainy
season, regularly succeed each other."
317. One of the causes which make the west coast of Africa so
Sanitalyinfluencesof very unhealthy when compared with places in corland and sea breezes. responding latitudes on the opposite side of the Atlantic, as in Brazil, is no doubt owing to the difference in the land
and sea breezes on the two sides. On the coast of Africa the landbreeze is "universally scorching hot."" There the land-breeze is
the trade-wind. It has traversed the continent, sucking up by the
way disease and pestilence from the dank places of the interior.
Reeking with miasm, it reaches the coast. Peru is also within the
trade-wind region, and the winds reach the west coast of South
America, as they do the west coast of Africa, by an overland path;
but, in the former case, instead of sweeping over dank places, they
come cool and fresh from the pure snows of the Andes. Between
this range and the coast, instead of marshes and a jungle, there is
* Jansen.




~ 318, 319.     RED FOGS AND SEA BREEZES.                  135
a desert-a rainless country, upon which the rays of the sun play
with sufficient force not only to counteract the trade-wind power
and produce a calm, but to turn the scale, and draw the air back
from the sea, and so cause the sea-breeze to blow regularly.
318. On the coast of Africa, on the contrary, a rank vegetable
Influenceswhichreg- growth screens the soil from the scorching rays of
ulate their strength. the sun, and the rarefaction is not every day sufficient to do more than counteract the trade-wind force and produce
a calm. The same intensity of ray, however, playing upon the
intertropical vegetation of a lee shore, is so much force added to
the sea-breeze; and hence, in Brazil, the sea-breeze is fresh, and
strong, and healthful; the land breeze feeble, and therefore not so
sickly. Thus we perceive that the strength as well as regularity
of the land and sea breezes not only depend upon the topography
of a place, but also upon its situation with regard to the prevailing winds; and also that a given difference of temperature between land and water, though it may be sufficient to produce the
phenomena of land and sea breezes at one place, will not be adequate to the same effect at another; and the reason is perfectly
philosophical.
319. It is easier to obstruct and turn back the current in a slugLand breezes from gish than in a rapid stream.  So, also, in turning a
the west coast of Africa scorching hot. current of air first upon the land, then upon the sea
-very slight alternations of temperature would suffice for this on
those coasts where calms would prevail were it not for the land
and sea breezes, as, for instance, in and about the region of equatorial calms; there the air is in a state of rest, and will obey the
slightest call in any direction; not so in regions where the trades
blow over the land, and are strong.  It requires, under such circumstances, a considerable degree of rarefaction to check them
and produce a calm, and a still farther rarefaction to turn them
back, and convert them into a regular sea-breeze. Hence the
scorching land-breeze (~ 317) on the west coast of Africa: the
heat there may not have been intense enough to produce the degree of rarefaction required to check and turn back the southeast
trades. In that part of the world, their natural course is from the
land to the sea, and therefore, if this view be correct, the sea-breeze
should be more feeble than the land-breeze, neither should it last
so long.




136        THE PHYSICAL GEOGRAPHY OF THE SEA.
320. But on the opposite side-on the coast of Brazil, as at PerLand-breeze in Bra- nambuco, for instance —where the trade-wind comes
zil and Cuba. from the sea, we'should have this condition of things
reversed, and the sea-breeze will prevail for most of the timethen it is the land-breeze which is feeble and of short duration: it
is rarely felt. Again, the land and sea breezes in Cuba, and along
the Gulf shores of the United States, will be more regular in their
alternations than they are along the shores of Brazil or South Africa, and for the simple reason that the Gulf shores lie nearly parallel with the prevailing direction of the winds.  In Rio de Janeiro, the sea-breeze is the regular trade-wind made fresher by the
daily action of the sun on the land. It is worthy of remark, also,
that, for the reason stated by Jansen, the land and sea breezes in
the winter time are almost unknown in countries of severe cold,
though in the summer the alternation of wind from land to sea,
and sea to land, may be well marked.
321. " Happy he," remarks Jansen, "' who, in the Java Sea at
Night scenes when evening, seeking the land-breeze off the coast, finds
sailing with the landbreeze.       it there, after the salt-bearing, roaring sea-wind, and
can, in the magnificent nights of the tropics, breathe the refreshing land-breeze, ofttimes laden with delicious odors.*  The veil
of clouds, either after a squall, with or without rain, or after the
coming of the land-breeze, is speedily withdrawn, and leaves the
sky clearer during the night, only now and then flecked with dark
clouds floating over from the land. Without these floating clouds
the land-breeze is feeble.  When the clouds float away from the
sea, the land-breeze does not go far out from the coast, or is wholly replaced by the sea-breeze, or, rather, by the trade-wind.  If
the land-breeze continues, then the stars loom forth, as if to free
themselves from the dark vault of the heavens, but their light does
not wholly vanquish its deep blue, which causes the cold sacks to
come out more distinctly near the Southern Cross, as it smiles
consolingly upon us, while Scorpio, the emblem of the tropical climate, stands like a warning in the heavens. The starlight, which
is reflected by the mirrored waters, causes the nights to vie in
clearness with the early twilight in high latitudes. Numerous
shooting stars weary the eye, although they break the monotony
of the sparkling firmament. Their unceasing motion in the un* In the Roads of Batavia, however, they are not very agreeable.-JANsEN.




~ 321.           RED FOGS AND SEA BREEZES.                      137
fathomable ocean affords a great contrast to the seeming quiet of
the gently-flowing, aerial current of the land-breeze. But at times,
when, 30~ or 40~ above the horizon, a fire-ball arises which suddenly illumines the whole horizon, appearing to the eye the size
of the fist, and fading away as suddenly as it appeared, falling into
fiery nodules, then we perceive that, in the apparent calm of nature, various forces are constantly active, in order to cause, even
in the invisible air, such combinations and combustions, the appearance of which amazes the crews of ships. When the slender
keel glides quickly over the mirrored waters upon the wings of
the wind, it cuts for itself a sparkling way, and disturbs in their
sleep the monsters of the deep, which whirl and dart quicker than
an eight-knot ship; sweeping and turning around their disturber,
they suddenly clothe the dark surface of the water in brilliancy.
Again, when we go beyond the limits of the land-breeze, and come
into the continuous trade-wind, we occasionally see from the lowmoving, round black clouds (unless it thunders), light blue sparks
collected upon the extreme points of the iron belaying-pins, etc.;*
then the crew appear to fear a new danger, against which courage
is unavailing, and which the mind can find no power to endure.
The fervent, fiery nature inspires the traveler with deep awe.
They who, under the beating of the storm- and terrible violence
of the ocean, look danger courageously in the face, feel, in the presence of these phenomena, insignificant, feeble, anxious. Then they
perceive the mighty power of the Creator over the works of his
creation.  And how can the uncertain, the undetermined sensations arise which are produced by the clear yet sad light of the
moon? she who has always great tears in her eyes, while the stars
look sweetly at her, as if they loved to trust her and to share her
affliction.t  In the latter part of the night the land-breeze sinks
to sleep, for it seldom continues to blow with strength, but is always fickle and capricious.  With the break of day it again
awakes, to sport a while, and then gradually dies away as the sun
* I have seen this in a remarkable degree upon the south coast of Java; these
sparks were then seen six feet above the deck, upon the frames of timber (icoussen der
blokken), in the implements, etc.-JANSEN.
t Some one has ventured the remark that at full moon, near the equator, more
and darker dew falls than at new moon, and to this are ascribed the moonheads (maan
hoofden), which I have seen, however, but once during all the years which I have
spent between the tropics.-JANSEN.




138       THE PHYSICAL GEOGRAPHY OF THE SEA.
rises. The time at which it becomes calm after the land and sea
breezes is indefinite, and the calms are of unequal duration. Generally, those which precede the sea-breeze are rather longer than
those which precede the land-breeze. The temperature of the
land, the direction of the coast-line with respect to the prevailing
direction of the trade-wind in which the land is situated, the clearness of the atmosphere, the position of the sun, perhaps also that
of the moon, the surface over which the sea-breeze blows, possibly
also the degree of moisture and the electrical state of the air, the
heights of the mountains, their extent, and their distance from the
coast, all have influence thereon. Local observations in regard to
these can afford much light, as well as determine the distance at
which the land-breeze blows from the coast, and beyond which the
regular trade-wind or monsoon continues uninterruptedly to blow.
The direction of land and sea winds must also be determined by
local observations, for the idea is incorrect that they should always
blow perpendicularly to the coast-line. Scarcely has one left the
Java Sea-which is, as it were, an inland sea between Sumatra,
Borneo, Java, and the archipelago of small islands between both
of the last named-than, in the blue waters of the easterly part of
the East Indian Archipelago, nature assumes a bolder aspect, more
in harmony with the great depth of the ocean. The beauty of
the Java Sea, and the delightful phenomena which air and ocean
display, have here ceased. The scene becomes more earnest. The
coasts of the eastern islands rise boldly out of the water, far in
whose depths they have planted their feet. The southeast wind,
which blows upon the southern coasts of the chain of islands, is
sometimes violent, always strong through the straits which separate them from each other, and this appears to be more and more
the case as we go eastward. Here, also, upon the northern coast,
we find land-breezes, yet the trade-wind often blows so violently
that they have not sufficient power to force it beyond the coast.
Owing to the obstruction which the chain of islands presents to
the southeast trade-wind, it happens that it blows with violence
away over the mountains, apparently as the land-breeze does upon
the north coast; yet this wind, which only rises when it blows
hard from the southeast upon the south coast, is easily distin* Such is the case, among others, in the Strait of Madura, upon the heights of
Bezoekie.




~ 322, 323.    RED FOGS AND SEA BREEZES.                139
guished from the gentle land-breeze. The regularity of the land
and sea breezes in the Java Sea and upon the coasts of the northern range of islands, Banca, Borneo, Celebes, etc., during the east
monsoon, must in part be ascribed to the hinderances which the
southeast trade-wind meets inl the islands which lie directly in its
way-in part to the inclination toward the east monsoon which
the trade-4ind undergoes after it has come within the archipelago
-and, finally, to its abatement as it approaches the equator. The
causes which produce the land-breezes thus appear collectively
not sufficiently powerful to be able to turn back a strong tradewind in the ocean."
322. Seamen tell us of "red fogs" which they sometimes enRed fogsinthe MIei- counter, especially in the vicinity of the Cape de
terranean.   Verd Islands. In other parts of the sea also they
meet showers of dust. What these showers precipitate in the
Mediterranean is called " sirocco dust," and in other parts "African dust,y~ because the winds which accompany them are supposed to come from the Sirocco desert, or some other parched
land of the continent of Africa. It is of a brick-red or cinnamon
color, and it sometimes comes down in such quantities as to obscure the sun, darken the horizon, and cover the sails and rigging
with a thick coating of dust, though the vessel may be hundreds
of miles from the land.
323. Dr. Clymer, Fleet-surgeon of the African squadron, reRed fogs near the ports a red fog which was encountered in February,
equator.     1856, by the U. S. ship Jamestown.  "We were,"
says he, "immersed in the dust-fog six days, entering it abruptly
on the night of the 9th of February, in lat. 70 30' N., and long.
15~ W., and emerging from it (and at the same time from the
zone of the equatorial calms into the northeast trades) on the 15th
instant, in lat. 90 N., and long. 19~ W. With these winds we
beat to Porto Praya (in lat. 14~ 54' N., and long. 23~ 30' W.),
crossing a southwest current of nearly a mile an hour, arriving at
Porto Praya on the 22d of February. The red dust settled thickly on the sails, rigging, spars, and decks, from which it was easily
collected. It was an impalpable powder, of a brick-dust or cinnamon color. The atmosphere was so dusky that we could not
have seen a ship at midday beyond a quarter of a mile."t
* Prof. Ehrenberg calls it " Sea-dust."
t See Sailing Directions, 8th ed., vol. ii., p. 377.




140       THE PHYSICAL GEOGRAPHY OF THE SEA.
324. Now the patient reader, who has had the heart to follow
Putting tallies on me in a preceding chapter (IV.) around with " the
the wind.    wind in his circuits," will perceive that evidence in
detail is yet wanting to establish it as a fact that the northeast and
southeast trades, after meeting and rising up in the equatorial
calms, do cross over and take the paths represented by R S and
F G, Plate I. Statements, and reasons, and arguments enough
have already been made and adduced (~ 288) to make it highly
probable, according to human reasoning, that such is the case;
and though the theoretical deductions showing such to be the case
be never so plausible, positive proof that they are true can not
fail to be received with delight and satisfaction. Were it possible
to takle a portion of this air, which should represent, as it travels
along with the southeast trades, the general course of atmospherical circulation, and to put a tally on it by which we could follow
it in its circuits and always recognize it, then we might hope actually to prove, by evidence the most positive, the channels
through which the air of the trade-winds, after ascending at the
equator, returns whence it came. But the air is invisible; and it
is not easily perceived how either marks or tallies may be put
upon it, that it may be traced in its paths through the clouds.
The skeptic, therefore, who finds it hard to believe that the general circulation is such as Plate I. represents it to be, might consider himself safe in his unbelief were he to declare his willingness to give it up the moment any one should put tallies on the
wings of the wind, which would enable him to recognize that air
and those tallies again, when found at other parts of the earth's
surface. As difficult as this seems to be, it has actually been
done. Ehrenberg, with his microscope, has established, almost
beyond a doubt, that the air which the southeast trade-winds
bring to the equator does rise up there and pass over into the
northern hemisphere. The Sirocco or African dust, which he
has been observing so closely, has turned out to be tallies put
upon the wind in the other hemisphere; and this beautiful instrument of his enables us to detect the mark on these little tallies as
plainly as though those marks had been written upon labels of
wood and tied to the wings of the wind.
325. This dust, when subjected to microscopic examination, is
found to consist of infusoria and organisms whose habitat is not




~ 325.         RED FOGS AND SEA BREEZES,                141
They tell of a cross- Africa, but South America, and in the southeast
ing at the calm
belts.      trade-wind region of South America. Professor
Ehrenberg has examined specimens of sea-dust from the Cape de
Verds and the regions thereabout-from Malta, Genoa, Lyons, and
the Tyrol-and he has found a similarity among them as striking
as it would have been had these specimens been all taken from
the same pile. South American forms he recognizes in all of
them; indeed, they are the prevailing forms in every specimen
he has examined. It may, I think, be now regarded as an established fact that there is a perpetual upper current of air from
South America to North Africa; and that the volume of air
which flows to the northward in these upper currents is nearly
equal to the volume which flows to the southward with the northeast trade-winds, there can be no doubt. The "rain dust" has
been observed most frequently to fall in spring and autumn;
that is, the fall has occurred after the equinoxes, but at intervals
from them varying from thirty to sixty days, more or less. To
account for this sort of periodical occurrence of the falls of this
dust, Ehrenberg thinks it " necessary to suppose a dust-cloud to be
constantly swimming in the atmosphere by continuous currents of air,
and lying in the region of the trade-winds, but suffering _partial and
periodical deviations."  It has already been shown (~ 295) that the
rain or calm belt between the trades travels up and down the
earth from north to south, making the rainy season wherever it
goes. The reason of this will be explained in another place.
This dust is probably taken up in the dry, and not in the wet
season; instead, therefore, of its being "held in clouds suffering
partial and periodical deviations," as Ehrenberg suggests, it more
probably comes from one place about the vernal, and from another about the autumnal equinox; for places which have their
rainy season at one equinox have their dry season at the other.
At the time of the vernal equinox, the valley of the Lower Orinoco is then in its dry season-every thing is parched up with
the drought; the pools are dry, and the marshes and plains become arid wastes. All vegetation has ceased; the great serpents
and reptiles have buried themselves for hibernation;* the hum
of insect life is hushed, and the stillness of death reigns through
the valley. Under these circumstances, the light breeze, raising
* Humboldt.




142       THE PHYSICAL GEOGRAPHY OF THE SEA.
dust from lakes that are dried up, and lifting motes from the
brown savannas, will bear them  away like clouds in the air.
This is the period of the year when the surface of the earth in
this region, strewed with impalpable and feather-light remains of
animal and vegetable organisms, is swept over by whirlwinds,
gales, and tornadoes of terrific force; this is the period for the
general atmospheric disturbances which have made characteristic
the equinoxes. Do not these conditions appear sufficient to afford the "rain dust" for the spring showers?  At the period of
the autumnal equinox, another portion of the Amazonian basin
is parched with drought, and liable to winds that fill the air with
dust, and with the remains of dead animal and vegetable matter;
these impalpable organisms, which each rainy season calls into
being, to perish the succeeding season of drought, are perhaps
distended and made even lighter by the gases of decomposition
which has been going on in the period of drought. May not,
therefore, the whirlwinds which accompany the vernal equinox,
and sweep over the lifeless plains of the Lower Orinoco, take up
the "rain dust" which descends in the northern hemisphere in
April and May? and may it not be the atmospherical disturbances which accompany the autumnal equinox that take up the
microscopic organisms from the Upper Orinoco and the great
Amazonian basin for the showers of October?
326. The Baron von Humboldt, in his Aspects of Nature, thus
Iumboldt's descrip- contrasts the wet and the dry seasons there:
tion of the dust-whirlwinds of the Orinoco. "When, under the vertical rays of the neverclouded sun, the carbonized turfy covering falls into dust, the indurated soil cracks asunder as if from the shock of an earthquake.
If at such times two opposing currents of air, whose conflict produces a rotary motion, come in contact with the soil, the plain assumes a strange and singular aspect. Like conical-shaped clouds,
the points of which descend to the earth, the sand rises through
the rarefied air on the electrically-charged centre of the whirling
current, resembling the loud water-spout, dreaded by the experienced mariner. The lowering sky sheds a dim, almost straw-colored light on the desolate plain. The horizon draws suddenly
nearer, the steppe seems to contract, and with it the heart of the
wanderer. The hot, dusty particles which fill the air increase its
suffocating heat, and the east wind, blowing over the long-heated




~ 327.         RED FOGS AND SEA BREEZES.                143
soil, brings with it no refreshment, but rather a still more burning
glow. The pools which the yellow, fading branches of the fanpalm had protected from evaporation, now gradually disappear.
As in the icy north the animals become torpid with cold, so here,
under the influence of the parching drought, the crocodile and the
boa become motionless and fall asleep, deeply buried in the dry
mud..... The distant palm-bush, apparently raised by the
influence of the contact of unequally heated and therefore unequally dense strata of air, hovers above the ground, from which
it is separated by a narrow intervening margin. Half-concealed
by the dense clouds of dust, restless with the pain of thirst and
hunger, the horses and cattle roam around, the cattle lowing dismally, and the horses stretching out their long necks and snuffing
the wind, if haply a moister current may betray the neighborhood
of a not wholly dried-up pool...... At length, after the long
drought, the welcome season of the rain arrives; and then how
suddenly is the scene changed! I..... Hardly has the surface
of the earth received the refreshing moisture, when the previously
barren steppe begins to exhale sweet odors, and to clothe itself
with killingias, the many panicles of the paspulum, and a variety
of grasses. The herbaceous mimosas, with renewed sensibility to
the influence of light, unfold their drooping, slumbering leaves to
greet the rising sun; and the early song of birds and the opening
blossoms of the water plants join to salute the morning."
327. The arid plains and deserts, as well as high mountain
Are the great des- ranges, have, it may well be supposed, an influence
erts centres of circulation?      upon the movements of the great aerial ocean, as
shoals and other obstructions have upon the channels of circulation in the sea. The deserts of Asia, for instance, produce (~ 299)
a disturbance upon the grand system of atmospherical circulation,
which, in summer and autumn, is felt in Europe, in Liberia, and
away out upon the Indian Ocean, as far to the south as the equinoctial line. There is an indraught from all these regions toward
these deserts. These indraughts are known as monsoons at sea;
on the land, as the prevailing winds of the season. Imagine the
area within which this indraught is felt, and let us ask a question
or two, hoping for answers. The air which the indraught brings
into the desert places, and which, being heated, rises up there,
whither does it go? It rises up in a column a few miles high and




144       THE PHYSICAL GEOGRAPHY OF THE SEA.
many in circumference, we know, and we can imagine that it is
like a shaft many times thicker than it is tall; but how is it crowned? Is it crowned like the stem of a mushroom, with an efflorescence or ebullition of heated air flaring over and spreading out
in all directions, and then gradually thinning out as an upper current, extending even unto the verge of the area whence the indraught is drawn? If so, does it then descend and return to the
desert plains as an indraught again?  Then these desert places
would constitute centres of circulation for the monsoon period;
and if they were such centres, whence would these winds get the
vapor for their rains in Europe and Asia? Or, instead of the
mushroom shape, and the flare at the top in all directions from
centre to circumference, does the uprising column, like one of
those submarine fountains which are said to be in the Gulf Stream
off the coast of Florida, bubble up and join in with the flow of
the upper current? The right answers and explanations to these
questions would add greatly to our knowledge concerning the general circulation of the atmosphere. It may be in the power of
observation and the microscope to give light here. Let us hope.
328. The color of the "rain dust," when collected in parcels
The color of "sea- and sent to Ehrenberg, is "brick-red," or "yellow
dust."       ochre;" when seen by Humboldt in the air, it was
less deeply shaded, and is described by him2 as imparting a " straw
color" to the atmosphere. In the search of spider-lines for the
diaphragm of my telescopes, I procured the finest and best threads
from a cocoon of a dirty-red color; but the threads of this cocoon,
as seen singly in the diaphragm, were of a golden color; there
would seem, therefore, no difficulty in reconciling the difference
between the colors of the rain dust when viewed in little piles by
the microscopist, and when seen attenuated and floating in the
wind by the great traveler.
329. It appears, therefore, that we here have placed in our hands
A clew leading into a clew, which, attenuated and gossamer-like though
the chambers of the
south.      it at first appears, is nevertheless palpable and
strong enough to guide us along through the "circuits of the
wind' even unto " the chambers of the south."  The frequency
of the fall of " rain dust" between the parallels of 17~ and 25~
north, and in the vicinity of the Cape Verd Islands, is remarked
upon with emphasis by the microscopist. It is worthy of remark,




~ 330, 331.     RED FOGS AND SEA BREEZES.                  145
because, in connection with the investigations at the Observatory,
it is significant. The latitudinal limits of the northern edge of
the northeast trade-winds are variable.  In the spring they are
nearest to the equator, extending sometimes at this season not farther from the equator than the parallel of 15~ north. The breadth
of the calms of Cancer is also variable; so also are their limits.
The extreme vibration of this zone is between the parallels of
17~ and 38~ north, according to the season of the year.
330. According to the hypothesis (~ 210) suggested by my reRed fogs do not al- searches, this is the region in which the upper curways occur at the
same place, but they rents of atmosphere that ascended in the equatorial
occur on a northeast
anldsouthwestrange. calms, and flowed off to the northward and eastward, are supposed to descend. This, therefore, is the region in
which the atmosphere that bears the "rain dust,' or "African
sand," descends to the surface; and this, therefore, is the region,
it might be supposed, which would be the most liable to showers
of this "dust." This is the region in which the Cape Verd Islands are situated; they are in the direction which theory gives to
the upper current of air from the Orinoco and Amazon with its
" rain dust," and they are in the region of the most frequent showers of " rain dust:" all of which, though they do not absolutely
prove, are nevertheless strikingly in conformity with this theory
as to the circulation of the atmosphere.
331. It is true that, in the present state of our information, we
Conditions requisite can not tell why this " rain dust" should not be
to the production of
a sea fog.   gradually precipitated from this upper current, and
descend into the stratum  of trade-winds, as it passes from the
equator to higher northern latitudes; neither can we tell why the
vapor which the same winds carry along should not, in like manner, be precipitated on the way; nor why we should have a thunder-storm, a gale of wind, or the display of any other atmospherical phenomenon to-morrow, and not to-day: all that we can say
is, that the conditions of to-day are not such as the phenomenon
requires for its own development.  Therefore, though we can not
tell why the "sea-dust" should not always fall in the same place,
we may nevertheless suppose that it is not always in the atmosphere, for the storms that take it up occur only occasionally, and
that when up, and in passing the same parallels, it does not, any
more than the vapor from a given part of the sea, always meet
K




146       THE PHYSICAL GEOGRAPHY OF THE SEA.
with the conditions-electrical and others-favorable to its descent, and that these conditions, as with the vapor, may occur now
in this place, now in that. But that the fall does occur always in
the same atmospherical vein or general direction, my investigations would suggest, and Ehrenberg's researches prove. Judging
by the fall of sea or rain dust, we may suppose that the currents
in the upper regions of the atmosphere are remarkable for their
general regularity, as well as for their general direction and sharpness of limits, so to speak. We may imagine that certain electrical conditions are necessary to a shower of "sea-dust" as well
as to a thunder-storm; and that the interval between the time of
the equinoctial disturbances in the atmosphere and the occurrence
of these showers, though it does not enable us to determine the
true rate of motion in the general system of atmospherical circulation, yet assures us that it is not less on the average than a certain rate. We can not pretend to prescribe the conditions requisite for bringing the dust-cloud down to the earth. The radiation
from the smoke-dust-as the particles of visible smoke may be
called-has the effect of loading each little atom of smoke with
dew, causing it to descend in the black fogs of London. Any circumstances, therefore, which may cause the dust that ascends as a
straw-colored cloud from the Orinoco to radiate its caloric and
collect moisture in the sky, may cause it to descend as a red fog
in the Atlantic or Mediterranean.
332. I do not offer these remarks as an explanation with which
What is the agent we ought to rest satisfied, provided other proof can
that guides the air  1
across the calm belts? be obtained; I rather offer them in the true philosophical spirit of the distinguished mricroscopist himself, simply as
affording, as far as they are entitled to be called an explanation,
that explanation which is most in conformity with the facts before us, and which is suggested by the results of a novel and beautiful system of philosophical research. It is not, however, my
province, or that of any other philosopher, to dictate belief. Any
one may found hypotheses if he will state his facts and the reasoning by which he derives the conclusions which constitute the
hypothesis. Having done this, he should patiently wait for time,
farther research, and the judgment of his peers, to expand, confirm, or reject the doctrine which he may have conceived it his
duty to proclaim. Thus, though we have tallied the air, and put




~ 332.        RED FOGS AND SEA BREEZES.              147
labels on the wind, to " tell whence it cometh and whither it goeth," yet there evidently is an agent concerned in the circulation
of the atmosphere whose functions are manifest, but whose presence has never yet been clearly recognized. When the air which
the northeast trade-winds bring down meets in the equatorial calms
that which the southeast trade-winds convey, and the two rise up
together, what is it that makes them cross? where is the power
that guides that from the north over to the south, and that from
the south up to the north?  The conjectures in the next chapter
as to "the relation between magnetism and the circulation of the
atmosphere" may perhaps throw some light upon the answer to
this question.




148         THE PHYSICAL GEOGRAPHY OF THE SEA.
CHAPTER VII.
~ 341-369.-THE  BASTING OF THE TRADE-WINDS, THE CROSSING
AT THE CALM  BELTS, AND THE MAGNETISM  OF THE ATMOSPHERE.
341. HALLEY'S theory of the trade-winds, especially so much
HIalley's theory not of it as ascribes their easterly direction to the effect
fully confirmed by
observations.  of the diurnal rotation of the earth, seems to have
been generally received as entirely correct. But it is only now,
since all the maritime nations of the world have united in a common system of research concerning the physics of the sea, and occupied it with observers, that we have been enabled to apply the
experimentlum crucis to this part of that famous theory.  The abstract logs, as the observing-books are called, have placed within
my reach no less than 632,460 observations-each one itself being
the mean of many separate ones-upon the force and direction of
the trade-winds. It appears from these that diurnal rotation being regarded as the sole cause does not entireiy account for the easting of these winds.
342. From these observations the following table has been comObserved course of piled.  It shows the mean annual direction of the
the trade-winds.   trade-winds in each of the six belts, north and south,
between the parallels of 30~ and the equator, together with the
number of observations from  which the mean for the belt is derived:
BN.E. Trades.          S.E. Trades.
Course.    No. of Obs.    Course.    No. of Obs.
300 and 25~  N. 510   E.  68,777   S. 46~ E.  66,635
250 and 200    510 30'     44,527     490 20'     66,395
200 and 150    530 30'     33,103     520         46,604
150 and 10~    52~0 30'   30,339      490 40'    43,817
10~ and 50     530 30'    36,841      510 40'    54,648
50 and 00     540 30'     67,829     480 40'     72,945
Mean.... N. 52~ 45' E.         S. 49~ 33' E.
Between the equator and 50 north, the annual average duration
of the trades is 67 days for the northeast/ and 199 for the southeast, with a mean direction for the latter-which are the prevail



~ 343, 344.    EASTING OF THE TRADE-WINDS, ETC.               149
ing winds between those parallels-of S. 47~ 30' E. According to
the Halleyan theory they should be southwest winds.
343. In the Atlantic the average velocity of the southeast is
Velocitios ofthetrade- greater than the average velocity of the northeast
wvinds.       trades.*  I estimate one to be from 14 to 18, the
other from about 25 to 30 miles an hour. Assuming their velocity to be 14 and 25, the following de partures show the miles of
easting which" the trade-winds average per hour through each of
the above-named belts:
HOURLY RATE OF DEPARTURE ACROSS THE TRADE-WIND BELTS.
Between      N.E. Trades.     S.E. Trades.
Easting per Hour.   Easting pet Hour.
30~ and 25~ 10.9 miles.         18. miles.
250 and 20~    11.  "l          19.  lC
200 and 150    11.2  "          19.7  "
15~ and 100    11.   "      j   19.1  "'
10~ and 50     11,2  "          19.6  "
50 and 00     11.4  "          18.8  "
344. That diurnal rotation does impart easting to these winds
Difference between there is no doubt; but the path suggested by the
observation and theory.          table does not conform to that which, according to
any reasonable hypothesis, the trade-winds would follow if left to
obey the forces of diurnal rotation alone, as they would do were
diurnal rotation the sole cause of their easting.  As these winds
approach the equator, the effect of diurnal rotation becomes more
and more feeble.  But the table shows no such diminution of effect. They have as much easting between 5~ and 0~ as they have
between 30~ and 25~.  Nay, the southeast trades between the
equcator and 5~ N.-where, by the Halleyan theory, they should
have westing-have as much easting (~ 342) as they have between
30~ and 25~ S.  We can not tell how much the air is checked in
its easterly tendency by resisting agents, by friction, etc., but we
know that tendency is ten times stronger between 30~ and 25~
than it is between 5~ and 0~, and yet actual observations show no
difference in their course. This table reminds us that diurnal rotation should not, until more numerous and accurate observations
shall better satisfy the theory than those half a million and more
now do, be regarded as the sole cause of the easterly direction of
the trade-winds. It suggests either that other agents are concern* "Average Force of the Trade-winds," p. 857, vol. ii., Maury's Sailing Directions, 1859.




150       THE PHYSICAL GEOGRAPHY OF THE SEA.
ed in giving the trade-winds their easting, or that the effect of the
upper and counter current, when drawn down and turned back
(~ 223), is such as to counteract their unequal turning in obedience
to the varying forces of diurnal rotation. No apology is needed
for applying the tests of actual observation to this part of the Halleyan theory, notwithstanding the general concurrence of opinion
as to its sufficiency. With equal favor that feature of it also was
received-which ascribes the rising up in the belt of equatorial
calms to the direct influence of the solar ray. But the advancement which has been made in our knowledge of physical laws
since Halley expounded his trade-wind theory suggested a review
of that feature, and it was found that, though the direct heat of
the sun is one of the agents which assists the air to rise there, it is
not the sole agent; the latent heat which is set free by condensing
vapor for the equatorial cloud-ring and its rains is now also (~ 245)
recognized as an agent of no feeble power in this calm belt.
345. Where shall those who are disposed to search look for this
Faraday's discovery other agent that is supposed to be'concerned with
of magnetism in the
air.        the trade-winds in their easting?  I can not say
where it is to be found, but, considering the recent discoveries in
terrestrial magnetism — considering the close relations between
many of its phenomena and those both of heat and electricity, the
question may be asked whether some power capable of guiding
"the wind in his circuits" may not lurk there. Oxygen comprises
more than one fifth part (two ninths) of the atmosphere, and Faraday has discovered that oxygen is para-magnetic. If a bar of
iron be suspended between the poles of a magnet, it will arrange
itself axially, and point toward them; but if, instead of iron, a bar
of bismuth be used, it will arrange itself equatorially, and point in
a direction perpendicular to that of the iron. To distinguish these
two kinds of forces, Dr. Faraday has said iron is para-magnetic,
bismuth dia-magnetic. Oxygen and iron belong to the same class,
and all substances in nature belong to one or the other of the two
classes of which iron and bismuth are the types.
346. This eminent philosopher has also shown that if you place
Lines of magnetic a magnetized bar of iron on a smooth surface, and
force.      sift fine iron filings down upon it, these filings will
arrange themselves in curved lines, as in Fig. 1; or, if the bar be
broken, they will arrange themselves as in F177g. 2. The earth it



~ 347.      EASTING OF THE TRADE-WINDS, ETC.              151
Fig. 1.                  Fig. 2.
-///.~= ~       // iiiii~/iiI.'
self or the atmospheric envelope by which it is surrounded, is a
most powerful magnet, and the lines of force which proceed wheth
er from its interior its solid shell or vaporous covering, are held
to be just such lines as those are which surround artificial magnets; proceed whence they may, they are supposed to extend
through the atmosphere, and to reach even to the planetary spaces.
Many eminent men and profound thinkers, Sir David Brewster
among them, suspect that the atmosphere itself is the seat of terrestrial magnetism.  All admit that many of those agents, both
thermal and electrical, which play highly important parts in the
meteorology of our planet, exercise a marked influence upon the
magnetic condition of the atmosphere also.
347. Now, when, referring to Dr. Faraday's discovery (~ 345),
The magnetic influ- and the magnetic lines of force as shown by the
ece of the ai and oxygen iron filings (~ 346), we compare the particles of oxspots on the sun.  ygen gas to these minute bits of ferruginous dust
that arrange themselves in lines and curves about magnets-when
we reflect that this great magnet, the earth, is surrounded by a
para-magnetic gas, to the molecules of which the finest atom from
the file is in comparison gross and ponderous matter-that the entire mass of this air is equivalent to a sea of mercury covering the
earth around and over to the depth of 30 inches, and that this




152       THE PHYSICAL GEOGRAPHY OF THE SEA.
very subtile mass is in a state of unstable equilibrium, and in perpetual commotion by reason of various and incessant disturbing
causes-when we reflect farther upon the recent discoveries of
Schwabe and of Sabine concerning the spots on the sun and the
magnetic elements of the earth, which show that if the sun or its
spots be not the great fountain of magnetism, there is at least reason to suspect a close alliance between solar and terrestrial magnetism; that certain well-known meteorological phenomena, as
the aurora, come also within the category of magnetic phenomena; that the magnetic poles of the earth and the poles of maximum cold are at the same spot; that the thermal equator is not
parallel to or coincident with either the terrestrial or with that
which the direct solar ray would indicate, but that it follows, and
in its double curvatures conforms to the magnetic equator; moreover, when we reflect upon Barlow's theory and Fox's observations, which go to show that the direction of metallic veins of the
northern hemisphere, which generally lie northeast and southwestwardly, must have been influenced by the direction of the magnetic meridians of the earth or air-when, I say, we reflect upon
magnetism in all its aspects, we may well inquire whether such a
mass of highly magnetic gas as that which surrounds our planet
does not intervene, by reason of its magnetism, in influencing the
circulation of the atmosphere and the course of the winds.
348. This magnetic sea, as the atmosphere may be called, is conThe needle in its di- tinually agitated; it is disturbed in its movements
rnO.l eariations, the by various influences which prevent it from adjustpgeea inth electic- ing itself to any permanent magnetic or other dytension, ll have the namical status; and its para-magnetic properties are
same hours for their        a       r    g
maximaandminima. known to vary with every change of pressure or
of temperature. The experiments of Faraday show that the magnetic force of the air changes with temperature; that it is least
near the equator, and greatest at the poles of maximum cold; that
it varies with the seasons, and changes night and day; nay, the
atmosphere has regular variations in its electrical conditions expressed daily at stated hours of maximum and maininum tension.
Coincident with this, and in all parts of the world; but especially
in sub-tropical latitudes, the barometer also has its maxima and
minima readings for the day. So also, and at the same hours, the
needle attains the maxima and minima of its diurnal variations.




~ 349.      EASTING OF THE TRADE-WINDS, ETC.             153
Without other time-piece, the hour of the day may be told by
these maxima and minima, each group of which occurs twice a
day and at six-hour intervals. These invisible ebbings and flowings-the diurnal change in the electrical tension-the diurnal
variation of the needle, and the diurnal rising and falling of the
barometer, follow each other as closely and as surely, if not quite
as regularly, as night the day. Any cause which produces changes
in atmospheric pressure invariably puts it in motion, giving rise
to gentle airs or furious gales, according to degree; and here, at
least, we have a relation between the movements in the air and
the movements of the needle so close that it is difficult to say
which is cause, which effect, or whether the two be not the effects
of a common cause.
349. Indeed, such is the nature of this imponderable called magThequestionraisedby netism, and such the suggestions made by Faramodern researches.  day's discoveries, that the question has been raised
in the minds of the most profound philosophers of the age whether the various forces of light, heat, and gravitation, of chemical
affinity, electricity, and magnetism, may not yet be all traced to
one common source. Surely, then, it can not be considered as unphilosophical to inquire of magnetism for some of the anomalous
movements that are observed in the atmosphere. These anomalies are many; they are not confined to the easting of the tradewinds; they are to be found in the counter-trades and the calm
belts also. There is reason to believe, as has already been stated
(~ 288), that there is a crossing of the winds at the calm belts
(~ 212), and it was promised to go more into detail concerning the
circumstances which seem to favor this belief. Our researches
have enabled us, for instance, to trace from the belt of calms, near
the tropic of Cancer, which extends entirely across the seas, an efflux of air both to the north and to the south. From the south
side of this belt the air flows in a steady breeze, called the northeast trade-winds, toward the equator (Plate I.); on the north side
of it, the prevailing winds come from it also, but they go toward
the northeast. They are the well-known westerly winds which
prevail along the route from this country to England in the ratio
of two to one. But why should we suppose a crossing to take
place here? We suppose so from these facts: because throughout
Europe, the land upon which these westerly winds blow, precipi



154       THE PHYSICAL GEOGRAPHY OF THE SEA.
tation is in excess of evaporation, and because at sea they are going from a warmer to a colder climate, and therefore it may be inferred that nature exacts from them what we know she exacts
from the air under similar circumstances, but on a smaller scale,
before our eyes, viz., more precipitation at sea than evaporation.
In other words, they probably leave in the Atlantic as much vapor
as they take up from the Atlantic. Then where, it may be asked,
does the'vapor which these winds carry along, for the replenishing of the whole extra-tropical regions of the north, come from?
They did not get it as they came along in the upper regions, a
counter-current to the northeast trades, unless they evaporated the
trade-wind clouds, and so robbed those winds of their vapor. They
certainly did not get it from the surface of the sea in the calm belt
of Cancer, for they did not tarry long enough there to become saturated with moisture. Thus circumstances again pointed to the
southeast trade-wind regions as the place of supply. This question has been fully discussed in Chapter V., where it has been
shown they did not get it from the Atlantic. Moreover, these researches afforded grounds for the supposition that the air of which
the northeast trade-winds are comiposed, and which comes out of
the same zone of calms as do these southwesterly winds, so far from
being saturated with vapor at its exodus, is dry; for near their po~ lar edge, the northeast trade-winds are, for the most part, dry winds.
350. Facts seem to confirm this, and the calm belts of Cancer
Vwet and dry air of and Capricorn both throw a flood of light upon the
the calm belts. subject. These are two bands of light airs, calms,
and baffling winds, which extend entirely around the earth. The
air flows out north and south from,these belts. That which comes
out on the equatorial side goes to feed the trades, and makes a dry
wind; that which flows out on the polar side goes to feed the
counter-trades (~ 349), and is a rain wind. How is it that we can
have from the same trough or receiver, as these calm belts may
be called, an efflux of dry air on one side and of moist on the
other? Answer: upon the supposition that the air without rain
comes from one quarter, that with rain from another-that, coming from opposite directions to this place of meeting, where there
is a crossing, they pass each other in their circuits. They both
meet here as upper currents, and how could there be a crossing
without an agent or influence to guide them? and why should we




~ 351, 352.    EASTING OF THE TRADE-WINDS, ETC.        155
not look to magnetism for this agent as well as to any other, of
the influences which are concerned in giving to the winds their
force and direction?
351. HE that established the earth " created it not in vain; He
Principles according formed it to be inhabited."  And it is presumptuto which the physical mtchinery of our OUS, arrogant, and impious to attempt the study of
studied.    its machinery upon any other theory: it was made
to be inhabited. How could it be inhabitable but for the sending
of the early and the latter rain? How can the rain be sent except by the winds? and how can the fickle winds do their errands
unless they have a guide? Suppose a new piece of human mechanism were shown to one of us, and we were told the object of it
was to measure time; now, if we should seek to examine it with
the view to understand its construction, would we not set out upon
the principle-the theoryJ —that it was made to measure time?
By proceeding on any other supposition or theory we should be
infallibly led into error. And so it is with the physical machinery of the world. The theory upon which this work is conducted
is that the earth was made for man; and I submit that no part of
the machinery by which it is Imaintained in a condition fit for him
is left to chance, any more than the bit of mechanism by which
man measures time is left to go by chance.
352. That I might study to better advantage the workings of
Division into wind- the atmospherical machinery in certain aspects, I
bands.      divided the sea into bands 50 of latitude in breadth,
and stretching east and west entirely around the earth, but skipping over the land. There are twelve of these bands on each side
of the equator that are traversed more or less frequently by our
fleet of observers; they extend to the parallel of 60~ in each hemisphere. To determine the force and direction of the wind for each
one of these bands, the abstract logs were examined until all the
data afforded by 1,159,533 observations were obtained; and the
mean direction of the wind for each of the four quarters in every
band was ascertained. Considering difference of temperature between these various bands to be one of the chief causes of movement in the atmosphere —that the extremes on one hand are near
the equator, and on the other about the poles-considering that
the tendency of every wind (~ 234) is to blow along the arc of a
great circle, and therefore that every wind that was observed in




156         THE PHYSICAL GEOGRAPHY OF THE SEA.
any one of these bands must have moved in a path crossing these
bands more or less obliquely, and that therefore the general movements in the atmosphere might be classed accordingly, as winds either with northing or with southing in them. We have so classed
them; and we have so classed them that we might study to more
advantage the general movements of the great atmospherical machinery. See Plate XV.
353. Thus, when, after so classing them, we come to examine
The medialbands. those movements in the band between 5~ and 10~
south, and to contrast them with the movements in the band between 550 and 60O south, for example, we find the general movements to be exactly in opposite directions.  Observations show
that during the year the winds in the former blow toward the
equator 283, and from it 73 days; and in the latter they blow
toward the pole for 224, and from it 132 days.  These facts show
that there must be a place of rarefaction-of low barometer, an indraught toward the poles as well as the equator, and that consequently, also, there must be a medial line or band somewhere between the parallels of 10 and 550 south, on one side of which the
prevailing direction of the wind is toward the equator, on the
other toward the pole.  So, in the northern hemisphere, the same
series of observations point this medial band out to us. They show
that one is near the calm belt of Capricorn, the other near the
calm belt of Cancer, and that they both probably lie between the
parallels of 356 and 40~, where the winds north and south are
equal, as per table.
Winds with Northing and Winds with Sout/hing in each Hemisphlere, expsressed by the
Average Nusmber of Days for which they blow annually.
Northern HIemisphere.        Southern Hemisphere.
____Bands.    Northing.  Southing.  No. of Obs. Northing.  Southing.  No. of Obs.
Between     Days.    Days.               Days.    Days.
00 and 50     78       268     67,829       84      269      72,945
50 and 100    158      182     36,841       73      283      54,648
100 and 150    278       73     27,339       82      275      43,817
150 and 200    272       81     33,103      91       266      46,604
200 and 250    246      101     44,527      128      227      66,395
250 and 300    185     -162     68,777      146      208      66,635
300 and 350    155      195     62,514      150      204      76,254
350 and 400    173      178     41,233      178      177    107,231
400 and 450    163      186     33,252      202      155      63,669
450 and 500    164      188     29,461      209      148      29,132
500 and 550    147      204     41,570      208      151      14,286
550 and 690    141      213      17,874     224      132      13,617
504,320                      655,233
1],159,553




~ 354.      EASTING OF THE TRADE-WINDS, ETC.            157
The wind curves (Plate XV. and the table) afford a very striking
view of these medial bands, as the parallels in either hemisphere
between which the winds with northing and the winds with southing are on the yearly average exactly equal. In the northern
hemisphere the debatable ground appears by the table to extend
pretty nearly from 25~ to 50~ N. By the plate the two winds first
become equal between 25~ and 30~; the two curves then recede
and approach very closely again, but without crossing, between
35~ and 40~. In the southern hemisphere, the conflict between
the polar and equatorial indraught, as expressed by winds with
southing and winds with northing, is more decided. There the
two curves march, one up, the other down, and cross between
the parallels of 350 and 40~ S., thus confirming what from other
data we had already learned, viz., that the condition of the atmosphere is more unstable in the northern than it is in the southern
hemisphere.
354. Such, for the winds at sea, is their distribution between
The rainless regions the two halves of the horizon in the several bands
andthe calm belts. and in each hemisphere. Supposing a like distribution to obtain on shore, we shall find it suggestive to trace the
calm belts of the tropics across the continents (Plate VIII.), and
to examine, in connection with them, the rainless regions of the
earth, and those districts of country which, though not rainless,
are nevertheless considered as " dry countries," by reason of the
small amount of precipitation upon them. So, tracing the calm
belt of Cancer, which at sea lies between the parallels of 28~
and 37~ (Plate VIII.), but which, according to Sir John IHerschel,* reaches higher latitudes on shore, it will be perceived that
the winds that flow out on the north side blow over countries
abounding in rivers, which countries are therefore abundantly supplied with rains. Hence we infer (~ 350) that those winds are rcain
winds. On the other hand, the winds that flow out on the equatorial side blow either over deserts, rainless regions, or dry countries. Hence we infer that these winds are dry winds. These
" dry" winds traverse a country abounding in springs and rivers
in India, but it is the monsoons there which bring the water for
them. The winds which come out of this calm belt on its equatorial side give out no moisture, except as dew, until they reach
* ~ 273, p. 614, vol. xvii. (Phys. Geog.), Encyclopedia Britannica.




158       THE PHYSICAL GEOGRAPHY OF THE SEA.
the sea, and are replenished with vapor thence in sufficient quantities to make rain of; whereas the winds which come out on the
polar side leave moisture enough as they come for such rivers as
the Obi, the Yenisei, the Lena, and the Amoor, in Asia; the Missouri, the Sascatchawan, the Red River of the North, and others,
in America. Between this calm belt and the head waters of these
rivers there are no seas or other evaporating surfaces, neither are
they so situated with regard to the sea-coast that they may be, as
the shores of Eastern China and the Atlantic slopes of the United
States are, supplied with vapor by the winds from the sea-board.
When we consider the table (~ 353), the situation of the rainless
regions and dry countries with regard to the calm belt of Cancer,
we are compelled to admit that, come whence it may and by what
channels it may, there are flowing out of this calm belt two kinds
of air, one well charged with moisture,,the other dry and thirsty
to a degree.
355. The supposition that the dry air came from the north and
The theory of the the moist from the south, and both as an upper curcrossigs restacted, rent, is the only hypothesis that is consistent with
and the facts recon-1
ciled by it.  all the known facts of the case. The dry air gave
up all its moisture when, as a surface wind, it played upon the
frozen summits of the northern hills; the wet obtained its moisture when, as the southeast trade-winds, it swept across the bosom
of intertropical seas of the southern hemisphere. Rising up at the
equator, it did not leave all its moisture with the cloud-ring, but,
retaining a part, conveyed it through the cloud region, above the
northeast trades, to this calm belt, where there was a descent and
a crossing. The fact that these dry places are all within or on
the equatorial side of this calm belt, while countries abounding
with rains and well watered with running streams are to be found
all along its polar side, is clearly indicative of a crossing. Upon
no other supposition can we account for the barrenness on one
side, the fertility on the other. The following are also links in
the chain of facts and circumstances which give strength to the
supposition that the rains for the Lena and the Missouri are
brought across the calm belt of Cancer by those currents of air
which flow thence toward the pole as the prevailing countertrades or southwesterly winds of the extra-tropical north. We
have already seen (~ 353) that, on the north side of this calm zone




~ 355.      EASTING OF THE TRADE-WINDS, ETC.          159
of Cancer, the prevailing winds on the surface are from this zone
toward the pole, and (Plate, ~ 215) that these winds return as A,
B, C through the upper regions from the pole; that, arriving at
the calms of Cancer, this upper current, A, B, C, meets another
upper current, S, R, from the equator, where they neutralize each
other, produce a calm, descend, and come out as surface winds,
D, E, or the trade-winds; and as T, U, or the counter-trades.
Now observations have shown that the winds represented by T, U
are rain winds; those represented by D, E, dry winds; and it is evident that A, B, C could not bring any vapors to these calms to
serve for T, U to make rains of; for the winds represented by
A, B, C have already performed the circuit of surface winds as
far as the pole, during which journey they parted with all their
moisture, and, returning through the upper regions of the air to the
calm belt of Cancer, they arrived there as dry winds. The winds
represented by D, E are dry winds; therefore it was supposed
that these are, for the most part, but a continuation of the winds A,
B3, C. On the other hand, if the winds A, B, C, after descending,
do turn about and become the surface winds T, U, they would first
have to remain a long time in contact with the sea, in order to be
supplied with vapor enough to feed the great rivers, and supply
the rains for the whole earth between us and the north pole. In
this case, we should have an evaporating region at sea and a
rainless region ashore on the north as well as on the south side
of this zone of Cancer; but investigation shows no such region.
Hence it was inferred that B, C and R, S do come out on the
surface as represented by Plate I. But what is the agent that
should lead them out by such opposite paths? According to this
mode of reasoning, the vapors which supply the rains for T, U
would be taken up in the southeast trade-wind region by O, Q,
and conveyed thence along the route Q, R, S to T. And if this
mode of reasoning be admitted as plausible-if it be true that R,
S carry the vapor which, by condensation, is to water with showers the extra-tropical regions of the northern hemisphere, Nature,
we may be sure, has provided a guide for conducting S, T across
this belt of calms, and for sending it on in the right way. Here
it was, then, at this crossing of the winds, that I thought I first
saw the footprints of an agent whose character I could not comprehend. Can it be the magnetism that resides in the oxygen of




160       THE PHYSICAL GEOGRAPHY OF THE SEA.
the air?  Heat and cold, the early and the latter rain, clouds and
sunshine, are not, we may rely upon it, distributed over the earth
by chance; they are distributed in obedience to laws that are as
certain and as sure in their operations as the seasons in their
rounds. If it depended upon chance whether the dry air should
come out on this side or on that of this calm belt, or whether the
moist air should return or not whence it came-if such were the
case in nature, we perceive that, so far from any regularity as to
seasons, we should have, or might have, years of drought the most
excessive, and then again seasons of rains the most destructive;
but, so far from this, we find for each place a mean annual proportion of both, and that so regulated withal, that year after year
the quantity is preserved with remarkable regularity. Having
thus shown that there is no reason for supposing that the upper
currents of air, when they meet over the calms of Cancer and Capricorn, are turned back to the equator, but having shown that
there is reason for supposing that the air of each current, after descending, continues on in the direction toward which it was traveling before it descended, we may go farther, and, by a similar
train of circumstantial evidence, afforded by these researches and
other sources of information, show that the air, kept in motion on
the surface by the two systems of trade-winds, when it arrives at
the belt of equatorial calms and ascends, continues on thence, each
current toward the pole which it was approaching while on the
surface. In a problem like this, demonstration in the positive
way is difficult, if not impossible. We must rely for our proof
upon philosophical deduction, guided by the lights of reason; and
in all cases in which positive proof can not be adduced, it is permitted to bring in circumstantial evidence; and the circumstantial evidence afforded by my investigations goes to show that the
winds represented by 0, Q, ~ 215, do become those represented by
R, S, T, U, V, A, and A, B, C, D, E, F respectively. In the first
place, 0, Q represents the southeast trade-winds-i. e., all the winds
of the southern hemisphere as they approach the equator; and is
there any reason for supposing that the atmosphere does not pass
freely from one hemisphere to another?  On the contrary, many
reasons present themselves for supposing that it does. If it did
not, the proportion of land and water, and consequently of plants
and warm-blooded animals, being so different in the two hemi



~ 355.      EASTING OF THE TRADE-WINDS, ETC.            161
spheres, we might imagine that the constituents of the atmosphere
in them would, in the course of ages, probably become different
also, and that consequently, in such a case, man could not safely
pass from one hemisphere to the other. Consider the manifold
beauties in the whole system of terrestrial adaptations; remember
what a perfect and wonderful machine (~ 261) is this atmosphere;
how exquisitely balanced and beautifully compensated it is in all
its parts. We know that it is perfect; that in the performance of
its various offices it is never left to the guidance of chance-no,
not for a moment. Wherefore I was led to ask myself why the
air of the southeast trades, when arrived at the zone of equatorial
calms, should not, after ascending, rather return to the south than
go on to the north? Where and what is the agency by which its
course is decided?  Here I found circumstances which again induced me to suppose it probable that it neither turned back to the
south nor mingled with the air which came from the regions of
the northeast trades, ascended, and then flowed indiscriminately
to the north or the south. B3ut I saw reasons for supposing that
what came to the equatorial calms as the southeast trade-winds
continued to the north as an upper current, and that what had
come to the same zone as northeast trade-winds ascended and continued over into the southern hemisphere as an upper current,
bound for the calm zone of Capricorn. And these are the principal reasons and conjectures upon which these suppositions were
based: At the seasons of the year when the area covered by the
southeast trade-winds is large, and when they are evaporating most
rapidly in the southern hemisphere, even up to the equator, the
most rain is falling in the northern. Therefore it is fair to suppose that much of the vapor which is taken up on that side of the
equator is precipitated on this.. The evaporating surface in the
southern hemisphere is greater, much greater, than it is in the
northern; still, all the great rivers are in the northern hemisphere,
the Amazon being regarded as common to both; and this fact, as
far as it goes, tends to corroborate the suggestion as to the crossing of the trade-winds at the equatorial calms. Taking. the laws
and rates of evaporation into consideration, I could find (Chapter
V.) no part of the ocean of the northern hemisphere from which
the sources of the Mississippi, the St. Lawrence, and the other
great rivers of our hemisphere could be supplied. A regular seL




162       THE PHYSICAL GEOGRAPHY OF THE SEA.
ries of meteorological observations has been carried on at the military posts of the United States since 1819. Rain maps of the
whole country* have been prepared from these observations by
Mr. Lorin Blodget at the surgeon general's office, and under the
direction of Dr. Cooledge, U. S. A. These maps, as far as they
go, sustain these views in a remarkable manner, for they bring
out facts in a most striking way to show that the dry season in
California and Oregon is the wet season in the Mississippi Valley. The winds coming from the southwest, and striking upon
the coasts of California and Oregon in winter, precipitate there
copiously. They then pass over the mountains robbed in part of
their moisture. Of course, after watering the Pacific shores, they
have not as much vapor to make rains of, especially for the upper
Mississippi Valley, as they had in the summer time, when they
dispensed their moisture, in the shape of rains, most sparingly upon
the Pacific coasts. According to these views, the dry season on
the Pacific slopes should be the wet, especially in the upper Mississippi Valley, and vice versa. Blodget's maps show that such is
actually the case. Meteorological observations in the " Red River
country" and other parts of British America would throw farther
light and give farther confirmation, I doubt not, both to these
views and to this interesting question. These army observations,
as expressed in Blodget's maps, reveal other interesting features,
also, touching the physical geography of the country. I allude
to the two isothermal lines 45~ and 65~ (Plate VIII.), which include between them all places that have a mean annual temperature between 45~ and 650. I have drawn, for the sake of comparison, similar lines on the authority of Dove and Johnston (A.
K., of Edinburgh), across Europe and Asia. The isotherm of 65~
skirts the northern limits of the sugar-cane, and separates the intertropical from the extra-tropical plants and productions. I have
drawn these two lines across America in order to give a practical
exemplification of the nature of the advantages which the industrial pursuits and the political economy of the country would derive by the systematic extension of our meteorological observations from the sea to the land. These lines show how much we
err when we reckon climates according to parallels of latitude.
The space that these two isotherms of 45~ and 65~ comprehend
* See Army Meteorological Observations, published 1855.




~ 355.      EASTING OF THE TRADE-WINDS, ETC.           163
between the Mississippi and the Rocky Mountains, owing to the
singular effect of those mountains upon the climate, is larger than
the space they comprehend between the Mississippi and the Atlantic. l1yetographically it is also different, being dryer, and possessing a purer atmosphere. In this grand range of climate between the meridians of 100~ and 110~ W,, the amount of precipitation is just about one half of what it is between those two isotherms east of the Mississippi. In this new country west of it,
winter is the dry, and spring the rainy season. It includes the
climates of the Caspian Sea, which Humboldt regards as the most,
salubrious in the world, and where he found the most delicious
fruits that he saw during his travels. Such was the purity of the
air there, that polished steel would not tarnish even by night exposure. These two isotherms, with the remarkable loop which
they make to the northwest, beyond the Mississippi, embrace the
most choice climates for the olive, the vine, and the poppy; for
the melon, the peach, and almond. The finest of wool may be
grown there; and the potato, with hemp, tobacco, maize, and all the
cereals, may be cultivated there in great perfection. No climate
of the temperate zone will be found to surpass in salubrity that
of this Piedmont trans-Mississippi country. The calm zone of
Capricorn is the duplicate of that of Cancer, and the winds flow
from it as they do from that, both north and south, but with this
difference: that on the polar side of the Capricorn belt they prevail from the northwest instead of the southwest, and on the equatorial side from the southeast instead of the northeast. Now if it
be true that the vapor of the northeast trade-winds is condensed
in the extra-tropical regions of the southern hemisphere, the following path, on account of the effect of diurnal rotation of the
earth upon the course of the winds, would represent the mean circuit of a portion of the atmosphere moving according to the general system of its circulation over the Pacific Ocean, viz.: coming
down from the north as all upper current, and appearing on the
surface of the earth in about longitude 120~ west, and near the
tropic of Cancer, it would here commence to blow the northeast
trade-winds of that region. To make this clear, see Plate VII., on
which I have marked the course of such vapor-bearing winds; A
being a breadth or swath of winds in the northeast trades; B, the
same wind as the upper and counter-current to the southeast




164       THE PHYSICAL GEOGRAPHY OF THE SEA.
trades; and C, the same wind after it has descended in the calm
belt of Capricorn, and come out on the polar side thereof, as the
rain winds and prevailing northwest winds of the extra-tropical
regions of the southern hemisphere. This, as the northeast trades,
is the evaporating wind. As the northeast trade-wind, it sweeps
over a great waste of waters lying between the tropic of Cancer
and the equator. Meeting no land in this long oblique track over
the tepid waters of a tropical sea, it would, if such were its route,
arrive, somewhere about the meridian of 140~ or 1500 west, at the
belt of equatorial calms, which always divides the northeast from
the southeast trade-winds. Here, depositing a portion of its vapor
as it ascends, it would, with the residuum, take, on account of diurnal rotation, a course in the upper region of the atmosphere to
the southeast, as far as the calms of Capricorn. Here it descends
and continues on toward the coast of South America, in the same
direction, appearinrg now as the prevailing northwest wind of the
extra-tropical regions of the southern hemisphere. Traveling on
the surface from warmer to colder regions, it must, in this part of
its circuit, precipitate more than it evaporates. Now it is a coincidence, at least, that this is the route by which, on account of the
land in the northern hemisphere, the northeast trade-winds have
the fairest sweep over that ocean. This is the route by which
they are longest in contact with an evaporating surface; the route
by which all circumstances are most favorable to complete saturation; and this is the route by which they can pass over into the
southern hemisphere most heavily laden with vapors for the extra-tropical regions of that half of the globe; and this is the supposed route which the northeast trade-winds of the Pacific take to
reach the equator and to pass from it. Accordingly, if this process of reasoning be good, that portion of South America between
the calms of Capricorn and Cape Horn, upon the mountain ranges
of which this part of the atmosphere, whose circuit I am considering as a type, first impinges, ought to be a region of copious precipitation. Now let us turn to the works on Physical Geography,
and see what we can find upon this subject. In Berghaus and
Johnston-department Hyetography-it is stated, on the authority of Captain King, R. N., that upward of twelve feet (one hundred and fifty-three inches) of rain fell in forty-one days on that
part of the coast of Patagonia which lies within the sweep of the




~ 356.      EASTING OF THE TRADE-WINDS, ETC.            165
winds just described. So much rain falls there, navigators say,
that they sometimes find the water on the top of the sea fresh and
sweet. After impinging upon the cold hill-tops of the Patagonian
coast, and passing the snow-clad summits of the Andes, this same
wind tumbles down upon the eastern slopes of the range as a dry
wind; as such, it traverses the almost rainless and barren regions
of cis-Andean. Patagonia and South Buenos Ayres, Plate VIII.
These conditions, the direction of the prevailing winds, and the
amount of precipitation, may be regarded as evidence afforded by
nature, if not in favor of, certainly not against, the conjecture that
such may have been the voyage of this vapor through the air. At
any rate, here is proof of the immense quantity of vapor which
these winds of the extra-tropical regions carry along with them
toward the poles; and I can imagine no other place than that
suggested, whence these winds could get so much vapor.
356. Notwithstanding the amount of circumstantial evidence
The question, Howl that has already been brought to show that the air
can two currents of
aircross? answered. which the northeast and the southeast trade-winds
discharge into.the belts of equatorial calms, does, in ascending,
cross —that from the southern passing over into the northern, and
that from the northern passing over into the southern hemisphere
(see 0, Q, IR, S, and D, E, F, G, ~ 215) —yet some have implied
doubt by asking the question, " How are two such currents of air
to pass each other?" And, for the want of light upon this point,
the correctness of my reasoning, facts, inferences, and deductions
have been questioned. In the first place, it may be said in reply,
the belt of equatorial calms is often several hundred miles across,
seldom less than sixty; whereas the depth of the volume of air that
the trade-winds pour into it is only about three miles, for that is
supposed to be about the height to which the trade-winds extend.
Thus we have the air passing into these calms by an opening on
the north side for the northeast trades, and another on the south
for the southeast trades, having a cross section of three. miles vertically to each opening. It then escapes by an opening upward,
the cross section of which is sixty or one hundred, or even three
hundred miles. A very slow motion upward there will carry off
the air in that direction as fast as the two systems of trade-winds,
with their motion of twenty miles an hour, can pour it in; and that
curds or flakes of air can readily cross each other and pass in




166       THE PHYSICAL GEOGRAPHY OF THE SEA.
different directions without interfering the one with the other, or
at least without interfering to that degree which prevents, we all
know. The brown fields in summer afford evidence in a striking
manner of the fact that, in nature, flakes, or streamlets, or curdles
of air do really move among each other without obstruction.
That tremulous motion which we so often observe above stubblefields, barren wastes, or above any heated surface, is caused by the
ascent and descent, at one and the same time, of flakes of air at
different temperatures, the cool coming down, the warm going up.
They do not readily commingle, for the astronomer, long after
nightfall, when he turns his telescope upon the heavens, perceives
and laments the unsteadiness they produce in the sky. If the air
brought to the calm belt by the northeast trade-winds differ in
temperature (and why not?) from that brought by the southeast
trades, we have the authority of nature for saying that the two
currents would not readily commingle (~ 98). Proof is daily afforded that they would not, and there is reason to believe that the
air of each current, in streaks, or patches, or flakes, does thread its
way through the air of the other without difficulty. Therefore we
may assume it as a postulate which nature concedes, that there
is no difficulty as to the two currents of air, which come into those
calm belts from different directions, crossing over, each in its proper direction, without mingling.
857. The same process of reasoning which conducted us (~ 355)
The rain winda in the into the trade-wind region of the northern hemiMississippi Valley. sphere for the sources of the Patagonian rains, now
invites us into the trade-wind regions of the South Pacific Ocean
to look for the vapor springs of the Mississippi. If the rain winds
of the Mississippi Valley come from the east, then we should have
reason to suppose that their vapors were taken up from the Atlantic Ocean and Gulf Stream; if the rain winds come from the south,
then the vapor springs might, perhaps, be in the Gulf of Mexico;
if the rain winds come from the north, then the great lakes might
be supposed to feed the air with moisture for the fountains of that
river; but if the rains come from the west, where, short of the
great Pacific Ocean, should we look for the place of evaporation?
Wondering where, I addressed a circular letter to farmers and
planters of the Mississippi Valley, requesting to be informed as to
the direction of their rain winds. I received replies from Virginia,




~ 358.      EASTING OF THE TRADE-WINDS, ETC.           167
Mississippi, Tennessee, Missouri, Indiana, and h)io; and, subsequently, from Colonel W. A. Bird, Buffalo, New York, who says,
"The southwest winds are our fair-weather winds; we seldom
have rain from the southwest." Buffalo may get much of its rain
from the Gulf Stream with easterly winds. But I speak of the
Mississippi Valley; all the respondents there, with the exception
of one in Missouri, said, "The southwest winds bring us our rains."
These winds certainly can not get their vapors from the Rocky
Mountains, nor from the Salt Lake, for they rain quite as much
upon that basin as they evaporate from it again; if they did not,
they would, in the process of time, have evaporated all the water
there, and the lake would now be dry. These winds, that feed the
sources of the Mississippi with rain, like those between the same
parallels upon the ocean, are going from a higher to a lower temperature; and the winds in the Mississippi Valley, not being in
contact with the ocean, or with any other evaporating surface to
supply them with moisture, must bring with them from some sea
or another that which they deposit. Therefore, though it may be
urged, inasmuch as the winds which brought the rains to Patagonia (~ 355) came direct from the sea, that they therefore took up
their vapors as they came along, yet it can not be so urged in this
case; and if these winds could pass with their vapors from the
equatorial calms through the upper regions of the atmosphere to
the calms of Cancer, and then as surface winds into the Mississippi Valley, it was not perceived why the Patagonian rain winds
should not bring their moisture by a similar route. These last are
from the northwest, from warmer to colder latitudes; therefore,
being once charged with vapors, they must precipitate as they go,
and take up less moisture than they deposit. The circumstance
that the rainy season in the Mississippi Valley (~ 355) alternates
with the dry season on the coast of California and Oregon, indicates that the two regions derive vapor for their rains from the
same fountains.
358. During the discussion of this subject, my friend Baron von
Ehrenberg and lhis Gerolt, the Prussian minister, had the kindness to
microscope.  place in my hand Ehrenberg's work, " Passat-Staub
und Blut-Regen."  Here I found another clew leading across the
calm places. That celebrated microscopist reports that he found
South American infusoria in the blood-rains and sea-dust of the




168       THE PHYSICAL GEOGRAPHY OF THE SEA.
Cape Verd Islands, Lyons, Genoa, and other places (~ 325); thus
confirming, as far as such evidence can, the indications of our observations, and increasing the probability that the general course
of atmospherical circulation is in conformity with the suggestions
of the facts gathered fromn the sea as I had interpreted them, viz.,
that the trade-winds of the southern hemisphere, after arriving at
the belt of equatorial calms, ascend and continue in their course
toward the calms of Cancer as an upper current from the southwest, and that, after passing this zone of calms, they are felt on
the surface as the prevailing southwest winds of the extra-tropical
parts of our hemisphere; and that, for the most part, they bring
their moisture with them from the trade-wind regions of the opposite hemisphere. I have marked on Plate VII. the supposed
track of the "Passat-Staub,"' showing where it was taken up in
South America, as at P, P, and where it was found, as at S, S;
the part of the line in dots denoting where it was in the upper
current, and the unbroken line where it was wafted by a surface
current; also on the same. plate is designated the part of the South
Pacific in which the vapor-springs for, the Mississippi rains are
supposedto be. The hands (I) point out the direction of the
wind. Where the shading is light, the vapor is supposed to be carried by an upper current.. Such is the character of the circumstantial evidence which induced me to suspect that some agent,
whose office in the grand system of atmospherical circulation is
neither understood nor recognized, was at work in- these calm
belts and other places. It may be electrical, or it may be magnetic, or both conjoined.
359. The more we study the workings of the atmospherical
Quetelet's observa- machinery of our planet, the more are we impresstions.       ed with the conviction that we as yet know, very
little concerning its secret springs, and the little "' governors" here
and there which regulate its movements. My excellent friend M.
Quetelet, the astronomer royal at Brussels, has instituted a most
excellent series of observations upon' atmospherical electricity.
He has shown that there is in the upper regions of the air a great
reservoir of positive electricity, which increases as the temperature
diminishes. So, too, with the magnetism of the oxygen in the upper regions.
360. In the southern hemisphere, we may, by reason of its great




~ 361.       EASTING OF THE TRADE-WINDS, ETC.            169
At sea in the south- aqueous area, suppose the general law of atmosern hemisphere we pherical movements to be better developed than it
have the rule, on
lnd inthe nor,the'tn is in the northern hemisphere. We accordingly
thie goeneral circul see by the table (~ 353) that the movements north
tion  of the atmosphere.       and south between 45~ and 50~ correspond with the
movements south and north between 250 and 30~; that as you
go from the latter band toward the equator the winds with southing in them increase, while the winds with northing in them increase as you go from the former toward the pole.
361. This is the law in both hemispheres, thus indicating that
The magnetic poles, there must be in the polar regions, as in the equathe poles of the wind
and of cold coincident. torial, a calm place, where these polar-bound winds
cease to go forward, rise up, and commence their return (~ 214) as
an upper current. So we have theoretically a calm disc, a polygon-not a belt-about each pole. The magnetic poles and the
poles of maximum cold (~ 347) are coincident. Do.not those
calm discs, or "poles of the wind," and the magnetic poles, cover
the same spot, the two standing in the relation of cause and effect?
This question was first asked several years ago,* and I was then
moved to propound it by the inductions of theoretical reasoning.
Observers, perhaps, may never reach those inhospitable regions
with their instruments to shed more light upon this subject'; but
Parry and Barrow have found reasons to believe in the existence
of a perpetual calm about the north pole, and, later, Bellot has reported the existence of a calm region within the frigid zone. Professor J. H. Coffin, in an elaborate and valuable papert on the
"WINDS OF THE NORTHERN HEMISPHERE," arrives by deduction
at a like conclusion. In that paper he has discussed the records
at no less than five hundred and seventy-nine meteorological stations, embracing a totality of observations for two thousand eight
hundred and twenty-nine years. He places his" meteorological
pole"-pole of the wifids-near latitude 84~ north, longitude 105~
west. The pole of maximum cold, by another school of philosophers, Sir David Brewster among them, has been placed in latitude 800 north, longitude 100~ west; and the magnetic pole, by
still another school,4 in latitude 73~ 35' north, longitude 950 39'
west. Neither of these poles is a point susceptible of definite and
* Maury's Sailing Directions.
t Smithsonian Contributions to Inowledge, vol. vi., 1854.  ~ Gauss.




170       THE PHIYSICAL GEOGRAPHY OF THE SEA.
exact position. The polar calms are no more a point than the
equatorial calms are a line; and, considering that these poles are
areas or discs, not points, it is a'little curious that philosophers in
different parts of the world, using different data, and following up
investigation each through a separate and independent system of
research, and each aiming at the solution of different problems,
should nevertheless agree in assigning very nearly the same position to them all. Are these three poles grouped together by
chance or by some physical cause? By the latter, undoubtedly.
Here, then, we have another of those gossamer-like clews, that
sometimes seem almost palpable enough for the mind, in its happiest mood, to lay hold of, and follow up to the very portals of
knowledge, where we pause and linger, fondly hoping that the
chambers of hidden things may be thrown open, and that we may
be permitted to behold and contemplate the mysteries of the winds,
the frost, and the trembling needle. In the polar calms there is
(~ 215) an ascent of air; if An ascent, a diminution of pressure
and an expansion; and if expansion, a decrease of temperature.
Therefore we have palpably enough a connecting link here between the polar calms and the polar place of maximum cold.
Thus we establish a relation between the pole of the winds and
the pole of cold, with evident indications that there is also a physical connection between these and the magnetic pole. Here the
outcroppings of a relation between magnetism and the circulation
of the atmosphere again appear.
362. Thousands of observations, made by mariners and recordThe barometer in the ed in their abstract logs, have enabled us to de1wind bands. termine approximately the mean height of the barometer for the various bands (~ 352) at sea. Between the parallels of 36~ S. and 50~ N., Lieut. Andrau, of the Dutch Navy, has
collected from the abstract logs at the Meteorological Institute of
Utrecht no less than 83,334 observations on the height of the barometer in the following bands:




~ 363-365.      EASTING OF THE TRADE-WINDS, ETC.                           171
Number of Observations and Mean Height of the Barometer (temperature 32~) between
the Parallels of 360 S. and 50~ N.
North.      Barometer.   No.        South.        Barometer.   No.
00 and 50 (1)  29.915       5114    00 and 5~        29.940       3692
50 and 100      29.922      5343    5~ and 100       29.981       3924
100 and 150      29.964      4496   10~ and 150       30.028       4156
15~ and 200      30.018      3592   150 and 20~       30.060       4248
200 and 250      30.081      3816   200 and 250       30.102       4536
250 and 30~ 30.149           4392   25~ and 30~ 30.095             4780
300 and 350      30.210      4989   30~ and 36~ (1)  30.052        6970
350 and 40~      30.124      5103   420 53'            29.90 (5)
40~ and 450      30.077      5899   450 0'             29.66 (6)
450 and 500      30.060      8282   490 08'            29.47
510 29'          29.99  (2)         510 33'            29.50
590 51'          29.88 (3)           540 26'           29.35
78~ 37'          29.759 (4)          550 52'           29.36
60~ 0'            29.11
660 0'            29.08
74~ 0'           28.93
(1) From 50~ N. to 36~ S. the observations are the mean of 83,334 taken from "Maandelijksche
Zeilaanwijziffgen van Java naar het Kanaal Koninklijk Nederlandsch Meteorologisch Instituut, 1859."
(2) Greenwich; mean of 4 years' observations.
(3) St. Petersburg; mean of 10 years' observations.
(4) Dr. Kane; 12,000 observations (mean of 1T months' observations).
(5) Hobart Town; mean of 10 years' observations.  (6) Sir J. C. Ross; " Erebus and Terror."
363. The diagram of the winds (Plate I.) has been constructed
More atmosphere in SO as to show  by  its shaded border this unequal
the                                       atmospouthern  the atmosphere  between  two
sphere.          hemispheres.  Htave we  not here  proof that'the
southern hemisphere (~ 261) is indeed the boiler to this mighty
atmospherical engine? The aqueous vapor rising from its waste
of waters drives the air away from  the austral regions, just as the
vapor that is formed in the real steam-boiler expels the air from
it. This difference of atmosphere over the two halves of the
globe, as indicated by the barometer, is very suggestive.
364. Admiral Fitzroy has also reduced from  the abstract logs
A standard of com- in the Meteorological Department of the Board of
parison for the barometer at sea.  Trade in London  a great number of barometrical
observations.  He claims to have discovered  that about 50 N.
in the Atlantic Ocean the pressure of the atmosphere  is so uniform  as to  afford navigators a  natural standard by which, out
there at sea, they may, as they pass to and fro, compare their barometers.  This pressure is said to be so uniform, that after allowing for the six-hourly fluctuations, the mariner may detect
any error in his barometer amounting to the two or three thousandth part of 4n inch.
365. According to the views presented in ~ 358 and Plate VII.,




172       THE PHYSICAL GEOGRAPHY OF THE SEA.
Southeast trade-winds the southeast trade-winds, which reach the shores
having no moisture
traced over into rain- of Brazil near the parallel of Rio, and which blow
less regions of the
northern hemisphere. thence for the most part over the land, should be
the winds which, in the general course of circulation, would be
carried, after crossing the Andes and rising up in the belt of
equatorial calms, toward Northern Africa, Spain, and the South
of Europe. They might carry with them the infusoria of Ehrenberg (~ 358), but, according to this theory, they would be wanting in moisture. Now, are not those portions of the Old World,
for the most part dry countries, receiving but a small amount of
precipitation? Hence the general rule: those countries to the
north of the calms of Cancer, which have large bodies of land
situated to the southward and westward of them, in the southeast trade-wind region of the earth, should have a scanty supply
of rain, and vice versa. Let us try this rule: The extra-tropical
part of New Holland comprises a portion of land thus situated
in the southern hemisphere. Tropical India is to the northward
and westward of it; and tropical India is in the northeast tradewind region, and should give extra-tropical New Holland a slender supply of rain. But what modifications the monsoons of the
Indian Ocean may make to this rule, or what effect they may
have upon the rains in New Holland, my investigations in that
part of the ocean have not been carried far enough for final decision; though New Holland is a dry country.
366. The earth is nearer to the sun in the summer of the southEach hemisphere re- ern hemisphere than it is in the summer of the norththeies r amouet of rn; consequently, it has been held that one hemiheat.       sphere annually receives more heat than the other.
But the northern summer is 7.7 days longer than the southern;
and Sir John Herschel has shown, and any one who will take the
trouble may demonstrate, that the total amount of direct solar
heat received annually by each hemisphere is identically the
same, and therefore the northern hemisphere in its longer summer makes up with heat for the greater intensity but shorter
duration of the southern summer. But though the amount of
heat annually impressed by the sun upon each hemisphere be
identically the same, it by no means follows that the amount radiated off into space by each hemisphere again is also identically
the same. There is no reason to believe that the earth is grow



~ 367, 368.    EASTING OF THE TRADE-WINDS, ETC.            173
ing warmer or cooler, and therefore we infer that the total amount
of heat received annually by the whole earth is again annually radiated from the whole earth. Nevertheless, the two hemispheres
may radiate very unequally.
367. Direct observations concerning the amount of radiation
The northern radi- from different parts of the surface of our planet are
ates most.   meagre, and the results as to quantity by no means
conclusive; but we have in the land and sea breezes a natural index to the actinometry of sea and land, which shows that the radiating forces of the two are'very different.  Notwithstanding
the temperature of the land is raised so much above that of the
waters during the day, its powers of radiation* are so much greater than those of water that its temperature falls during the night
below that of the sea, and so low as to produce the land-breeze.
From  this fact it may be inferred that the hemisphere that has
most land dispenses most heat by radiation.
368. The question now may be well put: Since the two hemiAnother proof of the spheres receive annually the same amount of heat
crossings at the calm
belts.       from the sun, and since the northern hemisphere,
with its greater area of land, radiates most, whence does it derive
the surplus?  The theory of the crossing at the calm belts indicates both the way and the means, and suggests the answer; for
it points to the latent heat of vapor that is taken up in the southern hemisphere, transported by the winds across the calm belts,
and liberated, as the clouds drop down their fatness upon northern fields. It is not only the difference of radiating power between land and water that makes the northern continents the
chimneys of the earth, but the difference of cloud in a continental
and an oceanic sky must also greatly quicken the radiating powers of the northern hemisphere. Radiation goes on from the upper surface of the clouds and from the atmosphere itself, but we
know that clouds in a great measure obstruct radiation from the
sufface of the earth; and as the surface of the earth receives more
of the direct heat of the sun than the atmosphere, the point under
discussion relates to the mode in which the surface of the earth
gets rid of that heat. It gets rid of it chiefly in three ways: some
is carried off by convection in the air; some by evaporation; and
some by radiation; and such is the interference of clouds with
this last-named process, that we are told that during the rainy




174       THE PHYSICAL GEOGRAPHY OF THE SEA.
season in intertropical countries, as on the coast of Africa, there
is often not radiation enough to produce the phenomena of land
and sea breezes. The absence of dew in cloudy nights is a familiar
instance of the anti-radiating influence of clouds. The southern
hemisphere, being so much more aqueous, is no doubt much more
enveloped with clouds where its oceans lie, than is the northern
where its continents repose, and therefore it is that one hemisphere radiates more than the other.
369. Thus, by observing and discussing, by resorting to the
Facts and pearls. force of reason and to the processes of induction,
we have gathered for the theory that favors the air-crossings at
the calm belts fact upon fact, which, like pearls for the necklace,
only require a string to hang them together.




~ 370-372.         CURRENTS OF THE SEA.                   175
CHAPTER VIII.
~ 370-409.-CURRENTS OF THE SEA.
~ 370. WE here set out with the postulate that the sea, as well
Obedient to order. as the air, has its system of circulation, and that this
system, whatever it be, and wherever its channels lie, whether in
the waters at or below the surface, is in obedience to physical
laws. The sea, by the circulation of its waters, doubtless has its
offices to perform in the terrestrial economy; and when we see
the currents in the ocean running hither and thither, we feel that
they were not put in motion without a cause.  On the contrary,
we know they move in obedience to some law of Nature, be it
recorded down in the depths below, never so far beyond the reach
of human ken; and being a law of Nature, we know who gave it,
and that neither chance nor accident had any thing to do with its
enactment. Nature grants us all that this postulate demands, repeating it to us in many forms of expression; she utters it in the
blade of green grass which she causes to grow in climates and
soils made kind and genial by warmth and moisture that some
current of the sea or air has conveyed far away from under a
tropical sun.  She murmurs it out in the cooling current of the
north; the whales of the sea tell of it (~ 158); and all its inhabitants proclaim it.
371. The fauna and the flora of the sea are as much the creaThe fauna anflora tures of climate (~ 164), and are as dependent for
of the sea.  their well-being upon temperature as are the fauna
and the flora of the dry land. Were it not so, we should find
the fish and the algTe, the marine insect and the coral, distributed
equally and alike in all parts of the ocean. The arctic whale
would delight in the torrid zone, and the habitat of the pearl oyster would be also under the iceberg, or in the frigid waters of
polar seas.
372. Nevertheless, though the constituents of sea water be the
Those of southern same in kind, we must not infer that they are the
unlike those of northern seas.    same in degree for all parts of the ocean, for there




176        THE PHYSICAL GEOGRAPHY OF THE SEA.
is a peculiarity, perhaps of temperature, perhaps of transparency,
which marks the inhabitants of trans-equatorial seas.  MM. Pcron and Le Sueur, who have turned their attention to the subject,
assert that out of many thousand cases they did not find a single
one in which the inhabitants of trans-equatorial were not distinguishable from those of their species in cis-equatorial seas.
373. Water, while its capacities for heat are scarcely exceeded
The capacity of wa- by those of any other substance, is one of the most
terto convey heat. complete of non-conductors. Heat does not permeate water as it does iron, for instance, or other good conductors.  Heat the top of an iron plate, and the bottom  becomes
warm; but heat the top of a sheet of water, as in a pool or basin,
and that at the bottom remains cool.  The heat passes through
iron by conduction, but to get through water it requires to be
conveyed by a motion, which in fluids we call currents. Therefore the study of the climates of the sea involves a knowledge of
its currents, both cold and warm.  They are the channels through
which the waters circulate, and by means of which the harmonies
of old ocean are preserved.
374. Hence, in studying the system of oceanic circulation, we
Currents of the sea set out with the very simple assumption, viz., that
to be considered in
pairs.       from whatever part of the ocean a current is found
to run, to the same part a current of equal volume is bound to return; for upon this principle is based the whole system of currents and counter-currents of the air as well as of the water.
Hence the advantage of considering them as the anatomist does
the nerves of the human system-in pairs.  Currents of water,
like currents of air, meeting from various directions, create gyrations, which in some parts of the sea, as on the coast of Norway,
assume  the appearance of whirlpools, as though the water were
drawn into a chasm below.  The celebrated Maelstrom is caused
by such a conflict of tidal or other streams. The late Admiral
Beechey, R.N.,* gave diagrams illustrative of many "rotatory
streams in the English Channel, a number of which occur between
the outer extremities of the channel tide and the stream of the
oceanic or parent wave."  " They are clearly to be accounted
for," says he, " by the streams acting obliquely upon each other."
* See an interesting paper by him on Tidal Streams of the North Sea and English
Channel, pp. 703; Phil. Transactions, Part ii., 1851.




~ 375, 376.        CURRENTS OF THE SEA.                    177
375. It is not necessary to associate with oceanic currents the
Marine currents do idea that they must, of necessity, as on land, run
not, like those on
land, run of neces- fromn a higher to a lower level.  So far from this
sity from higher to
lower levels.  being the case, some currents of the sea actually run
up hill, while others run on a level.  The Gulf Stream is of the
first class (~ 83).
376. The currents which run from the Atlantic into the MedThe Red Sea current. iterranean, and from the Indian Ocean into the Red
Sea, are the reverse of this. IHere the bottom of the current is
probably a water-level, and the top an inclined plane, running
down hill. Take the Red Sea current as an illustration.  That
sea lies, for the most part, within a rainless and riverless district.
It may be compared to a long and narrow trough. Being in a
rainless district, the evaporation from it is immense; none of the
water thus taken up is returned to it either by rivers or rains. It
is about one thousand miles long; it lies nearly north and south,
and extends from latitude 13~ to the parallel of 300 north. From
May to October, the water in the upper part of this sea is said to
be two feet lower than it is near the rnouth.*  This change or difference of level is ascribed to the effect of the wind, which, prevailing from the north at that season, is supposed to blow the water out. But from May to October is also the hot season; is is the
season when evaporation is going on most rapidly; and when we
consider how dry and how hot the winds are which blow upon this
sea at this season of the year; that it is a narrow sea; that they
blow across it, and are not saturated, we may suppose the daily
evaporation to be immense. The evaporation from this sea and
the Persian Gulf is probably greater than it is from any other
arms of the ocean. We know that the waste from canals by evaporation, in the summer time, is an element which the engineer,
when taking the capacity of his feeders into calculation, has to consider. With him it is an important element; how much more so
must the waste by evaporation from this sea be when we consider
the physical conditions under which it is placed. Its feeder, the
Arabian Sea, is a thousand miles from its head; its shores are
burning sands; the evaporation is ceaseless; it is a natural evaporating dish (~ 525) on a grand scale; none of the vapors which
the scorching winds that blow over it carry away are returned to
* Johnston's Physical Atlas.
M




178       THE PHYSICAL GEOGRAPHY OF THE SEA.
it again in the shape of rains. The Red Sea vapors are carried
off and precipitated elsewhere. The depression in the level of its
head waters in the summer time, therefore, it appears, is owing to
the effect of evaporation, as well as to that of the wind blowing
the waters back. The evaporation in certain parts of the Indian
Ocean is supposed to be (~ 103) from three fourths of an inch to
an inch daily. Whatever it be, it is doubtless greater in the Red
Sea. Let us assume it, then, in the summer time to average only
half an inch a day. Now, if we suppose the velocity of the current which runs into that sea to average, from mouth to head,
twenty miles a day, it would take the water fifty days to reach
the head of it. If it lose half an inch from its surface by evaporation daily, it would, by the time it reaches the Isthmus of Suez,
have lost twenty-five inches from its surface. Thus the waters of
the Red Sea ought to be lower at the Isthmus of Suez than they
are at the Straits of Babelmandeb. Independently of the forcing
out by the wind, the waters there ought to be lower from two
other causes, viz., evaporation and temperature; for the temperature of that sea is necessarily lower at Suez, in latitude 30~, than
it is at Babelmandeb, in latitude 13~. To make it quite clear that
the surface of the Red Sea is not a sea level, but is an inclined
plane, suppose the channel of the Red Sea to have a perfectly
smooth and level floor, with no water in it, and a wave ten feet
high to enter the Straits of Babelmandeb, and to flow up the channel, like the present surface current, at the rate of twenty miles a
day for fifty days, losing daily, by evaporation, half an inch; it is
easy to perceive that, at the end of the fiftieth day, this wave would
not be so high by two feet (twenty-five inches) as it was the first
day it commenced to flow. The top of that sea, therefore, may
be regarded as an inclined plane, made so by evaporation.
377. But the salt water, which has lost so much of its freshness
Upper and under cur- by evaporation, becomes salter, and therefore heavrents through straits.
explained.   ler. The lighter water at the Straits can not balance the heavier water at the Isthmus, and the colder and salter,
and therefore heavier water, must either run out as an under current, or it must deposit its surplus salt in the shape of crystals,
and thus gradually make the bottom of the Red Sea a salt-bed, or
it must abstract all the salt from the ocean to make the Red Sea
brine-and we know that neither the one process nor the other is




~ 378.             CURRENTS OF THE SEA.                   179
going on. Hence we infer that there is from the Red Sea an under and outer current, as there is from the Mediterranean through
the Straits of Gibraltar, and that the surface waters near Suez are
salter than those near the mouth of the Red Sea.  And, to show
why there should be an outer and under current from each of
these two seas, let us suppose the case of a vat of oil and a vat of
wine connected by means of a narrow trough-the trough being
taken to represent the straits connecting seas the waters of which
differ as to specific gravity.  Suppose the trough to have a floodgate, which is closed until we are ready for the experiment. Now
let the two vats be filled, one with wine the other with oil, up to
the same level. The oil is introduced to represent the lighter water as it enters either of these seas from the ocean, and the wine
the same water after it has lost some of its freshness by evaporation, and therefore has become salter and heavier.  Now suppose
the flood-gate to be raised, what would take place? Why, the oil
would run in as an upper current, overflowing the wine, and the
wine would run out as an under current.
378. The rivers which discharge their waters into the MediterThe Mediterranean ranean are not sufficient to supply the waste of
current.     evaporation, and it is by a process similar to this
that the salt which is carried in from the ocean is returned to the
ocean again; were it not so, the bed of that sea would be a mass
of solid salt. The equilibrium of the seas is a physical necessity.
Were it to be lost, the consequences would be as disastrous as
would be any other derangement in the forces of attraction. Without doubt, the equilibrium of the sea is preserved by a system of
compensation as exquisitely adjusted as are those by which the
"music of the spheres" is maintained.  It is difficult to form an
adequate conception of the immense quantities of solid matter
which the current from the Atlantic, holding in solution, carries
into the Mediterranean. In his abstract log for lMarch 8th, 1855,
Lieutenant William Grenville Temple, of the United States ship
Levant, homeward bound, has described the indraught there:
"Weather fine; made 1- pt. lee-way. At noon, stood in to Almiria Bay, and anchored off the village of Roguetas. Found a
great number of vessels waiting for a chance to get to the westward, and learned from them that at least a thousand' sail are
weather-bound between this and Gibraltar. Some of them have
been so for six weeks, and have even got as far as Malaga, only
NVL ~V~LJ -'~I.IV.LU ~~)M~IIVUVI 3rv~u* rI   u ~-YY0




180       THE PHYSICAL GEOGRAPHY OF THE SEA.
to be swept back by the current. Indeed, no vessel had been able
to get out into the Atlantic for three months past." Now, suppose this current, which baffled and beat back this fleet for so
many days, ran no faster than two knots the hour. Assuming its
depth to be 400 feet only, and its width seven miles, and that it
carried in with it the average proportion of solid matter-say one
thirtieth-contained in sea water; and admitting these postulates
into calculation as the basis of the computation, it appears that
salts enough to make no less than 88 cubic miles of solid matter,
of the density of water, were carried into the Mediterranean during these 90 days. Now, unless there were some escape for all
this solid matter, which has been running into that sea, not for 90
days merely, but for ages, it is very clear that the Mediterranean
would, ere this, have been a vat of very strong brine, or a bed of
cubic crystals.
379. We have in this fact, viz., the difficulty of egress from the
The Suez Canal. Mediterranean, and the tedious character of the navigation, under canvas, within it, the true secret of the indifference
which, in commercial circles in England and the Atlantic states
of Europe, is manifested toward the projected Suez Canal. But
to France and Spain on the Mediterranean, to the Italian States,
Greece, and Austria, it would be the greatest commercial boon of
the age. The Mediterranean is a great gulf running from west to
east, penetrating the Old World almost to its very centre, and separating its most civilized from its most savage parts. Its southern shores are inhabited, for the most part, by an anti-commercial
and thriftless people. On the northern shores the climates of
each nation are nearly duplicates of the climates of her neighbors
to the east and the west; consequently, these nations all cultivate
the same staples, and their wants are similar: for a commerce
among themselves, therefore, they lack the main elements, viz.,
difference of production, and the diversity of wants which are the
consequence of variety of climates. To reach these, the Mediterranean people have had to encounter the tedious navigation and
the sometimes difficult egress —just described-from  their sea.
Clearing the Straits of Gibraltar, their vessels do not even then
find themselves in a position so favorable for reaching the markets of the world as they would be were they in Liverpool or off
the Lizard. Such is the obstruction which the winds and the current from the Atlantic offer to the navigation there, that vessels




~ 380, 381.         CURRENTS OF THE SEA.                        181
bound to India from the United States, England, or Holland, may
often double the Cape of Good Hope before one sailing with a
like destination from  a Mediterranean port would find herself
clear of the Straits of Gibraltar.  It is therefore not surprising
that none of the great commercial marts of the present day are
found on the shores of this classic sea.  The people who inhabit the hydrographic basin of the Mediterranean-which includes
the finest parts of Europe-have, ever since the discovery of the
passage around the Cape of Good Hope, been commercially pent
up.  A  ship-canal across the Isthmus of Suez will let them  out
into the commercial world, and place them within a few days of
all the climates, wants, supplies, and productions of India. It will
add largely to their wealth and prosperity. As these are increased, trading intercourse is enhanced, and so by virtue of this
canal they will become better customers for England and Holland,
and all other trading nations whose ports are havens of the Atlantic.  Occupying this stand-point in their system of commercial
economy, the people of the United States await with a lively interest the completion of the Suez Canal.
380. Of all parts of the ocean, the warmest water, the saltest and
Hydrometricalobserv- the heaviest too, is said to be found in the seas of
ations at sea wanted. the Indian Ocean.  A good series of observations
there with the hydrometer, at the different seasons of the year, is
a desideratum. Taking, however, such as we have upon the density of the water in the Red Sea and the Mediterranean, and upon
the under currents that run out from these seas, let us examine
results.
381. Several years ago, Mr. Morris, chief engineer of the OriSpecific gravity of ental Company's steam-ship Ajdaha, collected specied Sea water.   imens of Red Sea water all the way from  Suez to
the Straits of Babelmandeb, which were afterward examined by
Dr. Giraud, who reported the following results:*
Latitude.  Longitude. Spec. Grav. Saline Cont.
o         o                e1000 parts.
No. 1. Sea at Suez   -       -        1027     41.0
No. 2. Gulf of Suez 27.49   33.44     1026      40.0
No. 3. Red Sea    24.29     36.      1.024     39.2
No. 4.  do.      20.55      38.18     1026      40.5
No. 5.  do.      20.43      40.03     1024     39.8
No. 6.  do.      14.35      42.43     1024     39.9
No. 7.  do.      12.39      44.45     1023     39.2
* Transact. of the Bombay Geograph. Soc., vol. ix., May, 1849, to August, 1850.




182        THE PHYSICAL GEOGRAPHY OF THE SEA.
These observations agree with the theoretical deductions just announced, and show that the surface waters at the head are heavier
and salter than the surface waters at the mouth of the Red Sea.
382. In the same paper, the temperature of the air between
Evaporation from. Suez and Aden often rises, it is said, to 90~, " and
probably averages little less than 75~ day and night all the year
round.  The surface of this sea varies in heat from 65~ to 85~,
and the difference between the wet and dry bulb thermometers
often amounts to 250~-in the kamsin, or desert winds, to from 30~
td 40~; the average evaporation at Aden is about eight feet for
the year." " Now assuming," says Dr. Buist, "the evaporation of
the Red Sea to be no greater than that of Aden, a sheet of water
eight feet thick, equal in area to the whole expanse of that sea, will
be carried off annually in vapor; or, assuming the Red Sea to be
eight hundred feet in depth at an average-and this, most assuredly, is more than double the fact-the whole of it would be dried
up, were no water to enter from the ocean, in one hundred years.
The waters of the Red Sea, throughout, contain some four per cent.
of salt by weight-or, as salt is a half heavier than water, some 2.7
per cent. in bulk-or, in round numbers, say three per cent. In
the course of three thousand years, on the assumptions just made,
the Red Sea ought to have been one mass of solid salt, if there
were no current running out."  Now we know the Red Sea is
more than three thousand years old, and that it is not filled with
salt; and the reason is, that as fast as the upper currents bring the
salt in at the top, the under currents carry it out at the bottom.
383. MEDITERRANEAN CURRENTS.-With regard to an under
TnHI MEDITERRANEAN current from the Mediterranean, we may begin by
CURRENTS.     remarking that we know that there is a current always setting in at the surface from the Atlantic, and that this is a
salt-water current, which carries an immense amount of salt into
that sea. - We know, moreover, that that sea is not salting up; and
therefore, independently of the postulate (~ 374) and of observations, we might infer the existence of an under current, through
which this salt finds its way out into the broad ocean again.*
* Dr. Smith appears to have been the first to conjecture this explanation, which
he did in 1673 (vide Philosophical Transactions). This continual indraught into
the Mediterranean appears to have been a vexed question among the navigators and
philosophers even of those times. Dr. Smith alludes to several hypotheses which




~ 38, 385.            CURRENTS OF THE SEA.                           183
384. With regard to this outer and under current, we have obThe drift of the servations telling of its existence as long ago as
Phcenix.       1712.  "In the year 1712," says Dr. Hudson, in a
paper communicated to the Philosophical Society in 1724, " Monsieur du L'Aigle, that fortunate and generous commander of the
privateer called the Phcenix, of Marseilles, giving chase near
Ceuta Point to a Dutch ship bound to Holland, came up with her
in the middle of the Gut between Tariffa and Tangier, and there
gave her one broadside, which directly sunk her, all her men being saved by Monsieur du L'Aigle; and a few  days after, the
Dutch ship, with her cargo of brandy and oil, arose on the shore
near Tangier, which is at least four leagues to the westward of
the place where she sunk, and directly against the strength of the
current, which has persuaded many men that there is a recurrency
in the deep water in the middle of the Gut that sets outward to
the grand ocean, which this accident very much demonstrates;
and, possibly, a great part of the water which runs into the Straits
returns that way, and along the two coasts before mentioned; otherwise this ship must, of course, have been driven toward Ceuta,
and so upward.  The water in the Gut must be very deep; several of the commanders of our ships of war having attempted to
sound it with the longest lines they could contrive, but could never find any bottom."
385. In 1828, Dr. Wollaston, in a paper before the PhilosophSaltness of theMedi- ical Society, stated that he found the specific graviterranean.     ty of a specimen of sea water, from  a depth of six
hundred and seventy fathoms, fifty miles within the Straits, to
had been invented to solve these phenomena, such as subterraneous vents, cavities,
exhalation by the sun's beams, etc., and then offers his conjecture, which, in his own
words, is, "that there is an under current, by which as great a quantity of water is
carried out as comes flowing in. To confirm which, besides what I have said above
about the difference of tides in the offing and at the shore in the Downs, which necessarily supposes an under current, I shall present you with an instance of the like
nature in the Baltic Sound, as I received it from an able seaman, who was at the
making of the trial. He told me that, being there in one of the king's frigates, they
went with their pinnace into the mid stream, and were carried violently by the current; that, soon after this, they sunk a bucket with a heavy cannon ball to a certain
depth of water, which gave a check to the boat's motion; and, sinking it still lower
and lower, the boat was driven ahead to the windward against the upper current:
the current aloft, as he added, not being over four or five fathoms deep, and that the
lower the bucket was let fall, they found the under current the stronger."




184       THE PHYSICAL GEOGRAPHY OF THE SEA.
have a " density exceeding that of distilled water by more than
four times the usual excess, and accordingly leaves, upon evaporation, more than four times the usual quantity of saline residuum.
Hence it is clear that an under current outward of such denser
water, if of equal breadth and depth with the current inward near
the surface, would carry out as much salt below as is brought in
above, although it moved with less than one fourth part of the
velocity, and would thus prevent a perpetual increase of saltness
in the Mediteraanean Sea beyond that existing in the Atlantic."
The doctor obtained this specimen of sea water from Captain,
now Admiral Smyth, of the English Navy, who had collected it
for Dr. Marcet. Dr. Marcet died before receiving it, and it had
remained in the admiral's hands some time before it came into
those of Wollaston. It may, therefore, have lost something by
evaporation; for it is difficult to conceive that all the river water,
and three fourths of the sea water which runs into the Mediterranean, is evaporated from it, leaving a brine for the under current havingfour times as much salt as the water at the surface of
the sea usually contains. Very recently, M. Coupvent des Bois is
said to have shown, by actual observation, the existence of an
outer and under current from the Mediterranean.
386. However that may be, these facts, and the statements of
The escape of salt the Secretary of the Geographical Society of Bonmand heavy water by
under currents.   bay (~ 382), seem to leave no room to doubt as to
the existence of an under current both from the Red Sea and
Mediterranean, and. as to the cause of the surface current which
flows into them. I think it a matter of demonstration.  It is accounted for ( 3877) by the salts of the sea. Writers whose opinions are entitled to great respect differ with me as to the conclusiveness of this demonstration. Among those writers are Admiral
Smyth, of the British Navy, and Sir Charles Lyell, who also differ
with each other. In 1820, Dr. Marcet, being then engaged in
studying the chemical composition of sea water, the admiral, with
his usual alacrity for doing " a kind turn," undertook to collect
for the doctor specimens of Mediterranean water from various
depths, especially in and about the Straits of Gibraltar. Among
these was the one (~ 385) taken fifty miles within the Straits from
the depth of six hundred and seventy fathoms (four thousand and
twenty feet), which, being four times salter than common sea wa



~ 387.              CURRENTS OF THE SEA.                    185
ter, left, as we have just seen, no doubt in the mind of Dr. Wollaston as to the existence of this under current of brine.  But the
indefatigable admiral, in the course of his celebrated survey of
the Mediterranean, discovered that, while inside of the Straits the
depth was upward of nine hundred fathoms, yet in the Straits
themselves the depth across the shoalest section is not more than
one hundred and sixty* fathoms.  "Such being the case, we can
now prove," exclaims Sir Charles Lyell, " that the vast amount
of salt brought into the Mediterranean does not pass out again by
the Straits; for it appears by Captain Smyth's soundings, which
Dr. Wollaston had not seen, that between the Capes of Trafalgar
and Spartel, which are twenty-two miles apart, and where the
Straits are shallowest, the deepest part, which is on the side of
Cape Spartel, is only two hundred and twenty fathoms.t  It is
therefore evident, that if water sinks in certain parts of the Mediterranean, in consequence of the increase of its specific gravity, to
greater depths than two hundred and twenty fathoms, it can never flow out again into the Atlantic, since it must be stopped by
the submarine barrier which crosses the shallowest part of the
Straits of Gibraltar.":
387. According to this reasoning, all the cavities, the hollows,
Vertical circulation and the valleys at the bottom of the sea, especially
in the sea a physical
necessity.   in the trade-wind region, where evaporation is so
constant and great, ought to be salting up or filling up with brine.
Is it probable that such a process is actually going on? No.
According to this reasoning, the water at the bottom of the great
American lakes ought to remain there forever, for the bottom of
Erie is far below the barrier which separates this lake from the
Falls of Niagara, and so is the bottom of every one of the lakes
below the shallows in the straits or rivers that connect them as
a chain. WIe may presume that the water at the bottom of every
extensive and quiet sheet of water, whether salt or fresh, is at the
bottom by reason of specific gravity; but that it does not remain
there forever we have abundant proof. If so, the Niagara River
would be fed by Lake Erie only from that layer of water which
is above the level of the top of the rock at the Falls. Consecquently, wherever the breadth of that river is no greater than it
* "The Mediterranean."            t One hundred and sixty, Smyth.: Lyell's Principles of Geology, p. 334-5, ninth edition. London, 1853.




186        THE PHYSICAL GEOGRAPHY OF THE SEA.
is at the Falls, we should have a current as rapid as it is at the
moment of passing the top of the rock to make the leap. To see
that such is not the way of Nature, we have but to look at any
common mill-pond when the water is running over the dam. The
current in the pond that feeds the overflow is scarcely perceptible,
for " still water runs deep."  Moreover, we know it is not such a
skimming current as the geologist would make, which runs from
one lake to another; for wherever above the Niagara Falls the
water is deep, there we are sure to find the current sluggish, in
comparison with the rate it assumes as it approaches the Falls;
and it is sluggish in deep places, rapid in shallow ones, because it
is fed from below. The common " wastes" in our canals teach us
this fact.
388. The reasoning of this celebrated geologist appears to be
The bars at the founded upon the assumption that when water, in
mnouths of the Mi- consequence of its specific gravity, once sinks below
sissippi an illustra-  c
tion.         the bottom of a current where it is shallowest, there
is no force of traction, so to speak, in fluids, nor any other power, which can draw this heavy water up again. If such were the
casei we could not have deep water immediately inside of the bars
which obstruct the passage of the great rivers into the sea. Thus
the bar at the mouth of the Mississippi, with only fifteen feet of
water on it, is estimated to travel out to sea at rates varying from
one hundred to twenty yards a year. In the place where that bar
was when it was one thousand yards nearer to N-ew Orleans than
it now is, whether it were fifteen years ago or a century ago, with
only fifteen or sixteen feet of water on it, we have now four or
five times that depth. As new bars were successively formed
seaward from the old, what dug up the sediment which formed
the old, and lifted it up from where specific gravity had placed it,
and carried it out to sea over a barrier not more than a few feet
from the surface? Indeed, Sir Charles himself makes this majestic stream to tear up its own bottom to depths far below the top
of the bar at its mouth.  He describes the Mississippi as a river
having nearly a uniform breadth to the distance of two thousand
miles from the sea.*  He makes it cut a bed for itself out of the
* "From near its mouth at the Balize, a steam-boat may ascend for two thousand miles with scarcely any perceptible difference in the width of the river."-L-2yell,
p. 263.




~ 389.             CURRENTS OF THE SEA.                    187
soil, which is heavier than Admiral Smyth's deep sea water, to
the depth of more than two hundred feet* below the top of the
bar which obstructs its entrance into the sea.  Could not the
same power which scoops out this solid matter for the Mississippi
draw the brine up from the pool in the Mediterranean, and pass
it out across the barrier in the Straits? The currents which run
over the bars and shoals in our rivers are fed from the pools above
with water which we know comes from depths far below the top
of such bars. The breadth of the river where the bar is may be
the same as its breadth where the deep pool is, yet the current in
the pool may be so sluggish as scarcely to be perceptible, while it
may dash over the bar or down the rapids with mill-tail velocity.
Were the brine not drawn out again from the hollow places in
the sea, it would be easy to prove that this indraught into the
Mediterranean has taken, even during the period assigned by Sir
Charles to the formation of the Delta of the Mississippi-one of
the newest formations-salt enough to fill up the whole basin of
the Mediterranean with crystals. Admiral Smyth brought up
bottom with his briny sample of deep-sea water (six hundred and
seventy fathoms), but no salt crystals.
389. The gallant admiral-appearing to withhold his assent
Views of Admiral both from Dr. Wollaston in his conclusions as to
Smyth and Sir C.
Lyell.       this under current, and from the geologist in his
inferences as to the effect of the barrier in the Straits —suggests
the probability that, in sounding for the heavy specimen of sea
water, he struck, a brine spring. But the specimen, according to
analysis, was of sea water, and it is not necessary to call in the
supposition of a brine spring to account for this heavy specimen.
If we admit the principle assumed by Sir Charles Lyell, that water from the great pools and basins of the sea can never ascend to
cross the ridges which form these pools and basins, then the harmonies of the sea are gone, and we are forced to conclude they
never existed. Every particle of water that sinks below a submarine ridge is, ipso facto, by his reasoning, stricken from  the
channels of circulation, to"become thenceforward forever motionless matter.  The consequence would be " cold obstruction" in
* "The Mississippi is continually shifting its course in the great alluvial plain,
cutting frequently to the depth of one hundred, and even sometimes to the depth of
two hundred and fifty feet. "-Lyell, p. 273.




188        THE PHYSICAL GEOGRAPHY OF THE SEA.
the depths of the sea, and a system of circulation between different seas of the waters only that float above the shoalest reefs and
barriers. If the water in the depths of the sea were to be confined there, doomed to everlasting repose, then why was it made
fluid, or why was the sea made any deeper than just to give room
for its surface currents to skim along? If water once below them
must remain below them-and they are shallow —why were the
depths of the ocean filled with fluid instead of solid matter?
Doubtless, when the seas were measured and the mountains stood
in the balance, the solid and fluid matter of the earth were adjusted in exact proportions to insure perfection in the terrestrial machinery. I do not believe in the existence of any such imperfect
mechanism, or in any such failure of design as the imparting of
useless properties to matter, such as fluidity to that which is
doomed to be stationary would imply. To my mind, the proofs
-the theoretical proofs —the proofs derived exclusively from reason and analogy-are as clear in favor of this under current from
the Mediterranean as they were in favor of the existence of Leverrier's planet before it was seen through the telescope at Berlin.
Now suppose, as Sir Charles Lyell maintains, that none of these
vast quantities of salt which this surface current takes into the
Mediterranean find their way out again. It would not be difficult to show, even to the satisfaction of that eminent geologist,
that this indraught conveys salt away from the Atlantic faster
than all the fresh-water streams empty fresh supplies of salt into
the ocean. Now, besides this drain, vast quantities of salts are
extracted from sea water for coral reefs, shell banks, and marl
beds; and by such reasoning as this, which is perfectly sound and
good, we establish the existence of this under current, or else we
are forced to the very unphilosophical conclusion that the sea
must be losing its salts, and becoming less and less briny.
390. THE CURRENTS OF THE INDIAN OCEAN. —By carefully
CURRENTs OF TuE I- examining the physical features of this sea (Plates
DIAN OCEAN.  VIII.,and IX.), and studying its conditions, we are
led to look for warm currents that have their genesis in this
ocean, and that carry from it volumes of overheated water, probably exceeding in quantity many times that which is discharged
by the Gulf Stream from its fountains (Plate VI.). The Atlantic
Ocean is open at the north, but tropical countries bound the In



~ 391.            CURRENTS OF THE SEA.                  189
dian Ocean in that direction. The waters of this ocean are hotter
than those of the Caribbean Sea, and the evaporating force there
(~ 300) is much greater. That it is greater we might, without
observation, infer from the fact of a higher temperature and a
greater amount of precipitation on the neighboring shores (~ 298).
These two facts, taken together, tend, it would seem, to show that
large currents of warm water have their genesis in the Indian
Ocean. One of them is the well-known Mozambique current,
called at the Cape of Good Hope the Lagulhas current. Another
of these warm currents from the Indian Ocean makes its escape
through the Straits of Malacca, and, being joined by other warm
streams from the Java and China Seas, flows out into the Pacific,
like another Gulf Stream, between the Philippines and the shores
of Asia. Thence it attempts the great circle route (~ 118) for the
Aleutian Islands, tempering climates, and losing itself in the sea
as its waters grow cool on its route toward the northwest coast
of America.
391. Between the physical features of this, the "Black Stream"
The Black Stream of of the Pacific, and the Gulf Stream of the Atlantic,
the Pacific contrasted with the Gulf there are several points of resemblance. Sumatra
Stream of the Atlantic.         and Malacca correspond to Florida and Cuba; Borneo to the Bahamas, with the Old Providence Channel to the
south, and the Florida Pass to the west. The coasts of China
answer to those of the United States, the Philippines to the Bermudas, the Japan Islands to Newfoundland. As with the Gulf
Stream, so also here with this China current, there is a counter
current of cold water between it and the shore. The climates of
the Asiatic coast correspond with those of America along the Atlantic, and those of Columbia, Washington, and Vancouver resemble those of Western Europe and the British Islands; the
climate of California (State) resembles that of Spain; the sandy
plains and rainless regions of Lower California reminding one of
Africa, with its deserts between the same parallels, etc. Moreover, the North Pacific, like the North Atlantic, is enveloped,
where these warm waters go, with mists and fogs, and streaked
with lightning. The Aleutian Islands are almost as renowned for
fogs and mists as are the Grand Banks of Newfoundland. A
surface current flows north from Behring's Strait into the Arctic
Sea; but in the Atlantic the current is from, not into the Arctic




190       THE PHYSICAL GEOGRAPHY OF THE SEA.
Sea: it flows south on the surface, north below; Behring's Strait
being too shallow to admit of mighty under currents, or to permit
the introduction from the polar basin of any large icebergs into
the Pacific. Behring's Strait, in geographical position, answers
to Davis' Strait in the Atlantic; and Alaska, with its Aleutian
chain of islands, to Greenland. But instead of there being to the
east of Alaska, as there is to the east of Greenland, an escape into
the polar basin for these warm waters of the Pacific, a shore-line
intervenes; being cooled here, and having their specific gravity
changed, they are turned down through a sort of North Sea along
the western coast of the continent toward Mexico. They appear
here as a cold current. The effect of this body of cool water upon
the littoral climate of California is very marked. Being cool, it
gives freshness and strength to the sea-breeze of that coast in
summer time, when the "cooling sea-breeze" is most grateful.
These contrasts show the principal points of resemblance and of
contrast between the currents and aqueous circulation in the two
oceans. The ice-bearing currents of the North Atlantic are not
repeated as to volume in the North Pacific, for there is no nursery
for icebergs like the frozen ocean and its Atlantean arms. The
seas of Okotsk and Kamtschatka alone, and not the frozen seas of
the Arctic, cradle the icebergs for the North Pacific.
392. The Lagulhas current, as the Mozambique is sometimes
The Lagulhas cur- called, skirts the coast of Natal as our Gulf Stream
rent and the storms
of the Cape.  does the coast of Georgia, where it gives rise to the
most grand and terrible displays of thunder and lightning that are
any where else to be witnessed. Missionaries thence report to me
the occurrence there of thunder-storms in which for hours consecutively they have seen an uninterrupted blaze of lightning,
and heard a continuous peal of thunder. Reaching the Lagulhas
banks, the current spreads itself out there in the midst of cooler
waters, and becomes the centre of one of the most remarkable
storm-regions in the world. My friend and fellow-laborer, Lieut.
Andrau, of the Dutch Navy, has made the storms upon these
banks a specialty for study. He has pointed out from the abstract logs at Utrecht the existence there of some curious and
interesting atmospherical phenomena to which this body of warm
-water gives rise. The storms that it calls up come rushing from
the westward-sweeping along parallel with the coast of Africa,




~ 393, 394.        CURRENTS OF THE SEA.                   191
they curve along it. Though so near the land, they seldom reach
it. They march into these warm waters with furious speed;
reaching them with a low barometer, they pause and die out.
That officer has conferred a boon upon the Indiamen of all flags,
for he has taught them how to avoid these dreadful winter storms
of the Cape.
393. There is sometimes, if not always, another exit of warm
The currents and water from the Indian Ocean. It seems to be an
drift of the Indian
Ocean.      overflow of the great intertropical caldron of India-seeking to escape thence, it works its way polarward more
as a drift than as a current.  It is to the Mozambique current
what the northern flow of warm waters in the Atlantic (~ 141) is
to the Gulf Stream. This Indian overflow is very large. The
best indication of it is afforded by the sperm whale curve (Plate
IX.). This overflow finds its way south midway between Africa
and Australia, and appears to lose itself in passing around a sort
of Sargasso Sea, thinly strewed with patches of weed. Nor need
we be surprised at such a vast flow of warm water as these three
currents indicate from the Indian Ocean, when we recollect that
this ocean (~ 392) is land-locked on the north, and that the temperature of its waters is frequently as high as 90~ Fahr.  There
must, therefore, be immense volumes of water flowing into the
Indian Ocean to supply the waste created by these warm currents.
394. On either side of this warm current that escapes from the
The ice-bearing cur- intertropical parts of the Indian Ocean, but especialrents from the Ant-  -
arctic regions.   ly on the Australian side, an ice-bearing current
(Plate IX.) is found wending its way from the Antarctic regions
with supplies of cold water to modify climates and restore the
aqueous equilibrium in that part of the world.  There is a general drift up into the South Atlantic of ice-bearing waters from
Antarctic seas. The icebergs brought thence, being often very
large and high, are drifted to the eastward by the " brave west
winds" of those regions.  Hence the icebergs that are so often
seen to the south of the Cape of Good Hope. They set off for
the Atlantic, but were driven to the eastward by the west winds
of these latitudes.  The Gulf Stream  seldom  permits icebergs
from Arctic waters to reach the parallel of 40~ in the North Atlantic, but I have known the ice-bearing current which passes east
of Cape Horn into the South Atlantic to convey its bergs as far




192       THE PHYSICAL GEOGRAPHY OF THE SEA.
as the parallel of 37~ south latitude. This is the nearest approach
of icebergs to the equator. These currents which run out from
the intertropical basin of that immense sea-Indian Ocean-convey along immense volumes of water containing vast quantities
of salt, and we know that sea water enough to convey back equal
quantities of salt, and salt to keep up supplies for the outgoing
currents, must flow into the intertropical regions of the same sea;
therefore, if observations were silent upon the subject, reason
would teach us to look for currents here that keep in motion immense volumes of water.
395. THE CURRENTS OF THE PACIFIC. —-he contrast has been
The currentsofthe drawn (~ 391) between the Japan or "Black
Pacific-Drift-wood. Stream" of the North Pacific, and the Gulf Stream
of the North Atlantic.  The course of the former has never been
satisfactorily traced out. There is (Plate IX.), along the coast of
California and Mexico, a southwardly movement of waters, as
there is along the west coast of Africa toward the Cape de Verd
Islands. In the open space west of this southwardly set along
the African coast there is the famous Sargasso Sea (Plate IX.),
which is the general receptacle of the drift-wood and sea-weed of
the Atlantic. So, in like manner, to the west from California of
this other southwardly set, lies the pool into which the drift-wood
and sea-weed of the North Pacific are generally gathered, but in
small quantities. I have received from Johnston's Islands (17~ N.,
169~ 30' W), which are near the edge of this pool, specimens of
drift-wood from the Columbia; and also of the red cedar of California. The immense trees from Oregon and California that have
been cast up on these guano islands were probably drifted down
with the cool California current into the northeast trades, and by
them wafted along to the west, thus showing that the currents
of the North Pacific flow in a sort of circle, on the outer edge of
which lie the Japanese and Aleutian Islands, and the northwest
coast of America.
396. The natives of the Aleutian Islands, where no trees grow,
Thelack Current of depend upon the drift-wood cast ashore there for
the Pacific, like the
Gulf Stream, salter all the timber used in the construction of their
than the adjacent
waters.      boats, fishing-tackle, and household gear. Among
this timber, the camphor-tree, and other woods of China and Japan, are said to be often recognized. In this fact we have addi



~ 397-399.          CURRENTS OF THE SEA.                    193
tional evidence touching this China Stream, as to which (~ 395)
but little, at best, is known.  " The Japanese," says Lieutenant
Bent,*X in a paper read before the American Geographical Society,
January, 1856, "are well aware of its existence, and have given
it the name of' Kuro-Siwo,' or Black Stream, which is undoubtedly derived from the deep blue color of its water, when compared
with that of the adjacent ocean."  From this we may infer (~ 71)
that the blue waters of this China Stream also contain more salt
than the neighboring waters of the sea.
397. The Cold Current of Olkotsk.-Inshore of, but counter to
The Current of the "Black Stream," along the eastern shores of
Okotslk.     Asia, is found (~ 391) a streak, or layer, or current
of cold water answering to that between the Gulf Stream and the
American coast.  This current, like its fellow in the Atlantic, is
not strong enough at all times sensibly to affect the course of
navigation; but, like that in the Atlantic, it is the nursery (~ 158)
of most valuable fisheries.  The fisheries of Japan are quite as
extensive as those of Newfoundland, aad the people of each country are indebted for their valuable supplies of excellent fish to the
cold waters which the currents of the sea bring down to their shores.
398. Humboldt's Current.-The currents of the Pacific are but
Humboldt's Current. little understood. Among those about which most
is thought to be known is the Humboldt Current of Peru, which
the great and good man whose name it bears was the first to dis.
cover. It has been traced on Plate IX. according to the best information-defective at best-upon the subject.  This current is
felt as far as the equator, mitigating the rainless climate of Peru
as it goes, and making it delightful. The Andes, with their snowcaps, on one side of the narrow Pacific slopes of this intertropical
republic, and the current from the Antartic regions on the other,
make its climate one of the most remarkable in the world; for,
though torrid as to latitude, it is such as to temperature that cloth
clothes are seldom felt as oppressive during any time of the year,
especially after nightfall.
399. Between Humboldt's Current and the great equatorial
The "desolate" re- flow there is an area marked as the " desolate region.        gion," Plate IX.  It was observed that this part of
* Lieutenant Bent was in the Japan Expedition with Commodore Perry, and used
the opportunities thus afforded to study the phenomena of this stream.
N




194       THE PHYSICAL GEOGRAPHY OF THE SEA.
the ocean was rarely visited by the whale, either sperm or right;
why, it did not appear; but observations asserted the fact. Formerly, this part of the ocean was seldom whitened by the sails of
a ship, or enlivened by the presence of man. Neither the industrial pursuits of the sea nor the highways of commerce called him
into it. Now and then a roving cruiser or an enterprising whaleman passed that way; but to all else it was an unfrequented part
of the ocean, and so remained until the gold-fields of Australia
and the guano islands of Peru made it a thoroughfare. All vessels bound from Australia to South America now pass through it,
and in the journals of some of them it is described as a region almost void of the signs of life in both sea and air. In the South
Pacific Ocean especially, where there is such a wide expanse of
water, sea-birds often exhibit a companionship with a vessel, and
will follow and keep company with it through storm and calm for
weeks together.  Even those kinds, as the albatross and Cape
pigeon, that delight in the stormy regions of Cape Horn and the
inhospitable climates of the Antartic regions, not unfrequently
accompany vessels into the perpetual summer of the tropics. The
sea-birds that join the ship as she clears Australia will, it is said,
follow her to this region, and then disappear. Even the chirp of
the stormy-petrel ceases to be heard here, and the sea itself is said
to be singularly barren of life.
400. In the intertropical regions of the Pacific, and among the
Polynesian drift. heated waters of Polynesia, a warm current or drift
of immense volume has its genesis. It rather drifts than flows to
the south, laving, as it goes, the eastern shore of Australia and
both shores of New Zealand. These are the waters in which the
little corallines delight to build their atolls and their reefs. The
intertropical seas of the 1Pacific afford an immense surface for evaporation. No rivers empty there; the annual fall of rain there, except in the " Equatorial Doldrums," is small, and the evaporation is
all that both the northeast and the southeast trade-winds can take
up and carry off. I have marked on Plate IX. the direction of the
supposed warm-water current which conducts these overheated
and briny waters from the tropics in mid ocean to the extra-tropical regions where precipitation is in excess. Here, being cooled,
and agitated, and mixed up with waters that are less salt, these
overheated and over-salted waters from the tropics are replen



~ 401.            CURRENTS OF THE SEA.                  195
ished and restored to their rounds~ in the wonderful system of
oceanic navigation.
401. There are also about the equator in this ocean some curiE~quatorial currents. OUS currents, which I have called the " Doldrum
Currents" of the Pacific, but which I do not understand, and as to
which observations are not sufficient yet to afford the proper explanation or description. There are many of them, some of which,
at times, run with great force. On a voyage from the Society to
the Sandwich Islands I encountered one running at the rate of
ninety-six miles a day. These currents are generally found setting to the west. They are often, but not always, encountered in
the equatorial Doldrums on the voyage between the Society and
the Sandwich Islands. In Captain Pichon's abstract log of the
French corvette "L'Eurydice," from Honolulu to Tahiti, in August, 1857, a " doldrum" current is recorded at 79 miles a day,
west by north. HIe encountered it between 1~ N. and 4o S., where
it was 300 miles broad. On the voyage to Honolulu in July of
the same year, he experienced no such current; but in 6~ N. he
encountered one of 36 miles, setting southeast, or nearly in the
opposite direction. This current does not appear to have been
more than 60 miles broad. What else should we expect in this
ocean but a system of currents and counter-currents apparently
the most uncertain and complicated? The Pacific Ocean and the
Indian Ocean may, in the view we are about to take, be considered as one sheet of water. This sheet of water covers an area
quite equal in extent to one half of that embraced by the whole
surface of the earth; and, according to Professor Alexander Keith
Johnston, who so states it in the new edition of his splendid Physical Atlas, the total annual fall of rain on the earth's surface is
one hundred and eighty-six thousand, two hundred and forty cubic imperial miles. Not less than three fourths of the vapor
which makes this rain comes from this waste of waters; but supposing that only half of this quantity, i. e., ninety-three thousand,
one hundred and twenty cubic miles of rain falls upon this sea,
and that that much, at least, is taken up from it again as vapor,
this would give two hundred and fifty-five cubic miles as the
quantity of water which is daily lifted up and poured back again
into this expanse.'It is taken up at one place and rained down
at another, and in this process, therefore, we have agencies for




196       THE PHYSICAL GEOGRAPHY OF THE SEA.
multitudes of partial and conflicting currents-all, in their set and
strength, apparently as uncertain as the winds.
402. The better to appreciate the operation of such agencies in
The influence of rains producing currents in the sea, now here, now there,
and evaporation upon
currents.    first this way, and then that, let us, by way of illustration, imagine a district of two hundred and fifty-five square
miles in extent to be set apart, in the midst of the Pacific Ocean,
as the scene of operations for one day. We must now conceive a
machine capable of pumping up, in the twenty-four hours, all the
water to the depth of one mile in this district. The machine must
not only pump up and bear off this immense quantity of water,
but it must discharge it again into the sea on the same day, but
at some other place. Now here is a force for creating currents
that is equivalent in its results to the effects that would be produced by bailing up, in twenty-four hours, two hundred and fiftyfive cubic miles of water from one part of the Pacific Ocean, and
emptying it out again upon another part. The currents that would
be created by such an operation would overwhelm navigation and
desolate the sea; and, happily for the human race, the great atmospherical machine which actually does perform every day, on
the average, all this lifting up, transporting, and letting down of
water upon the face of the grand ocean, does not confine itself to
an area of two hundred and fifty-five square miles, but to an area
three hundred thousand times as great; yet, nevertheless, the
same quantity of water is kept in motion, and the currents, in the
aggregate, transport as much water to restore the equilibrium as
they would have to do were all the disturbance to take place upon
our hypothetical area of one mile deep over the space of two
hundred and fifty-five square miles. Now when we come to recollect that evaporation is lifting up, that the winds are transporting, and that the clouds are letting down every day actually such
a body of water, we are reminded that it is done by little and little
at a place, and by hair's breadths at a time, not by parallelopipedons one mile thick, and that the evaporation is most rapid and
the rains most copious, not always at the same place, but now
here, now there. We thus see actually existing in nature a force
perhaps quite sufficient to give rise to just such a system of currents as that which mariners find in the Pacific (~ 401)-currents
which appear to rise in mid ocean, run at unequal rates, sometimes




~ 403.            CURRENTS OF THIE SEA.                 197
east, sometimes west, but which always lose themselves where they
rise, v.iz., in mid ocean.
403. UNDER CURRENTS.-Lieutenant J. C. Walsh, in the U. S.
UNDER CURRENTS- schooner " Taney," and Lieutenant S. P. Lee, in the
Parker's deep- sea
sounding.    U. S. brig " Dolphin," both, while they were carrying oh a system of observations in connection with the WIND AND
CURRENT CHARTS, had their attention directed to the subject of
submarine currents. They made some interesting experiments
upon the subject. A block of wood was loaded to sinking, and,
by means of a fishing-line or a bit of twine, let down to the depth
of one hundred or five hundred fathoms, at the will of the experimenter. A small barrel as a float, just sufficient to keep the block
from sinking farther, was then tied to the line, and the whole let
go from the boat. To use their own expressions, " It was wonderful, indeed, to see this barrega move off, against wind, and sea, and
surface current, at the rate of over one knot an hour, as was generally the case, and on one occasion as much as 1i3 knots. The
men in the boat could not repress exclamations of surprise, for it
really appeared as if some monster of the deep had hold of the
weight below, and was walking off with it."*  Both officers and
men were amazed at the sight. The experiments in deep-sea
soundings have also thrown much light upon the subject of under currents. There is reason to believe that they exist in all,
or almost all parts of the deep sea, for never in any instance yet
has the deep-sea line ceased to run out, even after the plummet
had reached the bottom. If the line be held fast in the boat, it
invariably parts, showing, when two or three miles of it are out,
that the under currents are sweeping against the bight of it with
what seamen call a sw.iggingforce, that no sounding twine has yet
proved strong enough to withstand. Lieutenant J. P. Parker, of
the United States frigate Congress, attempted, in 1852, a deep-sea
sounding off the coast of South America. He was engaged with
the experiment eight or nine hours, during which time a line nearly ten miles long was paid out. Night coming on, he had to part
the line (which he did simply by attempting to haul it in) and return on board. Examination proved that the ocean there, instead of being over ten miles in depth, was not over three, and
that the line was swept out by the force of one or more under
* Lieutenant Walsh.




198       THE PHYSICAL GEOGRAPHY OF THE SEA.
currents. But in what direction these currents were running is
not known.
404.. Vertical circulation is as important in the sea as it is in
The compressibility the air (~ 231). In striving to understand the
in the oceanic circulathieotn.creafccif  physical machinery of our planet and to comprelation.      hend its workings, we must, if we would learn; proceed upon the principle (~ 351) that at creation the waters were
measured, the hills weighed, and the atmosphere meted out, and
that each was endowed with its peculiar properties so proportioned and so adjusted as exactly to answer its purposes in the grand
design. And, consequently, we are entitled to infer that fluidity
instead of solidity was imparted to a certain quantity of matter
which we call water, to enable it to perform the offices to be required of fluid matter, and which solid matter was not adapted to
perform in the terrestrial economy.  By this mode of reasoning
we are taught to regard the fluidity of all the water in the sea as
a physical necessity-and by this mode of reasoning we are required to reject as insufficient any hypothesis touching the system of aqueous circulation on our planet which ignores, even in
the profoundest depths of the ocean, an interchange of its particles between the bottom and the top. Were such interchange
not to take place-were the water in the sea which once sinks below the level of its horizontal circulation doomed to remain there
forever, it would not be difficult to show that the sea would lose
its balance and its counterpoises; that, not being able to preserve
its status, the water at the bottom would have grown heavier and
heavier, while that at the top would have become lighter and
lighter, until the one became saturated with salt, the other entirely fresh. To prevent this state of things, we recognize the influences of the winds and tides, as well as the necessity of vertical
movements in the sea. Whence, therefore, let us inquire, when
a given quantity of water once finds its way to the bottom of the
sea, whence-since it goes there by virtue of its own specific gravity-whence is power to be derived for bringing it up again? for
sooner or later, according to this view, up it must come. We thus
arrive precisely at one of those points (~ 287) at which hypothesis
becomes absolutely necessary if we would make further progress.
Here, therefore, let us pause to search among the physics of the
sea for such a power and the foundation for hypothesis. Leslie




~ 404.            CURRENTS OF THE SEA.                199
has pointed out exactly such a power for the atmospheric ocean
-a power which, after the heaviest air has settled at the bottom
of its subtile sea-after the lightest has come to rest at the top,
and the whole arranged itself according to specific gravity-can
haul that which is below to the top, and send that which is on the
top down into the recesses and cavities below. Suppose the entire atmosphere to be, from the bottom to the top, nearly of the
same temperature, and in a perfect state of quiescent equilibrium,
and that from some cause a certain volume of air above has its
specific gravity so changed that it commences to descend. As it
descends the pressure upon it increases-and air, being compressed, contracts and gives out heat. A like volume ascends to take
its place, and in ascending it expands and grows cool. Thus
the total mass, and the total pressure, and the total amount of caloric remain the same; but there is a transfer of heat from the top
to the bottom, by which the -equilibrium of the mass is destroyed,
and a force established at the bottom of the atmospherical ocean
which, with the assistance of an agent at the top to alter specific
gravity, is capable of sending up the heavy air from the bottom,
of drawing down the light from the top, and of turning, in course
of time, the whole atmosphere upside down. All philosophers
acknowledge the power of this omnipresent agent in the air, and
that, by alternately assuming the latent and the sensible form, it,
to say the least, assists to give to the atmosphere the dynamical
force required for its system of vertical circulation as well as its
horizontal. So with water and the salt sea where we do have an
agent that is continually altering specific gravity at the surface.
Notwithstanding the Florentine experiment upon water in the
gold ball, it has since been abundantly proved that water is compressible-so much so, that at the depth of ninety-three miles its
density would be doubled. Consequently, a given quantity of
water-such, for instance, as a cubic foot measured at the surface
-would not, if sunk to the depth of four miles, measure a cubic
foot by seventy-two cubic inches. As a rule, the compressibility
of water in the depths of the sea is one per cent. for every 1000
fathoms. Here, then, in the latent heat which is liberated in the
processes of descent, have we not a power which is capable of
sending up to the top water from the uttermost depths of the sea;?
Suppose that this cubic measure of water, by supplying vapor to




200        THE PHYSICAL GEOGRAPHY OF THE SEA.
the winds at the surface, to have its saltness so increased as to alter its specific gravity to sinking: Like the air, it is compressed,
and contracts in its descent, giving out heat, raising the temperature, and changing the specific gravity of like quantities in the various thermal strata through which it has to pass.  Thus heat is
conveyed from the top to the bottom of the sea, there to be liberated and impart to its waters dynamical force for their upward
movement.  This is the power we paused to search for: whatever be its amount it is in the nature of a vera causca, and we must
therefore recognize it, if not as the sole agent, nevertheless as one
of the principal agents which Nature employs in the system. of
vertical circulation that has been ordained for the waters of the
sea.
405. Now, but for the salts of the'sea, this process could not go
Assisted byits salts. 0on so long as the laws of thermal dilatation remain
as they are for sea water. Unlike fresh water, which expands as
it is cooled below 39~.5, sea water contracts until it has passed its
freezing point and attained the temperature of 25~.6.*  Were it
not for its salts, sea water once on the surface within the tropics
would, by reason of its warmth and thermal dilatation, remain on
the surface. Vertical circulation would be confined to polar seas,
and many of the living creatures that inhabit its waters would
perish for the lack of currents to convey them their food.
406. If we except the tides, and the partial currents of the sea,
The origin of currents. Such as those that may be created by the wind, we
may lay it down as a rule (~ 103) that all the currents of the ocean
owe their origin to difference of specific gravity between sea water at one place and sea water at another; for wherever there is
such a difference, whether it be owing to difference of temperature
or to difference of saltness, etc., it is a difference that disturbs equilibrium, and currents are the consequence. The heavier water
goes toward the lighter, and the lighter whence the heavier comes;
for two fluids differing in specific gravity (~ 106), and standing
at the same level, can no more balance each other than unequal
weights in opposite scales of a true balance.  It is immaterial, as
before stated, whether this difference of specific gravity be caused
by temperature, by the matter held in solution, or by any other
thing; the effect is the same, namely, a current. That the sea,
* See Prof. Hubbard's experiments, vol. i., Sailing Directions.




~ 407, 408.       CURRENTS OF THE SEA.                  201
in all parts, holds in solution the same kind of solid matter; that
its waters in this place, where it never rains, are not'salter than
the strongest brine; and that in another place, where the rain is
incessant, they are not entirely without salt, may be taken as evidence in proof of a system of currents or of circulation in the sea,
by which its waters are shaken up and kept mixed together as
though they were in a phial.
407. CURRENTS OF THE ATLANTIC.-The principal currents of
Currents of the At- the Atlantic have been described in the chapter on
lantic.      the Gulf Stream. Besides this, its eddies and its
offsets, are the equatorial current (Plate VI.), and the St. Roque or
Brazil Current. Their fountain-head is the same: it is in the
warm waters about the equator, between Africa and America.
The former, receiving the Amazon and the Orinoco as tributaries
by the way, flows into the Caribbean Sea, and becomes, with the
waters (~ 103) in which the vapors of the trade-winds leave their
salts, the feeder of the Gulf Stream. The Brazil Current, coming
from the same fountain, is supposed to be divided by Cape St.
Rogue, one branch going to the south under this name (Plate IX.),
the other to the westward. This last has been a great bugbear to
navigators, principally on account of the difficulties which a few
dull vessels falling to leeward of St. Roque have found in beating
up against it. It was said to have caused the loss of some English transports in the last century, which fell to leeward of the
Cape on a voyage to the other hemisphere; and navigators, accordingly, were advised to shun it as a danger.
408. This current has been an object of special investigation
TheSt. Roquecurrent. during my researches connected with the Wind
and Current Charts, and the result has satisfied me that it is neither a dangerous nor a constant current, notwithstanding older
writers. Horsburgh, in his East India Directory, cautions navigators against it; and Keith Johnston, in his grand Physical Atlas, published in 1848, thus speaks of it: "This current greatly
impedes the progress of those vessels which cross the equator
west of 23~ west longitude, impelling them beyond Cape St.
Roque, when they are drawn toward the northern coast of Brazil, and can not regain their course till after weeks or months of
delay and exertion." So far from this being the case, my researches abundantly prove that vessels which cross the equator




202       THE PHYSICAL GEOGRAPHY OF THE SEA.
five hundred miles to the west of longitude 23~ have no difficulty
on account bf this current in clearing that cape. I receive almost
daily the abstract logs of vessels that cross the equator west of
30~ west, and in three days from that crossing they are generally
clear of that cape. A few of them report the current in their
favor; most of them experience no current at all; but, now and
then, some do find a current setting to the northward and westward, and operating against them at the rate of twenty miles a
day. The intertropical regions of the Atlantic, like those of the
other oceans (~ 401), abound with conflicting currents, which no
researches yet have enabled the mariner to unravel so that he
may at all times know where they are and tell how they run, in
order that he may be certain of their help when favorable, or
sure of avoiding them if adverse.
409. There are other currents, such as the Greenland Current,
The Greenlana Cur- the cold current from Davis' Strait, the ice-bearing
rent.        current from the Antarctic regions, all setting into
the Atlantic and the Gulf Stream, one branch of which finds its
way into the Arctic Sea; the other (~ 89) finds its way back to
the south partly as Rennell's current, all of which have been well
treated of in Chap. II., or are delineated on Plates VI. and IX.
Judging by these, there would seem to be a larger flow of polar
waters into the Atlantic than of other waters from it, and I can
not account for the preservation of the equilibrium of this ocean
by any other hypothesis than that which calls in the aid of under
currents. They, I have no doubt, bear an important part in the
system of oceanic circulation.




~ 420, 421.  THE SPECIFIC GRAVITY OF THE SEA, ETC.       203
CHAPTER IX.
420-40. —THE SPECIFIC GRAVITY OF TITE SEA, AND THE
OPEN WATER IN THE ARCTIC OCEAN.
420. THE crust of the planet upon which we live, with the
Interesting physical forces that have been and are at work upon it, is
inquiries.  the most interesting subject of physical inquiry and
study that can claim the attention of diligent students. Precisely
as the progress of man has been upward and onward, precisely
has he looked more earnestly and with deeper longings toward
the mysteries that encircle this crust. It is but a shell, and at
most we can reach only a little way either above or below its very
surface, and yet upon the tablets of this thin shell are the records
of all that he may ever know concerning this his cosmical hearthstone.
421. Researches have been carried on from the bottom of the
Voyages of discovery deepest pit to the top of the highest mountain, but
to the North Pole.  these have not satisfied. Voyages of discovery,
with their fascinations and their charms, have led many a noble
champion both into the torrid and frigid zones; and notwithstanding the hardships, sufferings, and disasters to which many
northern parties have found themselves exposed, seafaring men,
as science has advanced, have looked with deeper and deeper
longings toward the mystic circles of the polar regions. There
icebergs are framed and glaciers launched. There the tides have
their cradle, the whales their nursery. There the winds complete
their circuits, and the currents of the sea their round in the wonderful system of oceanic circulation. There the Aurora Borealis
is lighted up and the trembling needle brought to rest; and there
too, in the mazes of that mystic circle, terrestrial forces of occult
power and of vast influence upon the well-being of man are continually at play. Within the arctic circle is the pole of the
winds and the poles of the cold, the pole of the earth and of
the magnet. It is a circle of mysteries; and the desire to enter
it, to explore its untrodden wastes and secret chambers, and to




204       TIHE PHYSICAL GEOGRAPHY OF THE SEA.
study its physical aspects, has grown into a longing. Noble daring has made Arctic ice and waters classic ground. It is no feverish excitement nor vain ambition that leads man there. It is a
higher feeling, a holier motive-a desire to look into the works
of creation, to comprehend the economy of our planet, and to
grow wiser and better by the knowledge. Soon after the discovery of America, John Cabot and his sons, with five ships, sailed
upon the first Arctic expedition. Between that year and the
present no less than 155 vessels, besides boat and land parties,
have at various periods, and with divers objects in view, been sent
from Europe and America up into those inhospitable regions.
Whatever may have been the immediate object of these various
expeditions, whether to enlarge the fields of commerce, to carry
the Bible, to spread civilization, to push conqcuests, or to bring
back contributions to science, it has never lost sight of the promise made by Columbus of a western route to India.
422. Like the air, like the body, the ocean must have a system
Thefirst suggestions of circulation for its waters. No other hypothesis
Actic oeain tle will explain the fact which observations reveal concerning the saltness of the sea, the constituents of sea water, and
many other phenomena. An attentive study of the currents of
the sea, and a close examination of the laws which govern the
movements of the waters in their channels of circulation through
the ocean, will lead any one irresistibly to the conclusion that always, in summer and winter, there must be, somewhere within
the arctic circle, a large body of open water. This open water
must impress a curious feature upon the physical aspects of those
regions. The whales had taught us to suspect the existence of
open water in the arctic basis, and in their mute way told of a
passage there, at least sometimes. It is the custom among whalers
to have their harpoons marked with date and the name of the
ship; and Dr. Scoresby, in his work on arctic voyages, mentions
several instances of whales that have been taken near the Behring's Strait side with harpoons in them bearing the stamp of ships
that were known to cruise on the Baffin's Bay side of the American continent; and as, in one or two instances, a very short time
had elapsed between the date of capture in the Pacific and the
date when the fish must have been struck on the Atlantic side, it
was argued therefore that there was a northwest passage by which




~ 423, 424.  THE SPECIFIC GRAVITY OF THE SEA, ETC.     205
the whales passed from one side to the other, since the stricken
animal could not have had the harpoon in him long enough to
admit of a passage around either Cape Horn or the Cape of Good
Hope.
423. The whale-fishing is, among the industrial pursuits of the
lHalpoons-habits of sea, one of no little importance; and when the systhe whales.    tem of investigation out of which the "Wind and
Current Charts" have grown was commenced, the haunts of this
animal did not escape attentive examination. The log-books of
whalers were collected in great numbers, and patiently examined, co-ordinated, and discussed, in order to find out what parts
of the ocean are frequented by this kind of whale, what parts by
that, and what parts by neither. (See Plate IX.) Log-books
containing the records by different ships for hundreds of thousands of days were examined, and the observations in them coordinated for this chart. And this investigation, as Plate IX.
shows, led to the discovery that the tropical regions of the ocean
are to the right whale as a sea of fire, through which he can not
pass, and into which he never enters. The fact was also brought
out that the same kind of whale that is found off the shores of
Greenland, in Baffin's Bay, etc., is found also in the North Pacific,
and about Behring's Strait, and that the right whale of the northern hemisphere is a different animal fromn that of the southern.
Thus the fact was established that the harpooned whales did not
pass around Cape Horn or the Cape of Good Hope, for they were
of the class that could not cross the equator. In this way we
were furnished with circumstantial evidence affording the most
irrefragable proof that there is, at times at least, open water communication through the Arctic Sea from one side of the continent
to the other, for it is known that the whales can not travel under
the ice for such a great distance as is that from one side of this
continent to the other. But this did not prove the existence of
an open sea there; it only established the existence-the occasional existence, if you please — of a channel through which
whales had passed. Therefore we felt bound to introduce other
evidence before we could expect the reader to admit our proof,
and to believe with us in the existence of an open sea in the Arctic Ocean.
424. There is an under current setting from the Atlantic through




206        THE PHYSICAL GEOGRAPHY OF THE SEA.
The under current Davis' Strait into the Arctic Ocean, and there is a
nto athe Artic surface current setting out.  Observations have
ences.       pointed out the existence of this under current
there, for navigators tell of immense icebergs which they have
seen drifting rapidly to the north, and against a strong surface current. These icebergs were high above the water, and their depth
below, supposing them to be parallelopipeds, was at least seven
times greater than their height above. No doubt they were drifted
by a powerful under current. Now this under current comes from
the south, where it is warm, and the temperature of its waters is
perhaps not below 30~; at any rate, they are comparatively warm.
There must be a place somewhere in the Arctic seas where this under current ceases to flow north, and begins to flow south as a surface current; for the surface current, though its waters are mixed
with the fresh waters of the rivers and of precipitation in the polar basin, nevertheless bears out vast quantities of salt, which is
furnished neither by the rivers nor the rains.  These salts are
supplied by the under current; for as much salt as one current
brings in, other currents must take out, else the polar basin would
become a basin of salt; and where the under current transfers its
waters to the surface, there is, it is supposed, a basin in which the
waters, as they rise to the surface, are at 30~, or whatever be the
temperature of the under current, which we know must be above
the freezing point, for the current is of water in a fluid, not in a
solid state. An arrangement in nature, by which a basin of considerable area in the frozen ocean could be supplied by water
coming in at the bottom and rising up at the top, with a temperature not below 30~, or even 27".2-the freezing point of sea water-would go far,to mitigate the climate in the regions round
about.
425. And that there is a warmer climate somewhere in that inIndicationsofamild- hospitable sea, the observations of many of the exer climate.  plorers who have visited it indicate. Its existence
may be inferred also from the well-known fact that the birds and
animals are found at certain seasons migrating to the north, evidently in search of milder climates. The instincts of these dumb
creatures are unerring, and we can imagine no mitigation Of the
climate in that direction, unless it arise from the proximity, or the
presence there of a large body of open water.  It is another fur



~ 426, 427.  THE SPECIFIC GRAVITY OF THE SEA, ETC.         207
nace (~ 151) in the beautiful economy of Nature for tempering
climates there.
426. The hydrographic basin of the Arctic Ocean is large, and
Iow the littoral wa- it delivers into that sea annually a very copious
ters, by being diluted
from the rivers and drainage.  Such an immense volume of fresh wathe rains, serve as a
mantle for the salter ter discharged into so small a sea as the Arctic
and warmer sea water below.    Ocean is must go far toward diluting its brine.
Fig. 2, Plate X. (~ 433), shows the extent to which the brine of
our littoral seas is diluted by the drainage from the Atlantic slopes
of the United States.  It will be observed by that figure that
suddenly after crossing the parallel of 34~ N. the water begins to
grow cooler and lighter.  The observations for these two curves
are a part of the celebrated series made by Captain Rodgers in the
U. S. ship Vincennes all the way from Behring's Straits by the
way of Cape Horn to New York.  He cleared the inner edge of
the Gulf Stream in 340~, where the waters began to grow cooler
and lighter, and so continued to do as he approached the shore.
The remarkable and sudden approach of the thermal and specific
gravity curves after crossing 34~ N. can be explained by no other hypothesis than this, viz.  the surface water of the sea was so
diluted with the fresh water from the Chesapeake, the Delaware,
and New York Bays, that, notwithstanding the temperature decreased as Rodgers approached the shore, yet the specific gravity
decreased also, because the saltness decreased by reason of the increasing proportion of river water as he neared the shore. And
thus we have in our own waters an illustration and an example
of how cool and light-because not so salt-water may be made
to cover and protect as with a mantle a sheet of warmer, but salter and heavier water below.
427. The mean specific gravity of the Arctic Ocean water as
An under current of observed by Rodgers, and reduced to the freezing
warm but salt and
heavy water.    point (27~.2) of sea water, was 1.0263.  The specific gravity of the Gulf Stream water, as observed by him, and
reduced to the same temperature (27~.2), was 1.0303. If these be
taken as fair specimens of the water 6f the torrid and frigid zones,
it would appear that the waters of intertropical seas have 15 per
cent. more salt in them than the surface water of the Arctic Ocean
has. It is to be regretted that the hydrometer has not been more
frequently used in the Arctic Ocean, for a careful series of obser



208       THE PHYSICAL GEOGRAPHY OF THE SEA.
vations upon the specific gravity of the water there at the surface
and at various depths would indicate to us not only the extent
to which the water there is diluted by the rivers and the rains,
but it would yield other highly interesting results. Now this
salt and heavy water, whose specific gravity at 27~.2 would have
been 1.0303, is the very water which Rodgers observed in the
Gulf Stream on its way to the arctic regions.  This is the water
which, after passing the Grand Banks, and meeting the diluted
water as an ice-bearing current from the north, dips down, but
continues its course as an under current. It is protected from
farther loss of heat, after the manner of our own littoral waters,
by the colder but lighter current from the north, until it enters
the Arctic Ocean, there to rise up like a boiling spring in the
centre of an open sea.
428. Relying upon a process of reasoning like this, and the deDe Haven's water ductions flowing therefrom, Lieutenant De Haven,
sky.         when he went in command of the American expedition in search of Sir John Franklin and his companions, was
told, in his letter of instructions, to look, when he should get well
up into Wellington Channel, for ain open sea to the northward
and westward. He looked, and saw in that direction a "water
sky."  Captain Penny afterward went there, found open water,
and sailed upon it. The open sea in the Arctic Ocean is probably not always in the same place, as the Gulf Stream (~ 126) is
not always in one place. It probably is always where the waters
of the under currents are brought to the surface; and this, we may
imagine, would depend upon the freedom of ingress for the under
current. Its course may perhaps be modified more or less by
the ice on the surface, by changes, from whatever cause, in the
course or velocity of the stirface current, for obviously the under
current could not bring more water into the frozen ocean than the
surface current would carry out again, either as ice or water. Every winter, an example of how very close warm water in the sea
and a very severe climate on the land or the ice may be to each
other is afforded to us in the case of the Gulf Stream and the Labrador-like climate of New England, Nova Scotia, and Newfoundland. In these countries, in winter, the thermometer frequently
sinks far below zero, notwithstanding that the tepid waters of the
Gulf Stream may be found with their summer temperature within
one day's sail of these very, very cold places.




~ 429.    THE SPECIFIC GRAVITY OF THE SEA, ETC.         209
429. Dr. Kane reports an open sea north of the parallel of 82~.
Dr. Kane.  To reach it, his party crossed a barrier of ice 80 or
100 miles broad. Before gaining this open water, he found the
thermometer to show the extreme temperature of - 60~. Passing
this ice-bound region by traveling north, he stood on the shores of
an iceless sea, extending in an unbroken sheet of water as far as
the eye could reach toward the pole. Its waves were dashing on
the beach with the swell of a boundless ocean. The tides ebbed
and flowed in it, and I apprehend that the tidal wave from the
Atlantic can no more pass under this icy barrier to be propagated
in seas beyond, than the vibrations of a musical string can pass
with its notes a fret upon which the musician has placed his finger.
The swell of the sea can not pass wide fields or extensive barriers
of ice; for De Haven, during his long imrprisonment and drift
(~ 474), found the ice so firm that he observed regularly from an
artificial horizon placed upon it, and found the mercury always
" perfectly steady."  These tides, therefore, must have been born
in that cold sea, having their cradle about the North Pole. If
these statements and deductions be correct, then we infer that most,
if not all the unexplored regions about the pole are covered with
deep water; for, were this unexplored area mostly land or shallow water, it could not give birth to regular tides. Indeed, the
existence of these tides, with the immense flow and drift which annually take place from the polar seas into the Atlantic, suggests
many conjectures concerning the condition of these unexplored
regions. Whalemen have always been puzzled as to the place of
breeding for the right whale. It is a cold-water animal, and, following up this train of thought, the question is prompted, Is not
the nursery for the great whale in this polar sea, which has been
so set about and hemmed in with a hedge of ice that man may
not trespass there? This providential economy is still farther
suggestive, prompting us to ask, Whence comes the food for the
young whales there? Do the teeming waters of the Gulf Stream
(~ 160) convey it there also, and in channels so far down in the
depths of the sea that no enemy may waylay and spoil it on the
long journey? Seals were sporting and water-fowl feeding in this
open sea of Dr. Kane's. Its waves came rolling in at his feet, and
dashing with measured tread, like the majestic billows of old ocean,
against the shore. Solitude, the cold and boundless expanse, and
TO




210       THE PHYSICAL GEOGRAPHY OF THE SEA.
the mysterious heavings of its green waters, lent their charm to
the scene. They suggested fancied myths, and kindled in the ardent imagination of the daring mariners many longings. The
temperature of its waters was only 36~! Such warm water could
get there from the south only as a current far down in the depths
below. The bottom of the ice of this eighty miles of barrier was
no doubt many-perhaps hundreds of-feet below the surface
level. Under this ice there was also doubtless water above the
freezing point.
430. Nor need the presence of warm water within the arctic
Undercurrentschange circle excite surprise, when we recollect that the
temperature slowly.  cold waters of the frigid zone are transferred to
the torrid without changing their temperature perhaps more than
70 or 80 by the way. This transfer of cold waters for a part of
the way may take place on the surface, and until the polar flow
(~ 89) dips down and becomes submarine. At any rate, officers
on the Coast Survey have found water at the bottom of the Gulf
Stream, in latitude 25~ 30' N., as low in temperature as 35~.
Now, if water flowing out of the polar basin at the temperature
of 28~ may, by passing along the secret paths of the sea, reach the
Gulf of Mexico in summer at a temperature of only 30 above the
freezing point of fresh water, why may not water, leaving the torrid zone at a temperature of 82~, and traveling by the same hidden ways, reach the frigid zone without losing more than the cold
currents gained in temperature, viz., 7~? In 1840, Sir James C.
Ross, being in the antarctic regions with the surface water at
32~, found the temperature in depth to be 38~.8 at 400 fathoms,
and 39~.8 at 600. At a greater depth there is a greater pressure; and there ought to be (~ 404) a stated temperature, that
after passing a certain depth in the deep sea grows higher and
higher as the depth increases. The thermal laws of "deep-sea"
temperatures for fresh and for salt water are very different. In
September, when the surface water of Loch Lomond and Loch
Katrine-Scottish lakes-which are between 500 and 600 feet
deep, is 58~, that at the bottom is uniformly 41~, which is very
near the point of maximum density for fresh water.  Saussure
has shown the same for the Italian lakes; only, at the depth of
1000 feet in the Lake of Geneva, it was a little warmer, probably
on account of pressure (~ 404), than it was at less depth in Lakes




~ 431.    THE SPECIFIC GRAVITY OF THE SEA, ETC.         211
Lucerne and Thun. In these it was 41~, or 1~ colder than the
bottom of Geneva, their surface water being about 60~. In Lago
Sabatino, near Rome, with the surface water at 770, Barlocci reports 44~ at the depth of 490 feet. The winter in Rome is not severe enough to cool such a mass of water below 44~. But with the
exception of the Lake of Geneva, which is deep enough to have
the temperature of its water somewhat influenced by pressure
(~ 404), the law is uniform; as you descend in fresh-water lakes,
the temperature decreases to that of maximum density. Saussure
extended his experiments to the Gulfs of Nice and Genoa-saltwater bays in the neighborhood of his fresh-water lakes. Here,
with the surface temperature of 69~, he found even at the depth of
1720 feet, the water no cooler than 55~.8. This salt water might
have been cooled 30~ lower before it would have reached the
maximum density (25~.6) of average sea water. We see that the
severest winters are not sufficient to bridge our deep fresh-water
lakes over with ice, though their waters, being cooled below 39~.5,
grow light, and remain on the surface to be frozen. On the contrary, sea water contracts, grows heavy, and sinks, until the whole
basin, from the bottom to the top, be reduced to 27~.2. Yet many
confess no surprise at the openwater in fresh-water lakes that are
comparatively shallow, while they can conceive of no such thing
in the Arctic Ocean, though it be very much deeper than the
deepest fresh-water lakes!
431. At the very time that the doctor was gazing with longing
Solid matter annual- eyes upon these strange green waters (~ 429), there
ly drifted out of the
polar basin.    is known to have been a powerful drift setting out
from another part of this Polar Sea, and carrying with it from its
mooring the English exploring ship Resolute, which her officers
and men had abandoned fast bound in the ice several winters
before.  This drift carried a field of ice that covered an area
not less than 300,000 square miles, through a distance of a thousand miles to the south.  The drift of this ship was a repetition of De Haven's celebrated drift (~ 474); for in each case
the ice in which the vessel was fastened floated out and carried
the vessel along with it; by which I mean to be understood as
wishing to convey the idea that the vessel was not drifted through
a line or an opening in the ice, but, remaining fast in the ice,
she was carried along with the whole icy field or waste. This




212       THE PHYSICAL GEOGRAPHY OF THE SEA.
field of ice averaged a thickness of not less than seven feet;
at least that was the case with De Haven. A field of ice covering
to the depth of seven feet an area of 300,000 square miles, would
weigh not less than 18,000,000,000 tons. This, then, is the quantity of solid matter that is drifted out of the polar seas through
one opening-Davis' Straits-alone, and during a part of the year
only. The quantity of water which was required to float and
drive this solid matter out was probably many times greater than
this. A quantity of water equal in weight to these two masses
had to go in. The basin to receive these inflowing waters, i. e.,
the unexplored basin about the North Pole, includes an area of
a million and a half square miles; and, as the outflowing ice and
water are at the surfface, the return current must be submarine.
A part of the water that it bears probably flows in beneath Dr.
Kane's barrier of ice (~ 429).
432. These two currents, therefore, it may be perceived, keep
Volumeofwaterkept in motion between the temperate and polar regions
iancticlon b tliel of the earth a volume of water, in comparison with
11oW.        which the mighty Mississippi, in its greatest floods,
sinks clown to a mere rill. On the borders of this ice-bound sea
Dr. Kane found subsistence for his party-another proof of the
high temperature and comparative mildness of its climate.
433. The Brussels Conference recommended the systematic use
The hydrometer at of the hydrometer at sea. Captain Rodgers, Lieus'ea.       tenant Porter, and Dr. Ruschenberger, all of the
United States Navy, with Dr. Raymond, in the American steamer
Golden Age, and Captain Toynbee, of the English East Indiaman
the Gloriana, have all returned to me valuable observations with
this instrument.  Rodgers, however, has afforded the most extended series. It embraces 128~ of latitude, extending from 71~ in
one hemisphere to 570 in the other. And here I beg to remark,
that those navigators who use the hydrometer systematically and
carefully at sea are quietly enlarging for us the bounds of knowledge and our field of research. These observations have already
led to the discovery of new and beneficent relations in the workshops of the sea. In the physical machinery of the universe
there is no compensation to be found that is more exquisite or
beautiful than that which, by means of this little instrument, has
been discovered in the sea between its salts, the air, and the sun.




~ 434, 435.  THE SPECIFIC GRAVITY OF THE SEA, ETC.       213
The observations made with it by Captain Rodgers, on board the
U. S. ship Vincennes, have shown that the specific gravity of sea
water varies but little in the trade-wind regions, notwithstanding the change of temperature. The temperature was a little
greater in the southeast trade-wind region of the Pacific; less
in the Atlantic. But, though the sea at the equatorial borders of
the trade-wind belt is some 20~ or 25~ warmer than it is on the
polar edge, yet the specific gravity of its waters at the two places
in the Atlantic differs but little. Though the temperature of the
water was noted, his observations on its specific gravity have not
been corrected for temperature.  The object which the Brussels
Conference had in view when the specific gravity column was
introduced into the sea-journal was, that hydrographers might
find in it data for computing the dynamical force which the sea
derives for its currents from the difference in the specific gravity
of its waters in different climes. The Conference held, and rightly held, that a given difference as to specific gravity between the
water in one part of the sea and the water in another would give
rise to certain currents, and that the set and strength of these
currents would be the same, whether such difference of specific
gravity arose from difference of temperature or difference of saltness, or both.
434. According to Rodgers' observations, the average specific
Specific gravity of gravity of sea water, as it is taken from the sea on
average sea water. the parallels of 34~ north and south, at a mean temperature of 64~, is just what, according to thermal laws, it ought
to be; but its specific gravity when taken from the equator, at a
mean temperature of 81~, is much greater than, according to the
same laws, it ought to be. The observed difference of its specific
gravity at 64~ and 81~ is.0015; whereas, according to thermal
laws, it ought to be.0025, or 67 per cent. greater than it actually
is. What makes this difference'? Let us inquire:
435. The anomaly is in the trade-wind region, and is best deAn anomaly. veloped (Fig. 2, page 214) in the North Atlantic, between the parallel of 40~ and the equator. Though it is sufficiently apparent both in the North and South Pacific (Fig. 1)-it
is marked by the Gulf Stream in the North Atlantic-commencing at the polar borders of these winds, the anomaly is developed as you approach the equator. The water grows warmer, but




PLATE X.
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5!_                                                                                                                   V F   I I I J       I I I I   I I I
4...........
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Alp
74
76
7
Amp,
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A 147-a
7f                                                                                                                                          -Do.       CIO.    S. -Lat,
Lz 3__                                                                                                                                      Temp, e Xunfa& X.Lat,
DO.   do  S, ZaA
J,   1.1.1     I     11   I   I   I     I  I -J   I   I




~ 436, 437.  THE SPECIFIC GRAVITY OF THE SEA, ETC.       215
not proportionably lighter. This is the trade-wind region. These
winds evaporate as they go; but can it be possible that they are
so regulated and adjusted, counterpoised and balanced, that the
salt which they, by evaporation, leave behind, is just sufficient to
counterbalance the dilatation due the increasing warmth of the
sea? It is even so.
436. It is the trade-winds, then, which prevent the thermal and
Influence of the trade- specific gravity curves from conforming with each
inds upon the Spe- other in intertropical seas. The water they suck up
eific  gravity  of eea
water.        is fresh water, and the salt it contained, being left
behind, is just sufficient to counterbalance, by its weight, the effect of thermal dilatation upon the specific gravity of sea water
between the parallels of 34~ north and south. As we go from
340 to the equator, the water grows warm and expands. It would
become lighter, but the trade-winds, by taking up vapor without
salt, makes the water salter, and therefore heavier.  The conclusioli is, the proportion of salt in sea water, its expansibility between 62~ and 82~ (for its thermal dilatability varies with its temperature), and the thirst of the trade-winds for vapor are, where
they blow, so balanced as to produce perfect compensation; and
a more beautiful compensation call not, it appears to me, be found
in the mechanism of the universe than that which we have here
stumbled upon. It is a triple adjustment: the power of the sun
to expand, the power of the winds to evaporate, and the quantity
of salts in the sea-these are so proportioned and adjusted that
when both the wind and the sun have each played with its forces
upon the intertropical waters of the ocean, the residuum of heat
and of salt should be just such as to balance each other in their
effects, and to preserve the aqueous equilibrium of the torrid zone.
437. Nor are these the only adjustments effected by this excompensatinginflu- quisite combination of compensations. If all the
encs.  intertropical heat of the sun were to pass into the
seas Upon which it falls, simply raising the temperature of their
waters, it would create a thermo-dynamical force in the ocean
capable of transporting water scalding hot from the torrid zone,
and spreading it, while still in the tepid state, around the poles.
The annual evaporation from the trade-wind region of the ocean
has been computed, according to the most reliable observations
(~ 300), to be as much as 16 feet, which is at the rate of half an




216       THE PHYSICAL GEOGRAPHY OF THE SEA.
inch per day. The heat required for this evaporation would raise
from the normal temperature of intertropical seas to the boiling
point a layer of water covering the entire ocean to the depth of
more than 100 feet. Such increase of temperature, by the consequent change which it would produce upon the specific gravity
of the sea, would still further augment its dynamical power, until, even in the Atlantic, there would be force enough to put in
motion and feed with boiling-hot water many Gulf Streams. But
the trade-winds and the seas are so adjusted that this heat, instead
of penetrating into the depths of the ocean to raise the temperature of its waters, is sent off by radiation or taken up by the vapor, carried off by the winds, and dispensed by the clouds in the
upper air of distant lands. Nor does this exquisite system of
checks and balances, compensations and adjustments, end here.
In equatorial seas the waters are dark blue, in extra-tropical they
are green.  This difference of color bears upon their heat-absorbing properties, and it comes in as a make-weight in the system of
oceanic climatology, circulation, and stability. Now, suppose
there were no trade-winds to evaporate and to counteract the dynamical force of the sun; this hot and light water, by becoming
hotter and lighter, would flow off in currents, with almost mill-tail
velocity, toward the poles, covering the intervening sea with a
mantle of warmth as with a garment. The cool and heavy water of the polar basin, coming out in under currents, would flow
equatorially with equal velocity. IHow much, if to any extent,
the former warm climates of the British Islands and Northern
Asia may be due to such a warm covering of the sea, may perhaps, at some future time, be considered worthy of special inquiry. WVe have already seen (~ 434) that there is something
else besides temperature that is at work in effecting changes in
the specific gravity of sea water. Whatever increases or diminishes its saltness, increases or diminishes its specific gravity; and
the agents that are at work in the sea doing this are sea shells,
the rivers, and the rains, as well as the winds. Between 35~ or
40~ and the equator, evaporation is in excess of precipitation; at
any rate, there is but little precipitation except under the equatorial cloud-ring (see Storm and Rain Chart, Plate XIII.); and
though, as we approach the equator on either side from these
parallels, the solar ray warms and expands the surface water of




~ 438, 439.  THE SPECIFIC GRAVITY OF THE SEA, ETC.      217
the sea, the winds, by the vapor they carry off and the salt they
leave behind, prevent it from making that water lighter.
438. Thus two antagonistic forces are unmasked, and, being
Nicely adjusted. unmasked, we discover in them a most exquisite
adjustment-a compensation-by which the dynamical forces
that reside in the sunbeam and the trade-wind are made to counterbalance each other; by which the climates of intertropical seas
are regulated; and by which the set, force, and volume of oceanic
currents are measured. This compensation is most beautiful; it
explains the paradox (~ 434), gives volume to the harmonies of
the sea, and makes them louder in their songs of Almighty praise
than the noise of many waters. Philosophers have admired the
relations between the size of the earth, the force of gravity, and
the strength of fibre in the flower-stalk of plants (~ 303), but how
much more exquisite is the system of counterpoises and adjustments here presented between the sea and its salts, the winds and
the heat of the sun! The capacity of the sun to warm, of the
sea water to expand, the quantity of salts these contain, and the
power of the wind to suck up vapor, are all in such nice adjustment the one with the other, that there is the most perfect compensation. By it they make music in the sea, and the harmony that
comes pealing thence, though not of so lofty a strain, is nevertheless, like the song of the stars, divine.
439. Suppose there were no winds to suck up fresh water from
A thermal tide. the brine of the ocean; that its average depth were
3000 fathoms; that the solar ray were endowed with power to
penetrate with its heat from the top to the bottom; and that, from
bottom to top, the seas of each hemisphere, in thermal alternation
with the seasons, were raised to summer heat and lowered to winter temperature: the change of sea level from summer to winter,
and from winter to summer, in one hemisphere, would, from this
cause alone, be upward of 125 feet; and in its rise and fall we
should have, from pole to pole, the ebb and flow of a great thermal tide that would turn with the sun in the ecliptic, and tell the
seasons by the march on the tide staff of its rising and falling
waters. But difference of level would not be all that would give
strength and volume to this tide; difference of specific gravity
would lend its weight as so much dynamical force, which difference would create an upper and under annual tide from one




218       THE PHYSICAL GEOGRAPHY OF THE SEA.
hemisphere to the other. This, double disturbance of equilibrium
would not give rise to a tidal wave-mere motion without translation-but to a tidal flow and reflow of water from one hemisphere to the other in volumes of vast magnitude, power, and
majesty. This is an exaggerated view of the dynamical force of
the sunbeam; but it is presented to show the origin of the thermal tide shown on Plate IV.  The difference between the actual
and the supposed thermal tides is one of degree merely; for the
sea water that is liable to any considerable change of temperature,
instead of reaching from the bottom to the top, is scarcely more
than a " pellicle" to the ocean. Nevertheless, it is a regular periodical flow and reflow between the poles and the equator. It is
the annual ebb of this tide which fills the upper half of the North
Atlantic with icebergs every spring and summer. The heated
portion forms a stratum or layer which is thickest at,the equator,
and which comes to the surface near the polar edge of the temperate zones; it then dips again as it recedes toward the region
of perpetual winter.
440. The observations of Kotzebue, Admiral Beechey, and Sir
T'heisothermal floor James C. Ross first suggested the existence in the
of the ocean. ocean of this isothermal floor. Its temperature, according to Kotzebue, is 36~. The depth of this bed of water of invariable and uniform temperature is computed to be 1200 fathoms
at the equator. It gradually rises thence to the parallel of about
56~ N. and S., where it crops out, and there the temperature of the
sea, from top to bottom, is conjectured to be permanently at 36~.
The place of this outcrop, no doubt, shifts with the seasons, vibrating up and down, i. e., north and south, after the manner of the calm
belts. Proceeding, in our description, onward to the frigid zones,
this aqueous stratum of an unchanging temperature dips again,
and continues to incline till it reaches the poles at the depth of
750 fathoms. So that on the equatorial side of the outcrop the
water above this floor is the warmer, but on the polar side the
supernatant water is the colder. By this floor, with its waters of
one uniform and permanent temperature, "the ocean," says Sir
John Herschel, " is divided into three great regions-two polar
basins in which the surface temperature is below, and one medial
zone in which it is above 390.5,* being 80~ at the equator; and
~ This remark was made by Sir John on the supposition, probably, that the max



~ 411, 442.   THE SPECIFIC GRAVITY OF THE SEA, ETC.                       219
at the poles, of course, the freezing point of sea water. It will be
very readily understood that in this statement there is nothing
repugnant to hydrostatical laws, the compressibility of water insuring an increase of density in descending within much wider
limits of temperature than here contemplated."
441. The temperature of 39~.5 was assigned to this floor probThermal dilatation ably under the supposition that sea water follows
of the water.    fresh in  its laws  of thermal dilatation.  Not so:
while fresh water attains its maximum  density at 390.5, average
sea water does not arrive at its degree of maximum density until
it passes its freezing point (270.2) and reaches the temperature of
25~.6. In the winter of 1858 a very elaborate series of observations was conducted at the National Observatory, by  Professor
Hubbard, upon the thermal dilatation of sea water, and with the
following results, 60~ being the standard temperature:
Tl/ermafl Dilratation of Sea Water.*
Temp.  Dilatation.  Temp. | Dilatation.  Te- p.  Dilatation..Temp.  Dilatation.
o                  o
22    0.99807      32     0.99795      50     0.99895    110         0950
23         801     33         797      55         943    120         1218
24         798     34         800      60     1.00000    130         1506
25         795     35         803      65         067    140         1804
26         793     36         806      70         142    150        2118
27         792     37         810      75         221    160        2460
28         791     38         814      80         309    170        2823
29         791     39         819      85         402    180        3192
30         792     40.99823      90         503    190        3588
31         793     45     0.99856    100         0716    200      1.03993
442. The dilatation of the glass tube is included in this table.
Experiments on the To determine the freezing point of average sea wafreezing point.    ter, I filled a glass jar 18 inches high, and 3 inches
imum density of sea water was at the same temperature as that of fresh, but it is
some 12~ or 1.4~ lower.
* This agrees more nearly with Despretz (p. 245) than with Dr. Marcet.  The
latter states that sea water decreases in weight to the freezing point until actually
congealed.  In four experiments Dr. Marcet cooled sea water down to between 18~
and 190 Fahr., and found that it decreased in bulk till it reached 22~, after which
it expanded a little, and continued to do so till the fluid was reduced to between 19~
and 18~, when it suddenly expanded, and became ice with a temperature of 28~.
It should always be recollected that a saturated solution of common salt does not
become solid, or converted into ice, at a less temperature than 4~ Fahr.; and, therefore, if the sea should be, as is sometimes supposed, more saline at great depths,
and as it Appears to be in the Mediterranean from the experiments of Dr. Wollaston,
ice could not be formed there at the same temperature as it could nearer the surface.
-(Vide M. de la Becihe, Manual Geology, p. 22.)




220         THE PHYSICAL GEOGRAPHY OF THE SEA.
in diameter, with specimens of average sea water obtained in midocean and near the equator. On the 12th of February, 1858, the
thermometer in the shade being 23~, I exposed this jar of water,
with a standard thermometer immersed, to the out-door temperature.  When the thermometer in the jar reached 27~, small crystals of ice, like macles of snow, were observed to form  near the
bottom, to rise, and to increase as they rose.  In, truth, the phenomenon presented most beautifully in miniature a snow-storm
reversed, for the flakes appeared literally to "fall upward;" and
while it was " snowing up" in the jar, covering the top with ice,
the water in it rose in temperature from  27~.2 to 280, thus
showing the maximum density of the water to be not above 27~.2.
As soon, and invariably as soon, as.the first crystals of ice began
to appear, the water immediately rose to 280, and there remained
as long as the process of congelation was going on.  In some instances the water was brought down, as in a confined vessel, to
18~ before freezing; but as soon as freezing commenced, the thermometer would mount up to 280.  The same water was used for
the following series of observations upon the thermal changes of
the specific gravity of sea water, fresh water being the unit:
Temperature 270.1 Spec. grav. 1.0290  Temperature 380.0 Spec. grav. 1.0287
"c    280.3,"         89       "     430~.5  "4         86
cc    280.8     "        91       "     54~.7     "        775'"    29~.0     "        885    "i    550.5       4        77
"     29.5    4"         906     "4    62~.5       "       69
"     300.0     "        885      4     630.5     "        675
4"    32~.0     "        88       "     G64.5      "        665
"     34~.0     "        88       "     800.5      "        43
"'    340~.4             89       "      880~.3    "        30
"     35~.2     "        89       "    *930.3      "    1.0221
443. All these experiments unite in showing that sea water at
Sea water at sum- equatorial temperatures is many times more exmer more expansible than sea water pansible than sea water at polar temperatures; that
at winter temperature.         is, sea water, according to its rate of dilatation
(~ 441), will expand about seventeen times as much for 50, when
its temperature is raised from  85~, as it will when raised from
28~; and yet, according to Plate X., the curves of temperature
and specific gravity are symmetrical in polar, non-symmetrical in
equatorial seas.  These experiments, and the compressibility of
* Specific gravity at 200~-0.9908.




~ 444, 445.  THE SPECIFIC GRAVITY OF THE SEA, ETC.       221
sea water (~ 404), show that we have not yet data sufficient to
establish the depth, or even the existence of such an isothermal
floor (~ 440) all the way from pole to pole.
444. "' The physical consequences of this great law, should it
Data for Plate X. be found completely verified by farther research,
are in the last degree important."  The observations which furnished the data for Fig. 1 were made in the North Pacific between the months of August, 1855, and April, 1856, and in the
South Pacific during April and May; whereas for Fig. 2 the
southern observations were made in May and June, the northern
in June and July.
445. It is well to bear this difference as to season north and
Athermaltide: itebbs south in mind, and to compare these curves with
and flows once a year. those of the thermal charts; for the two together
indicate the existence in the ocean of a thermal tide, which, as before stated (~ 439), ebbs and flows but once a year. By this figure
the South Atlantic appears to be cooler and heavier than the northern. The season of observation, however, is southern fall and winter vice northern summer. In January, February, and March, the
waters of the southern ocean are decidedly warmer, as at the opposite six months they are decidedly cooler, parallel for parallel, than
those of the northern oceans. Thus periodically differing in temperature, the surface waters of the two hemispheres vary also in
specific gravity, and give rise to an annual ebb and flow —an upper and an under tide-not from one hemisphere to the other, but
between each pole and equator. In contemplating the existence
and studying the laws of this thermal tide we are struck with the
compensations and adj astments that are allotted to it in the mechanism of the sea; for these feeble forces in the water remind one
of the quantities of small value-residuals of compensation —with
which the astronomer has to deal when he is working out the geometry of the heavens. He finds that it is these small quantities
which make harmony in the celestial spaces; and so, too, it is the
gentle forces like this in the waters which preserves the harmony
of the seas. Equatorial and polar seas are of an invariable temperature, but in middle latitudes the sunbeam has power to wrinkle
and crumple the surface of the sea by alternate expansion and
contraction of its waters. In these middle latitudes is the cradle
of the tiny thermal tide here brought to light; feeble, indeed, and




222       THE PHYSICAL GEOGRAPHY OF THE SEA.
easily masked are its forces, but they surely exist. It may be that
the thermometer and hydrometer are the only instruments which
are nice enough to enable us to detect it. Its footprints, nevertheless, are well marked in our tables showing (~ 441) the thermal
dilatation of sea-water. The movements of the isothermal lines,
marching up and down the ocean, show by signs not to be mistaken its rate and velocity. These movements are well represented on the thermal charts. The tiny ripplings of this feeble tide
have, we may be sure, their office to perform in the general system
of aqueous circulation in the sea. Their influence may be feeble, like-small perturbations in the orbits of planets; but the physicist is no more at liberty to despise the one than the astronomer
is to neglect the other.
446. The problem that we now have in hand, and which is repSea waterofthe south- resented by the diagrams of Plate X., is to put the
ern cooler and heavier,
parallel for parallel, seas in scales, the ocean in a balance, and to weigh
than sea water of the
northern hemisphere. in the specific gravity bottle the waters of the
northern with the waters of the southern hemisphere. By Fi]g. 2
it would appear that both the water and the air of the south Atlantic are decidedly cooler and likewise heavier, parallel for parallel, than the waters of the north Atlantic; but this difference may
be more apparent than real; for the observations were made in the
northern summer on this side, and in the southern fall and winter
on the other side of the equator. Iad we a series of observations
the converse of this, viz., winter in the north Atlantic, summer in
the south, perhaps the latter would then appear to be specifically
the lighter; at any rate, the mean summer temperature of each
Atlantic, north and south, is higher than its mean winter temperature, and consequently the specific gravity of the waters of each
must change with the seasons. A diagram-had we the data for
such a one-to show these changes, would be very instructive;
it would show beautifully, by its marks, the ebb and flow of this
new-born tide of the ocean. By Fig. 1 the south Pacific also outweighs the north in specific gravity; but here again the true difference, whatever it be, is somewhat masked by the time of year
when the observations were made. Those north were made during the fall, winter, and spring; those south, during the fall and
first winter months of that hemisphere. Nevertheless, the weight
of the observations presented on Plate X. does, as far as they




~ 446.    THE SPECIFIC GRAVITY OF THE SEA, ETC.             223
go, indicate that the seas of the southern do outweigh in specific
gravity the seas of the northern hemisphere in the proportion of
1.0272 to 1.0262 of specific gravity.* Daubeny, Dove, et al., have
pointed out an excess of salt contained in sea water south of the
equator, as compared with that contained in sea water north.
447. These indications, as far as they go, and this view of the
Testimonyofthehy- subject, whatever future investigations may show to
daoete i rosivgs oaf be its true worth, seem to lean in support of the idea
the calm belts.   advanced and maintained by facts and arguments
in Chapter IV., viz., that the southern seas are the boiler and the
northern hemisphere the condenser for the grand atmospherical
engine, which sucks up vapor from the south to feed the northern
hemisphere with rains.  If it be true-and Dove also thinks it is
— that the clouds which supply our fountains with rains for the
great American lakes, and with rains for the majestic watercourses of Europe and Asia, Northern Africa and America, are
replenished from seas beyond the equator, then the waters of the
ocean south should be a little salter, and therefore specifically a
little heavier, parallel for parallel, and temperature for temperature, than the waters of cis-equatorial seas. We begin to find that
the hydrometer is bearing testimony in support of the evidence
adduced in Chapters IV. and VII., to show that when the tradewinds meet and rise up in the equatorial calm belt, the atmosphere
which comes there as southeast trade-winds passes with its vapor
over into the northern hemisphere. We had not anticipated that
this little instrument could throw any light upon this subject; but
if, as it indicates, the sea water of the other hemisphere be salter
and heavier than the sea water of this, what makes it so but evaporation, and what prevents currents from restoring its equilibrium
but the winds, which are continually sucking up vapor from the
brine of trans-equatorial seas, and pouring it down as fresh water
upon cis-equatorial seas and land? It is taking out of one scale of
the balance and putting into the other; and the difference of specific gravity between the sea water of the opposite hemisphere may
give us a measure for determining the amount of fresh water that
is always in transitu. Certainly, if evaporation and rains were to
cease, if the rivers were to dry up, and the sea-shells to perish, the
* According to Dr. Marcet, the southern ocean contains more salt than the northern in the proportion of 1.02919 to 1.02757.




224       THE PHYSICAL GEOGRAPHY OF THE SEA.
waters of the ocean would, in the course of time, become all of the
same saltness, and the only difference of specific gravity in the sea
would be due to thermal agencies. After having thus ceased, if
evaporation were then to commence only in the other hemisphere,
and condensation take place only in this, half the difference, as to
saltness of the sea water in opposite hemispheres, would express
the ratio in volumes of fresh water, whether as vapor or liquid,
that would then be kept in transitu between the two hemispheres.
But it evaporates on both sides and precipitates on both; nevertheless, more on one side than on the other, and the difference of
saltness will still indicate the proportion in transitu. If we follow
the thermal and specific gravity curves from the parallels of 30~340 to the equator (Fijs. 1 and 2, Plate X.), we see, as I have said,
that sea water in this part of the ocean does not grow lighter in
proportion as it grows warmer. This is accounted for on the supposition (~ 435) that the effects of the thermal dilatation on the specific gravity is counteracted by evaporation. Now, if we knew
the thickness of the stratum which supplies the fresh water for this
evaporation, we should not only have a measure for the amount
of water which as vapor is sucked up and carried off from the
trade-wind regions of the sea, to be deposited in showers onil other
parts of the earth, but we should be enabled to determine als6 the
quantity which is evaporated in one hemisphere and transported
by the clouds and the winds to be precipitated in the other.
These are questions which are raised for contemplation merely;
they can: not be answered now; they grow out of some of the
many grand and imposing thoughts suggested by the study of the
revelations which the hydrometer is already beginning to make
concerning the wonders of the sea. Returning from this excursion toward the fields of speculation, it will be perceived that these
observations upon the temperature and density of sea water have
for their object to weigh the seas, and to measure in the opposite
scales of a balance the specific gravity of the waters of one hemisphere with the specific gravity of the waters of the other. This
problem is quite within the compass of this exquisite system of
research to solve. But, in order to weigh the seas in this manner,
it is necessary that the little hydrometric balance by which it is
to be done should be well and truly adjusted.
448. From these premises it would not be difficult to show that




~ 449.    THE SPECIFIC GRAVITY OF THE SEA, ETC.         225
Amount of salt in, the saltness of the sea is a physical necessity. In
and mean ssePecif some of the aspects presented, the salts of the sea
ter.         hold the relation in the terrestrial mechanism that
the balance-wheel does to the machinery of a watch. Without
them, the climates of the earth could not harmonize as they do;
neither could the winds, by sucking up vapor, hold in check the
expansive power (~ 437) of tropical heat upon the sea; nor counteract, by leaving the salts behind, the thermal influence of the sun
in imparting dynamical force to marine currents; nor prevent the
solar ray from unduly disturbing the aqueous equilibrium of our
planet. As evaporation goes on from a sea of fresh water, the level only, and not the specific gravity, of the remaining water is
changed. The waters of fresh intertropical seas would, instead
of growing heavy by reason of evaporation between the tropics,
become lighter and lighter by reason of the heat; while the water of fresh polar seas would grow heavier and heavier by reason
of the cold-a condition which, by reason of evaporation and precipitation, is almost the very reverse of that which nature has ordained for the salt sea, and which, therefore, is the wisest and the
best. The average amount of salts in sea water is not accurately
known. From such data as I have, I estimate it to be about 4
per cent. (.039), and the mean specific gravity sea water at 60~ to
be about 1.0272. Supposing these conditions to be accurateand they are based on data which entitle them to be considered
as not very wide of the mark-the hydrometer and thermometer,
with the aid of the table (~ 441), will give us a direct measure for
the amount of salt in any specimen of sea water into which the
navigator will take the trouble to dip these two instruments.
449. These specific gravity and thermal curves, as they are
Light cast by Plate presented on this Plate (X.), throw light also on the
X. on the open sea
in the Arctic Ocean. question of an open sea in the Arctic Ocean. That
open sea is like a boiling spring (~ 427) in the midst of winter,
which the severest cold can never seal up; only it is on a larger
scale than any spring, or pool, or lake, and it is fed by the under
currents with warm water from the south, which, by virtue of its
saltness (see Fig. 2), is heavier than the cool and upper current
which runs out of the polar basin, and which is known as an icebearing current. It is the same which is felt by mariners as far
down as the Grand Banks of Newfoundland, and recognized by
P




226       THE PHYSICAL GEOGRAPHY OF THE SEA.
philosophers off the coast of Florida. This upper current, though
colder than its fellow below, is lighter, because it is not so salt.
Figure 2 reveals to us a portion of sea between the parallels of
34~ and 40~ north, exactly in such a physical category as that in
which this theory presents the Arctic Ocean. Here, along our
own shores, the thermal curve loses 12~ of heat; and what does
the specific gravity curve gain in the same interval?  Instead of
increasing up to 1.027, according to the thermal law, it decreases
to 1.023 for the want of salt to sustain it. Now recollect that
the great American chain of fresh water lakes never freezes over.
Why? Because (~ 430) of their depth and their vertical circulation. The depths below are continually sending water above 32~
to the surface, which, before it can be cooled down to the freezing
point, sinks again. Now compare the shallow soundings in these
lakes with the great depths of the Arctic Ocean; compute the vast
extent of the hydrographic basin which holds this polar sea; gauge
the rivers that discharge themselves into it; measure the rain,
and hail, and snow that the clouds pour down upon it; and then
contrast its area, and the fresh water drainage into it, with the
like of Long Island Sound, Delaware Bay, and the Chesapeake;
consider also the volume of diluted sea water between our shoreline and the Gulf Stream; strike the balance, and then see if the
arctic supply of fresh water be not enough to reduce its salts as
much as our own fresh water streams are diluting the brine of
the sea under our own eyes. The very Gulf Stream water, which
the observing vessel left as she crossed the parallel of 34~ and entered into those light littoral waters, was bound northward. Suppose it to have flowed on as a surface current until it, with its salts,
was reduced to the temperature of 40~. Its specific gravity at that
temperature would have been 1.030, or specifically 30 per cent.
heavier than the sea water of our own coasts. Could two such
currents of water meet any where at sea, except as upper and
under currents? If water that freezes at 32~, that grows light and
remains on the surface as you cool it below 39~, is prevented from
freezing in our great fresh water lakes by vertical circulation,
how much more would-both vertical and horizontal circulation
prevent congelation in the open polar sea, that is many times
deeper and larger than the lakes, and the water of which contracts all the way down to its freezing point of 27~.2.




~ 450-452.  THE SPECIFIC GRAVITY OF THE SEA, ETC.         227
450. The heaviest water in the sea, uncorrected for the temperThe heaviest water. ature, as shown by the observations before us, is
1.028.  This water was found (Figs. 1 and 2) off Cape Horn.
Let us examine a little more closely into the circumstances connected with the heaviest water on our side of the equator. It was
a specimen of water from the Sea of Okotsk, which is a sea in a
riverless region, and one where evaporation is probably in excess
of precipitation-thus fulfilling the physical conditions for heavy
water.  The Red Sea is in a riverless and rainless region. Its
waters ought to be heavier than those of any other mere arm of
the ocean, and the dynamical force arising from the increase of
specific gravity acquired by its waters after they enter it at Babelmandeb is sufficient to keep up a powerful inner and outer current through those straits.  At the ordinary meeting of the Bombay Geographical Society for November, 1857, the learned secretary stated that recent observations then in his possession, and
which were made by Mr. Ritchie and Dr. Giraud (~ 381), go to
show that the saltest water in the Red Sea is where theory (~ 377)
makes it, viz., in the Gulf of Suez; and that its waters become
less and less salt thence to its mouth, and even beyond, till you
approach the'meridian of Socotra; after which the saltness again
increases as you approach Bombay.
451. Its waters, from the mouth of the straits for 300 or 400
Chapman's experi- miles up, have been found as high in temperature
ments.       as 95~ Fahrenheit-a sea at blood heat! The experiments of Professor Chapman, of Canada, which indicated as
law-the salter the water the slower the evaporation, seem to suggest an explanation of this, at least in part. Evaporation ought
to assist in keeping the surface of intertropical seas cool in the
same way that it helps to cool other wet surfaces. And if the
waters of the Red Sea become so salt that they can not m'ake vapor enough to carry off the excessive heat of the solar ray, we
may be sure that nature has provided means for carrying it off.
But for the escape which these highly heated waters are, by means
of their saltuess, enabled to make from that sea, its climate as
well as the heat of its waters, would be more burning and blasting than the sands of Sahara. Even as it is, the waters of this sea
are hotter than the air of the desert.
452. There is another indication which this little instru-ment




228        THE PIIYSICAL GEOGRAPHY OF THE SEA.
The hydrometer in- has afforded concerning the status of the sea, and
dicates the rainy
atitutdes at sea.   which deserves notice. We are at first puzzled
with the remarkably light water between 9~ and 16~ S., FAg. 1,
and in Fig. 2 between 7~ and 9~ N., as well as in 19~ N. But, after
a little examination, we are charmed with the discovery that the
hydrometer points out the rainy regions at sea. Rodgers' observations on his homeward passage from San Francisco to Cape
Horn furnish the data for the curves (Fig. 1) between 37~ N. and
57~ S. Now Plate VIII. shows that the equatorial calm belt lies
south of the line where it is intersected by the homeward route
from California. It also shows that when he crossed the " Doldrums" in the Atlantic, that belt was in north latitude about 70~10~, and that when he was in 18~-20~ N. (F4y. 2) he was then passing through the offings of what are called the " Leeward Islands"
of the West Indies, and that these are rainy latitudes at sea —the
first two being under the cloud ring, the last being near the land
in the trade-wind region, and confirming the remark so often made
concerning the influence of islands at sea upon vapor, clouds, and
precipitation.
453. The most comprehensive view that we are permitted to
Astronomicalvie,. take of cosmical or terrestrial arrangements and
adaptations is at best narrow and contracted. Nevertheless, in
studying the mechanism which Wisdom planned and the Great
Architect of nature designed for the world, we sometimes fancy
that we can discover a relation between the different parts of the
wonderful machinery, and perceive some of the reasons and almost
comprehend parts of the design which Omnipotent Intelligence
had in view when those relations were established. Such fancies,
rightly indulged, are always refreshing; and the developments of
the hydrometer which we have been studying point us to one of
them. This fancied discovery is, that a sea of fresh water instead
of salt would not afford the compensations that are required in
the terrestrial economy; we also fancy that we have almost discovered a relation between the orbit of the earth and the arrangement of land and water on its surface and their bearing upon
climate. Our planet passes its perihelion during the southern
summer, when it is nearer the centre and source of light and heat
by more than three millions of miles than it is at its winter solstice, so that, on the Ist of January, the total amount of heat re



~ 454, 455.  THE SPECIFIC GRAVITY OF THE SEA, ETC.        229
ceivedl by the earth is about -T more than it receives during a day
in July, when it is in aphelion.* January is the midsummer month
of the southern hemisphere, consequently that half of the globe
receives more heat in a day of its summer than the other half receives in a day of the northern summer. But the northern summer is a week the longer, by reason of the ellipticity of the earth's
orbit.  What becomes of this diurnal excess of southern summer
heat, be it in its aggregate never so small, and why does it not accumulate in trans-equatorial climes? So far from it, the southern
hemisphere is the cooler.
454. In the southern hemisphere there is more sea and less
The latent heat of land than in the northern. But the hydrometer
vapor.       indicates that the water in the seas of the former
are salter and, heavier than the waters of seas cis-equatorial; and
man's reasoning faculties suggest, in explanation of this, that this
difference of saltuess or specific gravity is owing to the excess of
evaporation in the southern half, excess of precipitation in the
northern half of our planet.  " When water passes, at 212~ Fahrenheit, into steam, it absorbs 1000~ of heat, which becomes insensible to the thermometer, or latent; and conversely, when steam
is condensed into water, it gives out 10000 of latent heat, which
thus becomes free, and affects both the thermometer and the
senses. Hence steam of 212~ Fahrenheit will, in condensing, heat
five and a half times its own weight of water from the freezing to
the boiling point."-M'7   Culloch. Now there is in the southern a
very much larger water surface exposed to the sun than there is
in the northern hemisphere, and this excess of heat is employed
in lifting up vapor from that broad surface, in transporting it
across the torrid zone and conveying it to extra-tropical northern
latitudes, where the vapor is condensed to replenish our fountains,
and where this southern heat is set free to mitigate the severity
of northern climates.
455. In order to trace a little farther, in our blind way, the
Its influence upon evidences of wisdom and design, which we imagine
climates.    we can detect in the terrestrial arrangement of land
and water, let us fancy the southern hemisphere to have the land
of the northern, and the northern to have the water of the southern, the earth's orbit remaining the same. Is it not obvious to
* Sir John Herschel.




230       THE PHYSICAL GEOGRAPHY OF THE SEA.
our reason that by this change the whole system of climatology
in both hemispheres would be changed? The climates of our
planet are as obedient to law as the hosts of heaven. They are
as they were designed to be; and all those agents which are concerned in regulating, controlling, and sustaining them are "ministers of His." Johnston, in the chapter to Plate XVIII. of his great
Physical Atlas, thus alludes to the seas, land, and climates of the
two hemispheres: " The mild winter of the southern hemisphere,
plus the contemporaneous hot summer of the northern hemisphere, necessarily gives a higher sum of temperature than the
cool summer of the southern, plus the cold winter of the northern
hemisphere. The above described relations appear to furnish the
motive power in the machinery of the general atmosphere of the
earth in the periodical conversion of the aqueous vapors into
liquid form. In this manner the circuit of the fluid element, the
essential support of all vegetable and animal life, no longer appears to depend on mere local coolings, or on the intermixture of
atmospheric currents of different temperatures; but the unequal
distribution of land and sea in the northern and southern hemispheres supplies an effectual provision, from whence it necessarily
follows that the aqueous vapor, which from the autumnal to the
vernal equinox is developed to an immense extent over the southern hemisphere, returns to the earth, in the other half of the year,
in the form of rain or snow. And thus the wonderful march of
the most powerful steam-engine with which we are acquainted,
the atmosphere, appears to be permanently regulated. The irregular distribution of physical qualities over the earth's surface is
here seen to be a preserving principle for terrestrial life. Professor Dove considers the northern hemisphere as the condenser in
this great steam-engine, and the southern hemisphere as its water
reservoir; that the quantity of rain which falls in the northern
hemisphere is, therefore, considerably greater than that which
falls in the southern hemisphere; and that one reason of the
higher temperature of the northern hemisphere is that the larger
quantity of heat which becomes latent in the southern hemisphere
in the formation of aqueous vapor is set free in the north in great
falls of rain and snow."
456. In this view of what our little hydrometer has developed
or suggested, we trace the principles of compensation and adjqst



~ 457, 458. THE SPECIFIC GRAVITY OF THE SEA, ETC.        231
The results of the ment, the marks of design, the evidence of adaptmarine hydrometer. ation between the orbit of the earth and the time
from the vernal to the autumnal, and from the autumnal to the
vernal equinox; between the arrangement of the land in one
hemisphere and the arrangement of the water in the other; between the rains of the northern and the winds of the southern
hemisphere; between the vapor in the air and the salts of the
sea; and between climates on opposite sides of the equator. And
all this is suggested by merely floating a glass bubble in sea water during a voyage in the Pacific! Thus even the little hydrometer, in its mute way, points the Christian philosopher to the evidences of design in creation.  That the arrangements suggested
above are adapted to each other, this instrument affords us evidence as clear as that which the telescope and the microscope
bear in proof that the eye, in its structure, was adapted to the
light of heaven. The universe is the expression of one thought,
and that it is so every new fact developed in the progress of our
researches is glorious proof.
457. In the course of our investigations into the physics of the
Barometer indications sea, 100,000 observations of the barometer, and
of an open sea,    more than a million on the direction of the winds,
have been discussed. They indicate an open water in the Arctic
Ocean. They show that about the poles there is a high degree
of aerial rarefaction-higher, indeed, than there is about the equator; for the barometer not only stands lower in this place of polar
calms than it does in the equatorial calm belt, but the inrushing
air comes from a greater distance to the cold than to the warm
calms.*
458. The question may be asked, Whence comes the heat that
Polar rarefaction. expands and rarefies the atmosphere in these polar
places? The answer is, it comes from the condensation of vapor.
The south pole is surrounded by water, the north pole by land.
But the unexplored regions within the arctic basin are for the
most part probably sea, within the antarctic, land. The rarefaction
produced in the latter by the latent heat of vapor is such that the
mean height of the barometer there is about 28 inches, while that
in the arctic calm place is such as to reduce the barometer there to
a mean not far from 29.5 inches. In the equatorial calm its mean
* Plate IV., Nautical Monograph No. 1.




232        THE PHYSICAL GEOGRAPHY OF THE SEA.
height is about 29.9 inches. The hypothesis of an open sea in
the Arctic Ocean becomes necessary to supply a source for this
vapor; for the winds, entering the Arctic Ocean as they do after
passing over the land and mountain heights of America, Europe,
and Asia, must be robbed of much of their moisture ere they reach
that ocean; it will require an abundant supply of vapor to create
there by precipitation and the liberation of latent heat a degree
of rarefaction sufficient to cause a general movement of the air
polarward for the distance of 40~ of latitude all around. That
there is an immense volume of comparatively warm water going
into the Arctic Ocean is abundantly shown by observation, and
the rising up there of this water to the surface would afford heat
and vapor enough for a vast degree of rarefaction.
459. The records of arctic explorations, together with the whaleThe middle ice. men's accounts of " middle ice" in Baffin's Bay and
Davis' Straits, go to confirm this view, which is further elaborated
in the next chapter (~ 475). The facts there stated, and this
"middle ice," go to show that every winter a drift takes place which
brings out of the Frozen Ocean a tongue of ice a thousand miles or
more in length: it is the compact and cold " middle ice."  In our
fresh-water streams it is the middle ice that first breaks up; that
which is out of the way of the current remains longest. Not so
in this bay and strait; there the littoral ice first gives way, leaving an open channel on either side in spring and early summer,
while the "middle ice" remains firm and impassable. The explanation is simple enough.  The middle ice was formed in
the severe cold of more northern latitudes, from which it has
drifted down, while that on the sides was formed in the less severe climates of the bay and straits. This winter tongue of ice,
which we know by actual observation is in motion from December till May, must, during that time, be detached from the main
mass of ice in the Arctic Ocean, consequently there must be water between the ice that is in motion and the ice that is at rest.
Not only so: in early summer the whalemen will run up to the
north in the open water at the side of the 1" middle ice" in Davis'
Strait and Baffin's Bay, even as far sometimes as Cape Alexander
in 78~,:to look for a crossing-place. Here, though so far north,
they will find the "middle ice" gone, or so broken up that they
can cross over to the west side. They trace it up thus far, be



~ 460.    THE SPECIFIC GRAVITY OF THE SEA, ETC.          233
cause at the south, and in spite of a higher thermometer, they find
the "middle ice" compact and firm, so much so as to be impassable. In this fact we recognize another circumstance favoring
the theory of an open sea at the north, and giving plausibility to
the conjecture that this " middle ice" drifts out from the southern
edge of the open sea as fast as it is formed during the winter.
According to this conjecture, the thickest part of the " middle
ice" should be that which has been exposed to the longest and
severest cold, and this is probably that which began to be formed
on the edge of the open sea in January. As it drifted to the
south it continued to form and grow thick, and perhaps would be
the last to melt; while that which began to be formed at the
edge of the open sea in March or April would drift out, and not
attain much thickness before it would cease to freeze and commence to thaw. It is this spring-made "middle ice" which, as it
drifts to the south, would, being thin, be the first to break up;
and experience has taught the whalemen to look north for the
first breaking up and the earliest passage through the "middle
ice."
460. The open sea, therefore, is, it may be inferred, at no great
Position of the open distance from the several straits which, leading in
seia.        a northwardly direction, connect Baffin's Bay with
the Arctic Ocean. It is through these straits that the winter drift
takes place. The ice in which the Fox, the Resolute, the Advance, and the Rescue each drifted a thousand miles or more,
came down through these straits. The fact of this annual winter
drift from the Arctic Ocean is a most important one for future
explorers. Had Captain Franklin known of it, he might have
put his vessels in the line of it, and so escaped the rigors of that
second winter. It would have brought him safely to the parallel
of 65~ or 60~, and set him free, as it did four other vessels, in the
glad waters of the Atlantic Ocean.




234        THE PHYSICAL GEOGRAPHY OF THE SEA,
CHAPTER X.
~ 461-499. —TE SALTS OF THE SEA.
461. THE brine of the ocean is the ley of the earth (~ 43).
The brine of the From it the sea derives dynamical power, and its
ocean.       currents their main strength. Hence, to understand
the dynamics of the ocean, it is necessary to study the effects
of its salts upon the equilibrium  of its waters; wherefore this
chapter is added to assist in the elucidation of what has already
been said concerning the currents and other phenomena of the
sea. Why was. the sea made salt?  It is the salts of the sea
that impart to its waters those curious anomalies in the laws of
freezing and of thermal dilatation which have been described in
a previous chapter (IX.).  It is the salts of the sea that assist the
rays of heat to penetrate its bosom;* but for these, the solar ray,
instead of heating large masses of water like the Gulf Stream,
would play only at or near the surface, raising the temperature of
the waters there, like the sand in desert places, to an inordinate
degree.  The salts of the sea invest it with adaptations which it
could not possess were its waters fresh. Were they fresh, they
would attain their maximum density at 39~.5 instead of 25~.6,
and the sea then would not have dynamical force enough to put
the Gulf Stream in motion, nor could it regulate those climates
we call marine.
462. Were the sea fresh and not salt, Ireland would never
Were the sea of fresh have presented those ever-green shores which have
wrater-     I won for her the name of "Emerald;" and the
climate of England would have vied with Labrador for inhospitality.  Had not the sea been salt, the torrid zone would have
been hotter and the frigid colder for lack of aqueous circulation; had the sea not been salt, intertropical seas would have been
at a constant temperature higher than blood heat, and the polar
oceans would have been sealed up in everlasting fetters of ice,
A- Melloni has shown that the power of salt water to transmit heat is very much
greater than that of fresh.




~ 463.               THE SALTS OF THE SEA.                      235
while certain parts of the earth would have been deluged with
rain. Had the seas been of fresh water, the amount of evaporation, the quantity of rain, the volume and size of our rivers, would
all have been different from what they are; the quantity of electricity in the air would have been permanently changed from
what it is, and its tension in the sky would have been exceedingly feeble. In the evaporation of fresh water at normal temperatures, but little of that-fluid is evolved; while vapor from salt water carries off vitreous, and leaves behind resinous electricity in
abundance. Hence, with seas of fresh water, our thunder-storms
would be feeble contrivances, flashing only with such sparks as
the vegetable kingdom might, when the juices of its plants were
converted into vapor, lend to the clouds.  It might seem strange,
this idea that the thunderbolt of the sky, the sheet-lightning of
the clouds, and the forked flashes of the storm, all have their
genesis chiefly in the salts of the sea, and so it would be held
were it not that Faraday has shown that a single grain of water
and a little zinc can evolve electricity enough for a thunder-clap;
therefore, were there no salts in the waters of the ocean, the sound,
of thunder would scarce be heard in the sky*-there would be
no Gulf Stream, and no open sea in the Arctic Ocean.
463. As a general rule, the constituents of sea water are as
Uniform character constant in their proportions as are the components
ofsea water.  of the atmosphere.  It is true that we sometimes
come across arms of the sea, or places in the ocean, where we find
the water more salt or less salt than sea water is generally; but
this circumstance is due to local causes of easy explanation. For
instance: when we come to an armn of the sea, as the Red Sea
(~ 376), upon which it never rains, and from which the atmosphere is continually abstracting, by evaporation, fresh water from
the salt, we may naturally expect to find a greater proportion of
salt in the sea water that remains than we do near the mouth of
* The great American lakes afford, it may be supposed, a considerable portion of
the vapor which goes to make rain for the hydrographic basin in which they are.
Visiting the Lake country in 1858, I was struck with the fact that so few trees bore
the marks of lightning. The rule appeared to be, the nearer the lakes, the more rare
was it for one of these ornaments of the forest to have been defaced by lightning;
and, on inquiry from the Lake Board of Underwriters, I was informed that among
the records of lake disasters there was not a single instance of a vessel having been
struck by lightning on the great American lakes!




236       THE PHYSICAL GEOGRAPHY OF THE SEA.
some great river, as the Amazon, or in the regions of constant
precipitation, or in other parts, as on the polar side of 40~ in the
North Atlantic, where it rains more than it evaporates. Yet in
the case of the Red Sea, and all such natural salt-pans, as that and
other rainless portions of the sea may be called, there is, on account of currents which are continually bearing away the water
that has given off its vapors and bringing forward that which is
less concentrated as to brine, a moderate degree of saltness which
its waters can not exceed. We moreover find that, though the constituents of sea water, like those of the atmosphere, are not for
every place invariably the same as to their proportions, yet they
are the same, or nearly the same, as to their character. When,
therefore, we take into consideration the fact that, as a general
rule, sea water is, with the exception above stated, every where
and always the same, and that it can only be made so by being
well shaken together, we find grounds on which to base the conjecture that the ocean has its system of circulation, which is well
calculated to excite our admiration, for it is as wonderful as the
circulation of the blood.
464. In order to investigate the effect of the salts of the sea
Hypotheses.  upon its currents, and to catch a glimpse of the
laws by which the circulation of its waters is governed, hypothesis, in the present meagre state of absolute knowledge with regard
to the subject, seems to be as necessary to progress as is a cornerstone to a building. To make progress with such investigations,
we want something to build upon. In the absence of facts, we
are sometimes permitted to suppose them; only, in supposing
them, we should take not only the possible, but the probable;
and in making the selection of the various hypotheses which are
suggested, we are bound to prefer that one by which the greatest
number of phenomena can be reconciled. When we have found,
tried, and offered such a one, we are entitled to claim for it a respectful consideration at least, until we discover it leading us into
some palpable absurdity, or until some other hypothesis be suggested which will account equally as well, but for a greater number of phenomena. Then, as honest searchers after truth, we
should be ready to give up the former, adopt the latter, and hold
it until some other better than either of the two be offered. With
this understanding, I venture to offer an hypothesis with regard




~ 465.            THE SALTS OF THE SEA.                 237
to the agency of the salts or solid matter of the sea in imparting
dynamical force to the waters of the ocean, and to suggest that
one of the purposes which, in the grand design, it was probably
intended to accomplish by having the sea salt, and not fresh, was
to impart to its waters the forces and powers necessary to make
their circulation complete. In the first place, we rely mainly upon
hypothesis or conjecture for the assertion that there is a set of
currents in the sea by which its waters are conveyed from place
to place with regularity, certainty, and order. But this conjecture
appears to be founded on reason, and we believe it to be true;
for if we take a sample of water which shall fairly represent, in
the proportion of its constituents, the average water of the Pacific
Ocean, and analyze it, and if we do the same by a similar sample
from the Atlantic, we shall find the analysis of the one to resemble that of the other as closely as though the two samples had
been taken from the same bottle after having been well shaken.
Hfow, then, shall we account for this, unless upon the supposition
that sea water from one part of the world is, in the process of
time, brought in contact and mixed up with sea water from all
other parts of the world? Agents, therefore, it would seem, are
at work, which shake up the waters of the sea as though they
were in a bottle, and which, in the course of time, mingle those
that are in one part of the ocean with those that are in another as
thoroughly and completely as it is possible for a man to do in a
vessel of his own construction. This fact as to uniformity of components appears to call for the hypothesis that sea water which today is in one part of the ocean, will, in the process of time, be found
in another part the most remote. It must, therefore, be carried
about by currents; and as these currents have their offices to perform in the terrestrial economy, they probably do not flow by
chance, but in obedience to physical laws; they no doubt, therefore, assist to maintain the order and preserve the harmony which
characterize every department of God's handy-work, and as such
we treat them.
465. This hypothesis about currents is based upon our faith in
Arguments afforde the physical adaptations with which the sea is inby cornalies in favor of.      vested. Take, for example, the coral islands, reefs,
beds, and atolls with which the Pacific Ocean is studded and garnished. They were built up of materials which a certain kind




238       THE PHYSICAL GEOGRAPHY OF THE SEA.
of insect quarried from the sea water. The currents of the sea
ministered to this little insect-they were its hod-carriers. When
fresh supplies of solid matter were wanted for the coral rock upon
which the foundations of the Polynesian Islands were laid, these
hod carriers brought them in unfailing streams of sea water, loaded with food and building materials for the coralline. The obedient currents, therefore, must thread the widest and the deepest seas,
for they never fail to come at the right time, nor refuse to go
after they have ministered to the hungry creature. Unless the
currents of the sea were employed to carry off from this insect
the waters that have been emptied by it of their lime, and to bring
to it others charged with more, it is evident the little creature
would have perished for want of food long before its task was
half completed. But for currents, it would have been impaled in
a nook of the very drop of water in which it was brought forth;
for it would have soon secreted the lime contained in this drop,
and then, without the ministering aid of currents to bring it more,
it would have perished for the want of food for itself and materials for its edifice; and thus, but for the benign currents which
took this exhausted water away, there we perceive this emptied
drop would have remained, not only as the grave of the little architect, but as a monument in attestation of the shocking monstrosity that there had been a failure in the sublime system of terrestrial adaptations-that the sea had not been adapted by its
Creator to the well-being of all its inhabitants. Now we do know
that its adaptations are suited to all the wants of every one of its
inhabitants-to the wants of the coral insect as well as to those
of the whale. Thus our simple hypothesis acquires the majesty
of truth, for we are now prepared boldly to assert we know that
the sea has its system of circulation, because it transports materials for the coral rock from one part of the world to another;
because its currents receive them from the rivers, and hand them
over to the little mason for the structure of the most stupendous
works of solid masonry that man has ever seen-the coral islands
of the sea. Thus, and, moreover, by a process of reasoning which
is perfectly philosophical, we are irresistibly led to conjecture
that there are regular and certain, if not appointed channels
through which the water travels from one part of the ocean to
another, and that those channels belong to an arrangement which




~ 466.            THE SALTS Op THE SEA.                  239
may make, and which, for aught we know to the contrary, does
make the system of oceanic circulation as complete, as perfect,
and as harmonious as is that of the atmosphere or the blood.
Every drop of water in the sea is as obedient to law and order as
are the members of the heavenly host in the remotest regions of
space; for when the morning stars sang together in the almighty
anthem, we are told "the waves also lifted up their voice" in
chorus; and doubtless, therefore, the harmony in the depths of the
ocean is in tune with that which comes from the spheres above.
We can not doubt it; for, were it not so, were there no channels
of circulation from one ocean to another, and if, accordingly, the
waters of the Atlantic were confined to the Atlantic, or if the waters of the arms and seas of the Atlantic were confined to those
arms and seas, and had no channels of circulation by which they
could pass out into the ocean, and traverse different latitudes and
climates-if this were so, then the machinery of the ocean would
be as incomplete as that of a watch without a balance-wheel.
466. For instance, take the Red Sea and the Mediterranean by
Ditto by the Red way of illustration.  Upon the Red Sea there is no
Sea.         precipitation; it is a rainless region; not a river
runs down to it, not a brook empties into it; therefore there is no
process by which the salts and washings of the earth, which are
taken up and held in solution by rain or river water, can be
brought down into the Red Sea. Its salts come from the ocean,
and the air takes up from it, in the process of evaporation, fresh
water, leaving behind, for the currents to carry away, the solid
matter which, as sea water, it held in solution. On the other
hand, numerous rivers discharge themselves into the Mediterranean, some of which are filtered through soils and among minerals which yield one kind of salts or soluble matter, another river
runs through a limestone or volcanic region of country, and brings
down in solution solid matter-it may be common salt, sulphate
or carbonate of lime, magnesia, soda, potash, or iron-either or all
may be in its waters. Still, the constituents of sea water from
the Mediterranean and of sea water from the Red Sea are quite
the same. But the waters of the Dead Sea have no connection
with those of the ocean; they are cut off from its channels of circulation, and are therefore quite different, as to their components,
from any arm, frith, or gulf of the broad ocean. Its inhabitants




240        THE PHYSICAL GEOGRAPHY OF THE SEA.
are also different from those of the high seas.  "The water which
evaporates from the sea is nearly pure, containing but very minute
traces of salts. Falling as rain upon the land, it washes the soil,
percolates through the rocky layers, and becomes charged with
saline substances, which are borne seaward by the returning currents. The ocean, therefore, is the great depository of every thing
that water can dissolve and carry down from the surface of the
continents; and, as there is no channel for their escape, they of
course consequently accumulate."*  They would constantly accumulate, as this very shrewd author remarks, were it not for the
shells and insects of the sea and other agents mentioned.
467. HIow, therefore, shall we account for this sameness of comA general system of pound, this structure of coral (~ 465), this stability
circulation required
for the ocean.    as to animal life in the sea, but upon the supposition of a general system of circulation in the ocean, by which, in
process of time, water from one part is conveyed to another part
the most remote, and by which a general interchange and commingling of the waters take place?  In like manner, the constituents of the atmosphere, whether it be analyzed at the equator or
the poles, are the same. By cutting off and shutting up from the
general channels of circulation any portion of sea water, as in the
Dead Sea, or of atmospheric air, as in mines or wells, we can easily fill either with gases or other matter that shall very much affect its character, or alter the proportion of its ingredients, and
affect the health of its inhabitants; but in the open sea or open
air we can do no such thing.
468. The principal agents that are supposed to be concerned in
Dynamical agents. giving circulation to the atmosphere, and in preserving the ratio among its components, are light, heat, electricity, and
perhaps magnetism. But with regard to the sea, it is not known
what office, if any, is performed by electricity, in giving dynamical force to its system of circulation. The chief motive power
from which marine currents derive their velocity has been ascribed
to heat; but a close study of the agents concerned has suggested
that an important —nay, a powerful and active agency in the system of oceanic circulation is derived from the salts of the sea water, through the instrumentality of the winds, of marine plants,
and animals. These give the ocean great dynamical force. Let
* Youman's Chemistry.




~ 468.            THE SALTS OF THE SEA.                241
us, for the sake of illustrating and explaining the nature of this
force, suppose the sea in all its parts-in its depths and at the surface, at the equator and about the poles-to be of one uniform
temperature, and to be all of fresh water; and, moreover, that
there be neither wind to disturb its surface, nor tides nor rains to
raise the level in this part, or to depress it in that. In this case,
there would be nothing of heat to disturb its equilibrium, and
there would be no motive power (~ 461) to beget currents, or to
set the water in motion by reason of the difference of level or of
specific gravity due to water at different densities and temperatures. Now let us suppose the winds, for the first time since the
creation, to commence to blow upon this quiescent sea, and to
ruffle its surface; they, by their force, would create partial surface
currents, and thus agitating the waters, as they do, but only for a
little way below the surface, would give rise to a feeble circulation
in the supposed sea of fresh water. The. surface currents thus
created would set with the wind, giving rise to counter currents
in the shape of under-tows and eddies. This, then, is one of the
sources whence power is given to the system of oceanic circulation; but, though a feeble one, it is one which exists in reality,
and, therefore, need not be regarded as hypothetical. Some (~ 79)
think it the "'sole cause!"  Let us next call in evaporation and
precipitation, with heat and cold — more powerful agents still.
Suppose the evaporation to commence from this imaginary freshwater ocean, and to go on as it does from the seas as they are. In
those regions, as in the trade-wind regions, where evaporation is
in excess of precipitation (~ 545), the general level of this supposed sea would be altered, and immediately as much water as is
carried off by evaporation would commence to flow in from north
and south toward the trade-wind or evaporating region to restore
the level. On the other hand, the winds would have taken this
vapor, borne it off to the extra-tropical regions, and precipitated
it, we will suppose, where precipitation is in excess of evaporation.
Here is another alteration of sea level by elevation instead of by
depression; and hence we have the motive power for a surface
current from each pole toward the equator, the object of which is
only to supply the demand for evaporation in the trade-wind regions-demand for evaporation being taken here to mean the difference between evaporation and precipitation for any part of the
Q




242       THE PHYSICAL GEOGRAPHY OF THE SEA.
sea. Now imagine this sea of uniform temperature to be suddenly stricken with the invisible wand of heat and cold, bringing its
waters to the various temperatures at which they at this instant
are standing.  This change of temperature would make a change
of specific gravity in the waters, which would destroy the equilibriurn of the whole ocean; upon this a set of currents would immediately commence to flow, namely, a current of cold and heavy
water to the place of the warm, and a current of warm and lighter
to the place of the cold. The motive power of the currents thus
created would be difference of specific gravity arising from difference of temperature in fresh water. We have now traced the effect of two agents, which, in a sea of fresh water, would tend to
create currents, and to beget a system of aqueous circulation; but
a set of currents, and a system of circulation which, it is readily
perceived, would be quite feeble in comparison with those which
we find in the salt sea. One of these agents would be employed
in restoring, by means of one or more polar currents, the water
that is taken from one part of the ocean by evaporation, and deposited in another by precipitation. The other agent would be
employed in restoring, by the forces due difference of specific
gravity, the equilibrium, which has been disturbed by heating,
and of course expanding, the waters of fhe torrid zone on one
hand, and by cooling, and consequently contracting, those of the
frigid zone on the other. This agency would, if it were not modified by others, find expression in a system of currents and counter currents, or rather in a set of surface currents of warm and
lighter water, from the equator toward the poles, andcl in another
set of under currents of cooler, dense, and heavy water from the
poles toward the equator.
469. Such, keeping out of view the influence of the winds,
Currents without which we may suppose would be the same whether
wind.       the sea were salt or fresh, would be the system of
oceanic circulation were the sea all of fresh water. But fresh water, in cooling, begins to expand near the temperature of 40~,*
and expands more and more till it reaches the freezing point, and
ceases to be fluid. This law of expansion by cooling would impart a peculiar feature to the system of oceanic circulation were
the waters all fresh, which it is not necessary here to notice far* 390.5 




~ 470.             THE SALTS OF THE SEA.                   243
ther than to say it call not exist in seas of salt water, for salt water (~ 405) contracts as its temperature is lowered, and until it
passes its freezing point.  Hence, in consequence of its salts,
changes of temperature derive increased power to disturb the
equilibrium of the ocean. If this train of reasoning be good, we
may infer that, in a system of oceanic circulation, the dynamical
force to be derived from difference of temperature, where the waters are all fresh, would be quite feeble; and that, were the sea
not salt, we should (~ 462) probably have no such current in it as
the Gulf Stream. So far we have been reasoning hypothetically,
to show what would be the chief agents, exclusive of the winds, in
disturbing the equilibrium of the ocean were its waters fresh and
not salt. And whatever disturbs equilibrium  there may be regarded as the primuvm mobile in any system of marine currents.
470. Let us now proceed another step in the process of exInfluence of salts nd plaining and illustrating the effect of the salts of the
evaporation.  sea in the system  of oceanic circulation.  To this
end, let us suppose the imaginary ocean of fresh water suddenly
to become that which we have, namely, an ocean of salt water,
which contracts as its temperature is lowered (~ 441) till it reaches 25~.6. Let evaporation now commence in the trade-wind region, as it was supposed to do (~ 468) in the case of the fresh-water seas, and as it actually goes on in nature-and what takes
place?  Why, a lowering of the sea level, as before.  But as the
vapor of salt water is fresh, or nearly so, fresh water only is taken
up from the ocean; that which remains behind is therefore more
salt. Thus, while the level is lowered in the salt sea, the equilibrium  is destroyed because of the saltness of the water; for the
water that remains after the evaporation takes place is, on account
of the solid matter held in solution, specifically heavier than it
was before any portion of it was converted into vapor. The vapor is taken from the surface water; the surface water thereby
becomes more salt (~ 463), and, under certain conditions, heavier;
when it becomes heavier, it sinks; and hence we have, due to the
salts of the sea, a vertical circulation, namely, a descent of heavier
-because salter and cooler-water from the surface, and an ascent
of water that is lighter-because it is not so salt, or, being as salt,
is not so cool (~ 404)-from the depths below.  This vapor, then,
which is taken up from the evaporating regions (~ 293), is carried




244       THE PHYSICAL GEOGRAPHY OF THE SEA.
by the winds through their'channels of circulation, and poured
back into the ocean where the regions of precipitation are; and
by the regions of precipitation I mean those parts of the ocean,
as in the polar basins, where the ocean receives more fresh water
in the shape of rain, snow, etc., than it returns to the atmosphere
in the shape of vapor. In the precipitating regions, therefore,
the level is destroyed, as before explained, by elevation; and in
the evaporating regions, by depression; which, as already stated
(~ 468), gives rise to a system of surface currents, moving on an
inclined plane, from the poles toward the equator. But we are
now considering the effects of evaporation and precipitation in
giving impulse to the circulation of the ocean where its waters
are salt. The fresh water that has been taken from the evaporating regions is deposited upon those of precipitation, which,
for illustration merely, we will locate in the north polar basin.
Among the sources of supply of fresh water for this basin, we
must include not only the precipitation which takes place over
the basin itself, but also the amount of fresh water discharged into
it by the rivers of the great hydrographical basins of Arctic Europe, Asia, and America. This fresh water, being emptied into
the Polar Sea and agitated by the winds, becomes mixed with the
salt; but as the agitation of the sea by the winds is supposed to
extend to no great depth (~ 468), it is only the upper layer of salt
water, and that to a moderate depth, which becomes mixed with
the fresh. The specific gravity of this upper layer, therefore, is
diminished just as much as the specific gravity of the sea water
in the evaporating regions was increased. And thus we have a
surface current of saltish water from the poles toward the equator, and an under current of water salter and heavier from the
equator to the poles. This under current supplies, in a great
measure, the salt which the upper current, freighted with fresh
water from the clouds and rivers, carries back.
471. Thus it is to the salts of the sea that we owe that feature
The under currents in the system of oceanic circulation which causes
owing entirely to the
salts of tea water.  an under current to flow from the Mediterranean
into the Atlantic (~ 385), and another (~ 377) from the Red Sea
into the Indian Ocean. And it is evident, since neither of these
seas is salting up, that just as much, or nearly just as much salt
as the under current brings out, just so much the upper currents




~ 472, 473.        THE SALTS OF THE SEA.                   245
carry in.  We now begin to perceive what a powerful impulse is
derived from the salts of the sea in giving effective and active
circulation to its waters.  Hence we infer (~ 461) that the currents of the sea, by reason of its saltness, attain their maximum
of volume and velocity.  Hence, too, we infer that the transportation of warm water from the equator toward the frozen regions of
the poles, and of cold water from the frigid toward the torrid zone,
is facilitated; and consequently here, in the dynamical power which
the sea derives from its salts, have we not an agent by which climates are mitigated-by which they are softened and rendered
much more salubrious than it would be possible for them to be were
the waters of the ocean deprived of their property of saltness?
472. This property of saltness imparts to the waters of the
A property peculiar ocean another peculiarity, by which the sea is still
to seas of salt water. better adapted for the regulation of climates, and it
is this: by evaporating fresh water from  the salt in the tropics,
the surface water becomes heavier than the average of sea water
(~ 427).  This heavy water is also warm water; it sinks, and being a good retainer, but a bad conductor of heat, this warm water
is employed in transporting through under currents heat for the
mitigation of climates in far-distant regions. Now this also is a
property which a sea of fresh water could not have (~ 430). Let
the winds take up their vapor from a sheet of fresh water, and
that at the bottom is not disturbed, for there is no change in the
specific gravity of that at the surface by which that at the bottom
may be broyught to the top; but let evaporation go on, though
never so gently, from salt water, and the specific gravity of that
at the top will soon be so changed as (~ 404) to bring that from
the very lowest depths of the sea to the top.
473. If all the salts of the sea were precipitated and spread
Quantity of salt in out equally over the northern half of this continent,
the sea.     it would, it has been computed, cover the ground
one mile deep.  What force could move such a mass of matter on
the dry land? Yet the machinery of the ocean, of which it forms
a part, is so wisely, marvelously, and wonderfully compensated,
that the most gentle breeze that plays on its bosom, the tiniest insect that secretes solid matter for its sea-shell, is capable of putting it instantly in motion.  Still, when solidified and placed in a
heap, all the mechanical contrivances of man, aided by the tre



246        THE PHYSICAL GEOGRAPHY OF THE SEA.
mendous forces of all the steam and water power of the world,
could not, in centuries of time, move even so much as an inch this
matter which the sunbeam, the zephyr, and the infusorial insect
keep in perpetual motion and activity.
474. If these inferences as to the influences of the salts upon
Deductions. the currents of the sea be correct the same cause
which produces an under current from the Mediterranean (~ 471),
and an under current from the Red Sea into the ocean, should
produce an under current from the ocean into the north polar basin; for it may be laid down as a law, that whenever two oceans,
or two arms of the sea, or two sheets of water, differing as to saltness, are connected with each other, there are currents between
them, viz., a surface current from, and an under current into the
sea of lightest water. In every case, the hypothesis with regard
to the part performed by the salt, in giving vigor to the system
of oceanic circulation, requires that, counter to the surface current
of water with less salt, there should be an under current of water
with more salt in it. That such is the case with regard both to
the Mediterranean and the Red Sea has been amply shown in
other parts of this work (~ 471), and abundantly proved by other
observers. That, in obedience to this law, there is a constant current setting out of the Arctic Ocean through Davis' and other
straits thereabout, which connect it with the Atlantic Ocean, is
generally admitted. Lieutenant De Haven, United States Navy,
when in command of the American expedition in search of Sir
John Franklin, was frozen up with his vessels-the Advance and
the Rescue-in mid-channel near Wellington Straits; and during
the nine months that he was so frozen, his vessels, like H. B. M.
ship Resolute and the Fox (~ 431), each holding its place in the
ice, were drifted with it bodily for more than a thousand miles toward the south.
475. The drift of these vessels is sufficient, were there no other
Drift of the Reso- evidence, to establish the existence of an open sea
lute.       in the Arctic Ocean; for this drift can not be accounted for upon any other hypothesis, as a slight examination
of the arctic regions on a terrestrial globe, and a careful study of
the facts p. 231-3, and other phenomena of the case, will show.
476. About the middle of September, 1850, being in latitude
De Haven's drift. 740 40', and in the fair way of Wellington Channel,




~ 477.              THE SALTS OF THE SEA.                      247
De Haven found himself, with the Advance, frozen in her tracks,
as M'Clintock did the Fox,  in August, 1857, who tried to reach
the shore, but he was fast bound, and drifting to the west.  De
Haven, after having been carried as far as 75~ 25', and M'Clintock
as far as 75~ 30', say within nine hundred miles of the pole, their
northerly course was arrested, and then commenced with each
that celebrated drift of a thousand miles to the south, and which
from  December lasted, the one till June, the other till April
25th.  These vessels were not drifted through the ice, but with
the ice; for in lat. 65~ 30', when De Haven was liberated on the
9th of June, he had the same " hummocks," the same snow-drifts,
and the same icy landscape which set out with him on December
2d, when he commenced his drift from the parallel of 750 25'.t
477. Now, upon the theory of no open water, and upon the
An  anti-polynian supposition of an ice-covered sea that seals up in
view.         winter all the unexplored regions of the north, let
us, in imagination, take a survey of that sea just as the anti-polynians, according to their theory, would have it. Let the time of
the survey be at the beginning of winter, when De Haven commenced his southwardly drift.  From the Advance to the polea distance of 900 miles —no water is to be seen; the frost has
bridged it all over.  From the pole to the distance of 900 miles
beyond, and all around, it is one field of thick-ribbed ice. The
flat, and tame, and dreary landscape may be relieved here and
there, perhaps, by islands, capes, and promontories dotting the surface, but nevertheless it is now at least as cold-being winterfrom the pole all around to the parallel of 75~, as it was in
early fall when De Haven, being near that parallel in WVellington
Channel, found his vessel fast bound with fetters by the frostking.  WVherefore we may suppose that these theorists would admit the whole to be frozen by December.  So that, according to
the anti-polynian view, we have, measuring from  the pole as a
centre, a disc of ice more than five thousand miles in circumfer* A screw yacht of 177 tons.
t De Haven was frozen in lat. 740 40', long. 920 55'; was carried up to 75~0 295'
N., and thence down to 660 15' N., 580 35' W., when he was liberated. The Fox
was frozen in 75~ 30' N., 640 W.; was carried west to 69~ in the same latitude,
and thence down to 630 50' N., and 570 W., when she was liberated. The Resolute
was abandoned in lat. 740 40', long. 101~ 20', and was picked up afloat off Cape
Mercy in (;5~ N.




248       TIIE PHYSICAL GEOGRAPHY OF THE SEA.
ence, and extending quite down to the shores of Arctic America
and Asia. Such is the aspect presented by the polar sea without
an open water in winter; and on the 2d of December-the moment before this remarkable drift commenced; and when it did
commence —was the entire sheet of ice with which we have supposed the Arctic Ocean to be covered put in motion, or was that
only put in motion which drifted out? By the hypothesis there
is no open water in all the circumference of this sea into which
the ice might drift. We therefore may well ask the anti-polylians again, How did this drift commence? for commence it did;
its movement was out of that sea, and from the pole toward the
equator, and so it continued for six months at the average rate of
5-1 miles a day. But whence-on what parallel-did it commence?  WVas the whole disc in motion from the shores of Siberia over across by way of the north pole toward Wellington Channel? If one part of this disc be put in motion, either the whole
must be, or there must be a split or a rent with open water between. If, during the winter and spring-the coldest period-the
edge of this ice-disc nearest Wellington Channel be carried by
the currents a thousand miles toward the south, the edge along
the Russian shores on the opposite side must have been drifted
toward the north a thousand miles also, and so leave an open water behind. Now we simply know there was no such drifting up
from the Siberian shores, and the case is put simply to show that
in any case the northerly edge of the drifting ice must have come
from open water; for if we deny the existence of an open water
in that direction, then we must go back and admit that at the beginning of the drift there was ice all the way from Wellington
Channel to the north pole, and thence all the way from the north
pole to the nearest land beyond, which is supposed to be the Siberian shores of the Old World. But, on the other hand, we must
also admit the fact-for the Advance, the Rescue, the Fox, and the
Resolute are witnesses of it-that a tongue of this ice 1000 miles
long was in each of these winters thrust out of the polar basin
down through Baffin's Bay into Davis' Straits. These ships came
down upon it. It would be difficult for those who oppose the
existence of an open water here in the Arctic Ocean to discover
a force there which, during the extreme cold months of the northern night, when the ice is making all the time, could tear from




~ 478.               THE SALTS OF THE SEA.                      249
its fastenings and move 52 miles a day all through the winter and
spring a disc of ice seven feet thick* and 1800 geographical miles
in diameter.  Yet such seem to be the conditions which the-absence of open water would require; for, when the Advance was
thawed out, there was a thousand miles of ice to the northward
of her, and between her and WVellington Channel.  This 1000
miles of ice had drifted out of the polar basin during her journey
to the south; for when she was liberated there was doubtless a
continuous sheet of ice between her in lat. 65~, and Wellington
Channel in lat. 750. This tongue of ice is what the whalemen
call the middle ice of Baffin's Bay.  When the Advance was at
WVellington Channel, this thousand miles of ice must, according
to the anti-polynians, have been to the north of her; or, according
to the other school, it must, as it drifted toward the south, have
been forming toward the north at the edge of an open sea (~ 459).
And toward the north De Haven saw a water-sky, and toward the
north Penny found an open sea and sailed upon it.
478. Upon the supposition that the ice which drifts out of the
The drift explained. Arctic Ocean in the dead of winter is formed on
the edge of an open water not far from the channel through which
it drifts, we can account for all the known facts which attended
the celebrated drifts of De Haven, M'Clintock,t and the Resolute.  Upon no other theory can these well-known and well-authenticated facts be reconciled. If there be no open water during
this winter drift, which there is reason to believe takes place annually, both the Advance, Fox, and the Resolute indicate that the
whole icy covering-the frost-shell of the polar sea in wintermust have drifted bodily far enough, on these three several occasions at least, to set each vessel a thousand miles on her way toward the south.  And thus, without bringing in again the long
chain of evidence from Chapter IX., the physical necessity of an
open sea in the Arctic Ocean is proved..
* De Haven found the ice upon which his vessel was brought out 7 feet 2 inches
thick.                                       t In the Fox, 1857-1858.
t "The Fox accomplished another of those remarkable drifts which can be explained upon no other hypothesis but that of an open water in the Arctic Ocean, and
that, too, not far from the entrance into it of some of the channels which connect it
with Baffin's SBay on the polar side of 75~. The Fox was attempting to pass from
Melville Bay over to Lancaster Sound, in August, 1857, when, on the 18th day of
that month she fell in with ice, in which she was finally fiozen up, and remained so




250          THE PHYSICAL GEOGRAPHY OF THE SEA.
479. On the first of April De Haven measured the ice, and
Thickness of a win- found it seven feet two inches thick.  It was formed
ter's ice.      probably mostly of rain and river water, which, like
our own littoral waters (~ 426), protect the salter and heavier waters
below  from  the cold, for De Haven invariably found the temperature of the water under the ice 28~, which is the temperature
for 242 days, during which time she was drifted to the southward 1194 miles, which
gives an average rate of five miles a day.
" This drift-the drift of the Resolute, of the Advance, and Rescue, each upward
of a thousand miles-appears to indicate that a similar drift takes place every year.
They show the existence of a polynia, and indicate that the open sea is to be sought
for at no great distance from Kennecdy's Channel on the one hand, and Maury's on
the other. This conclusion is reached by a process of reasoning of this sort:
"When each one of these vessels was released from her cold fetters, there was
doubtless behind her, and between her place of release and her place of original imprisonment, an uninterrupted reach of a thousand miles covered with ice; which ice,
during the fall, the winter, and early spring, drifted out of the Arctic Ocean. Now
we have the choice of two suppositions, and of only two, in explanation of this phenomenon, and they are: Either that the great body of all the winter-formed ice of
the Arctic Ocean must have drifted in an unbroken mass over toward Baffin's Bay;
for these vessels were brought out upon a tongue of ice thrust through that bay down
into Davis' Straits; or that this tongue must have been separated from the main
mass, leaving behind that from which it had been severed.
"By the latter supposition all the known facts of the case may be reconciled; by
the former, not one.
" If we suppose this drifting field of ice to be formed -upon the very verge of an open
sea, and to drift to the south as fast as it is formed, then the whole phenomenon becomes one of easy solution. At any rate, we are now possessed of a physical fact
which probably would have returned Captain Crozier and his companions to us all
safe and sound had they been aware of its existence; and that fact is in this oftoccurring, if not regular and annual, southward drift of ice from the Arctic Ocean
down through Baffin's Bay into Davis' Strait.  Captain Franklin, being ignorant of
it, placed his vessels out of its reach on the south, where he was frozen in and died,
and where Captain Crozier, his successor, remained imprisoned for eighteen months,
and then abandoned his ships; their drift in the mean time, and for obvious reasons,
being almost, if not quite insensible, except as influenced by the summer thaw and
"winter wedgings."  Now if those vessels, with their scurvy-riddled, frostworn, and
disabled crews, could have been placed farther to the north, as in B1arrow's Strait, or
in the fairway of any of those channels connecting with it from the northward and
westward, or with Baffin's Bay, the probabilities are that this regularly-recurring
winter drift would have brought them down safely into milder climates, and into the
glad waters of the Atlantic Ocean, as it did those four other vessels.
"The frequent, if not the regular annual occurrence of this drift down through
Baffin's Bay is a fact which will be considered by all future arctic explorers as one
of great importance, for it affords the means of escaping from the Arctic Ocean in
the severest winter."- Transactions of tihe Am. Geo.'ociety, 1860.




~ 480, 481.         THE SALTS OF THE SEA.                      251
that average sea water invariably assumes during the process of
congelation (~ 442). Moreover, the specific gravity of the surface
water which Rodgers measured in the Arctic Ocean was (~ 427) less
than that of average sea water-a fact in confirmation of this conjecture as to the office of rain and river water in the polar seas.
The freezing-point of the strongest brine is 4~; consequently, the
freezing-point of water in the sea varies according to the proportion of salts from 40 all the way up to just below 32~.  Thus the
salts of the sea impart to its waters an elasticity, as it were, giving
a law, a sort of sliding-scale both for the thermal dilatation and
of congelation, which varies between that of fresh water and the
saltest sea waters according to the degree of their saltness.
480. Rodgers tried with his hydrometer and thermometer the
Layers of water of waters of the Arctic Ocean at the surface, below,
diterent thempcIa- and at the bottom, and as often as he tried he found
Ocean.        this arrangement: warm and light water on the top,
cool in the middle, "hot and heavy" at the bottom.  His experiments were made near Behring's Straits in August, 1855, between
the parallels of 71~-2~, and are as per example following:
Date.    Depth.   Temp.  Sp. Grav.          Place.
Aug. 13  surface.   43.8.0264   Lat. 72~ 2' Long. 1740 37' W.
"     20 fath.   33.5.0266    "L.L "    " 
z" s  40 fath.'  40.5.0266    "    "     "      "
Aug. 15  surface.   42.5.0258       710 21' "  1750 22'
12 fath.    39.8.0264    "   "4    c   "s
I"    25 fath.t  40.2.0264
1 Near bottom.
Assuming the surface water which Rodgers used for these experiments to be a fair average of arctic surface waters generally,
this table affords data that show the proportion of rain and river
water that the Arctic Ocean receives annually.  The quantity
may be inferred from the fact that average sea water has tell per
cent. more salt than Rodgers's arctic.
481. Returning now to the drift of the ice, and the drift of the
The ice-bearing drift Advance and her followers, we see that, so far as
fom the Arctic  like currents are concerned, we have in the Arctic
the ordinary drift c
from the Baltic.    Ocean a repetition merely of the more familiar phenomenon that is seen in the Baltic, where (~ 383, note) an under
current of salt water runs in, and an upper current of brackish
water runs out. Then, since there is salt always flowing out of
the north polar basin, we infer that there must be salt always




252        THE PHYSICAL GEOGRAPHY OF THE SEA.
flowing into it, else it would either become fresh, or the whole
Atlantic Ocean would become more and more briny, and be finally silted up with salt. It might be supposed, were there no evidence to the contrary, that this salt was supplied to the polar seas
from the Atlantic around North Cape, and from the Pacific through
Behring's Straits, and through no other channels.  But, fortunately, arctic voyagers, who have cruised in the direction of Davis'
Straits, have confirmed by their observations a law of nature
(~ 474), and afforded us proof positive as to the fact of this other
source for supplying the polar seas with salt. They tell us of an
under current setting from the Atlantic toward the polar basin.
They describe huge icebergs, with tops high up in the air, and of
course the bases of which extend far down into the depths of the
ocean, ripping and tearing their way with terrific force and awful
violence through the surface ice or against a surface current, on
their way into the polar basin.
482. Passed Midshipman S. P. Griffin, who commanded the brig
Icebergs  drifting Rescue in the American searching expedition aftnorth.       er Sir John Franklin, informs me that, on one occasion, the two vessels were endeavoring, when in Baffin's Bay,
to warp up to the northward against a strong surface current,
which of course was setting to the south; and that, while so engaged, an iceberg, with its top many feet above the water, came
"drifting up" from the south, and passed by them "like a shot."
Although they were stemming a surface current against both the
berg and themselves, such was the force and velocity of the under current that it carried the berg to the northward faster than
the crew could warp the vessel against a surface but counter current.  They hooked on to it, and were towed to the north by: it.
Captain Duncan, master of the English whale-ship Dundee, says,
at page 76 of his interesting littlfie narrative:* "December 18th
(1826). It was awful to behold the immense icebergs working
their way to the northeast from us, and not one drop of water to
be seen; they were working themselves right through the middle of the ice."  And again, at page 92, etc.: "Febrzuary 23d.
Latitude 68~ 37' north, longitude about 630 west. The dreadful
apprehensions that assailed us yesterday by the near approach of
* Arctic Regions; Yoyage to Davis' Strait, by Dorea Duncan, Miaster of the Ship
IDundee, 1826, 1827.




~ 483.            THE SALTS OF THE SEA.                 253
the iceberg were this day most awfully verified. About three
P.M. the iceberg came in contact with our floe, and in less than
one minute it broke the ice; we were frozen in quite close to the
shore; the floe was shivered to pieces for several miles, causing
an explosion like an earthquake, or one hundred pieces of heavy
ordnance fired at the same moment. The iceberg, with awful but
majestic grandeur (in height and dimensions resembling a vast
mountain), came almost up to our stern, and every one expected
it would have run over the ship..... The iceberg, as before
observed, came up very near to the stern of the ship; the intermediate space between the berg and the vessel was filled with
heavy masses of ice, which, though they had been previously
broken by the immense weight of the berg, were again formed
into a compact body by its pressure. The berg was drifting at
the rate of about four knots, and by its force on the mass of ice
was pushing the ship before it, as it appeared, to inevitable destruction. Feb. 24th. The iceberg still in sight, but drifting away
fast to the northeast. Feb. 25th. The iceberg that so lately threatened our destruction had driven completely out of sight to the
northeast from us."
483. Now, then, whence, unless from the difference of specific
Temperature of the gravity due sea water of different degrees of saltunder current. ness and temperature, can we derive a motive power in the depths of the sea, with force sufficient to give such tremendous masses of ice such a velocity?  WVhabt is the temperature of this under current? Rodgers's observations (~ 480) would
seem to indicate that at the depth of 150 feet it is not below 40~.
Assuming the water of the surface current which runs out with
the ice to be all at 280, as De Haven found it (~ 479), we observe
that it is not unreasonable to suppose that the water of the under
current, inasmuch as it comes from the south, and therefore from
warmer latitudes, is not so cold; and if it be not so cold, its temperature, before it comes out again, must be reduced to 28~, or
whatever be the average temperature of the outer but surface current. Dr. Kane found the temperature of the open sea in the Arctic Ocean (~ 429) as high as 360.  Can water in the depths below
flow from the mild climate of the temperate zones to the severer
climates of the frigid zone without falling below 36~? To what,
in the depths of the sea, can a warm current of large volume im



254       THE PHYSICAL GEOGRAPHY OF THE SEA.
part its heat?  The temperature of sea water from the tropics in
which ice is forming is invariably (~ 442) 28~. Does not the circumstance of De Haven's invariably finding this to be the temperature below the ice on which he drifted tend to confirm the
conjecture (~ 479) about the ice and the river water?
484. This under polar current water, then, as it rises to the top,
It comes to the sur- and is brought to the surface by the agitation of the
farce.       sea in the arctic regions, gives out its surplus heat
to warm the atmosphere there till the temperature of this warm
under current water is lowered to the requisite degree for going
out on the surface. Hence the water-sky of those regions. And
the heat that it loses in falling from its normal temperature, be
that what it may, till it reaches the temperature of 28~, is so much
caloric set free in the polar regions, to temper the air and mitigate the climate there. Now is not this one of those modifications
of climate which may be fairly traced back to the effect of the
saltness of the sea in giving energy to its circulation?  Moreover,
if there be a deep sea in the polar basin, which serves as a receptacle for the waters brought into it by this under current, which,
because it comes from toward the equatorial regions, comes from
a milder climate, and is therefore warmer, we cal easily imagine
why there might be an open sea in the polar regions-why Lieutenant De Haven, in his instructions (~ 428), was directed to look
for it; and why both he and Captain Penny, of one of the English searching vessels, and afterward Dr. Kane, found it there.
And in accounting for this polynia, we see that its existence is not
only consistent'with the hypothesis with which we set out, touching
a perfect system of oceanic circulation, but that it may be ascribed,
in a great degree at least, if not wholly, to the effect produced by
the salts of the sea upon the mobility and circulation of its waters.
Here, then, is an office which the sea performs in the economy of
the universe by virtue of its saltness, and which it could not perform were its waters altogether fresh. And thus philosophers
have a clew placed in their hands which will probably guide them
to one of the many hidden treasures that are embraced in the true
answer to the question, " Why is the sea salt?"
485. SEA SHELLS.-We find in sea water other matter besides
SEA sELTs —their common salt. Lime is dissolved by the rains and
influence upon currents.      the rivers, and emptied in vast quantities into the




~ 486.            TIlE SALTS OF THE SEA.                 255
ocean. Out of it, coral islands and coral reefs of great extentmarl-beds, shell-banks, and infusorial deposits of enormous magnitude, have been constructed by the inhabitants of the deep.
These creatures are endowed with the power of secreting, apparently for their own purposes only, solid matter, which the waters
of the sea hold in solution. But this power was given to them
that they also might fulfill the part assigned them in the economy
of the universe. For to them, probably, has been allotted the
important office of assisting to give circulation to the ocean, of
helping to regulate the climates of the earth, and of preserving
the purity of the sea. The better to comprehend how such creatures may influence currents and climates, let us again suppose
the ocean to be perfectly at rest-that throughout, it is in a state
of complete equilibrium-that, with the exception of those tenants
of the deep which have the power of extracting from it the solid
matter held in solution, there is no agent in nature capable of disturbing that equilibrium —and that all these fish, etc., have suspended their secretions, in order that this state of a perfect aqueous equilibrium and repose throughout the sea might be attained.
In this state of things-the waters of the sea being in perfect equilibrium -a single mollusk or coralline, we will suppose, commences his secretions, and abstracts from the sea water (~ 465)
solid matter for his cell. In that act this animal has destroyed
the equilibrium of the whole ocean, for the specific gravity of that
portion of water from which this solid matter has been abstracted is altered. Having lost a portion of its solid contents, it has
become specifically lighter than it was before; it must, therefore,
give place to the pressure which the heavier water exerts to push
it aside and to occupy its place, and it must consequently travel
about and mingle with the waters of the other parts of the ocean
until its proportion of solid matter is returned to it, and until it attains the exact degree of specific gravity due sea water generally.
486. How much solid matter does the whole host of marine
Solid matter secreted plants and animals abstract from sea water daily?
by them.      Is it a thousand pounds, or a thousand millions of
tons? No one can say. But, whatever be its weight, it is so
much of the power of gravity applied to the dynamical forces of
the ocean. And this power is derived from the salts of the sea,
through the agency of sea-shells and other marine animals, that




256        THE PHYSICAL GEOGRAPHY OF THE SEA.
of themselves scarcely possess the power of locomotion. Yet they
have power to put the whole sea in motion, from the equator to
the poles, and from top to bottom. But we have yet to inquire
how far may currents be due to the derangement of equilibrium
arising from the change of specific gravity caused by the secretions of the myriads of marine animals that are continually at
work in various parts of the ocean.  These little creatures abstract from sea water solid matter enough to build continents of.
And, also, we have to remember as to the extent to which equilibrium in the sea is disturbed by the salts which evaporation
leaves behind. Thus, when we consider the salts of the sea in one
point of view, we see the winds and the marine animals operating
upon the waters, and, in certain parts of the ocean, developing by
their action upon the solid contents of the same those very principles of antagonistic forces which hold the earth in its orbit, and
preserve the harmonies of the universe.
487. In another point of view, we see the sea-breeze and the
Dynamical force de- sea-shell, in performing their appointed offices, act-from.  ing so as to give rise to a reciprocating motion in
the waters; and thus they impart to the ocean dynamical forces
also for its circulation.  The sea-breeze plays upon the surface;
it converts only fresh water into vapor, and leaves the solid matter behind. The surface water thus becomes specifically heavier,
and sinks. On the other hand, the little marine architect below,
as he works upon his coral edifice at the bottom, abstracts from
the water there a portion of its solid contents; it therefore becomes specifically lighter, and up it goes, ascending to the top with
increased velocity, to take the place of the descending column,
which, by the action of the winds, has been sent down loaded with
fresh food and materials for the busy little mason in the depths
below. Seeing, then, that the inhabitants of the sea, with their
powers of secretion, are competent to exercise at least some degree
of influence in disturbing equilibrium, are not these creatures entitled to be regarded as agents which have their offices to perform
in the system of oceanic circulation, and do they not belong to its
physical geography? Their influences upon the economy of the
sea are like those outstanding quantities which the astronomer
finds in the periods of heavenly bodies. He calls them perturbations; for short, or even during considerable intervals, their effects




~ 488.            THE SALTS OF TIIE SEA.                 257
may be inappreciable, but, unless there was a balance provided
somewhere-a pendulum that requires ages for a vibration-they
would, during the progress of time, accumulate so as to produce
disorder, and finally cause the destruction of worlds. So, too, with
the salts of the sea, and those little microscopic inhabitants of its
waters. They take care of its outstanding quantities of solid matter, and by their influence preserve harmony in the ocean. It is
immaterial how great or how small that influence may be supposed to be; for, be it great or small, it is cunmulative; and we
therefore may rest assured it is not a chance influence, but it is an
influence exercised by design, and according to the commandment
of Him whose "voice the winds and the sea obey."  Thus God
speaks through sea-shells to the ocean.
488. It may therefore be supposed that the arrangements in the
Their physical rela- economy of nature are such as to require that the
t~ions.      various kinds of marine anim-als, whose secretions
are calculated to alter the specific gravity of sea water, to destroy
its equilibrium, to beget currents in the ocean, and to control its
circulation, should be distributed according to order. Upon this
supposition —the like of which nature warrants throughout her
whole domain-we may conceive how the marine animals of
which we have been speaking may impress other features upon
the physical relations of the sea by assisting also to regulate climates, and to adjust the temperature of certain latitudes. For instance, let us suppose the waters in a certain part of the torrid
zone to be 90~, but, by reason of the fresh water which has been
taken from them in a state of vapor, and consequently by reason
of the proportionate increase of salts, these waters are heavier than
waters that may be cooler, but not so salt (~ 105). This being the
case, the tendency would be for this warm, but salt and heavy water, to flow off as an under current toward the polar or some other
regions of lighter water. Moreover, if the sea were not salt, there
would be no coral islands to beautify its landscape and give variety to its features; sea-shells and marine insects could not operate upon the specific gravity of its waters, nor give diversity to
its climates; neither could evaporation give dynamical force to
its circulation; its waters, ceasing to contract as their temperature
falls below 39~, would give but little impulse to its currents, and
impart no motion (~ 404) to its waters in the depths below: thus
IR




258       THE PHYSICAL GEOGRAPHY OF THE SEA.
its circulation would be torpid, and its bosom lack animation.
This under current may be freighted with heat to temper some
hyperborean region or to soften some extra-tropical climate, for
we know that such is among the effects of marine currents. At
starting, it might have been, if you please, so loaded with solid
matter that, though its temperature were 90~, yet, by reason of
the quantity of such matter held in solution, its specific gravity
might have been greater even than that of extra-tropical sea water
generally at 280. Notwithstanding this, it may be brought into
contact, by the way, with those kinds and quantities of marine organisms that shall. abstract solid matter enough to reduce its specific gravity, and, instead of leaving it greater than common sea
water at 280, make it less than common sea water at 40; consequently, in such a case, this warm sea water, when it comes to the
cold latitudes, would be brought to the surface through the instrumentality of shell-fish, and various other tribes that dwell far
down in the depths of the ocean. Thus we perceive that these
creatures, though they are regarded as beings so low in the scale
of creation, may nevertheless be regarded as agents of much importance in the terrestrial economy; for we now comprehend how
they are capable of spreading over certain parts of the ocean those
benign mantles of warmth which temper the winds, and modify,
more or less, all the marine climates of the earth.
489. The makers of nice astronomical instruments, when they
The regulators of the have put the different parts of their machinery tosea.         gether, and set it to work, find, as in the chronometer, for instance, that it is subject in its performance to many irregularities and imperfections; that in one state of things there is
expansion, and in another state contraction among cogs, springs,
and wheels, with an increase or diminution of rate. This defect
the makers have sought to overcome; and, with a beautiful display of ingenuity, they have attached to the works of the instrument a contrivance which has had the effect of correcting these
irregularities by counteracting the tendency of the instrument to
change its performance with the changing influences of temperature. This contrivance is called a compensation; and a chronometer or clock that is well regulated and properly compensated
will perform its office with certainty, and preserve its rate under
all the vicissitudes of heat and cold to which it may be exposed.




~ 490.            THE SALTS OF THE SEA.                  259
In the clock-work of the ocean and the machinery of the universe, order and regularity are maintained by a system of compensations. A celestial body, as it revolves around its sun, flies
off under the influence of centrifugal force; but immediately the
forces of compensation begin to act; the planet is brought back
to its elliptical path, and held in the orbit for which its mass, its
motions, and its distances were adjusted. Its compensation is perfect. So, too, with the salts and the shells of the sea in the machinery of the ocean; from them are derived principles of compensation the most perfect; through their agency the undue effects of heat and cold, of storm and rain, in disturbing the equilibrium, and producing thereby currents in the sea, are compensated,
regulated, and controlled. The dews, the rains, and the rivers are
continually dissolving certain minerals of the earth, and carrying
them off to the sea. This is an accumulative process; and if it
were not conmpensated, the sea would finally become, as the Dead
Sea is, saturated with salt, and therefore unsuitable for the habitation of many fish of the sea. The sea-shells and marine insects
afford the required comnpensation.  They are the conservators of
the ocean. As the salts are emptied into the sea, these creatures
secrete them again and pile them up in solid masses, to serve as
the bases of islands and continents, to be in the process of ages
upheaved into dry land, and then again dissolved by the dews
and rains, and washed by the rivers away into the sea again.
490. The question as to whence the salts of the sea were origWhence does the sea inally derived, of course has not escaped the attenderive its salts? tion of philosophers. I once thought with Darwin
and those other philosophers who hold that the sea derived its
salts originally from the washings of the rains and rivers. I now
question that opinion; for, in the course of the researches connected with the " Wind and Current Charts," I have found evidence, from the sea and in the Bible, which seems to cast doubt
upon it. The account given in the first chapter of Genesis, and
that contained in the hieroglyphics which are traced by the hand
of Nature on the geological column as to the order of creation,
are marvelously accordant. The Christian man of science regards
them both as true; and he never overlooks the fact that, while
they differ in the mode and manner as well as in the things they
teach, yet they never conflict; and they contain no evidence go



260       THE PHYSICAL GEOGRAPHY OF THE SEA.
ing to show that the sea was ever fresh; on the contrary, they
both afford circumstantial evidence sufficient for the belief that
the sea was salt as far back as the morning of creation, or at least
as the evening and the morning of the day when the dry land appeared. That the rains and the rivers do dissolve salts of various
kinds from the rocks and soil, and empty them into the sea, there
is no doubt. These salts can not be evaporated, we know; and
we also know that many of the lakes, as the Dead Sea, which receive rivers and have no outlet, are salt. Hence the inference by
some philosophers that these inland water-basins received their
salts wholly from the washings of the soil; and consequently the
conjecture arose that the great sea derived its salts from the same
source and by the same process. But, and per contra, though
these solid ingredients can not be taken out of the sea by evaporation, they can be extracted by other processes. We know that
the insects of the sea do take out a portion of them, and that the
salt ponds and arms which, from time to time in the geological
calendar, have been separated from the sea, afford an escape by
which the quantity of chloride of sodium in its waters-the most
abundant of its solid ingredients —is regulated.  The insects of
the sea can not build their structures of this salt, for it would dissolve again, and as fast as they could separate it. But here the
ever-ready atmosphere comes into play, and assists the insects in
regulating the salts. It can not take them up from the sea, it is
true, but it can take the sea away from them; for it pumps up
the water from these pools that have been barred off, transfers it
to the clouds, and they deliver it back to the sea as fresh water,
leaving the salts it contained in a solid state behind. These are
operations that have been going on for ages; proof that they are
still going on is continually before our eyes; for the "' hard water" of our fountains, the marl-banks of the valleys, the salt-beds
of the plains, Albion's chalky cliffs, and the coral islands of the
sea, are monuments in attestation. These masses of solid matter
have been secreted from the sea waters; they express the ability.of these creatures to prevent the accumulation of salts in the sea.
491. There is no proof nor is there any reason for the belief,
Theirantiquity. that the sea is growing salter or fresher. Hence
we infer that the operations of addition and extraction are reciprocal and equal; that the effect of rains and rivers in washing




~ 492.            THE SALTS OF THE SEA.                 261
down is compensated by the processes of evaporation and secretion
in taking out. If the sea derived its salts originally from the rivers, the geological records of the past would show that river beds
were scored out in the crust of our planet before the sea had deposited any of its fossil shells and infusorial remains upon it. If,
therefore, we admit the Darwin theory, we must also admit that
there was a period when the sea was without salt, and consequently without shells or animals either of the silicious or calcareous
kind. If ever there were such a time, it must have been when
the rivers were collecting and pouring in the salts which now
make the brine of the ocean. But while the paleontological records of the earth, on one hand, afford no evidence of any such
fresh-water period, the Mosaic account is far from being negative
with its testimony on the other. According to it, we infer that
the sea was salt as'early, at least, as the fifth day, for it was on
that day of creation that the waters were commanded to "bring
forth abundantly the moving creature that hath life." It is in
obedience to that command that the sea now teems with organisms; and it is marvelous how abundantly the obedient waters do
bring forth, and how wonderful for variety as well as multitude
their progeny is. All who pause to look are astonished to see
how the prolific ocean teems and swarms with life. The moving
creatures in the sea constitute in their myriads of multitudes one
of the "wonders of the deep."
492. It is the custom of Captain Foster, of the American ship
Insects of the se — Garrick, who is one of my most patient of obtheir abundance.  servers, to amuse himself by making drawings in
his abstract log of the curious animalculse which, with the microscope, he finds in the surface water alongside; and though he has
been following the sea for many years, he never fails to express
his wonder and amazement at the immense numbers of living
creatures that the microscope reveals to him in sea water. Hitherto his examinations related only to the surface waters, but in
the log now before me he went into the depths, and he was more
amazed than ever to see how abundantly the waters even there
bring forth. "Jcanuary 28th, 1855. In examining animalculse in
sea water, I have," says he, " heretofore used surface water. This
afternoon, after pumping for some time from the stern pump seven feet below the surface, I examined the water, and was surprised




262       THE PHYSICAL GEOGRAPHY OF THE SEA.
to find that the fluid was literally alive with animated matter, embracing beautiful varieties."  Of some he says, " Numerous heads,
purple, red, and variegated."  There is wonderful meaning in
that word ABUNDANTLY, as it stands recorded in that Book, and
as it is even at this day repeated by the great waters, a striking
instance of which has been furnished by Piazzi Smyth, the Astronomer Royal of Edinburgh, during his voyage in 1856 on an
astronomical expedition to Teneriffe. On that occasion he fell in
with the annual harvest of meduse (~ 160) that are sent by the
Gulf Stream to feed the whales. They were in the form of hollow gelatinous lobes, arranged in groups of five or nine, with an
orange vein down the centre of each lobe. Thus each animal
consisted of an aggregation of lobes, with an orange-colored vein
or stomach in each lobe. "Examining," says he, "in the microscope, a portion of one of the orange veins, apparently the stomach of the creature, it was found to be extraordinarily rich in
diatomes, and of the most bizarre forms, as stars, Maltese crosses,
embossed circles, semicircles, and spirals. The whole stomach
could hardly have contained less than seven hundred thousand;
and when we multiply these by the number of lobes, and then by
the number of groups, we shall have some idea of the countless
millions of diatomes that go to make a feast for the medusse;
some of the softest things in the world thus confounding and devouring the hardest, the flinty-shelled diatomacee."  Each one
of these sea-nettles, as they are sometimes called, had in his stomachs not less than five or six millions of these flinty shells, the
materials for which their builders had collected from the silicious
matter which the rains washed out from the mountains, and which
the rivers bring down to the sea. the medusa have the power
of sucking in the sea water slowly, drop by drop, at one end, and
of ejecting it at the other. From this they derive both food and
locomotion; for in the passage of the water, they strain it and
collect the little diatomes. Imagine, then, how many drops of
water in the sea, which, though loaded with diatomes, never pass
through the stomach of the medusle. Imagine how many the
whale must gulp down with every mouthful of medusse. Imagine how deep and thickly the bottom of the sea must, during the
process of ages, have become covered with the flinty shells of these
little creatures.  And then recollect the command which was




~ 493, 494.       THE SALTS OF THE SEA.                  263
given to the waters of the sea on the fifth day, and we may form
some idea of how literally they have obeyed this order, bringing
forth most abundantly even now " the moving creature that hath
life," and doing it in obedience to that command.@
493. In the waters of the Pacific Ocean, the calcareous matter
Ditto, calcareous in seems to be in excess, for the microscopic shells
the Pacific, silicious
in the Atlantic.  there, as well as the conch and the coral, are built
mostly of lime. In contemplating this round of compensations,
the question may be asked, Where is the agent that regulates the
supply of solid materials for the insects of the sea to build their
edifices of? Answer: The rivers. They bring down, and pour
into the sea continually, the pabulum which those organisms require. This amount again depends upon the quantity and power
of the rains to wash out from the solid rock; and the rains depend upon the amount of vapor that the sea delivers to the winds,
which, as Chapman's observations show, depends directly upon
the salts of the sea.
494. So far the two records agree, and the evidence is clear
The records of the that the sea was salt when it received this comsea and of revelation
agree.       mand. Do they afford any testimony as to its condition previously?  Let us examine.  On the second day of creation the waters were gathered together unto one place, and the
dry land appeared. Before that period, therefore, there were no
rivers, and consequently no washings of brine by mists, nor dew,
nor rains from the valleys among the hills. The water covered
the earth. This is the account of revelation; and the account
which Nature has written, in her own peculiar characters, on the
mountain and in the plain, on the rock and in the sea, as to the
early condition of our planet, indicates the same. The inscriptions on the geological column tell that there was a period when
the solid parts of the earth's crust which now stand high in the
air were covered by water. The geological evidence that it was
so, with perhaps the exception of a solitary mountain peak here
and there, is conclusive; and when we come to examine the fossil remains that are buried in the mountains and scattered over
the plains, we have as much reason to say that the sea was salt
when it covered or nearly covered the earth, as the naturalist,
when he sees a skull or bone whitening on the wayside, has to
say that it was once covered with flesh. Therefore we have rea* These are important facts that will bear repetition-~ 161, 162.




264       THE PHYSICAL GEOGRAPHY OF THE SEA.
son for the conjecture that the sea was salt "in tie beginning,"
when " the waters under heaven were gathered together unto one
place," and the dry land first appeared; for, go back as far as we
may in the dim records which young Nature has left inscribed
upon the geological column of her early processes, and there we
find the fossil shell and the remains of marine organisms to inform us that when the foundations of our mountains were laid
with granite, and immediately succeeding that remote period
when the primary formations were completed, the sea was, as it
is now, salt; for had it not been salt, whence could those creeping things which fashioned the sea-shells that cover the tops of
the Andes, or those madrepores that strew the earth with solid
matter that has been secreted from briny waters, or those infusorial deposits which astound the geologist with their magnitude
and extent, or those fossil remains of the sea which have astonished, puzzled, and bewildered man in all ages —whence, had not
the sea been salt when its metes and bounds were set, could these
creatures have obtained solid matter for their edifices and structures. Much of that part of the earth's crust which man stirs
up in cultivation, and which yields him bread, has been made
fruitful by these " salts," which all manner of marine insects,
aqueous organisms, and sea-shells have secreted from the ocean.
Much of this portion of our planet has been filtered through the
sea, and its insects and creeping things are doing now precisely
what they were set about when the dry land appeared, namely,
preserving the purity of the ocean, and regulating it in the due
performance of its great offices. As fast as the rains dissolve the
salts of the earth, and send them down through the rivers to the
sea, these faithful and everlasting agents of the Creator elaborate
them into pearls, shells, corals, and precious things; and so, while
they are preserving the sea, they are also embellishing the land
by imparting new adaptations to its soil, fresh beauty and variety
to its landscapes. Whence came the salts of the sea originally is
a question which perhaps never will be settled satisfactorily to
every philosophic mind, but it is sufficient for the Christian philosopher to recollect that the salts of the sea, like its waters and
the granite of the hills, are composed of substances which, when
reduced to their simple state, are found for the most part to be
mere gaseous or volatile matter of some kind or other. Thus we




~ 495.            THE SALTS OF THE SEA.                  265
say that granite is generally composed of feldspar, mica, and
quartz, yet these three minerals are made of substances more or
less volatile in combination  with oxygen gas. Iron, of which there
is merely a trace, is the only ingredient which, in its uncombined
and simple state, is not gaseous or volatile. Now was the feldspar of the granite originally formed in one heap, the mica in
another, and the quartz in a third, and then the three brought together by some mighty power, and welded into the granite rock
for the everlasting hills to stand upon? or were they, as they
were formed of the chaotic matter, made into rock? Sea water is
composed of oxygen and hydrogen, and its salts, like the granite,
also consist of gases and volatile metals. But whether the constituents of sea water, like those of the primitive rocks, were brought
together in the original process of formation, and united in combination as we now find them in the ocean, or whethei- the sea
was fresh "in the beginning," and became salt by some subsequent process, is not material to our present purpose.  Some geologists suppose that in the chalk period, when the ammonites,
with their huge chambered shells, lived in the sea, the carbonaceous material required by these creatures for their habitations
must have been more abundant in its waters than it now is; but,
though the constituents of sea water may have varied as to proportions, they probably were never, at least since "its waters
commenced to bring forth," widely different from what they now
are. It is true, the strange cuttle-fish, with its shell twelve feet
in circumference, is no longer found alive in the sea: it died.out
with the chalk period; but then its companion, the tiny nautilus,
remains to tell us that even in that remote period the proportion
of salt in sea water was not unsuited to its health, for it and the
coral insect have lived through all the changes that our planet
has undergone since the sea was inhabited, and they tell us that
its waters were salt as far back, at least, as their records extend,
for they now build their edifices and make their habitations of
the same materials, collected in the same way that they did then,
and, had the sea been fresh in the interim, they too would have
perished, and their family would have become extinct, like that
of the great ammonite, which perhaps ceased to find the climates
of the sea, not the proportion of its salts; suited to its well-being.
495. Did any one who maintains that the salts of the sea were




266        THE PHYSICAL GEOGRAPHY OF THE SEA.
Cubic miles of sea originally washed down into it by the rivers and
salt.        the rains ever take the trouble to compute the quantity of solid matter that the sea holds in solution as salts?  Taking the average depth of the ocean at three miles, and its average
saltness at 31 per cent., it appears that there is salt enough in the
sea to cover to the thickness of one mile an area of ten millions
of square miles. These ten millions of cubic miles of crystal
salt have not made the sea any fuller. All this solid matter has
been received into the interstices of sea water without swelling
the mass; for chemists tell us that water is not increased in volume by the,salt it dissolves. Here we have therefore displayed
before us an economy of space calculated to surprise even the
learned author himself of the " Plurality of Worlds."
496. There has been another question raised which bears upon
The saltness of water what has already been said concerning the offices
retards evaporation. which, in the sublime system of terrestrial arrangements, have been assigned to the salts of the sea. On the 20th of
January, 18552 Professor Chapman, of the University College, Toronto, communicated to the Canadian Institute a paper on the
" Object of the Salt Condition of the Sea," which, he maintains, is'mcainly intended to regulate evaporation."  To establish this hypothesis, he shows by a simple but carefully conducted set of experiments that, the salter the water, the slower the evaporation
from it; and that the evaporation which takes place in 24 hours
from water about as salt as the average of sea water is 0.54 per
cent. less in quantity than from fresh water.  "This suggestion
and these experiments give additional interest to our investigations into the manifold and marvelous offices which, in the economy of our planet, have been assigned by the Creator to the salts
of the sea.  It is difficult to say what, in the Divine arrangement,
was the mnain object of making the sea salt and not fresh. Whether it was to assist in the regulation of climates, or in the circulation of the ocean, or in re-adapting the earth for new conditions
by transferring solid portions of its crust from one part to another, and giving employment to the corallines and insects of the sea
in collecting this solid matter into new forms, and presenting it
under different climates and conditions; or whether the main object was, as the distinguished professor suggests, to regulate evaporation, it is not necessary now or here to discuss. I think we




~ 497.            THE SALTS OF THE SEA.                  267
may regard all the objects of the salts of the sea as mnain objects.
But we see in the professor's experiments the dawn of more new
beauties, and the appearance of other exquisite compensations,
which, in studying the' wonders of the deep,' we have so often
paused to contemplate and admire. As the trade-wind region
feeds the air with the vapor of fresh water, the process of evaporation from the sea is checked, for the water which remains, being
salter, parts with its vapor less readily; and thus, by the salts of
the sea, floods may be prevented. But again, if the evaporating
surface were to grow salter aind salter, whence would the winds
derive vapor duly to replenish the earth with showers; for the
salter the surface, the more scanty the evaporation. Here is compensation, again, the most exquisite; and we perceive how, by
reason of the salts of the sea, drought and flood, if not prevented,
may be, and probably are, regulated and controlled; for that compensation which assists to regulate the amount of evaporation is
surely concerned in adjusting also the quantity of rain. Were
the salts of the sea lighter instead of heavier than the water, they
would, as they feed the winds with moisture for the cloud and the
rain, remain at its surface, and become more niggardly in their supplies, and finally the winds would howl over the salt-covered sea
in very emptiness, and instead of cool and refreshing sea-breezes to
fan the invalid and nourish the plants, we should have our gentle
trade-winds coming from the sea in frightful blasts of parched, and
thirsty, and blighting air. But sea salts, with their manifold and
marvelous adaptations, come in here as a counterpoise, and, as the
waters attain a certain degree of saltness, they become too heavy
to remain longer in contact with the thirsty trade-winds, and are
carried down, because of their weight, into the depths of the ocean;
and thus the winds are dieted with vapor in due and wholesome
quantities."-MAURY's Sailing Directions, 7th ed., p. 862.
497. Since the offices which, in the operations of the physical
The harmonies of the machinery of the earth, have been assigned to the
ocean.        salts of the sea, are obviously so important and
manifold, it is fair FOR US to presume that, as for the firmament
above, so with that below, the principles of conservation were in
the beginning provided for each alike, for the world in the sky and
the drop in the sea; that when the Creator gathered the waters
together into one place, and pronounced his handiwork " GO OD,"




268       THE PHYSICAL GEOGRAPHY OF THE SEA.
some check or regulator had already been provided for the one as
well as the other —checks which should keep the sea up to its
office, preventing it from growing, in the process of ages, either
larger or smaller, fresher or salter. As we go down into the
depths of the sea, we find that we are just beginning to penetrate
the chambers of its hidden things, and to comprehend its wonders.
The heart of man was never rightly attuned to the music of the
spheres until he was permitted to stand with his eye at the telescope, and then, for the first time, the song of the morning stars
burst upon him in all their glory. And so it is with the harmonies of old Ocean when contemplated through the microscope;
then every drop of water in the sea is discovered to be in tune
with the hosts of heaven, for each stands forth a peopled world.
498. Catching, as we contemplate the hosts of heaven through
The microscope and the telescope and the moving creatures of the sea
the telescope. through the microscope, the spirit of Chalmers, and
borrowing his fine imagery, let us draw a contrast between the glories of the heavens and the wonders of the insect world of earth and
sea, as they are presented through these instruments to the mind
of a devout philosopher:'one leads him to see a world in every
atom, the other a system for every star. One shows him that this
vast globe, with its mighty nations and multitudinous inhabitants,
is but a grain of sand in the immensity of space; the other, that
every particle of clay that lies buried in the depths of the sea has
been a living habitation, containing within it the workshops of a
busy population. One tells him of the insignificance of the world
we inhabit; the other redeems it from that insignificance by
showing in the leaves of the forest, in the flowers of the field, and
in every drop of water in the sea, worlds as numberless as the
sands on its shores, all teeming with life, and as radiant as the
firmament with glories. One suggests that, beyond and above all
that is visible to man, there are fields of creation which sweep
immeasurably along, and carry to the remotest regions of space
the impress of the Almighty hand; the other reminds us that,
within and beneath all that minuteness which the eye of man has
been able to explore, there may be a region of invisibles, and
that, could we draw aside the veil that hides it from our senses,
we should behold a theatre of as many worlds as astronomy has
unfolded-a universe within the compass of a point so small as to




~ 499.            THE SALTS OF THE SEA.                  269
elude the highest power of the microscope, but where the wonder-working finger of the Almighty finds room for the exercise of
his attributes-where He can raise another mechanism of worlds,
filling and animating them all with the evidences of His glory.'
When we lay down the microscope, and study the organisms of
the sea by the light of reason, we find grounds for the belief that
the sea was made salt in the beginning, for the marine fossils that
are found nearest the foundation of the geological column remind
us that in their day the sea was salt; and then, when we take up
the microscope again to study the foraminiferse, the diatomes, and
corallines, and examine the structure of the most ancient inhabitants of the deep, comparing their physiology with that of their
kindred in the fossil state, we are left to conjecture no longer, but
are furnished with evidence and proof the most convincing and
complete that the sea is salt from a physical necessity.
499. Thus we behold sea-shells and animalcule in a new light.
Sea-shells and ani- May we not now cease to regard them as beings
malculse in a new
light.       which have little or nothing to do in maintaining
the harmonies of creation?  On the contrary, do we not see in
them the principles of the most admirable compensation in the
system of oceanic circulation?  We may even regard them as regulators, to some extent, of climates in parts of the earth far removed from their presence. There is something suggestive, both
of the grand and the beautiful, in the idea that, while the insects
of the sea are building up their coral islands in the perpetual summer of the tropics, they are also engaged in dispensing warmth to
distant parts of the earth, and in mitigating the severe cold of the
polar winter. Surely an hypothesis which, being followed out,
suggests so much design, such perfect order and arrangement, and
so many beauties for contemplation and admiration as does this,
which, for want of a better, I have ventured to offer with regard
to the solid matter of the sea water, its salts and its shells-surely such an hypothesis, though it be not based entirely on the results of actual observation, can not be regarded as wholly vain or
as altogether profitless.




270       THE PHYSICAL GEOGRAPHY OF THE SEA.
CHAPTER XI.
~ 501-526.-THE CLOUD REGION, TIIE EQUATORIAL CLOUDRING, AND SEA FOGS.
501. To simplify the discussion of these phenomena, let us conCloud dregion-high- sider fogs at sea to be in character like clouds in
eatinthe calmbelts. the sky. So treating them, and confining our attention to them as they appear to the mariner, we discover that
the cloud region in the main is highest in the trade-wind and calm
belts, lowest in extra-tropical regions.
502. At sea, beyond " the offings," fogs are rarely seen between
roJgess regions. the parallels of 30~ N. and S. Sea fogs, therefore,
may be considered a rare phenomenon over one half of the surface of the globe. These fogless regions, though certain parts of
them  are not unfrequently visited by tempests, tornadoes, and
hurricanes, are nevertheless much less frequented by gales of
wind, as all furious winds are called, than are the regions on the
polar side of these two parallels.
503. Taking the Atlantic Ocean, north and south, as an index
The most stormy lati- of what takes place on other waters, the abstract
tudes.       logs of the Observatory show, according to the
records of 265,304 observing days contained therein, that for every gale of wind that seamen encounter on the equatorial side
of these two parallels of 30~ N. and S., they encounter 10.4 on
the polar side, and that for every fog on the equatorial they encounter 83 on the polar side. As a rule, fogs and gales increase
both in numbers and frequency as you recede from the equator.
The frequency of these phenomena between the parallels of 50
N. and 5~ S., compared with their frequency between the parallels of 45~ and 50~ N. and S., is as 1 to 103 for gales, and as 1 to
102 for fogs. The observations do not extend beyond the parallels of 60~. It appears from these, however, that both the most
stormy and foggy latitudes in the North Atlantic are between the
parallels of 45~ and 50~; that in the South Atlantic the most




~ 504-506.           THE CLOUD REGION, ETC.                       271
stormy latitudes are between the parallels of 55~ and 60~, the most
foggy between 50~ and 55~.
504. How suggestively do these two groups of phenomena reInfluences of the Gulf mind us, on the one hand, of the Gulf Stream  and
Stream acthar in c  the ice-bearing currents of the north, and, on the
the south.     other, of Cape Htorn  and the antarctic icebergs
which cluster off the Falkland Islands!@
505. Sea fogs within 20~ on either side of the equator are things
Sea fogs rare within of rare occurrence. Within this distance, however,
20~ of the equatorred fogs.      on the north side, red fogs of " sea-dust" (~ 322) are
not unfrequently encountered by navigators.  These can scarcely
be considered as coming within the category of sea fogs. The
falling of this dust in the form of fog is no doubt owing to those
influences (~ 331), the effects of which are so often observable
morning and evening in the settling smoke from neighboring
chimneys. The fogs which ht early dawn are discovered hovering over our cities or skirting the base of the hills, are of the same
sort. These particles of dust, like the atoms of smoke, are brought
into conditions favorable for radiation on occasions when the air
in which they are floating happens to have a high dew point.
Thus each one of these innumerable little atoms of smoke and
microscopic particles of sea-dust become loaded with dew, and being made visible, have the appearance of fog.  Red fogs, therefore, do not properly come under our classification of sea fogs.
506. On the polar side of 40~ at sea the weather is for the most
Cloudless regions and part cloudy.  On the equatorial side, and espeheightof clouds at sea. cially within the trade-wind region, it is for the
most part clear until we approach the cloud-ring, where clouds
again indicate the normal state of the sky at sea.  What is the
height of the cloud region at sea? for vapor plane it can scarce
be called.  As yet our sailor observers have not turned their attention either to the height or the velocity of clouds.  It is to be
* Captain Chadwick reports, by letter of 30th April, 1860, an iceberg, first seen by
him 14th September, 1859, in S. lat. 52~ 25', long. 570 8' W.; next, October 10th,
in 47~ 15' S., 590~ 30' W., by the Wild Pigeon. Five days later he fell in with it in
lat. 450 40', long. 58~ 40'. It was last seen 7th November, in lat. 43~ 44' S., long.
570 14' W., by the British ship "City of Candy." Whether this were the same
"berg" or not, it shows that icebergs are not unknown to the north of the Falkland
Islands, as, indeed, the aqueous isotherm of 600, Plate IV., indicates by its sharp
curve about those islands.




272         THE PHYSICAL GEOGRAPHY OF THE SEA.
hoped that they will.  Observations here are to be made rather
under the direction of the commander of a fleet or squadron than
of a single ship, and it is hoped that some of the distinguished
admirals and brave old commodores who cruise about the world,
with willing hearts and ready hands for the cause we advocate,
may signalize their flag by contributing, for the advancement of
human knowledge touching the physics of the sea and the machinery of the air, a series of well-conducted observations upon
the force of the trade-winds,' upon the height and velocity of the
clouds, the height and velocity of the waves, etc., in different parts
of the ocean.
507. Commodore Wiillerstorf, of the Austrian frigate Novara,
Height and velocity made an interesting series of observations upon the
of waves -plan for
determining.   height and velocity of the waves during his cruise
in that vessel upon his last scientific mission. These no doubt
will be published with the other important results of that admirably-conducted expedition.  The most simple plan for determining
the velocity of waves, and it may be hourly practiced on board
of every vessel, is the plan which is followed by Captain Ginn, of
the American ship John Knox, one of our co-operators.  ~When
he heaves the log with the seas following, instead of hauling in
the line immediately, he leaves the chip to tow, watching till he
observes it on the crest of a wave; he then turns the glass, or
notes his watch, and marks the time it takes the wave to reach
the ship.  The usual velocity of the waves in the Atlantic is 22-3
miles an hour, off Cape Horn 26-8.t
508. It would afford a pleasant and agreeable diversion for a
* See Maury's Sailing Directions, vol. ii., "Average Force of the Trade-winds."
Fronz Captain Ginn's Abstract Log.
"Saturday, September 11th, 1858, doubling Cape Horn. The long regular swell
during this part of the day afforded me another opportunity of trying the velocity
of the waves. This I did by paying out the log-line enough to be equal to 13 knots
with the 14-second glass; then by watching the chip-to which I had fixed a piece
of white rag to render it more distinguishable-as it appeared on the crest of a welldefined wave, and turning the glass at the same time, and then noting where the
crest of the wave is at the moment the glass is' out.'
"I have several times before tried the experiment in this way with the same length
of line out astern, and have always found about the same rate for the velocity, namely, 22 to 23 miles an hour; but to-day I found it to be considerably more, namely,
26 to 28 miles an hour. Thus the crest of a wave would pass, while the 14-second
glass ran out, from the place where the log-chip was towing astern (13 knots) to just
ahead of the ship. The length of the ship is equal to about 6'- knots; the ship's
speed at the time was 8 knots; thus, 13+61+8=271-. A few days ago I tried the




~ 509.            THE CLOUD REGION, ETC.                   273
Determining  the squadron of men-of-war, as they pursue their voyheight of clouds at
hsea.         age at sea, to amuse themselves and instruct their
friends at home with observations upon all such phenomena.
Those who are willing to undertake the clouds will have no difficulty in devising a plan both for the upper and the lower strata.
509. Over the land the cloud region is thought to vary from
Cloudregionatseain three to five miles in height; there the height of
the shape of a double
inclined plane.. clouds is known to be very variable. At sea it is no
doubt less so. Here the cloud region is somewhat in the form of
a double inclined plane, stretching north and south from the equatorial cloud-ring as a sort of ridge-pole. In the balloon ascents
which have taken place from the Kew Observatory in England,
it has been ascertained that there the cloud region is from 2000 to
6500 feet high, with a thickness varying from 2000 to 3000 feet,
and that its temperature at the top is not lower than it is at the
bottom of the cloud, notwithstanding its thickness.  We are also
indebted to Piazzi Smyth for interesting observations on the cloud
region in the belt of northeast trades and of the upper counter
current there. They were made from the Peak of Teneriffe, at the
height of 12,200 feet, during the months of August and September, 1856.*  The cloud region of the trades was between 3000 and
5000 feet high; of the upper or southwest current, it was above
the mountain. Islands only a few hundred feet high are generally cloud-capped in the trade-wind regions at sea; another indication that, with a given amount of moisture in the wind, the cloud
region is higher at sea than it is over the land.  For most of the
time during his sojourn on the Peak, the sea was concealed from
view by the cloud stratum below, though the sky was clear overhead. Farther to the north, in the Atlantic, however, as in the
fog region about the meeting of the cool and warm currents near
the Grand Banks, the look-out at the masthead often finds himself above the fog or cloud in which the lower parts of the ship
are enveloped.  Going still farther toward the north and reaching
the ice, the cloud region would again, for obvious reasons, mount
up until you reached the open sea there, when again it would
touch the earth with its smoke.
same experiment, and found the velocity to be 22 to 23. What has accelerated the
velocity of these waves? Has the soundings any thing to do with it?"
* Teneriffe. An Astronomer's Experiment. London, 1858.
S




274        THE PHYSICAL GEOGRAPHY OF THE SEA.
510. In the harbor of Callao, in Peru, which is filled with the
Fogs in the harbor cool waters of Humboldt's current, I have seen the
of Callao.   bay covered with a fog only a few inches high. I
have seen fogs there so dense, and with outlines so sharp, as
to conceal from view the row-boats approaching the ship's side.
These fogs, especially early in the morning, are sometimes so
thick as to conceal from view not only the boat, but the persons
of the crew up to the neck, so as to leave nothing visible but
two rows of trunkless heads nodding catenaries at the oars, skimming through the air and dancing on the fog in a manner at
once both magical and fantastic. At other times the cloud stratum is thicker and higher. Then may be seen three masts coming into port with topgallant-sails and royals set, but no ship.
These sails, nicely trimmed and swelling to the breeze in the sky,
skim along over the clouds, and seem like things in a fairy scene.
However, there are influences exerted in the formation of clouds
and fogs over and near the land which appear not to be felt at
sea.
511. In the extra-tropical north, the cloud region is high over
The cloudy latitudes. the land, low over the water; and, as a rule, the
farther inland, the dryer the air and the higher the cloud region.
In the circum-antarctic regions, where all is sea, the rising vapors
form themselves into clouds low down, and keep the face of the
sky almost uninterruptedly obscured. The southern eaves of the
cloud plane (~ 509), like the calm belts, vary their latitude as the
sun does its declination, though their place is generally found between the parallels of 50~ and 70~ S.-farther or nearer according
to the season; but under this edge, wherever it be, the mariner's
heart is seldom made glad by the cheering influences of a clear
sky. If not wrapped in mist, or covered with snow, or pelted
with hail, or drenched with rain, as he sails through these latitudes, he is dispirited under the influences of the gloomy and
murky weather which pervades those regions. His hope in the
"brave west winds" and trust in the prowess of a noble ship are
then his consolation and his comfort.
512. Such are the quantities of vapor rising up from the enWhy there should be girdling ocean about those austral regions, that it
less atmosphere  in
the southern than tn keeps permanently expelled thence a large portion
the northern hemisphere.      of the atmosphere. The specific gravity of dry air




~ 513.           THE CLOUD REGION, ETC.                275
being 1, that of aqueous vapor is 0.6 (~ 252). According to the
table (~ 362), the mean height of the barometer at sea, between
the equator and 78~ 37' north, is 30.01; while its mean height in
lat. 70~ S. is 29.0. To explain the great and grand phenomena
of nature by illustrations drawn from the puny contrivances of
human device is often a feeble resort, but nevertheless we may,
in order to explain this expulsion of air from the watery south,
where all is sea, be pardoned for the homely reference. We all
know, as the steam or vapor begins to form in the tea-kettle, it expels air thence, and itself occupies the space which the air occupied. If still more heat be applied, as to the boiler of a steam-engine, the air will be entirely expelled, and we have nothing but
steam above the water in the boiler. Now at the south, over this
great waste of circumfluent waters, we do not have as much heat
for evaporation as in the boiler or the tea-kettle; but, as far as it
goes, it forms vapor which has proportionacly precisely the same
tendency that the vapor in the tea-kettle has to drive off the air
above and occupy the space it held. Nor is this all. This austral vapor, rising up, is cooled and condensed. Thus a vast
amount of heat is liberated in the upper regions, which goes to
heat the air there, expand it, and thus, by altering the level, causing it to flow off. This unequal distribution of atmosphere between the two halves of the globe is represented in barometric
profile by Plate I. (~ 215)-the shading around the periphery of
the circle being intended to represent the relative height, and the
scales standing up in it the barometric column..513. This part of the southern ocean where the barometer
Influenceofantarctic shows diminished pressure is frequented by iceiebergs ins xpellnrg bergs, many of them very large and high, and some
regions.     of them sending up towers, minarets, and steeples,
which give them the appearance in the distance of beautiful cities
afloat. Each one of them is a centre of condensation. Could an
eye from aloft look down upon the scene, the upper side of the
cloud stratum would present somewhat the appearance of an immense caldron, boiling, and bubbling, and intumescing in the upper
air. These huge bergs condense the vapor, and the liberated heat
causes the air above them to swell out, and to stand like so many
curiously-shaped fungi above the general cloud level. And thus,
where the icebergs are thick, the clouds are formed low down.




276        THE PHYSICAL GEOGRAPHY OF THE SEA.
Icebergs, like islands, facilitate the formation of clouds and promote precipitation.
514. Turn we now to the equatorial cloud-ring. Seafaring
The horse latitudes people have, as if by common consent, divided the
-the doldrums.  ocean off into regions, and characterized them according to the winds; e. g., there are the "trade-wind regions,"
the " variables," the " horse latitudes," the "doldrums," etc.
The "horse latitudes" are the belts of calms and light airs
(~ 210) which border the polar edge of the northeast trades.
They were so called from the circumstance that vessels formerly
bound from New England to the West Indies, with a deck-load
of horses, were often so delayed in this calm belt of Cancer, that,
for the want of water for their animals, they were compelled to
throw a portion of them overboard.  The " equatorial doldrums"
is another of these calm places (~ 212). Besides being a region
of calms and baffling winds, it is a region noted for its rains and
clouds, which make it one of the most oppressive and disagreeable places at sea. The emigrant ships from Europe for Australia have to cross it.  They are often baffled in it for two or
three weeks; then the children and the passengers who are of
delicate health suffer most. It is a frightful grave-yard on the
way-side to that golden land. A vessel bound into the southern
hemisphere from Europe or America, after clearing the region of
variable winds and crossing the "horse latitudes," enters the
northeast trades. Here the mariner finds the sky sometimes
mottled with clouds, but for the most part clear. Here, too, he
finds his barometer rising and falling under the ebb and flow of
a regular atmospherical tide, which gives a high and low barometer every day with such regularity that the hour within a few
minutes may be told by it. The rise and fall of this tide, measured by the barometer, amounts to about one tenth (0.1) of an
inch, and it occurs daily and every where between the tropics:
the maximum about 10h. 30m. A.M., the minimum between 4h.
and 5h. P.M., with a second maximum  and minimum  about 10
P.M. and 5 A.M.* The diurnal variation of the needle (~ 344)
changes also with the turning of these invisible tides.  Continuing his course toward the equinoctial line, and entering the region
* See paper on Meteorological Observations in India, by Colonel Sykes, Philosophical Transactions for 1850, part ii., page 297.




~ 515, 516.       THE CLOUD REGION, ETC.                   277
of equatorial calms and rains, the navigator feels the weather to
become singularly close and oppressive; he discovers here that
the elasticity of feeling which he breathed from the trade-wind
air has forsaken him; he has entered the doldrums, and is under
the "'cloud-ring."
515. I find in the journal of the late Commodore Arthur SinA frigate under the clair, kept on board the United States frigate Concloud-ring.  gress during a cruise to South America in 1817-18,
a picture of the weather under this cloud-ring that is singularly
graphic and striking.  He encountered it in the month of January, 1818, between the parallel of 4~ north and the equator, and
between the meridians of 190 and 23~ west.  He says of it, " This
is certainly one of the most unpleasant regions in our globe. A
dense, close atmosphere, except for a few hours after a thunderstorm, during which time torrents of rain fall, when the air becomes a little refreshed; but a hot, glowing sun soon heats it
again, and but for your awnings, and the little air put in circulation by the continual flapping of the ship's sails, it would be almost insufferable.  No person who has not crossed this region
can form an adequate idea of its unpleasant effects.  You feel a
degree of lassitude unconquerable, which not even the sea-bathing,
which every where else proves so salutary and renovating, can
dispel. Except when in actual danger of shipwreck, I never
spent twelve more disagreeable days in the professional part of
my life than in these calm latitudes. I crossed the line on the
17th of January, at eight A.M., in longitude 21~ 20', and soon
found I had surmounted all the difficulties consequent to that
event; that the breeze continued to freshen and draw round to
the south-southeast, bringing with it a clear sky and most heavenly temperature, renovating and refreshing beyond description.
Nothing was now to be seen but cheerful countenances, exchanged
as by enchantment from that sleepy sluggishness which had borne
us all down for the last two weeks."
516. One need not go to sea to perceive the grand work which
Subjects whichatsea the clouds perform in collecting moisture from the
present themselves
for contemplation. crystal vaults of the sky, in sprinkling it upon the
fields, and making the hills glad with showers of rain. Winter
and summer, "the clouds drop fatness upon the earth."  This
part of their office is obvious to all, and I do not propose to con



'278      THE PHYSICAL GEOGRAPHY OF THE SEA.
sider it now. But the sailor at sea observes phenomena and witnesses operations in the terrestrial economy which tell him that,
in the beautiful and exquisite adjustments of the grand machinery
of the atmosphere, the clouds have other important offices to perform besides those merely of dispensing showers, of producing
the rains, and of weaving mantles of snow for the protection of
our fields in winter. As important as are these offices, the philosophical mariner, as he changes his sky, is reminded that the
clouds have commandments to fulfill, which, though less obvious,
are not therefore the less benign in their influences, or the less
worthy of his notice. He beholds them at work in moderating
the extremes of heat and cold, and in mitigating climates. At
one time they spread themselves out; they cover the earth as
with a mantle; they prevent radiation from its crust, and keep it
warm. At another time they interpose between it and the sun;
they screen it from his scorching rays, and protect the tender
plants from his heat, the land from the drought; or, like a garment, they overshadow the sea, defending its waters from the intense forces of evaporation. Having performed these offices for
one place, they are evaporated and given up to the sunbeam and
the winds again, to be borne on their wings away to other places
which stand in need of like offices.  Familiar with clouds and
sunshine, the storm and the calm, and all the phenomena which
find expression in the physical geography of the sea, the rightminded mariner, as he contemplates "the cloud without rain,"
ceases to regard it as an empty thing; he perceives that it performs many important offices; he regards it as a great moderator
of heat and cold-as a "compensation" in the atmospherical
mechanism which makes the performance perfect. Marvelous are
the offices and wonderful is the constitution of the atmosphere.
Indeed, I know of no subject more fit for profitable thought on
the part of the truth-loving, knowledge-seeking student, be he
seaman or landsman, than that afforded by the atmosphere and
its offices. Of all parts of the physical machinery, of all the contrivances in the'mechanism of the universe, the atmosphere, with
its offices and its adaptations, appears to me to be the most wonderful, sublime, and beautiful. In its construction, the grandeur
of knowledge is displayed. The perfect man of Uz, in a moment
of inspiration, thus bursts forth in laudation of this part of God's




~ 517.            THE CLOUD REGION, ETC.                   279
handiwork, demanding of his comforters, "But where shall wisdom be found, and where is the place of understanding? The
depth saith, it is not in me; and the sea saith, it is not with me.
It can not be gotten for gold, neither shall silver be weighed for
the price thereof. No mention shall be made of coral or of pearls,
for the price of wisdom is above rubies. Whence, then, cometh
wisdom, and where is the place of understanding? Destruction
and Death say, we have heard the fame thereof with our ears.
God understandeth the way thereof, and he knoweth the place
thereof; for he looketh to the ends of the earth, and seeth under
the whole heaven; to make the weight for the winds; and he
weigheth the waters by measure.  When he made a decree for the
rain, and a way for the lightning of the thunder, then did he see it
and declare it; he prepared it, yea, and searched it out."*  When
the pump-maker came to ask Galileo to explain how it was that
his pump would not lift water higher than thirty-two feet, the philosopher thought, but was afraid to say, it was owing to "the weight
of the winds;" and though the fact that the air has weight is here
so distinctly announced, philosophers never recognized the fact until within comparatively a recent period, and then it was proclaimed by them as a great discovery. Nevertheless, the fact was set
forth as distinctly in the book of nature as it is in the book of revelation; for the infant, in availing itself of atmospherical pressure
to draw milk from its mother's breast, unconsciously proclaimed it.
517. The barometert stands lower under this cloud-ring than
The barometer un- on either side of it (~ 362).  After having crossed
der the cloud-ring. it, the attentive navigator may perceive how this
belt of clouds, by screening the parallels over which he may have
found it to hang from the sun's rays, not only promotes the precipitation which takes place within these parallels at certain periods, but how, also, the rains are made to change the places upon
which they are to fall; and how, by traveling with the calm belt
of the equator up and down the earth, this cloud-ring shifts the
surface from which the heating rays of the sun are to be excluded;
and how, by this operation, tone is given to the atmospherical
circulation of the world, and vigor to its vegetation.
* Job, chap. xxviii.
t Observations now show that the thermometer stands highest under the cloudring. Indeed, the indications are that it coincides with the thermal equator.




280       THE PHYSICAL GEOGRAPHY OF THE SEA.
518. Having traveled with the calm belt to the north or south,
Its motions.  the cloud-ring leaves a clear sky about the equator;
the rays of the torrid sun then pour down upon the solid crust of
the earth there, and raise its temperature to a scorching heat. The
atmosphere dances (~ 356), and the air is seen trembling in ascending and descending columns, with busy eagerness to conduct the
heat off and deliver it to the regions aloft, where it is required to
give dynamical force to the air in its general channels of circulation. The dry season continues; the sun is vertical; and finally
the earth becomes parched and dry; the heat accumulates faster
than the air can carry it away; the plants begin to wither, and the
animals to perish. Then comes the mitigating cloud-ring. The
burning rays of the sun are intercepted by it: the place for the
absorption and reflection, and the delivery to the atmosphere of
the solar heat, is changed; it is transferred from the upper surface
of the earth to the upper surface of the clouds.
519. Radiation from land and sea below the cloud-belt is thus
Meteorological proc- interrupted, and the excess of heat in the earth is
esses. b    delivered to the air, and by absorption carried up
to the clouds, and there transferred to their vapors to prevent excess of precipitation. In the mean time, the trade-winds north
and south are pouring into this cloud-covered receiver, as the
calm and rain belt of the equator may be called, fresh supplies in
the shape of ceaseless volumes of heated air, which, loaded to
saturation with vapor, has to rise above and get clear of the clouds
before it can commence the process of cooling by radiation. In
the mean time, also, the vapors which the trade-winds bring from
the north and the south, expanding and growing cooler as they
ascend, are being condensed on the lower side of the cloud stratum, and their latent heat is set free, to check precipitation and
prevent a flood. While this process and these operations are going on upon the nether side of the cloud-ring, one not less important is, we may imagine, going on upon the upper side. There,
from sunrise to sunset, the rays of the sun are pouring down without intermission. Every day, and all day long, they play with
ceaseless activity upon the upper surface of the cloud stratum.
When they become too powerful, and convey more heat to the
cloud vapors than the cloud vapors can reflect and give off to the
air above them, then, with a beautiful elasticity of character, the




~ 520.           THE CLOUD REGION, ETC.                281
clouds absorb the surplus heat. They melt away, become invisible, and retain, in a latent and harmless state, until it is wanted at
some other place and on some other occasion, the heat thus imparted. We thus have an insight into the operations which are
going on in the equatorial belt of precipitation, and this insight
is sufficient to enable us to perceive that exquisite indeed are the
arrangements which Nature has provided for supplying this calm
belt with heat, and of pushing the snow-line there high up above
the clouds, in order that the atmosphere may have room to expand, to rise up, overflow, and course back into its channels of
healthful circulation. As the vapor is condensed and formed into
drops of rain, a two-fold object is accomplished; coming from the
cooler regions of the clouds, the rain-drops are- cooler than the air
and earth below; they descend, and by absorption take up the
heat which has been accumulating in the earth's crust during the
dry season, and which can not now escape by radiation.
520. In the process of condensation, these rain-drops, on the
Snow-line mounts other hand, have set free a vast quantity of latent
up as it crosses the
equatorial calm belt. heat, which has been gathered up with the vapor
from the sea by the trade-winds and brought hither. The caloric
thus liberated is taken by the air and carried up aloft still farther,
to keep, at the proper distance from the earth, the line of perpetual
congelation. Were it possible to trace a thermal curve in the upper regions of the air to represent this line, we should no doubt
find it mounting sometimes at the equator, sometimes on this side,
and sometimes on that of it, but always so mounting as to overleap this cloud-ring. This thermal line would not ascend always
over the same parallels: it would ascend over those between
which this ring happens to be; and the distance of this ring from
the equator, north or south, is regulated according to the seasons.
If we imagine the atmospherical equator to be always where the
calm belt is which separates the northeast from the southeast
trade-winds, then the loop in the thermal curve, which should represent the line of perpetual congelation in the air, would be always found to stride this equator; and it may be supposed that
a thermometer, kept sliding on the surface of the earth so as always to be in the middle of this rain-belt, would show very nearly the same temperature all the year round; and so, too, would a
barometer the same pressure, though the height of the atmos



282        THE PHYSICAL GEOGRAPHY OF THE SEA.
phere over this calm belt would, in consequence of so much heat
and expansion, be very much greater than it is over the tradewinds or tropical calms.
521. Returning and taking up the train of contemplation as to
Offices of the cloud- the office which this belt of clouds, as it encircles
ring.        the earth, performs in the system of oceanic adaptations, we may see how the cloud-ring and calm zone which it
overshadows perform the office both of ventricle and auricle in
the immense atmospherical heart, where the heat and the forces
which give vitality and power to the system are brought into play
-where dynamical strength is gathered, and an impulse given to
the air sufficient to send it thence through its long and tortuous
channels of circulation.
522. Thus this ring, or band, or belt of clouds is stretched
It actsas aregulator. around our planet to regulate the quantity of precipitation in the rain-belt beneath it; to preserve the due quantum of heat on the face of the earth; to adjust the winds; and
send out for distribution to the four corners vapors in proper
quantities to make up to each river-basin, climate, and seasonvits
quota of sunshine, cloud, and moisture. Like the balance-wheel
of a well-constructed chronometer, this cloud-ring affords the grand
atmospherical machine the most exquisitely-arranged self-compJensation.  If the sun fail in his supply of heat to this region, more
of its vapors are condensed, and heat is discharged from its latent
store-houses in quantities just sufficient to keep the machine in
the most perfect compensation. If, on the other hand, too much
heat be found to accompany the rays of the sun as they impinge
upon the upper circumference of this belt, then again on that side
the means of self-compensation are ready at hand; so much of
the cloud-surface as may be requisite is then resolved into invisible vapor-for of invisible vapor are made the vessels wherein
the surplus heat of the sun is stored away and held in the latent
state until it is called for, when it is instantly set free, and becomes a palpable and an active agent in the grand design.
523. Ceaseless precipitation goes on under this cloud-ring.
The latent heat lib- Evaporation under it is suspended almost entirely.
orated in the processes of condensa- We know that the trade-winds encircle the earth;
tion from and under
the cloud-ring, true that they blow perpetually; that they come from
cause of the tradewinds.       the north and the south, and meet each other near




~ 524, 525.        THE CLOUD REGION, ETC.                283
the equator; therefore we infer that this line of meeting extends
around the world..By the rainy seasons of the torrid zone, except where it may be broken by the continents, we can trace the
declination of this cloud-ring, stretched like a girdle around our
planet, up and down the earth; it travels after the sun up and
down the ocean, as from north to south and back. It is broader
than the belt of calms out of which it rises. As the air, with its
vapors, rises up in this calm belt and ascends, these vapors are
condensed into clouds, and this condensation is followed by a turgid intumescence, which causes the clouds to overflow the calm
belt, as it were, both to the north and the south. The air flowing
off in the same direction assumes the character of winds that form
the upper currents that are counter (Plate I.) to the trade-winds.
These currents carry the clouds still farther to the north and south,
and thus make the cloud-ring broader. At least we infer such to
be the case, for the rains are found to extend out into the tradewinds, and often to a considerable distance both to the north and
the south of the calm belt.
524. Were this cloud-ring luminous, and could it be seen by an
Imagined appear- observer from one of the planets, it would present to
ance of the cloud- him an'appearance not unlike the rings of Saturn
ring to a distant ob- i  a   pra
server.      do to us. Such an observer would remark that this
cloud-ring of the earth has a motion contrary to that of the axis of
our planet itself-that while the earth was revolving rapidly from
west to east, he would observe the cloud-ring to go slowly, but
only relatively, from east to west. As the winds which bring
this cloud-vapor to this region of calms rise up with it, the earth
is slipping from under them; and thus the cloud-ring, though
really moving from west to east with the earth, goes relatively
slower than the earth, and would therefore appear to require a
longer time to complete a revolution. But, unlike the rings of
Saturn through the telescope, the outer surface, or the upper side
to us, of this cloud-ring would appear exceedingly jagged, rough,
and uneven.
525. The rays of the sun, playing upon this peak and then upon
Thunder.  that of the upper cloud-surface, melt away one set
of elevations and create another set of depressions. The whole
stratum is, it may be imagined, in the most turgid state; it is in
continued throes when viewed from above; the heat which is




284       THE PHYSICAL GEOGRAPHY OF THE SEA.
liberated from below in the process of condensation, the currents
of warm air ascending from the earth, and of cool descending from
the sky, all, we may well conceive, tend to keep the upper cloudsurface in a perpetual state of agitation, upheaval, and depression.
Imagine in such a cloud-stratum an electrical discharge to take
place; the report, being caught up by the cloud-ridges above, is
passed from peak to peak, and repeated from valley to valley, until the last echo dies away in the mutterings of the distant thunder. How often do we hear the voice of the loud thunder rumbling and rolling away above the cloud-surface, like the echo of
artillery discharged among the hills! tHence we perceive or infer that the clouds intercept the progress of sound, as well as of
light and heat, through the atmosphere, and that this upper surface is often like Alpine regions, which echo back and roll along
with rumbling noise the mutterings of the distant thunder.;526. It is by trains of reasoning like this that we are continuExceeding interest ally reminded of the interest which attaches to the
attached to physical
researchat sea.   observations which the mariner is called on to
make. There is no expression uttered by nature which is unworthy of our most attentive consideration-for no physical fact
is too bald for study-and mariners, by registering in their logs
the kind of lightning, whether sheet, forked, or streaked, and the
kind of thunder, whether rolling, muttering, or sharp, may be furnishing facts which will throw much light on the features and
character of the clouds in different latitudes and seasons. Physical facts are the language of Nature, and every expression uttered by her is worthy of our most attentive consideration, for it is
the voice of WISDOM.




~ 531.   THE GEOLOGICAL AGENCY OF THE WINDS.          285
CHAPTER XII.
531-555. —THE GEOLOGICAL AGENCY OF THEE WINDS.
531. PROPERLY to appreciate the various offices which the winds
The sea and air re- and the waves perform, we must regard nature as
garded as parts of
th~esamemachine. a whole, for all the departments thereof are intimately connected. If we attempt to study in one of them, we
often find ourselves tracing clews which insensibly lead us off into
others, and, before we are aware, we discover ourselves exploring
the chambers of some other department. The study of drift takes
the geologist out to sea, and reminds him that a knowledge of
waves, winds, and currents, of navigation and hydrography, are
closely and intimately connected with his specialty. The astronomer directs his telescope to the most remote star or to the nearest planet in the sky, and makes an observation upon it. He can
not reduce this observation, nor make any use of it, until he has
availed himself of certain principles of optics-until he has consulted the thermometer, gauged the atmosphere, and considered
the effect of heat in changing its powers of refraction. In order
to adjust the pendulum of his clock to the right length, he has to
measure the water of the sea and weigh the earth. Hie, too, must
therefore go into the study of the tides; he must examine the
earth's crust, and consider the matter of which it is composed,
from pole to pole, circumference to centre; and in doing this, he
finds himself, in his researches, alongside of the navigator, the
geologist, and the meteorologist, with a host of other good fellows,
each one holding on by the same thread, and following it up into
the same labyrinth-all, it may be, with different objects in view,
but, nevertheless, each one feeling sure that he is to be led into
chambers where there are stores of knowledge and instruction especially for him. And thus, in undertaking to explore the physical geography of the sea, I have found myself standing side by
side with the geologist on the land, and with him, far away from
the sea-shore, engaged in considering marine fossils, changes of




286       THE PHYSICAL GEOGRAPHY OF THE SEA.
climates, the effects of deserts upon the winds, or the influence of
mountains upon rains, or some of the many phenomena which
the inland basins of the earth-those immense indentations on its
surface that have no sea-drainage-present for contemplation and
study.
532. Among the most interesting of these last is that of the
The level of the Dead Sea. Lieutenant Lynch, of the United States
IDead Sea.  Navy, has run a level from that sea to the Mediterranean, and finds the former to be about one thousand three hundred feet below the general sea-level of the earth. In seeking to
account for this great difference of water level, the geologist examines the neighboring region, and calls to his aid the forces of elevation and depression which are supposed to have resided in the
neighborhood; he then points to them as the agents which did the
work. Truly they are mighty agents, and they have diversified
the surface of the earth with the most towering monuments of
their power. But is it necessary to suppose that they resided in
the vicinity of this region? May they not have come from the
sea, and been, if not in this case, at least in the case of other inland basins, as far removed as the other hemisphere? This is a
question which I do not pretend to answer definitely. But the
inquiry as to the geological agency of the winds in such cases is
a question which my investigations have suggested. It has its
seat in the sea, and therefore I propound it as one which, in accounting for the formation of this or that inland basin, is worthy,
at least, of consideration.
533. Is there any evidence that the annual amount of precipitaAn ancient river tion upon the water-shed of the Dead Sea, at some
from it.    former period, was greater than the annual amount
of evaporation from it now is? If yea, from what part of the sea
did the vapor that supplied the excess of that precipitation come,
and what has cut off that supply? The mere elevation of the rim
and depression of the lake basin would not cut it off. If we establish the fact that the Dead Sea at a former period did send a
river to the ocean, we carry along with this fact the admission that
when that sea overflowed into that river, then the water'that fell
from the clouds over the Dead Sea basin was more than the winds
could convert into vapor and carry away again; the river carried
off the excess to the ocean whence it came (~ 260).




~ 534, 535. THE GEOLOGICAL AGENCY OF THE WINDS.         287
534. In the basin of the Dead Sea, in the basin of the Caspian,
Precipitation and of the Sea of Aral, and in the other inland basins of
evaporation in the
Dead Sea valley.  Asia, we are entitled to infer that the precipitation
and evaporation are at this time exactly equal. Were it not so, the
level of these seas would be rising or sinking. If the precipitation
were in excess, these seas would be gradually becoming fuller;
and if the evaporation were in excess, they would be gradually
drying up; but observation does not show, nor history tell us,
that either is the case. As far as we know, the level of these seas
is as permanent as that of the ocean, and it is difficult to realize
the existence of subterranean channels between them and the great
ocean. Were there such a channel, the Dead Sea being the lower,
it would be the recipient of ocean waters; and we can not conceive
how it should be such a recipient without ultimately rising to the
level of its feeder.
535. It may be that the question suggested by my researches
Whence come its has no bearing upon the Dead Sea; that local elerains?       vations and subsidences alone were concerned in
placing the level of its waters where it is. But is it probable that,
throughout all the geological periods, during all the changes that
have taken place in the distribution of land and water surface
over the earth, the winds, which in the general channels of circulation pass over the Dead Sea, have alone been unchanged?
Throughout all ages, periods, and formations, is it probable that
the winds have brought us just as much moisture to that sea as
they now bring, and have just taken up as much water from it as
they now carry off? Obviously and clearly not. The salt-beds,
the water-marks, the geological formations, and other facts traced
by Nature's own hand upon the tablets of the rock, all indicate
plainly enough that not only the Dead Sea, but the Caspian also,
had upon them, in former periods, more abundant rains than they
now have. Where did the vapor for those rains come from? and
what has stopped the supply? Surely not the elevation or depression of the Dead Sea basin. My researches with regard to the
winds have suggested the probability (~ 290) that the vapor which
is condensed into rains for the lake valley, and which the St. Lawrence carries off to the Atlantic Ocean, is taken up by the southeast trade-winds of the Pacific Ocean. Suppose this to be the
case, and that the winds which bring this vapor arrive with it in




288       THE PHYSICAL GEOGRAPHY OF THE SEA.
the lake country at a mean dew-point of 50~. Let us also admit
the southwest winds to be the rain winds for the lakes generally, as well as for the Mississippi Valley; they are also, speaking
generally, the rain winds of Europe, and, I have no doubt, of
extra-tropical Asia also.
536. Now suppose a certain mountain range, hundreds of miles
The influence of to the southwest of the lakes, but across the path of
mountain ranges. these winds, with their dew-point at 500, were to be
suddenly elevated, and its crest pushed into the regions of snow,
having a mean temperature at its summit of 300 Fahrenheit.
The winds, in passing that range, would be subjected to a mean
dew-point of 30~; and, not meeting (~ 297) with any more evaporating surface between such range and the lakes, they would have
no longer any moisture to deposit at the supposed lake temperature of-50~; for they could not yield their moisture to any thing
above 30~. Consequently, the amount of precipitation in the lake
country would fall off; the winds which feed the lakes would cease
to bring as much water as the lakes now give to the St. Lawrence.
In such a case, that river and the Niagara would drain them to
the level of their own beds; evaporation would be increased by
reason of the dryness of the atmosphere and the want of rain, and
the lakes would sink to that level at which, as in the case of the
Caspian Sea, the precipitation and evaporation would finally become equal.
537. There is a self-regulating principle that would bring about
How thelevelofCas- this equality; for as the water in the lakes becomes
pians is reduced. lower, the area of its surface would be diminished,
and the amount of vapor taken from it would consequently become less and less as the surface was lowered, until the amount of
water evaporated would become equal to the amount rained down
again, precisely in the same way that the amount of water evaporated from the sea is exactly equal to the whole amount poured
back into it by the rains, the fogs, and the dews.* Thus the great
lakes of this continentuwould remain inland seas at a permanent
level; the salt brought from the soil by the washings of the rivers
and rains would cease to be taken off to the ocean as it now is;
and finally, too, the great American lakes, in the process of ages,
would become first brackish, and then briny. Now suppose the
water basins which hold the lakes to be over a thousand fathoms
* The quantity of dew in England is about five inches dnring a year.-Glaisher.




~ 538.    THE GEOLOGICAL AGENCY OF THE WINDS.          289
(six thousand feet) deep. We know they are not more than four
hundred and twenty feet deep; but suppose them to be six thousand feet deep. The process of evaporation, after the St. Lawrence has gone dry, might go on until one or two thousand feet
or more were lost from the surface, and we should then have
another instance of the level of an inland. water-basin being far
below the sea-level, as in the case of the Dead Sea; or it would
become a rainless district, when the lakes themselves would go
dry. Or let us take another case for illustration. Corallines are
at work about the Gulf Stream; they have built up the Florida
Reefs on one side, and the Bahama Banks on the other. Suppose
they should build up a dam across the Florida Pass, and obstruct
the Gulf Stream; and that, in like manner, they were to connect
Cuba with Yucatan by damming up the Yucatan Pass, so that the
waters of the Atlantic should cease to flow into the Gulf of Mexico. What should we have?  The depth of the marine basin
which holds the waters of that Gulf is, in the deepest part, about
a mile. We should therefore have, by stopping up the channels
between the Gulf and the Atlantic, not a sea-level in the Gulf, but
we should have a mean level between evaporation and precipitation. If the former were in excess, the level of the Gulf waters
would sink down until the surface exposed to the air would be
just sufficient to return to the atmosphere, as vapor, the amount
of water discharged by the rivers-the Mississippi and others,
into the Gulf. As the waters were lowered, the extent of evaporating surface would grow less and less, until Nature should establish the proper ratio between the ability of the air to take up
and the capacity of the clouds to let down. Thus we might have
a sea whose level would be much farther below the water-level
of the ocean than is the Dead Sea.
538. There is still another process, besides the one already alThe formation of in- luded to, by which the drainage of these inland baland basins-a third
process.    sins may, through the agency of the winds, have
been cut off by the great salt seas, and that is by the elevation
of continents from the bottom of the sea in distant regions of the
earth, and the substitution caused thereby of dry land instead of
water for the winds to blow upon. Now suppose that a continent should rise up in that part of the ocean, wherever it may be,
that supplies the clouds with the vapor that makes the rain for
T




290       THE PHYSICAL GEOGRAPHY OF THE SEA.
the hydrographic basin of the great American lakes. What
would be the result?  Why, surely, fewer clouds and less rain,
which would involve a change of climate in the lake country; an
increase of evaporation from it, because a decrease of precipitation
upon it; and, consequently, a diminution of cloudy screens to protect the waters of the lakes from being sucked up by the rays of
the sun; and consequently, too, there would. follow a low stage
for water-courses, and a lowering of the lake-level would ensue.
539. So far, I have instanced these cases only hypothetically;
Examples.  but, both in regard to the hydrographical basins of
the Mexican Gulf and American lakes, I have confined myself
strictly to analogies. Mountain ranges have been upheaved across
the course of the winds, and continents have been raised from the
bottom of the sea; and, no doubt, the influence of such upheavals
has been felt in remote regions by means of the winds, and the effects which a greater or less amount of moisture brought by them
would produce. In the case of the Salt Lake of Utah, we have
an example of drainage that has been cut off, and an illustration
of the process by which Nature equalizes the evaporation and precipitation. To do this, in this instance, she is salting up the basin
which received the drainage of this inland water-shed. Here we
have the appearance, I am told, of an old channel by which the
water used to flow from this basin to the sea. Supposing there
was such a time and such a water-course, the water returned
through it to the ocean was the amount by which the precipitation used to exceed the evaporation over the whole extent of
country drained through this now dry bed of a river.  The
winds have had something to do with this; they are the agents
which used to bring more moisture from the sea to this watershed than they carried away; and they are the agents which now
carry off from that valley more moisture than is brought to it,
and which, therefore, are making a salt-bed of places that used to
be covered by water. In like manner, there is evidence that the
great American lakes formerly had a drainage with the Gulf of
Mexico; for boats or canoes have been actually known, in former
years, and in times of freshets, to pass from the Mississippi River
over into the lakes. At low water, the bed of a dry river can be
traced between them. Now the Salt Lake of Utah is to the southward and westward of our northern lake basin; that is the quar



~ 540.    THE GEOLOGICAL AGENCY OF THE WINDS.          291
ter (~ 357) whence the rain-winds have been supposed to come.
May not the same cause which lessened the precipitation or increased the evaporation in the Salt Lake water-shed, have done the
same for the water-shed of the great American system of lakes?
If the mountains to the west-the Sierra Nevada, for instancestand higher now than they formerly did, and if the winds which
feed the Salt Lake valley with precipitation formerly had, as I
suppose they now have, to pass the summits of these mountains, it
is easy to perceive why the winds should not convey as much vapor across them now as they did when the summit of the range was
lower and not so cool. The Andes, in the trade-wind region of
South America, stand up so high, that the wind, in order to cross
them, has to part with all its moisture (~ 297), and consequently
there is, on the west side, a rainless region. Now suppose a range
of such mountains as these to be elevated across the track of the
winds which supply the lake country with rains; it is easy to perceive how the whole country to the leeward of such range, and
now watered by the vapor which such winds bring, would be converted into a rainless region. I have used these hypothetical
cases to illustrate a position which any philosopher, who considers
the geological agency of the winds, may with propriety consult,
when he is told of an inland basin the water-level of which, it is
evident, was once higher than it now is; and that position is that,
though the evidences of a higher water-level be unmistakable and
conclusive, it does not follow therefore that there has been a subsidence of the lake basin itself, or an upheaval of the water-shed
drained by it. The cause which has produced this change in the
water-level, instead of being local and near, may be remote; it
may have its seat in the obstructions to " the wind in his circuits,"
which have been interposed in some other quarter of the world,
which obstructions may prevent the winds from taking up or from
bearing off their wonted supplies of moisture for the region whose
water-level has been lowered.
540. Having therefore, I hope, made clear the meaning of the
The influence of the question proposed, by showing the manner in which
South American continentupon the cli- winds may become important geological agents,
mate of the Dead
Sea.        and having explained how the upheaving of a
mountain range in one part of the world may, through the winds,
bear upon the physical geography of the sea, affect climates, and




292       THE PHYSICAL GEOGRAPHY OF THE SEA.
produce geological phenomena in another, I return to the Dead
Sea and the great inland basins of Asia, and ask, How far is it
possible for the elevation of the South American continent, and
the upheaval of its mountains, to have had any effect upon the
water-level of those seas? There are indications (~ 535) that they
all once had a higher water-level than they now have, and that
formerly the amount of precipitation was greater than it now is;
then what has become of the sources of vapor? What has diminished its supply? Its supply would be diminished (~ 538)
either by the substitution of dry land for water-surface in those
parts of the ocean which used to supply that vapor; or the quantity of vapor deposited in the hydrographical basins of those seas
would have been lessened if a snow-capped range of mountains
(~ 536) had been elevated across the path of these winds, between
the places where they were supplied with vapor and these basins.
A chain of evidence which it would be difficult to set aside is
contained in the chapters beginning severally at pp. 71, 127, and
148, going to show that the vapor which supplies the extra-tropical regions of the north with rains comes, in all probability, from
the trade-wind regions of the southern hemisphere.
541. Now if it be true that the trade-winds from that part of
The pathofthe S.E. the world take up there the water which is to be
tradhe-,'irtdelrn hn- rained in the extra-tropical north, the path ascribed
isphere.    to the southeast trades of Africa and America, after
they descend and become the prevailing southwest winds of the
northern hemisphere, should pass over a region of less precipitation generally than they would do if, while performing the office
of southeast trades, they had blown over water instead of land.
The southeast trade-winds, with their load of vapor, whether great
or small, take, after ascending in the equatorial calms, a northeasterly direction; they continue to flow in the upper regions of
the air in that direction until they cross the tropic of Cancer.
The places of least rain, then, between this tropic and the pole,
should be precisely those places which depend for their rains upon
the vapor which the winds that blow over southeast trade-wind
Africa and America convey. Now, if we could trace the path of
the winds through the extra-tropical regions of the northern hemisphere, we should be able to identify the track of these Andean
winds by the droppings of the clouds; for the path of the winds




~ 542, 543. THE GEOLOGICAL AGENCY OF THE WINDS.         293
which depend for their moisture upon such sources of supply as
the dry land of Central South America and Africa can not overshadow a country that is watered well. It is a remarkable fact
that the countries in the extra-tropical regions of the north that
are situated to the northeast of the southeast trade-winds of South
Africa and America-that these countries, over which theory
makes these winds to blow, include all the great deserts of Asia,
and the districts of least precipitation in Europe. A line from the
Galapagos Islands through Florence in Italy, another from the
mouth of the Amazon through Aleppo in Holy Land (Plate VII.),
would, after passing the tropic of Cancer, mark upon the surface
of the earth the route of these winds; this is that "lee country"
(~ 298) which, if such be the system of atmospherical circulation,
ought to be scantily supplied with rains. Now the hyetographic
map of Europe, in Johnston's beautiful Physical Atlas, places the
region of least precipitation between these two lines (Plate VII.).
542. It would seem that Nature, as if to reclaim this " lee" land
Relaysfor supplying from the desert, had stationed by the wayside of
them with vapor by
the way.    these winds a succession of inland seas to serve
them as relays for supplying them with moisture. There is the
Mediterranean, with its arms, the Caspian Sea and the Sea of
Aral, all of which are situated exactly in this direction, as though
these sheets of water were designed, in the grand system of aqueous arrangements, to supply with fresh vapor winds that had already left rain enough behind them to make an Amazon and an
Orinoco of.' ow that there has been such an elevation of land
out of the water we infer from the fact that the Andes were once
covered by the sea, for their tops are now crowned with the remains of marine animals. ~When they and their continent were
submerged-admitting that Europe in general outline was then
as it now is —it can not be supposed, if the circulation of vapor
were then such as it is supposed now to be, that the climates of
that part of the Old World which is under the lee of those mountains were then as scantily supplied with moisture as they now are.
When the sea covered South America, nearly all the vapor which
is now precipitated upon the Amazonian water-shed was conveyed
thence by the winds, and distributed, it may be supposed, among
the countries situated along the route (Plate VII.) ascribed to them.
543. If ever the Caspian Sea exposed a larger surface for evap



294        THE PHYSICAL GEOGRAPHY OF THE SEA.
Adjustments in this oration than it now does-and no doubt it did; if
hygrometry of CasIians.      the precipitation in that valley ever exceeded the
evaporation from it, as it does in all valleys drained into the open
sea, then there must have been a change of hygrometrical conditions there. And admitting the:vapor-springs for that valley to
be situated in the direction supposed, the rising up of a continent
from the ]ottom of the sea, or the upheaval of a range of mountains in certain parts of America, Africa, or Spain, across the route
of the winds which brought the rain for the Caspian water-shed,
might have been sufficient to rob them of the moisture which they
were wont to carry away and precipitate upon this great inland
basin. See how the Andes have made Atacama a desert, and of
Western Peru a rainless country: these regions have been made
rainless simply by the rising up of a mountain range between
them and the vapor-springs in the ocean which feed with moisture
the winds that blow over those now rainless regions.
544. That part of Asia, then, which is under the lee of southCountriesintheterm- ern trade-wind Africa, lies to the north of the tropic
perate zone of this               7
hemisphere that are Of Cancer, and between two lines, the one passing
under the lee of land
in the trade-wind re- through Cape Palmas and Medina, the other through
gions of the other
are dry countries.  Aden and Delhi. Being extended to the equator,
they will include that part of it which is crossed by the continental southeast trade-winds of Africa after they have traversed
the greatest extent of land surface (Plate VII.). The range which
lies between the two-lines which represent the course of the American winds with their vapors, and the two lines which represent
the course of the African winds with their vapors, is the range
which is under the lee of winds that have, for the most part, traversed water surface or the ocean in their circuit as southeast tradewinds. But a bare inspection of Plate VII. will show that the
southeast trade-winds which cross the equator between longitude
15~ and 50~ west, and which are supposed to blow over into this
hemisphere between these two ranges, have traversed land as well
as water; and the Trade-wind' Chart* shows that it is precisely
those winds which, in the summer and fall, are converted into
southwest monsoons for supplying the whole extent of Guinea
with rains to make rivers of. Those winds, therefore, it would
seem, leave much of their moisture behind them, and pass along
*Series of Maury's Wind and Current Charts.




~ 545.    THE GEOLOGICAL AGENCY OF THE WINDS.          295
to their channels in the grand system of circulation, for the most
part, as dry winds. Moreover, it is not to be supposed that the
channels through which the winds blow that cross the equator
at the several places named are as sharply defined in nature as the
lines suggested, or as Plate VII. would represent them to be.
545. The whole region of the extra-tropical Old World that is
Their situation,and included within the ranges marked is the region
the range of dry
idse f d  which has most land to windward of it in the southern hemisphere. Now it is a curious coincitcence, at least, that all
the great extra-tropical deserts of the earth, with those regions in
Europe and Asia which have the least amount of precipitation
upon them, should lie within this range. That-they are situated
under the lee of the southern continents, and have but little rain,
may be a coincidence, I admit; but that these deserts of the Old
World are placed where they are is no coincidence-no accident:
they are placed where they are, and as they are, by design; and
in being so placed, it was intended that they should subserve
some grand purpose in the terrestrial economy.  Let us see,
therefore, if we can discover any other marks of that design —any
of the purposes to be subserved by such an arrangement-and
trace any connection between that arrangement and the supposition which I maintain as to the place where the winds that blow
over these regions derive their vapors. It will be remarked at
once that all the inland seas of Asia, and all those of Europe except the semi-fresh-water gulfs of the north, are within this range.
The Persian Gulf and the Red Sea, the Mediterranean, the Black,
and the Caspian, all fall within it. And why are they planted
there?  Why are they arranged to the northeast and southwest
under this lee, and in the very direction in which theory makes
this breadth of thirsty winds to prevail? Clearly and obviously,
one of the purposes in the divine economy was, that they might
replenish with vapor the winds that are almost vaporless when
they arrive at these regions in the general system of circulation.
And why should these winds be almost vaporless?  They are almost vaporless because their route, in the general system of circulation, is such, that they are not brought into contact with a watersurface from which the needful supplies of vapor are to be had; or,
being obtained, the supplies have since been taken away by the cool
tops of mountain ranges over which these winds have had to pass.




296        THE PHYSICAL GEOGRAPHY OF THE SEA.
546. In the Mediterranean, the evaporation is greater than the
The Mediterranean precipitation.  Upon the Red Sea there never falls
itllin it.   a drop of rain; it is all evaporation.  Are we not,
therefore, entitled to regard the Red Sea as a make-weight, thrown
in to regulate the proportion of cloud and sunshine, and to dispense rain to certain parts of the earth in due season and in proper quantities?  Hiave we not, in these two facts, evidence conclusive that the winds which blow over these two seas come, for the
most part, from a dry country-from  regions which contain few
or no pools to furnish supplies of vapor?
547. Indeed, so scantily supplied with vapor are the winds
Heavy evaporation. which pass in the general channels of circulation
over the water-shed and sea-basin of the Mediterranean, that they
take up there more water as vapor than they deposit.  But, throwing out of the question what is taken up from the surface of the
Mediterranean itself, these winds deposit more water upon the water-shed whose drainage leads into the sea than they take up from
it again. The excess is to be found in the rivers which discharge
themselves into the Mediterranean; but so thirsty are the winds
which blow across the bosom of that sea, that they not only take
up again all the water that those rivers pour. into it, but they are
supposed by philosophers to create a demand for an immense current from the Atlantic to supply the waste.  It is estimated that
three* times as much water as the Mediterranean receives from
its rivers is evaporated from its surface.  This may be an overestimate, but the fact that evaporation from it is in excess of the
precipitation, is made obvious by the current which the Atlantic
sends into it through the Straits of Gibraltar; and the difference,
we may rest assured, whether it be much or little, is carried off to
modify climate elsewhere-to refresh with showers and make
fruitful some other parts of the earth.
548. The great inland basin of Asia, which contains the Sea of
The winds that give Aral and the Caspian, is situated on the route which
rains to Siberian riv- this hypothesis requires these thirsty winds from
ers have to cross the
steppes of Asia.   southeast trade-Nwind Africa and America to take;
and so scant of vapor are these winds when they arrive in this
basin, that they have no moisture to leave behind; just as much
as they pour down they take up again and carry off. We know
VFide article "Physical Geography," Encyclopedia Britannica.




~ 549.    THE GEOLOGICAL AGENCY OF' THE WINDS.           297
(~ 260) that the volume of water returned by the rivers, the rains,
and the dews, into the whole ocean, is exactly equal to the volume
which the whole ocean gives back to the atmosphere; as far as our
knowledge extends, the level of each of these two seas is as permanent as that of the great ocean itself. Therefore, the volume
of water discharged by rivers, the rains, and the dews, into these
two seas, is exactly equal to the volume which these two seas
give back as vapor to the atmosphere.  These winds, therefore,
do not begin permanently to lay down their load of moisture, be
it great or small, until they cross the Oural Mountains.  On the
steppes of Issam, after they have supplied the Amazon and the
other great equatorial rivers of the south, we find them first beginning to lay down more moisture than they take up again. In
the Obi, the Yenesi, and the Lena is to be found the volume
which contains the expression for the load of water which these
winds have brought from  the southern hemisphere, from the
Mediterranean, and the Red Sea; for in these almost hyperborean
river-basins do we find the first instance in which, throughout the
entire range assigned these winds, they have, after supplying the
Amazon, etc., left more water behind them than they have taken
up again and carried off. The low temperatures of Siberian Asia
are quite sufficient to extract from these winds the remnants of
vapor which the cool.mountain-tops and mighty rivers of the
southern hemisphere have left in them.
549. Here I may be permitted to pause, that I may call attenI-Io climates in one tiOlln to another remarkable coincidence, and admire
hemisphere depend the marks of design, the beautiful and exquisite adupon the arrangement of lnd in the justments that we here see provided, to insure the
other, and upon tehe
course of the winds. perfect workings of the great aqueous and atmospherical machine. This coincidence-may I not call it cause and
effect?-is between the hygrometrical conditions of all the countries within, and the hygrometrical conditions of all the countries
without, the range included within the lines which I have drawn
(Plate VII.) to represent the route in the northern hemisphere of
the southeast trade-winds ctfler they have blown their course over
the land in South Africa and America. Both to the right and
left of this range are countries included between the same parallels in which it is, yet these countries all receive more water from
the atmosphere than they give back to it again; they all have




298       THE PHYSICAL GEOGRAPHY OF THE SEA.
rivers running into the sea. On the one hand, there is in Europe
the Rhine, the Elbe, and all the great rivers that empty into the
Atlantic; on the other hand, there are in Asia the. Ganges, and
all the great Chinese rivers; and in North America, in the latitude of the Caspian Sea, is our great system of fresh-water lakes;
all of these receive from the atmosphere immense volumes of water, and pour it back into the sea in streams the most majestic. It
is remarkable that none of these copiously-supplied water-sheds
have, to the southwest of them in the trade-wind regions of the
southern hemisphere, any considerable body of land; they are, all
of them, under the lee of evaporating surfaces, of ocean waters in
the trade-wind regions of the south. Only those countries in the
extra-tropical north which I have described as lying under the
lee of trade-wind South America and Africa are scantily supplied
with rains. Pray examine Plate VII. in this connection. It tends
to confirm the views taken in Chapter VII. The surface of the
Caspian Sea is about equal to that of our lakes; in it, evaporation
is just equal to the precipitation;  Our lakes are between the same
parallels, and about the same distance from the western coast of
America that the Caspian Sea is from the western coast of Europe; and yet the waters discharged by the St. Lawrence give us
an idea of how greatly the precipitation upon it is in excess of the
evaporation. To windward of the lakes, and in the trade-wind
regions of the southern hemisphere, is no land; but to windward
of the Caspian Sea, and in the trade-wind region of the southern
hemisphere, there is land. Therefore, supposing the course of the
vapor-distributing winds to be such as I maintain it to be, ought
they not to carry more water from the ocean to the American
lakes than it is possible for them to carry from the land-from the
interior of South Africa and America- to the valley of the Caspian Sea? In like manner (~ 365), extra-tropical New Holland
and South Africa have each land-not water-to the windward of
them in the trade-wind regions of the northern hemisphere, where,
according to this hypothesis, the vapor for their rains ought to be
taken up: they are both countries of little rain; but extra-tropical South America has, in the trade-wind region to windward of
it in the northern hemisphere, a great extent of ocean; and the
amount of precipitation (~ 299) in extra-tropical South America
is wonderful. The coincidence, therefore, is remarkable, that the




~ 550.   THE GEOLOGICAL AGENCY OF THE WINDS.           299
countries in the extra-tropical regions of this hemisphere, which
lie to the northeast of large districts of land in the trade-wind regions of the other hemisphere, should be scantily supplied with
rains; and likewise, that those so situated in the extra-tropical
south, with regard to land in the trade-wind region of the north,
should also be scantily supplied with rains.
550. Having thus remarked upon the coincidence, let us turn to
Terrestrial adapta- the evidences of design, and contemplate the beautions.      tiful harmony displayed in the arrangement of the
land and water, as we find them along this conjectural " windroad." (Plate VII.) Those who admit design in terrestrial adaptations, or who have studied the economy of cosmical arrangements, will not be loth to grant that by design the atmosphere
keeps in circulation a certain amount of moisture; that the water of which this moisture is made is supplied by the aqueous surface of the earth, and that it is to be returned to the seas again
through rivers and the process of precipitation; for were it not
so, there would be a permanent increase or decrease of the quantity of water thus put and kept in circulation by the winds, which
would be followed by a corresponding change of hygrometrical
conditions, which, in turn, would draw after it permanent changes
of climate; and permanent changes of climate would involve the
ultimate well-being of myriads of organisms, both in the vegetable and anlimal kingdoms. The quantity of moisture that the atmosphere keeps in circulation is, no doubt, just that quantity
which is best suited to the well-being, and most adapted to the
proper development of the vegetable and animal kingdoms; and
that quantity is dependent upon the arrangement and the proportions that we see in nature between the land and the water-between mountain and desert, river and sea. If the seas and evaporating surfaces were changed, and removed from the places they
occupy to other places, the principal places of precipitation probably would also be changed: whole families of plants would wither and die for want of cl6ud and sunshine, dry and wet, in proper
proportions and in due season; and, with the blight of plants,
whole tribes of animals would also perish. Under such a chance
arrangement, man would no longer be able to rely upon the early
and the latter rain, or to count with certainty upon the rains being sent in due season for seed-time and harvest. And that the




300       THE PHYSICAL GEOGRAPHY OF THE SEA.
rain will be sent in due season we are assured from on high; and
when we recollect who it is that " sendeth" it, we feel the conviction strong within us, that He that sendeth the rain has the winds
for his messengers; and that they may do his bidding, the land
and the sea were arranged, both as to position and relative proportions, where they are, and as they are.
551. It should be borne in mind that, by this hypothesis, the
The Red Sea and its southeast trade-winds, after they rise up at the equavapors.     tor (Plate I.), have to overleap the northeast tradewinds. Consequently, they do not touch the earth until near the
tropic of Cancer (see the bearded arrows, Plate VII.), more frequently to the north than to the south of it; but for a part of every year, the place where these vaulting southeast trades first
strike the earth, after leaving the other hemisphere, is very near
this tropic. On the equatorial side of it, be it remembered, the
northeast trade-winds blow; on the polar side, what were the
southeast trades, and what are now the prevailing southwesterly
winds of our hemisphere, prevail. Now examine Plate VII., and
it will be seen that the upper half of the Red Sea is north of the
tropic of Cancer; the lower half is to the south of it; that the latter is within the northeast trade-wind region; the former, in the
region where the southwest passage winds are the prevailing
winds. The River Tigris is probably evaporated from the upper
half of this sea by these winds; while the northeast trade-winds
take up from the lower half those vapors which feed the Nile with
rain, and which the clouds deliver to the cold demands of the
Mountains of the Moon. Thus there are two " wind-roads" crossing this sea: to the windward of it each road runs through a
rainless region; to the leeward there is, in each case, a river rained
down. The Persian Gulf lies, for the most part, in the track of
the southwest winds; to the windward of the Persian Gulf is a
desert; to the leeward, the River Indus.  This is the route by
which theory would require the vapor from the Red Sea and
Persian Gulf to be conveyed, and this is the direction in which
we find indications that it is conveyed. For to leeward do we
find, in each case, a river, telling to us, by signs not to be mistaken, that it receives more water from the clouds than it gives
back to the winds.
552. Is it not a curious circumstance, that the winds which




~ 552.   THE GEOLOGICAL AGENCY OF THE WINDS.           301
Certainseasand des- travel the road suggested from the southern hemierts considered as
counterpoises in the sphere should, when they touch the earth on the
terrestrial machinery.        polar side of the tropic of Cancer, be so thirsty,
more thirsty, much more, than those which travel on either side
of their path, and which are supposed to have come from southern
seas, not from southern lands?  The Mediterranean has to give
those winds three times as much vapor as it receives from them
(~ 547); the Red Sea gives them as much as they can take, and
receives nothing back in return but a little dew (~ 376); the Persian Gulf also gives more than it receives. What becomes of the
rest? Doubtless it is given to the winds, that they may bear it off
to distant regions, and make lands fruitful, that but for these sources
of supply would be almost rainless, if not entirely arid, waste, and
barren. These seas and arms of the ocean now present themselves to the mind as counterpoises in the great hygrometrical
machinery of our planet.-As sheets of water placed where they
are to balance the land in the trade-wind region of South America and South Africa, they now present themselves. When the
foundations of the earth were laid, we know who it was that
" measured the waters in the hollow of his hand, and meted out
the heavens with a span, and comprehended the dust of the earth
in a measure, and weighed the mountains in scales, and the hills
in a balance;" and hence we know also that they are arranged
both according to proportion and to place. Here, then, we see
harmony in the winds, design in the mountains, order in the sea,
arrangement for the dust, and form for the desert. IHere are
signs of beauty and works of grandeur; and we may now fancy
that, in this exquisite system of adaptations and compensations,
we can almost behold, in the Red and Mediterranean Seas, the
very waters that were held in the hollow of the Almighty hand
when he weighed the Andes and balanced the hills of Africa in
the comprehensive scales. In that great inland basin of Asia
which holds the Caspian Sea, and embraces an area of one million
and a half of geographical square miles, we see the water-surface
so exquisitely adjusted, that it is just sufficient, and no more, to
return to the atmosphere as vapor exactly as much moisture as
the atmosphere lends in rain to the rivers of that basin —a beautiful illustration of the fact that the span of the heavens was
meted out according to the measure of the waters. Thus we are




302       THE PHYSICAL GEOGRAPHY OF THE SEA.
entitled to regard (~ 542) the Mediterranean, the Red Sea, and
Persian Gulf as relays, distributed along the route of these thirsty
winds from the continents of the other hemisphere, to supply them
with vapors, or to restore to them that which they have left behind to feed the sources of the Amazon, the Niger, and the Congo.
553. The hypothesis that the winds from South Africa and
Hypothesis support- America do take the course through Europe and
ed by facts.  Asia which I have marked out for them (Plate
VII.), is supported by so many coincidences, to say the least, that
we are entitled to regard it as probably correct, until a train of
coincidences at least as striking can be adduced to show that such
is not the case. Returning once more to a consideration of the
geological agency of the winds in accounting for the depression
of the Dead Sea, we now see the fact palpably brought out before
us, that if the Straits of Gibraltar were to be barred up, so that no
water could pass through them, we should have a great depression
of water-level in the Mediterranean. Three times as much water
(~ 547) is evaporated from that sea as is returned to it through
the rivers. A portion of water evaporated from it is probably
rained down and returned to it through the rivers; but, supposing it to be barred up: as the demand upon it for vapor would
exceed the supply by rains and rivers, it would commence to dry
up; as it sinks down, the area exposed for evaporation would decrease, and the supplies to the rivers would diminish, until finally
there would be established between the evaporation and precipitation an equilibrium, as in the Dead and Caspian Seas. But, for
aught we know, the water-level of the Mediterranean might, before this equilibrium were attained, have to reach a stage far below that of the Dead Sea level. The Lake Tadjura is now in the
act of attaining such an equilibrium. There are connected with
it the remains of a channel by which the water ran into the sea;
but the surface of the lake is now five hundred feet below the
sea-level, and it is salting up. If not in the Dead Sea, do we not,
in the valley of this lake, find outcropping some reason for the
question, What have the winds had to do with the phenomena
before us?
554. The winds, in this sense, are geological agents of great
power. It is not impossible but that they may afford us the
means of comparing, directly, geological events which have taken




~ 555.    THE GEOLOGICAL AGENCY OF THE WINDS.              303
HI-Io, by thie Ainds, place in one hemisphere, with geological events in
the age of certain
geological phenome- another: e. g., the tops of the Andes were once at
na in our hemisphere
may be comparaed the bottom of the sea. —Which is the oldest formawith the age of those
in the other.    tion, that of the Dead Sea or the Andes?  If the
former be the older, then the climate of the Dead Sea must have
been hygrometrically very different from what it now is. In regarding the winds as geological agents, we can no longer consider
them as the type of instability. We should rather treat them in
the light of ancient and faithful chroniclers, which, upon being
rightly consulted, will reveal to us truths that nature has written
upon their wings, in characters as legible and enduring as any
with which she has ever engraved the history of geological events
upon the tablet of the rock.
555. The waters of Lake Titicaca, which receives the drainage
The Andes older than of the great inland basin of the Andes, are only
the Dead Sea as an inland wvater.  brackish, not salt.  Hence we may infer that this
lake has not been standing long enough to become briny, like the
waters of the Dead Sea; consequently, it belongs to a more recent
period. On the other hand, it will also be interesting to hear
that my friend, Captain Lynch, informs me that, in his exploration
of the Dead Sea, he saw what he took to be the dry bed of a river
that once flowed from it. And thus we have two more links,
stout and strong, to add to the chain of circumstantial evidence
going to sustain the testimony of this strange and fickle witness
which I have called up from the sea to testify in this presence
concerning the works of Nature, and to tell us which be the older
-the Andes, watching the stars with their hoary heads, or the
Dead Sea, sleeping upon its ancient beds of crystal salt.




304        THE PHYSICAL GEOGRAPHY OF THE SEA.
CHAPTER XIII.
~ 560-575. —-THE DEPTHS OF THE OCEAN.
560. "WE dive," says Schleiden,j "into the liquid crystal of
Submarine scenery. the Indian Ocean, and it opens to us the most wondrous enchantments, reminding us of fairy tales in childhood's
dreams. The strangely branching thickets bear living flowers.
Dense masses of meandrinas and astrTeas contrast with the leafy,
cup-shaped expansions of the explanarias, the variously-ramified
AMadrepores, which are now spread out like fingers, now rise in
trunk-like branches, and now display the most elegant array of
interlacing branches. The coloring surpasses every thing; vivid
green alternates with brown or yellow; rich tints of purple, from
pale red-brown to the deepest blue. Brilliant rosy, yellow, or
peach-colored Nullipores overgrow the decaying masses, and are
themselves interwoven with the pearl-colored plates of the Retipores, resembling the most delicate ivory carvings. Close by
wave the yellow and lilac fans, perforated like trellis-work, of the
Gorgonias.  The clear sand of the bottom is covered with the
thousand strange forms and tints of the sea-urchins and star-fishes.
The leaf-like flustras and escharas adhere like mosses and lichens to the branches of the corals; the yellow, green, and purplestriped limpets cling like monstrous cochineal insects upon their
trunks. Like gigantic cactus-blossoms, sparkling in the most ardent colors, the sea anemones expand their crowns of tentacles
upon the broken rocks, or more modestly embellish the flat bottom, looking like beds of variegated ranunculuses. Around the
blossoms of the coral shrubs play the humming-birds of the ocean,
little fish sparkling with red or blue metallic glitter, or gleaming
in golden green, or in the brightest silvery lustre. Softly, like
spirits of the deep, the delicate milk-white or bluish bells of the
jelly-fishes float through this charmed world. Here the gleaming
violet and gold-green Isabelle, and the flaming yellow, black, and
vermilion-striped coquette, chase their prey; there the band-fish
* "The Plant.'




~ 560.          THE DEPTHS OF THE OCEAN.                305
shoots, snake-like, through the thicket, like a long silver ribbon,
glittering with rosy and azure hues. Then come the fabulous
cuttle-fish, decked in all colors of the rainbow, but marked by no
definite outline, appearing and disappearing, intercrossing, joining
company and parting again, in most fantastic ways; and all this
in the most rapid change, and amid the most wonderful play of
light and shade, altered by every breath of wind, and. every slight
curling of the surface of the ocean. When day declines, and the
shades of night lay hold upon the deep, this fantastic garden is
lighted up in new splendor. Millions of glowing sparks, little
microscopic medusas and crustaceans, dance like glow-worms
through the gloom. The sea-feather, which by daylight is vermilion-colored, waves in a greenish, phosphorescent light. Every
corner of it is lustrous. Parts which by day were perhaps dull
and brown, and retreated from the sight amid the universal brilliancy of color, are now radiant in the most wonderful play of
green, yellow, and red light; and, to complete the wonders of the
enchanted night, the silver disk, six feet across, of the moon-fish,*
moves, slightly luminous, among the cloud of little sparkling
stars. The most luxuriant vegetation of a tropical landscape can
not unfold as great wealth of form, while in the variety and splendor of color it would stand far behind this garden landscape, which
is strangely composed exclusively of animals, and not of plants;
for, characteristic as the luxuriant development of vegetation of
the temperate zones is of the sea bottom, the fullness and multiplicity of the marine Fauna is just as prominent in the regions of
the tropics. Whatever is beautiful, wondrous, or uncommon in
the great classes of fish and Echinoderms, jelly-fishes and Polypes,
and the Mollusks of all kinds, is crowded into the warm and crystal waters of the tropical ocean-rests in the white sands, clothes
the rough cliffs, clings, where the room is already occupied, like
a parasite, upon the first comers, or swims through the shallows
and depths of the elements-while the mass of the vegetation is
of a far inferior magnitude. It is peculiar in relation to this that
the law valid on land, according to which the animal kingdom,
being better adapted to accommodate itself to outward circumstances, has a greater diffusion than the vegetable kingdom —for
the polar seas swarm  with whales, seals, sea-birds, fishes, and
* Orthagoriscus mola.
U




306       THE PHYSICAL GEOGRAPHY OF THE SEA.
countless numbers of the lower animals, even where every trace
of vegetation has long vanished in the eternally frozen ice, and
the cooled sea fosters no sea-weed-that this law, I say, holds good
also for the sea, in the direction of its depth; for when we descend, vegetable life vanishes much sooner than the animal, and,
even from the depths to which no ray of light is capable of penetrating, the sounding-lead brings up news at least of living infusoria. "-SCOLEIDEN'S Lectu6res, p. 403-406.
561. Until the commencement of the plan of deep-sea soundIgnorance concerning ings, as they have been conducted in the American
the depth  of "blue
water."       navy, the bottom of what the sailors call " blue water" was as unknown to us as is the interior of any of the planets
of our system. Ross and Dupetit Thouars, with other officers of
the English, French, and Dutch navies, had attempted to fathom
the deep sea, some with silk threads, some with spun-yarn (coarse
hemp threads twisted together), and some with the common lead
and line of navigation. All of these attempts were made upon
the supposition that when the lead reached the bottom, either a
shock would be felt, or the line, becoming slack, would cease to
run out.
562. The series of systematic experiments recently made upon
Early attempts at this subject shows that there is no reliance to be
deep-sea soundings placed on such a supposition, for the shock caused by
~nce.       striking bottom can not be communicated through
very great depths. Furthermore, the lights of experience show
that, as a general rule, the under currents of the deep sea have
force enough to take the line out long after the plummet has
ceased to do so. Consequently, there is but little reliance to be
placed upon deep-sea soundings of former methods, when the
depths reported exceeded eight or ten thousand feet.
563. Attempts to fathom the ocean, both by sound, and pressvariousmethods tried ure, had been made, but out in " blue water" evor proposed.  ery trial was only a failure repeated. The most
ingenious and beautiful contrivances for deep-sea soundings were
resorted to. By exploding petards, or ringing bells in the deep
sea, when the winds were hushed and all was still, the echo or reverberation from the bottom might, it was held, be heard, and the
depth determined from the rate at which sound travels through
water. But, though the concussion took place many feet below




~ 564.         THE DEPTHS OF THE OCEAN.               307
the surface, echo was silent, and no answer was received from the
bottom. Ericsson and others constructed deep-sea leads having
a column of air in them, which, by compression, would show the
aqueous pressure to which they might be subjected. This was
found to answer well for ordinary purposes, but in the depths of
the sea, where the pressure would be equal to several hundred
atmospheres, the trial was more than this instrument could stand.
Mr. Baur, an ingenious mechanician of New York, constructed,
according to a plan which I furnished him, a deep-sea sounding
apparatus. To the lead was attached, upon the principle of the
screw propeller, a small piece of clock-work for registering the
number of revolutions made by the little screw during the descent; and, it having been ascertained by experiment in shoal water that the apparatus, in descending, would cause the propeller
to make one revolution for every fathom of perpendicular descent,
hands provided with the power of self-registration were attached
to a dial, and the instrument was complete. It worked beautifully
in moderate depths, but failed in blue water, from the difficulty
of hauling it up if the line used were small, and from the difficulty
of getting it down if the line used were large enough to give the
requisite strength for hauling it up. An old sea-captain proposed
a torpedo, such as is sometimes used in the whale fishery for blowing up the monsters of the deep, only this one was intended to explode on touching the bottom. It was proposed first to ascertain
by actual experiment the rate at which the torpedo would sink,
and the rate at which the sound or the gas would ascend, and so,
by timing the interval, to determine the depth. This plan would
afford no specimens of the bottom, and its adoption was opposed
by other obstacles. One gentleman proposed to use the magnetic
telegraph. The wire, properly coated, was to be laid up in the
sounding-line, and to the plummet was attached machinery, so
contrived that at the increase of every 100 fathoms, and by means
of the additional pressure, the circuit would be restored, somewhat
after the manner of Dr. Locke's electro-chronograph, and a message would come up to tell how many hundred fathoms up and
down the plummet had sunk. As beautiful as this idea was, it
was not simple enough in practical application to answer our purposes.
564. Greater difficulties than any presented by the problem of




308        THE PHYSICAL GEOGRAPHY OF TXHE SEA.
Physical problems deep-sea soundings had been overcome in other demore difficult than partments of physical research. These plans and
that of measuring
the depth of the sea attempts served to encourage, nor were they fruitplished.     less, though they proved barren of practical results.
Astronomers had measured the volumes and weighed the masses
of the most distant planets, and increased thereby the stock of
human knowledge. Was it creditable to the age that the depths
of the sea should remain in the category of an unsolved problem?
Its "' ooze and bottom" was a sealed volume, rich with ancient
and eloquent legends, and suggestive of many an instructive lesson that might be useful and profitable to man. The seal which
covered it was of rolling waves many thousand feet in thickness.
Could it not be broken?  Curiosity had always been great, yet
neither the enterprise nor the ingenuity of man had as yet proved
itself equal to the task. No one had succeeded in penetrating,
and bringing up from beyond the depth of two or three hundred
fathoms below the aqueous covering of the earth any specimens
of solid matter for the study of philosophers.
565. The honor of the first attempt to recover specimens of the
The deep-sea sound- bottom from great depths belongs to Peter the Great,
ing apparatus of Peter the Great.   of Russia. That remarkable man and illustrious
monarch constructed a deep-sea sounding apparatus especially for
the Caspian Sea. It was somewhat in the shape of a pair of icehooks, and such as are seen in the hands of the " ice-man" as, in
his daily rounds, he lifts the blocks of ice from his cart in the
street for delivery at the door. It was so contrived that when it
touched the bottom the plummet would become detached, and the
hook would bring up the specimen.
566. The sea, with its myths, has suggested attractive themes
A plan of deep-sea to all people in all ages. Like the heavens, it afsounding devised for
the American navy. fords an almost endless variety of subjects for
pleasing and profitable contemplation, and there has remained in
the human mind a longing to learn more of its wonders and to
understand its mysteries. The Bible often alludes to them. Are
they past finding out?  How deep is it? and what is at the bottom of it?  Could not the ingenuity and appliances of the age
throw some light upon these questions?  The government was
liberal and enlightened; times seemed propitious; but when or
how to begin, after all these failures, with this interesting prob



~ 566.          THE DEPTHS OF THE OCEAN.                 309
lem, was one of the difficulties first to be overcome. It was a
common opinion, derived chiefly from a supposed physical relation, that the depths of the sea are about equal to the heights of
the mountains. But this conjecture was, at best, only a speculation. Though plausible, it did not satisfy. There were, in the
depths of the sea, untold wonders and inexplicable mysteries.
Therefore the contemplative mariner, as in mid-ocean he looked
down upon its gentle bosom, continued to experience sentiments
akin to those which fill the mind of the devout astronomer when,
in the stillness of the night, he looks out upon the stars, and wonders. Nevertheless, the depths of the sea still remained as fathomless and as mysterious as the firmament above. Indeed, telescopes of huge proportions and of vast space-penetrating powers
bad been erected here and there by the munificence of individuals,
and attempts made with them to gauge the heavens and sound out
the regions of space. Could it be more difficult to sound out the
sea than to gauge the blue ether and fathom the vaults of the sky?
The result of the astronomical undertakings*- lies in the discovery
that what, through other instruments of less power, appeared as
clusters of stars, were, by these of larger powers, separated into
groups, and what had been reported as nebulhe could now be resolved into clusters; that, in certain directions, the abyss beyond
these faint objects is decked with other nebulae, which these great
instruments may bring to light, but can not resolve; and that there
are still regions and realms beyond, which the rays of the brightest sun in the sky have neither the intensity nor the force to reach,
much less to penetrate. And what is more, these monster instruments have revealed to us, in those distant regions, forms or aggregations of matter which suggest to some the idea of the existence of physical forces there that we do not understand, and which
raise the question in speculative minds, Is gravitation a universal thing, and do its forces penetrate every abyss of space?  Could
we not gauge the sea as well as the sky, and devise an instrument
for penetrating the depths of the ocean as well as the depths of
space?  Mariners were curious concerning the bottom of the sea.
Though nothing thence had been brought to light, exploration
had invested the subject with additional interest, and increased
the desire to know more. In this state of the case, the idea of a
* See the works of IIerschel and Rosse, and their telescopes.




310       THE PHYSICAL GEOGRAPHY OF THE SEA.
common twine thread for a sounding-line, and a cannon ball for a
sinker, was suggested. It was a beautiful conception; for, besides
its simplicity, it had in its favor the greatest of recommendations
— it could be readily put into practice.
567. Well-directed attempts to fathom the ocean began now to
The great depths and be made with such a line and plummet, and the
failures of the first attempts.      public mind was astonished at the vast depths that
were at first reported. Lieutenant Walsh, of the United States
schooner " Taney," reported a cast with the deep-sea lead at thirty-four thousand feet without bottom. His sounding-line was an
iron wire more than eleven miles in length. Lieutenant Berryman, of the United States brig "Dolphin," reported another unsuccessful attempt to fathom mid-ocean with a line thirty-nine
thousand feet in length. Captain Denham, of her Britannic majesty's ship'a Herald," reported bottom in the South Atlantic at
the depth of forty-six thousand feet; and Lieutenant J. P. Parker, of the United States frigate " Congress," afterward, in attempting to sound near the same region, let go his plummet, and saw
it run out a line fifty thousand feet long as though the bottom
had not been reached. There are no such depths as these. The
three last-named attempts were made with the sounding-twine of
the American navy, which has been introduced in conformity
with a very simple plan for sounding out the depths of the ocean.
It involved for each cast only the expenditure of a cannon ball,
and twine enough to reach the bottom. This plan was introduced
as a part of the researches conducted at the National Observatory, and which have proved so fruitful and beneficial, concerning the winds and currents, and other phenomena of the ocean.
These researches had already received the approbation of the Congress of the United States; for that body, in a spirit worthy of
the representatives of a free and enlightened people, had authorized the Secretary of the Navy to employ three public vessels to
assist in perfecting the discoveries, and in conducting the investigations connected therewith.
568. The plan of deep-sea soundings finally adopted, and now
The plan finally in practice, is this: Every vessel of the navy, when
adopted.    she puts to sea, is, if she desires it, furnished with a
sufficient quantity of sounding-twine, carefully marked at every
length of one hundred fathoms-six hundred feet-and wound on




~ 569.         THE DEPTHS OF THE OCEAN.                311
reels of ten thousand fathoms each. It is made the duty of the
commander to avail himself of every favorable opportunity to
try the depth of the ocean, whenever he may find himself out
upon " blue water."  For this purpose he is to use a cannon ball
of 32 or 68 pounds as a plummet. Having one end of the twine
attached to it, the cannon ball is to be thrown overboard from a
boat, and suffered to take the twine from the reel as fast as it will.
The reel is made to turn easily. A silk thread, or the common
wrapping-twine of'the shops, would, it was thought, be strong
enough for this purpose, for it was supposed there would be no
strain upon the line except the very slight one required to drag
it down, and the twine having nearly the specific gravity of sea
water, this strain would, it was imagined, be very slight. Moreover, when the shot reached the bottom, the line, it was thought
(~ 561), would cease to run out; then breaking it off, and seeing
how much remained upon the reel, the depth of the sea could be
ascertained at any place and time simply at the expense of one
cannon ball and a few pounds of common twine.
569. But practical difficulties that were not expected at all
Discovery of currents were lurking in the way, and afterward showed
in the depths of the
sea.         themselves at every attempt to sound; and it was
before these practical difficulties had been fairly overcome that
the great soundings (~ 567) were reported. In the first place, it
was discovered that the line, once started and dragged down into
the depths of the ocean, never would cease to run out (~ 562),
and, consequently, that there was no means of knowing when, if
ever, the shot had reached the bottom. And, in the next place,
it was ascertained that the ordinary twine (~ 566) would not do;
that the sounding-line, in going down, was really subjected to
quite a heavy strain, and that, consequently, the twine to be used
must be strong; it was therefore subjected to a test which required it to bear a weight of at least sixty pounds freely suspended in the air. So we had to go to work anew, and make several
hundred thousand fathoms of sounding-twine especially for the
purpose. It was small, and stood the test required, a pound of it
measuring about six hundred feet in length. The officers intrusted with the duty soon found that the soundings could not
be made from the vessel with any certainty as to the depth. It
was necessary that a boat should be lowered, and the trial be made




312        THE PHYSICAL GEOGRAPHY OF THE SEA.
from it; the men with their oars keeping the boat from drifting,
and maintaining it in such a position that the line should be "' up
and down" the while.  That the line would continue to run out
after the cannon ball had reached bottom, was explained by the
coljecture that there is in the ocean, as in the air, a system of currents and counter currents one above the other, and that it was
one or more of these submarine currents, operating upon the bight
of the line, which caused it to continue to run out after the shot
had reached the bottom. In corroboration of this conjecture, it
was urged, with a truth-like force of argument, that it was these
under currents, operating with a swigging force upon the bights
of the line-for there might be several currents running in different directions, and operating upon it at the same time-which
caused it to part whenever the reel was stopped and the line held
fast in the boat.
570. A powerful train of circumstantial evidence was this (and
Evidencein favor of it was derived from a source wholly unexpected),
a regular system of
oceanic circulation. going to prove the existence of that system of oceanic circulation which the climates, and the offices, and the adaptations of the sea require, and which its inhabitants (~ 465) in their
mute way tell us of. This system of circulation commenced on
the third day of creation, with the " gathering together of the waters," which were " called seas;" it will probably continue as long
as sea water shall possess the properties of saltness and fluidity.
571. In making these deep-sea soundings, the practice is to
Method of malking a time the hundred fathom marks (~ 568) as they sucdeep-sea sounding.  cessively go out; and by always using a line of the
same size and "make," and a sinker of the same shape and weight,
we at last established the law of descent.  Thus the mean of our
experiments gave us, for the sinker and twine used,
2 m. 21 s. as the average time of descent from 400 to 500 fathoms.
3 m. 26 s.              "     "  " 1000 to 1100  "
4 m. 29 s.              "     "  " 1800 to 1900  "
572. Now, by aid of the law here indicated, we could tell very
The law of the plum- nearly when the ball ceased to carry the line out,
met's descent. and when, of course, it began to go out in obedience to the current and drift alone; for currents would sweep the
line out at a uniform  rate, while the cannon ball would drag it
out at a decreasing rate. The development of this law was certainly an achievement, for it enabled us to show that the depth




~ 573.          THE DEPTHS OF THE OCEAN.                 313
of the sea at the places named (~ 567) was not as great as reports
made it. These researches were interesting; the problem in hand
was important, and it deserved every effort that ingenuity could
suggest for reducing it to a satisfactory solution.
573. As yet, no specimens of the bottom had been brought up.
Brooke's sounding The line was too small, the shot was too heavy,
apparatus.   and it could not be weighed; and if we could reach
the bottom, why should we not know its character?  In this state
of the case, Passed Midshipman J. M. Brooke, United States Navy,
who, at the time, was associated with me on duty at the Observatory, proposed a contrivance by which the shot, on striking the
bottom, would detach itself from the line, and send up a specimen of the bottom. This beautiful contrivance, called Brooke's
Deep-sea Sounding Apparatus, is represented below. A is a
cannon ball, having a hole through it for the rod B. Figure 1
represents the rod, B, and the slings, D D, with the shot slung,
ready for sounding. Figu~re 2 represents the apparatus in the
Fig. 1.                        Fig. 2.
B"~______ Bi




314       THE PHYSICAL GEOGRAPHY OF THE SEA.
act of striking the bottom; it shows how the shot is detached,
and how specimens of the bottom are brought up, by adhering to
a little soap or tallow,* called "arming,"' in the cup, C, at the
lower end of the rod, B. With this contrivance specimens of
the bottom have been brought up from the depth of nearly four
miles.
574. The greatest depths at which the bottom of the sea has
The deepest part of been reached with the plummet are in the North
theAtlantic Ocean. Atlantic Ocean, and the places where it has been
fathomed do not show it to be deeper than twenty-five thousand
feet. The deepest place in this ocean (Plate XI.) is probably
between the parallels of 35~ and 40~ north latitude, and immediately to the southward of the Grand Banks of Newfoundland.
The first specimens have been received from the coral sea of the
Indian Archipelago and from the North Pacific. They were collected by the surveying expedition employed in those seas. A
few soundings have been made in the South Atlantic, but not
enough to justify deduction as to its depths or the precise shape
of its floor.
575. The friends of physical research at sea are under obligaDeep-sea soundings tions to the officers of the English navy for much
by the English
navy.        valuable information touching this interesting subject. Certain officers in that service have taken up the problem
of deep-sea soundings with the most praiseworthy zeal, energy,
and intelligence. Dayman in the Atlantic, Captains Spratt and
Mansell in the Mediterranean, with Captain Pullen in the Red
Sea, have all made valuable contributions to the stock of human
knowledge concerning the depths and bottom of the sea. To
Mansell and Spratt we are indebted for all we know about deepsea soundings in the Mediterranean, as we are to Pullen for those
in the Red Sea. By their lines of soundings, their maps and
profiles, they have enabled physical geographers to form, with
some approach toward correctness, an idea as to the orography
of the basins which hold the water for these two seas. We are
also indebted to the French for deep-sea soundings in the Mediterranean. That sea appears to be about two miles deep in the
deepest parts, which are in the isleless spaces to the west of Sardinia and to the east of Malta.
* The barrel of a common quill attached to the rod has been found to answer
better.




~ 580-582.  THE BASIN AND BED OF THE ATLANTIC.         315
CHAPTER XIV.
~ 580-618. —THE BASIN AND BED OF THE ATLANTIC.
580. THE wonders of the sea are as marvelous as the glories
The wonders of the of the heavens; and they proclaim, in songs divine,
sea.        that they too are the work of holy fingers. Among
the revelations which scientific research has lately made concerning the crust of our planet, none are more interesting to the student of nature; or more suggestive to the Christian philosopher,
than those which relate to the bed and bottom of the ocean.
581. The basin of the Atlantic, according to the deep-sea soundItsbottomand Chim- ings made by the American and English navies,
borazo.     is shown on Plate XI. This plate refers chiefly to
that part of the Atlantic which is included within our hemisphere.
In its entire length, the basin of this sea is a long trough, separating the Old World from the New, and extending probably from
pole to pole. As to breadth, it contrasts strongly with the Pacific
Ocean. From the top of Chimborazo to the bottom of the Atlantic, at the deepest place yet reached by the plummet in that ocean,
the distance, in a vertical line, is nine miles.
582. Could the waters of the Atlantic be drawn off so as to
An orographic view. expose to view this great sea-gash which separates
continents, and extends from the Arctic to the Antarctic, it would
present a scene the most rugged, grand, and imposing. The very
ribs of the solid earth, with the foundations of the sea, would be
brought to light, and we should have presented to us in one view,
in the empty cradle of the ocean, " a thousand fearful wrecks,"
with that array of dead men's skulls, great anchors, heaps of pearl
and inestimable stones, which, in the poet's eye, lie scattered on
the bottom of the sea, making it hideous with sights of ugly death.
To measure the elevation of the mountain-top above the sea, and
to lay down upon our maps the mountain ranges of the earth, is
regarded in geography as an important thing, and rightly so.
Equally important is it, in bringing the physical geography of
the sea regularly within the domains of science, to present its




316        THE PHYSICAL GEOGRAPHY OF THE SEA.
orology, by mapping out the bottom of the ocean so as to show
the depressions of the solid parts of the earth's crust there, below
the sea-level.
583. Plate XI. presents the latest attempt at such a map. It
Plate XI.  relates exclusively to the bottom of that part of the
Atlantic Ocean which lies north of 10~ south. It is stippled with
four shades: the darkest (that which is nearest the shore-line)
shows where the water is less than six thousand feet deep; the
next, where it is less than twelve thousand feet deep; the third,
where it is less than eighteen thousand; and the fourth, or lightest, where it is not over twenty-four thousand feet deep. The
blank space south of Nova Scotia and the Grand Banks includes
a district within which casts showing very deep water have been
reported, but which subsequent investigation and discussion do
not appear to confirm. The deepest part of the North Atlantic
is probably somewhere between the Bermudas and the Grand
Banks, but how deep it may be yet remains for the cannon ball and
sounding-twine to determine. The waters of the Gulf of Mexico
are held in a basin about a mile deep in the deepest part. THE
BOTTOM OF THE ATLANTIC, or its depressions below the sea-level,
are given, perhaps, on this plate with as much accuracy as the
best geographers have been enabled to show, on a map, the elevations above the sea-level of the interior either of Africa or
Australia.
584. "What is to be the use of these deep-sea soundings?" is,,What'stlleuse" of a question that often occurs; and it is as difficult
deep-sea soundings? to be answered in categorical terms as Franklin's
question, "What is the use of a new-born babe?"  Every physical fact, every expression of nature, every feature of the earth,
the work of any and all of those agents which make the face of
the world what it is, and as we see it, is interesting and instructive. Until we get hold of a group of physical facts, we do not
know what practical bearings they may have, though right-minded men know that they contain many precious jewels, which the
experts of philosophy will not fail to bring out, polished and
bright, and beautifully adapted, sooner or later, to man's purposes.
Already we are obtaining practical answers to this question as to
the use of deep-sea soundings; for, as soon as they were announced to the public, they forthwith assumed a practical bearing




~ 585-587.  THE BASIN AND BED OF THE ATLANTIC.           317
in the minds of men with regard to the question of a submarine
telegraph acr6ss the Atlantic.
585. There is, at the bottom of this sea, between Cape Race, in
The  telegraphic Newfoundland, and Cape Clear, in Ireland, a replateau.     markable steppe, which is already known as the telegraphic plateau, and has already been made famous by the attempts
to run a telegraphic cable across the ocean upon it. In August,
1858, a cable was laid upon it from Valencia in Ireland to Trinity
Bay in Newfoundland, and a few messages were passed through
it, when it ceased to work. Whether messages can ever be successfully sent, in a commercial sense, through such a length of continuous submarine wire, is by no means certain; but that the
wires of 1858 so soon ceased to pass any current at all was no
doubt owing to the fact that the cable was constructed upon erroneous principles. Its projectors, in planning its construction,
did not, unfortunately, avail themselves of the light which our
deep-sea soundings had cast upon the bed of the ocean.
586. It was upon this plateau that Brooke's sounding apparatus
The first specimens brought up its first trophies from the bottom of the
of deep-sea  soundings.        sea. These specimens the officers of the Dolphin
judged to be clay; but they took the precaution to label them,
carefully to preserve them, and, on their return to the United
States, to send them to the proper bureau. They were divided;
a part was sent for examination to Professor Ehrenberg, of Berlin, and a part to the late Professor Bailey, of West Point-eminent microscopists both. The latter thus responded:
587. " I am greatly obliged to you for the deep soundings you
Bailey's letter. sent me last week, and I have looked at them with
great interest. They are exactly what I have wanted to get hold
of. The bottom of the ocean at the depth of more than two miles
I hardly hoped ever to have a chance of examining; yet, thanks
to Brooke's contrivance, we have it clean and free from grease, so
that it can at once be put under the microscope. I was greatly
delighted to find that all these deep soundings are filled with microscopic shells; not. a particle of sand or gravel exists in them.
They are chiefly made up of perfect little calcareous shells (Foraminifera), and contain, also, a number of silicious shells (Diatomaceme). It is not probable that these animals lived at the depths
where these shells are found, but I rather think that they inhabit




318        THE PHYSICAL GEOGRAPHY OF THE SEA.
the waters near the surface; and when they die, their shells settle to the bottom.  With reference to this point, I shall be very
glad to examine bottles of water from various depths which were
brought home by the Dolphin, and any similar materials, either'bottom,' or water from other localities. I shall study them carefully.     The results already obtained are of very great imterest, and have many important bearings on geology and zoology.
I hope you will induce as many as possible to collect
soundings with Brooke's lead, in all parts of the world, so that we
can map out the animalcule as you have the whales.  Get your
whalers also to collect mud from pancake ice, etc., in the polar regions; this is always full of interesting microscopic forms."
588. Lieutenant Brooke, of the North Pacific Exploring ExSpecimens from the pedition, procured specimens of the bottom from the
coral sea,   depth of 2150 fathoms in the coral sea, lat. 130 S.,
long. 162~ E.  With regard to these, the admirable and lamented
Bailey wrote in 1855, "You may be sure I was not backward in
taking a look at the specimens you sent me, which, from their locality, promised to be so interesting. The sounding from 2150
fathoms, although very small in qucntity, is not so bad in quality,
yielding representatives of most of the great groups of microscopic organisms usually found in marine sediments.  The predominant forms are silicious spicules of sponges. Various forms of
these occur: some long and spindle-shaped, or acicular; others
pin-headed; some three-spined, etc., etc.  The Diatomes (silicious
infusoria of Ehrenberg) are very few in number, and mostly fragmentary.  I found, however, some perfect valves of a coscinodiscus.  The Foraminifera (Polythalamia of Ehrenberg) are very
rare, only one perfect shell being seen, with a few fragments of
others.  The polycistineme are present, and some species of haliomma were quite perfect. Fragments of other forms of this group
indicate that various interesting species might be obtained if we
had more of the material. You will see by the above that this
deep sounding differs considerably from those obtained in the Atlantic. The Atlantic soundings were almost wholly composed of
calcareous shells of the Foraminifera; these, on the contrary, contain very few Foraminifera, and are of a silicious rather than a
calcareous nature.  This only makes the condition of things in
the Northern Atlantic the more interesting."




~ 589-591.   THE BASIN AND BED OF THE ATLANTIC.            319
589. The first noticeable thing the microscope gives of these
They belong to the specimens is, that all of them are of the animal, not
ynimale not to the  
animalb, enot to thnel one of the mineral or vegetable kingdom.  The
vegetable or mineralgd
kiingdom.    ocean teems with life, we know.  Of the four elements of the old philosophers-fire, earth, air, and water-perhaps
the sea most of all abounds with living creatures. The space
occupied' on the surface of our planet by the different families of
animals and their remains is inversely as the size of the individual.  The smaller the animal, the greater the space occupied by his
remains. Though not invariably the case, yet this rule, to a certain extent, is true, and will, therefore, answer our present purposes, which are simply those of illustration. Take the elephant
and his remains, or a microscopic animal and his, and compare
them. The contrast, as to space occupied, is as striking as that
of the coral reef or island with the dimensions of the whale.  The
grave-yard that would hold the corallines is larger than the graveyard that would hold the elephants.
590. We notice another practical bearing in this group of physQuiet reigns in the ical facts that Brooke's apparatus fished -up from
depths of the sea.  the bottom of the deep sea. Bailey, with his microscope (~ 587), could not detect a single particle of sand or
gravel among these little mites of shells. They were from the
great telegraphic plateau (~ 585), and the inference is that there, if
any where, the waters of the sea are at rest. There was not motion enough to abrade these very delicate organisms, nor current
enough to sweep them about and mix up with them a grain of
the finest sand, nor the smallest particle of gravel torn from the
loose beds of debris that here and there strew the bottom of the sea.
This plateau is not too deep for the wire to sink down and rest
upon, yet it is not so shallow that currents, or icebergs, or any
abrading force can derange the wire after it is once lodged there.
591. As ProfessorBailey remarks (~ 587), the animalculae, whose
Is there life in them? remains Brooke's lead has brought up from the
bottom of the deep sea, probably did not live or die there. They
would have had no light there, and, had they lived there, their
frail little texture would have been subjected, in its growth, to
the pressure of a column of water twelve thousand feet high,
equal to the weight of four hundred atmospheres.  They probably lived and died near the surface, where they could feel the




320       THE PHYSICAL GEOGRAPHY OF THE SEA.
genial influences of both light and heat, and were buried in the
lichen caves below after death.
592. Brooke's lead and the microscope, therefore, it would
The ocean in a new seem, are about to teach us to regard the ocean in
light.      ca new light. Its bosom, which so teems with animal life-its face, upon which time. writes no wrinkles, makes no
impression, are, it would now seem, as obedient to the great law
of change as is any department whatever either of the animal or
the vegetable kingdom.  It is now suggested that henceforward
we should view the surface of the sea as a nursery teeming with
nascent organisms, its depths as the cemetery for families of living creatures that outnumber the sands on the sea-shore for multitude. Where there is a nursery, hard by there will be found
also a grave-yard-such is the condition of the ahimal world.
But it never occurred to us before to consider the surface of the
sea as one wide nursery, its every ripple a cradle, and its bottom
one vast burial-place.
593. On those parts of the solid portions of the earth's crust
Leveling agencies. which are at the bottom of the atmosphere, various
agents are at work, leveling both upward and downward. Heat
and cold, rain and sunshine, the winds and the streams, all, assisted by the forces of gravitation, are unceasingly wasting away the
high places on the land, and as perpetually filling up the low.
But in contemplating the leveling agencies that are at work upon
the solid portions of the crust of our planet which are at the bottom of the sea, one is led, at first thought, almost to the conclusion
that these leveling agents are powerless there. In the deep sea
there are no abrading processes at work; neither frosts nor rains
are felt there, and the force of gravitation there is so paralyzed
that it can not use half its power, as on dry land, in tearing the
overhanging rock from the precipice and casting it down into the
valley below.
594. WVhen considering the bottom of the ocean, we have, in
The offices of ani- the imagination, been disposed to regard the waters
malcaul.     of the sea as a great cushion, placed between the air
and the bottom of the ocean, to protect and defend it from these
abrading agencies of the atmosphere. The geological clock may,
we thought, strike new periods; its hands may point to era after
era; but, so long as the ocean remains in its basin, so long as its




~ 595, 596.  THE BASIN AND BED OF THE ATLANTIC.         321
bottom is covered with blue water, so long must the deep furrows and strong contrasts in the solid crust below stand out bold,
ragged, and grandly. Nothing can fill up the hollows there; no
agent now at work, that we know of, can descend into its depths,
and level off the floors of the sea. But it now seems that we forgot the myriads of animalculhe that make the surface of the. sea
sparkle and glow with life: they are secreting from its surface
solid matter for the very purpose of filling up those cavities below. These little marine insects build their habitations at the
surface, and when they die, their remains, in vast multitudes, sink
down  and settle upon the bottom.  They are the atoms of which
mountains are formed — plains spread out. Our marl-beds, the
clay in our river-bottoms, large portions of many of the great
basins of the earth, are composed of the remains of just such little creatures as these, which the ingenuity of Brooke has enabled
us to fish up from the depth of nearly four miles (twenty thousand feet) below the sea-level. These Foraminifera, therefore,
when living, may have been preparing the ingredients for the
fruitful soil of a land that some earthquake or upheaval, in ages
far away in the future, may be sent to cast up from the bottom of
the sea for man's use.
595. The study of these " sunless treasures," recovered with so
The study of them much ingenuity from the rich bottom of the sea,
profitable.  suggests new views concerning the physical economy of the ocean. It not only leads us into the workshops of the
inhabitants of the sea-shows us through their nurseries and cemeteries, and enables us to study their economy-but it conducts
us into the very chambers of the deep. Our investigations go to
show that the roaring waves and the mightiest billows of the
ocean repose, not upon hard or troubled beds, but upon cushions
of still water; that every where at the bottom of the deep sea
the solid ribs of the earth are protected, as with a garment, from
the abrading action of its currents, and the cradle of its restless
waves is lined by a stratum of water at rest, or so nearly at rest
that it can neither wear nor move the lightest bit of drift that
once lodges there.
596. The tooth of running water is very sharp. See how the
Theabrasion of cur- Hudson has eat through the Highlands, and the
rents.       Niagara cut its way through layer after layer of the
X




322       THE PHYSICAL GEOGRAPHY OF THE SEA.
solid rock. But what are the Hudson and the Niagara, with all
the fresh water-courses of the world, by the side of the Gulf
Stream and other great " rivers in the ocean?" And what is the
pressure of fresh water upon river-beds in comparison with the
pressure of ocean water upon the bottom of the deep sea? It is
not- so great by contrast as the gutters in the streets are to the
cataract. Then why have not the currents of the sea worn its
bottom away? Simply because they are not permitted to get
down to it. Suppose the currents which we see at and near the
surface of the ocean were permitted to extend all the way to the
bottom in deep as well as shallow water, let us see what the pressure and scouring force would be where the sea is only 3000
fathoms deep-for in many places the depth is even greater than
that. It is equal there, in round numbers, to the pressure of six
hundred atmospheres. Six hundred atmospheres, piled up one
above the other, would press upon every square foot of solid matter beneath the pile with the weight of 1,296,000 pounds, or 648
tons.
597. The better to comprehend the amount of such a pressure,
Their pressure on let us imagine a column of water just one foot
the bottom.  square, where the sea is 3000 fathoms deep, to be
frozen from the top to the bottom, and that we could then, with
the aid of some mighty magician, haul this shaft of ice up, and
stand it on one end for inspection and examination. It would be
18,000 feet high; the pressure on its pedestal would be more than
a million and a quarter of pounds; and if placed on a ship of 648
tons burden, it would be heavy enough to sink her. There are
currents in the sea where it is 3000 fathoms deep, and some of
them-as the Gulf Stream-run with a velocity of four miles an
hour, and even more. Every square foot of the earth's crust at
the bottom of a four-knot current 3000 fathoms deep would have
no less than 506,880-in round numbers, half a million-of such
columns of water daily dragging, and rubbing, and scouring, and
chafing over it, under a continuous pressure of 648 tons. What
would the bottom of the sea have to be made of to withstand such
erosion? Water running with such a velocity, and with the friction upon the bottom which such a pressure would create, would
in time wear away the thickest bed, though made of the hardest
adamant. Why, then, has not the bottom of the sea been worn




~ 598, 599.   THE BASIN AND BED OF THE ATLANTIC.        323
away?'Why have not its currents cut through the solid crust in
which its billows are rocked, and ripped out from the bowels of
the earth the masses of incandescent, molten matter which geologists tell us lie pent up and boiling there?
598. If the currents of the sea, with this four-mile velocity at
Why they can not the surface, and this hundreds of ton pressure in its
chafe it.    depths, were permitted to chafe against its bed, the
Atlantic, instead of being two miles deep and 3000 miles broad,
would, we may imagine, have been long ago cut down into a narrow channel that might have been as the same ocean turned up
on edge, and measuring two miles broad and 3000 deep. But
had it been so cut, the proportion of land and water surface would
have been destroyed, and the winds, for lack of area to play upon,
could not have sucked up from the sea vapors for the rains, and
the face of the earth would have become as a desert without water. Now there is a reason why such changes should not take
place, why the currents should not uproot nor score the deep bed
of the ocean, why they should not throw out of adjustment any
physical arrangement whatever in the ocean; it is because that in
the presence of everlasting wisdom a compass was set upon the face
of the ceep; because its waters were measured in the hollow of the Almighty hand; because bars and doors were set to stay its proud waves;
and because, when He gave to the sea His decree that its waters should
not pass His command, He laid the foundations of the world so fast
that they should not be removed forever.
599. By bringing up specimens from the depths of the ocean,
What it consists of. and studying them through the microscope, it has
been ascertained that the bed of the ocean is lined with the microscopic remains of its own dead, with marine feculences which
lie on the bottom as lightly as rests the gossamer in a calm at
the bottom of the atmospherical ocean. How frail yet how
strong, how light yet how firm are the foundations of the sea!
Its waves can not fret them, its currents can not wear them, for
the bed of the deep sea is protected from abrasion by a cushion
of still and heavy water. There it lies-that beautiful arrangement-spread out over the bottom of the deep, and covering its
foundations as with a garment, so that they may not be worn.
If the currents chafe upon it now here, now there, as in shallow
seas they sometimes do, this protecting cushion is self-adjusting;




324       THE PHYSICAL GEOGRAPHY OF THE SEA.
and the moment the unwonted pressure is removed the liquid
cushion is restored, and there is again compensation.
600. The discovery of this arrangement in the oceanic maThe causes that pro- chinery suggests that the streams of running water
uceretsiear i te in the sea play rather about its surface than in its
surface.     depths; that the causes which produce currents
reside at and near the surface; that they are changing heat and
alternating cold with their powers of contraction and expansionwinds and sea-shells with evaporation and precipitation; and it
is certain that none of these agents appear capable' of reaching
very far down into the depths of the great and wide sea with their
influences. They go not much, if any, farther down than the
light can reach. On the other hand, the most powerful agents in
the atmosphere reside at and near its bottom; so that, where these
two great oceans meet-the aqueous and the aerial-there we
probably have the greatest conflict and the most powerful display
of the forces that set and keep them in motion, making them to
rage and roar.
601. The greatest depth at which running water is to be found
Their depth. in the sea is probably in the narrowest part of
the Gulf Stream, as, coming from its mighty fountain, it issues
through the Florida Pass. The deep-sea thermometer shows that
even here there is a layer of cold water in the depths beneath,
so that this "river in the sea" may chafe not against the solid
bottom. What revelations of the telescope, what wonders of the
microscope, what fact relating to the physical economy of this
terrestrial globe, is more beautiful or suggestive than some of the
secrets which have been fished up from the caverns of the deep,
and brought to light from the hidden paths of the sea?
602. In my researches I have as yet found no marks of running
The cushion of still water impressed upon the foundations of the sea
water - its thick- 
ness.       beyond the depth of two or three thousand feet.
Should future deep-sea soundings establish this as a fact in other
seas also, it will prove of the greatest value to submarine telegraphy. What may be the thickness of this cushion of still water that covers the bottom of the deep sea is a question of high interest, but we must leave it for future investigation.
603. In Chapter X. (The Salts of the Sea), I have endeavored
to show how sea-shells and marine insects may, by reason of the




~ 604, 605.  THE BASIN AND BED OF THE ATLANTIC.          325
The conservators of offices which they perform, be regarded as compenthe sea.     sations in that exquisite system of physical machinery by which the harmonies of nature are preserved. But
the treasures of the lead and revelations of the microscope present
the insects of the sea in a new and still more striking light. We
behold them now, serving not only as compensations by which
the motions of the water in its channels of circulation are regulated and climates softened, but acting also as checks and balances
by which the equipoise between the solid and the fluid matter of
the earth is preserved. Should it be established that these microscopic creatures live at the surface, and are only buried at the
bottom of the sea, we may then view them as conservators of the
ocean; for, in the offices which they perform, they assist to preserve its status by maintaining the purity of its waters.
604. Does any portion of the shells which Brooke's sounding
Thile anti-biotic view rod brings up from the bottom of the deep sea live
the meet natral  there; or are they all the remains of those that
lived near the surface in the light and heat of sun, and were buried
at the bottom of the deep after death? Philosophers were divided in opinion upon this subject. The facts, as far as they went,
seemed at first to favor the one conjecture nearly as well as the
other. Under these circumstances, I inclined to the anti-biotic hypothesis, and chiefly because it would seem to conform better with
the Mosaic account of creation. The sun and moon were set in
the firmament before the waters were commanded to bring forth
the living creature; and hence we infer that light and heat are
necessary to the creation and preservation of marine life; and since
the light and heat of the sun can not reach to the bottom of the
deep sea, my own conclusion, in the absence of positive evidence
upon the subject, has been, that the habitat of these mites of things
hauled up from the bottom of the great deep is at and near the
surface. On the contrary, others maintained, and perhaps with
equal reason, the biotic side of the question. Professor Ehrenberg, of Berlin, is of this latter class.
605. This is an interesting question. It is a new one; and it
The question stated. belongs to that class of questions which mere discussion helps to settle. It is therefore desirable to state both
sides-present all the known facts; and then, provided with such
lights as they afford, we may draw conclusions.




326       THE PHYSICAL GEOGRAPHY OF THE SEA.
606. As soon as the deep-sea specimens were mounted on the
The arguments of slides of the microscope, the two great masters of
the biotics.  that instrument-Bailey of West Point, and Ehrenberg of Berlin, discovered the greater part of the small calcareous
carapaces to be filled with a soft pulp, which both admitted to be
fleshy matter. From this fact the German argued that there is
life at the bottom of the deep sea; the American (~ 587), that
there is only death and repose there.
607. "The other argument," says Ehrenberg, "for life in the
Ehllrenberg's state- deep which I have established is the surprising
ment of them.    quantity of new forms which are wanting in other
parts of the sea. If the bottom were nothing but the sediment
of the troubled sea, like the fall of snow in the air, and if the biolithic curves of the bottom were nothing else than the product
of the currents of the sea which heap up the flakes, similarly to
the glaciers, there would necessarily be much less of unknown and
peculiar forms in the depths. The surface and the borders of the
sea are much more productive and much more extended than the
depths; hence the forms peculiar to the depths should not be
perceived. The great quantity of peculiar forms and of soft
bodies existing in the innumerable carapaces, accompanied by the
observation of the number of unknowns, increasing with the depths
-these are the arguments which seem to me to hold firmly to the
opinion of stationary life at the bottom of the deep sea."
608. The anti-biotics, on the other hand, quoted the observaThe anti-biotic view. tions of Professor Forbes, who has shown that, the
deeper you go in the littoral waters of the Mediterranean, the
fewer are the living forms.
609. As for the number of unknowns increasing with the depth
Their arguments (~ 607), they contend that the tides, the currents, and
based on the tides. the agitation of the waves all reach to the bottom in
shallow water; that they sweep and scour from it the feculences
of the sea, as these insect remains may be called, and bear them off
into deep water. After reaching a certain depth, then this sediment passes into the stratum of quiet waters that underlie the
roaring waves and tossing currents of the surface, and through
this stratum these organic remains slowly find their way to the
final place of repose as ooze at the bottom of the deep sea.
Through such agencies the ooze of the deep sea ought, said the




~ 610, 611.   THE BASIN AND BED OF THE ATLANTIC.           327
anti-biotics, to be richer than that of shallow water with infusorial
remains; mud and all the light sedimentary matter of river waters
are deposited in the deep pools, and not in the shoals and rapids
of our fresh-water streams; so we ought, reasoned they of this
school, to have the most abundant deposits at the bottom of the
deep sea.
610. The anti-biotics referred to the antiseptic preperties of
On the antiseptic sea water, and told how it is customary with mariproperties of sea water.         ners, especially with the masters of the sailing packets between Europe and America, to "corn" fresh meat by sinking it to great depths overboard. If they sink it too deep, or let
it stay down too long, it becomes too salt.  According to them,
this process is so quick and thorough, because of the pressure and
tho affinity which not only forces the water among the fibres of
the meat, but which also induces the salt to leave the water and
take to the meat; and that the fleshy part of these microscopic
organisms have been exposed to powerful antiseptic agents is
proved by the fact that they are brought up in the middle of the
ocean, and remain on board the vessel exposed to the air for
months before they reach the hands of the microscopist; some of
them have remained so exposed for more than a year, and then
been found full of fleshy matter: a sure proof that it had been preserved from putrefaction and decay by processes which it had undergone in the sea, and before it was raised into the air.
611. Thus the anti-biotics held that these little creatures were
on pressure. preserved for a while after death, and until they
reached a certain depth, by salt, and afterward by pressure. They
held that certain conditions are requisite in order that the decay
of organic matter may take place; that the animal tissues of these
shells during the process of decay are for the most part converted
into gases; that these gases, in separating from the animal compound, are capable of exerting only a certain mechanical force,
and no more; that this force is not very great; and, unless it were
sufficient to overcome the pressure of deep-sea water, their separation could not go on, and that, consequently, there is a certain
depth in the sea beyond which animal decomposition or vegetable
decay can not take place.  In support of this view, they referred
to thewell-known effects of pressure in arresting or modifying
the energies displayed by certain chemical affinities; and in proof




328       THE PHYSICAL GEOGRAPHY OF THE SEA.
of the position that great compression in the sea prevents putrefaction, they referred to the fact well known to the fishermen of
Nantucket and New Bedford, viz., that when a whale that they
have killed sinks in shallow water, he, as the process of decay
commences, is seen to swell and rise; but when he sinks in deep
water, the pressure is such as to prevent the formation of the distending gases, and he never does rise. Some of these specimens
have come from depths where the pressure is equal to that of 400
or 500 atmospheres. Specimens have been obtained by Lieutenant Brooke, in the Pacific, with " fleshy parts" among them, at the
depth of 3300 fathoms, and where the pressure is nearly 700 atmospheres. We have brought up fleshy matter from the deep sea as
deep down as we have gone; and we may infer that if we were
to go to 4000 fathoms, we should still find pulpy matter among
the dead organisms there. At that depth, or a little over, common air, according to "Mariotte's law," would be heavier than
water, and an air bubble down there, if one may imagine such a
thing, would be heavy enough to sink. Under such conditions,
and with the antiseptic agencies of the sea, the fleshy matter of
these infusoria might be preserved at the bottom of the deep sea
for a great length of time.
612. Moreover (~ 604), the anti-biotics pointed to the first chapArgumentsfrom the ter of Genesis to show that light and heat were orBible.      dained before the waters were commanded to bring
forth. Hence they maintained that light and heat are necessary
to marine life. In the depth of the sea there is neither light nor
heat, wherefore they brought in circumstantial evidence from the
Bible to sustain them in their view.
613. This was an exceedingly interesting question, and we
A plan for solving could suggest but one way of deciding it, which
the question.    was this: Many of these little organisms of the sea
are in the shape of plano-convex discs; all such, when alive, live
with the convex side up, tile flat side dcown; but when placed
dead in the water and allowed freely to sink, the force of gravity
always, and for obvious reasons, causes all such forms to sink
with the convex side down. Brooke's lead will bring up these
shells exactly as they lie on the bottom, and so he proposed to
observe with regard to their manner of lying. Of course, if they
lived at the bottom, they would die as they lived, and lie as they




~ 614.        THE BASIN AND BED OF THE ATLANTIC.                        329
died, for (~ 590) there is nothing to turn them  over after death at
the bottom  of the deep sea, consequently their skeletons would be
brought up in the quills of the sounding machine flat side down,
convex side up.
614. But, before there was an opportunity of trying this plan,
An unexpected solu- Ehrenberg himself afforded the solution in a most
tion afforded.  unexpected way; and in soundings from  a great
depth in the Mediterranean, among them  he found many freshwater shells with their fleshy parts still in them, though the specimens were taken from  the middle of the Mediterranean.  That
savant, with his practiced eye, detected among them Swiss forms,
which must have come down  the Danube, and so out into the
Mediterranean hundreds of miles, and on journeys which would
require months, if not years, for these slowly-drifting creatures to
accomplish. And so the anti-biotics maintain that their doctrine
is established.*
* In a paper upon the organic life-forms from unexpected great depths of the
Mediterranean, obtained by Captain Spratt from deep-sea soundings between Malta
and Crete, in 1857, and read before the Berlin Academy, November 27, 1857, Ehrenberg said, "' Especially striking among all the forms of the deep are the Phytolitharia, of which fifty-two in number are found. It would not be strange if these
fifty-two forms were spongoliths, since we expect to find sponge in the sea. But a
large number, not less than twenty kinds of Phytolitharia, are fresh-water and land
forms. Hence the question arises, How came these forms into those depths in the
middle of the sea?
"' Naturally one looks at first to the Nile and the coasts; but the sea current carries
the turbid Nile water eastward; for the current, according to Captain Smyth, especially in the middle of the sea, not only in the Levant, but also in the southern edge, is
clearly a constant eastwardly one. Besides, there are among the forms some northern ones-e. g., Eunotia triodon, Cam]pylodiscus clypeus, and many gallionella.  This
peculiarity may, perhaps, indicate a lower return current, hitherto observed only at
Gibraltar, which probably brings into this basin the forms from the northern European rocks. Thus, for instance, the Danube may bring the Swiss forms in that circulation. But, on the other hand, a highly striking agreement with the forms of the'trade-wind dust' is not to be overlooked.
" In reference to the question of permanent life in these most recent deep-sea materials, it may be observed, that the forms which we find are astonishingly well preserved, and in very large proportion, sometimes forming the principal mass of the
earthy bottom.
"The striking fact, moreover, that every one who has the opportunity to compare
accurately the microscopic forms of the whole land and sea under great variety of
circumstance does, out of even the smallest specimens of the bottom, deduce so
much that is new and peculiar to him, is no light testimony to show that the depth
is not merely a collection of rubbish of the dead surface-life, however much there




330          THE PHYSICAL GEOGRAPHY OF THE SEA.
615. Having thus discovered that the most frail and delicate
A discovery suggest- organisms of the sea can remain in its depths for
ed by it.        an  indefinite  length  of time without showing  a
single trace of decay, we find ourselves possessed of a fact which
suggests many beautiful fancies, some touching thoughts, and a
few useful ideas; and among these last are found reasons for the
conjecture that the gutta percha or other insulating material in
which the conducting wires of the sub-Atlantic telegraph and
other deep-sea lines are incased, becomes, when lodged beyond a
certain depth, impervious to the powers of decay; that, with the
weight of the sea upon them, the destructive agents which are so
busy in the air can not find room  for play.  Curious that destruction and decay should be imprisoned and rendered inoperative at
the bottom of the great deep!
616. Specimens of the " ooze and bottom  of the sea" have also
Specimens from thi  been obtained by the ingenuity of Brooke from  the
three oceans all tell
the same story.    depth of 2700 fathoms in the North Pacific, and
examined by Professor Bailey.* We have now had specimens
must be of fragments which naturally and undoubtedly deposit themselves there. I
have considered this final remark necessary, because the distinguished sea-knower in
Washington, often so kindly supplying and instructing me with material, has recently, in a report on Sub-oceanic Geography, New York, January 8, 1857, page 5, and
yet more in detail in a late private letter, expressed a view opposite to that here laid
down by me, in which, however, I can not coincide, for the reasons given above."' West Point, N. Y., January 29, 1856.
"'MY DEAl. SIn,-I have examined with much pleasure the highly interesting
specimens collected by Lieutenant Brooke, of the United States Navy, which you
kindly sent me for microscopic analysis, and I will now briefly report to you the results of general interest which I have obtained, leaving the enumeration of the organic contents and the description of new species for a more complete account, which
I hope soon to publish. The specimens examined by me were as follows, viz.:
"No. 1. Sea bottom, 2700 fathoms; lat. 56~ 46' N., long. 168~ 18' E.; brought
up July 19, 1855, by Lieutenant Brooke, with Brooke's lead.
" No. 2. Sea bottom, 1700 fathoms; lat. 60~ 15' N., long. 1700 53' E.; brought
up as above, July 26, 1855.
"No. 3. Sea bottom, 900 fathoms; temperature (deep sea) 320, Saxton; lat. 600
30' N., long. 175~ E.
"A careful study of the above specimens gave the following results:
"1st. All the specimens contain some mineral matter, which diminishes in proportion to the depth, and which consists of minute angular particles of quartz, hornblende, feldspar, and mica.
"2d. In the deepest soundings (No. l and No. 2) there is the least mineral matter, the organic contents, which are the same in all, predominating, while the reverse
is true of No. 3.




THE BASIN AND BED OF THE ATLANTIC.                        331
from  the bottom  of "blue water" in the narrow  Coral Sea, the
broad Pacific, and the long Atlantic, and they all tell the same
story, namely, that the bed of the ocean is a vast cemetery. The
c" 3d. All these specimens are very rich in the silicious shells of the Diatomacem,
which are in an admirable state of preservation, frequently with the valves united,
and even retaining the remains of the soft parts.
"4th. Among the Diatomes the most conspicuous forms are the large and beautiful discs of several species of coscinodiscus.  There is also, besides many others, a
large number of a new species of rhizosolenia, a new syndendrium, a curious species of chntoceros, with furcate horns, and a beautiful species of asteromphalhs,
which I propose to call Asteromphalus Brookei, in honor of Lieutenant Brooke, to
whose ingenious device for obtaining deep soundings, and to whose industry and zeal
in using it, we are indebted for these and many other treasures of the deep.
"5th. The specimens contain a considerable number of silicious spicules of sponges,
and of the beautiful silicious shells of the polycistinece. Among the latter I have
noticed Cornutella clathrata of Ehrenberg, a form occurring frequently in the Atlantic soundings. I have also noticed in all these soundings, and shall hereafter describe and figure, several species of eucyrtidium, halicalyptra, a perichlamidium, a
stylodictya, and many others.
"1 6th. I have not been able to detect even a fragment of any of the calcareous
shells of the polythalamia. This is remarkable, from the striking contrast it presents to the deep soundings of the Atlantic, which are chiefly made up of these calcareous forms. This difference can not be due to temperature, as it is well known
that polythalamia are abundant in the Arctic Seas.
" 7th. These deposits of microscopic organisms, in their richness, extent, and the
high latitudes at which they occur, resemble those of the antarctic regions, whose
existence has been proved by Ehrenberg, and the occurrence in these northern
soundings of species of asteromphalus and chsetoceros is another striking point of
resemblance. These genera, however, are not exclusively polar forms, bhut, as I have
recently determined, occur also in the Gulf of Mexico and along the Gulf Stream.
"8th. The perfect condition of the organisms in these soundings, and the fact
that some of them retain their soft portions, indicate that they were very recently in
a living conditions but it does not follow that they were living when collected at such
immense depths. As among them are forms which are known to live along the
shores as parasites upon the algm, etc., it is certain that a portion, at least, have
been carried by oceanic currents, by drift ice, by animals which have fed upon them,
or by other agents, to their present position. It is hence probable that all were removed from shallower waters, in which they once lived. These forms are so minute,
and would float so far when buoyed up by the gases evolved during decomposition,
that there would be nothing surprising in finding them in any part of the ocean,
even if they were not transported, as it is certain they often are, by the agents above
referred to.
" 9th. In conclusion, it is to be hoped that the example set by Lieutenant Brooke
will be followed by others, and that, in all attempts to make deep soundings, the effort to bring up a portion of the bottom will be made. The soundings from any part
of the ocean are sure to yield something of interest to microscopic analysis, and it is
as yet impossible to tell what important results may yet flow from their study.




332        THE PHYSICAL GEOGRAPHY OF THE SEA.
ocean's bed has been found every where, wherever Brooke's
sounding-rod has touched, to be soft, consisting almost entirely of the remains of infusoria. The Gulf Stream has literally
strewed the bottom of the Atlantic with these microscopic shells;
for the Coast Survey has caught up the same infusoria in the
Gulf of Mexico and at the bottom  of the Gulf Stream  off the
shores of the Carolinas, that Brooke's apparatus brought up from
the bottom of the Atlantic off the Irish coast.
617. The unabraded appearance of these shells, and the almost
Their suggestions. total absence among them of any detritus from the
sea or foreign matter, suggest most forcibly the idea of perfect repose at the bottom of the deep sea. Some of the specimens are
as pure and as free from the sand of the seat as the snow-flake
that falls, when it is calm, upon the lea, is from the dust of the
earth. Indeed, these soundings suggest the idea that the sea, like
the snow-cloud with its flakes in a calm, is always letting fall upon
its bed showers of these microscopic shells; and we may readily
imagine that the'"sunless wrecks," which strew its bottom, are,
in the process of ages, hid under this fleecy covering, presenting
the rounded appearance which is seen over the body of the traveler who has perished in the snow-storm. The ocean, especially
within and near the tropics, swarms with life. The remains of
its myriads of moving things are conveyed by currents, and scattered and lodged in the course of time all over its bottom.  This
process, continued for ages, has covered the depths of the ocean as
with a mantle, consisting of organisms as delicate as the macled
frost, and as light in the water as is down in air.
618. The waters of the Mississippi and the Amazon, together
The work of readap- with all the streams and rivers of the world, both
tation, how carried
on.           great and small, hold in solution large quantities of
lime, soda, iron, and other matter. They discharge annually into
the sea an amount of this soluble matter, which, if precipitated and
collected into one solid mass, would no doubt surprise and astonish the boldest speculator with its magnitude.  This soluble mat"The above is only a pr-eliminary notice of tle soundings referred to. I shall proceed without delay to describe and figure the highly interesting and novel forms
which I have detected, and I hope soon to have them ready for publication.
"Yours, very respectfully,                   J. W. BAILEY.
" Lieutenant M. F. MARnY, Nationbl Observatory, Washington City, D. C."




~ 618.     THE BASIN AND BED OF THE ATLANTIC.           333
ter can not be evaporated. Once in the ocean, there it must remain; and as the rivers are continually pouring in fresh supplies
of it, the sea, it has been argued, must continue to become more
and more salt. Now the rivers convey to the sea this solid matter mixed with fresh water, which, being lighter than that of the
ocean, remains for a considerable time at or near the surface.
Here the microscopic organisms of the deep-sea lead are continually at work, secreting this same lime and soda, etc., and extracting from the sea water all this solid matter as fast as the rivers
bring it down and empty it into the sea. Thus we haul up from
the deep sea specimens of dead animals, and recognize in them the
remains of creatures which, though invisible to the naked eye,
have nevertheless assigned to them a most important office in the
physical economy of the universe, viz., that of regulating the saltness of the sea (~ 489). This view suggests many contemplations.
Among them, one, in which the ocean is presented as a vast chemical bath, in which the solid parts of the earth are washed, filtered,
and precipitated again as solid matter, but in a new form, and with
fresh properties. Doubtless it is only a readaptation-though it
may be in an improved form —of old, and perhaps effete matter, to
the uses and well-being of man. These are speculations merely;
they may be fancies without foundation, but idle they are not, I
am sure; for when we come to consider the agents by which the
physical economy of this our earth is regulated, by which this or
that result is brought about and accomplished in this beautiful system of terrestrial arrangements, we are utterly amazed at the offices which have been performed, the work which has been done,
by the animalcule of the water. But whence come the little silicious and calcareous shells which Brooke's lead has brought up,
in proof of its sounding, from the depth of over two miles? Did
they live in the surface waters immediately above? or is their
habitat in some remote part of the sea, whence, at their death, the
currents were sent forth as pall-bearers, with the command to deposit the dead corpses where the plummet found them?




334       THE PHYSICAL GEOGRAPHY OF THE SEA.
CHAPTER XV.
~ 621-680.-SEA ROUTES, CALM BELTS, AND VARIABLE WINDS.
621. PLATE VIII., so far as the winds are concerned, is supplePractical results of mental to Plate I. The former shows the monsoon
physicalresearches at
sea.        regions, and indicates the prevailing direction of the
winds in every part of the ocean; the latter indicates it generally
for any latitude, without regard to any particular sea. Plate VIII.
also exhibits the principal routes across the ocean. This plate indicates the great practical results of all the labor connected with
this vast system of research; its aim is the improvement of navigation; its end, the shortening of voyages. Other interests and
other objects, nay, the great cause of human knowledge, have been
promoted by it; but the advancement that has been given to these
do not, in this utilitarian age, and in the mind of people so eminently practical as mariners are, stand out in a relief half so grand
and imposing as do those achievements by which the distant isles
and marts of the sea have, for the convenience of commerce, been
lifted up, as it were, and brought closer together by many days'
sail.
622. So to shape the course on voyages as to make the most of
Time-tables.  the winds and currents at sea is the perfection of
the navigator's art. Htow the winds blow and the currents flow
along this route or that, is no longer matter of opinion or subject
of speculation, but it is a matter of certainty determined by actual
observation.  Their direction has been determined for months and
for seasons, along many of the principal routes, with all the accuracy of which results depending on the doctrine of chances are capable; and farther, these results are so certain that there is no longer any room for the mariner to be in doubt as to the best route.
When a navigator undertakes a voyage now, he does it with the
lights of experience to guide him. The winds and the weather
daily encountered by hundreds who have sailed on the same voyage before him, and " the distance made good" by each one from
day to day, have been tabulated in a work called Sailing Direc



~ 623-625.    SEA ROUTES, CALM BELTS, ETC.             335
tions, and they are so arranged that he may daily see how much
he is ahead of time, or how far he is behind time; nay, his path
has been literally blazed through the winds for him on the sea;
mile-posts have been set up on the waves, and finger-boards planted, and time-tables furnished for the trackless waste, by which the
ship-master, on his first voyage to any port, may know as well
as the most experienced trader whether he be in the right road
or no.
623. From New York to the usual crossing of the equator on
Close running. the route to Rio the distance, by an air line, is about
3400 miles; but the winds and currents are such as to force the
Rio bound vessel out of its direct line. Nevertheless, they have
been mapped down, studied, and discussed so thoroughly that we
may, using as arguments the data obtained, compute with remarkable precision the detour that vessels sailing from New York or
any other port, and attempting this route to the equator at the
various seasons of the year, would have to make. This computation showed that, instead of 3400 miles, the actual distance to be
accomplished through the water by vessels under canvas on this
part of the voyage would be 4093 miles. More than a hundred
sailing vessels have tried it by measuring and recording the distance actually sailed from day to day; their mean distance is 4099
miles, consequently their actual average differs only six miles from
the computed average.*
624. The best-navigated steam-ships do not sail closer than this,
Adesideratumonship- and a better proof of the accuracy of our knowlboard.       edge concerning the prevailing direction of the
winds at sea could not be afforded. Unfortunately, anemometers
are not used on shipboard. Had they been in common use there,
and had we been furnished with data for determining the force
of the wind as well as its direction, we could compute the time as
well as the distance required for the accomplishment of any given
voyage under canvas. Thus the average time required to sail
from New York to the equator might be computed within an
hour, for it has been computed within an hour's sail-six miles
(~ 623).
625. By the knowledge thus elaborated from old and new logbooks and placed before the nautical world, the average passage
* P. 146, vol. ii., Maury's Sailing Directions.




336          THE PHYSICAL GEOGRAPHY OF THE SEA.
Iow passages have from Europe or the United States to all ports in the
been shortened.    southern hemisphere has been shortened ten days,
and to California a month and a half.* Between England and her
golden colony in the South Seas the time required for the round
voyage has been lessened fifty days or more, and from Europe to
India and China the outward passage has been reduced ten days.
Such are some of the achievements that commend this beautiful
system  of research to the utilitarian spirit of the age.
626. The route that affords the bravest winds, the fairest sweep,
Fast sailing. and the fastest running to be found among ships,
is the route to and from  Australia.  But the route which most
tries a ship's prowess is the outward-bound voyage to California.
The voyage to Australia and back carries the clipper ship along
a route which for more than 300~ of longitude runs with the
" brave west winds" of the southern hemisphere.  With  these
winds alone, and with their bounding seas which follow fast, the
modern clipper, without auxiliary  power, has accomplished  a
greater distance in a day than any sea steamer has ever becn
known to reach. With these fine winds and heaving seas those
ships have performed their voyages of circumnavigation in 60
days.
627. The sea voyage to California, Columbia, and Oregon is
Thelongest voyage. the longest voyage in the world - longest both
as to time and distance.  Before these researches were extended
to the winds and currents along that route, the average passage
both from Europe and America to our northwest coast was not
less than 180 days. It has been reduced so as to average only
* "During the last year [1859] the 8th edition of Maury's Sailing Directions, in
two quarto volumes, has been published at the Observatory in Washington. It affords abundant evidence of the activity, to which allusion has already been made, in
this field of research, and with regard to which all geographers feel the most lively interest.'" Official tables have been received from San Francisco, showing the vessels that
have arrived at that port during the year, with the length of passage. Of those arriving direct, via Cape Horn, 124 were from the Atlantic ports of the United States,
and 34 from Europe. Of these 124, 70 are known to have had the Wind and Current Charts on board; their average passage was 135 days, which is 11 days less
than the average of those from the United States, and 24 days less than the average
of those from Europe without the Charts. When these researches commenced, the
general average was 180 days from the United States, and 183 from Europe to California."-Journal Americanz Geographical Society.




~ 628-630.     SEA ROUTES, CALM BELTS, ETC.              337
135 days. This route is now so well established, and the winds of
the various climates so well understood, that California bound vessels sailing about the same time from the various ports of Europe
and America are, if they be at all of like prowess, almost sure to
fall in with and speak each other by the way.
628. The calm belts at sea, like mountains on the land, stand
Obstructions to the mightily in the way of the voyager, but, like mountnavigator.   ains, they have their passes and their gaps. In the
regions of light airs, of baffling winds, and deceitful currents, the
seaman finds also his marshes and his "mud-holes" on the water.
But these, these researches have taught him how best to pass or
entirely to avoid. Thus the forks to his road, its turnings, and the
crossings by the way, have been so clearly marked by the winds
for him that there is scarcely a chance for him who studies the
lights before him, and pays attention to the directions given, to
miss his way.
629. The arrows of Plate VIII. are supposed to fly with the
Plate vIII.  wind; the half-bearded and half-feathered arrows
denote monsoons or periodic winds; the clotted bands, the regions
of calm and baffling winds. Monsoons, properly speaking, are
winds which blow one half of the year from one direction, and
the other half from an opposite, or nearly an opposite direction.
The time of the changing of these winds, and their boundaries at
the various seasons of the year, have been discussed in such numbers and mapped down in such characters that the navigator who
wishes to take advantage of them or to avoid them altogether is
no longer in any doubt as to when and where they may be found.
630. Let us commence the study of the calm belts as they are
Deserts.  represented on Plates I. and VIII.  Both the monsoons and trade-winds are also represented on the latter. They
often occupy the same region. But, turning to the trade-winds
for a moment, we see that the belt or zone of the southeast tradewinds is broader than the belt or zone of northeast trades. This
phenomenon is explained by the fact that there is more land in
the northern hemisphere, and that most of the deserts of the earth
-— as the great deserts of Asia and Africa —are situated in the
rear, or behind the northeast trades; so that, as these deserts become more or less heated, there is a call-a pulling back, if you
please-upon these trades to turn about and restore the equilibriY




338        THE PHYSICAL GEOGRAPHY OF THE SEA.
um which the deserts destroy. There being few or no such regions in the rear of the southeast trades, the southeast trade-wind
force prevails, and carries them over into the northern hemisphere.
631. We see by the plate that the two opposing currents of
Diurnal rotation.  wind, called "the trades," are so unequally balanced that the one recedes before the other, and that the current
from the southern hemisphere is larger in volume; i. e., it moves
a greater zone or belt of air. The southeast trade-winds discharge
themselves over the equator-i. e., across a great circle —into the
region of equatorial calms, while the northeast trade-winds discharge themselves into the same region over a parallel of latitude,
and consequently over a small circle. If, therefore, we take what
obtains in the Atlantic as the type of what obtains entirely around
the earth, as it regards the trade-winds, we shall see that the
southeast trade-winds keep in motion more air than the northeast
do, by a quantity at least proportioned to the difference between
the circumference of the earth at the equator and at the parallel
of latitude of 9~ north. For if we suppose that those two perpetvial currents of air extend the same distance from the surface of
the earth, and move with the same velocity, a greater volume
from the south should, as has already been shown (~ 343), flow
across the equator in a given time than would flow from the north
over the parallel of 9~ in the same time; the ratio between the
two. quantities would be as radius to the secant of 9~. Besides
this, the quantity of land lying within and to the north of the region of the northeast trade-winds is much greater than the quantity within and to the south of the region of the southeast tradewinds. In consequence of this, the mean level of the earth's surface within the region of the northeast trade-winds is, it may reasonably be supposed, somewhat above the mean level of that part
which is within the region of the southeast trade-winds.  And as
the northeast trade-winds blow under the influence of a greater
extent of land surface than the southeast trades do, the former are
more obstructed in their course than the latter by the forests, the
mountain ranges, unequally heated surfaces, and other such like
inequalities.
632. That the land of the northern hemisphere does assist to
Theland in the north- turn these winds is rendered still more probable
rn hemisphere.   from this circumstance: All the great deserts are




~ 633-635.     SEA ROUTES, CALM BELTS, ETC.              339
in the northern hemisphere, and the land surface is also, much
greater on our side of the equator.  The action of the sun upon
these unequally absorbing and radiating surfaces in and behind,
or to the northward of the northeast trades, tends to check these
winds, and to draw in large volumes of the atmosphere, that otherwise would be moved by them, to supply the partial vacuum
made by the heat of the sun, as it pours down its rays upon the
vast plains of burning sands and unequally heated land surfaces
in our overheated hemisphere.  The northwest winds of the
southern are also, it may be inferred, stronger than the southwest
winds of the northern hemisphere.
633. That the southeast trade-winds should, as observations
Why the southeast (~ 343) have shown, be stronger  than the northtrades are the stronger.         east trade-winds, is due in part also to the well-established fact that the southern (~ 446) is cooler than the northern hemisphere. The isothermal lines of Dove show that the air
of the southeast is also cooler than the air of the northeast tradewinds. Being cooler, the air from the cool side would, for palpable causes, rush with greater velocity into the equatorial calm
belt than should the lighter air from the warmer or northern
side. The fact that the air in the lower latitudes of the southern
hemisphere is the cooler will assist to explain many other contrasts presented by the meteorological conditions on opposite
sides of the equator. Plate XIII. shows that we have more
calms and more fogs, more rains and more gales, with more
thunder, on one side than the other, and that the atmosphere preserves its condition of unstable equilibrium with much more uniformity, being subject to changes less frequent and violent on the
south side of the equator than on the north side.
634. The highest summer temperature in the world is to be
Their uniformity of found in the extra-tropical countries of the north.
temperature.  The greatest extremes of temperature are also to be
found among the valleys of the extra-tropical north. In the extra-tropical south there is but little land, few valleys, and much
water; consequently the temperature is more uniform, changes are
less sudden, and the consequent commotions in the air less violent.
635. Following up these facts with their suggestions, we disThe mean place ofthe cover the key to many phenomena which before
equatorialcalmbelt. were locked up in "the chambers of the south."




340        THE PHYSICAL GEOGRAPHY OF THE SEA.
The belt of equatorial calms which separates the two systems of
trade-winds is, as we know (~ 295), variable as to its position. It
is also variable in breadth. Sometimes it covers a space of several degrees of latitude, sometimes not more than one. Its southern edge, in spring, sometimes goes down to 5~ S; its northern
edge, in autumn, often mounts up to the parallel of 15~ N. The
key to these phenomena has been found; with it in hand, let us
proceed to unlock, first remarking that the mean position of the
equatorial calm belt in the Atlantic is between the equator and
9~ N., and. that as it is there, so I assume it to be in other oceans.
636. This calm belt is produced by the meeting of the two
Never at rest.  trade-winds, and it occupies strictly a medial position between them. It is in the barometric valley, between the
two barometric ridges (~ 858, Fig.) from which the trade-winds
flow. If one "-trade" be stronger than the other, the stronger will
prevail so far as to force their place of meeting over and crowd it
back upon the weaker wind. It is evident that this place of meeting will recede before the stronger wind, until the momentum of
the stronger wind is so diminished by resistance, and its strength
so reduced as exactly to be counterbalanced by the weaker wind.
Then this calm place will become stationary, and so remain, until,
for some cause, one or the other of the meeting winds gains
strength or loses force; then the stronger will press upon the
weaker, and the calm belt will change place and adcljust itself to
the new forces. The changes that are continually going on in the
strength of the winds keep the calm belt in a trembling state,
moving now to the north, now to the south, and always shifting
its breadth or its place under the restless conditions of our atmosphere.
637. The southern half of the torrid zone is cooler than the
The calm belts occupy northern, and, parallel for parallel, the southeast
medial positions.  trade-winds are consequently cooler than the northeast. They both flow into this calm belt, where the air, expanding, ascends, flows off above, produces a low barometer, and so
makes room for the inflowing current below. Now if the tradewind air which flows in on one side of this calm belt be heavier,
whether from temperature or pressure, than the trade-wind air
which flows in on the other, the wind from the heavy side will be
the stronger. This is obvious, for it is evident that if the differ



~ 638, 639.    SEA ROUTES, CALM BELTS, ETC.              341
ence of temperature of the ascending column and the inflowing
air were scarcely perceptible, the difference of specific gravity between the inflowing wind and the uprising air would be scarcely
perceptible, and the movement of the inflowing wind would be
very gentle; but if the difference of temperature were very great,
the difference of specific gravity would be very great, and the violence of the inrushing wind proportionably great. Because the
southern half of the torrid zone is the cooler, the difference in temperature between the air of the calm belt and the air of the tradewinds is greater, parallel for parallel, in the southeast than in the
northeast trade-winds; consequently, the southeast trade-winds
should be - as observations show them to be -stronger than
the northeast, and consequently, also, their meeting should take
place, not upon the equator, but upon that side of it where the
weaker winds prevail, and this is also in accordance (~ 343) with
facts.
638. It follows from these premises that the winter trade-winds
Strength of the trade- should be stronger than the summer. In our sumwinds varies with the
seasons.     mer, the air which the northeast trade-winds put in
motion has its temperature raised and brought more nearly up to
that of the air in the calm belt. At the same time, the temperature of the air which the southeast trade-winds put in motion is
proportionably lowered. Thus they increase in strength, while
the northeast diminish; the consequence is, they push their place
of meeting with the northeast trades far over on this side of the
equator, and for two or three months of the year maintain the polar edge of the calm belt as high up as the parallel of 15~ N. But
with the change of seasons these influences are all transposed and
brought into play on opposite sides only in the southern summer the strength of the soitheast and the temperature of the northeast trade-winds are diminished so as to admit of the edge of the
calm belt being pressed down only as far as 5~ instead of 15~ S.
The causes which produce this alternation of trade-wind strength
are cumulative; consequently, the northeast trade-winds should
be weakest in August or September, strongest in February or
March, after the period of maximum heat in one case and of minimum in the other.
639. In the other hemisphere, the period of strongest trades is
coincident with that of the minimum in this. These deductions are




342        THE PHYSICAL GEOGRAPHY OF THE SEA.
Sailing through them also confirmed by observations; for such is the difin fall and winter. ference as to strength and regularity of the northeast trade-winds in September and February, that the average
passage through them from New York to the line is 26.4 clays in
the winter against 38.8 in the fall month.
640. Thus it appears that the equatorial calm belt is made to
A thermal adjust- shift its place with the seasons, not by reason of the
ment.        greater intensity of the solar ray in the latitude
where the calm belt may be at that season, but by reason of the
annual variations in the energy of each system of trades; which
variations (~ 638) depend upon the changes in the temperature
and barometric weight of the air which each system puts in motion.  This calm belt, therefore, may be considered as a thermal
adjustment-the dynamical null-belt —between the trade-winds of the
two hemis2heres.
641. The observations on the barometer at sea (~ 855) shed
The barometerin the light on this subject. According to the Dutch,
trade-winds and eluatorial calms.  that instrument stands higher by 0.055 inch in the
southeast than it does in the northeast trade-winds.  According to the observations of American navigators, it stands 0.050
inch higher.-   The former determination is derived from 30,873,
the latter from 1899 observations; therefore 0.055 inch is entitled
to most weight.  The trade-winds are best developed between
the parallels of 5~ and 20~. The mean barometric pressure between these parallels is 29.968 inches for the northeast, and 30.023
inches for the southeast trade-winds; while for the calm belt it is
29.915 inches.  The pressure, therefore, upon the air in each of
the trade-winds is greater than it is in the calm belt; and it is this
difference of pressure, from whatever cause arising, that gives the
wind in each system  of trades its velocity.  The difference between the calm belt and trade-wind pressure is 0.108 for the southeast and 0.053 for the northeast.  According to the barometer,
then, the southeast should be stronger than the northeast tradewinds, and according to actual observations they are.t
642. Now if we liken the equatorial calm belt with its diminExperiments in the ished pressure to a furnace, the northeast and the
French Navy.    southeast trade-winds may be not inaptly likened
* Maury's Sailing Directions: "Barometric Anomalies off Cape Horn."
t Nautical Monograph, No. 1.




~ 642.            SEA ROUTES, CALM  BELTS, ETC.                       343
to a pair of double bellows that are blowing into it. In excess
of barometric pressure, the former is a bellows with a weight of
3.8 lbs., the latter with a weight of 7.8 lbs. to the square foot.  It
is this pressure which, like the weight upon the real bellows in
the smithy, keeps up the steady blast; and as the effective weight
upon the one system of trades is about double that upon the other, the one under the greatest pressure should blow with nearly
double the strength of the other, and this appears, both from  actual observations and calculations, as well as from  direct experiments ordered in the French brig of war "Zebra," by Admiral
Chabannes, to be the case.*
* Letter to Admiral Chabannes, with extract of his reply thereto:
"Observatory, Washington, 8th April, 1859.
"MR  DEARi ADMIRAL,-My last was dated 15th January, ultimo. I hope the
charts and vol. i., 8th ed. Sailing Directions, and part of vol. ii. in the sheets, came
safely to hand. Vol. ii. is just out, and I hasten, in homage of my respect, and as a
token of good-will, to lay a copy before you.
"Permit me, if you please, to call your attention to the chapter on the'Average
F orce of the Trade-zoinds,' p. 857, and especially to the table of comparative speed
(of sailing vessels) through the northeast and southeast trade-winds of the Atlantic, p.
865. The average speed, you observe, is nearly the same, notwithstanding that through
the southeast trades the wind is aft, through the northeast just abaft the beam.' In order to treat this question thoroughly, it is very desirable to know the difference in the speed of-vessels when sailing with the same wind aft, with it quartering, with it a point or two abaft the beam, and with it close hauled. With a good
series of experiments upon this subject, we should be able to arrive at definite conclusions with regard to the average difference in force not only of the two systems
of trade-winds, but of the winds generally in various parts of the ocean.
"I If we assume that a wind which, being dead aft, drives a vessel at the rate of six
knots, will, when brought nearly abeam, drive her eight knots-an in this chapter I
have supposed-and then, if we apply the dynamical law of the resistance increasing
as the squares of the velocity of the ship, we should be led to the remarkable conclusion that the average velocity of the northeast to southeast trades of the Atlantic is
as 36 to 64. Therefore, in conducting these experiments, it would be very desirable
to know the area of canvas that fairly feels the wind when it is aft, and the area
upon which the wind blows when the ship is hauled up. Suffice it to say, that the
facts which we already have indicate that the southeast trades, both of the Atlantic
and Indian Oceans, are fresher than the northeast trades of the Atlantic. May we
infer from this that the southeast trades of the Pacific are also fresher than the northeast trades of that ocean? If we may so infer and be right, then there is another
step which we may take with great boldness, and pronounce the atmospherical circulation of the southern hemisphere to be much more active than that of the northern. And having reached this round in the ladder up which I am soliciting you to
accompany me, we are prepared to pause and take a view of some of the new physical aspects which these facts and this reasoning spread out before us.




344          THE PHYSICAL GEOGRAPHY OF THE SEA.
643. With these barometric observations, and the assumed fact
"That the atmospherical circulation is more active in the southern than in the
northern hemisphere appears to be indicated also by the "brave west winds" of the
extra-tropical south. L If the air performs its circuit more rapidly through one system
of trade-winds than the other, then it follows that it must perform its circuit more
rapidly also along those regions through which it has to pass in order to reach such
rapid trades. Consequently, there should be a treat difference between the gales
of the northern and those of the southern hemisphere. If we suppose the general
circulation of the northern hemisphere to be sluggish, the air in its circuits there
would have time to tarry by the way, as it were, and to blow gales of wind from all
points of the compass.  On the contrary, if the general circulation of the southern
hemisphere be brisk and active, the air in its general circuits, like a fast train on the
railway, would not have so much time to tarry by the way, because, like the cars, it
ozust be up to time. Hence, admitting this view of the matter to be correct (and you
perceive that for the want of the experiments already alluded to we are groping in
the darkness of conjecture), though we might expect gales of wind in the extratr'opical regions of the south, yet they would, for the most part, blow withl the prevailing direction of the wind, and not against it.  Thus the gales on the polar side
of Calpricorn should, particularly at sea, have westing in them always-almost.
"In corroboration of this view, I may mention, on the authority of a paper just
received from Lieutenant Van Gogh, of the Dutch Navy, that the gales of wind
which take place between the meridians of 14~ and 32~ E., and between the parallels of 330 and 370 south, have been discussed at the Meteorological Institute of
Utrecht.  For this purpose he tabulated the results for the whole year of 17,810 observations-an observation comprehending a period of eight hours. According to
these observations, it is blowing a gale of wind off the Cape of Good Hope 7.16 per
cent. of the whole year, and from the following quarters: namely, between N.N.W.
and S.S.W. 6.43 per cent.; fiom all other quarters, 0.73 per cent.
I" Perhaps you may find it convenient to institute, with some of the vessels of your
fleet, a regular series of experiments in the southeast trades upon speed, when sailing at various angles with the course of the wind.  Besides answering our immediate purpose, the results might enable us to convert ships into very good anemometers
for all winds except gales.
"Paldon me for being so tedious upon this subject.  If you have felt me so, pray
ascribe it to my desire to get by actual experiment an expression in the average speed
of ships for the actual force and velocity of the winds.
"Wishing you all success and good luck in the investigation which you have in
hand, pray believe me, my dear admiral, yours very truly,     M. F. MAIJRY.
"Admiral C. DE CIIABANNeS, Commander-in-chief of the French[
Naval Division of Brazil and La Plata, Rio de Janeiro." 
Extract of a letter in reply to the foregoing:
"Montevideo, January 25, 1860.
"MY DEAR SIR,-  *  *       *  As you have indicated to me in your letter of
April, I have caused to be made, by a brig of my division, experiments upon the
comparative velocities wind abaft and wind abeam with a given force of wind, but I
have not yet been able to deduce any positive rule, the experiments not having been
sufficiently multiplied. I can, however, give as a result that the increase of head1 See also Plate XIII., and ~ 632 and ~ 633.




~ 644.           SEA ROUTES, CALM BELTS, ETC.                  345
Difference in tons of that the mean pressure of the atmosphere is 15 lbs.
the barometric pressure upon the north- upon the square inch, we may readily determine in
east and southeast
trade-winds.  tons the total by which the superincumbent pressure upon the southeast trade-winds between the parallels of 5~
and 20~ exceeds that upon the northeast between corresponding
parallels.  For the whole girdle of the earth, the excess of pressure
upon the southeast trade-winds is 1,235,250  nillions of tons.
This is the superincumbent weight or pressure which is urging
the southeast trade-winds forward faster than the northeast.  It
is inconceivably great; and to bring it within comprehensible
terms, the mariner will be still astonished to hear that the weight
of atmosphere which is bearing down upon the deck of a first
class clipper ship is 15 or 20 tons greater when he is sailing in
her through the southeast than it is when he is sailing in her
through the northeast trade-winds.
644. The question now  suggests itself, Why should the baWhy the barometer rometer stand higher in the southeast than it does
should stand higher
in the soulteast ill the northeast trade-winds?  The theory of a
than in the northeast trade-winds.  crossing at the calm belts affords the answer.  The
air which the northeast trade-winds deliver into the calm belt is
not as heavily laden with moisture as that of the southeast trades.
It is not as heavily laden for two reasons; one is, the southeast
trade-wind belt is broader than the northeast; consequently, in
the former there is more air in contact with the evaporating surface.  In the next place, the northeast trade-wind belt includes
more land within it than the southeast; consequently, when the
two winds arrive at the calm belt, they are, for this reason, also
unequally charged with moisture.  Now, when they rise up and
precipitate this moisture, more heat is liberated from  the southeast than from the northeast trade-wind air; the latter, therefore,
is the cooler and the more compact; and as, by the theory of the
crossings, it flows off to the south as an upper current, it presses
upon the barometer with more weight than the warmer and more
moist air that feeds the current which is above and counter to the
northeast trades.  There is not in the whole range of marine meway given by wind abeam over the headway with wind aft has been a little less than
two knots; when the velocity with wind aft was from 6 to 8 knots, the force of the
wind aft might be expressed by 4, and of the wind abeam by 6. *    * *
"C. DE CHABANNES."




346       THE PHYSICAL GEOGRAPHY OF THE SEA.
teorology a single well-established fact that is inconsistent with
the theory of a crossing at the calm belts.
645. The geological record affords evidence that the climates
Cataclysms.  of the earth were once very different from what they
are now; that at one time intertropical climates extended far up
toward the north; at another time polar climates reached, with
their icebergs and their drift, far down toward the equator; that
in remote ages most of what we now call dry land was covered
with water, for we find on the mountains and far away in the interior of continents deposits many feet thick, consisting of seashells, marine animals, and organic productions of many sorts.
These fossils, marks, and traces indicate that since their day ages
inconceivably great have elapsed. Not only so: the lines of drift,
and boulders, and gashes with which the earth is scored and strewecd, afford reason for the conjecture that there have been cataclysms, in which the waters have swept from north to south, and
again from south to north, bearing with them icebergs, huge blocks
of stone, rubble, drift, and sediment of various sorts. Lieutenant
Julien, M. Le Iton, and M. Adhemar have, with marked ability,
treated of this subject. They maintain that our earth has a "secular" as well as an annual summer and winter; that these "secular"
seasons depend upon the precession of the equinoxes, and that the
length of each is consequently 10,500 of our years; and that it is
the melting of the polar ices in the "secular" season of one hemisphere, and their recongelation in the " secular" winter of the other,
that causes a rush of the sea from one hemisphere into the other;
and so cataclysms are produced at regular intervals of 10,500 years.
In consequence of the inclination of the axis of the earth to the
plane of its orbit, we have our change of seasons; and in consequence of the ellipticity of that orbit, the spring and summer of
our hemisphere are at present longer than those of the southern.
During the excess of time that the sun tarries on our side of the
equator, the southern nights are prolonged, so that the night of
the south pole-the antarctic winter-is annually a week longer
(~ 366) than the arctic. Thus, during the period of 10,500 years,
the antarctic regions will experience 142 years of night, or winter, in the aggregate, more than the arctic. Therefore it is manifest, say the cataclysmatists, that, though the two hemispheres do
receive annually the same amount of solar heat, yet the amount




~ 646.          SEA ROUTES, CALM BELTS, ETC.                347
dispensed by radiation is very much greater on one side of the
equator than the other. The total effect of the alternate cooling
down on each side of the equator causes an accumulation of ice at
the pole-when the nights are longest-sufficient, say they, to disturb the centre of gravity of the earth, causing it to take up its position on the icy side of the equator. As the ice accumulates, so
is the water drawn over from the opposite hemisphere. Such,
briefly stated, is the theory which has found very ingenious and
able advocates in the persons of MM. Julien* and Adhemar.t
646. This theory is alluded to here, not for the purpose of disAre the climates ofthe cussion, but for the purpose of directing attention
earthchanging?    to certain parts of this work in connection with it,
as Chapters VII. and XXI., for example, and of remarking upon
the stability of terrestrial climates. Though the temperate regions be cooler in the southern than in the northern hemisphere,
it does not appear certain that the climates of the earth are now
changing. Observations upon the subject, however, are lacking.
The question is one of widespread and exceeding interest; and it
may be asked if we have not in the strength of the trade-winds a
gauge, or in their barometric weight an index, or in the equatorial
calm belt a thermometer-each one of the most delicate construction and sensitive character-which would, within the compass of
human life, afford unerring indications of a change of climates, if
any such change were going on?  If the temperature of the S.E.
trade-winds, or the barometric pressure upon the N.E. (~ 641),
were to be diminished, the S.E. trades would force this calm belt
still farther to the north, and we might have a regular rainy season in what is now the great desert of Sahara; for where this calm
belt is (~ 517) there is the cloud-ring, with its constant precipitation. Therefore, if there be any indications that the southern edge
of the great desert is gradually approaching the equator, it favors
the supposition that the southern hemisphere is growing warmer;
but if the indications be that the southern edge of the desert is
receding from the equator, then the fact would favor the supposition that the southern hemisphere is growing still cooler.  Nor
* Courants et Revolutions de l'Atmosphere et de La Mer, comprenant une theorie nouvelle sur les D6luges P6riodiques. Par Felix Juliez, Lieutenant de Vaisseau,
etc. Paris, 1860.
t Revolutions de La Mer. DWluges Periodiques. Par J. Adhlmar., Paris, 1860.




348        THE PHYSICAL GEOGRAPHY OF THE SEA.
are these the only latchets which a study of this calm belt and of
the winds enables us to lift.
647. Theory suggests, and observation, as far as it goes, seems
Temperature of the to confirm the suggestion, that the N. E. and S. E.
trade-winds and calm
belte.       trade-winds enter the equatorial calm belt at the
same temperature. I have followed 100 vessels with their thermometer across the equatorial calm belt of the Atlantic, and another 100 across it in the Pacific. Assuming its mean position to
be as these observations indicate it to be-viz., between the parallels of 3~ and 9~ N. —the mean temperature is 81~ at its northern,
81.4~ at its southern edge, and 82~ in the middle of it. These
200 logs were taken at random, and for all months. The temperature of the air was noted also in each trade at the distance of 5~
from its edge of the calm belt. Thus the temperature of the N.E.
trades, 5~ from the north edge of the calm belt, or in 14~ N., is
78.2~; at a like distance in the S.E. trades from the equatorial
edge, or in 2~ S., the mean temperature is 80.2~.  From this it
would seem that, in traversing this belt of 5~, the temperature
of the N.E. is raised twice as much as the temperature of the
S.E. trades; which is another indication that the velocity of the
S.E. is nearly or quite double the velocity of the N.E. trades
(~ 642). For if it be supposed that it takes the N.E. trades twice
as long to traverse 5~ of latitude as it does the S.E., it is evident
that the former would be exposed twice as long to the solar ray,
and receive twice the amount of heat that is imparted to the S.E.
trade-winds in traversing given differences of latitude.  Thus the
position of the calm belt, the barometer, the thermometer, and the
rate of sailing, all indicate the S.E. trade-winds to be the stronger.
It appears, moreover, that the temperature of the S.E. trade-wind
is in 2~ S. below the temperature of the N.E. in 90 N., the latter
being 810, the former 80.2~.
648. The foregoing observations show that after these winds
Thethermalequator. enter the calm belt, the air they bring into it continues to rise, and this also is what might well be anticipated, for
the sun continues to pour down upon it. But while the temperature of the surface is kept down by the rain-drops from above, the
temperature of the air in the whole belt is raised both by the direct heat of the sun and the latent heat which is set free by the
constant (~ 514) and oftentimes heavy precipitation there. This




~ 649, 650.    SEA ROUTES, CALM BELTS, ETC.                349
latent heat is much more effective than is the direct heat of the
sun in rarefying the air; consequently we here unmask the influences which place the thermal equator in the northern hemisphere.
649. Nor is this the only chamber into which this calm belt
Anatural actinometer key conducts us. Parallel for parallel (~ 446), the
in the trade-winds. southern hemisphere is cooler than the northern;
that is, the mean temperature for the parallel of 40~ south, for example, is below the mean temperature for the parallel of 40~ north,
and so of corresponding parallels between 40~ and the equator.
It appears, moreover, that the mean temperature of the northeast
trade-winds as they cross the parallel of 9~ north, and the mean
temperature of the southeast trade-winds as they cross the equator, is about the same (~ 647). The difference of temperature, then,
between the southeast trades as they cross the parallel of 90 south,
and as they cross the equator, expresses the diference in the thermal forces which give difference of energy to the dynamical power of the trade-winds.  Not only so: it expresses the difference of
temperature between the two corresponding parallels of 90 north
and 9~ south, and discovers to us a natural actinometer on a grand
scale, and of the most delicate and beautiful kind.
650. This actinometer measures for us the heat which the southHeatdailyreceivedby east trade-winds receive between the moment of
the southeast tradewinds.        crossing the parallel of 9~ south and their arrival
at the equator, for the heat thus received is just sufficient (~ 644)
to bring so much of the southeast up to the temperature which the
northeast trades have as they cross the parallel of 9~ north. To
complete this measurement of heat, we should know how long it
takes the southeast trade-winds to get from the parallel of 9~ south
to the equator. According to the estimate, it takes about a day;
but, knowing the exact time, we should have in the band of winds
an actinometer which would disclose to us the average quantity of
heat daily impressed by the sun upon the atmosphere at sea between the equator and 9~ south. I say it takes about a day, and
so infer from these data, viz.: The mean annual direction of the
southeast trade-winds between 10~ south and the line is south 400
east.*  WVe suppose their average velocity to be (~ 343) about 25
miles an hour.  At this rate it would take them 29h. 22m. 30s. to
reach the equator. During this time they receive more heat than
* Maury's Nautical Monograph, No. 1.




350       THE PHYSICAL GEOGRAPHY OF THE SEA.
they radiate, and the excess is just sufficient to raise them from
the normal temperature of the northeast trades as they enter the
calm belt in 90 north. A series of observations on the temperature of the air in latitude 9~ south at sea would, for the farther
study of this subject, possess great value.*
651. If these views be correct, we should expect to find the
Equatorial calm belt equatorial calm belt changing its position with night
never stationary.  and day, and yielding to all those influences, whether secular, annual, diurnal, or accidental, which are capable of producing changes in the thermal condition of the trade-winds. The
great sun-swing of this calm belt from north to south is annual in
its occurrence; it marks the seasons and divides the year (~ 296)
into wet and dry for all those places that are within the arc of its
majestic sweep.  But there are other subordinate and minor influences which are continually taking place in the atmosphere, and
which are also calculated to alter the place of this calm belt, and
to produce changes in the thermal status of the air which the
trade-winds move.  These are, unusually severe winters or hot
summers, remarkable spells of weather, such as long continuous
rains or droughts over areas of considerable extent, either within
or near the trade-wind belts. It is tremblingly alive to all such
influences, and they keep it in continual agitation; accordingly
we find that such is its state that within certain boundaries it is
continually changing place and limits.  This fact is abundantly
proved by the speed of ships, for the log-books at the Observatory
show that it is by no means a rare occurrence for one vessel, after
she may have been dallying in the Doldrums for clays in the vain
effort to cross that calm belt, to see another coming up to her with
fair winds, and crossing the belt after a delay in it of only a few
hours instead of days.
652. Hence we infer that the position of the equatorial calm
It varies with the belt is determined by the difference of strength bestrengthof thetradewinds.       tween the northeast and southeast trade-winds,
which difference, in turn, depends upon difference of barometric
pressure (~ 642), and difference in temperature between them in
corresponding latitudes north and south. In it the air which they
* The mean temperature of sea water in the Atlantic is, for 90 north, 800.26, 565
obs.; equator, 790.63, 269 obs.; and 90 south, 78~0.96, 223 obs.-Miaury's D2ermal
Colarts.




~ 653, 654.    SEA ROUTES, CALM BELTS, ETC.              351
bring ascends. Now if we liken this belt of calms to an immense
atmospherical trough, extending, as it does, entirely around the
earth, and if we liken the northeast and southeast trade-winds to
two streams discharging themselves into it, we shall see that we
have two currents perpetually running in at the bottom, and that,
therefore, we must have as much air as these two currents bring in
at the bottom to flow out at the top. What flows dut at the top
is carried back north and south by these upper currents, which
are thus proved to exist and to flow counter to the trade-winds.
653. Captain Wilkes, of the Exploring Expedition, when he
Precipitationinit. crossed this belt in 1838, found it to extend from
4~ north to 12~ north. HIe was ten days in crossing it, and during those ten days rain fell to the depth of 6.15 inches, or at the
rate of eighteen feet and upward during the year. In its motions
from south to north and back, it carries with it the rainy seasons
of the torrid zone, always arriving at certain parallels at stated
periods of the year; consequently, by attentively considering
Plate VIII., one can tell what places within the range of this zone
have, during the year, two rainy seasons, what one, and what are
the rainy months for each locality.
654. Were the northeast and the southeast trades, with the belt
The appearance of the of equatorial calms, of different colors, and visible
calm belts from a distant planet.  to an astronomer in one of the planets, he might,
by the motion of these belts or girdles alone, tell the seasons with
us. He would see them at one season going north, then appearing stationary, and then commencing their return to the south.
But, though he would observe (~ 295) that they follow the sun in
his annual course, he would remark that they do not change their
latitude as mnuch as the sun does his declination; he would therefore discover that their extremes of declination are not so far
asunder as the tropics of Cancer and Capricorn, though in certain
seasons the changes from day to day are very great. He would
observe that these zones of winds and calms have their tropics or
stationary nodes, about which they linger near three months at a
time; and that they pass from one of their tropics to the other in a
little less than another three months. Thus he would observe the
whole system of belts to go north from the latter part of May till
some time in August. Then they would stop and remain nearly
stationary till winter, in December; when again they would com



352          PHYSICAL GEOGRAPHY OF THE SEA.
mence to move rapidly over the ocean, and down toward the
south, until the last of February or the first of March; then again
they would become stationary, and remain about this, their southern tropic, till May again. Having completed his physical examination of the equatorial calms and winds, if the supposed observer should now turn his telescope toward the poles of our
earth, he would observe a zone of calms bordering the northeast
trade-winds on the north (~ 210), and another bordering the southeast trade-winds'on the south (~ 213).  These calm zones also
would be observed to vibrate up and down with the trade-wind
zones, partaking (~ 296) of their motions, and following the declination of the sun. On the polar side of each of these two calm
zones there would be a broad band extending up into the polar
regions, the prevailing winds within which are the opposites of
the trade-winds, viz., southwest in the northern and northwest
in the southern hemisphere.  The equatorial edge of these calm
belts is near the tropics, and their average breadth is 10~ or 12'~
On one side of these belts (~ 210) the wind blows tperpetually toward the equator; on the other, its prevailing direction is toward
the poles. They are called (~ 210) the "horse latitudes" by seamen.
655. Along the polar borders of these two calm belts (~ 296)
Rainy seasons of the we have another region of precipitation, though
topical calm belt. generally the rains here are not so constant as they
are in the equatorial calms. The precipitation near the tropical
calms is nevertheless sufficient to mark the seasons; for whenever these calm zones, as they go from north to south with the
sun, leave a given parallel, the rainy season of that parallel, if it
be in winter, is said to commence. Hence we may explain the
rainy season in Chili at the south, and in California at the north.
656. We can now understand why the calm belts of Cancer
Their position. and Capricorn occupy a medial position between
the trades and the counter-trades; why, on one side of it, the prevailing direction of the wind should be polarward, on the other
toward the equator; and we also discover the influences which
determine their geographical position.
657. An accumulation of atmosphere over one part of the earth's
A meteorological law. surface implies a depression over some other part,
precisely as the piling up of water into a wave above the sea level involves a corresponding depression below; and in meteorol



~ 658-660.     SEA ROUTES, CALM BELTS, ETC.              353
ogy it may be regarded as a general law, that the tendency of all
winds on the surface is to blow from the, place where the barometer is higher to the place where the barometer is lower. This
meteorological law is only a restatement of the dynamical truism
about water seeking its own level.
658. The mean height of the barometer in the calm belts of the
The barometer in the tropics is greater (Plate I.) than it is in any other
calm belts.  [atitude. The mean height of the barometer in the
equatorial calm belt is less than it is on any other parallel between
the tropical and equatorial calm belts.  The difference for the
calm belt of Cancer is 0.25 inch. This difference is permanent.
It is sufficient to put both systems of trade-winds in motion, and
to create an indraught of air flowing perpetually toward the equatorial calm belt from the distance of two thousand miles on each
side of it.
659. In like manner, as we go from either tropical calm belt toWinds with northing ward the nearest pole, the barometric pressure beand winds with southing in them.  comes less and less.  The meteorological law just
announced requires the prevailing wind on the polar side of these
calm belts to be from them and in the direction of the poles; and
observations (Plate I.) show that such is the case. Dividing the
winds in each hemisphere into winds with northing and winds
with  southing in them, actual observation shows that they balance
each other in the southern hemisphere between the parallels of
350 and 400, and in the northern between the parallels of 25~ and
50~; that between these parallels the average annual prevalence
of winds with northing and of winds with southing in them is the
same, the difference being so small'as to be apparently accidental; that, proceeding from the medial band toward the pole, polarbound winds become more and more prevalent, and proceeding
from it toward the equator, equatorial-bound winds become more
and more prevalent.  Now, in each case, the prevailing winds
blow (~ 657) from the high to the low barometer (Plate I.).
660. The fact of two barometric ridges encircling the earth, as
Thebarometricriages. the high barometer of the tropical calm belts do,
and as they may be called (Plate I.), suggests a place of low barometer on the polar side as naturally as the ascent of a hill on
one side suggests to the traveler a descent on the other; and, had
not actual observations revealed the fact, theory should have taught
z




354       THE PHYSICAL GEOGRAPHY OF THE SEA.
us (~ 654) the existence of a low barometer toward the polar regions as well as toward the equatorial.
661. Let us contemplate for a moment this accumulation of air
Theymakeadepres- in the tropical belt about the earth in each hemision in the atmosphere.       sphere. Because it is an accumulation of atmospheric air about the calms-because the barometer stands higher
under the calm belt of Capricorn, for instance, than it does on any
other parallel between that calm belt and the pole on one side, or
the equator on the other, it is not to be inferred that therefore
there is a piling-a ridging up of the atmosphere there.  On the
contrary, were the upper surface of our atmosphere visible, and
could we take a view of it from above, we should discover rather
a valley than a ridge over this belt of greatest pressure; and over
the belt of least pressure, as the equatorial calm belt, we should
discover (~ 520), not a valley, but a ridge, and for these reasons:
In the belts of low barometer, that is, in both the equatorial and
polar calms, the air is expanded, made light, and caused to ascend
chiefly by the latent heat that is liberated by the heavy precipitation which takes place there.  This causes the air which ascends
there to rise up and swell out fari above the mean level of the
great aerial ocean. This intumescence at the equatorial calm belt
has been estimated to be several miles above the general level of
the atmosphere.. This calm belt air, therefore, as it boils up and
flows off through the upper regions, north and south, to the tropical calm belts, does not so flow by reason of any difference of
barometric pressure, like that which causes the surface winds to
blow, but it so flows by reason of difference as to level.
662. The tropical calm belts (~ 278) are places where the mean
The upper surface of amount of precipitation is small. The air there is
the atmosphere.   comparatively dry air. So far from being expanded by heat, or swelled out by vapor, this air is contracted by cold,
for the chief source of its supply is through the upper regions,
from the equatorial side, where the cross section between any two
given meridians is the larger; and this upper current, while on its
way from the equator, is continually parting with the heat which
it received at and near the surface, and which caused it to rise under the equatorial cloud-ring. In this process it is gradually contracted, thus causing the upper surface of the air to be a sort of
double inclined plane, descending from the equator and from the
poles to the place of the tropical calm belts.




~ 663-665.    SEA ROUTES, CALM BELTS, ETC.              355
663. Observations show that the mean weight of the barometer
Windsinthesouthern in high southern is much less (Plate I.) than it is
isthonge nothaen ihendi in corresponding high northern latitudes; consein the northern hemisphere.      quently, we should expect that the polar-bound
winds would be much more marked on the polar side of 40~ S.,
than they are on the polar side of 40~ N. Accordingly, observations (Plate XV.) show such to be the case; and they moreover
show that the polar-bound winds of the southern are much fresher than those of the northern hemisphere.
664. To appreciate the force and volume of these polar-bound
The waves and gales winds in the southern hemisphere, it is necessary
off the Cape of Good
Hope.       that one should "run them down" in that waste of
waters beyond the parallel of 40~ S., where "the winds howl and
the seas roar." The billows there lift themselves up in long ridges
with deep hollows between them. They run high and fast, tossing their white caps aloft in the air, looking like the green hills
of a rolling prairie capped with snow, and chasing each other in
sport. Still, their march is stately and their roll majestic. The
scenery among them is grand, and the Australian-bound trader,
after doubling the Cape of Good Hope, finds herself followed for
weeks at a time by these magnificent rolling swells, driven and
lashed by the "brave west winds" most furiously. A sailor's
bride, performing this voyage with her gallant husband, thus alludes in her "abstract log" to these rolling seas: "We had some
magnificent gales off the Cape, when the coloring of the waves,
the transition from gray to clear brilliant green, with the milkywhite foam, struck me as most exquisite. And then in rough
weather the moral picture is so fine, the calmness and activity
required is such an exhibition of the power of mind over the elements, that I admired the sailors fully as much as the sea, and, of
course, the sailor in command most of all; indeed, a sea voyage
more than fulfills my expectations."
665. It appears, therefore, that the low barometer about the
winds blow from a poles and the low barometer of the equator cause
high to a low barometer.       an inrush of wind, and in each case the rushing
wind comes from the high and blows toward the low barometer;
that in one hemisphere the calm belt of Capricorn, and in the other the calm belt of Cancer, occupies the medial line between these
places of low barometer.




356        THE PHYSICAL GEOGRAPHY OF THE SEA.
666. It appears, moreover, that the polar rarefaction is greater
Polar rarefaction. than the equatorial, for the mean height of the austral barometer is very much below that of the equatorial, and,
consequently, its influence in creating an indraught is felt at a
greater distance-even at the distance of 50~ of latitude from the
south pole, while the influence of the equatorial depression is felt
only at the distance of 30~ in the southern, and of 25~ in the
northern hemisphere. The difference as to degree of rarefaction
is even greater than this statement implies, for the influx into the
equatorial calm belt is assisted also by temperature in this, that
the trade-winds blow from cooler to warmer latitudes.  The reverse is the case with the counter-trades; therefore, while difference of thermal dilatation assists the equatorial, it opposes the polar influx.
667. Thus we perceive that the tropical calm belts are simply
The tropical calm an adjustment between the polar and equatorial
belts caused by the calms; that the tropical calm belts assume their popolar and equatorial            p                          p
calms.       sition and change their latitude in obedience to the
energy with which the influence of the heated and expanding columns of air, as they ascend in the polar and equatorial calms, is
impressed upon them.
668. This explanation of the calm places and of the movements
The meteorological of the low austral barometer shows, comparatively
poweroflatentheat. speaking, how much the latent heat of vapor, and
how little the direct heat of the sun has to do in causing the air
to rise up and flow off from these calm places, and, consequently,
how little the direct action of the solar ray has to do either with
the trades or the counter-trades. It regulates and controls them;
it can scarcely be said to create them.
669. The fact of a low barometer off Cape Horn was pointed
The low barometer out* as long ago as 1834. It was considered an
off Cape Horn. anomaly peculiar to the regions of Cape Horn. It
is now ascertained by the comparison of 6455 observations on the
polar side of 40~ south, and about 90,000 in all other latitudes,
that the depression is not peculiar to the Cape Horn regions, but
that it is general and alike in all parts of the austral seas, as the
following tables, compiled from the log-books of the Observatory
by Lieutenants Warley and Young, show:
* American Journal of Science, vol. xxvi., p. 54 (1834).




~ 670-672.        SEA ROUTES, CALM BELTS, ETC.                     357
~ 670.                  BAROMETRIC TABLE.
Mean Height of the Barometer as observed between
I_____________  the Meridians of          Mean of al
the Parallels of  20 W. and 1400~. 140t~ E. and 8S~ W. Off Cape Horn.
the Parallels of
No. of Barom. No. of Barom. No. of Barom. No. of  Barom.
Obs.  Inches.  Obs. Inches.  Obs. Inches.  Obs.  Inches.
400 S. and 430 S. 1115  29.90   210  29.84   378  29.86   1703  29.88
43    "45       738.80   155.73   237.75   1130.78
45    " 48      611.58   226.71   337.68  - 1174.63
48    " 50      175.53   247.56   250.61    672.62
50    " 53      108.35   198.45   359.56    665.48
53    " 55        6.14   92.35   377.37    475.36
7.27    64.42  1055.28   1126.29
671. These are the observed heights; for the want of data, no
Barometer at the corrections have been applied to them; and for the
poles.         want of numbers sufficient to give correct means,
they lack that uniformity which larger numbers would doubtless
give.  They show, however, most satisfactorily, that ai low  baTometer is not peculiar to Cape Horn regions alone; they show
that it is common to all high southern latitudes; and other observations (~ 362) show that it is peculiar to these and not to northern latitudes.  Projecting on a diagram, A, with parallels of latitude and the barometric scale as ordinates and abscissa, a curve
S, which will best represent the observations (~ 670), and continuing it to the south pole-also projecting another curve, N, which
will best represent the observations (~ 362) on the polar side of 40~
N., and continuing it to the north pole-we discover that if the
barometric pressure in polar latitudes continues to decrease for
the unknown as it does for the known regions, the mean height
of the barometer would be at the north pole about 29.6, at the
south about 28 inches.  These lines, N  and S, represent what
may be called the barometric descent of the counter-trades.
672. The rarefaction of the air in the polar calms is, as we
The "brave west have seen (~ 667), sufficient to create an indraught all
winds" —their barometric descent.   around to the distance of fifty degrees of latitude
from  the south pole; also (~ 662) the rarefaction in the belt of
equatorial calms is sufficient to extend with its influence no farther than thirty degrees of latitude.  This fact also favors the
idea suggested by the diagram (~ 671), that the mean height of
the barometer in the polar calms is very much less than it is in
the equatorial.  Moreover, the counter-trades of the southern
hemisphere are very much stronger (~ 626) than the counter



358       THE PHYSICAL GEOGRAPHY OF THE SEA.
DIAGRAM A.
JAT. M40~    50o    600    700    80~0    90o
Baxiometer ao.
29indicate such to be the case. In other words, the "brave west'7.2
winds" of the southern hemisphere have the greatest "barometric descent," and should therefore be, as they are, the strongest of
the four winds.
673. Farther information may be gained upon the subject of




~ 674, 675.    SEA ROUTES, CALM BELTS, ETC.                359
Study of the mon- high and low barometers, of the' barometric desoons affords farther
information touch- cvity of winds," and of the meteorological influing the calm belts. ence of diminished atmospheric pressure by studying the calm- belts in connection with the monsQons.
674. Before, however, we proceed to these, let us take a hasty
Thesouthwestwinds of glance at the winds in certain other parts of the
The Atlantic.  ocean. The winds which most prevail on the polar side of the calm belt of Cancer, and as far as 50~ N. in the Atlantic, are the west winds.  "' Wind and weather in this part of
the ocean," says Jansen, " are very unreliable and changeable;
nevertheless, in the summer months, we find permanent north
winds along the coast of Portugal. These north winds are worthy
of attention, the more so from the fact that they occur simultaneously with the African monsoon, and because we then find
northerly winds also in the Mediterranean, and in the Red Sea,
and farther eastward to the north of the Indian monsoon.  When,
between the months of May and November, during which the African monsoon prevails, the Dutch ships, which have lingered in
the calm belt of Cancer, run with the northeast trade and direct
their course for the Cape Verd Islands, then it seems as if they
were in another world.  The sombre skies and changeable-alternately chilly and sultry-weather of our latitudes are replaced
by a regular temperature and good settled weather. Each one
rejoices in the glorious heavens, in which none save the little
trade-clouds are to be seen-which clouds in the trade-wind region make the sunset so enchanting.  The dark blue water, in
which many and strange kinds of echinas sport in the sunlight,
and, when seen at a distance, make the sea appear like one vast
field adorned with flowers; the regular swellings of the waves
with their silvery foam, through which the flying-fishes flutter;
the beautifully-colored dolphins; the diving schools of tunniesall these banish afar the monotony of the sea,e awake the love of
life in the youthful seaman, and attune his heart to goodness.
Every thing around him fixes his attention and increases his astonishment.
675. " If all the outbreathings of heartfelt emotion which the
* When we, as our forefathers did, preserve in the journals all that we observe at
sea, then we shall have abundant material with which to keep ourselves pleasantly
occupied.




360       THE PHYSICAL GEOGRAPHY OF THE SEA.
Sailing through the contemplation of nature forces from the sailor were
trade-wind.  recorded in the log-books, how much farther should
we be advanced in the knowledge of the natural state of the sea!
Once wandering over the ocean, he begins to be impressed by the
grand natural tableau around him with feelings deep and abiding.
The most splendid forecastle is lost in the viewless surface, and
brings home to us the knowledge of our nothingness; the greatest ship is a plaything for the billows, and the slender keel seems
to threaten our existence every moment. But when the eye of
the mind is permitted to wander through space and into the depths
of the ocean, and is able to form a conception of Infinity and of
Omnipotence, then it knows no danger; it is elevated-it comprehends itself. The distances of the heavenly bodies are correctly
estimated; and, enlightened by astronomy, with the aid of the
art of navigation, of which Ma-ury's Wind and Current Charts
form an important part, the shipmaster marks out his way over
the ocean just as securely as any one can over an extended heath.
Hie directs his course toward the Cape Verd- Islands, and is carried there by the lively trade-wind. Yet beyond the islands,
sooner or later, according to the month, the clear skies begin to
be clouded, the trade-wind abates and becomes unsteady, the
clouds heap up, the thunder is heard, heavy rains fall; finally, the
stillness is deathlike, and we have entered the belt of calms. This
belt moves toward the north from May to September. It is a remarkable phenomenon that the annual movements of the trades
and calm belts from south to north, and back again, do not directly
follow the sun in its declination, but appear to wait until the temperature of the sea-water puts it in motion. If a ship which has
come into the belt of calms between May and September could
lie still in the place where it came into this belt-cast anchor, for
example —then it would perceive a turning of the monsoon or of
the trade-wind. It would see the belt of calms draw away to the
north, and afterward get the southwest monsoon, or, standing
more westerly, perhaps the southeast trade. On the contrary,
later than September, this ship lying at anchor will see the northeast gradually awake. The belt of calms then moves toward the
south, and removes from the ship, which remains there anchored
on the north side.'"7
* Natuurkiindige Beschrijving der zeeen, door M. F. Maury, LL.D., Luitenant




~ 676, 677.     SEA ROUTES, CALM BELTS, ETC.                361
676. The investigations that have taken place at the ObservatoThe influence of thle ry show that the influence of the land upon the
land upon the winds
at sea.        normal directions of the wind at sea is an immense
influence.  It is frequently traced for a thousand miles or more
out upon the ocean. For instance, the action of the sun's rays
upon the great deserts and arid plains of Africa, in the summer
and autumnal months, is such as to be felt nearly across the Atlantic Ocean between the equator and the parallel of 13~ north.
Between this parallel and the equator, the northeast trade-winds,
during these seasons, are arrested in their course by the heated
plains of Africa, as observation shows they are in India, and instead
of " blowing home" to the equator, they stop and ascend over the
desert sands of the continent.  The southeast trade-winds, arriving
at the equator during this period, and finding no northeast trades
there to contest their crossing the line, continue their course, and
blow home as a southwest monsoon to the deserts, where they ascend. These southwardly monsoons bring the rains which divide
the seasons in these parts of the African coast. The region of the
ocean embraced by these monsoons is cuneiform in its shape, having its base resting upon Africa, and its apex stretching over till
within 10~ or 150 of the mouth of the Amazon.  Indeed, when
we come to study the effects of South America and Africa (as
developed by the Wind and Current Charts) upon the winds at
sea, we should be led to the conclusion-had the foot of civilized
man never trod the interior of these two continents-that the climate of one is humid; that its valleys are, for the most part, covered with vegetation, which protects its surface from the sun's
rays; while the plains of the other are arid and naked, and, for
the most part, act like furnaces in drawing the winds from the sea
to supply air for the ascending columns which rise from its overheated plains. Pushing these facts and arguments still farther,
these beautiful and interesting researches seem already sufficient
almost to justify the assertion that, were it not for the great desert
of Sahara and other arid plains of Africa, the western shores of
that continent, within the trade-wind region, would be almost, if
not altogether, as rainless and sterile as the desert itself.
677. Lieutenant Jansen has called my attention to a vein of
der Nord-Amerikaansche Marine, vertaald door M. II. Jansen, Luitenant der Zee.
(Bijdrage.) Dordrecht, P. K. Braat. 1855.




362       THE PHYSICAL GEOGRAPHY OF THE SEA.
A "GuL Stream" in wind which forms a current in the air as remarkthe air.     able as that of the Gulf Stream is in the sea. This
atmospherical Gulf Stream is in the southeast trade-winds of the
Atlantic. It extends from near the Cape of Good Hope, in a direct line to the equator, on the meridian of Cape St. Roque (Plate
VIII.). The homeward route from the Cape of Good Hope lies
in the middle of this vein; in it the winds are more steady than
in any other part of the Atlantic.  On the edges of this remarkable aerial current the wind is variable and often fitful; the homeward-bound Indiaman resorts to and uses this stream in the atimosphere as the European-bound American does the Gulf Stream.
It is shaded on the plate.
678. These investigations, with their beautiful developments,
Counterpoises. eagerly captivate the mind; giving wings to the
imagination, they teach us to regard the sandy deserts, and arid
plains, and the inland basins of the earth, as compensations in the
great system of atmospherical circulation. Like counterpoises to
the telescope, which the ignorant regard as incumbrances to the
instrument, these wastes serve as make-weights, to give certainty
and smoothness of motion-facility and accuracy to the workings
of the machine.
679. WVhen we travel out upon the ocean, and get beyond the
Normal stateof the at- influence of the land upon the winds, we find ourmosphere.     selves in a field particularly favorable for studying
the general laws of atmospherical circulation. Here, beyond the
reach of the great equatorial and polar currents of the sea, there
are no unduly heated surfaces, no mountain ranges, or other obstructions to the circulation of the atmosphere-nothing to disturb
it in its natural courses. The sea, therefore, is the field for observing the operations of the general laws which govern the
movements of the great aerial ocean. Observations on the land
will enable us to discover the exceptions, but from the sea we
shall get the rule. Each valley, every mountain range and local
district, may be said to have its own peculiar system of calms,
winds, rains, and droughts. But not so the surface of the broad
ocean; over it the agents which are at work are of a uniform
character.
680. RAIN-WINDS are the winds which convey the vapor from,ain-winds.  the sea, where it is taken up, to other parts of the




~ 680.        SEA ROUTES, CALM BELTS, ETC.              363
earth, where it is let down either as snow, hail, or rain. As a general rule, the trade-winds (~ 293) may be regarded as the evaporating winds; and when, in the course of their circuit, they are
converted into monsoons, or the variables of either hemisphere,
they then generally become also the rain-winds-especially the
monsoons-for certain localities. Thus the southwest monsoons
of the Indian Ocean are the rain-winds for the west coast of Hindostan (~ 298). In like manner, the African monsoons of the Atlantic are the winds which feed the springs of the Niger and the
Senegal with rains. Upon every water-shed which is drained
into the sea, the precipitation, for the whole extent of the shed so
drained, may be considered as greater than the evaporation, by the
amount of water which runs off through the river into the sea.
In this view, all rivers may be regarded as immense rain-gauges,
and the volume of water annually discharged by any one as an
expression of the quantity which is annually evaporated from
the sea, carried back by the winds, and precipitated throughout the whole extent of the valley that is drained by it. Now, if
we knew the rain-winds from the dry for each locality and season generally throughout such a basin, we should be enabled to
determine, with some degree of probability at least, as to the part
of the ocean from which such rains were evaporated. And thus,
nowithstanding all the eddies caused by mountain chains and
other uneven surfaces, we might detect the general course of the
atmospherical circulation over the land as well as the sea, and
make the general courses of circulation in each valley as obvious
to the mind of the philosopher as is the current of the Mississippi,
or of any other great river, to his senses.




364c      THE PHYSICAL GEOGRAPHY OF THE SEA.
CIHAPTER XVI.
~ 681-711. —MONSOONS.
681. MONSOONS are, for the most part, trade-winds deflected.
The cause of. When, at stated seasons of the year, a trade-wind
is turned out of its regular course, as from one quadrant to another, it is regarded as a monsoon. The African monsoons of
the Atlantic (Plate VIII.), the monsoons of the Gulf of Mexico,
and the Central American monsoons of the Pacific are, for the
most part, formed of the trade-winds which are turned back or
deflected to restore the equilibrium which the overheated plains
of Africa, Utah, Texas, and New Mexico have disturbed. Thus
with regard to the northeast and the southwest monsoons of the
Indian Ocean, for example: a force is exerted upon the northeast trade-winds of that sea by the disturbance which the heat
of summer creates in the atmosphere over the interior plains of
Asia, which is more than sufficient to neutralize the forces which
cause those winds to blow as trade-winds; it arrests them and
turns them back; but, were it not for the peculiar conditions of
the land about that ocean, what are now called the northeast monsoons would blow the year round; there would be no southwest
monsoons there; and the northeast winds, being perpetual, would
become all the year what in reality for several months they are,
viz., northeast trade-winds.
682. Upon India and its seas the monsoon phenomena are deThe region of. veloped on the grandest scale. They blow over all
that expanse of northern water that lies between Africa and the
Philippine Islands. Throughout this vast expanse, the winds that
are known in other parts of the world as the N.E. trades, are here
called N.E. monsoons, because, instead of blowing from that quarter for twelve months, as in other seas, they blow only for six.
During the remaining six months they are turned back, as it were;
for, instead of blowing toward the equator, they blow away from it,
and instead of N.E. trades we have S.W. monsoons.




~ 683-686.             MONSOONS.                      36,5
683. If the N.E. trade-winds blow toward the equator by reason
A low barometer in (~ 657) of the lower barometer of the calm belt there,
Northern India. we should —seeing them turned back and blowing
in the opposite direction as the S.W. monsoon-expect to find toward the north, and at the place where they cease to blow, a lower barometer than that of the equatorial calm belt. The circumstances which indicate the existence of a low.summer barometer
-the period of the S.W. monsoon-in the regions about northern
India are developed by the law which (~ 657) requires the wind
to blow toward that place where there is least atmospheric pressure.
684. The S.W. monsoons commence at the north, and "back
The S.W. monsoons down," or work their way toward the south. Thus
"backing down."  they set in earlier at Calcutta than they do at Ceylon, and earlier at Ceylon than they do at the equator. The average rate of travel, or "backing down to the south," as seamen express it, is from fifteen to twenty miles a day. It takes the S.W.
monsoons six or eight weeks to " back down" from the tropic of
Cancer to the equator. During this period there is a sort of barometric ridge in the air over this region, which we may call the
monsoon wave. In this time it passes from the northern to the
southern edge of the monsoon belt, and as it rolls along in its invisible but stately march, the air beneath its pressure flows out
from under it both ways-on the polar side as the S.W. monsoon,
on the equatorial as the N.E.
685. As the vernal equinox approaches, the heat of the sun
How they begin. begins to play upon the steppes and deserts of Asia
with power enough to rarefy the air, and cause an uprising sufficient to produce an indraught thitherward from the surrounding
regions. The air that is now about to set off to the south as the
N.E. monsoon is thus arrested, turned back, and drawn into this
place of low barometer as the S.W. monsoon. These plains become daily more and more heated, the sun more and more powerful, and the ascending columns more and more active; the area
of inrushing air, like a circle on the water, is widened, and thus
the S,W. monsoons, "backing down" toward the equator, drive
the N.E. monsoons from the land, replace them, and gradually extend themselves out to sea.
686. Coming now from the water, they bring vapor, which,




366         THE PHYSICAL GEOGRAPHY OF THE SEA.
The sun assisted by being condensed upon the hill-sides, liberates its
the latent heat of vapor.           latent caloric, and so, adding fuel to the flame, assists the sun to rarefy the air, to cause it to rise up and flow off
more rapidly, and so to depress the barometer still more.  It is
not till the S.W. monsoons have been extended far out to sea that
they commence to blow strongly, or that the rainy season begins
in India.  By this time the mean daily barometric pressure in this
place of ascending air, which is also a calm place, has become less
than it is in the equatorial calm belt; and the air which the S.E.
trade-winds then bring to the equator, instead of rising up there
in the calm belt, pass over without stopping, and flows onward to
the calms of Central Asia as the S.W. monsoon.  It is drawn over
to supply the place of rarefaction over the interior of India.
687. The S.W. monsoon commences to change at Calcutta, in
The rain-fallinIndia. 22~ 34' N., in February, and extends thence out to
sea at the rate of fifteen or twenty miles a day; yet these winds
do not gather vapor enough for the rainy season of Cherraponjie,
in lat. 25~ 16', to commence with until the middle or last of April,
though this station, of all others in the Bengal Presidency, seems
to be most favorably situated for wringing the clouds. Selecting
from Colonel Sykes's report of the rain-fall of India those places
nearest the same meridian, and about 2~ of latitude apart, the following statement is made, with the view of showing, as far as such
data can show, the time at which the rainy season commences in
the interior:
Lat.  Long. March. April. May.  June. July. Aug. Sept. Oct....o   0     in,   in.   in,  in.   in.  in.   in.  in.
Poorie........ 19 48 85 49...    1    1    5   14    7    4...
Baitool...... 21 51 77 58......    1    4   15    9    4
Sangor....... 23 50 78 47...... 2    2   15   12   13    1
Humeerpore. 26 7 79 47.........           7   13   11    5    1
Bareilly......  28 12 79 34.........    3   17    8    2    3
Fe;ozepore..i 30 57.74 41...           1   19......
Simla......... 31 6 77 11   1...    1    4   18   12..
Cherraponjie 25 16 91 43   1    28  115  147   99  104   72   40
2    29  120  173  210  163  100 i 45
It is June before the S.W. monsoons have backed down as far as
the equator and have regularly set in there.
688. These positions are selected without regard to elevation
ts infuences upon the above the sea level.  Of course, when the S.W.
monsoons.       monsoon comes only from  a short distance out to
sea, as in April it does, it is but lightly loaded with moisture.




~ 689, 690.                MONSOONS.                              367
The low country can not condense it, and it then remains for the
mountain stations in the interior, such as Cherraponjie, to get the
first rains of the-season; and a most interesting physical problem
may be here put on the road to solution by the question, Does not
the rainy season of the S.W. monsoon commence at the high stations in the interior, as on the sides of the Himalaya, earlier than
in the flat country along the sea-coast?
689. With the view of investigating certain monsoon phenomeThe march of-the na, recourse was had to our great magazine of unmonsoons.      digested facts, the abstract logs; and after discussing not less than 11,697 observations on the winds at sea between
the meridians of 80~ and 85~ E., and from Calcutta to the equator,
results were obtained for the following table, in which is stated in
days the average monthly duration of the N.E. and S.WV. winds at
sea between the parallels of
22~ and 20~ N. 20~ and 15~ N. 15~ and 10~ N. 100 and 50 N.  50 and 00 N.
Days. Days. Days. Days. Days. Days. Days. Days. Days. Days.
N.E.  S.W.  N.E.  S.W.. E.  S..  N.   S.W.  N.E.  S.W.
January..  17    61   21      2    23     1    20    1    19    3t
February   11   11    13      6    19     3    22    1    16    2
Mar ch.....  4    18*    7    15    18;5   13    0    15    2
April......   2   24   2    22*    6    12     6   11      4   14*
May........   1   26   1    24     3    21*    1   23*    0   19
June.......   0   28   1    27     0    29     1   25      0   24
July.......   2   24   1    27     0    30     0   28      0   24
August....   0   28     1    24     0    24      1   22     0   18
September   6   14t    1    18      0    23     0   26      1   18
October...   9    6    12     6t    8    10      6   16    4   14
November  11    6    25       2    21      2t   10    6t    5   14
December  27    0    26       1    24      1    15    3    12   11
* Setting in of the S.W. monsoon.         t Ending of the S. W. monsoon.
It appears from this table that between Calcutta and the line the
S.W. monsoons are the prevailing winds for seven months, the
N.E. for five.
690. Resorting to the graphic method of engraved squares for
Their conflict-it be- a farther discussion of these figures, it appears by
gins at the north.   the Diagram B that in February the northeast and
southwest winds are in equal conflict between the parallels of 20~
and 22~; that in March the former have backed down as far as
the parallel of 16~-15~-the  medial line between  them  from
which each monsoon is blowing-and where, again, the conflict
of "back to back" is equally divided as to time of mastery (12
days) on either side. By the month of June they (the southwest)




368       THE PHYSICAL GEOGRAPHY OF THE SEA.
DIAGRAM B.
02      ~ 200   J5"   100    ]8
fairly gained the ascendency, and so remain masters of the
field until October, when the bi-annual conflict is again commenced at the north. The vanquished northeast trades now lead
off in the attack, and, as the Diagram C shows, the two combatants have force enough about the parallel of 15' north to\ blow
during this month 9 days each. The conflict, instead of being
"back to back," is now face to face; instead of blowing away
from the medial line, they blow toward it; instead of being a
place of high, the medial line is now (~ 657) a place of low barometer. By November the northeast monsoon has pushed the
place of equal contest as far down as the parallel of 50 north.
691. Each monsoon, like the trade-winds, blows from a higher
The barometric de- to a lower barometer. Taking up the clew from
scentofthemonsoons, this fact, and resorting again to the graphic method for illustration, we may ascertain, with considerable accuracy,
not only the relative strength of the northeast and southwest monsoons of the sea, but also the mean height of the barometer in the
interior of India during the southwest monsoon, supposing that
monsoon to go no farther than the mountain range, which may be
taken at a mean to be about the parallel of 30~ north. Now, tak



~ 691.                   MONSOONS.                       369
DIAGRAM C.
220 200~.5    O1~       50     O
ing the mean  eight of the barometer at the eatorial calm belt
to be (~ 862) 29.92 inches; the mean height in the calm belt
20   50 (~~           150    200 h  m -l
of Cancer to be 30.21 inches, the, line N.E. of the Diagram 
will represent the average barometric declivity of the northeast
DIAGRAM D.
00     5~    100    15,~   20~   25,~   20~
AA




370        THE PHYSICAL GEOGRAPHY OF THE SEA.
monsoons generally. The mean height of the barometer during
the three months of June, July, and August, when the southwest
monsoons are at their height, is,;For Calcutta....................................... 29.55 inches.
" Bombay.......................................29.65
" Madras......2................ 29.73 "
The line S.W. represents the mean barometric declivity of the
southwest monsoons at their height, and indicates that at their
northern edge, supposed to be the parallel of 30~ north, the barometer stands at about 29.45 inches.  This barometric declivity
indicates that the southwest are stronger than the northeast monsoons, and observation shows that they are.*
692. These are the winds-the southwest monsoons-which,
Thesummerrainsof coming from the sea, carry into the interior rains
Cherraponjie.    for the great water-shed of India.  They bear with
them  an immense volume of vapor, as is shown by the rivers,
and confirmed by the rain-fall of Cherraponjie, and at 126 other
stations. Cherraponjie is 4500 feet above the sea level. It reaches quite up to the cloud region, and receives a precipitation of
5371 inches during the southwest monsoon, from May to August inclusive.  Col. Sykes reported to the British Association,
at its meeting in 1852, the rain-fall at these 127 places, which are
between the parallels of 200 and 340 in India.  According to this
report, the southwest monsoons pour down during the three summer months upon this water-shed 29k inches of rain.  The latent
heat that is liberated during the condensation of the vapor for all
this rain expands the air, causing it to boil over, flow of, and leave
a low barometer —a diminished atmospheric pressure throughout
all the region south of the Himalaya.
693. As long ago as 1831, Dove maintained that the southwest
Dov6 and the mon- monsoon was the southeast trade-wind rushing forsoons.       ward to fill the vacant places over the northern
deserts. Dove admits the proofs of this to be indirect, and acknowledges the difficulty of finding out and demonstrating the
problem.
694. But any navigator who, during the summer months, has
The southeast trades occasion to traverse the Indian Ocean from north
passing into southwest
monsoons.     to south, may find that it is so. The outward* Dr. Buist.




~ 695-697.                MONSOONS.                          371
bound Indiaman, who, when on his way to Calcutta, crosses the
equator in August, for example, will find the southeast trades, as
he approaches the line, to haul more and more to the south. As
he advances still farther north they get to the west of south.  Finally, he discovers that he has got the regular southwest monsoons, and that he has passed from the southeast trades into them
without any intervening calm.  This in summer is the rule; it
has its exceptions, but they are rare. Examining the logs of a
number of vessels taken at random for the passage in August, we
find, by 421 observations therein recorded, they had the wind
thus:
Southeast from 100 to 50 south..................... 0 calms.
South    "   5~ south to equator...............3    "
Southwest " equator to 50 north................3  "
Southwest " 5~ to 100 north....................0  "
695. In like manner, and with like force, Jansen maintains that
LieutenantJansen. the northwest monsoon of Australia is the northeast trade-wind turned aside.
696. The influence exerted upon the winds by the deserts of
Monsoonsin the Pa- Africa and the overheated plains of Asia is felt at
tific.       sea for a thousand miles or more.  Thus, though
the desert of Cobi and the sun-burned plains of Asia are, for the
most part, north of latitude 30~, their influence in causing monsoons (~ 692) is felt south of the equator (Plate VIII.). So, too,
with the great desert of Sahara and the African monsoons of the
Atlantic; also with the Salt Lake country and the Mexican
monsoons on one side, and those of Central America in the Pacific on the other.  The influence (~ 298) of the deserts of Arabia
upon the winds is felt in Austria and other parts of Europe, as
the observations of Kriel, Lamont, and others show.  So, also, do
the islands, such as the Society and Sandwich, that stand far
away from any extent of land, have a very singular but marked
effect upon the wind.  They interfere with the trades very often,
and turn them back; for westerly and equatorial winds are common at both these groups in their winter time. Some hydrographers have even taken those westerly winds of the Society Islands to be an extension of the monsoons of the Indian Ocean.
697. It is a curious thing is this influence of islands in the
trade-wind region upon the winds in the Pacific.  Every naviga



372       THE PHYSICAL GEOGRAPHY OF THE SEA.
Influence of coral tor who has cruised in those parts of that ocean has
reefs upon winds often turned with wonder and delight to admire
the gorgeous piles of cumuli, heaped up and arranged in the most
delicate and exquisitely beautiful masses that it is possible for
fleecy matter to assume. Not only are these cloud-piles found capping the hills among the islands, but they are often seen to overhang the lowest islet of the tropics, and even to stand above coral
patches and hidden reefs, " a cloud by day," to serve as a beacon
to the lonely mariner out there at sea, and to warn him of shoals
and dangers which no lead or seaman's eye has ever seen or
sounded out. These clouds, under favorable circumstances, may
be seen gathering above the low coral island, and performing
their office in preparing it for vegetation and fruitfulness in a
very striking manner. As they are condensed into showers, one
fancies that they are a sponge of the most delicately elaborated
material, and that he can see, as they " drop down their fatness,"
the invisible but bountiful hand aloft that is pressing it out.MAURY'S Sacling -Directions, 7th ed., p. 820.
698. Land and sea breezes are monsoons in miniature, for they
Monsoons in minia- depend in a measure upon the same cause. In the
ture.       monsoons, the latent heat of vapor which is set
free over the land is a powerful agent. In the land and sea
breezes, the heat of the sun by day and the radiation of caloric by
night are alone concerned. In the monsoons the heat of summer
and cold of winter are also concerned. But could the experiment
be made with two barometers properly placed-one at sea and
the other on land, but both within the reach of land and sea
breezes —they would show regular alternations. In the sea
breeze the land barometer would be low and the sea high, and
vice versa in the land breeze; and when the barometer was highest and when it was lowest it would be calm.
699. It is these calm bands or " medial belts," as the crest and
The changing of the trough of the barometric wave may be called,
monsoons,   which, with their canopy of clouds, follow the departing and herald the coming monsoon. They move to and fro,
up and down the earth, like the sun in declination.  As they
have a breadth of 200 or 300 miles, they occupy several days in
passing any given parallel, and while they overshadow it, then
the monsoons are dethroned.  During the interregnum, which




~ 700, 701.             MONSOONS.                       373
lasts a week or two, the fiends of the storm hold their terrific
sway in these bands. The changing of the monsoons is marked
by storm  and tempest. Becalmed in them, moanings are said
by seamen to be heard in the air-a sign of the coming storma warning of impending danger to ship and crew. Then the
props and stays are taken away from the air, and the wind seems
ready to rush violently hither and thither, and whenever there is
from any cause a momentary disturbance oaf the equilibrium. In
such an atmosphere, the latent heat that is liberated by every
heavy rain-shower has power to brew a storm. Throughout the
monsoon region, the people know beforehand, almost to a day,
the coming of this interregnum, which they call the changing of
the monsoons, for the annual changing at the same place is very
regular.
700. Theory, therefore, points to a place in Northern India,
How the calm belt of which is near the northern limits of the southwest
Cancer is pushed to
the north.   monsoon, where the mean height of the barometer
during the rainy season (~ 691) is about 29.5 inches, the mean
height at the equator being 29.92 inches. Into this monsoon place
of low barometer over the land the wind rushes from the northeast as well as the southwest. The place of high pressure toward
the north from which it rushes is under the calm belt of Cancer.
Hence this belt is also pushed north, and made to occupy, in summer at least, the position over land somewhat like that assigned
to it on Plate VIII. In the southwest monsoon the Malabar
coast has its rainy season, so that the air over the peninsula is
permanently kept more or less in a rarefied state, as actual observations abundantly show.
701. The equatorial calm belt in the Indian Ocean is a deThe cnrved form of cided curve. The peculiar form may be ascribed
the eqnatorial calm to the meteorological influence of the Indian penbelt in the Indian                                     1'
-Ocean.     insula upon the calm belt, and in this way: The
northeast monsoon brings the rainy season to the Coromandel
coast and to the east coast of Ceylon. This rainy season embraces the land rather than the sea. The latent heat that is liberated during these rains, together with the effect of the solar ray
upon this tongue of land, has the effect of expanding the air over
it, and so deadening the northeast monsoon. In the mean time,
the meteorological influences from Africa on one side, and Aus



374       THE PHYSICAL GEOGRAPHY OF THE SEA.
tralia on the other, tend to draw the wind in toward the land,
and so retard the edges of the southeast trades, thus giving the
calm belt the curved form shown in the plate.
702. In the winter time, and during the northeast monsoon,
The winter mon- there is in the calm belt which intervenes between
soons.      that monsoon and the southeast trades a belt of
winter or westerly monsoons. It, too, is curved, as shown (Plate
VIII.) by the two lines drawn to represent its mean limits about
the 1st of March. This is a most remarkable phenomenon, for
which no satisfactory explanation has been suggested. It extends nearly, if not entirely, across the Pacific Ocean also, and the
winds all the way prevail from the westward. The extreme
breadth of this winter monsoon belt is about 9~ or 10~ of latitude.
In the Indian Ocean, its middle is between the equator and 5~
S.; in the Pacific, between the equator and 50 N.; in the Atlantic, between 5~ and 100 N. In the Atlantic it is a summer monsoon easily to be accounted for. This belt of sub-monsoons,
considering its great length and small breadth, is one of the most
remarkable phenomena in marine meteorology.
703. The northwest monsoons of Australia come from this belt;
The monsoons of there it is widened, for these winds extend far down
Australasia.    the west'coast of that continent. The Malayan and
Australasian archipelago have a complication of monsoons and
sub-monsoons. The land and sea breezes impart to them peculiar
features in many places, especially about the changing of the monsoons, as described by Jansen in his appendix to the Dutch edition
of this work: " We have-seen," says he, " that the calms which precede the sea-breeze generally continue longer, and are accompanied
with an upward motion of the' air; that, on the contrary, those
which precede the land-breeze are, in the Java Sea, generally of
shorter duration, accompanied by a heavy atmosphere, and that
there is also an evident difference between the conversion of the
land-breeze into the sea-breeze, and of the latter into the former.
Even as the calms vary, so there appears to be a marked difference between the changing of the monsoons in the spring and in
the autumn in the Java Sea. As soon as the sun has crossed the
equator, and its vertical rays begin to play more and more perpendicularly upon the northern hemisphere, the inland plains of
Asia, North Africa, and of North America are so heated as to




~ 70T.                  MONSOONS.                        375
give birth to the southwest monsoons in the China Sea, in the
North Indian Ocean, in the North Atlantic, and upon the west
coast of Central America: then the northwest monsoon disappears from the East Indian Archipelago, and gives place to the
southeast trade-wind, which is known as the east monsoon, just as
the northwest wind, which prevails during the southern summer,
is called the west monsoon. This is the only northwest monsoon
which is found in the southern hemisphere. While in the northern hemisphere the northeast trade-wind blows in the China Sea
and in the Indian Ocean, in the East Indian Archipelago the west
monsoon prevails; and when here the southeast trade blows as
the east monsoon, we find the southwest monsoon in the adjacent
seas of the northern hemisphere.  Generally the westerly monsoons blow during the summer months of the hemisphere wherein they are found.
704.' "In the Java Sea, during the month of February, the
Thunder andlight- west monsoon blows strong almost continually;
ning.        in March it blows intermittingly, and with hard
squalls; but in April the squalls become less frequent and less
severe. Now the changing commences; all at once gusts begin
to spring up from the east: they are often followed by calms.
The clouds which crowd themselves upon the clear sky give
warning of the combat in the upper air which the currents there
are about to wage with each other. The electricity, driven thereby out of its natural channels, in which, unobserved, it has been
performing silently, but with the full consciousness of its power,
the mysterious task appointed to it, now displays itself with dazzling majesty; its sheen and its voice fill with astonishment and
deep reverence the mind of the sailor-so susceptible, in the
presence of storm and darkness, to impressions that inspire feelings both of dread and anxiety, which by pretended occupations
he strives in vain to conceal.*  Day and night we now have
thunder-storms.  The clouds are in continual movement, and the
darkened air, laden with vapor, flies in all directions through the
skies.  The combat which the clouds seem to court and to dread
appears to make them more thirsty than ever. They resort to
extraordinary means to refresh themselves; in tunnel form, when
* No phenomena in nature make a deeper impression upon the sailor than a dark
thunder-storm in a calmn at sea.-JANSEN.




376         THE PHYSICAL GEOGRAPHY OF THE SEA.
time and opportunity fail to allow them to quench their thirst
from the surrounding atmosphere in the usual manner, they descend near the surface of the sea, and appear to lap the water directly up with their black mouths.  Water-spouts thus created
are often seen in the changing season, especially among small
groups of islands, which appear to facilitate their formation.*
The water-spouts are not always accompanied by strong winds;
frequently more than one is seen at a time, whereupon the clouds
whence they proceed disperse in various directions, and the ends
of the water-spouts bending over finally causes them to break in
the middle, although the water which is now seen foaming around
their base has suffered little or no movement laterally.
705. "Yet often the wind prevents the formation of waterWater-spouts.  spouts.  In their stead the wind-spout shoots up
like an arrow, and the sea seems to try in vain to keep it back.
The sea, lashed into fury, marks with foam the path along which
the conflict rages, and roars with the noise of its water-spouts;
and woe to the rash mariner who ventures therein It  The height
of the spouts is usually somewhat less than 200 yards, and their
diameter not more than 20 feet, yet they are often taller and
thicker; when the opportunity of correctly measuring them has
been favorable, however, as it generally was when they passed
between the islands, so that the distance of their bases could be
accurately determined, I have never found them higher than 700
yards, nor thicker than 50 yards. In October, in the Archipelago of Rio, they travel from northwest to southeast. They seldom
last longer than five minutes; generally they are dissipated in
less time. As they are going away, the bulbous tube, which is as
palpable as that of a thermometer, becomes broader at the base,
and little clouds, like steam  from  the pipe of a locomotive, are
continually thrown off from the circumference of the spout, and
* I never saw more water-spouts than in the Archipelago of Bioun Singen during the changing. Almost daily we saw one or more. —JANSEN.
t The air-spouts near the equator always appear to me to be more dangerous than
the water-spouts. I have once had one of the latter to pass a ship's length ahead of
me, but I perceived little else than a waterfall in which I thought to come, yet no
wind. Yet the water-spouts there also are not to be trusted. I have seen such
spouts go up out of the water upon the shore, where they overthrew strong isolated
frame houses. I have, however, never been in a situation to observe in what direction they revolved.-JNsme-N




~ 706.                         MONSOONS.                                377
gradually the water is released, and the cloud whence the spout
came again closes its mouth.*
706. "6 During the changing of the monsoons, it is mostly calm
The east monsoon in or cool, with gentle breezes, varied with rain-storms
the Java Sea.   and light gales from  all points  of the compass.
They are harassing to the crew, who, with burning faces under
the clouded skies,t impatiently trim  the sails to the changing
winds.  However, the atmosphere generally becomes clear, and,
contrary to expectation, the northeast wind comes from  a clear
sky; about the coming of the monsoon it is northerly. Now the
* Miniature water-spouts may be produced artificially by means of electricity, and
those in nature are supposed to be caused by the display of electrical phenomena.
"'From the conductor of an electrical machine," says Dr. Bonzano, of New Orleans,
"suspend by a wire or chain a small metallic ball (one of wood covered with tinfoil), and under the ball place a rather wide metallic basin containing some oil of
turpentine, at the distance of about three quarters of an inch. If the handle of the
machine be now turned slowly, the liquid in the basin will begin to move in different
directions, and form whirlpools. As the electricity on the conductor accumulates,
the troubled liquid will elevate itself in the centre, and at last become attached to
the ball. Draw off the electricity from the conductor to let the liquid resume its position: a portion of the turpentine remains attached to the ball. Turn the handle
again very slowly, and observe now the few drops adhering to the ball assume a conical shape, with the apex downward, while the liquid under it assumes also a conical
shape, the apex upward, until both meet. As the liquid does not accumulate on the
ball, there must necessarily be as great a current downward as upward, giving the
column of liquid a rapid circular motion, which continues until the electricity from
the conductor is nearly all discharged, silently, or until it is discharged by a spark
descending into the liquid. The same phenomena take place with oil or water.
Using the latter liquid, the ball must be brought much nearer, or a much greater
quantity of electricity is necessary to raise it.
" If, in this experiment, we let the ball swing to and fro, the little water-spout will
travel over its miniature sea, carrying its whirlpools along with it. When it breaks
up, a portion of the liquid, and with it any thing it may contain, remains attached
to the ball. The fish, seeds, leaves, etc., etc., that have fallen to the earth in rainsqualls, may have owed their elevation to the clouds to the same cause that attaches
a few drops of the liquid, with its particles of impurities, to the ball."
[By reference to Plate XIII., we see that the phenomenon of thunder and lightning
is of much more frequent occurrence in the. North than in the South Atlantic; and
Iinafer that we have more electrical phenomena in the northern than in the southern
hemisphere.  Do water-spouts occur on one side of the equator more frequently than
they do on the other? I have cruised a great deal on the southern hemisphere, and
never saw a water-spout there. According to the log-books at the Observatory, they
occur mostly on the north side of the equator.-M.
t At sea the face and hands burn (change the skin) much quicker under a clouded than under a clear sky.-JANSEN.




378         THE PHYSICAL GEOGRAPHY OF THE SEA.
clouds are again packed together; the wind dies away, but it will
soon be waked up to come again from another point. Finally,
the regular land and sea breezes gradually replace rain, and tempests, calms, and gentle gales.  The rain holds up during the
day, and in the Java Sea we have the east monsoon.  It is then
May. Farther to the south than the Java Sea the east monsoon
commences in April.*  This monsoon prevails till September or
October, when it turns to become the west monsoon.  It has
seemed to me that the east monsoon does not blow  the same in
every month, that its direction becomes more southerly, and its
power greater after it has prevailed for some time.t
707. "It is sufficiently important to fix the attention, seeing
currents.   that these circumstances have great influence upon
the winds in the many straits of the Archipelago, in which strong
currents run most of the time. Especially in the straits to the
east of Java these currents are very strong.  I have been unable
to stern the current with eight-mile speed.  However, they do not
always flow  equally strong, nor always in the same direction.
They are probably the strongest when the tidal current and the
equatorial current meet together.  It is said that the currents in
the straits during the east monsoon run eighteen hours to the
north and six hours to the south, and the reverse during the west
monsoon.  The passing of the meridian by the moon appears to
be the fixed point of time for the turning of the currents. It is
probable that the heated water of the Archipelago is discharged
to the north during the. east monsoon, and to the south during the
west monsoon.
708. "As the sea makes the coming of the southern summer
Marking thleseasons. known to the inhabitants of the Java coast,4 the
* In the northeast part of the Archipelago the east monsoon is the rainy monsoon.
The phenomena in the northeast part are thus wholly different from those in the Java
Sea.-JANSEN.
j As is well known, the Strait of Soerabaya forms an elbow whose easterly outlet
opens to the east, while the westerly outlet opens to the north. In the beginning of
the east monsoon the sea-wind (east monsoon) blows through the westerly entrance
as far as Grissee (in the elbow); in the latter part of this monsoon, the sea-wind
blows, on the contrary, through the easterly entrance as far as Sambilangan (the narrow passage where the westerly outlet opens into the sea).-JANSEN.
I In the Archipelago we have generally high water but once a day, and, with the
equinoxes, the tides also turn. The places which have high water by day in one
nmonsoon get it at night in the other.-JANSEN.




~ 709-711.               MONSOONS.                       379
turning of the east monsoon into the west monsoon commences.
After the sun has finished its yearly task in the northern hemisphere, and brings its powerful influence to operate in the southern
hemisphere, a change is at once perceived in the constant fine
weather of the east monsoon of the Java Sea. As soon as it is at
its height upon the Java Sea (6~ south), then the true turning of
the monsoon begins, and is accomplished much more rapidly than
the spring turning. The calms then are not so continuous.  The
combat in the upper atmosphere appears to be less violent; the
southeast trade, which has blown as the east monsoon, does not
seem  to have sufficient strength to resist the aggressors, who,
with wild storms from the northwest and west, make their superiority known. Upon and in the neighborhood of the land, thunder-storms occur, but at sea they are less frequent.
709. "The atmosphere, alternately clear and cloudy, moves
Conflicts in the air. more definitely over from the northwest, so that it
appears as if no combat was there waged, and the southeast gives
place without a contest. The land-breezes become less frequent,
and the phenomena by day and night become, in a certain sense,
more accordant with each other.  Storms of wind and rain beneath a clouded sky alternate with severe gales and steady winds.
In the last of November the west monsoon is permanent.
710. "Such are the shiftings.  But what have they to do with
Passing of the calm the general system of the circulation of the atmosbelts.       phere?  Whenever we read attentively the beautiful meditations of the founder of the Meteorology of the Sea, and
follow him in the development of his hypothesis, which lays open
to view the wheels whereby the atmosphere performs its varied
and comprehensive task with order and regularity, then it will
not be necessary to furnish proof that these turnings are nothing
else than the passing of a belt of calms which separates the monsoons from each other, and which, as we know, goes annually with
the sun from the south to the north, and back over the torrid
zone to and fro.
711. " So also the calms, which precede the land and sea winds,
Where they are, there are turned back. If, at the coming of the landthe changing of the
monsoonsisgoingon. wind in the hills, we go with it to the coast-to
the sea, we shall perceive that it shoves away the calms which
preceded it from the hills to the coast, and so far upon the sea as




380           THE PHYSICAL GEOGRAPHY OF THE SEA.
the land-wind extends. Here, upon the limits of the permanent
monsoon, the place for the calms remains for the night, to be
turned back to the land and to the hills the following day by the
sea-wind. In every place where these calms go, the land and sea
winds turn back. If various observers, placed between the hills
and the sea, and between the coast and the farthest limit of the
land-wind, noted the moment when they perceived the calms, and
that when they perceived the land-wind, then by this means they
would learn how broad the belt of calms has been, and with what
rapidity they are pushed over the sea and over the land. And
even though the results one day should be found not to agree very
well with those of another, they would at least obtain an average
thereof which would be of value. So, on a larger scale, the belt
of calms which separates the monsoons from each other presses
in the spring from the south to the north, and in the fall from the
north to the south, and changes the monsoons in every place
where it presses.'"
* Bijdrage Natuurkiindige Beschrijving der zeen, vertaald door M. H. Jansen, Luitenant ter zee.




~ 720.          THE CLIMATES OF THE SEA,              381
CHAPTER XVII.
~ 720-735.-THE CLIMATES OF THE SEA.
720. THERMAL charts, showing the temperature of the surface
A I"milky way"' in the of the Atlantic Ocean by actual observations made
ocean,       indiscriminately all over it, and at all times of the
year, have been published by the National Observatory. The isothermal lines which these charts enable us to draw, and a few of
which are traced on Plate IV., afford the navigator and the philosopher much valuable and interesting information touching the circulation of the oceanic waters, including the phenomena of their
cold and warm currents; these lines disclose a thermal tide in the
sea, which ebbs and flows but once a year; they also cast light
upon the climatology of the sea, its hyetographic peculiarities, and
the climatic conditions of various regions of the earth; they show
that the profile of the coast-line of intertropical America assists
to give expression to the mild climate of Southern Europe; they
also increase our knowledge concerning the Gulf Stream, for they
enable us to mark out, for the mariner's guidance, that "milky
way" in the ocean, the waters of which teem, and sparkle, and
glow with life and incipient organisms as they flow across the Atlantic. In them are found the clusters and nebulas of the sea
which stud and deck the great highway of ships on their voyage
between the Old World and the New; and these lines assist to
point out for the navigator their limits and his way. They show
this via lactea to have a vibratory motion in the sea that calls to
mind the graceful wavings of a pennon as it floats gently to the
breeze. Indeed, if we imagine the head of the Gulf Stream to be
hemmed in by the land in the Straits of Bemini, and to be stationary there, and then liken the tail of the Stream itself to an immense pennon floating gently in the current, such a motion as such
a streamer may be imagined to have, very much such a motion,
do my researches show the tail of the Gulf Stream to have. Running between banks of cold water (~ 71), it is pressed now from
the north, now from the south, according as the great masses of sea
water on either hand may change or fluctuate in temperature.




382       THE PHYSICAL GEOGRAPHY OF THE SEA.
721. In September, when the waters in the cold regions of the
The vibrations of the north have been tempered, and been made warm
Gulf Stream.  and light by the heat of summer, its limits on the
left are as denoted by the line of arrows (Plate VI.); but after
this great sun-swing, the waters on the left side begin to lose their
heat, grow cold, become heavy, and press the hot waters of this
stream into the channel marked out for them. Thus it acts like
a pendulum, slowly propelled by heat on one side and repelled by
cold on the other. In this view, it becomes a chronograph for the
sea, keeping time for its inhabitants, and marking the seasons for
the great whales; and there it has been for all time vibrating to
and fro, once every year, swinging from north to south, and from
south to north again, a great self-regulating, self-compensating
liquid pendulum.
722. In seeking information concerning the climates of the
Sea and land climates ocean, it is well not to forget this remarkable concontrasted.   trast between its climatology and that of the land,
namely: on the land February and August are considered the
coldest and the hottest months; but to the inhabitants of the sea,
the annual extremes of cold and heat occur in the months of March
and September.  On the dry land, after the winter "is past and
gone," the solid parts of the earth continue to receive from the
sun more heat in the day than they radiate at night, consequently
there is an accumulation of caloric, which continues to increase
until August. The summer is now at its height; for, with the
close of this month, the solid parts of the earth's crust and the atmosphere above begin to dispense with their heat faster than the
rays of the sun can impart fresh supplies, and, consequently, the
climates which they regulate grow cooler and cooler until the
dead of winter again. But at sea a different rule'seems to prevail.
Its waters are the store-houses' in which the surplus heat of summer is stored away against the severity of winter, and its waters
continue to grow warmer for a month after the weather on shore
has begun to get cool. This brings the highest temperature to
the sea in September, the lowest in March. Plate IV. is intended
to show the extremes of heat and cold to which the waters  not
the ice-of the sea are annually subjected, and therefore the isotherms of 40~, 500, 600, 70~, and 80~ have been drawn for March
* Vide Chap. XXII., Actinometry of the Sea.




~ 722.             THE CLIMATES OF THE SEA.                        383
PLATE IV.
515 S    715  vlu ~  emo BIs 1  415  I    i.o 2,15   20o 4 5-o, 10  1,5........ ~                                                ____  c~    __. ____ ___._.., —~-r~~q....        ilM ~D E~i
II~~,~__ _!         _...  HI jt'.lJ L_ _
_____       NAZOECS.           __ IS i-I
L~#iffr~  iQi                          A    _
~~. —I ~-f —-— %,,,,,  
[Azorei  T
109~~~~~~~
aq-                                              - El
F   l                   );_:,                     ___________
~   -~'~ -/....         -....''  — s'
1?lula'~: _!  t(11i1,  II  lrotl0r_____________.
iI~~~~~~~~~~~~~~~~~~~~~~~~~i~~~~~~~ —-F-,,~~; —-~ —- ---- - -i —l
OF THEI!:~
AT~LANTIC OCEA
I   I                  J~~~~on nzsncMARH AND SEPrTEMBER..
CAiell                                         Mar Janech.
rOB September.
710 6j5 610 515i~-5ATLANTIC OCEAN




384       THE PHYSICAL GEOGRAPHY OF THE SEA.
and September, the months of extreme heat and extreme cold to
the inhabitants of the "great deep."  Corresponding isotherms
for any other month will fall between these, taken by pairs.
Thus the isotherm of 70~ for July will fall nearly midway between the same isotherms (70~) for March and September.
723. A careful study of this plate, and the contemplation of
Plate IV.  the benign influence of the sea upon the climates
which we enjoy, suggest many beautiful thoughts; for by such
study we get a glimpse into the arrangements and the details of
that exquisite machinery in the ocean which enables it to perform
all its offices, and to answer with fidelity its marvelous adaptations. How, let us inquire, does the isothermal of 80~, for instance,
get from its position in March to its position in September?  Is
it wafted along by currents, that is, by water which, after having
been heated near the equator to 800, then flows to the north with
this temperature? Or is it carried there simply by the rays of
the sun, as the snow-line is carried up the mountain in summer?
WVe have reason to believe that it is carried from one parallel to
another by each of these agents acting together, but mostly
through the instrumentality of currents, for currents are the chief
agents for distributing heat to the various parts of the ocean.
The sun with his rays would, were it not for currents, raise the
water in the torrid zone to blood heat; but before that can be
done, they run off with it toward the poles, softening, and mitigating, and tempering climates by the way. The provision for
this is as beautiful as it is benign; for, to answer a physical adaptation, it is provided by a law of nature that when the temperature of water is raised, it shall expand; as it expands, it must become lighter, and just in proportion as its specific gravity is altered, just in that proportion is equilibrium in the sea destroyed.
Arrived at this condition, it is ordained that this hot water shall
obey another law of nature, which requires it to run away, and
hasten to restore that equilibrium. Were these isothermal lines
moved only by the rays of the sun, they would slide up and down
the ocean like so many parallels of latitude-at least there would
be no break in them, like that which we see in the isotherm of
80~ for September. It appears from this line that there is a part
of the ocean near the equator, arid about midway the Atlantic,
which, with its waters, never does attain the temperature of 80~




~ 723.           THE CLIMATES OF THE SEA.               385
in September. Moreover, this isotherm of 80~ will pass, in the
North Atlantic, from its extreme southern to its extreme northern
declination-nearly two thousand miles-in about three months.
Thus it travels at the rate of about twenty-two miles a day. Surely, without the aid of currents, the rays of the sun could not drive
it along that fast. Being now left to the gradual process of cooling by evaporation, atmospherical contact, and radiation, it occupies the other eight or nine months of the year in slowly returning south to the parallel whence it commenced to flow northward.
As it does not cool as rapidly as it was heated, the disturbance of
equilibrium by alteration of specific gravity is not so sudden, nor
the current which is required to restore it so rapid. Hence the
slow rate of movement at which this line travels on its march
south. Between the meridians of 25~ and 30~ west, the isotherm
of 60~ in September ascends as high as the parallel of 56~ N.
In October it reaches the parallel of 50~ north. In November
it is found between the parallels of 45~ and 47~, and by December it has nearly reached its extreme.southern descent between
these meridians, which it accomplishes in January, standing then
near the parallel of 40~. It is all the rest of the year in returning northward to the parallel whence it commenced its flow
to the south in September. Now it will be observed that this is
the season-from September to December-immediately succeeding that in which the heat of the sun has been playing with greatest activity upon the polar ice. Its melted waters, which are thus
put in motion in June July, and August, would probably occupy
the fall months in reacaing the parallels indicated. These waters,
though cold, and rising gradually in temperature as they flow
south, are probably fresher, and if so, probably lighter than the
sea water; and therefore it may well be that both the warmer
and cooler systems of these isothermal lines are made to vibrate
up and down the ocean principally by a gentle surface current in
the season of quick motion, and in the season of the slow motion
principally by a gradual process of calorific absorption on the one
hand, and by a gradual process of cooling on the other. We
have precisely such phenomena exhibited by the waters of the
Chesapeake Bay as they spread themselves over the sea in winter. At this season of the year, the charts show that water of
very low temperature is found projecting out and overlapping the
BB




386       THE PHYSICAL GEOGRAPHY OF THE SEA.
usual limits of the Gulf Stream. The outer edge of this cold water, though jagged, is circular in its shape, having its centre near
the mouth of the bay. The waters of the bay, being fresher than
those of the sea, are therefore, though colder, yet lighter (~ 426)
than the warmer waters of the ocean. And thus we have repeated
here, though on a smaller scale, the phenomenon as to the flow
of cold waters from the north, which force the surface isotherm
of 60~ from latitude 56~ to 40~ during three or four months.
Changes in the color or depth of the water, and the shape of the
bottom, etc., would also cause changes in the temperature.of certain parts of the ocean, by increasing or diminishing the capacities of such parts to absorb or radiate heat; and this, to some extent, would cause a bending, or produce irregular curves in the
isothermal lines. After a careful study of this plate, and the
Thermal Charts of the Atlantic Ocean, from which the materials
for the former were derived, I am led to infer that the mean temperature of the atmosphere between the parallels of 56~ and 40~
north, for instance, and over that part of the ocean in which we
have been considering the fluctuations of the isothermal line of
60~, is at least 60~ of Fahrenheit, and upward, from January to
August, and that the heat which the waters of the ocean derive
from this source-atmospherical contact and radiation-is one of
the causes which move the isotherm of 60~ from its January to
its September parallel. It is well to consider another of the
causes which are at work upon the currents in this part of the
ocean, and which tend to give the rapid southwardly motion to
the isotherm of 60~. We know the mean *dew-point must always
be below the mean temperature of any given place, and that, consequently, as a general rule, at sea the mean dew-point due the
isotherm of 60~ is higher than the mean dew-point along the isotherm of 50~, and this, again, higher than that of 40-~, this than
30~, and so on. Now suppose, merely for the sake of illustration,
that the mean dew-point for each isotherm be 5~ lower than the
mean temperature, we should then have the atmosphere which
crosses the isotherm of 60~, with a mean dew-point of 55~, gradually precipitating its vapors until it reaches the isotherm of 50~,
with a mean dew-point of 45~; by which difference of dew-point
the total amount of precipitation over the entire zone between
the isotherms of 60~ and 50~ has exceeded the total amount of




~ 724.          THE CLIMATES OF THE SEA.                 387
evaporation from the same surface. The prevailing direction of
the winds to the north of the fortieth parallel of north latitude is
from the southward and westward (Plate VIII.); in other words,
it is from the higher to the lower isotherms. Passing, therefore,
from a higher to a lower temperature over the ocean, the total
amount of vapor deposited by any given volume of atmosphere,
as it is blown from the vicinity of the tropical toward that of the
polar regions, is greater than that which is taken up again. The
area comprehended on Plate VIII. between the isotherms of 40~
and 50~ Fahrenheit is less than the area comprehended between
the isotherms 50~ and 60~, and this, again, less than the area between this last and 700, for the same reason that the area between
the parallels of latitude 50~ and 60~ is less than the area between
the parallels of latitude 40~ and 50~; therefore, more rain to the
square inch ought to fall upon the ocean between the colder isotherms of 10~ difference, than between the warmer isotherms of
the same difference. This is an interesting and an important
view, therefore let me make myself clear. The aqueous isotherm
of 50~,' in its extreme northern reach, touches the parallel of 60~
north. Now between this and the equator there are but three
isotherms, 60~, 70~, and 80~, with the common difference of 10~.
But between the isotherm of 400 and the pole there are at least
five others, viz., 400, 300, 200, 100, 00, with a common difference
of 10~. Thus, to the north of the isotherm 50~, the vapor which
would saturate the atmosphere from zero, and perhaps far below,
to near 40~, is deposited, while to the south of 50~ the vapor
which would saturate it from the temperature of 50~ up to that
of 80~ can only be deposited. At least, such would be the case
if there were no irregularities of heated plains, mountain ranges,
land, etc., to disturb the laws of atmospherical circulation as they
apply to the ocean.
724. Having therefore, theoretically, at sea more rain in high
The effects of night latitudes, we should have more clouds; and theretend day urPon the fore it would require a longer time for the sun,
water.       with his feeble rays, to raise the temperature of the
cold water which, from September to January, has brought the
isotherm of 60~ from latitude 56~ to 40~, than it did for those cool
surface currents to float it down. After this southward motion
of the isotherm of 60~ has been checked in December by the cold,




388       THE PHYSICAL GEOGRAPHY OF THE SEA.
and after the sources of the current which brought it down have
been bound in fetters of ice, it pauses in the long nights of the
northern winter, and scarcely commences its return till the sun
recrosses the equator, and increases its power as well in intensity
as in duration. Thus, in studying the physical geography of the
sea, we must take cognizance of its actinometry also, for here we
have the effects of night and day, of clouds and sunshine, upon
its currents and its climates, beautifully developed. These effects
are modified by the operations of certain powerful agents which
reside upon the land; nevertheless, feeble though those of the
former class may be, a close study of this plate will indicate that
they surely exist.
725. Now, returning toward the south: we may, on the other
A belt of uniform hand, infer that the mean atmospherical temperatemperature atsea. ture for the parallels between which the isotherm
of 80~ fluctuates is below 80~, at least for the nine months of its
slow motion. This vibratory motion suggests the idea that there
is probably, somewhere between the isotherm of 80~ in August
and the isotherm of 600 in January, a line or belt of invariable or
nearly invariable temperature, which extends on the surface of
the ocean from one side of the Atlantic to the other. This line
or band may have its cycles also, but they are probably of a long
and uncertain period.
726. The fact has been pretty clearly established by the disThe western half of coveries to which the wind and current charts have
the Atlantic warmer
than the eastern. led, that the western half of the Atlantic Ocean is
heated up, not by the Gulf Stream alone, as is generally supposed,
but by the great equatorial caldron to the west of longitude 35~,
and to the north of Cape St. Roque, in Brazil. The lowest reach
of the 80~ isotherm for September-if we except the remarkable
equatorial flexure (Plate IV.) which actually extends from 40~
north to the line-to the west of the meridian of Cape St. Roque,
is above its highest reach to the east of that meridian. And, now
that we have the fact, how obvious, how beautiful, and striking is
the cause! Cape St. Roque is in 5~ 30' south. Now study the
configuration of the Southern American Continent from this cape
to the Windward Islands of the West Indies, and take into account also certain physical conditions of these regions: the Amazon, always at a high temperature because it runs from west to




~ 727.          THE CLIMATES OF THE SEA.                 389
east, is pouring an immense volume of warm water into this part
of the ocean. As this water and the heat of the sun raise the
temperature of the ocean along the equatorial sea-front of this
coast, there is no escape for the liquid element, as it grows warmer and lighter, except to the north. The land on the south prevents the tepid waters from spreading out in that direction as
they do to the east of 350 west, for here there is a space, about
18 degrees of longitude broad, in which the sea is clear both to
the north and south. They must consequently flow north. A
mere inspection of the plate is sufficient to make obvious the fact
that the warm waters which are found east of the usual limits assigned the Gulf Stream, and between the parallels of 30~ and 40~
north, do not come from the Gulf Stream, but from this great
equatorial caldron, which Cape St.Roque blocks up on the south,
and which dispenses its overheated waters up toward the fortieth
degree of north latitude, not through the Caribbean Sea and Gulf
Stream, but over the broad surface of the left bosom of the Atlantic Ocean.
727. Like the western half of the North Atlantic Ocean, the westThe vwarmest sides of ern half of every one of the three great oceans is
oceans and the coldest shores of conti- the warmer. The great flow of warm water in the
nents in juxtaposition.        North Pacific is with the " Black Stream of Japan,"
on the Asiatic side; in the South Pacific it is with the Polynesian
drift, on the Australian side: opposite to these, and on the eastern
side, are the Humboldt current in one hemisphere, and the California current in the other-.cold currents both. In the South Indian
Ocean, the warm water is with the Mozambique current on the African side, and the cold drift on the Australian; and in the South
Atlantic, Plate IV. shows that, parallel for parallel, the littoral waters of Brazil are many degrees warmer than those on the African side. Thus at sea the climatic conditions of the land are reversed, for the coldest side of the ocean is on the warmest side of
the continent, and vice versa. The winds from extra-tropical seas
temper the climates of the shores upon which they blow, not so
much by the sensible heat they convey as by the latent heat which
is liberated from the vapor they bring. This being condensed, as
upon the British Islands and Western Europe, sets free heat enough
not only to soften the climate, but to rarefy the air to such an extent as to be observed in the mean barometric pressure.




390       THE PHYSICAL GEOGRAPHY OF THE SEA.
728. Here we are again tempted to pause and admire the beauThe climates of Eu- tiful revelations which, in the benign system of terthe in shflened bo restrial adaptations, these researches into the physics
Brazil.      of the sea unfold and spread out before us for contemplation. In doing this, we shall have a free pardon from
those at least who delight "to look through nature up to nature's
God."  What two things in nature can be apparently more remote in their physical relations to each other than the climate of
Western Europe and the profile of a coast-line in South America?
Yet this plate reveals to us not only the fact that these relations
between the two are the most intimate, but makes us acquainted
with the arrangements by which such relations are established.
The barrier which the South American shore-line opposes to the
escape, on the south, of the hot waters from this great equatorial
caldron of St. Roque, causes them to flow north, and in September, as the winter approaches, to heat up the western half of the
Atlantic Ocean, and to cover it, as far up as the parallel of 40~ N.,
with a mantle of warmth above summer heat. Here heat to temper the winter climate of Western Europe is stored away as in an
air-chamber to furnace-heated apartments; and during the winter,
when the fire of the solar rays sinks down, the westwardly winds
and eastwardly currents are sent to perform their office in this benign arrangement.  Though unstable and capricious to us they
seem to be, they nevertheless "fulfill His commandments" with
regularity and perform their offices with certainty. In tempering
the climates of Europe with heat in winter that has been bottled
away in the waters of the ocean during summer, these winds and
currents are to be regarded as the flues and regulators for distributing it at the right time, and at the right places, in the right
quantities. By March, when " the winter is past and gone," the
furnace which had been started by the rays of the sun in the previous summer, and which, by autumn, had heated up the ocean
in our hemisphere, has cooled down. The caldron of St. Roque,
ceasing in activity, has failed in its supplies, and the chambers of
warmth upon the northern sea, having been exhausted of their
heated water (which has been expended in the manner already explained), have contracted their limits. The surface of heated water which, in September, was spread out over the western half of
the Atlantic, from the equator to the parallel of 40~ north, and




~ 729.          THE CLIMATES OF THE SEA.                 391
which raised this immense area to the temperature of 80~ and upward, is not to be found in early spring on this side of the parallel of 8~ north. The isotherm of 80~ in March, after quitting the
Caribbean Sea, runs parallel with the South American coast toward Cape St. Roque, keeping some 8 or 10 degrees from it.
Therefore the heat dispensed over Europe from this caldron fails
off in March. But at this season the sun comes forth with fresh
supplies; he then crosses the line and passes over into the northern hemisphere; observations show that the process of heating
the water in this great caldron for the next winter is now about
to commence. In the mean time, so benign is the system of cosmical arrangements, another process of raising the temperature of
Europe commences. The land is more readily impressed than
the sea by the heat of the solar rays; at this season, then, the
summer climate due these transatlantic latitudes is modified by
the action of the sun's rays directly upon the land. The land receives heat from them, but, instead of having the capacity of water for retaining it, it imparts it straightway to the air; and thus
the proper climate, because it is the climate which the Creator
has, for his own wise purposes, allotted to this portion of the earth,
is maintained until the marine caldron of Cape St. Roque and the
tropics is again heated and brought into the state for supplying
the means of maintaining the needful temperature in Europe during the absence of the sun in the other hemisphere. Thus the
equable climates of Western Europe are accounted for.
729. In like manner, the Gulf of Guinea forms a caldron and a
The Gulf of Guinea furnace, and spreads out over the South Atlantic an
and the climate of
Pattgonia.   air-chamber for heating up in winter and assisting
to keep warm the extra-tropical regions of South America. Every
traveler has remarked upon the mild climate of Patagonia and the
Falkland Islands. "Temperature in high southern latitudes," says
a very close observer, who is co-operating with me in collecting
materials, " differs greatly from the temperature in northern. In
southern latitudes there seem to be no extremes of heat and cold,
as at the north. Newport, Rhode Island, for instance, latitude 41~
north, longitude 71~ west, and Rio 1Negro, latitude 41~ south, and
longitude 63~ west, as a comparison: in the former, cattle have to
be stabled and fed during the winter, not being able to get a living
in the fields on account of snow and ice. In the latter, the cattle




392       THE PHYSICAL GEOGRAPHY OF THE SEA.
feed in the fields all winter, there being plenty of vegetation and
no use of hay. On the Falkland Islands (latitude 51-2~ south),
thousands of bullocks, sheep, and horses are running wild over
the country, gathering a living all through the winter."  The
water in the equatorial caldron of Guinea overflows to the south,
as that of St. Roque does to the north; it carries to Patagonia and
the Falkland Islands warmth, which, uniting with the heat set
free by precipitation during the passage of the vapor-laden west
winds across the Southern Andes, carries beyond latitude 50~ in
the other hemisphere the winter climate of South Carolina on one
side of the North Atlantic, or of the " Emerald Island" on the other.
730. All geographers have noticed, and philosophers have freShore-lines.  quently remarked upon the conformity as to the
shore-line profile of equatorial America and equatorial Africa. It
is true, we can not now tell the reason, though. explanations founded upon mere conjecture have been offered, why there should be
this sort of jutting in and jutting out of the shore-line, as at Cape
St. Roque and the Gulf of Guinea, on opposite sides of the Atlantic; but one of the purposes, at least, which this peculiar configuration was intended to subserve, is without doubt now revealed to
us. We see that, by this configuration, two cisterns of hot water
are formed in this ocean, one of which distributes heat and warmth
to western Europe; the other, at the opposite season, tempers the
climate of eastern Patagonia. Phlegmatic must be the mind that
is not impressed with ideas of grandeur and simplicity as it contemplates that exquisite design, those benign and beautiful arrangements, by which the climate of one hemisphere is made to
depend upon the curve of that line against which the sea is made
to dash its waves in the other. Impressed with the perfection of
terrestrial adaptations, he who studies the economy of the great
cosmical arrangements is reminded that not only is there design
in giving shore-lines their profile, the land and the water their
proportions, and in placing the desert and the pool where they
are, but the conviction is forced upon him also that every hill
and valley, with the grass upon its sides, is a part of the wonderful mechanism, each having its offices to perform in the grand design. March is, in the southern hemisphere, the first month of
autumn, as September is with us; consequently, we should expect
to find in the South Atlantic as large an area of water at 80~ and
upward in March, as we should find in the North Atlantic for Sep



~ 731-733.      THE CLIMATES OF THE SEA.                 393
tember. But do we?  By no means. The area that is covered
on this side of the equator with water at 80~ and upward is nearly
double that on the other. Thus we have the sea as a witness to
the fact which the winds had proclaimed, viz., that summer in the
northern hemisphere is hotter than summer in the southern.
731. Pursuing the study of the climates of the sea, let us now
Sudden changes in turn to Plate VI. Here we see at a glance how the
the water thermlometer.        cold waters, as they come down from the Arctic
Ocean through Davis's Straits, press upon the warm waters of the
Gulf Stream, and curve their channel into a horse-shoe. Navigators have often been struck with the great and sudden changes in
the temperature of the water hereabouts. In the course of a single day's sail in this part of the ocean, changes of 15~, or 200, and
even of 30~, have been observed to take place in the temperature
of the sea. The cause has puzzled navigators long, but how obvious is it now made to appear! This "' bend" is the great receptacle of the icebergs which drift down from the north; covering
frequently an area of hundreds of miles in extent, its waters diff-e
as much as 20~, 25~, and in rare cases even as much as 30~ of temperature from those about it. Its shape and place are variable.
Sometimes it is like a peninsula, or tongue of cold water projected
far down into the waters of the Gulf Stream. Sometimes the
meridian upon which it is inserted into these is to the east of 40~,
sometimes to the west of 50~.
732. By its discovery we have clearly unmasked the very seat
The fogs of Newfound- of that agent which produces the Newfoundland
land.         fogs. It is spread out over an area frequently embracing several thousand square miles in extent, covered with
cold water, and surrounded on three sides, at least, with an immense body of warm. May it not be that the proximity to each
other of these two very unequally heated surfaces out upon the
ocean would be attended by atmospherical phenomena not unlike
those of the land and sea breezes?  These warm currents of the
sea are powerful meteorological agents. I have been enabled to
trace in thunder and lightning the influence of the Gulf Stream
in the eastern half of the Atlantic as far up as the parallel of 55~
N., for there, in the dead of winter, a thunder-storm is not unusual.
733. These isothermal lines of 50~, 600~, 700, 80~, etc., may
Aqueous isothermal illustrate for us the manner in which the climates
lines.      in the ocean are regulated. Like the sun in the




394       THE PHYSICAL GEOGRAPHY OF THE SEA.
ecliptic, they travel up and down the sea in declination, and serve
the monsters of the deep for signs and for seasons.
734. It should be borne in mind that the lines of separation, as
The meeting of cool drawn on Plate IX., between the cool and warm
and warm waters.  waters, or, more properly speaking, between the
channels representing the great polar and equatorial flux and reflux, are not so sharp in nature as this plate would represent
them. In the first place, the plate represents the mean or average
limits of these constant flows-polar and equatorial; whereas, with
almost every wind that blows, and at every change of season, the
line of meeting between their waters is shifted. In the next place,
this line of meeting is drawn with a free hand on the plate, as if
to represent an average; whereas there is reason to believe that
this line in nature is variable and unstable as to position, and
as to shape rough and jagged, and oftentimes deeply articulated.
In the sea, the line of meeting between waters of different temperatures and density is not unlike the sutures of the skull-bone
on a grand scale-very rough and jagged; but on the plate it is
a line drawn with a free hand, for the purpose of showing the
general direction and position of the channels in the sea, through
which its great polar and equatorial circulation is carried on.
735. Now, continuing for a moment our examination of Plate
The direction of aque- IV., we are struck with the fact that most of the
onus isotherms on opposite sides of the sea. thermal lines there drawn run from the western
side of the Atlantic toward the eastern, in a northeastwardly direction, and that, as they approach the shores of this ocean on
the east, they again turn down for lower latitudes and warmer
climates. This feature in them indicates, more surely than any
direct observations upon the currents can do, the presence, along
the African shores in the North Atlantic, of a large volume of
cooler waters. These are the waters which, having been first
heated up in the caldron (~ 726) of St. Roque, in the Caribbean
Sea, and Gulf of Mexico, have been made to run to the north,
charged with heat and electricity to temper and regulate climates
there. Having performed their offices, they have cooled down;
but, obedient still to the " Mighty Voice" which the winds and the
waves obey, they now return by this channel along the African
shore to be again replenished with warmth, and to keep up the
system of beneficent and wholesome circulation designed for the
ocean.




~ 740, 741.       TIDE-RIPS AND SEA DRIFT.                 395
CHAPTER XVIII.
~ 740-772.-TIDE-RIPS AND SEA DRIFT.
740. WE never tire of the sea; like the atmosphere, it is a labThe glories ofthe sea. oratory in which the most exquisite processes are
continually going on. Its flora and its fauna, its waves and
its tides, its currents and its salts, all in themselves afford profitable subjects of study and charming themes for thought. [But as
interesting as they are individually, and as marvelous too, they
are not half so marvelous, nor nearly so wonderful, as the offices
which, with their aid, the sea performs in the physical economy
of our planet. In this aspect the sea, with its insects, its salts,
and its vapors, is a machine of the most beautiful construction.
Its powers are vast, multitudinous, and varied. It is so stable
and true in its work that nothing can throw it out of gearing, and
yet its compensations are so delicate that the task of preserving
them is assigned to the tiniest of its inhabitants, and to agents
apparently the most subtle and fickle. They preserve its harmonies and make its adjustments, in beauty and sublimity of effect, to vie with the glories of the heavens.
741. There is a movement of the waters of the ocean which,
Drift described. though it be a translation, yet it does not amount
to what is known to the mariner as " current," for our nautical
instruments and the art of navigation have not been brought to
that state of perfection which will enable navigators generally to
detect as currents the flow to which I allude as drif. If an object
be set afloat in the ocean, as at the equator, it would, in the course
of time, even though it should not be caught up by any of the
known currents, find its way to the icy barriers about the poles,
and again back among the tepid waters of the tropics.  Such an
object would illustrate the drift of the sea, and by its course would
indicate the route which the surface-waters of the sea follow in
their general channels of circulation to and fro between the equator and the poles.




396       THE PHYSICAL GEOGRAPHY OF THE SEA.
742. The object of Plate IX., therefore, is to illustrate, as far as
Plate IX   the present state of my researches enable me to do,
the circulation of the ocean as influenced by heat and cold, and to
indicate, on one hand, the routes by which the overheated waters
of the torrid zone escape to cooler regions, and to point out, on
the other, the great channel-ways through which the same waters,
after having been deprived of this heat in the extra-tropical or
polar regions, return again toward the equator; it being assumed
that the drift or flow is from the poles when the temperature of
the surface water is below, and from the equatorial regions when
it is above that due the latitude. Therefore, in a mere diagram,
as this plate is, the numerous eddies and local currents which are
found at sea are disregarded. Of all the currents in the sea, the
Gulf Stream is the best defined; its limits, especially those of the
left bank, are always well marked, and, as a rule, those of the
right bank, as high as the parallel of the thirty-fifth degree of
latitude, are quite distinct, being often visible to the eye. The
Gulf Stream shifts its channel (~ 124), but nevertheless its banks
are often very distinct. Ships, in crossing the edges of it, can
sometimes know it by the color of the water; at other times they
find, as they pass along, the temperature of the water to change
8~ or 10~ in the course of as many minutes; as an example of
this, I quote from the abstract log of the "Herculean," in which
Captain William M. Chamberlain, being in latitude 33~ 39' north,
longitude 74~ 56' west (about one hundred and thirty miles east
of Cape Fear), remarks: " Moderate breezes, smooth sea, and fine
weather. At ten o'clock fifty minutes, entered into the southern
(right) edge of the Stream, and in eight minutes the water rose
six degrees; the edge of the stream was visible, as far as the eye
could see, by the great rippling and large quantities of Gulf weed
-more'weed' than I ever saw before, and I have been many
times along this route in the last twenty years."  In this diagram,
therefore, I have thought it useless to attempt a delineation of
any of those currents, as the Rennell Current of the North Atlantic, the "connecting current" of the South, "Mentor's Counter
Drift," " Rossel's Drift of the South Pacific," etc., which run now
this way, now that, and which are frequently not felt by navigators at all. In overhauling the log-books for data for this chart,
I have followed vessels with the water thermometer to and fro




~ 742.           TIDE-RIPS AND SEA DRIFT.               397
across the seas, and taken the registrations of it exclusively for
my guide, without regard to the reported set of the currents.
When, in any latitude, the temperature of the water has appeared too high or too low for the latitude, the inference has been
that such water was warmed or cooled, as the case may be, in other latitudes, and that it has been conveyed to the place where
found through the great channels of oceanic circulation. If too
warm, it is supposed that it had its temperature raised in warmer
latitudes, and therefore the channel in which it is found leads
from the equatorial regions. On the other hand, if the water be
too cool for the latitude, then the inference is that it has lost its
heat in colder climates, and therefore is found in channels which
lead from the polar regions. The arrow-heads point to the direction in which the waters are supposed to flow. Their rate, according to the best information that I have obtained, is, at a mean,
only about four knots a day-rather less than more. Accordingly, therefore, as the immense volume of water in the antarctic regions is cooled down, it commences to flow north. As indicated
by the arrow-heads, it strikes against Cape Horn, and is divided
by the continent, one portion going along the west coast as Hum.
boldt's Current (~ 398); the other, entering the South Atlantic,
flows up into the Gulf of Guinea, on the coast of Africa. Now, as
the waters of this polar flow approach the torrid zone, they grow
warmer and warmer, and finally themselves become tropical in
their temperature. They do not then, it may be supposed, stop
their flow; on the contrary, they keep moving, for the very
cause which brought them from the extra-tropical regions now
operates to send them back. This cause is to be found in the difference of the specific gravity at the two places. If, for instance,
these waters, when they commence their flow from the hyperborean regions, were at 30~, their specific gravity will correspond to
that of sea water at 300. But when they arrive in the Gulf of
Guinea or the Bay of Panama, having risen by the way to 80~, or
perhaps 85~, their specific gravity becomes such as is due sea water of this temperature; and, since fluids differing in specific gravity can no more balance each other on the same level than can
unequal weights in the opposite scales of a true balance, this hot
water must now return to restore that equilibrium which it has
destroyed in the sea by rising from 30~ to 80~ or 85~. Hence it




398       THE PHYSICAL GEOGRAPHY OF THE SEA.
will be perceived that these masses of water which are marked as
cold are not always cold. They gradually pass into warm; for
in traveling from the poles to the equator they partake of the
temperature of the latitudes through which they flow, and grow
warm. Plate IX., therefore, is only introduced to give general
ideas; nevertheless, it is very instructive. See how the influx of
cold water into the South Atlantic appears to divide the warm
water, and squeeze it out at the sides, along the coasts of South
Africa and Brazil. So, too, in the North Indian Ocean, the cold
water again compelling the warm to escape along the land at the
sides, as well as occasionally in the middle. In the North Atlantic and North Pacific, on the contrary, the warm water appears to
divide the cold, and to squeeze it out along the land at the sides.
The impression made by the cold current from Baffin's Bay upon
the Gulf Stream is strikingly beautiful.
743. Another feature of the sea expressed by this plate is a sort
The great bend in the of reflection or recast of the shore-line in the temGulfStream.
(Gulf Stream.  perature of the water.  This feature is most striking in the North Pacific and Indian Ocean. The remarkable intrusion of the cool into the volume of warm waters to the southward of the Aleutian Islands is not unlike that which the cool
waters from Davis's Straits make in the Atlantic upon the Gulf
Stream. In sailing through this "horse-shoe," or bend in the
Gulf Stream (~ 731), Captain N. B. Granat, of the American ship
Lady Arbella, bound from Hamburg to New York, in May, 1854,
passed, from daylight to noon, twenty-four large "bergs," besides
several small ones, "the whole ocean, as far as the eye could
reach, being literally covered with them. I should," he continues, "judge the average height of them above the surface of the
sea to be about sixty feet; some five or six of them were at least
twice that height, and, with their frozen peaks jutting up in the
most fantastic shapes, presented a truly sublime spectacle."
744. The " horse-shoe" of cold in the warm water of the North
The hdrse-shoein the Pacific, though extending 5 degrees farther toward
Japan current.   the south, can not be the harbor for such icebergs.
The cradle of those of the Atlantic was perhaps in the Frozen
Ocean, for they may have come thence through Baffin's Bay.
But in the Pacific there is no nursery for them. The water in
Behring's Strait is too shallow to let them pass from that ocean




~ 745, 746.        TIDE-RIPS AND SEA DRIFT.                     399
into the Pacific, and the climates of Russian America do not favor
the formation of large bergs.  But, though we do not find in the
North Pacific the physical conditions which generate icebergs like
those of the Atlantic, we find them  as abundant with fogs.  The
line of separation between the warm and cold water assures us of
these conditions.
745. What beautiful, grand, and benign ideas do we not see exThe animalcule of the pressed in that immense body of warm waters
sea.            which are gathered together in the middle of the
Pacific and Indian Oceans!  It is the woinb of the sea.  In it
coral islands innumerable have been fashioned, and pearls formed
in "great heaps;" there multitudes of living things, countless in
numbers and infinite in variety, are hourly conceived.  With
space enough to hold the four continents and to spare, the tepid
waters of this part of the ocean teem with nascent organisms.*
They sometimes swarm so thickly there that they change the color of the sea, making it crimson, brown, black, or white, according
to their own hues.  These patches of colored water sometimes extend, especially in the Indian Ocean, as far as the eye can reach.
The question, "What produces them?" is one that has elicited
nmuch discussion in seafaring circles. The Brussels Conference
deemed them an object worthy of attention, and recommended special observations with regard to them.
746. Capt. W. E. KINGMAN, of the American clipper ship the
Colored patches. Shooting Star, reports in his abstract log a remarkable white patch, which he encountered in lat. 8~ 46' S., long. 1050
30' E., and which, in a letter to me, he thus describes: " Thursday,
July 27, 1854. At 7h. 45m. P.M., my attention was called to notice
the color of the water, which was rapidly growing white.  Knowing that we were in a much frequented part of the ocean, and having never heard of such an appearance being observed before in
this vicinity, I could not account for it. I immediately hove the
*' It is the realm of reef-building corals, and of the wondrously-beautiful assemblage of animals, vertebrate and invertebrate, that live among them or prey upon them.
The brightest and most definite arrangements of color are here displayed. It is the
seat of maximum development of the majority of marine genera. It has but few relations of identity with other provinces. The Red Sea and Persian Gulf are its offsets."-From Professor Forbes's Paper on the "Distribution of Marine Life." Plate
31st, Johnston's Physical Atlas, 2d ed.: WinV. Blackwood & Sons, Edinburgh and
London, 1854.




400       THE PHYSICAL GEOGRAPHY OF THE SEA.
ship to and cast the lead; had no bottom at 60 fathoms. I then
kept on our course, tried the water by thermometer, and found it
to be 785~  the same as at 8 A.M. We filled a tub, containing
some 60 gallons, with the water, and found that it was filled with
small luminous particles, which, when stirred, presented a most remarkable appearance. The whole tub seemed to be active with
worms and insects, and looked like a grand display of rockets and
serpents seen at a great distance in a dark night; some of the serpents appeared to be six inches in length, and very luminous.
We caught, and could feel them in our hands, and they would
emit light until brought within a few feet of a lamp, when, upon
looking to see what we had, behold, nothing was visible; but, by
the aid of a sextant's miagnifier, we could plainly see a jelly-like
substance without color. At last a specimen was obtained of
about two inches in length, and plainly visible to the naked eye;
it was about the size of a large hair, and tapered at the ends. By
bringing one end within about one fourth of an inch of a lighted
lamp, the flame was attracted toward it, and burned with a red
light; the substance crisped in burning something like a hair, or
appeared of a red heat before being consumed. In a glass of the
water there were several small round substances (say -1th of an
inch in diameter), which had the power of expanding to more than
twice their ordinary size, and then contracting again; when expanded, the outer rim appeared like a circular saw, only that the
teeth pointed toward the centre. This patch of white water was
about 23 miles in length, north and south, divided near its centre
by an irregular strip of dark water half a mile wide; its east and
west extent I can say nothing about. I have seen what is called
white water in about all the known oceans and seas in the world,
but nothing that would compare with this in extent or whiteness.
Although we were going at the rate of nine knots, the ship made
no noise either at the bow or stern. The whole appearance of
the ocean was like a plain covered with snow. There was scarce
a cloud in the heavens, yet the sky, for about ten degrees above
the horizon, appeared as black as if a storm was raging; the stars
of the first magnitude shone with a feeble light, and the'Milky
Way' of the heavens was almost entirely eclipsed by that through
which we were sailing. The scene was one of awful grandeur;
the sea having turned to phosphorus, and the heavens being hung




~ 747.           TIDE-RIPS AND SEA DRIFT.               401
in blackness, and the stars going out, seemed to indicate that all
nature was preparing for that last grand conflagration which we.
are taught to believe is to annihilate this material world. After
passing through the patch, we noticed that the sky, for four or
five degrees above the horizon, was considerably illuminated,
something like a faint aurora borealis. We soon passed out of
sight of the whole concern, and had a fine night, without any conflagration (except of midnight oil in trying to find out what was
in the water). I send you this because I believe you request your
corps of'one thousand assistants' to furnish you with all such
items, and I trust it will be acceptable. But as to its furnishing
you with much, if any, information relative to the insects or animals that inhabit the mighty deep, time will only tell; I can not
think it will."
747. These discolorations are no doubt caused by organisms
Whence the Red Sea of the sea, but whether wholly animal or wholly
derives its name. vegetable, or whether sometimes the one and sometimes the other, has not been satisfactorily ascertained. I have
had specimens of the coloring matter sent to me from the pinkstained patches of the sea. They were animalculse well defined.
The tints which have given to the Red Sea its name may perhaps be in some measure due to agencies similar to those which,
in the salt-makers' ponds, give a reddish cast (~ 71) to the brine
just before it reaches that point of concentration when crystallization is to commence. Some microscopists maintain that this
tinge is imparted by the shells and other remains of infusoria
which have perished in: the growing saltness of the water. The
Red Sea may be regarded, in a certain light, as the scene of natural salt-works on a grand scale. The process is by solar evaporation. No rains interfere, for that sea (~ 376) is in a riverless
district, and the evaporation goes on unceasingly, day and night,
the year round. The shores are lined with incrustations of salt,
and the same causes which tinge with red (~ 71) the brine in the
vats of the salt-makers probably impart a like hue to the arms and
ponds along the shore of this sea. Quantities, also, of slimrnv, red
coloring matter are, at certain seasons of the year, washed up
along the shores of the Red Sea, which Dr. Ehrenberg, after an
examination under the microscope, pronounces to be a very delicate kind of sea-weed: from this matter that sea derives its name.
Cc




402       THE PHYSICAL GEOGRAPHY OF THE SEA.
So also the Yellow Sea. Along the coasts of China, yellowishcolored spots are said not to be uncommon. I know of no examination of this coloring matter, however. In the Pacific Ocean I
have often observed these discolorations of the sea. Red patches
of water are most frequently met with, but I have also observed
white or milky appearances, which at night I have known greatly
to alarm navigators by their being taken for shoals.
748. These teeming waters bear off through their several chanThe escape of warm nels the surplus heat of the tropics, and disperse it
waters  from the Pacific.      among the icebergs of the Antarctic. See the immense equatorial flow to the east of Australia, and which I have
called the Polynesian Drift. It is bound for the icy barriers of
that unknown sea, tliere to temper climates, grow cool, and return
again, refreshing man and beast by the way, either as the Humboldt current, or the ice-bearing current which enters the Atlantic around Cape Horn, and changes into warm again as it enters
the Gulf of Guinea. It was owing to this great southern flow from
the coral regions that Captain Ross was enabled to penetrate so
much farther south than Captain 5Wilkes on his voyage to the
Antarctic. The North Pacific, except in the narrow passage between Asia and America, is closed to the escape of these warm
waters into the Arctic Ocean. The only outlet for them is to the
south. They go down toward the antarctic regions to dispense
their heat and get cool; and the cold of the Antarctic, therefore,
it may be inferred, is not so bitter as is the extreme cold of the
Frozen Ocean of the north.
749. The warm flow to the south from the middle of the Indian
Ditto from the Indian Ocean is remarkable. Masters who return their
Ocean.        abstract logs to me mention sea-weed, which I suppose to be brought down by this current, as far as 45~ south.
There it is generally, but not always, about 5 degrees warmer
than the ocean along the same parallel on either side.
750. But the most unexpected discovery of all is that of the
A wide current. warm flow along the west coast of South Africa, its
junction with the Lagulhas current, called, higher up, the Mozambique, and then their starting off as one stream to the southward.
The prevalent opinion used to be that the Lagulhas current, which
has its genesis in the Red Sea (~ 390), doubled the Cape of Good
Hope, and then joined the great equatorial current of the Atlantic




~ 751.           TIDE-RIPS AND SEA DRIFT.               403
to feed the Gulf Stream. But my excellent friend, Lieutenant
Marin Jansen, of the Dutch Navy, suggested that this was probably not the case. This induced a special investigation, and I
found as he suggested, and as is represented on Plate IX. Captain
N. B. Grant, in the admirably well-kept abstract log of his voyage
from New York to Australia, found this current remarkably developed. He was astonished at the temperature of its waters, and
did not know how to account for such a body of warm water in
such a place. Being in longitude 14~ east, and latitude 390 south,
he thus writes in his abstract log: " That there is a current setting to the eastward across the South Atlantic and Indian Ocean
is, I believe, admitted by all navigators. The prevailing westerly
winds seem to offer a sufficient reason for the existence of such a
current, and the almost constant southwest swell would naturally
give it a northerly direction. But why the water should be warmer here (380 40' south) than between the parallels of 35~ and 370
south, is a problem that, in my mind, admits not of so easy solution, especially if my suspicions are true in regard to the northerly set. I shall look with much interest for a description of the'currents' in this part of the ocean." In latitude 38~ south, longitude 6~ east, he found the water at 56~. His course thence was
a little to the south of east, to the meridian of 41~ east, at its intersection with the parallel of 42~ south. Here his water thermometer stood at 500, but between these two places it ranged at
60~ and upward, being as high on the parallel of 39~ as 73~.
Here, therefore, was a stream-a mighty "river in the ocean"one thousand six hundred miles across from east to west, having
water in the middle of it 23~ higher than at the sides. This is
truly a Gulf Stream contrast. What an immense escape of heat
from the Indian Ocean, and what an influx of warm water into
the frozen regions of the south! This stream is not always as
broad nor as warm as Captain Grant found it. At its mean stage
it conforms more nearly to the limits assigned it in the diagram
(Plate IX).
751. Instances of commotions in the sea at uncertain intervals
Commotions in the are not unfrequent. There are some remarkable
sea.         disturbances of the sort which I have not been able
wholly to account for. Near the equator, and especially on this
side of it in the Atlantic, mention is made, in the " abstract log,"




404       THE PHYSICAL GEOGRAPHY OF THE SEA.
by almost every observer that passes that way, of "tide-rips,"
which are a commotion in the water not unlike that produced by
a conflict of tides or of other powerful currents. These "tiderips" sometimes move along with a roaring noise, like rifts over
rocks in rivers, and the inexperienced navigator always expects to
find his vessel drifted by them a long way out of her course; but
when he comes to cast up his reckoning the next day at noon, he
remarks with surprise that no current has been felt.
752. Tide-rips present their most imposing aspect in the equaHumboldt's descrip- torial regions. Humboldt met some in 34~ N.,
tion of tide-rips.  and thus describes them: " WVhen the sea is perfectly calm, there appear on its surface narrow belts, like small
rivulets, and in which the water runs with a noise very perceptible to the ear of an experienced pilot. On the 15th of June, in
about 340 36' N., we found ourselves in the midst of a great number of these belts of currents; we were able to determine their direction by the compass. Some were flowing to the N.E.; others E.N.E., although the general motion of the ocean, indicated
by a comparison of the log and the longitude by chronometer,
continued toward the S.E."  It is very common to see a mass of
motionless water crossed by ridges of water which run in different directions. This phenomenon may be observed every day
on the surface of our lakes; but it is more rare to find partial
movements impressed by local causes on small portions of water
in the midst of an oceanic river occupying an immense space,
and moving in a constant direction, although with an inconsiderable velocity. In this conflict of currents, as in the oscillation of
waves, our imagination is struck with these movements, which
seem to penetrate each other, and by which the ocean is incessantly agitated.
753. Horsburgh, in his East India Directory, thus remarks on
Horsburgh's. them, when speaking of the northeast monsoon
about Java: " In the entrance of the Malacca Straits, near the
Nicobar and Acheen Islands, and between them and Junkseyion, there are often very strong ripplings, particularly in the
southwest monsoon; these are alarming to persons unacquainted,
for the broken water makes a great noise when the ship is passing through the ripplings in the night. In most places ripplings
are thought to be produced by strong currents, but here they are




~ 754, 755.      TIDE-RIPS AND SEA DRIFT.                405
frequently seen when there is no perceptible current. Although
there is no perceptible current experienced so as to produce an error in the course and distance sailed, yet the surface of the water
is impelled forward by some undiscovered cause. The ripplings
are seen in calm weather approaching from a distance, and in the
night their noise is heard a considerable time before they come
near. They beat against the sides of a ship with great violence,
and pass on, the spray sometimes coming on deck; and a small
boat could not always resist the turbulence of these remarkable
ripplings."
754. Captain Higgins, of the "Maria," when bound from New
Tide-rips in theAtlan- York to Brazil, thus describes, in his abstract log,
tic.         one of these " tide-rips," as seen by him, 10th October, 1855, in N. lat. 140, W. long. 34~: " At 3 P.M. saw a tiderip; in the centre, temp. air 80~, water 81~. From the time it
was seen to windward, about three to five miles, until it had passed to leeward out of sight, it was not five minutes. I should
judge it traveled at not less than sixty miles per hour, or as fast
as the bores of India. Although we have passed through several
during the night, we do not find they have set the ship to the
westward any; it may be that they are so soon passed that they
have no influence on the ship, but they certainly beat very hard
against the ship's sides, and jarred her all over. They are felt
even when below, and will wake one out of sleep."
755. Captain TWakeman, of the "Adelaide," in January, 1856,
Mock vigias.  lat. 110 21' N., long. 33~ 33' W., encountered " tiderips" which broke and foamed with such violence that he took
them for breakers or a shoal. They sometimes are most alarming. Approaching through the stillness of the night with a roaring noise, and in the shape of tremendous rollers combing and
foaming, they seem to threaten to overwhelm vessel and crew;
but, breaking over the deck, they pass by, and in a few moments
the sea is as smooth and as unruffled as before. Many of the
" vigias" which disfigure our charts have no other foundation than
the foam of a tide-rip. Captain Arquit's log of the "Comet"
gives an account of many tide-rips which he encountered also in
the northeast trade-wind region of the Atlantic. Thus, November
15, 1855, lat. 7~ 34' N., long. 40~ 30' W.: " Many tide-rips, which
we had a good opportunity of observing when becalmed. They




406          THE PHYSICAL GEOGRAPHY OF THE SEA.
came up in ridges as long as the eye could reach, from  all parts of
the compass, but mostly from  the E.  I examined the ridges very
closely, but could not see any fine drift-matter of any kind, as you
can on the ridges of currents in many parts of the ocean.  We
have had no currents unless they have been from  different directions, and one counteracting the other.  November 16th, lat. 60
07' N.: Light winds and pleasant. There has been no time since
noon to midnight but there have been tide-rips either in sight or
hearing, mostly tending N.E. and S.W. in long narrow  ridges.
From  8 P.M. to 9 P.M. the ocean appeared like a boiling  caldron, which we sailed through for three miles.  The bubbling
made a loud noise, which we heard for a long time after we had
sailed through it. The ship had a very singular motion, like
striking her keel on a soft muddy bottom  in a short rough seaway-the same as I have felt in the harbor of Montevideo. The
motion was noticed by all on board.  We have had a current of
fifteen miles going west.  I have often noticed tide-rips in this
part of the ocean before, particularly when bound home (for I
have never been where I am now, bound out, before), and have
mentioned them in my abstract log, but they were different from
what we had last night. The ship would come to and fall off
three points without any regard to the rudder."
756. But, besides tide-rips, bores, and eagres,* there are the sud* The bores of India, of the Bay of Fundy, and the Amazon are the most celebrated. They are a tremulous tidal wave, which at stated periods comes rolling in
from the sea, threatening to overwhelm and ingulf every thing that moves on the
beach. This wave is described, especially in the Bay of Fundy, as being many feet
high; and it is said oftentimes to overtake deer, swine, and other wild beasts that
feed or lick on the beach, and to swallow them up before the swiftest of foot among
them have time to escape. The swine, as they feed on muscles at low water, are
said to snuff the " bore," either by sound or smell, and sometimes to dash off to the
cliffs before it rolls on.
The eagre is the bore of Tsien-Tang River. It is thus described by Dr. Macgowan,
in a paper before the Royal Asiatic Society, 12th January, 1853, and as seen by him
from the city of Hang-chow in 1848:
"At the upper part of the bay, and about the mouth of the river, the eagre is
scarcely observable; but, owing to the very gradual descent of the shore, and the rapidity of the great flood and ebb, the tidal phenomena even here present a remarkable appearance. Vessels, which a few moments before were afloat, are suddenly
left high and dry on a strand nearly two miles in width, which the returning wave as
quickly floods. It is not until the tide rushes beyond the mouth of the river that it
becomes elevated to a lofty wave constituting the eagre, which attains its greatest




~ 756.                TIDE-RIPS AND SEA DRIFT.                          407
Bores, eagres, and the don disruptions of the ice which arctic voyagers tell
earthquake wave of
Lisbon.          of, the immense icebergs which occasionally appear
magnitude opposite the city of Hang-chow. Generally there is nothing in its aspect,
except on the third day of the second month, and on the eighteenth of the eighth, or
at the spring-tide about the period of the vernal and autumnal equinoxes, its great
intensity being at the latter season. Sometimes, however, during the prevalence of
easterly winds, on the third day after the sun and moon are in conjunction, or in
opposition, the eagre courses up the river with hardly less majesty than when paying
its ordinary periodical visit. On one of these unusual occasions, when I was traveling in native costume, I had an opportunity of witnessing it, on December 14th,
1848, at about 2 P.M.
" Between the river and the city walls, which are a mile distant, dense suburbs extend several miles along the banks.  As the hour of flood-tide approached, crowds
gathered in the streets running at right angles with the Tsien-Tang, but at safe distances. My position was a terrace in front of the TRI-wYAVE Temple, which afforded a good view of the entire scene. On a sudden all traffic in the thronged mart
was suspended, porters cleared the front street of every description of merchandise,
boatmen ceased lading and unlading their vessels, and put out in the middle of the
stream, so that a few moments sufficed to give a deserted appearance to the busiest
part of one of the busiest cities of Asia. The centre of the river teemed with craft,
from small boats to huge barges, including the gay'flower-boats.' Loud shouting
from the fleet announced the appearance of the flood, which seemed like a glittering
white cable, stretched athwart the river at its mouth, as far down as the eye could
reach. Its noise, compared by Chinese poets to that of thunder, speedily drowned
that of the boatmen; and as it advanced with prodigious velocity-at the rate, I
should judge, of twenty-five miles an hour-it assumed the appearance of an alabaster wall, or, rather, of a cataract four or five miles across, and about thirty feet high,
moving bodily onward. Soon it reached the advanced guard of the immense assemblage of vessels awaiting its approach.  Knowing that the bore of the Hooghly,
which scarcely deserves mention in connection with the one before me, invariably
overturned boats which were not skillfully managed, I could not but feel apprehensive for the lives of the floating multitude. As the foaming wall of water dashed
impetuously onward, they were silenced, all being intensely occupied in keeping their
prows toward the wave which threatened to submerge every thing afloat; but they
all vaulted, as it were, to the summit with perfect safety. The spectacle was of
great interest when the eagre had passed about one half way among the craft. On
one side they were quietly reposing on the surface of the unruffled stream, while those
on the nether portion were pitching and heaving in tumultuous confusion on the
flood; others were scaling with the agility of salmon the formidable cascade.  This
grand and exciting scene was but of a moment's duration; it passed up the river in
an instant, but from this point with gradually diminishing force, size, and velocity,
until it ceased to be perceptible, which Chinese accounts represent to be eighty miles
distant from the city. From ebb to flood tide the change was almost instantaneous;
a slight flood continued after the passage of the wave, but it soon began to ebb. Having lost my memoranda, I am obliged to write from recollection.  My impression
is that the fall was about twenty feet; the Chinese say that the rise and fall is sometimes forty feet at Hang-chow. The maximum rise and fall at spring-tides is prob



408          THE PHYSICAL GEOGRAPHY OF THE SEA.
in groups near certain latitudes, the variable character of all the
currents of the sea-now fast, now slow (~ 401), now running this
way, then that-all of which may be taken as so many signs
of the tremendous throes which occur in the bosom of the ocean.
Sometimes the sea recedes from the shore, as if to gather strength
for a great rush against its barriers, as it did when it fled back
to join with the earthquake and overwhelm Callao in 1746, and
again Lisbon nine years afterward.
757. Few persons have ever taken the trouble to compute (~ 402)
Rains at sea and how  much the fall of a single inch of rain over an
their effect upon its
equilibrium.    extensive region in the sea, or how much the change
even of two or three degrees of temperature over a few thousand
square miles of its surface, tends to disturb its equilibrium, and
consequently to cause an aqueous palpitation that is felt from  the
equator to the poles.  Let us illustrate by an example: The surface of the Atlantic Ocean covers an area of about twenty-five
millions of square miles. Now, let us take one fifth of this area,
and suppose a fall of rain one inch deep to take place over it.
This rain would weigh three hundred and sixty thousand millions
of tons; and the salt which, as water, it held in solution in the
ably at the mouth of the river, or upper part of the bay, where the eagre is hardly
discoverable. In the Bay of Fundy, where the tides rush in with amazing velocity,
there is at one place a rise of seventy feet; but there the magnificent phenomenon
in question does not appear to be known at all. It is not, therefore, where tides attain their greatest rapidity, or maximum rise and fall, that this wave is met with,
but where a river and its estuary both present a peculiar configuration.
" Dryden's definition of an eagre, appended in a note to the verse above quoted
from the T/hrenodia Augssstalis, is,' a tide swelling above another tide,' which he says
he had himself observed in the River Trent.  Such, according to Chinese oral accounts, is the character of the Tsien-Tang tides-a wave of considerable height rushes suddenly in from the bay, which is soon followed by one much larger.  Other accounts represent three successive waves riding in; hence the name of the temple
mentioned, that of the Three Waves. Both here and on the Hooghly I observed
bhut one wave; my attention, however, was not particularly directed to this feature
of the eagre. The term should, perhaps, be more comprehensive, and express'the
instantaneous rise and advance of a tidal wave;' the Indian barbarism' bore' should
be discarded altogether.
" A very short period elapsed between the passage of the eagre and the resumption
of traffic. The vessels were soon attached to the shore again; women and children
were occupied in gathering articles which the careless or unskillful had lost in the
aquatic melee. The streets were drenched with spray, and a considerable volume of
water splashed over the banks into the head of the grand canal, a few feet distant."
- Vide Transactions of Chinese Branch of the Royal Asiatic Society.




~ 758.            TIDE-RIPS AND SEA DRIFT.               409
sea, and which, when that water was taken up as vapor, was left
behind to disturb equilibrium, weighed sixteen millions more of
tons, or nearly twice as much as all the ships in the world could
carry at a cargo each. This rain might fall in an hour, or it might
fall in a day; but, occupy what time it might in falling, this rain
is calculated to exert so much force-which is inconceivably great
-in disturbing the equilibrium of the ocean. If all the water
discharged by the Mississippi River during the year were taken
up in one mighty measure, and cast into the ocean at one effort,
it would not make a greater disturbance in the equilibrium of the
sea than would the supposed rain-fall. Now this is for but one
fifh of the Atlantic, and the area of the Atlantic is about one
fifth of the sea-area of the world; and the estimated fall of rain
was but one inch, whereas the average for the year is (~ 757) sixty inches; but we will assume it for the sea to be no more than
thirty inches. In the aggregate, and on an average, then, such
a disturbance in the equilibrum of the whole ocean as is here supposed occurs seven hundred and fifty times a year, or at the rate
of once in twelve hours. Moreover, when it is recollected that
these rains take place now here, now there; that the vapor of
which they were formed was taken up at still other places, we
shall be enabled to appreciate the better the force and the effect
of these irregular movements in the sea.
758. Between the hottest hour of the day and the coldest
Dittoofcloud andsun- hour of the night there is frequently a change
Sline.        of four degrees in the temperature of the sea.*
Let us, therefore, the more thoroughly to appreciate those agitations of the sea which take place in consequence of the diurnal
changes in its temperature, call in the sunshine, the cloud without
rain, with day and night, and their heating and radiating processes. And to make the case as strong as to be true to nature
we may, let us again select one fifth of the Atlantic Ocean for
the scene of operation. The day over it is clear, and the sun
pours down his rays with their greatest intensity, and raises the
temperature two degrees. At night the clouds interpose, and
prevent radiation from this fifth, whereas the remaining four
fifths, which are supposed to have been screened by clouds, so as
to cut off the heat from the sun during the day, are now looking
* Vicle Admiral Smyth's Memoir of the Mediterranean, p. 125.




410       THE PHYSICAL GEOGRAPHY OF THE SEA.
up to the stars in a cloudless sky, and serve to lower the temperature of the surface-waters, by radiation, two degrees. Here, then,
is a difference of four degrees, which we will suppose extends
only ten feet below the surface. The total and absolute change
made in such a mass of sea water by altering its temperature two
degrees is equivalent to a change in its volume of three hundred
and ninety thousand millions of cubic feet. And yet there are
philosophers who maintain (~ 123) that evaporation and precipitation, changes of temperature and saltness, and the secretions of insects, are not to be reckoned among the current-producing agents
of the sea-that the gentle trade-winds do it all!
759. Do not the clouds, night and day, now present themselves
Day and night. to us in a new light? They are cogs, and rachets,
and wheels in that grand and exquisite machinery which governs
the sea, and which, amid all the jarring of the elements, preserves
the harmonies of the ocean.
760. The log-books of not less than 1843 vessels cruising on
Logs overhauled for the polar side of 35~ S. have, by the officers of the
kelp and ice. Observatory, been overhauled for kelp and ice. Of
these, 367-or one in five-mentioned kelp or sea-weed east of
Cape Horn; 142 mention " rock-weed and drift matter" between
the previous meridian and 100 W, and chiefly between 35~ and 40~
S.  "Long kelp" is also found by Australian traders after passing
the Cape of Good Hope; 146 logs make mention of it between the
meridians of 40~ and 120~ E. It most abounds along this line, however, between the meridians of 45~ and 650 E., and the parallels of
42~ and 48~ S. These sargassos are sketched with a free hand on
Plate IX.
761. Sea-weed is frequently mentioned also by the homewardA sargasso in the bound Australian traders on their way to Cape
South Pacific.    Horn: this collection has (~ 139) already been alluded to. It now appears that instead of three, there are really
five true sargassos, as shown on Plate IX.
762. The weedy space, marked as such, about the Falkland IslSea-weed about the ands, is probably not a true sargasso. The seaallkland Islands.  weed reported there probably comes from the Straits
of Magellan, where immense masses of it grow. These straits are
so encumbered with sea-weed that steamers found great difficulty
in making their way through it. It so encumbers their paddles as
to make frequent stoppages necessary.




~ 763-767.        TIDE-RIPS AND SEA DRIFT.                 411
763. The sargasso to the west of the Cape of Good Hope, though
The African sargasso. small, is perhaps the best defined of them all. Mention is generally made of it in the log as " rock-weed" and " drift
matter."  Now when it is recollected that weeds have been found
as frequently nearly (~ 760) in this small space as they have been
in the large space between the Cape and Australia, the reader
will be able to form a more correct idea as to the relative abundance of weed in these seas of weeds.
764. By going far enough south, icebergs may be found on any
Icebergs.   meridian; but in searching for them, we can only
look where commerce carries our colleagues of the sea. Out of
the 1843 tracks traced on the polar side of 35~ S., only 109 make
mention of ice. Few of these went, except in doubling Cape Horn,
beyond the parallel of 55~ S., therefore we have not been able to
trace the ice back into the "chambers of the frost."  We can only
say that north of 500 antarctic icebergs most abound between the
meridians of 15~ W. and 55~ E.
765. As a rule, the bergs which are the largest last longest, and
The largest drift far- approach nearest to the equator. Here, then, is the
thest.       great line of antarctic- drift; by studying it we
may perhaps catch a glimmer of light from south polar shores.
These icebergs, be it remembered, have drifted north through a
belt of westerly winds. Their course, therefore, was probably not
due north, but to the east of that rhomb.
766. Tracing this line of drift, then, backward in a southwesterThe line of antarctic ly direction, it should guide us to that part of the
drift.       southern continent where the icebergs have their
principal nursery.  This would take us to the sources of the Humboldt current, and seem to indicate that these glaciers are launched in its waters; but, as their motion is slow, the winds bear the
bergs to the east, while the general drift sets them to the north.
767. Arrived at this point, fiords, deep bays, and capacious
Necessity for, and ad- gulfs loom up before the imagination, reminding us
vantages of an antarctic expedition.    to ask the question, Is there not embosomed in the
antarctic continent a Mediterranean, the shores of which are favorable to the growth and the launching of icebergs of tremendous
size? and is not the entrance to this sea near the meridian of
Cape Horn, perhaps to the west of it?  Circumstances like these
beget longings, and we sigh for fresh antarctic explorations. Sure



412       THE PHYSICAL GEOGRAPHY OF THE SEA.
ly, when we consider the advantages which the improvements of
the age, the lights of the day, would afford an exploring expedition there now; when we reflect upon the drawbacks and difficulties with which former expeditions thither had to contend; when
we call to mind the facilities with which one might be conducted
now: surely, I say, when we thus reflect, no one can doubt as to
the value and importance of the discoveries which a properly
equipped expedition would now be sure to make.
768. In those regions there are doubtless elements of commerCommercial conaider- cial wealth in the number of seals and abundance
ations.      of whales, if in nothing else. It seems to be a
physical law that cold-water fish are more edible than those of
warm water. Bearing this fact. in mind as we study Plate IX.,
we see at a glance the places which are most favored with good
fish-markets. Both shores of North America, the east coast of
China, with the west coasts of Europe and South America, are
all washed by cold waters, and therefore we may infer that their
markets abound with the most excellent fish. The fisheries of
Newfoundland and New England, over which nations have wrangled for centuries, are in the cold water from Davis' Strait. The
fisheries of Japan and Eastern China, which almost, if not quite,
rival these, are situated also in the cold water. Neither India,
nor the east coasts of Africa and South America, where the warm
waters are, are celebrated for their fish.
769. Three thousand American vessels, it is said, are engaged
Valueofthefisheries. in the fisheries. If to these we add the Dutch,
French, and English, we shall have a grand total, perhaps, of not
less than six or eight thousand, of all sizes and flags, engaged in
this one pursuit. Of all the industrial pursuits of the sea, however, the whale fishery is the most valuable. Wherefore, in treating of the physical geography of the sea, a map for the whales,
it was thought, would be useful; it has so proved itself.
770. The sperm whale is a warm-water fish. The right whale
Sperm whales. delights in cold water. An immense number of
log-books of whalers have been discussed at the National Observatory with the view of detecting the parts of the ocean in which
the whales are to be found at the different seasons of the year.
Charts showing the result have been published; they form a part
of the series of Maury's Wind and Current Charts.




~ 771, 772.      TIDE-RIPS AND SEA DRIFT.                413
771. In the course of these investigations, the discovery was
Asea of fire to them. made that the torrid zone is, to the right whale,
as a sea of fire, through which he can not pass; that the right
whale of the northern hemisphere and that of the southern are
two different animals; and that the sperm whale has never been
known to double the Cape of Good Hope-he doubles Cape
Horn.
772. With these remarks, and the explanation given on Plate
Right whales.  IX., the parts of the ocean to which the right whale
most resorts, and the parts in which the sperm are found, may be
seen at a glance. The sargassos, or places of weed, are also repre.
sented on this plate.




414A      THE PHYSICAL GEOGRAPHY OF THE SEA.
CHAPTER XIX.
~ 781-808.-STORMS, HURRICANES, AND TYPHOONS.
781. PLATE V. iS constructed from data furnished by the Pilot
Plate v.   Charts, as far as they go, that are in process of construction at the National Observatory. For the Pilot Charts, the
whole ocean is divided off into "fields" or districts of five degrees
square, i. e., five degrees of latitude by five degrees of longitude,
as already explained on page xxxii., Plate V. -Now, in getting out
from the log-books materials for showing, in every district of the
ocean, and for every month, how navigators have found the winds
to blow, it has been assumed that, in whatever part of one of these
districts a navigator may be when he records the direction of the
wind in his log, from that direction the wind was blowing at that
time all over that district; and this is the only assumption that is
permitted in the whole course of the investigation. Now if the
navigator will draw, or imagine to be drawn in any such district,
twelve vertical columns for the twelve months, and then sixteen
horizontal lines through the same for the sixteen points of the
compass, i. e., for N., N.N.E., N.E., E.N.E., and so on, omitting the
by-points, he will have before him a picture of the " Investigating
Chart" out of which the " Pilot Charts" are constructed. In this
case the alternate points of the compass only are used, because,
when sailing free, the direction of the wind is seldom given for
such points as N. by E., W. by S., etc. Moreover, any attempt, for
the present, at greater nicety would be over-refinement, for navigators do not always make allowance for the aberration of the
wind; in other words, they do not allow for the apparent change
in the direction of the wind caused by the rate at which the vessel may be moving through the water, and the angle which her
course makes with the true direction of the wind. Bearing this
explanation in mind, the intelligent navigator will have no difficulty in understanding the wind diagram (Plate V.), and in forming a correct opinion as to the degree of credit due to the fidelity
with which the prevailing winds of the year are represented on
Plate VIII. As the compiler wades through log-book after log



~ 782.      STORMS, HURRICANES, AND TYPHOONS.           415
book, and scores down in column after column, and upon line after line, mark upon mark, he at last finds that, under the month
and from the course upon which he is about to make an entry,
he has already made four marks or scores, thus ( I I   ). The one
that he has now to enter will make the fifth, and he "scores and
tallies," and so on until all the abstracts relating to that part of
the ocean upon which he is at work have been gone over, and his
materials exhausted. These "fives and tallies" are exhibited on
Plate V. Now, with this explanation, it will be seen that in the
district marked A (Plate V.) there have been examined the logs
of vessels that, giving the direction of the wind for every eight
hours, have altogether spent days enough to enable me to record
the calms and the prevailing direction of the winds for eight
hours, 2144 times: of these, 285 were for the month of September; and of these 285 observations for September, the wind is reported as prevailing for as much as eight hours at a time: from
N., 3 times; from N.N.E., 1; N.E., 2; E.N.E., 1; E., 0; E.S.E.,
1; S.E., 4; S.S.E., 2; S., 25; S.S.W., 45; S.W., 98; W.S.W.,
24; NW., 47; W.N..W., 17; N.W., 15; N.N.W., 1; Calms (the
little O's), 5; total, 285 for the month in this district.  The number expressed in figures denotes the whole number of observations
of calms and winds together that are recorded for each month and
district. In C, the wind in May sets one third of the time from
west. But in A, which is between the same parallels, the favorite quarter for the same month is from S. to S.W., the wind setting one third of the time from that quarter, and only 10 out of
221 times from the west; or, on the average, it blows from the
west only 1. day during the month of May. In B, notice the
great " sun swing" of the winds in September, indicating that the
change from summer to winter, in that region, is sudden and violent; from winter to summer, gentle and gradual. In some districts of the ocean, more than a thousand observations have been
discussed for a single month, whereas, with regard to others, not
a single record is to be found in any of the numerous log-books
at the National Observatory.
782. The China seas are celebrated for their furious gales of
Typhoons.   wind, known among seamen as typhoons and white
squalls. These seas are included on the plate (VIII.) as within
the region of the monsoons of the Indian Ocean. But the mon



416       THE PHYSICAL GEOGRAPHY OF THE SEA.
soons of the China Sea are not five-month monsoons (~ 681);
they do not prevail from the west of south for more than two or
three months. Plate V. exhibits the monsoons very clearly in a
part of this sea. In the square between 15~ and 20~ north, 110~
and 115~ east, there appears to be a system of three monsoons;
that is, one from northeast in October, November, December, and
January; one from east in March and April, changing in May;
and another from the southward in June, July, and August, changing in September. The great disturber of the atmospheric equilibrium appears to be situated among the plains and steppes of
Asia; their influence extends to the China Seas, and about the
changes of the monsoons these awful gales, called typhoons and
white squalls, are experienced.
783. In like manner, the Mauritius hurricanes, or the cyclones
The Mauritius hurri- of the Indian Ocean, occur during the unsettled
canes.      state of the the atmospheric equilibrium  which
takes plac~e at that debatable period during the contest between
the trade-wind force and the monsoon force (~ 699), and which debatable period occurs at the changing of the monsoon, and before
either force has completely gained or lost the ascendency. At
this period of the year, the winds, breaking loose from their controlling forces, seem to rage with a fury that would break up the
very fountains of the deep.
784. So, too, with the VWest India hurricanes of the Atlantic.
The Yest India hurri- These winds are most apt to occur during the
canes.       months, of August and September.  There is,
therefore, this remarkable difference between these gales and
those of the East Indies: the latter occur about the changing
of the monsoons, the former during their height. In August
and September, the southwest monsoons of Africa and the southeast monsoons of the WVest Indies are at their height; the agent
of one drawing the northeast trade-winds from the Atlantic into
the interior of New Mexico and Texas, the agent of the other
drawing them into the interior of Africa. These two forces,
pulling in opposite directions, assist now and then to disturb the
atmospheric equilibrium to such an extent that the most powerful revulsions in the air are required to restore it. "The hurricane season in the North Atlantic Ocean," says Jansen, "occurs
simultaneously with the African monsoons; -and in the same sea



~ 785, 786.   STORMS, HURRICANES, AND TYPHOONS.          417
son of the year in which the monsoons prevail in the North Indian Ocean, in the China Sea, and upon the Western coast of Central America, all the seas of the northern hemisphere have the hurricane season. On the contrary, the South Indian Ocean has its
hurricane season in the opposite season of the year, and when the
northwest monsoon prevails in the East Indian Archipelago.
785. Under the head of hurricanes, typhoons, and tornadoes, I
Tihe cyclone theory. include all those gales of wind which are known as
cyclones. These have been treated of by Redfield in America,
Reid in England, Tom of Mauritius, and Piddington of Calcutta,
with marked ability, and in special works. I refer the reader to
them. The theory of this school is, that these are rotary storms;
that they revolve against the hands of a watch in the northern,
and with the hands of a watch in the southern hemisphere; that
nearer the centre or vortex the more violent the storm, while the
centre itself is a calm, which travels sometimes a mile or two an
hour, and sometimes forty or fifty; that in the centre the barometer is low, rising as you approach the periphery of the whirl;
that the diameter of these storms is sometimes a thousand miles,
and sometimes not more than a few leagues; that they have their
origin somewhere between the parallels of 10~ and 20~ north and
south, traveling to the westward in either hemisphere, but increasing their distance from the equator, until they reach the parallel of 25~ or 30~, when they turn toward the east, or "recurvate," but continue to increase their distance from the equatori. e., they first travel westwardly, inclining toward the nearest
pole; they then recurve and travel eastwardly, still inclining toward the pole; that such is their path in both hemispheres, etc.
786. The questions why these storms should recurve, and why
Puzzling questions. they should travel as they do, and why they should
turn with the hands of a watch in the southern, and against them
in the northern hemisphere, are still considered by many as puzzles, though it is thought that their course to the westward in
the trade-wind region, and to the eastward in the counter-trades,
is caused by the general movement of the atmosphere, like the
whirls in an angry flood, which, though they revolve, yet they
are borne down stream with the currents as they do revolve.
The motion polarward is caused, the conjecture is, by the fact
that the equatorial edge of the storm has, in consequence of diur) D




418       THE PHYSICAL GEOGRAPHY OF THE SEA.
nal rotation, a greater velocity than its polar edge. There seems,
however, to be less difficulty with regard to their turning than
with regard to their course; the former is now regarded as the
resultant of diurnal rotation and of those forces of translation
which propel the winds along the surface of our planet. This
composition of the forces of the revolving storm, and this resolution of them, are precisely such (~ 215) as to produce opposite rotation on opposite sides of the equator.
787. Many of the phenomena connected with these storms still
Espy's theory. remain to be explained; even the facts with regard
to them are disputed by some. The late Professor Espy, after
having discussed for many years numerous observations that have
been made chiefly on shore, maintained that the wind does not
blow around the vortex or place of low barometer, but directly
toward it. He held that the place of low barometer, instead of
being a disc, is generally an oblong, in the shape of a long trough,
between two atmospherical waves; that it is curved with its convex side toward the east; that it is sometimes nearly straight, and
generally of great length from north to south, reaching in America
from the Gulf of Mexico to the great lakes and beyond, and having but little breadth in proportion to its length; that it travels
east, moving side foremost, requiring about two days to go from
the Mississippi to St. John's, Newfoundland; that on either side
of it, but many miles distant, there is a ridge of high barometer;
that the wind on either side of the line of low barometer, in which
there is little or no wind, blows toward it, etc., and, in support of
these positions, he advanced this theory: "When the air in any
locality acquires a higher temperature or a higher dew-point than
that of surrounding regions, it is specifically lighter, and will ascend; in ascending, it comes under less pressure, and expands;
in expanding from diminished pressure, it grows colder about a
degree and a quarter for every hundred yards of ascent; in cooling as low as the dew-point (which it will do when it rises as
many hundred yards as the dew-point at the time is below the
temperature of the air in degrees of Fahrenheit), it will begin to
condense its vapor into cloud; in condensing its vapor into water or cloud, it will evolve its latent caloric; this evolution of latent caloric will prevent the air from cooling so fast in its farther
ascent as it did in ascending below the base of the cloud now




~ 787.     STORMS, HURRICANES, AND TYPHOONS            419
forming; the current of the air, however, will continue to ascend,
and grow colder about half as much as it would do if it had no
vapor in it to condense; and when it has risen high enough to
have condensed, by the cold of expansion from diminished pressure, one hundredth of its weight of vapor, it will be about fortyeight degrees less cold than it would have been if it had no vapor
to condense nor latent caloric to give out-that is, it will be about
forty-eight degrees warmer than the surrounding air at the same
height; it will, therefore (without making any allowance for the
higher dew-point of the ascending current), be about one tenth
lighter than the surrounding colder air, and, of course, it will continue to ascend to the top of the atmosphere, spreading out in all
directions above as it ascends, overlapping the air in all the surrounding regions in the vicinity of the storm, and thus, by increasing the weight of the air around, cause the barometer to rise
on the outside of the storm, and fall still more under the stormcloud by the outspreading of air above, thus leaving less ponderable matter near the centre of the upmoving column to press on
the barometer below. The barometer thus standing below the
mean under the cloud in the central regions, and above the mean
on the outside of the cloud, the air will blow on all sides from
without, inward, under the cloud. The air, on coming under the
cloud, being subjected to less pressure, will ascend and carry up
the vapor it contains with it, and as it ascends will become colder by expansion from constantly diminishing pressure, and will
begin to condense its vapor in cloud at the height indicated before, and thus the process of cloud-forming will go on. Now it
is known that the upper current of air in the United States moves
constantly, from a known cause, toward the eastward, probably a
little to the south of east; and as the upmoving column containing the cloud is chiefly in this upper current of air, it follows that
the storm-cloud must move in the same direction. And over
whatever region the storm-cloud appears, to that region will the
wind blow below; thus the wind must set in with a storm from
some eastern direction, and, as the storm-cloud passes on toward
the eastward, the wind must change to some western direction,
and blow from that quarter till the end of the storm."*
* The Fourth Meteorological Report of Prof. James P. Espy; Senate Doc. 65,
34th Congress, 3d session.




420       THE PHYSICAL GEOGRAPHY OF THE SEA.
788. According to Dove's " Law of Rotation," which is said to
Dov6s law.  hold good in the northern hemisphere, and is supposed to obtain in the southern also, the wind being N.W. and
veering, it ought to veer by W. to S.W., and so on, against the
hands of a watch. This "law" is explained thus: Suppose a ship
d'   a,3
\a         w
be in S. lat. off Cape Horn as at a, with a low barometer to the
north of her, as at C, where the air ascends as fast as it comes
pouring in from all sides. The ship, let it be supposed, is just on
the verge of, but exterior to the vortex, or that place where the
wind commences to revolve. The first rush of the air at a will
be directly for the centre, C; consequently, a ship so placed
would report the storm as commencing with the wind at south.
For the sake of illustration, we will suppose this place of low barometer to be stationary, and the air, as it rushes in, to ascend at
the disc, C. Thus the area of inrushing air will gradually enlarge itself by broad spreading, like a circle on the water, until
it be compassed by a circle with a radius, CS, of indefinite length.
The air then, on the meridian, S C V, but to the south of a, will
not blow along this meridian and pass over the ship; in consequence of the diurnal rotation of the earth, it will take a direction, S a', to the westward; and the arrow d a, representing a
S.S.E. wind, will now show the direction of the wind at a. Thus
the ship will report that the wind commenced at south, and gradually hauled to S.S.E., i. e., against the hands of a watch; and so
the arrows b' a' will represent the direction of the wind at each




~ 789.      STORMS, HURRICANES, AND TYPHOONS.           421
station, a' a' a', when the storm commenced, and the arrows d'
a' the direction afterward, thus showing it to have veered against
the hands of a watch. And this is the direction in which the
forces of diurnal rotation, when not mastered by opposing forces,
always require the wind, when not blowing round in spirals and
a whirl, to haul in the southern hemisphere. Now, paradoxical
as it may at first seem, it is also the forces of diurnal rotation that
give that same wind, when it is blowing round in spirals, its first
impulse to march round in the contrary direction, or with the
hands of a watch; but this is as it should be-it hauls one way,
and marchzes the other. After passing a, and each of the other
stations, a' a', the rush of wind is sufficient, let us suppose, to
create a whirl. The wind at a' a' a', continuing on with a circular motion, is represented thenceforward in its course by the
curved arrows a e, a' e'. The wind coming from the east and the
west has no direct impulse from diurnal rotation, but the wind on
either side of it has, and hence the prime vertical wind is carried
around with the rest. If, now, we imagine the disc GC to be put
in motion, and the storm to become a traveling one, we shall have
to consider the composition and resolution of other forces also,
such as those of traction, aberration, and the like, before we can
resolve the whirlwind.
789. But the cyclonologists do not locate their storms in such
Bernouilli's formula. high latitudes as the parallels of Cape Horn. Hence
we might safely infer, one would suppose, that in high southern
latitudes a north wind has a tendency to incline to the westward
and a south wind to the eastward; and the cause of this tendency
is in operation, whether the place of low barometer be a disc or
an oblong, for it is in obedience to the trade-wind law, as expounded by Halley, that it so operates; and it will also be the
case whether the wind be caused by an influx into the place of
low, or the efflux from the place of high barometer; or, as is
generally the case, by both together. If the distance between
the place of high and low barometer were always the same, then
a given difference of barometric pressure would always be followed by a wind of the same force or velocity. By expanding Bernouilli's formula for the velocity of gas jets under given pressures, Sir John F. W. Herschel has computed* the velocity and the
* See article Meteorology, Encyclopedia Britannica, 1857.




422        THE PHYSICAL GEOGRAPHY OF THE SEA.
force with which currents of air or winds would issue under cer.tain differences of barometric pressure. Under the most favorable conditions, i. e., when the places of high and of low barometer
are in immediate juxtaposition, as on the inside and outside of an
air-pump, an effective difference of 0.006 inch in the barometric
pressure would create a breeze with a velocity of seven miles the
hour. Such a wind is capable of exerting a horizontal pressure
of 0.2 lb. the square foot, thus:
Diff Pressure  Velocity of Wind.  Horizontal Pressure.  Strength of Wind.
0.006 inch. 7 miles per hour.   02 lbs. per sq. foot. Gentle air.
0.010 "   14 "    "        0.9 "      "       Light breeze.
0.016 "   2L "    "        1.9 "      "       Good sailing breeze.
0.06  "   41"    "         7.5 "'            A gale.
0.14  "   61' "         16.7'; "           Great storm.
0.25  "   82 "    "       30.7 "      "       Tempest.
0.41  "   92  "    "      37.9 "      "  Devastating hurricane.
Changes, however, in the barometer, amounting to five or six
times these differences, are observed to take place at sea without
producing winds exceeding in velocity the rates above. This is
because the places of high and low barometer at sea are far apart,
and because, also, of the obstructions to the winds afforded by the
inequalities of the earth's surface.
790. But, in this view of the subject, the importance of a daily
Predictingstorms. system  of weather reports by telegraph on shore,
and across the water between Europe and America when the subAtlantic cable is well laid, looms up and assumes all the proportions of one of the great practical questions of the age. We may
conjecture, as the probable result of observation, that the greater
the distance between the place of high and low barometer, the less
the velocity of wind for a given barometric difference would be.
Professor Buys Ballot has discovered, practically, the numerical
relation between the force of the wind and given barometric differences for certain places in Holland. With the view of ascertaining like relations for this country, it has been proposed to establish a cordon of meteorological stations over the United States,
each station being required to report daily to the Observatory in
Washington, by telegraph, the height of the barometer, force of
wind, etc. By such a plan, properly organized, we might expect
soon to be able to give the ships, not only on the great lakes, but
in our sea-port towns also, timely warning of many a gale, and to




~ 791, 792.   STORMS, HURRICANES, AND TYPHOONS.        423
send by telegraph to Europe warning of many a one long before
it could traverse the Atlantic. The contributions which the magnetic telegraph is capable of making for the advancement of meteorology will enable us to warn the ships in our Gulf ports, as
well as those of Cuba, of the, approach of every hurricane or tornado that visits those regions.
791. But, returning to the cyclone theory: though the wind
The changing of the be blowing around in spirals against the hands of
wind in a cyclone. the watch, yet, from the fact that the centre about
which it is blowing is also traveling along, the changes of the
wind, as observed by a vessel over which the storm is passing,
will not, under all circumstances, be against the sun in the northern, or with the sun in the southern hemisphere. The reason is
obvious. This point is worth studying, and any one who will resort to "' moving diagrams" for illustration will be repaid with edification. Piddington's horn cards are the best; but let those who
have them not cut a disc of paper of any convenient diameter,
say 2- inches, and then cut out a circle of 2 inches from the middle; this will leave a ring half an inch broad upon which to
draw arrows representing the course of
the wind. Suppose them to be drawn for
///  %\the northern hemisphere, as in the annexed diagram: lay the paper ring on the
chart; suppose the ship to be in the N.E.
quadrant of the storm, which is traveling
north, the storm will pass to the west, but
the wind  will change from S.E. to S., and
so on to the west, with the hands of a
watch, though it be revolving about the centre against the hands
of a watch; still the rule for finding the direction of the centre
holds good: Face the wind, and the centre in the northern hemisphere will be to the right; in the southern, to the left.
792. Suppose that in the case before us the storm is traveling
Te windstronger on to the north at the rate of 20 miles the hour, and
one side than the other.         that the wind is revolving around the centre also
at the rate of 20 miles the hour: when the vortex bears west
of the ship, the wind will be south. It is going 20 miles to the
north with the body of the storm, and 20 miles around the
centre; total force of the wind, 40 miles an hour on the east




424       THE PHYSICAL GEOGRAPHY OF THE SEA.
side. Now imagine yourself on the other side, that is, that you
are in the northwest quadrant, and that the storm is traveling due
north as before; the vortex will pass east of you, when the wind
should have changed from N.E. to north, turning against the
hands of a watch; but when the wind is north, it is, in the case
supposed, traveling south at the rate of 20 miles an hour around
the storm, while the progressive movement of the storm itself is
north at the rate of 20 miles an hour. One motion exactly caneels the other, and there is, therefore, a line of calm and light, or
moderate or not so heavy winds on one side of the centre, while
on the other side there is a line of maximum violence; in other
words, in every traveling cyclone the wind blows harder on one
side than the other. This is the case in both hemispheres; and
by handling these moving diagrams for illustration, the navigator
will soon become familiar with the various problems for determining the direction of the vortex, the course it is traveling, its distance, etc. Therefore, when it is optional with the navigator to
pass the storm on either side, he should avoid the heavy side.
These remarks apply to both hemispheres.
793. Captain Toynbee asks if it rains more in one quarter of a
The rainy quadrantof cyclone than another? In cyclones that travel fast,
a cyclone.   I suppose there would be most rain in the cfter quarter; with those that have little or no progressive motion, I conjecture that the rainy quarter, if there be one, would depend upon
the quarter whence that wind comes that brings most rain. The
rain in a cyclone is supposed to come from the moisture of that
air which has blown its round and gone up in the vortex; there it
expands, grows cool, and condenses its vapor, which spreads out
at top like a great mushroom in the air, the liberated heat adding
fury to the storm.
794. Such, briefly stated, are the two theories. They appear
Erroneou theories. to me, from such observation and study as I have
been able to bestow, to be neither of them wholly right or altogether wrong. Both are instructive, and the suggestions of one
will, in many instances, throw light upon the facts of the other.
That rotary storms do frequently occur at sea we know, for vessels have sometimes, while scudding before the wind in them,
sailed round and round.  The United States brig "Perry" did
this a few years ago in the West Indies; and so did the "Charles




~ 795, 796.   STORMS, HURRICANES, AND TYPHOONS.        425
Hieddle" in the East Indies: she went round and round a cyclone
five times.
795. From such observations as I have been able to obtain
The windin a true upon the subject, I am  induced to believe, with
cyclone blows in spirals.       Thom, that the wind in a cyclone does not blow
round in a circle, but around in spirals. Nay, I go farther, and
conjecture that it is only within a certain distance of the vortex
that the wind gyrates, and that the gyrating column is never
hundreds of miles in diameter, as the advocates of this theory make
it: I shall allude to this again. The low barometer at the centre
is owing, in part, to two causes; one is the condensation of vapor,
with its liberated heat, as maintained by Espy; the other is the
action of a real centrifugal force, which applies to all revolving
bodies. In weighing the effect of this centrifugal force upon the
low barometer, care should be taken not to give it an undue
weight. It is not sufficient to cause the air to fly off in a tangent.
The lateral atmospheric pressure would prevent that, if the centrifugal force were liever so great; and the lower the barometer
in the centre, the greater would be the pressure of the surrounding air. The proper weight, therefore, due the centrifugal force
I hold to be not very great, though it is appreciable to this extent: The storm having commenced revolving, the flow of air into
the vortex is retarded, not prevented, by centrifugal tendency;
and this retardation assists in causing the barometer to stand lower than it would if there were no revolution. Any one who has
watched the little whirlwinds so often seen during summer and
fall, or who can call to mind the whirls or " sucks" in a mill-poind,
or at the lock in a canal when the water is drawn off at the bottom, may appreciate the extent to which the centrifugal tendency
will help to make a low barometer at the centre of a cyclone.
796. The low barometer, the revolving storm, and the ascendAnillustration. ing column require for a postulate the approach
by spirals of the wind from circumference to centre. The wind
blows toward the place of low barometer; that is admitted by all.
It can only reach that place by a direct or by a curvilinear motion. If by the former, then there can be no revolution; but if
there be'revolution, then the air, while as wind it is revolving
around the centre in the gyrations of the storm, is approaching
the centre also. Hence we derive the elements of a spiral curve;




426        THE PHYSICAL GEOGRAPHY OF THE SEA.
and the physical necessity for spiral motion is demonstrated from
the fact that there is circular motion and an uprising in the centre.
This spiral movement and the uprising may be illustrated by familiar examples: The angles and corners of the Observatory,
and its wings, are so arranged that at a certain place there is, with
westerly winds, always a whirlwind. This whirlwind is six to
eight feet in diameter; and when there is snow, there is a pile of
it in the centre, with a naked path, in the shape of a ring, three or
four feet broad about it. It is the spiral motion which brings the
drift-snow to the centre or vortex, and the upward motion not being strong enough to carry the snow up, it is left behind, forming
a sort of cone, which serves as a cast for the base of the vortex.
If you throw chips or trashy matter into the lock of a canal and
watch them, you will see that as they come within the influence
of the " suck" they will approach the whirl by a spiral until they
reach the centre, when, notwithstanding they may be lighter than
the water, they will be "sucked" down. Here we see the effects
of centrifugal force upon a fluid revolving within itself. The
"suck" is funnel-shaped. As it goes dclown, the lateral pressure
of the water increases; it counteracts more and more the, effect
of centrifugal force, and diminishes, by its increase, the size of the
" suck. "
797. So, too, with the little autumnal whirlwinds in the road
Dust whirlwinds and and on the lawn: the dust, leaves, and trash will
water-spouts. be swept in toward the centre at the bottom, whirl
round and round, go up in the middle, and be scattered or spread
out at the top. I recollect seeing one of these whirlwinds pass
across the Potomac, raising from the river a regular water-spout,
and, when it reached the land, it appeared as a common whirlwind, its course being marked, as usual, by a whirling column of
leaves and dust. These little whirlwinds are, I take it, the great
storms of the sea in miniature; and a proper study of the miniature on land may give us an idea of the great original on the
ocean.
798. The unequally heated plain is thought to be the cause of
A vera causa. the one. But there are no unequally heated plains
at sea; nevertheless, the pfrimum mnobile there is said, and rightly
said, to be heat. Electricity, or some other imponderable, may
be concerned in the birth of the whirlwind both ashore and afloat.




~ 799.      STORMS, HURRICANES, AND TYPHOONS.            427
But that is conjecture; the presence of heat is a fact. In the
middle of the cyclone there is generally rain, or hail, or snow;
and the amount of heat set free during the process of condensing
the vapor for this rain, or hail, or snow, is sufficient to raise from
the freezing to the boiling point more than five times the whole
amount of water that falls. This vast amount of heat is set free,
not at the surface of the sea, it is true, but in the cloud-region,
and where the upward tendency of the indraught is still farther
promoted. What sets the whirlwind a brewing is another question; but its elements being put in motion, there is a diminished
barometric pressure, first, on account of centrifugal tendency; next,
on account of the ascending column of air, which expands and
ascends-ascends and expands on account of such diminished
pressure — and next, though not least, on account of the heat
which is set free by the condensation of the vapor which forms
the clouds and makes the rain. This heat expands and pushes
aside the upper air still more.
799. After much study, I find some difficulties about the cyObjections to the the- clone theory that I can not overcome. They are
ory.         of this sort: I can not conceive it possible to have
a cyclone with a revolving and traveling disc 1000, 500, or even
100 miles in diameter, as the expounders of the theory have it.
Is it possible for a disc of such an attenuated fluid as common
air, having 1000 miles of diameter with its less than wafer-like
thickness in comparison, to go traveling over the earth's surface
and revolving about a centre with tornado violence? WVith the
log-books of several vessels before me that are supposed to have
been in different parts of the same cyclone, I have a number
of times attempted to project its path, but I always failed to
bring out such a storm as the theory calls for. One or two vessels may do it; but is their testimony sufficient?  I think not.
Take as many as six or seven at sea, and their records never
prove the existence of such a storm as the theory calls for. I
make a distinction between the hauling of the wind in consequence of diurnal rotation of the earth, and the rotation of the
wind in the cyclone in consequence of its centripetal force. For
the sake of illustrating my difficulties a little farther, let us suppose a low barometer with a revolving storm to occur at A in the
southern hemisphere. Let the storm be traveling toward B. Let




428        THE PHYSICAL GEOGRAPHY OF THE SEA.
observers be at c", d, and e, and let c" and d be each several hundred miles from A. Now, then, will not the air at c" and d blow
north and east as directly for the place of low barometer as it
would were that place an oblong, NA, instead of a disc, as per the
arrows?  And why should it be a disc in preference to an ellipse,
a square, an oblong, or any figure, be it never so irregular?  The
trade-winds answer, and show
c"?-~          A     I     V_  the equatorial calm belt-an ob/,........  ---. -----.... —_ —---
long-as their place of meeting.
SBut the cyclonologists, instead
of permitting the wind at the
t e                         distance c" to blow to the east,
and at d to blow to the north,
merely because there is a low
barometer east of c" and north of d, require it so to blow because,
by their theory, there is a low barometer east of d and south of c"! 
Thus, to reach its theoretical place of destination, the wind must
blow in a direction at right angles to that destination! It would
require a rush of inconceivable rapidity so to deflect currents of
air while they are yet several hundred miles from the centre of
gyration. Moreover, the two cyclonologists, c" and d, would differ with each other as to the centre of the storm. The one in ship
d would place it to the east of him, or in that direction, but the
other, c", would place it to the south of him, as in the direction c'.
The gyrating disc of a cyclone can never, I apprehend, exceed
a few miles in diameter.  On shore we seldom find it exceeding in breadth as many rods, in most cases not as many fathoms, as its advocates give it miles at sea.  I think the dust-whirl
in the street is a true type of the tornado (cyclone) at sea.  Imagine such a case to occur in nature as the one just supposed.
With the observations of d alone before him, the cyclonologist
would say the storm was traveling west, but passing north; with
the log of c", he would say it travels west, but will pass south of
us. By the rule, ship d would be led toward the real track of the
storm, i. e., into danger, and ship c away from it.*
800. There are in the various parts of the storm at least three
The three forces. forces at work in effecting a change of wind, as ob* See letter to Commodore W5iillerstorf, p. 457, vol. ii., 8th ed. Maury's Sailing
Directions.




~ 801-803.   STORMS, HURRICANES, AND TYPHOONS.         429
served on board ship at sea. (1.) One is diurnal rotation: it
alone can never work a change of direction exceeding 90~; (2.)
another is the varying position or traveling motion of the place
of barometric depression: the change effected by it can not exceed 180~; (3.) and the third is the whirling motion imparted by
the rush to a common centre-the whirl of water at the floodgate of the mill, the whirlwind in the street.
801. Hence it appears that in a storm the wind may shift from
The effect of each. any one of three causes, and we are not entitled to
call it a cyclone unless the wind shift more than 180~. If the
change of direction be less than 90~, the shifting may be due to
diurnal rotation alone; if it be less than 1800, the shifting may,
and is probably, due to (1) and (2). The sailor has therefore no
proof to show that he has been in a cyclone unless the wind during the storm changed its direction more than 180~. Cyclones,
there is reason to believe, are often whirlwinds in a storm. This
may be illustrated by referring again to our miniature whirlwinds
on the land; there we often see a number of them at one time
and about the same place; and they often appear to skip, raging
here, then disappearing for a moment, then touching the ground
again, and pursuing the former direction.
802. Observations have proved that this is the case on land,
A torm withinastorm. and observations have not established that this is
not the case at sea; observations are wanting upon this subject.
Tornadoes on the land often divide themselves, sending out branches, as it were. It remains to be seen whether cyclones do not do
the same at sea; and whether, in those widespread and devastating storms that now and then sweep over the ocean, there be only
one vortex or several; and if only one, whether the whole storm
partake of the cyclone character. In other words, may there not
be a storm within a storm-that is, a cyclone traveling with the
storm and revolving in it? I ask the question because the theory does not satisfy all the facts observed.
803. The celebrated Black Sea storm of 1854, which did so
The Black Sea storm much damage to the allied fleet, is still maintained
of 1854.    by some to be a true cyclone; and by the observations of some of the vessels a cyclone may be made out. But if
we take the observations of all of them, and discuss them upon
the supposition that the whole storm was a cyclone, it will puzzle




430        THE PHYSICAL GEOGRAPHY OF THE SEA.
any one to make any thing of them.  Admiral Fitz Roy, in the
Meteorological Papers of the Board of Trade, published diagrams
of the winds as observed during that storm on board of various
vessels in various parts of that sea. I have not been able to reconcile them with the cyclone theory. Espy maintains that they
confirm his theory; and his (~ 787) is anti-cyclonic.
804. The cyclones of the North Atlantic take their rise generCyclones of the North ally (~ 785) somewhere between the parallels of 10~
Atlantic.      and 20~ north.  They take a westerly- course until
they fall in with the Gulf Stream, when they turn about and run
along upon it until their force is expended. The atmosphere over
the Gulf Stream is generally well charged with moisture, and in
this fact perhaps will be found the reason why the path of the
storm is laid along the Gulf Stream.
The hurricane sea-   805. The following table is from  Birt's HandEOn.          book of Storms:
Average Number of Cyclones or HIurricanes which have occurred in different Mlonths
of the Year, and in various Regions.
Locality.  Jan.  Feb.  Mar.  April.  May.  Jun.  July.  Aug.  Sep.   Oct.  Nov.  Dec. I Total.
West Indies....   1  2            4  15 36 25 27  1  2 113
S. Indian Ocean  9  13  10   8   4.........  1  1  4  3  53
Mauritius........ 9  15  15   8.......6  53
Bay of Bengal...     1   1   7   3...  1...  7  6  3  30
China Sea................     2   5   5   18   10  6...    46
806. The vortex of a cyclone is often and aptly compared to a
Cyclones in the Misis- meteor.  I have often observed the paths of such
sippi Valley.  through the forests of the Mississippi Valley, and
the path has in no instance that has fallen under my observation
been more than a few hundred yards broad.  There the track of
these tornadoes is called a " wind-road," because they make an
avenue through the wood straight along, and as clear of trees as
if the old denizens of the forest had been felled with an axe.  I
have seen trees three or four feet in diameter torn up by the
roots, and the top, with its limbs, lying next the hole whence the
roots came.  Nevertheless, the passage of the meteor, whose narrow path was marked by devastation, would create a great commotion in the air, and there would be high winds raging for several miles on either side of the " wind-road." But (~ 799) let us
consider for a moment the effect of the diurnal rotation of the earth
upon one of these revolving discs 1000 miles in diameter: its height




~ 807.     STORMS, HURRICANES, AND TYPHOONS.            431
would scarcely be two miles, and its thickness would not be as
great, in proportion to its diameter, as half the thickness of this
leaf is to the length of an inch. Now the difference in rate of the
diurnal rotation between the northern and southern limbs of the
disc would be sufficient, irrespective of any other power, to break
it up. Suppose its southern limb to be in 20~ N., its northern limb
would be 1000 miles, say 17~, farther north, that is, in 37~. Diurnal rotation would carry to the east the air in the southern limb
at the rate of 845 miles an hour; but when this same air comes
round on the northern limb, diurnal rotation would carry it eastward at the rate only of 720 miles. Because the wind hauls in a
particular way, it does not, as by diagram (~ 799) it has been
shown, follow that it is blowing in a circle, or that the centre
of the storm is at right angles to its line of direction.
807. In the extra-tropical regions of each hemisphere furious
Extra-tropical gales. gales of wind also occur. One of these, remarkable
for its violent effects, was encountered on the 24th of December,
1853, about three hundred miles from Sandy Hook, latitude 390
north, longitude 70~ west, by the "San Francisco," steam-ship.
That ship was made a complete wreck in a few moments, and she
was abandoned by the survivors, after incredible hardships, exertions, and sufferings. Some months after this disaster I received
by the California mail the abstract log of the fine clipper ship' Eagle Wing" (Ebenezer H. Linnell), from Boston to San Francisco. She encountered the ill-fated steamer's gale, and thus describes it: "December 24th. Latitude 39~ 15' north, longitude
62~ 32' west. First part threatening weather; shortened sail; at
4 P.M. close-reefed the top-sails and furled the courses. At 8
P.M. took in fore and mizzen top-sails; hove to under close-reefed main top-sail and spencer, the ship lying with her lee rail under water, nearly on her beam-ends. At 1 30 A.M. the fore and
main top-gallant-masts went over the side, it blowing a perfect
hurricane. At 8 A.M., moderated; a sea took away jib-boom
and bowsprit cap. In my thirty-one years' experience at sea, I
have never seen a typhoon or hurricane so severe. Lost two men
overboard-saved one.  Stove skylight, broke my barometer,
etc., etc." Severe gales in this part of the Atlantic —-i.e., on the
polar side of the calm belt of Cancer-rarely occur during the
months of June, July, August, and September. This appears to




432       THE PHYSICAL GEOGRAPHY OF THE SEA.
be the time when the fiends of the storm are most busily at work
in the West Indies. During the remainder of the year, these extra-tropical gales, for the most part, come from the northwest.
But the winter is the most famous season for these gales. That
is the time when the Gulf Stream has brought the heat of summer
and placed it (~ 172) in closest proximity to the extremest cold of
the north. And there would, therefore, it would seem, be a conflict between these extremes; consequently, great disturbances in
the air, and a violent rush from the cold to the warm. In like
manner, the gales that most prevail in the extra-tropics of the
southern hemisphere come from the pole and the west, i. e., southwest.
-808. Storm and Rain Charts for the Atlantic Ocean have alStorlland Rain Charts. ready been published by the Observatory, and
others for the other oceans are in process of construction. The object of such charts is to show the directions and relative frequency of calms, fogs, rain, thunder, and lightning.  These charts
are very instructive.  They show that that half of the atmospherical coating of the earth which covers the northern hemisphere-if we may take. as a type of the whole what occurs onl
either side of the equator in the Atlantic Ocean-is in a much
less stable condition than that which covers the southern.




~ 811-813. THE WINDS OF THE SOUTHERN HEMISPHERE.    43z
CHAPTER XX.
~ 811-841.-THE WINDS OF THE SOUTHERN HEMISPHERE.
811. A WORK of this sort, which is progressive, must necessariRepetition often nece- ly bear with it more or less of repetition.  It emsary.         bodies the results of the most extensive system of
philosophical observations, physical investigation, and friendly cooperation that has ever been set on foot. As facts are developed,
theories are invented or expanded to reconcile them. As soon as
this is done, or in a short time thereafter, some one or more of the
fleets that are out reconnoitring the seas for us returns with additional facts for our store-house of knowledge. ~Whether these tend
to confirm or disprove the theory, a restatement is often called for;
hence the repetition, of which the case before us is an example.
812. The facts stated in Chap. XV. go to show that the southThe S.E. and N.E. east trade-winds are stronger than the northeast.
trade-winds pot in a
balance.     The barometer tells us (~ 643) that between the
parallels of 5~ and 200 the southeast trade-winds bear a superincumbent pressure upon the square foot of nearly 4 pounds
greater than that to which the northeast trades are subjected.
Such an excess of superincumbent pressure upon a fluid so elastic
and subtle as air ought to force the southeast trade-winds from
under it more rapidly than the lighter pressure forces the northeast. Observations showing that such is or is not the case should
not be ignored.
813. I have evidence from all the vessels in a fleet numbering
Observations by 2235 no less than 2235 sail to show that the southeast
vessels,      are stronger than the northeast trades. Every one
of these vessels passed through both systems of trade-winds. The
knots run per hour by each one of them, as they passed through
the southeast trades of the Indian Ocean and through both systems of the Atlantic, have been discussed from crossing to crossing.  The average result in knots per hour is expressed in the annexed table, p. 434. The comparison is confined to the rate of
sailing between the parallels of 10~ and 25~, because this is the
belt of steadiest trades.
EE




434          THE PHYSICAL GEOGRAPHY OF THE SEA.
Average Speed through the Trade-winds of the North Atlantic and South Indian
Oceans.
Knots per Hour from
100 to 150. - 15~ to 200. I 20~ to 25.  Average.    Course steered through
Month.'' U   Trade rs.
~Month.   3 e4  I r i                Q1     N.E. Trades. S.E. Trades. 
Z E       Z 0'  3   eat    d (N. Atlantic.) (S. I. Ocean.)
January......8    64  74   7    6    6    7    64  N. 490 W.  S. 690W.
February..... 74  6    6    63  5    6    6    6   N. 46 W.. 
March........8    7    7    7    57     6I  61   61  N. 47  W.        " 
April.......... 7    7   54   7'4-  4 6    6    6  N. 48  W.  S. 700~W.
May...........  8S7  8    61  7~4  6    6    7    7   N. 46 W.        "
June.......... 9    71  8    74   54   7    74   7   N. 43  W.        " 
July...........  5~  8    8    8'   64   7    64   7i  N. 46 W.  "c
August........ 44 7{  6    84   4:  7    5    7 —  N. 40  W. S. 690 W.
September.... 5   8f   6    8    4    6I  5    74  N. 50  W.  "
October.....  74   84  64   8    6    5    6-I  74  N. 45 W.!         "
November....  6    8    6    7    4-      54       3 63  N. 495 W. 
December....6    6    61    6    5    5    6    6   N. 48 W.. 
Means...... 7         6    7 5 6 6 7   N. 47 W. S. 690 W.
Average course steered through the N.E. trades of the N. Atlantic Ocean, N.. 4 W.
tr      " "      ":" S.E. trades of the S. Indian Ocean, W.S.W.
Average Speed through the Trade-winds of the North and South Atlantic Oceans.
Knots per Hour from                      [
250 to 200. 200 to 15~. 150 to 100.  Average.    Courlse steered through
Month.      u; ~ 
c5;  3 e4 Xws X  i a;Iwo Fi4 4'  S.E. Trades. N.E. Trades.
Ca r 4 R;   i P    vi P       (S. Atlantic.) (N. Atlantic.)
January......  6    5    5_    5z  5-  74-  6    6   N. 540 W.  S. 210 E.
February.....  41  5    5~  64   6    7    54   6   N. 55 W.  S. 25  E.
March........ 6'  44 6    61 6    71 6    64  N. 55  W.  S. 22 E.
April.......... 54 5]  54  64  (3 6    7    6    64  N. 53  W.  S. 22- E.
May........... 5    5    54   64   64  7    6    6   N.55  W.  S. 244 E.
Jun e........... 5    6    6    6    7    5    6(   5-  N. 55 W.  S. 28 E.
July........... 5 7    6    74~ 6    4-  6    6   N. 55 W.  S. 27 E.
August........ 5    5    1 5     6    6    4    5i  51  N. 55  W.  S. 28~ E.
September... 51  31 61  51   7   5    64  44  N. 55  W.  S. 221 E.
October..... 51  44   6   44   54   4    51  44  N.56 W.  S. 20  E.
November.... 6    4    6   54   64  54   64  5   N. 55  W.  S. 22- E.
December.... 5     44   5    6    64   7    5-   5   N. 55 W.  S. 23  E.
Means......'5.5   51   6  6 6    6    6    5.   N. 55  W.  S. 240 E.
Average course steered through the S.E. trades of the S. Atlantic, N.W. by W.
"       "        N.E. trades of the N. Atlantic, S.S.E.
814. It is well to observe, that on  each of these three oceans,
Ships used as anemom- though the direction of the wind is the same, the
eters.            course  steered by  each fleet is different; consequently, these anemometers are at different angles with the wind;
through the southeast trades the wind is nearly aft in the Atlantiq, and quartering in  the Indian Ocean, giving an  average sailing speed of 7 knots an hour in the latter, and of 6 in the former;




~ 815, 816. THE WINDS OF THE SOUTHERN HEMISPHERE.            435
while through the northeast trades the average speed is 6] knots
an hour one way (N.W. i  W.), with the wind just abaft the beam,
and 5T the other (S.S.E.), with the wind at a point not so favorable for speed. Indeed, most of the ships which average a S.S.E.
course through this part of the northeast trade-wind belt are close
hauled; therefore the average strength of the trades here can not
be fairly compared with the average strength where the fleet have
free winds. What is the difference in the strength of such winds,
which, impinging upon the sails, each at the particular angle indicated above, imparts the aforesaid velocities?  Moderate winds,
such as these are, give aship her highest speed generally when
they are just abaft the beam, as they are for a northwest course
through the northeast trades of the N. Atlantic. So, to treat these
ships as anemometers which will really enable us to measure the
comparative strength of the winds, we should reduce the average knots per hour to the average speed of a mean ship sailing
through average " trades" in each ocean, with' the wind impinging upon her sails at the same angle for all three, as, for example,
just abaft the beam, as in the North Atlantic.
815. Let us apply to the average speed through the South AtlanVelocity of the trade- tic and Indian Oceans such a correction. Through
winds.       the former the wind is aft; through the latter, quartering. If we allow two knots as a correction for the one, and
one knot for the other, we shall not be greatly out. Applying
this correction, we may state the speed of a mean ship sailing
with average trades just abaft the beam to be as follows:
Through the N.E. of the Atlantic......... 6+ knots per hour.*
t"  "s S.E.  "     "......... 8  "   "  "
cc    " S.E. "  Indian Ocean.. 8     "  "'
I do not take into this comparison the force of the N.E. trades on
a S.S.E. course (~ 813), because the winds along this route are
known not to be as steady as they are farther away from the African coast. Thus it is clearly established that the S.E. trades are
stronger than the N.E., and so they should be if there be a crossing
of winds in the calm belt of CGaprlcorn.
816. The counter-trades of the southern hemisphere move, as
* The correctness of this estimate is sustained by experiments which Admiral
Chabannes, in command of the French fleet on the coast of Brazil, has been so kind
as to institute. See note, p. 343-5.




436       THE PHYSICAL GEOGRAPHY OF THE SEA.
Ditto of the counter- before stated, toward their pole more steadily and
trades.      briskly than do the counter-trades of the northern
hemisphere.  To give an idea of the difference of the strength of
these two winds, I cite the fact that vessels sailing through the
latter, as from New York to England, average 150 miles a day.
Along the corresponding latitudes through the former, as on a
voyage to Australia, the average speed is upward of 200 miles a
day.  Consequently, the counter-trades of the southern hemisphere transport in given times larger volumes of air toward the
south than our counter-trades do toward the north.  This air returns to the tropical calm belts as an upper current. If, descending there, it feeds the trade-winds, then, the supply being more
abundant for the S.E. trades than for the N.E., the S.E. trades
must be the stronger; and so they are; observations prove them
so to be. Thus the crossing of the air at the tropical calm belts,
though it may not be proved, yet it is shown to be so very probable that the onus of proof is shifted. It now rests with those
who dispute the crossing to prove their theory the true one.
817. Arrived at this point, another view in the field of conjecThewavestheygetup. ture is presented, which it is proper we should
pause to consider. The movements of the atmosphere on the
polar side of 40~ N. are, let it be repeated, by no means so constant from the west, nor is the strength of the westerly winds
there nearly so great on the average as it is in the extra-tropical
regions of the south.  This fact is well known among mariners.
Every one who has sailed in that southern girdle of waters which
belt the earth on the polar side of 40~, has been struck with the
force and trade-like regularity of the westerly winds which prevail there. The waves driven before these winds assume in their
regularity of form, in the magnitude of their proportions, and in
the stateliness of their march, an aspect of majestic grandeur that
the billows of the sea never attain elsewhere. No such waves
are found in the trade-winds; for, though the S.E. trades are quite
as constant, yet they have not the force to pile the water in such
heaps, nor to arrange the waves so orderly, nor to drive them so
rapidly as those " brave" winds do. There the billows, chasing
each other in stately march, look, with their rounded crests and
deep hollows, more like mountains rolling over a plain than the
waves whinch we are accustomed to see.  Many days of con



~ 818, 819. THE WINDS OF THE SOUTHERN HEMISPHERE.        437
stant blowing over a wide expanse of ocean are required to get
up such waves. It is these winds and waves which, on the voyage to and from Australia, have enabled the mode-n clipper-ship
to attain a speed, and, day after day, to accomplish runs which at
first were considered, even by the nautical world, as fabulous, and
are yet regarded by all with wonder and admiration.
818. Seeing, therefore, that we can bring in such a variety of
A meteorological co- facts and circumstances, all tending to show that the
rollary.     southeast trade-winds are stronger than the northeast, and that the westerly winds which prevail on the polar side
of 40~ S. are stronger and more constant than their antoecian fellows of the north, we may consider it as a fact established, independently of Plate XIII., that the general system of atmospherical circulation is more active in the southern than it is in the northern hemisphere. And, seeing that it blows with more strength
and regularity from the west in the extra-tropical regions of the
southern than it does in the extra-tropical regions of the northern
hemisphere, we should deduce, by way of corollary, that the counter-trades of the south are not so easily arrested in their course, or
turned back in their circuits, as are those of the north. Consequently, moreover, we should not, either in the trades or the counter-trades of the southern hemisphere, look for as many calms as
in those of the northern systems.
819. Therefore, holding to this corollary, we may consider the
Facts established. following as established facts in meteorology: That
the S.E. trade-winds are stronger than the N.E.; that the N.W.
passage-winds-the counter-trades of the south —are stronger and
less liable to interruption in their circuits than the S.W., the counter-trades of the north; that the atmospherical circulation is more
regular and brisk in the southern than it is in the northern hemisphere; and, to repeat: since the wind moves in its circuits more
briskly through the southern than it does through the northern
hemisphere, it consequently has less time to tarry or dally by the
way in the south than in the north; hence the corollary just stated.
But observations also, as well as mathematically-drawn inferences, show that calms are much less prevalent in the southern hemisphere. For this inference observations are ample; they are grouped together by thousands and tens of thousands, both on the Pilot
and the Storm and Rain Charts. These charts have not been com



438         THE PHYSICAL GEOGRAPHY OF THE SEA.
pleted for all parts of the ocean, but as far as they have been constructed the facts they utter are in perfect agreement with the
terms of this corollary.
820. These premises being admitted, we may ascend another
Atmospherical cilrcl- round on this ladder, and argue that, since the atlation more active in
the sothern than in mosphere moves more briskly and in  more conthe northern hemisphere.        stant streams through its general channels of circulation in the southern than it does through them  in the northern
hemisphere; and that, since it is not arrested in its courses by
calms as often in the former as it is inll the latter, neither should
it be turned back by the way, so as to blow in gales from the direction opposite to that in which the general circulation carries it.
The atmosphere, in its movements along its regular channels of
circulation, may be likened, that in the southern hemisphere to a
fast railway train; that of the northern to a slow.  The slow train
may, when "steam  is up," run as fast as the fast train, but it is not
obliged to get through so quick; therefore it may dally by the
way, stop, run back, and still be through in time.  Not so the fast;
it has not time to stop often or to run back far; neither have the
counter-trades of the south time to blow backward; consequently,
such being the conditions, we should also expect to find in the extra-tropical south a gale with easting in it much more seldom than
in the extra-tropical north.
821. We shall appeal to observations for the correctness of this
Galeinthetwohemi- conjecture, and claim  for it, also, as presently will
spheres.         appear, the dignity of an established truth.
Average Number qof Gales (to the 1000 Observations) with Easting and with'VMesting in
them between the correspondi'ng Parallels in the North and South Atlantic, as shown
by the Storml and Rain C(iarts.
North.    South.
Number of observations............17, 274    8756
Between 400 and 45~,   Gales in 1000 do. with easting...  23       12
4 "    "  do. "' westing..       66       82
Number of observations...........   11,425    5548
Between 45~ and 500~   Gales in 1000 do. with easting...   24       1
( "    "  do. "  westing..      106       61
iNumber of observations.........4.. 4,816    5169
Between 500 and 55~,   Gales in 1000 do. with easting...  24       10
{ "     "  do. "  westing..     144  97
Thus the Storm  and Rain Charts show that between the parallels
of 400 and 55~ there were in the northern hemisphere 33,515 ob



~ 822.     THE WINDS OF THE SOUTHERN HEMISPHERE.                        439
servations, and that for every 1000 observations there were 24
gales with easting and 105 with westing.  In the southern, there
were 19,473 observations, and for every 1000 of these there were
5 gales with easting and 80 with westing in them. Those for the
southern hemisphere are only for that part of the ocean through
which vessels pass on their way to and fro around Cape IIorn.
That part of this route which lies between 40  and 55~ S. is under the lee of South America; and Patagonia, that lies east of the
Andes, is almost a rainless region; consequently, we might expect
to find more unsteady winds and fewer rains in that part of the
ocean where the observations for the southern part of the tables
were made than we should expect to meet with well out to sea,
as at the distance of two or three thousand miles to the eastward
of Patagonia.  So that the contrast presented by the above statement would probably be much greater did our observations extend entirely across the South, as they do across the North Atlantic.  But as it is, the contrast is very striking.  In some aspects,
the meteorological agents of the two hemispheres, especially those
forces which control the winds and the weather, differ very much.
The difference is so wide as to suggest greater regularity and rapidity of circulation on one side of the equator than on the other.
822. Average Number of Calms to the 1000 Observations between the Parallels of
Calms in the two 300 and 550 in the North and South Atlantic, and between the
hemispheres.      Parallels of 300 and 60~ in the North and South ~Pacific Oceans,
as showsn by the Pilot Charts.
Atlantic.           Pacific.
Between the Parallels of
Between the Parallels of  North.   South.    North.  Sooth.
30~ and 350, No. of observations...... 12,935   15, 842    22,730   44,846
Calms to the 1000 do............    46    26         34        35
35~ and 400, No. of observations...... 22,136   23, 439    13, 939   6, 275
Calms to the 1000 do................    37    24         31       23
400 and 450, No. of observations...... 16,363    8,203    12,400   31,889
Calmns to the 1000 do..............    45     27        53        23
450 and 500, No. of observations......  8,907    4,188    15,897  4,940
Calms to the 1000 do..................38     25         35       21
500 and 55~, No. of observations......  3,519    3,660    32,804  9,728
Calms to the 1000 do...................  40   16         32        17
550 and 600, No. of observations......                 15,470     9,111
Calms to the 1000 do.................                    43        21
Total No. of observations......... 63,050   55,327   113,240  166,829
Average calms to the 1000 do.      41       24         39        25
Each one of these observations embraces a period of eight hours;
the grand total, if arranged consecutively, with the observations




440       THE PHYSICAL GEOGRAPHY OF THE SEA.
drawn out each to occupy its period separately, would be equal
to 373 years. They exhibit several curious and suggestive facts
concerning the difference of the atmospherical stability in the two
hemispheres.
823. If we would discover the seat of those forces which proThe propelling power duce this difference in the dynamical status of the
of tlhe inds. two great aerial oceans that envelop our planet,
we should search for them in the unequal distribution of land and
water over the two hemispheres. In one the wind is interrupted
in its circuits by the continental masses, with their wooded plains,
their snowy mantles in winter, their sandy deserts in summer, and
their mountain ranges always. In the other there is but little
land and less snow. On the polar side of 40~ S. especially, if we
except the small remnant of this continent that protrudes beyond
that parallel in the direction of Cape Horn, there is scarcely an
island. All is sea. There the air is never dry; it is always in
contact with a vapor-giving surface; consequently, the winds there
are loaded with moisture, which, with every change of temperature, is either increased by farther evaporation or diminished by
temporary condensation.  The propelling power of the winds in the
southern hemisphere resides chiefly in the latent heat of the vapor which
they suck uzp from the engirdling sea on the polar side of Capricorn.
824. The Storm and Rain Charts show that within the tradeLt. VanGogh's Storm wind regions of both hemispheres the calm and rain
andRain hart.  curves are symmetrical; that in the extra-tropical
regions the symmetry is between the calm and fog curves; and
also, especially in the southern hemisphere, between the gale and
rain curves. Lieutenant Van Gogh, of the Dutch Navy, in an interesting paper on the connection between storms near the Cape
of Good Hope and the temperature of the sea,* presents a storm
and rain chart for that region. It is founded on 17,810 observations, made by 500 ships, upon wind and weather, between 14~
and 32~ E., and 33~ and 370 S. By that chart the gale and rain
curves are so symmetrical that the phenomena of rains and gales
in the extra-tropical seas present themselves suggestively as cause
and effect. The general storm and rain charts of the Atlantic
* De Stirmen nabij de Kaap de Goede Hoop in verband beschouwd met de Temperatuur der Zee.




~ 825, 826. THE WINDS OF THE SOUTHERN HEMISPHERE.          441
Ocean, prepared at the National Observatory, hold out the same
idea. Let us examine, expand, and explain this fact.
825. We ascribe the trade-winds to the equatorial calm-belt.
The "brave west But to what shall we ascribe the counter-trades, parr.arctio,,ind tbY ticularly. of the southern hemisphere, which blow
antarctic regions.  with as much regularity toward the pole as the
northeast trades of the Atlantic do toward the equator? Shall we
say that those winds are drawn toward the south pole by heat,
which causes them to expand and ascend in the antarctic regions?
It sounds somewhat paradoxical to say that heat causes the winds
to blow toward the poles as well as toward the equator; but, after
a little explanation, and the passing in review of a few facts and
circumstances, perhaps the paradox may disappear. It is held as
an established fact by meteorologists that the average amount of
precipitation is greater in the northern than in the southern hemisphere; but this, I imagine, applies rather to the land than the
sea. On the polar side of 40~ it is mostly water in the southern,
mostly land in the northern hemisphere. It is only now and
then, and on rare occasions, that ships carry rain-gauges to sea.
We can determine by quantitive measurements the difference in
amount of precipitation on the land of the two hemispheres, and
it is the result of this determination, I imagine, that has given
rise to the general remark that the rain-fall is greater for the
northern than it is for the southern hemisphere. But we have
few hyetographic measurements for quantity at sea; there the
determinations are mostly numerical.  Our observers report the
" times" of precipitation, which, whether it be in the form of rain,
hail, or snow, is called by the charts, and in this discussion, rain.
Among such a large corps of observers, rain is sometimes, no
doubt, omitted in the log; so that, in all probability, the charts do
not show as many " times" with rain as there are " times" actually
with rain at sea. This omission, however, is as likely to occur in
one hemisphere as in the other. Still, we may safely assume that
it rains oftener in all parts of the sea than our observations, or the
rain charts that are founded on them, indicate.
826. With the view of comparing the rains at sea between the
Relative frequency of parallels of 55~ and 60~, both in the North and
rains and gales at sea. South Atlantic, we have taken from the charts the
following figures:




442       THE PHYSICAL GEOGRAPHY OF THE SEA.
South-Observations, 8410; gales, 1228; rains, 1105
North —    "    526;  "  135;  "   64
Gales to the 1000 observations.. S. 146;   N. 256
Rains   "        ". S. 131;   N. 121
That is, for every 10 gales, there are in the southern hemisphere
9 rains, and inll the northern 4.7. In which hemisphere does most
water fall on the average during a rain at sea?  Observations do
not tell, but there seems to be a philosophical reason why it should
rain not only oftener, but more copiously at sea, especially in the
extra-tropical regions, in the southern hemisphere than in those
of the northern.  1On the polar side of 40~ N., for example, the
land is stretched out in continental masses, upon the thirsty bosom
of which, when the air drops down its load of moisture, only a
portion of it can be taken up again; the rest is absorbed by the
earth to feed the springs. On the polar side of 40~ S. we have
a water instead of a land surface, and as fast as precipitation takes
place there, the ocean replenishes the air with moisture again. It
may consequently be assumed that a high dew-point —at least one
as high as the ocean can maintain in contact with winds blowing
over it, and going from warmer to cooler latitudes all the time —is
the normal condition of the air on the polar side of 400 S., whereas on the polar side of 40~ N. a low dew-point prevails.  The
rivers to the north of 40~ could not, I reckon, if they were all
converted into steam, supply vapor enough to make up this average difference of dew-point between the two hemispheres.  The
symmetry of the rain and storm curves on the polar side of 40~
S. suggests that it is the condensation of this vapor which, with
the liberation of its latent heat, gives such activity and regularity
to the circulation of the atmosphere in the other hemisphere.
827. On the polar side of 40~ S., near Cape Horn, the gauge of
The rain-faIl of Cape Captains King and Fitzroy showed a rain-fall of
1Iorn and Cherraponjie.      153.75 inches in 41 days. There is no other place
except Cherraponjie where the precipitation approaches this in
amount. Cherraponjie (~ 299) is a mountain station in India,
4500 feet high, which, in lat. 25~ N., acts as a condenser for the
monsoons fresh from the sea. But on the polar side of lat. 45~, in
the northern hemisphere, it is, except along the American shores
of the North Pacific, a physical impossibility that there should be
a region of such precipitation as King and Fitzroy found on the




~ 828.   THE WINDS OF THE SOUTHERN HEMISPHERE.          443
western slopes of Patagonia-a physical impossibility, because
the peculiar combination of conditions required to produce a Patagonian rain-fall are wanting on the polar side of 45~ N. There is
not in the North Atlantic water surface enough to afford vapor
for such an amount of precipitation. In the North Pacific the
water surface may be broad and ample enough to afford the vapor, but in neither of these two northern sheets of water are the
winds continuous enough from the westward to bring in the
requisite quantities of vapor from the sea. MIoreover, if the westerly winds of the extra-tropical north were as steady and as strong
as are those of the south, there is lacking in the north that continental relief-mountain ranges rising abruptly out of the sea,
or separated from it only by lowlands-that seems to be necessary
to bring down the rain in such floods. Colonel Sykes* quotes the
rain-fall of Cherraponjie at 605.25 inches for the 214 days from
April to October, the season of the southwest monsoons. Computing the Cape Horn rains according to the ratio given by King
and Fitzroy for their 41 days of observation, we should have a
rain-fall in Patagonia of 825 inches in 214 days, or a yearly
amount of 1368.7 inches. Neither the Cape Horn rains, nor the
rains any where at sea on the polar side of 45~ S., are periodical.
They are continuous; more copious, perhaps, at some seasons
than at others, but abundant at all.
828. Now, considering the extent of water surface on the polar
Influence of highlands side of the southeast trade-wind belt, we see no
upon precipitation. reason why, on these parallels, the engirdling air
of that great watery zone of the south should not, entirely around
the earth, be as heavily charged with vapor as was that which
dropped this flood upon the Patagonian hills. If those mountains had not been there, the condensation and the consequent
precipitation would probably not have been as great, because the
conditions at sea are less apt to produce rain; but the quantity of
vapor in the air would have been none the less, which vapor was
being borne in the channels of circulation toward the antarctic
regions for condensation and the liberation of its latent heat; and
we make, as we shall proceed to show, no violent supposition if,
in attempting to explain this activity of circulation south of the
equator, we suppose a cloud region, a combination of conditions
* Rleport of the British Association for 1852, ij. 256.




444        THE PHYSICAL GEOGRAPHY OF THE SEA
in the antarctic circle peculiarly favorable to heavy and almost
incessant precipitation. But, before describing these conditions,
let us turn aside to inquire how far precipitation in the supposed
cloud region of the south may assist in giving force and regularity
to the winds of the southern hemisphere.
829. If we take a measure, as a cubic foot, of ice at zero, and
The latent heat of apply heat to it by means of a steady flame that
VapOr.       will give off heat at a uniform rate, and in such
quantities that just enough heat may be imparted to the ice to
raise its temperature 1~ a minute, we shall find that at the end of
32 minutes the ice will be at 32~. The ice will now begin to
melt; but it and its water-the heat being continued —will remain
at 32~ for 140 minutes, when all the ice will have become water
at 32~.*  This 140~ of heat, which is enough to raise the temperature of 140 cubic feet of ice one degree from any point below 32~,
has been rendered latent in the process of liquefaction. Freeze
this water again, and this latent heat will become sensible heat, for
heat no more than ponderable matter can be annihilated. But if,
after the cubic foot of ice has been converted into water at 32~, we
continue the uniform supply of heat as before and at the same rate,
the water will, at the expiration of 180 minutes more, reach the
temperature of 212 —the boiling point-and at this temperature it
will remain for 1030 minutes, notwithstanding the continuous supply of heat during the interval. At the expiration of this 1030
minutes of boiling heat, the last drop of water will have been converted into steam; but the temperature of the steam will be that
only of the boiling water; thus, in the evaporation of every measure of water, heat enough is rendered latent during the process to
raise the temperature of 1030 such measures one degree. If this
vapor be now condensed, this latent heat will be set free and become sensible heat again. Hence we perceive that every rain-drop
that falls from the sky has, in its process of condensation, evolved
heat enough to raise one degree the temperature of 1030 raindrops. But if, instead of the liquid state, as rain, it come down
in the solid state, as hail or snow, then the heat of fluidity, amounting to enough to raise the temperature of 140 additional drops
one degree, is also set free.
830. We have in this fact a clew to the violent wind which
* See Espy's Philosophy of Storms.




~ 831.    THE WINDS OF THE SOUTHERN HEMISPHERE.    445
The cause of the boil- usually accompanies hail-storms.  In the hailterous weather off Cape
-Ioron.      storm congelation takes place immediately after
condensation, and so quickly that the heat evolved during the two
processes may be considered as of one evolution. Consequently,
the upper air has its temperature raised much higher than could
be done by the condensing only. So also the storms which have
made Cape Horn famous are no doubt owing, in a great measure,
to this heavy Patagonian rain-fall. The latent heat which is liberated by the vapor as it is condensed into rain there, has the effect
of producing a great intumescence in the air of the upper regions
round about them, which in turn produces commotion in the air below. But this is digressive. Therefore let us take up the broken
thread, and suppose, merely for illustration, such a rain-fall as
King and Fitzroy encountered in Patagonia to have taken place
under the supposed cloud region of the antarctic circle, and to
have been hail or snow instead of rain, then the total amount of
caloric set free among the clouds, in those 41 days of such a flood,
would be enough to raise from freezing to boiling six and a half
times as much water as fell. But if the supposed antarctic pre.
cipitation come down in the shape of rain, then the heat set free
would be sufficient only to raise from freezing to boiling about
54 as much water as the flood brought down. We shall have,
perhaps, a better idea of the amount of heat that would be set
free, in the condensation and congelation in the antarctic regions
of as much vapor as it took to make the Patagonian rain-fall, if
we vary the illustration by supposing this rain-fall of 153.75
inches to extend over an area of 1.000 square miles, and that it
fell as snow or hail. The latent heat set free among the clouds
during these 41 days would have been sufficient to raise from the
freezing to the boiling point all the water in a lake 1000 square
miles in area and 83T1 feet in depth. The unknown area of the
antarctic is eight millions of square miles. We now see howv
the cold of the poles, by facilitating precipitation, is made to react
and develop heat, to expand the air, and give force to the winds. 
831. Thus we obtain another point of view from which we may
Offices of icebergs in contemplate, in a new aspect, the icebergs which
the meteorological machinery.     the antarctic region send forth in such masses and
numbers. They are a part of the meteorological machinery of
our planet. The offices which they perform as such are most im



446       THE PHYSICAL GEOGRAPHY OF THE SEA.
portant, and oh, how exquisite! While they are in the process
of congelation the heat of fluidity is set free, which, whether it be
liberated by the freezing of water at the surface of the earth, or
of the rain-drop in the sky, helps in either case to give activity
and energy to the southern system of circulation by warming and
expanding the air at its place of ascent. Thus the water, which,
by parting with its heat of liquefaction, has expended its meteorological energy in giving dynamical force to the air, is like the exhausted steam of the engine; it has exerted its power and become
inert. It is, therefore, to be got out of the way. In the grand
meteorological engine which drives the wind through his circuits,
and tempers it to beast, bird, and plant, this waste water is collected into antarctic icebergs, and borne away by the currents to more
genial climes, where the latent heat of fluidity which they dispensed to the air in the frigid zone is restored, and where they
are again resolved into water, which, approaching the torrid zone
in cooling streams, again joins in the work and helps to cool the
air of the trade-winds, to mitigate climate, and moderate the gale.
For, if the water of southern seas were warmer, evaporation would
be greater; then the S.E. trade-winds would deliver vapor more
abundantly to the equatorial calm belts: this would make precipitation there more copious, and the additional quantity of heat
set free would give additional velocity to the inrushing tradewinds. Thus it is, as has already been stated, that, parallel for
parallel, trans-equatorial seas are cooler than cis-equatorial; thus
it is that icebergs are employed to push forward the winds in the
polar regions, to hold them back in the equatorial; and thus it is
that, in contemplating the machinery of the air, we perceive how
icebergs are " coupled on," and made to perform the work of a
regulator, with adjustments the most beautiful, and compensations
the most exquisite, in the grand machinery of the atmosphere.
832. With this illustration concerning the dynamical force
The antarctic calm which the winds derive from the vapor taken up in
place a region of constantpreciritation. one climate and transported to another, we may
proceed to sketch those physical features which, being found in
the antarctic circle, would be most favorable to heavy and constant precipitation, and, consequently, to the development of a
system of aerial circulation peculiarly active, vigorous, and regular for the aqueozus hemisphere, as the southern in contrast with




~ 833.    THE WINDS OF THE SOUTHERN HEMISPHERE.          447
the northern one may be called. These vapor-bearing winds
which brought the rains to Patagonia are-I wish to keep this
fact in the reader's mind-the counter-trades of the southern hemisphere. As such they have to perform their round in the grand
system of aerial circulation, and as, in every system of aerial circulation there must be some point or place at which motion ceases
to be direct and commences to be retrograde, so there must be a
place somewhere on the surface of our planet where these winds
cease to go forward, stop, and commence their return to the north;
and that place is, in all probability, within the antarctic regions. Its
precise locality has not been determined, but I suppose it to be a
band or disc —an area-within the polar circle, which, could it be
explored, would be found, like the equatorial calm belt, a place
of light airs and calms, of ascending columns of air, a region of
clouds, of variable winds, and constant precipitation.
833. But, be that as it may, the air which these vapor-bearing
Also of a low barom- winds-vapor-bearing because they blow over such
eter.        an immense tract of ocean-pour into this stoppingplace has to ascend and flow off as an upper current, to make room
for that which is continually flowing in below. In ascending it
expands and grows cool, and, as it grows cool, condensation of its
vapor commences; with this, vast quantities of latent heat, which
converted the water out at sea into vapor for these winds, are set
free in the upper air. There it reacts by warming the ascending
columns, causing them still farther to expand, and so to rise higher and higher, while the barometer sinks lower and lower. This
reasoning is suggested not only by the facts and circumstances already stated as well known, but it derives additional plausibility
for correctness by the low barometer of these regions. In the
equatorial calm belts the mean barometric pressure is about 0.25
inch less than it is in the trade-winds, and this diminution of pressure is enough to create a perpetual influx of the air from either
side, and to produce the trade-winds. Off Cape Horn the mean,
barometric pressure* is 0.75 inch less than in the trade-wind regions. This is for the parallel say of 57 —8~ S. According to
the mean of 2472 barometric observations made along that part
only of the route to Australia which lies between the meridians
* Maury's Sailing Directions, 6th ed., 1854, p. 692; ditto, 8th ed., 1859, vol. ii., p.
450.




448       THE PHYSICAL GEOGRAPHY OF THE, SEA.
of the Cape of Good Hope and Melbourne, the mean barometric
pressure on the polar side of 42~ S. has been shown by Lieutenant Van Gogh, of the Dutch Navy, to be 0.33 inch less than it is
in the trade-winds. The mean pressure in this part of the South
Indian Ocean is, under winds with casting in them, 29.8 inches;
ditto, under winds with westing, 29.6 inches. Plate I. shows a supposed mean pressure in the polar calms of not more than 28.75
inches.
834. To what, if not to the effects of the condensation of vapor
Aqueouo vapor the borne by those surcharged winds, and to the imcause ofboth.    mense precipitation in the austral regions, shall
we ascribe this diminution of the atmospherical pressure in high
south latitudes?  It is not so in high north latitudes, except about
the Aleutian Islands of the Pacific, where the sea to windward is
also wide, and where precipitation is frequent, but not so heavy.
The steady flow of " brave" winds toward the south would seem
to call for a combination of physical conditions about their stopping-place exceedingly favorable to rapid, and heavy, and constant precipitation. The rain-fall at Cherraponjie and on the
slopes of the Patagonian Andes reminds us what those conditions
are. There mountain masses seem to perform in the chambers
of %he upper air the office which the jet of cold water does for the
exhausted steam in the condenser of the engine. The presence
of land, not water, about this south polar stopping-place is therefore suggested; for the sea is not so favorable as the mountains
are for aqueous condensation.
835. By the terms in which our proposition has been stated, and
The topographicalfea- the manner in which the demonstration has been
tures of the antarctic
bands.       conducted, the presence in the antarctic regions of
land in large masses is called for; and if we imagine this land to
be relieved by high mountains and lofty peaks, we shall have in
the antarctic continent a most active and powerful condenser. If,
again, we tax imagination a little farther, we may, without transcending the limits of legitimate speculation, invest that unexplored
land with numerous and active volcanoes. If we suppose this also
to be the case, then we certainly shall be at no loss for sources of
dynamical force sufficient to give that freshness and vigor to the
atmospherical circulation which observations have abundantly
shown to be peculiar to the southern hemisphere. Neither under




~ 836, 837. THE WINDS OF THE SOUTHERN HEMISPHERE.    449
such physical aspects need it be any longer considered paradoxical to ascribe the polar tendency of the " brave west winds" to rarefaction by heat in the antarctic circle. This heat is relative, and
though it be imparted to air far below the freezing-point, raising
its temperature only a few degrees, its expansive power for that
change is as great when those few degrees are low down as it is
when they are high up on the scale. If such condensation of vapor
do take place, then liberation of heat and expansion of air must
follow, and consequently the oblateness of the atmospherical covering of our planet will be altered; the flattening about the poles
will be relieved by the intumescence of the expanded and ascending air, which, protruding above the general level of the aerial
ocean, will receive an impulse equatorially, as well from the mere
derangement of equilibrium as from the centrifugal forces of the
revolving globe. And so this air, having parted with its moisture, and having received the expansive force of all the latent heat
evolved in the process of vaporous condensation, will commence
its return toward the equator as an upper current of dry air.
836. Arrived at this point of the investigation, we may conA perpetualcyclone. template the whole system of these "brave west
winds" in the light of an everlasting cyclone on a gigantic scale.
The antarctic continent is in its vortex, about which the wind, in
the great atmospherical ocean all around the world, from the pole
to the edge of the calm belt of Capricorn, is revolving in spiral
curves, continually going with the hands of a watch, and twisting
from left to right.
837. In studying the workings of the various parts of the physDiscovery of design in ical machinery that surrounds our planet, it is althe meteorological machinery.      ways refreshing and profitable to detect, even by
glimmerings never so faint, the slightest tracings of the purpose
which the Omnipotent Architect of the universe designed to accomplish by any particular arrangement among its various parts.
Thus it is in this instance: whether the train of reasoning which
we have been endeavoring to follow up, or whether the arguments which we have been adducing to sustain it be entirely
correct or not, we may, from  all the facts and circumstances
that we have passed in review, find reasons sufficient for regarding in an instructive, if not in a new light, that vast waste of waters which surrounds the unexplored regions of the antarctic cirFF




450       THE PHYSICAL GEOGRAPHY OF THE SEA.
cle: it is a reservoir of dynamical force for the winds-a regulator in the grand meteorological machinery of the earth. The
heat which is transported by the vapors with which that sea loads
its superincumbent air is the chief source of the motive power
which gives to the winds of the southern hemisphere, as they
move through their channels of circulation, their high speed,
great regularity, and consistency of volume. And this insight
into the workings of the wonderful machinery of sea and air we
obtain from comparing together the relative speed of vessels as
they sail to and fro upon intertropical seas!
838, Such is the picture which, after no little labor, much reIndications which the search, and some thought, the winds have enabled
winhds afford concern- us to draw of certain unexplored portions of our
gions of the south.  planet. As we have drawn the picture, so, from
the workings of the meteorological machinery of the southern
hemisphere, we judge it to be. The evidence which has been introduced is meteorological in its nature, circumstantial in its character, we admit; but it shows the idea of land in the antarctic regions-of much land, and high land —to be plausible at least.
Not only so: it suggests that a group of active volcanoes there
would by no means be inconsistent with the meteorological phenomena which we have been investigating. True, volcanoes in
such a place may not be a meteorological necessity. We can
not say that they are; yet the force and regularity of the winds
remind us that their presence there would not be inconsistent
with known laws. According to these laws, we may as well imagine the antarctic circle to encompass land as to encompass water. WVe know, ocularly, but little more of its topographical features than we do of those of one of the planets; but, if they be
continental, we surely may, without any unwarrantable stretch
of the imagination, relieve the face of nature there with snowclad mountains, and diversify the landscape with flaming volcanoes. None of these features are inconsistent with the phenomena
displayed by the winds. Let us apply to other departments of
physics, and seek testimony from other sources of information.
None of the evidence to be gathered there will appear contradictory-it is rather in corroboration. Southern explorers, as far
as they have penetrated within the antarctic circle, tell us of high
lands and mountains of ice; and Ross, who went farthest of all,
saw volcanoes burning in the distance.




~ 839, 840. THE WINDS OF THE SOUTHERN HEMISPHERE.    451
839. The unexplored area around the south pole is about twice
Their extent; Plate as large as Europe. This untraveled region is cirxv.           cular in shape, the circumference of which does not
measure less than 7000 miles. Its edges have been penetrated
here and there, and land, wherever seen, has been high and rugged.
Plate XIV. shows the utmost reach of antarctic exploration. The
unexplored area there is quite equal to that of our entire frigid
zone. Navigators on the voyage from the Cape of Good Hope
to Melbourne, and from Melbourne to Cape Horn, scarcely ever
venture, except while passing Cape Horn, to go on the polar side
of 55~ S. The fear of icebergs deters them. These may be seen
there drifting up toward the equator in large numbers and large
masses all the year round. I have encountered them myself as
high up as the parallel of 37~-8~ S. The belt of ocean that encircles this globe on the polar side of 55~ S. is never free from icebergs. They are found in all parts of it the year round. Many of
them are miles in extent and hundreds of feet thick. The area on
the polar side of the 55th parallel of south latitude comprehends
a space of 17,784,600 square miles. The nursery for the bergs, to
fill such a field, must be an immense one; such a nursery can not
be on the sea, for icebergs require to be fastened firmly to the
shore until they attain full size. They therefore, in their mute
way, are loud with evidence in favor of antarctic shore lines of
great extent, of deep bays where they may be formed, and of lofty
cliffs whence they may be launched.
840. There is another physical circumstance which obtains genA physical law con- erally with regard to the distribution of land and
cerning the distribu- water over the surface of the earth, and which, as
tion of land and wa-        s c
ter.         far as it goes, seems to favor the hypothesis of much
land about the south pole; and that circumstance is this: It seems
to be a physical necessity that land should not be antipodal to land.
Except a small portion of South America and Asia, land is always
opposite to water. Mr. Gardner has called attention to the fact
that only one twenty-seventh part of the land is antipodal to land.
The belief is, that on the polar side of 70~ north we have mostly
water, not land. This law of distribution, so far as it applies, is in
favor of land in the opposite zone. Finally, geographers are agreed
that, irrespective of the particularized facts and phenomena which
we have been considering, the probabilities are in favor of an antarctic continent rather than of an antarctic ocean.




452       THE PHYSICAL GEOGRAPHY OF THE SEA.
841. "There is now no doubt," says Dr. Jilek, in his Lehrbuch
Dr. Jiek.    der Oceanographie, "that around the south pole
there is extended a great continent mainly within the polar circle,
since, although we do not know it in its whole extent, yet the portions with which we have become acquainted, and the investigations made, furnish sufficient evidences to infer the existence of
such with certainty.  This southern or antarctic continent advances farthest northward in a peninsula S.S.E. of the southern
end of America, reaching in Trinity Land almost to 620 south
latitude.  Outwardly these lands exhibit a naked, rocky, partly
volcanic desert, with high rocks destitute of vegetation, always
covered with ice and snow, and so surrounded with ice that it is
difficult or impossible to examine the coasts very closely. * * *
842. "The principal discoverers of these coasts are (Wilkes),
Antarctic expeditions. Dumont d'Urville, and Ross (the younger), of whom
the latter in 1842 followed a coast over 100 miles between 72~ and
79~ south latitude, and 160~ and 170~ east longitude, to which
he gave the name Victoria Land, and on which he discovered a
volcano (Erebus) 10,200 feet high in 167~ east longitude and 77~
south latitude, as well as another extinct one (Terror) 10,200 feet
high, and then discovered the magnetic south pole."'
~ Text-book of Oceanography for the Use of the Imperial Naval Academy, by Dr.
August Jilek, Vienna, 1857.




~ 850-852.     THE ANTARCTIC REGIONS, ETC.               453
CHAPTER XXI.
~ 850-878.-THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY.
850. DURING our investigations of the winds and currents,
Indications of a mild facts and circumstances have been revealed which
climate about the
south pole.  indicate the existence of a mild climate-mild by
comparison-within the antarctic circle. They plead most eloquently the cause of exploration there. The facts and circumstances which suggest mildness of climate about the south pole
are these: a low barometer, a high degree of aerial rarefaction,
and strong winds from the north.
851. The winds were the first to whisper of this strange state
The storyofthe winds. of things, and to intimate to us that the antarctic
climates are very unlike the arctic for rigor and severity. In dividing the sea into wind-bands (~ 352) or longitudinal belts 5~ of
latitude broad each, I excluded from the subjoined table observations from those parts of the sea, such as the North Indian Ocean,
the China Sea, and all those seas where monsoons prevail.  The
object was to investigate the general movements of the atmosphere,
and therefore all regions which presenit exceptional cases to the
general law were excluded as above. The grouping was not carried beyond 60~ north and south, for the lack of observations on
the polar side of those parallels. The number of observations
thus remaining was 1,159,353. These were then divided simply
into two classes for each belt, viz., polar winds* and equatorial
winds. They were then reduced to terms of a year, and the
average prevalence of each wind in days deduced therefrom, as
per Plate XV. and table on the next page.
852. This table reveals a marked difference in the atmospherThe null belts.  ical movements north, as compared with the atmospherical movements south of the equator. The equatorial winds
of the northern hemisphere are in excess only between the parallels of 10~ and 30~; i. e., they are dominant over a zone 20~
of latitude in breadth, while the equatorial winds of the southern
* Polar winds blow toward the pole, equatorial towuard the equator.




454          THE PHYSICAL GEOGRAPHY OF THE SEA.
Polar and Equatorial Winds.
Northern Hemisphere.            Southern Hemisphere.
Equa- Polar   Excess i1        Polar Equa-  Excess in
Belts.    No. of  torial.       Days.    No. of        toal.   Days.
Obsvuns.            Equa-       Obsv'ns.                 ]LiquaDays. Days. torial. Polar.     Days. Days. Polar. EqtoaBetween
O~ andI50  67,829   79  268...  189  72,945   83  269...  186
5  " 10  36,841  158  183...  25  54,648   72  283...  211
10  " 15  27,339  278   73  205...  43,817   82  275...  1.93
15  " 20  33,103  273   91  182...  46,604   91  266...  175
20  " 25  44,527  246  106  140...  66,395  128  227...   99
25  " 30  68,777  185  163   22...  66,635  147  208...   61
30    -35  62,514  155  195....   40  76,2541  1 50  2041...   54
35  " 40  41,233  173  179...    6 107,231  178  178 10             0
40  " 45  33, 252  163  186...   23  63, 669  202  155   47
45  "50  29,4611 164  189...   2 25  29,132  209   148   61...
50  "55  41,570  148  203...   55  14,286  208   151   57...
55' 60  17,874  142  213...   71  13,617  224  132   92...
hemisphere hold the mastery from  35~ S. to.10o  N.; i. e., they prevail over a belt 45~ in breadth, while the others cover a space
not half so broad.   This table, moreover, shows that the debatable ground between the winds, or what may be called the null
belt, in this general movement from  poles toward the equator, and
from equator toward the poles, is, in the northern hemisphere,
between the parallels of 25~ and 50~. In the southern the field
of battle is narrowed down to a single belt (between 35~ and
40~); here the two winds exactly counterbalance  each  other.
As one proceeds from  this medial belt, the winds increase belt
for belt very nearly paripassu; on the polar side, the polar winds
-on the equatorial, the equatorial winds, gaining more and more
in days of annual duration, and more and more in average velocity each.
853. The fact that the influence of the polar indraught upon
Extent of the polar the winds should extend from the antarctic to 400
indraught.      S., while that from  the arctic is so feeble as scarcely to be felt in 500 N., is indicative enough as to difference in degree of aerial rarefaction over the two regions. The significance
of this fact is enhanced by the "brave west winds," which, being
bound to the place of greatest rarefaction, rush more violently
along to their destination than do the counter-trades of the northern hemisphere.  Why should these polar-bound winds of the two
hemispheres differ so much in strength and prevalence, unless there
be a much more abundant supply of caloric, and, consequently, a
higher degree of rarefaction, at one pole than the other?




~ 854-856.         THE ANTARCTIC REGIONS, ETC.                          455
854. In the southern hemisphere —and our attention is now diThe rarefaction of the rected exclusively to that-the polar winds on the
air over polar regions. south side of 40~ are very much stronger than are
the equatorial winds on'the north side of 35~: a fact indicative
of a greater degree of rarefaction about the place of polar calms
than we have in the equatorial calm belt.
855. That such is the case is also suggested by the fact that
Barometrical observa- the indraught into the antarctic calm  place is felt
tions.            (~ 854) at the distance of 50~ from  the pole all
round, while the equatorial indraught is felt no farther than 35~
from  the equator; and that such is the case is proved by the barometer.  Lieutenant Andrau, of the Meteorological Institute of
Utrecht, has furnished us from the Dutch logs with 83,334 observations on the height of the barometer between the parallels of 50~
N. and 386~ S. at sea.  Lieutenants Warley and Young have extracted from the log-books of this office, taken at random, 6945
observations on the barometer south of 40~ at sea.  Dr. Kane has
furnished us with the mean height of the barometer in lat. 780
37' N., according  to 12,000  hourly  observations  made  during
his imprisonment of 17 months in the ice there.  The annals
of Greenwich and St. Petersburg give us the mean height of the
barometer in lat. 510 29' N. according to three years' observations, and in lat. 590 51' N. according to ten years of observation. Such are the sources of the following table:
Ml]ean hIeight of the Barometer.
Latitude.   IBarometer. No. of Obs'ns.  Latitude.    Barometer. No. of Obs'ns.
00 to 50 Northl 29.915      5114       00 to 50 South 29.940    3692
5 to 10   "   29.922        5343       5 to 10   "   29.981       3924
10 to 15   "   29.964        4496      10 to 15  "'   30.028       4156
15 to 20   "   30.018        3592      15 to 20   "   30.060    4248
20 to 25   "   30.081        3816      20 to 25'"  30.102    4536
25 to 30   "   30.149        4392      25 to 30   "   30.095       4780
30 to 35   "   30.210        4989     30 to 36*  "   30.052    6970
35 to 40   c"  30.124        5103     40 to 43   "   29.88         1703
40 to 45   "   30.077        5899      43 to 45   "   29.78        1130
45 to 50*  "   30.060        8282      45 to 48   "'   29.63       1174 
510 29'     "   29.814t Greenwich    48 to 50   "   29.62           672
590 51'     " 4   29.88   St. Petersburg 50 to 53'   29.48       665
780 37'     4   29.759  Dr. Kane      53 to 55   "   29.36          475
561              29.29      1126
* Maandelijksche Zeibaanwijzingen van Java naar HIet Kanaal. Als Uitkomsten Wetenschap en
Ervaring Aangaande Winden en Zeestroomingen in Sommige Gedeetten Van Den Oceaan Uitgegenen
Door Heet Koninklijk Nederlandsch Meteorologische Institut. Utrecht, 1859.
t The mean height of the tarometer for Englaaud generally is 29.940.-Admiral Fitz Roy.
856. Captains Wilkes, U. S. N., and Clarke Ross, R. N., both,




456         THE PHYSICAL GEOGRAPHY OF THE SEA.
The low austral ba- during the expeditions to the South Seas in 1839rometer.      41, had occasion to remark upon the apparent deficiency of atmosphere over the extra-tropical regions of the southern hemisphere; and the low barometer off Cape Horn had attracted the attention of navigators at an early day.  I observed
it in 1831 when doubling the Cape as master of the U. S. S. Falmouth, and wrote a paper on it, which was published in the
American Journal of Science in 1833-4. The more abundant
materials which the abstract logs have placed within my reach
enable me to go more fully into this subject. To ascertain whether these " barometric anomalies," as they are called, are peculiar to
the regions about Cape Horn, or whether they are common to
high southern latitudes in all longitudes, the observations about
Cape Horn were arranged in one group; those between 20~ W.
and 140~ E. in another; and those between 140~ E. and 80~ W.
in another, with the following results. (They are all on the polar
side of 40~ S.)
Mean Height of the Barometer, as observed between
the Meridians of
the Parallels of o20 W. and 1400 E. 1400 E. and 800 W. Off Cape Horn.   Mean of all.
No. of Barom. No. of Barom. No. of Barom. No. of Barom.
Obs'ns. Inches. Obs'ns. Inches. Obs'ns. Inches.'Obs'ns. Inches.
400~ S. and 430 S. 1115  29.90  210  29.841  378  29.86  1703  29.88
43   " 45       738.80  155.73   237.75  1130.78
45   " 48       611.58  226.71   337.68  1174.63
48'" 50       175.53  247.56   250.61   672.62
50   " 53       108.35  198.45   359.56   665.48
53       55       6.17   92.35   377.37   475.36
S. of 550         7.27   64.42  1055.28  1126.29
857. The instruments used for these observations were for the
Discussion of observa- most part the old-fashioned marine barometer, to
tions.          which no corrections have been applied.  The discrepancies of this table evidently arise from the lack of numbers
sufficient to mask these sources of error, or from the influence of
the land, and not from  any difference as to the mean height of
the barometer along the same parallels at sea in any one of the
three divisions. In this discussion, the observations of each group
and every band were arranged according to the month. These
monthly tables are not repeated here, but they do not indicate
any decided change in the barometric pressure in high southern
latitudes according to the season. The barometer there stands
low the year round.




.LThe irregularities of the curve in the higher northern latitudes are probably owing to the observations at Greenwich, St. Petersburg, ct
al., which, being on the land, are more exceptional than the others, all of which were made at sea.
z3                                                                                                                 _'30-0                                                                                                                SP..0
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06
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I~....,-,,..... 2:.
Izi,8
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o 
00
c491:




458       THE PHYSICAL GEOGRAPHY OF THE SEA.
858. Resorting to the graphic method, and using the table (~ 855)
Barometric curve at for the purpose, the barometric curve of the diasea.         gram (p. 457) has been projected from pole to pole.
859. Professor Schouw has given us the mean height of the baDitto over the land. rometer for 32 places on the
land'between the parallels of 33~ S. and 75~ _  _.  
30' N. They afford materials for the annexed diagram, and show the exceptional
character of the meteorological influences    7       _ _
which rule on shore when compared with
those which rule at sea. There is barely a
resemblance between this profile of the at-   6
mosphere over the land and the profile of
it (~ 858) over the sea, so different are these
influences.  The irregularities over the _        
land are chiefly owing to the difference in
the amount of precipitation at one station
as compared with the amount at another.
Those islands, as the Sandwich and Society,
which are so situated as to bring down a
heavy precipitation, are as chimneys to te  _ _ 
atnmosplhere. The latent heat which is liberated by the vapor they condense has the
effect of bringing down the barometer, and
of causing, during the rainy season, an indraught thitherward from  many miles at   ]0
sea. Such is the rarefaction produced by
the liberation of this heat, that its effect is,
as the pilot charts show, felt and confessed E       o r
by the winds at the distance out to sea of
more than a thousand miles from the Sandwith Islands.  Thus the land and the islands give us, in the circulation of the atmosphere, systems within systems. In the Mississippi and all great rivers, the general 2 2movement of the waters, notwithstanding
the eddies and the whirlpools, is down 
stream with the current.  So with the at:
mosphere: its general movements are indi-        _




~ 860, 861.     THE ANTARCTIC REGIONS, ETC.                459
cated by observations at sea; its eddies and whirlpools are created by the mountains, and the islands, and other inequalities
which obstruct its flow in the regular channels. The mean reading of the barometer when the rainy season in India is at its height
is 0.4 inch less than it is in the midst of the dry.
860. The figure (~ 858) shows the observations in the southern
Agreement ofobserva- hemisphere to be so accordant, and the curve ittions at sea.  self so regular, that we feel no hesitation about
projecting it into the vacant spaces of the south, and asserting,
with all the boldness consistent with the true spirit of philosophical deduction, that, whether the actual barometric pressure at the
south pole be as low as 28.14~ or not, it is nevertheless very
much lower in the antarctic than in the arctic regions.
861. The question now arises, Whence this unequal distribuThe question why the tion of atmosphere between the two hemispheres,
barometer should stand
lower about the south, and why should the mean height of the barometer
than the north pole.
considered.   in circumpolar regions be so much less for the
austral than for the boreal?  No one, it is submitted, will attempt
to account for this difference by reason of any displacement of
the geometrical centre of the earth with regard to its centre of attraction, in consequence of the great continental masses of the
northern hemisphere; neither can it be ascribed to any difference
in the forces of gravitation arising from the oblateness of our
globe; neither can it be accounted for by the effects of diurnal
rotation after the Halleyan theory: that would create as low a
barometer at one pole as the other. The air, in its motions to the
east and its motions to the west, is in equipoise between the parallels of 35~ and 40~ N., 250 and 30~ S. There is near each pole
and about the equator a place of permanently low barometer.
The air from all sides is continually seeking to restore the equilibrium by rushing into these places of rarefaction and reduced
pressure; consequently there ought to be between each pole and
the equator a place of high barometer from which the air on one
side flows toward the equator, on the other toward the pole. Observation (~ 855) shows this high place to be between the parallels of 250 and 40~ in the north, and of 20~ and 300 in the southern hemisphere: thus the barometer as well as the winds (Plate
XV.) indicate a greater degree of rarefaction about the south than
about the north pole.  Were there no friction, and were the at



460       THE PHYSICAL GEOGRAPHY OF THE SEA.
mosphere ordained to move without resistance, the air from these
null belts would carry with it to the polar calms the easterly motion which it had acquired from the earth in its motion around
its axis at these null belts. Were this motion so impressed, the
wind would arrive, rushing with an hourly velocity about the
polar calm places of 700 miles in the arctic, and 800 in the antarctic. Such a velocity would impart a centrifugal force sufficient
to keep the air away from the poles and produce almost a vacuum
there. In this state of things, the same air would continue to
revolve about the poles were not some other agent, such as heat,
brought in to expand and drive it away. Being expanded and
puffed out above the general atmospherical level, but retaining its
velocity-for the supposition is that it moves without frictionand returning through the upper regions, it would flow back as it
went, viz., as a westerly wind, and arrive at its null belt in the direction of the meridian. But the wind has friction, and is resisted
in every movement; the atmosphere partakes of the spheroidal
form, which has been impressed upon the earth itself by its axial
rotation. That form is to it the form of stability. The water
at the pole is 13 miles nearer to the centre of the earth than the
water at the equator; but there is not on that account any tendency in the sea to flow back from the equator toward the poles;
neither is there any tendency to motion one way or the other in
the atmospherical ocean by reason of the oblateness of its surface.
To produce the polar and equatorial movements of the air, there
must be an agent both at the equator and the poles to prevent such
stability by constantly disturbing equilibrium there, and that agent
is heat; therefore, whatever be the degree of polar depression due
the barometer in consequence of axial rotation, such depression
could, of itself, produce neither trade nor counter-trade wind; it
could no more produce currents in the air than in the sea,- nor
could axial rotation produce a high barometer at one pole, a low
barometer at the other; consequently, the difference in the pressure of the atmosphere about the two poles, as shown by the diagram (~ 858), can not be ascribed to the influence of axial rotation.
It is doubtless due to the excess in antarctic regions of aqueous
vapor and its latent heat.
862. The arctic circle lies chiefly on the land, the antarctic on
the water. As the winds enter one, they are loaded with vapor;




~ 863, 864.     THE ANTARCTIC REGIONS, ETC.                461
Psychrometryofpolar but on their way to the other they are desiccated
winds.        (~ 826).  Northern mountains and the hills wring
from them water for the great rivers of Siberia and Arctic America. These winds, then, sweep comparatively dry air across the
arctic circle; and when they arrive at the calm disc-the place of
ascent there-the vapor which is condensed in the act of ascending does not liberate heat enough to produce a rarefaction sufficient
to call forth a decided indraught from a greater distance in the surrounding regions than 40~ (~ 852); and the rarefaction being not
so great, the barometer is not so low there as in antarctic regions.*
863. Nevertheless, there is rarefaction in the arctic regions.
Aerial rarefaction The winds show it, the barometer attests it, and the
aboutthenorth pole. fact is consistent with the Russian theory of a
polynia in polar waters.  The presence within the arctic circle of
a considerable body of comparatively warm water, which observation has detected going into it as an under current-which induction shows must rise up and flow out as a surface current-would
give forth vapor most freely. This vapor, being lighter than air,
displaces a certain quantity of atmosphere. Rising up and being
condensed, it liberates its latent heat in the cloud region, and so,
by raising temperature, causes the moderate degree of rarefaction
which the barometer at sea, at Greenwich, at St. Petersburg, and
in the arctic ice indicates.
864. Within the antarctic circle, on the contrary, the winds bring
Ditto about the south air which has come over the water for the distance
pole.         of hundreds of leagues all around; consequently, a
large portion of atmospheric air is driven away from the austral regions by the force of vapor, which fills the atmosphere there. Now
there must be a place-an immense disc, with irregular outlines, it
may be, and probably is-where these polar winds (~ 855) cease to
go forward, rise up, and commence to flow back as an upper current.
If the physical aspects-the topographical features in and about
this calm place —be such as to produce rapid condensation and
heavy precipitation (Chap. XX.), then we shall have, in the latent
heat liberated from all this vapor, an agent sufficient not only to
produce a low barometer and a powerful indraught, but quite adequate also to the mitigation of climate there.
* Captain M'Clintock, during his arctic explorations in the schooner Fox, records
the barometer as high as 31 inches.




462        THE PHYSICAL GEOGRAPHY OF THE SEA.
865. Mere altitude, with its consequent refrigeration, does not
Influences favorable to seem as favorable as mountain peaks and solid surheavy precipitation. faces to the condensation and precipitation of vapor
in the air.  In the trade-wind regions out at sea it seldom rains;
but let an island rise never so little above the water, and the precipitation upon it becomes copious.  Colonel Sykes (~ 827) reports* the rain-fall at Cherraponjie, a mountain station 4500 feet
high in India, lat. 250 16' N., long. 910 43' E., to be 577.6 inches
during the six months of S.W. monsoons-from May to October.
Surely no one will maintain that this vapor, after rising from the
sea, reached the height of 4500 feet for the first time when it was
blown upon Cherraponjie.  Islands in the South Sea are everlastingly cloud-capped.  If it be mere refrigeration that condenses
this vapor, why, one might ask, should not the clouds form at the
same height above the sea, whether there be an island below or
not, and why should not these clouds precipitate as copiously upon
the water as they do upon the land?  We only know that they
do not.
866. Captains King and Fitz Roy exposed their rain-gauge on
The climates of corre- the western slopes of the Patagonian Andes, and
lapodtings orte and it collected 153.75 inches in forty-one days; that
south.        is, at the rate, as already (~ 827) stated, of 1368.7
inches the year. The latent heat that is liberated during these
rains gives to Eastern Patagonia its mild climate.  It is this latent
heat which causes the irregularity in the barometric curve (~ 858)
between the parallels of 500-55~ S. Here the westerly winds
prevail; they carry over to the eastern coasts the air that, in passing the mountains, is warmed by this liberated heat; and thus, as
already (~ 729) explained, we have an exception to the rule under
which meteorologists ascribe cold and severe climates to the windward or western, soft and mild to the leeward or eastern, shores
of extra-tropical oceans. Labrador and the Falkland Islandst are
in corresponding latitudes north and south. They are both on
the windward side of the Atlantic; they occupy relatively the
same position with regard to the wind.  Labrador is almost uninhabitable on account of the severity of its climate, but in the
~ Report of the twenty-second meeting of the British Association for the Advancement of Science, held at Belfast in September, 1852.
jt Maury's Sailing Directions, sixth edition, p. 553.




~ 867, 868.    THE ANTARCTIC REGIONS, ETC.               463
Falkland Islands and their neighboring shores the cattle find pasturage always in winter. The thermometrical difference of climate
at these two places, north and south, may be taken as a sort of
index to the relative difference between the arctic and antarctic
climates of our planet.
867. Along the eastern base of the Rocky Mountains the isoThermal difference therms mount up* toward the north in consequence
between arctic and
antarctic climates. Of the heavy winter precipitation upon the western
slopes of these mountains. The heat which is required to convert the water of the Columbia and other rivers into vapor is set
free on the mountain range, and the upper Missouri is by this heat
kept open for navigation long after the lower and more southern
portion of it is frozen up.
868. In the preceding chapter the circumstances have been
ow the temperature considered which favor the idea that most of the
of air may be raised unknown surface of the antarctic circle is not only
by crossing mountains.        land, but that its coasts are probably highlands;
that in its topographical features it presents all the conditions
that are required for the rapid condensation of the vapor with
which the impinging air from the sea is loaded, and that in the
valleys beyond mild climates may be expected. The aqueous
vapor which the air carries along is one of the most powerful
modifiers of climates. It is to the winds precisely what coals are
to the steam-ship at sea-the source of motive power. The condensation of vapor is for one what the consumption of fuel is for
the other; only with the winds the same heat may be used over
and over again, and for many purposes.  By simply sending
moist air to the top of snow-capped mountains, condensing its
moisture, and bringing it down to the surface again, it is made
hot. Though by going up the air be cooled, it is expanded,
and receives as sensible heat the latent heat of its vapor; being
brought down to the surface again, and compressed by the whole
weight of the barometric column, it is hotter than it was before
by the amount of heat received from its vapor. That we may
form some idea as to the modifying influences upon climate which
-might arise from this source, let us imagine the air as it impinges
upon the antarctic continent to be charged with vapor at the
temperature of 400. In order to arrive at the place of polar
* Blodget's Climatology of the United States.




464       THE PHYSICAL GEOGRAPHY OF THE SEA.
calms, it has to cross a mountain range, we will suppose, the summits of which are pushed high up into the regions of perpetual
snow. As this air, with its moisture, rises, it expands, cools, and
liberates the latent heat of its vapor, which the air receives in the
sensible form. Now suppose the expansion due the height of the
mountain-top to be sufficient to lower the temperature of dry air
to — 50~; but, on account of the latent heat which is liberated from
the vapor of the moist air, the temperature of the air that has
ascended, instead of falling as it crosses the mountain to -50~, as
dry air would do, falls, in consequence of the condensation of its
vapor, no lower than -30~. Thus, in the case supposed, heat
enough has been set free to raise the temperature of the newly-arrived air 20~. Consequently, when this air, which, at the temperature of 40~, came from the sea loaded with vapor, passes the mountain, it loses vapor, but receives heat; descending into the valleys
beyond, it is again compressed by the weight of the barometric
column, which, let us assume, is the same in the valley as at the
sea level on the other side of the mountain. The temperature of
this air now, instead of being 40~, will be 60~. A powerful modifier of climate is the latent heat of vapor in the air.
869. There is not only reason to suppose that the topographAurora australis. ical features and the climates of the antarctic regions differ greatly from the topographical features and climates
of the arctic, but there is reason to suppose a difference in other
physical aspects also.  The aurora points to these.  "On the
morning of the second of September last," says Capt. B. P. Howes,
in his abstract log of the " Southern Cross," lat. 58~ S., long. 70~
W., " at about half past one o'clock, the rare phenomenon of the
aurora australis manifested itself in a most magnificent manner. Our ship was off Cape Horn in a violent gale, plunging furiously into a heavy sea, flooding her decks, and sometimes burying her whole bows beneath the waves. The heavens were black
as death: not a star was to be seen when the brilliant spectacle
first appeared. I can not describe the awful grandeur of the
scene; the heavens gradually changed from murky blackness till
they became like livid fire, reflecting a lurid, glowing brilliancy
over every thing. The ocean appeared like a sea of vermilion
lashed into fury by the storm; the waves, dashing furiously over
our sides, ever and anon rushed to leeward in crimson torrents.




~ 870, 871.     THE ANTARCTIC REGIONS, ETC.               465
Our whole ship, sails, spars, and all, seemed to partake of the
same ruddy hues.  They were as if lighted up by some terrible
conflagration. Taking all together, the howling, shrieking storm,
the noble ship plunging fearlessly beneath the crimson-crested
waves, the furious squalls of hail, snow, and sleet driving over
the vessel and falling to leeward in ruclddy showers, the nmysterious balls of electric fire resting on our mast-heads, yard-arms,
etc., and, above all, the awful sublimity of the heavens, through
which coruscations of auroral light would often shoot in spiral
streaks and with meteoric brilliancy, altogether presented a scene
of terrible grandeur and awful sublimity surpassing the wildest
dreams of fancy. Words fail to convey any just idea of the magnificence it presented.  One must see it and feel it in order to realize it. I have written this because I believe it an unusual occurrence to see the Isouthern lights' at all, and also because this
was far superior, and, in fact, altogether different from our northern lights, as seen from the latitude of Boston."
870. Some objections to these views respecting the comparaAn erroneos opin- tive mildness of antarctic climates are suggested
on0.         by common opinion.  It is an opinion which is
generally received among physicists that the southern is colder
than the northern hemisphere, and that the austral are more severe than the boreal climates, and that the antarctic icebergs,
both as to size and numbers, are witnesses of the fact. These
objections have weight; they deserve consideration.
871. The answer is as follows: Between lat. 400 or lat. 450
Tropical regions of and the equator, and parallel for parallel, the souththe souther henmi- ern hemisphere is cooler than the northern.  Reasphere cooler, extra-tropical warmer, son teaches, and observations show that it is so.
than those of the  t
northern.    But beyond 450 S. observations are wanting, and
we are left to reason and conjecture. That the southern hemisphere should, till within a certain distance of the pole, be warmer in winter and cooler in summer, and have a mean annual temperature less than that of our hemisphere, may be explained by the
fact that the southern hemisphere has more water; that the vapor
which is taken up from trans-equatorial seas and condensed into
rains for cis-equatorial rivers conveys with it a vast amount of heat
which the southern hemisphere receives from the sun. It is rendered latent by evaporation on one side of the equator, and made
G G




466        THE PHYSICAL GEOGRAPHY OF THE SEA.
sensible by precipitation on the other.  Much of it is set free in
the equatorial calm belt, and it is this heat which assists mightily
to maintain the thermal equator in its northern position.
872. So, in like manner, the vapor that is borne to the antFormation of south- arctic regions by the polar-bound winds transports
ern icebrgs.    immense volumes of heat from the more temperate
latitudes of the south, and sets it free again in the polar regions
there. And as for the southern icebergs, they are rather of fresh
than of salt water; and they are the channels through which the
water that the winds carry there as vapor finds its way back
again. Being fresh water, and falling on the antarctic declivities
of the land, it is by rills, and streams, and rains brought together,
and by constant accretions formed into glaciers of a size and
thickness that are almost impossible to be formed out of sea water
unless it be dashed up as spray. Moreover, on the arctic ocean
the rains are not so copious, and for that reason, though the climate be more severe, icebergs, or, rather, glaciers, are not formed
on so grand a scale. - Southern icebergs are true- glaciers afloat.
Arctic winds are dry enough to evaporate much of the ice and
snow that fall and form in the north polar basin.  As compared
with arctic climates, antarctic are marine, arctic continental; and
for the very reason that the English Channel is cooler in summer
and warmer in winter tthan the Canadian, so is winter at the south
pole much less severe than that of the north.  The difference between the two polar climates is, as the barometer indicates, even
greater than is the difference between a Canadian and an English
winter.
873. As tending to confirm these views touching the mildness
Mild climate in 63~ S. of unknown antarctic climates, the statement of
Captain Smyley, an American sealer, may be mentioned.  Ile
planted a self-registering thermometer on the South Shetlands,
lat. 630 S., and left it for several winters, during which time it
went no lower than — 5  Fahr.*
874. The low barometer and the implied heavy precipitation in
Antarctic ice-drift. the antarctic regions are not the only witnesses that
may be called up in favor of bluffs and bold shores to the antarctic continent. The icebergs, in their mute way, tell that the physical features of that unexplored land are such, in its northern
* Maury's Sailing Directions.




~ 875, 876.    THE ANTARCTIC REGIONS, ETC.               467
slopes, as to favor the formation of glaciers on the shore, to become
the huge icebergs that, on their journey to the milder climates of
the north, are encountered far away at sea. After a somewhat
attentive, but by no means a thorough examination and study of
antarctic icebergs as they endanger the routes of navigation, the
idea has been suggested that information may be gathered from
them concerning antarctic regions which would be highly useful
to any future expedition thitherward.
875. The conditions required for Gulf-Stream-like currents, or
Antarctic currents. a rapid flow and reflow of equatorial and polar
waters between the torrid and the frigid zones, as in the northern
hemisphere, are not to be found about the antarctic regions. Of
all the currents that come from those regions, Humboldt's current
is by far the most majestic.  It is believed also to be the least sluggish of them all. It certainly conveys the coldest water thence
to the torrid zone; and yet it appears not to come from a nursery
of icebergs, for in its line of march fewer icebergs are found than
are encountered on the same parallels between other meridians,
but where feebler currents flow. [From  the arctic regions the
strongest currents bring down the most icebergs; not so from the
antarctic.  Hence the inference that, though icebergs have been
encountered off the shores of the antarctic continent wherever they
have been approached, yet it is only those which have been launched from particular points of that frost-bound coast which are stout
enough to bear transportation to the parallel of 40~ south. In
Humboldt's current it is rare to see an iceberg as far from the pole
as the parallel of the fifty-fifth degree of south latitude; but off
the Cape of Good Hope on one side of the Atlantic, and Cape
Corrientes on the other, antarctic icebergs are sometimes seen as
far as the parallel of 35~, often as far as 40~. Lieutenants Warley
and Young, after having examined the logs of 1843 ships cruising
on the polar side of 350 S., report the great antarctic ice-drift to
be toward the Falkland Islands on one hand, and the Cape of Good
Hope on the other.
876. These facts and the stories of the icebergs are very sugAntarctic explorations gestive. In mute eloquence and with great power
demanded.     they plead the cause of antarctic exploration.
Within the periphery of that circle is included an area equal in
extent to the one sixth part of the entire landed surface of our




468        THE PHYSICAL GEOGRAPHY OF THE SEA.
planet.*  Most of this immense area is as unknown to the inhabitants -of the earth as is the interior of one of Jupiter's satellites.
With the appliances of steam to aid us, with the lights of science
to guide -us, it would be a reproach to the world to permit such
a large portion of its surface any longer to remain unexplored.
For the last 200 years the Arctic Ocean has been a theatre for
exploration; but as for the antarctic, no expedition has attempted to make any persistent exploration, or even to winter there.
877. England through Cook and Ross; Russia- through Bilrormer expeditions. lingshausen; France through D'Urville; and the
United States through Wilkes, have sent expeditions to the South
Sea. They sighted and sailed along the icy barrier, but none of
them spent the winter or essayed to travel across and look beyond the first impediment. The expeditions which have been
sent to explore unknown seas have contributed largely to the
stock of human knowledge, and they have added renown to nations, lustre to diadems. Navies are not all for war. Peace has
its conquests, science its glories; and no navy can boast of brighter chaplets than those which have been gathered in the fields of
geographical exploration and physical research.
878. The great nations of the earth have all, with more or less
An lappeal for others. spirit, undertaken to investigate certain phenomena
touching the sea, and, to make the plans more effectual, they have
agreed to observe according to a prescribed formula. The observations thus made have brought to light most of the facts
and circumstances which indicate the existence within the antarctic circle of a mild climate-mild by comparison.  The observations which have led to this conclusion were made by fellow-laborers under all flags. It is hoped that this circumstance may
vindicate, in the eyes of all, the propriety of an appeal in this
place for antarctic exploration, and plead for it favorable consideration among all nations.
* The area of the antarctic circle is 8,155,600 square miles.




~ 879.             THE ACTINOMETRY OF THE SEA.                           469
CHAPTER XXII.
~ 879-893. —THE ACTINOMETRY  OF THE SEA.
879. ONE of the columns in the man-of-war log of the BrusA new field.    sels Conference calls for the temperature of the
water below as well as at the surface of the sea. Only a few
entries have been made in this column; but these, as far as they
go, seem to indicate that the warmest water, especially in tropical
seas, is not to be found at the top, but in a stratum  a little way
down.  What is the depth of this stratum, and what may be the
thermal difference between its waters and those of the surface,
are questions for future observations to settle.  Indeed, this subject opens a new field of inquiry; it is one from  which much useful and instructive information is doubtless to be obtained by any
one of our co-operators who patiently and with diligence will enter upon the investigation.*
* On the 26th of March, 1852, the late Passed Midshipman A. C. Jackson,
U. S. N., being in the Gulf Stream, lat. 340 55' N., long. 740 8' NV., found the temperature of the water 74.50 at the surface, 790 at the depth of six feet, and 86.5~ at
the depth of 16t feet. Again, on the 30th, in lat. 24~ 10' N., long. 80~ 11' Wv. (near
the edge of the Gulf Stream), he tried the temperature of the water by another carefally conducted set of observations, and found it 78~ at the surface, and 79.5~ at the
depth of 16- feet. The sea was rough, and he did not, for that reason, observe the
temperature at six feet. The temperature of the air in the shade was 69.50 on the
26th, and 79~0 on the 30th.  (Vide p. 59, 5th ed., Maury's Sailing Directions, 1853.)
Extract of a Letter from J. Berminzgehan, C/lief Engineer of tlhe Ameerican Steamer
" Golden Age," dated Bay of Panamac, Jlne 29, 1860, and addressed to Lieut. Jo]n
M. Brooke, U.S. N.
"On our late trip from San Francisco (June 5) to this port, we experienced the
most remarkably fine weather and smooth sea that I have ever witnessed on the Pacific, or any where else.
"On the 14th, while crossing the Gulf of Tehuantepec, we found the temperature
of the sea water on the surface (where it had not been disturbed by the progress of
the vessel) 880, and upon taking the temperature at the same time ten feet below the
surface, the mean of three thermometers gave 90~. Temperature of atmosphere, 93'.
" I do not exactly understand why the temperature of the sea water should be so
much greater at a distance of ten feet from the surface than it was immediately upon
the surface.
I" Mr. Agassiz (a son of Professor Agassiz) was on board, and he and myself made




470        THE PHYSICAL GEOGRAPHY OF THE SEA.
880. The observations that we possess do not prove that the
The warmest waters warmest water of intertropical seas is not at the
in the eea-whelro are surface: they go no farther than to show that it
they? at or below the
surface?      is sometimes not at the surface, and to suggest
that, in all probability, it is generally below, especially in " blue
water." Reason suggests it also. Supposing that, as a rule, the
hottest water is below the surface, we may, in order to stimulate
research, encourage investigation, and insure true progress, propound a theory in explanation of the phenomenon, looking to future observations to show how far it may hold good.
881. The flow of heat from the sun is held to be uniform, and
The annual supply of the quantity of it that is annually impressed upon
solar heat uniform.  the earth is considered as a constant.  The sun
spots may make this " constant" a variable, but the amount annually received by the earth is so nearly uniform that our best instruments have not been able to show us any variation in its uniformity. Some maintain that climates are undergoing a gradual change
as to temperature.  However this may be as to certaini localities,
Baron Fourier, after a long and laborious calculation, claims to
have shown that if the earth had been once heated, and, after
having been brought to any given temperature, if it had then
been plunged into a colder medium, it would not, in the space of
1,280,000 years, be reduced in temperature more than would, in
one second of time, a 12-inch globe of like materials if placed
under like conditions. It may be assumed that, for the whole
earth, there has not been, since the invention of the thermometer, any appreciable change in the temperature of the crust of
our planet.
882. The earth receives from the sun heat enough daily, it has
Quantity of heat dai- been said (~ 271), to melt a quantity of ice suffilyimpressed upon thei
earth.         cient to incase it in a film 11 inch thick.  What
becomes of this heat after it is so impressed? how is it dispensed
by the land? how by the sea?  Let us inquire.
883. The solar ray penetrates the solid parts of the earth's crust
only to the depth of a few inches, but, striking its fluid parts with
repeated tests of the temperature of the water during the four hours we were running through it-the warm belt.
"Ninety degrees is the highest temperature that I have ever known the water of
the ocean to attain."




~ 884-886.     THE ACTINOMETRY OF THE SEA.                 471
How far below the sur- its light and heat, it penetrates the sea to depths
face does the heat of
the sunpenetrate?  more or less profound,. according to the transparency of its waters. Let us, in imagination, divide these depths,
whatever they may be, into any number of stratifications or layers
of equal thickness. The direct heat of the sun is supposed to be
extinguished in the lowest layer; the bottom layer, then, will receive and absorb the minimum amount of heat, the top the maximum; consequently, each layer, as we go from the top to the bottom, will receive less and less of the sun's heat.
884. Now, which will retain most heat and reach the highest
The stratum of warm- temperature?  Not the top layer, or that to which
est water.    most heat is imparted, because by evaporation heat
is. carried off from the surface of the sea almost as fast as by the
sun it is impressed upon the surface of the sea; not the bottom
layer, because that receives a minimum, which, though it can not
escape by evaporation, may nevertheless fail to make any marked
change in temperature-fail, not by reason of no evaporation, but
by the ever-changing movements which, considering the length of
time required to heat the lower stratum by such slow and gradual accumulation of heat, would alter its place and vary its condition, and, indeed, remove it beyond the reach of the observer.
885. The layer, therefore, which accumulates most heat and
Its position. becomes warmest, should be neither at the bottom
nor at the top, but intermediate, the exact temperature and depth
of which it is for observation to determine. To encourage such
determination and the investigations which it suggests is the main
object of this chapter.
886. In conducting such investigations, several questions are
Tlhe diaerent sbjects to be considered, such as the transparency and
for observation.    specific gravity of the water, its pphosphorescence;
the face of the sky, whether clear or cloudy; the state of the sea,
whether smooth or rough; the condition of the weather, whether
calm or windy. Then the temperature should be tried, at various
depths and at various hours of the night and day, in order to ascertain not only the maximum temperature and average depth of
the warmest stratum in the day, but the difference in its temperature and position by day and by night. These observations will
afford the data, also, for computing the amount of solar heat that
penetrates the bosom of the sea, as well as the amount that is ra



472       THE PHYSICAL GEOGRAPHY OF THE SEA.
diated thence again. They will reveal to us knowledge concerning its actinometry in other aspects. We shall learn how absorption by, as well as radiation from, the under strata is affected by
a rough sea, as when the waves are leaping and tossing their white
caps, and how by its glassy surface, as when the winds are hushed
and the sea smooth.
887. Here we are reminded, also, to anticipate the discovery
Expected discoveries. of new beauties and fresh charms among the wonders of the sea. We have seen (~ 366) that while the heat of the
sun iS impressed alike upon sea and land, nevertheless the solid
part of the earth's crust radiates much more freely than the fluid.
On the land the direct heat of the sun operates only upon a mere
shell a few inches in thickness; at sea it penetrates into the depths
below, and operates upon a layer of water many feet thick. The
solid land-crust has its temperature raised high by day and cooled
low down by night; but the most powerful sun, after beating down
all day with its fiercest intensity upon this liquid covering, has
not power to raise its temperature more than three or four degrees. This covering serves as a reservoir for the solar heat. In
the depths below it is concealed from the powers of intense radiation, and held by the obedient ocean in readiness to be brought
to the surface from time to time, and as the winds and the clouds
call for it. Here it is rendered latent by the forces of evaporation, and in this form, having fulfilled its office in the economy
of the ocean, it passes off into the air, there to enter, in mysterious
ways, upon the performance of its manifold tasks.
888. As evaporation goes on by day or night, the upper straActinic processes. turn iS rendered heavier by reason of both the heat
and the fresh water which are borne away by evaporation; the upper water, having been thus rendered both salter and cooler, has its
specific gravity increased so much the more. On the other hand, the
strata below, receiving more heat by day than they dispense again
by radiation day and night, grow actually warmer and specifically
lighter; and thus, by unseen hands and the "clapping of the
waves," the waters below are brought to the surface, and those on
the surface carried down to unknown depths; and thus, also, we
discover new and strange processes which have been ordained for
the waters of the ocean in their system of vertical circulation.
889. Thus we arrive at the conclusion that the ocean is the




~ 890.         THE ACTINOMETRY OF THE SEA.                 473
The reservoirs of heat. great reservoir of sensible, as the clouds are of latent heat; that in these two chambers it is innocuously stored,
thence to be dispensed by processes as marvelous as they are benignant and wise, to perform its manifold offices in the economy
of our planet.  It is this heat which gives " his circuits" to the
winds and circulation to the sea; it is it that fetches from the
ocean. the clouds that make " the earth soft with showers."  Stored
away in the depths of intertropical seas, it is conveyed along, by
" secret paths," to northern climes, there to be brought to the surface in due season, given to the winds, and borne away to temper
the climates of Western Europe, clothing the British Islands as
they go, in green, and causing them  to smile under the genial
warmth even in the dead of winter.
890. WVe may note, also, another peculiarity as to the differs
The radiating powers ence in the direct heat-absorbilng and radiating
of earth, air, and water compared.  properties of sea, land, and air.  It is one which
presents the atmosphere in the light of a regulator between the
two on one hand, and the heating powers of the sun on the other.
It is suggestive, also, of other benign compensations and lovely
offices in the physical machinery of our planet. Both land and.
water receive more heat from the sun than they radiate again;
but the atmosphere receives less heat cdirect from the sunt than it
radiates off again into space. As the heat comes from the sun,
part of it is absorbed by the atmosphere, but the largest portion
of it is impressed upon the land and water. From these a portion passes off into the atmosphere by conduction, while another
portion is radiated directly off into the realms of space. ~What
becomes of the remainder?  Let us inquire, for there is a remainder; and unless means for its escape were provided, the land and
water, especially the latter, would continue to grow warmer and
warmer, and so produce confusion in the terrestrial economy.
The remainder of this heat, being that which is neither radiated
by sea and land directly off into space, nor imparted to the air by
conduction from them, is absorbed in the processes of evaporation. It is then delivered to the atmosphere, latent in the vesicles
of vapor, to be set free in the cloud region, rendered sensible and
imparted to the upper air, whence it is sent off by radiation into
the "emptiness of space."  Thus the air, with its actinometry,
presents itself in the light of a thermal adjustment, by which the




474        THE PHYSICAL GEOGRAPHY OF THE SEA.
land and sea are prevented from becoming seething hot, and by
which they are enabled to perform their wonderful offices with
certainty and regularity.
891. Thus, perhaps, we discover a new office for the waves in
An office for waves in the physical economy of the ocean. Is it not to
the sea.      them that has been assigned the task of bringing
up, by their agitation of the surface, the layers of warm water
that are spread out below? and are they not concerned also, as
they draw up the genial waters, in regulating the supply of heat
for the winds by night, as well as in cold or cloudy days, for the
purposes of evaporation?  Thus even the waves of the sea are
made, by this beautiful study, to present themselves as parts, important parts, in the terrestrial machinery.  WVe now view them,
as it were, like balance-wheels in the complicated system of mechanism by which the climates of the earth are governed. If the
waves did not stir up the heated waters from below (~ 881), the
winds would evaporate slowly by night for the want of adequate
supplies of caloric; the consequence would be less precipitation
and a more scanty supply of latent heat for liberation in the cloud
region.  As a consequence of this, the winds would have less motive power, and the whole climatic arrangements of our planet
would be different from what they are.
892. It is curious to think that this subtile thing, called heat,
A reflection concern- which we have been contemplating, now as latent
ing heat.     ill the clouds above, now as sensible in the waters
below, comes from the same source whence originally came 4the
heat which has been packed away in seams of coal and stored in
the bowels of the earth for ages and ages, to be called forth by
man at will, for his own comfort, pleasure, and convenience; that
this protean thing is the agent which controls sea and winds, and
they it; that it is it which has lifted up the mountains, which
clothes the world with beauty, and keeps the stupendous fabric
of the universe in motion; and that, after all, this mighty agent
is only that gentle thing that " warms in the sun!"
893. Pursuing this subject, the philosophical mariner, as he sails
Probable relation be- along and records observations for these purposes,
tween the actinometry
oftheseaanditsdepth. may fancy —and perhaps rightly-that he has
traced to the actinometry of the sea one of the physical conditions
which, when the depths of the ocean were laid, had its weight
with the ALMIGHTY ARCHITECT.




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RECENT DISCOVERY
AND
ADVENTURE IN AFRICA.
The following list includes all the standard works in which are recorded the labors of those Explorers, Travelers, and Hunters who have, within the last ten years, contributed so greatly to our
knowledge of the Geography, Ethnology, and Natural History of the long mysterious interior of
Africa. These works are all finely and abundantly illustrated, and embrace the entire round of
Recent Exploration.
A COMPANION WORK
TO
BURTON, LIVINGSTONE, AND BARTH.
Du Chaillu's Travels in Equatorial Africa.
Du Chaillu's Four Years' Travel and Adventure in the Unexplored Regions
of Equatorial Africa.  With full'Accounts of the Manners and Customs of the
Cannibal Tribes of Central Africa; of the Habits of the Gorilla and other hitherto unknown Man-like Apes; and of Hunts after the Gorilla and other
strange Animals.  With nsnmerous Illustrations.  8vo, Muslin.  (In Preparation.)
The Lake Regions of Central Africa.
A  Picture of Exploration.  By RICHARD F. BURTON, Capt. H.M.I. Army;
Fellow and Gold Medalist of the Royal Geographical Society.  With Maps
and Engravings on Wood.  8vo, Muslin, $3 00.  (Uniform  with Barthz and
Livirgstone.)
Captain Burton is an amateur Ulysses. ** * A  into the heart of Central Africa may well be
more active mind was never accompanied by a classed among the boldest and most successful
livelier pen.-Literary Gazette.            achievements in the annals of inland discovery.
Captain Burton's march of a thousand miles -London Spectator.
Livingstone's South Africa.
Missionary Travels and Researches in South Africa; including a Sketch of
Sixteen Years' Residence in the Interior of Africa, and a Journey from the
Cape of Good Hope to Loando on the West Coast; thence across the Continent, down the River Zambesi, to the Eastern Ocean.  By DAVID LIVINGSTONE, LL.D., D.C.L. With Portrait, Maps by AERowsSMITH, and numerous
Illustrations.  8vo, Muslin, $3 00; Half Calf, $4 00.
The African Columbus has broken the egg, ship-how he has sounded unknown lakes, broand let the world into his secret. What he has ken through thorny jungles, navigated unknown
achieved, and endured, and conquered; the rivers, opened to light a world teeming with floral,
witchcraft which, for sixteen years, he has used animal, and mineral wonders-obtaining ingress
against a vertical sun and a malign climate-  for science, for commerce, for religion-and leadhow he has run the gauntlet of carnivores, and  ing after him, as the special spoils of his expedipachyderms, and ophidia —how he has lived on lion, a throng of colored indigeni, drawn along
roots, and locusts, and frogs, and moistened his by no other fetters save of love and admiration.
mouth only with rain or river water-how he has So runs the story of his book-a book not so much
striven with thirst and fever, with the loss of let- of travel and adventure as, in its purport and
ters, and the absence of intelligent compa.nion- spacious relation, a veritable poem.-Athenceum.




2              Becent Discovery and Adventure in -4fricca.
Dr. EBarth's North and Central AfriEoa
Travels and Discoveries in North and Central Africa.  Being a Journal of an
Expedition undertaken under the Auspices of H.B.M's Government, in the
Years 1849-1855.  By HENRY BARThTI, Ph.D., D.C.L.  Profusely and elegantly Illustrated.  Complete in 3 vols. 8vo, Muslin, $7 50; Sheep, $8 25; Half
Calf; $10 50.
The researches of Dr. Barth are of the highest appointed in the narrative of Dr. Berth, which,
interest. Few men have existed so qualified, sprinkled withl anecdotes, varied with glittering
both by intellectual ability and a vigorous bodily, descriptions of landscapes and manners, written
constitution, for the perilous part of an African  with vigor and simplicity, and disclosing amid
discoverer as Dr. Barth.-London Times.       the gloom of Africa the secrets of centuries, is a
His discoveries, in fact, are parallel with those  rich repertory of kenowledge, and deserves to take
of Dr. Livingstone in the South.  We confess its place among the classics of travel. —London
that such a relation has for us an intense inter- Leader.
est; we are sure that no serious reaocer will be disAndaersson's Lake Ngaml
Lake lNgami; or, Explorations and Discoveries during Four Years' Wanderings in the Wilds of Southwestern Africa.  By CHARLES JOHIN ANDERSSON.
W~Vith numerous Illustrations, representing Sporting Adventures, Subjects of
Natural Histor'y, Devices for Destroying Wild Animals, &c.  New Edition.
12mo, Muslin, 75 cents.'This narrative of African Explorations and  to the geology, the scenely, products, and reDiscoveries is a very important geographical sources of the region explored, with notices of
work. It contains the account of two journeys  the religion, manners, and customs of the native
made between the years 1850 and 1854, in the  tribes. The continual sporting adventures and
first of whicll the countries of the Damaras and  other remarkable occurrences, intermingled with
the Ovambo, previously scarcely known in Eu-  the narrative of travel, mnake the book as interrope, were explored; and in the second the new- esting to read as a romance, as, indeed, a good
ly-discovered Lake Nganli was reached by a route  book of travels ought always to be. The illusthat was deemed impracticable, but which proves trations by Wolfe are admirably designed, and
to be the shortest and the best. The work con- most ofthem represent scenes as striking as any
tains much scientific and accurate information as.  itnessed by Jeules Gerard or Gordon Cummicng.'
Cumming's Hu lter's Life'in Africa.
Five Years of a Hunter's Life in the Interior of South Africa.  With Notices
of the Native T'ribes, and Anecdotes of the Chase of the Lion, Elephant, Hippopotamnus Giraffe, Rhinoceros, &c.  With Illustrations.  2 vols. 12mo, M{Iuslin, $1 75.
" The writer of this work appears to be a fierce, from the charms of English society in the tangled
blood-thirsty Nimrod, cwhose highest ideal is depths of the African forest. Every page is redfound in the destruction of wild beasts, and who. olent of gunpowder, and you almost hear the
relates his adventures with the same eagerness growl of the victim as lie falls beneath the unof passion -whichl led him to expatriate himself  erring shot of the mighty hunter."
Wilson's AfriaeE
Western Africa: its History, Condition, and Prospects.  By Rev. J. LEIGHTON WnILSON, Eighteen Years a Missionary in Africa, and now one of the Secretaries of the Presbyterian B3oard of Foreign Missions.  With numerous Engravings.  12mo, Muslin, $1 25.
"Mr. Wilson is probably better acquainted  which have been elaborated some of the most
than any other man with Western Africa and  valuable contributions that have been recently
its inhabitants. During a residence of almost made to the sciences of ethnology and philology.
twenty years he repeatedly visited all portions I-e is a careful and shrewd observer, and presents
of the coast, mastered the principle languages the results of his observations in an excellent
of the natives, composed grammars and diction- style. Iis book is a valuable addition to our
aries, and published books in them. I-e has knowvledge of a country which is rapidly rising
either written or furnished the materials from  in importance."
Published by HlARPER & BROTHDERS, Franklin Square, N. Y.
HIAPE; & BROTraS will send either of the above WVorks by Mail, postage paid (for any distance
in the United States under 3000 miles), on receipt of the Money.