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TEACHERS'
GEOGRAPHY
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YALE
UNIVERSITY LIBRARY

TEACHERS' GEOGRAPHY

MAN AND CLIMATE
WITH PRACTICAL EXERCISES

NEW EDITION

MARK JEFFERSON
Michigan State Normal College

Published by the Author at
YPSILANTI :: MICHIGAN
1912

Copyright, 1912, by Mark Jefferson

PURPOSE
These notes are planned to facilitate the work of the Teachers' course for the stu
dent by putting in his hand a statement of principles that will be amplified and illustrated
in the class room, and formulating the illustrative exercises he is to perform.
The work is a Teachers' Course in the State Normal College. That means that it is
12 weeks of work thought essential to the professional preparation of the teacher who
can give but one term to this department. The time period is not deliberate choice, but
traditional. The 12 weeks' course is our unit. Given that unit it has seemed most pru
dent to subdivide the professional work into: 1 The Teachers' Course, and 2 Regional
Geography; (a) Geography of America, (b) Geography of Europe. We wish our stu
dents to have a modern point of view in geography. We have therefore to treat of the
principles involved in modern doctrine on the subject. The time limitation narrows this
course to a portion of the subject matter; the distribution of Man, Climate, which is the
first controlling condition of that distribution, and the construction of simple maps.

1
1. If Geography is concerned with the earth and irian, as soon as we have some
idea of the distribution of land and water on our globe, it becomes of interest to know
where this man is. A glance at the map on page 9 (Figs. 5 and 6) is necessary at this
point. The depth of shades on it corresponds to the density of the population of the
various regions, close and crowded where the map is black, many men living in little
space, and grading through lighter shades to blank areas which are practically uninhab
ited, though crossed from time to time by the solitary hunter or prospector or wandering
bands of nomads. A very hasty glance at this map shows the great unevenness of our
occupation of the earth. If man is gregarious he has at the same time a tendency to fall
into groups that are singularly isolated. We were aware that more than half of mankind
lives in Asia but we may not have realized how persistently Asiatic men crowd into the
southeastern corner of their continent, leaving a good half of its surface uninhabited.
Again we knew that the Australians were few, but we had no idea that all the men of
that part of the world lived close to the southern and eastern coasts of their Island-con
tinent and on the neighboring islands. We knew of Europe as the home of many, many
nations, and nations that have figured much in history, literature, art and science, but
was it clear to our minds how completely man and his works have occupied that conti
nent and that continent alone? Europe is the only continent with almost no desert
spaces. Ninety percent of the surface of the continent is settled. The rugged, rocky
uplands of its mountains and the frozen Arctic plain of northern Russia are the only bits
of Europe to deny abiding places to Europe's peoples. This is the more noticeable in
the light of the wide blank spaces on the map of each of the other continents, ranging
from two and a half millions of square miles in Australia to nearly eight millions in Asia,
space enough for the whole continent of North America. There are not people enough
in the whole world to settle Asia as closely as Europe is settled.
2. In the New World lands, in which I include South Africa and Australia with the
Americas, another glance at the map shows but thin settling, so different from Eurasian
grades that one cannot help thinking of the newness as a possible explanation of their
scanty peopling. In that case there are to be vast enlargements in the total of humanity
in these new fields. But we should not form hasty conclusions as to the effect of time.
The facts of Asia and Europe are opposed to such a view. Contrasts of density there are
by no means to be explained in terms of time elapsed. Mesopotamia and most of North
Africa have had time and history enough. Think of Egypt and Babylon and Persia and
Syria and Phoenicia. Yet how thinly are they peopled to-day! In general it is the lands
about the Baltic and the North Sea, new lands all in European history, that far excel in
density the historic shores of the Mediterranean. Italy is only an apparent exception to
this statement. It is true that she is only surpassed on the North Sea by Britain, Holland
and Belgium in density of population, but it is to geographic conditions and not length of
time that she owes this; geographic conditions that she alone of Mediterranean countries
shares with central and northern Europe and that must have contributed no little to her
ancient dominance. In Asia, too, the central deserts have historic remains of high
antiquity, though the populous lands of to-day are also old.
3. The effects of natural laws are as complex as their causes. Time has great
changes in store for the peopling of the newer lands. There will be great growth in
numbers, great adjustment to environment, which will set in operation in the New World
those processes long at work in the Old. These processes, this adjustment to environ-

ment, all this is geography, a science whose problems are admirably set before us by the
seeming lawlessness of man's distribution on the earth. We need not hesitate to read in
the thorough peopling of Europe alone among the continents the unconscious verdict of
millions of vigorous, restless, homeseeking men that they have found in Europe man's
fittest environment, a verdict justified by the careful investigations of modern scholars.
So in Asia the southern and southeastern border has greatest geographic fitness. These
considerations form a logical introduction to the facts of geography; a criterion for the
importance and rank in the science of those facts is given at once by their ability to an
swer the question that here arises: wherein consists the fitness of this region for man?
Before attempting to answer this question let us point out that the brevity of the new
world history has not hindered geographic agencies from guiding the spread of culture
here. Florida has "been known longer than Michigan but is not settled so completely;
nor is Newfoundland. The guidance has not always been so effective, has not taken a
form so final, but the problems here are identical. The examination of new world land
scapes, the investigation of new world resources have been barely begun. Man is rich
in all these lands, which include Australia and South Africa as was said above. He has
abundant lands to cultivate so he does not yet feel the stimulus of need. It is there
fore a more superficial and temporary aspect of his environment to which he reacts,
but the reaction is no less certain.
4. For North America it needs but a glance at the rainfall map at page 13 to per
ceive the great similarity between it and the population map. Rains have a very final
word in assigning Man permanent abodes in his groupings about the Earth. The 100th
meridian (see also p. 9) sharply separates rainy lands from arid in all of the continent
north of the thirtieth parallel, and roughly bounds even thin populations on the west, as
the homeseekers who ventured into western Kansas in 1890 found to their cost. But
while man has not closely occupied parts of the continent that have less than 20 inches
of rain, neither does he at once become more abundant with greater rainfall anywhere.
The small empty spaces in Florida and Central America are not due to defect of rain.
The very dense areas are not found occurring with very heavy rainfall. It is wholly
doubtful if man's prosperity is favored at all by more than 40 or 50 inches of rain. For
these reasons we shall call rainfall less than twenty inches a year scanty,
over twenty sufficient, over forty abundant, and over eighty excessive. For
. the rest, the conditions of the areas of dense population are pretty strongly contrasted.
Man lives easily amid the exuberance of the tropics, in a fruitful land with a climate that
imposes on man little need of shelter and clothing. The much larger area of very dense
population toward New England on the other hand is in that belt of energetic American
life between Baltimore and Boston in which resides so much of American culture, thrift
and business; where are so many large cities, so many great universities, so many associ
ations with great men and great deeds in the history of the United States.
South of the thirtieth parallel the rain falls from the Atlantic to the Pacific and
men have no such east and west division as in Canada and the United States. The
islands of rainfall that accompany the chief mountain ranges of the western plateaus are
matched by islands of population, which stream even beyond the rainbelts along the
river valleys that lead flood waters out into arid country, and make agriculture pos
sible with irrigation. Canada is seen to be largely rainless and empty.

5. Labrador is apparently well watered enough for occupation but there is little
soil on its wilderness of rocks, as in most of the country north of the St. Lawrence and
the line of Great Lakes between Lake Ontario and the mouth of the Mackenzie river.
So along the Pacific coast of Canada and Alaska there is rain enough. Overmuch
mountain and bare rock deter man from settlement. Norway, which has a

FIG. 1. THE SCANT SOIL OF NORWAY.
similar position in Europe, has 96 percent of her surface uninhabitable mountains. So
with abundant rains, she has but 18 people to the square mile in a continent where the
average is a hundred. Yet even so moderate a peopling as Norway's — it would corres
pond to the dots of our diagram — has been the result of a thousand years of national life.

UnINHAB
Switze(^land_ 1900

FIG. 2. UNINHABITED SWITZERLAND.

And that thousand years has been of much significance. Switzerland shows the
same thing with a history reaching back of the Christian era. The black shades
on the accompanying map are nearly uninhabited and mark out very clearly the
Alps on the south and the Jura on the northwest. All America is so new to
civilized man that no energetic effort has yet been made with us to occupy any but the
best lands. It is for this reason, in part, that the population is still denser toward the
New England region, the points of early settlement and near approach to the mother
country. It is by no means clear that this is always to be so. A glance at the world map does
indeed show that none of the world's very dense populations is wholly without contact
with the sea, though they extend inland in Southern Germany, India and China eight
hundred to a thousand miles, and one sees the Atlantic density of population creeping
across Pennsylvania and Ohio to the shores of the lower lakes. The mountains of Alaska
may not always deter men, but to-day their influence is strong.
Thus mountains are seen to draw men and repel them. In the arid lands of the
western United States the cooling lift they give the winds brings very welcome
rain. There every mountain is a green place, wooded and grassed, an island in the
desert expanse. Men live there of necessity, not on the mountains, that men rarely
do, but in the valleys between, and therefore always in limited numbers. The Rocky
Mountain valleys support the people of the western States, but their population will
never be dense. Further east where the lowland rains are sufficient, one may see on the
large diagram how the population thins at the Ozarks, the mountains of Virginia, West
Virginia, in the Catskills and Adirondacks of New York, and in the mountains of northern
New England. For however densely the valleys are settled there is always useless land
above. 6. Other areas of thinner population in the Eastern United States occur in the
swamps along the Mississippi in Arkansas and Louisiana. Here is too much water rather
than too little, as in the Everglades near the tip of Florida, almost without people for
lack of drainage.
Turning our glance westward from Florida toward the Pacific we find Lower Califor
nia without water or people, but in Central America again an unpeopled strip across
Yucatan coincides with a strip of exceptionally heavy rainfall. The rain belt does not,
however, continue along the Honduran and Nicaraguan coasts which are equally without
population. The difficulty here is probably the great heat, more intense on the Caribbe
an than on the Pacific coast. The name Mosquito coast, applied to the Nicaraguan strip,
has its own implications. Here plants may thrive better than men, as on the plains of
the Amazon. The dense population about the city of Mexico occupies a basin of rather less than
twenty inches of rain, but is easily watered from the surrounding heights.
7. Men seek the heights in the tropic regions not directly because of the heat be
low, but rather because of the overwhelming luxuriance of the vegetation and the preva
lence of human ailments in the combination of heat and reeking dampness on the low
lands. To clear away the forest is a heavy undertaking even in our northern open
woods. The opening up of Michigan was not to be compared for rapidity with that of
the prairie states where the land was ready for the plow when the owner came to it. In

the wet regions of the tropics the forests are inconceivably dense. To leave the trail is
not merely difficult, it is a sheer impossibility. Plants grow not merely on the ground
but on each other until the whole space between the tree top and the ground is filled
with a mat of interlacing growths. To make a clearing in such a tangle is a huge labor,

FIG. 3. IN THE WOODS ON MT. MISERY, ST. KITTS
to maintain it an endless one. Kipling's "Letting in the Jungle" well conveys the idea
of vegetation fairly obliterating a village. Perhaps the day will come when these
forests must be tamed, but in America four centuries of Latin dominion has made no
impression on them. Dominica in the West Indies is as impassable off the narrow road
as when Columbus gave it a name.
8. It cannot be accident that the peopling of Australia, South Africa, and Madagas
car is all to the east (see p. 14). Let us see therefore what peculiarity each of these has
in its eastern parts. Each (see p. 16) has abundant rain on the east, steadily diminishing
to scanty on the west. A glance at some political map of South Africa is instructive. On
the west, reaching from the Atlantic more than half way across the continent, are the
great deserts of German Southwest Africa and Bechuanaland, then succeed for another
considerable distance the semi-arid uplands of the Boer country further east, now Orange
river and Transvaal colonies, and then, under the rugged slopes of the Drakensberg, by
which the plateau breaks down on the east, the well watered gardens of Natal. This
thrice repeated topographic, climatic, and distributive group of features is a proper
characteristic of an eastward rotating earth. Were the motion reversed the three
populous regions would be blighted with ensuing drought. It is not by chance that our
people thin out so suddenly at the hundredth meridian, that the Pacific coasts of America
are populated for thirty degrees on each side of the equator, then desert for the next ten
degrees toward the poles in each hemisphere, thence peopled again beyond the forties.
Surely the great things in geography are the agencies that have governed such a distri
bution of mankind.
9. Upon careful examination of data that are now fairly obtainable for the whole
world, at least as far as broader features go, it appears that the first requisite for a great

6
population group is broad soil-covered plains for their home; the second, sufficient rain
fall on these plains; the the third, a temperature neither too low for plants nor so high as
to provoke vegetation to become man's oppressor rather than his servant. History re
veals man in the old world settling down more and more firmly and growing more and
more prosperous under these conditions. The new world has many a hint of similar
tendencies. In the matter of rainfall Europe is singularly happy. She suffers less from drought
than any other continent. Only the Spanish interior and southeast, and the steppes of
east Russia are limited in population from this cause. Thus it happens that Russia's pop
ulation leans so decidedly westward as the map shows and that of the Iberian peninsula
is so close a reflection of its rainfall and therefore marginal. Her areas of excessive rain
are very small.
So much of Australia is arid that only her eastern border can ever become populous.
10. The distribution of people in South America is somewhat peculiar. The dens
est population is rather over twenty-six to a square mile, that is, a little more than the
average density of the United States. The patches of moderate population are at once
seen to lie always within 400 miles of the sea. A northeast southwest line through the
center of the continent would have a region to the southeast with almost all the patches
on the coast; another to the northwest with none at the coast, but all near it. What de
termines this arrangement? The mountains of the continent; for South America, though
endowed with two of the greatest river systems of the world, leaves the greatest of
these solitary and deserted and finds its mountains all-determining for the homes of its
nations. A glance at any map showing relief reveals the fact that the populations of the
northwest lie along the high valleys of the Andes, and that the thin peopling,

FIG. 4. CUZCO IN A HIGH VALLEY OF THE ANDES, 11,000 FEET ABOVE THE SEA

indicated by the dots, observes a similar behavior down to the tropic of Capricorn. In
Peru and Ecuador the moderate population reaches the coast, while in Columbia and
Venezuela the transition is from moderate along the central Andean chains to thin at
the coast and on the plains of the Amazon.
The vast basin of the Amazon is seen to be all but deserted. Brazil has its people
gathered along its eastern border, where it, too, is high, but the people have not drawn
away from the coast as on the Pacific. Tropical South America has its people in the five
mountain republics of the northwest — Venezuela, Columbia, Ecuador, Peru and Bolivia,
and on the elevated eastern sea border in Brazil. The Amazon basin is a great hinterland
on which all have claims, for the most part ill defined or in dispute, but in which none
have any significant number of citizens. It is in complete possession of aboriginal sav
ages, apart from isolated trading posts along the waters. The equatorial position, of
course, is the cause. The dominant races seek the mountains to escape from the heat
and moisture of the lowlands. The tropical Andes are the great rain producers of their
continent in the cooling lift they give to the trade winds that blow from the Atlantic
against their eastern slope, but their upper valleys are drier and are the truly temperate
regions of the world. North of the twentieth parallel South America hardly knows
greater differences between summer and winter temperatures than five or ten degrees.
A lowland heat of 75 to 85 degrees proves very favorable to rubber, sugar cane, coffee
and cacao, but man ever since Inca days has preferred the drier, cooler mountains, al
ways with the same narrow range. In the Andean republics the denser populations live
where the thermometer ranges mostly between 50 and 60 degrees or 55 and 65 degrees.
11. South of the tropic the Andes serve to part men as well as the waters. The
high valleys there are too bleak for permanent homes. There the Andes are a wall, a
boundary. They are not essentially in Chile and the Argentine, but east of Chile and
west of the Argentine Republic, a relation entirely different from that which prevails
further north. The lowlands in the south have distinct summers and winters, hot and
cool respectively. They are somewhat short of moisture, notably in the western Argen
tine plains, under the wind shadow o*f the Andes, for in this region of westerly winds the
rains come from the Pacific or from disturbances that sweep eastward across the conti
nent. The plains here, narrow in Chile, broad in the Argentine, are the home of pros
pering, thriving men, of communities that are taking part in modern life, with schools,
railroads and active commerce, that puts them in contact with the other active peoples
of the earth.
12. There are not very many people in the world in comparison with its area.
Texas would hold them all and give each man, woman and child a square seventy feet on
each edge. They could stand much closer than that. Two thousand people can- stand in
a mile-long line very easily. They will have two and two thirds feet between the cen
ters of their bodies. A square mile so covered would have four millions on it, and the
whole sixteen hundred millions of the world's people could stand in the little state of
Rhode Island, and have abundant room to spare.
13. But standing room is a very different thing from living room or "Sustenance
Space", the area from which a man can draw his food or clothing. This varies greatly
with the man's occupation, being very large for hunters and fishers, smaller for grazing

nomads and lumbermen; smaller still for agriculturists. Thus it happens that there is a
close relation between density of population and the occupations widely prevalent
through a region. Generally these relations hold all over the world except in India,
China and Japan. Thus hunting and fishing may support from two to eight people per
square mile and they must of course be savages or barbarians, lacking as they do agri
culture and the manufacturing arts. Grazing and lumbering may prevail with densities
of 8 to 26 people. So all four of these occupations are likely to occur in one part or an
other of the dotted areas of the map (p. 9, see numbers on the Legend.) The student
should check this up somewhat for himself by examining regions where he knows that
lumbering, for instance, is general, to see what the map indication is there.

14. DISTRIBUTION OF POPULATION IN NORTH AMERICA. FIG. 5
1. What one word best describes the density of population of North America north
of the 50th parallel? 2. Has Canada more thin population north of 50° or scanty south
of it? 3. In what states does a very dense population occur? 4. Name seven regions
of dense population. 5. About what proportion of the United States is moderately
peopled? Where? 6. How do the scanty and thin grades of population compare in
area west of the 100th meridian? 7. Compare the density of population in the United
States east and west of the 100th meridian? 8. Explain (7) by Rainfall map. 9. De
scribe and explain the density of population of Florida. 10. What is the principal grade
of population south of the 30th parallel? 11. Why is there not the same difference at
the 100th meridian as in the United States? (See Rain map.) 12. Describe the east
and west arrangement of grades of density of population in Central America and explain
it. 13. What style of agriculture appears to be most prevalent in North America? 14.
Describe the density of population along the Pacific coast from Vancouver Island to
Lower California. 15. Explain it. 16. In general how well are the West Indies
settled? 17. Why is northern Mexico so thinly peopled? 18. In what river valley do
the people of Canada mostly live? Why? 19. What are the main agricultural regions
of the United States? 20. What appear to be the occupations of northern and southern
Michigan? 21. What five states have the largest area of scanty population. 22. What
five are most uniformly moderately peopled?

15. For agriculture, predominant where the population densities are from 26 to 250,
we distinguish two types. These might be called large farm and small farm agriculture'
but better names are extensive and intensive agriculture, putting the emphasis on the de
gree of thoroughness with which the ground is worked. The extensive or large farm
agriculture characterizes regions where the density of population is from 26 to 125 per
sons to the square mile. This is typical of southern Michigan. Here the farm house is
apt to have four indwellers, and the numbers allow from 6 to 31 such farms in a square
mile. Each farm must run therefore from 106 to 20 acres in size, as a matter of fact we
know they are mostly of forty, rarely of eighty acres. In the same way we may estimate
that the intensive farming prevalent with population densities of 126 to 250 people to the
square mile implies farms of ten or twenty acres. But they will be more thoroughly
tilled and will yield much larger crops for the same area. Note the following figures

Fig. 5

10
from the 1909 Year Book of the U. S. Department of Agriculture. They are averages
for the twenty years 1889 — 1908 of the yields of five important crops in bushels per acre
for United States (extensive), and Germany and United Kingdom (intensive):

U. S.

Germany

U. Kingdom

Potatoes

90

197

186

Wheat

14

29

33

Oats

29

50

45

Barley

26

34

35

Rye

16

25

27 (Ireland)

It must not be supposed that extensive agriculture is bad agriculture. The table
shows a German acre of land yielding about as much as two of ours. It involves more
than twice as much labor though, each added bushel of yield costing a greater and
greater increase of labor. Where land is cheap and labor dear, as with us, extensive
farming is appropriate.
Two thirds of our farms are of more than 50 acres each; more than two thirds of
British farms are of less than 50 acres and of Germany's four fifths are of less than
twenty-five acres.

16. For densities of population above 250 per square mile the predominant pursuits
are the manufacturing industries except in eastern Asia, where an agriculture so intense
prevails that there is nothing like it elsewhere, with the population running to 1000 and
2000 to the mile.
If we add to these grades of density cities, with over ten thousand to the mile, but
too small of area to be perceptible on a map so small as these, we have in the population
map a rough means of judging what men do as well as where they live.

17. Distribution of Population in Europe. Fig. 6
1. Name countries with regions of very dense population. 2. Name countries
where scanty population occurs. 3. What countries have regions of thin population?
4. Describe the largest area of very dense population in Europe. 5. What two coun
tries have spots of very dense population? 6. What grade of population is most wide
spread about the shores of the Baltic Sea? 7. Locate the three population-regions of
the Baltic. 8. Describe the density of population about the North Sea. 9. Describe
the distribution of population in Italy. 10. Describe the distribution in the Iberian Pen
insula. 11. What is the average population-density of the Mediterranean shores? 12.
What countries have mostly the dense and very dense grades of population? 13. What
is the most striking contrast between the distribution of population in Great Britain and
the Iberian peninsula? 14. Compare the density of population in east and west Eu
rope. 15. Compare the population-densities along the 40th and 50th parallels. 16.
In what three countries do the population-densities accord best with the data of the rain
fall map? 17. About what point is Danish life centered? 18. Compare the dis
tribution of people and rainfall in the Turkish Empire. 19. What sort ot agriculture
prevails in Italy? 20. What appear from the map to be the chief occupations in
England? In northernmost Scotland?

11

Fig. 6

12
18. Distribution of Population in Asia. Fig. 9
1. Name six groups of very dense population. 2. Locate and describe three
areas of scanty population. 3. What American population— group corresponds in its
position in its continent to that of China? 4. What ones to Asia Minor and Palestine?
5. Describe the distribution of population in Japan, India and China. 9. Compare
the distribution of people and rainfall in China. (See p. 14.) 7. What grade of pop
ulation occurs in the region of excessive rain in India? Is that also true in other conti
nents? 8. In general why are the inhabited parts of Asia in the south and east?
9. Judging by density of population where is grazing most carried on?
19. Distribution of Population in Africa. Fig. 9
1. Describe the areas of scanty population. 2. What does the map of annual
rainfall show there? 3. Where is the most densely settled part of the continent? 4.
Has it rain? How do the people manage to live there? 5. Why is west Madagascar
scantily settled? 6. In general how well do the rain and population maps of Africa
correspond? 7. To judge by density of population what are the main occupations in
Africa? 8. In general how is Africa settled?
20. Distribution of Population in South America. Fig. 10
1. How wide is South America's strip of thin to moderate population? (See di
mensions of the meshes of the map net at the right border of the left hand hemisphere.)
2. Where does the strip run? 3. What is its relation to the region of excessive
rainfall? 4. Is this relation found anywhere else in the world? 5. In general
what grade of rainfall is most often associated with considerable population? 6. What
countries have strips of moderate population on the coast? 7. What countries have
moderate population in the mountains? 8. What countries have but two grades of
population density? 21. Distribution of People in Australia. Fig. 9 and Fig. 10
1. What fraction of Australia has scanty population? 2. About how many
square miles of inhabited area has Australia? (See areas in the margin of the northern
hemisphere.) 3. In what respects does the distribution of population fail to agree with the rain
fall map? 4. Explain the grade of population of northern Australia. 5. What
are probable occupations of Australia's people?

13

W M W W tj' 60

Fig. 7

Fig. 8. Excessive, abundant, moderate and scanty rainfall

14

DISTRIBUTION OF PEOPLE

GRADE OF PEOPLING
Very dense
Dense
ModerateThinScanty

Fig. 9
LEGEND
SHADE Black Cross lined
LinesDots
Blank -

PEOPLE TO ONE SQUARE MILE
250 or more
125 to 250
126 to 125
2V4 to 26
less than 2V2

IN THE WORLD

15

.-3-JV

Fig. 10

From data in Supan's Bevoelkerung der Erde,
Statesman's Year-Book and U. S. Census,

16

ANNUAL RAINFALL OF THE

Fig. 11
LEGEND

SHADE

RAINFALL

Black

Excessive

Ruled lines

Abundant

Dots

Sufficient

Blank

Scant

DETAILS

An annual rainfall, including melted snow, of over 80 inches
An annual fall of from 40 to 80 inches.
An annual fall of from 20 to 40 inches.
Less than twenty inches in the year.

17

WORLD (INCLUDES MELTED SNOW)

Fig. 12

After Herbertson.
In the blank areas agriculture is hardly possible without irrigation. Within them he all the
world's deserts.

18
22. Annual Rainfall, North America. Fig. 7
1. What parts of the map show rain where no men live? 2. Why is this? 3.
What meridian is a rainfall boundary in the United States? 4. Describe the rainfall
of Canada. 5. Describe that of Mexico. 6. What is the shape of the scanty rain
area? 7. What percentage of the total area of the continent is made up by areas
with more than scanty rainfall? 23. Annual Rainfall, Europe. Fig. 8
1. Is there any region of sufficient annual rain where the population is scanty?
2. About what grade of population corresponds to the large area of scanty rain?
3. What grade of rainfall prevails in the parts of Europe most densely populated?
4. Compare the distribution of rainfall in the Scandinavian and Iberian peninsulas.
5. Does Europe's abundant rainfall mostly correspond with the denser population?
6. Which is rainier, east or west Europe? 7. Which more populous? 8. What
percentage of Europe has sufticient and abundant rain?
24. Annual Rainfall, Asia. Fig. 11
1. Where is there excessive rain? 2. How much of Asia is dry? Where?
3. Locate the sufficient rains. 4. Describe the distribution of rainfall in India
5. How well does it agree with the distribution of people? 6. Explain the distribution
of population in connection with rainfall in the northernmost of the Philippine Islands
(Luzon). 7. Compare the rainfall and population of eastern and western Turkey.
8. Compare the rainfall and population densities of the East Indies in detail.
25. Annual Rainfall, Africa. Fig. 11
1. What percentage of Africa is dry? 2. Compare it with Europe in this res -
pect. 3. Where is Africa's excessive rain? 4. Compare the distribution of rain
fall in northernmost and southernmost Africa with that of people. 5. Does Africa
anywhere show heavier population where the rainfall is excessive? 6 Illustrate.
26. Annual Rainfall, South America. Fig. 12
1. Locate areas of excessive rain. 2. How much of the continent is dry? 3.
Describe the larger area of scanty rain. 4. What is the population grade along it?
5 How does South America compare with other continents in the general supply of
rainfall? 6. What four countries have each four grades of rainfall? 7. Describe
the rainfall of the Argentine Republic and Chile.
27. Australia, Annual Rainfall. Figs. 11 and 12
1. What proportion of Australia is dry? Where? 2. Where are the excessive
rains? 3. How does Australia compare with other continents in raininess? 4.
Australia and the United States have about the same area: how do their rainy areas
compare? 5. Which is rainier: New Zealand, Tasmauia or Victoria?
28. The student who has worked his way to this point will see the great control
over man and his occupations that is exercised by rainfall. We shall now set forth the
chief principles on which the distribution of rain depends. This involves a brief study
of climate.

19
CLIMATE
29. It is important for teaching to recognize that climate is an abstraction, an ideal
derived from the reality — weather. What is with us to-day is weather. It will be wea
ther to-morrow that will affect us then. Only by examination of a long review of past
weather can we come to any conception of the climate in which we have lived. The
local weather thus becomes the appropriate point of attack for the study of climate. The
daily weather map enables us to extend the area of observation over most of North
America, and becomes our most effective single means of instruction in all that pertains
to climate. 30. Both climate and weather reside in the lower air. Events above may be very
different, indeed they commonly are. The conditions and changes of the upper air are
of great interest to the student of weather, as helping us to understand what goes on
below, but the events of our weather occur where we pass our lives, at the bottom of
the ocean of air.
The conditions of the lower atmosphere that concern us in this study are chiefly:
TEMPERATURE,PRESSURE (Air good and bracing or muggy and oppressive),
MOTION (Winds),
The Presence and Condition of Water (Rain, clouds, dew and water vapor).
Temperature of the Lower Air
, 31, How does it appear to you that this weather element ranks in importance for
us? Does it matter more or less than rain?
You will henceforth observe each morning at as early an hour as you are in the
habit of going out of doors, how the temperature compares with that of the day before.
It should not be supposed that the reading of the thermometer replaces this exercise for
the student. It is perfectly possible to read the thermometer and record its indication in
the book without ever thinking what it means. It is desired that the student come to
class with a mind active with regard to the weather. The daily consideration of the
question whether it is warmer, or cooler than the day before, or whether the temperature
is not perceptibly different, will be found useful. A sufficient record is one of the words,
"warmer," "colder," or "stationary." Any doubt is to be covered by the use of the
word "stationary."
32. It will appear very soon that the characteristic of our temperature is change — change
through the day, change through the year, and change from day to day, apparently regardless
of seasons. In what follows we look for the causes of this changeability.
EXERCISE 1. — Temperature of Ground, Air and Water. A — Summer
33. On a cloudless day take the temperature of some dirt that has been dried and
some water in a pail, which have been exposed to the sun and air for equal lengths of
time. The dirt and water should be set out early in the morning, and may remain out all
night, if necessary. Make several readings of the thermometer each time, so that you
may be sure of the accuracy of your results. In taking temperature in the sun, the bulb
of the thermometer is to be placed in the loose surface dirt, or just beneath the surface
of the water on which the sun has been shining.. During the measure, be sure the ther
mometer bulb is shaded. As the shaded ground may cool off some during the observa
tion, try a fresh place when the temperature ceases to rise. Always keep onlookers
from shading ground or water, the temperature of which is to be taken. Note the time
of the observation. Air temperatures will be given in class.

20
Everyone should make observations as early in the morning and as late in the after
noon as possible and about half the class at noon, the other half at one.
Make a neat, clean record of the temperatures, similar to the following:

Temperatures

Reading

Time

Ground

Water

Air

Morning-Noon— 1 O'Clock—
Afternoon-

-
1. Which heats up more rapidly, the ground or water? 2. Does either get as hot
at one as at noon? 3. Which cools off faster? 4. Which gets hotter ?
B— Winter
When the snow is on the ground it is desirable to take snow temperatures. Students
will make a series of such observations on any bright day in winter, when the ground is
snow covered and the sun is shining on the snow to be studied. Make such observations
at about 8 a. m., 10 a. m., noon, 2 p. m., and 4 p. m., or, as many of those hours as possi
ble. 1. Does the temperature of the snow ever vary? 2. How warm can it become?
3. How cold? 4. If you find variation, what is the cause?
34. Physically the heat of the air consists in the rapidity of vibration of its parti
cles; the faster they go the hotter the air. So too, of the ground, its heat consists of the
rapidity of the vibrations of its particles. Heat is communicated from one body to an
other in two ways, (1) by conduction, when the bodies are close together, (2) by radia
tion at all sorts of distances. It is believed that it travels not as heat but as vibrations of
all pervading ether*, which occupies not merely space but extends through all gases
and even some other bodies. The insolation then comes to us from the sun as vibrations
of the ether which do not much heat the air in passing through it. as we may see when
it warms pleasantly a south wall on a still winter day after passing through very cold air.
So the radiation from the earth into the upper air and space is by the same sort of vibra
tions of the ether, which do not materially warm the air in passing through. Conduction,
on the other hand, is illustrated by the warming ot the air from the ground on which it
rests. The ground being warmer than the air, its particles are vibrating faster than are
those of the air. They are therefore supposed to hurry the adjacent air particles along
in their swings until these too go more nearly at the same rate as the earth particles. Of
course in doing this they lose some of their own speed and the result is a cooler earth as
well as a warmer air. In usual language we say heat has been conducted from the.
ground to the air. And all the time that the lower air is being warmed by conduction
heat is radiating away from the ground through it to be lost in space, without much effect
on the air on the way. For conduction one body must be warmer than the other, but ra
diation goes on all the time from cold bodies as well as hot, though its amount is propor
tional to the temperature. A hot body radiates more heat than a cold one. And so sum
mer and winter, day and night, in cold and heat alike, heat is radiating away from the
earth, just as on all clear days insolation comes to the earth through warm air or cold.
Lodge.— The ^ther of Space. Nature, Jan. U, 1909, p. 322.
21

35. The effects of the sun's rays are different according to the thing they fall on.
Clear air allows them to pass through with little effect on it, so that a goqd deal of insola
tion reaches the surface of the earth below. If this is land it heats up readily; if water,
much less, since the rays pass through water somewhat as through air, although less
freely. Anyone who has bathed on a sandy shore knows how strongly bits of stone or
metal becomes heated in the sunshine, far more than water ever does. Shallow waters
attain a more agreeable temperature than deeper water, because the rays are able to pass
through and warm the bottom, which warms the water in turn. The waters of lake Erie,
which is shallow, become quite warm in summer, those of lake Superior, which is deep
are always icy cold. The land surfaces are thus seen to be most sensible to the sun's
warming power. For one thing the effects on solids are confined to the surface layers.
At a very moderate depth below the surface of rock or dirt exposed to the sunlight, no
warming at all occurs. At a desert station in Turkestan, the mean temperature of the
ground in the heat of the day, is 90°, but just before sunrise, 41°. Sixteen inches under
ground the temperatures are 58.5° and 57.4° respectively, almos't a uniform temperature
from day to night. Most of the heat is concentrated in the five or six inches of depth
just below the surface. In water the penetration is far greater. Some lakes in the tem
perate zone are warmed by the sun's rays as much as 40 feet below the surface. The
effect is therefore distributed through a mass of water so thick that each component
layer is but little warmed. Moreover, a great part of the effect of the sun's rays on the
water surface is used in evaporation, without causing any sensible rise in temperature.
Finally, water is a very hard thing to warm. From all of these causes it results that the
ocean surface, or the surface of a deep lake is slow to warm and slow to cool.
36. Clean air is so much more transparent to insolation than water, that at times
when the sun is high, three-fourths of the sun's heating power may become effective on
the ground after passing through the whole depth of the air. Mainly, then, it is the dry
land that is warmed by the sun. The most important point for the study of the weather
is that the air is mostly warmed by the ground on which it rests and little by the rays of
the sun that pass through it. The air temperatures never become so high as those of the
ground. By what process does the ground warm the air (see 34) ?
As the air gets most of its warmth from the ground, the upper air is always cold,
with little variation from day to night. The daily range of temperature in the lower air
near Boston, is in the mean 9°. By sending up kites with self-recording thermometers
attached, it is learned that the range at 3000 feet elevation above is less than 1°. The
1000-foot Eiffel tower at Paris showed considerably less difference between day and
night temperatures at the top than near the ground, an observation that is corroborated
by numerous observations in different parts of the world.
37. August 14, 1898, the following temperatures were
noted at Askabad, in southern Turkestan, in the air, and on
the surface of the ground, a' fine, dry clay. The conditions
are those of the desert, and the temperatures high. The
sun set that day at 6.30 p. m. 1. How much warmer did the
ground get than the air? 2. When did the ground get
warmest? 3. What was the range of temperatures on the
surface of the ground that day? 4. In the air? It will be
noticed that neither ground nor air was warmest at noon.
The curve here given (Fig. 13) reproduces some of the tem-

Hour

Air

Ground

A.M. 8

82°

91°

10

92

137

12

102

158

P.M. 2

103

160

4

106

150

6

101

129

8

87

95

10

86

88

12

86

81

A.M. 2

86

80

4

83

80

6

81

79

22

peratures of the table, the horizontal lines representing time, and the vertical ones tem
perature, each observation being represented by a dot. Thus the dot on the 10 o'clock
line is at 92°, onSthe 12 o'clock line at 102°, as in the table.

fl

9

1

0 1

1 1

2 1

2

3

4

5

6

7

8

9

lb l

l l

2 1

2

3

4

5

6

7

in

n

1
00
q
0
30
R
0
80
7
0
70
Fig. 13. Temperature, Askabad, August 14, 1898
EXERCISE 2 — Askabad Temperature Curves
38. In Fig. 13 is drawn one of the two temperature curves for which data are given.
Can you tell which one? Draw in the other one from the data, letting one square count
horizontally for one hour, vertically for 10°. Both curves should be on the same diagram.
1. Which reaches its maximum temperature first, the ground or the air? 2. At
what time in the afternoon do they both have the same temperature? 3. After that
time which radiates its heat more rapidly? 4. How great is the range of temperature
of the ground? How great that of the air? 6. How great is it in this region at the
same season of the year? See air temperatures for Ypsilanti in Ex.3. 7. In what re
gion of the world is Turkestan, and what kind of a climate does it have? 8. In what
way does that explain the extreme temperatures recorded? 9. Name some other region
where the climatic conditions are similar, and where you would expect similar extremes.
39. In general the heat received by the ground depends on the height of the sun in
the sky. It is greater, therefore, at noon than in the morning, greater in summer than in
winter, and greatest in the tropics where the sun at times stands overhead. Let the page
of this book represent the surface of a town or city, as the book lies flat open on the
table. If the sun should shine right down on it from above, the bundle of rays that touch
the page would be as thick through as the
page is wide. If, however, the sun shines
on the page from a point little above the
norizon, a very thin bundle, containing a
few rays and little heat, spreads over the
same surface. Thus the thick bundle of
noon rays s s' (Fig. 14) renders much
more heat to the surface in which A B is
a line than the thin bundle of slanting
rays s" s'"; although each bundle is just
wide enough to shine on the whole
width of A B.
Fig. 14
In the United States, of course, the sun is never overhead but its heating power is
greater in proportion as it gets higher in the sky.
40. Working against this warming by the sun is the radiation by which the earth
is always giving up heat, even while the sun is shining down upon it; most at the season
when the earth is warm, but always in considerable amount. Whether the earth is gain-
23

ing or losing heat at any moment, depends on the relation of this radiation to insolation,
or solar warming. From the tables of temperature given, and from the January temper
atures at Ypsilanti, we learn that the maximum or greatest heat does not occur until
afternoon. 1. While the earth is warming which must always be greater, insolation or radiation?
2. If it is warmer at one than at noon, is insolation or radiation greater between those hours?
3. When is insolation greatest? 4. What change is it undergoing from noon to one? 5. How
can a diminishing insolation still cause the earth to get warmer? (See 1) 6. What is the re
lation of insolation and radiation at the moment of greatest heat? 7. Before that moment?
after? 8. Why is it not hottest at noon? At Askabad the ground was steadily gaining heat
as the sun rose higher in the sky. If there was heat lost by radiation, it was lees than was
received from the sun at the same time. At 2 p. m. the maximum temperature of 160° was at
tained. From that moment we must regard the loss by radiation as greater than the insolation,
and the ground cooled off steadily.
The same effect is observable in the air temperatures, and here the maximum comes
still later.
EXERCISE 3. — Diurnal Temperature Curves at Ypsilanti and on the Atlantic Ocean
41. Construct curves by these data,
placing the long way of the page right and
left and then counting each square of the
quadrille paper vertically as one degree,
horizontally as one hour. Make each
curve continuous through the two days
and place all on one diagram. Both days
were clear. The observations in the last
two columns were made on the steamer
United States, moving east fifteen miles
per hour. All large vessels crossing the
ocean make such observations at these
hours and record them in a ship's journal
known as its "log."
1. Locate places in the atlas. 2. At which of the three places was the air warmer?
3. Why? 4. Where was the daily range of temperature greater? 5. How great?
6. Do the Ypsilanti observations show the effect of the sunshine— say from 5 a. m. to 7
p. m.? 7. Do the air temperatures over the ocean show anything similar? Notice the
behavior of the curve about five each morning and again at seven each night. Draw a
straight line along that whole curve for the air temperatures over the ocean in such a
way that it runs as near as possible to all the temperature dots and you will be able to
detect a sun effect each day. The ship is getting into cooler and cooler air but during
daylight the cooling is checked. 8. Can you find any sun effect in the curves for the
temperature of the water? 9. Suppose the United States was passing across bands of
cooler and warmer water, some 50, some 300 miles wide as the steamer travels. Would
that explain the water temperatures? 10. Look up Gulf Stream in the Encyclopedia to
learn more about this.*
42. The curves of paragraph 41 show how moderate are the changes in the temperature
of the ocean air in our latitudes from day to night. So too the summer air out there is little
*The Gulf Stream, J. E. Pillsbury, Washington, '91. Chart at page 507.

Ypsilanti

41° N

53° W.

1904

Hour

AirT.

AirT.

Water T.

July 9

0

67°

71°

72°

4

63

69

72

8
68
72
70
Noon
77
70
72.5
4
81
70
72.5
8
72
63
74
12
69
61
72.5
July 10
42 N.
45 W.
0
69°
61
72.5
4
63
60
67
8
68
62
69
Noon
77
61.5
66
4
81
60
68
8
72
56
67
12
69
56
68
24

warmer than that of winter. The west winds, that are the commonest of all the winds in our
zone, blow this mild ocean air over the western lands of Europe and give them their mild
climate, much less hot in summer and less cold in winter than in eastern Europe in the same
latitudes. Central Ireland has mean temperatures of 46° and 60° in February and August
respectively, as compared with 20° and 68° in the same latitude in Russia. The Atlantic
waters, on the Irish coast, have temperatures at the same seasons, of 50° and 60°. Is that
warm water? EXERCISE 4
43. Draw four temperature curves from the data in the following table, which
gives average hourly temperatures for summer and winter months at Ypsilanti and Cuzco.
Put all four curves on a single diagram with one square of the quadrille paper for 2°
vertically and one hour horizontally. 1. Where is Cuzco? 2. In what lati
tude? 3. At what altitude? 4. Does the
curve for the temperate zone represent the
more temperate weather? 5. How much
warmer are summer days at Cuzco than winter
ones? 6. Cuzco has distinct wet and dry
seasons, with 34 and 63 per cent respectively of
clear sky. That will help to answer the ques
tions that follow. The effect of clouds is (1) to
prevent the sun's rays from reaching the
ground and (2) to hinder the earth's heat from
radiating away. That of course would have an
effect on the day and night temperatures at any
place. Thus in the table of hourly temperatures at Ypsilanti for January (see paragraph
48) the 29th was clear and the 30th cloudy. 7. Would clouds lift or lower the day
part of the curve? 8. How would they affect the night part? 9. How the daily
range of temperature? 10. When has Cuzco less daily range? 11. When has Cuzco
clouds and rain? 12. Is January or July summer at Ciizco? 13. Which curve
should run among higher temperatures? 14. Which does run higher? Why? (see
questions 7 and 8). 15. Why do the nights differ more than the days ?
EXERCISE 5. — Curves for Clear and Cloudy Days
44. Select from paragraphs 48 and 49, one day at each place that from the resem
blance of the data to those for Ypsilanti air in Exercise 3, you think may be clear days,
and construct the curves, labeling them with the date.
Select one day for each place that from its differences from the type of Exercise 3 at
Ypsilanti, seems to be a cloudy day, and construct its temperature curve. State briefly
the considerations that govern you in making the selection.
EYERCISE 6
45. It will help toward clear thought if, in speaking of this afternoon maximum of
temperature, we refer its time, not to noon, but to the thing which fixes noon; the sun's
height in the sky.
1, When in the day— in terms of the sun's height in the sky— is it hottest? AFTER
THE MOMENT OF HIGHEST SUN! The sun is highest of all the year for us on June

Cuzco

Ypsilanti

Jan.

July

Jan.

July

0

48

38

14

65

2

47

36

14

64

4

46

35

14

62

6

46

34

14

65

8

49

41

14

68

10

55

51

17

74

N

60

57

20

77

2

59

59

21

79

> 4

56

56

20

77

6

54

49

18

75

8

51

44

16

72

10

49

40

15

67

O

48

38

14

65

25
21st, the summer solstice. 2. When in the year, in similar terms to those just sugges
ted, is it hottest? Let us row construct annual temperature curves for Cuzco and Ypsi
lanti, counting one square of the quadrille paper vertically for a degree and two squares
horizontally for a month. We shall use the mean or average temperature of the whole
month and consider the date that of the middle of the month.

Cuzco Ypsilanti
January  51 5 24 5
February  51 9 23 0
March  52.2 32.6
April  51.3 46 3
May  49.6 56.8
June  46 6 66 1
July  45.0 69.8
August  48.1 67.7
September... 49.9 61.3
October  512 49.4
November  51.8 36.8
December  51.2 27.1

3. At Ypsilanti at what date in the year is it hottest?
4. At what date is the sun highest? 5. What is the time
of greatest heat in teims of the time of high sun? The
Cuzco curve is peculiar. 6. When does it appear to be
hottest at Cuzco? Hottest must here be laken to mean
hotter than just before and just afterward. In that sense
could there be two hottest moments? 7. How often is
the sun high at Cuzco? 8. At what seasons, as we call
them? 9. At that time at what point in the Cuzco sky is
the sun? 10. When is it hottest at Cuzco, with respect
to the high sun? 11. Why are not the two high moments six months apart? The
sun crosses the Cuzco zenith on the 12th of February and 30th of October.
46. The student should now add to his daily weather record the direction of the
wind and the force of the wind as expressed in the Hazen wind scale.
Force of the Wind
0— Calm.
1 — Moves leaves of trees.
2 — Moves branches.
3 — Sways branches, lifts dust.
4 — Sways trees, lifts twigs from ground.
5 — Breaks small branches.
6 — Destroys everything. Hurricane.
47. The temperature of a day may be ascertained by averaging the observations of
a thermometer read every hour, but so many readings are very troublesome to make.
Where the expense ($25) does not prevent, an instrument like our thermograph gives
good results with very moderate care. A much less expensive instrument that is little
trouble to use is the maximum and minimum thermometer, to be seen in our laboratory
and explained at page 60 of Davis' Meteorology. By referring to the temperatures given
in 48, we readily make out the relation of the half sum of maximum and minimum tem
peratures to the mean of the twenty-four hourly observations. On January 1st, the
minimum was 12°, maximum 24°, their half sum, 12+24^-2=18. The mean of the
twenty-four hour values is 19°. 1. On the second the half sum is 4° to a mean of 7°. 3.
1. How is it on the third, fourth, fifth, and sixth? 2. Make the same comparison
for the mean values at the bottom of the page in both 48 and 49. The two numbers are
usually within a degree of each other. For very many places in the world this is our
only means of getting the temperatures. Those for Ypsilanti in 45 result from 15 years
of such observations.

26

48- HOURLY TEMPERATURES AT YPSILANTI, MICHIGAN
JANUARY, 1904

MORNING

AFTERNOON

Jan.

1| 2| 3

4 1 5

6

7

1 8

| 9 | 10 | 11 | N

1 1 2|

3 1

4 | 5 | 6 1 7 | 8 9 | 10

11 | Mt.

Mean

123

23 12
-4

24 12
-6

24 11
-7

24 10
-7

22 10
-8

22 9
-9

21 8
-8

19 7
-7

18 7
-5

20 7
0

21 7
3

22 85

22 9 7

22 10 9

22 10 10

21 1010

1710 8

16 9 7

16 85

15 65

13 2 6

12 06

12
-2 5

12
-4 5

19.1 73 1.2

4 5
6

4
-6 14

2
-6 12

2
-6 12

1
-7 13

0
-7 14

_2-6 16

-3 -4 17

-3-1 19

0 2
20

4 6
•22

9
9
24

11
11
24

11
12
25

1018
28

1016
28

10 14
27

8
14
25

7
14
24

4
14
23

2
13
22

1
13
23

-1 16
24

-2 16
24

-4 14
24

3.4
6.6
21.0

78
9

24 3224

253322

2534 22

24 3423

243422

2434
22

213521

20
3521

203422

203522

213523

24
3624

243624

25
3324

263324

28
3323

293222

293122

293122

29
3022

312922

31
2721

312620

3124 14

25.6
32.3 22.0

10 11
12

12
20 19

10
2020

6
19
20

4
19
21

4
18
21

4
18
22

6
17
22

9
15
22

1113
22

1312
23

16 14
24

1815
24

1917
25

20 18
25

20 17
25

20 17
25

20 17
25

20 18
25

20 18
25

20 19
26

20 19
26

20 19
25

202024

202024

14 7
17.5
23.3

131415

20
23 18

2224 18

2424 19

2424 18

2523 16

2623 17

26 20 18

26 20 17

26 20 18

262121

262223

272225

27
2225

2622
25

25
23 24

242324

23 22
24

23
2224

2422
23

24
2222

242122

222022

22 20
22

21 18
22

24.3 21 8
21.1

161718

22 10 6

22 11 5

23 12 4

23 13 4

23 13 4

24 13 4

27 12 4

28 11 4

30 11 4

31 11 8

31 1110

30 13
13

27 1413

23 1412

22 14
11

20 14 8

1912 7

18
12 5

16
12 4

1511 2

1410 2

1311 2

1210 3

12 7
4

21.9 11 8
60

19
20
21

4
3632

6
3632

7
36
32

7
36
32

7
3632

8
36
31

8
36
30

9
3630

10
3631

12
3632

14
3732

18
36
32

213632

2534 33

283433

303332

323232

34 3232

353232

363231

3632
•31

363231

363230

36 32
30

20.634.4
31.5

22
2324

3128 6

3227 5

32 26 4

3226 3

34
26 1

34
26 0

3426
-1

3426
-1

33 27 0

34 28 2

3428 4

3228 5

3228 5

3228 5

3226 5

3125 2

3022
-1

2820
-3

28 17
-4

28 14
-5

28 11
-6

28 10
-6

28 10
-6

28 10
-6

31.2 22.6 0.3

25
2627

-7 46

-7 46

-7 46

-7 45

-7 5
4

-6 64

-6 6
3

-5 7
0

-4 80

-1 10 3

2
10 6

4
11 9

7
1210

8
12
10

7
14 10

6
1310

6
11 8

6
10 5

593

4 82

49 1

490

4 7
0

4 6 1

0.68.34.7

28 29
30

3 4
-2

4 6
-2

46
-1

4 53

4 55

4 67

469

3 7
12

5
10
17

7
15
22

10
17
25

12
18
26

14
2028

15
2129

17
2127

1719
26

1516
26

12
11
27

9
12
27

6 7
27

5 1
28

4
-127

5
-2 26

4
-226

7.8
9.5
18.5

31
Mean

25
14.2

25
14.3

24
14.2

25
14.2

26
14.1

26
14 3

26
14.2

28
14.5

28
15:3

28
17.1

28
18.1

28
19.7

27
20.4

25
20;7

24
20 6

22
19.9

22
18.8

20
18.1

20
17.5

18
16.5

17
16.0

16
15.4

16
15.1

16
14.5

23.316.6

27

49. HOURLY TEMPERATURES AT HAVANA, CUBA
JANUARY, 1904

| MORNING

AFTERNOON

Jan.

1 | 2| 3| 4| St 6| 7 | 8| 9|10|11| N

1 | 2| 3 | 4 | 5 | 6 | 7 | 8| 9 | 10 1 11 | Mt.

Mean

1

64

64

63

63

63

63

621

64

67

68

701

72

73

73

73

73

72

70

69

68

67

66

65

65

67.4

2

64

64

63

63

63

61

61

66

70

73

75

76

76

76

77

76

74

72

71

70

69

68

67

66

69.2

3

64

64

64

63

62

63

64

68

73

76

78

76

76

75

75

75

75

74

74

74

72

72

72

71

70.8

4

71

71

70

70

70

70

71

70

71

71

71

72

72

73

73

74

72

71

71

71

71

70

69

69

71.0

5

70

70

70

69

68

67

67

67

68

69

70

70

70

68

67

67

67

66

65

66

66

67

66

66

67.8

6

65

65

66

68

68

67

67

65

68

73

74

73

73

73

73

73

72

70

68

67

66

65

64

64

68.6

7

63

62

62

62

61

61

61

63

67

71

72

73

74

76

77

75

74

74

73

70

69

67

67

67

68.4

8

67

71

71

72

72

72

71

70

70

71

71

72

69

70

70

70

70

68

68

67

67

67

66

67

69.5

9

66

66

65

65

64

64

64

64

66

69

70

70

72

71

70

71

70

68

67

65

64

62

61

60

66.4

10

60

60

60

58

57

57

58

60

64

70

73

74

75

78

77

77

77

75

74

70

70

70

70

70

68.1

11

68

68

69

68

68

68

68

68

72

75

77

79

81

77

78

80

79

77

74

72

71

71

71

70

72.9

12

70

70

69

69

69

67

67

70

74

78

80

80

79

79

78

77

77

76

74

72

71

70

69

68

73.0

13

67

66

65

66

65

65

65

66

68

74

76

77

78

78

78

78

77

77

74

72

71

69

69

69

71.2

14

69

67

66

66

66

66

66

66

67

69

68

67

66

66

65

65

64

64

63

63

62

61

61

60

65.1

15

60

61

61

60

61

61

61

65

66

67

68

68

69

70

70

69

69

68

66

65

64

63

60

60

64.7

16

59

60

60

60

60

60

61

63

67

70

70

75

73

73

74

74

74

72

69

68

67

66

65

64

66.8

17

64

64

64

63

62

62

61

62

66

73

74

73

73

74

75

74

74

73

72

71

70

68

66

65

68.5

18

64

63

62

61

60

60

60

63

66

71

70

73

74

74

74

74

74

72

71

71

72

71

70

68

68 3

19

68

67

68

68

69

69

69

71

71

74

75

74

74

74

73

73

73

72

71

71

72

70

71

70

71.1

20

67

68

70

69

68

67

68

68

69

72

73

74

74

75

75

74

74

72

71

70

70

69

69

68

70 6

21

66

65

65

66

65

63

63

64

68

71

74

76

76

78

78

78

79

78

75

74

74

71

71

68

71.1

22

67

67

68

66

67

66

65

70

73

74

75

78

79

80

81

80

79

77

76

75

74

74

73

74

73.3

23

74

73

72

71

71

71

70

71

71

71

73

75

78

79

80

80

79

78

77

76

75

74

74

73

74.4

24

73

73

72

72

70

70

68

66

63

64

64

64

65

63

63

62

61

63

64

65

65

66

66

66

66.3

25

66

67

66

66

67

69

68

68

69

70

73

74

76

76

77

77

77

76

74

74

73

72

71

70

71.5

26

69

69

69

69

69

68

67

70

71

74

75

79

80

78

76

73

73

72

72

70

70

70

70

69

71 8

27

69

69

68

67

67

66

65

66

68

74

77

76

77

77

77

76

76

77

76

75

74

72

71

71

72.1

28

70

68

67

68

67

67

67

68

69

' 73

74

76

78

79

78

79

78

77

75

74

73

71

71

71

72.4

29

70

70

69

68

68

66

66

69

72

76

78

79

82

84

84

83

82

79

76

75

74

73

73

71

74.4

30

71

71

71

70

70

69

69

70

71

71

72

73

73

73

74

74

73

73

73

73

71

72

72

72

71.7

31

72
67.;

71
67. (

69
66.7

68
66.'

68
66.(

67
)65.(

66
65.'

66
*66.i

71
68.S

76
71.S

77
73.1

79
74.0

80

82
74.9

83
75.C

83
74.7

82
74.2

80
72.9

Jl
J 71.6

74
70.6

73
69.8

72
69.C

71
68.4

71
67.9

74 1

Mean

74.7

70 1

EXERCISE 7— Heat Used in Evaporating Water

Hour

April 16

Apiil 17

0

28°

25°

2

24

24

4

20

24

6

20

26

8

23

34

10

26

39

Noon

28

44

2

30

47

4

30

47

6

29

44

8

28

40

10

27

38

12

25

36

50. Plot curves for Ypsilanti. April 16: Sky
clear, wind west, velocity 1, ground covered with 1
inch of snow. April 17: sky clear, wind northwest,
velocity 1, ground bare all day.
Each square on the quadrille ruled paper verti
cally equals 2°, horizontally, 1 hour. Explain the
difference in the temperature for the two days as
shown by the curves.

28
1. What was the maximum temperature the first day? 2. The minimum?
3. The range? 4. What the maximum the second day? 5. The minimum? 6.
The range? 7. Is there anything about snow to keep it from getting hotter than
30°? 8. Why didn't it get warmer on the 16th? 9. What is the maximum tem
perature for days with snow on the ground? Of course a strong wind might bring.
warm air or cold air from a distance. We are supposing there is little wind and that the
changes in temperature are those due to local causes. 10. What work had the inso
lation to do on the 17th? 11. What additional work on the 16th?
Air Tends to Expand when Heated, and to Yield to Pressure when Cooled
51. Why dees air expand when heated? The particles of air are believed to be in
rapid motion, vibrating in seme way back and forth. The faster the vibration, the hotter
the air. The particles are of course too small to see with the most powerful microscope;
the distances through which they move are doubtless also very small, and the speed of
the motion very great, even for bodies at ordinary temperatures. That is our general
conception of warm bodies. If the vibrations are more rapid when the air is warmer, to
heat a mass of air is to set its particles vibrating faster, but it is also natural, therefore,
to think of these particles as pounding on the walls that confine them, and demanding
more space and taking it, if not resisted by a force too great. Similarly when air is
cooled, its particles are thought of as vibrating more slowly, and moving through smaller
spaces. They may be supposed, therefore, to strike less vigorously against the side of
the containing vessel. If under pressure, it is intelligible that such air should yield to
the pressure and contract. Much confusion in the theory of the winds arises from the loose
doctrine that warmed air rises and cooled air sinks. A good test between this and the
view stated at the head of this paragraph is to isolate some air, warm it and cool it and
note its behavior. EXERCISE 8
52. Apparatus: A flask fitted with a rubber stopper, having a single hole through
which a long glass tube is fitted, and a glass of water.
Invert the flask, allowing the end of the tube to dip into the water. Note the level
of the water in the glass and in the tube. Now warm the flask with both hands; note
and record what happens. What would have happened had there been no outlet? Car
rying the apparatus out of doors or to the open window, causes what to happen? What
would have happened had there been no outlet? Drawings should be made of the appa
ratus, showing the stand of water in glass and tube in all three stages of the experiment.
What is your opinion of the sufficiency of the statement that warm air rises? Did it in
this case? That cold air sinks? Did it? If warm air rises, why is not the upper air
warmer than the lower? Is it?
Where Air Expands Under Pressure and Does Work, it Loses Heat
53. Two 250 cubic centimeter flasks are each fitted with a thermometer to record
temperature, the first tightly stoppered and the second connected to a U tube containing
mercury. A scale mounted by the U tube serves to register any variation in the height
of the mercury. The heat is very satisfactorily furnished by two candles of the same
size. Be careful in setting up apparatus to get all connections air tight, and that the
candles are of the same size and mounted with the flame the same distance under the
flasks (not less than four inches). After the apparatus has been carefully set up take
the temperature, light the candles and record the temperatures in the two flasks every

29
minute, also the height of the mercury in the U tube. Record it until no further varia
tion in the height of the mercury occurs. Tabulate your results. Explain any difference
in the temperatures noted in the two flasks. Suppose we could apply the heat from the
combustion of a unit of fuel to warm a quart of air enclosed in a glass flask with a rubber
stopper and tube dipping into mercury, as in the experiment. Let us further suppose
that no heat is lost, that the air expands with the heat, pushing the mercury down in
the tube, and also becomes one degree warmer. Now if the experiment could be repeat
ed with all the quantities and conditions the same, except that the quart of air was con
tained in a strong vessel that would not let it expand, the result would be that the air
would rise in temperature more than one degree, although its original temperature was
the same, the initial quantity of air the same, the original pressure the same, and the
amount of heat used the same. The result may be stated thus: the amount of heat that
somewhat warms air that is free to expand, will produce a greater rise in temperature in
the same quantity of air confined. If less warming is produced upon air that expands,
what becomes of the rest of the heat in this case? The answer is that it is used up in
the work done. When the air in the flask expanded, it had to push the mercury up in
the tube, and that was work. To do work energy is needed. The only energy at hand
to do the work was the heat supplied, and whatever energy was devoted to expansion
could not also appear as a rise in temperature.
Air is Cooled by Expansion
54. Now if the flask of air that was closed by the mercury in the U tube could be
placed under the receiver of an air pump and some of the air pumped out of the receiver,
the air within the flask would expand, would push down the mercury in the near side of
the tube and up, of course, in the other. This would be doing work, but we are not
now supplying heat to do this work with. If the temperature of the air in the flask
were noted before and after the experiment, what should we see? Energy that was just
now occupied in what we might call heat work— moving the air particles back and forth
at the rate proper for the temperature — has now been diverted to lift a little mercury
against gravity. Only a part of it, therefore, is now engaged in heat work, or, we may
say, the air has been cooled in expanding against pressure. If a quantity of air is com
pressed into a strong vessel and allowed to stand until it has taken the temperature of
the room, it will suffer a distinct fall of temperature if allowed to expand under pressure,
as in the previous experiment. In this case it has only its own heat to call on to do the
work of expansion, and as soon as that is done the temperature falls. It appears, there
fore, that not only does heat cause expansion, but that expansion taking place, as it usu
ally does, against pressure, uses up heat and causes cooling. This must not be taken to
mean that expanding air always falls perceptibly in temperature, the fall is only percept
ible when no external heat is supplied to it, or not enough to do the work. When exter
nal heat is supplied, the temperature rises all the time the air expands. In thought only
do we have a succession of events; first, the air warmed x plus y degrees; second, the
air, expanding, uses up some of its heat and cools through y degrees, with the final
result of a rise in temperature of x degrees and an increase in volume. In reality heat
ing and expansion are simultaneous. Some of the heat is applied to the heating, while
the rest is used in expansion.
For the air that was not allowed to expand, all the energy supplied was applied to
raising the temperature, which accordingly rose higher than that of the expanding air.

30
Air is Warmed by Compression
55. On the other hand when air is compressed by the application of force, the
energy used is transformed into heat and the air warmed. When gases are mechanically
compressed, provision has to be made by the circulation of cold water or otherwise, to
get rid of the heat generated. (Tyndall's Heat as a Mode of Motion, lecture I and III,
may be read in this connection.) Geographic Applications
56. All of the layers of air in which the phenomena of the weather take place, are
under pressure from the atmosphere above. If this pressure diminishes, the air expands,
and is thereby cooled. Conversely, when the pressure increases, the air is compressed
and warmed. As the winds move over the surface of the earth, at times they ascend
and descend the slopes of the mountains. When they ascend they go nearer the surface
of the ocean of air. In that case there is less air above them, so they are able to expand
and lift the air above, which cools the winds because of the work done. In general, AIR
THAT RISES expands AND COOLS. When the winds descend they go deeper below the
surface of the ocean of air. As this puts more and more air above them, they yield to
the increasing pressure, contract, and are warmed by this compression. In general
again, AIR THAT SINKS IS COMPRESSED AND WARMED.
Since the pressure of the atmosphere at various levels is pretty well known, it is possible
to calculate these changes of temperature due to ascent and descent of air. They amount to
5.2° per thousand feet and are known as adiabatic temperature changes. They apply only to
air that rises and falls. A person climbing a thousand feet up on the side of a mountain
would not find it 5.2° cooler above unless the air went up with him. It often occurs to stu
dents at this point that these doctrines are contradictory. Descending air is compressed
and warmed, but since warmth causes air to expand, it may seem as if the work of com
pression would be at once undone by the action of the heat generated. The difficulty is
apparent only. Heat does not cause expansion but a tendency to expand. Whether a
gas expands or not depends on the pressure to which it is subjected. To say that .de
scending air is compressed is to say that it has not enough expansive energy, EVEN WITH
WHAT is ADDED TO IT BY THE HEAT OF COMPRESSION, to enable it to resist the press
ure of the air above.
It is often taught that cold, lofty mountains cool the warm winds that blow on them
from oceans and thus make them drop their moisture as rain. We have seen that the
cooling is really adiabatic cooling within the air itself and therefore not caused by the
mountains. Observation at many observatories on mountains shows higher temperatures
there than kites reveal at the same height in the free air. Furthermore if it were not
so, and the air were warmer than the mountain, since the air is constantly flowing over
the mountains today, tomorrow, next year, next century and for thousands and thou
sands of years it is evident that such enormous volumes of warm air must rather warm
the mountain than be cooled by it, for the hugest chain is of insignificant bulk beside
such masses of air as that.
Master and memorize the following argument: —
The wind is moving lower air .
When:—

wind comes to a mountain,
1 Wind has less air above.
2 It expands and lifts air above.
3 This work cools wind.
4 This forms clouds.

wind goes by a mountain top,
1 Wind has more air above.
2 Air above settles down on wind and com
presses it.
3 This work warms wind.
4 This dissolves clouds,

31
EXERCISE 9— Cold Aloft
57. Calculate the diminution of temperature per thousand feet of ascent from the
data in the following table. As an illustration of the method to be followed: Geneva is
seen to be 2230 feet lower than Chamonix; this by the printed table. Also 9° warmer.
In this case therefore it was found to be 9° cooler for an ascent of 2230 feet, how much
is that for every 1000 feet? 9°h-2.2=4.°1, nearly.

Place

Time

Station and Elevation

Temp.

July 5-18, '88, Mean Values

1312 feet

73°

July 5-18, '88, Mean Values . 3542 feet

6"4°

Pass (Col du Geant) 

July 5-18, '88, Mean Values

11152 leet

37°

Kite Observations

Dodge City, Ks 
Dodge City, Ks 

July 23, '98, 10 A. M.
July 23, '98, 10 A. M.
July 23, '98,2:10 P. M.
July 23, '98, 2:10 P. M.
June 29, '98, 10 A. M.
June 29, '98, 10 A. M.

GroundKite 5795
Ground Kite 5419
Ground Kite 4477

81°59°

85.5°

61°
Dodge City, Ks 
80°
Dodge City, Ks 
67°
Pierre,' S. Dak 
June 22, '98, 11 A. M.
June 22, '98, 11 A. M.
GroundKite 5492
87°
Pierre S. Dak 
75.3°
June 11, '98, 11 A. M.
June 11, '98, 11 A. M.
GroundKite 5351
81°
55.9
June 12, '98, 9 A. M.
June 12, '98, 9 A. M.
June 26, '98, 8:25 A. M.
June 26, '98, 8:25 A. M.
Ground Kite 5319
GroundKite 3146
79.5°
58°
Clevelard, O 
76°
65°
May 12, '98, 8:30 A. M.
May 12, '98, 8:30 A. M.
June 14, '98, 6 A. M.
June 14, '98, 6 A. M.
GroundKite 8211
Ground Kite 2143
67°
44.5°
77.5°
72 4°
Balloon Observations
Mean of all times and places..
9840
16400
32800
19° 3°
-67°
After computation of the rate of decrease per thousand feet of ascent in each indivi
dual case in the foregoing table: — 1. What seems to be the nearest whole number of
degrees to express the rate of diminution? Do NOT take an average, the figures are
not comparable. This decrease of temperature is due to the fact that as you ascend from
the earth you go away from the immediate source of most of the heat of the air. If,
however, AIR rises and cools by expansion against pressure, its decrease of temperature
is 5.2° per thousand feet of rise. 2. That being the case, what would be the temper
ature which Geneva air would assume if lifted to Chamonix? 3. Under those circum
stances would it weigh more or less per unit of volume than the Chamonix air? The
following consideration will help you decide: — suppose you have two open flasks of the
same size full of air at the same temperature. Warm one of them. What will happen?
Will air go in or out? Will it weigh more or less? A good balance will easily show the
difference. 4. What would happen to it? Try the same in several cases. 5.
What do you find to be true? 6. From this would you conclude that cold air is al
ways heavy, hot air always light?
The United States Weather Bureau
58. Every morning observations are taken of thermometers, wind vanes and other
instruments at some ninety stations in various parts of the United States. The results,
together with some contributed from neighboring countries, are'combined by telegraph to
32
make a daily forecast of the weather. The total cost of the service of the Weather Bu
reau to the nation is near a million and a half dollars a year. What do the people get for
their money? Not certain forewarning of every rain. That the Weather Bureau cannot
give. What we do get from the Weather Burean, however, is worth many times the ap
propriation every year. It is a service in three forms: (1) The saving of life and prop
erty in ships on the seas and lakes by warning the people of dangerous storms, (2) the
saving of life and property along great rivers by warning the people of dangerous floods,
and (3) the saving of perishable foods, growing or in transit, by warning the people of
severe frosts. Vessels in port, on the great lakes or oceans, are warned by the Weather
Bureau of every serious storm that is liable to affect them. There are practically no fail
ures in these warnings. The slighter changes in the weather cannot be predicted with
certainty, but the great ones that endanger life, can le foretold with great accuracy, and
none of them now find us unawares. Prudent shipmasters remain in port on such occa
sions. How real is the saving that comes from these warnings is shown by occasional
failures of captains to heed them, as in the disastrous case of the Portland, at Boston,
November 26, 1898.* Another storm that afforded many illustrations of the utility of the
storm warnings was the great Gulf storm of September 1906.t Almost equally great is
the saving accomplished by the river service, notably in the Ohio and Mississippi valleys
where many people live. No dangerous rise in these rivers but is foretold by the Weather
Bureau in time for dwellers on the lowlands to escape to the higher land and carry mov
able property beyond the reach of flood. Even the probable hour and height of flood at
various points is pretty well announced beforehand. A recent illustration was the Ohio
flood of February 19, 1908.1: So many perishable foodstuffs, largely fruit and vegetables,
are now constantly in transit across the country, so many grow in regions like California
and Florida, liable to be visited by destructive frosts, that forewarning of all cold waves
makes possible great saving of property by protecting growing crops from frost and
warming or affording other artificial protection to those in transit. Reference might be
made to the frost of January 20, 1908, in Florida.§ Shippers of such goods now rarely
fail to enquire of the Weather Bureau about the temperature conditions to be expected
during the time of an important shipment. There is certainly no department of the nat
ional government that brings a handsomer return on an investment of the people's
money. Reports on these four references should be brought into class in writing, the
first by students whose names begin with letters from A to F, inclusive; the second by
those with letters G to L, the third M to R and the fourth by the rest of the class.
EXERCISE 10. — Drawing Isotherms
59. We shall best familiarize ourselves with the details of the daily weather map
if we practice some parts at least of its construction. To this end we will use data tele
graphed to Washington to construct a map of isotherms.
Isotherms are lines drawn through places having the same temperature They are
commonly drawn at intervals of 10° though places having temperatures evenly divisible
by ten, as 0 , 10°, 20°, 30°, etc. Usually the temperatures given are either higher or
lower than the desired temperature. In such cases do not merely draw the isotherm be
tween the two places, one of which has a higher and one a lower temperature than the
temperature desired, but make an exact estimate each time. We have 27° and 35° for
instance arid wish to place the isotherm of 30° in that neighborhood. We should place a
point A of the distance from the place having a temperature of 27° to the one having a
temperature of 35° and through that point draw the isotherm.
'Monthly Weather Review, 1898, p. 493. ,M„„fV,, ZT. 77 ~ :
tMonthly Weather Review 1906 p. 416. SMonthw w»aSer £ev!ew' !%>&, P. 19.
^Monthly Weather Review, 1908, p. 2.

33

Making use of the above principle in drawing isothermal lines, draw the isotherms
for one of the days, the data for which are given below:

Eleva
tion in
feet.

Pressure

Tempera ture

Eleva
tion in
feet.

TEMPERA TURE

Father Point 
Chatham 
Haliiax 
Quebec 
Montreal 
Albany 
Boston  ,.,
New York 
Parry Sound 
Buffalo. 
Oswego 
Binghamton 
Philadelphia 
Washington 
Norfolk  ...
Charleston...., 
Sault Ste. Marie..
Alpena 
Saugeen  , 
Detroit 
Toledo.,  ....
Erie 
Cleveland 
Cincinnati ..; 
Knoxville 
Jacksonville 
Tampa 
Key Uest- 
White River 
Port Arthur 
Marquette 
Escanaba 
Green Bay 
Milwaukee..:.:.....Chicago 
Louisville 
Cairo  —
Chattanooga 
Memphis 

100100
227
293 60
97
125
314600 768
335 123117112 57
48
624609 656 730
674 714762
628
10C4- 4336 22
1147 608 734612617671 824 525359 762399

30.40 .40.38.42 .42.43.44 .43.30 .39.42.42 .42.41.41 24
.17 23
.32.30 .28.36 32
.25.24.18.15 .14.08 05
.13.17 .16.28 .18.22.13.21 .05

30 03
'"'bo
29.64 .55.66.67 .73 .67
.75 70

.77.83 .87
.96 .86.79 .73.86.90.80
29.8830.01

29.98

30.01 .03
.12
30.02

29.97
29.9730 01
30.05 .01 .05

-7
-13 20
-4
-1 7
9
13 10 12 78
20202640 21 1710
20 22 15 18
2833
46 50
63 22 1720202328303136 37
33

43

5050 56
62626649 59 59

68 7173
11 504960 61616464

75

783736 39

56586566 70
68

Duluth 
St. Paul 
Lacrosse 
Davenport 
Kansas City 
Fort Smith 
New Orleans....
Galveston 
Minnedosa 
Winnepeg 
Moorhead 
Huron...' 
Omaha 
Dodge 
Abi'ene 
Qu'Appelle 
Bismarck 
Pierre 
Rapid City 
North Platte....
Denver 
Prince Albert....
Battleford 
Swift Current...
Havre 
Miles City 
Lander 
El Paso 
Calgarj 
Medicine Hat..
Helena 
Modena 
Kamloops 
Spokane 
Winnemucca...Los Angeles....
Portland, Ore..
San Francisco.

702837 720599
963 481 54 54
1671 757
935
13Q61103
2504 1749
2134 16741460
32512826 5290 13981500
242324942372 53723767 226321714108 50001160 1943
4340 330'
>153 153

30.02 29.96
30.03 30.0429.98
29 86
30.02
29.87 30 12
.12
30.1229 89
29.8529.69
29.77 30 09
30.12
29.9530,0129 84
29.9530.27 .31 .30.30
.10 .13.00 .35
.33 .22
.31.31.40.36.23
.20
30.29

.17
.15 .08 06
.13 .06
.03.01 .43.43
.32 .34
.20
30 08
29 98
30.34 .44 .40
.38 24
30 17
30.27 .24.27.25 .36
30.20 29.88
30.13 .23
30.18 29.88
29 98
30.1129.99
30 02
30.00 30.03

283131
32333848 53
00 10
2320303051 1115
22 2226
26 6 7
15
2121 20
40 8
15
25 19
17
31 18
43 37
42

4048 53
60
63 71 75
76
4141 44
48 566473
40
43 484855 56
4143 434445 50 72
48 464749 605051576058

Weather Isothermals, Surface Isothermals, and Sea Level Isothermals
60. When we wrote thermometer
readings on the map and drew isotherms
through places of the same temperature
and between cooler and warmer places,
we were preparing a map showing
WEATHER. Most of the isotherms used
in books are CLIMATIC and show average
or usual conditions rather than actual
ones. In such cases the numbers used
are the averages of long series of obser
vations. If all the temperatures for the
month of June for many years are aver
aged and represented by isothermal
Fig. IS. Normal Surface Temperatures for June lines, the result is CLIMATIC and shows

34

the distribution of temperatures usual at that season. Such a map is the accompanying
figure 15, showing normal surface temperatures for the month. It is supposed to show
the temperatures to be expected at any place in the country at any time. It fails to do so,
however, at present, because the number of points of observation is entirely too small.
Some stations are high and, therefore, cooler than neighboring places, others in valleys
are warmer than the country around. Isotherms drawn from such data cannot expect to
represent the country correctly. Thus two valley stations in the mountains might each
have a temperature of 30 degrees. But the isotherm drawn from one to the other might
very likely pass across a mountain range, several thousand feet above. The temperature
up there may be near zero, yet the map reports it as 30 degrees. Any such map has this
defect unless the observation stations are numerous enough to represent the actual to
pography, which is never the case. The difficulty is met by "Reduction to Sea Level."
The air is known to be cooler and cooler as one ascends above the level of the sea. From
kite and balloon studies and others along the slopes of the mountains, it is seen that the
temperatures of high places are lower than they would be if the ground were lower. A
series of corrections has been prepared by which temperatures at all heights are reduced
to the level of the sea. The United States Weather Bureau adopts the following values: —
December to February  1°.5 per 1000 ft.
March to May and September to November  2°.0 per 1000 ft.
June to August  2°. 5 per 1000 ft.
Thus a place 5000 feet above sea level has a normal surface temperature for June of
62.5°. The reduction to sea level for that tme and height is 5 times 2.5° or 12.5°. The
corresponding sea level temperature is 75°. If all the values are so reduced to sea level,
and a system of isotherms drawn with the resulting numbers we shall obtain the distribu
tion of temperatures
about as they would
be if the whole surface
of the country could
be smoothed down to
the level of the sea.
Fig. 16 is such a map
of sea level isotherms
for June. Though it
does not correspond
to any actual condi
tions, it does enable
us to learn the normal
surface temperature
at any point and any
elevation. Thus the
sea level June normal
for Toledo is 70°, the
elevation 674 feet.
Fig. 16. Sea Level Normals for June Subtracting % of 2.5°
or 1.6°, we have a surface normal of 68.4°, about as shown by Fig. 15.
EXERCISE 11— Spells of Weather
61. Construct temperature curves for January, for both Ypsilanti and Havana
using the mean temperatures of the days as given in the right-hand columns of tables 48

35
and 49, calling each square of quadrille paper one degree vertically and horizontally one
day. Both curves may be placed on one diagram. 1. Does any diurnal sun effect
show in this curve? 2. Does either curve show that the air got steadily warmer or
colder through the month? 3 Which curve shows the more distinct spells of weather?
4. How many warm spells at Ypsilanti? 5. How many cold? 6. How many
days did that make a spell' last on an average? These spells are the special characteristic
of our weather except, usually, in May, June, July and August. Now construct diurnal
curves for both places with the mean hourly temperatures from the bottom of the tables.
Put them on the same diagram, using the same temperature scale but calling one square
horizontally one hour, This enables us to compare the diurnal temperature ranges with
what we might call the spell ranges, the differences between the cold spells and the warm
ones that follow or precede. 7. At which place is the spell range greater than the
diurnal? 8 How many times as great? This too is characteristic, a feature of the
climates of these places. At the one place temperature changes are mostly from daylight
warmth to nightly cooling, at the other this signifies much less than change from warm
spell to cold and back. At one of the places days may be even colder than nights, as on
January 7th and 11th.
Irregularity of Temperature Distribution in Longitude
62. From the isothermal map it appears that places on the same parallel of latitude
have differing temperatures. This is not only due to different elevations above the sea,
but also because the sun's rays fall on surfaces so different even where the rays have the
same inclination. Land and water do not heat up equally under the sun, nor do bare
and grass covered lands. The red and yellow desert of North Africa, the blue Atlantic,
and the plant-covered lands bordering the Gulf, do not undergo equal heating, so it is not
strange that the air above them has varying temperatures. A continent or large island,
like Australia, Madagascar, New Zealand, or Great Britain is always warmer than the
neighboring sea in summer and also cooler in winter; for the land not only heats up more
under the sun's rays, but also cools off faster in winter.
Seasonally and with the spells of weather that succeed each other in our latitudes very
great differences in temperature result from the importation of southern and northern
air on the wind. Spring is due with us, for instance, when the sun reaches a certain
elevation in the sky; it is apt to come with a week of south wind.
Pressure
63. It has been pointed out that we live at the bottom of the ocean of air just as
the inhabitants of the sea bottom pass their lives at the bottom of the ocean of water.
But the gaseous nature of our atmospheric ocean gives it great peculiarities. A shell
fish in deep water has always the same amount of water above him, and about him it is
always still. There are tiny changes in the quantity of water as waves pass above, and
there are slow movements of sidewise drifts and currents. Entirely insignificant, how
ever, both of these in comparison with what occurs in the air. We have very great
differences in the amount of air above us and it moves about on the earth's surface with
the high velocity of the storm winds. Some knowledge of the varying amount of air
above is necessary to understand the winds. It is not possible to feel it directly; its man
ifestation is in that somewhat vague thing called air pressure, and the instrument that
shows it, the barometer. It is so grounded, however, on changes of temperature that we
may form an idea of it very readily by noting temperature changes. Paragraph 65 will
help the student see what a barometer is and how air pressure is only a vague name for
the quantity of air over the spot being studied.

36
We shall now regard the rising of the barometer as indicating that more air is coming to
the region, its falling as signifying less air present, i. e. some air is going away.
Balancing Columns, Water and Mercury
64. Materials: 2 glass jars, 18 inches high, and 3 and \lA inches wide respectively.
1 glass tube, 36 inches long, Vi-inch wide. 1 pound of mercury.
' Put some mercury in the bottom of the smaller jar, stand the glass tube in the mer
cury, and pour water upon the mercury in the jar until the water is 13 inches deep. Note
what happens within the glass tube. Make a measurement of height above mercury in
jar. If the water is now withdrawn with a siphon, notice what happens within the
tube as the water level falls in the jar. In siphoning, the water should be run into an
empty jar, so that if any mercury comes over it may not be lost. If the water in the ser
vice pipe contains lime or other salts, distilled water should be used.
Repeat the experiment in the larger jar. When you have a column of water 13
inches deep over the mercury in this jar, how does it compare in bulk and weight with
the water in the first experiment? Suppose we had a jar a foot wide, and put water in it
13 inches deep over mercury in which a tube had been previously placed, what would
happen within the tube?
Suppose a bowl of mercury with a tube standing in it were placed in a pond or tank,
so that the mercury was just 13 inches under the water surface, while the tube projected
above the water surface, what would happen?
What one quantitative condition must always be fulfilled in these experiments to get
a column of mercury to balance a 13-inch column of water? To balance any column of
water? In all these cases both fluids have been visible, but once we know the principle, the
water might be concealed, and we could still judge of its height very accurately by the
height of the mercury in the tube.
We might in the same way balance a column of gas against the mercury. Thus the
heavy violet vapors of iodine weigh V1207 as much as mercury? How long a tube filled
with iodine vapor would balance one inch of mercury? How many inches? How many
feet? In the calculation we might disregard the compression of the vapor in the bottom
of the column by the weight of the vapor above. That would require a long tube, in
deed, but it would be conceivable. Although it would be balancing gas against liquid,
both would still be visible on account of the violet color of the gas. But as long as the
mercury is visible, the same balance might be made with a colorless gas like air. Air
under standard conditions weighs l/vmi as much as mercury. How many inches, feet
and miles of air in a column would balance an inch of mercury?
65. A barometer is really a tube in which a column of mercury balances the atmos
phere of air. By the height of the mercury column we judge the height the air column
would have if it were of uniform density and composition throughout. The mercury in
the barometer at sea-level, stands about 30 inches high. How high a column of homoge
neous air, equally dense from top to bottom, would that represent in miles?
We have thought of a bowl of mercury in which a tube is placed and the whole
lowered into the pond. As long as the tube projects above water, its walls keep the
mercury within from experiencing the pressure or weight of the column of water that
rests on the mercury in the bowl without. As for the atmosphere in these experiments,
it presses on the mercury inside the tube and on the water without alike, so it is just the
same as if it exerted no pressure at all.

37
Now our thought of the atmosphere is of a widespread layer of air resting upon the
earth, thin or rare above where the high mountains reach up into it, thicker or denser
below where the weight of the upper layers that rest upon it presses it together. There is
probably air a hundred miles above the surface of the earth, yet remembering that the
earth is 8000 miles through, while vastly the greater part of the whole atmosphere is
compressed into the lower ten miles, we see that it is a relatively thin film, fairly com
parable to the skin of an apple. Let us now try to imagine a bowl of mercury with its
tube set into this ocean of air just as we thought of another set into a pond. The tube
must always be thought of as long enough to reach up through the whole thickness of
the atmosphere. Thus there will be no air within the tube, it being kept out by the glass
walls. The mercury rises within the tube to balance the weight of air without on the
surface of the mercury in the bowl. The hundred-mile-long tube would not be needed.
If its walls could be fused together a few inches above the top of the mercury in the tube
so as to keep the air out, the balancing would go on just the same. If more air came to
that neighborhood, as in the crest of a wave, the column of mercury within the tube
must rise to balance it. That is essentially what a barometer is, and how it works.
66. That "the air presses'' is believed to be an easier conception for beginners than
the "pressure of the air." As a form of words both may mean the same thing, but only
one reality, the air, is involved, and the first statement may be regarded as the direct
statement of act. The pressure, on the other hand, has no real existence except as a
word. It is not a thing at all. Suppose the result of the action be a broken window.
It is the air that breaks it and not the pressure. This is just as true as if we were talking
of a ball flung at a window. The ball really breaks the glass, though we may use a var
iety of other phrases about it, each of which may have some value of its own; as, the
force of the ball breaks the window, the momentum, etc.. the glass was broken by the
impact of the ball, a boy broke the glass with a wild ball, the blow of the ball upon the
window broke it. Yet upon examination it appears every time to be the ball that breaks
the glass. All abstract nouns have the same indirect relation to reality. Thus in the
sentence "This man's influence on the community is powerful," the influence is the sub
ject of the verb, but the man is the real agent. This appears in the direct statement,
"The man influences the community strongly." "The wife's energy supplemented the
ability of the husband." "The energetic wife helped the able husband." It is not pre
tended .that the direct form is universally preferable. In the last example the
first or indirect statement is much better. But in cases where quantities
enter that are to be measured and thought of as acting, there is a great gain for
elementary presentation in the direct statement and the avoidance of the ab
stract noun. It is air that affects the barometer, and not pressure of the air. If more
pressure does not imply more air, it means nothing at all. Of course there is no reason
why anyone who has once become familiar with the instrument should avoid the conven
ient word. But, though entirely justified and in the very best use, it is often a cause of
early misunderstanding. Barometer Corrections
67. Unlike the thermometer, the barometer readings need correction before they
are transferred to the weather map. The corrections are two, for temperature and ele
vation. Since mercury expands with heat, the amount of mercury needed at any moment
to balance the atmospheric column will measure more or less inches according as the
instrument is in a cold or warm room. To have a means of comparing the readings of
different instruments, it is necessary to allow for the temperature by calculating what the

38

length of the column of mercury would have been had the temperature been that of
freezing water. This is called the reduction to freezing point and must be applied to all
readings of good barometers.
The reason for the second correction, the reduction to sea level, is that we desire to
know the distribution of atmospheric pressures at some uniform level. That the pressure
varies at different levels we know. To understand the winds it is necessary to find out
whether it is constant at any one level. So the readings are always reduced to sea level.
Read the thermometer and barometer outside the window and those within. Where
is it colder? How much? Where is the barometer "higher?" How much? Divide the
difference in barometer readings by the number of degrees difference in temperature to
ascertain how much the outer barometer seems to have fallen per degree of greater cold
outside. The published tables of corrections for temperature allow for the expansion of
the mercury, the glass tube, and the brass scale and do NOT apply to a barometer with
wooden scale such as is used in these experiments. The wood is more affected by mois
ture than heat, but changes with absorbed moisture are too irregular to be calculated.
The amount added for reduction to sea level is rudely indicated by the following table:

Outside Temperature

0°

30°

60°

90°

Elevation

In.

In.

In.

In.

1000 feet

1 21

1.13

1.06

1.02

2000 •'

2.34

2 21

2 08

1.97

3000 "

3.45

3.25

3 07

2.91

4000 "

4.51

4.25

4.02

3.83

5000 "

5.52

5.22

4.86

4.69

Reduce your outside observation to sea level.
EXERCISE 12— Drawing Isobars
68. Isobars are lines drawn through places having the same air pressure. They
are commonly drawn on weather maps for intervals of one-tenth of an inch through
places having pressures ending in even tenths as 30.1, 30.2, 30.3, 30.4, etc. In many
places where pressures are given they are higher or lower than the desired pressure. In
such cases do not merely draw the isobar between the two places, one of which has a
higher and one a lower pressure than the pressure desired, but make an exact "estimate
each time. We have, for example, two places having pressures of 30.10 and 30.30 and
wish to draw the isobar of 30.20 in that neighborhood. We should locate a point just
half way between the two places and draw our isobar through that point because 30.2
must necessarily lie just half way between 30.1 and 30.3. The method is the same one
used in drawing isotherms.
Making use of this principle as shown in the class exercise, chart the isobars for one
of the dates for which data are furnished in the table in section 59.
Relation of Air Temperatures and Pressures
69. The system of isobars drawn with the readings for date A shows a grouping of
low barometers in the central valley, west of the Mississippi with higher barometer read
ings grouped over the Rockies and again over the Allegheny mountains; for date B high
barometers on the 100th meridian and low in the St. Lawrence valley. Remembering that
the readings have been reduced to sea level, what thought about the depth of the air over

39
various parts of the country would explain such distributions of pressure on the supposi
tion that the temperature is the same everywhere? Does that suggest a level upper sur
face of the atmosphere like that of the ocean? Of course our supposition is improbable.
The temperatures are not the same everywhere. The isothermals show differences even
on the same parallel of latitude. You have learned from the daily weather map, that there
is definite association of temperatures with the areas of high and low barometer. You
are, therefore, in a position to judge the sort of error involved in our assumption of uni
form temperatures all over the country on dates A and B. What are the real conditions
of temperature in the country that morning? As warm air expands and occupies more
space, while cold air contracts and occupies less, we must modify our previous thought
about the depth of air in various places. What shall we now believe about the air surface?
70. The relation between pressure and temperature is a causal one. The pressure
varies because the heat varies. Suppose the air over the continent of Australia to be
warmer than the air around. Being warm the air tends to expand and mound up there
overhead. 1. Would this make the pressure there less? 2. Would it make the air
there weigh less? 3. Would the barometers go up or down because of this tendency
to expand? 4. Why not? 5. Is a bar of iron lighter or heavier when hot? 6. Why
should a mass of air be? 7. Is it true that warm air is light? 8. If some air in a
bag weighs a pound, will it weigh less when we warm it? The only sense in which
warming makes it lighter is that it expands and occupies an amount of space that would
at the lower temperature be occupied by a greater amount and weight of air. 9. What
will happen instead? 10. If some air goes away above how will that affect the bar
ometers below over the sea? 11. How in Australia? 12. Under such circum
stances the winds will blow in toward Australia from all around. This actually happens
every summer. 13. Why? 14. Would you say such winds are caused by tem
perature or differences of temperature? 15. Which is the more immediate cause,
difference of temperature or difference of pressure? 16. What causes the difference
of pressure? The sun's heat causes a change in the condition of the air. 17. What
is this change? Motion is involved in this change, but it is motion within the mass and
not motion of the mass. The familiar statement that hot air rises is convenient some
times, like the statement that the sun rises, but neither is exact. The lower air is always
much warmer than the air high above the earth, but it is usually quite content to stay
below without any tendency to rise, being so compressed by the weight of the air above
that is not so light, quart for quart, as it is. Expansion, with motion within the mass is
the only direct result of heat. But this expansion gives an opportunity to another force
to cause motion of the mass. 18. What is this force? 19. Is the first tendency
to motion of the mass active above or below? It is at this moment that change of press
ure appears. The pressure of the air is merely a manifestation of its weight and cannot
change unless the quantity of air changes. If air goes away there will be less air, less
weight and less pressure. And wherever more air goes there will be more air, more
weight and more pressure. The depth of the atmosphere to sea level is to be thought of
as fairly constant since an excess of depth anywhere at once begins to find a remedy by
the action of gravity. .
71. Heat causes a tendency to expand; expansion gives gravity a chance to move off air
above, this causes unequal pressures within and without the warm area in the air below, une
qual pressure below sets the lower air moving or causes winds. Do the winds then generally
move towards places that are cooler or warmer than places around? It is familiar that

40
the sun is always high in the sky near the equator, causing greater heating there than
near the poles. Nearer the poles are alternate seasons of high sun or summer, and low
sun or winter, when the rays more nearly graze the earth's surface and warm it much
less. Thus the strip of highest temperature and lowest pressure migrates across the
equator with the sun twice each year. We shall presently find winds and rainfall migra
ting similarly. The mercurial barometer should now be read daily and the result record
ed in the note book. Saturday and Sunday readings may be taken from the barograph
sheet posted every Monday. The barograph should also be glanced at each day to see
whether the barometer is at the moment rising or falling, and this fact be recorded.
EXERCISE 13. — Inferring Isotherms to Isobars
72. By a study of our collection of mounted weather maps or the series printed on
pp. 44-53 determine which is warmer, the front or the rear of the cyclone. Notice how
this is expressed by the isothermal lines. To discover this the student had best confine
his attention to low pressure areas that are strongly developed and which are shown
completely, i. e. are not partly over the ocean. From these same maps determine which
have the lower temperatures associated with them — areas of high or low pressure. The
temperatures you are. here concerned with, are those along the same parallels of latitude.
You are to note the temperature along the same east and west line through a cyclone, or

Fig. 17. Pressures for March 3, 1904. Isotherms to be added by the student with the help of
temperatures marked at the eastern coast
from cyclone to anti-cyclone. You will be helped by considering whether it becomes
colder or warmer at a place where isotherms that pass to the south are bent northward
toward it. Note the effect that areas of high and low pressure have upon the direction
of the isotherms. After you have succeeded in determining to your satisfaction the tem
perature relations existing in the cyclone and between the cyclone and anti-cyclone, ex-

41

press it in isotherms on both the engraved maps of isobars accompanying the exercise
Fig. 17 and 18. Draw your isotherms at intervals of 10°, using as your starting points the

Fig. 18.

Pressure system for January 19, 1904. Isotherms to be put in by the student with
the help of temperatures marked at the east coast

temperature given on the map and estimating for intermediate temperatures. Draw your
isotherms just as though the only factor causing them to deviate from a straight east and
west line were the areas of high and low pressure, and assume hat a difference of each
tenth of an inch on the barometer will place the isotherm a tenth of an inch out of an east-
west course, like a parallel, through the points on the east coast where the temperature
is marked. Winds
73. The wind is the lower air moving. The motion is from a region of high pressure
to one of low pressure, and these differences of pressure almost always have their cause in
differences of temperature. Among the simplest cases are the continental winds of Aus
tralia, referred to in paragraph 70, and shown in the diagrams (Figs. 19 and 20).

^ — \'-_ <* r u-

^-^i

^ ¦ 1

t &
Y^Yt
'~w'
Fig. 19. January. Fig. 20. July.
EXERCISE 14— Cyclonic Winds
74. By an inspection of the -weather maps (pp. 44-53) for Jan. 20, 21, 22, 23 and 24,
1902, what would you decide to be the general movement of the air around areas of low
pressure— toward or away from the center?
42
2. On the map of Jan. 21, 1902, how do the winds seem to be blowing about the low
pressure area centered over eastern Tennessee? 3. Are they blowing straight toward
the center? 4. If not, to which side of center, right or left? Look straight north of
the area on Lake Erie. 5. If the winds there blew straight AT the area they would be
north winds. 6. Are they? If they go west of south they turn to the right, i. e. to
THEIR right of straight ahead. 7. Do winds at stations straight to west of Tennessee,
go toward southeast (right) or north east (left)? 8. As you look at the other maps
again, does the same thing seem on the average to be true?
State in general terms the movement of the air around the cyclone. Illustrate by a
diagram, using six arrows to show the direction of the wind, and show to the instructor.
Make the shaft of each arrow straight and one-half inch long.

50 60 70 80 90 100 110 120
Fig. 21. Winter monsoon, January, February

50 60 70 80 90 100 110 120

Fig. 22. Summer monsoon, July, August

43
75. How will the land and sea pressures near Australia compare in December? Such
seasonal alternations of the winds from the sea and land are called MONSOONS. North
America has less pronounced but perceptible monsoons. (Fig. 23 and 24). They are
most strongly developed in the northern Indian Ocean. (Fig. 29.) 2. In what season

Fig. 23. Average winds of the United States, December

Fig. 24. Average winds of the United States, July
will southern Asia be warmest? 3. When will it have the lowest pressure?

Why does the southwest monsoon blow there in summer?
monsoon in winter?

5. Why the northeast

^*.

January 21, 1902

January 21, 1902.

CD

January 22, 1902

-J

January 23, 1902

00

January 24, 1902

49

UIo

May 27,. 1902

51

a!

52

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54
Land and Sea Breezes
76. When such an alternation of winds is diurnal instead of seasonal, they are
called land and sea breezes. Like all winds these are named from their point of origin.
They are observed on most sea shores and on many lakes, being distinct in summer on
Lakes Huron and Michigan, on days of feeble general circulation of the air. In winter
the land is usually colder than the lake, even by day, so the lake breeze is absent.
Lake or sea breezes that blow by day to the heated land are always stronger than
the land breeze of the night, mostly because the rougher land surface offers more resist
ance to the passing of the air than the water does. It is always the case that the wind
blows faster on the water than on land. For the same reason, kites, balloons and clouds
show the movements of the upper air to be much more rapid than the winds below.
Mountain winds confirm us in this view of the effect of friction in retarding the wind at
the earth's surface.
Average wind velocity in miles per hour at various shore and inland stations: —

Block Island

17.2

Key West

10.5

Boston

11.8

Salt Lake City

6.0

Chicago

17.0

San Francisco

10.6

Cincinnati

7.7

Wood's Hole

15.8

Galveston

10.9

Denver

8.0

Hatteras

13 9

Pike's Peak

18.0 (36.0 in winter)

Kansas City

8.6

Mt. Washington

340

EXERCISE 15— Anti-cyclonic Winds
77. Examine the weather maps for January 20, 21, 22, 23 and 24, 1902, and deter
mine whether the air around the areas of high pressure seems to be moving outward or
toward the center of the area.
1. On the map for January 23, do you detect anything besides the outward move
ment of the air? 2. Do the winds blow straight out, to the right of straight out, or
to the left of straight out? 3. Do you discover any verification of your conclusion
on the maps for other days?
State in general terms the movement of the air in the anti-cyclone. Illustrate by a
diagram as you did for air movement in the cyclone.
The Winds of Observation
78. We should gather material for the study of the winds by noting the direction
and force of the wind each morning with the principal changes during the day. We may
use the data gathered from a wider area on the daily weather map, and we may note the
effect of the prevalent wind on the trees. This is often well shown on fruit trees, which
yield the more readily as the ground is kept soft by cultivation, unless, indeed, the farmer
has been prudent enough to plant his trees leaning against the wind, as is sometimes
done. In what direction does this make the tree lean with us? Select isolated trees in
the country, to which the wind has free access, and note the unequal development of the
branches. The best time to observe this effect is in the leafless season, when the growth
of the twigs is seen to be much influenced. Most affected, perhaps, are the poplars, and
after them the willow, maple, elm, buttonwood, hickory, oak, and black walnut, in order.
The cottonwood appears to yield very little to the influence. Find examples of this influ
ence of prevailing winds. If the wind observations have been kept since the beginning
of the course, it now appears clearly that the west ones are the more frequent. 1. What
percentage of all have you in that direction? 2. Is the wind effect on the trees in
the same direction? The winds of observation for us are in the northern belt of wes
terly winds. They extend around the world between 30 and 60 degrees of north latitude.

55

There is a similar belt in the southern hemisphere and in these two regions live the most
progressive and energetic races of the world. But we do not need to keep weather
observations to know that there are many other winds than westerlies here. In the lab
oratory exercise on the winds about areas of low barometer we found them blowing in
every direction, it is true, but with two common rules of conduct, so to say? 3. What
were these?
79. The diagram of planetary winds, Fig. 25, shows the average winds as they
would blow on an earth without land. They are not real winds of the weather. None of

Fig. 25. The winds as they would be on an ocean-covered globe
our east winds show for instance, since they are fewer than the west winds and disappear
in the average. Also all land winds are weaker than sea winds because of the friction of
the surface of the land. So both trades and westerlies are much checked on lands.

Fig. 26. World Isobars

56

EXERCISE 16— Wind
,v* 80. Our

Effect on Trees
winds are prevailingly from the same
general direction. This is shown plainly by many
trees. Go from the city westward in open country.
Examine the trees from the southward or northward. When you think you perceive a
wind effect, go to a point east or west of the tree. Is it now symmetrical? Sketch the
tree from two directions at right angles. Observe and describe the wind effect on it.
EXERCISE 17. — Monsoon Temperatures
81. Construct curves of < annual temperature at Calcutta and Nagpur, India, from the
following data, using one square of the quadrille paper vertically for one degree and two
squares horizontally for a month. Both places should be looked up in the atlas. Cal
cutta is in latitude 22J4 N., 88J4 E: Nagpur in 21 N., 79 E.
Notice the date of maximum temperature on these two
curves. 1. Is it usual? See paragraph 45. 2.
Which monsoon is blowing in India in summer? It blows
much more strongly than the winter monsoon, and comes
on very suddenly. 3. Does anything on the curve
indicate the change in the monsoon? 4. What is the
date of the change, apparently? 5. Why does the
maximum temperature come early at these places?

Calcutta Nagpur

January 
February ..,
March 
April 
May 
June 
July 
August 
September..October 
November..December.,

64 70
808585 84
8382
82 8073
65

68 74
83
8894 86808080 7972
67

82. The fact of rotational deflection may be simply stated thus :
For a person in the northern hemisphere the earth turns from right to left. This
causes all straight lines on it to turn to the left. A body, or mass of air that starts off
along a line holds its direction and therefore seems to turn to the right. When we go
into the southern hemisphere our point of view has changed, it is as if we looked at a
picture from the back. The earth and lines on it turn to the right and whatever moves
off straight starting on a line, seems presently to turn off to the left from that line. The
deflection is greatest at the poles and nothing at the equator. Why are such winds about
a low barometer and their attendant circumstances in the air called a cyclone? Why are
the winds and other conditions about an area of high barometer said to make up an anti
cyclone. Perhaps the most interesting thing about an anti-cyclorte is that its winds are
really governed by the same two rules of conduct as the cyclone. Both are illustrated
on the diagrams of Australia and its seasonal winds. 1. When is the Australian wind
system like a cyclone? 2. When is it like an anti-cyclone? 3. Is there not a differ
ence each time? 4. Did you learn from *Foucalt's pendulum why the trades have
more southing than the westerlies have northing? Of course in the southern hemisphere
the sun moves from right to left since the people there live, as it were, on the under side
of the equator and see all our directions reversed, just as a man would who read dia
grams from the back of the paper.
EXERCISE 18.— Inferring Winds to Isobars
83. You have now determined the actual direction of the winds in the cyclone and
anti-cyclone.

*Foucault's Pendulum; Young's Astronomy, p. U0;
Geography, 1899, p. 298.

Report Chief Signal Office, 1885, part 2, p. 181; Journal of School

57
On figures 17 and 18, indicate by arrows the wind directions you would expect.
Make each arrow half an inch in length and draw two for each 10° mesh of the map.
Water Vapor, Clouds and Rain
84. Water vapor is always present in the air. Even in the desert enormous quan
tities of water are always present in this form. Water vapor is transparent and invisible.
The bluest sky, the clearest air contains it. Clouds are made of little particles of water,
not of water vapor. Mist is cloud seen from the inside. Cloud is mist seen from the out
side. The steam inside the tea kettle is invisible as would be noted were the kettle made
of glass. Close to the spout nothing is seen to issue. Only a little way off appears the
mist of water particles called steam. It really consists of water drops condensed from
the steam by the cold air. Probably most of the water vapor in the air comes from the
trade wind belts of ocean on either side of the equator. This map of the world, Fig. 28,
shows the distribution of the Salter parts of the ocean surface. 1. What has the great
saltness of these parts of the ocean to do with the supply of water vapor in the air? 2.

140

Fig. 28. Saltness of ocean water. The saltest water is lined and the least salt is blank.
Are the trades growing warmer or colder as they advance? 3. Why? 4. Are they
gaining in power to take up water? 5. Is the sky often cloudy in the trade winds?
The percentage of cloudiness in Fig. 29 will enable you to answer the question.

Fig.'- 29. Lined areas have cloudy sky more than half, the time.

58

85. Vapor is formed from water at all temperatures. The water particles are be
lieved to be in a state of rapid motion. Our thought of evaporation is that occasionally
one of these particles near the surface plunges out into the air. This, as has been said,
occurs at all temperatures, but naturally more at higher temperatures, when the parti
cles are moving faster. When this process has gone on long enough to cause a great
number of particles to exist in the vapor condition, it is not difficult to believe that occa
sionally one of these particles plunges back into the water. This should happen oftener
as the space above the water becomes fuller of vapor. But presently there must come a
moment when as many plunge in in a given time as emerge. At this moment the greatest
possible amount of vapor exists in the space and it is said to be saturated. If more heat
be now applied the emergence of particles becomes more active and more vapor can be
contained in the given space. If it be cooled, emergence is checked and the quantity of
water vapor that can be contained in the space is diminished. In usual phrase warm air
has a greater capacity for water vapor than cold air, though the air has nothing to do
with it; the same evaporation occurs into an empty space as into air and faster, perhaps
because the air acts as a hindrance to the movement of the particles.
86. Experiment has shown that air containing 4 grains of water vapor to the cubic
foot is saturated at 50°. That is at that temperature 4 grains and no more of water could
be evaporated into it. If cooled below 50° some of the vapor will take the form of dew
or cloud. Experiments further show that a fall in temperature to 30° would condense
about half of the water vapor, while a rise to 70° would enable it to take up another 4
grains to the cubic foot if it could get it. If it got no more water it would be said to have
become drier in view of its increased capacity for moisture. For ordinary thought air is
dry when it will dry other things. In this sense it is no part of drying air to take water
away from it; on the contrary we might add two grains of water to the cubic foot while
we raised it to 70°, and as it would still have a capacity for two grains of water it would
be drier than it was at 50°. The effective moisture of the air is thus seen to be as much
dependent on temperature as on water content. A better name for this sort of moisture
is relative humidity. It is said to be 100 per cent, when the air is saturated, as is air at
50° with four grains of water vapor to the cubic foot, but the same air heated to 70°
without gain or loss of water would have a relative humidity of 50 per cent, containing
only four out of a possible eight grains.
87. To illustrate actual values of relative humidity, the following table is inserted of
average monthly temperatures and humidities observed at Detroit in 1898, at 8 a. m.,
Eastern time:

1898

January ...
February ..
March 
April 
May 
June 
July 
August 
September.October....NovemberDecember.

Tempera ture

26.2
24.1 55.340.859.4
66.1 69.7
67.8 61.7
49.1 34.8
25.4

Grains Vapor to
1 Cubic Foot of Air

Possibly Actually

1.671.53
2.422 95
5.64 7.11 7 91
7.48
6.123 97
2..»8 1.62

1.44141 194
2.013.615.19
6.17 613 4,83
3.30 1.95 1 38

Relative
Humidity

86
92 80
6864 7378
82 79
838285

Pints Water
Room 21

3.93.8 5.3
55
9.2
14.2 16.916.7
13 2
9.1
5.3 3.8

59

At the average temperature observed in January, 26.2°, 1.67 grains of water vapor
suffice to saturate a cubic foot of air, but as there were present only 1.44 grains the rela
tive humidity is said to be "Vi-m or 86 per cent. If our room measures 42 by 34 by 14
feet, multiplying the cubic feet in it by the grains of water to the cubic foot actually pre
sent in any month we shall get the number of grains of water present. Divide this by
7300, the number of grains in a pint, and thus verify one or two of the numbers in the
last column. It seems surprising to find so large a quantity of water contained in the air.
And the table shows that it is precisely in the summer months, when the sky is clear
three-fourths of the time that the air contains most moisture, fully four times as much as
in January when the sky is clear only a third of the time. Yet the summer air is drier,
or better, the relative humidity is less, as the table shows. 1. How much vapor to
the cubic foot can the January air still take up? 2. How much the August air?
Strange as it seems the clear skies of August contain much more water vapor than the
cloudy skies of February. The desert of Sahara has about as much water vapor in its
air in summer as moist England, yet the desert temperature is so high that the air is dry,
i. e. the relative humidity is not more than forty or fifty per cent. 3. What relative
humidity is usual here? (See Climatology of the United States, Michigan.)
"Thus the air even above the dry ground of the desert contains a considerable
amount of water vapor, brought from the neighboring seas and coast regions by air cur
rents and by the diffusive power of the water vapor itself. The
rainless character of the desert is caused, not by a lack of water
vapor in the air, but by the absence of conditions leading to its
condensation." 88. The accompanying table contains the possible water
contents at the given temperatures. 1 . What was the water
content in grains to the cubic foot of the air in the room at the
time of the experiment? 2. How many pints of water?
Construct a curve from this table, using one square of
quadrille paper, vertically, for 2°, and horizontally for 14 a
I grain of water vapor.
EXERCISE 19 — Measuring Moisture in the Air
Materials: A thermometer, glass of water and thin cotton cloth 1x4 inches.
89. Take the temperature of the air in the room and the water, which should have
the same temperature, and will if it has stood in the room long enough. Dry the ther
mometer and again take the temperature of the air. Place a little water on the ther
mometer bulb and note what happens. Can you explain? The warmth of the mercury
is being used to do work. What work? Now wrap the bulb with the cloth which is
twisted into a rude wick and dipped into the water in the tumbler. The temperature
falls and in five or ten minutes will reach its lowest point. Note the temperature reached
and by the following diagram ascertain the relative humidity.
Dry 73°, wet 71°, difference 2°, relative humidity 90 per cent.
90. Human interest in the water vapor in the air is in relative humidity which
affects our comfort, and precipitation, which conditions life. 1. What are the con
ditions that lead to the condensation of water vapor? The fall of temperature that will
be thought of as the cause, is due to some upward movement of the air and the expan
sion that must result. Such ascents occur in the equatorial regions, in cyclones and at

Possible

Tempera

No. of Grains of

ture.

Water Vapor

per cu. ft.

0°

0.54

10°

0.84

20°

130

30°

1.97

40°

2.86

50°

4 09

60°

5.76

70°

7.99

80°

10 95

90°

14.81

100°

19.79

60

61
mountain slopes. The last case has already been referred to. 2. In the first two
what lifts the air? 3. Are there any movements of the air round about that cause
the central air to rise ?
It is now seen that there are several belts about the earth with rain conditions. One
has a good deal of uprising air at all times. 4. Where is this belt? 5. What are
its rain conditions? In another belt the air rises only at mountain slopes. 6. What
sort of skies and what sort of lands should prevail at other points in this belt? 7.
Which belt is it? Another has two different arrangements for causing the air to rise.
8. Which is this? Finally it is observed that two of these three belts occur necessarily
in pairs. 9. Which ones? It is now possible to locate doldrum, trade-mountain and
west-wind rainfall on the blank map.
EXERCISE 20— Our Irregular Rainfall
91. Examine the table below of rainfall at Lansing, Michigan. 1. In what month
is the rainfall greatest? 2. In what least? By what percent of the average monthly
rainfall (2.77 inches) is it least? 4. In how many years does the table show that the
wettest month had less than the average rainfall? 5. What percent of all the years is
that? 6. Has summer or winter greater rainfall here? 7. Is that good or bad for
our crops? Construct a diagram of four horizontal lines one above the other with their
left ends in the same vertical line. The length of each line will represent the sum of the
rainfall of three consecutive months, one for the three of greatest and one for each other
group of three months. Let one-half inch in the diagram represent one inch of rainfall.

Ykar

Jan

Fhb.

Mar.

Apr.

May

Junk

July

Aug.

Skpt.

Oct

Nov.

Dkc.

Ykar

1880 

2 67
2.27 1.13
0.98 1.92 !.59
2.27 3.36 1 69
1.67
2.71 1.071.05 1.84
1.75
2 66
1 11
3.62 3 77
2.05 1.431.6-5
0 38
1 54
2.82

1.85
3 92
2.59
4 49
3.240 45
1 64
5 87
1 74
1.021.85
2.35 1 64
2.31 1 67
0.62 1 08
1.22
2 16
1 65
2 84
1 26
0.56 3 10
1.53

2.00
2.14 3 66
0 34
3.71 6.402.83 1.30
2.02 I 14
1.31
2 48
1.49
3.78 1.261.141.15
3.203 73
.3.17 2.202.97
4.12 1.52
3.87

7 06
1.651.85 1.89
2.122.38 1.51
0.98 1.29
1.70
3 23
2 45
2.405 30
3 31
1.12
2 05
2.43 2.04 1.93
2 30
2.29 i.69
4.40 1 70

6.81 2 97
4.33 6.314 34
1 85
3.00 2.12
3.653.86
6 22
1.84
6.314 08
6.512.05 2.67
3.442 16
3.284.25 2.67
3.91 2.07
'3 60

6 96
3 66
5 51
9.913 09
5.88
2.14 1.45
2.073.65
4 03
2.26
4.81 7.19 1.81 1 24
3.393 68
4.55 1.15
2.19
3.757.07
4.162.79

6.00 1.63
1 84
10.12 3.24
2.04
0.64 1.681 80
2.670 52
2.91
3 08
0.98 1.451.72
7.107.36 1.46
2.625.096 33
6.994.79 2.15

6 02
2.05
4.040.21 1.34
6 75
5.70
0.93 1.84
0.18 3.065 27
3.26
0 73
0.005.383 28
2.0^2.99
0 33
3 86
3 24
0 39
5.682.76

4.13 3 24
1.07
3.372 71
3 46
6 05
5.53
2.060.832.39 1.37
2.802.34
2.76
086 6 27
0.912.532.24 1.27 1 88
' 5 66
3,92 2:35

2 84
5 60
3.103 64
6.13
3 60
1 15
2 28
3.03
0 75
4 96
0 77
1.00
4.55 1 98
0 87
0.87 2.143.66'3.113.51
4.87 1 65
1.99
2.20

2.38
4.39 1.75
4 08
1.60
3.05 1.37
2 06
3 33
2 59
2 91
4 39
2.612.46 1.05
3 91
2 98
3 39
2 60
1 86
3 88
1.32
2 30
1.45
0 07

0 66
1 76
1 30
0.93 2.77
2.86 1.22
2.51 1 25
2.68 1.35 1 89
1.61
3 96
1.14
5.83
0.72 1.95
1.271.61
0.47
2.90 2.32
2.06 1.27

49

1881 

35

1882 

32

1883 

46

1S84 

36

1885 

40

1886 

29^

1887 

30

1888 

26

1889 

23

1890 

34*4

1891 

29

1892 

32

1893 

39^

1894 

25

1895 

27

1S96 

33

1897 

35

1S9S 

33

1899 

25

1900 

33

1901 

35

1902 

37

1903 

37

1904 

27

2.00

2.11

2.52

2.44

3.77

3 93

3.45

2.84

2.88

2 73

2.55

1 93

33.1

At Boston the annual rainfall is 45.4 in.
distributed as in the table. i
Fill out the Lansing columns.
BOSTON
LANSING
Inchp= Per Ct.
Inches Per Ct.
Feb.,
Mar.,
Apr .
.. 11-4 • 25
May,
June,
July.
. 10.5 25
Aug.,
Sept.
, Oct. .
• 11.5 25
Nov.,
Dec,
Jan..
27
•" 12.0 "
45.4
100
62

Maps
92. The ball shape of the earth makes it impossible to draw maps correctly on any
thing but a ball, Any map on flat paper is necessarily somewhat distorted. A familiar
illustration is the cracking of a half orange peel that has been removed intact in its nat
ural form, on pressing it down on the table. Another good one is had when you attempt
to wrap a ball up in paper. Flat paper cannot be accommodated to it. Such surfaces —
those to which a flat paper cannot be adjusted by mere rolling or wrapping, are known
as warped. A trial, however, will quickly show that for a small part of the earth's sur
face, the disagreement between the ball surface and a plane is not very great. A circle
of paper half an inch in diameter, placed upon a six-inch globe, comes near enough to
resting upon the surface to make the part of the map traced through it fairly identical
with that on the globe. Such a circle on that scale is 660 miles in diameter, about big
enough to contain all the Great Lakes and the country about them; the whole of the
British Islands, or any European country except Russia, Sweden or Norway. So there
are many maps in which the distortion is of little account. Maps of whole continents,
however, are necessarily somewhat distorted, and no map of the whole world, or even a
hemisphere, can help misrepresenting shapes and sizes. Different methods of map-
drawing, or "projection," as itis called, are devised to render maps of large areas available
for various purposes, one considering the needs of the navigator, another that of persons
wishing to compare areas, and others wishing a map that gives a comparative view of
the whole world at once. The study of projection utilizes the highest skill of the mathe
matician. But simple constructions will give some good results. The device by which
maps are drawn on the globe is the use of latitude and longitude, parallels and meridians.
Something of the sort is rendered necessary by the fact that a ball has neither a begin
ning nor an end.
93. Meridians and parallels cover the surface of a globe with a network of meshes.
These are said to be ten-degree meshes when meridians and parallels alike are ten de
grees apart, four degree meshes when these are four degrees apart, and so on. On
most maps meridians and parallels are the same number of degrees apart, but many globes
have fifteen-degrees paces between meridians and ten-degree spaces between parallels,
for purely mechanical reasons. The shapes of the meshes are different in different lati
tudes. If meridians and parallels are the same number of degrees apart what is the shape
of the enclosed meshes near the equator? What near the poles? What at intermediate
latitudes? To draw a map we must, first prepare the right net. Let us try to draw Borneo,
using a five-degree mesh and making it a ten millionth as long
or as wide as the real island.
The northern parallel is 10° north, the southern one 5°
south. 1. How many spaces shall we use in latitude? The
western meridian is 105° east, the eastern one 120° east. 2.
East of what? 3. How many spaces shall we use in longi
tude? 4. How many meshes will there be in the finished
map-net? The following table gives the dimensions of the ten-
degree meshes of the actual world in inches, full size:
Fig. 30.^Borneo

'z—

) i

o

0

^> o
1 5 1

fl

J) t,
S 1 0

63

Lat

slant height
for cone

0
10
20 30 4050 60 70
80

infinite
1,424,078,254 690,100,982435,243,224299,636,802 211,093,357 145,324,237 91,655,43644,415,856

5. How many inches is a ten-millionth of ten de
grees on the equator?
6. How many a ten-millionth of ten degrees on
the 10th parallel?
7. How many ten degrees on the meridian?
8. Let us call the meshes squares, of four and a
half inches each way. How much would five-degree

10° on
parallel
43,821,397
43,159,99241,190,721
37,982,129 33,615,52428,223,172 21,965,743 15,032,175 7,634,237
Ten degrees oi latitude is 43,747,944 inches.
squares measure?
9. Construct a square 6% inches on each edge and subdivide into 9 squares. 10.
Number them as in the cut arrd-ptil an uutei 'rraroe-ea-Awtl^foes"^^ an inch
¦asay-from the inner frame lm&3. 11. Now draw Borneo on it faintly with a very
soft pencil. Put dots in the middle of each mesh. They will help you draw
the coast lines across the meshes. Notice where the coast line cuts the meridians and
parallels and make these crossing points right before attempting to draw the coast line.
When the coast line looks as good as you can make it darken it. On the finished map
the coast should show more plainly than any other line. Parallels and meridians should
be as fine and faint as you can draw them. They are only helps; the outline of the
country is the real thing.
94. To make a ten-degree map net for North America on the scale of a hundred-
millionth. Materials. You need now two drawing pencils, a HHH for points and lines,
and a B for outlines of coasts or boundaries. Both need special sharpening to long,
needle points, very much sharper than any point we use on a pencil for writing. You
cannot make a good map without this special pencil point. Also a flexible paper rule
divided into tenths of an inch and perforated with a small hole at the zero point for the
point of the pencil so that you can draw circles up to a radius of 12 inches with it. A
small celluloid triangle will be very useful. 1. As fig. 31 shows, the northern latitude
is 70°, the southern 10°. 2. What is the mid
dle latitude? 3. According to the table in
paragraph 93, the tangent to the real world at lat
itude 40° is 299,636,802 inches long. 4. How
long shall we take that? What is our scale? 5.
How do we get three inches? 6. On a sheet
of the blank paper detached from the back of the
book, draw a straight line parallel to the long ed
ges of the sheet through the middle. 7. At the
middle of the line place a dot. Call the line the
100th meridian and the dot its intersection with the
Fi_g:3AJ!'el-f°r-?,?r* *™ri??_. 40th parallel. 8. Put another dot on the line
three inches north of this dot. -Put a faint little circle about this upper dot and call it the
center of circles. 9. From this center draw a circle with a three inch radius. It must
pass through the lower dot. Why? The circle so drawn represents the fortieth parallel
of north latitude. 10. We need other riots above and below 40° along the middle
meridian for every tenth degree of latitude: 50°, 60°, and 70°, and 30°, 20°, and 10°. 11.
How long is ten degrees of latitude? See table in paragraph 93. 12. How long shall
we take it on our scale? 13. Place those dots. The table also tells us how far apart

64
ten degree meridians are on the fortieth parallel. 14. How far shall we take them?
Shall we call it 33 or 34 hundredths of an inch? 15. Call our middle meridian the
100th west of Greenwich and place dots for meridians over to 30° W. and to 170° west
longitude. 16. Draw a rectangular frame that shall enclose all the dots in latitude
and longitude with the north-south sides parallel to the middle meridian. 17. Now
from the center of circles draw arcs of circles through all the dots along the middle line.
Draw only those parts of the circles that can be drawn within the frame. 18. The
meridians pass through the dots on the fortieth parallel and the center of circles, but
only that part ot each is to be drawn which lies within the frame. 19. Number as in
cut and add outer frame. EXERCISE 21
95. To draw Europe on the scale 1 : 50,000,000. Northernmost latitude 70°N,
southernmost 30°N, mid-latitude 50°N. From the table in paragraph 93 we get values
for our scale of 10° latitude, 0.875 inches; radius for 50°, 4.22 inches; 10° longitude on
the 50th parallel, 0.564 inches. NOTE: These nets should be made of very fine lines, so
fine as to be hard to see when held at arm's length. Beginners invariably make them too
dark, too heavy, and above all too wide, for they attempt to draw with a pencil point
such as they write with. This work requires a pencil with a needle point, altogether too
sharp and thin to write with. The first thing to do at each of these exercises, therefore,
is to sharpen the pencil. It will then need very light handling to preserve the point.
Attention to this detail makes it possible to measure to hundredths of an inch.
Directions: — 1. Draw a four-inch square near the bottom of the paper. 2. Num
ber the center of it 50°. 3. Draw the 20th meridian through the center, the full length
of the paper. 4. Mark also the 70°, 60°, 40°, and 30° points along the meridian, with
the value of the 10° space given above. 5. Put a dot on the extended 20th meridian
4.22 inches above the 50° point. This is the Center of Circles. 6. From this center
draw arcs within the frame through all the points marked, and through the 50° point
make the arc across the whole sheet of paper, i. e., not merely within the frame, as in
the other cases. 7. Along this 50th parallel lay off spaces of ten degrees of longitude,
five to the west and five to the east of the 20th meridian. 8. Connect each of these
points with the Center of Circles with the ruler edge, and draw that part of the lines that
falls within the frame. 9. -Number meridians and parallels and enclose in a 4% inch
square. 10. To accustom your eye to the outline of the continent of Europe make a
tracing of it on rice paper from figure 6. 11. Draw Europe freehand on your net
from Fig. 6. EXERCISE 22
96. To draw South America on the scale 1-100,000,000. From 20° N to 60° S.
What is the middle latitude? Take the values, of radius for 20° and the ten-degree
space's from the table in paragraph 93. Frame measures 4 , inches in latitude by 3
inches in longitude. As this continent is in the southern hemisphere, the meridians con
verge southward, so the frame should be drawn near the top of the paper, and the Center
of Circles falls on the mid-meridian extended, below the frame. This mid-meridian is 60°
W. Outline of continent to be first traced and then drawn on the net.

65
EXERCISE 23
97. To draw Australia. Scale 1-50,000,000. Here again meridians converge south
ward. Take frame 4 inches square. Will the Center of Circles fall on the paper? For
mid-meridian usel35° E. . It should be drawn only in dots. The object is to get the
140th and 130th meridians on either side of the middle of the net. Then proceed as
before. EXERCISE 24
98. To draw Africa. Scale 1-60,000,000. 1. The middle meridian (20° E) and
the equator may be drawn as straight lines that cross in the middle of the paper, at right
angles, and each about 6!4 inches long. 2. Complete the square of which these two
lines are diameters. It is the frame. 3. Lay off four ten-degree spaces along the 20th
meridian on each side of the equator and draw straight lines parallel to the equator
through these eight points for the parallels. 4. Lay off ten-degree spaces (longitude)
along the equator, four to the east and four to the west. 5. Do the same on each
parallel, using always the ten-degree space of longitude for that parallel, which is taken
from the table and reduced to our scale as usual. 6. Draw curves through these
points with the help of the ruler. Number and draw map as usual.
99. Scales. 1. How many inches in a mile? 2. A map on the scale 1-100,000,-
000 has one inch where nature has a hundred million inches; how many miles is that?
3. How many miles to an inch on a map of the scale 1-100,000,000? 4. How many
miles to an inch on our map of Europe in paragraph 95? 5. How many on the map of
Africa in paragraph 98? 6. How many miles to the inch on a scale of a millionth ? 7.
If a map has 395 miles to an inch, what is its approximate scale-ratio? 8. What is the
scale-ratio for a map with a hundred miles to the inch?
EXERCISE 25
100. To draw New Zealand on the scale 1-8,000,000 with a two-degree mesh. 1.
Ten degrees on the meridian to that scale is 5.46 inches. How much is two degrees?
2 Similarly take from the table the values of two degrees on the 40th and 50th parallels.
3. Draw the 172nd meridian through the middle of the paper parallel to the long edges.
4. Lay off eight spaces along its middle portion, each 1.094 inches long. What do these
spaces represent? The bottom one is to be numbered 50°. NOTE: When there is less
than 20° of latitude in a country the parallels may be drawn as straight lines parallel to
the equator without much error. Draw straight lines through the division points on the
meridian and at right angles to the meridian, extending two inches to the left of it and
three to the right. 6. On the 40th parallel, toward middle of net, lay off spaces of 0.84
inch, two to the left and three to the right of the 172nd meridian. 7. On the 50th par
allel lay off similar spaces of 0.706 inch. 8. Draw meridians through these points and
number. 9. Draw New Zealand from Fig. 32.
101. Maps of most moderate-sized countries may be drawn as in exercise 25. The
following lines show how to draw the parallels as curves.
EXERCISE 26
Repeat Nos. 1 to 4 of paragraph 100. 5. Number the dots along the meridian,
putting 50° at the bottom and 34° at the top. 6. Draw perpendiculars through the 40°
and 50° points, two inches to the left and three to the right of the 172nd meridian. 7.
Lay off divisions along these two lines as in numbers 6 and 7 of paragraph 100.

66

8. Draw meridians and number 168°to 178° E. 9.
meridian, at right angles to it at the 36th parallel.
half a longitude space on each side of the meridian.

Lay your ruler across the 172nd
10. Draw a short line for about

34 To make this wholly clear we may
add that the line so drawn will cross the
172nd meridian at right angles and will
as extend about half way to the nearest
meridians right and left. 11. Suppose
you end the line so drawn about half way
between 172 and 174, do not lift the pen
cil point from the paper there, but rather
« bear on it lightly so that it forms a pivot
about which you then turn the ruler
edge, lifting the left end and lowering the
42. right slightly, until the ruler is now per
pendicular to the 174th meridian. 12
M Now draw from the point where the pen
cil pivoted across the 174th meridian and
on half way to 176. In this way a line is
IG drawn that looks very like a curve and
crosses all the meridians at right angles.

172. 174 176
Fig. 32

Temperatures

102. The usual data for temperatures are isothermal lines. They always represent
temperatures reduced to sea level, though practically all geographies and physical geog
raphies fail to mention that fact. It is the best way to draw isothermal lines. All met
eorologists know it and how to use such a map, but teachers and school children do not.
If a teacher tries to learn from such a map the temperature on the summit of the Hima
layas she finds it to be 50° or 60° in winter, and 80° or 90° in summer. Of course she
knows there is ice and snow up there the year around and the map cannot be right.
She does not know it has to be corrected for altitude before any of its indications become
those of the actual surface, and finding it mentally indigestible she wisely lets it alone in
all her work. Kdppen's map on the contrary is for actual surface temperatures, and
while it suffers certain defects inherent in all such maps, it does give a rough idea of the
actual temperatures all over the surface of the earth and a fairly accurate one in those
regions where men live. Note what our diagram indicates on the Himalayas.

67
103. Temperatures. North America. Fig. 34
1. What ocean shores are always cold? 2. What ocean has shores with hot
summer and cold winter? 3. What parts of Mexico are always hot? Why? 4.
What temperature has Mexico City? • 5. What temperatures prevail in most of Can
ada? In most of the United States? In Mexico? 6. What sort of summers and
winters has Florida? Maine? 7. What three types of temperature occur on the
California coast? 8. Name three large cities with hot summer and cold winter?
9. Name two with mild summer and cold winter? 10. Name one with hot summer
and mild winter? 104. Temperatures. Europe. Fig. 33
1. State England's summers and winters. 2. Name other countries of similar
temperature. 3. State the temperature of Portugal. 4. Compare North Sea-
Baltic countries with Mediterranean countries. 5. What different sorts of summers
occur in Russia? Winters? 6. What temperature type is most widespread in
Europe? 7. Name three large cities with hot summers and cold winters. 3. What
ones can you name with mild summer and cold winter?
105. Temperatures. Asia. Fig. 33
1. What parallel approximately bounds most of cold Asia? 2. Locate and
bound other cold regions? 3. What parallel bounds hot Asia? Exceptions? 4.
Where are the hot-and-cold regions? 5. Explain the interruptions. 6. Name
three countries that have hot summers and cold winters. 7. Where is it mild the
year around? 8. State the temperature of India, China and Japan.

68

TEMPERATURE REGIONS

Fig. 33
LEGEND

SHADE
Black
Vertical lines
Horizontal lines
Slanting lines
Blank

TEMPERATURE
Always Mild
Always cold
Always hot

DETAILS
Hottest month averages under 68°
coldest over 50°
Warmest month averages under 50°
Coolest month averages over 68°
Hot summer and Cold winter Averaging over 68° and under 50°*
One season Mild the other Toward the Cold areas the Extreme
Extreme season will be a Cold winter, toward
the Hot areas a Hot summer.

*For at least a month each.

69

OF THE WORLD

Fig. 34
Redrawn from Koppen as given by Ward in Bulletin Am. Geog. Soc. July, 1905, with slight altera
tions in United States.
It will help the eye in reading these diagrams if the student will now shade the Cold areas a very
pale blue with a colored pencil,* the Hot areas a pale red, and the Hot and Cold season regions with a
red line on the first, fifth and ninth spaces between the slanting lines and so on with a blue one on the
third, seventh and eleventh, thus making lines alternately red, white, blue, white and so on.
In coloring the Cold areas do not overlook a small one between the thirtieth and fortieth parallels
of north latituae. If the map were large enough to show them there would be other blue dots and lines
on various other high mountain peaks and crests.

The six School Crayons in assorted colors sold in a box for five cents by the American Lead Pencil Co., are excellent for
tinting maps.

70
106. Temperatures. Africa. Fig. 33.
1. Locate and bound and explain the mild areas. 2. Locate and bound the hot-
and-cold regions. 3. Give the parallels approximately bounding the hot regions. 4.
Where in Africa are the cold winters and mild summers? 5. Explain and tell whether
people probably live there.
107. Temperatures. South America. Fig. 34.
1. Locate and bound and explain the "always mild" regions. 2. Locate and
bound the "always hot" regions. 3. Where, if the scale of the map were large enough
to show it, might there be thin lines of dots of "always cold?" 4. What percentage
of South America has hot-and-cold seasons? 5. Name a large city with hot summer
and cold winter. 6. State the temperatures of Bogota, Lima, Rio Janeiro and Caracas.
108. Temperatures. Australia. Figs. 33 and 34.
1. Where are the hot regions? 2. What regions are always mild? Why? 3.
What towns have hot summer and cold winter? 4. State the temperatures of New
Zealand. 5. State the temperatures of Melbourne, Sydney and Wellington.
109. Rainfall for June, July and August. North America. Fig. 36.
1. Where are two areas of scant rain? 2. What percentage of Canada has light
to heavy rain? 3. State the rainfall of the Pacific Coast in three items. 4. State
it for the United States. 5. State it south of the 30th parallel.
110. Rainfall for December, January and February. North America. Fig. 38.
1. State it for the Pacific Coast. 2. State it for the region south of the 30th
parallel. Include the islands. 3. Locate the heavy rainfall of the eastern United
States. 4. Locate the scant rainfall of the continent. 5. What two areas of heavy
rain seem to have moved in latitude from summer to winter.
111. Rainfall of June, July and August. Europe. Fig. 35.
1. Explain the heavy rain of Great Britain and Scandinavia. 2. By what mech
anism does Russia get its rain? (§90) 3. Compare the rain of the Baltic-North Sea
countries with that of the Mediterranean. 4. State the rain of Germany.
112. Rainfall of December, January and February. Europe. Fig. 37.
1. What general movement of the rains in latitude has occurred? 2. State the
rainfall of Germany. 3. State the rainfall of the Mediterranean countries. 4. Com
pare east and west Europe.
113. Rainfall of June, July and August. Asia. Fig. 35.
1. Where are the heavy rains? 2. Where are the light rains? 3. Where are
the doldrum, trade-mountain and westerly rains? 4. Compare with Europe in (1)
and (2). 5. Where are the two dry regions? 6. Is this more like Europe or
North America? Why?
114. Rainfall of December. January and February. Asia. Fig. 37.
1 . What part of the continent is occupied by areas of heavy rain? 2. Compare
with North America and Europe. 3. Why should this be so? See text § 75, and
compare facts for June, July and August. 4. What populous countries have rain at
all seasons. 115. Rainfall of June, July and August. Africa. Fig. 35.
1. Locate and explain the northernmost patch of heavy rain. 2. Locate and
explain the southernmost patch of heavy rain. 3. Locate and explain the middle belt
of heavy rain. 4. Locate and explain two dry regions.

71
116. Rainfall of December, January and February. Africa. Fig. 37.
1. Locate and explain the northern belt of heavy rain. 2. Locate and explain
the southern belt of heavy rain. 3. Locate and explain two dry areas. 4. Where
is there heavy rain in both seasons? 5. Lake Chad is in 13° north latitude, 13° east
longitude. What difference might be observed in it from July to January? 6. In
what month should the Nile be in flood? Allow a month or two for the rains to drain
from equatorial swamps into the Nile valley. 7. State three African illustrations of
seasonal migrations of rain.
117. Rainfall of June, July and August. South America. Fig. 36.
1. Are these summer rains? (Have you tinted as suggested under the legend?)
2. State the position of the doldrum rains. 3. Are there any trade wind rains? 4.
Which are clearly west wind rains? 5. Describe the rainfall of the Pacific Coast.
6. Tell the shape, size and position of the dry area. 7. Describe the rainfall along
the Andes. ,
118. Rainfall for December, January and February. South America. Fig. 38.
1. Is this winter rain? 2. Where are there trade wind rains? 3. Explain the
dry area in 10° south latitude. 4. Was there any seasonal migration of rain? 5.
Describe the dry areas. 6. What regions have rain in both seasons? 7. Describe
the rainfall of the Argentine Republic.
119. Rainfall of June, July and August. Australia. Figs. 35 and 36.
1. What season's rain is this? 2. What two wind belts yield it? 3. What
parts of Australia are dry? 4. State the rainfall of New Zealand.
120. Rainfall of December, January and February. Australia. Figs. 37 and 38.
1. What rains are those of the north? 2. State the rain of southern Australia.
3. What parts of Australia and New Zealand have rain in both seasons? 4. What
rain belts have now moved south?
121. Plant Regions. North America. Fig. 40.
1. What percent of Canada is summer forest? Of the United States? 2. What
three other types of vegetation occur in the United States in order of area occupied?
3. Where shall a New York man go to get quickest to a wet tropic forest? 4. How
much desert and grass land has the United States?* 5. What do we call the grass
lands of North America? 6. Why are they not as populous as the summer forests?
7. Explain the forest of south eastern United States.
122. Plant Regions. Europe. Fig. 39.
1. What two types of forest occur in Europe? Where? 2. What percentage of
Europe is in summer woods? 3. Distinguish steppes from grass lands in Hungary and
Russia. 4. Give reasons. 5. What North American types of forest are wanting?

* It has long been a vexed question as to the absence of trees in a soil which seems to be most suitable for their develop
ment Probably the most ancient explanation was the occurrence of prairie fires, but it seems evident that some general
natural condition rather than an artificial one is responsible for such an extensive area. A possible explanation is as fol
lows- The extensive plains of the West develop the strong and dry winds which prevail over the prairie region, and this
brings about extremes of heat and drouth, in soite of the character of the soil. In such conditions a tree in a germinating
condition could not establish itself. The prairies, therefore, represent a sort of broad beach between the Western plains and
the Eastern forests The eastward limit of the prairie has probably d»p3nded upon the limit of the dry winds, which are
gradually modified as they move eastward, until they cease to be unfavorable to forest growth. The forest does not begin
abruptly upon the eastern limit of the prairie, but appears first a cl imp of tre^s, with interspersed meadows, and finally as a
dense forest mass. Of course, the forest display of the eastern border of the prairie has been imniasely interfered with by
man— Coulter, Plant Relations, page 236-8.

72

RAINFALL OF THE WORLD IN JUNE, JULY

Fig. 35 (p. 72)

LEGEND
SHADE RAINFALL DETAILS
Ruled lines - - Heavy - - More than ten inches of rain and melted snow in the three
months.
Dots - - - Light - From six to ten inches in the three months.
Blank Scant - Less than six inches in the three months.

73

AND AUGUST (INCLUDES MELTED SNOW)

Fig. 36
After Supan.
It will add much significance to the diagrams if the student will now tint with pale red the shaded
and dotted areas north of the tropic of Cancer, 23 V% ° north, as symbolic of summer or warm season
rains, and with pale blue the shaded and dotted areas south of the tropic of Capricorn, symbolizing cold
season or winter rains. That the zone within the tropics remains uncolored means that it does not
have true summer and winter.

74

RAINFALL OF THE WORLD IN DECEMBER, JANUARY

Fig. 37 (p. 74)
LEGEND

SHADE

RAINFALL

Ruled lines

Heavy

Dots

- Light

Blank -

Scant

DETAILS

More than ten inches of rain and melted snow fall in
the three months.
From six to ten inches in the three months.
Less than six inches in the three months.

75

AND FEBRUARY (INCLUDING MELTED SNOW)

Fig. 38
After Supan.
It will add much significance to the diagram if the student will now tint with a pale shade of blue
the ruled and dotted areas north of the tropic of Cancer, 23'/4 ° north latitude, as symbolic of winter or
cold season rain, and the similar areas south of the tropic of Capricorn with pale red, symbolizing sum
mer or warm season rains. The Inter-tropical region remains uncolored, as being without true winters
and summers.

76

PLANT REGIONS

Fig. 39
LEGEND

SHADE
1. Black
2. Black Spots -
3. Dots
4. Black Bars
5. Black Triangles
6. Circles
7

VEGETATION
Wet Tropic Forests
Wet season Tropic Forests
Tropic Open Woods
Sub-Tropic Wet Forests
Leathery Leaf Thickets
Summer Forests

Stars of sixty degrees like a snow-flake Alpine Plants
8. Broken lines - - - Grass Land or Steppes
9. Small Dots -.-.-- Tundra

77

OF THE WORLD

Fig. 40
After Schimper DETAILS
1. Warmth and rains at all seasons. Air plants abound. Forests are quite impassible.
2. Less dense. A season of drouth compels trees to drop their leaves and rest. Along the streams
this does not happen. Temperature still high. Air plants less numerous.
3. Warm but severe season of drouth allows only isolated trees in broad expanses of bush or grass.
Continuous forest along streams only.
4. Less luxuriant than near the equator. Evergreen; but interspersed are trees that drop their
leaves, not in dry, but in a cold season— winter.
5. Always in regions of winter rain, 30° or 40° from the equator. The leaves are tough enough to
withstand considerable summer drought. Oleanders are typical. Trees moderate sized, gnarled
and less abundant than shrubs. Trees stunted by getting water enough for growth in the cold
season only.
6. Moderate rain and winter cold severe enough to arrest growth or cause leaves to fall. These
forests may usually be traversed without hewing a path, but have fine trees which get their
growth in a moist summer.
7. Stunted plants that live on cold, windy mountain summits.
8. With forests along the streams. Increasing drought changes grass land to steppe, the steppe to desert.
9. Low shrubs and herbs that imperfectly cover the ground which is frozen ten months in the year.

78
123. Plant Regions. Asia. Fig. 39
1. To what rainfall does the wet tropic forest correspond? 2. What Asiatic
countries have deserts? 3. State the plant regions of China and India. 4. State
the plant regions of Japan and Dutch East Indies. 5. What percentage of Asia has
summer forests? What countries? 6. Where are the leathery leaf thickets?
124. Plant Regions. Africa. Fig. 39
1. What types of forest are lacking? Why? 2. Equatorial Africa has many
rivers. What report might a traveler along them make of the plant type there? 3.
What is the real type? Why? See fig. 11 4. In what other parts of the world
have we found the Cape Town vegetation?
125. Plant Regions. South America. Fig. 40
1 . What is the only plant type missing? Why? 2. What are the plant regions
of Chile? 3. What those of the Argentine Republic? 4. In what wind belts are
the wet tropic forests? 5. What large country has most of the tropic forests? 6.
Why are alpine plants so much more abundant than in North America?
126. Plants. Australia. Figs. 39 and 40
1. What sort of forests prevail in the thickly settled ports of Australia? 2.
Where are the leathery leaf thickets found? 3. Explain the forests of the north.
4. Why should New South Wales and the southern island of New Zealand have plant
regions so coutrasted in position?

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