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 3/ Yariovis forms of tke 
 
 a( Cirro stratus or ^raiieclond 
 
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A TEEATISE 
 
 CAUSES AND PRINCIPLES 
 
 METEOROLOGICAL PHENOMENA 
 
 TWO ESSAYS; 
 
 ON MARSH FEVERS 
 
 THE OTHER 
 
 ON THE SYSTEM OF EQUALITY, PROPOSED BY MR. OWEN 
 OP NEW LANARK, FOR AMELIORATING THE CONDITION OF MANKIND. 
 
 BY GRAHAM HUTCHISON, 
 
 GLASGOW: 
 ARCHIBALD FULLARTON AND CO.; 
 
 MACLACHLAN & STFAVART, EDINBURGH; ORP^ & SMITH, LONDON. 
 MDCCCXLIII. 
 

 BOSTON COLLEGE 
 
TO THE 
 
 BRITISH ASSOCIATION 
 
 FOR THE ADVANCEMENT OF SCIENCE, 
 
 THE FOLLOWING TREATISE 
 
 ON THE 
 
 CAUSES AND PRINCIPLES OF METEOROLOGICAL PHENOMENA, 
 
 WITH THE TWO ANNEXED ESSAYS, 
 
 IS RESPECTFULLY DEDICATED BY 
 
 THE AUTHOR. 
 
PREFACE. 
 
 Among all the Sciences, there is none which so 
 frequently, or so generally obtrudes itself upon the 
 attention of mankind, or is so often the subject of 
 conversation, as that of which we are about to treat. 
 But though this be the case, there is no science 
 which presents such a list of familiar phenomena, 
 that have hitherto defied all attempts at explanation. 
 In the following Treatise, a variety of new views and 
 explanations of meteorological phenomena are ad- 
 vanced; and it is principally on account of these, that 
 this volume is printed. 
 
 Besides the Treatise on the Causes and Principles 
 of Meteorological Phenomena, two Essays are like- 
 wise published. One of these contains a compila- 
 tion of the more important facts and information, 
 collected from various sources, relative to Marsh 
 Fevers, a knowledge of which may be useful, in 
 preserving the lives of many who have occasion to 
 visit our colonial settlements in the East or West 
 
M PREFACE. 
 
 Indies, or other countries where such diseases pre- 
 vail. The other is an Exposition of the Erroneous 
 Nature of Mr Owen's Plan for ameliorating the 
 Condition of Mankind, accompanied with Observa- 
 tions on the Measures and Policy calculated to pro- 
 mote that desirable Object. These two Essays are 
 selected from a variety of papers read by the Author 
 to a Literary Society in Glasgow, in consequence of 
 their affording a greater amount of information on 
 the subjects of which they profess to treat, than any 
 of the others. 
 
CONTENTS. 
 
 Page 
 
 Introduction, . . . . . . 1 
 
 Chap. I. — Of the Atmosphere, 
 Height of the atmosphere, 
 Its specific gravity and density, 
 Its composition, .... 
 
 Its mean pressure, and the proportions of its elements 
 
 permanent, .... 
 
 Its colour, ..... 
 
 Its capacity for moisture. 
 Diminution of temperature upon ascending perpendic 
 
 larly, ..... 
 
 Source whence the atmosphere is supplied with humidity, 
 Laws by which evaporation is regulated. 
 Reasons why the atmosphere is usually more or less under 
 
 saturated with humidity, 
 Mean hygrometric state of the atmosphere. 
 
 Chap. II — Of the Classification of Clouds, 
 
 Of the Cirrus or Curl-cloud, . . . ' 
 
 Of the Cumulus or Stacken-cloud, 
 
 Of the Stratus or Fall-cloud, 
 
 Of the Cirro-cumulus or Sonder-cloud, 
 
 Of the Cirro-stratus or Wane-cloud, 
 
 Of the Cumulo-stratus or Twain-cloud, 
 
 6 
 
 7 
 8 
 
 10 
 17 
 
 20 
 
 21 
 30 
 
 33 
 34 
 35 
 37 
 
 38 
 39 
 42 
 
 Of the Cumulo-cirro'Stratus, or Nimbus, or Rain-cloud, 44 
 
Vlll CONTENTS. 
 
 Vagf 
 
 Chap. III. — On the Causes and Principles which determine 
 
 the formation of Clouds, . . . .46 
 
 Circumstances in which clouds are formed, arranged under 
 four heads, and which are subsequently denominated 
 causes of their formation, . . . .40 
 
 Of the first cause of the formation of clouds, viz. when a 
 diminution of the atmospheric temperature, unaccom- 
 panied by atmospheric rarefaction or transportation, 
 takes place, . . . . .47 
 
 Of the second cause of the formation of clouds, viz. when 
 a diminution of the atmospheric temperature, arising 
 from atmospheric rarefaction, takes place, . . 60 
 
 Of the third cause of the formation of clouds, viz. when a 
 diminution of the atmospheric temperature, arising 
 from the transportation of air from a warm to a cold 
 climate by the agency of winds, takes place, . 80 
 
 Of the fourth cause of the formation of clouds, viz. when 
 an intermixture, and consequent reduction to a mean 
 temperature, of different portions of air saturated or 
 nearly saturated with humidity, and previously of 
 different temperatures, takes place, . . .86 
 
 Reasons why windy weather is productive of clouds and 
 rain; and why a prevailing stillness in the atmosphere 
 is favourable to dry weather, and a cloudless sky, . 103 
 
 Objections to the preceding opinions answered ; and points 
 
 of difficult solution hypothetically explained, . 107 
 
 Chap. IV. — On Circumstances erroneously supposed to pro- 
 duce Clouds, . . . . .121 
 
 Atmospheric intermixture, produced by contrary winds, 
 
 erroneously supposed to produce clouds, . .121 
 
 The collision of the upper and lower halves of the atmo- 
 sphere erroneously supposed to produce clouds, . 121 
 
 A change of wind erroneously supposed to produce clouds, 124 
 
 The periodic succession of weather in warm latitudes de- 
 scribed, . . . . . .135 
 
 Cause of the rainy season in intertropical climates hypo- 
 thetically explained, . . . .138 
 
CONTENTS. 
 
 IS 
 
 Chap. V. On the Causes and Principles which determine 
 
 the structure, suspension, elementary differences, and 
 dissolution of clouds; together with a new hypothetical 
 explanation of the cause of thunder, and the electriza- 
 tion of Clouds, ..... 
 
 Of the Structure of clouds, .... 
 
 Of the Suspension of clouds, .... 
 
 Of the Elementary Differences of clouds, 
 
 Of the Dissolution of clouds ; and of variations in the 
 capacity of the air for dissolving moisture, and sus- 
 pending vesicles, ..... 
 
 Of Thunder, and the Electrization of clouds, 
 
 Ghap. VI Of Rain, Snow, Sleet, Hail, Dew, Hoarfrost, 
 
 and Falling Mist, 
 Of Rain, 
 Of Snow, 
 Of Sleet, 
 Of Hail, 
 
 Of Dew and Hoarfrost, 
 Of Falling Mist, 
 
 Page 
 
 152 
 152 
 155 
 163 
 
 172 
 
 178 
 
 196 
 196 
 213 
 215 
 215 
 222 
 224 
 
 Chap. VII. — On the Causes and Principles which regulate 
 and determine the variations of temperature 07i the 
 earth's surface, . . . . .227 
 
 Of the mean temperature as affected by difference of lati- 
 tude, both by sea and land, . . . 227 
 
 Of the time when the maximum, minimum, and mean an- 
 nual temperatures occur in the atmosphere, and also 
 at different depths below the surface of the ground, 229 
 
 Of the variations in the temperature of water, at different 
 
 depths, &c. . . . . .231 
 
 Of the maximum, minimum, and mean diurnal temper- 
 atures, ...... 233 
 
 Of the mean annual temperature in different latitudes, . 236 
 
 Of the causes which modify the mean annual temperature 
 on land in different latitudes. — Of the line of perpetual 
 congelation and glaciers, .... 240 
 h 
 
CONTENTS. 
 
 Page 
 
 Of the decrement in the mean annual temperature, upon 
 receding from the ocean to the north of the 30th par- 
 allel of latitude, and of isothermal lines, . . 247 
 
 Of the increment in the mean annual temperature upon 
 receding from the ocean, within the 30th parallel of 
 latitude, ...... 255 
 
 Of the mean temperature of America relative to Ihat of 
 
 Europe, . . . • • • 256 
 
 Of the coldness of Europe in ancient times. — Of modifica- 
 tions in the temperature of the ocean in different 
 places, &c. . . . • .258 
 
 Of the diminution in the annual range of temperature upon 
 
 approaching the ocean, &c. . . . 260 
 
 Of Professor Lyell's hypothesis regarding the variation in 
 the mean temperature, as affected by the proportions 
 of land and water, . . . . 26 1 
 
 Of temperature as affected by wind, by atmospheric still- 
 ness, by clouds, by cities, by the falling of rain, &c. 262 
 
 Of the lowest and highest atmospheric temperatures hitherto 
 
 observed, &c. . . . . . 267 
 
 Chap. VIII. — On the Causes and Principles which produce 
 winds, and which regulate and determine their direc- 
 tion, velocity, a?id characteristic qualities, 
 
 Preliminary observations explanatory of the cause, direc- 
 tion, and velocity of winds, so far as they result from 
 differences in the temperature of the atmosphere, 
 
 Of the Regular or Trade-wind, 
 
 Of Periodic Winds. — Of Sea and Land breezes. 
 
 Of Monsoons, 
 
 Of the Etesian Wind, 
 
 Of the Ornithian Wind, 
 
 Of Irregular Winds, 
 
 Of the Hurricane or Typhon, 
 
 Of the Whirlwind, 
 
 Of the Waterspout or Syphon, 
 
 Of Pillars of Sand, 
 
 Of Hot Winds, 
 
 269 
 
 269 
 283 
 287 
 291 
 295 
 295 
 297 
 317 
 325 
 329 
 331 
 332 
 
CONTENTS. Xi 
 
 Pag-e 
 
 Of the Sirocco, . . . . . 333 
 
 Of the Harmattan, . . . . . 334, 
 
 Of the Simoom, . . . . . 334 
 
 Of the characteristic qualities of Winds, with directions 
 
 for avoiding their injurious effects, . . . 337 
 
 Of the uses of Winds, . . - . . . 342 
 
 Chap. IX. — On Prognostications of the Weather, with ex- 
 planations of the principles on which they depend, 344 
 Of Prognostications founded on past experience, . 344 
 
 Of Barometrical Prognostications, . . . 345 
 
 Of Prognostications of the Weather by means of Hygro- 
 meters, . . . . . . 360 
 
 Of Prognostications of the Weather from the appearances 
 
 of Clouds, ..... 364 
 
 Of Prognostications of the Weather from the colour of the 
 
 sky, and the appearances of the heavenly bodies, . 366 
 Of Prognostications of the Weather from the direction and 
 
 force of the Wind, . . . .371 
 
 Of Prognostications of the Weather from the moon's age, 374 
 Of the Prognostications of the Rainbow, . . 377 
 
 Of the Prognostications of a cold and also of a mild winter, 378 
 Of Cycle Prognostications, .... 382 
 
 Chap. X. — Of rare and imperfectly understood Meteorologi- 
 cal Phenomena, . . . . . 392 
 
 Of the Ignis Fatuus, ..... 392 
 
 Of Falling Stars, . . . . .394 
 
 Of Fireballs and Meteoric Stones, . . .395 
 
 Of Dry Fogs, ...... 404 
 
 Of Halos, Parhelia, or Mocksuns and Mockmoons, , 410 
 
 Of the Mirage and unusual Refractions, . . 412 
 
 Of the Aurora Borealis, or Northern Lights, . . 415 
 
 A Summary of the more important information collected 
 from various sources, relative to Marsh Fevers ; with 
 observations on the various measures recommended for 
 the prevention of this class of Epidemics, . .431 
 
I CONTENTS. 
 
 Prefatory Observations, . . . . 433 
 
 Summary of information relative to Marsh Fevers, . 438 
 
 Treatment of Patients, .... 487 
 
 Preventive measures, . . . . . 490 
 
 A?i Exposition of the Erroneous Nature of Mr Otvens 
 Plan for ameliorating the condition of ManMnd, ac- 
 companied with Observations on the Measures and Po- 
 licy/ calculated to promote that desirable Object, . 509 
 Appendix, ..... 643 
 Table oe Temperatures, .... 645 
 
 ERRATA. 
 
 Page 18, line 22, for " 5 inches," read " 4 inches." 
 — 448, — 25, for " Gottingen," — " Gotteiiburg." 
 
 4 
 
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 'AiiteurcUc Ciir^ 
 
 ]5J T A 
 
 R C 
 
 I C 
 
 E A 
 
 F 
 
INTRODUCTION. 
 
 Meteorology is that department of Physical 
 Science which treats of Atmospheric Phenomena. It 
 comprehends a considerable number of subjects ; and 
 each of these contains a great variety of details. Se- 
 veral of the phenomena to be treated of are so mu- 
 tually dependent upon each other, that with a view to 
 explain their causes, it is difficult to decide upon what 
 arrangement ought to be adopted. For instance, 
 variations of temperature on different parts of the 
 earth's surface disturb the atmospheric equilibrium, 
 and give rise to aerial currents ; while, on the other 
 hand, aerial currents, according as their direction is 
 from a cold or a warm climate, produce important al- 
 terations in the temperature of the incumbent atmo- 
 sphere. Again, variations in the atmospheric tempera- 
 ture are principally instrumental in the formation and 
 dissolution of clouds ; while, on the other hand, the 
 existence of clouds reduces the temperature of the 
 subjacent atmosphere during day and summer, while 
 it augments it during night and winter. In such cases, 
 it is immaterial which subject is first considered. 
 
 A 
 
INTRODUCTION. 
 
 Perhaps the following arrangement is as well calcu- 
 lated to render the various phenomena treated of in- 
 telligible, as any other. Without farther introduction, 
 we proceed with our subject. 
 
ON THE CAUSES AND PRINCIPLES 
 
 METEOROLOGICAL PHENOMENA. 
 
 CHAPTER I. 
 
 OF THE ATMOSPHERE ITS HEIGHT DENSITY COMPOSI- 
 TION — COLOUR CAPACITY FOR MOISTURE DIMINUTION 
 
 OF TEMPERATURE UPON ASCENDING PERPENDICULARLY, 
 TOGETHER WITH AN EXPLANATION OF THE MORE OBVIOUS 
 REASONS WHY THE ATMOSPHERE IS USUALLY MORE OR 
 LESS UNDERSATURATED WITH HUMIDITY. 
 
 The globe which we inhabit is every where sur- 
 rounded by a thin, invisible, elastic fluid, called the 
 air, or atmosphere. From the duration of twilight, 
 arising from the refraction of light, and also from 
 calculations relative to the rarefaction of air, consider- 
 ed in conjunction with the effect of increasing cold 
 as we ascend, in diminishing the elasticity of gaseous 
 particles, it has been concluded, that the atmosphere 
 of our earth cannot extend to a greater altitude than 
 45 miles above the level of the sea. About this de- 
 gree of elevation, it has been estimated, that the 
 gravity of the air will equal its elasticity; and this 
 of itself will limit and prevent its farther extension. 
 Farther, from the expansibility of air by means of heat. 
 
4 ON THE CAUSES AND PRINCIPLES 
 
 considered in conjunction with the similarity of the 
 mean barometrical pressure at the level of the sea in 
 all latitudes, which indicates a sameness in the abso- 
 lute amount of air incumbent over all latitudes, it has 
 been concluded, that the greatest elevation of the at- 
 mosphere is in the equatorial, or warmest regions of 
 the earth ; and that its elevation gradually diminishes 
 towards the polar, or coldest regions. 
 
 Air, when the barometer stands at 30 inches, and 
 the thermometer at 60°, (which, in similar estimates, 
 is always understood when nothing different is men- 
 tioned,) is 828 times hghter than water ; and its spe- 
 cific gravity in such circumstances is usually denoted 
 1.000. Owing to the inferior aerial strata having to 
 bear the weight of all those above, the density of the 
 atmosphere has been found, in ascending perpendicu- 
 larly, to diminish in the ratio of compression. The 
 density, therefore, decreases in geometrical progres- 
 sion, while the height increases in arithmetical pro- 
 gression. From this circumstance it is obvious, that 
 though the atmosphere extends to the height of 45 
 miles, the great bulk of it is contained within a com- 
 paratively limited distance from the earth's surface. 
 It has been estimated, that on reaching the perpen- 
 dicular altitude of 18,000 feet above the level of the 
 sea, one-half of the atmosphere is surmounted. And, 
 accordingly, a barometer at such an elevation would 
 stand at 15 inches, while underneath, at the level of 
 the sea, it stood at 30 inches. 
 
 Though the air we breathe was formerly considered 
 a simple substance, it is now known to be a compound. 
 Its constituents are nitrogen, oxygen, and carbonic 
 
OF METEOROLOGICAL PHENOMENA. 6 
 
 acid gases, and aqueous vapour, existing in a state, 
 not of chemical combination, but of uniform intermix- 
 ture, with each other. Of the gases, nitrogen and 
 oxygen are its principal elements ; the proportions 
 being 79 parts of the former to 21 of the latter, by 
 bulk ; and 76.701 to 23.299, by weight. The pro- 
 portion of carbonic acid is very small, varying accord- 
 ing to different estimates, (for it is difficult to ascer- 
 tain its precise amount,) from g-^th to j^th part of the 
 other two gases. The proportions of the two prin- 
 cipal gaseous elements of the atmosphere, nitrogen 
 and oxygen, are the same relatively to each other in 
 all latitudes, and, so far as observations have ex- 
 tended, at all heights, and in all places, where there 
 is a free communication with the external air. But 
 the proportion of carbonic acid relative to that of 
 the other two gases is said to vary, being greater 
 in summer than in winter, and during night than dur- 
 ing day. 
 
 Owing to the variations in the quantity of carbonic 
 acid in the atmosphere, its presence there was by 
 some considered accidental. Saussure, however, as- 
 certained that it existed in the atmosphere at the top 
 of Mont Blanc, 15,662 feet high, in similar propor- 
 tion as at the level of the sea. And Gay Lussac, 
 who ascended at Paris, in a balloon, to the height of 
 22,960 feet, the greatest ever reached by man, analyzed 
 air which he had obtained at that elevation, and found 
 that the relative proportions of its gaseous elements, 
 including the carbonic acid, were the same as at the 
 surface of the earth. These observations have suffi- 
 ciently established the fact of carbonic acid being a 
 
6 ON THE CAUSES AND PRINCIPLES 
 
 permanent constituent of the atmosphere, notwith- 
 standing its alleged variableness in quantity. 
 
 The relative proportion of aqueous vapour con- 
 tained in the atmosphere is extremely variable, and is 
 regulated in a great measure by the temperature of 
 the air. It appears from Saussure's experiments, that 
 a cubic foot of air, of the temperature of 66°^ is able 
 to hold, in invisible solution, 11 or 12 grains of water. 
 Now, as the weight of the cubic foot of air at the 
 above temperature, and under an atmospheric pressure 
 equal to 30 inches of mercury, is about 570 grains, 
 air at the temperature of dd" is capable of dissolving 
 about a 50th part of its own weight of water. After 
 making allowance for the rapid diminution in the 
 capacity of the air for moisture, as its temperature 
 lowers in ascending perpendicularly, it has been 
 estimated, that in Great Britain, during summer, the 
 weight of water present in the atmosphere frequently 
 amounts to g^th of the whole ; whereas, during winter, 
 it often does not exceed g~th of the whole. In warm 
 latitudes, the weight of aqueous vapour contained in 
 the atmosphere is frequently double what it is, during 
 summer, in Great Britain ; and, on the other hand, 
 in the polar regions, during winter, the proportion is 
 extremely small, in comparison with what it ever is in 
 the temperate climate of Britain. Dr Dalton sup- 
 poses that the medium quantity of vapour held in solu- 
 tion by the atmosphere may amount to ,^th of its bulk. 
 
 The mean pressure of the atmosphere seems to have 
 undergone no change since observations were first 
 made with the barometer. From a meteorological 
 journal kept by the celebrated Mr Locke, at Gates, 
 
OF METEOROLOGICAL PHENOMENA. 7 
 
 in Essex, the mean annual pressure for the year 1692, 
 was 29.58, which is nearly the mean height observed 
 in every quarter of the globe at present, after making 
 allowance for the altitude of the place of observation 
 above the level of the sea. A similar remark applies 
 to the permanency of its constituent proportions. No 
 alteration, in this respect, has taken place since air 
 has been correctly analyzed. Hence, notwithstanding 
 the absorption, and evolution of the several elements 
 of the atmosphere, constantly going on during the 
 growth and decay of vegetables ; and likewise during 
 the support of combustion, and animal life, and all 
 other chemical processes, whether natural or artificial j 
 it is inferred, that the amount of atmosphere sur- 
 rounding the globe, and the proportions of its several 
 elements are permanent quantities, regulated by fixed 
 though unknown laws ; and resulting probably from 
 properties permanently inherent in the atmospheric 
 materials themselves. If heat be the principal agent 
 in determining the proportion of matter that exists in 
 the gaseous state around the earth, (as it probably is, 
 though its influence in this respect may be also as- 
 sisted by light and electricity,) the permanency in the 
 amount of atmosphere must be ascribed to the mean 
 temperature of the globe, considered as a whole, be- 
 ing continually the same ; and to the attractive forces 
 mutually subsisting between the atmospheric elements 
 and heat, and all other terrestrial materials, being also 
 permanently the same. 
 
 The blue colour of the sky was formerly supposed 
 to be owing to the visibility of the atmosphere when 
 viewed in mass ; but from later observations it ap- 
 
8 ON THE CAUSES AND PRINCIPLES 
 
 pears, that what was attributed to the whole com- 
 pound, belongs exclusively to one of its constituents, 
 viz. the aqueous vapour; and it is now thought that 
 its gaseous elements are altogether colourless and in- 
 visible. Upon this point Dr Thomson says, " the 
 blue colour of the sky is occasioned by the vapours 
 which are always mixed with air, and which have the 
 property of reflecting the blue rays more copiously 
 than any other. This has been proved by the experi- 
 ments which Saussure made with his cyanometer at 
 different heights above the surface of the earth. He 
 found that the colour of the sky always corresponds 
 with a deeper shade of blue the higher the observer 
 is placed above the earth's surface. Consequently, 
 at a certain height, the blue will disappear altogether, 
 and the sky appear black, that is to say, will reflect 
 no light at all." Saussure accordingly found that the 
 sky, when viewed perpendicularly upwards from the 
 top of Mont Blanc, appeared nearly jet black, that is, 
 reflected almost no light. This he ascribed to the 
 extremely small amount of aqueous vapour existing in 
 the atmosphere above that elevation. Dr Thomson 
 likewise remarks, that the colour of the sky becomes 
 always lighter in proportion as the amount of vapours 
 mixed with the air increases, and I may be allowed to 
 add, in proportion as they are less thoroughly dis- 
 solved thereby. Hence it is evident that the colour 
 of the sky is produced by them. 
 
 As the meteorological phenomena of most frequent 
 occurrence, and which, on that account, it is of most 
 importance to understand, depend upon the relation 
 subsisting between the temperature of the atmosphere 
 
OF METEOROLOGICAL PHENOMENA. 9 
 
 and the amount of aqueous vapour which it is capable 
 of holding in a state of invisible solution, we shall here 
 notice the principal facts explanatory thereof. 
 
 If air contained in a close vessel be allowed to 
 communicate freely with a surface of water beneath, 
 and contained in the same vessel, it is usually found 
 that a portion of the water slowly disappears, by as- 
 suming the state of invisible vapour intermixed with 
 the air in the vessel. If the temperature remain sta- 
 tionary, evaporation by and by ceases. If the tem- 
 perature be augmented after evaporation has ceased, 
 an additional portion of the water begins again to dis- 
 appear by vaporization. If, on the other hand, the 
 temperature be gradually lowered after evaporation 
 has ceased, a portion of the water previously vapor- 
 ized is gradually precipitated ; and if the reduction of 
 temperature be stopped at any point, deposition of 
 moisture simultaneously ceases. And so on for every 
 increment, or decrement of temperature. The utmost 
 amount of water which air at any given temperature 
 can hold in invisible solution, is called its capacity for 
 moisture j and air so loaded with moisture, is said to 
 be saturated therewith. The point of saturation, in 
 reference to its indicating the degree of atmospheric 
 humidity, at which, during a gradual reduction of tem- 
 perature, the precipitation of moisture in the forms of 
 dew, mist, or clouds, commences, is also called the 
 dew point, or point of deposition or precipitation. 
 
 As the capacity of air for moisture varies with its 
 temperature, the attention of philosophers has been 
 directed to ascertain the relative ratio of variation. 
 Different results have been obtained by different ex- 
 
 B 
 
10 ON THE CAUSES AND PRINCIPLES 
 
 perimenters, which it is unnecessary separately to 
 particularize. All we mean to do, in order to com- 
 municate a general understanding of this, and other 
 meteorological phenomena, where the results obtained 
 by different experimenters vary, is to adopt either one 
 of the results, or a mean estimate of the more im- 
 portant of them, as an approximation to the truth. 
 Judo-ino- from the experiments which have been made, 
 it appears, that while the temperature of air increases 
 in arithmetical progression, its capacity for holding 
 moisture in invisible solution increases in geometri- 
 cal progression, or very nearly so. And for every 
 increment of temperature amounting to about 23.4 
 degrees by Fahrenheit's scale, the capacity of air for 
 moisture is doubled. Thus, if the capacity of air for 
 moisture be denoted 1 at the temperature of zero, it 
 will be 2, or double the zero capacity at the tempera- 
 ture of 23° .4 ; 4, or quadruple the zero capacity at the 
 temperature of 46°. 8 ; 8, or eight times the zero ca- 
 pacity at the temperature of 70°.2 ; and 16, or six- 
 teen times the zero capacity at the temperature of 
 93°.6, &c. 
 
 It has been ascertained that the temperature of the 
 atmosphere in all latitudes diminishes on ascending 
 perpendicularly from the level of the sea ; but the 
 rate of diminution, as determined by different ob- 
 servers, and even by the same observers at different 
 times and places, varies greatly. It appears also that 
 the rate of diminution is more rapid in summer than 
 in winter. Of this latter fact Sir John Leslie, in the 
 article CUmate,in the Supplement to the Encyclopaedia 
 Britannica, gives the following satisfactory explana- 
 
OF METEOROLOGICAL PHENOMENA. 11 
 
 tion : — *' Since the heat derived from the sun is 
 chiefly accumulated at the surface of the earth, the 
 changes of temperature which take place through the 
 year in the elevated strata of our atmosphere must 
 evidently be less than what are experienced below. 
 The lofty tracts of air remote from the primary scene 
 of action, preserve nearly an equable temperature, 
 and scarcely feel the extreme heat of summer, or win- 
 ter's frost. In ascending the atmosphere, the de- 
 crease of warmth is hence more rapid in the fine sea- 
 son, and more slow in the darkened period of the 
 year." 
 
 Besides the cause above assigned for the different 
 results obtained by different experimenters, there are 
 obviously a variety of other modifying circumstances, 
 the separate or conjoint influence of which, in con- 
 sequence of their variable and uncertain nature, it is 
 impossible accurately to appreciate. The more im- 
 portant of these are as follow : 1st, The commu- 
 nication upwards, whether by calorific radiation, re- 
 flection, conduction, or aerial convection,* of the 
 ever-varying diversity of temperature, to which land 
 and water relatively to each other, are in different 
 climates subjected, during day and night, and the dif- 
 ferent seasons of the year. 2d, The transportation 
 of air from warmer, or from colder latitudes, by means 
 
 * Convection is a very suitable term introduced by meteorolo- 
 gists to denote the power which one body has in carrying another 
 along with it. Thus clouds and vapours are carried along with 
 the atmospheric current ; and aerial convection in the text above, 
 means, the power of air, when its specific gravity is diminished by 
 heat, to carry that heat along with it in its ascent. 
 
1-2 ON THE CAUSES AND PRINCIPLES 
 
 of atmospheric currents. 3cl, The evolution of heat 
 which accompanies the formation of clouds; and, on 
 the contrary, its absorption, when clouds and mists are 
 converted into invisible vapour. 
 
 There is even some reason to believe, that the 
 average ratio of decrease of temperature is not the 
 same at different altitudes. Playfair remarks that the 
 decrease seems to be somewhat slower, but not very 
 considerably, as we ascend. And Dr Prout, in his 
 * Bridgewater Treatise,' says, " some late researches 
 have rendered it probable, that while, at different 
 heights, the rate of the decrease of temperature is 
 uniform, the rate of altitude increases constantly, and 
 according to laws very similar all over the world; that 
 is to say, supposing the first 252 feet are equal to one 
 degree; the second degree will be equal to 255 feet; 
 the third to 258; the fourth to 261 ;" &c. Humboldt 
 found in ascending, that the ratio of decrement was 
 less in the region of the air where clouds were form- 
 ed, than what it was nearer the surface of the earth; 
 and that it again became greater at a higher altitude. 
 This he properly ascribed to the evolution of heat, 
 which accompanies the formation of clouds. From 
 the various results obtained by different persons at 
 different times and places, with a view to determine 
 this point, meteorologists are now unanimous in 
 adopting one degree of Fahrenheit as the mean rate 
 of decrement for every 300 feet of perpendicular as- 
 cent, and extending to all attainable altitudes. Hence 
 we see, that from this cause, the mean temperature of 
 the atmosphere at the top of a mountain 3000 feet 
 high, should be 10 degrees lower than at its base. 
 
OF METEOROLOGICAL PHENOMENA. 13 
 
 And at the top of Mont Blanc, which is 15,662 feet 
 high, the mean temperature should be 52j degrees 
 lower than at the level of the sea in the same latitude. 
 
 Two causes have been assigned for the diminution 
 of temperature in ascending perpendicularly from the 
 earth's surface. The first is, that owing to the per- 
 meability of the atmosphere to the solar rays, the heat 
 thereby imparted to the earth, is absorbed, and accu- 
 mulated at, and near its surface ; and only slowly recom- 
 municated to the incumbent atmosphere. Hence, it 
 is supposed, that as a less and less amount of the 
 solar heat accumulated at the earth's surface is impart- 
 ed to the atmospheric strata, according as they be- 
 come more distant from the seat of accumulation; 
 the temperature of the atmosphere, in receding per- 
 pendicularly from the earth's surface, must undergo a 
 gradual diminution. 
 
 The preceding explanation is exceedingly unsatis- 
 factory, as will be evident by referring to analogical 
 phenomena. Thus when the general temperature is 
 increasing, whether in consequence of radiation from 
 the sun, a fire, or any heated body, it is found, that 
 the surface of all solids exposed to such calorific radi- 
 ation, acquires a higher temperature, that is, heats 
 faster, than the air around them, and through which 
 the heat radiates. And on the contrary, during the 
 time that the temperature is upon the decline, the 
 surface of all solids stands at a lower temperature, 
 that is, cools faster, than the air around them. Now 
 this case is exactly analogous to the one under con- 
 sideration. The surface of the earth is alternately 
 heating and cooling during day and night, and also 
 
14 ON THE CAUSES AND PRINCIPLES 
 
 during summer and winter. When heating during 
 day or summer, its surface is warmer than the air 
 immediately incumbent; but when cooling during 
 night or winter, it is colder. And from Dr Wells* 
 observations it appears, that the excess of coldness of 
 the earth's surfece during night or winter, as well as 
 the excess of heat during day or summer, is slowly 
 communicated to the air immediately incumbent, and 
 in proportion to its proximity. Thus it was found, 
 that during clear calm nights, the temperature of the 
 atmosphere, instead of sinking, actually rose, and that 
 with considerable rapidity, from the surface of the 
 earth to the height of 220 feet above it; and how 
 much higher was not ascertained, in consequence of 
 observations not being extended to greater altitudes. 
 When this fact is considered in conjunction with the 
 circumstance of the rapidity with which the tempera- 
 ture of the higher atmospheric strata, would be as- 
 similated to that of the lower by means of aerial con- 
 vection, were there no counteractive cause, it is ob- 
 vious, that the explanation above given, though it may 
 account for slight variations in the ratio, in which tem- 
 perature decreases upon ascending perpendicularly 
 during day and night, and during summer and winter, 
 does not at all account for the constant mean rate of 
 decrement observed in ascending perpendicularly all 
 over the surface of the globe, and extending to all 
 attainable heights. 
 
 The second cause assigned in order to explain the 
 fact under consideration, is the increase of capacity 
 for absorbing caloric, which air acquires, when sub- 
 jected to a gradual diminution of aerial pressure, ac- 
 
OF METEOROLOGICAL PHENOMENA. 15 
 
 cording as the amount and weight of the superincum- 
 bent atmosphere diminishes in ascending perpendicu- 
 larly. Upon this point, Dr Prout, in his Bridgewater 
 Treatise, page 270, says : " Dr Dalton, and after- 
 wards Sir John Leslie more completely, have at- 
 tempted to show, that the equilibrium of heat in an 
 atmosphere is obtained when each of its molecules, or 
 in other words, when the same weight of air, in the 
 same perpendicular column, is possessed of the same 
 quantity of heat. Now, since atmospheric pressure 
 diminishes with the height, according to a certain 
 law, it is obvious, that the same weight of air, at the 
 surface of the earth, and in the higher regions, will 
 occupy very different spaces. But since the absolute 
 quantity of heat is exactly the same in both portions, 
 it is likewise obvious, that in the higher regions of the 
 atmosphere, from the increased capacity of the air for 
 heat, the quantity of latent heat is augmented, while 
 the quantity remaining sensible becomes less. Hence 
 the temperature of the air diminishes as we ascend, 
 exactly in the proportion that its latent heat, that is to 
 say, its capacity for heat as produced by rarefaction, 
 increases." Dr Thomson, in his work on Heat and 
 Electricity, says : " It has been experimentally ascer- 
 tained, that as the volume of air increases, its specific 
 heat augments in the same proportion." And in a 
 subsequent passage, he says : " The same weight of 
 air, at all elevations above any place, contains exactly 
 the same quantity of heat. So that if a quantity of 
 air were suddenly transported from an elevated region 
 to the level of the sea, its density would be continually 
 increasing during its descent, while its specific heat 
 
lU ON THE CAUSES AND PRINCIPLES 
 
 would diminish in the same proportion, and, when it 
 reached the level of the sea, its temperature in conse- 
 quence would be just as high as that of other portions 
 of air in the same latitude and elevation. Air, there- 
 fore, does not feel cold in consequence of faUing from 
 an elevated situation, though this be an opinion com- 
 monly entertained, but in consequence of its being 
 suddenly transported from a more northerly to a more 
 southerly situation." 
 
 The preceding hypothesis seems to afford a per- 
 fectly satisfactory explanation of the fact under consi- 
 deration, were it not for an objection suggested by an 
 experiment, which we will here relate. If a thermo- 
 meter be suspended in the exhausted receiver of an 
 air-pump, or in a Torricellian vacuum, it stands at the 
 same degree of temperature as one suspended exter- 
 nally in the unrarefied atmosphere ; and variations of 
 temperature affect both thermometers in the same 
 manner, and ultimately to the same degree. It is true, 
 that upon exhausting the air suddenly, by means of 
 an air-pump, a delicate thermometer suspended in the 
 receiver sinks ; but then it very soon regains its former 
 temperature without any re-admission of air. Now, 
 judging from analogy, this latter circumstance seems to 
 indicate, that the permanent reduction of temperature 
 as we ascend in the atmosphere, is not owing to the 
 increased capacity of air for heat when its compression 
 or density is diminished ; for, if such were the case, 
 a correspondingly permanent reduction of temperature 
 should be exhibited, one would think, by a thermo- 
 meter in an exhausted, or partially exhausted receiver. 
 
 No attempt seems to be made by any writer whose 
 
OF METEOROLOGICAL PHENOMENA. 17 
 
 works I have consulted, to reconcile the phenomena 
 exhibited during the performance of the experi- 
 ment stated above, with the explanatory hypothesis 
 quoted from Prout and Thomson. Nevertheless, 
 from the corroboration which the hypothesis receives, 
 from the circumstance of the temperature of the air 
 actually diminishing as we ascend, in the proportion 
 that its capacity for heat, as produced by rarefaction, 
 increases ; and also from this circumstance explaining 
 what seems to be overlooked, viz. the otherwise inex- 
 plicable fact of the warmer air below having no ten- 
 dency to change places with the colder air above, so 
 long as the mean rate of decrement is preserved, I 
 am disposed to think, that the increased capacity of 
 the air for heat, according as the superior aerial com- 
 pression diminishes, is either the true cause, or rather 
 a constant and necessary concomitant of the true cause 
 of the mean rate of decrement of temperature, upon 
 ascending perpendicularly from the level of the sea. 
 
 When the humidity or dryness of the atmosphere 
 is mentioned, reference is made, not to the absolute 
 amount of moisture in the air, but to the amount in 
 relation to its capacity. The more undersaturated 
 the atmosphere is, the drier it is said to be ; and the 
 stronger is its influence in promoting evaporation from 
 moist surfaces. On the contrary, the nearer it ap- 
 proaches to saturation, the more humid it is ; and the 
 less its influence in promoting evaporation. 
 
 The parent source from whence the atmosphere, 
 when undersaturated, derives a supply of aqueous va- 
 pour, is the ocean ; and the process by which it is sup- 
 plied is called evaporation. It is true that from every 
 
 c 
 
18 ON THE CAUSES AND PRINCIPLES 
 
 moist land surf\ice evaporation also takes place. But 
 as the land itself derives its moisture from the atmo- 
 sphere, in the forms of rain, dew, &c. ; and as a con- 
 siderable proportion of the moisture which is precipi- 
 tated upon the land is returned to the ocean by means 
 of rivers, it is obvious that the land would soon become 
 thoroughly and permanently dried up, were it not sup- 
 plied with humidity from the ocean, through the 
 agency of evaporation and atmospheric currents. 
 
 Various attempts have been made to determine the 
 annual quantity of water which the land derives from 
 the ocean through the agency of atmospheric currents. 
 Some have endeavoured to ascertain this point by 
 calculating the amount of water evaporated from land 
 at a mean temperature, relative to the estimated 
 annual amount thereupon precipitated ; and others 
 have made estimates of the amount of water annually 
 returned to the ocean by means of rivers, relative to 
 the quantity precipitated from the atmosphere upon 
 the land drained by these rivers. Dr Thomson esti- 
 mates the annual amount of water (including dew, 
 vvhich he estimates at 5 inches,) precipitated upon the 
 land, and reduced to a mean for the whole surface of 
 Great Britain, to be about 36 inches ; while the 
 quantity evaporated may be about 32 inches ; |ths 
 therefore of the water annually precipitated upon this 
 island, he supposes, is again evaporated from the land, 
 and only ith is returned to the ocean by means of 
 rivers ; and of course only ^th is derived from the 
 ocean through the agency of atmospheric currents. 
 Dr Dalton, on the other hand, estimated the proportion 
 of water annually carried off by the rivers in England 
 
OF METEOROLOGICAL PHENOMENA. 19 
 
 and Wales, as amounting to 13 inches. The differ- 
 ence between these two estimates show how httle de- 
 pendence can be attached to them. Besides, in dif- 
 ferent latitudes, and even in diflferent countries in the 
 same latitude, the proportion evaporated relative to 
 what is condensed, must, for obvious reasons, vary 
 extremely ; and though the proportions applicable to 
 Great Britain could be ascertained, they would be 
 applicable no where else. In inland champaign 
 countries, in temperate latitudes, where little rain 
 falls, almost the whole water precipitated upon the 
 land will be again evaporated from it ; and hardly any 
 of it returned to the ocean by means of rivers. On 
 the other hand, in countries bordering upon the sea ; 
 and in small, or moderately sized islands, particularly 
 where the dechvity from the central parts of the land 
 towards the sea is considerable ; and where the rains 
 fall in great quantities at particular seasons, with long 
 intervals of dry weather ; the greater part of the wa- 
 ter precipitated from the atmosphere upon the land 
 will be returned to the ocean by means of rivers, and 
 only a moderate proportion of it evaporated. In short, 
 the circumstances of different countries are in this 
 respect so various, that no rules universally applicable 
 can be laid down. In general, however, provided 
 other things be equal, the proportion of water preci- 
 pitated upon the land which is returned to the ocean 
 by rivers, will be greater the colder and the calmer 
 the climate is ; also greater in proportion as the rains 
 are more copious for the latitude, and restricted to 
 particular seasons, so that the intervals of dry wea- 
 ther, (when, in consequence of the dryness of the 
 
20 ON THE CAUSES AND PRINCIPLES 
 
 ground, no evaporation is going on,) may be the 
 longer; and likewise greater, in proportion as the 
 land is better fitted for allowing the water to run off 
 speedily, whether in consequence of natural declivi- 
 ties, or artificial draining ; and vice versa. 
 
 Evaporation, as we before stated, is the name given 
 to the process by which the atmosphere is replenished 
 with humidity from moist surfaces underneath, when, 
 from causes hereafter to be mentioned, it has become 
 undersaturated. Now the laws by which evaporation 
 is regulated are as follow : — 
 
 1. It goes on with greater rapidity according as 
 the incumbent atmosphere is more undersaturated 
 with humidity ; and with diminishing rapidity as it 
 approaches saturation, at which point it ceases alto- 
 gether. 
 
 2. Supposing the atmosphere undersaturated to a 
 given extent, evaporation proceeds with greater ra- 
 pidity according as the evaporating surface becomes 
 warmer. And supposing the atmosphere saturated, 
 evaporation will, notwithstanding, commence so soon 
 as the temperature of the evaporating surface is raised 
 higher than that of the atmosphere. In fact, the 
 point of saturation at which evaporation ceases, is de- 
 termined, not by the temperature of the air, but by 
 that of the evaporating surface. But as the tempera- 
 ture of the air regulates the amount of vapour which it 
 can hold in invisible solution, all moisture evaporated 
 by means of heat applied to the evaporating surface 
 after the air is saturated, is condensed into the visible 
 form of mist, so soon as it is cooled down to the aerial 
 temperature by intermixture with the incumbent air. 
 
OF METEOROLOGICAL PHENOMENA. 21 
 
 3. Supposing the atmosphere undersaturated to 
 any given extent, evaporation proceeds with greater 
 rapidity according as the velocity of the wind in- 
 creases, for, in such circumstances, fresh undersatu- 
 rated portions of air are successively brought more 
 rapidly in contact with the evaporating surface. 
 
 Though air in communication with water has a 
 tendency to become saturated with moisture, yet 
 when hygrometric observations are made, it is ge- 
 nerally found that the atmosphere is more or less un- 
 dersaturated ; and accordingly, that a greater or less 
 reduction of temperature must ensue before any pre- 
 cipitation of humidity can take place. The cause of 
 this, and also of the circumstances which tend to bring 
 the atmospheric humidity up to the point of satura- 
 tion, and sometimes beyond it, so that precipitation 
 ensues, will be obvious, by considering the vicissi- 
 tudes of temperature to which the atmosphere is sub- 
 jected during the alternate succession of day and 
 night, and the different seasons of the year j and also 
 during the progressive movements of atmospheric 
 currents over land and water of different degrees of 
 elevation, and of different temperatures. 
 
 During night, the capacity of the atmosphere for 
 moisture, in consequence of the diminution of tem- 
 perature which then ensues, is considerably less than 
 during day. Hence, though the atmosphere during 
 day be considerably undersaturated with moisture, it 
 gradually approximates this degree of dampness as 
 the temperature declines upon the approach of night. 
 And provided it reaches the point of saturation pre- 
 vious to the coldest period of the night, the farther 
 
22 ON THE CAUSES AND PRINCIPLES 
 
 sinking of temperature causes precipitation of mois- 
 ture into the visible forms of dew, mist, and cloud ; 
 and consequently does not increase the atmospheric 
 dampness, hygrometrically speaking ; for in hygrome- 
 try, no estimate is made of moisture, except it be held 
 in invisible solution by the atmosphere. Now, sup- 
 posing the atmosphere to have reached the point of 
 saturation during the coldest period of the night, it 
 follows, that, as its temperature again rises, and its 
 capacity for humidity increases, upon the return, and 
 during the advance of day, the atmosphere must 
 gradually become more and more undersaturated. 
 And this result is not restricted to the atmosphere in- 
 cumbent upon the land : for even over the ocean, 
 (though in a less degree than over the land,) the at- 
 mosphere usually becomes hygrometrically drier dur- 
 ing day, in consequence of evaporation not being suf- 
 ficiently copious to supply the air with moisture so 
 rapidly as its capacity for it increases with the then 
 advancing temperature. These observations explain 
 the reason why night air is usually damper, and to 
 those whose constitutions are injured by a humid at^ 
 mosphere, more unwholesome than that of day. They 
 also explain the reason why more moisture is convert- 
 ed into clouds and mist, and precipitated upon the 
 surface of the earth in the forms of dew and rain dur- 
 ing night, than during day : and, upon a similar prin- 
 ciple, more during the fall of the year, when the 
 temperature and capacity of the air for moisture are 
 upon the decline, than during the opposite season, 
 when the temperature and capacity of the atmosphere 
 for moisture are advancing. 
 
OF METEOROLOGICAL PHENOMENA. 23 
 
 Again, when the wind blows from a cold towards a 
 warmer chmate, which, as will be subsequently ex- 
 plained, is its prevailing direction over the earth, 
 though not in this climate, the air, by communicating 
 with a progressively warmer surface, has its tempera- 
 ture and capacity for aqueous vapour more rapidly in- 
 creased, than it is supplied with humidity by evapora- 
 tion. This explains the reason why northerly winds, 
 in northern latitudes, are usually drier, and of course 
 promote evaporation from all moist surfaces more 
 rapidly than those of equal thermometric temperature 
 from the south. The piercing, refrigerating, and 
 withering influence commonly ascribed to north and 
 north-east winds in this island, particularly during 
 the spring of the year, is owing, not so much to their 
 absolute thermometric coldness, (though that too has 
 its influence,) as to their undersaturated state of dry- 
 ness, and consequently to their greatly increased effect 
 in abstracting heat from the human body, and from all 
 other moist surfaces, by accelerating evaporation. 
 
 When the wind, on the contrary, blows from a warm 
 towards a colder latitude, and has its temperature 
 slowly reduced by communicating with a progressively 
 colder surface underneath, its capacity for aqueous 
 vapour is simultaneously diminished. Hence the air 
 in such circumstances, though previously much under- 
 saturated, gradually approaches the point of satura- 
 tion. And if this hygrometric condition of the at- 
 mosphere goes on increasing, aqueous vapour begins 
 at length to be precipitated into the visible state of 
 clouds and mist, and subsequently descends to the 
 earth in the forms of rain, snow, &c. This is one rea- 
 
24 ON THE CAUSES AND PRINCIPLES 
 
 son why southerly winds, which in our northern latitude 
 blow from a warm towards a comparatively cold clim- 
 ate, are usually damper and more prolific of clouds 
 and rain than those from a northerly direction. 
 
 Ao-ain, when the wind blows from the ocean in 
 summer, particularly during its latter half, the atmo- 
 sphere becomes gradually undersaturated as it ad- 
 vances over the land ; and, upon the same principle, 
 when it blows in the contrary direction, viz. from the 
 land towards the ocean, during the opposite season of 
 the year, it in like manner gradually becomes under- 
 saturated as it approaches the ocean, and vice vei^sa. 
 The reason of these results will appear obvious by 
 comparing the annual range of temperature which the 
 surface of the land undergoes with that of the ocean. 
 
 In temperate latitudes, the annual range of heat to 
 which the surface of the Atlantic ocean is subjected, 
 is limited to about 9 degrees of Fahrenheit ; whereas, 
 that of the surface of the land, in corresponding lati- 
 tudes on the continent of Europe, at no great dis- 
 tance from the ocean, may be about 90 degrees. The 
 temperature of the ocean varies, therefore, no more 
 than about 4^ degrees from the mean for the latitude, 
 during the coldest and warmest periods of the year ; 
 whereas, that of the land varies about 45 degrees from 
 the mean annual temperature. In like manner, dur- 
 ing day and night, the temperature of the surface of 
 the ocean undergoes little variation, compared to that 
 of the land. And it may be laid down as a general 
 law, that in a given latitude, the nearer any place is 
 to the ocean, the more limited is the range of tem- 
 perature both daily and annually j and, on the con- 
 
OF METEOROLOGICAL PHENOMENA. 25 
 
 trary, the farther from the ocean, the more extensive 
 is the range of temperature. 
 
 Now, as the temperature of the surface of the ocean 
 varies but very little throughout the year, from the 
 mean degree of heat for the latitude, compared to that 
 of the land ; and as the temperature of the earth's 
 surface, whether it be land or water, is gradually com- 
 municated upwards to the incumbent atmosphere, it 
 follows, that an atmospheric current from the ocean 
 towards the land, during the summer half of the year, 
 or from the land towards the ocean, during the winter 
 half, is analogous to the instance previously given, of 
 a wind blowing from a cold towards a warmer climate. 
 In both cases, the air in its progress, by communicat- 
 ing with a warmer substance underneath, has its tem- 
 perature and capacity for moisture gradually increased. 
 And hence, unless counteracted by other causes, must 
 become more or less undersaturated, and, accordingly, 
 less liable to give birth to clouds and rain. 
 
 From the same premises, it follows, on the other 
 hand, that an atmospheric current from the land 
 towards the ocean, during the summer half of the 
 year, or from the ocean towards the land, during the 
 winter half, is analogous to the other previously given 
 instance, of a wind blowing from a warm towards a 
 colder climate. In both cases, the air in its progress, 
 by communicating with a colder surface underneath, 
 has its temperature and capacity for moisture gradually 
 diminished ; and hence, unless counteracted by other 
 circumstances, must have a tendency to get saturated 
 with moisture, and, accordingly, to become more liable 
 to give birth to clouds and rain. 
 
 D 
 
t2G ON THE CAUSES AND PRINCIPLES 
 
 These observations, in part, explain the reason why 
 a wind blowing from the ocean towards the land, dur- 
 ing the warmest period of the year, so seldom brings 
 rain, in comparison with what it does during the cold- 
 est season. They also explain the reason why a wind 
 blowing from the land towards the ocean, during 
 summer, may sometimes be found saturated with 
 moisture upon reaching the sea-coast, or within a short 
 distance of land ; whereas, when the wind blows from 
 the same direction during winter, it may be expected 
 almost invariably to be much undersaturated, and, 
 accordingly, to bring fair weather. 
 
 Again, when the wind blows over mountain ranges, 
 or elevated lands, its temperature and proportionate 
 capacity for moisture is reduced, as already stated, by 
 one degree for every 300 feet of perpendicular ascent. 
 Now, supposing, for the sake of illustration, that the 
 height of the elevated lands is 3000 feet, and that the 
 atmospheric current before reaching them is saturated 
 with humidity, it is obvious, that the lower stratum of 
 air, in surmounting such an elevation, must undergo a 
 reduction of temperature equal to 10 degrees ; and, 
 accordingly, moisture is converted in such quantity 
 into clouds, (which partly discharge themselves in rain 
 upon the earth's surface, and partly pass onwards with 
 the wind at a great altitude,) that after the same stratum 
 of the atmospheric current has crossed the elevated re- 
 gions, and regained its former low level and tempera- 
 ture, it ought to be 10 degrees of temperature undersa- 
 turated. This explains the reason why the atmosphere 
 is less humid, and why less rain falls to the leeward, than 
 to the windward of high lands and mountain ranges. . , 
 
OF METEOROLOGICAL PHENOMENA. 27 
 
 Upon similar principles, when winds blow over ex- 
 tensive tracts of dry land, where they encounter a 
 variety of the circumstances already enumerated, which 
 rob the air of a portion of its moisture, without being 
 proportionally replenished from a watery surface under- 
 neath, a greater or less degree of atmospheric under- 
 saturation is the usual result. Hence the reason why 
 near the coast on continents, (as is exemplified in the 
 United States of North America,) the air is more 
 humid, and more rain falls when the wind blows from 
 the ocean, than when it blows from the opposite direc- 
 tion, over an extensive tract of land. And, according 
 to the same principle, it may be laid down as a general 
 law, that the more remote any place is from the ocean, 
 provided other circumstances be equally favourable, 
 the more undersaturated with moisture ought to be the 
 usual character of the atmosphere, and the smaller the 
 annual amount of rain. 
 
 It may be here noticed, that when speaking of air 
 becoming undersaturated in consequence of passing 
 over extensive tracts of land, it supposes the surface 
 of such land, or at least a large proportion of it, to be 
 dry. When the surface of land is thoroughly wet, 
 and its temperature is as high as that of the ocean, 
 evaporation proceeds with as great rapidity from its 
 surface as from that of the ocean. And supposing a 
 thoroughly moistened land surface to be warmer than 
 that of the ocean, as is usually the case in the end of 
 summer, and beginning of autumn, evaporation from 
 its surface should go on more rapidly than from that 
 of the ocean. Besides, the saline ingredients of the 
 ocean render its waters less liable to evaporation; so 
 
28 ON THE CAUSES AND PRINCIPLES 
 
 that even from this cause alone, a land surface thor- 
 oughly moistened with fresh water, is supposed to sup- 
 ply aqueous vapour to an undersaturated atmosphere, 
 more speedily than the surface of the ocean. In form- 
 ing meteorological conclusions regarding the circum- 
 stances calculated to produce atmospheric dryness, 
 or dampness, it should therefore be always recollect- 
 ed, that a wind blowing over land thoroughly moisten- 
 ed by previous rainy weather, is not necessarily a dry 
 wind, unless some of the other circumstances before 
 stated, such as blowing from a cold direction, or over 
 elevated lands, render it so. In reality, such a wind, 
 so far as dryness or dampness is concerned, is much 
 the same as though it blew from the sea: the hygro- 
 metric condition of the atmosphere in both cases, 
 being usually very little above the point of saturation. 
 These observations explain the reason why, after con- 
 tinued wet weather, the chance of rain, other things 
 being equally favourable, is usually as great when the 
 wind blows from the land, as when it blows from the 
 ocean. They also explain the reason why, when the 
 wind changes, and blows from the sea, in continental 
 countries previously thoroughly dried by long droughts, 
 the first rains usually fall near the coast. And, pro- 
 vided the wind from the sea continues prevalent, 
 gradually as the land gets moistened to a greater and 
 greater distance from the sea, so as to become an 
 evaporating surface, capable of replenishing an un- 
 dersaturated atmosphere with humidity, so does the 
 rainy weather extend itself farther into the interior. 
 
 Having thus given an enumeration of the more 
 obvious circumstances which produce variations in the 
 
OF METEOROLOGICAL PHENOMENA. 29 
 
 hygrometric condition of the atmosphere, it need 
 hardly be remarked, that those circumstances may be 
 observed at different times and places acting either 
 in union with, or in opposition to, each other. In 
 the former case, their effect becomes more powerful; 
 in the latter, the influence of one cause neutralizes 
 that of another. In endeavouring, therefore, to ac- 
 count for the conditions of the atmosphere in refer- 
 ence to dryness and dampness, the circumstances 
 favourable to the one state, must be balanced against 
 those favourable to the other. For according as there 
 happens to be a more favourable combination of cir- 
 cumstances for producing the one effect or the other, 
 so is the result more certain; and the general char- 
 acter of the weather more strongly marked; and vice 
 versa. 
 
 When it is considered, that the hygrometric damp- 
 ness of the atmosphere is prevented from ever ex- 
 ceeding the point of saturation by the precipitation 
 of moisture which then commences; and, in accord- 
 ance with our previous observations, that a variety 
 of causes tending to reduce it below that point, are 
 in constant operation in one quarter or another; we 
 have a sufficient explanation of the fact of air, though 
 in free communication with the ocean, and other col- 
 lections of water on the earth's surface, being usually 
 more or less undersaturated. Hence the reason why 
 water exposed to the atmosphere usually evaporates 
 with more or less rapidity; a result which could not 
 take place, were the air previously saturated with 
 moisture, and its temperature as high as that of the 
 water. 
 
30 ON THE CAUSES AND TRINCIPLES 
 
 From the hygrometric observations made with a 
 view to ascertain the state of the atmosphere as to 
 dryness in various situations, and at different heights 
 above the level of the sea, it has been calculated, that 
 the mean point of deposition for the whole atmo- 
 sphere surrounding the globe, is about 6 degrees be- 
 low the mean temperature. Of course, it is to be 
 understood, that some proportion of the atmosphere 
 is at all times fully saturated with humidity ; but that 
 this is balanced by a larger proportion more or less 
 undersaturated beyond 6 degrees. The general result 
 therefore is, that the atmospheric temperature requires 
 to sink on an average 6 degrees, before moisture held 
 in invisible solution by the air, begins to assume the vi- 
 sible forms of mist and clouds; and also, before depo- 
 sition of humidity in the form of dew can commence. 
 
 From observations made in the years 1815 and 
 1818 it appears, that the mean quantity of moisture 
 in the atmosphere on any given day, corresponds, in 
 this climate, nearly with what would produce com- 
 plete saturation at the minimum temperature of that 
 day. Owing, however, to variations in the weather 
 from wet to dry, and the contrary, this coincidence 
 does not take place every day; but holds very nearly 
 in the means of the whole year. Thus the mean 
 point of deposition for each month in the year, cor- 
 responds very nearly with the mean minimum tem- 
 perature of the days throughout the month. 
 
 Proceeding upon the principle of the mean point 
 of deposition being 6 degrees below the capacity of 
 the mean temperature, the following table, * showing 
 
 * Hygrometry, — Edinburgh Encyclopaedia. 
 
OF METEOROLOGICAL PHENOMENA. 
 
 31 
 
 the mean amount of aqueous vapour, reduced to the 
 state of water contained in the atmospheric columns 
 for every 5 degrees of latitude from the equator to 
 either pole, has been calculated. 
 
 Lati- 
 tude. 
 
 Mean Tem. 
 perature. 
 
 Column of Water 
 equal to Column of 
 Vapour in Inches. 
 
 Lati. 
 tude. 
 
 Mean Tem- 
 perature. 
 
 Column of Water 
 equal to Column of 
 Vapour in Inches. 
 
 
 
 85. 
 
 8.315 
 
 50 
 
 53.3 
 
 2.882 
 
 5 
 
 84.6 
 
 8.112 
 
 55 
 
 48.8 
 
 2.468 
 
 10 
 
 83.4 
 
 7.809 
 
 60 
 
 44.5 
 
 2.124 
 
 15 
 
 81.4 
 
 7.326 
 
 65 
 
 40.6 
 
 1.854 
 
 20 
 
 78.7 
 
 6.717 
 
 70 
 
 37.3 
 
 1.647 
 
 25 
 
 75.4 
 
 6.037 
 
 75 
 
 34.6 
 
 1.495 
 
 30 
 
 71.5 
 
 5.315 
 
 80 
 
 32.6 
 
 1.391 
 
 35 
 
 67.2 
 
 4.611 
 
 85 
 
 31.4 
 
 1.332 
 
 40 
 
 62.7 
 
 3.968 
 
 90 
 
 31. 
 
 1.313 
 
 45 
 
 58. 
 
 3.385 
 
 
 
 
 By the preceding table it appears, that if the whole 
 aqueous vapour contained in the air at the equator 
 were condensed, and precipitated, it would cover the 
 surface of the earth only to the depth of 8.315 inches; 
 and that the amount diminishes more rapidly than the 
 mean temperature as we advance towards either pole. 
 
 In intertropical and temperate latitudes, it is pro- 
 bable that the calculations in the preceding table are 
 tolerably near the truth. But they are obviously very 
 erroneous in high latitudes, in consequence of the 
 mean temperature being taken at greatly above what 
 it ought to have been, as determined, in recent years, 
 by actual observation. It may be also mentioned, 
 that the above table, as well as all other hygrometric 
 estimates, gives merely the amount of aqueous vapour 
 held in a state of invisible solution by the atmosphere. 
 
32 ON THE CAUSES AND PRINCIPLES, &C. 
 
 and does not include the amount previously precipi- 
 tated, and suspended in the air in the visible forms of 
 clouds and mist. If the proportion of vapour con- 
 densed into the visible forms of mist or clouds were 
 to be estimated, in conjunction with what is held in 
 invisible solution, the air would have to be stated as 
 being frequently oversaturated with moisture. In 
 wet weather, for instance, when hygrometers indicate 
 that the air is saturated with humidity, the existence 
 of clouds indicates a degree of atmospheric oversatu- 
 ration, to the extent of moisture which the clouds con- 
 tain. The phrase oversaturation is, therefore, in this 
 point of view, correct enough; and to avoid circum- 
 locution, we shall on many occasions make use of it. 
 At the same time, as the amount of aqueous vapour 
 contained in the forms of mist and clouds cannot be 
 accurately ascertained, and does not affect the condi- 
 tion of the atmosphere, so as to indicate, when tested 
 by hygrometers, a degree of dampness beyond the 
 point of saturation, in estimates such as the one we 
 have been considering, it is perhaps as well omitted 
 altogether. 
 
CHAPTER II. 
 
 OF THE CLASSIFICATION OF CLOUDS, AND THE PHENOMENA 
 EXHIBITED DURING THEIR FORMATION, TOGETHER WITH 
 A DESCRIPTION OF THE VARIED APPEARANCES WHICH 
 THE DIFFERENT DENOMINATIONS PRESENT, AND OF THE 
 CHANGES WHICH THEY UNDERGO. 
 
 Notwithstanding the infinitely diversified figures 
 and appearances which clouds present, they have been 
 arranged by Howard into seven classes, and desig- 
 nated as follows : — The Cirrus, the Cumulus, the 
 Stratus, the Cirro-cumulus, the Cirro-stratus, the 
 Cumulo-stratus, and the Cumulo-cirro-stratus, or 
 Nimbus. Of these, the three first, viz. the Cirrus, 
 the Cumulus, and the Stratus, are considered primary 
 forms. The fourth and fifth, viz. the Cirro-cuinulus, 
 and the Cirro-stratus, are considered intermediate 
 forms, from their presenting appearances somewhat 
 between those of the primary clouds, of which their 
 names are respectively composed. The sixth and 
 seventh, viz. the Cumulo-stratus, and the Cumulo- 
 cirro-stratus, or Nimbus, are considered compound, 
 from being apparently formed by the union and trans- 
 formation of other denominations of cloud. 
 
 Rather than trust to my own very limited observa- 
 tions enabling me to describe the progressive forma- 
 tion, together with the varied appearances and changes 
 which the different classes of clouds above enumer- 
 
34 ON TIIK CAUSES AND PRINCIPLES 
 
 ated undergo, I will borrow largely, and frequently 
 without altering the language, from the article in the 
 Supplement to the Encyclopaedia Britannica, entitled 
 " Cloud." Adhering then to the usual arrangement, 
 we shall now proceed to describe, 
 
 1. The CiiTus, (see fig. 1.) or Curl-cloud. The 
 most usual form of this species of cloud resembles a 
 distended lock of hair. It consists of separate fibrous- 
 looking, or hair-like stripes of cloud, parallel to each 
 other, and not unfrequently curled, or slightly bent 
 towards one, and more rarely, towards both extremi- 
 ties. In appearance, it is the thinnest, the lightest, 
 and the most rarefied of all the denominations of 
 cloud ; and in conformity with its appearance, it oc- 
 cupies a more elevated region in the atmosphere than 
 any of the other kinds, floating usually, according to 
 Dalton, from 3 to 5 miles above the level of the sea. 
 
 This species of cloud is continually changing its 
 figure. After a continuance of clear weather, the 
 cirrus first makes its appearance in the form of a white 
 thread stretched across a portion of the sky. To this 
 line others are successively added laterally, so as ul- 
 timately to present the appearance of a number of 
 parallel white threads of cloud. This form is called 
 the linear cirrus. At other times, in addition to the 
 above, lines of the same kind are sent off" in oblique 
 or transverse directions, so that the cloud presents the 
 appearance of net-work. This species is called the 
 reticulated cirrus. " The comoid cirrus^ vulgarly 
 called by the country people of England, the mare's- 
 tail cloud, is however the proper cirrus. It has the 
 appearance of a distended lock of white hair, or of a 
 
OF METEOROLOGICAL PHENOMENA. 35 
 
 bunch of wool pulled out into fine pointed ends, from 
 whence it has derived its name, comoid. This form 
 of the cirrus is most commonly an accompaniment of 
 a variable state of the atmosphere, and often forebodes 
 wind and rain. In very changeable weather, the di- 
 rection of the tails of this kind of cirrus varies consi- 
 derably in the course of a few hours. When the tails 
 have a constant direction towards the same point of 
 the compass for any considerable time, it has been 
 frequently observed that a gale has sprung up from 
 the quarter to which they had pointed." 
 
 2. The Cumulus, (see fig. 7.) or Stacken-cloud, or 
 cloud of day, as it is sometimes called, is characterized 
 by a flattened base, and a heaped or cumulated super- 
 structure. It floats at a much lower level than the 
 cirrus, varying perhaps from 3000 feet to two miles 
 above the level of the sea. In its appearance it is the 
 most picturesque of all the denominations of cloud, 
 and when opposed to the sun, reflects from its piled- 
 up sides a brilhant white colour, as pure as that of 
 snow. 
 
 " The best time for viewing the progressive forma- 
 tion of the cumulus is in fine settled weather. If 
 we then observe the sky about the time of sunrise, or 
 soon afterwards, we shall see small specks of cloud 
 here and there in the atmosphere. These often ap- 
 pear to be the result of small gatherings, or concen- 
 trated points of the stratus or evening mist, which, 
 rising in the morning, grows into small masses of 
 cloud, while the circumjacent atmosphere becomes 
 clearer." 
 
 " As the sun rises these clouds get larger,— two or 
 
30 ON THE CAUSES AND PHINCIPLES 
 
 three which are near each other coalesce, — and at 
 length a large cloud is formed, which, assuming a 
 cumulated and irregularly hemispherical shape, has 
 received the name of cumulus or stacken-cloud. This 
 may properly be denominated the cloud of day, as it 
 usually subsides in the evening, in a manner which 
 forms the exact counterpart to its formation in the 
 morning. It breaks up into small fragments and 
 evaporates, and is succeeded again by the stratus or 
 fall-cloud, which has been called the cloud of night 
 by some writers, on account of the period in which it 
 prevails." 
 
 " There are some varieties in the forms of the 
 cumulus which deserve particular notice, as they 
 seem to be connected with electrical phenomena. In 
 some kinds of fine weather, when these clouds form 
 soon after sunrise, increase through the day, and sub- 
 side in the evening, they are of a more hemispherical 
 form than when they occur in changeable weather. 
 When these well-formed cumuli prevail during many 
 days together, the weather is settled, and the atmo- 
 spherical electrometer has been observed not to vary 
 much in its indications. These cumuli are whitish- 
 coloured, and reflect a fine strong silvery light when 
 opposed to the sun. The cumuli which are seen in 
 the intervals of showers are more variable in form ; 
 they are more fleecy, and have irregular protuberances. 
 Sometimes they are of a blackish colour, like the 
 clouds which the sailors call scud, and at other times 
 they seem of a tuberculated form. Cumuli may, at 
 any time, increase so as to obscure the sky, and they 
 then generally inosculate, and begin to assume that 
 
OF METEOROLOGICAL PHENOMENA. 37 
 
 density of appearance which characterizes the twain- 
 cloud, or cwnulo 'Stratus."* 
 
 3. The Stratus, (see fig. 9.) or Fall-cloud, or cloud 
 of night, as it is sometimes called, from the time it 
 usually makes its appearance, are the meteorological 
 names given to fogs and mists, which, in extensive 
 sheets, chiefly during night, cover the earth's surface, 
 and disappear usually in the morning wdth the advanc- 
 ing temperature of day. Sometimes, particularly in 
 calm weather, and during the coldest period of the 
 year, when, owing to the obliquity of the sun's rays, 
 his influence is not sufficiently strong to dissipate 
 them, this species of cloud rests upon the earth's sur- 
 face, perhaps for a week or a fortnight without inter- 
 mission. 
 
 The best opportunity for observing the formation 
 of the stratus, is on a fine still evening, after a hot 
 day in the end of summer or beginning of autumn, 
 at which time this species of cloud is very prevalent. 
 *' We shall then observe, that as the cumuli, which 
 have prevailed through the day, decrease, a white 
 mist forms by degrees close to the ground, or extends 
 only for a short distance above it. This cloud arrives 
 at its density about midnight, or between that time 
 and morning, and it generally disappears after sun- 
 rise. The stratus has often been found positively 
 electrified, and its component particles do not wet 
 leaves or other substances connected with the earth. 
 It has been supposed that the earth below it, and 
 probably the air above it, contained a negative coun- 
 tercharge. The stratus should be distinguished from 
 that variety of the cirro-stratus, or wane-cloud, which 
 
38 ON THE CAUSES AND PRINCIPLES 
 
 looks much like it in external appearances, and whicli 
 has usually a similar state of electricity with the earth. 
 The criterion whereby we may judge, to which of the 
 two modifications to refer a mist, is, that the stratus 
 does not wet objects it alights on, but the cirro-stratus 
 moistens every thing." 
 
 4. The Cirro-ciwiuluSj (see fig. 2.) or Sonder- 
 cloud, consists of small, roundish, well-defined masses 
 of clouds, separated, or sometimes only nearly sepa- 
 rated, from each other, and closely arranged in exten- 
 sive horizontal beds. This cloud has more resem- 
 blance to the cumulus than to the cirrus. In fact, 
 it seems to consist of small, imperfectly or flatly form- 
 ed cumuli arranged in horizontal beds. 
 
 " This cloud is subject to some varieties in the size 
 and figure of its orbicular masses, and in their nearer 
 or more distant approximation to each other. Its 
 most striking feature is observable before or about 
 the time of thunder-storms in summer. The com- 
 ponent nubeculcB are then very dense in their struc- 
 ture, very round in their form, and in closer apposi- 
 tion than usual, (see fig. 2.) This kind of sonder- 
 cloud is so commonly a forerunner of storms, that it 
 has been frequently spoken of by poets as a tempest- 
 uous prognostic. In rainy and variable weather, a 
 variety of this cloud appears, strikingly contrasted 
 with the above-mentioned kind, being of a light, 
 fleecy texture, and its nuheculce having no very regu- 
 lar form. Under these circumstances, it is sometimes 
 so light and flimsy in its texture as to approach very 
 nearly to the nature of the cirro-stratus. Sometimes 
 this kind of cirro-cumulus consists of nuheculcs so 
 
OF METEOROLOGICAL PHENOMENA. 39 
 
 small as scarcely to be discernible ; the sky seems 
 speckled with innumerable little round white, and 
 almost translucid spots. The cirro-cumulus of fair 
 summer weather is of a middle nature, neither being 
 so dense as the stormy variety, nor so light as the one 
 last described. Its nuheculcB vary in size, and in the 
 degree of their proximity. In certain kinds of fine 
 dry weather, with light gales of north and easterly 
 wind, small detachments of cirro-cumulus rapidly 
 form and subside again, which do not lie in one plane, 
 but, in general, these clouds are in horizontal arrange- 
 ment. The formation of cirro-cumulus is either spon- 
 taneous, that is, unpreceded by any other cloud ; or, 
 2d, it may result from the changes of some other 
 modification. Thus the cirrus or cirro-stratus often 
 changes into cirro-cumulus, and vice i')ersa. When 
 this cloud prevails in summer, we may, in general, 
 anticipate an increase of temperature ; and, in win- 
 ter, it often precedes the breaking up of a frost, and 
 indicates warm and wet weather. In warm weather 
 during summer, several extensive beds of this cloud, 
 ranged in different altitudes, and viewed by moon- 
 light, have a very beautiful and picturesque appear- 
 ance, and have been compared by poets to a flock of 
 sheep at rest. The cirro-cu7nulus either subsides 
 slowly, as if by evaporation, or it changes into some 
 other modification of cloud. 
 
 5. The Cirro-stratus, (see fig. 3, 4, and 5.) or 
 Wane-cloud. The form of this cloud, which is least 
 apt to be confounded with that of other denomina- 
 tions, is often seen on fine summer evenings, when 
 it presents the appearance of a bed or layer of cloud, 
 
40 ON THE CAUSES AND PRINCIPLES 
 
 of considerable length, but neither broad nor deep, 
 and seemingly stationary at a great altitude above the 
 earth's surface, (see fig. 5.) " All the varieties of 
 this cloud are characterized by shallowness, or great 
 horizontal extent, in proportion to their vertical depth; 
 so that when the cirrus^ or any other cloud, is ob- 
 served to assume this form, we may generally expect 
 that it will end in a cirro-stratus. The cirrus, for 
 example, after having existed some time in the higher 
 regions of the atmosphere, often descends lower ; its 
 fibres become more regularly horizontal ; and it puts 
 on, by degrees, the character of the wane-cloud. The 
 cirrus more frequently changes to the cirro-stratus 
 than the cirro-cwnulus does, and the cirro-cumulus 
 more frequently than the cumulus. 
 
 " The cirro-stratus being once formed, sometimes 
 re-assumes the character of the modification from 
 which it originated, but more frequently it evaporates 
 by degrees, or, by inosculating with some other modi- 
 fication, produces the twain-cloud, and eventually falls 
 in rain. 
 
 " The cirro-stratus seldom remains long in the 
 same form, but is observed to be constantly subsid- 
 ing by degrees ; hence it has been called the w'ane- 
 cloud from the old English verb to wane, to decline, 
 or waste away. There are many varieties in the 
 figure of the cirro-stratus, some of which are more 
 transitory than others. Sometimes this cloud is dis- 
 posed in wavy bars or streaks, in close horizontal ap- 
 position, and these bars vary almost infinitely in size 
 and shape. A flat, and nearly horizontal cloud, com- 
 posed of such streaks, is very common, particularly 
 
OF METEOROLOGICAL PHENOMENA. 41 
 
 in variable weather, in summer. The bars, which com- 
 pose this variety, are generally confused in the middle, 
 and are more distinct towards the edges, (see fig. 3.) 
 A variety not unlike this is seen on fine summer 
 evenings, and constitutes what has been denominated 
 the Mackerel-back Sky. It is often very high in the 
 atmosphere. We have observed that, on ascending 
 lofty mountains, the apparent distance of this cloud 
 seems hardly diminished, while the cumulus^ or 
 stacken-cloud, has been sailing along on a level with 
 the point of observation, or even below it. Another 
 common variety of cirro-stratus differs from the last 
 in being one plane and long streak, thickest in the 
 middle, and wasting away at its edges. This, when 
 viewed in the horizon, has the appearance of fig. 5. 
 It often seems to alight on the summits of the cumulo- 
 stratus as represented in the plate j and in these cases, 
 the density of the large twain-cloud increases in pro- 
 portion as these long wane-clouds form, and evaporate 
 on their summit ; a circumstance which looks as if 
 the great density of the cloud depended on the inos- 
 culation and subsequent intermixture of the two dif- 
 ferent modifications with each other. The result of 
 this intermixture, and the consequent density of the 
 cloudy mass, is eventually the formation of the nim- 
 bus, and the fall of rain. Another principal variety 
 of the cirro-stratus, is one which consists of small 
 rows of little clouds curved in a peculiar manner. It 
 is called the Cj/nioid Cirro-stratus, and it is a sure 
 indication of stormy weather, (see fig. 4.) Imme- 
 diately below this in the plate, is the representation 
 of another less perfectly formed, having more of the 
 
 F 
 
42 ON THE CAUSES AND PRINCIPLES 
 
 character of the sonder-cloud. It is a variety often 
 produced when a large cumulus passes under a long 
 line of cirro-stratus, like that in fig. 5, and is also a 
 sign of variable and stormy weather. The last va- 
 riety of cirro-stratus to be mentioned, is that large 
 and shallow veil of cloud, which extensively over- 
 spreads the sky, particularly in the evening, and dur- 
 ing the night, and through which the sun and moon 
 but faintly appear. It is in this cloud that those pe- 
 culiar refractions of the sun and moon's light, called 
 Halos, Mock-suns, &c., usually appear, and which is 
 the surest prognostic we are acquainted with of an 
 impending fall of rain or snow. To these principal 
 varieties of the cirro-stratus others less frequent might 
 be added ; but, as their forms are almost innumer- 
 able, every meteorologist must observe them for him- 
 self. The usual termination of the cirro-stratus is, 
 by forming an intimate union with somio other cloud 
 to produce rain. In general, therefore, the prevalence 
 of the wane-cloud is always a sign of a fall of rain or 
 snow. At other times, this cloud evaporates, or 
 changes into some other modification, as previously 
 observed." 
 
 6. The Cicmulo-sfratus, (see fig. 6.) or Twain- 
 cloud, is a compound of the cumulus and the cirro- 
 stratus ; the cirro-stratus being either intermingled 
 with the cumulus, or widely extending its base, so 
 that while the base is flat, and united like the cirro- 
 stratus, the superstructure resembles large cumuli, 
 rising from the base in the forms of detached moun- 
 tains and rocks. 
 
 " The Cumulo-stratus may be always regarded as 
 
OF METEOROLOGICAL PHENOMENA. 43 
 
 a stage towards the production of rain, and it fre- 
 quently forms in the following manner : — The cumu- 
 lusy which in common passes along in the current of 
 the wind, seems retarded in its progress, — increases 
 in density, — spreads out laterally, — and at length 
 overhangs the base in dark and irregular protuberances. 
 The change to the cumulo-stratus often takes place 
 at once in all the cumuli which are near to each 
 other J and their bases uniting, while the superstruc- 
 tures remain asunder, rising up with mountain-like or 
 rocky summits, the whole phenomena has a fanciful 
 appearance. The change from cumulus to cumulo- 
 stratus is often preceded by the cirro-stratus, or some 
 other of the hghter modifications, coming over in an 
 upper current, and alighting on the summit of the 
 cumulus. Long lines of wane-cloud often appear for 
 a length of time attached transversely to the summits 
 of the twain-cloud, and give them the appearance of 
 being transfixed by shafts, (see fig. 6.) Cumuli 
 sometimes meet together, and begin to be arranged 
 along with joined bases, without acquiring the dense 
 black colour of the cumulo-stratus, and, as the change 
 is gradual, we may view the cloud in an intermediate 
 state. Twain-clouds vary somewhat in appearance. 
 Those in which hard hail showers and thunder storms 
 form, look extremely black before the change to rain, 
 and have a most picturesque but menacing aspect, as 
 they are seen slowly coming up with the wind. The 
 cumulo-stratus sometimes evaporates, or changes 
 again to cumulus, and sometimes it forms itself spon- 
 taneously, without the precurrence of any other cloud, 
 and disappears again. But, in general, it ends at last 
 
44 ON THE CAUSES AND PRINCIPLES 
 
 ill uie nwihus, and Tails in rain. Frequently, in a 
 long range of these clouds, one part changes into 
 nimbus, and rains, while the other remains a cumulo- 
 stratus, (see fig. 8.) But this is not frequently the 
 case. Having given this sketch of the modifications, 
 it must be observed, that masses of cloud sometimes 
 appear hardly referable to any of them ; but even 
 then, if watched long enough, they will be found to 
 put on sufficient of the character of some of the mo- 
 difications to be registered under its name." 
 
 7. The Cumulo-cirro-stratus or Nimbus, or Rain- 
 cloud, is that cloud, or aggregation of clouds, from 
 which rain is falling. It usually presents the appear- 
 ance of a horizontal layer of aqueous vapour, over 
 which clouds of the cirro-stratus kind are spread ; 
 while other clouds of the cumulus form enter it later- 
 ally, and from beneath. 
 
 " Any of the six above described modifications may 
 increase so much as to obscure the sky, without end- 
 ing in rain, before which, the pecuhar characteristic 
 of the rain-cloud may always be distinguished. The 
 best manner of getting a clear idea of the formation 
 of the nimbus, is by observing a distant shower, in 
 profile, from its first formation to its fall in rain. We 
 may then observe the cumulus first arrested, as it were, 
 in its progress, then a cirt'us, or cirro-stratus, may 
 appear to alight on the top of it. The change to 
 cumulo-stratus then goes on rapidly, and this cloud, 
 increasing in density, assumes that black and threat- 
 ening appearance which is a known indication of rain. 
 Shortly afterwards, the very intense blackness is 
 changed for a more grey obscurity, and this is the 
 
OF METEOROLOGICAL PHENOMENA. 45 
 
 criterion of the actual formation of water, which now 
 begins to fall, while a cirriform crown of fibres ex- 
 tends from the upper parts of the clouds, and small 
 cumuli enter into the under part. After the shower 
 has spent itself, the different modifications appear 
 again in their several stations ; the cirrus, cirro-stra- 
 tuSf] or perhaps the cirro-cimiulus, appears in the 
 higher regions of the air, while the remaining part of 
 the broken nimbus assumes the form of a flocky cu- 
 muhis, and sails along in the current of wind which is 
 next the earth. When large cumulo-strati begin to ap- 
 pear again, they indicate a return of the rain; and these 
 processes are constantly going on in showery weather, 
 when the rapid formation and destruction of rain- 
 clouds goes on, and is attended by the other modifi- 
 cations in succession, in the manner above described. 
 In continued rainy days, we cannot observe the upper 
 parts of the nimbus, which extends for miles over 
 large tracts of country ; but we have no doubt that 
 the same processes go on slower and on a larger 
 scale in continued rainy weather, which are more 
 conspicuous in the rapid and partial formation of 
 showers." 
 
CHAPTER III. 
 
 ON THE CAUSES AND PRINCIPLES WHICH DETERMINE THE 
 FORMATION OF CLOUDS. 
 
 It has been already stated, that the capacity of the 
 ah* for holdmg moisture in invisible solution, increased 
 and decreased in geometrical progression, while its 
 temperature increased and decreased in arithmetical 
 progression. But though the precipitation of moist- 
 ure into the visible form of mist or clouds, may arise 
 either from a reduction in the temperature of the at- 
 mosphere, or from a reduction in reference to its ca- 
 pacity, still as there are a variety of circumstances in 
 which such reductions of temperature occur, for the 
 sake of being better understood, we shall arrange 
 them under the four following heads : — 
 
 1. When a diminution of the atmospheric temper' 
 ature unaccompanied by atmospheric rarefaction, or 
 transportation, takes place. 
 
 2. When a diminution of the atmospheric temper- 
 ature arising from atmospheric rarefaction takes 
 place. 
 
 3. When a diminution of the atmospheric temper- 
 ature, arising from the transportation qf air from a 
 waim to a cold climate by the agency of winds, takes 
 place. 
 
 4. When an intermia;ture, and consequent reduc- 
 
ON THE CAUSES AND PRINCIPLES, &C. 47 
 
 tion to a mean temperature^ of different portions 
 of air of previously different temperatures^ takes 
 place. 
 
 If any one, or any combination of these circum- 
 stances happen to occur, when the atmosphere is pre- 
 viously saturated with humidity ; or supposing the 
 atmosphere previously somewhat undersaturated, if 
 they take place to such an extent as to produce over- 
 saturation, a precipitation of moisture into the visible 
 form of cloud or mist, is the necessary consequence. 
 
 We shall treat of these four causes of the forma- 
 tion of clouds separately in their order as above. 
 
 A diminution of the atmospheric temperature in- 
 dependent of, and unaccompanied either by rarefac- 
 tion, or transportation of air, takes place, in the gra- 
 dual transition from the maximum temperature of day, 
 to the minimum of night j and from the maximum 
 temperature of summer, to the minimum of winter. 
 
 Of these two transitions, individually considered, 
 the former, viz. from the maximum temperature of 
 day to the minimum of night, produces, in a given 
 number of hours, a greater reduction of temperature 
 than the latter. Its influence, however, in this re- 
 spect though greatest, is chiefly hmited to the atmo- 
 spheric strata near the ground. Hence the cloud 
 most frequently, and most extensively formed by it, 
 occupies a similar low position, and is denominated, 
 in meteorological language, the stratus or fall-cloud, 
 or sometimes the cloud of night, from the time it 
 usually makes its appearance. It comprehends, and 
 is commonly applied exclusively to those low creeping 
 fogs or mists, which, on clear still nights, cover plains. 
 
48 ON THE CAUSES AND TRINCIPLES 
 
 hollows, &c.; but under this title we mean to treat of 
 all foirs and mists whatever. 
 
 The causes and principles which determine and 
 reo'ulate the formation of the stratus, are, with some 
 additions hereafter to be noticed, the same as those 
 which, according to Dr Wells, determine and regu- 
 late the deposition of dew. These we shall endea- 
 vour to explain. From Dr Wells' observations, it 
 appears, that a thermometer, laid upon grass during 
 calm clear nights, exhibited an atmospheric tempera- 
 ture lower, sometimes by as much as 10 degrees, than 
 one suspended in the air four feet above the grass. 
 It was farther found by the observations of Mr Six of 
 Canterbury, that the atmospheric temperature con- 
 tinued gradually to rise according to a diminishing 
 ratio, in ascending perpendicularly above four feet, so 
 that at the altitude of 220 feet, (and observations were 
 not extended higher,) the atmosphere, on favourable 
 nights, exhibited a thermometric temperature as much 
 as 10 degrees higher than it did at four feet above the 
 ground. 
 
 From the circumstance of the reduction of tem- 
 perature being always greater, in proportion as the 
 surface of the ground immediately under was better 
 fitted for radiating caloric, Dr Wells demonstrated 
 that the phenomena exhibited by the above thermo- 
 metric observations during night, were produced by 
 the escape of heat from the earth's surface by radia- 
 tion, being then more rapid than the supply by con- 
 duction from underneath. This circumstance induced 
 a considerable degree of coldness on the earth's sur- 
 face, beyond what the atmosphere a few feet above 
 
OF METEOROLOGICAL PHENOMENA. 49 
 
 exhibited, before the supply of caloric became equal 
 to the amount that escaped, and the progressive in- 
 crease of temperature which the air manifested upon 
 ascending perpendicularly to the height of 220 feet, 
 arose from this superior coldness being slowly com- 
 municated upwards to the incumbent atmospheric 
 strata, with diminishing effect, according as they were 
 farther removed from the surface of the ground. 
 
 On cloudy nights little or no reduction of tempera- 
 ture close to the earth's surface took place, beyond 
 what was exhibited four feet above it. This Dr Wells 
 ascribed to the partial interruption given to the radia- 
 tion of heat from the earth's surface by clouds, the 
 effect of which was, that the supply of heat from un- 
 derneath by conduction, without the accelerating aid 
 of any sinking of temperature on the earth's surface, 
 then became equal to the amount that escaped by 
 radiation. That this was the true explanation he 
 proved by the fact, that, upon the supervention of a 
 cloud, the thermometer placed upon the grass very 
 soon rose to the same, or nearly the same tempera- 
 ture, as the one four feet above it ; and that after the 
 cloud had passed away, the thermometer on the grass 
 very soon sunk to its former temperature, while the 
 other remained almost stationary. He also demon- 
 strated the accuracy of the above explanation, by pro- 
 ducing analogous results by means of artificial awnings. 
 Thus, by covering the thermometer laid upon the grass 
 with a piece of paste-board, shaped like the roof of a 
 house, and open to the atmospheric current at both 
 ends, the reduction of temperature, as indicated by 
 the thermometer, was prevented in the same manner 
 
 G 
 
50 ON THE CAUSES AND PRINCIPLES 
 
 as it was by the supervention of clouds. A similar 
 effect was produced by an awning of thin muslin, and 
 in a less degree by the shade of trees, houses, or other 
 elevated objects, which, to any extent, limited or re- 
 duced the view of the sky, as seen from the place 
 where the thermometer was laid. 
 
 On windy nights, Dr Wells found that no reduc- 
 tion in the atmospheric temperature close to the 
 ground took place, beyond what was exhibited by a 
 thermometer four feet above it. And in fact, other 
 things equal, the sinking of the atmospheric tempera- 
 ture close to the ground was greater, in proportion as 
 the air subjected to observation was calmer, and from 
 its local position, such as being on a low-lying plain, 
 or in a slight hollow, less liable to be displaced by 
 slowly progressing aerial currents. This effect of 
 wind, and the similar one produced by slopes, such as 
 the sides of hills present, in consequence of their al- 
 lowing the cooled, and, therefore, the specifically 
 heavier aerial particles nearest the ground to roll 
 downwards, Dr Wells very properly ascribed to the 
 circumstance of uncooled portions of air from above, 
 being rapidly and successively brought into contact 
 with the radiating surface ; the temperature of which 
 was prevented from sinking, in consequence of the 
 caloric which those uncooled portions of air commu- 
 nicated. 
 
 These and similar observations Dr W^ells success- 
 fully applied to explain the phenomena of dew. In 
 order to ascertain the amount of dew deposited, he 
 usually employed swandown, which, being one of the 
 best radiators of caloric, indicated, by means of the 
 
OF METEOROLOGICAL PHENOMENA. 51 
 
 sinking of a thermometer laid upon it, compared with 
 one suspended four feet above it, the degree of cold- 
 ness induced upon the earth's surface by radiation ; 
 and, by the additional weight it acquired, indicated 
 the amount of dew deposited upon it. By varying 
 his experiments, with a view to prevent mistakes as 
 to the source from whence the dew was derived, he 
 proved that it neither resulted from evaporation from 
 the earth's surface, nor from the exudation of plants. 
 And by comparing the amounts deposited, with the 
 reduction of temperature induced upon the earth's 
 surface by radiation, he satisfactorily demonstrated 
 that it was a deposition from the atmospheric strata 
 nearest the ground, arising from the coldness there- 
 from communicated. 
 
 The preceding observations enable us to under- 
 stand the leading phenomena connected with the most 
 frequent formation of the stratus. When upon the 
 approach, or during the continuance of night, the tem- 
 perature of the aerial particles nearest the ground 
 sinks, in consequence of the radiation of heat from 
 the earth's surface, to the extent required to produce 
 the slightest degree of oversaturation, the deposition 
 of dew commences. And the formation of the stratus 
 begins to make its appearance, so soon as the cold- 
 ness thus induced upon the earth's surface is slowly 
 propagated upwards in sufficient intensity to produce 
 atmospheric oversaturation. 
 
 By way of illustrating this department of our sub- 
 ject, we will state a variety of the phenomena pre- 
 sented during the formation of this species of cloud, 
 and subjoin the explanation. 
 
52 ON THE CAUSES AND PRINCIPLES 
 
 1. The stratus begins to form close to the surface 
 of the ground, and gradually extends itself upwards, 
 and usually does not exceed a very limited altitude. 
 This, agreeably to the foregoing principles, is owing 
 to the fact of the coldness induced upon the earth's 
 surface by the escape of radiating heat, being soonest 
 communicated in sufficient intensity to produce over- 
 saturation to the aerial particles nearest the ground ; 
 and from that degree of coldness, being afterwards so 
 slowly communicated upwards, as only to reach a very 
 limited height before the return of day. 
 
 2. The stratus during- its formation is densest near- 
 est the surface of the ground, and gradually diminishes 
 in density upwards. This, as was demonstrated by 
 the thermometric observations of Dr Wells, is owing 
 to the coldness induced upon the earth's surface by 
 radiation, being communicated to the incumbent aerial 
 strata with less diminished intensity, according to their 
 greater proximity to the ground. 
 
 3. Provided other circumstances be equally favour- 
 able, (which is always understood,) the deposition of 
 dew, and the formation of the stratus^ commence 
 earlier in the evening, according as the hygrometric 
 condition of the lower atmosphere is nearer the point 
 of saturation, before the radiation of heat from the 
 earth's surface, upon the approach of evening, begins. 
 This is owing to a smaller depression of temperature 
 being then requisite to produce atmospheric oversatu- 
 ration ; and, consequently, the radiation of heat from 
 the earth's surface effects this depression earlier in the 
 evening, because having less to do, it does it in less 
 time. 
 
OF METEOROLOGICAL PHENOMENA. 53 
 
 4. On certain nights seemingly favourable, from 
 the calmness of the air, and the clearness of the sky, 
 to the deposition of dew, and the formation of the 
 strafusj neither dew nor mist make their appearance. 
 This, which is of frequent occurrence in inland dry 
 countries, is owing to an unusual dryness, or under- 
 saturated condition of the atmosphere ; the reduction 
 of temperature effected by radiation not being suffi- 
 cient, in such cases, to reduce the capacity of the air 
 for moisture, below the point of saturation. 
 
 5. The stratus may frequently be seen during night 
 overspreading meadows and level grass fields, to the 
 depth of a foot or two, while the surface of a gravel 
 road, passing through the midst of these, remains per- 
 fectly free from this species of cloud. This, as de- 
 monstrated by Dr Wells' observations, is owing to 
 the surface of meadows and grass fields being better 
 adapted for radiating caloric, and, consequently, for 
 exhibiting a greater degree of thermometric depres- 
 sion of temperature during night than gravel roads. 
 Hence the reason that over meadows and grass fields 
 the temperature of the air may be reduced below the 
 point of saturation, and precipitation of moisture into 
 the form of mist may accordingly take place ; while 
 over the gravel road the temperature of the air may 
 not be sufficiently depressed to produce oversatura- 
 tion ; and, accordingly, no mist will there make its 
 appearance : and so of all other analogous cases. 
 
 6. In the summer half of the year, the stratus 
 formed during night disappears in the morning, or 
 early in the day ; whereas, during winter, fogs fre- 
 quently continue for many successive days and nights 
 
54 ON THE CAUSES AND PRINCIPLES 
 
 without intermission. The reason of this is, that, 
 during the summer half of the year, the heat of the 
 sun upon the return of day, is sufficient to dissipate 
 fogs formed during the coldness of night, by recon- 
 verting them into invisible vapour ; whereas, during 
 winter, owing to the obliquity with which the sun's 
 rays then fall upon the earth, the small amount of 
 heat thereby communicated during day, is not unfre- 
 quently insufficient to accomplish this object. 
 
 7. In equally serene evenings, the stratus is more 
 prevalent in the beginning of autumn than in the end 
 of spring, or beginning of summer ; and, in general, 
 its formation is more extensive, and of more frequent 
 occurrence, in the fall of the year ; and, in fact, so 
 long as the temperature is declining, than it is in the 
 opposite season of the year, when the temperature is 
 advancing. The reason of this is, that, in the former 
 case, the declination of temperature from the maxi- 
 mum of summer to the minimum of winter, co-oper- 
 ates with the diurnal sinking of temperature, upon 
 the approach of evening, in producing atmospheric 
 oversaturation ; whereas, in the latter case, the ad- 
 vancing temperature from the minimum of winter to 
 the maximum of summer, in some degree counteracts 
 the tendency to atmospheric oversaturation, occa- 
 sioned by the diurnal sinking of temperature upon the 
 approach, and during the continuance of night. 
 
 We will now state cases in which a stratus, or fog, 
 is formed in circumstances so far disconnected with 
 those in which dew makes its appearance, that a 
 simultaneous deposition of this commodity may, or 
 may not, take place. 
 
OF METEOROLOGICAL PHENOMENA. 55 
 
 The formation of a stratus or mist of this kind, 
 may result from a general sinking of the atmospheric 
 temperature, either totally disconnected with, or only 
 partially assisted by the upward propagation of the 
 nocturnal coldness induced upon the earth's surface 
 by calorific radiation. Such fogs, hke all others, only 
 make their appearance, in this climate, in still wea- 
 ther ; and occur most frequently when the tempera- 
 ture is rapidly declining upon the approach, or during 
 the depth, of winter. Their formation may com- 
 mence at any altitude above the earth's surface, where 
 the atmosphere, upon the reduction of its tempera- 
 ture, becomes first oversaturated, upon which con- 
 dition their existence, like that of all other fogs, de- 
 pends ; and their perpendicular thickness, which is 
 sometimes great, is necessarily co-extensive with the 
 depth of atmosphere that becomes oversaturated. 
 Damp low-lying flat countries, such as Holland, 
 where the air is frequently loaded with moisture, and 
 where the sinking of temperature in the fall of the 
 year is considerable, are, in accordance with our pre- 
 vious observations, most subject to this kind of fog. 
 
 Fog of a different kind, or rather arising from a 
 different cause, (for from whatever source or union of 
 sources originating, they all equally consist of mois- 
 ture existing in some imperfectly understood state, 
 between invisible vapour and water ;) fog, I say, 
 arising from a different cause from any of those which 
 precede, frequently makes its appearance in still wea- 
 ther over the surface of water, and nowhere else. 
 This species of fog may usually be seen floating over 
 the surface of canals, and deep pools, in a calm morn- 
 
50 ON THE CAUSES AND PRINCIPLES 
 
 ing, after a clear frosty night, upon the first introduc- 
 tion of cold weather in the fall of the year. It arises 
 from the surface of water being warmer than the in- 
 cumbent atmosphere. The temperature of the mois- 
 ture evaporated in such circumstances from the warm 
 watery surface underneath, sinks upon intermixing 
 with the colder atmosphere immediately incumbent ; 
 and so soon as the air thus supplied with humidity be- 
 comes oversaturated, this species of fog begins to show 
 itself. Vapour seen issuing from the steam-pipe of 
 a steam-engine, or from the mouth of a kettle of boil- 
 ing water, is analogous in its formation to this kind of 
 fog. The vapour, upon intermixing with the cold air 
 as it issues from the steam-pipe, is suddenly condensed 
 in such quantities as to produce atmospheric oversa- 
 turation, and thus forms the visible mist which is 
 commonly called steam. But as this mist gets separ- 
 ated farther from the steam-pipe from whence it is- 
 sued, it is gradually dispersed, and reconverted into 
 the invisible state by evaporation, and aerial diffusion, 
 and solution. 
 
 The preceding observations sufficiently explain the 
 nature and origin of this description of fog, and what 
 follows will explain the laws by which its individual 
 density varies and is regulated. 
 
 1. Supposing the evaporating surface of a given 
 extent, and the atmospheric temperature at a given 
 point, the higher the temperature of the water is 
 above that point, the faster will evaporation go on 
 from its surface, and, of course, the greater will be 
 the amount of vapour formed and condensed in a 
 given time. 
 
OF METEOROLOGICAL PHENOMENA. 57 
 
 2. The stiller the atmosphere is, the less liable 
 will the condensed vapour be to be blown away, and 
 dissipated. 
 
 3. The nearer the hygrometric condition of the at- 
 mosphere is previously to the point of saturation, the 
 less of the evaporated moisture will disappear by aerial 
 diffusion and solution. 
 
 According therefore as a more favourable combin- 
 ation of these three circumstances happen to occur, 
 so is this species of fog more certain to make its ap- 
 pearance, and also to exhibit a greater degree of 
 density ; and vice versa. 
 
 The fog or haze which makes its appearance over 
 the sea when its surface is warmer than the incum- 
 bent atmosphere, is identical in the causes and prin- 
 ciples of its formation with that which we last describ- 
 ed. This condition of the temperature of the atmo- 
 sphere, in reference to that of the subjacent ocean, 
 may occur, when a wind blows for a short time over 
 a sea surface from the polar towards the equatorial re- 
 gions, and more particularly when it blows during 
 winter, from an extensive, and more northerly cold 
 land surface towards the ocean, and a warmer latitude. 
 The cold atmosphere thus transported, by remaining 
 incumbent upon a comparatively warm sea surface, at 
 length becomes saturated with the moisture therefrom 
 evaporated. If the surface of the sea was of the same 
 temperature with the incumbent atmosphere, evapor- 
 ation would cease whenever the hygrometric condi- 
 tion of the atmosphere reached the point of satura- 
 tion, and no fog, unless a sinking of temperature oc- 
 curred, would make its appearance. But the conse- 
 
 H 
 
58 ON THE CAUSES AND PRINCIPLES 
 
 quence of the sea being warmer than the incumbent 
 air, is, that evaporation continues to go on from its 
 surface, after the atmosphere has become saturated, 
 and, accordingly, when, without a rise of temperature, 
 it can contain no more vapour in invisible solution. 
 Hence an amount of moisture corresponding to what 
 is evaporated after the air has become saturated, is 
 condensed as it gets cooled by intermixture with the 
 cold incumbent atmosphere, and gives birth to the 
 description of fogs under consideration. Fogs pro- 
 duced in the manner above narrated, may be of any 
 density, from the thinnest perceptible haze to the 
 thickest mist. 
 
 Fogs on the coast of North America, and particu- 
 larly along the course of the Gulph stream, are fre- 
 quently produced in the manner above described. A 
 cold atmosphere, transported by a north-west wind 
 during winter, from the frigid latitudes of North 
 America, comes sometimes to rest upon the then 
 comparatively warm surface of the Atlantic ocean : 
 and this inequality of temperature is further aug- 
 mented, and therefore the more apt to occasion fogs, 
 along the track by which the Gulph stream conveys 
 an immense body of water from the equatorial towards 
 the polar regions, which, when subjected to thermo- 
 metric examination, is found to be several degrees 
 warmer than other parts of the Atlantic, equally dis- 
 tant from the equator. 
 
 It may be remarked, that the formation of all fogs 
 where the subjacent surface is warmer than the in- 
 cumbent atmosphere, as is the case in the two pre- 
 ceding instances, is assisted by the sinking down, and 
 
OF METEOROLOGICAL PHENOMENA. 59 
 
 intermixture of the cold aerial strata above with those 
 below, which have become relatively heated in conse- 
 quence of their greater proximity to the warm surface 
 underneath. 
 
 Fog sometimes makes its appearance at sea in op- 
 posite circumstances to those last mentioned, viz. 
 when the atmosphere is warmer than the surface of 
 the sea. This may occur when the wind subsides 
 after blowing with force a day or two over a sea sur- 
 face, from a warm towards a colder latitude; and more 
 particularly, after blowing, during summer, from a 
 southerly, heated, and, at the same time, damp land 
 surface towards the ocean, and a colder latitude. If 
 in either of these cases the superior coldness of the 
 subjacent surface of the ocean be communicated to 
 the incumbent atmosphere in sufficient intensity to 
 produce oversaturation, fog begins to appear. 
 
 Another way in which a limited portion of the sur- 
 face of the ocean is frequently rendered much colder 
 than the incumbent atmosphere, is when large ice- 
 bergs, frozen in some bay or inlet, are carried out to 
 sea, and transported by winds, tides, and currents, to 
 a warmer chmate. The same thing also happens 
 when great quantities of ice, frozen in some large 
 river, such as the St Lawrence in North America, are 
 carried by its current to the ocean upon the breaking 
 up of the frost. In places and seasons of the year 
 when icebergs are to be apprehended, such as near 
 the coast of Newfoundland, during the latter half of 
 spring, or beginning of summer, this species of fog, 
 accompanied by a sudden, and otherwise inexpHcable 
 coldness, gives warning to the mariner, during night. 
 
60 ON THE CAUSES AND PRINCIPLES 
 
 of his being in the vicinity of icebergs. In such 
 cases, vessels, in order to avoid danger, generally lie 
 tOi and wait the return of daylight. This kind of fog, 
 like the preceding, and analogously to all others, be- 
 gins to present itself whenever the coldness of the 
 subjacent ocean is communicated to the atmosphere 
 in sufficient intensity to produce oversaturation. 
 
 Having thus given a detailed explanation of a va- 
 riety of circumstances, in which a diminution of 
 temperature, unaccompanied by atmospheric rare- 
 faction, occasions a precipitation of moisture into the 
 visible form of cloud or mist, we now proceed to 
 consider those, in which the second mentioned cause 
 of the formation of clouds, viz. a diminution of atmo- 
 spheric temperature arising Ji'om its rarefaction, 
 occurs. 
 
 The effect of a reduction of temperature occa- 
 sioned by atmospheric rarefaction, in causing a pre- 
 cipitation of moisture into the visible form of cloud 
 or mist, may be exhibited upon a small scale by means 
 of an air-pump. If the air within the glass-receiver, 
 attached to this machine, be suddenly rarefied, its 
 temperature, as is exhibited by a delicate thermome- 
 ter placed within the receiver, immediately sinks; and 
 simultaneously with this reduction of temperature, a 
 mist or haze within the receiver makes its appear- 
 ance, which disappears again as the temperature rises, 
 whether the rise be occasioned by the readmission of 
 air, or by the passage of caloric by conduction through 
 the glass, without the readmission of air. When the 
 temperature within and without the receiver have be- 
 come equal without the air being readmitted, its re- 
 
OF METEOROLOGICAL PHENOMENA. 61 
 
 admission causes the temperature within the receiver 
 to rise above what it will continue to remain at. 
 
 The explanation of the phenomena, exhibited dur- 
 ing the performance of the above experiment, is the 
 following : — The sinking of temperature, exhibited by 
 the thermometer within the receiver, as a -portion of 
 air is withdrawn, is owing to the calorific capacity of 
 the remaining portion being increased by rarefaction. 
 The circumstance of the temperature afterwards ris- 
 ing within the receiver to its previous elevation with- 
 out any readmission of air, shows that a portion of 
 the caloric within the receiver has been withdrawn 
 along with the air ; and as caloric ceases to be with- 
 drawn by suction when the air ceases to be farther 
 rarefied thereby, it shows that the withdrawn caloric is 
 attached to the air by affinity or attraction ; and that 
 this abstraction of caloric has so far destroyed the 
 calorific equilibrium, upon which equahty of temper- 
 ature depends, that caloric entirely separate from 
 aerial particles, in obedience to the preponderance of 
 calorific repulsion, is forced from without through the 
 glass into the inside of the receiver, till the calorific 
 equilibrium and equality of temperature is again re- 
 stored. The rise of temperature within the receiver 
 beyond what it will remain at, which takes place 
 upon the readmission of air, after equality of temper- 
 ature within and without the receiver has been estab- 
 lished, also proves that a portion of caloric is firmly 
 attached by attraction to the ponderable portion of 
 aerial particles. Now, provided it be admitted, (and 
 there is no reason for doubt upon this point,) that a 
 part of the invisible aqueous vapour, proportioned to 
 
62 ON THE CAUSES AND PRINCIPLES 
 
 the relative amounts of air and vapour previously 
 within the receiver, is abstracted along with the air, 
 it is obvious, that if the temperature within the re- 
 ceiver remained unaltered by the abstraction of a por- 
 tion of air, instead of a part of the remaining aque- 
 ous vapour being thereupon condensed into the visi- 
 ble form of mist, the capacity of the diminished 
 quantity of air remaining within the receiver for hold- 
 ing moisture in invisible solution, would be increased. 
 Or again, if the capacity of air for moisture diminished 
 in the same ratio as its temperature was lowered by 
 rarefaction, and vice versa, increased in the same 
 ratio as its temperature was raised by condensation, 
 the abstraction of a portion of air could have no in- 
 fluence whatever in causing a precipitation of moist- 
 ure, within the receiver, into the visible form of mist. 
 In short, if such were the case, the dryness or damp- 
 ness of the air, hygrometrically speaking, that is to 
 say, its dryness or dampness relative to its capacity 
 for moisture, would not be liable to alteration either 
 by rarefaction or condensation. The true cause, there- 
 fore, of the appearance of mist within the receiver, as 
 the air is suddenly rarefied by the process of exhaus- 
 tion, results from the circumstance formerly stated, of 
 the capacity of the air for moisture diminishing more 
 rapidly than its temperature. While the temperature 
 of air diminishes in arithmetical progression, its capa- 
 city for moisture diminishes in geometrical progres- 
 sion. Hence, supposing the air within the receiver 
 to be exactly saturated with humidity, if its tempera- 
 ture be then lowered by rarefaction, a quantity of 
 moisture proportioned to the difference of ratio in 
 
OF METEOROLOGICAL PHENOMENA. 63 
 
 which the aqueous capacity of air diminishes more 
 rapidly than its temperature, would be precipitated 
 into the visible form of mist. 
 
 A similar rarefaction of the atmosphere, and conse- 
 quent reduction of its temperature and capacity for 
 moisture, to what may be thus effected artificially, on 
 a small scale, by means of an air-pump, is naturally 
 produced on a large scale, when atmospheric currents, 
 impelled by a preponderance of barometrical pressure, 
 rise, while surmounting hills and elevated lands. The 
 lower aerial strata as they ascend, expand by means 
 of their elasticity, to a bulk proportionally greater, as 
 the amount of air above them, and the pressure thereby 
 produced diminishes. This expansion or rarefaction 
 is accompanied by a proportional reduction of temper- 
 ature. And this reduction of temperature produces, 
 and is attended by a diminished capacity for moisture, 
 proportioned, as before stated, to the difference of 
 ratio in which the aqueous capacity of air diminishes 
 more rapidly than its temperature. 
 
 Such is the arrangement of causes and effects by 
 which atmospheric currents, in rising from a low level 
 to surmount hills and elevated lands, have a tendency 
 to become oversaturated with humidity, and thus to 
 give birth to clouds. Of course, the altitude at which 
 the temperature of the ascending current becomes so 
 depressed by rarefaction that oversaturation com- 
 mences, will mark the lower boundary where clouds 
 begin to form. And this boundary will be lower or 
 higher, according as the hygrometric condition of the 
 atmospheric current, before beginning to ascend, is 
 nearer to, or more distant from, the point of saturation. 
 
(54 ON THE CAUSES AND PRINCIPLES 
 
 The formation of clouds, according to the princi- 
 ples above described, is finely illustrated by the phe- 
 nomena daily exhibited, during the dry season, over 
 what are called the Liguanea, or Port- Royal moun- 
 tains, in the island of Jamaica. These mountains are 
 situated about four or five miles to the north-east by 
 east of Kingston, the principal port in the island, and 
 their height above the level of the sea is from four to 
 five thousand feet. During the dry season, from the 
 beginning of November till the middle of April, the 
 sea and land breezes alternately succeed each other, 
 with an intermediate interval of atmospheric stillness, 
 in the following manner : — From sunrise till about 10 
 o'clock in the forenoon, it is usually perfectly calm. 
 About 10 o'clock the sea breeze blowing at Kingston 
 from the east, or rather a little to the south of east, 
 commences, and continues till about half-past three in 
 the afternoon, when it gradually and entirely subsides. 
 The interval of atmospheric stillness which ensues 
 lasts till a short time after sunset, when the land breeze 
 begins, blowing from the central parts of the island in 
 every direction towards the circumference, and, of 
 course, at Kingston, blowing from the north-west. 
 The land breeze continues all night, and till about 
 sunrise, when it also gradually and entirely subsides ; 
 and then the same routine which we have now de- 
 scribed, again commences, and it is repeated every day 
 during the whole of the dry season. 
 
 About eleven o'clock every forenoon, or between 
 that time and mid-day, the summits of the Port-Royal 
 mountains begin to be covered with clouds ; which, 
 though thin, fleecy, and transparent at first, gradually 
 
OF METEOROLOGICAL PHENOMENA. (>5 
 
 increase in density till about one o'clock. By this 
 time, the upper portions of the mountains, when 
 viewed from Kingston, seem to be wholly enveloped 
 in dense clouds — rain is apparently falling in torrents 
 — flashes of lightning are seen, and the sound of dis- 
 tant thunder is heard. About half-past two o'clock 
 in the afternoon, the clouds, gradually diminishing in 
 density, begin to quit the mountains, so that their 
 summits again become visible as in the morning, and 
 so continue till about eleven o'clock of the following 
 day. The clouds, after quitting the mountains, rise 
 gradually to a greater altitude, and float very slowly 
 westward, assuming, as they proceed, the appearance of 
 large heaped up cumuli. Such is a description of 
 what occurs every day throughout the dry season, 
 from the beginning of November till the middle of 
 April. During the whole of this lengthened period, 
 hardly a cloud is ever to be seen, except those formed 
 over the distant mountains, during the continuance of 
 the sea breeze, and which float slowly westward after 
 quitting the mountains, as above described. 
 
 That the formation of the clouds, in the case above 
 narrated, is the result of diminished temperature, and 
 consequently of diminished capacity for moisture, as 
 the atmospheric current becomes rarefied in its ascent 
 over the mountains, is obvious from comparing the 
 coincidences between the respective periods of time 
 when the clouds begin to appear — reach their greatest 
 density — and afterwards quit the mountains as their 
 farther formation ceases ; with those, when the sea 
 breeze commences — attains its greatest velocity — and 
 afterwards gradually and entirely subsides. The sea 
 
66 ox THE CAUSES AND PHINCIPLES 
 
 breeze blowing from the south-east by east begins at 
 Kingston about 10 o'clock, and the mountains (which, 
 though only five miles distant from Kingston, are 
 perhaps 12 or 15 from the sea in the direction of the 
 sea breeze,) begin to be covered with clouds by 
 11 o'clock, or between that time and noon. Now, 
 when it is considered, that the air resting upon the 
 land intermediate between the sea and the Port- Royal 
 mountains, must have become much heated, and 
 therefore much undersaturated during the interval of 
 atmospheric stillness before 10 o'clock, it is not at all 
 likely that any degree of atmospheric oversaturation, 
 and consequent formation of cloud, could take place, 
 till the less undersaturated portion of air that had 
 previously reclined over the sea during the interval of 
 atmospheric stillness, had reached the summits of the 
 mountains. And as the force of the sea breeze is at 
 first small, and only increases, and extends itself in- 
 land by slow degrees ; and as the less undersaturated 
 portion of the atmosphere which had previously re- 
 clined over the sea, has 12 or 15 miles to travel over 
 land, before reaching the mountains, the circum- 
 stance of an hour, or from that to two hours, elapsing 
 after the sea breeze has commenced on the shore at 
 Kingston, before the mountains become covered with 
 clouds, is just what might be expected to happen. 
 
 Again, as the heat of the surface of the land, and 
 of the atmosphere immediately incumbent, in warm 
 climates, relative to that of the sea, and of the atmo- 
 sphere thereupon incumbent, increases till about one 
 o'clock in the afternoon, the velocity of the Seabreeze 
 which is produced and regulated by this difference of 
 
OF METEOROLOGICAL PHENOMENA. 67 
 
 temperature, increases also till about the same time ; 
 and afterwards gradually diminishes till about three 
 o'clock, when it entirely subsides. Now the phe- 
 nomena presented by the clouds over the Port-Royal 
 mountains, are in exact accordance with what might 
 be expected to result from this variation in the force 
 of the sea breeze. When its velocity arrives at its 
 diurnal maximum about one o'clock, a greater amount 
 of air must undergo rarefaction, and consequent de- 
 pression of temperature, and diminution in capacity 
 for moisture, in its ascent over the mountains in a 
 given time, than at any other period. And when this 
 circumstance is considered along with the fact, that, 
 according as the velocity of the breeze becomes 
 greater, less time is allowed for the damp sea air to 
 become heated and undersaturated before reaching* 
 the mountains, it is only what might be expected, 
 that the clouds, owing to their more rapid and more 
 copious formation, should then increase in density so 
 much as to occasion torrents of rain ; and that their 
 density should again gradually diminish, and the rain 
 cease, as the sea breeze subsides. Accordingly, about 
 half-past two o'clock, when the sea breeze may be 
 supposed to have so far subsided among the moun- 
 tains, as to be no longer capable of forming clouds, 
 and causing rain, the remaining clouds, as they be- 
 come specifically lighter by the heat of the sun's rays, 
 gradually rise above the mountain tops, and, moving 
 slowly westward, assume the picturesque appearance 
 of massy heaped up cumuli. These clouds, agree- 
 ably to the usual character of cumuli, descend, upon 
 the approach, and during the early part of night, to a 
 
08 ON THE CAUSES AND PRINCIPLES 
 
 lower altitude, and, breaking up into smaller pieces, 
 slowly dissolve and disappear by evaporation. A 
 cloudless sky thereafter ensues over the whole hori- 
 zon, and continues till the usual period of the follow- 
 ing day, when a similar nebulous creation makes its 
 appearance, and which, after passing through a like 
 course of existence, dissolves and evanishes in a si- 
 milar manner. 
 
 Such is a description of the mode in which clouds 
 are formed by the reduction of temperature, and con- 
 sequently of aqueous capacity, which attends the rare- 
 faction of atmospheric currents, while surmounting 
 hills and elevated lands. 
 
 Mountains of themselves, that is to say, without 
 wind, can form no clouds ; and winds of themselves, 
 that is to say, without the aid of the atmospheric rare- 
 faction which accompanies their exaltation while pass- 
 ing over mountains, are, in this respect, equally inef- 
 ficient. Hence, over the Port-Royal mountains, be- 
 fore the sea breeze reaches them, the sky is as clear 
 and unclouded as in any other part of the horizon. 
 And, on the other hand, the sea breeze causes no 
 formation of clouds immediately over Kingston, or 
 over any other portion of the land where there are no 
 mountains. In short, mountains in all climates may 
 be regarded as passive instruments in the formation 
 of clouds, only during windy weather. And when- 
 ever their height is such, that the temperature of the 
 lower atmospheric strata, while surmounting them, 
 becomes so much reduced as to cause oversaturation, 
 the formation of clouds must take place. Hence, the 
 higher the mountains, the more certain they are dur- 
 
OF METEOROLOGICAL PHENOMENA. 69 
 
 ing windy weather to cause the formation of clouds ; 
 and the nearer the hygrometric condition of the aerial 
 strata, before beginning to ascend the mountains, is 
 to the point of saturation, the less height will suffice 
 for that purpose. 
 
 Accidental coldness on the tops of mountains, be- 
 yond what results from their height, sometimes adds 
 to their efficacy in causing the formation of clouds. 
 Such may be occasioned by snow-falls during the cold 
 season remaining unmelted, or only partially melted, 
 (as frequently happens on the northern exposure of 
 mountains,) till long after the returning heat of spring 
 and summer has rendered the falling of snow, at cor- 
 responding altitudes, extremely improbable. 
 
 When at Arrochar, about the end of April or be- 
 ginning of May of the current year, (1834,) I had an 
 opportunity of witnessing the influence of such acci- 
 dental coldness in forming clouds. The mountains 
 around this sequestered and romantic spot may vary 
 in height from two to three thousand feet, and, at the 
 time alluded to, patches, or possibly if more nearly 
 inspected, fields of snow were to be seen on diff'erent 
 parts of their rugged and fantastically shaped summits. 
 The weather during the morning of observation was 
 exceedingly fine and mild for the season of the year. 
 Loch Long reposed in perfect stillness — not a breath 
 of wind could be felt in the valley, and it could only 
 be ascertained that the atmosphere above the moun- 
 tains had a very slow progressive motion towards the 
 east, by observing the change of position, which small 
 fleecy clouds, here and there floating at an elevation 
 similar to that of the mountains, underwent, when 
 
70 ON THE CAUSES AND PRINCIPLES 
 
 viewed for sometime in relation to the mountain-tops. 
 These fleecy clouds had probably been originally con- 
 centrated portions of mist which had formed, and 
 rested during the previous night in hollows and places 
 sheltered from the atmospheric progression, near the 
 tops of mountains between Arrochar and the Atlantic, 
 and which had been raised from their beds, but not 
 entirely dissipated by the heat of the morning sun. 
 
 The circumstance that particularly attracted my 
 attention, was the sudden increase in density, and the 
 equally sudden expansion, to perhaps three or four 
 times their previous bulk, which those small fleecy 
 clouds underwent in the course of not more than a 
 minute of time, when they touched upon the moun- 
 tain-tops where I saw snow lying ; and also when they 
 touched other localities, where, from the lowness of 
 my place of observation, I could not see, but believed 
 snow to be lying. These clouds, thus augmented in 
 volume, instead of dissolving by evaporation with the 
 advancing temperature of day, rose to a greater alti- 
 tude while crossing Loch Long, and floating very 
 slowly eastward, gradually congregated together, and 
 assumed, as I watched them in my progress tow^ards 
 Helensburgh, in the course of the forenoon, the ap- 
 pearance of ranges of cumuli. This happened when 
 over the whole horizon to the south, where the hills 
 are less elevated, no cloud was to be seen. 
 
 Another circumstance that attracted my attention 
 was, that I never could observe any formation of cloud 
 taking place in any part of the atmosphere while pro- 
 gressing over the snow, except where a small cloud 
 previously existed. The coldness, therefore, com- 
 
OF METEOROLOGICAL PHENOMENA. 71 
 
 municated by the snow, though sufficient for increas- 
 ing the density and size of clouds previously formed, 
 was not so great as to originate them, where none 
 were before visible. Now, when it is considered, 
 that at the time of observation, the force of the wind, 
 as indicated by the extreme slowness with which the 
 clouds were progressing, was so small as probably to 
 be insufficient to communicate motion to the lower 
 aerial strata, when obstructed by the rising acclivity 
 of hills, it may be concluded, that the augmentation 
 of bulk, which the clouds underwent upon approach- 
 ing the vicinity of the snow, was entirely owing to the 
 accidental coldness thereby communicated, and not at 
 all produced by the ascent, and consequent rarefaction 
 and reduction of the temperature of the lower aerial 
 strata. 
 
 The circumstance also of no nebulous formation 
 taking place in any part of the atmosphere while 
 passing over the snow, except where some small cloud 
 previously existed, showed that the air in the vicinity 
 of those small fleecy clouds, was much nearer the 
 point of saturation, than at a distance from them. 
 Indeed, when it is considered that clouds consist of 
 moisture in an intermediate state between invisible 
 vapour and water, and that that moisture is favour- 
 ably circumstanced for evaporation, from being not 
 only surrounded, but completely intermixed with air, 
 it might have been concluded, without observing the 
 fact above stated, that the hygrometric condition of 
 the atmosphere in the vicinity of all clouds, must be 
 very near the point of saturation, for otherwise they 
 would rapidly dissolve. 
 
7*2 ON THE CAUSES AND PRINCIPLES 
 
 The case above narrated, together with that which 
 preceded of the Port-Royal mountains in Jamaica, 
 satisfactorily account for the great prevalence of 
 clouds, not only immediately over the mountains 
 where they are formed, but also for some distance to 
 leeward. And as the formation of clouds is the con- 
 stant forerunner of wet weather, they also account for 
 the greater abundance of rain in mountainous dis- 
 tricts, than in those of a champaign low lying char- 
 acter. 
 
 By way of illustrating this department of our sub- 
 ject a little farther, I shall here relate, and explain the 
 phenomena which presented themselves on another 
 occasion, which I had an opportunity of witnessing 
 when residing one summer at Brodick-Bay, in the 
 island of Arran. During the time I stopped there, 
 I had twice previously ascended in clear weather to 
 the top of Goatfell, which is the highest mountain in 
 the island, and may be about 2900 feet in height. 
 Being then young, my curiosity was not satisfied with 
 the view from the top in clear weather, I wished also 
 to see what could be seen when the mountain was 
 enveloped in mist and clouds. Accordingly, one day 
 when two-thirds of the mountain was shrouded in mist, 
 and invisible from its base, I prevailed upon a stranger 
 gentleman belonging to the navy to ascend along with 
 me ; and from my previous knowledge of the hill, I 
 undertook, notwithstanding the mist, to direct our 
 journey without the assistance of a guide. It was 
 one of those calm days, when the whitish colour and 
 hazy thick appearance of the air, when viewed per- 
 pendicularly upwards, indicated its being greatly over- 
 
OF METEOROLOGICAL PHENOMENA. 73 
 
 saturated with moisture ; and when a very slight in- 
 crease to the density of the aqueous vapour akeady 
 precipitated and suspended in the atmosphere, would 
 have caused it to descend in the form of drizzHng 
 rain. In our approach to the lower boundary of the 
 mist, it was obvious that it descended to a much 
 lower level over the mountain, than it did in the at- 
 mosphere at a distance from it. Except this, no me- 
 teorological phenomenon of importance presented it- 
 self till we reached the steep part, which may be called 
 the cone of the mountain,, and had advanced so far up 
 it, as to be within perhaps about 300 feet of perpen- 
 dicular height from the top. The mist hitherto had 
 not been remarkable for its density, though in this re- 
 spect it had very slowly increased from the time we 
 entered within its limits. Its appearance was that of 
 ordinary whitish coloured mist, floating in moderate 
 density a few feet above the surface of the ground, 
 and in rapidly diminishing thickness from that eleva- 
 tion downwards to the ground. During our farther 
 ascent, however, the density of the mist increased 
 with appalling rapidity ; so much so, that at the sum- 
 mit of the mountain, it was greatly denser than any 
 thing of the kind I ever witnessed ; and instead of 
 floating chiefly above our heads, and in diminishing 
 quantity underneath, as it had previously done, it 
 now extended to the ground in all its denseness. The 
 ground was quite dry, and there was no visible depo- 
 sition of moisture upon our clothes lower than about 
 300 feet perpendicular from the top. At this eleva- 
 tion, however, the ground assumed the appearance of 
 dampness -, and moisture, at first in such small quan- 
 
 K 
 
74 ON THE CAUSES AND PRINCIPLES 
 
 tity as to be almost imperceptible, began to be depo- 
 sited upon our clothes. In our farther ascent, this 
 condition of the atmosphere gradually increased, so 
 that, at the summit of the mountain, we found our- 
 selves surrounded with an exceedingly dense mist, at- 
 tended with drizzling rain. The gentleman who ac- 
 companied me being desirous of obtaining a view 
 from the top, and having no other opportunity of as- 
 cending, as he purposed to leave the island the fol- 
 lowing morning, it was agreed that we should remain 
 twenty minutes, to see if the mist would clear away. 
 In the meantime, to shelter ourselves from the 
 drizzling rain, we crept under a granite rock project- 
 ing from the brow of the hill. Having waited the 
 length of time agreed upon, without the mist showing 
 any signs of disappearing, or the rain of abating, we 
 commenced our descent ; and the same phenomena 
 we had seen in ascending, in reversed order again 
 presented themselves. The mist rapidly decreased 
 in density ; and when we got beyond about 300 feet 
 of perpendicular descent from the top, the rain ceased, 
 and the ground appeared perfectly dry. I conceive 
 it therefore presumable, that though there was no rain 
 at a lower level than about 300 feet perpendicular 
 from the summit of the mountain, it rained above that 
 elevation, the quantity increasing towards the top, in 
 a drizzling form during the whole day. 
 
 Such were the meteorological phenomena which 
 presented themselves ; and these we shall now en- 
 deavour to explain. 
 
 The first circumstance requiring consideration, is 
 the descent of the mist to a lower level over the 
 
OF METEOROLOGICAL PHENOMENA. 75 
 
 mountain than it did in the surrounding atmosphere 
 free of the mountain. Provided the force of the wind 
 had been considerable, I should have supposed that 
 the descent of the mist was more apparent than real; 
 and that it was owing principally to the circumstance 
 of additions being made to its lower portion, by the 
 rarefaction of the lower aerial strata while ascending 
 the mountain. But as the atmosphere at the time 
 was so near a state of perfect stillness, that it could 
 with difficulty be determined in which direction it was 
 moving, I am disposed to attribute the descent of the 
 mist in this case, chiefly to an attractive force which 
 mountains usually exert upon clouds and mist, so as 
 visibly to draw them downwards, and, in some degree, 
 to arrest, or retard their progress while passing over 
 them. Such attractive influence may arise in various 
 ways, such as, from clouds being over or undercharged 
 with electricity relative to the subjacent earth. It is 
 certain that clouds, on some occasions, are actuated 
 by one or other of these relative electrical conditions, 
 and, in my opinion, such occurs more frequently than 
 is generally supposed. It may arise also from the 
 subjacent earth exerting a stronger attractive influence 
 upon the precipitated aqueous vapours composing 
 clouds, than upon the gaseous elements which com- 
 pose the atmosphere ; and this may be occasioned by 
 the former being more apt to acquire by induction, a 
 difl"erent electrical state from the subjacent earth, or 
 that diff'erent state in a stronger degree, than the latter. 
 To the preceding opinion it may be objected, that 
 if mountains attract clouds and mist downwards, the 
 density of the mist, agreeably to the law of distance, 
 
76 Ox\ THE CAUSES AND PRINCIPLES 
 
 should have increased as it approached the surface of 
 the ground ; whereas, before reaching the cone of the 
 mountain, though the mist appeared to float in consi- 
 derable density a few feet above the surface of the 
 ground, its density, instead of increasing, rapidly di- 
 minished from that elevation to the ground. 
 
 The explanation of this seeming contradiction to 
 the hypothesis of mountains attracting clouds, is the 
 following : — The preceding portion of the summer 
 had been remarkable for heat and dryness ; and, as 
 always happens in such circumstances, the ground, 
 at and near its surface, must have acquired a higher 
 temperature than the atmosphere. According there- 
 fore to the principle of caloric being always directed 
 in its movements by the preponderance of calorific 
 repulsion, it follows, that the surface of the ground 
 must have been gradually imparting a portion of its 
 previously absorbed caloric to the air, and this more 
 particularly, as the higher atmospheric strata were at 
 that time so loaded with precipitated aqueous vapours, 
 as to be altogether impervious to the calorific rays of 
 the sun. The mist, therefore, which we have sup- 
 posed to have been attracted downwards by the moun- 
 tain to a lower level than its specific gravity would 
 have otherwise determined, and possibly also in some 
 slight degree formed by its influence in elevating, and 
 thereby depressing the temperature of the slow-mov- 
 ing atmospheric current, was partially dissolved, and 
 reconverted into the invisible state, and also rendered 
 specifically lighter by the heat which was gradually 
 emanating from the ground. Owing, however, to the 
 great increase in the density of the mist, and the 
 
OF METEOROLOGICAL PHENOMENA. 77 
 
 cooling effect of the moisture deposited upon the 
 ground at and near the summit of the mountain, the 
 previously absorbed caloric, by the time we ascended, 
 was probably emanating from the ground in such 
 small quantity, (if at all,) as to be incapable of dis- 
 solving any appreciable proportion of it. And, con- 
 sequently, the mist there appeared to extend in undi- 
 minished density to the surface of the ground. 
 
 The most remarkable fact, however, was the quan- 
 tity of drizzling rain that was falhng at the summit of 
 the mountain, when within such a short distance, as 
 about 300 feet of perpendicular height down the steep 
 sides of its cone, it was perfectly dry. It is obvious 
 that had the mist been as dense, and its particles as 
 large and heavy, at an equal elevation in the surround- 
 ing atmosphere clear of the cone of the mountain, as 
 they were immediately over it, drizzling rain, contrary 
 to what we experienced, must have been falhng upon 
 us during our whole ascent. Now, when it is consi- 
 dered that the drizzling rain was limited to the upper 
 part of the cone of the hill, which, from its height, 
 may be supposed to have reached those atmospheric 
 strata where the mist was floating in greatest density ; 
 and, when it is farther considered, that the air may 
 have been progressing at the rate of a mile or two in 
 the hour, (a thing which happens, as is evident by 
 observing smoke, in almost the calmest weather we 
 ever have in this country,) it is probable, that the in- 
 crease in the density of the mist, and the running to- 
 gether of its particles into drops, so as to give rise to 
 drizzling rain, was partly occasioned by the attractive 
 influence of the mountain in concentrating the mist 
 
78 ON THE CAUSES AND PRINCIPLES 
 
 near its summit, and partly also by the interruption, 
 exaltation, and intermixture, of conflicting atmospheric 
 currents, while surmounting the cone of the hill. 
 
 The case above narrated and explained aff'ords an 
 illustration, though not a good one, of the influence 
 of mountains in robbing the aerial current of a por- 
 tion of its moisture. Owing to the extremely limited 
 extent of the summit of Goatfell, its influence in this 
 respect must have been very inconsiderable. But 
 supposing that a lengthened mountain range of equal 
 elevation, (and the greater its height the more power- 
 ful its influence,) had extended transverse to the at- 
 mospheric current, it is obvious, that the air to lee- 
 ward must have contained less moisture than it did to 
 windward, in proportion to the quantity deposited upon 
 the mountains, and returned to the sea by rivers. It 
 is upon this principle that the want of rain in the 
 kingdom of Peru, lying to the west of the Andes, (as 
 well as all similar cases,) is usually accounted for. 
 The trade-wind, which in that region blows uniformly 
 from the east, is robbed of a large proportion of its 
 moisture while passing over this elevated range of 
 mountains. And the moisture so precipitated, origi- 
 nates, and is returned to its parent source by those 
 immense rivers which traverse the South American 
 continent, from the Andes eastward to the Atlantic 
 ocean. 
 
 Another way in which the atmospheric temperature 
 may be reduced by aerial rarefaction, though probably 
 of little efficacy in the formation of clouds, is where 
 the amount of atmosphere over any place becomes less, 
 and which is indicated by a sinking of the barometer. 
 
OF METEOROLOGICAL PHENOMENA. 79 
 
 Such may occur when the atmospheric temperature, 
 on the continent of Europe, sinks rapidly upon the ap- 
 proach of winter, below what it is in this island. In that 
 case the first effect is, that a portion of the upper half of 
 the atmosphere floats over upon the cold and depressed 
 air of the continent. And this, until re-action is pro- 
 duced in the lower half of the atmosphere, should oc- 
 casion a sinking of the barometer in this country, and 
 a rarefaction of the aerial strata, which will be greater 
 the more elevated, and the nearer they are to those 
 which have been withdrawn. On the other hand, an 
 increase in the amount of air vertical to any place, 
 and which is indicated by a rise in the barometer, 
 may slightly assist in accelerating the dissolution of 
 clouds, by means of the aerial condensation and evo- 
 lution of heat which it occasions. Such may proba- 
 bly be one reason, though not the most important, 
 why a sinking of the barometer is an indication of wet 
 weather ; and why a rise in that instrument prognos- 
 ticates dryness. 
 
 Another way in which the diminution of atmo- 
 spheric temperature arising from atmospheric rarefac- 
 tion takes place, is when cold currents of air, in con- 
 sequence of their greater specific gravity, insinuate 
 themselves underneath, and gradually uplift warmer 
 atmospheric strata to a colder altitude. In the next 
 chapter we will endeavour to show that what is called 
 the rainy season in intertropical climates, is partly, if 
 not principally produced in this manner. 
 
 But the great bulk of clouds in temperate and cold 
 climates are formed independently of aerial rarefaction 
 produced by mountains, for they frequently originate 
 
so ON THE CAUSES AND PRINCIPLES 
 
 where none are to be found, such as at sea, and when 
 no aerial rarefaction occurs. They hkewise are formed 
 in circumstances totally different from those in which 
 fogs and mist make their appearance ; for instead of 
 originating in, and being restricted to, the portion of 
 the air nearest the ground, they are formed and float 
 only in high regions of the atmosphere. This brings 
 us to the consideration of the third cause of the forma- 
 tion of clouds, viz. when a diminution of the atmo- 
 spheric temperature, arising from the transportation 
 of air from a warm to a cold climate, hy the agency 
 of winds, takes place. 
 
 When treating, in the first chapter, of the causes 
 which produced an undersaturated state of the atmo- 
 sphere with regard to humidity, the influence of a 
 wind blowing from a warm towards a cold climate in 
 producing clouds, and causing rain, was fully explained. 
 As this, however, appears to be the principal cause of 
 the formation of clouds, at least in all temperate and 
 cold latitudes, we may recapitulate the substance of 
 what was formerly stated. 
 
 When the wind blows from a southerly direction in 
 the northern hemisphere, or from a northerly direction 
 in the southern hemisphere, air is thereby transported 
 from a warm to a comparatively cold climate. And as it 
 cools in advancing towards colder latitudes, its capacity 
 for moisture gradually diminishes. Hence, though 
 previously undersaturated with humidity, it gradually 
 approaches the point of saturation, and at length over- 
 saturation, and the formation of clouds commences. 
 And when the clouds, in the progress of formation, 
 acquire the requisite degree of density, rain ensues. 
 
OF METEOROLOGICAL PHENOMENA. 81 
 
 On the other hand, when the wind blows from a 
 northerly direction in the northern hemisphere, or from 
 a southerly direction in the southern hemisphere, air 
 is thereby transported from a cold towards a compara- 
 tively warm climate ; and, as it becomes warmer in 
 advancing towards a warmer latitude, its capacity for 
 moisture gradually increases. Hence, though previ- 
 ously saturated with humidity, it gradually becomes 
 more or less undersaturated ; and clouds previously 
 formed slowly dissolve by evaporation, and dry wea- 
 ther, and a cloudless sky, is the consequence. 
 
 These observations explain the reason why southerly 
 winds in the northern hemisphere, and northerly winds 
 in the southern hemisphere, are more prolific of clouds 
 and wet weather than winds from the opposite direc- 
 tion. It may be added, however, that when the wind, 
 in its progress from a warm towards a cold climate, 
 has crossed mountain ranges, or other elevated lands 
 immediately previous; and also when it has just passed 
 over an extensive tract of dry and heated land, it may 
 have become so much undersaturated thereby, that 
 for a considerable distance to leeward, any reduction 
 of temperature which it undergoes, may be insuffi- 
 cient, or perhaps little more than sufficient, to bring 
 up its hygrometric condition to the point of saturation. 
 In the former circumstances no clouds can be formed ; 
 in the latter, their formation may not be sufficiently 
 copious to produce rain. 
 
 Again, when the wind blows from the ocean towards 
 the land during winter, when the surface of the former 
 is much warmer than that of the latter ; and also when 
 it blows from the land towards the ocean during sum- 
 
 L 
 
82 ON THE CAUSES AND PRINCIPLES 
 
 mer, when the land is much warmer than the ocean, 
 the circumstances and the explanation are analogous 
 to the instance already given of the wind blowing from 
 a warm towards a cold climate. In such cases, the 
 atmosphere as it becomes colder has its capacity for 
 moisture diminished. Hence, though previously un- 
 dersaturated, it gradually approaches the point of satu- 
 ration. And so soon as oversaturation begins to be 
 thereby effected, the formation of clouds commences. 
 Of course, in the case of the wind blowing from the 
 ocean towards the land during winter, the formation 
 of clouds and wet weather takes place over the land ; 
 whereas, in the case of the wind blowing from the land 
 towards the ocean during summer, the formation of 
 clouds and wet weather occurs at sea. It requires, 
 however, to be noticed, that the wind from the ocean 
 is much more likely, in the above circumstances, to 
 produce clouds and wet weather on shore, than the 
 wind from the land is to occasion clouds and wet wea- 
 ther at sea. The reason of this difference is, that 
 wind blowing from the ocean is always either saturated, 
 or nearly saturated, with moisture, and therefore apt 
 to give birth to clouds and rain, when the slightest 
 reduction of temperature takes place. Whereas, wind 
 blowing from the land is frequently so much undersa- 
 turated, that all the reduction of temperature which it 
 undergoes, may not be sufficient to bring up its hygro- 
 metric condition to the point of saturation, and, of 
 course, no clouds, in such circumstances, can be 
 formed. 
 
 In the reverse circumstances to those above ex- 
 plained, viz. when the wind blows from the ocean 
 
OF METEOROLOGICAL PHENOMENA. 83 
 
 towards the land in summer, especially during its latter 
 half, when the heat of the land relatively to that of the 
 sea is greatest ; and also when it blows from the land 
 towards the ocean, during the coldest period, of win- 
 ter, the circumstances and the explanation are analo- 
 gous to the other previously given instance, of a wind 
 blowing from a cold towards a warm climate. In such 
 cases the atmosphere, as it becomes warmer, has its 
 capacity for moisture increased. Hence, though pre- 
 viously saturated with humidity, it gradually becomes 
 more or less undersaturated, and clouds previously 
 formed gradually evaporate and disappear. The former 
 of the winds above mentioned is therefore favourable 
 to fair weather on shore ; and the latter is still more 
 favourable to fair and cloudless weather at sea. 
 
 In our insular situation, surrounded by, and at no 
 great distance from, the ocean in any direction, the 
 truth of the preceding remarks is not so apparent. 
 But on continental shores, such as the United States 
 of America, and other similar localities, the explana- 
 tions thereby afforded of the different kinds of wea- 
 ther, which, during the specified seasons, accompany 
 certain winds, demonstrate their accuracy. 
 
 At Marseilles, situated in the south of France, and 
 on the coast of the Mediterranean, in north latitude 
 43° 18', the truth of the principles which we have 
 endeavoured to explain in the preceding pages, is 
 strikingly illustrated. During winter, and early in 
 spring, (and it is only to these periods of the year that 
 our immediate remarks apply,) the most frequent 
 changes in the direction of the wind are from north 
 to south, and the reverse, viz. from south to north. 
 
84 ON THE CAUSES AND PRINCIPLES 
 
 The most prevalent direction, however, is from the 
 north. The wind from this direction, during the sea- 
 son of the year above mentioned, is denominated the 
 Mistral. It continues generally for three successive 
 days at a time, its velocity being usually considerable, 
 and sometimes great, especially on the third day. 
 During the continuance of this wind, neither a cloud 
 nor the slightest haze can be seen. The colour of 
 the sky is dark blue, which indicates that the air is 
 extremely undersaturated with humidity, and that the 
 aqueous vapour therein contained is thoroughly dis- 
 solvedo This wind is so remarkable for dryness, and 
 its power of absorbing humidity from all moist surfaces 
 so great, that plants and vegetables of every kind have 
 their juices extracted by it to such an extent, that 
 during the cold season, when the severity of a nor- 
 therly wind there is only felt, they present a stunted 
 and withered appearance, greatly beyond anything 
 ever seen in this country ; and, like our north-east 
 wind in spring, which it resembles, but much sur- 
 passes in refrigerating influence, it is extremely pierc- 
 ing and cold. — We shall now explain the causes of 
 these phenomena. 
 
 The absence of every thing like haze, or cloud, 
 during the continuance of this wind, as well as the 
 characteristic dryness of the atmosphere, and the 
 other peculiarities therefrom resulting, are owing to 
 the conjoint influence of the following very favourable 
 combination of circumstances : — 1. This wind blows 
 with considerable, and sometimes great velocity, in 
 the direct course from a cold towards a warm climate, 
 viz. from north to south, over the central districts of 
 
OF METEOROLOGICAL PHENOMENA. 85 
 
 France, which, during winter, experience a degree of 
 cold seldom or never felt in this island. Hence, 
 agreeably to the principles we have been explaining, 
 as the atmosphere is gradually becoming warmer, and 
 its capacity for moisture increasing, it is simultane- 
 ously becoming more or less undersaturated ; and 
 consequently no formation of clouds, during its con- 
 tinuance, can take place. 2. It blows from the land 
 towards the sea, during the season of the year, (viz. 
 winter,) when the surface of the former is much 
 colder than that of the latter. This circumstance, by 
 contributing to render the transition from a cold to a 
 comparatively warm climate greater, and more sud- 
 den, adds to the influence of the one above-mention- 
 ed, in increasing the hygrometric dryness of the aerial 
 current as it approaches the Mediterranean coast, 
 upon which Marseilles is situated. 3. It blows over 
 from 500 to 600 miles of dry land, and in its passage 
 crosses ranges of elevated mountains. The combined 
 influence of these and the preceding circumstances, 
 which are all separately favourable to dryness, pro- 
 duces an extremely undersaturated state of the atmo- 
 sphere with regard to humidity. Hence, whatever 
 clouds or haze may have existed before the wind 
 shifted to this direction, are rapidly dissolved by it. 
 And as no clouds can be formed during its continu- 
 ance for the reasons above-mentioned, neither cloud 
 nor haze are visible. 
 
 On the other hand, when the wind, after blowing 
 for some time from the north, suddenly changes, and 
 blows from the south, that is, from the Mediterranean, 
 the combination of circumstances are reversed. And 
 
86 ON THE CAUS£S AND PRINCIPLES 
 
 being now as favourable for producing an oversaturated 
 state of the atmosphere with regard to humidity, and 
 a clouded sky, as they previously were for producing 
 the opposite condition, the formation of the clouds, 
 aided also by the rising grounds in the neighbour- 
 hood of Marseilles, rapidly goes on ; and rainy wea- 
 ther soon follows. But whenever the wind again 
 shifts from the south to the north, and the Mistral 
 begins to blow, the rain ceases, and the clouds dis- 
 solve and disappear with astonishing rapidity. 
 
 We now come to treat of the fourth cause of the 
 formation of clouds, viz. When an intermixture^ and 
 consequent reduction to a mean temperaturey of dif- 
 ferent portions of air, of previously different tempera- 
 tures, takes place. 
 
 It having been revealed by Saussure's experiments, 
 that while the temperature of air increases in arith- 
 metical progression, its capacity for moisture advances 
 in geometrical progression, Dr Hutton was led to 
 account for rain upon the principle, that, if different 
 portions of atmosphere, previously saturated with hu- 
 midity, and of different temperatures, were intermixed, 
 a precipitation of moisture must take place. This 
 mode of accounting for the precipitation of humidity 
 from the atmosphere has been denominated, from the 
 name of its author, the Huttonian theory of rain. 
 But, as the precipitation of moisture into the visible 
 form of mist or clouds, is not always attended, or 
 even followed by the falling of rain, (for clouds, after 
 being formed, frequently again evaporate without pro- 
 ducing rain,) and as there never is rain without clouds, 
 it might, with more propriety, have been denominated 
 
OF METEOROLOGICAL PHENOMENA. 87 
 
 the Huttonian theory of clouds. We shall here en- 
 deavour fully, and precisely, to explain its principles. 
 
 It has been already stated that the capacity of the 
 air for humidity, when reduced to a mean rate, doubles 
 itself for every increment of temperature amounting 
 to 23.4 degrees.* Accordingly, if the capacity of the 
 air at the temperature of 23.4 be denominated 2; its 
 capacity, at the temperature of 46.8, must be denomi- 
 nated 4 ; and at the temperature of 70.2, must be 8. 
 Now, supposing two equal portions of air previously 
 saturated with moisture, the temperature of the one 
 being 23.4, and that of the other 70.2, to be inter- 
 mixed, so as to produce a mean of 46.8. It is ob- 
 vious, by comparing the separate capacities of the two 
 portions of air at their respective temperatures, with 
 the capacity of both reduced to a mean temperature, 
 that intermixture must produce a precipitation of hu- 
 midity. Thus, the number denoting the aqueous ca- 
 pacity of the air at the mean temperature of 46.8 is 
 4 ; but the mean capacity of the air for the two ex- 
 treme temperatures, denoted respectively by the num- 
 bers 2 and 8, is 5. Hence, it appears, that -th of the 
 whole aqueous vapour which the two supposed por- 
 tions of atmosphere are capable of dissolving when 
 separate, would be precipitated upon their acquiring 
 a mean temperature by intermixture. 
 
 For the sake of avoiding confusion, the above cal- 
 culation makes no allowance for the deduction which 
 would have to be made for the evolution of heat, 
 
 * According to Leslie, the capacity of the air for moisture, 
 when reduced to a mean rate, doubles itself for every increment of 
 temperature, amounting to 27 degrees. 
 
88 ON THE CAUSES AND PRINCIPLES 
 
 which accompanies the conversion of invisible into vi- 
 sible vapour. If the atmosphere was previously so 
 much undersaturated, that the intermixture of two 
 equal portions of different temperatures did not pro- 
 duce any precipitation of humidity, their intermixture 
 would necessarily reduce them to a mean tempera- 
 ture. But as heat is always evolved when any con- 
 version of moisture from the invisible to the visible 
 state takes place, the result of intermixture, when 
 precipitation occurs, will be a temperature more or 
 less above the mean, according to the amount of mois- 
 ture precipitated. And as the capacity of air for dis- 
 solving humidity increases with its temperature, ac- 
 cording to the previously stated ratio, it is obvious, 
 that the proportion of moisture precipitated, upon the 
 intermixture of different portions of saturated air of 
 different temperatures, must be somewhat less than 
 the principle adopted in the preceding calculation 
 gives. 
 
 Now, as analogous results to those above stated, 
 are produced by every intermixture of atmospheric 
 strata of different temperatures, it follows, that if the 
 different strata be saturated with humidity when se- 
 parate, intermixture must always produce precipita- 
 tion ; and if they be undersaturated when separate, 
 intermixture, if it fall short of producing precipitation, 
 will, at all events, bring them nearer the point of sa- 
 turation. 
 
 But though the principle, according to which 
 clouds may be formed, by the intermixture of differ- 
 ent portions of air of different temperatures, has been 
 discovered, the circumstances in which such inter- 
 
OF METEOROLOGICAL PHENOMENA. 89 
 
 mixture takes place in nature, has never, so far as my 
 very limited reading goes, been pointed out. Upon 
 this point Dr Prout * says, " Clouds probably de- 
 pend altogether on convection ; and result from the 
 intermixture of strata of air of different temperatures, 
 and in different states of saturation, in the higher re- 
 gions of the atmosphere. 
 
 " Such," continues Dr Prout, " is the general 
 opinion of the formation of clouds ; but it must be 
 confessed that there are considerable difficulties about 
 the subject ; and that the mere assumption of strata 
 of different temperatures, more or less saturated with 
 vapour, and having the motions supposed to depend 
 upon such different temperatures and degrees of sa- 
 turation, seems quite inadequate to account for all 
 the phenomena connected with the formation and ap- 
 pearance of clouds." 
 
 In what follows, I will endeavour to point out, and 
 explain, the circumstances in which intermixture of 
 different portions of air of different temperatures takes 
 place, so as to occasion the formation of clouds, ac- 
 cording to the Huttonian principle. 
 
 In order to understand the circumstances above al- 
 luded to, let it be recollected, that the temperature of 
 the atmosphere diminishes at the mean rate of one 
 degree of Fahrenheit for every 300 feet of perpendi- 
 cular ascent ; and that this, as explained by Leslie, 
 results from the capacity of air for heat being increas- 
 ed in exact proportion as it becomes rarefied by the 
 diminution of atmospheric pressure. This explana- 
 
 * Bi'idgewater Treatise, p. 316. 
 M 
 
90 ON TlU^ CAUSES AND PRINCIPLES 
 
 lion, we casually remarked while commenting upon it, 
 might be applied to explain the otherwise inexplicable 
 fact, of the cold air in the higher atmospheric regions, 
 having no tendency to change places with the warm 
 air below, so long as the mean rate of decrement was 
 preserved. That this application is correct, is obvi- 
 ous from considering, that, in an atmospheric column 
 extending perpendicularly upwards from the ground, 
 the diminution of temperature which each molecule 
 manifests, according as it is higher up the column, 
 results not from its having less heat attached to it, 
 but from that heat being expanded over a proportion- 
 ally larger space. The colder molecules above are 
 therefore absolutely of the same weight, and specifi- 
 cally also, except for the difference arising from the 
 different degrees of force by which they are com- 
 pressed at different altitudes, with the warmer ones 
 below, and consequently can have no tendency to dis- 
 place them. 
 
 Now, the only circumstance in which an intermix- 
 ture of different portions of the atmosphere of differ- 
 ent temperatures takes place, is when the upper 
 molecules of air have severally a smaller amount of 
 heat attached to them, and consequently, after mak- 
 ing allowance for the rarefaction arising from the di- 
 minution of atmospheric compression as their posi- 
 tion becomes more elevated, are specifically heavier 
 than those helow. 
 
 Admitting then, (though this point possibly re- 
 quires re-examination,) that the decrement of one de- 
 gree of Fahrenheit for every 300 feet of perpendicu- 
 lar ascent, is the exact ratio at which every particle or 
 
OF METEOROLOGICAL PIIENOMENA. 91 
 
 stratum of air is at every elevation, specifically of the 
 same weight, except for the difference resulting from 
 its being less compressed, according as its position is 
 more elevated, intermixture must take place at any 
 altitude, where the ratio in which the decrement of 
 the atmospheric temperature exceeds one degree of 
 Fahrenheit for every 300 feet of perpendicular ascent. 
 And the more it exceeds this ratio, the greater will 
 be the tendency of the upper strata to sink down, and 
 intermix with those below. On the other hand, at 
 whatever altitude the ratio in which the decrement of 
 atmospheric temperature is less than one degree of 
 Fahrenheit for every 300 feet of ascent, the upper 
 and lower particles will be more unfavourably circum- 
 stanced for intermixing, than when the temperature de- 
 creases at the mean rate of one degree for every 300 
 feet of ascent. The reason of this is, that in the 
 former case, viz. when the temperature decreases at 
 a less ratio than one degree for every 300 feet of as- 
 cent, — the lower aerial particles are colder, and con- 
 sequently specifically heavier than those above, after 
 the necessary allowance is made for the greater atmo- 
 spheric compression to which they are subjected. 
 Whereas, in the latter case, after the necessary recti- 
 fication arising from difference of compression is 
 made, (and which, in what follows, is always to be 
 understood without being again mentioned,) the up- 
 per and lower aerial particles are precisely of the same 
 temperature, and the same specific gravity. 
 
 Provided the commonly received opinion, that the 
 upper half of the atmosphere moves in an opposite 
 direction from the lower, was in all cases correct, a 
 
02 ON THE CAUSES AND PllINCirJ.ES 
 
 sinking down and intermixture of the upper with the 
 lower half of the atmosphere would take place, when- 
 ever the wind in the lower half blew from a warm to- 
 wards a comparatively cold climate. In this case, a 
 warmer and lighter atmosphere would be brought un- 
 derneath a colder and heavier one. For instance, if 
 the direction of the wind in the lower half of the at- 
 mosphere be from the equatorial towards the polar 
 regions, while that of the upper half is from the polar 
 towards the equatorial ; the former will be transport- 
 ing the heated air of a warm to a cold climate, while 
 the latter is transporting the cold air of a cold, to a 
 warm climate. The consequence of this will be, that 
 the decrement of temperature at the plane where the 
 two currents meet, will be much greater than the rate 
 of one degree for 300 feet of ascent. Hence, the 
 aerial particles of the upper current will be colder, 
 and therefore specifically heavier than those of the 
 lower current ; and consequently, will sink down and 
 intermix with them. Now, provided the upper and 
 lower currents of air be saturated with humidity when 
 separate, the precipitation of moisture into the visible 
 form of cloud will begin so soon as intermixture com- 
 mences. And if they be undersaturated when sepa- 
 rate, intermixture, if it fall short of producing preci- 
 pitation, will, at all events, bring them nearer the 
 point of saturation. Of course, the sinking down and 
 intermixture of the upper half of the atmosphere with 
 the lower, and the consequent formation of cloud, 
 supposing the atmosphere previously saturated with 
 humidity, will go on with greater rapidity, according 
 as the coldness and gravity of the undermost strata of 
 
OF METEOROLOGICAL PHENOMENA. 93 
 
 the upper half, exceed those of the uppermost strata 
 of the lower half. And as the sinking down, and in- 
 termixture of the upper aerial particles with the lower, 
 is a slow and gradual process, it may be added, that 
 if one or both currents be previously somewhat under- 
 saturated, but not to the extent required to prevent 
 their intermixture and reduction to a mean tempera- 
 ture, producing a state of oversaturation, the forma- 
 tion of cloud will commence earlier after intermixture 
 has begun, according as both currents, (and particu- 
 larly the lower, as its aqueous capacity is greatest,) 
 are previously nearer the point of saturation. 
 
 On the contrary, if the direction of the wind in the 
 lower half of the atmosphere be from the polar towards 
 the equatorial regions, that is, from a cold towards a 
 warm climate, while that of the upper half is from the 
 equatorial towards the polar, the former will be trans- 
 porting the cold air of a cold to a warm climate, while 
 the latter is transporting the warm air of a warm to a 
 cold climate. The consequence of this will be, that 
 at the plane where the two currents meet, the decre- 
 ment of temperature will be less than the rate of one 
 degree for 300 feet of ascent. Hence, the aerial par- 
 ticles of the upper current will be warmer and speci- 
 fically lighter than those of the lower; and conse- 
 quently, no sinking down nor intermixture of the 
 former with the latter, nor formation of clouds de- 
 pendent upon intermixture, can take place. 
 
 Provided it could be demonstrated that the com- 
 monly received opinion upon this point is correct, 
 viz. that the upper half of the atmosphere always moves 
 in the opposite direction from the lower, it is obvious, 
 
\)-i ON THE CAUSES AND PKINC'irLES 
 
 that the intermixture of atmospheric strata of different 
 temperatures would occur in the circumstances above 
 explained ; and that the formation of clouds, as ex- 
 emplified in nature, would harmonize therewith. That 
 the upper half of the atmosphere moves in the oppo- 
 site direction to the lower, in the case of sea and land 
 breezes, monsoons, and generally, when the prevailing 
 direction of the wind in the lower half of the atmo- 
 sphere is from a cold towards a warm climate, (espe- 
 cially if the increment in the aerial temperature within 
 a moderate distance horizontally be considerable,) 
 can hardly be doubted. In such cases the atmosphere 
 in the warm climate, by being expanded upwards, in 
 consequence of superior temperature to a greater ele- 
 vation than that in the colder climate, generates a cur- 
 rent in the upper half of the atmosphere from the for- 
 mer towards the latter. But while this current dimi- 
 nishes the atmospheric pressure over the warm district, 
 by withdrawing a portion of air from the upper extre- 
 mity of the atmospheric columns thereupon incumbent, 
 it simultaneously suppUes air to the atmospheric co- 
 lumns, and consequently, increases the atmospheric 
 pressure over the cold district. Hence, a counter- 
 current in the lower half of the atmosphere, from the 
 cold towards the warm climate, is generated and main- 
 tained. 
 
 The preceding principle of accounting for the 
 simultaneous existence of two opposite atmospheric 
 currents, cannot be applied to any case where the 
 direction of the wind in the lower half of the atmo- 
 sphere is from a warm towards a cold climate, as is 
 exemphfied during winter by a west or south-west 
 
OF METEOROLOGICAL PHENOMENA. 95 
 
 wind blowing from the Atlantic towards Britain, and 
 the western shores of Europe. In such circumstances, 
 to suppose that an opposite current simultaneously 
 blows in the upper half of the atmosphere from a cold 
 towards a warm climate, would be reversing the prin- 
 ciple which determines the prevaiHng direction of the 
 wind. The proximate cause of wind is a difference 
 in the incumbent atmospheric pressure in different 
 places, at a similar elevation in reference to the level 
 of the sea. And the direction of the wind at all sim- 
 ilar altitudes above the level of the sea, is always from 
 where the incumbent atmospheric pressure, or in other 
 words, from where the incumbent amount of air, (that 
 is, the amount of air above the altitude of observation,) 
 is greater, to where it is less. But even though the 
 amount of atmosphere were the same over the cold as 
 over the warm climate, the atmospheric columns, in 
 consequence of being colder, would be less elevated 
 over the former than over the latter. Hence, it is 
 impossible, according to dynamical principles, that a 
 current in the upper half of the atmosphere from the 
 cold to the warm climate can exist, while the wind 
 near the earth's surface is blowing in the opposite 
 direction. 
 
 Now, the rainy direction of the wind in all latitudes 
 beyond the tropics, is when it blows in the lower half 
 of the atmosphere from a warm towards a compara- 
 tively cold climate. But we have above demonstrated, 
 that in such circumstances no opposite current in the 
 upper half of the atmosphere can exist. Hence, the 
 intermixture of aerial strata of different tempera- 
 tures, by which the formation of clouds might be ex- 
 
9(3 ON THE CAUSES AND PRINCIPLES 
 
 plained, cannot result from the opposite direction of 
 tlie wind in the upper and lower halves of the atmo- 
 sphere, bringing a colder and heavier air to rest over 
 a warmer and lighter one. 
 
 When we come to treat of irregular winds, we will 
 endeavour to show that the prevailing south-west wind 
 in Britain, and along the western shores of Europe, 
 is owing to the mean atmospheric pressure being 
 greater over the Atlantic Iving to the south-west, than 
 over Britain and the western parts of Europe. And 
 this, we conceive, is produced partly by the augmen- 
 tation which the atmosphere over the Atlantic, in the 
 direction of the Gulf of Mexico, is continually receiv- 
 ing in the form of aqueous vapour, supplied from the 
 watery surface underneath, and partly by the diminu- 
 tion which the atmosphere, in its north-east progress 
 toward a colder climate, sustains, by the descent of a 
 large proportion of that aqueous vapour in the form 
 of rain. 
 
 Supposing it granted, that the west and south-west, 
 which are the rainy winds in Britain, and in the western 
 countries of Europe, are owing to the causes above 
 mentioned ; I am disposed to think, that the whole 
 atmosphere, from the earth upwards to its summit, 
 must generally move in the same direction, not only 
 in this case, but in all others, when the wind blows 
 from a warm towards a comparatively cold climate. 
 At the same time, as air becomes denser in the ratio 
 of compression, I infer, that in such cases, the force 
 which produces wind, viz. the superiority of atmo- 
 spheric pressure in one place over another, at an equal 
 altitude above the level of the sea, increases as we 
 
OF METEOROLOGICAL PHENOMENA. 97 
 
 approach the surface of the earth. Consequently, 
 except for the counteractive resistance of friction on 
 the surface of the earth, and which must be propa- 
 gated upwards with diminishing effect from one aerial 
 stratum to another, that the velocity of the wind also 
 increases the nearer we descend in the atmosphere to 
 the earth's surface. For these reasons, together with 
 the fact of moisture being abstracted in the form of 
 rain, only from the aerial strata within a limited dis- 
 tance of the earth's surface, I am inclined to think, 
 that the greatest velocity of the atmospheric current 
 is, in most cases, restricted to within a mile, or per- 
 haps two, of the level of the sea ; and that above 
 some such altitude, its velocity gradually decreases. 
 This opinion is somewhat confirmed by the great ve- 
 locity with which clouds, suspended at a low altitude, 
 apparently move, when compared with those at a 
 greater elevation, even after allowance is made (esti- 
 mated, however, merely by ocular observation,) for 
 the optical illusion produced by the greater distance 
 of the latter. 
 
 Now, upon the supposition that the velocity of a 
 wind blowing from a warm towards a cold climate, be- 
 gins to diminish at the elevation of 5000 or 6000 feet 
 above the level of the sea, the air underneath this al- 
 titude, in consequence of having been transported 
 from a more southern climate, should be warmer, and 
 specifically lighter, than that which moves with dimin- 
 ished velocity above. Hence, the sinking down and 
 intermixture of the superior with the inferior strata, 
 and the consequent formation of clouds, may be going 
 on at that moderate degree of elevation. And upon 
 
 N 
 
98 ON THE CAUSES AND PRINCIPLES 
 
 the supposition that the velocity of the atmospheric 
 current gradually diminishes on ascending perpendi- 
 cularly above the altitude of 5000 or 6000 feet, each 
 atmospheric stratum should be warmer than that 
 immediately above it, for the same reason, viz. its 
 having been transported, in the same time, from a 
 more southerly, and therefore a warmer climate. Con- 
 sequently, the sinking down and intermixture of the 
 superior with the inferior strata, should be going on 
 in such circumstances, not only at the elevation of 
 5000 or 6000 feet, but for a great distance above. 
 
 On the other hand, when the wind blows from a 
 cold towards a warm climate, provided its velocity 
 gradually diminishes upon ascending above the eleva- 
 tion of 5000 or 6000 feet, the inferior atmospheric 
 strata, in consequence of having been transported a 
 greater distance in the same time, should be colder 
 and heavier than those above. Hence, in this case, the 
 superior atmospheric strata should have no tendency 
 to sink down and intermix with those below them, and 
 consequently, no formation of clouds, arising from the 
 intermixture of aerial strata of different temperatures, 
 can in such circumstances occur. 
 
 Provided the commonly received notion, that the 
 upper half of the atmosphere moves in the opposite 
 direction of the lower half, had been correct ; when 
 the latter blows from a warm climate, the intermixture 
 of atmospheric strata of different temperatures, accord- 
 ing to the principles previously explained, would have 
 been an exceedingly prolific cause of the formation of 
 clouds. But upon the principle which we have ad- 
 vanced, that when the wind blows from a warm towards 
 
OF METEOROLOGICAL PHENOMENA. 99 
 
 a cold climate, the whole atmosphere moves in the 
 same direction, with merely a gradual diminution in 
 its velocity above the altitude of 5000 or 6000 feet, 
 (and this conclusion itself requires to be re-examined,) 
 the intermixture of atmospheric strata of different 
 temperatures, may be regarded as exerting an inferior 
 influence in the formation of clouds, and one which is 
 merely auxihary to the third cause of their formation, 
 viz. the reduction of temperature which attends the 
 transportation of air from a warm to a cold climate, 
 by means of atmospheric currents. 
 
 Another case in which intermixture of atmospheric 
 strata of different temperatures should take place, is 
 when a greater degree of heat is communicated to 
 aerial strata at any given altitude, than what is im- 
 parted to those above them. Thus Humboldt found, 
 that the rate in which the temperature of the atmo- 
 sphere diminished upon ascending perpendicularly, 
 became less in the region of the atmosphere where 
 clouds are formed, than what it was either below or 
 above. This he ascribed to heat evolved during the 
 conversion of invisible vapour into clouds. Suppos- 
 ing, therefore, that clouds are forming in the atmo- 
 sphere, in consequence of the transportation of air 
 from a warm to a cold climate, the evolved heat must 
 raise the temperature, and diminish the specific grav- 
 ity of the atmospheric strata, where their formation is 
 taking place. Consequently, the aerial strata imme- 
 diately above, which have not participated in this ac- 
 cidental accession of warmth, must begin to sink down 
 and intermix with them. And this intermixture must 
 necessarily assist in increasing, and in some degree 
 
100 ON THE CAUSES AND PRINCIPLES 
 
 perpetuating, the formation of clouds. But it is not 
 only at their formation that clouds Communicate addi- 
 tional warmth to the adjoining atmospheric strata ^ 
 they are also subsequently indirect agents in raising 
 the temperature of the atmosphere in their immediate 
 neighbourhood. Thus they partially arrest the solar 
 heat in its progress to the earth during day, and in its 
 retrocession by radiation from the earth during night. 
 The heat so arrested may be spent partly, perhaps, in 
 dissolving the clouds ; but it must also be partly com- 
 municated by conduction to the neighbouring atmo- 
 sphere. This augmentation of temperature, by di- 
 minishing the specific gravity of the atmospheric strata 
 in which the clouds float, causes those above, which 
 have not participated in this accidental accession of 
 warmth, to sink down and intermix with them, and 
 thus to assist in their formation. 
 
 Hence we see that the existence of clouds in the 
 atmosphere exerts an influence in promoting their 
 farther formation. Not only the heat evolved during 
 their formation, but that which is subsequently arrested 
 by them, tends to increase, in their immediate neigh- 
 bourhood, the mean rate at which the temperature of 
 the atmosphere upon ascending perpendicularly dimin- 
 ishes. And this, agreeably to the principles already 
 explained, occasions a sinking down and intermixture 
 of the superior atmospheric strata with those immedi- 
 ately below J and, provided the intermixing strata be 
 previously saturated with humidity, must produce an 
 additional formation of clouds. 
 
 As the solar heat accumulates at the earth's sur- 
 face without imparting almost any additional warmth 
 
OF METEOROLOGICAL PHENOMENA. 101 
 
 to the atmosphere through which it radiates, the aug- 
 mentation of temperature which the air undergoes 
 during day, is chiefly communicated upwards from 
 the earth's surface. Owing to this circumstance the 
 accession of warmth which the diff"erent atmospheric 
 strata acquire during day, diminishes upon ascending 
 perpendicularly from the earth's surface. Hence, 
 agreeably to the principle of the equilibrium of the 
 atmospheric strata being disturbed, whenever the de- 
 crement of temperature upon ascending perpendicu- 
 larly exceeds one degree for every 300 feet, a sink- 
 ing down and intermixture of the superior with the 
 inferior strata, must, in such circumstances, take 
 place. But, as the augmentation of temperature 
 above alluded to, is almost always spent (at least over 
 dry land, where it is greatest,) in producing an under- 
 saturated state of the atmosphere with regard to hu- 
 midity, the sinking down and intermixture of the 
 strata referred to above, has seldom or never any in- 
 fluence in producing clouds. 
 
 The preceding observations sufficiently explain the 
 principles upon which the formation of clouds, result- 
 ing from the intermixture of saturated, or nearly sa- 
 turated atmospheric strata of different temperatures 
 depend, and the circumstances in which it occurs. It 
 is therefore unnecessary further to enlarge upon this 
 point. 
 
 Since the promulgation of the Huttonian theory of 
 rain, it has been generally believed by meteorologists, 
 that the formation of clouds in the higher regions of 
 the atmosphere, is principally owing to the cause 
 which we have been last considering, viz., the inter- 
 
102 ON THE CAUSES AND PRINCIPLES 
 
 mixture of atmospheric strata of different tempera- 
 tures. But, after having reviewed all the more im- 
 portant circumstances in which intermixture of atmo- 
 spheric strata of different temperatures can reason- 
 ably be supposed to occur, and which is altogether 
 omitted by other meteorological writers, I am in- 
 clined to think, that this fourth cause has much less 
 influence in the formation of clouds, than the one 
 previously treated of, viz., when a diminution of the 
 atmospheric temperature, arising from the transporta- 
 tion of air from a warm to a comparatively cold cli- 
 mate by the agency of winds, takes place. It is ob- 
 vious, however, that the cause of the formation of 
 clouds last treated of, must always co-operate less or 
 more with the two considered immediately previous. 
 And, owing to this circumstance, it is difficult to ap- 
 preciate their separate influence. 
 
 We have now, at considerable length, explained 
 the causes and principles which determine the forma- 
 tion of clouds. It is evident, upon reviewing the 
 subject, that, with the exception of some of the cir- 
 cumstances enumerated under the first cause of the 
 existence of clouds, wind is a necessary agent in their 
 formation. If there was no such thing as wind, which 
 would be the case if the air was not liable to expan- 
 sion by means of heat, no clouds, with the exception 
 of mists and fogs, could ever make their appearance. 
 All the moisture evaporated in such circumstances 
 during day, would be returned to the earth in the 
 forms of dew and falling mist during night. Even 
 in our windy climate, the proportion of moisture, 
 averaged for the whole of Great Britain, which is re- 
 
OF METEOROLOGICAL PHENOMENA. 103 
 
 turned to the earth in the form of dew, (and it is only 
 during intervals of perfectly calm, or nearly perfectly 
 calm weather that dew is deposited,) has been esti- 
 mated by Dr Thomson, to be only 4 inches out of 
 the total 36. 
 
 Nor does the existence of wind without the co- 
 operation of other circumstances necessarily produce 
 clouds. For instance, if the whole surface of the 
 earth was level like that of the ocean, and if the di- 
 rection of the wind was always from a cold towards a 
 warmer climate, and the temperature of the different 
 aerial strata was always such, that a colder and heavier 
 atmosphere never came to rest over one that was 
 warmer and hghter, no clouds could be formed. But, 
 as this is not the case, and as the kind of weather at 
 any given time and place, is a result affected and mo- 
 dified by a variety of antecedent and existing circum- 
 stances, which may be acting more or less either in 
 union, or in opposition to each other, it is necessary, 
 in order to a correct understanding of meteorological 
 phenomena, that we should explain the modifications, 
 which different degrees of velocity in the atmospheric 
 current may be expected to produce. 
 
 In general then it may be remarked, that whatever 
 effect a wind of moderate velocity is calculated to 
 produce upon the hygrometric condition of the atmo- 
 sphere, will be increased by every increment in its ve- 
 locity, and diminished by every decrement. Thus, if 
 the wind blows from a warm towards a cold climate, 
 great rapidity of motion, by allowing less time for 
 cooling, will transport a warm atmosphere to a cold 
 climate with less diminution of its previous tempera- 
 
104 ON THE CAUSES AND PRINCIPLES 
 
 ture than if it moved with moderate velocity. Con- 
 sequently, it must undergo a greater diminution of 
 temperature and of capacity of moisture, (and which 
 must occasion a proportionally greater amount of 
 rain,) before being accommodated to the temperature 
 and aqueous capacity of the air in the climate to 
 which it has been transported. Hence, one reason 
 why strong southerly winds, particularly during the 
 winter season, are more productive, in this and all 
 northern climates, of clouds and wet weather, than 
 gentle gales from the same direction. 
 
 Again, every increase to the strength of the wind 
 renders the unevenness of the earth's surface more ef- 
 fective in robbing the air of a portion of its moisture 
 in the following ways : — -1. It causes the atmospheric 
 current to surmount a greater number of hills and 
 elevated lands in a given time. 2. By increasing the 
 atmospheric agitation, it drives the particles of preci-. 
 pitated vapour composing mists and clouds together, 
 so as to form drops of rain ; and thus, by increasing 
 their gravity, accelerates their descent to the surface 
 of the earth. 
 
 But, while every increment to the velocity of the 
 wind renders the unevenness of the earth's surface 
 more effective in robbing the air of a portion of its 
 moisture, it, at the same time, promotes evaporation, 
 and thereby more speedily replenishes it again with 
 humidity. Thus, though the atmosphere may be 
 rendered much undersaturated in its passage, during 
 windy weather, over hills and elevated lands, humidity 
 is thereafter supplied to it according to the law, that 
 evaporation from all moist surfaces proceeds with 
 
OF METEOROLOGICAL PHENOMENA. 105 
 
 greater rapidity according as the incumbent atmo- 
 sphere is hygrometrically drier. Of course, the more 
 rapidly, and the more completely the air is robbed of 
 its moisture in passing over mountains or elevated 
 lands, the more is evaporation subsequently accelerated. 
 
 Again, during calm weather, evaporation only pro- 
 ceeds with a rapidity proportional to that with which 
 the vapour is carried off, and intermixed with the in- 
 cumbent atmosphere in consequence of its tendency 
 to diffuse itself equally. Now, this tendency to aerial 
 diffusion is mechanically assisted during windy wea- 
 ther, and evaporation is accordingly promoted, in con- 
 sequence of fresh undersaturated portions of air be- 
 ing then brought successively, and rapidly, into con- 
 tact with the evaporating surface. Owing to this me- 
 chanical assistance, Saussure found, by experiments 
 performed at Geneva, that wind moving at the rate of 
 22 feet in a second, triples the quantity evaporated in 
 calm air. 
 
 The aggregate amount of water precipitated from 
 the atmosphere upon the earth's surface, must be ex- 
 actly the same as that which is raised therefrom by 
 evaporation. Consequently, whatever increases eva- 
 poration, whether it be increase of temperature, or in- 
 crease in the velocity of the wind, must correspond- 
 ingly increase the aggregate amount of water precipi- 
 tated. But though this be the case, the proportion 
 of aqueous vapour which passes into the form of cloud 
 before descending, relative to the aggregate amount 
 of water evaporated, is much greater in climates where 
 windy weather prevails, than in those of an opposite 
 character. 
 
106 ON THE CAUSES AND PRINCIPLES 
 
 The atmospheric variation of temperature during 
 day and night, is found to diminish with the perpen- 
 dicular altitude above the surface of the ground; and 
 this variation near the surface of the ground, is much 
 greater in calm, than it is in windy weather. Owing 
 to the agitation and intermixture of the various aerial 
 strata during windy weather, the difference between 
 the temperature of the higher and lower atmospheric 
 strata is restricted both by night and day, chiefly to 
 the decrease of one degree for every 300 feet of per- 
 pendicular ascent. During calm weather, however, 
 while the temperature of the lower aerial strata is 
 much higher than those at a greater altitude during 
 day, the reverse, as was formerly stated, is the case 
 by night. Now, as the hygrometric condition of the 
 atmosphere, and of its various strata, is chiefly regu- 
 lated by variations of temperature, it is obvious that 
 during calm clear weather, the diff"erence between the 
 hygrometric dryness by day, and dampness by night, 
 of the lower atmospheric strata, will be much greater 
 than during windy and cloudy weather. Hence, dur- 
 ing calm clear weather, though the lower atmospheric 
 strata may become much undersaturated during the 
 heat of day, they frequently become so much oversa- 
 turated as to precipitate humidity during the coldness 
 of night ; and accordingly, a greater or less propor- 
 tion of the water evaporated from the earth's surface 
 during day, is gradually returned to it by deposition 
 in the form of dew during night, without ever passing 
 into the state of cloud. In inland champaign coun- 
 tries where long calms prevail, and in warm climates, 
 during what is called the dry season, this condition 
 
OF METEOROLOGICAL PHENOMENA. 107 
 
 of the atmosphere frequently continues for v/eeks and 
 months together, without any of those elevated clouds 
 being formed, from which alone rain is precipitated. 
 During windy weather, however, when, for reasons 
 already explained, the temperature of the aerial strata 
 immediately incumbent upon the earth's surface does 
 not sink lower during night, than that of those at a 
 greater altitude, no dew falls ; and consequently, 
 all the moisture then evaporated, (and which is greater 
 than in the opposite circumstances,) before descend- 
 ing, passes into the state of cloud, and is returned to 
 the earth in the forms of rain, snow, and hail. 
 
 The preceding observations sufficiently explain the 
 reasons why windy weather is peculiarly productive of 
 clouds and rain ; and why a prevailing stillness in the 
 atmosphere is favourable to dry weather and a cloud- 
 less sky. Accordingly, it is observed, that in windy 
 climates, in windy years, and in windy seasons of the 
 year, there is more cloudy and wet weather than in 
 those of an opposite character. Last winter (1833-4) 
 was remarkable for the prevalence of high winds, and 
 their direction being chiefly from rainy points, viz. 
 between south and west inclusive, it turned out, in 
 accordance with the principles we have been explain- 
 ing, to be one of the wettest winters on record, over 
 the whole of Great Britain and Ireland. 
 
 Before concluding this chapter, several not very 
 important circumstances which require explanation, 
 may be noticed. Thus it once occurred to me, that 
 the formation of clouds in the higher regions of the 
 air might be accounted for upon the principle, that as 
 aqueous vapour has a greater capacity for heat, and is 
 
108 ON THE CAUSES AND PRINCIPLES 
 
 specifically lighter than air in the proportion nearly of 
 5 of the former, to 8 of the latter, aqueous vapour 
 ought to rise in the atmosphere till increasing cold- 
 ness, by condensing it into the visible and heavier 
 state of cloud, prevented its farther ascent. But 
 though the greater specific lightness of vapour than 
 air, acting in conjunction with the greater calorific 
 capacity of the former, and consequent susceptibility 
 of losing, or gaining a larger proportion of heat, with 
 an equal diminution, or increment of temperature 
 than the latter, may possibly not only determine the 
 height in the atmosphere to which vapour can ascend, 
 but also the proportions which at different tempera- 
 tures can exist in invisible solution in a given space ; 
 still there are facts which demonstrate that clouds are 
 not the result of their joint agency. For instance, if 
 aqueous vapour, in consequence of being specifically 
 lighter than air, had a tendency to ascend till it was 
 condensed by coldness in the higher regions of the 
 atmosphere, an unclouded sky, particularly at sea, 
 would never be seen. In such circumstances, the 
 condensation of vapour, and the formation of cloud in 
 the higher regions of the atmosphere, would be con- 
 stantly going on, with a rapidity at all times propor- 
 tional to the amount of moisture evaporating under- 
 neath. Now, the continuance of fair weather, and a 
 cloudless sky, for weeks, and even months, (which 
 frequently occurs in more southern latitudes,) not 
 only on shore, but also at sea, is incompatible with 
 such a hypothesis. Indeed this fact leads us to in- 
 fer, that the ascending tendency of aqueous vapour, 
 arising from its being specifically fighter than air, is 
 
OF METEOROLOGICAL PHENOMENA. 109 
 
 counteracted when the atmosphere becomes saturated 
 with moisture ; and that any diminution of tempera- 
 ture, such as may be supposed to occur during night, 
 or the fall of the year, affects the higher regions of 
 the air so slowly and so slightly, in comparison with 
 the lower, as merely to occasion a gradual subsidence 
 of the aqueous vapour towards the earth's surface, 
 without converting any part of it, unless assisted by 
 other causes, into the visible form of cloud. Now, 
 agreeably to the views we have already given of the 
 formation of clouds, a continuance of fair weather, 
 and an unclouded sky, for weeks and months, at cer- 
 tain seasons of the year, results either from there being 
 little or no wind ; or from its direction being favour- 
 able to dry weather, such as blowing from a cold 
 towards a comparatively warm climate ; or from a 
 quarter in which it is robbed of humidity by passing 
 over elevated mountains, or an extensive tract of dry 
 land, without being proportionally replenished by eva- 
 poration from a watery surface underneath. On the 
 other hand, the continuance of wet weather, which in 
 certain climates often follows a continuance of dry 
 weather ; and in general, the frequency of wet wea- 
 ther, during particular seasons of the year, results from 
 the direction of the wind being in the former case for 
 a continuance of time, and in the latter, on frequent 
 occasions, favourable to wet weather, such as blowing 
 from the sea and a warmer climate. 
 
 From the preceding observations, it appears that 
 clouds, without the assistance of some other cause of 
 their formation, do not result from the tendency of 
 aqueous vapour to ascend, in consequence of its less 
 
110 ON THE CAUSES AND PRINCIPLES 
 
 specific gravity than air, till it gets condensed by 
 coldness in the higher regions of the atmosphere. 
 Nevertheless, I am disposed to think that this ascend- 
 ing tendency of aqueous vapour, must have some in- 
 fluence in bringing the elevated atmospheric strata 
 sooner up to the point of saturation, than those near 
 the earth's surface. For instance, let us suppose that 
 all the atmospheric strata, to the elevation of 20,000 
 feet, are in an equal degree undersaturated with humi- 
 dity. Let us suppose also that the temperature of 
 these different strata, to that elevation, is remaining 
 unchanged ; that there is no wind ; and that the atmo- 
 sphere is getting gradually supplied with humidity by 
 evaporation from a watery surface underneath. In 
 this case, if the aqueous vapour was of the same spe- 
 cific gravity as air, and accordingly, had no tendency 
 to ascend, the different atmospheric strata would be 
 sooner brought up to the point of saturation, accord- 
 ing as they were less elevated above the earth's sur- 
 face. The circumstance, however, of clouds after a 
 continuance of serene weather, first making their ap- 
 pearance in very elevated regions of the atmosphere, 
 favours the opinion, that those strata are usually near- 
 est the point of saturation ; and when equally under- 
 saturated with those below, are soonest brought up to 
 the point of saturation ; and, on these accounts, most 
 apt to give birth to clouds when any reduction of tem- 
 perature occurs. Thus, after a continuance of calm 
 weather, and a cloudless sky, the first visible indica- 
 tion of an approaching change, is usually the appear- 
 ance of cirri, the most elevated of all clouds. 
 
 To the preceding opinion it might be objected, 
 
OF METEOROLOGICAL PHENOMENA. Ill 
 
 that if the atmospheric strata, at a great elevation above 
 the earth's surface, are usually nearer the point of 
 saturation than those underneath, the rising slope of a 
 hill or elevated lands during windy weather, by uplift- 
 ing and depressing the temperature, not only of the 
 undermost strata of the atmospheric current, but of 
 all those above, should cause clouds to form, not on 
 or near the summits of hills and mountains, but in 
 general, at a considerable altitude above them. While 
 it may be admitted, agreeably to the second cause 
 mentioned of the formation of clouds, that any slope 
 or rising ground will have some effect in uplifting the 
 whole atmosphere immediately vertical, while sur- 
 mounting it, (and the stronger the wind the greater 
 will be its influence in this respect,) still I am dis- 
 posed to think, that the strata are uphfted in a rapidly 
 diminishing degree, according as they are more ele- 
 vated above the rising ground. Suppose a hill or the 
 slope of the land were to rise from the sea-shore at an 
 angle of 10 degrees from the horizontal, to the height 
 of 1000 feet, I very much doubt if the atmospheric 
 strata, at the elevation of two miles, would be uplifted 
 100 feet, or even so much while surmounting it, by 
 any wind however strong. And this opinion is so far 
 confirmed by the fact, that it has never yet been ob- 
 served, that the barometer sinks less rapidly in ascend- 
 ing a mountain during windy weather, than it does 
 during calm weather. If the preceding opinion be 
 correct, it is obvious that the undermost strata, in 
 consequence of being farthest uphfted, should be the 
 most apt, in such circumstances, to become oversatu- 
 rated, and to give birth to clouds. The disposal of 
 
112 ON THE CAUSES AND PRINCIPLES 
 
 the air in such cases may be accounted for, partly by 
 the retardation which the lower portion of the atmo- 
 spheric current undergoes while approaching the rising 
 ground, and partly by the increased velocity which the 
 elasticity of the air communicates, when it has reached 
 its summit. 
 
 It must be confessed, however, that it is difficult 
 to explain how clouds, especially during windy wea- 
 ther and night, should be formed only between the 
 elevation of 2000 and 20,000 feet above the level of 
 the sea. The circumstance of the stratus, or fall- 
 cloud, during calm clear nights beginning to form close 
 to the surface of the ground, and gradually extending 
 itself upwards, proves that the aerial strata nearest the 
 earth's surface are equally susceptible, upon a suffi- 
 cient reduction of temperature taking place, of giving 
 birth to clouds, with those at a greater elevation. 
 And the fact that the fall-cloud has seemingly no ten- 
 dency to ascend in the atmosphere, until its component 
 particles are expanded, and rendered specifically lighter 
 by the heat of returning day, shows that the specific 
 gravity of a cloud at its first formation may be so great 
 as to cause it to float as low as the level of the sea. 
 
 During day, the greater augmentation of tempera- 
 ture which the atmospheric strata, near the surface of 
 the ground, undergo, than those at a greater altitude, 
 might be supposed to counteract, and prevent the 
 formation of clouds within a Hmited distance of the 
 earth's surface. But, during windy nights, when the 
 surface of the ground, and the atmospheric strata 
 thereupon incumbent, are apt to become at least as 
 cold as the aerial strata at a greater elevation, it is 
 
OF METEOROLOGICAL PHENOMENA. 113 
 
 difficult to assign a satisfactory reason, why clouds 
 never form nor float at a small elevation, such as 
 from 100 to 600 feet above the level of the sea. This 
 appears more remarkable, when it is considered, that 
 clouds are principally formed when the wind blows 
 from a warm towards a cold climate. In this case, 
 the lower portion of the atmospheric current, by com- 
 municating in its progress with a colder and colder 
 surface underneath, must have its temperature and 
 capacity for moisture gradually reduced. Hence it 
 might be anticipated, that, however much undersatu- 
 rated previously, its hygrometric condition would be 
 ultimately brought up to the point of saturation ; 
 and, thereafter, if the same cause continued to ope- 
 rate,-— that is, if the wind continued to blow from the 
 same direction, — it seems reasonable, a -prioTi, to ex- 
 pect, that clouds should either be formed amongst 
 the undermost aerial strata, or that moisture should 
 be precipitated on the earth's surface. Moreover, 
 the fact of no clouds making their appearance, in such 
 circumstances, under 1500 feet above the level of the 
 sea, is more remarkable when it is considered, that 
 the reduction of temperature, above mentioned, af- 
 fects the aerial strata nearest the ground soonest, and 
 to the greatest extent, and all those above later, and 
 in less degree, according as they recede upwards. 
 And hence, reasoning, a priori^ it might be antici- 
 pated, that the formation of clouds, in such circum- 
 stances, should always commence at the surface of 
 the ground, and extend upwards ; whereas, with the 
 exception of the stratus^ which only originates in still 
 weather, their formation commences generally be^ 
 
 p 
 
114 ON THE CAUSES AND PRINCIPLES 
 
 tween 8000 and 20,000 feet above the earth's surface, 
 and subsequently extends downwards. 
 
 The circumstance under consideration, viz. why 
 clouds never form nor float, during windy nights, at a 
 lower altitude than 1500 feet above the level of the 
 sea, we do not pretend to be able satisfactorily to ex- 
 plain. It may possibly, however, result from the 
 influence of various causes, such as the following, 
 operating more or less in union with each other. 
 
 1. The principal component materials of the surface 
 of the earth, and also the saline ingredients contained 
 in the ocean, exert an attractive force upon moisture 
 dissolved in the atmosphere ; and the air, while it 
 also exerts a similar attractive influence for moisture, 
 has less power, according as it is nearer the point of 
 saturation, in resisting that of the subjacent earth and 
 sea. Now, as all attractive or repulsive forces, ex- 
 erted by one body upon another, diminish as the 
 square of the distance between them increases ; the 
 attraction exerted by the earth and sea, upon the 
 aqueous vapour contained in the air, should become 
 less, as the square of the distance, upon receding up- 
 wards from the earth's surface, increases. Hence, it 
 is not improbable, that when the wind blows from a 
 warm towards a cold climate, and the transported air 
 gradually becomes damper, and consequently, less 
 able to retain its humidity, the earth and sea, accord- 
 ing to the principle upon which hygrometers are 
 usually constructed, may at length begin to abstract 
 moisture from the lower atmospheric strata j and the 
 amount abstracted should increase as they approach 
 the point of saturation. Owing to this abstraction of 
 
OF METEOROLOGICAL PHENOMENA. 115 
 
 humidity, the lower atmospheric strata, which, in con- 
 sequence of greater proximity to the abstracting sur- 
 face, should be most affected thereby, may, in gene- 
 ral, be kept somewhat drier than the point of satura- 
 tion, when the more elevated strata, in consequence 
 of being less under the influence of the earth's attrac- 
 tion for moisture, may become so much oversatu- 
 rated, as to give birth to clouds and rain. 
 
 As an attractive influence subsists between caloric 
 and humidity, it may possibly be owing to the supe- 
 rior coldness of the ground relative to that of the in- 
 cumbent atmosphere, assisted, perhaps, by the still- 
 ness of the air, that the moisture composing the stra- 
 tus, and fogs in general, is so slowly attracted from 
 the lower aerial strata by the subjacent earth. 
 
 2. The circumstance previously adverted to, of the 
 elevated aerial strata becoming sooner saturated with 
 moisture than those underneath, in consequence of 
 the ascending tendency of aqueous vapour, arising 
 from its less specific gravity than air, may also have 
 some influence in producing the phenomenon under 
 consideration. Thus, when the wind blows from a 
 warm towards a comparatively cold climate, even 
 though the aerial strata nearest the ground may un- 
 dergo a greater reduction of temperature in a given 
 time, than those at a considerable altitude ; still, the 
 greater proximity of the latter to the point of satura- 
 tion, may cause them to become first oversaturated 
 with humidity. 
 
 3. Provided the conjecture which we formerly ad- 
 vanced be correct, viz. that above a certain altitude, 
 the velocity of the atmospheric current gradually di- 
 
116 ON THE CAUSES AND PRINCirLES 
 
 minishes ; the intermixture of the upper with the 
 lower atmospheric strata, according to principles ex- 
 plained when treating of the fourth cause of the for- 
 mation of clouds, may also assist in causing the ele- 
 vated aerial strata to become sooner saturated with 
 moisture, so as to give birth to clouds and rain, than 
 those underneath. And when once clouds are formed, 
 the continuance of the intermixing process, in conse- 
 quence of the heat evolved during their formation, 
 and afterwards arrested by them, may account for the 
 perpetuation of the formation of clouds in the higher 
 regions of the atmosphere ; while the air near the 
 earth's surface remains undersaturated with humidity, 
 and free of clouds. 
 
 4. The fact of all clouds formed during windy wea- 
 ther, floating at an elevation of at least 1500 feet 
 above the level of the sea, proves, that the specific 
 gravity of such clouds is never so great as to cause 
 them to descend nearer the earth's surface. Hence 
 it may be inferred, that though small quantities of 
 moisture may be precipitated from the atmosphere 
 into the vesicular form underneath the above altitude, 
 still those vesicles may rise to that altitude, before 
 being concentrated in sufficient quantities to form a 
 visible cloud. 
 
 5. Judging from the fact of the amount of rain that 
 falls being greater, as estimated by rain gauges, and 
 the drops being larger, the nearer we approach the 
 surface of the earth, and the lower the earth is at the 
 place of observation, it seems probable, that descend^ 
 ing rain possesses the property of attracting, and 
 thereby ^vithdrawing a portion of the aqueous vapour 
 
OF METEOROLOGICAL PHENOMENA. 117 
 
 from the air ; and consequently, of undersaturating 
 the lower atmosphere through which it passes in its 
 descent to the earth. 
 
 The circumstance of clouds never making their 
 appearance at an elevation much higher than 20,000 
 feet above the level of the sea, may possibly be 
 owing, either to the coldness and lightness of the air 
 at that altitude being such, that aqueous vapour can- 
 not rise to a greater elevation, in consequence of its 
 then tendency to condensation. Or, provided aque- 
 ous vapour ascends much beyond that altitude, its 
 quantity may be so small beyond that elevation, that 
 when precipitated from the atmosphere by a reduc- 
 tion of temperature, and thereby increased in specific 
 gravity so as to descend, it may fall a considerable 
 distance before the widely separated aqueous particles 
 can unite ; and after uniting, before they congregate 
 in sufficient quantity to form a visible cloud. This 
 last result may be conceived to take place at the alti- 
 tude where the cirri, the most elevated, as well as 
 the thinnest and most transparent denomination of 
 clouds, make their appearance. 
 
 At what degree of coldness moisture becomes in- 
 capable of existing in the state of vapour, I do not 
 know. But as aqueous vapour has a greater capacity 
 for heat, and consequently during an equal reduction 
 of temperature, must lose a larger proportion of calo- 
 ric than air ; and as the specific gravity of bodies 
 increases during a given reduction of temperature in 
 proportion, or nearly in proportion, as they part with 
 caloric, it is obvious, that at some unknown elevation, 
 and which will vary with the latitude and season of 
 
118 ON THE CAUSES AND nUNCIPLES 
 
 the year, according as the temperature at that eleva- 
 tion varies, aqueous vapour must become specifically 
 as heavy as air, and consequently will thereafter have 
 no tendency to ascend higher. Hence it may be in- 
 ferred, that no aqueous vapour can exist in the atmo- 
 sphere beyond the altitude where the degree of cold- 
 ness is such that aqueous vapour becomes specifically 
 as heavy as air. 
 
 The only farther circumstance which we purpose 
 to notice in this chapter is, that when a strong wind 
 blows from a warm towards a comparatively cold cli- 
 mate, rain, on some occasions, only begins to fall, 
 and on others, falls more copiously after the wind has 
 somewhat abated, or perhaps altogether ceased, or 
 even for a short time after it has changed to a dry di- 
 rection, than it did, so long as it continued high. The 
 explanation of this fact may depend upon the sepa- 
 rate, or conjoint influence of the following circum- 
 stances : — 1. When the wind blows strongly from a 
 warm towards a cold climate, a warmer atmosphere is 
 thereby transported to a cold climate, than what would 
 otherwise have there existed. And though the tem- 
 perature of the air may be getting gradually reduced 
 during its progress thither, still the heated atmosphere 
 may not acquire the reduced temperature of the cli- 
 mate to which it has been transported, till a consider- 
 able time after the wind has abated, or altogether 
 ceased, or perhaps even changed its direction. Now, 
 either of these events may occur before the tempera- 
 ture and capacity of the elevated aerial strata for mois- 
 ture, is so much reduced as to precipitate a sufficiency 
 of humidity into the form of clouds to produce rain. 
 
OF METEOROLOGICAL PHENOMENA. 119 
 
 The heated atmosphere brought by the wind may 
 have been previously considerably undersaturated ; 
 and the reduction of temperature which it sustains 
 during its rapid transportation to a colder climate 
 may be insufficient, or little more than sufficient, to 
 bring its hygrometric condition up to the point of 
 saturation. In such circumstances, the continuance 
 of the reduction of the atmospheric temperature, af- 
 ter the wind has ceased, or changed its direction, 
 may occasion clouds and rain in abundance, while the 
 reduction of temperature which it previously under- 
 went during its transportation to a colder climate, 
 may have produced no rain, and few clouds of any 
 considerable depth, or density. When rain attends 
 a wind blowing from a colder climate, it can only be 
 explained upon the above principle, viz., that the 
 more elevated aerial strata have been previously trans- 
 ported from a warmer climate, and are still undergo- 
 ing a reduction of temperature. 
 
 2. The oversaturation of the atmosphere, and con- 
 sequent additional formation of clouds, arising from 
 the sinking down and intermixture of the colder at- 
 mospheric strata above, with those warmer strata be- 
 low, where the clouds have already begun to form, as 
 was explained when treating of the fourth cause of 
 the formation of clouds, may also assist in rendering 
 clouds, and the fall of rain, more abundant after the 
 wind has abated, or even changed its direction, than 
 what they were so long as it continued high. 
 
 3. The velocity of a high wind must in some de- 
 gree prevent the sinking down and intermixture of 
 colder air above, with any aerial stratum that happens 
 
120 ON THE CAUSES AND PRINCIPLES, &C. 
 
 to be warmer below. Hence, in all the cases before 
 enumerated, when the formation of clouds depend 
 upon, or is assisted by, the intermixture of saturated, 
 or nearly saturated, aerial strata of different tempera- 
 tures, the subsidence of the wind should for a short 
 time be accompanied by an increased formation of 
 clouds, and a more copious fall of rain. Accordingly, 
 it is frequently observed, that so long as the wind con- 
 tinues high, clouds are not formed of sufficient depth 
 and density to produce rain. On such occasions, 
 when the wind abates, the assistance of the intermix- 
 ing process rapidly increases the density of the clouds 
 already in the process of forming, and causes them to 
 descend to a lower level. At length their component 
 particles becoming too contiguous to remain separate, 
 begin to unite. Their specific gravity being thereby 
 augmented, they now rapidly descend ; and partly by 
 means of farther unions ; and partly by condensing 
 and receiving additions from all aqueous particles 
 which they either attract, or come in contact with in 
 their fall, they ultimately reach the surface of the earth 
 in the form of drops of rain. 
 
CHAPTER IV. 
 
 ON CIRCUMSTANCES ERRONEOUSLY SUPPOSED TO PRODUCE 
 CLOUDS. 
 
 Professor Playfair, in his Outlines of Natural 
 Philosophy, after explaining the ratio in which the 
 capacity of air for moisture varies with alterations of 
 temperature, states, "7)f therefore large portions of 
 the atmosphere, of different temperatures, and satu- 
 rated, or nearly saturated, with humidity, be driven 
 against one another by contrary winds, the conse- 
 quence must be a precipitation of humidity, or the 
 formation of clouds." 
 
 In the passage above quoted, the reader might be 
 led to believe, that Playfair supposes, that two large 
 portions of atmosphere, on the same horizontal level, 
 and of different temperatures, might be driven against 
 one another by contrary winds, just as if they were 
 projected by the force of immense bellowses placed 
 opposite each other. This, however, being contrary 
 to the principles which regulate the direction of winds, 
 never happens in nature, and therefore is never the 
 cause of the formation of clouds. 
 
 The formation of clouds, according to the Hut- 
 tonian theory, is also supposed to arise from the colli- 
 sion of the upper and lower halves of the atmosphere, 
 which, agreeably to the commonly received opinion, 
 
 Q 
 
122 ON THE CAUSES AND PRINCIPLES 
 
 are supposed to be always moving in opposite direc- 
 tions. Thus Play fair says : " Professor Leslie has 
 shown that the collision of opposite currents of air, of 
 different temperatures, may furnish a supply sufficient 
 for the production of the heaviest rain." Experiments 
 on Heat and Moisture, p. 130. And Playfair adds, 
 *' The mixture of different portions of air is likely to 
 take place most frequently, where the two opposite 
 currents already mentioned come in contact with one 
 another. This is at the height of 18,000 feet and 
 upwards." 
 
 When treating, in the preceding chapter, of the 
 fourth cause of the formation of clouds, we endea- 
 voured to show that it was only when the lower half 
 of the atmosphere blew from a cold towards a com- 
 paratively warm climate, such as is exemplified by 
 monsoons and sea and land breezes, that an opposite 
 current in the upper half of the atmosphere can simul- 
 taneously exist. And we demonstrated, that in the 
 opposite circumstances, when the lower atmosphere 
 blows from a warm towards a cold climate, it is physi- 
 cally impossible that there can be simultaneously a 
 contrary current in the upper half of the atmosphere. 
 Now, as by far the greatest proportion of rain in thfs, 
 and almost all other climates beyond the tropics, falls 
 when the lower atmosphere blows from a warm towards 
 a comparatively cold chmate, it is obvious, that the 
 clouds and rain, produced in such circumstances, do 
 not result from the collision of opposite currents sim- 
 ultaneously existing in the upper and lower halves of 
 the atmosphere. 
 
 But supposing, for the sake of argument, that the 
 
OF METEOROLOGICAL PHENOMENA. 1'23 
 
 commonly received opinion, of opposite currents al- 
 ways existing in the upper and lower halves of the 
 atmosphere, were correct, the collision of the upper 
 and under atmospheric currents should be as great 
 when the former is blowing from a warm towards a 
 cold climate, and the latter from a cold towards a warm 
 climate, as it is in the opposite circumstances. But 
 we have seen, as in the example previously given of 
 the Mistral, at Marseilles, that clouds are only formed 
 when the lower half of the atmosphere blows from a 
 warm towards a cold climate ; and that they dissolve 
 and disappear in the reverse circumstances. Hence 
 collision of the upper and lower atmospheric currents 
 is not the cause of the formation of clouds. 
 
 When we come to treat of the causes and princi- 
 ples of winds, it will appear in those cases where op- 
 posite currents in the upper and lower halves of the 
 atmosphere exist, that at the plane which separates 
 the two halves, the atmospheric strata must be in 
 equihbrium, and can have no horizontal motion what- 
 ever. And it will also be evident, that, though the 
 horizontal movements of the upper and lower halves 
 of the atmosphere may gradually increase with the 
 distance from the plane which separates them, still, 
 for a considerable space on either side of it, the mo- 
 tion must be very slow j and accordingly, coUision 
 between the upper and under atmospheric currents 
 can hardly be said in such circumstances to take 
 place. In short, the sinking down and intermixture 
 of the superior with the inferior aerial strata, which, 
 as was explained when treating, in the preceding 
 chapter, of the fourth cause of the formation of clouds, 
 
124 ON THE CAUSES AND PRINCirLES 
 
 can only take place wlien the aerial particles of the 
 former are colder and heavier than those of the lat- 
 ter, after making due allowance for the different de- 
 grees of atmospheric compression to which they are 
 subjected, is totally a different thing from the colli- 
 sion spoken of by meteorologists. This is evident 
 from considering, that the sinking down and intermix- 
 ture of the superior with the inferior strata, must go 
 on so long as the former are colder and specifically 
 heavier than the latter. And this may continue for a 
 considerable time after the atmospheric currents have 
 subsided into a perfect calm. 
 
 Another circumstance, erroneously supposed to be 
 a cause of the formation of clouds, and the faUing of 
 rain, is a change of wind. The most important 
 facts upon which this opinion is founded, are the fol- 
 lowing : — ] . During calm^ or nearly calm weather, 
 rain, 'particularly in warm climates, or, in the sum- 
 mer season, in temperate latitudes, is usually pre- 
 ceded and ushered in with a breeze, and not unfre- 
 quently by a greater or less change in the direction 
 of the wind. 2. In intertropical climates generally 
 the rainy season occurs when the sun approaches the 
 zenith, at which time the winds are most imriable. 
 3. The change of the monsoons in the East Indies 
 is alvjays accompanied with the formation of dense 
 clouds, and lieavy falls of rain ; whereas when the 
 trade-winds blow uniformly, hardly any rainfalls. 
 
 In support of the notion, that a change of wind is a 
 cause of rain. Professor Playfair, in his Outlines of 
 Natural Philosophy, says : " There is in our climate 
 hardly any instance of rain without a change of wind. 
 
OF METEOROLOGICAL PHENOMENA. 125 
 
 and very rarely a change of wind without rain in a 
 greater or smaller quantity." This statement of 
 Playfair's is so far from being correct, that he must 
 certainly have made it without any examination of 
 the facts himself. 
 
 Owing to the peculiar situation of Britain, sur- 
 rounded by the sea on every side, together with the 
 impossibility of ascertaining what is, or may pre- 
 viously have been, the precise direction and force of 
 the wind in the upper half of the atmosphere, we 
 cannot for certain predict, even though the direction 
 of the wind in the lower half of the atmosphere be 
 given, that we shall have either dry or wet weather on 
 any day of the year. But, judging from my own ob- 
 servations, the chances of rainy, or of fair weather, are 
 obviously greater or less, in proportion as there exists 
 at the time, and immediately previous, a more or less 
 favourable combination of circumstances for producing 
 one or other of these results. In short, I feel war- 
 ranted in stating, that even in any part of Great Bri- 
 tain, a knowledge of the general principles which we 
 have already explained regarding the causes which 
 tend to produce an oversaturated state of the atmo- 
 sphere with regard to humidity, together with a 
 knowledge of the direction and force of the wind, 
 and the distance of the place of observation from the 
 sea, and its position in relation to surrounding ele- 
 vated lands, afford us the best means of accounting 
 for all changes of weather. Thus, at Glasgow, where 
 my observations have been made, (though the same 
 rule, for obvious reasons, will not apply to parts of the 
 island differently circumstanced with regard to dis- 
 
126 ON THE CAUSES AND PRINCIPLES 
 
 tance from the sea, and intervening high lands in dif- 
 ferent directions,) when the wind blows from a warm 
 direction, and from the nearest sea, such as from 
 the south or south-west during the coldest period of 
 the year, (and the stronger it blows the more cer- 
 tain is the result,) the general character of the wea- 
 ther is warm for the season of the year, but cloudy 
 and wet. And instead of there being hardly any in- 
 stance of rain in our climate without a change of 
 wind, as Playfair states, the weather, so long as the 
 wind blows from that direction, during that season of 
 the year, usually continues wet, showery, and un- 
 settled, with only casual dry days, and these chiefly 
 when the wind abates. On the contrary, when the 
 wind blows from the opposite quarter, viz., from the 
 north, or north-east, during the same season of the 
 year, the general character of the weather is cold, and 
 dry, with only casual wet or snowy days ; and these 
 are usually attended with a low state of the barome- 
 ter, and a considerable force of wind. And, instead 
 of a change of wind from the former direction to the 
 latter being productive of rain in a greater or smaller 
 quantity, as ought to be the case if Playfair's state- 
 ment were correct, almost every person knows that it 
 is usually, and almost immediately, productive of dry 
 weather. 
 
 On continental coasts, where a great extent of land 
 lies in one direction, and the ocean on the other, such 
 as on the coast of the United States of America, the 
 point from whence the wind blows, in accordance 
 with the principles already explained, determines the 
 kind of weather. In the United States of America, 
 
OF METEOROLOGICAL PHENOMENA. 127 
 
 when the wind blows from the land, especially if its 
 direction be somewhat to the north of west, dry wea- 
 ther, and a cloudless sky, particularly during the cold 
 season of the year, permanently continues ; whereas, 
 when it blows from the ocean, especially if its direc- 
 tion be somewhat to the south of east, the general 
 character of the weather is cloudy and wet. In such 
 cases, the mere change of wind separately considered, 
 has no perceptible influence in forming clouds and 
 causing rain. No sooner does the wind shift from 
 the ocean to the land, than the wet weather ceases, 
 and the clouds gradually dissolve into invisible vapour. 
 And, on the contrary, when the wind shifts from the 
 land to the ocean, the previously clear sky, very soon 
 becomes overcast with clouds, and rainy unsettled 
 weather commences. 
 
 The instance formerly given and explained of the 
 opposite kinds of weather experienced during winter 
 at Marseilles, according as the wind blows from the 
 north or the south, also confirms the opinions we have 
 advanced. Thus, a change in the direction of the 
 wind at Marseilles, during the cold season of the 
 year, from north to south, is uniformly attended, or 
 very soon followed, by the appearance of clouds, and 
 the faUing of rain. But when it changes, during the 
 same season of the year, to the opposite direction, in- 
 stead of producing rain in greater or smaller quantity, 
 as Playfair's statement would lead us to expect, the 
 clouds disappear with astonishing rapidity. 
 
 In the preceding examples, it is obviously the 
 quarter to which the wind shifts, and not the mere 
 change, which determines the character of the wea- 
 
1*28 ON THE CAUSES AND PRINCIPLES 
 
 ther. But let us take cases where the dryness of the 
 direction to which the wind veers, cannot be assigned 
 as the reason why the change is not accompanied 
 with rain in greater or smaller quantity. 
 
 At Kingston, in the island of Jamaica, during what 
 is called the dry season, viz. from November till 
 April, those gentle winds, denominated Sea and Land 
 breezes, occur alternately in succession ; and though 
 the direction of the wind, during that lengthened pe- 
 riod, changes twice every twenty-four hours, still, with 
 the exception of clouds formed over the distant moun- 
 tains, according to the second mentioned cause of 
 their formation, there is almost constantly a cloudless 
 sky, and hardly ever a drop of rain. 
 
 In hke manner, during our finest and clearest wea- 
 ther, such as we frequently have during the summer 
 months, the direction of the wind frequently shifts in 
 our chmate several times in the course of a day ; but 
 these changes, so far as I have observed, have no in- 
 fluence in forming clouds, and causing rain. I shall 
 only farther add, that after carefully comparing, by 
 means of a meteorological table which I have kept, 
 the coincidences between a change of wind, and the 
 formation of clouds, I have found the discrepancies 
 so numerous, as to convince me, that the coincidences, 
 save those which were more properly referable to other 
 causes, and which were partly balanced by equally 
 objectionable discrepancies, are merely accidental. 
 Hence, I have come to the conclusion, that in this 
 climate, contrary to Playfair's statement, a change of 
 wind, considered separately from its direction and ve- 
 locity, is never the cause of the formation of clouds, 
 
OF METEOROLOGICAL PHENOMENA. 129 
 
 and the falling of rain ; though, as I will shortly have 
 occasion to show, the formation of clouds and the 
 falling of rain is frequently the cause of a change of 
 wind. 
 
 We shall now advert to the several phenomena 
 upon which the hypothesis we have been considering 
 is founded ; and as we proceed, will illustrate our 
 subject, by attempting to give some plausible ex- 
 planation of them. 
 
 The first point then to be considered is, that dur- 
 ing calm, or nearly calm weather, rain, particulai'ly 
 in warm climates, or in the summer season in ifiland 
 temperate latitudes, is usually preceded and ushered 
 in hy a breeze or gust of wind ; and notunfrequent- 
 ly by a greater or less change in the direction of the 
 loind. I am inclined to think that it is principally 
 owing to this and analogous facts not being properly 
 understood, that a change in the direction of the 
 wind has been supposed to be the cause of the for- 
 mation of clouds and the falhng of rain ; whereas, as 
 I shall endeavour to show, the previous formation of 
 clouds and the falling of rain, is, in all such cases, 
 the cause of the breeze and of the change of wind." 
 
 When we come to treat of the causes of wind, it 
 will appear, that, provided the barometrical pressure, 
 (that is, the atmospheric pressure as estimated by a 
 barometer,) at all equal altitudes above the level of 
 the sea were the same, there could be no wind ; for, 
 in that case, the atmosphere would be everywhere in 
 equilibrium, and could have no tendency to move in 
 one direction more than in another. On the con- 
 trary, at whatever equal altitudes any difference in the 
 
 R 
 
130 ON THE CAUSES AND PRINCIPLES 
 
 barometrical pressure takes place, the atmosphere, at 
 such altitudes, in obedience to the preponderance of 
 lateral pressure, will begin to move horizontally in 
 order to restore the equilibrium, from where the 
 pressure is greater to where it is less. The proxi- 
 mate cause therefore of atmospheric currents, is un- 
 equal barometrical pressui^e in different places, at 
 equal altitudes above the level of the sea. 
 
 Now, owing to the expansibility of air by means of 
 heat, a perpendicular column containing a given 
 amount of warm air, is longer than one containing a 
 similar amount of cold air; and consequently, the 
 upper portions of the former, from wanting sufficient 
 lateral support, must flow over upon the latter. But 
 this, while it diminishes the barometrical pressure of 
 the longer columns, proportionally increases that of 
 the shorter. And accordingly, while the upper por- 
 tions of the longer columns of warm air are flowing 
 over upon the top of the shorter columns of cold air, 
 an equivalent extent of the lower extremity of the 
 shorter columns, in obedience to the preponderance 
 of barometrical pressure, moves in the opposite direc- 
 tion. 
 
 The preceding observations show, that an equal 
 barometrical pressure at all equal altitudes above the 
 level of the sea, could only exist, provided the tem- 
 perature of the atmosphere at all equal altitudes 
 around the globe were alike. This, however, can 
 never happen. The causes of difference of tempera- 
 ture over different parts of the earth's surface, are 
 numerous, and ever varying with regard to each other 
 during the alternations of day and night, and the dif- 
 
OF METEOROLOGICAL PHENOMENA. 131 
 
 ferent seasons of the year. And as the various tem- 
 peratures of the different parts of the earth's surface, 
 whether land or water, are slowly communicated up- 
 wards to the portion of air immediately incumbent, it 
 is impossible that an universal equilibrium of the at- 
 mosphere can ever take place. In conformity, there- 
 fore, with these observations, we lay down the gene- 
 ral principle, that whatever produces a simultaneous 
 difference of temperature in different portio?is of the 
 atmosphere, at equal altitudes above the level of the 
 sea, necessarily gives rise to inequalities of barome- 
 trical pressure, and thus remotely becomes the cause 
 of wind. 
 
 With these preliminary remarks, we are now pre- 
 pared to understand how the supervention of clouds, 
 and the falling of rain, at one place and not at an- 
 other, should become the cause of a breeze and of a 
 change of wind. 
 
 When clouds, whether formed during night, or 
 transported by aerial currents, supervene any district 
 of a country, the surface of the ground, and the por- 
 tion of the atmosphere underneath them, receives a 
 less proportion of solar heat during day, than those 
 places over which no clouds are formed. Hence the 
 temperature becomes higher in the latter localities 
 than in the former ; and the atmospheric columns, 
 agreeably to the expansibility of air by means of heat, 
 become more expanded upwards over the latter than 
 over the former. In like manner, the descent of 
 moisture in the forms of rain, snow, or hail, adds to 
 the effect, by bringing down and communicating to 
 the lower atmospheric strata, in its passage, a portion 
 
132 ON THE CAUSES AND PRINCIPLES 
 
 of the coldness which it acquired at the altitude at 
 which it was formed. Now, the depression of tem- 
 perature which the lower atmospheric strata undergo, 
 is necessarily accompanied with a corresponding con- 
 densation, which must produce a sinking downwards 
 of the whole superincumbent atmosphere. Hence, 
 in accordance with our previous remarks, the upper 
 extremity of the atmospheric columns where no clouds 
 are formed, and no rain has fallen underneath, must 
 flow, in obedience to the force of gravity, towards the 
 places where clouds are formed and rain has fallen. 
 And on the contrary, in obedience to the preponder- 
 ance of barometrical pressure, the lower portion of 
 the atmosphere must blow from where rain has fallen 
 and condensation has taken place, to where no rain 
 has fallen and no condensation taken place. 
 
 Now, as the upper portion of the air all around 
 where rain has fallen, moves towards the place where 
 the greatest condensation and sinkingdownof the atmo- 
 sphere occurs, the barometrical pressure there becomes 
 greatest. Hence, the direction of the breeze at the 
 surface of the earth, (except for modifications result- 
 ing from some more general cause of wind,) is from 
 where the condensation under the cloud is greatest, 
 to every point around, where no rain has fallen, and 
 no condensation has taken place. Unless, therefore, 
 the previous direction of the wind, and the point of 
 greatest aerial condensation under the cloud, and the 
 place where the observer is situated, be all in one 
 straight line, the direction of the wind, upon the near 
 approach of the cloud, will shift, at the surface of the 
 earth, more or less towards the quarter where the 
 
OF METEOROLOGICAL PHENOMENA. 133 
 
 falling of rain has produced the greatest aerial con- 
 densation, and consequently, where the barometrical 
 pressure under the cloud is greatest. 
 
 For the sake of illustration, let us suppose that 
 the direction of the wind, by which the cloud is pro- 
 pelled, is from south to north, and that a meridian 
 line, passing through the centre of the cloud from 
 north to south, is the line of greatest aerial condensa- 
 tion, and greatest barometrical pressure ; it is ob- 
 vious in this case, that, to an observer stationed on 
 the ground, to the east or west of that line, the di- 
 rection of the wind, (that is, in meteorological lan- 
 guage, the direction from which the wind blows,) will 
 shift, on the near approach of the cloud, more or less 
 towards the line of greatest condensation ; and the 
 degree of shifting, under the anterior margin of the 
 cloud, will be greater or less, according as the place 
 of observation is farther eastward or westward of the 
 line of greatest aerial condensation. It may be far- 
 ther noticed, that after the rain has continued for 
 some time, and the aerial condensation, and barome- 
 trical pressure, has become about equal for a consi- 
 derable distance around the place where the observer 
 is situated ; the local and transitory cause of wind, 
 produced by the falling of rain, comes to have less in- 
 fluence in modifying, and altering the previous more 
 general cause of the atmospheric current. Hence 
 the reason, that though the wind, at the surface of the 
 earth, may augment its velocity, and, in some degree, 
 change its direction upon the approach of a shower, 
 still, after the rain has continued for a short time, it 
 
134 ON THE CAUSES AND PRINCIPLES 
 
 is usually observed gradually to subside to its previous 
 velocity, and to regain its former direction. 
 
 Again, the force of the breeze, occasioned by the 
 falling of rain at one place and not at another, is de- 
 termined by the conjoint influence of two circum- 
 stances, viz. the difference of barometrical pressure at 
 the respective places, and their proximity to each 
 other. The greater the difference of barometrical 
 pressure between the tw^o places, and the nearer they 
 are to each other, the stronger is the breeze, and 
 vice versa. So great is the influence of proximity 
 in this respect, that an extremely small, and almost 
 imperceptible difference of barometrical pressure 
 between two contiguous places, will give rise to a 
 considerable breeze of wind ; whereas, when the 
 places are very distant from each other, a great differ- 
 ence in barometrical pressure will produce only an 
 inconsiderable effect. Now the place where the dif- 
 ference of barometrical pressure, occasioned by the 
 falling of rain, is greatest within a given distance, is 
 under the skirts of the cloud. Hence the reason that 
 a shower of rain in calm weather, such as usually pre- 
 vails in warm latitudes, or in inland champaign coun- 
 tries, is commonly preceded, and ushered in by a 
 breeze, or gust of wind ; and when wind previously 
 existed, by an increase to its velocity. And the rea- 
 son why these effects are usually stronger, and more 
 observed in hot climates, and in the summer season 
 in temperate latitudes, than in cold climates, or in the 
 winter season in temperate latitudes, is because the 
 sinking of temperature, and the aerial condensation 
 
OF METEOROLOGICAL PHENOMENA. 135 
 
 occasioned by the falling of rain, is usually greater in 
 the former circumstances than in the latter. 
 
 The preceding observations satisfactorily demon- 
 strate, that it is not the change of wind, as is com- 
 monly supposed, which in warm and nearly calm wea- 
 ther is the cause of rain, but that the rain, in such 
 circumstances, is frequently the cause of a change of 
 wind. And though our remarks, in illustrating this 
 point, may appear unnecessarily lengthened, still, by 
 accounting for other attendant phenomena, subse- 
 quent explanations upon analogous points will be ren- 
 dered unnecessary. 
 
 We will now proceed to consider the second fact 
 upon which the hypothesis that a change of wind pro- 
 duces rain is founded, viz. that in intertropical cli- 
 mates generally, the rainy season begins when the sun 
 approaches the zenith, at which time the winds are 
 most variable. 
 
 Before commenting upon this fact, it may be proper 
 to describe the succession of weather which occurs 
 periodically in warm latitudes. And as an example 
 of what happens generally in other intertropical cli- 
 mates, we will select the weather at Kingston, situated 
 on the south side of the island of Jamaica, in 18° north 
 latitude. It must be recollected, however, that in 
 applying the following description of the weather to 
 other intertropical climates, allowance must be made 
 for the peculiarities of local situation in reference to 
 sea and land, and the difference in the time of the year 
 when the sun in different latitudes crosses the zenith. 
 
 Kingston, in the island of Jamaica, is visited annu- 
 ally with two rainy seasons, severally commencing 
 
136 ON THE CAUSES AND PRINCIPLES 
 
 about the time the sun crosses the zenith. The first, 
 or moderate rains, as it is commonly called, begins 
 about the latter end of April or beginning of May, 
 and lasts for about six weeks. It consists merely of 
 transient showers, by no means frequent or of long 
 continuance, and alternate dry weather. The second, 
 or principal rainy season, begins about the middle of 
 August, and does not terminate till the end of Octo- 
 ber, or middle of November. It consists chiefly of 
 alternate heavy showers, continuing for an hour or 
 two, and dry weather. It is during the principal rainy 
 season only that hurricanes happen. They consist of 
 very heavy rain and furious wind. In their most vio- 
 lent forms they seldom continue longer than a few 
 hours J but when they assume a less formidable cha- 
 racter, they sometimes last for perhaps two or three 
 days without intermission. From the middle of No- 
 vember till the latter end of April, and also from the 
 middle of June till August, which are usually deno- 
 minated the dry seasons, a cloudless sky, except for 
 clouds formed over the distant mountains, continues 
 almost without interruption. And though at any time 
 during these periods of the year an accidental shower 
 may fall, such a thing is then of rare occurrence. 
 
 During the dry seasons, the sea and land breezes 
 alternate in succession, both in the course of 24 hours, 
 blowing on different days, and at different times of 
 the day, with different degrees of force, sometimes 
 very gently, and at other times with considerable 
 vehemence. During the rainy season, the alternate 
 regularity of the sea and land breezes is commonly, 
 but not constantly, interrupted. Dead calms, accom- 
 
OF METEOROLOGICAL PHENOMENA. 137 
 
 panied with torrents of rain and lightning, are then of 
 frequent occurrence. And upon the whole, if we ex- 
 cept hurricanes, there is usually at Kingston less wind 
 during the rainy, than during the dry season. In other 
 intertropical climates, where the regular trade wind 
 from east to west blows continually throughout the 24 
 hours, its regularity is in like manner more or less in- 
 terrupted during the rainy season. Such is a brief 
 description of the periodic succession of weather 
 which occurs in intertropical climates. 
 
 From our previous observations upon the influence 
 of rain in depressing the temperature of the lower at- 
 mosphere, so as eventually to give rise to inequali- 
 ties in the barometrical pressure in contiguous places, 
 it is obvious, that interruption to the alternate regu- 
 larity of the sea and land breezes at Kingston, and 
 also to the more uniform easterly trade wind which 
 prevails in other hot climates, must be produced by 
 the local and temporary influence of clouds and rain 
 during the wet season. Even the amount of rain es- 
 timated by weight, which, in hot climates descends 
 in a short time in particular spots, is so great as to 
 cause slight simultaneous inequalities of barometrical 
 pressure in diff"erent places at no great distance from 
 each other. And this of itself is suflficient to disturb 
 the regularity of the winds in hot climates. Now, 
 when it is considered, that there is no apparent rea- 
 son why the variableness of the winds, during the 
 rainy season, should produce wet weather ; and an 
 obvious one why wet showery weather should produce 
 variableness in the winds, the only admissible conclu- 
 sion is, not that the uncertainty of the winds is the 
 
 s 
 
1«38 ON THE CAUSES AND PRINCIPLES 
 
 cause of the showery weather, but that the showery 
 weather is the cause of the uncertainty of the winds. 
 
 An inquiry of great meteorological importance, 
 which is silently evaded by meteorological writers, 
 and which we formerly left for subsequent considera- 
 tion, here suggests itself. The inquiry alluded to is 
 into the cause of the rainy season in hot climates. 
 Why does the rainy season in intertropical climates 
 generally commence when the sun approaches the ze- 
 nith, and continue during what should otherwise be 
 the warmest period of the year ? 
 
 In advancing a hypothesis in order to explain this 
 point, it is again necessary, for the sake of being un- 
 derstood, to anticipate our observations regarding the 
 causes and principles of winds, by remarking, that the 
 most general cause of wind is the gradual decrease of 
 the mean annual temperature from the equatorial to 
 the polar regions. The result of this decrease of 
 temperature is, that the prevailing direction in which 
 the lower half of the atmosphere moves, is from the 
 polar towards the equatorial regions ; and on the con- 
 trary, the prevailing direction of the upper half is 
 from the equatorial towards the polar regions. And 
 from the perfect equality, or rather, the nearly per- 
 fect equality of the mean barometrical pressure at the 
 level of the sea in all latitudes, it is concluded, that 
 the amounts of air transported by these opposite cur- 
 rents are equal. 
 
 Now, in order to perpetuate these opposite cur- 
 rents, and connect them together, so that the one 
 should become the source from whence the other is 
 supplied with air, it is obvious, that, according as the 
 
OF METEOROLOGICAL PHENOMENA. 139 
 
 upper aerial strata in the colder latitudes of the polar 
 regions are supplied with warmer air from a southerly 
 direction, so must the whole atmosphere be there 
 slowly descending towards the surface of the earth. 
 In like manner, according as the lower aerial strata in 
 the warmer latitudes of the equatorial regions become 
 heated, and uplifted by the insinuation of colder and 
 denser currents from the north and south, which gra- 
 dually get heated and uplifted in their turn, so must 
 the atmosphere be there subjected to a gradual ascen- 
 sion from the surface of the earth. And thus the 
 chain connecting the prevailing current of the upper 
 half of the atmosphere from the equatorial towards 
 the polar regions, and of the lower half from the po- 
 lar towards the equatorial, becomes complete. 
 
 Judging from the length of time that the rainy sea- 
 son in intertropical climates continues, the breadth of 
 the zone which it covers, must be somewhere be- 
 tween 1000 and 1500 miles. But this zone does not 
 remaiQ stationary. In consequence of the sun's de- 
 clining gradually and successively on either side of 
 the plane of the equator, to the extent of 23i degrees 
 in the opposite seasons of the year, the warmest lati- 
 tudes, that is, those over which the sun, during the 
 earth's diurnal rotation, becomes most vertical, and 
 which correspond with the zone where the atmo- 
 sphere is gradually ascending from the earth's sur- 
 face, are continually shifting northward or southward, 
 with the apparent path of the sun in the ecliptic. 
 Now, judging from the circumstance of the rainy 
 season, in intertropical climates, commencing gene- 
 rally upon the sun's approach to the zenith, and be- 
 
140 ON THE CAUSES AND PRINCIPLES 
 
 ing at its height, in any given latitude, at the time 
 when the atmosphere should have the greatest ten- 
 dency to ascend perpendicularly, viz. about the time 
 when the subjacent earth and incumbent atmosphere 
 acquire their maximum temperature ; and which, ac- 
 cording to analogy, is some time after the sun has, 
 crossed the zenith. And judging also from the cir- 
 cumstance of the rains gradually diminishing, and at 
 length terminating, about the period when, from the 
 increasing obliquity of the sun's rays, the given lati- 
 tude can no longer be supposed to be one of those 
 over which the atmosphere is ascending ; I conclude 
 that the rains, during the rainy season in hot climates, 
 are produced by the ascent of the atmosphere in the 
 following manner. 
 
 The aqueous vapour which the atmosphere con- 
 tains is carried up along with the ascending current, 
 (just as smoke is carried up with the heated air from 
 a chimney,) till the increasing coldness, consequent 
 upon the rarefaction of the atmosphere as it rises, 
 causes the invisible vapour to be precipitated into 
 clouds. And these increasing in density by a con- 
 tinuance of the causes which produced them, at length 
 discharge themselves in heavy showers of rain. 
 
 By inspecting a thermometer it will be observed, 
 that, during summer, the atmospheric temperature, 
 near the earth's surface, begins to sink immediately 
 after the shower commences. This is owing to the 
 rain bringing down a portion of the coldness it has 
 acquired at the elevation from which it descends. 
 The consequence of this sinking of the temperature 
 in the lower atmosphere is, that the ascension of the 
 
OF METEOROLOGICAL PHENOMENA. 141 
 
 air, and the formation of cloud, is for a time sus- 
 pended. Gradually, however, as the lower atmo- 
 sphere again becomes heated, whether by the sun's 
 rays, or by the emission of caloric previously absorbed 
 by the earth, the ascension of the air and the forma- 
 tion of cloud again commences ; and a similar renewal 
 of causes and consequences to those above described 
 goes on in succession. 
 
 The preceding observations explain the reason why 
 the rainy season, in intertropical climates, consists 
 chiefly of alternate heavy showers and dry weather. 
 This alternation, however, is farther assisted by another 
 circumstance. The immense quantity of caloric which 
 is evolved during the conversion of invisible vapour 
 into clouds, warms the atmospheric strata where this 
 conversion takes place. And after clouds are formed, 
 the temperature of the atmospheric strata in which 
 they float is farther augmented by the solar heat ar- 
 rested by them in its progress towards the earth's sur- 
 face during day, and in its retrocession from the earth's 
 surface during night. In accordance with these views, 
 Humboldt, as was formerly stated, found in ascending, 
 that the ratio in which the temperature of the air de- 
 creased, was less in the region of the atmosphere 
 where clouds were formed, than what it was either 
 below or above that altitude. This he ascribed to 
 the evolution of heat which accompanies the forma- 
 tion of clouds. The consequence of this increased 
 temperature in the region of the atmosphere where 
 clouds are formed is, that the aerial particles at a greater 
 altitude, which have not participated in this accession 
 of heat, are relatively colder and heavier than those 
 
142 ON THE CAUSES AND PRINCIPLES 
 
 below ; and accordingly, begin to sink down and in- 
 termix with them, and thus add to the formation of 
 cloud. Hence we see, that the formation of cloud, 
 in intertropical climates, occasioned by the depression 
 of temperature which the atmosphere sustains as it 
 becomes rarefied in ascending, and which is compre- 
 hended under the second mentioned cause of the for- 
 mation of clouds, gives rise to one of the cases ex- 
 plained, and included under the fourth cause of their 
 formation, viz. an intermixture and consequent re- 
 duction to a mean temperature of different portions 
 of saturated or nearly saturated air, of previously dif- 
 ferent temperatures. The co-operation of this addi- 
 tional cause of the formation of clouds, of course in- 
 creases the amount formed, and assists in continuing 
 the process of formation for a longer time. But while 
 it does so, (and it has this effect in all climates,) it is 
 at the same time preparing the atmosphere for an in- 
 terval of dry weather. While the intermixing process 
 is going on, the air is gradually getting robbed of a 
 portion of its moisture. But the heat evolved during 
 the formation of clouds, is at the same time gradually 
 diffusing itself amongst the more elevated aerial strata, 
 till at length those regions of the atmosphere become 
 so much undersaturated as to be incapable of produc- 
 ing blouds, even with the aid of some slight intermix- 
 ture, until again supplied with humidity by evapora- 
 tion from the subjacent surface of the earth. 
 
 The third cause of the formation of clouds, viz. the 
 reduction of temperature, and diminished capacity for 
 moisture, which air undergoes by being transported 
 by winds from a warm towards a comparatively cold 
 
OF METEOROLOGICAL PHENOMENA. 143 
 
 climate, and which, as formerly stated, is the principal 
 one in temperate and cold latitudes, can hardly be 
 conceived to have much influence in producing the 
 rainy season in intertropical chmates. The atmo- 
 spheric temperature within the torrid zone undergoes 
 very little alteration throughout the year. And the 
 mean annual temperature within the tropics, which 
 comprehends a zone 47 degrees of latitude in breadth, 
 is so uniform, that the decrement, on receding from 
 the equator to either tropic, hardly exceeds 8 degrees. 
 Hence any reduction of temperature, and consequent 
 diminution of capacity for moisture, which the air 
 within the tropics can, in ordinary circumstances, sus- 
 tain, by being transported from a warm towards a 
 colder latitude, is so trifling, as to be altogether in- 
 sufficient to account for the rainy season ; and hardly 
 sufficient to account for rain in any quantity, however 
 small. 
 
 As the atmosphere is warmer, and therefore more 
 elevated, in the latitudes where the rainy season is 
 occurring, than in those either to the north or south, 
 it is from this zone that the currents in the upper half 
 of the atmosphere are continually diverging to the 
 north and south. Hence, the supervention of cold 
 currents in the upper half of the atmosphere cannot 
 be admitted to be the cause of the rainy season. 
 Nevertheless, it might be supposed, that the rainy 
 season in intertropical climates might be accounted 
 for, according to the fourth cause of the formation of 
 clouds, without the aid of the supervention of cold 
 currents in the upper regions of the atmosphere. 
 Thus the ground and the aerial strata in its immediate 
 
144 ON THE CAUSES AND PRINCIPLES 
 
 vicinity, might be conceived to acquire a much greater 
 degree of warmth when the sun is vertical, than the 
 more elevated atmospheric strata ; and accordingly, 
 that the formation of clouds might be produced by 
 the latter sinking down and intermixing with the 
 former. In answer to this objection it may be re- 
 marked, that if the formation of clouds during the 
 rainy season occurred only on shore, and during day, 
 the hypothesis above stated would be so far supported 
 by these circumstances, as to give it some degree of 
 plausibility. But when it is considered, that the forma- 
 tion of clouds, during the rainy season, goes on by 
 night as well as by day, and particularly, as it occurs 
 also at sea, where the lowest aerial strata, even during 
 day, become very little, if at all, warmer than those at 
 a greater altitude, it is obvious, that the hypothesis 
 above given is insufficient of itself to explain the phe- 
 nomena. 
 
 Again, if the formation of clouds during the rainy 
 season be owing to an ascension of the atmosphere, 
 the place of which is supplied by colder currents from 
 the north and south, it might be asked by way of ob- 
 jection, why the rising up of the atmosphere over the 
 land during the continuance of the sea breeze, and 
 the ascension of the atmosphere over the sea adjoin- 
 ing the land during the land breeze, does not produce 
 similar effects ? This is a more difficult objection to 
 answer than the preceding. It may be remarked, 
 however, that there is a considerable difference be- 
 tween the cases. The rainy season continues from 
 two to three months ; and the hygrometric condition 
 of the lower atmosphere, during all that period, never 
 
OF METEOROLOGICAL PHENOMENA. 145 
 
 rises much above the point of saturation. On the 
 other hand, the sea breeze continues only for four or 
 five hours, during the warmest period of the day ; and 
 before the atmosphere over the land begins to ascend, 
 its temperature must be so much raised, that its hy- 
 grometric condition must be much drier than the 
 point of saturation. Nov^^, when it is considered, that 
 the ascent of the atmosphere which makes way for 
 the sea breeze, from being spread over a large sur- 
 face, is so slow as not to be perceptible, (unless when 
 obstructed by mountains in its progress inland,) and 
 that the aqueous vapour contained in the ascending 
 current, is ever tending to diffuse itself equally 
 amongst the undersaturated aerial strata upwards, and 
 downwards, and all around, it does not appear won- 
 derful that no clouds should be formed by the slow 
 ascension of a much undersaturated atmosphere dur- 
 ing the short period of four or five hours, which is the 
 length of time the sea breeze lasts. 
 
 In like manner, during the continuance of the land 
 breeze, the air which comes off the land is colder, and 
 heavier, than that which rests generally over the sea. 
 On this account, it is probable, that there is no as- 
 cension of the atmosphere over the sea immediately 
 adjoining the land ; and that the upper extremity of 
 the atmospheric columns over the land are wholly 
 supplied by horizontal currents from a distance, and 
 that the ascension of the atmosphere which supplies 
 these lateral currents, may be so widely extended, 
 and the ascent accordingly so slow, as not to be cap- 
 able of producing clouds during the short time the 
 land breeze continues. 
 
14G ON THE CAUSES AND PRINCIPLES 
 
 Whether the preceding explanation of what we 
 conceive to be the principal, and the most general 
 cause of the rainy season be correct or not, the cir- 
 cumstance of its occurring at the time when the sun 
 becomes most vertical, and accordingly, when the 
 equatorial regions of the earth would otherwise be- 
 come almost uninhabitable with heat, is obviously a 
 Providential arrangement in creation to serve a use- 
 ful purpose. Clouds, during this season, moderate 
 the warmth, by acting as screens to intercept the 
 scorching rays of a vertical sun, while the temperature 
 of the earth is farther mitigated by the descent of 
 rain, and by evaporation from its moistened surface. 
 Thus we see that the rains, which are indispensably 
 necessary in order to vegetation, occur in accordance 
 with the prospective wisdom and beneficence mani- 
 fested in all the other arrangements in nature, at the 
 season of the year when their cooling influence is most 
 required. 
 
 We come now to consider the third fact adduced 
 in support of the hypothesis, that a change of wind is 
 one of the causes of the formation of clouds, and of 
 the falling of rain, viz., that the change of the Mon- 
 soons in the East Indies, and Indian ocean gener- 
 ally, is always accompanied with the formation of 
 dense clouds, and heavy falls of rain ; whereas, when 
 the Monsoon blows uniformly, hardly any rainfalls. 
 
 In order to show the erroneous application of this 
 fact, it may be premised, that the Monsoons are an- 
 alogous to sea and land breezes, with this difference, 
 that the former blows for many hundred miles in one 
 direction, and takes a year to perform its revolution, 
 
OF METEOROLOGICAL PHENOMENA. 147 
 
 that is, blows half a year in one direction, and half a 
 year in the opposite, whereas, the latter is only felt at 
 sea within a few miles of the land, and extends only 
 a few miles inland from the sea, and performs its re- 
 volution in the course of 24 hours. During the sum- 
 mer half of the year, the surface of the land in the 
 East Indies, together with the incumbent atmosphere, 
 become warmer than the surface of the Indian ocean, 
 and the atmosphere thereupon incumbent ; but dur- 
 ing the winter half of the year, the reverse is the case. 
 Hence the Monsoon, or season wind, (which is the 
 meaning of the term,) according to the principle 
 which determines the prevaihng direction of the wind, 
 blows from the ocean towards the land during the 
 warmer half of the year ; and from the land towards 
 the ocean during the colder half. And in both cases, 
 the upper half of the atmosphere is supposed to be 
 moving in the opposite direction of the lower. 
 
 Now, when the Monsoon blows uniformly, whether 
 from the land or from the ocean, (except during the 
 rainy season, when the winds are always somewhat 
 irregular,) the case is analogous to the one formerly 
 explained, of a wind blowing from a cold towards a 
 warm climate. The aerial particles of the upper half 
 of the atmosphere are, in such circumstances, warmer, 
 and lighter than those of the lower half; and accord- 
 ingly, the former have no tendency to sink down and 
 intermix with the latter, which, as formerly explained, 
 is necessary towards the production of clouds, accord- 
 ing to the fourth cause of their formation. Hence 
 the reason, that when the Monsoon blows uniformly, 
 
148 ON THE CAUSES AND PRINCIPLES 
 
 whether over the land or over the ocean, hardly any 
 rain falls. 
 
 Immediately previous to the change of the Mon- 
 soon, the circumstances are different. In consequence 
 of the velocity which the atmosphere has acquired, by 
 moving in one direction for a considerable time and 
 distance, the surface towards which the lower half is 
 blowing has actually become colder than that from 
 which it blows, for some time before the Monsoon 
 changes. Thus, as the sun advances northward in 
 the spring of the year, the temperature of the surface 
 of the land in the East Indies, and other southern 
 parts of Asia, though previously lower, gradually be- 
 comes higher than that of the Indian ocean, which 
 forms their southern boundary. Now, the Monsoon, 
 though its regular direction be from a cold towards a 
 comparatively warm surface, in consequence of its 
 acquired velocity, does not change from the land to 
 the ocean, till some time after the surface of the land 
 has become warmer than that of the ocean. During 
 this period, therefore, a lighter atmosphere is brought 
 by the wind, underneath a heavier one ; and a sink- 
 ing down and intermixture of the latter with the for- 
 mer, and the formation of clouds consequently takes 
 place. The vacillation and unsteadiness in the di- 
 rection and force of the wind, immediately before the 
 change of the Monsoon, arises from the undulatory 
 propagation of aerial currents, resulting partly from 
 the difference of temperature which the atmosphere 
 over the land undergoes during day and night, being 
 much greater than that over the ocean ; and partly 
 from inequalities in the amount of heat evolved by 
 
OF METEOROLOGICAL PHENOMENA. 149 
 
 the unequal formation of cloud in different places. 
 While this unsteadiness in the wind continues, though 
 its prevailing direction, in obedience to the prepon- 
 derating influence of its acquired velocity, be still 
 from the land, the atmospheric columns over the ocean 
 beinof then colder than those over the land, are not 
 sufficiently elevated to support a current in the upper 
 half of the atmosphere, from the ocean towards the 
 land. The consequence of the co-operation of this 
 circumstance with the prevailing direction of the wind 
 from the land towards the ocean in the lower half of 
 the atmosphere is, that the amount of air, in prepara- 
 tion for a blast, is accumulating, and the barometrical 
 pressure increasing, over the Indian ocean ; while the 
 amount of air, and the barometrical pressure over the 
 land, in the southern parts of Asia, is diminishing. 
 This at length produces a general and decided reac- 
 tion in the atmospheric current. Dense clouds, which 
 for some days previous have been forming, and accu- 
 mulating in masses proportional to the warmth of the 
 climate, and the capacity of the air for moisture, are 
 now seen rolling with appalling subhmity from the 
 ocean towards the land. It is the change of the 
 Monsoon. The wind with full reactive violence now 
 blows a hurricane, — rain descends in torrents, — vivid 
 flashes of lightning follow each other in rapid succes- 
 sion, and thunder in one continued roar, only distin- 
 guished by intervals of less loudness, lasts for several 
 hours. This periodic thunder-storm is said to be so 
 tremendous, in comparison with any thing of the kind 
 ever witnessed in Britain, that when heard for the first 
 time by natives of this country, it makes the stoutest 
 
150 ON THE CAUSES AND PRINCIPLES 
 
 heart quake. And even those who after long resi- 
 dence have become somewhat accustomed to it, are 
 impressed, during its continuance, with feehngs of 
 mingled awe and devotion. 
 
 After the storm has lasted for two or three hours the 
 thunder ceases, but the rain continues for two or three 
 days. As the southern portions of India are within 
 the torrid zone, the south-west Monsoon, which sets 
 in about the beginning of June, is the commence- 
 ment of the rainy season. The two or three first days 
 of constant rain are therefore succeeded by occasional 
 heavy showers, which gradually increase in frequency 
 and continuance till about the middle of July, when 
 the rainy season is at its height. But after the de- 
 scription and hypothetical explanation previously given 
 of the rainy season in intertropical latitudes, and as 
 the causes which give birth to the rains are the same 
 in India as in other warm climates, we need not far- 
 ther enlarge upon this point. 
 
 Before concluding this subject, it may be remarked, 
 that in climates, and in seasons of the year, when the 
 winds are variable, from whatever cause arising, it 
 may be easily conceived that a colder and heavier at- 
 mosphere may frequently, in such circumstances, be 
 brought to rest over one that is warmer and specifi- 
 cally lighter. And this, agreeably to the fourth cause 
 of the formation of clouds, necessarily occasions the 
 production of clouds, by giving rise to a sinking down 
 and intermixture of the upper with the lower atmo- 
 sphere. In this way, variable winds, or rather the 
 relative variations of temperature in neighbouring 
 localities, and of which variable winds are merely an 
 
OF METEOROLOGICAL PHENOMENA. 151 
 
 indication, are frequently, though not always, instru- 
 mental in bringing about that disturbance in the calo- 
 rific equilibrium of the higher and lower atmospheric 
 currents, which occasions the formation of clouds and 
 the falhng of rain. Hence, variable winds may with 
 greater propriety be regarded as being incidentally 
 and indirectly accessory to the formation of clouds, 
 rather than as the immediate causes thereof. 
 
CHAPTER V. 
 
 ON THE CAUSES AND PRINCIPLES WHICH DETERMINE THE 
 STRUCTURE, SUSPENSION, ELEMENTARY DIFFERENCES, AND 
 DISSOLUTION OF CLOUDS ; TOGETHER WITH A NEW HYPO- 
 THETICAL EXPLANATION OF THE CAUSE OF THUNDER, AND 
 THE ELECTRIZATION OF CLOUDS. 
 
 Of the Structure of Clouds. — Mists and clouds 
 seem to consist of a multitude of hollow vesicles, or 
 bladders, the coatings of which are inconceivably thin, 
 and similar in structure to those usually blown from 
 soap-suds. These vesicles vary in size, according to 
 the measurement of de Saussure, from ^^ to J- of an 
 
 ' 4222 2620 
 
 English inch in diameter. M. de Saussure, senior, 
 while travelling amongst the Alps, happened to be 
 enveloped in a mist, the vesicles of which he described 
 as being as large as peas. The remarkable magni- 
 tude of these vesicles compared with those seen by 
 other observers, throws doubt upon the truth of the 
 statement. 
 
 That clouds and mist consist of hollow vesicles, is 
 farther proved by the circumstance of their specific 
 gravity being such, that they remain suspended in the 
 air without any tendency to descend,, and even on 
 frequent occasions are seen to ascend ; whereas, if 
 they consisted of round drops without any internal 
 vacuity, their descent would be rapid. Water is 828 
 times heavier than air ; and it has been calculated, 
 
ON THE CAUSES AND PRINCIPLES, &C. 153 
 
 that a drop whose diameter is no more than ~th of 
 an inch, would acquire a descending velocity of nine 
 or ten feet per second. Besides, if clouds consisted 
 of drops without any internal vacuity, every time the 
 beholder looked towards them with his back to the 
 sun, he would see a rainbow ; but this is not the 
 case except when rain is falling. 
 
 Dr Thomson, in his valuable work on Heat and 
 Electricity, page 274, says, " But though there is no 
 doubt that clouds consist of a congeries of vesicles, 
 we have no conception of the way in which these ve- 
 sicles are formed." Farther on in the same page, he 
 says, " The formation of clouds seems to be con- 
 nected with electricity, though in what way the vesi- 
 cular form is induced by electricity, we have no con- 
 ception. The vesicles seem to be all charged with 
 the same kind of electricity. This causes them to 
 repel each other, and of course, prevents them from 
 uniting into drops of rain." 
 
 It does not appear to me to be a matter of much 
 difficulty to conceive how the vesicular form should 
 be induced by electricity, provided we can explain 
 how they become, and how they continue electrified. 
 We shall submit the following hypothesis by way of 
 attempting to explain the phenomenon. 
 
 Bodies generally, if not universally, become elec- 
 trified, that is, surcharged with electricity, upon be- 
 ing suddenly condensed. The evolution of electri- 
 city in such cases, may result either from their elec- 
 trical capacity being diminished by condensation, in 
 the same manner as their calorific capacity is thereby 
 diminished j or it may result from a diminution in 
 
 u 
 
154 ON THE CAUSES AND PRINCIPLES 
 
 their electric capacity consequent upon the increase 
 of temperature which bodies acquire during conden- 
 sation. This may originate in a repulsive force, 
 which, for various reasons, I am disposed to think, 
 subsists between caloric and electricity ; so that an 
 increase of the one, diminishes the capacity of bodies 
 for holding the other in affinity. I am inclined to 
 think that both these causes co-operate in producing 
 the phenomenon in question. Now, it seems proba- 
 ble, that when aqueous vapour is converted into the 
 visible form of cloud or mist, two, or likely more, 
 particles are merely united together ; and that heat 
 and electricity, according to the principles above 
 stated, are simultaneously evolved during the con- 
 densation which then takes place. Such is the man- 
 ner in which I conceive the aqueous particles com- 
 posing mists and clouds become, at their first forma- 
 tion, surcharged with electricity j and one reason 
 why they continue, at least for some time, surcharged, 
 is the circumstance of their being surrounded with 
 air, a non-conductor of electricity. 
 
 Again, we know that the particles of electricity re- 
 pel each other, and in obedience to this force, that 
 the particles of surplus electricity distribute themselves 
 over the surface of bodies as far separate as possible. 
 Now, if it be admitted that electricity and aqueous 
 vapour are mutually attractive, (of which there is no 
 doubt,) the reason why the condensed vapour should 
 assume the vesicular form is obvious. The particles 
 of the surplus electricity attached externally by at- 
 traction to the particles of condensed aqueous vapour, 
 draw it out into the vesicular form by means of their 
 
OF METEOROLOGICAL PHENOMENA. 155 
 
 mutual repulsion. And after it is once drawn out in- 
 to the vesicular shape, and filled with air, (for it can- 
 not be supposed that a thin film of water is impervi- 
 ous to air,) it is probable that it retains this form, 
 even though the surplus electricity constituting the 
 surcharge, may escape.* 
 
 It might be supposed that the atmospheric com- 
 pression would prevent the aqueous particles from 
 originally assuming the vesicular form. But be it 
 recollected, that this is only one force acting against 
 another. Without the compressing force of the ex- 
 ternal air, the mutual repulsion of the particles of 
 surplus electricity, would distend the vesicle till it 
 burst from the thinness of its coating. Hence the 
 atmospheric compression may be conceived to be the 
 cause which counteracts the mutual repulsion of the 
 particles of surplus electricity, so as to limit the dis- 
 tension of the vesicles to the dimensions previously 
 stated. 
 
 Of the Suspension of Clouds. — But then comes 
 
 * Since writing the above, I find that Dr Thomson has previ- 
 ously formed a similar opinion. In his work on Heat and Elec- 
 tricity, page 440, he says, " Air, and all gases, are non-conduc- 
 tors ; but vapour and clouds which are composed of it, are con- 
 ductors. Clouds consist of small hollow bladders of vapour, 
 charged each with the same kind of electricity. It is this electric 
 charge which prevents the vesicles from uniting together, and fall- 
 ing down in the form of rain. Even the vesicular form which the 
 vapour assumes, is probably owing to the particles being charged 
 with electricity. The mutual repulsion of the electric particles 
 may be considered as sufficient, (since they are prevented from 
 leaving the vesicle by the action of the surrounding air, and of the 
 surrounding vesicles,) to give the vapour the vesicular form." 
 
156 ON THE CAUSES AND PRINCIPLES 
 
 the inquiry, how the distension of the vesicles so di- 
 minishes their specific gravity as to cause their sus- 
 pension at an elevation in the atmosphere. Upon 
 this point, Dr Thomson, in his work on Heat and 
 Electricity, page 274, says — " Nor is it easy to con- 
 ceive why these vesicles are sometimes lighter than 
 air, sometimes a little heavier, and sometimes exactly 
 of the same specific gravity as the air in which they 
 float. Indeed, if the aerial matter with which these 
 vesicles are filled were saturated with moisture, while 
 the air in which they float is dry, we would see a rea- 
 son why they should be lighter than air. On such 
 a supposition the clouds should rapidly disappear. 
 Accordingly we find that, when clouds rise in the 
 atmosphere, they speedily diminish in size, and at 
 last vanish away ; being gradually converted again 
 into vapour. If the air within the vesicles were in 
 the same state with respect to moisture as the air 
 in which the cloud floats, the vesicles should be 
 heavier than air, and constitute what we distinguish 
 by the name of Jogs.'* 
 
 Upon this quotation it may be remarked, that as 
 aqueous vapour is specifically lighter than air nearly 
 in the proportion of 5 to 8, it is obvious, that if the 
 vesicles were wholly filled with aqueous vapour to 
 the exclusion of air, which is by no means probable j 
 or agreeably to Dr Thomson's supposition, if the air 
 within the vesicles is more nearly saturated with mois- 
 ture, than that by which they are surrounded ; the 
 less specific gravity of the aeriform matter within the 
 vesicles might, upon aerostatic principles, compensate 
 for the greater weight of the pelhcles of water com- 
 
OF METEOROLOGICAL PHENOMENA. 157 
 
 posing the vesicles, and thus enable them to float at 
 an elevation in the atmosphere, in the same manner 
 as balloons float. After reflecting, however, upon the 
 preceding explanation of the suspension of vesicles in 
 the atmosphere, I am inclined to think that it is not 
 the true one. There is reason for behoving that the 
 air by which the vesicles composing clouds are imme- 
 diately surrounded, is always either saturated, or very 
 nearly saturated, with moisture ; and in rainy weather 
 this condition of the atmosphere extends downwards 
 to the surface of the earth. But, even in this case, 
 clouds continue to float at an altitude of 2000 feet 
 and upwards above the level of the sea. Now, if it 
 be admitted that the air in rainy weather which sur- 
 rounds the vesicles is saturated with humidity, the 
 buoyancy of clouds, in such circumstances, cannot be 
 ascribed to the air within the vesicles being more 
 nearly saturated with humidity, than that in which they 
 float. But Dr Thomson proceeds : 
 
 " The most probable cause of the difference of 
 gravity between clouds and the air in which they float, 
 is a diff'erence in their temperature from that of the 
 surrounding medium." After reflecting upon this 
 point, I am inclined to think it probable, that the 
 temperature of clouds is usually higher than that of 
 the air at a similar altitude to that in which they float, 
 for the following reasons. In the first place, the heat 
 evolved during their formation should for a time pro- 
 duce this eff'ect. And in the second place, after their 
 formation, their temperature may be maintained at a 
 greater height than that of the surrounding air, in 
 consequence of their partially arresting and absorbing 
 
158 ON THE CAUSES AND PRINCIPLES 
 
 the solar heat, in its progress towards the earth during 
 day, and the radiation of caloric from the earth during 
 night. 
 
 But while the temperature of clouds is usually, and 
 probably always, higher than the air immediately sur- 
 rounding them, the variations of temperature which 
 they undergo must also be much greater than that of 
 the atmosphere at a similar altitude. This effect may 
 be partly attributed to the absence of the sun's heat- 
 ing influence during night, and the unequal obliquity 
 with which the solar rays strike upon clouds at differ- 
 ent periods of the day and seasons of the year ; and 
 partly to the unequal radiation of caloric from different 
 parts of the earth's surface at different times and places. 
 It is obvious that the aqueous vesicles composing 
 clouds must by some means or other displace an 
 amount of air, the weight of which is exactly equal to 
 their own weight. If they displaced more, their spe- 
 cific gravity would be less than that of the air by which 
 they were surrounded, and they would consequently 
 ascend to a greater altitude : if they displaced less, 
 their specific gravity would be greater than the air by 
 which they were surrounded, and they would accord- 
 ingly descend to a lower level. Now, as the vesicles 
 composing clouds, and the aeriform matter which they 
 contain, must be expanded, and rendered specifically 
 lighter by every increment of temperature, it may be 
 concluded, that their greater mean temperature than 
 that of the air in which they float, is one of the causes 
 of their suspension at an altitude in the atmosphere. 
 And the greater variations of temperature which they 
 undergo than that of the air in which they float, is 
 
OF METEOROLOGICAL PHENOMENA. 159 
 
 probably the principal reason why they have a tendency 
 to rise to a greater altitude at one time, and to de- 
 scend to a lower altitude at another. In warm cli- 
 mates, and in summer in temperate latitudes, the 
 amount of heat arrested by clouds during its radiation 
 towards the earth during day, and from the earth dur- 
 ing night, must be much greater than in cold climates, 
 or during winter in temperate latitudes. Hence the 
 temperature of clouds should exceed that of the atmo- 
 sphere at a similar altitude, in a greater degree in the 
 former circumstances, than in the latter. And this is 
 probably the chief cause why clouds usually float at 
 a greater elevation in the atmosphere in warm cli- 
 mates, and during summer in temperate latitudes, than 
 they do in cold climates, or during winter in temper- 
 ate latitudes. 
 
 But though the variations of temperature which 
 clouds undergo relative to that of the air by which 
 they are immediately surrounded, may be one, and 
 probably the principal cause which determines their 
 tendency to ascend at one time, and descend at an- 
 other ; still, when the great specific gravity of water, 
 composing the aqueous pellicle, compared to that of 
 air (viz. 828 to 1) is considered, any superiority of 
 temperature which the aeriform matter within the 
 pellicle can be conceived to acquire over that of the 
 surrounding medium, in consequence of arresting 
 radiating caloric, seems insufficient to account, not 
 only for the altitude at which they are usually sus- 
 pended, but even for their susceptibihty of suspension 
 in the atmosphere altogether. When the smallness 
 of the diameter of these vesicles is considered, it can- 
 
1(30 ON THE CAUSES AND PRINCIPLES 
 
 not be admitted that the pelhcle is so inconceivably 
 thin, that its superior gravity is balanced by the infe- 
 rior v^^eight of slightly heated air within. There is, 
 therefore, no other way of accounting for the specific 
 lightness of these aqueous vesicles, but by supposing 
 that they, by some means or other, prevent the aerial 
 particles approaching so near their surfaces, as the 
 particles of air do to each other. But how this effect 
 is produced it is not easy to conceive. 
 
 For want of a better, we submit the following con- 
 jectural explanation : — 
 
 Water is composed of hydrogen and oxygen, the 
 former being the strongest electro-positive, and the 
 latter the strongest electro-negative element known. 
 Now, upon the supposition that the two electric fluids 
 severally distribute themselves like caloric among con- 
 tiguous bodies, according to their several capacities 
 for them, it is probable, that in consequence of the 
 mutual attraction subsisting between the opposite 
 electric fluids, an increased proportion of the two 
 fluids will be concentrated by the union of two such 
 opposite electric elements, beyond what they would 
 severally concentrate, if existing separate, and in a 
 state of equal density with the compound formed by 
 their union. It is well known that an electric battery 
 cannot be charged in a vacuum ; for, in such circum- 
 stances, the electricity escapes as fast as it is commu- 
 nicated. This proves that air has the power of pre- 
 venting the escape of electricity ; and that this qua- 
 lity of air is not produced by its density enabling it 
 to confine electricity, in the same manner as a pitcher 
 retains water, is obvious from the fact, that the power 
 
OF METEOROLOGICAL PHENOMENA. 161 
 
 of air, in confining electricity, diminishes as its density 
 decreases. Tlie same thing is confirmed by the ana- 
 logous facts of bodies being in general better conduc- 
 tors, in proportion as they are more dense ; and of 
 the conducting power of sohds being increased by 
 artificial condensation, such as may be effected by 
 hammering. The only means, therefore, of explain- 
 ing the reason why air prevents the escape of electri- 
 city from a body surcharged with it, is by supposing 
 that it repels electricity. And as repulsive forces, so 
 far as yet determined, are always mutual, it must be 
 farther inferred that electricity exerts a repellent force 
 towards air. 
 
 Now, if it be admitted that the union of two oppo- 
 site electric elements enables them to concentrate a 
 greater amount of the two electric fluids, than they 
 would do if existing separately, and in a state of equal 
 density with that of the compound formed by their 
 union, it is by no means improbable that this addi- 
 tional amount of electricity so concentrated by the 
 mutual attraction of the opposite electric fluids, repels 
 the aerial particles most contiguous to the vesicle, in 
 such a manner as to produce a vacuity in which no 
 air exists close to its surface, internally, as well as ex- 
 ternally. And hence, in this way, a hollow bladder 
 of water, though itself greatly heavier than air, may 
 displace an amount of air equal in weight to itself, 
 and thus become specifically as light as the air at the 
 altitude at which it floats. 
 
 It need hardly be remarked, that the preceding 
 hypothesis, regarding the manner in which clouds are 
 suspended at an altitude in the atmosphere, is entirely 
 
 X 
 
162 ON THE CAUSES AND PRINCIPLES 
 
 conjectural, and is advanced chiefly to call attention 
 to a meteorological fact, which has not hitherto re- 
 ceived any satisfactory explanation. 
 
 The altitude in the atmosphere at which clouds are 
 suspended is exceedingly various. According to Gay 
 Lussac, their average height, in temperate latitudes, 
 is between 4500 and 6000 feet above the level of the 
 sea. Play fair makes it much higher. He says : 
 " clouds occupy a region in the atmosphere, elevated 
 at an average, between two and three miles above the 
 earth." Indeed the altitudes of the different denomi- 
 nations of clouds, and even of the same denomina- 
 tion at different times, is so various, as hardly to 
 admit of any mean being fixed upon. Gay Lussac's 
 estimate is certainly, however, much nearer the truth 
 than that of Playfair. Their medium height varies in 
 different circumstances. For instance, it is greater 
 in warm than in cold climates ; and also greater in 
 temperate latitudes during summer than during win- 
 ter; and somewhat greater during day than during 
 night. Their medium height is hkewise greater when 
 the barometer is high than when it is low. An inch 
 of difference in the height of the mercury in the baro- 
 meter, will make a difference in the medium height 
 of clouds of nearly 1000 feet. The cirri, the most 
 elevated of all clouds, may be estimated as floating 
 usually at an elevation somewhere between 15,000 
 and 18,000 feet.* On the other hand, the lower sur- 
 face of a dense cumulo-stratusy and of clouds gener- 
 ally from which rain is falling, (exclusive of mists and 
 
 * Dr Dalton conceives that the cirri float at an altitude varying 
 from three to five miles above the level of the sea. 
 
OF METEOROLOGICAL PHENOMENA, 163 
 
 fogs which reach to the ground,) usually descends, in 
 this country, to within 1500 or 2000 feet of the level 
 of the sea. This is evident by observing the altitude 
 where their lower surface, as they pass onwards with 
 the atmospheric current, envelops hills whose height 
 is known. 
 
 Of the Elementary Differences of Clouds. — No 
 difference between the vesicles composing the differ- 
 ent denominations of clouds has, so far as I am aware, 
 been pointed out by any meteorologist. The varia- 
 tions, however, in the specific gravity of the different 
 denominations of clouds, and even of different clouds 
 belonging to the same denomination, as is demon- 
 strated by the different altitudes in the atmosphere at 
 which they float, shows that some difference exists. 
 
 But though the actual cause of the difference in 
 the specific gravity of clouds has not been ascertained, 
 it may be conceived to arise in various ways. 
 
 1. Vesicles ought to become larger and specifically 
 lighter, as the air within them expands, from increase 
 of temperature, such as they may be supposed to 
 acquire by arresting a portion of the solar heat during 
 day. And, on the contrary, they ought to contract, 
 and become specifically heavier, as that acquired heat 
 escapes upon the approach, and during the continu- 
 ance of night. This, as we previously explained, is 
 a reason, and probably the principal one, why clouds 
 have a tendency to ascend, from sunrise till mid-day, 
 and to descend upon the approach of evening. It 
 may also, in some degree, account for the greater 
 elevation of clouds in warm than in cold climates ; 
 
164 ON THE CAUSES AND PRINCIPLES 
 
 and in temperate and frigid latitudes, for their greater 
 elevation in summer than in winter. 
 
 2. If the hypothesis which we have advanced re- 
 garding the cause of the suspension of vesicles com- 
 posing clouds in the atmosphere, be correct, the more 
 electrified they become, other things equal, the greater 
 should be the amount of air displaced around them ; 
 and accordingly, the higher they ought to float j and 
 vice versa. 
 
 3. Other things equal, (and this, exclusive of what 
 results from difference of temperature, I conceive to 
 be the principal cause of the original difference in the 
 specific gravity of vesicles,) the greater the amount of 
 water each vesicle contains, or in other words, the 
 thicker the aqueous pelHcle of which the vesicle con- 
 sists, relative to its diameter, the heavier it will be, 
 and of course the lower the altitude in the atmosphere 
 at which it ought to float j and vice versa. 
 
 Judging from the fact, that the different denomina- 
 tions of clouds often float for a length of time, at the 
 altitude in the atmosphere where they are formed, 
 without any apparent tendency, (except for the varia- 
 tions of temperature which they undergo,) either to 
 ascend or descend, it may be concluded that the ori- 
 ginal specific gravity of the vesicles of which they are 
 severally composed, is determined by the density of 
 the atmosphere where they are formed. If it be ad- 
 mitted, that the vesicular shape is produced by the 
 mutual repulsion of the particles of electricity, evolved 
 during the precipitation and conversion of invisible 
 vapour into the visible state of mist or cloud ; and 
 if it be admitted that the atmospheric compression, is 
 
OF METEOROLOGICAL PHENOMENA. 165 
 
 the force which prevents the mutual repulsion of the 
 particles of electricity, from distending the vesicles 
 till they burst from the thinness of their coating ; it 
 is obvious, other things equal, that the distension 
 of the vesicles, and the thinness of the pelUcles of 
 which they consist, will be greater, and their specific 
 gravity less, according as the air is less dense at the 
 place where they are formed. And hence the spe- 
 cific gravity of the vesicles composing clouds, will be 
 less according as the altitude in the atmosphere at 
 which they are formed is greater. Or in other words, 
 will be proportional to the density of the atmosphere 
 at the time and place of their formation. 
 
 Agreeably to the preceding principles it may be 
 inferred, that the vesicles of the cirri, the most ele- 
 vated of all clouds, should be more distended in dia- 
 meter, and should consist of a thinner peUicle of wa- 
 ter, and consequently be specifically lighter than those 
 of any other denomination of cloud. On the con- 
 trary, the vesicles of the stratus^ and of fogs in gene- 
 ral, that are formed and float close to the surface of 
 the ground, where the density of the atmosphere is 
 greatest, should be least distended. And relative to 
 their diameter, their pelHcles should consist of a 
 thicker film of water ; and they should consequently 
 be specifically heavier than those of any other deno- 
 mination of cloud. 
 
 But the cirri, as well as other denominations, are 
 frequently seen descending to a lower level, during 
 the progressive formation of clouds, when a decre- 
 ment of temperature cannot be supposed to be the 
 cause of their descent. And, on the other hand. 
 
166 ON THE CAUSES AND PRINCIPLES 
 
 clouds are frequently seen rfsing to a greater alti- 
 tude, (and this they do usually during their disso- 
 lution by evaporation,) when an increment of tem- 
 perature can hardly be supposed to be the cause of 
 their ascent. In the former of these cases, it is not 
 improbable, that the vesicles have their specific gra- 
 vity increased, by having additional suppHes of hu- 
 midity precipitated on their surfaces. In the latter, 
 it is not improbable, that in consequence of the air 
 around them being undersaturated with moisture, 
 their specific gravity is diminished by evaporation 
 from their surfaces, till from their increasing thinness, 
 they at length burst, and what remains of them be- 
 comes instantly re-converted into the state of invisible 
 vapour. 
 
 The next phenomenon presented by clouds which 
 we mean to consider, is the formation and dissolu- 
 tion of the cumulus. How does it come about, that 
 small concentrated portions of the stratus or even- 
 ing mist ; or in short, that any other small fleecy 
 clouds, visible on a fine settled summer morning, in- 
 stead of dissolving, gradually congregate, and become 
 converted, with the advancing temperature of day, 
 into the cumulus or stackencloud ? In what does 
 the conversion consist? And how comes it about, that 
 the cumulus, as the temperature declines upon the 
 approach of evening, breaks up into fragments, and 
 evaporates, after having resisted evaporation during 
 the heat of the day, when, according to the ordi- 
 nary principles by which evaporation is regulated, its 
 dissolution by evaporation ought to have gone on with 
 the greatest rapidity ? 
 
OF METEOROLOGICAL PHENOMENA. 167 
 
 Agreeably to the principles previously explained, 
 the slow ascent of concentrated portions of the even- 
 ing mist after sunrise, (and a similar remark is ap- 
 plicable to all clouds,) is to be ascribed to the in- 
 crease of temperature, and consequent diminished 
 specific gravity, which the remaining portions of un- 
 dissolved stratus acquire. In consequence of the so- 
 lar heat radiating through the atmosphere without in- 
 terruption where it is free of clouds, while it is par- 
 tially arrested and absorbed by clouds, the tempera- 
 ture of the vesicles of which the uplifted stratus, 
 and other similar fleecy clouds are composed, rises 
 more rapidly than that of the atmosphere at an equal 
 elevation, with the advancing heat of day. Hence 
 the reason of their becoming specifically lighter, and 
 expanding to a greater bulk, and rising to a greater 
 altitude. 
 
 The circumstance of their gathering together in 
 heaps, so as to form what is called the cumulus^ or 
 stackencloud, (and a similar observation may, in fact, 
 be made of all clouds,) proves, that though the ve- 
 sicles of which they are composed, be mutually re- 
 pellent within a certain distance, they are mutually 
 attractive beyond that distance. If the vesicles were 
 mutually repellent at all distances, instead of congre- 
 gating together into those masses which we call clouds, 
 they would separate as far as possible from each 
 other, and diffuse themselves equally throughout the 
 atmosphere. 
 
 The phenomenon, however, which is most different 
 from what might be expected beforehand, and which 
 we are most puzzled to account for, is that the cumu- 
 
168 ON THE CAUSES AND PRINCIPLES 
 
 lus seems to have little or no tendency to dissolve by 
 evaporation, during the heat of the day, when its 
 temperature must be greatest ; and that it rapidly 
 breaks up into fragments, and evaporates upon the 
 approach of evening, when its temperature must have 
 greatly diminished from what it previously was. Of 
 these facts, no satisfactory explanation, so far as I am 
 aware, has hitherto been given. And all we mean 
 now to do with that intention, is to advance a hypo- 
 thesis founded on the principles, that air and electri- 
 city, and caloric and electricity, are mutually repellent. 
 
 That what follows may be intelligible, it may be 
 stated, that I conceive electricity, like caloric, is ever 
 tending to distribute itself among contiguous bodies, 
 according to their different capacities for it j and that 
 electricity, when so distributed, is equally diffused 
 among, and intermixed with, the atoms of which 
 bodies are composed. Such is my notion of the dis- 
 tribution of electricity when there is no surcharge. 
 Now, supposing one of those bodies becomes sur- 
 charged with electricity, which may be effected by 
 heating it, the proportion of electricity which consti- 
 tutes the surcharge, I conceive distributes itself over 
 its surface. In such circumstances, if its surface be 
 brought into contact with conductors of electricity, 
 the surcharge instantly flies off; whereas, if it re- 
 main surrounded by non-conductors, which ought ra- 
 ther to be called bad conductors, it escapes only by 
 very slow degrees. We now proceed to state our 
 hypothesis. 
 
 That air and electricity are mutually repellent, we 
 endeavoured in a previous part of this chapter to 
 
OF METEOROLOGICAL PHENOMENA. 169 
 
 prove. That caloric and electricity are likewise so, 
 we infer from the fact, that bodies become electrified 
 plusy that is, become surcharged with electricity, 
 merely by increase of temperature ; and that the sur- 
 charge disappears as their temperature is again re- 
 duced. The consequence of this repulsion subsist- 
 ing between caloric and electricity is, that as the 
 amount of the one in any body is increased, its capa- 
 city for holding the other in affinity diminishes. Ac- 
 cording to this principle then, a cloud becomes sur- 
 charged with electricity as its temperature advances, 
 till the hottest time of the day, and the surcharge 
 gradually diminishes in the afternoon, as its tem- 
 perature again decreases. Now, when it is considered, 
 that the surcharge of electricity is distributed over the 
 external surface of the vesicle, and that it repels, and 
 is repelled by the surrounding air, it may be regarded 
 as forming a sort of electric skin or covering to the 
 particles of aqueous vapour composing the vesicle ; 
 and in this way may be conceived in some degree |to 
 prevent, or retard its evaporation, that is, the inter- 
 mixture and dispersion of its particles amongst those 
 of the surrounding air. In the afternoon, however, 
 as the temperature of the cumulus diminishes, and its 
 capacity for electricity accordingly increases, the re- 
 mainder of the surcharge of electricity, that is, the 
 amount which then remains distributed externally 
 over the surface of the vesicles, is absorbed by them. 
 And as the cause which we supposed to be that which 
 prevented, or at all events retarded the evaporation 
 of the cumulus during the heat of the day, has then 
 ceased to exist, its evaporation now goes on with 
 
 Y 
 
170 ON THE CAUSES AND PRINCIPLES 
 
 more or less rapidity, according as the surrounding 
 air is more or less undersaturated. Such is the only 
 hypothesis, imperfect though it be, which I can sug- 
 gest in order to explain why the cumulus, as its tem- 
 perature sinks upon the approach of evening, breaks 
 up into fragments, and evaporates. Without having 
 recourse to some such hypothesis, I do not see the 
 possibility of explaining how the cu7iiulus should con- 
 tinue to absorb the heat of the sun, and of course, 
 become warmer during day, and notwithstanding 
 show no symptoms of evaporating. And yet, when 
 its temperature sinks after sunset, that it should 
 rapidly evaporate. Such is contrary to the ordinary 
 law of evaporation, viz., that moisture evaporates with 
 greater rapidity, according as its temperature in- 
 creases ; and vice versa. 
 
 There are other circumstances which, in some 
 slight degree, support the preceding hypothesis. 
 But in order to understand these it may be premised, 
 that though air be what is called a non-conductor of 
 electricity, (and the drier it is, the better in this re- 
 spect,) still there is no non-conductor so perfect, as 
 altogether to prevent the escape of surplus electri- 
 city. Accordingly, the more rapidly the temperature 
 of a cloud is augmented, the more certain it is to be- 
 come surcharged with electricity ; and on the other 
 hand, the rise in its temperature may be so slow, that 
 the electricity may escape as fast as it is thereby 
 evolved. Now, it is principally in warm chmates, or 
 during the warm season of the year in temperate lati- 
 tudes, when clouds exposed to the sun rapidly in- 
 crease in temperature, that they assume the heaped- 
 
OF METEOROLOGICAL PHENOMENA. 171 
 
 up structure of the cumulus ; and this, in such cir- 
 cumstances, they always do during day. On the 
 contrary, in cold climates, and during winter in tem- 
 perate latitudes, when the heat which clouds derive 
 from the sun is trifling in amount, and slowly com- 
 municated ; and accordingly, when the electricity 
 evolved may be supposed to escape as fast as evolved, 
 the clouds usually present a stratified and horizon- 
 tally flattened appearance, and seldom or never that 
 of the heaped-up structure of the cumulus. 
 
 In the species of cloud denominated cumulo-stra- 
 tusy the reason of its lower portions, even during the 
 hottest period of a summer day, presenting a flatten- 
 ed stratified appearance, while its upper portions con- 
 sist of heaped-up cumuli, is to be ascribed to the cir- 
 cumstance of the solar heat being in a great measure 
 obstructed, and absorbed by the heaped-up cumuli^ 
 which compose its upper portions. In the winter sea- 
 son, a similar massy cloud would assume the appear- 
 ance of a dense cirro-stratus. 
 
 With the exception of the diflerence in the specific 
 gravity and electrization of clouds, the causes of 
 which we have endeavoured in the preceding pages to 
 explain, there does not appear to be any distinction 
 or difference between the vesicles which compose 
 their various denominations. That this is the case 
 is evident from the fact, that during the progressive 
 formation and dissolution of clouds, and during al- 
 terations in the atmospheric temperature, such as oc- 
 cur in the transitions from day to night, and from 
 night to day, clouds of one denomination may some- 
 
172 ON THE CAUSES AND PRINCIPLES 
 
 times be observed to be gradually converted into every 
 other. 
 
 Of the Dissolution of Clouds^ and of Variations in 
 the Capacity of the Air for Dissolving Moisture and 
 Suspending Vesicles. — The dissolution of clouds is 
 effected in two ways, viz., by falling in rain ; or by 
 evaporation and re-conversion into invisible vapour. 
 The former of these, which we mean first to consi- 
 der, is exemplified in the conversion of the cumulo- 
 stratus, and also of a dense cirro-stratus into the 
 nimbus, or rain-cloud. How does it come about that 
 the aqueous vesicles lose their vesicular form, and de- 
 scend to the earth in drops of rain ? Upon this point 
 the present state of meteorological science gives us 
 no information, and we are accordingly again left, in 
 forming an opinion, to the guidance of conjecture and 
 reflection. 
 
 Judging from the slow and gradual manner in which 
 rain descends, and also from the fact of a large pro- 
 portion of the cloud continuing suspended after the 
 rain has ceased, it may be inferred that no instanta- 
 neous or general conversion of the constitution of these 
 clouds takes place ; but that the vesicles, and only a 
 portion thereof, individually and successively lose their 
 vesicular form. Upon reflecting on the different de- 
 grees of rapidity with which rain falls at different times, 
 and in different climates, I am disposed to think that 
 the capacity of the atmosphere for suspending aqueous 
 vesicles is limited, and varies with its temperature. 
 And from the greater density of clouds in warm cli- 
 mates, as well as the greater amount of rain which 
 falls from them in a given time, it seems probable that 
 
OF METEOROLOGICAL PHENOMENA. 173 
 
 the capacity of the air for suspending vesicles, Uke its 
 capacity for holding moisture in invisible solution, in- 
 creases with its temperature. Vesicles of a given 
 specific gravity, upon their formation, may be sup- 
 posed at a given temperature, relative to that of the 
 air, to have a tendency to descend to, and not below, 
 a certain altitude in the atmosphere ; and owing to 
 their mutual repulsion, a given depth of atmosphere 
 must be loaded with them, before that degree of vesi- 
 cular density and compression, in which vesicular over- 
 saturation consists, takes place. In accordance with 
 these views, we infer, that when any portion of the 
 atmosphere becomes loaded with vesicles, so as to be 
 what may be called saturated with them, any farther 
 precipitation of moisture into the vesicular form, will 
 cause the vesicles, or some portion of them, to approx- 
 imate too near each other to remain asunder. The 
 consequence will be, that wherever such density oc- 
 curs, two or more of them will run together, just like 
 drops of spray brought with in the sphere of each other's 
 attraction. The united sides of the vesicles will thus 
 become their common centre, and the attractive influ- 
 ence exerted by the centre, upon the external parts 
 of the united vesicles, being proportional to the amount 
 of water there concentrated ; it seems probable, that 
 the exterior surface of the vesicles will be drawn 
 towards the centre where they are united ; and accord- 
 ingly, the vesicular form will be destroyed. The in- 
 creased gravity which the integrant particle of moisture 
 thus acquires will cause it to descend rapidly ; and 
 after destroying the vesicular constitution of, and ab- 
 sorbing, all vesicles with which it may have come in 
 
174 ON THE CAUSES AND TRINCIPLES 
 
 contact in its fall, and perhaps after uniting with other 
 integrant particles, which is most likely to occur in 
 windy weather, it ultimately reaches the surface of the 
 earth in the form of a drop of rain. 
 
 Judging from the largeness of the drops of rain, 
 and the great quantity that falls in a short time, im- 
 mediately after a thunder-storm, I am disposed to 
 think that the previously electrified condition of the 
 cloud, and of the air in which it floats, contributes, as 
 well as a high temperature, in increasing the amount 
 of moisture capable of being suspended in the vesi- 
 cular form in the atmosphere. Upon this principle, 
 the density of an electrified nimbus may be explained ; 
 and the successive discharges of electricity which pass 
 from the cloud to the earth, and which are abstracted 
 from the surrounding air, and the aqueous vesicles 
 therein suspended, may account for the sudden and 
 great descent of rain which succeeds, or rather con- 
 cludes, a thunder-storm. 
 
 The notion that the vesicles of which clouds are 
 composed must collapse, and fall to the earth in rain, 
 so soon as they cease to be electrified, is indirectly 
 disproved by the fact, that rain never falls until the 
 clouds have acquired a considerable degree of den- 
 sity; and always begins to fall when they have acquired 
 the requisite density. No reason can be assigned for 
 a dense cloud being more apt to lose its electricity, 
 than one that is thin and rarefied. And when it is 
 considered that the air, though what is called a non- 
 conductor, allows electricity to escape slowly through 
 it from any surcharged body, it can hardly be admitted 
 that thin rarefied clouds, which may continue to float 
 
OF METEOROLOGICAL PHENOMENA. 175 
 
 in the atmosphere for days, and even weeks, without 
 producing rain, can remain all that time surcharged 
 either with vitreous, or resinous, or with both kinds 
 of electricity. Nevertheless, when the vesicles com- 
 posing clouds are actually surcharged with electricity, 
 (that is, contain more of one, or of both electric fluids, 
 than they can continue to hold in affinity by means of 
 their inherent attraction for electricity,) it is reason- 
 able to suppose that this circumstance will increase 
 the capacity of the air for suspending them. The 
 mutual repulsion of the electric particles which con- 
 stitutes the surcharge, will assist other causes in pre- 
 venting the separate vesicles from uniting, until the 
 vesicular density and compression, that is, the proxi- 
 mity and compression of the vesicles all tending 
 towards the same horizontal altitude in the atmo- 
 sphere, has become so great, as to overcome this ad- 
 ditional repellent force. 
 
 In the same manner, the mutual repulsion of the 
 additional particles of caloric, which the aqueous vesi- 
 cles hold in affinity when the temperature of the at- 
 mosphere is increased, explains the reason why the 
 capacity of the air for vesicles increases with its tem- 
 perature. 
 
 The increasing capacity of the air for holding mois- 
 ture in invisible solution, as its temperature becomes 
 greater, admits of explanation upon the same princi- 
 ple. The mutual repulsion of the particles of caloric 
 which the particles of vapour severally hold in affinity, 
 and which increases as the atmospheric temperature 
 rises, is probably the cause which prevents the parti- 
 cles of vapour uniting, as they would otherwise do, in 
 
176 ON THE CAUSES AND PRINCIPLES 
 
 obedience to their mutual attraction, when they ap- 
 proached each other. When the atmospheric tem- 
 perature rises, the number of calorific particles at- 
 tached by affinity to each invisible particle of vapour 
 may be supposed to be increased. The consequence 
 is, that a stronger calorific repellent force now separ- 
 ates the particles of vapour, and greater proximity 
 amongst them must ensue, before union and conden- 
 sation into the visible form of mist or cloud can take 
 place. And in this capability of suspending a greater 
 number of separate aqueous particles in a given space, 
 an increased capacity of the air for holding moisture 
 in invisible solution consists. 
 
 According to the foregoing principles, supposing^ 
 the atmosphere already saturated with vesicles, what 
 is called drizzhng rain will be produced when the air 
 is still ; and the precipitation of humidity into the 
 vesicular form, continues to go on slowly and regu- 
 larly. Every increase in the rapidity with which the 
 precipitation of moisture into the vesicular form goes 
 on, by correspondingly accelerating the running to- 
 gether of the vesicles, will augment the size of the 
 drops of rain, and the amount that falls in a given time. 
 During windy weather, rain can never assume the 
 drizzling form. The agitation of the atmosphere in 
 such circumstances, favours the uniting of the inte- 
 grant particles of moisture so much, that they never 
 can reach the surface of the earth, except in drops of 
 considerable size. 
 
 In an undersaturated atmosphere, the dissolution of 
 a cloud by evaporation is a gradual process, and an 
 exact counterpart to its formation. So soon as the 
 
OF METEOROLOGICAL PHENOMENA. 177 
 
 aqueous film of which any vesicle is composed, be- 
 comes so thin by evaporation from its surface, that its 
 parts are unable longer to cohere, it bursts, and may 
 be supposed instantly to return to the state of invisible 
 solution. And as the air at the surface of a cloud 
 may be conceived to be more undersaturated than in 
 its centre, the vesicles nearest its surface are the first 
 to dissolve and disappear ; and so on successively till 
 the whole cloud vanishes from our sight. 
 
 The variations in the figure and apparent magni- 
 tude of clouds are to be ascribed, partly to their for- 
 mation by precipitation going on at one place, while 
 their dissolution by evaporation is going on at another; 
 partly also to inequalities in the force of the atmo- 
 spheric current at different portions of the cloud ; and 
 partly to the change of position relative to that of the 
 spectator, which clouds undergo, in their onward pro- 
 gress with the atmospheric current. 
 
 Regarding the uses of clouds, Dr Prout says, 
 " They are one great means by which water is trans- 
 ported from seas and oceans, to be deposited far inland 
 where water otherwise would never reach. Clouds 
 also greatly mitigate the extremes of temperature. 
 By day they shield vegetation from the scorching in- 
 fluence of the solar heat ; by night, the earth, wrapt in 
 its mantle of clouds, is enabled to retain that heat 
 which would otherwise radiate into space ; and is thus 
 protected from the opposite influence of the nocturnal 
 cold. These benefits arising from clouds, are most 
 felt in countries without the tropics, which are most 
 liable to the extremes of temperature. Lastly, whether 
 we contemplate them with respect to their form, their 
 
 z 
 
178 ON THE CAUSES AND PRINCIPLES 
 
 colour, their numerous modifications, or, more than 
 all, their incessant state of change: clouds prove a 
 source of never-failing interest, and may be classed 
 among the most beautiful objects in nature." 
 
 Of Tliimder, and the Electrization of Clouds. — 
 The only other meteorological phenomena which we 
 mean to consider in this chapter, are those presented 
 by a thunder-cloud. A thunder-storm is described by 
 Dr Thomson* as follows : — 
 
 " A thunder-storm in this country commonly com- 
 mences in the following manner. A low dense cloud 
 begins to form in a part of the atmosphere that was 
 previously clear. This cloud increases fast, but only 
 from its upper part, and spreads into an arched form, 
 appearing like a large heap of cotton wool. Its under 
 surface is level, as if it rested on a smooth plane. 
 The wind is hushed, and every thing appears preter- 
 naturally calm and still. 
 
 " Numberless small ragged clouds, like teazled 
 flakes of cotton, soon begin to make their appearance, 
 moving about in various directions and perpetually 
 changing their irregular surface, appearing to increase 
 by gradual accumulation. As they move about they 
 approach each other, and appear to stretch out their 
 ragged arms towards each other. They do not often 
 come in contact ; but after approaching very near each 
 other, they evidently recede either in whole, or by 
 bending away their ragged arms. 
 
 " During this confused motion, the whole mass of 
 small clouds approaches the great one above it ; and 
 
 * On Heat and Electricity, page 442. 
 
OK iVlKTIOOIlOI-OCilCAL IM I KNOIVI KN A. J 70 
 
 vvlien near it, llio clouds of the lower mass I'recjuently 
 coalesce with each other before they coalesce with the 
 upper cloud. But as frequently the upper cloud co- 
 akisces without tluun. Its lower surface, from hoiiig 
 level and smooth, now becomes ragged, and its tat- 
 ters stretch down towards the others, and long arms 
 are extended towards the ground. Tlie heavens now 
 darken apace, the whole mass sinks down ; wind rises, 
 and fre(|U(!ntly shifts in scjuails ; small clouds move 
 swiftly in various directions; lightning darts from 
 cloud to cloud. A spark is sometimes seen coexistent 
 through a vast horizontal extent, of a zigzag shape, 
 and of didbrciiit brilliancy in diHercint pnrts. Lightning 
 strikes between the clouds and tlie (Nirth, i"re(|uently in 
 two j)laces at once. A very heavy rain falls — the cloud 
 is dissipated, or it rises high and becomes light and 
 thin.* 
 
 " These electrical discharg(!S oI)viously dissipate) the 
 electricity, the cloud condenses into water, and occa- 
 sions the sudden and heavy rain which always termi- 
 nates a thunder-storm. The previous motions of the 
 clouds, which act like (electrometers, indicate the elec- 
 trical state of diderent parts of the atmosphere;." 
 
 Such is the descri[)tion ol" the j)henomena[)resented 
 by a thunder-storm. The inepiiry which now suggests 
 itself is, how does a cloud become electrified so as 
 to become a thunder-cloud? Upon this j)oint l)r 
 Thomsont says : 
 
 "In what way thesi; clouds come to be charged 
 
 * Itohison ; Siipplciuciit to Uiird iMliLiou of Uio 10iicycl(>i)(.'<liii 
 Britaiiriit^a, vol. ii. j»iij;(! (iHl. 
 
 I On Ilc'ut unci Electricity, i)ag(! 440. 
 
180 ON THE CAUSES AND PRINCIPLES 
 
 with electricity it is not easy to say. But as electri- 
 city is evolved during the act of evaporation, the pro- 
 bability is, that clouds are always charged with elec- 
 tricity, and that they owe their existence, or at least 
 their form, to that fluid. It is very probable that when 
 two currents of dry air are moving different ways, the 
 friction of the two surfaces may evolve electricity. 
 Should these currents be of different temperatures, a 
 portion of the vapour which they always contain will 
 be deposited ; the electricity evolved will be taken up 
 by that vapour, and will cause it to assume the vesi- 
 cular state constituting a cloud. Thus we can see in 
 general how clouds come to be formed, and how they 
 contain electricity. This electricity may be either 
 vitreous or resinous according to circumstances. And 
 it is conceivable, that by long-continued opposite cur- 
 rents of air, the charge accumulated in a cloud may be 
 considerable. Now, when two clouds charged, the one 
 with positive, and the other with negative electricity, 
 happen to approach within a certain distance, the 
 thickness of the coating of electricity increases on the 
 two sides of the clouds which are nearest each other. 
 This accumulation of thickness soon becomes so great 
 as to overcome the pressure of the atmosphere, and 
 a discharge takes place which occasions the flash of 
 lightning. The noise accompanying the discharge 
 constitutes the thunder clap, the long continuance of 
 which partly depends upon the reverberations from 
 neighbouring objects. It is therefore loudest, and 
 longest, and most tremendous, in hilly countries." 
 
 The preceding explanation of the manner in which 
 electricity accumulates in a cloud in sufficient quan- 
 
OF METEOROLOGICAL PHENOMENA. 181 
 
 tity to cause it to become what is called a thunder- 
 cloud, is by no means satisfactory. To suppose that 
 electricity is evolved by the friction of two currents of 
 dry air moving in different directions, is unsupported 
 by any evidence whatever, and is in some degree dis- 
 proved indirectly by the following facts. 
 
 1st. Clouds are most apt to become electrified, as 
 a previous quotation states, when "the wind is hushed, 
 and every thing appears preternaturally calm and still." 
 If the friction of currents of air moving in different 
 directions caused clouds to become electrified, thun- 
 der-storms should be most frequent during windy 
 weather. Whereas, they seldom occur, at least in this 
 climate, except during the stillest weather we ever 
 experience, and usually only after such has continued 
 for a length of time. 
 
 2d. If the friction of opposite currents of air was 
 the source whence thunder-clouds derived their elec- 
 tricity, thunder-storms should happen as frequently in 
 cold as in warm climates j and in temperate latitudes 
 as often during winter, as during summer ; and as fre- 
 quently during night, as during day. But the circum- 
 stance of the reverse being the fact, proves that the 
 hypothesis under consideration is erroneous. 
 
 In what manner then does a cloud become electri- 
 fied so as to become a thunder-cloud? I answer, 
 chiefly in consequence of having its temperature ra- 
 pidly augmented. Provided it be admitted that heat 
 and electricity are mutually repellent ; and that the 
 capacity of bodies for the one diminishes as the other 
 increases ; it is obvious, that if the heat communi- 
 cated by the sun to a cloud, diminish its capacity for 
 
182 ON THE CAUSES AND rRINClPLES 
 
 electricity faster than the evolved electricity escapes 
 through the non-conducting, or rather the very slow 
 conducting atmosphere, the cloud must become elec- 
 trified, that is, surcharged with electricity, and be 
 what is called a thunder-cloud. And it need hardly be 
 stated, that clouds will be more rapidly heated, and 
 of course, more speedily surcharged with electricity, 
 according as the sun is more vertical. The causes 
 therefore which we assigned for the conversion of 
 fleecy flattened clouds into cumuli^ are identical with 
 those which electrify clouds in general. In fact, a 
 cumulus is, in my opinion, an electrified cloud, though 
 perhaps less dense, and more slightly electrified, 
 more buoyant, and smaller in dimensions than those 
 which usually give birth to a thunder-storm. There 
 is likewise another diff"erence, viz., that cumuli, 
 though probably electrified themselves, usually float 
 in an atmosphere which is not electrified 5 whereas, 
 in this country at least, thunder-storms rarely occur, 
 but when the mass of the atmosphere is in a highly 
 electrified state. 
 
 We may submit the following facts in proof of the 
 hypothesis above advanced, viz., that clouds, previ- 
 ously not electrified, become electrified, and convert- 
 ed into thunder-clouds, merely by increase of tempera- 
 ture, provided the increase be so rapid, that their ca- 
 pacity for electricity diminishes with suflicient rapidi- 
 ty beyond that with which the surplus electricity, 
 evolved by increase of temperature, escapes through 
 the non-conducting atmosphere. 
 
 1. Thunder-storms are of more frequent occurrence 
 in warm than in cold climates. Indeed, in intertro- 
 
OF METEOROLOGICAL PHENOMENA. 183 
 
 pical climates, dense clouds, when exposed to the 
 sun*s vertical influence for any considerable time dur- 
 ing the heat of the day, become so much heated, and 
 of course so highly electrified, as almost always to oc- 
 casion thunder. The instance given in the 3d chap- 
 ter, of the clouds formed every day throughout the 
 dry season, over the Port- Royal mountains, in the 
 island of Jamaica, during the continuance of the sea 
 breeze, strongly confirms the hypothesis above ad- 
 vanced. By one o'clock, p.m., the upper portion of 
 those mountains, when viewed from Kingston, ap- 
 pears wholly enveloped in dense clouds — rain is appa- 
 rently falling in torrents — frequent flashes of lightning 
 are seen — and the sound of distant thunder is heard. 
 That it is the heat to which the clouds are in the 
 above case subjected, which causes their electrization, 
 and converts them into thunder-clouds, is evident 
 from the fact, that clouds similarly formed by atmo- 
 spheric currents surmounting hills in cold climates, 
 or during winter in temperate latitudes, never become 
 thunder-clouds, nor occasion thunder. 
 
 2. In temperate and cold latitudes thunder-storms 
 occur more frequently in summer than in winter. In 
 reality, they almost never occur during winter. Now 
 this fact, so far as it goes, confirms our hypothesis. 
 In summer, clouds arrest a much larger proportion of 
 solar heat in a given time than they do in winter. 
 Hence, during the former season, they become heat- 
 ed, and, according to our hypothesis, electrified more 
 rapidly, and in a greater degree, and consequently, 
 are more apt to occasion thunder, than during the 
 latter. 
 
184 ON THE CAUSES AND PRINCIPLES 
 
 3. In our climate thunder-storms happen almost 
 exclusively during the warmest periods of summer, 
 and almost always between mid-day and five o'clock 
 in the afternoon, during which period the clouds may 
 be supposed to have acquired their greatest diurnal 
 temperature. This, therefore, is the period of the 
 day, when, agreeably to our hypothesis, they ought to 
 have become most highly electrified, and be most apt 
 to occasion thunder. 
 
 4. During our warmest weather, when the air seems 
 to be highly electrified, and thunder-storms are going 
 about, the thunder-like appearances which the clouds 
 assume are most strongly marked during the warmest 
 period of the day ; and though no thunder may have 
 occurred, those appearances gradually subside, as the 
 temperature sinks upon the approach of evening. 
 These facts also support our hypothesis, viz. that the 
 augmentation of temperature which the clouds acquire 
 by arresting the solar heat during day, is the chief 
 cause of their electrization ; and that the diminution 
 of temperature which they undergo upon the approach 
 of evening, by increasing their capacity for electricity, 
 lessens the intensity of their electrified state. 
 
 6. The above hypothesis is farther confirmed by phe- 
 nomena seen by a party of French philosophers from 
 the summit of one of the Andes. Clouds which they 
 observed descending, and which had no appearance 
 of being electrified when near the altitude at which 
 they were, gradually assumed the appearance of thun- 
 der-clouds as they descended to a lower level, and ul- 
 timately gave birth to a thunder-storm upon the plains 
 beneath. In this case the clouds may be conceived 
 
OF METEOROLOGICAL PHENOMENA. 185 
 
 to have become electrified, partly by the increase of 
 temperature which they acquired in their descent to 
 a lower level, and partly by the increment of heat 
 which they acquired by arresting the rays of an almost 
 vertical sun. 
 
 It might be supposed, that the electricity evolved 
 during the conversion of invisible vapour into clouds 
 or mist, and which, in a previous part of the chapter, 
 we represented as the cause of moisture precipitated 
 from the atmosphere assuming the vesicular form, was 
 sufficient to explain the electrization of clouds. But 
 while I admit that electricity is evolved during the 
 formation of clouds, still I conceive that the amount 
 evolved is seldom or never sufficient, without the as- 
 sistance of subsequent augmentation of temperature, 
 to produce a thunder-storm. This opinion is con- 
 firmed by the fact, that a thunder-storm seldom or never 
 occurs during winter in temperate or cold latitudes, 
 be the formation of clouds ever so rapid. And, on 
 the contrary, thunder-storms in temperate and cold 
 latitudes usually occur during, and after a continuance 
 of the stillest and warmest summer weather, when the 
 clouds which give them birth are of such slow forma- 
 tion, as to continue hovering about, and gradually in- 
 creasing in size and density, for several days before 
 the thunder-storm occurs. 
 
 According to the hypothesis which we have now 
 advanced to explain the phenomena of thunder, a body 
 charged with electricity by friction, is not identical in 
 its electric state with a cloud charged by increase of 
 temperature. Friction produces a partial separation 
 of the two electric fluids. The rubber and the body 
 
18G ON TFIE CAUSES AND PRINCIPLES 
 
 rubbed severally acquire an additional amount of one 
 of the fluids, while they lose a proportional amount of 
 the other; and they severally gain and lose opposite 
 kinds. Hence the one body is surcharged with nega- 
 tive electricity, and undercharged with positive, rela- 
 tive to its capacity for the several kinds; while the 
 other body is surcharged, and undercharged, with the 
 opposite kinds relative to its capacity ; and upon this 
 partial separation of the two electric fluids, the elec- 
 tric phenomena, which the bodies severally present, 
 depend. On the other hand, when a cloud becomes 
 electrified by means of a rapid increase of tempera- 
 ture, it becomes surcharged with both fluids, in con- 
 sequence of its capacity for both kinds being thereby 
 diminished. And, upon the same principle, when its 
 temperature is rapidly reduced, it becomes under- 
 charged with both fluids, in consequence of its capa- 
 city for both kinds being thereby increased. In the 
 former case it gives off both kinds of electricity ; in 
 the latter it absorbs them. The reason why a cloud, 
 or the atmosphere, attracts a body charged with one 
 kind of electricity at one time, and repels it at another, 
 is owing to the circumstance of bodies possessing 
 generally, if not universally, different capacities for 
 the different kinds of electricity ; and when neither 
 surcharged nor undercharged, containing them in un- 
 equal proportions. Now, supposing the temperature 
 of any such body in a state of insulation to be aug- 
 mented, the surcharge of electricity thereby produced 
 will consist of a larger proportion of the one kind than 
 of the other. Hence, in consequence of the mutual 
 repulsion subsisting between similar electricities, it 
 
OF METEOROLOGICAL PHENOMENA. 187 
 
 will repel a body charged with the same kind of elec- 
 tricity, or a body holding in affinity a larger propor- 
 tion of the same kind of electricity, with that which 
 constitutes the largest proportion of its surcharge. 
 On the contrary, if the temperature of the same body 
 be rapidly reduced, so as to become undercharged, it 
 will show the strongest electric attraction for the fluid 
 for which it has the greatest capacity, and conse- 
 quently will now attract the body which it formerly 
 repelled. And whether electrified ^/ws or minus, it 
 may be expected, by means of the principle of induc- 
 tion, to alter or modify the electric state of any body 
 exposed by contiguity to its influence, and to be there- 
 by itself altered. Such I conceive is the chief reason 
 why the atmosphere, during its diurnal and annual 
 vicissitudes of temperature, (aided perhaps by the un- 
 equal rapidity with which its different strata are heated 
 and cooled,) appears to be sometimes negatively, and 
 at other times positively, electrified. 
 
 The reason why a thunder-cloud continues to give 
 a succession of electric discharges at short intervals, 
 may be explained as follows : — In such circum- 
 stances, the air, in consequence of an increase in its 
 temperature, has become generally overcharged with 
 electricity. Owing to its inferior conducting power, 
 none but the particles nearest the ground can dis- 
 charge themselves, and this they do separately, and 
 silently. The thunder-cloud, though surrounded by 
 the non-conducting air, is itself a conductor of elec- 
 tricity ; and in consequence of floating in the midst 
 of an atmosphere surcharged with electricity, after 
 discharging itself, soon becomes again charged by the 
 
188 ON THE CAUSES AND PRINCIPLES 
 
 air. The surface of the ground underneath a thun- 
 der-cloud and an electrified atmosphere, becomes, by 
 induction, undercharged with electricity. The con- 
 sequence is, that the surcharge of electricity con- 
 tained in the thunder-cloud, is attracted downwards 
 from its upper portions, and accumulated at its lower 
 surface. This causes the under surface of the cloud 
 to be attracted downwards towards the earth, and in 
 consequence of greater proximity to the ground, the 
 surcharge of electricity in the cloud becomes more 
 concentrated at its lower surface, while its upper por- 
 tions, in consequence of the descent of electricity 
 to its lower surface, become undercharged relative 
 to the surrounding air. Hence the upper portions 
 are gradually attracting electricity from the atmo- 
 , sphere, and acting as a source whence the accumu- 
 lated electricity at its lower surface is receiving addi- 
 tional supplies. At length a discharge of electricity 
 from the lower surface of the cloud to the earth takes 
 place, in consequence of the mutual repulsion of the 
 particles of accumulated electricity becoming so great, 
 as to overcome the insulating resistance of the non- 
 conducting atmosphere between the cloud and the 
 earth. After the discharge, electricity continues to 
 be collected in the cloud from the surrounding elec- 
 trified atmosphere, and gradually accumulates at its 
 lower surface, until another discharge takes place in 
 the same manner as above described. And thus the 
 thunder-storm continues, until the atmosphere, by 
 which the cloud is surrounded, is so robbed of its sur- 
 plus electricity, as to be unable to supply a sufficient 
 amount to the cloud to enable it to discharge itself. 
 
OF METEOROLOGICAL PHENOMENA. 189 
 
 Such is the manner in which I conceive a thunder- 
 cloud is enabled to afford a succession of electric dis- 
 charo^es. 
 
 Windy weather is unfavourable for the atmosphere 
 becoming surcharged with electricity. In conse- 
 quence of the aerial agitation which then exists, the 
 different aerial strata are frequently robbed of any sur- 
 charge which they may acquire, by being brought into 
 contact with the surface of the ground ; and this hap- 
 pens most extensively while the atmospheric current 
 is surmounting hills and elevated lands. Rainy wea- 
 ther is also unfavourable for the atmosphere becom- 
 ing surcharged with electricity, partly in consequence 
 of the rain, in its descent, carrying the surcharge to 
 the earth along with it, and partly in consequence of 
 a humid state of the atmosphere increasing its con- 
 ducting power. 
 
 In this country, thunder-storms occur almost ex- 
 clusively during the hottest period of the year, and 
 after calm and warm weather has existed for several 
 days, or perhaps weeks. The previous increase in 
 the temperature of the atmosphere is one reason, why, 
 in such circumstances, it becomes surcharged with 
 electricity ; and air being a bad conductor of electri- 
 city, the prevaihng atmospheric stillness causes it to 
 remain surcharged, with the exception of those strata 
 near, or in immediate contact with the surface of the 
 ground. 
 
 It may be objected to the preceding hypothesis of 
 the atmosphere, and of clouds becoming electrified by 
 increase of temperature, that thunder-storms some- 
 times happen, though rarely, during night, and during 
 
190 ON THE CAUSES AND PRINCIPLES 
 
 the cold season of the year. Be it recollected, how- 
 ever, that during a favourable combination of circum- 
 stances, even then the temperature of the air, as well 
 as of clouds floating therein, may be rapidly rising. 
 For instance, we may suppose, that in consequence 
 of the supervention of a previous very cold current of 
 air in the upper regions of the atmosphere, the forma- 
 tion of clouds, and the consequent evolution of heat, 
 according to principles previously explained, is rapidly 
 in progress. Let it be also supposed that the lower 
 half of the atmosphere is blowing very gently from a 
 cold towards a warm climate, and of course gradually 
 increasing in temperature, by communicating with a 
 warmer and warmer surface of ground underneath. 
 And let it be farther supposed, that the caloric previ- 
 ously absorbed by the surface of the earth, is now 
 radiating therefrom with increased rapidity, in conse- 
 quence of having been previously prevented from es- 
 caping at its ordinary rate, by a covering of snow, now 
 supposed to be melted. We may easily conceive that 
 such a combination of circumstances may increase the 
 temperature of the air, and of clouds floating therein, 
 so rapidly as to give birth to an electric condition of 
 the atmosphere, even during night in the depth of 
 winter. But the extreme rareness with which an 
 event so unfavourable to our hypothesis occurs, proves 
 that it is a mere exception to the general rule, arising 
 from some very uncommon and imperfectly under- 
 stood combination of circumstances. And on this 
 account, it can hardly be admitted as an argument to 
 disprove our hypothesis. On the other hand, the 
 fact of thunder-storms occurring most frequently in 
 
OF METEOROLOGICAL PHENOMENA. 191 
 
 climates, and in seasons of the year, and in periods 
 of the day, when, agreeably to our hypothesis, they 
 ought to happen, together with other proofs before 
 adduced, is strong evidence of its being true. 
 
 Thunder is more apt to occur, provided other 
 things be equally favourable, the lower the state of the 
 barometer is, and of course the less the altitude at 
 which the thunder-cloud floats ; but in this case, 
 though the electric discharges may be more frequent, 
 they are less loud. The reason of this is obvious 
 from the analogous effects produced while charging a 
 Leyden jar, by means of an electrifying machine. 
 The nearer the knob of the jar is brought to the prime 
 conductor, while the machine is in action, the smaller 
 are the electric sparks, and the more rapid their suc- 
 cession. On the contrary, the greater the distance 
 at which the sparks are drawn from the prime conduc- 
 tor, the larger they are, and the greater the interval 
 between them. The greater distance of the thunder- 
 cloud from the earth, is exactly analogous to that of 
 the Leyden jar from the prime conductor. In both 
 cases the electric charge requires to be stronger, in 
 order that the repellent force of the accumulated elec- 
 tricity, may be sufficiently powerful to force a passage 
 through a greater body of non-conducting intervening 
 atmosphere. 
 
 Thunder-clouds may be too small for producing 
 thunder. The utmost amount of electric charge 
 which they may be able to contain, in any ordinary 
 electric state of the atmosphere, may be insufficient 
 to force a passage to the ground through the interven- 
 ing air, from the altitude at which they float. That 
 
192 ON THE CAUSES AND PRINCIPLES 
 
 this is the fact, may be proven by the analogous in- 
 stance, of the distance at which sparks can be drawn 
 from a large Leyden jar when charged, or from a num- 
 ber of connected jars, being greater, than from one of 
 small dimensions. 
 
 According to principles nearly similar to the pre- 
 ceding, the larger an electrified cloud is, in equally 
 electrified states of the atmosphere, the more frequent 
 should be the discharges from it. The reason is, a 
 large cloud, owing to its greater extent, is more speed- 
 ily re-charged with electricity than a small one, in con- 
 sequence of being in contact with a greater amount 
 of electrified air, from which it slowly and silently 
 draws a fresh supply, to compensate for the amount it 
 has previously discharged. 
 
 The lightning corruscations seen on warm still 
 summer evenings passing from one cloud to another 
 in its vicinity, are produced by one of the clouds, viz. 
 that from which the corruscations emanate, being sur- 
 charged relative to the other. The reason why they 
 do not remain equally charged, after the electric equi- 
 librium may be supposed to have been estabhshed, 
 by the passage of a flash of lightning from the one to 
 the other, can only be explained on the supposition 
 that the cloud which receives the electricity, is sur- 
 rounded by an atmosphere, either less charged with 
 it, or in consequence of being damper or warmer, 
 better fitted for conducting it silently to the earth, 
 than that which surrounds the other cloud. 
 
 The portion of a thunder-cloud, from which the 
 lightning passes to the earth, is usually that which is 
 nearest the earth, and which hangs down, probably 
 
OF METEOROLOGICAL PHENOMENA. 
 
 193 
 
 from being attracted towards it. Dr Thomson says : * 
 *' I once witnessed a thunder-storm from the summit 
 of Lochnagar, a very high granite mountain in Aber- 
 deenshire. The thunder was at a great distance east. 
 The first clap was nearly due east, distant not less 
 than ten or twelve miles. The second was north-east, 
 and equally far off". Thick black clouds intervened 
 between me and the thunder, so that I saw no light- 
 ning. After watching the progress of the storm for 
 about half an hour, suddenly a white cloud 
 of a very peculiar appearance stretched it- 
 self between the part of the heavens where 
 the thunder was and the earth. This cloud 
 was composed of distinct parallel fibres, 
 bent as in the margin. This cloud con- 
 tinued about half an hour, during which it 
 conveyed away all the surplus electricity 
 from the clouds to the earth. For no more 
 thunder was heard, and the clouds dis- 
 charged themselves in a heavy shower of 
 rain which terminated the thunder-storm." 
 
 Any person may calculate his distance from the 
 place where an electric discharge occurs. As sound 
 travels at the rate of 1142 feet per second, all that is 
 necessary, is to estimate 1142 feet of distance for 
 every second of time that elapses between the flash 
 of lightning, and the instant at which he first hears 
 the sound of the thunder. 
 
 When overtaken in the country by a thunder-storm, 
 it is less safe to stand under a tree than in the open 
 
 * On Heat and Electricity, p. 444. 
 2 B 
 
194 ON THE CAUSES AND PRINCIPLES 
 
 fields. Perhaps the safest position, in such circum- ; 
 stances, is about six or seven yards beyond the far- 
 thest extending branches of a large tree. The rea- 
 son is, that lightning is more apt to strike a tall or 
 elevated object, than one that is short and near the 
 ground. For the same reason, a hollow is a safer 
 position than an eminence. And in like manner in 
 towns, the elevation of the buildings renders it per- 
 fectly safe to walk on the streets during a thunder- 
 storm, beyond the distance of a foot or two from the 
 houses. Within doors, contiguity to the walls is not 
 so safe as the centre of the apartment. And to be in 
 the neighbourhood of metallic substances, such as 
 bell-wires, fenders, and grates, is more hazardous than 
 at a httle distance from them. Placed on a bed, or 
 seated on a hair-cushioned chair, with your feet on 
 another, in the middle of an apartment, is a position 
 of almost perfect security, even though the lightning 
 strikes the building, and enters the room where you 
 happen to be. It is almost unnecessary, however, to 
 talk of one position being safer than another. If we 
 consider how seldom lightning injures any one of all 
 the numerous steeples throughout the country, though 
 severally surmounted with a metallic attractor in the 
 shape of a weathercock ; and how infinitely more 
 likely they are to be struck than we ; it will appear 
 obvious, that even were we to select the most danger- 
 ous position which art could devise, or science point 
 out, the chance of being hurt with lightning, during a 
 thunder-storm, is so small, as not to be appreciable. 
 In consequence of over-estimating the danger of being 
 injured by lightning, I once saw a person sit back 
 
OF METEOROLOGICAL PHENOMENA. 195 
 
 from a dinner-table during a very moderate thunder- 
 storm, for fear of the knives and forks attracting the 
 electric fluid. But in such circumstances, gentle 
 reader, even though the bell-wire be attached to the 
 back of your chair, you need give yourself no concern 
 about a passing thunder-storm. You run more risk 
 of dying of disease, or in consequence of some unfore- 
 seen accident, every hour you live, than of being in- 
 jured by lightning during the whole course of your 
 existence. 
 
CHAPTER VI. 
 
 OF RAIN, SNOW, SLEET, HAIL, DEW, HOAR-FROST, AND 
 FALLING MIST. 
 
 Of Rain. — That the formation of clouds is a ne- 
 cessary antecedent to rain, is proven by the fact, that 
 rain never falls unless the sky immediately vertical be 
 obscured by clouds. But though clouds be essential 
 to its production, they never produce it until they 
 have acquired a considerable degree of density. And 
 so soon as they are again reduced below the requisite 
 degree of density, whether this be effected by partial 
 dispersion, or by dissolution in the opposite forms of 
 rain, or evaporation, the falling of rain ceases. 
 
 In the preceding chapter, when treating of the dis- 
 solution of clouds, we gave a hypothetical explanation 
 of what we conceive takes place in the production of 
 rain. To save recapitulation, we refer the reader to the 
 passage alluded to. What we mean now to consider, 
 is the difference in the amount of rain that falls at dif- 
 ferent places, and the causes thereof. 
 
 Provided other things be equally favourable, the 
 annual amount of rain that falls, and the heaviness of 
 the showers, are greatest at the equator, and diminish 
 as we recede towards either pole. The reason of 
 this is obvious, when it is considered that the aqueous 
 capacity of the atmosphere, and evaporation, the pro- 
 
ON THE CAUSES AND PRINCIPLES, &C. 197 
 
 cess by which it is supplied with humidity, increase 
 with the warmth of the cUmate ; and accordingly, that 
 an equal reduction of temperature, or an equal inter- 
 mixture of different portions of saturated air of differ- 
 ent temperatures, will produce a greater precipitation 
 of humidity from the atmosphere, in a warm, than in 
 a cold climate. The following table, though, in con- 
 sequence of local peculiarities, it exhibits slight devi- 
 ations from the preceding rule, in general confirms its 
 truth. 
 
 N. Lat. Inches of rain. 
 
 Uleaborg, 65° 30' 13-3 
 
 Petersburgh, . . . . 59 56 17*5 
 
 Paris, 48 50 19-9 
 
 London, 51 31 22-2 
 
 Edinburgh, 55 58 24-5 
 
 England, (Dalton's mean), 31*3 
 
 Rome, 41 54 39-0 
 
 Vera Cruz, 19 5 63-8 
 
 Calcutta, 22 25 81-0 
 
 Bombay, 18 57 82-0 
 
 But though the annual amount of rain be greater 
 in warm than in cold climates, the number of rainy 
 days, that is, days on which rain falls without refer- 
 ence to its quantity, is greatest in cold climates. 
 This seems to be owing to the greater uncertainty in 
 the direction and force of the winds as we recede far- 
 ther from the torrid zone. Indeed, in all climates 
 lying within the 30th parallel of latitude, rainy weather 
 is for the most part restricted to particular seasons of 
 the year ; so that there are usually annual periods of 
 four, five, six, or eight successive months, during 
 which little or no rain falls. And even in all inland 
 
198 
 
 ON THE CAUSES AND PRINCIPLES 
 
 countries beyond the 30th parallel of latitude, rainy 
 weather is more or less restricted to particular seasons 
 of the year ; and this seems to be owing to the pre- 
 valent direction of the winds, during such periods, be- 
 ing unfavourable for the production of rain. 
 
 Proceeding upon the principle, that the causes 
 which occasion rain are equal, in the course of a year, 
 in all latitudes ; and that the amount produced by 
 those causes, is proportional to the quantity of aque- 
 ous vapour contained in the atmospheric columns in 
 different latitudes, and which was inserted in a tabular 
 form in our first chapter, the following table has been 
 calculated. 
 
 Lat. 
 
 Depth of rain 
 in inches. 
 
 . 
 
 . 73-17 
 
 5 . 
 
 . 71-39 
 
 10 . 
 
 . 68-72 
 
 15 . 
 
 . 64-47 
 
 20 . 
 
 . 59-11 
 
 25 . 
 
 . 53-12 
 
 30 . 
 
 . 46-77 
 
 35 . 
 
 . 40-58 
 
 40 . 
 
 . 34-92 
 
 45 . 
 
 . 29-79 
 
 Lat. 
 
 Depth of rain 
 in inches. 
 
 50 . 
 
 25-36 
 
 55 . 
 
 21-72 
 
 60 . 
 
 18-69 
 
 65 . 
 
 16-32 
 
 70 . 
 
 14-49 
 
 75 . 
 
 13-16 
 
 SO . 
 
 12-24 
 
 85 . 
 
 11-72 
 
 90 . 
 
 11-55 * 
 
 Owing to the inequalities in the amount of rain in 
 similar latitudes, arising from local circumstances, the 
 preceding table only gives an average approximation 
 to the truth. It is not, however, on this account, alto- 
 gether useless ; for, when compared with the mean 
 amount of rain ascertained to fall in any particular j 
 
 Hygrometry ; Edinburgh Encyclopedia. 
 
OF METEOROLOGICAL PHENOMENA. 199 
 
 place, it may serve to determine how far that amount 
 is affected by local circumstances. 
 
 The amount of rain observed to fall in the follow- 
 ing places, does not deviate far from what it ought to 
 be according to the above table. 
 
 Annual . , 
 
 Amount of Annual 
 
 Names of Places. Lat. rain observed ^""~"", 
 
 to fall. P*-'-" Table. 
 
 Vera Cruz, . . . 19-12 63-8 60*5 
 
 Charleston, . . . 32-40 48 43-5 
 
 Madeira, .... 32-40 35.5 43-5 
 
 Perth, in Scotland, . 56-23 21-5 21 
 
 On the other hand, in other places, the amount of 
 rain deviates exceedingly from what it ought to be 
 according to the table. Thus in Grenada, 105 inches 
 have been observed to fall in a year ; and at Leogane 
 in the island of St Domingo, as much as 150 has 
 fallen ; whereas, in some parts of Peru, and in Egypt, 
 rain is seldom or never seen. 
 
 'After the lengthened explanations which we gave 
 in the first and third chapters, of the circumstances 
 which produce clouds, and a saturated state of the at- 
 mosphere with regard to humidity, we will here give 
 little more than a summary of the causes which, sever- 
 ally and conjointly, increase or diminish the amount 
 of rain in different localities. 
 
 In general, the nearer the sea, the more elevated 
 the situation, and, if not on a hill, the nearer its vi- 
 cinity, and the more prevalent the direction of the 
 wind is from the sea, especially if, while coming from 
 the sea, it blows from a southerly direction in the 
 northern hemisphere, and from a northerly direction 
 in the southern hemisphere, the greater is the annual 
 
200 ON THE CAUSES AND PRINCIPLES 
 
 amount of rain for the latitude. On the contrary, 
 the farther distant from the sea, and the flatter and 
 more low-lying the country, and particularly if moun- 
 tains intervene, (and the higher the better,) between 
 the place of observation and the sea, and these be 
 distant from the place of observation at least twenty 
 miles, the less rain ought to fall for the latitude. 
 
 The localities where the greatest amount of rain 
 falls for the latitude, is probably on mountains near 
 the sea, of the height of 2000 feet and upwards in 
 warm climates; and 1500 feet and upwards in temper- 
 ate latitudes. I am not aware that the amount which 
 falls annually in such situations, has ever been esti- 
 mated by means of rain-gauges.* But that it is very 
 great, is inferred from the fact of mountains giving 
 birth to almost all, if not all, the large rivers in the 
 world ; and also from the frequency with which they 
 are enveloped in clouds, when the atmosphere at a 
 distance from them is entirely cloudless. Thus, as 
 before stated, in our third chapter, the summits of 
 the Port- Royal mountains in the island of Jamaica, 
 are enveloped in clouds, and rain there falls in tor- 
 rents every forenoon even during the dry season, 
 when in intertropical climates generally, except over, 
 or in the vicinity of mountains, rain or clouds sel- 
 dom make their appearance. 
 
 Provided mountains be 6000 feet or more in height 
 in temperate and cold climates, and 7000 feet or more 
 in warm climates, the rain is almost wholly precipi- 
 
 * At the Meteorological Station on the Great St Bernard, 
 which is said to be the highest in Europe, the annual amount of 
 rain is stated at 63.1 inches. 
 
OF METEOROLOGICAL PHENOMENA. 201 
 
 tated on their windward sides, and hardly any falls to 
 leeward of them. The reason of this is, that all the 
 denser species of clouds which produce rain in cham- 
 paign low-lying countries, usually float at a lower al- 
 titude than 6000 or 7000 feet. This explains the 
 reason why little or no rain falls in a large proportion 
 of the kingdom of Peru, lying to the west and lee- 
 ward of the Andes, whereas it rains almost incessant- 
 ly on the eastern flanks of that elevated range of 
 mountains. 
 
 If mountains, varying in height from 1200 to 3000 
 feet, lie immediately to the leeward of any place, or 
 even suppose a place be entirely surrounded by such, 
 instead of aff'ording protection from rain, they greatly 
 increase its amount. Thus, at Keswick, in the north 
 of England, which lies in a hollow, surrounded almost 
 in every direction by, and not farther distant than a 
 mile or two from, hills varying in height from 1000 
 to 3000 feet, more rain falls than in any place that 
 has yet been examined in England. The mean an- 
 nual amount of rain which falls there is no less than 
 67.5 inches, while, at Upminster, in the flat county 
 of Essex, unprotected by any hills, the mean annual 
 amount is only 19.5 inches. To understand the ex- 
 planation of the former of these cases, it must be re- 
 collected, that the aqueous vesicles which form clouds 
 do not descend to the earth's surface, until their spe- 
 cific gravity is increased by the slow and gradual pro- 
 cess of aggregation into what are called drops of rain. 
 Though mountains, therefore, of moderate elevation 
 may cause a precipitation of moisture from the atmo- 
 spheric current while passing over them, still a large 
 
 2 c 
 
'20l2 ON THE CAUSES AND PRINCIPLES 
 
 proportion of that moisture is wafted by winds to j? 
 greater or less distance in the form of clouds. Now, 
 the excess of rain in the vicinity of mountains, is 
 partly, if not principally, owing to the influence of 
 their elevated rugged summits, and irregular inter- 
 secting valleys, in producing a generally agitated state 
 of the atmosphere, and a conflict of aerial currents 
 moving in somewhat diff^erent directions. And the 
 mechanical eff'ect of such circumstances is, to drive 
 together, and congregate the component vesicles of 
 clouds into drops of rain, and thereby accelerate their 
 descent to the earth.* 
 
 At a distance, however, of twenty miles or more to 
 the leeward of hills of the above-mentioned mo- 
 derate elevation, the amount of water precipitated 
 among the hills, and returned to the sea by rivers, 
 essentially contributes to the hygrometric dryness of 
 the atmosphere, and to a diminution in the amount 
 of rain. Before reaching this distance from the 
 mountains, the atmospheric current has again reco- 
 vered its uniform unagitated progressive movement, 
 and, unless the formation of clouds, arising from some 
 other cause, be going on, the remainder of the clouds 
 formed by the mountains not previously precipitated 
 to the earth's surface in rain, is, by this time, either 
 dissolved, or so far in progress of dissolution by eva- 
 poration, as to be incapable of producing rain. 
 
 The following tablet of the mean annual amount 
 
 * The mean amount of rain obsei'ved to fall in twenty places in 
 the lower valleys at the base of the Alps, was 58.5 inches, 
 t Article England, — Edinburgh Encyclopsedia. 
 
OF METEOROLOGICAL PHENOMENA. 
 
 203 
 
 of rain that falls in different places in England, shows 
 the effect of local peculiarities : — 
 
 Counties Maritime. 
 
 Cumberland, 
 Westmoreland, 
 
 Lancashire, 
 
 Gloucestershire, 
 Somersetshire, 
 
 Cornwall, 
 
 Devonshire, 
 
 Hampshire, 
 
 Kent, 
 
 Essex, 
 Norfolk, 
 
 Yorkshire, . 
 
 Northumberland, 
 Lincolnshire, 
 
 Sussex, 
 
 Counties Inland. 
 
 Middlesex, 
 Surrej'-, 
 
 Places. 
 
 Keswick, 
 
 Carlisle, 
 
 Kendal, 
 
 Fellfoot, 
 
 Waith Sutton, 
 
 Lancaster, 
 
 Liverpool, 
 
 Manchester, 
 
 Tovvnley, 
 
 Crawshawbooth, 
 
 Haslingden, 
 Dalton, 
 Bristol, 
 
 Bridgewater, . 
 Minehead, 
 Ludguan, 
 
 Mount's bay, 
 Another place, 
 Plymouth, 
 Exeter, 
 Selbourne, 
 Fyfield, 
 Dover, 
 Upminster, 
 Norwich, 
 Dip, . 
 Barrovvby, near 
 Ferrybridge, 
 Gars-dale, near 
 
 burgh, 
 Sheffield, 
 Hull, 
 
 Widdrington, 
 Horn castle, 
 Chichester, 
 
 London, 
 S. Lambeth, 
 Chertsey, . 
 
 near^ 
 
 1 
 
 Leeds, 
 Sed- 1 
 
 Observed for 
 
 7 
 
 years, 
 
 I 
 
 11 
 
 .3 
 
 5 
 
 year, 
 
 years, 
 years, 
 years. 
 
 10 
 
 18 
 
 9 
 
 15 
 
 years, 
 years, 
 years, 
 years. 
 
 2 
 
 years, 
 
 1 
 
 year, 
 
 3 
 
 years. 
 
 o 
 
 years. 
 
 5 years, 
 
 1 year, 
 
 2 years, 
 
 9 years, 
 7 years, 
 
 5 years, 
 
 13 years, 
 1 year, 
 
 6 years. 
 
 2 years, 
 1 year, 
 1 year. 
 
 7 years, 
 9 years, 
 1 year. 
 
 Mean 
 Annual 
 Depth. 
 
 67.5 
 
 20.2 
 
 59.8 
 
 55.7 
 
 46. 
 
 45. 
 
 34.4 
 
 33. 
 
 41. 
 
 60. 
 
 49. 
 29.2 
 29.3 
 31.3 
 
 41. 
 
 29.9 
 
 46.5 
 
 33.2 
 
 37.2 
 
 25.9 
 
 37.5 
 
 19.5 
 
 25.5 
 
 25. 
 
 27.5 
 
 26.6 
 
 52.3 
 
 33. 
 
 26.98 
 21.2 
 26. 
 26.8 
 
 23. 
 
 22.7 
 
 25. 
 
204 
 
 ON THE CAUSES AND PRINCIPLES 
 
 
 
 
 Mean 
 
 Counties Inland. 
 
 Places. 
 
 Observed for 
 
 Annual 
 Depth. 
 
 Hertfordshire, . 
 
 Near Ware, . 
 
 5 years, 
 
 23. 
 
 Huntingdonshire, 
 
 Kimbolton, 
 
 5 years. 
 
 25. 
 
 Derbyshire, 
 
 Chatsworth, . 
 
 15 years. 
 
 27.8 
 
 Rutlandshire, 
 
 Lyndon, 
 
 43 years, 
 
 22.21 
 
 Northamptonshi re, 
 
 Oundle, 
 
 14 years, 
 
 23. 
 
 Brecon, . 
 
 
 1 year, 
 
 26.23 
 
 Staffordshire, 
 
 
 
 36. 
 
 Worcestershire, 
 
 
 
 29. 
 
 Nottinghamshire, 
 
 Nottingham, 
 
 1 year, 
 
 23. 
 
 
 West Bridgeford, 
 
 
 27. 
 
 The following table exhibits the annual amount of 
 rain that fell in several places in Scotland in the years 
 I8IO3 1811, and 1812:— 
 
 Edinbui'gh, 
 Bothwell Castle, 
 Glasgow, . . 
 Greenock, 
 Largs, . . . 
 Gordon Castle, 
 
 
 32.26 
 
 27.1 
 
 23.0 
 
 33.1 
 
 23.0 
 
 21.4 
 
 27.8 
 
 22.8 
 30.9 
 
 38.7 
 
 36.6 
 
 33.2 
 
 23.9 
 
 31.3 
 
 30.8 
 
 One of the most remarkable things with regard to 
 the different amounts of rain that fall in different 
 places, is, that while more appears to fall at an eleva- 
 tion of 600 feet above the level of the sea, than at 
 any less height underneath ; the amount collected in 
 rain-gauges below the altitude of 200 feet, increases 
 the nearer they are placed to the surface of the ground. 
 The following table* shows the amount of rain col- 
 lected in three rain-gauges, placed at different heights, 
 on the banks of the Tay, in the neighbourhood of 
 Perth, in Scotland : — 
 
 * Article Scotland,— Edinburgh Encyclopaedia. 
 
OF METEOROLOGICAL PHENOMENA. 205 
 
 Rain-gauge Rain-gauge, Rain-gauge, Average of 
 
 on a conical centre of Kinfaun'a the three 
 
 hill, 600 feet garden, 20 Castle, li9 feet rain-gauges, 
 
 above the sea. feet high. above the sea. 
 
 , 1814 33.84 20.05 15.59 23.61 
 
 1815 45.70 24.20 18.00 29.30 
 
 1816 52.43 24.95 19.61 32.33 
 
 1817 44.4 31.0 23.56 32.99 
 
 1818 31.10 28.07 17.89 26.35 ' 
 
 1819 22.36 28.60 30.20 27.05 
 
 1820 23.5 18.5 21.0 
 
 1821 21.18 29.00 25.09 
 
 1822 27.80 20.22 24.01 
 
 1823 33.45 26.31 29.88 
 
 By the above table it appears, that the amount of 
 rain collected in the rain-gauge at the top of the hill 
 600 feet high, was greater than at either of those 
 placed at a lower level ; but that more was in general 
 collected in the rain-gauge at the elevation of 20 feet, 
 than in the one at the height of 129 feet. 
 
 A more remarkable diJOference than the one above 
 stated, of the amount of rain collected in gauges placed 
 at different heights, is the following, given on the au- 
 thority of Dr Heberden. The amount of rain col- 
 lected in a rain-gauge, which he placed on the square 
 part of the roof of Westminster Abbey, in the year 
 1776, was 12 inches ; another on the top of a house 
 considerably lower than the first, collected 18 inches; 
 and another on the ground in the adjoining garden, 
 collected 22 inches. 
 
 The explanation usually given of the above and 
 similar facts, is, that the velocity of the wind on the 
 roof of Westminster Abbey, had been greater than at 
 either of the two points of observation underneath. 
 And in Hke manner, that the wind had been stronger 
 
206 ON THE CAUSES AND PRINCIPLES 
 
 at the top of the house, where the second highest 
 rain-gauge was erected, than in the adjoining garden, 
 where the undermost was placed. Consequently, 
 supposing the quantity of rain that fell to be the 
 same at the three points of observation, the quantity 
 that would be collected on a given amount of surface, 
 placed horizontally, in the form of a rain-gauge, should 
 be least where the wind was strongest. As an addi- 
 tional reason to the one above stated, it is probable, 
 that the rain, by bringing down a portion of the cold- 
 ness which it has acquired at the altitude at which it 
 was formed into drops, reduces the temperature of 
 the air through which it passes in its descent to the 
 ground. Hence the size of the drops is probably re- 
 ceiving augmentation the farther they descend, in 
 consequence of aqueous precipitation, produced by 
 the coldness communicated to the aerial strata through 
 which they pass in their descent. This is supposed 
 to be farther increased, by the condensation of mois- 
 ture evaporated from the earth's surface, during the 
 continuance of rain. 
 
 From the table inserted above it will also be seen, 
 that the amount of rain which falls at the same place 
 in different years, is very different. A similar remark 
 is apphcable to the corresponding months of different 
 years, as the under-noted statement shows. 
 
 Rain collected at Barlanerk. Rain-gauge. 
 
 In October, 1831, ... 5 inches 7-IOths. 
 
 In October, 1830, ... 1 inch 4-lOths. 
 
 From 8th to 31st October, 1829, 2 inches 3-lOths. 
 
 Such differences are to be ascribed partly, if not 
 wholly, to the different direction and velocity of the 
 
OF METEOROLOGICAL PHENOMENA. 207 
 
 winds in different years, and in the corresponding 
 months of different years. Thus at Glasgow, if the 
 prevailing direction of the wind be from the south or 
 south-west, (and the stronger it blows the greater the 
 effect,) during the months of December, January, 
 and February, the amount of rain will be immensely 
 greater than if the prevaiKng direction had been from 
 the opposite quarter. 
 
 The annual amount of rain that falls near the 
 western coast of Britain, is in general greater than 
 what falls near the eastern coast. This is owing to 
 the circumstance of air becoming usually hygrometri- 
 cally drier the farther it passes overland, in connection 
 with the fact of winds from the south-west being more 
 prevalent in this island, than winds from the south- 
 east. 
 
 Nor is a wind blowing from the sea towards the 
 land necessarily a rainy wind, provided the land be 
 warmer than the sea from which it blows. In such 
 circumstances, as the atmosphere progresses over the 
 land, it gradually becomes warmer and more under- 
 saturated, and accordingly less apt to give birth to 
 clouds and rain. This is the reason why it almost 
 never rains in Egypt, though the wind during a large 
 proportion of the year blows from the Mediterranean. 
 The aqueous vapour raised from that inland sea, is 
 carried with a northerly wind unprecipitated, till it 
 comes into collision with the elevated mountains in 
 the kingdom of Abyssinia. 
 
 The following Meteorological Register, with the 
 accompanying note of attestation, is copied from the 
 Glasgow Chronicle. 
 
'208 
 
 ON THE CAUSP:S AND PRINCIPLES 
 
 METEOROLOGICAL REGISTER KEPT AT ANDERSON'S 
 UNIVERSITY, 1833. 
 
 
 Rain. Thermometer. 
 
 Self-registering 
 Thermometer. 
 
 
 Day. 
 
 Night. 
 
 Total. 
 
 Morn. 
 
 Night. Mean. 
 
 Cold. 
 
 Heat. 
 
 Mean. 
 
 January, . 
 February, 
 March, . 
 April, . . 
 May, . . 
 June, . . 
 July, . . 
 August, . 
 September, 
 October, . 
 November, 
 December, 
 
 .11 
 
 1.23 
 
 .20 
 
 1.18 
 
 .15 
 
 1.99 
 
 .69 
 
 .54 
 
 .78 
 
 1.47 
 
 1.25 
 
 3.07 
 
 .12 
 
 2.21 
 
 .36 
 
 .44 
 
 .81 
 
 1.44 
 
 .62 
 
 .77 
 
 .79 
 
 1.52 
 
 1.02 
 
 3.56 
 
 .23 
 3.44 
 
 .56 
 1.62 
 
 .96 
 3.43 
 1.31 
 1.31 
 1.57 
 2.99 
 2.27 
 6.63 
 
 34.9 
 42.4 
 41. 
 
 48.1 
 
 60. 
 
 59.4 
 
 63.3 
 
 59.5 
 
 56.6 
 
 51. 
 
 43.9 
 
 42. 
 
 35.1 
 41. 
 
 38.6 
 43.9 
 55.2 
 
 55. 
 
 58.2 
 
 55.4 
 
 53.3 
 
 49. 
 
 43.3 
 
 40.6 
 
 35. 
 41.7 
 
 39.8 
 
 46. 
 
 57.6 
 
 57.2 
 
 60.7 
 
 57.5 
 
 54.9 
 
 50. 
 
 43.6 
 
 41.3 
 
 31w3 
 
 37.4 
 
 36. 
 
 41.2 
 
 66.1 
 
 51.4 
 
 53.7 
 
 50.1 
 
 49.3 
 
 45.6 
 
 39.3 
 
 38.6 
 
 38.1 
 
 43.4 
 
 44.7 
 
 52.5 
 
 49.1 
 
 65. 
 
 68.3 
 
 63.8 
 
 60.8 
 
 54.4 
 
 46.9 
 
 42.7 
 
 34.7 
 
 40.4 
 
 40.4 
 
 46.8 
 
 57.6 
 
 58.2 
 
 61. 
 
 57. 
 
 55.1 
 
 50. 
 
 43.1 
 
 40.6 
 
 Total, . 
 
 12.66 
 
 13.66 
 
 26.32 
 
 50.2 
 
 47.4 
 
 48.8 
 
 45. 
 
 52.4 
 
 48.7 
 
 " I inclose you the results of the Meteorological 
 Register kept in this Institution for 1833, in as far 
 as regards the quantity of rain and the temperature. 
 The observations are made with great care and accu- 
 racy by Mr Johnston, keeper of the Museum, and 
 registered twice a-day, viz. at half-past nine a. m. 
 and at half-past nine p. m. The register exhibits 
 the quantity of rain fallen during the day, which 
 amounts to 12.66 inches, and during the night to 
 13.66 ; together, 26| inches. The mean heat of the 
 year by the morning observations, is 50.2, and by the 
 evening ones, 47.4 ; the mean of both is 48.8. The 
 mean of the greatest cold of each day is 45, and of 
 the greatest heat 52.4, exhibiting a range of 7.4. 
 The mean of the self-registering thermometer is 48.7, 
 
OF METEOROLOGICAL PHENOMENA. 
 
 209 
 
 a^reeina: with the other series of thermometrical ob- 
 servations to the tenth part of a degree. 
 
 James Smith, 
 
 President, Anderson's University." 
 
 From the above table it appears that the amount of 
 rain which falls during the days throughout the year, 
 from half-past nine a. m. to half-past nine p. m., is 
 greater by about ;^ than what falls during the nights 
 throughout the year, from half-past nine p. m. to half- 
 past nine a.m. This may be explained on the prin- 
 ciple, that the reduction of temperature which takes 
 place during night, increases the precipitation from 
 the atmosphere. 
 
 The following register of rain also for 1833, was 
 kept by Dr Couper, at the Macfarlane Observa- 
 tory :— 
 
 January 
 
 0.256 
 
 February 
 
 2.609 
 
 March 
 
 0.598 
 
 April 
 
 1.072 
 
 May 
 
 0.778 
 
 June 
 
 2.617 
 
 July 
 
 1.082 
 
 August 
 
 0.936 
 
 September . 
 
 1.018 
 
 October 
 
 1.987 
 
 November 
 
 1.753 
 
 December . 
 
 5.202 
 
 19.908 
 
 It will be observed that the above table differs con- 
 2d 
 
'210 ON THE CAUSES AND PllINClPLES 
 
 siderably from the one previously inserted, tbougl) 
 the places where the observations were made are only 
 about one mile distant from each other. This dis- 
 crepancy may be ascribed, partly to differences in 
 the amount of rain that falls in neighbouring locali- 
 ties, and partly to inaccuracy in keeping the registers. 
 The latter register must be regarded as being the most 
 accurate, having been kept by a scientific individual, 
 while the former was not. 
 
 By the above table, as well as by other observa- 
 tions, it appears that the amount of rain during the 
 fall, is usually greater than during the spring of the 
 year. Thus, in the months of September, October, 
 and November, the amount of rain as given above, is 
 greater than in the opposite months of March, April, 
 and May. The reason of this is, that, during the for- 
 mer of these periods, (viz., the fall of the year,) the 
 temperature and capacity of the atmosphere for mois- 
 ture is diminishing ; whereas, during the latter, (viz., 
 spring,) the temperature and capacity of the atmo- 
 sphere for moisture is increasing. 
 
 The following statements are extracted from Cle- 
 land's Annals of Glasgow : — 
 
 " The average of rain which has fallen in Glas- 
 gow for 30 years, previous to 1790, is 29-j|^ inches.* 
 
 * By all the meteorological registers kept for many years past, 
 the annual amount of rain which has fallen at Glasgow is little 
 more than two-thirds of the mean stated above in the text. Glas- 
 gow, from its low-lying position, and from its being surrounded by 
 hills of moderate elevation in every direction, and being at the 
 same time at a considerable distance from any hills, is situated in 
 a dry locality for the latitude. The annual amount of rain at 
 
OF METEOROLOGICAL PHENOMENA. 
 
 211 
 
 The greatest quantity in any year, during that period, 
 was in 1775, which was 43-^ inches, and the least, 
 which was in the year 1788, was 19— inches. 
 
 " The Quantity of Rain that has fallen annually 
 in Glasgow, daring the following years, in inches 
 and decimal parts : — 
 
 1765 
 
 2477 
 
 1775 
 
 43.9 
 
 1785 
 
 27.19 
 
 1795 
 
 36.064 
 
 1805 
 
 15.382 
 
 " 1815. — The following is a Statement of tJie 
 Rain collected in Gauges, made hy the celebrated 
 Grichton of Glasgoiv : — 
 
 
 Bothwfll. 
 
 Glasgow. 
 
 Carbeth. 
 
 GreenoL'k 
 
 January- 
 
 . 0.886 
 
 1.135 
 
 0.750 
 
 0.809 
 
 February 
 
 . 2.276 
 
 2.312 
 
 4.855 
 
 3.928 
 
 March 
 
 2.883 
 
 2.457 
 
 5.563 
 
 5.485 
 
 April 
 
 0.783 
 
 0.925 
 
 1.430 
 
 1.267 
 
 May 
 
 2.765 
 
 2.104 
 
 3.684 
 
 3.128 
 
 June 
 
 1.586 
 
 1.246 
 
 1.831 
 
 1.820 
 
 July 
 
 2.040 
 
 1.531 
 
 1.711 
 
 1.235 
 
 August 
 
 2.600 
 
 2.354 
 
 3.638 
 
 2.647 
 
 September 
 
 . 2.328 
 
 2.275 
 
 5.552 
 
 4077 
 
 October 
 
 3.280 
 
 2.402 
 
 5.308 
 
 5.785 
 
 November 
 
 1.908 
 
 1.823 
 
 3.869 
 
 3.700 
 
 December 
 
 1.385 
 
 1.780 
 
 3.202 
 
 2.882 
 
 24720 
 
 22.844 
 
 41.393 
 
 36.763 
 
 Glasgow, must therefore have either diminished to little more 
 than two-thirds of what it was half a century ago ; or, which is 
 more probable, the registers referred to by Dr Cleland in the text, 
 must have been inaccurately kept. 
 
212 ON THE CAUSES AND PRINCU'LES 
 
 " Both well Castle is about 7 miles S.E. of Glas- 
 gow. Carbeth, 11 miles N.N.W. of Glasgow. 
 Greenock, 22 miles W. of Glasgow." 
 
 As the aggregate amount of heat which the earth 
 annually receives from the sun, and the amount of 
 moisture annually evaporated from the earth's sur- 
 face, probably undergo little or no variation ; the 
 aggregate amount of rain which falls on the earth's 
 surface, must in like manner be similar every year. 
 Hence, in conformity with this principle, it may be 
 inferred, that wetter seasons than ordinary in one 
 country, or climate, are simultaneously balanced by 
 seasons proportionally drier than ordinary, in some 
 other country, or climate. Such differences are 
 wholly to be ascribed to variations in the direction 
 and force of the winds in different seasons. And it 
 is farther probable, that the differences in the prevail- 
 ing direction and force of the winds, are also regu- 
 lated according to some compensating principles, by 
 which different countries within a limited number of 
 years, are supplied with their relative mean propor- 
 tions of rain. 
 
 It is recorded upon authentic evidence, that rain 
 sometimes of a yellow, and sometimes of a red colour, 
 has on rare occasions been observed to fall in various 
 places. In these cases, the colouring matter ap- 
 pears to have been derived from vegetable pollen of 
 the colours described, transported by winds, and pre- 
 cipitated to the earth, along with showers of rain. 
 Snow of a red colour has also been observed in Ice- 
 land. The colouring matter in this case was imput- 
 ed to a mixture of red ashes, ejected during a vol- 
 
or METEOROLOGICAL PHENOMENA. 213 
 
 canic eruption in the neighbourhood. It is also said 
 to be recorded upon authentic evidence, that, during 
 a strong gale of wind, herrings and other fish were 
 carried from the Frith of Forth, as far as Loch Le- 
 ven. It is likewise on record, that a shower of rats 
 once fell in Norway ; and also, that a shower of toads 
 fell near Porto-Bello, lying to the east of Edinburgh. 
 
 That vegetable pollen, one of the lightest and most 
 transportable of all substances, should be carried by 
 wind, and precipitated to the earth by a shower of 
 rain, is by no means unlikely. But that herrings and 
 other fish should be blown out of the Frith of Forth, 
 and transported twelve miles over land, by means of a 
 strong gale of wind, even though recorded on what is 
 called authentic evidence, is a very improbable cir- 
 cumstance. And how it came to pass, that any spe- 
 cies of wind whatever, even a whirlwind, should have 
 selected rats on one occasion, and toads on another, 
 for atmospheric transportation, and nothing else, may 
 be left to posterity to discover. 
 
 Of Snow. — When the atmospheric temperature at 
 which clouds begin to lose their vesicular constitu- 
 tion is below the freezing point, the aqueous particles 
 are congealed ; and provided the atmospheric tem- 
 perature continues below the freezing point down to 
 the surface of the earth, the frozen particles most 
 contiguous to each other, after uniting together while 
 descending, into various crystalline symmetrical ar- 
 rangements, ultimately reach the earth in the form of 
 flakes of snow. The precipitation of moisture into 
 the form of snow, is frequently exemplified on a small 
 scale, in high latitudes, by the admission of a current 
 
214 ON THE CAUSES AND PRINCIPLES 
 
 of the external air much below the freezing point, in- 
 to a heated apartment loaded with aqueous vapour. 
 Dr Robertson states, that, in a crowded assembly- 
 room at St Petersburgh, a stream of cold air was ac- 
 cidentally admitted into the room by a gentleman 
 breaking a pane of glass, on which the vapour in the 
 air was immediately congealed, and fell in the form of 
 snow flakes. 
 
 Within the torrid zone, snow is never seen except 
 on elevated mountains. The reason is, that at all 
 low altitudes the atmospheric temperature,' in that re- 
 gion of the earth, is always greatly above the freezing 
 point. For a similar reason in temperate latitudes, 
 the falling of snow is restricted to the colder season 
 of the year. But in the polar regions, almost the 
 whole moisture precipitated from the atmosphere dur- 
 ing all seasons of the year, descends to the earth in 
 this form. 
 
 Snow is characterized by the whiteness of its colour, 
 and by the spongy lightness of its texture. The for- 
 mer of these qualities, viz., its whiteness, is pecuhar- 
 ly useful for reflecting and increasing the amount of 
 light, in those dark and dreary regions where it is 
 constantly to be found. In those climates, even the 
 light of the stars, or of the aurora borealis, when as- 
 sisted by the reflection of snow, is sufficient in the 
 absence of the sun and moon, to enable the travel- 
 ler to direct his journey with perfect ease and safety. 
 
 The light spongy texture of snow, by diminishing 
 its power in conducting heat, renders it extremely 
 useful in protecting the more tender herbs and plants 
 from destruction, during the frigid season of the year. 
 
OF METEOROLOGICAL PHENOMENA. '215 
 
 And though in our temperate dimate, we are in the 
 habit of regardinof snow as the emblem of winter and 
 coldness, the qualities above-mentioned, have pointed 
 it out to the natives of polar latitudes, as a fit sub- 
 stance wherewith to construct their huts, in order to 
 protect themselves against the rigorous frost of an 
 arctic winter. Besides these useful purposes, the 
 gradual melting of the immense quantities of snovv^ 
 deposited in Alpine regions during winter, affords a 
 regular and constant supply of water to many rivers 
 on the continent, which would otherwise become un- 
 navigable during the heat and drought of summer. 
 
 Of Sleet. — When it is considered that the temper- 
 ature of the atmosphere decreases at the mean rate of 
 one degree of Fahrenheit for every 300 feet of per- 
 pendicular ascent, it may be easily conceived, that 
 the atmospheric temperature at a considerable altitude 
 may be below the freezing point, while at, and near 
 the earth's surface, it is above it. In this case, pre- 
 cipitated moisture descending in the frozen form of 
 flakes of snow, begins to melt so soon as it reaches 
 those atmospheric strata, the temperature of which is 
 above the freezing point. In such circumstances, 
 the snow, by the time it reaches the surface of the 
 earth, is partially melted ; and has received the name 
 of sleet. 
 
 Of' Hail. — Hail appears to be descending moisture 
 frozen, after being formed into drops of rain of greater 
 or less magnitude. 
 
 One of the difficulties which has puzzled meteoro- 
 logists to solve, is how it gets frozen in descending to 
 a lower altitude, while at a higher altitude, the parti- 
 
•J16 ON THE CAUSES AND PRINCIPLES 
 
 cles of precipitated moisture should have time to unite 
 together in the course of their descent, so as to form 
 drops of rain before being frozen. If the temperature 
 of the higher region, hke those underneath, be under 
 the freezing point, the aqueous vapour, so soon as 
 condensed into particles of the smallest size, would 
 congeal, and afterwards could only unite and aggre- 
 gate into the form of snow. And once formed into 
 snow, could not possibly assume the form of hail, with- 
 out being first melted into drops of rain, and there- 
 after frozen. It is obvious, therefore, that the atmo- 
 spheric strata at the higher altitude, contrary to the 
 principle of the aerial temperature decreasing upon 
 ascending perpendicularly, must have been warmer 
 than those underneath, and this is the point which 
 meteorologists are puzzled to explain. 
 
 The difficulty under consideration may be obviated 
 in two ways, both of which probably in different cir- 
 cumstances occur. First, supposing the precipitation 
 of moisture from the atmosphere at a great altitude to 
 be rapidly going on, the heat thereby evolved may be 
 sufficient to raise the temperature of the aerial strata, 
 where the aqueous precipitation is in progress, above 
 the freezing point ; while the atmospheric tempera- 
 ture for a considerable distance underneath, which 
 has not participated in this adventitious accession of 
 warmth, may be considerably below the freezing point. 
 In such circumstances, the aqueous particles, before 
 reaching the cold aerial strata underneath, may be so 
 far enlarged by uniting together, as to form drops of 
 rain ; and which, upon being frozen during their sub- 
 sequent descent through the colder aerial strata, be- 
 
OF METEOROLOGICAL PHENOMENA. ^17 
 
 come hailstones. Second, provided the opinion ad- 
 vanced in the preceding chapter be correct, viz. that 
 an electric state of the atmosphere increases its capa- 
 city for holding moisture, not only in invisible solu- 
 tion, but also in the visible form of cloud, it is pro- 
 bable, that in those electric states of the atmosphere, 
 vi'hen hail accompanies, or rather terminates, a thun- 
 der-storm, the amount of moisture which, in conse- 
 quence of the abstraction of electricity, is instantly 
 precipitated, may be so great, as to form drops of rain 
 of moderate size. And provided such takes place at 
 an altitude where the temperature is below 32°, hail, 
 instead of drops of rain, will instantly be formed. 
 
 Hail is chiefly restricted to the temperate latitudes 
 of the earth, and in these is most frequent during 
 spring and summer. Within the tropics, it seldom 
 falls at a lower altitude than from 1500 to 2000 feet 
 above the level of the sea. The explanation usually 
 given of this fact is, that the atmospheric temperature 
 which increases downwards to the surface of the earth, 
 is constantly so high in those regions, that hail never 
 descends to a lower altitude than that above men- 
 tioned, without being melted. 
 
 Hail also seldom or never falls in any latitude much 
 above GO". The reason of this is, that in high lati- 
 tudes the amount of aqueous vapour precipitated from 
 the atmosphere is so small, as to be incapable of rais- 
 ing the temperature of the aerial strata where it is 
 precipitated, sensibly above that of those underneath. 
 And if the atmospheric temperature where precipita- 
 tion of humidity is going on, or where the vesicles 
 are losing their vesicular form, and all underneath, be 
 
•218 ON THE CAUSES AND PRINCIPLES 
 
 under 32°, the aqueous particles, when only of their 
 first and smallest size, will be severally frozen as they 
 are precipitated ; and, as before stated, the only union 
 which they can thereafter adopt, without being again 
 melted, is that which they usually exhibit in the form 
 of a flake of snow. For a similar reason to the pre- 
 ceding, hail seldom falls in temperate latitudes during 
 winter. 
 
 In this country hail-storms seldom assume any re- 
 markable appearance. But in some other countries, 
 especially in the southern districts of France, between 
 the Alps and the Pyrenees, hail-storms are so violent, 
 and the hailstones so large, as frequently to lay waste 
 large districts of country. They are usually accom- 
 panied with thunder, and a violent squall or whirlwind. 
 On such occasions, individual hailstones have been 
 found to weigh as much as five ounces, and sometimes 
 more ; and, instead of presenting the usual globular 
 form, appear to be irregularly shaped angular masses 
 of ice. 
 
 It is observed that those remarkable hail-storms 
 which are accompanied with thunder usually occur in 
 the warmest period of the year, and very seldom dur- 
 ing night or winter. The same thing, however, may 
 be said regarding thunder-storms accompanied only 
 by rain. It is therefore presumable, that the hail is a 
 mere accompaniment to the thunder-storm, and more 
 or less dependent upon, or produced by it. Hence 
 the reason which we formerly assigned for thunder- 
 storms occurring most frequently during the warmest 
 period of the day, and of the year, is equally applica- 
 ble to hail-storms which accompany thunder. 
 
OF METEOROLOGICAL PHENOMENA. 219 
 
 The immense magnitude of the hailstones in such 
 storms, and the intensity of cold during the hottest 
 period of summer, requisite to freeze them in their 
 descent to the earth, has never been satisfactorily 
 accounted for. The only explanation offered is, that 
 they must have been originally formed at an altitude 
 in the atmosphere, where the temperature is greatly 
 below 32°, and in consequence of their extreme cold- 
 ness, that they acquired magnitude during their de- 
 scent, by condensing on their respective surfaces, the 
 copious vapours contained in the electrified cloud and 
 atmosphere through which they passed. The diffi- 
 culty, however, is not altogether obviated by this con- 
 jectural explanation. For supposing the atmospheric 
 temperature at the surface of the earth, immediately 
 previous to one of those hail-storms, to be at 72° of 
 Fah., (and which is only a moderate temperature for 
 the southern districts of France, during the hottest 
 period of the year, when such storms usually happen,) 
 it would require an elevation of 9000 feet, at the mean 
 decrement of one degree for every 300 feet of ascent, 
 before the freezing temperature of 32° was attained. 
 And supposing the atmospheric temperature at the 
 earth's surface to be at 82°, it would require an eleva- 
 tion of 12,000 feet before the freezing temperature 
 was reached. Now, when it is considered that the 
 medium height of clouds, according to Gay Lussac, 
 is between 4500 and 6000 feet, it looks like stretching 
 conjecture beyond admissible probability, to suppose 
 that the thunder-cloud extended to an altitude much 
 beyond 9000 feet in the one case, and much beyond 
 12,000 feet in the other, so that the hailstones at their 
 
220 ON THE CAUSES AND PRINCIPLES 
 
 first formation may have acquired such an intense de- 
 gree of coldness, as to be able, during their descent, 
 to congeal on their surfaces an amount of vapour suffi- 
 cient to account for their immense magnitude, by the 
 time they reach the ground. In such cases, it is 
 usual both for the learned and the ignorant to get 
 quit of the difficulty, by ascribing it to electricity. 
 But this is merely an evasion, and not a solution of 
 the question, unless it can be shown that water can 
 be frozen by means of electricity, at a lower tempera- 
 ture than 32°. 
 
 The simplest and the most plausible way of ex- 
 plaining the phenomenon, is to suppose that the 
 thunder-cloud is floating at an altitude where the 
 temperature of the atmosphere is below the freezing 
 point ; and that the mass of aqueous vapour concen- 
 trated and suspended in the vesicular form, is, in 
 consequence of electrization, so great, that the col- 
 lapsing and uniting of the vesicles, upon the escape 
 of the electric fluid in the form of lightning, at once 
 produces hailstones of the magnitude described. By 
 this means we get rid of the difficulty of supposing, 
 that the nuclei of the hail-stones are formed at an al- 
 titude sufficient to account for the acquisition of such 
 a degree of coldness, as to enable them to acquire the 
 magnitude described, by congealing on their surfaces 
 the aqueous vapours through which they pass in their 
 descent to the earth. 
 
 The squall of wind, or whirlwind, which accompa- 
 nies and ushers in the hail-storm, is no doubt pro- 
 duced by the depression of temperature which the 
 liail communicates to the lower atmosphere, in its 
 
OF METEOROLOGICAL PHENOMENA. 221 
 
 descent to the ground. The explanation of this fact 
 is analogous to that given in the fourth chapter, re- 
 garding the influence of a shower of rain in warm 
 climates, in producing sudden gusts, and sometimes a 
 change in the direction of the wind. That explana- 
 tion we need not here repeat. 
 
 On the supposition that hail-storms were occasioned 
 by an unequal distribution and accumulation of elec- 
 tricity in the atmosphere, it was proposed by certain 
 French philosophers to draw off the electric fluid by 
 means of lightning-rods, similar to those erected for 
 the protection of buildings ; and it is said that where 
 these have been introduced, they have had the de- 
 sired effect. I am not aware upon what extent of ex- 
 perience the supposed beneficial eff"ect of these hail- 
 rods is founded. But when it is considered that 
 the hailstones in question must have been formed at 
 an immense altitude, and that air is a non-conductor 
 of electricity, and consequently, that a hail-rod can 
 only affect the electrical condition of a very limited 
 amount of air in its immediate vicinity ; it is probable, 
 that their influence in afibrding protection against 
 hail and thunder-storms, may have been somewhat 
 over-estimated. At a random guess, I am inchned 
 to think, that a large tree, 80 feet high, would have 
 as much influence, by means of its numerous pointed 
 branches, in robbing the atmospheric current of its 
 surplus electricity, as a single hail-rod 40 feet in 
 height. There is no doubt, however, that lightning- 
 rods, if sufficiently numerous and sufficiently elevated, 
 which last can be best accomphshed by erecting them 
 along the summits of hills and rising grounds, would 
 
•2*2*2 ON THE CAUSES AND PRINCIPLES 
 
 in some degree assist in maintaining an electric equi- 
 librium between the atmosphere and the subjacent 
 earth ; and consequently, that they would have a cor- 
 responding influence in diminishing the frequency, 
 and mitigating the violence of such storms. 
 
 Of Deiu and Hoar-frost. — When treating of the 
 formation of the stratus or fall-cloud, in our third 
 chapter, we explained the causes and principles which, 
 according to the experiments of Dr Wells, determine 
 the formation of dew. To these, therefore, we refer, 
 and if more information be wanted, illustrations suf- 
 ficiently copious will be found in Dr Wells's Essay on 
 Dew. We shall only here briefly mention, that dew 
 consists of moisture precipitated from the aerial strata 
 nearest the ground, in consequence of coldness in- 
 duced by radiation of caloric from the earth's surface, 
 during calm clear nights, being communicated to those 
 strata in sufficient intensity to produce oversaturation. 
 
 In consequence of dew resulting from the depres- 
 sion of temperature arising from radiation, it falls most 
 copiously in those places where the surface of the 
 ground is best fitted for radiating caloric. Hence, 
 agreeably to the beneficent designs of Providence, by 
 which scarcity produces proportionate economy, and 
 by which all phenomena are adapted upon the wisest 
 principles to serve useful purposes, frugahty in its 
 distribution is observed to be proportionate to the 
 smallness of its quantity. Thus, when the air is dry, 
 and the quantity of dew that falls during night is very 
 limited in amount ; in accordance with the principles 
 which regulate the degree of coldness induced by ra- 
 diation on different parts of the earth's surface, the 
 
OF METEOROLOGICAL PHENOMENA. '223 
 
 deposition of dew seems as if it were reserved for those 
 vegetable productions, which stand most in need of 
 its moistenino- influence, and of the heat evolved dur- 
 ing its deposition, to protect them from the coldness 
 by which it is produced. " This fluid," says Dr 
 Wells, " appears chiefly where it is most wanted, on 
 herbage and low plants, avoiding, in great measure, 
 rocks, bare earth, and considerable masses of water. 
 Its production too, by another wise arrangement, 
 tends to prevent the injury that might arise from its 
 own cause ; since the precipitation of water, upon the 
 tender parts of plants, must lessen the cold in them, 
 which occasions it." 
 
 Hoar-frost is merely frozen dew. The great evolu- 
 tion of heat which attends the conversion of dew in- 
 to hoar-frost, is another wise arrangement by which the 
 coldness is farther mitigated ; and those herbs and 
 plants upon which dew is deposited, are farther pro- 
 tected from the extreme depression of temperature to 
 which they would otherwise be subjected. 
 
 The quantity of moisture that falls in the form of 
 dew, averaged for the whole of Great Britain, has 
 been estimated by Dr Dalton at five inches, and by 
 Dr Thomson, at four inches annually. I am not 
 aware upon what principle the estimate is made. But 
 when it is considered, that dew only falls during night; 
 and only when the nights are calm, and cloudless ; 
 and that the number of such nights throughout the 
 year, in our windy climate, is very limited. And 
 when it is farther considered, that little or none falls 
 on hills, or other acclivities ; nor on trees, or the 
 ground which they shelter ; and little or none on 
 
*2*24 ON THE CAUSES AND PRINCIPLES 
 
 rocks or roads. And, in short, when it is considered, 
 that the falHng of dew is chiefly restricted to hollows 
 and plains, consisting of grass fields, or uncovered 
 ploughed lands ; and particularly when the smallness 
 of the amount that falls in any night, is compared 
 with what falls of rain in a similar time, and which 
 is not limited to particular localities, nor to any pro- 
 portion of the day or night, it seems probable, that 
 five inches of dew annually, which is equal to ^th part 
 of all the moisture that falls in the different forms of 
 rain, snow, and hail, is double, or perhaps triple its 
 actual amount. 
 
 Of Falling Mist, — Falling mist is the only aque- 
 ous deposition which remains to be noticed. It com- 
 monly occurs in still vveather, and, in our chmate, 
 makes its appearance most frequently during the win- 
 ter season, when the temperature is either below, or 
 little above the freezing point. In the former case, 
 after having fallen, it has the same appearance as 
 hoar-frost ; in the latter, it resembles dew. Most 
 frequently it results from the same cause as dew, viz., 
 from the reduction of temperature, induced upon the 
 earth's surface by calorific radiation, being propagat- 
 ed upwards through the atmosphere in sufficient in- 
 tensity to produce aerial oversaturation. Frequently 
 this cause is assisted by a gradual sinking of the tem- 
 perature of the atmosphere generally. In some 
 countries, such as in a portion of Peru, almost the 
 whole moisture which the soil receives to support ve- 
 getation, is supplied from falhng mist and dew. In 
 others, such as Egypt, these are assisted by periodic 
 river inundations. The amount of moisture supplied 
 
OF METEOROLOGICAL PHENOMENA. 225 
 
 to the soil by falling mist, is, in some places, very 
 considerable. " In that part of Peru," says Dr 
 Thomson, " called Valles, which lies on the north 
 and south side of Lima, in south latitude 12°, bound- 
 ed on the east by the Andes, and on the west by the 
 Pacific ocean, it never rains at all. But, during win- 
 ter, the earth is covered with so thick a fog as to in- 
 tercept the rays of the sun. This fog appears almost 
 every day during winter, with a density that obscures 
 objects at any distance. About 10 or 11 o'clock it 
 begins to rise, but without being totally dispersed ; 
 though it is then no impediment to the sight, inter- 
 cepting only the direct rays of the sun by day, and 
 that of the stars by night. Sometimes it is so far dis- 
 persed that the disc of the sun becomes visible, but 
 the heat from his rays is still precluded. In the win- 
 ter, these vapours dissolve into a very small mist or 
 dew, which they call garua, and thus every where 
 moistens the earth. These garuas never fall in 
 quantities sufficient to damage the road, or incom- 
 mode the traveller; but they render the most arid 
 and barren parts fertile. They convert the disagree- 
 able dust in the streets of Lima into mud." 
 
 What is called an eastern liaai' on the east coast 
 of Britain, is also a falling mist, accompanied with an 
 east, or north-east wind. When its density becomes 
 considerable, it moistens the clothes of a person ex- 
 posed to it ; and this it does more readily, and with a 
 less degree of density, if he be going against the 
 wind. It is usually occasioned by the gradual con- 
 densation of the moisture evaporated from the sea, 
 
 2f 
 
226 ON THE CAUSES AND PRINCIPLES, &C. 
 
 when its surface is warmer than the incumbent atmo- 
 sphere. 
 
 We will only farther observe, that a falling mist 
 may occur in any circumstances, when the lower at- 
 mosphere undergoes a reduction of temperature, af- 
 ter it has reached the point of saturation. In such 
 circumstances, it may be considered the slightest de- 
 gree, and frequently forms the commencement of 
 drizzling rain. The case narrated in the third chap- 
 ter of the gradual conversion of floating, into falling 
 mist ; and of falling mist into drizzling rain, upon 
 ascending the upper portion of Goatfell in the island 
 of Arran, affords a striking exemplification of the 
 point under consideration. It was there stated, that 
 the ground was quite dry, and the mist produced no 
 visible deposition of moisture upon our clothes, lower 
 than about 300 feet perpendicular from the top. At 
 that elevation, however, the ground assumed the ap- 
 pearance of dampness ; and moisture, at first in such 
 small quantity as to be almost imperceptible, began 
 to be deposited upon our clothes. In our farther as- 
 cent, this condition of the atmosphere gradually in- 
 creased, so that at the summit of the mountain, we 
 found ourselves surrounded with an exceedingly dense 
 mist, attended with drizzHng rain. 
 
CHAPTER VII. 
 
 ON THE CAUSES AND PRINCIPLES WHICH REGULATE AND 
 DETERMINE THE VARIATIONS OF TEMPERATURE ON THE 
 earth's SURFACE. 
 
 Of the mean temperature as affected hy difference 
 of latitude, both hy sea and land. — The greater or 
 less mean temperature of the earth in any latitude, 
 obviously results from the different degrees of obli- 
 quity with which the sun's rays fall upon its surface, 
 during its diurnal revolution on its axis from west to 
 east. It is accordingly found, that the mean annual 
 temperature decreases as we recede from the equator 
 towards either pole. If the plane of the ecliptic cor- 
 responded with that of the equator, the mean diurnal 
 temperature of the earth in each latitude, would un- 
 dergo no variation throughout the year. Owing, 
 however, to the deviation of the plane of the ecliptic 
 from that of the equator, and consequently to the 
 sun's gradual declination from the equator towards 
 the north to the extent of 23i degrees, during our 
 summer ; and towards the south to a similar extent, 
 during our winter ; corresponding latitudes in the op- 
 posite hemispheres of the earth, are periodically and 
 simultaneously undergoing opposite variations of tem- 
 perature from the mean for the latitude. And the 
 extent of these variations, except what arises from 
 
228 ON THE CAUSES AND PRINCIPLES 
 
 circumstances hereafter to be noticed, is proportional 
 to the greater or less obliquity of the sun's rays, and 
 the variations in the length of the day in different 
 latitudes, and different seasons of the year. 
 
 Though the mean annual temperature for any given 
 latitude be nearly the same, whether it be land or 
 water, the extreme temperatures of summer and win- 
 ter are very much influenced thereby. In summer, 
 the surface of the sea is much colder than that of the 
 land at a distance from the sea in the same latitude ; 
 whereas, in winter it is much warmer. The mean 
 annual range of temperature of the surface of the At- 
 lantic, for the temperate zone, is only about 9°, and 
 that of the torrid zone is not above 4° ; whereas, the 
 annual range of temperature for inland continental 
 countries in temperate latitudes, exceeds 100°. In 
 like manner, in the equatorial regions, the extreme 
 atmospheric temperatures of day and night, over the 
 ocean, never exceed three or four degrees ; while 
 upon land, the difference often amounts to 9° or 10". 
 Between the 25th and 50th parallels of latitude, the 
 extremes in the diurnal range of temperature at sea 
 is only from 4° to 5° ; while at Paris it often amounts 
 to 20° or 30°. This great difference in the annual 
 and diurnal range of temperature between land and 
 ocean, is partly to be ascribed to the greater calor- 
 ific capacity of the latter; and partly to its power of 
 preserving uniformity of temperature, by increased 
 evaporation during the heat of day, and by the sinking 
 down, agreeably to statical principles, of the upper 
 particles, as they become colder and heavier than 
 those below, during night. 
 
OF METEOROLOGICAL PHENOMENA. 229 
 
 Within the tropics, the mean temperature of the 
 ocean is generally higher than that of the air in con- 
 tact with it. This is chiefly owing to the greater 
 mobility of the atmosphere, and consequently, to a 
 larger proportion of the solar heat being transferred to 
 colder latitudes by currents in the atmosphere, than 
 by currents in the ocean. 
 
 In the temperate zones, the mean diurnal tempera- 
 ture of the ocean is a little lower in summer, and a 
 little higher in winter, than the mean diurnal tempera- 
 ture of the incumbent air in the same parallel. This 
 is owing to the greater heat of the land in correspond- 
 ing latitudes during summer, and its greater coldness 
 in winter, being more freely communicated to the at- 
 mosphere over the ocean by aerial currents, than to 
 the subjacent water. 
 
 Of the time when the maximum^ minimum, and 
 m£an annual temperatures occur in the atmosphere, 
 and also at different depths below the surface of the 
 ground. — In temperate latitudes, such as from 35° to 
 55°, the greatest annual temperature of the atmosphere, 
 occurs from about a fortnight to three weeks after the 
 summer solstice ; and its lowest annual temperature, 
 about a similar length of time after the winter solstice. 
 In like manner, the mean annual temperature of the 
 atmosphere is attained, in spring and autumn, from 
 two to three weeks after the vernal and autumnal 
 equinoxes respectively. Nearer the equator than the 
 35th parallel of latitude, the maximum temperature of 
 summer, and the minimum of winter, will occur earlier 
 after the solstices ; and beyond the 55th parallel of 
 latitude, somewhat later, than the time above stated. 
 This is owing to the greater annual range of tempera- 
 
230 
 
 ON THE CAUSES AND TRINCIPLES 
 
 ture on receding from the equator towards either pole; 
 and consequently, to the increasing amount of heat 
 which the earth has to absorb during summer, and 
 give out during winter, before attaining its maximum 
 and minimum temperatures. 
 
 The farther we dig down below the surface of the 
 ground, the maximum temperature of summer, and 
 the minimum of winter, are longer after the summer 
 and winter solstices of being attained. And the an- 
 nual range of temperature gradually becomes less, 
 from the surface downwards, to the depth of between 
 forty and fifty feet, where the temperature remains 
 unaltered throughout the year. The following table* 
 exhibits a statement of the mean temperature of the 
 earth at the depth of one, two, four, and eight feet, 
 below the surface of the ground, for each month in 
 the years 1816 and 1817. 
 
 
 1816. 
 
 1817. 
 
 
 1 foot. 
 
 2 feet. 
 
 4 feet. 
 
 8 feet. 
 
 I foot. 
 
 2 feet. 
 
 4 feet. 
 
 8 feet. 
 
 January, . 
 
 33.8 
 
 36.3 
 
 40.7 
 
 43.0 
 
 35.6 
 
 38.7 
 
 40.5 
 
 45.1 
 
 February, 
 
 33.7 
 
 36.0 
 
 39.0 
 
 42.0 
 
 37.0 
 
 40.0 
 
 41.6 
 
 42.7 
 
 March, . 
 
 35.0 
 
 36.7 
 
 39.6 
 
 42.3 
 
 39.4 
 
 40.2 
 
 41.7 
 
 42.5 
 
 April, . . 
 
 39.7 
 
 38.4 
 
 41,4 
 
 43.8 
 
 45.0 
 
 42.4 
 
 42.6 
 
 42.6 
 
 May, . . 
 
 44.0 
 
 43.3 
 
 43.4 
 
 44.0 
 
 46.8 
 
 44.7 
 
 44.6 
 
 44.2 
 
 June, . 
 
 51.6 
 
 50.0 
 
 47.1 
 
 45.8 
 
 51.1 
 
 49.4 
 
 47.6 
 
 47.8 
 
 July, . . 
 
 54.0 
 
 52.5 
 
 50.4 
 
 47.7 
 
 55.2 
 
 55.0 
 
 51.4 
 
 49.6 
 
 August, . 
 
 50.0 
 
 52.5 
 
 50.6 
 
 49.4 
 
 53.4 
 
 53.9 
 
 52.0 
 
 50.0 
 
 September, 
 
 51.6 
 
 51.3 
 
 51.8 
 
 50.0 
 
 53.0 
 
 52.7 
 
 52.0 
 
 50.7 
 
 October, . 
 
 47.0 
 
 49.3 
 
 49.7 
 
 49.6 
 
 45.7 
 
 49.4 
 
 49.4 
 
 49.8 
 
 November, 
 
 40.8 
 
 43.8 
 
 46.3 
 
 45.6 
 
 41.0 
 
 44.7 
 
 47.0 
 
 47.6 
 
 December, 
 
 35.7 
 
 40.0 
 
 43.0 
 
 46.0 
 
 37.9 
 
 40.8 
 
 44.9 
 
 46.4 
 
 Mean of whole 
 year, 
 
 43.8 
 
 44.1 
 
 45.1 
 
 46.0 
 
 44.9 
 
 45.9 
 
 46.2 
 
 46.6 
 
 * Extracted from the article Climate in tlic Supplement to the I 
 Encyclopedia Britannica. ' 
 
OF METEOROLOGICAL PHENOMENA, 231 
 
 The observations from which the above table is 
 compiled, were made in the most satisfactory manner 
 by the directions, and under the superintendence, of 
 Mr Ferguson of Raith, in his garden, at Abbotshall, 
 about 50 feet above the level of the sea, and nearly a 
 mile from the shore of Kirkaldy, in latitude 5&' 10', 
 The thermometer, at the depth of one foot, reached 
 its maximum and minimum temperatures about three 
 weeks after the summer and winter solstices : its ex- 
 treme variation being 25°. The thermometer, at the 
 depth of two feet, reached its maximum and minimum 
 temperatures about four or five weeks after the sol- 
 stices : its extreme variation being 20°. The thermo- 
 meter at the depth of four feet did not reach its maxi- 
 mum and minimum temperatures, till nearly two 
 months after the solstices : its range being only 15°. 
 And the thermometer, at the depth of eight feet, did 
 not reach its maximum and minimum temperatures, 
 till nearly three months after the solstices of summer 
 and winter : and its range was only 9i°. These facts 
 show the slowness with which the increased tempera- 
 ture, during summer, penetrates the earth ; and the 
 corresponding slowness with which it is again returned 
 to, and emanates from the surface of the ground dur- 
 ing the cold season of the year. 
 
 Of the variations in the temperature of water at 
 different depths^ S^c. — The oscillations in the tem- 
 perature of the ocean, and also of deep lakes above 
 and below the mean for the latitude, is restricted in a 
 great measure to the surface. Below the depth of 
 fifteen or twenty fathoms, the annual variations of 
 temperature are not perceptible. In fresh-water, when 
 
23*2 ON THE CAUSES AND PRINCIPLES 
 
 the temperature at the surface is above 39°, the tem- 
 perature sinks as the depth becomes greater, until it 
 nearly reaches that point, when it remains stationary ; 
 and gradually as it approaches that point, the decre- 
 ments of temperature, for equal increments of depth, 
 become less. On the contrary, when the temperature 
 of the surface is below 39°, the temperature increases 
 with the depth, till it reaches that point, and at all 
 farther depths remains stationary. This is owing to 
 the mobility of water, in connection with the statical 
 law of its particles becoming heavier, with increase of 
 coldness, till they reach their maximum density at 39°. 
 Hence all the cold impressions communicated to the 
 surface, so long as the temperature remains above 39°, 
 are transmitted downwards by the sinking of the cold 
 particles, while the warm impressions remain chiefly 
 on the surface, till dissipated by evaporation, or radia- 
 tion. The following observations, as well as others, 
 (which, for the sake of brevity, we omit inserting,) 
 confirm the truth of these remarks: — On the 11th 
 September, the superficial water of Loch Katrine 
 being 57° 3', the thermometer let down ten fathoms 
 indicated 50° 6' ; at the depth of twenty fathoms, it 
 indicated 43° 1' ; and near the bottom, at 80 fathoms, 
 it indicated 41°. Saussure found the temperature of 
 the Lake of Geneva, at the depth of 1000 feet, to be 
 42°, and could discover no monthly variations under 
 160 feet. These observations afford an explanation 
 of the reason why the surface of deep lakes, even in 
 moderately high latitudes, never freezes. Owing to 
 the maximum density of water being at 39°, gradually 
 as the particles on the surface get cooled below that 
 
OF METEOROLOGICAL PHENOMENA. 233 
 
 point, they sink to the bottom. Consequently, be- 
 fore the surface can be frozen, or even before its tem- 
 perature can be reduced below 39°, the temperature 
 of the whole water to the bottom must be lowered to 
 that point. But the duration of cold weather, unless 
 in very high latitudes, is usually too short to produce 
 this effect, where the depth of water is considerable. 
 
 Between the tropics, and also in the temperate 
 zone, where the temperature of the surface of the 
 ocean is above that at which its density is greatest* 
 its temperature diminishes with the depth ; whereas, 
 in the Polar seas, where the heat at the surface is be- 
 low that at which its density is greatest, the tempera- 
 ture augments with the depth. The temperature of 
 the surface of the ocean has been found gradually to 
 decrease from the equator to the 70th parallel of lati- 
 tude, where it remains stationary. It is, therefore, 
 about this parallel where the mean temperature of the 
 ocean is nearly constant at all depths. 
 
 The great coldness experienced at the bottom of 
 deep caverns, and uncovered pits, and draw-wells, has 
 been explained upon the same principle as the cold- 
 ness near the bottom of deep lakes. During the 
 depth of winter, the cold air at the top of the cavern, 
 from its superior specific gravity, sinks down to the 
 bottom. But in summer, the warm air at the mouth 
 of the cavern, owing to its inferior specific gravity, 
 has no tendency to sink down and displace the cold 
 air below. 
 
 Of the maximum^ minimum^ and mean diurnal 
 
 temperatures Within the tropics, the maximum 
 
 diurnal temperature occurs about an hour after mid- 
 
 2 G 
 
234 ON THE CAUSES AND PRINCIPLES 
 
 day ; and gradually as we advance from the tropics to 
 higher latitudes, at least during summer, it becomes 
 later in the afternoon. The circumstance of the max- 
 imum diurnal temperature occurring sooner or later 
 after mid-day, seems chiefly to depend upon the de- 
 gree of rapidity, with which the falling of the sun's 
 rays upon the earth's surface increase in obliquity 
 after mid-day. Hence in temperate and high lati- 
 tudes, the nearer the summer solstice, the longer is it 
 after mid-day before the maximum diurnal tempera- 
 ture occurs. At Glasgow, situated in north latitude 
 55° 52', the maximum diurnal temperature, as indi- 
 cated by a thermometer shaded from the direct and 
 reflected rays of the sun, occurs at the summer sol- 
 stice, about three hours after mid-day ; whereas, at 
 the winter solstice, it takes place about an hour and 
 a half after mid-day. In higher latitudes it will occur 
 sooner after noon in winter; and later after noon in 
 summer, than at Glasgow. Upon this point it may 
 be remarked, that the diff'erences among meteorolo- 
 gists as to the length of time after mid-day, when the 
 maximum temperature occurs, are not wholly to be 
 ascribed to the diff"erence in the latitude, and the sea- 
 son of the year when the observations are made. They 
 also result from peculiarities around the place of ob- 
 servation, giving more or less hinderance to the pro- 
 gress of the calorific tide. The tides of the ocean 
 are longer of attaining their greatest height at any 
 place, according to the number of sinuosities and ob- 
 structions which they have to encounter in their 
 course. And in like manner, the calorific tide of day 
 is longer of attaining its maximum height, according 
 
OF METEOROLOGICAL PHENOMENA. 235 
 
 as the place of observation is better fitted for retard- 
 ing its approach. Of two thermometers which I have 
 been in the habit of observing, one was nearly an hour 
 later of reaching its maximum diurnal temperature 
 than the other. And analogously to the diminution 
 in the annual range of temperature, exhibited by ther- 
 mometers, according as they were sunk deeper in the 
 ground, the diurnal range of temperature exhibited 
 by the thermometer which was best protected from 
 the solar heat, and which was latest of arriving at its 
 maximum height, was least. 
 
 In similar parallels of latitude, it is said that the 
 maximum diurnal temperature occurs sooner at sea 
 than on land. But both by sea and land, and in all 
 latitudes, and seasons of the year, the minimum diurnal 
 temperature takes place about an hour before sunrise. 
 
 Various plans have been adopted for ascertaining 
 the mean][diurnal temperature. One of these is to 
 take the mean between the maximum temperature of 
 day, and the minimum of night. Another plan, but 
 hardly so good as the preceding, is to take the mean 
 between the temperatures of 10 o'clock, a.m. and 10 
 o'clock, P.M.; others take the mean between 9 o'clock, 
 a.m. and 9 o'clock, p.m. But the most perfect plan 
 that has been proposed, is to observe the temperature 
 every hour during day and night for a length of time 
 together, and to take the mean of the whole. Ac- 
 cording to Humboldt, between the parallels of 46 and 
 48, the thermometer, at the moment of sunsetting, 
 indicates in every season, very nearly the mean atmo- 
 spheric temperature of the day. This rule of Hum- 
 boldt's, however, will be found exceedingly defective 
 
236 
 
 ON THE CAUSES AND PRINCIPLES 
 
 if applied generally. For instance, about mid-sum- 
 mer, particularly in high latitudes, when the days are 
 very long, the instant of sunsetting will indicate a di- 
 urnal temperature much below the mean ; whereas, 
 about mid-winter, in high latitudes, when the days are 
 very short, the instant of sunsetting will indicate a 
 diurnal temperature much above the mean. 
 
 Of the mean annual temperature in different lati- 
 tudes — The following table, made out by Professor 
 Mayer of Gottingen, of the mean annual temperature 
 for each degree of latitude from the Equator to the 
 Poles, is the one generally adopted : — 
 
 Lat. 
 
 Centesimal. 
 
 Diff. 
 
 Fahrenheit. 
 
 Diff. 
 
 
 
 29.00 
 
 .00 
 
 84.2 
 
 .00 
 
 1 
 
 28.99 
 
 .01 
 
 84.2 
 
 .02 
 
 2 
 
 28.96 
 
 .03 
 
 84.1 
 
 .05 
 
 3 
 
 28.92 
 
 .04 
 
 84.0 
 
 .07 
 
 4 
 
 28.86 
 
 .06 
 
 83.9 
 
 .11 
 
 5 
 
 28.78 
 
 .08 
 
 83.8 
 
 .13 
 
 6 
 
 28.68 
 
 .10 
 
 83.6 
 
 .18 
 
 7 
 
 28.37 
 
 .11 
 
 83.4 
 
 .20 
 
 8 
 
 28.44 
 
 .13 
 
 83.2 
 
 .23 
 
 9 
 
 28.29 
 
 .15 
 
 82.9 
 
 .27 
 
 10 
 
 28.13 
 
 .16 
 
 82.6 
 
 .30 
 
 11 
 
 27.95 
 
 .18 
 
 82.3 
 
 .32 
 
 12 
 
 27.75 
 
 .20 
 
 82.0 
 
 .36 
 
 13 
 
 27.53 
 
 .22 
 
 81.6 
 
 .40 
 
 14 
 
 27.30 
 
 .23 
 
 81.1 
 
 .42 
 
 15 
 
 27.06 
 
 .24 
 
 80.7 
 
 .44 
 
 16 
 
 26.80 
 
 .26 
 
 80.2 
 
 .47 
 
 17 
 
 26.52 
 
 .28 
 
 79.7 
 
 .50 
 
 18 
 
 26.23 
 
 .29 
 
 79.2 
 
 .52 
 
 19 
 
 25.93 
 
 .30 
 
 78.7 
 
 .54 
 
 20 
 
 25.61 
 
 .32 
 
 78.1 
 
 .57 
 
 21 
 
 25.28 
 
 .33 
 
 77.5 
 
 .60 
 
 i 
 
OF METEOROLOGICAL PHENOMENA. 
 
 237 
 
 Lat. 
 
 Centesimal. 
 
 Diff. 
 
 Fahrenheit. 
 
 Diflf. 
 
 22 
 
 24.93 
 
 .35 
 
 76.9 
 
 .63 
 
 23 
 
 24.57 
 
 .36 
 
 76.2 
 
 .65 
 
 24 
 
 24.20 
 
 .37 
 
 75.6 
 
 .67 
 
 25 
 
 23.82 
 
 .38 
 
 74.9 
 
 .68 
 
 26 
 
 23,43 
 
 .39 
 
 74.2 
 
 .70 
 
 27 
 
 23.02 
 
 .41 
 
 73.5 
 
 .72 
 
 28 
 
 22.61 
 
 .42 
 
 72.7 
 
 .74 
 
 29 
 
 22.18 
 
 .43 
 
 71.9 
 
 .76 
 
 30 
 
 21.75 
 
 .43 
 
 71.1 
 
 .77 
 
 31 
 
 21.31 
 
 .44 
 
 70.3 
 
 .79 
 
 32 
 
 20.86 
 
 .45 
 
 69.5 
 
 .81 
 
 33 
 
 20.40 
 
 .46 
 
 68.7 
 
 .83 
 
 34 
 
 19.93 
 
 .47 
 
 67.9 
 
 .84 
 
 35 
 
 19.46 
 
 .47 
 
 67.0 
 
 .85 
 
 36 
 
 18.98 
 
 .48 
 
 66.2 
 
 .86 
 
 37 
 
 18.50 
 
 .48 
 
 65.3 
 
 .87 
 
 38 
 
 18.01 
 
 .49 
 
 64.4 
 
 .88 
 
 39 
 
 17.50 
 
 .49 
 
 63.5 
 
 .88 
 
 40 
 
 17.01 
 
 .49 
 
 62.6 
 
 .89 
 
 41 
 
 16.52 
 
 .49 
 
 61.7 
 
 .90 
 
 42 
 
 16.02 
 
 .50 
 
 60.8 
 
 .90 
 
 43 
 
 15.52 
 
 .50 
 
 59.9 
 
 .91 
 
 44 
 
 15.01 
 
 .51 
 
 59.0 
 
 .91 
 
 45 
 
 14.50 
 
 .51 
 
 58.1 
 
 .92 
 
 46 
 
 13.99 
 
 .51 
 
 57.2 
 
 .92 
 
 47 
 
 13.49 
 
 .50 
 
 56.3 
 
 .91 
 
 48 
 
 12.98 
 
 .51 
 
 55.4 
 
 .91 
 
 49 
 
 12.48 
 
 .50 
 
 54.5 
 
 .90 
 
 50 
 
 11.98 
 
 .50 
 
 53.6 
 
 .90 
 
 51 
 
 11.49 
 
 .49 
 
 52.7 
 
 .89 
 
 52 
 
 10.99 
 
 .50 
 
 51.8 
 
 .90 
 
 53 
 
 10.50 
 
 .49 
 
 50.9 
 
 .88 
 
 54 
 
 10.02 
 
 .48 
 
 50.0 
 
 .87 
 
 55 
 
 9.54 
 
 .48 
 
 49.2 
 
 .86 
 
 56 
 
 9.07 
 
 .47 
 
 48.3 
 
 .85 
 
 57 
 
 8.60 
 
 .47 
 
 47.5 
 
 .84 
 
 58 
 
 8.14 
 
 .46 
 
 46.6 
 
 .83 
 
 59 
 
 7.69 
 
 .45 
 
 45.8 
 
 .81 
 
 60 
 
 7.25 
 
 .44 
 
 45.0 
 
 .79 
 
238 
 
 ON THE CAUSES AND PRINCIPLES 
 
 Lat. 
 
 Centesimal. 
 
 Diff. 
 
 Fahrenheit. 
 
 Difif. 
 
 61 
 
 6.82 
 
 .43 
 
 44.3 
 
 .78 
 
 62 
 
 6.39 
 
 .43 
 
 43.5 
 
 .77 
 
 63 
 
 5.98 
 
 .41 
 
 42.8 
 
 .76 
 
 64 
 
 5.57 
 
 .41 
 
 42.0 
 
 .74 
 
 65 
 
 5.18 
 
 .39 
 
 41.3 
 
 .71 
 
 66 
 
 4.80 
 
 .38 
 
 40.6 
 
 .68 
 
 67 
 
 4.43 
 
 .37 
 
 40.0 
 
 .67 
 
 68 
 
 4.07 
 
 .36 
 
 39.3 
 
 .65 
 
 69 
 
 3.72 
 
 .35 
 
 38.7 
 
 .63 
 
 70 
 
 8.39 
 
 .33 
 
 38.1 
 
 .60 
 
 71 
 
 3.07 
 
 .32 
 
 37.5 
 
 .57 
 
 72 
 
 2.77 
 
 .30 
 
 37.0 
 
 .54 
 
 73 
 
 2.48 
 
 .29 
 
 36.5 
 
 .52 
 
 74 
 
 2.20 
 
 .28 
 
 36.0 
 
 .50 
 
 75 
 
 1.94 
 
 .26 
 
 35.5 
 
 .47 
 
 76 
 
 1.70 
 
 .24 
 
 35.1 
 
 .43 
 
 77 
 
 1.47 
 
 .23 
 
 34.6 
 
 .41 
 
 78 
 
 1.25 
 
 .22 
 
 34.2 
 
 .40 
 
 79 
 
 1.05 
 
 .20 
 
 33.9 
 
 .36 
 
 80 
 
 .86 
 
 .19 
 
 33.6 
 
 .34 
 
 81 
 
 .71 
 
 .17 
 
 33.3 
 
 .31 
 
 82 
 
 .56 
 
 .15 
 
 33.0 
 
 .27 
 
 83 
 
 .43 
 
 .13 
 
 32.8 
 
 .23 
 
 84 
 
 .32 
 
 .11 
 
 32.6 
 
 .20 
 
 85 
 
 .22 
 
 .10 
 
 32.4 
 
 .18 
 
 86 
 
 .14 
 
 .08 
 
 32.3 
 
 .15 
 
 87 
 
 .08 
 
 .06 
 
 32.2 
 
 .11 
 
 88 
 
 .04 
 
 .04 
 
 32.1 
 
 .07 
 
 89 
 
 .01 
 
 .03 
 
 32.0 
 
 .05 
 
 90 
 
 .00 
 
 .00 
 
 32.0 
 
 .01 
 
 Upon the above table it may be remarked, that in 
 high latitudes, where ice and snow are perpetually to 
 be found, the mean annual temperature given is much 
 higher than it ought to be. The Professor's state- 
 ment of the mean annual temperature at the pole 
 being 32° of Fah. is founded upon the fact, that the 
 ice is neither increasing nor decreasing. He forgets. 
 
OF METEOROLOGICAL PHENOMENA. 239 
 
 however, that the freezing point of salt water is con- 
 siderably lower than that of fresh. Water saturated 
 with salt does not freeze till the temperature sinks to 
 about 5° of Fah. ; and even with the moderate amount 
 of salt that sea water usually contains, instead of freez- 
 ing at 32°, it does not begin to freeze till the tempera- 
 ture sinks to 28° or 29°. Instead of 32°, therefore, 
 28° or 29° ought to have been the mean temperature, 
 according to the principle upon which the Professor's 
 estimate of the temperature in high latitudes is found- 
 ed. But judging from the facts communicated by 
 Captains Scoresby and Parry, regarding the atmo- 
 spheric temperature in high latitudes, even 28° or 29° 
 is greatly above the mean annual atmospheric tem- 
 perature at the pole. During the time Captain Parry 
 remained at Melville Island, the thermometer in the 
 ship was often observed as low as — 50° ; and at a 
 distance from the ship, even as low as 65 degrees be- 
 low zero ;* and judging from the fact that the distance 
 between Melville Island and the pole is upwards of 
 1000 miles, and that for a similar distance all around 
 the pole there is perpetual ice and snow, it is presum- 
 able, that the temperature at the pole is frequently, 
 during winter, considerably under — 55°. Now, 
 though the circumstance of the ice in the vicinity of 
 the pole, being neither upon the increase nor the de- 
 crease, proves, that the amount of heat which the ice 
 and water there receives during summer is the same 
 as that given off during winter, it does not prove that 
 
 * The lowest temperature hitherto produced artificially is 91° 
 under zero of Fahrenheit. — Dr ProuVs JBridgeivater Treatise. 
 
240 ON THE CAUSES AND PRINCIPLES 
 
 the mean annual temperature of the atmosphere, a 
 few feet above the ice, (which is always understood, 
 when temperature without any specification is men- 
 tioned,) is the same as that at which sea water freezes, 
 viz. 28° or 29". So long as the surface of the sea 
 and of the land is covered with unmelted ice or snow, 
 the heat communicated by the sun during summer, is 
 absorbed by the melting ice or snow ; and the tem- 
 perature of the incumbent atmosphere seldom rises, in 
 such circumstances, higher than about five or six de- 
 grees above that at which snow and ice melt. While, 
 therefore, the atmospheric temperature at the pole 
 may be five or six degrees above the freezing point 
 of sea water, for four or five months during summer, 
 it is probably from 40° to 80° below the freezing 
 point of sea water, for a corresponding length of time 
 during winter. Hence I conclude, that the mean 
 annual atmospheric temperature at the pole is not 
 above zero of Fahrenheit. 
 
 It may be farther remarked, that though the pre- 
 ceding table may give a tolerably correct statement of 
 the mean annual temperature for each latitude at sea, 
 and for small islands and places bordering on the sea; 
 it will be found much too high for all inland countries 
 in high or temperate latitudes, and too low for inland 
 countries within the torrid zone. 
 
 Of the causes vjhich modify the 7nean annual tem- 
 perature on land in different latitudes. — Of the line 
 of perpetual congelation, and glaciers. — On land, the 
 mean annual temperature for any given latitude is 
 modified by various circumstances. Thus it is low- 
 ered by every increase in the altitude of the place of 
 
OF METEOROLOGICAL PHENOMENA. 241 
 
 observation above the level of the sea. It is also 
 lowered by ice or snov^ frozen or deposited during 
 winter, being in the neighbourhood, whether on moun- 
 tains or elsewhere. It is likewise lowered by every 
 increase in the amount of water evaporated from the 
 soil, at or near the place of observation. It is also 
 lowered by every increase in the prevalence of north- 
 erly winds in the northern hemisphere, and of south- 
 erly winds in the southern hemisphere ; and raised 
 by every increase in the prevalence of winds blowing 
 from the contrary directions, in the respective hemi- 
 spheres. 
 
 The first of these circumstances which we shall 
 notice, is difference in the elevation of different places 
 above the level of the sea. We formerly mentioned, 
 that the temperature of the atmosphere decreased at 
 the rate of one degree of Fahrenheit, for every 300 
 feet of perpendicular ascent. Of course, in deter- 
 mining the mean annual temperature of any place by 
 means of the table, a deduction at the above rate of 
 one degree requires to be made, for every 300 feet 
 it stands above the level of the sea. 
 
 According to the law by which the temperature 
 decreases with the perpendicular altitude above the 
 level of the sea, it is obvious, that at a certain eleva- 
 tion, which decreases from the equator towards either 
 pole, the mean temperature must be as low as the 
 freezing point. Above this altitude, which is called 
 the line of perpetual congelation, snow remains un- 
 melted all the year round. The following table, com- 
 puted by Kirwan, exhibits the altitude of the line of 
 perpetual congelation above the level of the sea, for 
 
 2h 
 
242 
 
 ON THE CAUSES AND PRINCIPLES 
 
 every five degrees of latitude from the equator to the 
 pole. 
 
 Lat. 
 
 Mean height of term 
 of congelation. 
 
 . 
 
 15,577 feet. 
 
 5 . 
 
 15,457 
 
 10 . 
 
 15,067 
 
 15 . 
 
 14,498 
 
 20 . 
 
 13,719 
 
 25 . 
 
 . 13,030 
 
 30 . 
 
 . 11,592 
 
 35 . 
 
 10,664 
 
 40 . 
 
 9,016 
 
 45 . 
 
 7,658 
 
 50 . 
 
 6,260 
 
 55 . 
 
 4,912 
 
 60 . 
 
 3,684 
 
 65 . 
 
 2,516 
 
 70 . 
 
 1,557 
 
 75 . 
 
 748 
 
 80 . 
 
 120 
 
 The above table in very high latitudes is evidently 
 erroneous. The line of perpetual congelation at the 
 level of the sea, even for salt water, commences where 
 navigation towards either pole is interrupted by ice. 
 This occurs in the northern hemisphere at a much 
 lower parallel of latitude than the 80th ; and, accord- 
 ing to the accounts of Captain Cook, the ice around 
 the south pole extends to a much lower latitude than 
 that which surrounds the north. 
 
 Within the torrid zone, owing to the annual varia- 
 tion of temperature being very small, the snow form- 
 ing the line of perpetual congelation, on any elevated 
 range of mountains, such as the Andes in South 
 
OF METEOROLOGICAL PHENOMENA. 243 
 
 America, is distinctly marked, and continues through- 
 out the year without almost any alteration in its height. 
 As we recede from the tropics towards either pole, 
 owing to the increasing difference between the ex- 
 treme temperatures of summer and winter, the height 
 at which the snow hne commences is subject to con- 
 siderable variation. It rises with the increasing heat 
 of summer, and again sinks upon the approach, and 
 during the continuance of winter. For obvious rea- 
 sons, it is also higher on the southern side of moun- 
 tains, in the northern hemisphere, than on their 
 northern side ; and vice versa, higher on the northern 
 side of mountains, in the southern hemisphere, than 
 on their southern side. 
 
 What are called Glaciers originate chiefly in the 
 broad zone or belt, which exists only in temperate and 
 high latitudes, between the summer and winter lines 
 of perpetual congelation. They are generally to be 
 found occupying elevated valleys, surrounded by more 
 elevated mountains. They consist of winter snow 
 partially melted during summer, and again frozen into 
 ice during winter. In consequence of the snow that 
 falls during winter upon the glaciers, being assisted by 
 additional supplies, in the form of avalanches, from the 
 neighbouring mountains, they extend their icy frontiers 
 to a much lower altitude than even the winter line of 
 perpetual congelation. From Mont Blanc to the bor- 
 ders of the Tyrol, it is said there are no fewer than 
 400 glaciers, the greater part of which are six or seven 
 leagues long, by one half, or three quarters of a league 
 wide, and from 100 to 600 feet thick. A very few of 
 these are so small as a league in length. M. Ebel 
 
244 ON THE CAUSES AND PRINCIPLES 
 
 has calculated, that their aggregate extent would form 
 a single glacier of 150 square leagues. During sum- 
 mer, these immense fields of eternal ice, aided by the 
 snow on the mountains, become, for reasons hereafter 
 to be explained, centres from whence cold currents of 
 air diverge in every direction. Consequently, they 
 lower the mean annual temperature, not only in their 
 immediate vicinity, but to a great distance around. 
 And this effect is produced, like that which is occa- 
 sioned by the ice around the poles, and by mountain 
 snow in general, chiefly in consequence of the heat of 
 the sun's rays being absorbed by the melting snow 
 and ice during day and summer. Hence ice and 
 snow reduce the surrounding mean annual tempera- 
 ture of the atmosphere, principally by lowering the 
 summer temperature, or rather perhaps by preventing 
 the rise which would otherwise then take place ; while, 
 in consequence of the water resulting from the melt- 
 ing ice and snow being carried off by rivers, without 
 being again frozen, they have no influence in raising 
 the temperature during winter. 
 
 The mean annual temperature, in any given lati- 
 tude, is also lowered by every augmentation in the 
 amount of water evaporated from the soil, at or near 
 the place of observation. In all places, upon the 
 same parallel of latitude, the amount of heat annually 
 derived from the sun's rays may be considered equal. 
 Consequently, every thing which increases the rapidity 
 with which that heat is again carried ofl", lowers the 
 mean annual temperature. Now evaporation is one 
 of the principar means by which the solar heat com- 
 municated to the earth is again carried off". Water, 
 
OF METEOROLOGICAL PHENOMENA. 245 
 
 in its transition to vapour, absorbs no less than about 
 940 degrees of temperature ; and hence, whatever in- 
 creases the amount of water evaporated, lowers the 
 mean annual temperature of the district and neigh- 
 bourhood where it occurs. The mean annual tem- 
 perature of moor-land, and undrained districts of a 
 country, is generally found to be somewhat lower than 
 those that are cultivated and properly drained : and 
 this is almost exclusively to be ascribed to the greater 
 amount of moisture evaporated from the former, than 
 from the latter. Such districts, in consequence of 
 want of draining, almost always present a moistened 
 surface, so that evaporation goes on without almost 
 any interruption ; whereas, the surface of cultivated 
 and well-drained lands is frequently for lengthened 
 periods dry, and evaporation is consequently sus- 
 pended. Hence the reason that the quantity of 
 moisture annually evaporated from undrained lands is 
 greater, than from those that are drained and properly 
 cultivated. 
 
 In like manner, the mean annual temperature of 
 mountains, and of hilly and elevated lands in general, 
 is reduced by increased evaporation below what they 
 would be otherwise, even after due allowance is made 
 for their elevation above the level of the sea. The 
 increased evaporation, in such situations, is owing 
 partly to the more abundant supply of rain causing 
 them to present a more constantly moistened surface ; 
 and partly to such localities being more exposed to the 
 evaporative influence of the wind ; and partly also to 
 the large proportion of boggy undrained lands, which 
 are always to be found in mountainous or hilly districts. 
 
246 ON THE CAUSES AND TRINCIPLES 
 
 The mean annual temperature for the latitude is 
 also very much affected, by the prevalent direction and 
 force of the winds in different localities. Thus northerly 
 winds in the northern hemisphere, and southerly winds 
 in the southern, by transporting the cold air of a cold 
 to a warmer climate, reduce the temperature. And, 
 on the contrary, southerly winds in the northern hemi- 
 sphere, and northerly winds in the southern, by trans- 
 porting the warm air of a warm to a colder climate, 
 raise the temperature. And the stronger such winds 
 are, by allowing less time to the air to become warm 
 or cold during its progress, the greater their efficacy 
 in reducing the temperature in the one case, and aug- 
 menting it in the other. Upon this point, however, 
 it may be remarked, that northerly or southerly winds 
 have little influence in either depressing or raising the 
 temperature during summer, especially during its latter 
 half, compared to what they have during winter. The 
 reason is, that the greater length of the day during 
 summer, as the latitude becomes higher, compensates 
 in a great measure for the greater obliquity with which 
 the sun's rays fall upon the earth. And consequently, 
 differences of latitude, unless very great, then pro-' 
 duce very little difference in the mean diurnal tem- 
 perature. Thus the mean diurnal temperature at 
 mid-summer, will be nearly as great at the latitude of 
 60°, as at that of 40° ; but at mid-winter it will be very 
 different. Hence the mean annual temperature of 
 any place is much more affected by the greater or less 
 prevalence of northerly or southerly winds during the 
 cold, than during the warm, season of the year. 
 
 Again, owing to the smallness in the annual range 
 
OF METEOROLOGICAL PHENOMENA. 247 
 
 of the temperature of the ocean, compared to that of 
 the land, a wind from the ocean, and blowing along 
 the same parallel of latitude, is much warmer during 
 winter, and much colder during summer, than a wind 
 from the land. Consequently, on continental coasts, 
 the mean annual temperature is augmented by the 
 prevalence of winds from the ocean during the coldest 
 period of the year, and from the land during the warm- 
 est. On the contrary, the mean annual temperature 
 of such locahties is reduced by the prevailing direc- 
 tion of the winds, being from the land during winter, 
 and from the ocean during summer. 
 
 The influence of the prevailing direction of the wind 
 is exemplified along the northern shores of Africa. 
 Owing to the prevailing wind in that region of the 
 globe being from the Mediterranean, lying to the 
 north, the climate is cool, moist, and salubrious, for 
 the latitude, with the exception of about a fortnight 
 in the course of a year, when the wind blows from the 
 sandy desert lying to the south, and which is attended 
 with a degree of heat and dryness, that makes it al- 
 most resemble the scorching blast issuing from a fur- 
 nace. 
 
 Of the decrement in the mean annual temperature, 
 upon receding from the ocean, to the north of the 
 QOth parallel of latitude, and of isothermal lines. — 
 Playfair says : " As we go eastward from the shores 
 of the Atlantic, the mean temperature of any parallel 
 becomes lower, at a rate that may perhaps, for the 
 north part of the temperate zone, be estimated at a 
 degree for 150 miles. 
 
 " At St Petersburgh, lat. 59° 6&, about 750 miles 
 
248 ON THE CAUSES AND PRINCIPLES 
 
 \ 
 
 from what may be accounted the shores of the Atlan- 
 tic, the temperature is 5° 5' below the standard. The 
 medium temperature of January is no more than 10°. 
 By computation it ought to be greater than 32°. The 
 winter lasts from October to April, and the cold is 
 sometimes as great as the freezing point of mercury, 
 or — 39°. From a mean of several years the mean of 
 the winter cold is — 25°. 
 
 " It was at Krasnojark, lat. 56° 30', long. 93° east, i 
 that mercury was first known to freeze by natural cold. 
 
 " If we were to begin where any parallel intersects 
 the shore of the Atlantic, and draw on a map a line 
 along which the mean temperature should be con- 
 stantly the same as at the first-mentioned point, it 
 would incline greatly to the south. The point, for 
 instance, in the meridian of St Petersburgh, which 
 has the same temperature with the standard belonging 
 to the parallel of that city, is about 5° south of it, or | 
 in the latitude of 54° 30' nearly. 
 
 " In Irkutz, latitude 52° 15', longitude 105" east, 
 the mean temperature from October to April has 
 been known to be as low as 6° 8' below zero, a tem- 
 perature which for severity and duration exceeds any 
 thing that has yet been observed elsewhere. 
 
 " This increase of the severity of the winter, and 
 the consequent diminution of the mean temperature, 
 on going eastward, holds in all the latitudes north of 
 the parallel of 30° ; but the diminution is slower as 
 we approach that parallel ; and to the south of 30", 
 the mean heat increases on retiring from the ocean. 
 
 " This diminution takes place all the way to the 
 shores of the Pacific, or very near them. The climate 
 
OF METEOROLOGICAL PHENOMENA. 249 
 
 of Pekin is vastly more severe than that of the same 
 parallel (39° 54') in Europe." 
 
 The diminution of the mean annual temperature 
 upon receding from the ocean in all latitudes higher 
 than the 30th parallel, has been exhibited in a per- 
 spicuous manner by Humboldt, by means of what are 
 called isothermal Hues drawn upon a map. He divides 
 the northern hemisphere into the following six isother- 
 mal bands, or zones of equal temperature, viz. : — 
 
 1 The zone of mean annual temperature ranging from 32 to 41 
 
 2 from 41 to 50 
 
 3 ^ from 50 to 59 
 
 4 from 59 to 68 
 
 5 from 68 to 77 
 
 6 from 77 upwards. 
 
 Appended to this volume is a map, on which are 
 delineated the isothermal lines bounding the various 
 zones above described, and also a table of the tem- 
 peratures of the more important places contained in 
 the several isothermal zones. 
 
 Describing the distribution of temperature over the 
 northern hemisphere, Humboldt says : — 
 
 " The whole of Europe compared with the eastern 
 parts of America and Asia, has an insular climate ; 
 and upon the same isothermal line the summers be- 
 come warmer, and the winters colder, as we advance 
 from the meridian of Mont Blanc towards the east or 
 the west. Europe may be considered as the western 
 prolongation of the old continent ; and the western 
 parts 6f all continents are not only warmer, at equal 
 latitudes, than the eastern parts j but even in the 
 
 2i 
 
SfCJO ON THE CAUSES AND PRINCirLES 
 
 zones of equal annual temperature, the winters are 
 more rigorous, and the summers hotter, on the east- 
 ern coasts, than on the western coasts of the two con- 
 tinents. The northern part of China, like the Atlantic 
 region of the United States, exhibits seasons strongly 
 contrasted; while the coasts of New California, and the 
 embouchure of the Columbia, have winters and. sum- 
 mers almost equally temperate. The meteorological 
 constitution of countries towards the north-west, re- 
 sembles that of Europe as far as 50° or 52° of latitude. 
 Comparing, in the two systems of climates, the concave 
 and the convex summits of the same isothermal lines; 
 we find at New York, the summer of Rome, and the 
 winter of Copenhagen ; at Quebec, the summer of 
 Paris, and the winter of St Petersburgh. At Pekin, 
 also, where the mean temperature of the year is that 
 of the coasts of Brittany, the scorching heats of sum- 
 mer are greater than at Cairo, and the winters are as 
 rigorous as at Upsal. So also, the same summer 
 temperature prevails at Moscow in the centre of Rus- 
 sia, as towards the mouths of the Loire, notwithstand- 
 ing a difference of 11° of latitude ; a fact that strik- 
 ingly illustrates the effects of the earth's radiation, on 
 a vast continent deprived of mountains. This ana- 
 logy between the eastern coasts of Asia and America 
 sufficiently proves," continues Humboldt, " that the 
 inequalities of the seasons depend on the prolonga- 
 tion and enlargement of continents towards the pole ; 
 on the size of seas in relation to their coasts ; and on 
 the frequency of north-west winds ; and not on the 
 proximity of some plateau, or elevation, of the adja- 
 
OF METEOROLOGICAL PHENOMENA. 251 
 
 cent lands.* The great table lands of Asia do not 
 stretch beyond 52° of latitude ; and in the interior of 
 the new continent, all the immense basin, bounded by 
 the Alleghany range, and the Rocky mountains, is not 
 more than from 656 to 920 feet above the level of the 
 ocean." 
 
 Such are the facts as stated by Playfair and Hum- 
 boldt, the causes of which we will now endeavour to 
 point out. 
 
 One reason for the reduction of the mean annual 
 temperature upon going eastward from the shores of 
 the Atlantic, is the greater prevalence of northerly 
 winds. In Great Britain, and in general along the 
 western shores of Europe, by far the most prevalent 
 wind is from the south-west. Indeed, northerly 
 winds, that is, winds blowing from the north of due 
 east or west, are in this island, and along the western 
 shores of Europe, rare, and their force is almost al- 
 ways inconsiderable, when compared with winds blow- 
 ing from the south of due east, or due west. Hence 
 the mean annual temperature of Europe, and particu- 
 
 * The opinion above expressed by Humboldt is not altogether 
 correct. Proximity to mountains and elevated lands, has been 
 universally observed to have some influence in lowering the mean 
 annual temperature of the surface of the earth. In previous pas- 
 sages, to which we refer, we have attributed this result, partly to 
 the absorption of the solar heat during day and summer, by the 
 melting of ice and snow deposited on mountains during winter ; 
 and partly to evaporation of moisture, and the cooling influence 
 therefrom resulting, being greater in mountainous and hilly dis- 
 tricts, than in low-;lying champaign countries, where, comparative- 
 ly, little rain falls, and where the surface of the ground is dry dur- 
 ing a larger proportion of the year. 
 
252 ON THE CAUSES AND PRINCIPLES 
 
 larly of its western portions, is much augmented, in 
 consequence of the prevaiHng south and south-west 
 winds transporting a warm atmosphere to a compara- 
 tively cold climate. On the contrary, over a large 
 proportion of Asia, and the eastern parts of Europe ; 
 and in general as we go eastward from the shores of 
 the Atlantic, northerly winds become more prevalent. 
 Accordingly, the mean annual temperature, in such 
 regions of the earth, is reduced in consequence of the 
 prevailing winds transporting a cold atmosphere to 
 what would otherwise be a comparatively warm cli- 
 mate. 
 
 Another cause of the reduction of the mean annual 
 temperature as we go eastward from the shores of the 
 Atlantic, is the increasing hygrometric dryness of the 
 atmosphere on receding from the ocean. Over Great 
 Britain, and along the western shores of Europe, the 
 atmospheric temperature is somewhat supported, 
 especially during winter, by the heat evolved dur- 
 ing the condensation of invisible vapour into the vi- 
 sible states of dew, mist, and cloud. In addition hke- 
 wise to the heat obtained while clouds and mist are 
 forming, clouds and mist are essentially useful during 
 night and winter, (which are the seasons when they are 
 most prevalent,) in preventing the heat absorbed by the 
 earth during day and summer, from escaping by radia- 
 tion from its surface. On the contrary, in far inland 
 countries, owing to the hygrometric dryness of the at- 
 mosphere, almost no dew is deposited, and httle mist, 
 and few clouds are formed ; and of course, the atmo- 
 sphere therefrom derives little heat ; and the usual 
 cloudless state of the sky affords a greater facility to 
 
OF METEOROLOGICAL PHENOMENA. 253 
 
 the caloric absorbed during day and summer, to escape 
 by radiation during night and winter. 
 
 Another cause of the reduction in the mean annual 
 temperature, on going eastward from the shores of the 
 Atlantic, is, that the temperature of the lower atmo- 
 spheric strata, where thermometric observations are 
 always made, is more affected by a sinking, than by a 
 rise of temperature. Thus Playfair says : " The 
 greatest heat is much less above the mean tempera- 
 ture than the greatest cold below it. The mean tem- 
 perature for the whole surface of the earth may be 
 taken at 58" ; the greatest summer heat is only 42^ 
 above this ; the greatest winter cold is 98° under it." 
 The explanation of this fact is the following : — Dur- 
 ing day and summer, though the atmospheric strata 
 nearest the ground become warmer, they simultane- 
 ously become specifically hghter than those above. 
 Hence the augmentation of temperature near the 
 ground, during day and summer, is reduced below 
 what it would otherwise be, by the interchange of posi- 
 tion between the higher and lower atmospheric strata, 
 which is then constantly, though slowly and imper- 
 ceptibly, going on. On the contrary, during night 
 and winter, when the atmospheric strata nearest the 
 ground become colder than those above, as was deter- 
 mined by the observations of Dr Wells, they also be- 
 come specifically heavier, and accordingly, no inter- 
 mixture of the higher and lower atmospheric strata 
 then takes place. Of course, the counteraction to 
 the augmentation of temperature in the one case, and 
 the want of counteraction to its depression in the 
 other, satisfactorily account for the depression of tem- 
 
254 ON THE CAUSES AND TRINCIPLES 
 
 perature which the lower atmospheric strata undergo 
 during night and winter, being greater than the aug- 
 mentation during day and summer. 
 
 Now, since the depression of temperature below 
 the mean for the latitude, during night and winter, is 
 always greater than the augmentation above the mean 
 during day and summer, it follows, that the greater 
 the annual range of temperature is, the greater will 
 be the reduction of the mean annual temperature for 
 the latitude. It was formerly stated that the mean 
 annual range of temperature is much less over the 
 ocean than over the land ; and, owing to the inter- 
 change in the atmospheric temperature that takes 
 place between contiguous localities, the diurnal and 
 annual range in general becomes less over the land, 
 the nearer we approach the shores of the ocean. In 
 small islands, therefore, where the annual range of 
 temperature is either the same, or very little more, 
 than that of the ocean which surrounds them, . the 
 mean annual temperature is much higher than in 
 places far inland on the same parallel of latitude, pro- 
 vided it be beyond the 30th parallel. 
 
 Besides, the mean annual temperature of inland 
 countries is frequently reduced, in consequence of the 
 summer heat being absorbed by the melting of snow 
 deposited during winter. Thus, in the kingdom of 
 Thibet, which constitutes the highest table-land in 
 Asia, the snow deposited on the mountains contri- 
 butes to render its climate cold and inhospitable, 
 which, notwithstanding its general elevation above the 
 level of the sea, should be comparatively mild. *' At 
 28° 18' of north latitude, in the kingdom of Thibet, 
 
OF METEOROLOGICAL PHENOMENA. 255 
 
 not far from the torrid zone, the wind," says Captain 
 Turner, " was violently high in the month of Septem- 
 ber, and so sharp, that we dared not expose our faces 
 to its fury : the want of caution on the preceding day 
 had left on our faces sad memorials of its keen rude- 
 ness, and we now rode muffled up in such a manner 
 that we could but just breathe. Such also is the 
 intensity of frost in this quarter, that animals exposed 
 in the open fields are not unfrequently found dead, 
 with their heads absolutely split by its force. On the 
 summits of the hills springs are often seen arrested in 
 their fall by frost, and converted into solid monuments 
 of ice, firmly fixed till the heat of summer dissolves 
 them. Some of them are of prodigious bulk and alti- 
 tude, resembling immense columns, contributing, with 
 the universal nakedness of both hills and valleys, to 
 impress on the mind of the traveller an indelible con- 
 viction of the bleakness of the region, and the severity 
 of the climate." 
 
 Of the increment in the mean annual temper aturey 
 upon receding from the ocean, loithin the ^Oth parallel 
 of latitude. — The reason why the mean annual tem- 
 perature increases on retiring from the ocean nearer 
 the equator than the 30th parallel of latitude, is owing 
 to the amount of moisture evaporated from the land, 
 (and which diminishes on receding inland,) being 
 much less than the amount evaporated from the ocean 
 in corresponding latitudes, while the other causes pre- 
 viously enumerated, which produce cold in inland 
 countries, to the north of the 30th parallel, have in a 
 great measure ceased to operate. Nearer the equator 
 than the 30th parallel of latitude, the falling of rain is 
 
256 ON THE CAUSES AND PRINCIPLES 
 
 usually restricted to three or four months in the year. 
 Accordingly, during the greater part of the year, eva- 
 poration is suspended, in consequence of the surface 
 of the land being thoroughly dried up ; whereas, from 
 the surface of the ocean, evaporation goes on through- 
 out the year. Judging from the great heat commu- 
 nicated by winds blowing from the immense sandy 
 desert of Sahara, in Africa, it is probable that the 
 mean annual atmospheric temperature, in its more 
 central portions, is upwards of 100'' ; whereas, the 
 mean annual atmospheric temperature over the ocean, 
 at the equator, is only 85°.* This great difference in 
 the mean temperature, I ascribe to the heat commu- 
 nicated by the solar rays, being almost undiminished 
 by evaporation, in the former case, while it is thereby 
 greatly reduced in the latter. 
 
 Of the mean temperature of America, relative to 
 that of Europe. — In North America, the mean annual 
 temperature is lower, and the severity of winter greater, 
 than in corresponding latitudes in Europe. Playfair 
 says : " At Prince of Wales' fort, Hudson's Bay, lat. 
 59°, long. 92° west, the mean temperature is 20° under 
 the standard ; at Nain, in Labrador, 16° ; at Cam- 
 bridge, in New England (lat. 42° 25') 10 degrees. 
 Mercury has been supposed to be frozen by the natural 
 cold as far south as Quebec, lat. 47°." 
 
 " The low mean annual temperature in North Ame- 
 rica, compared with that of Europe in corresponding 
 latitudes, may be ascribed partly to the surface of the 
 land being more generally covered with forests ; but 
 
 * According to Humboldt, the mean annual temperature at the 
 equator is only 81^°; but this is generally considered too low. 
 
OF METEOROLOGICAL PHENOMENA. 257 
 
 it is principally owing to the want of draining, by 
 which a large proportion of the rain that falls is again 
 evaporated, and of course a smaller proportion is re- 
 turned to the sea by rivers. " Forests," says Play- 
 fair, *' tend to increase the cold by preventing the 
 sun's rays from striking the ground. Evaporation 
 produces cold ; and marshes and lakes are therefore 
 favourable to the severity of the weather." 
 
 Upon this quotation it may be remarked, that 
 though forests prevent the sun's rays from striking 
 the ground, they can hardly be said, on this account, 
 to increase the cold ; because they do not diminish 
 the annual amount of solar heat communicated. Their 
 influence in reducing the mean annual temperature, 
 seems to be owing, partly to the circumstance of their 
 being in foliage in summer, while they are without 
 leaves in winter. Consequently, they are more effi- 
 cacious in preventing the subjacent ground from ac- 
 quiring heat from the sun's rays during summer, than 
 in obstructing its escape by radiation during winter. 
 And owing to the great extent of surface which trees 
 present to the atmosphere, what heat they themselves 
 acquire during day and summer, is very speedily dis- 
 sipated during night and winter. The influence of 
 forests, however, in reducing the mean annual tem- 
 perature, is principally to be ascribed to their agency 
 in increasing evaporation, by presenting a larger eva- 
 porating surface to the action of the atmosphere, than 
 cleared land. 
 
 Connected with the influence of evaporation upon 
 the mean temperature, it may be remarked, that a 
 more extended system of what is called tile-draining, 
 
 2 k 
 
258 ON THE CAUSES AND PRINCIPLES 
 
 and all other means by which a larger proportion of 
 rain-water is returned to the sea by rivers, instead of 
 being evaporated from the soil, will tend to raise the 
 mean annual temperature of those countries, and those 
 districts of countries where it is generally introduced. 
 Hence it is probable, that lands which are at present 
 cold, bleak, barren, and seemingly unfit for cultiva- 
 tion, will, by proper draining, be ultimately rendered 
 comparatively warm, dry, and productive. 
 
 Of the coldness of Europe in ancient ti7nes. — Of 
 modifications in the temperature of the ocean in dif- 
 ferent places J ^c. — The reasons assigned for the 
 greater coldness of the climates of Europe in ancient 
 times, compared to what they are at present, are the 
 same as those which produce the superior coldness in 
 North America, compared with the same parallels of 
 latitude in Europe. Play fair, quoting Csesar, says, 
 " that the vine could not be cultivated in Gaul on ac- 
 count of the severity of the winter. The rein-deer 
 was then an inhabitant of the Pyrenees. The Tiber 
 was sometimes frozen over, and the ground about 
 Rome covered with snow for several weeks together." 
 In explanation of these phenomena, Playfair makes 
 the following observations : — " Cultivation may im- 
 prove a climate, 1^^, By the draining of marshes, and 
 lessening the evaporation, which is so great a cause 
 of cold ; 2^, By turning up the soil, and exposing it 
 to the rays of the sun ; 3^/, By thinning or cutting 
 down forests, which by their shade, prevented the 
 penetration of the sun's rays. The improvement 
 which is continually taking place in the climate of 
 North America, proves that the power of man ex- 
 
OF METEOROLOGICAL PHENOMENA. 259 
 
 tends to the phenomena, which, from the magnitude 
 and variety of their causes, appear most beyond its 
 reach. At Guiana, in South America, the rainy sea- 
 son has been shortened by the clearing of the coun- 
 try, and the warmth has been greatly increased. It 
 thunders continually in the woods, rarely in the culti- 
 vated parts." 
 
 The mean temperature in particular places in the 
 ocean, is somewhat modified by the waters discharged 
 into it by rivers, the temperature of which varies 
 with that of the land from whence it is derived. It is 
 also modified in particular tracks by currents originat- 
 ing within its own boundaries. The chief of these is 
 the Gulf stream. This immense current is supposed 
 to be produced by the influence of the friction of the 
 trade wind on the surface of the Atlantic, in depress- 
 ing the level of the ocean in the equatorial regions 
 near the coast of Africa, and elevating it in the Gulf 
 of Mexico. This circumstance being farther assisted 
 by the influence of the tides, and by the pecuharly 
 well-fitted curved configuration of the land for giving 
 birth to a current through the Gulf of Florida. After 
 passing through this outlet, it directs its course in 
 nearly a straight line towards the north-east by north; 
 and in this direction it has been traced to very high 
 latitudes in the Atlantic. Wherever it has been 
 traced, its temperature is from two to five degrees 
 V warmer, than that of other parts of the Atlantic, 
 equally distant from the equator. 
 
 The cause of the cold being greater in the higher 
 latitudes of the southern hemisphere than in the 
 northern, Playfair says, is " by no means sufficiently 
 
260 ON THE CAUSES AND PRINCIPLES 
 
 understood." It is probably chiefly owing to the in- 
 fluence of the Gulf stream ; and it may possibly be 
 assisted by the greater proximity of the sun to the 
 earth during what is summer in the southern hemi- 
 sphere, not sufl[iciently compensating both for the 
 consequently slightly increased obliquity with which 
 his rays then fall upon high southern latitudes ; and 
 for the shorter time that he remains on the south side 
 of the equator. 
 
 Of the diminution in the annual range of temper a- 
 ture, upon approaching the ocean, Sfc. — The diminu- 
 tion in the annual range of temperature in any given 
 latitude, according as the place of observation is nearer 
 the ocean, is to be ascribed to the proportionally 
 greater facility with which the temperature of the 
 ocean is, in such circumstances, communicated by 
 aerial currents to the land. In the small island of 
 Grenada, in the West Indies, the temperature in the 
 shade is maintained so uniform throughout the year, 
 by means of sea and land breezes, that it never ex- 
 ceeds 85", and never sinks below 80% being an annual 
 range only of 5°. At Glasgow, the greatest heat of 
 summer in ordinary years does not exceed 75° of Fah., 
 and it is seldom that it sinks below the temperature 
 of 20°, being an average annual range of 55°. At 
 Rothsay, in the Island of Bute, which lies nearer the 
 Atlantic, the annual range of temperature is under 
 40°, being at least 15° less than what it is at Glasgow. 
 The temperature will more frequently rise above 75° 
 at Glasgow, than above 70° at Rothsay ; and oftener 
 sink below 20° at Glasgow^ than below 30° at Rothsay. 
 78° is about the highest temperature the thermometer 
 
OF METEOROLOGICAL PHENOMENA. 261 
 
 has been observed to reach at Glasgow, and this de- 
 gree of elevation it attained last summer, (1834). 
 Fourteen degrees below zero, was the lowest that I 
 ever heard of it having fallen to ; and this occurred 
 one morning before sunrise, in the remarkably severe 
 winter of 1813-14. At St Petersburgh, the tempera- 
 ture usually rises about the warmest period of summer 
 to 75° or 80° ; and during the coldest period of winter 
 sinks to about 40° below zero, making an annual range, 
 in ordinary years, of no less than from 115° to 120° of 
 Fahrenheit. 
 
 Within, and in the vicinity of, the arctic circle, the 
 annual range of temperature, contrary to what might 
 be expected, is less than what it is in inland countries 
 lying in temperate latitudes. This is owing to the 
 diminution of the winter's cold, produced by the evo- 
 lution of heat, during the freezing of water ; and to 
 the diminution of the summer's heat, occasioned by 
 the absorption of caloric, during the melting of ice 
 and snow, which are constantly to be found in those 
 regions. 
 
 Of Professor LyeWs hypothesis regm^ding the vari- 
 ation in the mean temperature, as affected by the pro- 
 portions of land and water. — The fact of the mean 
 annual temperature decreasing beyond the 30th pa- 
 rallels of latitude, and increasing within them, accord- 
 ing as we recede from the ocean, has been had re- 
 course to in order to account for phenomena that are 
 involved in much mystery. Thus Professor Lyell, 
 from a variety of geological facts, concludes, that in 
 times anterior to historical records, the temperature 
 throughout the northern hemisphere, in the latitudes 
 
2G2 ON THE CAUSES AND PRINCIPLES 
 
 now occupied by Europe, Asia, and America, has 
 undergone a great diminution. This he endeavours 
 to account for, by supposing that alterations in the 
 proportions of land and water in the equatorial and 
 polar regions must have taken place. He conceives 
 that land in high latitudes, particularly if elevated, 
 such as exists in the northern parts of North America, 
 contributes to lower the mean temperature of neigh- 
 bouring countries; and that land in equatorial regions, 
 such as Africa, raises the mean temperature of all 
 surrounding countries. Hence he concludes, that 
 whenever a greater extent of land is collected in the 
 polar regions, the cold will augment ; and that the 
 same result will be produced when there shall be more 
 sea between and near the tropics ; and vice versa. 
 
 The truth of the preceding hypothesis is by no 
 means well established. In accordance with our pre- 
 vious observations, it must be admitted that an in- 
 crease of land in the equatorial regions would there 
 increase the temperature, in proportion as it diminished 
 evaporation, which is so great a cause of cold. But 
 it is very questionable how far the mean temperature, 
 in high and temperate latitudes, would be reduced 
 by an increase of land in the polar regions, where all 
 is ice and snow already. And the fact of the mean 
 temperature being lower in the southern hemisphere, 
 in high and temperate latitudes where there is no land, 
 than what it is in the northern, where there is a great 
 amount of land, is at variance with his conclusion. 
 
 Of temperature as affected bi/ wind, bi/ atmospheric 
 stillness, by clouds, by cities, by the falling of rain, 
 Sfc. — At Glasgow, and usually in islands surrounded 
 
OF METEOROLOGICAL PHENOMENA. 263 
 
 by the ocean, the coldest winter weather occurs in the 
 greatest absence of wind. The reason of this is, that 
 the temperature of the atmosphere incumbent upon 
 the surrounding ocean, is then much warmer than 
 that over the land. Of course, wind blowing in any 
 direction from the ocean during the coldest season of 
 the year, raises the atmospheric temperature over the 
 land. On continents, however, during the coldest 
 period of winter, when the wind blows from a cold di- 
 rection over a great extent of land, the temperature 
 usually sinks as the wind increases in force. Thus 
 the coldest weather during winter at Philadelphia in 
 north latitude 39° 57', is experienced when a strong 
 wind blows from the north, or rather the north-west. 
 In such cases, the temperature has sometimes been 
 observed to sink as low as 14° under zero of Fahren- 
 heit ; and instead of being coldest when the weather 
 is calmest, as happens in all insular climates, the 
 thermometer sinks lowest when the wind from that 
 quarter blows strongest. Besides, this wind, for rea- 
 sons previously explained, is extremely dry relative to 
 its capacity for moisture, and consequently, is felt to 
 be piercingly cold. Indeed so much is this the case, 
 that while it continues, the inhabitants of Philadelphia 
 keep within doors as much as possible, and when they 
 are under the necessity of going out in the way of 
 business, and have to proceed in opposition to the at- 
 mospheric current, they generally run with their heads 
 down, by way of sheltering the face,* 
 
 * In the beginning of the year 1835, a greater degree of cold 
 was experienced in the United States of America, than had oc- 
 curred within the recollection of the oldest inhabitants. In the 
 
264 ON THE CAUSES AND PRINCIPLES 
 
 The greater steadiness of frost and cold weather 
 during winter, and of warmth during summer, which 
 is experienced on the continent of Europe, and in all 
 inland countries, in comparison with what we are sub- 
 jected to in Great Britain, is owing to the extreme 
 temperatures during summer and winter, being more 
 apt in our insular windy climate to be affected, and 
 mitigated by clouds, and by atmospheric currents 
 from the surrounding ocean, than in inland countries. 
 
 In this climate, the variations in the mean warmth 
 of different summers, and the mean cold of different 
 winters, is in a great measure to be ascribed to the 
 greater or less amount of cloudy weather. During 
 day and summer, when the temperature of the earth 
 is upon the increase, clouds, by obstructing the solar 
 rays before reaching the earth, reduce the mean tem- 
 perature. On the contrary, during night and winter, 
 when the temperature of the earth is upon the de- 
 crease, clouds, by obstructing the radiation of heat 
 from the earth, raise the mean temperature. Hence, 
 the reason that a cloudy wet winter is always a warm 
 one ; and on the contrary, that a cloudy wet summer is 
 always a cold one, and produces a late harvest. And 
 hence also the reason why the temperature never rises 
 so much during day, nor sinks so much during night, 
 when the weather is cloudy, as when it is clear. 
 
 At Glasgow, the mean diurnal range of tempera- 
 neighbourhood of Philadelphia, latitude 39° 57', the thermometer 
 fell at one time as low as 30 degrees below zero of Fahrenheit. 
 This extreme cold was accompanied, and produced, by a strong 
 wind, almost amounting in force to a hurricane, from the north- 
 west. 
 
 
OF METEOROLOGICAL PHENOMENA. 265 
 
 ture exhibited by a thermometer suspended outside 
 of a window, with a northern exposure, and about 
 thirty feet above the ground, is from 7° to 8". Some- 
 times it was observed to be as much as 20° ; while at 
 other times it did not exceed 1° or 2°.* It was 
 greatest when the atmosphere was still, and the sky 
 cloudless ; and least when the wind was high, and the 
 sky obscured by clouds. The reason of its being less 
 when the wind was high, than when there was no wind, 
 is to be ascribed to the surface of the ground being 
 subjected to a greater diurnal range of temperature, 
 than the air immediately incumbent ; and to the 
 diurnal range of temperature exhibited by the atmo- 
 sphere becoming less, upon receding upwards from 
 the ground. Consequently, during windy weather, 
 the temperature of the lower atmospheric strata is 
 prevented from rising during day, or from sinking dur- 
 ing night so much as it would otherwise do, by the 
 intermixture of the higher strata with the lower, which 
 the aerial agitation during windy weather occasions. 
 The reason why clouds diminish the diurnal range of 
 temperature was explained in the preceding paragraph. 
 In large towns, such as Glasgow, and especially in 
 their more central parts, the mean temperature is 
 usually from two to five degrees higher, than what it 
 is in the surrounding country a few miles distant. 
 This is obviously owing, partly to the heat evolved 
 during the combustion of fuel in large towns, and 
 partly to the heat evolved by so many human beings 
 congregated together, whose bodies are kept at the 
 
 * The above statements are exclusive of variations resulting from 
 a change in the direction of the wind. 
 
 2 L 
 
266 ON THE CAUSES AND PRINCirLES 
 
 constant temperature of 96 degrees, by the chemical 
 process of respiration. 
 
 The falling of rain or hail, especially in warm 
 climates, or in summer in temperate latitudes, is 
 usually observed to produce a sudden depression of 
 temperature. This is owing to the rain bringing down 
 a portion of the coldness which it has acquired, at the 
 altitude at which it was formed into drops. The 
 sudden reduction of temperature, which is observed 
 immediately to succeed the heavy shower of rain or 
 hail which terminates a thunder-storm, and which the 
 peasantry ascribe to the fire being taken out of the 
 air by the thunder, is to be attributed to the above 
 cause, aided perhaps by the cooling influence of eva- 
 poration from the then watered surface of the ground. 
 
 On ascending perpendicularly, the mean annual, 
 and more especially the mean diurnal range of tem- 
 perature is said to decrease. This arises from the 
 variations of temperature which the atmosphere under- 
 goes, being communicated upwards from the surface 
 of the ground. Owing to the permeability of the air 
 to calorific radiation, little or none of the solar heat is 
 arrested till it reaches the ground. Here, therefore, 
 it accumulates during day and summer, and from this 
 surface of accumulation, by slow degrees, and in pro- 
 portions which diminish with the distance, an increase 
 of temperature is imparted to the subjacent terrestrial 
 strata, and to those of the incumbent atmosphere. 
 The temperature of the higher regions of the atmo- 
 sphere is, however, subject to vicissitudes, indepen- 
 dent of those which are slowly communicated upwards 
 from the subjacent earth. Thus the temperature of 
 
OF METEOROLOGICAL PHENOMENA. 267 
 
 the atmospheric strata is augmented in the region 
 where clouds float, by the evolution of heat which 
 attends their formation. And on the contrary, the 
 temperature of those same strata is reduced, by the 
 absorption of heat which accompanies the dissolution 
 of clouds by evaporation. The existence of clouds 
 likewise augments the temperature of those atmo- 
 spheric strata where they float, by the increase of 
 temperature which they themselves acquire, and com- 
 municate to the surrounding air, in consequence of 
 partially arresting the sun's rays during day, and the 
 radiation of caloric from the earth during night. 
 
 Of the lowest and highest atmospheric tempera- 
 tures hitherto observed^ ^c. — Fifty-five degrees under 
 zero of Fahrenheit, which was observed by Captain 
 Parry, at Melville Island, is the lowest authentic at- 
 mospheric temperature on record. Many instances 
 of high temperatures are incidentally noticed by tra- 
 vellers ; but it is difficult to say whether the tempera- 
 tures alluded to be those of the atmosphere shaded 
 from the reflected, as well as the direct rays of the 
 sun, or not. At Benares, the thermometer is recorded 
 to have stood at 110°, 113°, 118°. Burckhardt states, 
 that during a simoom at Esne, in Upper Egypt, the 
 thermometer rose in the shade to 121°, but he adds, 
 the air seldom remains longer than a quarter of an 
 hour in that state, or longer than the whirlwind lasts. 
 At Sierra Leon a, a thermometer placed on the ground 
 has been observed to indicate a temperature of 138°. 
 Humboldt gives many instances of the temperature at 
 the surface of the earth, amounting to 118°, 120°, and 
 129° : on one occasion he found the temperature of a 
 
268 ON THE CAUSES AND PRINCIPLES, &C. 
 
 loose and coarse granitic sand to be upwards of 140", 
 when a thermometer in the sun only indicated a tem- 
 perature of about 97°. 
 
 We shall conclude the subject of temperature by 
 remarking, that in consequence of the radiation of 
 caloric from the earth during calm and clear nights, a 
 greater degree of coldness is communicated to the in- 
 cumbent atmosphere, according as the surface of the 
 ground underneath is better fitted for radiating caloric ; 
 and according also, as the radiation of caloric there- 
 from is less obstructed by trees, buildings, or other 
 elevated objects, that partially obscure the view of the 
 sky. Thus under the shelter of trees, or contiguous 
 to stone walls, or other elevated objects, or on accli- 
 vities, the temperature of the incumbent atmosphere 
 sinks much less during clear calm nights, than it does 
 over level grass fields freely exposed to the view of 
 the sky. This subject is particularly worthy of the 
 attention of military men, in order to direct them dur- 
 ing cold weather in selecting fitting localities for ar- 
 mies to repose in the open air during night. To ob- 
 tain thorough information on this point, military men 
 may be recommended to study the principles that 
 regulate the radiation of caloric, (which may be found 
 in all systems of chemistry,) and are particularly re- 
 ferred to Dr Wells* Essay on Dew, where those prin- 
 ciples are practically illustrated by a copious detail of 
 experiments and observations. 
 
CHAPTER VIII. 
 
 ON THE CAUSES AND PRINCIPLES WHICH PRODUCE WINDS ; 
 AND WHICH REGULATE AND DETERMINE THEIR DIREC- 
 TION, VELOCITY, AND CHARACTERISTIC QUALITIES. 
 
 Preliminary observations explanatory of the causey 
 direction, and velocity of winds , so far as they result 
 from differences in the temperature of the atmosphere. 
 — If both the density, and the incumbent pressure of 
 the atmosphere were every where the same at the le- 
 vel of the sea, and at all equal altitudes above it, it 
 follows, according to the hydrodynamic principle of 
 equal weights balancing each other, and of fluids of 
 equal density having no tendency to displace one an- 
 other, that none of those horizontal motions of the 
 atmosphere denominated Winds, could take place. 
 On the other hand, when such inequalities, at equal 
 altitudes, from any cause whatever do arise, it in like 
 manner follows, from the analogous principle of the 
 impossibility of fluids remaining at rest when their 
 equilibrium is disturbed, or when the density of equal- 
 ly elevated strata is diff'erent, which necessarily dis- 
 turbs their equilibrium, that a horizontal motion of 
 the atmosphere must result. Winds, therefore, in 
 every case, whether at the level of the sea, or at any 
 elevation above it, originate in simultaneous inequali- 
 ties of atmospheric density, or simultaneous inequali- 
 
270 ON THE CAUSES AND PRINCIPLES 
 
 ties of incumbent atmospheric pressure at correspond- 
 ing levels, in different places. And, according to the 
 principle of fluids in their motions, obeying the pre- 
 ponderance of pressure, the direction of the wind 
 must always be from where the incumbent pressure is 
 greater, to where it is less. 
 
 From the experiments of Gay Lussac, it appears, 
 that air between the temperatures of 32° and 212° ex- 
 pands ^-^jth part of its bulk, for every augmentation 
 of temperature amounting to one degree of Fahren- 
 heit. Of course, for every increment of temperature, 
 amounting to 5°, the density of the atmosphere dimi- 
 nishes in consequence of expansion, rather more than 
 1 per cent. Hence it follows, that atmospheric co- 
 lumns of different temperatures, and containing the 
 same amount of air, will differ in height. And though 
 they exhibit the same barometrical pressure* at the 
 level of the sea, they will exhibit a different barome- 
 trical pressure at all equal heights above it. Simul- 
 taneous inequality in the barometrical pressure in 
 different places at the level of the sea, or at equal 
 elevations above it, is therefore the proximate cause of 
 winds ; and inequality in the temperature of the atmo- 
 sphere at the level of the sea, or at equal elevations 
 above it, is the chief cause of unequal barometrical 
 pressure in different places. 
 
 Agreeably to the estimate of Gay Lussac, air ex- 
 pands about 1 per cent, for every increment of tem- 
 perature amounting to 5°. Hence it follows, provid- 
 
 * By the term " barometrical pressure," the amount of incum- 
 bent atmospheric pressure, as estimated by a barometer, is always 
 meant. 
 
OF METEOROLOGICAL PHENOMENA. 271 
 
 eel the barometrical pressure be the same, that the at- 
 mosphere, at different times and places, must vary 
 considerably in height. Supposing the amounts of 
 air to be the same over two portions of the earth's 
 surface of equal extent, so that the barometrical pres- 
 sure at the level of the sea in both, should be similar; 
 it follows, upon the supposition that the atmosphere 
 extends to the elevation of 45 miles, that for every in- 
 crement of temperature which the one acquires over 
 the other amounting to 11°, provided this difference 
 of temperature extend to the summit of the atmo- 
 sphere, the warmest portion should be about one mile 
 more elevated than the other. Again, supposing that 
 the mean annual temperature of the atmosphere at 
 the poles is zero of Fahrenheit, and the mean annual 
 temperature at the equator 85° of Fahrenheit, it fol- 
 lows, provided the barometrical pressure at the level 
 of the sea in both places is the same, and provided 
 also that a difference of temperature, corresponding to 
 that at the level of the sea, extends in both places to 
 the summit of the atmosphere, that the height of the 
 atmosphere above the level of the sea at the equator, 
 should, upon the same principle of calculation, be 
 nearly eight miles more than at the poles. Accord- 
 ingly, if we suppose the height of the atmosphere at 
 the poles to be 45 miles, it ought to be nearly 53 at 
 the equator.* 
 
 * The above estimates are given, not as ascertained facts, but 
 in order to illustrate the point under consideration. As the mean 
 annual and diurnal range of temperature decreases, according to 
 Saussure, as we ascend in the atmosphere, it is probable, that the 
 difference in the atmospheric temperature, at equal altitudes above 
 
272 ON THE CAUSES AND PRINCIPLES 
 
 The result of the difference of elevation in the at- 
 mospheric columns, according to their different de- 
 grees of warmth, is, that the upper portion of the 
 higher columns, in obedience to the force of gravity, 
 begins to float over upon the top of those that are 
 less elevated. But while this diminishes the height, 
 and the barometrical pressure at the level of the sea, 
 of the warmer columns, it correspondingly increases 
 the height and barometrical pressure of the colder co- 
 lumns. Hence, while the upper portions of the 
 warmer, and consequently more elevated columns, 
 are floating over upon the top of those that are colder 
 and less elevated, the lower extremity of the colder 
 columns, in obedience to the preponderance of baro- 
 metrical pressure, begins to move in the opposite di- 
 rection ; and by the greater density of their particles, 
 insinuate themselves underneath, and slowly uplift 
 the warmer and lighter columns. 
 
 Agreeably to the preceding observations, the most 
 general cause of wind, is the gradual diminution in 
 the mean annual temperature from the equator to- 
 wards either pole ; and the prevailing direction in 
 which the upper half of the atmosphere moves, is 
 from the warm towards the colder climate, viz., from 
 the equatorial, towards the polar regions. And on 
 the contrary, the prevailing direction in which the 
 lower halfofthe atmosphere moves, is from the cold to 
 
 the level of the sea in different latitudes, also decreases on ascend- - 
 ing perpendicularly. Hence it may be inferred, that the difference 
 between the mean height of the atmosphere at the equator and the 
 poles, and between other places which differ in temperature at the 
 earth's surface, is greatly less than what is stated in the text. 
 
OF METEOROLOGICAL PHENOMENA. 273 
 
 the warmer climate ; and accordingly, from the polar 
 towards the equatorial regions. 
 
 Local winds in general result from greater local 
 depressions, or augmentations of temperature, which 
 the atmosphere undergoes over one district or coun- 
 try, beyond what it does over another adjoining. The 
 atmosphere over the cold district becomes depressed 
 in height relative to that over the warm district. Con- 
 sequently, a current in the upper half of the atmo- 
 sphere moves from the warm to the cold district, 
 while, from the additional weight which the latter 
 thus receives, a current in the half nearest the ground, 
 is propelled from the cold towards the warm district. 
 Hence, the prevaihng, or regular direction of winds 
 in the lower half of the atmosphere, (and it is only to 
 this half we refer when not otherwise stated,) is from 
 a cold towards a warm district or climate. 
 
 Since the prevailing movement of the lower half of 
 the atmosphere from a cold towards a warmer climate, 
 is a consequence of increased barometrical pressure 
 over the colder latitudes, resulting from the previous 
 movement of the upper portion of the atmospheric 
 columns from the warm towards the colder latitudes, 
 it might be expected, that the mean height of the ba- 
 rometer should increase from the equator towards ei- 
 ther pole. The following results of observations 
 made in different places in the northern hemisphere, 
 with all the necessary corrections for insuring accu- 
 racy, while they confirm this opinion, exhibit a less 
 difference than might have been anticipated, and lead 
 to the belief that a counteracting influence, to which 
 we will subsequently advert, exists : — 
 
 2 M 
 
274 ON THE CAUSES AND PRINCIPLES 
 
 
 Latitude. 
 
 Mean Baro- 
 metrical 
 Pressure. 
 
 Calcutta 
 
 22° 35' 
 
 29.776 
 
 London 
 
 51 31 
 
 29.827 
 
 Edinburgh 
 Melville Island . 
 
 55 56 
 
 74 30 
 
 29.835 
 
 29.884 
 
 The above results show how small a difference in 
 the mean barometrical pressure on receding from the 
 equator towards the pole, is sufficient to determine 
 the prevailing direction of the wind in the lower half 
 of the atmosphere. Playfair says, " If the surface of 
 the earth were wholly covered with water, so that 
 there were no part of it more disposed than another 
 to obstruct the motion of the air, or no part which 
 had a greater capacity than another of acquiring or 
 communicating heat, the air would probably circulate 
 continually from the poles to the equator, and back 
 again without any irregularity whatsoever." 
 
 Agreeably to the principle that the direction of the 
 wind at every altitude above the level of the sea, is 
 from where the barometrical pressure is greater to 
 where it is less ; the existence of two currents mov- 
 ing in opposite directions to each other, the one in 
 the upper half of the atmosphere, and the other in the 
 lower, can only be accounted for upon the supposi- 
 tion, that there is a plane intermediate between the 
 two currents, where the atmosphere is subjected to 
 an equal barometrical pressure in every direction ; 
 and consequently where there can be no wind. In 
 accordance with this opinion it is obvious, that on 
 ascending from the surface of the earth to this plane, 
 the average preponderance of barometrical pressure 
 
OF METEOROLOGICAL PHENOMENA. 275 
 
 from a colder to a warmer climate, will gradually di- 
 minish, ti Hit ceases altogether. And that beyond 
 this plane, the preponderance of barometrical pressure 
 will increase on ascending; and instead of being from 
 a cold to a warmer climate, as it was underneath the 
 plane of atmospheric stillness, it will now be in the 
 reverse direction, viz., from a warm towards a colder 
 climate. In general, therefore, the nearer the plane 
 of atmospheric stillness, whether above or below it, 
 the less should be the velocity of the wind ; and clouds, 
 the nearer they are to that plane, from being less un- 
 der the influence of wind, should appear the more sta- 
 tionary. 
 
 Judging from the fact of the barometrical pressure 
 at the level of the sea remaining nearly equal in all 
 latitudes, it is evident, that the amounts of air trans- 
 ported in contrary directions by the upper and lower 
 atmospheric currents, must be the same. And upon 
 the supposition, that the velocity of these opposite 
 currents are equal, it is inferred, that one half of the 
 atmosphere must be above, and the other half below 
 the plane of intermediate atmospheric stillness ; and 
 consequently, the mean height of this plane, (for it 
 may be supposed subject to more or less variation,) 
 must be about the altitude of 18,000 feet above the 
 level of the sea. 
 
 The notion that the prevailing direction in which 
 the upper half of the atmosphere moves is the reverse 
 of the lower half, is founded chiefly on inferences, 
 deduced from the difference in the mean temperature 
 of different latitudes, in connection with the ascer- 
 
27G ON THE CAUSES AND PRINCIPLES 
 
 tained expansibility of air by means of heat, and the 
 nearly similar barom rtrical pressure in all latitudes. 
 
 Upon this point my opinion is somewhat at vari- 
 ance with that which is commonly entertained. When 
 the wind in the lower half of the atmosphere blows 
 from a cold towards a warm climate, such as is ex- 
 emplified by monsoons, and sea and land breezes, 
 there can be no doubt of the existence of an opposite 
 current in the upper portions of the atmosphere. But 
 in all cases where the wind in the lower half of the at- 
 mosphere blows from a warm towards a cold climate, 
 we will subsequently endeavour to show, that this 
 universally received opinion of the existence of an op- 
 posite current in the upper half of the atmosphere, is 
 erroneous. Even in the cases of monsoons, and sea 
 and land breezes, no evidence of the existence of an 
 upper current moving in the reverse direction of the 
 lower half of the atmosphere, has yet been obtained 
 by observing the motions of the cirri, the most ele- 
 vated of all clouds. But if the half of the atmosphere 
 be surmounted at the height of 18,000 feet above the 
 level of the sea; and if cirri sometimes make their 
 appearance at an elevation of 25,000 feet, as some 
 meteorologists have estimated ; evidence of an upper 
 current, if it exist at all, should be obtained by observ- 
 ing their motions. 
 
 The only fact that I have met with, which affords 
 direct evidence that the upper half of the atmosphere 
 moves in an opposite, or in a different direction from 
 the lower, is the following : — During the eruption of 
 a volcano in St Vincent, in the year 1812, ashes and 
 sand ejected by the volcano were carried in dense 
 
OF METEOROLOGICAL PHENOMENA. 277 
 
 clouds as far as Barbadoes, on which island they fell 
 to the depth of nearly three-quarters of an inch. 
 . Now Barbadoes lies about a hundred miles east, or 
 rather a httle to the north of east, of St Vincent, and 
 the trade-wind blows so directly from the former to 
 the latter island, that a passage from St Vincent to 
 Barbadoes can only be effected by making a circuit of 
 many hundred miles. It is evident, therefore, that 
 the ashes and sand ejected from the volcano in St 
 Vincent, must have been transported to Barbadoes 
 by an upper current of air, moving in the opposite 
 direction from the regular trade-wind below. By in- 
 specting the relative positions of these islands, and the 
 nearest mainland of South America, by means of a 
 map, it will at once be perceived that the direction of 
 the upper current, in the above case, is, like that of 
 monsoons, and sea and land breezes, from a warm 
 towards a colder chmate, and is produced in a similar 
 manner. 
 
 The velocity with which winds move must be pro- 
 portional, after deducting the retardation caused by 
 friction, to the amount of force which produces them. 
 This force, as already stated, arises from the differ- 
 ences in the incumbent atmospheric pressure, to which 
 different portions of atmosphere at the same degree 
 of elevation in reference to the level of the sea, are 
 simultaneously subjected. Besides, agreeably to the 
 principle that determines the increase of velocity 
 which bodies subjected to a constant pressure acquire, 
 when the preponderance of pressure continues in one 
 direction, and consequently, when the wind continues 
 to blow from one point of the compass, the ratio in 
 
278 ON THE CAUSES AND PRINCIPLES 
 
 which its velocity should increase in successive equal 
 times, provided there was no counteractive resistance 
 produced by friction, and no diminution of impulse, 
 should be the same as that of a faUing body, viz. the 
 odd numbers, 1, 3, 5, 7, &c. It is obvious, however, 
 that friction must increase with the velocity of the at- 
 mospheric current. And it is hkewise obvious, upon 
 considering the circumstances which give rise to ine- 
 qualities in the incumbent atmospheric pressure at 
 equal altitudes, that were an atmospheric current con- 
 tinuing to increase in velocity, according to the above, 
 or any other ratio, it would soon restore the atmo- 
 spheric equilibrium, and thereby annihilate the im- 
 pulse by which it had been created. 
 
 There is another point regarding the velocity of 
 winds that requires explanation. Though a given 
 amount of inequality in the incumbent atmospheric 
 pressure, (say equal to one inch of mercury in a baro- 
 meter,) at corresponding levels, in different places, 
 must give rise to a certain determinate force, yet the 
 velocity of the current will depend upon the distance 
 between the two places. If, for instance, the atmo- 
 spheric pressure from one parallel of latitude, or of 
 longitude, to another a hundred miles distant, should 
 gradually diminish, so that the mercury in a barometer 
 stood one inch lower at one extremity of the distance 
 than at the other, it would give rise to an atmospheric 
 current whose velocity would be immensely greater, 
 than if the barometrical pressure only diminished a 
 similar amount in a distance of 500 miles. Friction, 
 which is the only circumstance that counteracts the 
 velocity of atmospheric currents, would, in the latter 
 
OF METEOROLOGICAL PHENOMENA. 279 
 
 case, be about five times greater than it was in the 
 former. In the one case, the force which we have 
 supposed equal to an inch of barometrical pressure, 
 would have to propel a horizontal atmospheric stratum 
 of 100 miles extent, subjected, all that distance, to the 
 counteracting friction of the surface of the ground, 
 propagated upwards from one aerial stratum to another, 
 and that of the upper half of the atmosphere propa- 
 gated downwards from one stratum to another. In 
 the other case, the same amount of force has to propel 
 a horizontal atmospheric stratum 500 miles in extent, 
 subjected, all that distance, to the counteracting fric- 
 tion of the ground, and that of superior atmospheric 
 strata.* 
 
 * It need hardly be remarked, that the degree of counteractive 
 resistance to the motion of the air, produced by friction, varies with 
 circumstances. 1. It diminishes as we recede from the surface 
 where the friction takes place. If we suppose each stratum of 
 aerial particles subjected to an equal degree of propelling force, 
 the velocity of the stratum nearest the stationary surface ought to 
 be most diminished by friction. The second stratum, supposing 
 it never to come in contact with the ground, would have its velo- 
 city retarded by friction upon the first. But as the motion of the 
 first stratum is only diminished, and not entirely overcome by fric- 
 tion upon the stationary surface of the ground, friction will only 
 retard that proportion of the velocity of the second stratum, which 
 exceeds the velocity of the first ; and that proportion of the velo- 
 city of the third stratum, which exceeds the velocity of the second, 
 &c. Hence the reason why on the top of a hill, steeple, or other 
 eminence, the velocity of wind is greater than it is near the surface 
 even of level ground. 2. The influence of friction in retarding the 
 velocity of atmospheric currents, must obviously increase with the 
 unevenness of the surface upon which friction takes place. Hence 
 in towns, where the houses break the force of the current, wind is 
 
280 ON THE CAUSES AND PIIINCIPLES 
 
 Before proceeding further we may here sum up the 
 more important part of the previous observations : — 
 . 1. Winds in every case, whether at the level of the 
 sea, or at any degree of elevation in the atmosphere, 
 arise from simultaneous inequalities of incumbent at- 
 mospheric pressure at corresponding levels, in differ- 
 ent places. Hence, an opposite current near the sur- 
 face of the ground from what is indicated by the mo- 
 tion of clouds in the higher regions of the atmosphere, 
 can only result from the incumbent pressure being 
 reversed at these different degrees of elevation. 
 
 2. Winds at every degree of elevation in the atmo- 
 sphere, uniformly blow in the direction soonest calcu- 
 lated to restore the atmospheric equilibrium, and 
 therefore always from where the incumbent pressure 
 is greater, to where it is less. 
 
 3. The velocity of winds increases with, and, were 
 it not for counteraction produced by friction, would 
 be exactly proportional to the amount of force which 
 produces them, with the addition of the velocity ac- 
 quired by the continuance of the force operating in 
 
 less felt than in the country ; and in the country, less where there 
 are trees, and other obstructing projections, than where the land is 
 clear of woods and level. A surface of water seems to give less 
 obstruction in the way of friction than the most level land. It 
 might be thought that no surface can be more uneven than that of 
 the ocean agitated by a storm : for though the elevations and de- 
 pressions be small, compared to what they are on land, they are 
 infinitely more numerous. Nevertheless, waves by their progres- 
 sive movement, so accommodate themselves to the friction of the 
 wind by which they are produced, that they give less obstruction 
 to atmospheric currents than any stationary land surface, however 
 level. 
 
OF METEOROLOGICAL PHENOMENA. 281 
 
 one direction. Hence, the greater the inequahty of 
 atmospheric pressure at corresponding levels in dif- 
 ferent places J the nearer these places are to each 
 other, (so that the wind may be the less retarded by 
 friction ;) and the more extended the respective sur- 
 faces over which these inequahties of atmospheric 
 pressure exist, (so that the wind may acquire its maxi- 
 mum velocity by continuing in one direction ;) the 
 greater ought to be the velocity of the wind j and 
 vice versa. 
 
 Before proceeding to apply the previous principles 
 to the explanation of the various winds observed to 
 blow on the earth's surface, we may insert the follow- 
 ing table : — 
 
 2 N 
 
•282 
 
 ON THE CAUSES AND PRINCIPLES 
 
 n 
 w 
 
 H 
 
 (a 
 
 o 
 
 A 
 « 
 H 
 
 < 
 •X. 
 
 Hardly perceptible.— TfoKse. 
 Just perceptible. — Rouse. 
 
 Gentle wind, — Rouse. 
 
 A gentle wind. — IJnd. 
 Pleasant wini.—Lind. 
 Pleasant brisk gale. — Rouse. 
 Fresh hreeze.-Littd. 
 Brisk gaie.—Rotise. 
 Very brisk. — Rouse. 
 Brisk gale. — Lind. 
 Very brisk — Rouse. 
 High wind.— Rouse 
 High wind — Lind. 
 
 Very high.— Rovse. 
 Great storm — Derham. 
 Very high.— iinrf. 
 Storm or tempest— iJoiMe. 
 Storm — Lind. , 
 Great storm.— iJoM^e. 
 Great storm. 
 
 Great storm.— ia Condnmine. 
 Very great storm.— Lj'rarf. 
 Hurricane. — Rouse. 
 Hurricane. — Lind. 
 Great hurricane. — Lind. 
 Very great hurricane.— iinrf. 
 Most violent hurricane.— X?nrf. 
 Hurricane that tears up trees, and throws 
 down buildings.— /fo!(.ye. 
 
 Observed by Rochon. 
 
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OF METEOROLOGICAL PHENOMENA. 283 
 
 By the preceding table it appears, that what Dr 
 Lind denominates a most violent hurricane, moves at 
 the rate of 107^ miles in an hour, and exerts a force 
 of 46.875 lbs. avoirdupois on a square foot of surface 
 presented to it. This, after all, is rather less than the 
 force that would be produced by a difference of baro- 
 metrical pressure, equal to two-thirds of an inch in 
 the height of a mercurial barometer, in two contiguous 
 places. When the barometer stands at 30 inches, the 
 atmospheric pressure is nearly fifteen pounds on the 
 square inch of surface. Of course, one inch in the 
 height of the mercury is equal to the pressure of half 
 a pound on the square inch of surface ; and equal to 
 72 pounds on the square foot of surface ; whereas, 
 the force of the hurricane above-mentioned, is only 
 equal to an atmospheric pressure of 46.875 lbs. on 
 the square foot of surface. 
 
 Winds are usually divided into regular, periodic, 
 irregular, and hot. Of these we shall treat separately 
 in their order. 
 
 Of the Regular or Trade-wind, — The only wind 
 classed under the head of regular, from its blowing in 
 the same, or nearly the same direction throughout the 
 year, is what is usually denominated the Trade-wind- 
 This wind, with some few exceptions, extends to aboui 
 the 30th parallel of latitude, on both sides of the 
 equator around the globe. Its direction is from east 
 to west, inclining to the north of east on the north 
 side of the equator, and to the south of east on the 
 south side of the equator.* The variations in its de- 
 
 * The direction of winds is always denoted by the point from 
 
"284: ON THE CAUSES AND PRINCIPLES 
 
 clination from due east towards the north, or south, 
 seem to be somewhat determined by the parallel over 
 which the sun is vertical. Thus, as the sun advances 
 from the equator towards the northern tropic, the 
 trade-wind on the south of the equator gradually blows 
 more from the south of east ; and on the contrary, 
 when the sun advances from the equator towards the 
 southern tropic, the trade-wind on the north of the 
 equator blows more from the north of east. In short, 
 the trade-wind blows from the east, and its deviations 
 from this direction are towards the parallel of latitude 
 where the sun is at the time vertical. 
 
 We formerly stated that the prevailing direction of 
 the wind in the lower half of the atmosphere, is from 
 the polar towards the equatorial regions. Now, the 
 trade-wind is supposed to result from the combined 
 influence of this prevailing direction of the atmo- 
 spheric current, and the rotation of the earth upon its 
 axis. At the poles the earth has no motion of rota- 
 tion ; but gradually in advancing from the poles to 
 the equator, the rotatory motion of the earth from 
 west to east increases. Accordingly, a north wind on 
 the north side of the equator, and a south wind on 
 the south side of the equator, blow from latitudes 
 where the earth's rotation on its axis is slower, to where 
 it is faster. But as this increased rotatory motion is 
 only slowly communicated by friction to the atmo- 
 
 which they blow, and never from that towards which they blow. 
 Thus a south-west wind means a wind blowing from the south- 
 west ; and when a wind is said to incline or decline towards the 
 south of east, it means that it blows from a point to the south of 
 east. 
 
OF METEOROLOGICAL PHENOMENA. 285 
 
 sphere, a wind from the polar regions is left behind, 
 and consequently, assuming a direction somewhat 
 contrary to the earth's motion on its axis from west to 
 east, blows from the north-east on the north side of 
 the equator, and from the south-east on the south side 
 of the equator. The collision of these two currents 
 from the opposite hemispheres, by neutrahzing and 
 destroying their respective northward and southward 
 movements, causes the atmosphere within the 30th 
 parallels of latitude, to assume the easterly direction 
 described above, and which, from its uniformity ren- 
 dering it susceptible of being taken advantage of for 
 commercial purposes, has been denominated the 
 Trade-wind. 
 
 For analogous reasons to those previously men- 
 tioned, it is supposed that as the atmospheric current 
 from the equator towards the poles, in the upper half 
 of the atmosphere, is blowing from latitudes where 
 the rotatory motion of the earth on its axis is quicker 
 to where it is slower, it must gradually get ahead of 
 the earth's rotation. Consequently, instead of blow- 
 ing from due south, it will assume a south-west direc- 
 tion on the north side of the equator, and instead of 
 blowing from due north, it will incline towards the 
 north-west on the south side of the equator. 
 
 The influence of the earth's rotation in modifying 
 the direction of the wind, as stated above, also explains 
 the reason for the greater prevalence of a north-east 
 than of a north-west wind, and of a south-west than of 
 a south-east wind, to the north of the 30th parallel of 
 latitude. 
 
 The trade^wind has been by some ascribed to the 
 
286 ON THE CAUSES AND PRINCirLES 
 
 attractions of the sun and moon. Upon this point 
 Playfair says : " They (the attractions of the sun and 
 moon,) have no doubt a tendency to produce in the 
 atmosphere an undulation backwards and forwards, 
 Hke the tides which they cause in the ocean. It does 
 not appear, however, that they could produce any con- 
 tinued progressive motion of the air, similar to that of 
 the trade-winds. Their effects also are too minute to 
 be perceived amid the action of so many more power- 
 ful causes." 
 
 There is no doubt that the tide, as exhibited in the 
 Atlantic ocean, resembles an immense wave undulat- 
 ing westward and eastward. But be it recollected 
 that its westward progress is interrupted by the Ame- 
 rican coast. Provided the ocean covered the whole 
 surface of the globe, in the same manner as the atmo- 
 sphere does, in place of an undulation moving west- 
 ward and back again, as is exhibited in the Atlantic 
 ocean, the two great waves composing the two tides 
 on opposite sides of the earth, would continually move 
 round the globe from east to west without any inter- 
 ruption. There is no doubt that the progress of the 
 tides would still be in the form of an undulation ; for it 
 is not to be supposed that any current could ever be 
 so rapid as to keep pace with them. In intertropical 
 climates their progressive motion is about 1000 miles 
 an hour. But as full tide does not take place in the 
 open ocean till, nearly three hours after the moon has 
 passed the meridian, a greater body of water subjected, 
 to the moon's attractive influence would be constantly 
 to the eastward, than what was to the westward of the 
 meridian where the moon was vertical. Hence I con- 
 
OF METEOROLOGICAL PHENOMENA. 287 
 
 ceive, that the attractive force exerted upon the smaller 
 body of water to the west of the moon, would not be 
 sufficient to resist the impulse given to the greater 
 body of water to the east of the moon, by the same 
 attractive power, together with the additional impulse 
 arising from the motion of the tides being always in one 
 direction. And hence I infer, that a current in the 
 ocean from' east to west, which would be strongest in 
 the equatorial regions where the moon is most vertical, 
 would be generated. Upon similar principles I con- 
 ceive, that the trade-wind may be partly owing to the 
 attractions of the sun and moon, and partly to the 
 cause previously explained. But how much of the 
 effect is to be ascribed to the one cause, and how 
 much to the other, I can form no opinion. 
 
 Of Periodic Winds. — The first of these we will 
 notice is what are usually denominated Sea and Land 
 Breezes. In all maritime or insular situations in warm 
 climates, where the sun is nearly vertical, and accord- 
 ingly, where it exerts a strong heating influence, the 
 surface of the land becomes warmer during day, and 
 in consequence of more rapid radiation, colder during 
 night, than that of the ocean. The consequence is, 
 that the atmosphere over the land, from participating 
 in its excess of warmth during day, is expanded up- 
 wards, and gives rise to a current in the upper por- 
 tions of the atmosphere from the land towards the sea ; 
 and this, in its turn, in accordance with the principles 
 already explained, gives rise to a current at the surface 
 of the earth, from the sea towards the land. During 
 night, however, when the surface of the land be- 
 comes colder than that of the adjoining sea, the atmo- 
 
288 ON THE CAUSES AND PRINCIPLES 
 
 spheric columns immediately incumbent upon the 
 land, by participating in its coldness, become more 
 depressed than those over the adjoining sea. Hence 
 the upper portions of the latter float over upon the 
 former. And in consequence of the additional weight 
 thereby communicated to the atmosphere over the 
 land, a current close to the earth's surface from the 
 land towards the sea is produced.* 
 
 Sea and land breezes, as above explained, afford the 
 best practical illustration of the causes which produce 
 winds when their direction is regular, (by which, wind 
 in the lower half of the atmosphere blowing from a 
 cold towards a warm chmate is meant,) and of the 
 principles which regulate their direction and velocity. 
 They occur in general in all maritime situations and 
 islands within the tropics. The sea breeze commences 
 usually about 10 o'clock, a.m., that being about the 
 time of day when the atmosphere over the land has be- 
 
 * In explaining the nature of sea and land breezes, it is usual to 
 say, that the air over the land, on becoming heated during day, 
 rises ; and that the colder air over the sea rushes in to fill up the 
 vacuity. This explanation is to a certain extent incorrect. Air 
 over the land (and this remark is applicable to air heated by what- 
 ever means,) does not rise because it is heated, nor in rising does 
 it leave any vacuity underneath. The only reason why heated air 
 rises, is because the particles of colder and heavier air, in conse- 
 quence of approximating nearer to each other, and nearer to the 
 surface of the ground, insinuate themselves underneath, and conse- 
 quently uplift the warmer particles. In short, a warmer and spe- 
 cifically lighter atmosphere is uplifted by a colder and heavier one, 
 just in the same manner as water poured into a vessel displaces, by 
 raising or uplifting, the air from its bottom. And just in the same 
 manner as that water would, in its turn, be raised and uplifted from 
 the bottom of the vessel, by pouring mercury into it. 
 
OF METEOROLOGICAL PHENOMENA. 289 
 
 come sufficiently heated, and expanded upwards, to 
 give rise to it. It continues increasing till about one 
 o'clock, P.M., when the air over the land has acquired 
 its highest temperature relative to that over the ocean. 
 After this time, its force gradually diminishes, till it 
 entirely subsides by three or four o'clock in the after- 
 noon. From this period till a little after sunset, the 
 temperature of the atmosphere over the land and ad- 
 joining ocean, is so nearly equal as to be incapable of 
 producing wind of any perceptible velocity. Shortly 
 after sunset, the air over the land, in consequence of 
 the coldness induced by the radiation of caloric from 
 the surface of the ground being propagated upwards, 
 begins to be colder than that over the ocean. Ac- 
 cordingly, the land breeze, which, in insular situa- 
 tions, blows from the centre of the island in every di- 
 rection towards the sea, commences and continues till 
 about sunrise, when it also entirely subsides. From 
 this time till 10 o'clock, a.m., when the sea breeze, as 
 before described, commences, the temperature of the 
 atmosphere over the land, and the adjoining sea, is 
 so nearly equal as to be incapable of producing a 
 breeze of any perceptible velocity. Such is the or- 
 der in which the sea and land breezes, during the 
 course of twenty-four hours, alternately succeed each 
 other. 
 
 The force of the respective sea and land breezes 
 varies with, and is proportional to, the difference of 
 barometrical pressure simultaneously over the land 
 and sea ; and the difference of barometrical pressure 
 results from, and is proportional to, the difference of 
 atmospheric temperature simultaneously over the land 
 
 2o 
 
290 ON THE CAUSES AND PRINCIPLES 
 
 and sea. Hence the reason that, when either the sea 
 or the land breeze commences, it does so very gently, 
 and gradually increases till it reaches its maximum ve- 
 locity, when the difference in the temperature of the 
 atmosphere over the sea and over the land is greatest. 
 And thereafter, its velocity gradually decreases, as 
 the difference of temperature above-mentioned dimi- 
 nishes, till it entirely subsides. 
 
 The locality where the force of the sea and land 
 breezes is greatest, is where the temperature of the 
 atmosphere within a limited distance horizontally, 
 undergoes the greatest change. This of course is 
 about the boundary where the sea and land meet. 
 The distance to which the land breeze is felt at sea, 
 and at which the sea breeze is felt inland, increases 
 and diminishes with the simultaneous difference of 
 temperature of the atmosphere over the sea and land, 
 upon which the existence and velocity of these re- 
 spective breezes depend. The land breeze, when it 
 first commences, is only felt to a very small distance 
 from the shore ; but gradually extends itself so as to 
 be felt on some occasions, to the distance of eight 
 or nine miles at sea. In Hke manner, the sea breeze 
 at first is only felt near the shore, but gradually ex- 
 tends itself, with diminishing velocity inland, to a si- 
 milar, or perhaps sometimes to a greater distance, 
 before becoming altogether imperceptible. 
 
 Such are the causes and principles which produce 
 sea and land breezes, and which regulate and deter- 
 mine their force, direction, duration, and the limits to 
 which they extend. And it may be farther added, that 
 in all quarters of the earth, whether by land or sea, 
 
OF METEOROLOGICAL PHENOMENA, 291 
 
 similar causes produce and regulate the force, direc- 
 tion, duration, and limits, of all breezes, resulting 
 from simultaneous differences of temperature in neigh- 
 bouring localities. 
 
 Of Monsoons. — The next class of periodic winds 
 of which we mean to treat, are those denominated 
 Monsoons, or Season-winds, as the term impHes. 
 The following facts communicated by the celebrated 
 Dr Halley, comprise almost all that is known respect- 
 ing these winds : — ■ 
 
 In that portion of the Indian ocean, lying between 
 Sumatra and the African coast, and from 3° of south 
 latitude to the Asiatic coast, including the Arabian 
 sea and the Gulf of Bengal, the monsoons blow from 
 the north-east from September to April, which is a 
 little too northerly for the general direction of the 
 trade-wind ; but from April to September,* they 
 change to the south-west ; and more in with the land, 
 to the west-south-west. During the former period 
 the wind is more steady, and the weather less liable to 
 sudden changes. 
 
 The explanation usually given of these opposite 
 monsoons is the following : — When the sun, by the 
 middle or end of April, has advanced considerably to 
 the north of the equator, the surface of the land along 
 the southern parts of Asia, within the boundaries de- 
 scribed, begins to be warmer than the surface of the 
 Indian ocean. This continues till some time in Sep- 
 tember, when the surface of the Indian ocean, in con- 
 
 * According to other accounts, the south-west monsoon does 
 not commence till about the latter end of May or beginning of 
 June. 
 
292 ON THE CAUSES AND PRINCIPLES 
 
 sequence of the southern dechnation of the sun, be- 
 gins to be warmer than that of the land, and so con- 
 tinues till April. Hence, in conformity with the prin- 
 ciple which regulates the direction of the winds, as 
 described when treating of sea and land breezes, the 
 atmospheric current in the lower half of the atmo- 
 sphere blows from where it is colder to where it is 
 warmer. And accordingly, from the Indian ocean 
 towards the land from April to September ; and from 
 the land to the Indian ocean from September to 
 April. In both cases, agreeably to the principles ex- 
 plained when treating of sea and land breezes, and 
 which need not be repeated, it is supposed that the 
 upper portion of the atmosphere is moving in an op- 
 posite direction from the lower. 
 
 The reason why the monsoon, from the end of 
 April to September, blows from the south-west in- 
 stead of due south, is to be ascribed to the rotatory 
 influence of the earth. A southerly wind to the north 
 of the equator, is blowing from where the rotatory 
 motion of the earth is quicker to where it is slower. 
 And as the atmospheric current, in its progress north- 
 wards, only loses its greater rotatory velocity by slow 
 degrees, it gradually gets ahead of the rotatory motion 
 of the earth from west to east. And accordingly, in- 
 stead of blowing from due south, it blows from the 
 south-west. 
 
 On the contrary, when the monsoon blows from the 
 land, from September to April, it blows from where 
 the rotatory motion of the earth is less to where it is 
 greater. Hence, in its progress southward, it is left 
 behind the rotatory motion of the earth, and blows 
 
OF METEOROLOGICAL PHENOMENA. 293 
 
 from the north-east instead of the north, for the same 
 reason as was assigned for the north-east direction of 
 the trade-wind to the north of the equator. 
 
 The reason why the wind is less steady, and the 
 weather more subject to sudden changes, from the end 
 of April to September, than what it is during the con- 
 tinuance of the opposite monsoon, from September 
 to the end of April, is to be ascribed to the influence 
 of a vertical sun, during the former period, in pro- 
 ducing what is called the rainy season. In the fourth 
 chapter we had occasion to explain how vicissitudes 
 of temperature, in neighbouring localities, are pro- 
 duced by partial showers ; and how these occasion 
 local disturbances, and temporary variations, in the 
 direction of the winds. 
 
 Upon similar principles to those explained, when 
 treating of sea and land breezes, and which we need 
 not here repeat, the force of the south-west monsoon 
 is felt strongest on land, and extends itself farthest 
 inland, at the time when the difference between the 
 temperature of the land and ocean becomes greatest; 
 and vice versa. And the calms and variableness in 
 the direction of the winds, which frequently occur for 
 some time previous to the change of the monsoon, is 
 to be ascribed, partly to the difl'erence of temperature 
 then existing over the land and adjoining sea, being 
 so inconsiderable as to be incapable of giving any de- 
 terminate direction to the winds ; and partly to the 
 influence of sea and land breezes, and other local 
 causes, which, in the absence of those of a stronger 
 and more general nature, begin to be felt. 
 
 Another of these monsoons is observed to take place 
 
294 ON THE CAUSES AND PRINCIPLES 
 
 between the island of Madagascar, and the coast of 
 Ajan, north of the equator. In that tract of sea, from 
 April to October, the wind blows with a steady breeze 
 about S.S.W.; but, from October to April, it re- 
 sumes the general direction of the trade-wind, and 
 varies from N.E. to E.N.E. 
 
 By inspecting a map it will be seen, that, in the 
 portion of the Indian ocean above described, the mon- 
 soon, from S.S.W. from April to October, blows in 
 what we have already described as being the regular 
 direction of the wind, viz. from a cold towards a warm 
 chmate. This point, therefore, requires no further 
 explanation. From the month of October to April, 
 the temperature of the most southern and most nor- 
 thern latitudes included in the portion of the Indian 
 ocean above described, is about equal. Hence, the 
 cause that produced the monsoon in the opposite half 
 of the year has ceased to exist j and, accordingly, the 
 trade-wind resumes its regular direction. 
 
 A monsoon, of a less constant character, occurs in 
 the Chinese seas, extending from Sumatra to Japan. 
 The periodical winds in this tract, seem to be greatly 
 influenced by the local and periodic diff'erences in the 
 atmospheric temperature over the land and the sea, 
 produced by the large islands which bound it on the 
 south, particularly Java, Borneo, and perhaps we may 
 add New Holland. Their prevailing direction, from 
 October to May, is from north to south, inclining a 
 little westward. 
 
 The prevailing direction of this season-wind, over 
 the extensive tract of sea above described, being, 
 like those previously accounted for, from a cold to- 
 
OF METEOROLOGICAL PHENOMENA. 295 
 
 wards a warm climate, requires no farther explana- 
 tion. 
 
 Under the head of Periodic winds we may notice 
 those denominated Etesian and Ornithian; so called 
 from its being observed that birds of passage take ad- 
 vantage of them, to assist them in their flight from 
 one clime to another. 
 
 Of the Etesian Wind. — This wind, which blows from 
 north to south, prevails very much over the continent 
 of Europe, and particularly in those southern countries 
 which form the northern boundary of the Mediterra- 
 nean. It commences about the summer solstice, and 
 continues usually for about six weeks without inter- 
 ruption. The direction of this periodic wind being, 
 like all those previously accounted for, from a cold 
 towards a warm climate, requires no further explana- 
 tion. 
 
 Of the Ornithian Wind. — This wind commences 
 about the beginning of March, and blows, with occa- 
 sional interruptions, from the south-west, for five or 
 six weeks. It prevails over the eastern portion of the 
 Mediterranean, and sweeps over Greece and Mace- 
 donia. The cause assigned for this wind, is the 
 melting of the snow on the mountains in the northern 
 parts of Africa. 
 
 In general it may be remarked, that, upon the ap- 
 proach of summer in temperate latitudes, the melting 
 of snow deposited during winter upon ranges of ele- 
 vated mountains, has a tendency to give rise to diverg- 
 ing currents of cold air in every direction. Owing to 
 the solar heat being absorbed by the melting snow 
 upon the approach, and during the continuance of 
 
296 ON THE CAUSES AND PRINCIPLES 
 
 summer, the atmosphere immediately incumbent upon 
 the mountains, is partly cooled, and partly prevented 
 from obtaining that accession of warmth during day, 
 which it would otherwise then acquire. The conse- 
 quence is, that the atmospheric columns over the 
 mountains are condensed, and depressed in height, 
 relative to those incumbent on the surrounding dis- 
 tricts. Hence the summits of the latter float over 
 upon those of the former, and the additional barome- 
 trical pressure thus communicated to the air over the 
 mountains, causes currents near the surface of the 
 earth to diverge from them in every direction. In 
 the neighbourhood, therefore, of all extensive moun- 
 tain ranges covered with snow, with their intermediate 
 valleys consisting of glaciers, such as in the Alpine 
 regions of Switzerland and the Tyrol, the wind, ex- 
 cept when overcome by some stronger and more gen- 
 eral cause, may be expected to blow from the moun- 
 tains, during the whole period that the melting of the 
 ice and snow is going on. 
 
 The prevailing winds in various quarters, which 
 may, perhaps, with more propriety be classed under 
 the head of regular than periodic, are such as are pro- 
 duced by difference of temperature, and blow from a 
 cold towards a comparatively warm climate. Such 
 winds admit of an obvious explanation, in consequence 
 of their direction being in accordance with the causes 
 and principles which produce and regulate the course 
 of winds in general. Thus, according to the accounts 
 of those who have recently visited very high latitudes 
 in the northern hemisphere, the prevailing direction 
 of the wind is there from the north; its variations 
 
OT METEOROLOGICAL PHENOMENA, 297 
 
 being chiefly confined within the north-east and north- 
 west points of the compass. Again, along the north- 
 ern coast of Africa, bounded by the Mediterranean, 
 the prevaihng direction of the wind throughout the 
 year is also from the north. In both these cases, the 
 prevaihng direction is from a cold to a warm climate, 
 and therefore in accordance with the principles already 
 explained which direct the course of winds in general. 
 In hke manner, over the Atlantic, within 300 miles 
 of the African coast, and especially in the warmer 
 latitudes, the wind, instead of blowing from east to 
 west, as is usual with the trade-wind, blows in the 
 contrary direction, viz. towards the coast of Africa. 
 This is usually ascribed to the great heat of the at- 
 mosphere in the interior of Africa, compared to that 
 over the Atlantic ocean in corresponding latitudes. 
 Of course this direction being on that account from 
 a cold to a comparatively warm climate, the explana- 
 tion is the same as that already given of similar cases. 
 Of Irregular Winds. — The winds which may be 
 classed under this head prevail generally in all cli- 
 mates between the 30th parallels of latitude, and the 
 poles. They also prevail, less or more, in intertropi- 
 cal climates during what is called the rainy season. 
 They obey no fixed laws, either with regard to their 
 velocity, or the periods of the year when they occur. 
 But what chiefly distinguishes them, is their uncertain 
 and variable nature, blowing sometimes from one direc- 
 tion, and sometimes from another; and as frequently 
 from a warm towards a colder climate, as in the oppo- 
 site, and more regular direction. Such winds, there- 
 fore, can never be predicted nor depended uponj and 
 
 2p 
 
298 ON THE CAUSES AND PRINCIPLES 
 
 do not admit of an explanation upon the principle, 
 that atmospheric currents are wholly produced by 
 variations in the temperature of the atmosphere. 
 
 We shall proceed to notice those irregular winds 
 to which we are most subject in this island, with a 
 view to introduce such explanatory observations, as 
 appear to be applicable not only to thera, but to irre- 
 gular winds in general. 
 
 In temperate climates north of the 30th parallel of 
 latitude, the prevailing direction of the wind over the 
 Atlantic ocean, and the western shores of Europe, is 
 from the west, and south-west. That this is the case, is 
 evident from comparing the average length of time, 
 taken by vessels in sailing from Great Britain to the 
 United States in North America, with that which they 
 occupy in returning. Thus, twenty-five days may be 
 about an average passage from New- York to Liver- 
 pool; whereas, thirty-five days is about an average 
 passage from Liverpool to New- York. The only 
 reason assigned for this fact, and it is an evasion rather 
 than an explanation of the difficulty, " is, that a cur- 
 rent of air, having that direction, seems to be neces- 
 sary to restore the equilibrium of the atmosphere, 
 which is so incessantly disturbed by the action of the 
 trade-winds." 
 
 In like manner, the fact of all the strongest winds 
 experienced in Great Britain during the winter half 
 of the year being from the south-west, that is, com- 
 ing from a warm towards a colder climate, is found 
 by meteorologists to be of equally difficult explana- 
 tion. 
 
 By way of explaining the above, and similar cases 
 
OF METEOROLOGICAL PHENOMENA. 299 
 
 of irregularity in the direction of the winds, we submit 
 the following' observations. 
 
 Near the beginning of the present chapter, we gave 
 a statement of the mean height of the barometer in 
 four different places, from Calcutta, in north latitude 
 22° 35', to Melville Island, north latitude 74° 30'. 
 By that statement it appeared, that the mean height 
 of the barometer increased from the equator towards 
 the pole so very slowly, that the difference between 
 the two extreme latitudes where the observations were 
 made, amounted to little more than the tenth of an 
 inch. Upon this result we remarked how small a 
 difference in the mean barometrical pressure, is suffi- 
 cient to determine the prevailing direction of the 
 wind in the lower half of the atmosphere, from the 
 polar towards the equatorial regions. 
 
 Agreeably to the principle, that the direction of the 
 wind is always from where the barometrical pressure 
 is greater, to where it is less, it follows, that its pre- 
 vaihng direction must be from w^here the mean baro- 
 metrical pressure is greater to where it is less. Now, 
 all we propose, in endeavouring to account for the 
 prevailing direction of the wind in Great Britain, and 
 along the western shores of Europe, being from the 
 west and south-west, is to assign a plausible reason 
 for the mean height of the barometer being greater, 
 be the difference ever so small, in the direction from 
 whence the wind blows, than what it is in the climates 
 towards which it blows. 
 
 In our first chapter we explained the reasons why 
 the mean hygrometric state of the atmosphere, was 
 considerably drier than the point of saturation. It 
 
300 ON THE CAUSES AND PRINCIPLES 
 
 was also there mentioned, that when the wind blew 
 from an extensive tract of land, and also when it blew 
 from a cold towards a warm climate, it became much 
 undersaturated. On the contrary, when it blew from 
 the ocean, and from a warm towards a colder climate, 
 it was generally either fully saturated with moisture, 
 or very little under the point of saturation. Now, it 
 is chiefly from the Atlantic, and by means of the pre- 
 vailing west and south-west winds, for which we are 
 now endeavouring to account, that Europe, and even 
 the western and northern parts of Asia, are supplied 
 with all that moisture which is returned to the ocean 
 by rivers. Hence it follows, that the barometrical 
 pressure of the atmosphere, in its progress over the 
 land, must diminish, according to the weight of aque- 
 ous vapour precipitated to the earth, and returned to 
 the sea by rivers. On the other band, an increased 
 barometrical pressure over the Atlantic, so as to oc- 
 casion a wind from the west or south-west along the 
 western shores of Europe, may arise in circumstances 
 such as the following. Let us suppose the wind to 
 blow from a northern direction, that is, from a cold to 
 a warmer climate, and particularly if a west or north- 
 west wind blows over upon the Atlantic from the 
 North American continent, (which is of frequent oc- 
 currence,) the atmosphere brought by such winds, is 
 at first greatly undersaturated with moisture. The 
 supply of humidity, however, which it soon receives 
 by evaporation from the surface of the Atlantic, is 
 neither more nor less than an augmentation to the 
 amount of atmosphere, and which necessarily increases 
 its barometrical weight. This I conceive gives rise 
 
OF METEOROLOGICAL PHENOMENA. 301 
 
 to an atmospheric current towards Europe, where its 
 eastern direction is farther assisted, by the diminution 
 of atmosphere, and accordingly of barometrical weight, 
 which it sustains, in consequence of its humidity being 
 partly precipitated to the earth, and returned to the 
 sea by rivers. 
 
 Upon similar principles, the great force of south- 
 west winds experienced in Great Britain, especially 
 during winter, may be ascribed to the diminution of 
 barometrical pressure which such winds undergo, in 
 consequence of the great amount of rain precipitated 
 during their north-east progress. Such, in my opin- 
 ion, are the causes which render winds from the west 
 and south-west more prevalent, and on an average 
 stronger, especially during the winter season, over the 
 Atlantic ocean to the north of the 30th parallel of 
 latitude, and along the western shores of Europe, than 
 from any other direction. 
 
 Similar causes to those above stated may be sup- 
 posed to render winds from the ocean, and from in- 
 land seas in all quarters of the earth, towards the land, 
 more prevalent and stronger than what they would 
 otherwise be. And hence the preceding observations 
 explain the chief cause of irregular winds, meaning 
 thereby, winds which blow from a different direction 
 than from a cold to a warm climate. 
 
 After reflecting upon the phenomena presented 
 by aerial currents, the conclusion to which I have 
 come is, that the two primary causes which disturb 
 the atmospheric equilibrium, and occasion winds, are, 
 Isty Simultaneous inequalities in the temperature of 
 the atmosphere at similar altitudes above the level of 
 
302 ON THE CAUSES AND PRINCIPLES 
 
 the sea ; and 2^/, Unequal augmentations and dimi- 
 nutions in the amount of atmosphere in different lo- 
 calities, occasioned by unequal amounts of aqueous 
 vapour being simultaneously added to the atmosphere 
 by evaporation in different localities ; and by unequal 
 amounts being simultaneously withdrawn from the 
 atmosphere, and precipitated to the earth, in different 
 places, in the forms of rain, snow, hail, &c. The 
 former of these may be regarded as the great cause of 
 regular and periodic winds j while the latter, by dis- 
 turbing that regularity, is the chief cause of irregular 
 winds of every description. 
 
 Another cause of irregularity in the direction of the 
 winds is reaction. It may be easily conceived that 
 great velocity given to the atmospheric current by any 
 cause, such, for instance, as the falling of a great 
 amount of rain along the western shores of Europe, 
 during a south-west wind, in the winter half of the 
 year, will occasion an accumulation of the atmosphere, 
 so as to give rise to increased barometrical pressure, 
 in the eastern parts of Europe, and western parts of 
 Asia, beyond the boundaries where the falling of rain, 
 at least in any considerable quantity, extends. The 
 consequence of this will be, that reaction will take 
 place, and the wind, instead of continuing to blow 
 from the south-west, will shift to the opposite direc- 
 tion, and blow from the north-east. This wind not 
 improbably returns to the Atlantic ocean nearly the 
 same identical atmosphere, deprived, however, of a 
 large proportion of its moisture, which formerly came 
 from that quarter. The same process as that which 
 has been already described, will, in such circumstances, 
 
OF METEOROLOGICAL PHENOMENA. 303 
 
 be again renewed. The cold dry atmosphere from 
 the north-east, will be gradually heated and replenish- 
 ed with humidity by evaporation from the surface of 
 the Atlantic. The supply of humidity which the at- 
 mosphere thus receives, will augment its volume and 
 increase its barometrical weight ; and thus will ulti- 
 mately give birth to a west or south-west wind blow- 
 ing towards the shores of Europe. A similar dimi- 
 nution in the atmospheric pressure, occasioned by the 
 descent of rain in the progress of the atmosphere from 
 a warm to a cold climate, will increase its velocity. 
 And a similar accumulation of air, and an increased 
 barometrical pressure, will take place in those eastern 
 regions, beyond where the rain reaches in any quanti- 
 ty, and this will ultimately again produce reaction, as 
 before described. The reason why the velocity of 
 the east and north-east winds is not nearly so great 
 as that of the west and south-west, is, that the former 
 is not usually assisted by the diminution of barome- 
 trical pressure, occasioned by the falling of rain, like 
 the latter. 
 
 Such I conceive are the causes why the most pre- 
 valent winds in this country, and along the western 
 shores of Europe, are from the south-west and west ; 
 and the next most prevalent, from the north-east and 
 east : and why the former are usually much stronger 
 than the latter. And such are the reasons, why the 
 change of wind from one of these directions to the 
 opposite, and back again, is of such frequent occur- 
 rence. 
 
 Reaction arising from atmospheric accumulation, 
 may also be expected to give a contrary direction to 
 
304 ON THE CAUSES AND PRINCIPLES 
 
 the wind in every case, where a diminution occurs in 
 the difference of tenaperature in different latitudes, 
 which has previously given birth to a wind of a deter- 
 minate velocity. Changes in the direction of the 
 wind arising from this cause, in connection with the 
 different degrees of rapidity with which different neigh- 
 bouring localities, and different latitudes, increase and 
 diminish in temperature, are of frequent occurrence 
 in most parts of the earth, during the sun's progress 
 to the north and south of the equator. And it need 
 hardly be remarked, that the accumulations of air in 
 particular regions, not only produce that irregularity 
 in the direction of the wind which we call reaction, 
 but causes further irregularity, by giving rise to di- 
 verging currents in every direction. In like manner 
 every rarefaction of the atmosphere in any particular 
 district, whether arising from increased heat, or sud- 
 den and great precipitations of moisture in the form 
 of rain, occasions further irregularity in the direction 
 of the winds, by causing converging currents in every 
 direction; and this ultimately again produces reaction. 
 
 In the 3d chapter, we stated our objections to the 
 commonly received opinion, that the upper half of the 
 atmosphere moves in all cases in the opposite direc- 
 tion of the lower ; and advanced the hypothesis, that, 
 when the wind in the lower half blows from a warm 
 towards a cold climate, as is exemplified in the case 
 of a south-west wind during winter, blowing from the 
 Atlantic towards the shores of Europe, no opposite 
 current can simultaneously exist in the upper half of 
 the atmosphere. 
 
 In the case of a wind in the lower half of the atmo- 
 
OF METEOROLOGICAL PHENOMENA. Q05 
 
 sphere blowing in the regular direction, from a cold 
 to a warm chmate, such as is exemplified by sea and 
 land breezes, and monsoons, the wind near the earth's 
 surface from the cold locality, is a consequence, and 
 a concomitant of the increased barometrical pressure, 
 occasioned by the previous commencement, and con- 
 tinuance of a current in the upper half of the atmo- 
 sphere, from the more elevated aerial columns over 
 the warm locality. But when the wind in the lower 
 half of the atmosphere blows from a warm towards a 
 cold climate, the atmospheric columns over the latter 
 must not only contain less air, (in order to account 
 for the direction of the wind near the earth's surface,) 
 but must be less elevated, in consequence of being 
 colder than what they are over the former. Hence, 
 according to pneumatical principles, when the wind 
 blows from the west or south-west during winter to- 
 wards the shores of Europe, it is physically impossible 
 that a contrary current in the upper half of the atmo- 
 sphere from the east or north-east can simultaneously 
 exist ; and the same observation is apphcable to all 
 other cases where the wind in the lower half of the 
 atmosphere blows from a warm towards a cold climate. 
 The atmosphere, like all other fluids, is subject to 
 the laws of gravity ; and it is just as impossible that 
 the upper half of the atmosphere can blow from any 
 district where the atmospheric columns are colder, and 
 less elevated, and contain less air, to where they are 
 warmer, and more elevated, and contain more air, as 
 it would be for a river to flow up a hill. 
 
 Reasoning according to dynamical principles, it 
 may be inferred, that, when the wind blows from a 
 
 2 Q 
 
300 ON THE CAUSES AND PRINCIPLES 
 
 warm towards a cold climate, the whole air from the 
 earth's surface to the summit of the atmosphere must 
 move simultaneously in the same direction. But as 
 air, like other elastic fluids, becomes denser in the 
 ratio of compression, I infer, that in such circum- 
 stances, the force that produces wind, viz., the supe- 
 riority of atmospheric pressure in one place over an- 
 other at an equal altitude above the level of the sea, 
 increases as we approach the earth's surface. Hence, 
 except for the counter influence of friction on the 
 earth's surface, and which must be propagated up- 
 wards with diminishing eff"ect from one aerial stratum 
 to another, the velocity of the wind should decrease 
 upon receding perpendicularly upwards from the level 
 of the sea. On these grounds, together with the fact 
 of moisture being abstracted in the form of rain only 
 from the aerial strata within a limited distance of the 
 level of the sea, I am disposed to think, that in most 
 cases, the velocity of the atmospheric current is nearly 
 equal for a considerable distance, such as perhaps for 
 a mile or two above the earth's surface ; but that be- 
 yond that altitude, its velocity gradually diminishes. 
 And as was formerly stated, this opinion is confirmed 
 by the great velocity with which clouds suspended at 
 a low altitude apparently move, when compared with 
 those at a greater elevation, even after an allowance 
 (not estimated, however, with sufficient scientific ac- 
 curacy,) is made for the optical illusion produced by 
 the greater distance of the latter. 
 
 Thus we see there are two principal varieties in 
 the movements of the atmospheric columns, viz., one 
 in which their upper extremities move in the opposite 
 
OF METEOROLOGICAL PHENOMENA. yU7 
 
 direction of their lower extremities ; and another 
 where the whole columns move in the same direction, 
 but with diminishing velocity from the earth upwards, 
 or perhaps with diminishing velocity upwards begin- 
 ning at the altitude of a mile or two above the level 
 of the sea. The former of these cases occurs when 
 the wind, in the lower half of the atmosphere, blows 
 from a cold towards a warm climate or locality ; and 
 is exemplified by sea and land breezes, and monsoons. 
 The latter occurs when the wind, in the lower half of 
 the atmosphere, blows in the direct, or in nearly the 
 direct line from a warm towards a cold climate. And 
 it does not matter whether this direction of the wind 
 be the result of reaction, or of additions made to the 
 atmosphere by evaporation of moisture from a watery 
 surface underneath. 
 
 Besides the two preceding varieties in the move- 
 ments of the atmospheric columns, others which must 
 occur in certain circumstances might easily be de- 
 duced. For instance, supposing a wind about the 
 end of April or October blowing in this chmate from 
 the west towards the shores of Europe, that is, blow- 
 ing along the same parallel of latitude at a time when 
 the atmospheric temperature over the land and ocean, 
 at the same distance from the equator, is about equal. 
 In this case, the wind from the west is occasioned by 
 a preponderance of atmospheric pressure near the 
 earth's surface over the Atlantic, when compared with 
 the atmospheric pressure over Europe. But though 
 the atmospheric pressure for many degrees both to 
 the south and north of the place of observation be the 
 same at the level of the sea, still, owing to the greater 
 
308 ON THE CAUSES AND PRINCIPLES 
 
 warmth and elevation of the atmospheric columns ly- 
 ing to the south, and consequently to the circum- 
 stance of the warm columns containing a smaller 
 amount of air within a given distance of the earth's 
 surface, than the cold columns, the preponderance of 
 atmospheric pressure at equal altitudes above the le- 
 vel of the sea, must veer more and more round to the 
 south of west, upon ascending perpendicularly. Hence, 
 though the wind blow directly from the west at the 
 surface of the earth, it will blow, in such circum- 
 stances, more and more from the south of west, the 
 higher we ascend in the atmosphere. 
 
 It might also be demonstrated, that a mountain 
 range would, in certain circumstances, modify, or even 
 reverse, the current in the upper portion of the atmo- 
 spherco For instance, suppose the trade-wind within 
 the tropics meeting with a range of mountains, such 
 as the Andes, running at right angles to the direction 
 of the wind, a current in the upper portions of the 
 atmosphere would be generated in the opposite direc- 
 tion. The principle according to which this result is 
 deduced is the following. The trade-wind blowing 
 constantly from the east, upon being partially inter- 
 rupted by the mountain range, gives rise to a perma- 
 nent accumulation of air, and a consequent greater 
 elevation of the atmospheric columns on the wind- 
 ward side of the mountains. Now, though the in- 
 creased barometrical pressure thus produced, may not 
 be sufficient altogether to overcome the force and 
 acquired velocity of the trade-wind near the earth's 
 surface, still as the force and velocity decrease upon 
 ascending perpendicularly, an elevation will be at 
 
OF METEOROLOGICAL PHENOMENA. 309 
 
 length reached, when the preponderance of barome- 
 trical pressure occasioned by the interruption of the 
 wind, and consequent accumulation of air, will not 
 only be overcome, but an opposite current, blowing 
 from west to east, will be generated. 
 
 Upon similar principles the direction of the wind 
 in the lower half of the atmosphere is more or less 
 altered, as if it were by reflection, upon meeting with 
 an elevated mountain range, running in any line be- 
 tween what is transverse and parallel to that of the 
 wind. In this case, the interruption of the atmo- 
 spheric current by the mountains, causes accumulation 
 of air, and slightly increased barometrical pressure on 
 their windward flanks. And this increased barome- 
 trical pressure, instead of checking the atmospheric 
 current, merely causes it to assume a reflected direc- 
 tion, at an angle corresponding to that of incidence. 
 It is said that a south-west wind, upon meeting with 
 the very elevated Himalaya mountains, forming the 
 northern frontier of India, is reflected in this manner. 
 
 Other varieties and alterations in the direction of 
 the winds dependent upon local causes, might be de- 
 duced in a similar manner. Those already given are, 
 however, sufficient to explain the principles upon 
 which the deductions are made. Let it only be re- 
 collected, that every superior elevation of the atmo- 
 spheric columns over any district, such as may result 
 from superior warmth, gives rise to a current in the 
 upper portions of the atmosphere, from that district 
 towards colder localities. Let it be also recollected, 
 that, near the earth's surface, the direction of the wind, 
 at any time and place, is the conjoint result of acquired 
 
310 ON THE CAUSES AND PRINCll'LES 
 
 velocity, and of the preponderance of atmospheric 
 pressure in one quarter of the horizontal circumfer- 
 ence, over the opposite. Of course, any local cause 
 which occasions increased accumulation of air, and 
 consequently increased barometrical pressure over any 
 district or portion of the earth's surface, such as supe- 
 rior coldness, increased evaporation, or interruptions 
 by mountains to the progress of the wind, exerts more 
 or less influence in originating wind from that quarter; 
 or in the case of wind blowing towards that quarter, 
 in reflecting it, and giving it a new direction away 
 from the district where increased barometrical pres- 
 sure exists. On the contrary, any local cause which 
 occasions diminished barometrical pressure, such as 
 superior warmth, or an unusual abstraction of aqueous 
 vapour from the atmosphere in the form of rain, has a 
 tendency to originate currents towards that quarter; 
 and where any atmospheric current previously exists, 
 exerts an influence in turning it aside from its pre- 
 vious direction towards that quarter, as if it were 
 thereby attracted. 
 
 Those very local squalls, or gusts of wind, which 
 are sometimes observed to issue out of particular 
 glens or valleys amidst a mountainous country, and 
 which, on the sea-coast, are so much dreaded by ma- 
 riners, are to be ascribed to the influence of the moun- 
 tains in obstructing the general progress of the atmo- 
 spheric current. The obstruction thus presented, 
 causes more or less atmospheric condensation and 
 compression, and this compression, by giving the air 
 increased elastic force, causes it to issue from those 
 glens and narrow passages through which its course 
 
OF METEOROLOGICAL PHENOMENA. 311 
 
 is directed, in the form of a squall or violent gust of 
 wind. 
 
 The reason why rising grounds, or hills, lying to 
 windward, generally afford little or no shelter from the 
 atmospheric current, especially if their acclivity be 
 very gradual, is owing to the increased atmospheric 
 pressure, and reactive force, which the wind acquires 
 upon reaching the summit of the hill or rising ground. 
 
 After the explanation previously given of the cause 
 of the prevalence of south-west winds along the west- 
 ern shores of Europe, it need hardly be repeated, that 
 inequahties in the amount of moisture evaporated from 
 different portions of the earth's surface, and which 
 vary in relation to each other at different times, (being 
 in reality equivalent to unequal creations of atmo- 
 sphere,) necessarily give rise to unequal barometrical 
 pressure in different places, and is, therefore, a cause 
 of irregular winds. On the other hand, unequal pre- 
 cipitation of moisture from the atmosphere in different 
 places, whether in the form of rain, hail, snow, or dew, 
 and which in reality is equivalent to unequal diminu- 
 tions of atmosphere, necessarily occasions unequal 
 barometrical pressure, and likewise produces irregu- 
 larity in the direction of the winds. 
 
 The general principle applicable to winds arising 
 from the above causes, is, that their direction, unless 
 counteracted by difference of temperature, or some 
 stronger or more general cause, should, in the one 
 case, be from where evaporation, or the augmentation 
 of atmosphere, is going on more rapidly, to where it 
 is proceeding more slowly; and in the other, from 
 where the amount of rain is less, to where it is greater. 
 
312 ON THE CAUSES AND PRINCIPLES 
 
 Or by compounding these two cases, the direction of 
 the wind, if freed from the influence of all other causes, 
 ought to be from where evaporation, or the augmenta- 
 tion of atmosphere, goes on most copiously, to where 
 the diminution of atmosphere, or of atmospheric 
 weight, by the precipitation of moisture in the form 
 of rain, proceeds with greatest rapidity. Hence, if 
 no other causes of wind existed, its prevailing direc- 
 tion ought to be from the ocean and a warmer climate, 
 towards a mountainous country situated in a colder 
 latitude. The former is where the amount of mois- 
 ture evaporated, is greatest relative to that which is 
 precipitated; the latter is where the greatest amount 
 of rain falls, relative to the quantity of moisture evap- 
 orated. 
 
 The circumstance of the addition to the atmosphere 
 by evaporation of moisture, relative to its diminution 
 by precipitation, being greater in warm than in cold' 
 climates, accounts for the increment in the mean ba- 
 rometrical pressure on receding from the equator to- 
 wards the poles, being so small as was formerly stated. 
 In reality, the natural direction of irregular winds, 
 meaning thereby, winds occasioned by unequal evap- 
 oration and precipitation of moisture in different local- 
 ities, if not influenced by other causes, is the reverse 
 of winds resulting from difference in the atmospheric 
 temperature in different places. The direction of the 
 former is from a warm towards a comparatively cold 
 climate, while that of the latter is from a cold towards 
 a comparatively warm climate. These two causes of 
 wind in some degree balance and counteract each 
 other, each of them gaining the ascendancy in sue- 
 
OF METEOROLOGICAL PHENOMENA. 313 
 
 cession. And the prevailing direction of the wind in 
 any place, and the degree of prevalence, is determined 
 by the mean preponderance of one of these causes 
 over the other. 
 
 The preceding observations partly explain the rea- 
 son why clouds, during showery weather, are peculiarly 
 directed towards, and along chains of mountains. The 
 result here alluded to is, however, partly illusory, and 
 partly real. Clouds appear to be directed toward 
 mountains, partly in consequence of the influence of 
 mountains in forming clouds during windy weather; 
 and partly in consequence of the local direction given 
 to the wind, by the local diminution of atmospheric 
 pressure, that results from the greater abundance of 
 rain which falls upon the mountains; and which the 
 altered direction, and augmented velocity of the wind, 
 farther contributes to increase. 
 
 The impetus given to the atmospheric current by 
 the diminution of barometrical pressure which attends 
 the falHng of rain, also explains the reason why windy 
 weather is more prevalent, and the winds generally 
 stronger, in showery than in dry weather; and also, 
 why they are stronger in showery weather among and 
 in the neighbourhood of mountains, where the greatest 
 amount of rain falls, than in champaign, low-lying 
 countries. 
 
 Clouds, as we remarked when treating of their sus- 
 pension in a former chapter, displace a weight of at- 
 mosphere equal to their own. It is therefore not 
 their formation, but their dissolution in the form of 
 rain, which diminishes barometrical pressure. Be- 
 sides, the falling of rain, particularly when in partial 
 
 2r 
 
314 ON THE CAUSES AND PRINCIPLES 
 
 showers, gives rise to irregular and variable winds, not 
 only by the local diminution of atmospheric pressure 
 which it occasions, but also by its influence in reduc- 
 ing the temperature of the atmosphere, through which 
 it passes in its descent to the earth. As this latter 
 influence of rain was treated of at length in our fourth 
 chapter, it need not be here repeated. 
 
 The irregularity and variableness in the direction 
 of the winds within the tropics, during what is called 
 the rainy season, is principally owing to the local and 
 unequal diminutions of barometrical pressure, together 
 with the irregular reduction of the temperature of the 
 lower atmosphere, which the frequent descent of par- 
 tial heavy showers of rain occasions. 
 
 The climates in which windy weather is most fre- 
 quent, are those where vicissitudes of temperature are 
 most sudden, and especially where those vicissitudes, 
 in neighbouring localities, are most unequal. Thus, 
 in far inland countries, where the atmospheric tem- 
 perature is usually nearly equal for a great distance 
 around, very little windy weather is experienced, in 
 comparison with what occurs on continental coasts, 
 where the atmospheric temperature over the land in 
 the one direction, and over the sea in the other, is 
 frequently very unequal. In like manner, in the 
 Pacific ocean, owing to its great extent, and the same- 
 ness of temperature which accordingly exists, during 
 all seasons of the year, to a great distance around, 
 much less wind is experienced than in seas of smaller 
 magnitude. 
 
 Upon analogous principles, in those seasons of the 
 year when the atmospheric temperature is undergoing 
 
OF METEOROLOGICAL PHENOMENA. 315 
 
 the most rapid alteration, and which, in neighbouring 
 locaHties, are always more or less unequal, high winds 
 are most frequent, and their direction most variable. 
 Thus, in temperate latitudes windy weather is of less 
 frequent occurrence during summer, when the atmo- 
 spheric temperature is much nearer equality for a great 
 distance around, than what it is during winter. The 
 high winds which are frequently observed to happen 
 about two or three weeks after the vernal, and more 
 particularly after the autumnal equinox, and which are 
 denominated equinoctial blasts, are principally to be 
 ascribed to the rapid and unequal alterations in the 
 atmospheric temperature in different localities, which 
 occur at these seasons of the year. And the greater 
 strength of the blasts which occur after the autumnal 
 than after the vernal equinox, is to be ascribed to the 
 greater amount of rain that usually falls about the 
 former period, when the temperature is declining, than 
 about the latter, when the temperature is advancing. 
 In like manner, in high polar latitudes, it has also 
 been observed, that the winds are strongest, and most 
 variable, during spring and autumn, when the atmo- 
 spheric temperature is undergoing its most rapid alter- 
 ation, and when, in different neighbouring localities, 
 it becomes most unequal. On the contrary, during 
 the height of summer, and also during the depth of 
 winter, when the atmospheric temperature in those 
 very high latitudes for a great distance around be- 
 comes nearly equal, there is almost no wind. 
 
 But to conclude this subject. When we observe 
 the irregularity with which land and water, together 
 with mountains, forests, cultivated and uncultivated 
 
316 ON THE CAUSES AND PRINCIPLES 
 
 soils, are distributed and intermixed over the earth's 
 surface J — and if we bear in mind the unequal aug- 
 mentations, and diminutions of temperature, which 
 they are simultaneously undergoing, during the alter- 
 nate successions of day and night, and the different 
 seasons of the year; — and when we at the same time 
 recollect the other causes previously mentioned, which 
 disturb the atmospheric equilibrium, the irregularity 
 in the direction of the winds, which is greatest in 
 those climates, and in those seasons of the year, when 
 the temperature is most subject to sudden and great 
 variations, is by no means surprising. 
 
 In certain localities, causes, which separately should 
 occasion opposite currents, neutrahze each other, and 
 produce atmospheric stillness. Thus, between the 
 meridians of Cape Verde and the eastermost islands 
 of the groupe which bear that name, there is a zone 
 350 miles in breadth, in which there is almost no 
 wind, except of the lightest and most variable descrip- 
 tion. Ships have here been known to be becalmed 
 for whole months. It has been denominated the 
 Rains on account of the great amount observed to 
 fall ; thunder is also here of frequent occurrence. 
 The reason assigned for the want of wind in this 
 quarter is, that it occupies a position where the trade- 
 wind blowing towards the west, is neutralized and no 
 more, by the cause previously assigned for the wind, 
 which, beyond the eastern boundary of this zone, blows 
 towards the heated shores of Africa. The reason of the 
 great abundance of rain in this region, is not properly 
 understood. It is possibly owing to the sinking down 
 and intermixture of cold aerial strata, brought by cur- 
 
OF METEOROLOGICAL PHENOMENA. 317 
 
 rents from the north and south in the upper regions 
 of the atmosphere, with the warmer strata underneath. 
 And it is probable, that corresponding amounts of air 
 are abstracted from this zone, to supply in part the 
 currents which diverge from it to the east and west. 
 The frequency of thunder here, is probably owing to 
 the conjoint influence of the unusual prevalence of 
 cloudy weather, and the rapid increase of tempera- 
 ture, and consequently of electrization, which the 
 clouds undergo, by exposure to the rays of a vertical 
 sun. 
 
 Calms in similar localities, and resulting from like 
 causes, prevail under the equator, in the western 
 hemisphere, between Cape St Francis and the Gal- 
 iapagos islands. And we are informed by Humboldt, 
 that the same sluggish state of the atmosphere, is 
 experienced on the western shores of America, be- 
 tween 13° 30' and 15° of north latitude, and 103° and 
 106° of west longitude, during the months of Febru- 
 ary and March. In the year which preceded that in 
 which he visited those seas, a dead calm of twenty- 
 eight days, with a want of water in consequence of it, 
 forced the crew of a ship newly built at Guayaquil, to 
 abandon a rich cargo of cocoa, and save themselves 
 in their boat, by making for the land eighty leagues 
 distant. 
 
 Of the Hurricane or Typhon. — The next irregu- 
 lar wind of which we mean to treat is the Hurricane. 
 This, which is the most violent of all winds, assumes 
 its most formidable aspect in the West Indies, the 
 Isle of France, and the Indian ocean. In the West 
 Indies, where we are best acquainted with its pheno- 
 
318 ON THE CAUSES AND PRINCIPLES 
 
 mena, it occurs only during the rainy season ; and 
 most frequently in the month of August. It con- 
 sists of furious wind, accompanied with thunder and 
 lightning, and torrents of rain. Generally, in its 
 most violent form, it does not last for more than two 
 or three hours. Torrents of rain, however, accom- 
 panied with wind so violent as almost to be entitled 
 to the name of a hurricane, sometimes continue in 
 intertropical climates, for one, two, or even three days. 
 A vivid, though perhaps an embellished descrip- 
 tion of a hurricane, which occurred when Columbus 
 was about to sail from Isabella island, is given by 
 Washington Irving as follows : — " About mid-day a 
 furious wind sprang up from the east, driving before 
 it dense volumes of cloud and vapour. Encountering 
 another tempest from the west, it appeared as if a 
 violent conflict ensued. The clouds were rent by in- 
 cessant flashes, or rather streams of lightning. At 
 one time they were piled up high in the sky, at an- 
 other they descended to the earth, filling the air with 
 a baleful darkness more impenetrable than the obscu- 
 rity of midnight. Wherever the hurricane passed, 
 whole tracts of forests were shivered, and stripped of 
 their leaves and branches, and those of gigantic size 
 which resisted the blast were torn up by the roots, 
 and hurled to a great distance. Groves were torn 
 from the mountain precipices, and vast masses of 
 earth and rock precipitated into the valleys with ter- 
 rific noise, choking the course of the rivers. The 
 fearful sounds in the air and on the earth, — the peal- 
 ing thunder, — the vivid lightning, — the howling of 
 the wind,- — the crash of falling trees and rocks filled 
 
OF METEOROLOGICAL PHENOMENA. 319 
 
 every one with affright, and many thought that the end 
 of the world was at hand. Some fled to caverns for 
 safety, for their frail houses were blown down, and the 
 air was filled with the trunks and branches of trees, 
 and even with fragments of rocks carried along by the 
 fury of the tempest. When the hurricane reached 
 the harbour, it whirled the ships round as they lay at 
 anchor, snapped their cables, and sunk three of them 
 to the bottom, with all who were on board. Others 
 were driven about, dashed against each other, and 
 tossed mere wrecks upon the shore, by the sweUing 
 surges of the sea, which, in some places, rolled for 
 three or four miles upon the land. The tempest 
 lasted for three hours. When it had passed away, and 
 the sun again appeared, the Indians regarded each 
 other with mute dismay. Never, in their memory, 
 nor in their traditions, had their island been visited 
 by such a tremendous storm. They believed that 
 the Deity had sent this fearful ruin to punish the 
 cruelties and crimes of the white men, and declared 
 that this people had moved the very air, the water, 
 and the earth, to disturb their tranquil life, and to de- 
 solate their island." 
 
 Two causes have been assigned for hurricanes, but 
 neither of them is by any means satisfactory. One of 
 them is, that large quantities of hydrogen supposed 
 to exist in the higher regions of the atmosphere, are 
 united to the oxygen of the air, and suddenly con- 
 densed into water by means of electricity ; and that 
 the vacuity or great rarefaction of the atmosphere 
 thereby occasioned, is the cause of the hurricane. 
 This explanation we consider entirely chimerical. 
 
320 ON THE CAUSES AND PRINCIPLES 
 
 For though hydrogen is one of the constituents of 
 aqueous vapour, there is no evidence whatever that it 
 exists in large quantities either as a separate gas, or 
 as one that is mixed with the atmosphere, in its more 
 elevated regions. 
 
 The other explanation of hurricanes is, that they 
 are occasioned by " the sudden destruction of large 
 portions of the atmosphere by means of electricity, 
 and by the subsequent rushing of the surrounding air 
 into the partial void which is thus formed." This 
 explanation we also consider somewhat chimerical; 
 for we have no evidence whatever of electricity having 
 power to destroy any portion of the atmosphere. It 
 is a maxim in chemical philosophy, that the annihi- 
 lation of even the smallest particle of matter never 
 takes place naturally, nor can be effected by artificial 
 means. The term destruction, therefore, as applied 
 to the atmosphere in the above quotation, can only 
 mean, that its elements are condensed by the agency 
 of electricity into liquids or sohds, and precipitated 
 to the earth. We know that aqueous vapour may be 
 condensed into water and precipitated to the earth. 
 But what liquids or solids are precipitated to the 
 earth, in consequence of the condensation of oxygen, 
 nitrogen, and carbonic acid gases, (for these seem 
 also included in the phrase " large portions of the at- 
 mosphere,") is left unexplained. 
 
 It is probable that hurricanes, in their more violent 
 forms, are occasioned by a favourable combination of 
 those circumstances which produce wind in general. 
 The chief of these is a sudden and widely extended 
 simultaneous diminution of barometrical pressure, 
 
OF METEOROLOGICAL PHENOMENA. 321 
 
 produced by a sudden, simultaneous, and widely-ex- 
 tended heavy fall of rain, which is a never-failing at- 
 tendant of the hurricane. The reason why the cir- 
 cumstance of the rarefaction being spread over a large 
 surface increases the force of the wind, is owing to its 
 setting in motion a greater amount of air in all direc- 
 tions around. A large vacuity is not so soon filled 
 up as a small one. And a large amount of air set in 
 motion, acquires velocity according as it is subjected 
 to a constant pressure for a longer time. Besides, 
 before reaction can commence, the impetus of a larger 
 amount of air in motion has to be overcome. Of 
 course, the aerial condensation, and the reaction of 
 the hurricane is stronger, according as the previous 
 rarefaction which gave the hurricane birth, is greater, 
 and more widely extended. We formerly stated that 
 clouds, in order to their suspension, must displace a 
 weight of atmosphere equivalent to their own. Of 
 course, when the very dense and widely-extended 
 clouds, (which are also constant concomitants of hur- 
 ricanes,) are suddenly and rapidly dissolved in rain, 
 the barometrical pressure is not only thereby reduced 
 in proportion to the weight of rain that falls, but the 
 space in the atmosphere which the clouds previously 
 occupied, is left void until filled up by the rushing 
 in of air. This cause is farther assisted by the sud- 
 den reduction of temperature, and condensation, 
 which the heated atmosphere beneath the clouds un- 
 dergoes, in consequence of the rain bringing down 
 the coldness which it had acquired, at the altitude 
 where it was formed into drops. The sudden co- 
 operation of these circumstances over a widely-ex- 
 
 2s 
 
322 ON THE CAUSES AND PRINCIPLES 
 
 tended surface, is sufficient to account for a great and 
 extensive rarefaction of the atmosphere, which must 
 necessarily occasion a sudden rush of air from all 
 quarters around, towards the centre of rarefaction. 
 And this, in my opinion, with the subsequent reac- 
 tion, arising from the accumulation of the concentrat- 
 ed currents of air, constitutes the hurricane. 
 
 The circumstances in which hurricanes usually 
 happen, are also favourable for the efficacy of the 
 causes above assigned for their production. They 
 are usually preceded by great warmth and atmospheric 
 stillness, and by a low state of the barometer, which 
 sinks much farther during their continuance. The 
 previous low state of the barometer maybe occasioned 
 by the great heat expanding and elevating the atmo- 
 spheric columns, so as to generate diverging currents 
 of air from their upper portions towards colder regions. 
 This circumstance, which, of itself, would ultimately 
 produce reaction, and give rise to a contrary current 
 near the earth's surface, is probably one of the com- 
 bination of circumstances which tends to increase the 
 fury of the blast. Again, hurricanes only occur in 
 warm climates, and during the most sultry w^eather in 
 the hottest season of the year. The great capacity 
 of heated air for containing moisture, both in the in- 
 visible state, and in the visible form of cloud, accounts 
 for the immense quantity of rain which falls in a short 
 time during a hurricane. Besides, the previous at- 
 mospheric stillness favours the air in sustaining the 
 utmost amount of humidity, both in clouds and in in- 
 visible solution, which, at any given temperature, it is 
 capable of retaining ; while the agitation of the atmo- 
 
OF METEOROLOGICAL PHENOMENA. 323 
 
 sphere during the hurricane produces the opposite 
 effect, and consequently strengthens the blast. The 
 clouds also, from the appearances previously pre- 
 sented, as well as from the thunderstorm which intro- 
 duces and accompanies the hurricane, seem to be in 
 a highly electrified condition. Owing to this addi- 
 tional circumstance, the air is enabled to suspend a 
 much larger amount of aqueous vapour in the form of 
 clouds. The vesicles of which these clouds are com- 
 posed being all severally strongly charged with elec- 
 tricity, repel each other. Hence, they do not unite, 
 until the vesicular condensation, arising from the great 
 amount of vesicles of similar specific gravity, all press- 
 ing downwards to the same horizontal level, becomes 
 much greater than it would otherwise be. So soon, 
 however, as the electric fluid begins to be abstracted 
 from the clouds in the form of lightning, the vesicles 
 rapidly unite, and give rise to the torrent of rain 
 which then commences ; and which, aided by reac- 
 tion arising from the previous low state of the baro- 
 meter, which is farther increased by the descent of 
 rain, is the chief cause of the hurricane. 
 
 Hurricanes are always accompanied by a very low 
 state of the barometer, and the wind is frequently di- 
 rected from every quarter, towards the point where 
 the atmospheric pressure is least. They are com- 
 monly propagated to windward ; that is, their influ- 
 ence is first felt at the place towards which the cur- 
 rent flows, and is gradually extended in the direction 
 from which it comes. This fact was ascertained by 
 Dr Franklin in the case of a strong wind from the 
 north-east, which occurred at Philadelphia in the year 
 
324 ON THE CAUSES AND nilNCIPLES 
 
 1740. It commenced at riiiladelphia at seven o'clock 
 in the evening, and by comparing the various accounts 
 which he received from the different places over which 
 it passed, he found that it began about an hour later 
 for every 100 miles towards the north-east. 
 
 From this fact it has been behoved, that all winds 
 are propagated in a similar manner to windward. This 
 opinion, however, I conceive to be erroneous. When 
 winds are produced by a sudden rarefaction of the 
 atmosphere in any particular quarter, they will always 
 be propagated to windward in the manner above de- 
 scribed. But when they are occasioned by an accu- 
 mulation, or condensation of the air, they will be pro- 
 pagated from the centre of accumulation to leeward. 
 Thus, when the reaction of the hurricane occurs after 
 the short interval of atmospheric stillness, the wind is 
 propagated from the centre of accumulation to lee- 
 ward, though the first beginning of the hurricane was 
 propagated to windward. It is also observed, that, in 
 those climates where sea and land breezes prevail, the 
 commencement of the sea-breeze, urged on from 
 where the preponderance of barometrical pressure is 
 greatest, is seen, by the ripple on the water, advancing 
 towards the shore, that is to leeward. It is probable, 
 however, that, in most cases, previously to the begin- 
 ning of wind, there is a very gradual decrease of baro- 
 metrical pressure over a great extent of surface. In 
 such circumstances, the current may commence nearly 
 about the same time all along the hne of decrement. 
 And if, in any portion of the hne, the decrement of 
 barometrical pressure be more rapid than in others, 
 the current will be there strongest, and first felt. 
 
or METEOROLOGICAL PHENOMENA. 325 
 
 Upon this point it need only be farther remarked, 
 that, in all cases of wind, whether arising from local 
 aerial rarefaction or condensation, the current is pro- 
 pagated to windward in the one case, and to leeward 
 in the other, with much greater rapidity than the air 
 is itself transported. 
 
 Of the Whirlwind. — The next species of irregular 
 wind of which we mean to treat is the whirlwind. 
 This remarkable wind is much more limited in its 
 extent than the hurricane, but within its sphere of 
 action equally destructive and appalling. The dia- 
 meter of the atmospheric column subjected to its in- 
 fluence, varies from a few feet to several hundred 
 yards, but the whirling motion seems to be greatest at 
 the circumference. It usually makes its appearance 
 during summer when the sky is covered with dense 
 clouds, and is preceded by sultry heat and a dead 
 calmness in the atmosphere. In short, the forerun- 
 ners of a whirlwind have a distant resemblance to those 
 of a hurricane, and a very strong analogy to, if not a 
 perfect identity with, those of a thunder or hailstorm, 
 by which it is sometimes attended. 
 
 The following account by Abbe Richard, of a whirl- 
 wind which happened in Burgundy, in the year 1755, 
 will give some idea of the phenomena presented, and 
 of the effects produced by this species of tempest, 
 when it assumes its most formidable character: — " An 
 extremely dark cloud, hanging low in the atmosphere, 
 and driven forward by a north wind, was observed to 
 cover the surface of the territory in which the small 
 town of Mirabeau is situated : it occasioned very sin- 
 gular appearances for about a league in length, and 
 
326 ON THE CAUSES AND PRINCIPLES 
 
 the half of that space in breath. Different whirhngs 
 appeared at once in this dark mass of condensed va- 
 pours; some hail fell, and thunder was heard; the 
 quickset hedge-rows, and most of the trees in the 
 vineyards, were rooted up; the httle river of Mira- 
 beau was carried more than sixty paces from its bed, 
 which remained dry; two men were enveloped in the 
 whirlwind, and carried to a distance without experi- 
 encing any injury; a young shepherd was lifted high 
 in the air, and thrown upon the banks of the river, 
 yet his fall was not violent, the whirlwind having placed 
 him on the verge where it ceased to act. In the woods 
 within its circle its effects were traced, by finding the 
 trees either twisted, or torn up by the roots. Some 
 sheep that were in the fields were enveloped and car- 
 ried to a distance; several of them were killed. It 
 unroofed the farm-houses; and after raging in this 
 manner for half an hour, the wind shifted to the south, 
 when the tempest immediately ceased." 
 
 The cause of the whirlwind is involved in still greater 
 obscurity than that of the hurricane. And the prin- 
 cipal difficulty lies in explaining how such a violent, 
 and rapid rotatory motion of the atmosphere, comes to 
 be all of a sudden produced. One mode in which it 
 has been accounted for is, " that the general stream 
 of the wind, in passing over a mountainous country, 
 is divided into a double current, each of which en- 
 countering the other at an angle, gives rise to that 
 violent spiral or whirling motion of the air denomi- 
 nated whirlwind." 
 
 This explanation we consider exceedingly unsatis- 
 factory. In the first place, it is not very apparent how 
 
OF METEOROLOGICAL PHENOMENA. 327 
 
 two converging currents meeting at an angle, after 
 having been separated by a mountain, should give rise 
 to the spiral or whirHng motion. One should rather 
 suppose that the collision of the two aerial currents, 
 would produce merely a thorough intermixture of the 
 atmospheric particles belonging to each of them, and 
 thereafter, a progressive motion of the united currents, 
 in a direction intermediate between those of the two 
 currents before they met. In the second place, if the 
 spiral or whirling motion was produced by the meeting 
 of two currents at an angle after passing on different 
 sides of a mountain, whirlwinds, instead of being very 
 rare phenomena, as they are, would occur frequently; 
 and would constantly make their appearance in the 
 same locality, whenever the wind happened to be blow- 
 ing in the direction, which caused the currents to meet 
 at the requisite angle. Now, what disproves the hypo- 
 thesis under consideration is, that no locality where 
 the terrific phenomena of the whirlwind frequently 
 present themselves, can be pointed out. Besides, 
 waterspouts at'sea, and moving pillars of sand in the 
 arid plains of Africa, which have been supposed to 
 depend upon similar causes with the whirlwind, make 
 their appearance where no mountains, supposed ne- 
 cessary to produce converging currents, are to be 
 found. 
 
 Others consider the whirlwind an electrical pheno- 
 menon, but they do not attempt to show how the 
 whirling motion of the air is produced by means of 
 electricity. Such an account of the matter, therefore, 
 communicates no information regarding the nature, or 
 origin of the point which is difficult to explain. 
 
328 ON THE CAUSES AND PRINCIPLES 
 
 If we were to venture upon advancing any hypo- 
 thesis in order to account for the nature of the whirl- 
 wind, we would ascribe it to local and sudden con- 
 densations of aqueous vapour, contained in an elec- 
 trified cloud. In the case of the whirlwind above 
 described by Abbe Richard, it was stated that " some 
 hail fell, and thunder was heard." It is therefore pre- 
 sumable, that the sudden condensation of part of the 
 aqueous vapour contained in the cloud, or possibly 
 perhaps in detached parts of the cloud, resulted from 
 the abstraction of the electric fluid at the time when 
 the thunder was heard. It was also stated, that the 
 extremely dark cloud supposed to give birth to the 
 whirlwind, appeared hanging low in the atmosphere. 
 The circumstance, however, of the condensed vapour 
 descending in the frozen form of hail, indicates that 
 the condensation of the aqueous vapour had taken 
 place at an altitude much higher than the base of the 
 cloud. Now, it is by no means improbable, that the 
 various whirlings that were seen at different places of 
 the cloud, resulted partly from local condensations of 
 the vesicles of the cloud into hail, and partly from the 
 condensation of the aqueous vapour in the lower part 
 of the cloud, together with the condensation of the 
 atmosphere underneath, in consequence of the cold- 
 ness communicated during the descent of the hail. 
 It is obvious that a sudden condensation of a portion 
 of the atmosphere thus produced, would occasion a 
 sudden rush of air from all directions towards the 
 centre of the cooled and contracted atmospheric co- 
 lumns. Provided the centre of condensation had been 
 stationary, the air rushing in, in all directions, would 
 
OF METEOROLOGICAL PHENOMENA. 329 
 
 meet in the centre, and no whirling motion would be 
 produced. But owing to the progression of the cloud, 
 and of the cooled atmospheric columns underneath, 
 the air rushing in from all directions, meets in such a 
 manner as to give rise to the whirling motion. Of 
 course, the more sudden the condensation of the 
 aqueous vapour and of the air underneath is, the 
 greater will be the force with which the surrounding 
 air will rush in to fill up the partial vacuity, and the 
 more rapid will be the rotatory motion communicated 
 to the converging currents. Such, in my opinion, is 
 the most probable manner, in which the spiral move- 
 ment of the atmosphere constituting the whirlwind is 
 produced. 
 
 It maybe objected to the above hypothesis, that, if 
 it were true, whirlwinds ought to accompany every 
 hailstorm, and even every thunderstorm. It is diffi- 
 cult to obviate this objection. But it is possible, 
 notwithstanding, that the whirlwind may be occasioned 
 as above explained. And the reason why they are 
 not of more frequent occurrence may be, that a cer- 
 tain relative rapidity of progression and of condensa- 
 tion of vapour, and a certain degree of previous den- 
 sity, size, depth, and electrization of cloud, must con- 
 cur, to cause the converging currents of air to meet 
 at the determinate angle necessary to produce the 
 rotatory motion. 
 
 Of the Waterspout or Syphon. — Similar causes to 
 those which produce a whirlwind on land, are con- 
 ceived to give rise to a waterspout at sea. It seems 
 to depend on some spiral movement, which originates 
 usually in a cloud of great density. When first ob- 
 
 2 T 
 
330 ON THE CAUSES AND PRINCIPLES 
 
 served to assume the appearance of a waterspout, it 
 resembles a dark cone hanging down from a very dense 
 cloud. As the cone extends itself downwards, the 
 sea underneath becomes very much agitated, and seems 
 to boil and foam up towards it. At length the cone 
 and sea underneath unite, and form one immense 
 tube, black at the borders, and white in the middle, 
 subjected to a rapid spiral movement, and extending 
 sometimes half a mile in length. This immense tube, 
 instead of remaining stationary, moves forward with 
 the progressive velocity of the wind; and along it a 
 great quantity of water in the form of spray, seems to 
 be whirled aloft with a rushing noise, and discharged 
 into the dark overhanging clouds. Towards the ter- 
 mination of this phenomenon, the black cloud draws 
 itself up in a ragged form, leaving, however, a thin 
 transparent tube, which reaches to the water where 
 this smoky appearance still continues. If the tube 
 separates in the middle, which not unfrequently hap- 
 pens, it gives way with a rushing noise, like that of a 
 cascade descending into a deep valley; and, in a short 
 time, the whole is dissipated in the clouds, or preci- 
 pitated in heavy rain. When a waterspout appears 
 overland, the dark cone suspended from the cloud 
 gradually extends itself downwards, and not unfre- 
 quently, in the end, discharges itself in very heavy 
 rain, which is found, upon examination, to be per- 
 fectly fresh, and like rain-water in general. 
 
 The force by which sea-water is carried up the tube 
 in the form of spray, is analogous to that by which 
 heavy bodies are uplifted by the whirlwind. When 
 a spiral movement is communicated to a given dia- 
 
OF METEOROLOGICAL PHENOMENA. 331 
 
 meter of atmospheric columns, a degree of rarefaction 
 in the interior of the moving columns, proportional 
 to the rapidity of the motion, is produced by the cen- 
 trifugal velocity. Accordingly, bodies getting within 
 the vortex of motion, will be carried along the tube 
 from where the centrifugal velocity is less, to where it 
 is greater. Hence, water may either be uphfted from 
 the sea to the cloud, or discharged from the cloud 
 to the sea, according as the centrifugal velocity of the 
 whirlwind increases from the sea towards the cloud, 
 or from the cloud towards the sea. The rising or 
 foaming up of the sea towards the cone, is the result 
 of atmospheric pressure forcing up the water into the 
 partial vacuity, formed by the centrifugal velocity of 
 the whirlwind. This force of course can only be sup- 
 posed to raise the w^ater in mass to the height of a 
 few feet. But even this degree of elevation must 
 expose it more completely to the force of the whirl- 
 wind, by which it is dashed into spray, and in this 
 divided form whirled aloft. 
 
 Of Pillm^s of Sand. — Another form in which the 
 whirlwind manifests its power, is in raising very light 
 sand, (such as is to be found in the arid plains of Af- 
 rica,) into the form of immense pillars subjected to a 
 whirling and progressive movement. Bruce describes 
 a remarkable exhibition of this kind, which he witness- 
 ed in his journey to Abyssinia. The description 
 however appears, by the more recent and more to be 
 relied on accounts of Burckhardt, to be somewhat ex- 
 aggerated. It is as follows : — " At one o'clock we 
 alighted among some acacia trees at Waadi el Hal- 
 boub, having gone twenty-one miles. We were here 
 
332 ON THE CAUSES AND PRINCIPLES 
 
 at once surprised and terrified, by a sight surely one 
 of the most magnificent in the world. In that vast 
 expanse of desert from west to north-west of us, we 
 saw a number of prodigious pillars of sand, at diff'erent 
 distances, at times moving with great velocity, at 
 others stalking on with majestic slowness. At inter- 
 vals we thought they were coming in a very few min- 
 utes to overwhelm us, and small quantities of sand 
 did actually more than once reach us ; again they 
 would retreat so as to be almost out of sight, their 
 tops reaching to the very clouds ; then the tops often 
 separated from the bodies, and these once disjoined, 
 dispersed in air and did not appear more ; sometimes 
 they were broken in the middle as if they were struck 
 by large cannon-shot. At noon they began to ad- 
 vance upon us with considerable swiftness, the wind be- 
 ing verystrong at north. Eleven ranged along the side 
 of us, about the distance of three miles j the greatest 
 diameter of the largest appeared to me at that dis- 
 tance, as if it would measure ten feet. They retired 
 from us with a wind at south-east, leaving an impres- 
 sion upon my mind to which I can give no name, 
 though surely one ingredient in it was fear, with a 
 considerable deal of wonder and astonishment. It 
 was in vain to think of flying ; the swiftest horse, or 
 fleetest sailing ship could be of no use to carry us out 
 of this danger; and the full conviction of this rivetted 
 me to the spot." 
 
 Of Hot Winds. — The winds usually included un- 
 der this head are the sirocco, the harmattan, and the 
 simoom. These winds have all a similar origin, and 
 possess the same characteristic qualities. 
 
OF METEOROLOGICAL PHENOMENA. 333 
 
 Of the Sirocco. — This wind blows from the deserts 
 lying to the south-west of Egypt. It is experienced 
 along the northern shores of Africa, all over the 
 Mediterranean sea, and even in Sicily, Italy, and 
 Spain. In an eastern direction it is experienced in 
 Egypt, Arabia, Persia, and even as far as Hindostan. 
 It is characterized by extreme dryness, and great heat. 
 The thermometer, even in Sicily, sometimes rises 
 during its continuance, as high as 110° of Fah. in the 
 shade. It is attended with a hazy obscurity in the 
 air, which causes the sun to appear of a blood-red 
 colour. This peculiarity seems to be owing to the 
 atmosphere being impregnated with an impalpable 
 powder, or extremely light sand, raised from thedeserts, 
 where this wind originates, and carried along with it ; 
 and which, during its continuance, is deposited on 
 the leaves of trees, and on the surface of all other 
 bodies exposed to it. Its effects upon the human 
 constitution, though usually much exaggerated, seem 
 to be to a certain extent deleterious. It in some 
 degree obstructs respiration, accelerates insensible 
 perspiration so much as to dry up all moisture from 
 the skin, and produces languor, and slight dejection 
 of spirits. As might be expected, its baneful influ- 
 ence is more felt in places near its source, than in 
 those at a distance. Thus along the northern shores 
 of Africa, its effects are stronger, than along the south- 
 ern shores of Europe. Its deleterious quahties seem 
 chiefly to depend upon its extreme dryness. Even at 
 Malta, after having passed over two hundred miles of 
 sea, this quality is supposed to be that which has the 
 greatest influence in rendering it unwholesome. In 
 
334 ON THE CAUSES AND PRINCIPLES 
 
 like manner at Madeira, the wind from the Great 
 Desert in Africa, which is similar to that of the sir- 
 occo, is so exceedingly dry, even after passing over 
 about two hundred miles of the Atlantic ocean, that 
 the nibs of pens, in consequence of its influence in 
 abstracting humidity from bodies, are bent in a re- 
 markable manner during its continuance. Its injuri- 
 ous eff"ects are best avoided by keeping as much with- 
 in doors as possible, and by frequently sprinkhng the 
 floors with water. 
 
 Of the Harmattan. — Harmattan is the name given 
 to a wind experienced on the coast of Guinea. As 
 it has probably the same source, and manifests similar 
 characteristic qualities with the sirocco above treated 
 of, it requires no farther description. 
 
 Of the Simoom. — The Simoom, or as it is some- 
 times called, the Kamsen, or the poisonous blast of 
 the desert, is the same wind as the sirocco experi- 
 enced in, or near the place where it originates. Its 
 characteristic qualities, viz., its dryness, warmth, and 
 impregnation with dust or sandy particles, are pre- 
 cisely the same as those of the sirocco, only some- 
 what increased, in consequence of being less mitigat- 
 ed by distant transportation. The deleterious eff"ects 
 of this wind appear to be more exaggerated and mis- 
 represented, than those of any other. For this the 
 following reasons may be assigned : — The sandy and 
 dusty surface of deserts exposed to the rays of a ver- 
 tical sun, becomes greatly warmer, especially during 
 the hottest period of the day, than the incumbent at- 
 mosphere. Hence, when wind suddenly springs up, 
 particularly about mid-day, in such locahties, the 
 
OF METEOROLOGICAL PHENOMENA. 335 
 
 clouds of heated dust thereby raised into the atmo- 
 sphere, communicate to the aerial current that sud- 
 den and great augmentation of temperature, and of 
 hygrometric dryness, which immediately and severely 
 affects the feelings, and even the health, of men and 
 animals exposed to it. Besides, in consequence of 
 the great augmentation of temperature, communicated 
 to the lower aerial strata by the rising of the heated 
 dust, lateral currents of colder air, (which in their 
 turn also become heated,) flow in underneath from all 
 directions, occasioning a sort of whirlwind, whereby the 
 dust is carried up to great altitudes in the atmosphere; 
 and thereafter transported by means of the aerial cur- 
 rent, before wholly descending, to great distances. 
 These observations explain the phenomena presented 
 by the Simoom, which, on reaching distant countries 
 in a mitigated form, has received the names of Si- 
 rocco, and Harmattan. They also, with the assist- 
 ance of the natural tendency to exaggerate whatever 
 is remarkable, afford a tolerably rational explanation 
 of all the exaggerated and marvellous statements, re- 
 garding the instantaneously morbific, and poisonous 
 qualities of the Simoom. 
 
 Burckhardt gives the following apparently true and 
 unexaggerated description of this wind : — " I never 
 observed that the simoom blows close to the ground, 
 as commonly supposed, but always observed the whole 
 atmosphere appear as if in a state of combustion. 
 The dust and sand are carried high into the air, 
 which assumes a reddish, or bluish, or yellowish tint, 
 according to the nature and colour of the ground 
 from which the dust arises. The yellow, however. 
 
336 ON THE CAUSES AND rillNCIPLES 
 
 always more or less predominates. In looking through 
 a glass, of a light yellow colour, one may form a 
 pretty correct idea of the appearance of the air, as I 
 observed it during a stormy simoom at Esne, in Up- 
 per Egypt, in May, 1813. The simoom is not always 
 accompanied by whirlwinds ; in its less violent de- 
 gree, it will blow for hours with httle force, although 
 with oppressive heat. When the whirlwind raises the 
 dust, it then increases several degrees in heat. In 
 the simoom at Esne, the thermometer mounted to 
 121° in the shade ; but the air seldom remains longer 
 than a quarter of an hour in that state, or longer than 
 the whirlwind lasts. The most disagreeable effect of 
 the simoom on man is, that it stops perspiration, dries 
 up the palate, and produces great restlessness. I 
 never saw any one lie down on his face to escape its 
 pernicious blast, as Bruce describes himself to have 
 done, in crossing the desert ; but during the whirl- 
 winds, the Arabs often hide their faces with their 
 cloaks, and kneel down near their camels, to prevent 
 the dust from hurting their eyes. Camels are always 
 much distressed, not by the heat, but by the sand 
 blowing into their large prominent eyes. They turn 
 round to endeavour to screen themselves by holding 
 down their heads : but this I never saw them do, ex- 
 cept in case of a whirlwind, however intense the heat 
 of the atmosphere might be. In June, 1813, going 
 from Esne to Siout, a violent simoom overtook me 
 upon the plain between Farshiout and Berdys. I was 
 quite alone, mounted upon a hght-footed hedjin. 
 When the whirlwind arose, neither house nor tree 
 was in sight j and while I was endeavouring to cover 
 
OF METEOROLOGICAL PHENOMENA. 3.37 
 
 my face with my handkerchief, the beast was made 
 unruly by the quantity of dust blown into its eyes, 
 and the terrible noise of the wind, and set off at a fu- 
 rious gallop. I lost the reins, and received a heavy 
 fall ; and not being able to see ten yards before me, 
 I remained wrapt up in my cloak on the spot where 
 I fell, until the wind abated, when pursuing my drome- 
 dary, I found it at a great distance, quietly standing 
 near a low shrub, the branches of which afforded some 
 shelter to its eyes." 
 
 Of the Characteristic Qualities of Winds. — The 
 qualities by which winds may be characterized, are 
 hot and dry ; cold and dry ; hot and moist ; cold and 
 moist ; and intermediate degrees. 
 
 Winds which come under the denomination of hot 
 and dry, are such as blow from an extent of heated land 
 parched up by long continued drought. The sirocco, 
 harmattan, and simoom, previously described, belong 
 to this class. One of the characteristics of these winds, 
 however, viz., that of being impregnated with dust 
 and sand, is not essential to the class under considera- 
 tion ; but arises from the accidental circumstance of 
 their blowing over a heated surface consisting of dust, 
 or very light sand. Such winds are exceedingly un- 
 wholesome. They dry the palate ; exhaust the body 
 of its juices ; produce languor, loss of appetite, rest- 
 lessness, and dejection of spirits ; and dispose the 
 human frame to suffer from ardent fevers, and bihous 
 disorders. Their deleterious influence is best guard- 
 ed against by keeping within doors as far as conveni- 
 ent ; by sprinkling the floors frequently with water ; 
 
 2u 
 
038 ON THE CAUSES AND PRINCIPLES 
 
 and by living upon an abstemious, cooling, and moist- 
 ening diet, during their continuance. 
 
 Winds which come under the denomination of 
 cold and dry, are such as blow, during cold weather, 
 from a cold towards a warm climate, over a great ex- 
 tent of land. On the continent of Europe, north and 
 north-east winds, and in the United States of Ame- 
 rica, north and north-west winds, during the coldest 
 period of the year, are usually of this description. 
 North-east winds experienced in Britain during spring, 
 though their characteristic qualities be somewhat mi- 
 tigated by crossing the German ocean, belong to this 
 class. Their piercing and refrigerating influence, is 
 partly owing to their thermometric coldness, and part- 
 ly to their dryness promoting evaporation, and there- 
 by carrying off heat more rapidly from the human 
 body, and all other moist surfaces. The influence of 
 garden walls in protecting fruit trees, and other vege- 
 table productions during cold weather, principally arises 
 from the shelter thereby afforded against the evapo- 
 rating influence of dry, undersaturated atmospheric 
 currents. 
 
 Winds remarkable for coldness and dryness, are 
 prolific of inflammatory diseases, such as sore throats, 
 tooth-achs, pleurisies, and coughs and colds. Long 
 exposure to them is peculiarly hurtful to asthmatic 
 people, being apt to bring on what is called an asth- 
 matic paroxysm. As exposure to such winds cannot 
 be avoided in cold climates, their baneful influence, 
 as well as that arising from cold in general, is best 
 guarded against by fortifying the body, by taking suf- 
 ficient exercise, and by being much in the open air. 
 
OF METEOROLOGICAL PHENOMENA. 339 
 
 To these means, one of the best auxiharies is the 
 cold bath, or if more convenient, bathing the body 
 every morning with a sponge and cold water, upon 
 getting out of bed. On the contrary, that which pro- 
 duces the greatest effect in relaxing the body, and 
 rendering it incapable of resisting cold impressions, 
 is, being much in warm apartments, particularly such 
 as are heated by crowds of human beings, as theatres 
 and concert-rooms. The injurious effects of such 
 crowded apartments might always be obviated, by the 
 free admission of fresh air, by allowing doors, or a 
 small portion of the upper part of windows to remain 
 open. What is called a draught of air which is so 
 absurdly dreaded, in place of being hurtful, is highly 
 beneficial even to those most exposed to it. Cold is 
 never hurtful unless it is felt disagreeable, and is only 
 hurtful in proportion as it is disagreeable. It is 
 questionable if, in such heated places, any individual 
 ever yet caught cold by exposure to a draught of air, 
 provided the temperature of the air, notwithstanding 
 the draught, remain in any considerable degree higher, 
 as it usually does, than that of sitting apartments in 
 dwelling-houses in general. Hundreds, on the other 
 hand, have lost their lives by the corporeal relaxation 
 induced by a heated apartment, rendering them in- 
 capable of withstanding every cold impression for se- 
 veral days thereafter, and which the free admission of 
 air would have, in a great measure, obviated. 
 1 Winds which come under the denomination of hot 
 and moist, are such as, during the warmest season of 
 the year, are accompanied with wet weather ; or such 
 as are experienced in sultry weather on the sea coast 
 
340 ON THE CAUSES AND PRINCIPLES 
 
 when the wind blows from the sea, and a warmer la- 
 titude. In all intertropical climates, the condition of 
 the atmosphere is uniformly hot and moist, during 
 what is called the Rainy season. In such climates, 
 this is also the sickly season, and that in which marsh 
 fevers prevail. It does not appear, however, that this 
 class of febrile diseases is produced by the immediate 
 influence of heat and moisture, for they never occur 
 at sea, miless infection has been previously imbibed 
 on shore. These diseases seem rather to be owing 
 to unknown volatile substances which emanate from 
 the soil, or from its vegetable productions, when sub- 
 jected to great heat and moisture. 
 
 In order to escape marsh-fevers, persons during the 
 sickly season in warm climates, particularly those re- 
 cently arrived from colder latitudes, should live tem- 
 perately, and beware of marshy, low-lying places. 
 They should also avoid going out, either during night, 
 or early in the morning; and their sleeping, as well 
 as sitting apartments, should be elevated above the 
 ground as far as convenient. 
 
 Winds which come under the denomination of cold 
 and moist, are such as prevail during wet weather in 
 high latitudes, or during rainy winter weather in tem- 
 perate latitudes; — such, also, as on the sea-coast blow 
 from the sea in high latitudes, even though the wea- 
 ther be dry. 
 
 An atmosphere unusually cold and moist, disposes 
 the human frame to suffer from dropsy, scrofula, and 
 other diseases that arise from relaxation, and want of 
 elasticity in the muscular fibre. Warm clothing, nour- 
 ishing and somewhat heating diet, and active exer- 
 
OF METEOROLOGICAL PHENOMENA. 341 
 
 cise, are in such circumstances the best guardians of 
 health. 
 
 The general influence of the prevaihng hygrometric 
 and thermometric condition of the atmosphere upon 
 the human constitution, may be deduced from a know- 
 ledge of the following facts. Atmospheric heat and 
 dryness, severally and conjointly, promote perspiration, 
 and, unless excessive, increase the elasticity and ac- 
 tivity of the body, and enliven the faculties of the 
 mind. On the contrary, atmospheric coldness and 
 dampness, severally and conjointly, obstruct perspira- 
 tion, and render the muscles of the body soft and 
 deficient in elasticity, and produce a dull, phlegmatic, 
 indolent temperament. Hence the general character 
 of nations, with regard to the natural constitution, and 
 temperament of body and mind, may, to a limited extent, 
 be understood, by merely being acquainted with the pre- 
 vailing hygrometric and thermometric conditions of the 
 atmosphere, to which they are subjected; and of these 
 a pretty accurate notion may be formed, from a geogra- 
 phical knowledge of the countries in which they reside. 
 
 It may also be remarked, that, owing to the powers 
 of the human constitution, in becoming fitted to en- 
 dure that to which it is accustomed, man is best adapted 
 for living in his native climate. And atmospheric con- 
 ditions, in proportion as they differ from those to which 
 he and his forefathers have been habituated, are usu- 
 ally more or less injurious to his constitution. If there 
 be any general exception to the preceding rule, it is, 
 that emigration to a warmer, and a more uniform cli- 
 mate, upon the approach of old age, promotes health, 
 and prolongs life. 
 
342 ON THE CAUSES AND PRINCIPLES 
 
 In general, those climates are to natives the health- 
 iest, and the most favourable to long life, in which the 
 atmospheric vicissitudes, with regard to heat and dry- 
 ness, are smallest and least sudden. Upon a similar 
 principle, the nearer the condition of the atmosphere, 
 with regard to heat and cold, and dryness and damp- 
 ness, is to the mean of what we have been most ac- 
 customed, it is the more salubrious. The increased 
 healthfulness, however, arising from such circumstan- 
 ces, is but very limited ; for, in proportion as the body 
 is less accustomed to thermometric and hygrometric 
 vicissitudes in the condition of the atmosphere, so 
 does it become less capable of bearing them. I have 
 been told by a person who long resided in the island 
 of Grenada, where the annual range of temperature 
 in the shade does not exceed 6°, that the human con- 
 stitution becomes so extremely sensitive to changes 
 of temperature, that a variation, even to the extent of 
 a single degree, is perceptibly felt by long residenters. 
 At Plymouth, which is situated on a neck of land in 
 the south-west of England, and very near the sea, in 
 all directions, except the north-east, the atmosphere 
 is usually mild, but very damp. I have been told that 
 the native inhabitants of this place and its neighbour- 
 hood, feel the coldness and dryness of north-east 
 winds during spring, much more severely than those 
 who reside in the more inland counties of England. 
 
 Of the uses of winds very httle need be said. As 
 a mechanical power, atmospheric currents have been 
 employed in propelling ships and windmills. As na- 
 tural agents, they are principally instrumental in mo- 
 derating the extremes of heat and cold, and in render- 
 
OF METEOROLOGICAL PHENOMENA. 343 
 
 ing the temperature more equal over the different 
 parts of the earth's surface. They are hkewise indis- 
 pensably necessary, as the means by which the land 
 is supplied with moisture evaporated from the ocean. 
 If their agency, in this respect, were all at once to 
 cease, the land would be soon converted into a barren 
 desert, where no vegetable production could exist, 
 and where man and all animals, for want of food, would 
 inevitably perish. 
 
CHAPTER IX. 
 
 ON PROGNOSTICATIONS OF THE WEATHER, WITH EXPLANA- 
 TIONS OF THE PRINCIPLES ON WHICH THEY DEPEND. 
 
 The attention paid to meteorological phenomena by 
 the mass of mankind in all ages and nations, has been 
 principally directed to the means of foretelhng the 
 changes, and character of the weather. With this 
 view, coincidences between certain kinds of weather, 
 and an endless variety of phenomena presented by 
 the celestial bodies, by clouds, and various other objects 
 in nature, both mineral and vegetable, together with 
 the cries and instinctive movements of animals, in- 
 cluding birds, beasts, fishes, insects, and reptiles, have 
 all been faithfully observed and recorded. And these, 
 without any inquiry as to the cause, nature, and ex- 
 tent of the coincidences, have been severally promul- 
 gated by their authors, as infallible indicators of the 
 forthcoming weather. 
 
 As we proceed, we will notice the more important 
 means by which the weather may, with more or less 
 probability, be foretold ; but for the sake of brevity, 
 will allow the mass of rubbish heaped upon this de- 
 partment of meteorological science, to remain un- 
 molested. 
 
 Of Prognostications founded on past Experience. — 
 In all intertropical climates, the returns of certain kinds 
 of weather are periodical. In such climates therefore, 
 
ON THE CAUSES AND PRINCIPLES, &C. 345 
 
 ail that is necessary by way of prognostication, is to 
 observe, and record the character of the weather that 
 usually prevails, during the different seasons of the 
 year. But though past experience may enable us to 
 predict within a few days of the time of the year, 
 when the rainy reason will commence and terminate; 
 it does not give us such precise information, as will 
 enable us to foretell the precise day on which such 
 events will occur. In like manner, though past ex- 
 perience may enable us in hot climates, to predict the 
 general character of the weather in any season of the 
 year, still it does not give such precise information as 
 will enable us to foretell that it will rain at any parti- 
 cular hour of a certain day, during the rainy season ; 
 though we may be able to predict with certainty, that 
 at that season of the year, the general character of the 
 weather will be wet. 
 
 As we recede beyond the tropics, the periodic re- 
 turns of certain kinds of weather are less regular, and 
 less to be depended upon. Notwithstanding, in all 
 climates, there is more or less similarity in the kind 
 of weather that occurs at certain seasons. And in 
 certain climates, and in particular times of the year, 
 periodic returns of the same description of weather, 
 are more regular than in others. In all climates there- 
 fore, but especially within the tropics, and also in all 
 inland countries in temperate and high latitudes, past 
 experience carefully recorded and averaged for a suc- 
 cession of years, is the best means of foretelling the 
 weather; and that from which the longest foreknow- 
 ledge may be derived. 
 
 Of Barometrical Prognosticatio7is. — Of all the in* 
 2x 
 
346 ON THE CAUSES AND PRINCIPLES 
 
 struments that have been employed for predicting the 
 weather, the barometer, or as it is sometimes called, 
 the weatherglass, is unquestionably the best. In 
 reality, it only intimates the atmospheric pressure, at 
 the time and place of observation. But the variations 
 in the atmospheric pressure have been found upon 
 comparing coincidences, to be very much connected 
 with the changes of weather. The following table, 
 which was formerly inserted, gives the mean annual 
 height of the barometer at the level of the sea, in four 
 different places. 
 
 Mean Baro- 
 Places Latitude. metrical 
 
 Pressure. 
 
 Calcutta ..... 22° 35' 29.776 
 
 London 31 31 29.827 
 
 Edinburgh 55 56 29.835 
 
 Melville Island . . . . 74 30 29.884 
 
 The annual range of the barometer is least within 
 the tropics, next least within the polar regions, and 
 greatest between the latitudes of 30° and 60°, where 
 the annual variations of temperature, and of humidity 
 in the atmosphere, upon which its oscillations depend, 
 are also greatest. 
 
 The following table of the mean annual range of 
 the barometer in a variety of places, confirms the pre- 
 ceding statement. 
 
 p, Mean annual range 
 
 ^^^'^^^- of the Barometer. 
 
 Quito . . . S. lat. 0" 13' about 1 line. 
 
 Peru . . . 1 of an inch. 
 
 Calcutta . . . N. lat. 22 35 | an inch. 
 
 Kathmandu . . lat. 27 30 .85 inch. 
 
 Capital of Japan . -.■ lat. 32 43 .85 do. 
 
OF METEOROLOGICAL PHENOMENA. 347 
 
 Places. 
 
 
 
 Mean annual ranjje 
 of the Barometer. 
 
 Paris 
 
 lat. 
 
 , 48° 50' 
 
 .1| inch. 
 
 Great Britain averaged . 
 
 
 
 2 inches.. 
 
 Petersburgh 
 
 lat. 
 
 59 56 
 
 2i do. 
 
 Melville Island . 
 
 lat. 
 
 74 30 
 
 1.86 inch. 
 
 The following are the principal rules, whereby the 
 weather may be prognosticated with more or less pro- 
 bability of being correct, by means of the barometer. 
 
 1st, A high steady state of the barometer, indicates 
 dry, calm, clear weather; being usually attended with 
 great heat in summer, and hard frost in winter. On 
 the contrary, a low and fluctuating state of the baro- 
 meter, indicates cloudy, wet, and windy weather; be- 
 ing usually attended by coldness for the season of the 
 year during summer, and mildness during winter. 
 
 2(1, When the barometer rises very rapidly to a 
 considerable height, it seldom remains long without 
 falling. And on the contrary, when it falls much and 
 rapidly, it seldom remains long without rising. Hence 
 such rapid variations in height indicate very change- 
 able weather, such as one day wet and windy, and 
 another dry and calm. The day when the barometer 
 sinks rapidly being usually cloudy, wet, and windy ; 
 the day when it rises rapidly, being usually clear, dry, 
 and calm. 
 
 3d, The barometer usually sinks lowest, and with 
 greatest rapidity, immediately previous to, and during 
 the continuance of very high winds ; and it continues 
 to sink so long as the velocity of the wind is increas- 
 ing ; but it begins always to rise, and that generally 
 with considerable rapidity, a short time before the wind 
 abates. 
 
348 ON THE CAUSES AND TRINCIPLES 
 
 4^/i, When the barometer rises very slowly and 
 steadily, it indicates that it will continue high, and 
 without much fluctuation, for a length of time. Hence 
 it prognosticates a continuance of calm, dry weather. 
 
 5//i, The barometer usually rises slightly when the 
 wind changes from a warm to a cold direction ; and 
 on the contrary, sinks when it changes from a cold to 
 a warm direction. Thus when the wind shifts from 
 south-west to north-east during winter, it usually 
 rises, and generally begins to do so before the change 
 of wind actually takes place j but when it shifts from 
 north-east to south-west during the same season of 
 the year, it usually falls. The former of these 
 changes commonly produces dry weather ; the latter, 
 rain. 
 
 Qth, A long continuance of a high state of the 
 barometer, is usually followed by a correspondingly 
 long continuance of a low state, and the contrary. 
 Hence the former of these barometrical conditions, 
 which is usually attended with calm, dry weather, 
 prognosticates a continuance of wet, and somewhat 
 windy weather, so soon as the change takes place. 
 And on the other hand, the latter of these conditions 
 prognosticates a continuance of dry, calm weather, 
 after the change of weather has taken place. 
 
 All the preceding rules show the great utility of a 
 barometer at sea, in order to foretell the propriety of 
 taking in sail, or the contrary, especially upon the ap- 
 proach, or during the continuance of night, when other 
 signs of wind cannot be so well observed. Indeed so 
 useful is this instrument for the above purposes, that 
 no vessel ought to be allowed to sail in temperate 
 
OF METEOROLOGICAL PHENOMENA. 349 
 
 latitudes, where the barometrical indications are strong- 
 est, without one. 
 
 How the sinkings, and risings, and different heights 
 of the barometer, prognosticate wet and dry weather 
 according to the preceding rules, has been conceived 
 to be of difficult explanation. The chief reason, how- 
 ever, appears to be, that windy and calm weather, and 
 also to a certain extent the direction of the wind, 
 upon which wet and dry weather so much depend, 
 may be thereby with more or less certainty prognosti- 
 cated. 
 
 Near the end of the third chapter we explained the 
 reasons, (and they need not be here repeated,) why 
 windy weather is peculiarly productive of clouds and 
 rain ; and why a prevailing stillness in the atmosphere 
 is favourable to dry weather, and a cloudless sky. The 
 difficulty therefore chiefly lies in explaining, how the 
 different heights, and fluctuations in the barometer, 
 indicate the variations in the direction and velocity of 
 the wind. 
 
 From comparing the range and fluctuations of the 
 barometer in different latitudes and localities, with the 
 annual range and vicissitudes of temperature, it is ob- 
 vious, that the former are in a great measure depend- 
 ent upon the latter. Thus, between the 50th and 
 60th parallels of latitude, where the annual range of 
 temperature is greatest, the barometrical range is also 
 greatest. And in localities having a great extent of 
 land in one direction, and of sea in the other, which 
 in general are the situations where the most sudden 
 and frequent vicissitudes of temperature occur, the 
 
350 ON THE CAUSES AND PRINCIPLES 
 
 barometer is likewise subject to the most sudden, and 
 frequent fluctuations in height. 
 
 It may be easily conceived how great and sudden 
 variations of temperature, produce corresponding fluc- 
 tuations in the barometer. Thus, if a reduction of 
 temperature be going on with rapidity over a large 
 extent of the earth's surface, while, in those which 
 are contiguous, a comparatively trifling reduction of 
 temperature is taking place, an atmospheric current 
 in the higher regions of the air will be generated, 
 from where the reduction of temperature is less, to 
 where it is greater. This will occasion an accumula- 
 tion of atmosphere, and an increased barometrical 
 pressure all over the region where the atmosphere has 
 undergone the greatest reduction of temperature. 
 The consequence will be, that a current in the lower 
 half of the atmosphere will ultimately be generated, 
 from the region of the earth where the barometrical 
 pressure has increased, to where it has decreased. 
 Owing, however, to the vis inertia of air, this latter 
 current does not originate, till the barometrical pres- 
 sure in the cold region, has become considerably 
 greater, than what it is in those regions towards which 
 the wind is about to blow. When the vis inertia, 
 however, is overcome, and the air has begun to move 
 in the direction from where the barometrical pressure 
 is greater, to where it is less, it gradually acquires an 
 increased velocity, in consequence of being subjected 
 to a constant pressure, for a length of time, in one 
 direction. Hence, a withdrawal of air is occasioned 
 from the region where accumulation previously ex- 
 isted J and before the acquired velocity of the aerial 
 
OF METEOROLOGICAL PHENOMENA. 351 
 
 current is checked by the reacting accumulation, and 
 increased barometrical pressure of the atmosphere, 
 the barometer sinks in consequence of the withdrawal 
 of air, as much below the mean height, as it previous- 
 ly stood above it. It is obvious likewise, that the 
 larger the extent of surface over which atmospheric 
 accumulation and increased barometrical pressure 
 take place, and the greater the degree in which they 
 do take place, the subsequent withdrawal of air, and 
 sinking of the barometer, and the reacting velocity of 
 the atmospheric current when at its maximum, will be 
 proportionally greater. In short, the alternate increase 
 and decrease in the atmospheric pressure in different 
 regions, as indicated by the alternate rising and sink- 
 ing of the barometer ; and the different degrees in 
 the velocity of the wind, by which these atmospheric 
 accumulations and depressions are reciprocally main- 
 tained between a warm and a colder climate, are ana- 
 logous to the oscillations of a pendulum. The higher 
 the pendulum is drawn from the perpendicular on the 
 one side, the higher it subsequently rises on the 
 other, and the more rapid is its motion through the 
 intermediate space. 
 
 Such is an explanation of the manner in which 
 great and rapid variations of temperature, w^hen spread 
 over a large extent of surface, alternately occasion 
 proportionate risings and sinkings of the barometer, 
 above and below its mean height; and which are ac- 
 companied with a proportionate velocity of wind in 
 the lower half of the atmosphere, blowing alternately 
 from a warm towards a cold, and from a cold towards 
 a warm climate. 
 
3-52 ON THE CAUSES AND PRINCIPLES 
 
 Simultaneous variations in the height of the baro- 
 meter in different places, are also occasioned by the 
 unequal evaporation of moisture from different parts 
 of the earth's surface, and likewise (and in a greater 
 degree, in consequence of its greater rapidity,) by the 
 unequal return of that moisture to the earth in the 
 form of rain. And these variations in the height of 
 the barometer produce winds, the velocity of which 
 is proportional to the difference of barometrical pres- 
 sure in different places, by which they are occasioned; 
 together with the acquired velocity, in consequence 
 of the preponderance of barometrical pressure being 
 for a length of time in the same direction. 
 
 When treating of irregular winds, in the eighth chap- 
 ter, it was explained how the falhng of rain had a local 
 influence in diminishing the barometrical pressure, so 
 as to produce wind. If, therefore, the precipitation 
 of moisture to the earth's surface, in the form of rain, 
 be proceeding with rapidity, in any part of the course 
 of an atmospheric current, in its progress from a warm 
 towards a cold climate, a sinking of the barometer is 
 necessarily occasioned, and an increased velocity in 
 the atmospheric current, towards where the rain is 
 falling, is produced. In fact, the sinking of the baro- 
 meter is frequently partly occasioned by the falling of 
 rain, either where the sinking of the barometer occurs, 
 or in some country not very distant. In the latter 
 case, wind, and subsequently rain, may be occasioned, 
 by the propagation of a similar sinking of the baro- 
 meter in all directions. Supposing, therefore, the 
 wind blowing gently from a warm towards a cold cli- 
 mate, such as from the south-west, during winter, 
 
OF METEOROLOGICAL PHENOMENA. 353 
 
 towards Great Britain, and the western shores of 
 Europe, the falhng of rain, in any part of its course, 
 sHghtly sinks the barometer where it takes place. 
 This increases the velocity of the wind, and the sink- 
 ing of the barometer is thereby propagated. Hence 
 the amount of rain in a given space is not only in- 
 creased, but the boundaries of the region where rainy 
 weather occurs is extended. This farther increases 
 the velocity of the atmospheric current, and the sink- 
 ino; of the barometer, in the direction from whence 
 the wind blows. From these observations it appears, 
 that in any given district, the sinking of the barome- 
 ter, and any augmentation thereof, may be either a 
 concomitant of the falling of rain, from which it re- 
 sults, or may indicate that falling of rain has already 
 begun in some other quarter towards which the wind 
 is blowing ; and that it may soon extend over the 
 whole region where wind has been excited, and the 
 sinking of the barometer propagated. 
 
 Again, the sinking or rising of the barometer indi- 
 cates whether the wind blows from a warm or a cold 
 climate. Thus it sinks when it shifts from a cold to 
 a warm direction, and usually continues low while it 
 blows from the latter. This has been supposed to be 
 owing to the air from a warm direction containing a 
 larger amount of aqueous vapour, (the specific gravi- 
 ty of which, compared with air, is as 5 to 8,) than 
 the air from a cold direction. The chief reason, how- 
 ever, is the diminution of barometrical pressure, re- 
 sulting from the general and widely extended falling 
 of rain, which occurs when the wind blows from a 
 warm towards a cold climate. On the other hand, 
 
 2 Y 
 
354 ON THE CAUSES AND PRINCIPLES 
 
 when the wind shifts from a warm to a cold direction, 
 the barometer usually rises, and generally continues 
 high so long as it blows from the latter. The reason 
 of this is, that when the wind blows from a cold to a 
 warm climate, it does so in consequence of a widely 
 extended accumulation of atmosphere, and increased 
 barometrical pressure, in colder regions. And as little 
 or no rain falls when the wind blows from a cold 
 towards a warm climate, no sinking of the barometer 
 is thereby occasioned. And for the same reason, its 
 progressive velocity is very seldom above ordinary ; 
 and not unfrequently so very slow, as hardly to be 
 perceptible. 
 
 The low state of the barometer, during very high 
 winds, has also been supposed to be partly owing to 
 the circumstance of the atmosphere being prevented 
 by its progressive, or if you choose, centrifugal ve- 
 locity, from exerting its full perpendicular pressure 
 upon the mercury in the basin of the barometer. And 
 on the contrary, the greater than the usual height of 
 the barometer, during very still weather, has been sup- 
 posed to be partly owing to the perpendicular atmo- 
 spheric pressure being then fully exerted. 
 
 The preceding observations enable us to under- 
 stand how the direction and force of the wind, and 
 consequently, how the weather is indicated and prog- 
 nosticated by the variations in the height of the baro- 
 meter. We may apply them to the explanation of 
 the rules which we have given for prognosticating the 
 weather by means of that instrument : — 
 
 Rule \st. A high steady state of the barometer in- 
 dicates dry, calm, clear weather, being usually attended 
 
OF METEOROLOGICAL PHENOMENA. 355 
 
 with great heat in summer, and hard frost in winter. 
 On the contrary, a low and fluctuating state of the 
 barometer indicates cloudy, wet, and windy weather ; 
 being usually attended by coldness, for the season of 
 the year, during summer, and mildness during winter. 
 If a low state of the barometer, or in other words, 
 if the atmospheric pressure, in any quarter of the 
 world, be less than ordinary, it is obvious that atmo- 
 spheric currents, in the lower half of the atmosphere, 
 must blow thither from where the barometer stands at 
 the mean height, or above it. Hence a low state of 
 the barometer, if the weather be calm, prognosticates 
 wind ; and if the weather be moderately calm, indi- 
 cates an increase of wind. If the direction of the 
 wind so occasioned be from a warm towards a com- 
 paratively cold climate, the temperature of the atmo- 
 sphere, and its capacity for humidity, will be gradually 
 reduced in its progress thither. Hence the formation 
 of clouds, and the subsequent falling of rain, agreeably 
 to the third cause of the formation of clouds, stated 
 in the third chapter, must ensue. On the contrary, 
 if the barometer stands much higher than ordinary, in 
 any quarter of the world, no aerial current, either in 
 the upper or under half of the atmosphere, can be ex- 
 pected to blow thither. And as a cold atmosphere 
 cannot, in such circumstances, be brought to rest over 
 a warm one, nor a warm atmosphere be transported 
 to a cold climate, which are the chief causes of the 
 formation of clouds, few or no clouds can, in such 
 circumstances be formed. Hence such a state of the 
 barometer indicates dry weather. When this state of 
 the barometer continues steady for a length of time. 
 
056 ON THE CAUSES AND PRINCIPLES 
 
 it indicates that equality in the atmospheric tempera- 
 ture, and the causes by which it is produced, are nearly 
 equal for a great distance around. And as wind re- 
 sults chiefly from great inequalities of temperature, in 
 places within a limited distance of each other, the cir- 
 cumstance of the barometer being steadily high for a 
 length of time, indicates the existence of circum- 
 stances favourable for producing dry, calm weather. 
 
 Rule 2d. When the barometer rises very rapidly to 
 a considerable height, it seldom remains long without 
 falling. And on the contrary, when it falls much and 
 rapidly, it seldom remains long without rising. Hence 
 such rapid variations in height indicate very change- 
 able weather, such as one day wet and windy, and 
 another dry and calm. The day, when the barometer 
 sinks rapidly, being usually cloudy, wet, and windy ; 
 the day, when it rises rapidly, being usually clear, dry, 
 and calm. 
 
 Upon this rule it may be remarked, that rapid fluc- 
 tuations in the height of the barometer, result from 
 changes in the atmospheric temperature going on with 
 very different degrees of rapidity, in places within a 
 limited distance of each other. In fact, the risings 
 and sinkings of the barometer in such cases, usually 
 result from the alternate accumulations, and corre- 
 sponding depressions of the atmosphere in warm and 
 in cold climates, which we formerly explained by the 
 analogous oscillations of a pendulum. When the wind 
 blows from the warm towards the cold district, rain 
 usually falls, and the velocity of the wind being there- 
 by augmented, the barometer stands low. So soon, 
 however, as atmospheric accumulation begins to take 
 
OF METEOROLOGICAL PHENOMENA. 357 
 
 place in the cold district, the velocity of the wind 
 gradually diminishes, till it entirely ceases. Subse- 
 quently reaction ensues from the cold towards the 
 warm district. And this agreeably to what was for- 
 merly stated, when treating of the formation of clouds, 
 is the direction which produces dryness, and conse- 
 quently is usually attended only by moderate or little 
 velocity in the atmospheric current. 
 
 Rule 3d. The barometer usually sinks lowest, and 
 with greatest rapidity, immediately previous to, and 
 during the continuance of very high winds ; and it 
 continues to sink so long as the velocity of the wind 
 is increasing ; but it begins always to rise, and that 
 generally with considerable rapidity, a short time be- 
 fore the wind abates. 
 
 We need only remark upon this rule, that the velo- 
 city of the wind increases in proportion as the baro- 
 metrical pressure in two different places is greater. 
 Wind being dependent upon the difference of baro- 
 metrical pressure in two different places, its velocity 
 augments, and the barometer sinks, as that difference 
 increases. The reason why the barometer in such 
 cases begins to rise, and that generally with consider- 
 able rapidity before the wind abates, is owing to the 
 atmospheric equilibrium being somewhat restored by 
 the influx of air, before the acquired velocity of the 
 atmospheric current is checked. 
 
 Rule Ath. When the barometer rises very slowly 
 and steadily, it indicates that it will continue high, 
 and without much fluctuation for a length of time. 
 Hence it prognosticates a continuance of calm, dry 
 weather. 
 
358 ON THE CAUSES AND PRINCIPLES 
 
 In explanation of this rule it may be remarked, 
 that the slow rising of the barometer indicates that 
 the atmospheric temperature is undergoing little al- 
 teration, and is getting somewhat assimilated to a 
 great distance around the place of observation. Such 
 a condition of the aerial temperature produces atmo- 
 spheric stillness ; and atmospheric stillness, as was 
 formerly explained, is favourable to the existence of 
 dry weather, and a cloudless sky. 
 
 Bide 5th. The barometer usually rises when the 
 wind changes from a warm to a cold direction ; and 
 on the contrary, sinks when it changes from a cold to 
 a warm direction. Thus when the wind shifts from 
 south-west to north-east during winter, it usually rises, 
 and generally begins to do so before the change of 
 wind actually takes place j but when it shifts from 
 north-east to south-west during the same season of 
 the year, it usually falls. The former of these changes 
 commonly produces dry weather; the latter, rain. 
 
 In explanation of this rule it may be remarked, 
 that when the wind shifts to the north-east during the 
 winter season, it is owing to a gradual accumulation 
 of atmosphere in colder latitudes. Accordingly, be- 
 fore the acquired velocity of the wind from a warm 
 direction is checked, the atmospheric equilibrium, 
 except for the acquired velocity, is somewhat restored; 
 and hence the reason that the barometer usually be- 
 gins to rise before the change of wind takes place ; 
 and consequently foretells that event. Farther, as a 
 wind from a cold direction is usually not only much 
 undersaturated with regard to humidity, and becom- 
 ing gradually more so in its progress, but is also un- 
 
OF METEOROLOGICAL PHENOMENA. 359 
 
 favourable for those intermixtures of the aerial strata 
 which produce clouds, a rising of the barometer when 
 the wind is out of the south, or south-west during 
 winter, prognosticates, not only a change in its direc- 
 tion, but also dry weather. And the falhng of rain 
 which attends a wind from a warm climate, such as a 
 south-west wind in Britain during winter, is the chief 
 reason of its greater velocity, and of the less barome- 
 trical pressure it exhibits, than a wind from the north- 
 east, which is usually accompanied by dry weather 
 during the same season of the year. 
 
 Rule 6th. A long continuance of a high state of 
 the barometer, is usually followed by a corresponding- 
 ly long continuance of a low state ; and the contrary. 
 Hence, the former of these barometrical conditions, 
 which is usually attended with calm, dry weather, prog- 
 nosticates a continuance of wet, and somewhat windy 
 weather, so soon as the change takes place. And on 
 the other hand, the latter of these conditions prognos- 
 ticates a continuance of dry, calm weather, after the 
 change has taken place. 
 
 The causes which produce the results stated in the 
 preceding rule, are not, and never will be, properly 
 understood, until the simultaneous direction and 
 force of the wind, together with the temperature and 
 height of the barometer in a great variety of distant 
 places, can be compared with each other, so that con- 
 clusions may be therefrom deduced. It may be re- 
 marked, however, that as a continued low state of the 
 barometer is usually concomitant with rainy, and 
 somewhat windy weather, the direction of the wind 
 being for the most part from a warm climate, such a 
 
360 ON THE CAUSES AND PRINCIPLES 
 
 State of the atmosphere with regard to weight, tem- 
 perature, and humidity, is ultimately produced in those 
 regions, where it has continued for a length of time 
 to blow towards, as causes the atmospheric current to 
 assume a contrary dry direction, for a somewhat pro- 
 portional period of time. Hence the proverbial rule 
 for prognosticating the weather : " Long fair, long 
 foul ;" and the contrary. 
 
 Of Prognostications of the Weather hy means of 
 Hygrometers. — The principle according to which the 
 mass of hygrometers have been constructed is, that a 
 certain degree of affinity between moisture and air, 
 and moisture and many other substances exists. And 
 that one substance attracts another for which it has an 
 affinity, with proportionally less force, according as it 
 is more nearly saturated with it. Thus, a hair, or a 
 piece of catgut, or packthread, may be used for hy- 
 grometric purposes. Each of these substances, as 
 well as most others, exerts a certain degree of attrac- 
 tion for moisture. Accordingly, as the air gets more 
 nearly saturated, and exerts a proportionally less at- 
 tractive force for humidity, those substances absorb 
 a greater amount of moisture ; and in doing so, ex- 
 pand in thickness, but diminish in length. On the 
 other hand, when the air becomes drier than usual, 
 and exerts a proportionally stronger attraction for 
 moisture, a portion of humidity is abstracted from 
 those bodies ; and this, while it diminishes their 
 thickness, increases their length. Hence the length 
 of such, or similar substances, fitted up and adjusted 
 to a scale of equal parts, according to various me- 
 chanical contrivances, has been employed as a mea- 
 
OF METEOROLOGICAL PHENOMENA. 361 
 
 surer of the dryness, and dampness of the atmo- 
 sphere. 
 
 The different degrees of rapidity with which mois- 
 ture evaporates, and reduces the temperature of the 
 evaporating surface, according to the state of the at- 
 mosphere with regard to humidity, is another prin- 
 ciple upon which hygrometers have been constructed. 
 But as we do not mean to describe meteorological 
 instruments generally, we need not farther enlarge 
 upon this point. 
 
 Our object in making remarks upon hygrometric 
 instruments is, that if the principles of their construc- 
 tion be understood, a great mass of weather indica- 
 tions held in esteem by the more ignorant part of the 
 population, and which depend upon the same prin- 
 ciples, become intelligible. 
 
 In the first and third chapters, the reasons were ex- 
 plained why a wind blowing from a warm towards a 
 cold chmate, though previously much undersaturated 
 with humidity, gradually approached the point of sa- 
 turation ; and it was farther explained how, by con- 
 tinuing in the same direction, clouds and rain were 
 ultimately produced. It was also explained, how, 
 when the wind shifted from a warm to a cold direc- 
 tion, the air soon becomes undersaturated with mois- 
 ture ; and how clouds previously formed have a tend- 
 ency in such circumstances to dissolve by evapora- 
 tion, and dry, clear weather ensues. Hence, hygro- 
 meters, by indicating the existing dryness or damp- 
 ness of the atmosphere, give information (though not 
 always accurately,) whether the wind be in a direction 
 favourable to the formation, or the dissolution of 
 
 2z 
 
362 ON THE CAUSES AND PRINCIPLES 
 
 clouds ; and consequently, afford a means by which 
 wet or dry weather may, to a limited extent, be prog- 
 nosticated. And supposing the hygrometer to indi- 
 cate great atmospheric dryness, even though the wind 
 should shift to a warm and rainy direction, it may take 
 one, two, or perhaps three days, before the reduction 
 of the temperature of the air consequent upon its 
 transportation to a colder climate, causes it to become 
 sufficiently damp, and before enough of moisture be 
 precipitated into the form of clouds, to occasion rain. 
 
 The great mass of what are called signs of fair, or 
 of wet weather, depend upon hygrometric principles. 
 Thus, a difficulty of opening windows, window-shut- 
 ters, and doors, and of drawing out wooden pegs, 
 have been considered signs of wet weather. The rea- 
 son is, wood, like all other hygrometric substances, 
 absorbs moisture, and expands in bulk as the air be- 
 comes damper. 
 
 In hke manner, the dampness, or sweating, as it is 
 called, of certain stones, chiefly such as contain saline 
 ingredients j and also the unusual dampness of salt, 
 are considered indications of wet weather ; and on the 
 contrary, their dryness indicates dry weather. The 
 reason is, such bodies, like hygrometric substances in 
 general, attract more moisture from the atmosphere, 
 according as it is nearer the point of saturation. 
 
 The peculiar cries and instinctive movements of 
 birds, beasts, insects, and reptiles, which have been 
 considered indications of wet and of dry weather, all 
 result from agreeable or disagreeable sensations by 
 which such animals are affected, when the state of the 
 atmosphere is hygrometrically dry, or damp. In reality, 
 
OF METEOROLOGICAL PHENOMENA. 363 
 
 the animals themselves know nothing of the cause of 
 the agreeable or disagreeable sensations, by which 
 they are affected. And though they manifest those 
 sensations by peculiar cries, and instinctive move- 
 ments, they possess no foreknowledge of the weather. 
 
 In like manner, persons subject to rheumatism, and 
 other complaints, become affected probably upon hy- 
 grometric principles, with their constitutional diseases, 
 when the atmosphere becomes damp ; and feel re- 
 lieved upon the return of dry weather. Such persons 
 may be considered living hygrometers. 
 
 Indeed, when it is considered, that perspiration is 
 more or less obstructed by increased dampness, and 
 that the feathers of birds, and the hair covering the 
 skin of beasts, as well as the muscular fibres of ani- 
 mals in general, are all better or worse hygrometers ; 
 it is no wonder that variations in the dryness or damp- 
 ness of the atmosphere, should give rise to agreeable 
 or disagreeable sensations. Nevertheless, as proper- 
 ly constructed hygrometric instruments, afford com- 
 paratively, much more accurate means of ascertaining 
 the different degrees of atmospheric dryness and 
 dampness ; and as all the subsequently mentioned in- 
 dications of wet or dry weather, are merely less per- 
 fect, and less precise methods of giving us similar in- 
 formation, they need be no longer regarded as wea- 
 ther prognosticators. 
 
 It may be remarked, however, that as hygrometers 
 only give information regarding the dryness and damp- 
 ness of the lower atmospheric strata by which they are 
 immediately surrounded, and which are affected by all 
 the vicissitudes of temperature which occur during 
 
3G4 OiN THE CAUSES AND PRINCIPLES 
 
 the alternations of day and night, they must be re- 
 garded, even when constructed upon the most im- 
 proved principles, as very imperfect instruments for 
 prognosticating the weather, which chiefly depends 
 upon changes going on in the elevated regions of the 
 atmosphere. They are also subject to another defect. 
 Like all other sohd bodies, they absorb radiating 
 caloric, and accordingly, grow warm more rapidly than 
 the atmosphere, when temperature is on the increase ; 
 and on the other hand, radiate caloric, and grow cold 
 more rapidly than the atmosphere, when temperature 
 is on the decrease. In the former case, they over- 
 indicate the dryness of the atmosphere ; in the latter, 
 they over-indicate its dampness. On these accounts 
 it has been frequently observed, that hygrometers 
 have indicated a considerable degree of dryness, par- 
 ticularly during day and summer, when rain of long 
 continuance was about to commence. And on the 
 other hand, they have frequently indicated a great de- 
 gree of dampness, and accordingly, have erroneously 
 prognosticated wet weather, particularly upon the ap- 
 proach, and during the continuance of night, when 
 atmospheric stillness, a cloudless sky, and a high 
 settled state of the barometer, gave us every assurance 
 of the continuance of dry weather. 
 
 Of the Prognostications of the Weather hy the ap- 
 pearances of clouds, — 1. When clouds are observed 
 to break up into fragments, and gradually to dissolve 
 by evaporation, it indicates that the region of the at- 
 mosphere in which they float is undersaturated with 
 moisture, and prognosticates dry weather. On the 
 contrary, after a continuance of dry weather, when 
 
OF METEOROLOGICAL PHENOMENA. 365 
 
 clouds are observed to form ; or when previously 
 formed, are observed to increase in bulk and density ; 
 and also when small detached clouds unite together 
 and form larger clouds, it indicates that the causes 
 immediately instrumental in the formation of clouds 
 are in operation, and prognosticates that wet weather 
 will soon follow. Indeed, the hygrometric condition 
 of the elevated regions of the atmosphere in which 
 clouds are formed, and whether causes favourable to 
 their formation or dissolution, and consequently, 
 whether causes favourable to subsequent wet or dry 
 weather, are then in operation, may with great cer- 
 tainty be prognosticated, by observing whether, and 
 with what rapidity, previously formed clouds, particu- 
 larly those of the fleecy kind, dissolve by evaporation, 
 or increase in bulk by farther precipitation of humidity. 
 
 2. When the whole sky is covered with clouds, 
 their farther formation and increase in bulk and den- 
 sity, is indicated by their descent to a lower level, and 
 their decrease, by their ascent. Accordingly, when 
 clouds begin to sit down on the tops of hills, (except 
 when this is the result of reduction of temperature, 
 upon the approach of night,) it prognosticates rain ; 
 and when they begin to rise above the hills, it prog- 
 nosticates dry weather. 
 
 3. Mist extending upwards from the surface of the 
 earth on a summer morning, foretells a dry warm day. 
 The peasantry give such a mist the name of heat, 
 meaning thereby that it foretells a warm day. Such 
 morning mists result from coldness, induced upon the 
 earth's surface by the radiation of caloric during night, 
 being propagated upwards to the atmosphere in suffi- 
 
36G ON THE CAUSES AND PRINCIPLES 
 
 cient intensity to produce atmospheric oversaturation,, 
 and the precipitation of moisture into the forms of dew 
 and mist. This only happens, as was formerly ex- 
 plained, when treating of the formation of the stratus, 
 during calm, starry, cloudless nights, which are the 
 usual concomitants, and among the most certain prog- 
 nosticators of dry settled weather. 
 
 4. During frosty weather, the dissolution of mist, 
 and the appearance of small detached roundish clouds 
 of the cirro-cumulus kind in elevated regions of the 
 atmosphere, and partly or wholly obscuring the sky, 
 foretell that the termination of the frost is at hand. 
 The reason is, that a sufficient degree of cold to pro- 
 duce frost on the surface of the earth in this climate, 
 even during the depth of winter, can only be main- 
 tained by the free radiation of caloric from the earth's 
 surface. Whenever, therefore, the radiation of caloric 
 from the earth's surface is interrupted or retarded by 
 a canopy of clouds, the heat slowly passing by conduc- 
 tion from underneath, upwards, and not, or only very 
 slowly, escaping by radiation, soon accumulates in 
 sufficient amount at the earth's surface, to cause the 
 frost to disappear. 
 
 Of Prognostications of ihe Weather from the co- 
 lour of the sky^ and the appearances of the heavenly 
 bodies. — The darker the colour of the sky is when 
 viewed perpendicularly upwards, the more it indicates 
 dry weather ; and on the contrary, the paler it is, the 
 more favourable to wet weather. It was formerly 
 stated that the gaseous elements of the atmosphere 
 were altogether invisible ; and that the sky would ap- 
 pear jet black, that is, would reflect no light what- 
 
OF METEOROLOGICAL PHENOMENA. 367 
 
 ever, were it not for the aqueous vapour which the 
 air contained. The circumstance of the sky present- 
 ing any colour therefore but jet black, is owing to the 
 reflection of light, (which is itself of a white colour,) by 
 aqueous vapour. And the reason assigned for the 
 blue shade is, that the blue rays are reflected more 
 copiously than any of the others. Now, as the de- 
 viation of the colour of the sky from jet black to blue 
 white, is produced by the power of aqueous vapour in 
 reflecting light ; it is obvious that the stronger the 
 light, or the larger the amount of aqueous vapour 
 contained in the atmosphere by which light is reflect- 
 ed, the paler the colour of the sky ought to be. And 
 on the contrary, the less hght, and the smaller the 
 amount of aqueous vapour contained in the air, the 
 nearer should the blue shade approach to black. In 
 forming an opinion of the future weather from the co- 
 lour of the sky, it is to be recollected, that the points 
 of observation compared at different times, must be 
 equally distant from the zenith, and from the direc- 
 tion of the sun. The reason why these circumstances 
 require to be attended to is, that the colour of the sky 
 becomes paler in proportion as the amount of light is 
 greater, or the point of observation nearer the direc- 
 tion of the sun, or nearer the horizon. Supposing 
 the amount of aqueous vapour contained in the air, 
 and the amount of light to be the same, most light is 
 reflected by the aqueous vapour which is nearest the 
 direction of the sun, and accordingly, the colour of 
 the sky becomes darker, the farther the point observed 
 recedes from the direction of that luminary. And 
 other things equal, the colour of the sky appears 
 
368 ON THE CAUSES AND PRINCIPLES 
 
 darker according as it is viewed more perpendicularly 
 upwards, because the amount of aqueous vapour con- 
 tained in the line of view which reflects the light, in- 
 creases from the zenith to the horizon. 
 
 When the colour of the sun or moon appears pale 
 and dull, it indicates wet weather ; and on the con- 
 trary, when it is bright and clear, it indicates dry wea- 
 ther. The nature of this prognostication is also ob- 
 vious. Though aqueous vapours reflect light, they 
 have a proportional influence in intercepting the di- 
 rect luminous rays of the sun and moon. Hence, 
 when the sun and moon look paler and duller than 
 usual, or in other words, give less light, it indicates 
 that the amount of aqueous vapour contained in the 
 intermediate atmosphere, relative to its capacity, is 
 greater than usual ; and that a larger proportion of 
 the light transmitted by the sun and moon, is thereby 
 intercepted. On the other hand, when the sun and 
 moon look brighter than usual, it indicates, that there 
 is an unusually small amount of aqueous vapour con- 
 tained in the intermediate atmosphere relative to its 
 capacity ; and accordingly, an unusually small pro- 
 portion of the sun and moon's light is thereby inter- 
 cepted. 
 
 For similar reasons, when the horns of the moon 
 are sharp, or when the margin of the moon generally 
 is well defined, it indicates dry weather ; and on the 
 contrary, when the horns of the moon are blunt, and 
 its margin somewhat ill-defined, it foretells wet wea- 
 ther. The nature of this prognostication is analo- 
 gous to the one preceding. When the amount of 
 aqueous vapour in the air is larger than usual, the 
 
OF METEOROLOGICAL PHENOMENA. 369 
 
 aqueous vapour contained in the atmosphere, in the 
 direction between the spectator, and the sky in ap- 
 parent contact with the margin of the moon, reflects 
 the moon's hght with so much intensity, that it can 
 hardly be distinguished from the direct rays of the 
 moon, rendered less vivid in consequence of a por- 
 tion of them being intercepted by aqueous vapour. 
 Hence, in such circumstances, the horns of the moon 
 appear blunt, and its margin somewhat imperfectly 
 defined. On the contrary, when the amount of aque- 
 ous vapour contained in the atmosphere is much 
 smaller than usual, a small portion of its direct rays 
 is intercepted, and less of its light is reflected by the 
 aqueous vapour contained in the atmosphere appa- 
 rently immediately exterior to the margin of the moon, 
 as seen by the spectator at the surface of the earth. 
 In such circumstances, the moon itself looks unusual- 
 ly clear and bright, while the colour of the sky by 
 which it is surrounded, is unusually dark. Hence, 
 owing to the contrast of its own brightness, and the 
 unusually dark coloured sky by which it is surrounded, 
 its horns appear sharp and vivid, and its margin ge- 
 nerally well defined. 
 
 In like manner, when the moon is surrounded by 
 an iris, it indicates rain. The reason of this is, that 
 the iris is produced by the moon's light being reflect- 
 ed by aqueous vapour contained in the atmosphere, 
 between the spectator and the sky apparently exterior 
 to the margin of the moon. The iris therefore indi- 
 cates an unusual quantity of moisture in the atmo- 
 sphere, and hence the reason that it indicates rain. 
 
 Supposing no moon visible, if the stars look larger 
 3 A 
 
370 ON THE CAUSES AND PRINCIPLES 
 
 and somewhat paler, less vivid, and at the same time 
 less numerous than usual, it indicates an unusual 
 amount of moisture in the atmosphere, and accord- 
 ingly foretells rain. On the contrary, when the stars 
 look smaller, more twinkling, and at the same time 
 more numerous than usual, it indicates an unusual 
 smallness in the amount of aqueous vapour in the at- 
 mosphere, and accordingly foretells dry weather. The 
 increased apparent size of the stars results from the 
 reflection of their light by aqueous vapour, contained 
 in the atmosphere immediately exterior to their ap- 
 parent margin. The diminution in their numbers re- 
 sults from many of them becoming invisible, in con- 
 sequence of a larger proportion of their direct rays 
 being intercepted, by the more than ordinary amount 
 of aqueous vapour contained in the atmosphere. 
 
 In reality, all the preceding prognostications of wet 
 or dry weather deduced from the colour of the sky, 
 and the appearances of the heavenly bodies, indicate 
 merely that more than the ordinary amount of aque- 
 ous vapour is contained in the atmosphere in the one 
 case ; and less than the ordinary amount in the other. 
 The reason why a greater than the ordinary amount 
 of aqueous vapour in the atmosphere foretells wet 
 weather, is, that in such circumstances, its amount is 
 usually upon the increase. And this may be owing 
 to the wind being in a rainy direction. On the con- 
 trary, the reason why a less than the ordinary amount 
 of aqueous vapour in the atmosphere foretells dry 
 weather, is, that the wind, in such circumstances, is 
 usually out of a dry quarter, and generally little of it. 
 Besides, clouds and rain are sooner produced by a 
 
OF METEOROLOGICAL PHENOMENA. 371 
 
 favourable combination of the ordinary causes, when 
 the air is saturated, or nearly saturated with aqueous 
 vapour, than when it is much undersaturated. Upon 
 the whole, weather prognostications deduced from the 
 colour of the sky, and the appearances of the heavenly 
 bodies, are fully as much to be depended on, as those 
 deduced from the indications of hygrometric instru- 
 ments. The former, though they give less precise 
 information, are free from several sources of error, 
 such as vicissitudes of temperature near the earth's 
 surface, and the circumstance of temperature being 
 upon the increase, or decrease, to which the latter are 
 exposed. 
 
 Of Prognostications of the Weather from the Di- 
 rection and Force of the Wi7id. — If we could pre- 
 dict how long the wind was to continue in the direc- 
 tion in which it happens to be, and without altering 
 its velocity ; and if we could also predict when, and 
 to what extent, its direction and velocity would alter, 
 prognostications of the weather deduced from the di- 
 rection and velocity of the wind, would be more to be 
 relied on, than any, or even all of those before-men- 
 tioned. Indeed, the claims which the before-men- 
 tioned prognostications of the weather have to cor- 
 rectness, or rather to the probability of being correct, 
 (for weather prognostications in this insular climate 
 have no higher pretensions than probability,) depend 
 chiefly on their indicating imperfectly, whether the 
 wind be blowing from a wet or a dry direction ; and 
 whether it be blowing with greater, or less velocity* 
 But though it cannot be predicted how long the di- 
 rection and velocity of the wind may continue without 
 
37'2 ON THE CAUSES AND nilNCirLES 
 
 changing, still, by prognosticating upon the supposi- 
 tion, that the direction and velocity of the wind will 
 continue as it is, there is more or less probability, at 
 least for one, two, or perhaps three days thereafter, 
 that our anticipations will be correct. Thus, if the 
 wind, during the winter season, be blowing with con- 
 siderable, or at times, with great violence from the 
 south-west, (that is, from a warm and wet direction,) 
 especially if it has been shortly previous for a consi- 
 derable length of time out of the east, or north-east, 
 it may be predicted, if wet weather has not already 
 commenced, that it will very soon begin ; and that it 
 will last one, two, or three days, or perhaps longer, — 
 the probability of the prediction being correct, dimi- 
 nishing in proportion as the anticipation of the di- 
 rection and velocity of the wind and weather con- 
 tinuing as it is, extends prospectively to a greater 
 length of time. On the other hand, if the wind, dur- 
 ing the same season of the year, blow from any point 
 between north and east inclusive, (that is, from a cold 
 and dry direction,) and with very little velocity, it may 
 be predicted, that the weather will continue dry and 
 frosty, or inclined to frost, for one, and with diminish- 
 ing probability of being correct, for two, three, or 
 more days thereafter. 
 
 At Glasgow, I have almost never seen it rain when 
 the wind was within three points of the compass, either 
 to the east or west of north. But a wind from these 
 points is, in this country, exceedingly rare. I have 
 frequently seen rain when the wind blew out of any 
 other point of the compass. At Glasgow, rain is of 
 much more frequent occurrence, when the wind is out 
 
OF METEOROLOGICAL PHENOMENx\. 373 
 
 of some point of the compass between south-east 
 and west inclusive, than when the wind is out of any 
 cold point of the compass to the north of west or of 
 south-east. 
 
 In general, the greater the velocity of the wind, 
 and more especially if it be out of a warm direction, 
 the greater is the probability of rain. And on the 
 contrary, the less the velocity of the wind, be its di- 
 rection what it may, but especially if it be out of a 
 cold direction, the less the probabihty of rain. 
 
 After the lengthened explanations given in the third 
 chapter, of the influence of certain directions of the 
 wind in forming clouds, and producing rain ; and of 
 certain other directions, in dissolving clouds and pro- 
 ducing fair weather, (and to which we refer,) it is un- 
 necessary farther to enlarge upon this department of 
 our subject. It may be remarked, however, that when 
 the wind is out of a cold and dry direction, and very 
 little of it, and all the other means of prognostication 
 indicate a continuance of dry weather ; a change of 
 the wind to a warm and wet direction, and an increase 
 in its velocity, very soon reverses the prognostications 
 to the indication of wet weather. 
 
 In all anticipations of the character of the weather, 
 it is advisable to draw our conclusions from a variety 
 of the means of prognostication. Thus not only the 
 present and immediately previous condition of the 
 barometer should be taken into account, but also the 
 direction and force of the wind, and the appearances 
 of the clouds and sky. The propriety of this recom- 
 mendation is evident from considering, that the dif- 
 ferent means of prognostication give sometimes the 
 
374 OxV THE CAUSES AND I'RlNCLrLES 
 
 same, and sometimes opposite, indications. If, for 
 instance, the barometer is high, and has been gradually 
 rising for several days previous, while the wind is from 
 a rainy direction, such as from the south-west in this 
 island, the probability of such a wind bringing rain is 
 much less than if the barometer was low, and had been 
 gradually sinking for several days previous. In like 
 manner, a cloudless, or nearly cloudless sky, is a less 
 certain indication of dry weather continuing, when a 
 wind of considerable velocity blows from a rainy 
 southerly direction, than when there is very little wind, 
 and its direction is from the north of due east, or due 
 west. 
 
 Of Prognostications of the Weather from the 
 Moon's age. — It has been very generally supposed 
 that at the change of the moon, or at some other fixed 
 period of the moon's age, the weather has a tendency 
 to undergo an alteration. This popular behef appears 
 to have no solid foundation in truth. It seems to 
 have originated, and to have been perpetuated, prin- 
 cipally in consequence of the moon being known to 
 be the chief agent in the production of tides in the 
 ocean ; and partly, perhaps, to the word change being 
 apphed not only to the weather, but to that period of 
 the moon's revolution when it comes most directly 
 between the earth and the sun. Thus a change of 
 moon, and a change of weather, are phrases in equally 
 common use. 
 
 Changes of weather may be from cold to warm, 
 from dry to wet, from calm to windy, or the contrary 
 of these. But no good reason can be assigned why 
 the moon should have more influence in producing 
 
OF METEOROLOGICAL PHENOMENA. 375 
 
 any of those changes of weather at one period of her 
 age, than at another. 
 
 It has never been ascertained that heat is commu- 
 nicated to the earth by the moon's rays. Conse- 
 quently, it can never be admitted that the moon has 
 any influence in changing the weather from cold to 
 warm, and from warm to cold ; nor in regulating in 
 any way the temperature on the earth's surface. In 
 fact, nothing is more certain, than that the variations 
 of temperature throughout the year, depend upon the 
 alternate progress of the sun to the north and south 
 of the equator, and not upon that of the moon. 
 
 Again, in all climates to the north and south of the 
 torrid zone, changes of weather from dry to wet, and 
 from wet to dry, depend chiefly upon certain altera- 
 tions in the direction of the wind ; and the altera- 
 tions in the direction of the wind which produce those 
 changes, are different in diff'erent countries. When 
 treating of winds, it was shown that their existence, 
 and variations in direction and velocity, principally 
 depend upon variations of temperature ; and upon the 
 diff'erent amounts of moisture evaporated, and con- 
 densed into rain, in diff'erent places ; and these also 
 chiefly depend upon variations of temperature. In- 
 deed, I have never seen it even hinted in the writings 
 of any meteorologist, that the moon had any influence 
 whatever, either in producing wind, or in regulating 
 its direction and velocity. Now, as the direction and 
 velocity of winds principally depend upon variations 
 of temperature, and as variations of temperature de- 
 pend upon the sun, and not upon the moon, it can 
 never be admitted that the moon has any influence in 
 
'M6 ON THE CAUSES AND PRINCIPLES 
 
 changing the weather, either from wet to dry, or from 
 dry to wet. 
 
 Again, though the change of moon happens at the 
 same time all over the earth, it is well known that 
 changes of weather are by no means simultaneous in 
 places not very distant from each other. And farther, 
 the changes of weather which occur even in countries 
 similarly situated with regard to the direction of land 
 and sea, and not very distant, are not unfrequently 
 the reverse of each other. Now, reasoning^ according^ 
 to analogy, the same cause, in similar circumstances, 
 is always expected to produce the same result. But 
 to ascribe wet weather at one time, and dry weather 
 at another, and more especially opposite kinds of 
 weather simultaneously existing in countries similarly 
 circumstanced, and not very distant from each other, 
 to the change of the moon, or to any other period of 
 her age, is attributing opposite effects to the same 
 cause. 
 
 It may be farther remarked, that after comparing, 
 by means of a meteorological journal, the times when 
 changes of weather occurred, with the changes of the 
 moon, and with other periods of her age, I am satis- 
 fied, that there is no connection between them. It 
 is usual for those who believe in the moon's influence, 
 to ascribe to the change of moon all alterations of the 
 weather which happen within two or three days there- 
 after. In this insular climate, where the weather is 
 so exceedingly variable, it is not surprising, that with 
 so much latitude in point of time, innumerable coin- 
 cidences should have been observed. It may be safely 
 asserted, however, that with a similar latitude, not only 
 
OF METEOROLOGICAL PHENOMENA. 377 
 
 the time when the moon changes, but any other period 
 of her age, might be at random fixed upon, and equally 
 satisfactory evidence of her influence in producing a 
 chansfe of weather would be obtained. 
 
 Of the Prognostications of the Rainbow. — When 
 the sun, relative to a spectator on the earth's surface, 
 is in an opposite direction of the heavens from a cloud 
 from which rain is falling, what is called a rainbow is 
 seen. It consists of two bows or arches of light, 
 stretching across the sky, and decomposed into their 
 elementary colours by refraction. The internal, or 
 principal rainbow, which is often seen without the 
 other, has the violet rays innermost, and the red rays 
 outermost ; and forms a segment of a circle, whose 
 diameter is 82°. The external, or fainter rainbow, 
 has the violet colour outermost, and the red inner- 
 most ; and forms part of a circle, whose diameter is 
 about 104°. 
 
 The rainbow is produced by the reflection of a por- 
 tion of the solar light, from the interior of the numer- 
 ous drops of falhng rain, to the spectator, after being 
 refracted into its elementary colours, according to their 
 different degrees of refrangibility, both in entering and 
 in emerging from the drops. And as the rain-drops 
 are spherical, the portion of light returned to the 
 spectator in the refracted state, from diff"erent portions 
 of the falling rain, previously undergoes the same 
 angular refractions and reflection. Consequently, the 
 angle formed by the sun, the spectator, and each 
 colour in every part of the rainbow, is the same. And 
 hence the reason that this phenomenon presents itself 
 in the form of a segment of a circle. 
 
 3 B 
 
378 ON THE CAUSES AND PRINCIPLES 
 
 When the sun's rays cease, in consequence of the 
 intervention of cloud, to strike upon any portion of 
 the falhng rain, where the rainbow is seen ; or when- 
 ever rain ceases to fall from any portion of the cloud, 
 that portion of the rainbow ceases to be visible. And 
 upon a similar principle, when clouds from which rain 
 is falhng wholly obscure the sky, and accordingly, 
 when the solar rays strike upon the upper surface of 
 the clouds, no rainbow is visible to a spectator on the 
 surface of the earth. 
 
 Clouds, so long as they consist of aqueous vapour 
 in the vesicular form, never produce a rainbow. It 
 is only moisture that has lost the vesicular constitu- 
 tion, and which is descending to the earth in the form 
 of rain, which produces this phenomenon. The fact 
 of spray which rises from a waterfall exhibiting, during 
 sunshine, the refracted colours of the rainbow, proves 
 that its constitution is analogous to that of falling rain, 
 and different from the ordinary vesicular constitution 
 of clouds. 
 
 The prognostication of the rainbow extends no 
 farther than giving intimation, that rain is falling from 
 the cloud where the rainbow is visible. If the direc- 
 tion of the wind be such, as to cause the cloud to 
 pass over the place where the observer of the rainbow 
 is situated, rain may there be expected soon to fall. 
 But if the direction of the wind be such as to cause 
 the cloud to pass, without becoming vertical to the 
 spectator, no rain in the situation where he is need 
 be expected. 
 
 Of the Prognostications of a cold, and also of a 
 mild winter. — ^The principal prognostication of a cold 
 
OF METEOROLOGICAL PHENOMENA. 379 
 
 winter, is unusual coldness during the preceding sum- 
 mer ; and this is always with greatest accuracy ascer- 
 tained by the unusual lateness of the harvest, A cold 
 summer is on all occasions a cloudy and wet one. 
 The reason why a cold, cloudy, wet summer, foretells 
 that a cold winter will probably follow, is that an 
 unusually large proportion of the solar heat, which 
 ought to be imbibed by the earth during summer, 
 is partly intercepted by clouds before reaching the 
 earth, and partly carried off from its surface by eva- 
 poration. During winter, the temperature of the at- 
 mosphere is principally supported by the retrocession 
 of solar heat, absorbed by the earth during the previous 
 summer. But if owing to the above-mentioned causes, 
 the amount of solar heat absorbed by the earth during 
 summer, be smaller than usual; the amount returned 
 to the atmosphere from the earth during winter, will 
 also be smaller. Hence, if other circumstances be in 
 an ordinary degree favourable to coldness, the reduc- 
 tion of the atmospheric temperature during winter 
 will be greater than usual. 
 
 Another prognostication of a cold winter, and which, 
 if it co-operates with the preceding prognostication, 
 increases its effect, is much rain in the fall of the year, 
 (namely, in August, September, and October,) fol- 
 lowed by an unusual prevalence of northerly and 
 easterly winds, during October and November. These 
 dry winds, by increasing evaporation from a thorough- 
 ly moistened soil, prematurely carry off a larger pro- 
 portion than usual of that heat, which, by its slow re- 
 trocession from the earth's surface, ought to mitigate 
 the atmospheric coldness during the depth of winter. 
 
380 ON THE CAUSES AND PRINCirLES 
 
 Hence, if other circumstances be in an ordinary de- 
 gree favourable to coldness during the coldest period 
 of winter, the atmospheric temperature should then 
 sink lower than usual. 
 
 The two preceding prognostications, viz. a cold 
 wet summer, and heavy rains in the fall of the year, 
 followed by an unusual prevalence of northerly and 
 easterly winds, occurred during the summer and fall 
 of 1708, and was succeeded in the end of that year, 
 and in the beginning of 1709, by one of the severest 
 winters on record. 
 
 Having observed that the two preceding prognosti- 
 cations of a cold winter, had occurred in the year 
 1830 to a greater extent than usual, I ventured to 
 predict in the Glasgow Chronicle Newspaper, (and 
 it was the only time I ever did so,) before any cold 
 weather commenced, that the winter would be colder 
 than ordinary. The prediction was to a certain extent 
 verified. The winter was colder than any that has 
 happened since, or than any that had occurred for at 
 least ten years previous. There was skating on the 
 Clyde at Glasgow that winter, on two separate occa- 
 sions, for about ten days each time ; and there was 
 subsequently an unusual fall of snow. It was, how- 
 ever, a mild winter, when compared with the remark- 
 ably severe one of 1814. 
 
 A mild winter may be prognosticated by the occur- 
 rence of the opposite circumstances to those previously 
 stated, which foretell a cold winter. The first of these 
 is a warm, dry summer, which can always be best as- 
 certained by the unusually early period at which har- 
 vest in such years commences. The other prognos- 
 
OF METEOROLOGICAL PHENOMENA. 381 
 
 tication is a small, or only a moderate amount of rain 
 in the fall of the year, attended and followed by an 
 unusual prevalence of south and south-west winds, of 
 very little, or only moderate velocity. 
 
 In our insular climate, the fulfilment of the prog- 
 nostications of a cold winter, may be prevented by the 
 unusual prevalence of south, and south-west winds, 
 (and the stronger, the more efficacious they are,) and 
 also by the unusual prevalence of clouds and wet wea- 
 ther, and even by dense fogs, during what should be 
 the coldest period of the year. In like manner, the 
 previous prognostications of a mild winter may be 
 rendered somewhat inaccurate, by the unusual preva- 
 lence of northerly and easterly winds of very little 
 velocity, and also by an unusual clearness of the sky, 
 and freedom from clouds, and dense fogs, during 
 what should be the coldest period of winter. 
 
 It has been remarked, that an unusual crop of what 
 are called heps and haws, prognosticates a severe 
 winter. As an abundant crop of these vegetable pro- 
 ductions results from, and indicates an excess of 
 moisture, and unusual coldness during the previous 
 summer, which may always be ascertained with more 
 precision by the lateness of the harvest, this prognos- 
 tication requires no farther explanation, and may be 
 altogether neglected. 
 
 Another prognostication of a cold winter is, the 
 arrival in the fall of the year, at an earlier period 
 than usual, of migratory birds, such as woodcocks, 
 which spend the summer in the northern parts of 
 Europe, and winter in this island. The early appear- 
 ance of such birds is supposed to indicate, that cold 
 
38*2 ON THE CAUSES AND PRINCIPLES 
 
 weather in the northern parts of the continent of Eu- 
 rope has commenced sooner, and with greater severi- 
 ty, than ordinary ; and that it will, in course of time, 
 extend to this country. I have repeatedly observed 
 prognostications of a cold winter, founded upon the 
 early appearance of migratory birds, announced in 
 newspapers. But whether it was owing to an error in 
 the announcement, or to some other cause, I have 
 never seen one of those predictions turn out correct. 
 
 In like manner, warm summers are predicted when 
 migratory birds, such as swallows, from Africa or the 
 south of Europe, arrive earlier in this country than 
 usual. Their early appearance is supposed to indi- 
 cate, that warm weather in southern climates has com- 
 menced sooner than usual, and that it will by and bye 
 extend to this country. 
 
 During calm clear weather, the minimum tempera- 
 ture of night may be prognosticated, by ascertaining the 
 hygrometric state of the atmosphere. The tempera- 
 ture, or perhaps one degree lower than the tempera- 
 ture at which the atmosphere becomes saturated with 
 moisture, and precipitation of humidity in the form of 
 mist commences, is the limit to its reduction during 
 night. The principle upon which this prognostica- 
 tion depends is, that the heat evolved during the con- 
 version of invisible vapour into mist and dew, pre- 
 vents the atmospheric temperature from being farther 
 reduced. 
 
 Of Cycle Prognostications. — It has been a com- 
 mon belief in different ages and nations, that after a 
 limited number of years, the same succession of wea- 
 ther in the different seasons of the year recurs, and 
 
OF METEOROLOGICAL PHENOMENA. 383 
 
 is repeated periodically. It does not appear, however, 
 that there is any satisfactory evidence founded on au- 
 thentic and precise observations of the weather, that 
 such is the case. Indeed, the circumstance of the 
 duration of the cycle being considered different by 
 different individuals, is a proof, that if it exists at all, 
 its duration has never been accurately ascertained. 
 Nine years, or some multiple of nine years, has been 
 generally fixed upon as the period of the cycle. Thus 
 nine, eighteen, thirty-six, and fifty-four years, have 
 been all severally fixed upon by different individuals. 
 According to Toaldo, the cycle consists of nine- 
 teen years ; and upon this supposition, a table of the 
 weather for several centuries has been made out. 
 The following portion of the table applicable to the 
 past and future years of the present period, and which 
 may be extended for any length of time, we subjoin 
 by way of example : — 
 
 ' Character of the Seasons. 
 
 1852 Warm and dry. 
 
 1853 Variable, moist. 
 
 1854 Variable. 
 
 1855 Warm and dry. 
 
 1856 Do. 
 
 1857 Do. 
 
 1858 Cold and moist. 
 
 1859 Mild and dry. 
 
 1860 Ordinary. 
 
 1861 Cold and moist. 
 
 1862 Cold, tolerably dry. 
 
 1863 Ordinary, cold and moist. 
 
 1864 Cold and moist. 
 
 1865 Rather cold and moist. 
 
 1866 Ordinary. 
 
 1795 . 
 
 , 1814 . 
 
 , 1833 
 
 1796 . 
 
 , 1815 , 
 
 . 1834 
 
 1797 . 
 
 , 1816 . 
 
 , 1835 
 
 1798 . 
 
 . 1817 , 
 
 , 1836 
 
 1799 , 
 
 . 1818 , 
 
 . 1837 
 
 1800 , 
 
 . 1819 . 
 
 , 1838 
 
 1801 . 
 
 . 1820 . 
 
 , 1839 
 
 1802 . 
 
 , 1821 . 
 
 , 1840 
 
 1803 , 
 
 . 1822 . 
 
 . 1841 
 
 1804 , 
 
 . 1823 , 
 
 . 1842 
 
 1805 . 
 
 , 1824 . 
 
 , 1843 
 
 1806 . 
 
 . 1825 . 
 
 , 1844 
 
 1807 , 
 
 , 1826 . 
 
 1845 
 
 1808 . 
 
 , 1827 . 
 
 , 1846 
 
 1809 . 
 
 . 1828 . 
 
 1847 
 
384 ON THE CAUSES AND PRINCIPLES 
 
 
 
 
 Character of the Seasons. 
 
 1810 . 
 
 . 1829 , 
 
 . 1848 . 
 
 , 1867 Ordinary. 
 
 1811 . 
 
 , 1830 . 
 
 , 1849 . 
 
 , 1868 Cold and dry. 
 
 1812 . 
 
 , 1831 . 
 
 , 1850 . 
 
 , 1869 Variable, moist. 
 
 1813 . 
 
 , 1832 . 
 
 , 1851 . 
 
 . 1870 Warm, dry. 
 
 It is difficult to compare the weather for a whole 
 year, with the very brief description given of it in the 
 preceding table. The only way of ascertaining whe- 
 ther the duration assigned to cycles be correct or not, 
 is to note those years, when the weather, during par- 
 ticular seasons, is very uncommon. Thus, the be- 
 ginning of the year 1795 was remarkable in Scotland, 
 for a greater snow-fall than had occurred for many 
 years previous ; and greater than any thing of the 
 kind that has taken place since. The snow-fall com- 
 menced that year on the 2d day of February, and, ow- 
 ing to the continuance of frost and cold weather, was 
 not wholly melted for a long time thereafter. Nine- 
 teen years subsequently, a more severe frost (not 
 however accompanied with snow,) occurred, than had 
 been seen for an unknown length of time previous, 
 and infinitely more severe than any thing that has 
 taken place since. By Christmas, 1813, there was 
 skating on the Clyde at Glasgow, and the ice conti- 
 nued unbroken till near the end of March, 1814. 
 Large masses of ice left on the banks of the river, af- 
 ter the ice broke up during a flood, measured eigh- 
 teen inches in thickness. And this, in consequence 
 of several days' thaw before the ice broke up, must 
 have been considerably less than what it had previ« 
 ously been. The thermometer which I was in the 
 habit of examining at that time, did not indicate any 
 
OF METEOROLOGICAL PHENOMENA. 385 
 
 temperature lower than T above zero of Fahrenheit, 
 — this probably being regarded by the maker of the 
 instrument, as being as low an indication of tempera- 
 ture as was ever required in this climate. During 
 this remarkable winter, however, every night between 
 9 and 10 o'clock, p.m., for a considerable length of 
 time, the mercury in the thermometer was sunk into 
 the bulb, which indicated that the temperature was 
 under T above zero of Fahrenheit. And one morn- 
 ing, about an hour before sunrise, it was stated in the 
 Chronicle newspaper, that, at their office, near the 
 centre of the city, the thermometer stood at the re- 
 markably low temperature of 14° below zero. Nor 
 was the severity of the cold restricted that winter to 
 Great Britain. I have been told by a gentleman who 
 was then residing in Sweden, that the frost was there 
 incomparably more severe that winter, than it had been 
 for at least sixty years previous. 
 
 If it be thought that the circumstance of the se- 
 vere frost in the beginning of 1814 being nineteen 
 years after the frost, and heavy fall of snow, in the be- 
 ginning of 1795, corroborates Toaldo's notion, that 
 the cycle consists of nineteen years j the fact of the 
 winter of 1833, viz., nineteen years after 1814, being 
 so mild, that the Clyde at Glasgow never froze at all, 
 disproves his hypothesis. 
 
 We may state other years that have been remark- 
 able, in order to afford points of future comparison, 
 with a view to ascertain whether cycles exist or not. 
 The winter of 1833-4, viz., November and Decem- 
 ber of 1833, and January of 1834, was the wettest 
 and windiest winter recollected to have ever happen- 
 
 3 c 
 
386 ON THE CAUSES AND PRINCIPLES 
 
 ed by the oldest person in Great Britain. That win- 
 ter was also remarkable for a mild temperature, and 
 for the almost total absence of frost, fog, and snow. 
 The summer of 1826 in Scotland, was the driest and 
 warmest, and produced the earliest harvest, that has 
 occurred since that time, or that had occurred for a 
 considerable period previous. 
 
 The cycle of eighteen years duration, is proved to 
 be untrue by the fact, that the winter beginning with 
 January 1832, viz., eighteen years after the great 
 frost, was so mild, that the ice upon the Clyde at 
 Glasgow, was never sufficiently thick for skating upon» 
 The cycle of nine years is also disproved by the win- 
 ter of 1822-3 being exceedingly mild, when com- 
 pared with the severe winter which occurred nine years 
 previous. The cycle of thirty-six years is somewhat 
 supported by the fact, that an unusually heavy fall of 
 snow occurred in Scotland in the beginning of Feb- 
 ruary 1831, just thirty-six years after the more re- 
 markable snow-fall which commenced on the 2d of 
 February 1795. There was this difference, however, 
 between the two : the snow-fall in 1795 continued on 
 the ground for a very long period thereafter; whereas, 
 that which happened in 1831, being succeeded by a 
 rapid thaw accompanied with rain, which produced 
 great river inundations, had entirely disappeared with- 
 in about a week of the time it fell. 
 
 The cycle of fifty-four years has been recently ad- 
 vanced by one George Mackenzie, who of late years 
 has annually issued a small quack-looking pubhca- 
 tion, entitled, a Manual of the Weather ; in which 
 he pretends to foretell the character of the weather 
 
OF METEOROLOGICAL PHENOMENA. 387 
 
 for every month of the succeeding year. I have only 
 examined the Manual which commences with No- 
 vember, 1833, that being the period when his year of 
 the weather begins. Upon comparing his predictions 
 with a meteorological Journal which I have kept, I 
 find, that whenever his prognostications are distinctly 
 marked, so as to admit of comparison with what ac- 
 tually occurred ; or when the weather happened in 
 any month to be very unusual, which frequently oc- 
 curred in that year, he has had the misfortune to be 
 oftener wrong than right. To enumerate all his er- 
 rors in prediction, small as well as great, is unneces- 
 sary. We will only notice the following by way of 
 sample : — Under the head of rain for the month of 
 December, 1833, he says, " Days rain, average ; 
 shght rains, under average ; mean rains, above aver- 
 age, — hence the average quantity of rain : conse- 
 quently this ought to be a fine month, notwithstand- 
 ing of some excess of strong wind ; and the more 
 welcome on account of its position, — mid month of 
 the winter quarter, — but the summer will more than 
 balance this rather unseasonable weather." 
 
 Instead of the amount of rain being only average, 
 and of its being a fine month, with only some excess 
 of strong wind, as the prediction tells us, it was one 
 of the stormiest and cloudiest months on record; and 
 the amount of rain that fell, was said to be greater 
 than had fallen in any month for at least thirty years 
 previous. By the register kept at the Macfarlane 
 Observatory, Glasgow, by Dr Couper, the total amount 
 of rain that fell in the year 1833 was 19.908 inches; 
 and of that quantity no less than 5.202 inches fell in 
 
388 ON THE CAUSES AND PRINCIPLES 
 
 December. By the register kept at Anderson's Uni- 
 versity, Glasgow, the total amount for the same year 
 was 20.32 inches; and of that quantity no less than 
 6.63 inches fell in December, being, by both regis- 
 ters, more than a fourth of the whole that fell during 
 the year; and as much as fell during any other three 
 consecutive months throughout the year. 
 
 In the month of April, 1834, he predicts an excess 
 of rain, whereas it turned out to be one of the driest 
 Aprils ever recollected. Again, he predicts during 
 the summer months of 1834, viz. May, June, and 
 July, an excess of cloudy, wet, and cold weather; and 
 that the harvest must be a late one. Instead of this 
 being the case, the summer of 1834 was warmer, 
 drier, and the sky in general considerably clearer than 
 usual; and the harvest all over Great Britain, was 
 earlier than it had been any year since the remarkably 
 dry summer of 1826. 
 
 He also predicts that the amount of foggy days 
 throughout the year, would be considerably over aver- 
 age; and that the sum total of frost would be a full 
 average, or inclined to over-average. Now, mark 
 what actually took place. Owing to the high winds 
 which prevailed throughout the winter, and which is 
 the only season when fogs occur in this island, there 
 was a remarkable deficiency of foggy weather. And 
 as to frost, I never witnessed a year in which there 
 was so little. To say more regarding Mackenzie's 
 Manual, would be taking more notice of it than the 
 trash it contains deserves. 
 
 The three most severe frosts recorded to have hap- 
 pened in this country, and in Europe generally, dur- 
 
OF METEOROLOGICAL PHENOMENA. 389 
 
 ing the last or present century, occurred in the begin- 
 ning of the years 1709, 1783, and 1814. The intervals 
 between these several years of great frost, are at vari- 
 ance with any of the periods assigned for the duration 
 of cycles. 
 
 According to Humboldt, the years in which the 
 greatest amount of rain fell in Mexico, are as follow: 
 1553, 1580, 1604, 1607, 1629, 1648, 1675, 1707, 
 1732, 1748, 1772, 1795. The intervals between the 
 above years, besides being irregular, are also at vari- 
 ance with any of the periods assigned for the duration 
 of the cycle. 
 
 The principle upon which the cycle of eighteen 
 years is said to be founded, is, that every eighteen 
 years, or a little more than eighteen years, the sun, 
 the moon, and the moon's node, come to the same 
 relative positions. The facts, however, which we have 
 above stated, show that that circumstance has no per- 
 ceptible influence in producing a recurrence of the 
 same kind of weather. 
 
 In a book entitled " A Rational Account of the 
 Weather," published in the year 1738, by John 
 Pointer, M.A., Rector of Slap ton, in the county of 
 Northampton, and diocese of Peterborough, a series 
 of wet seasons, which seem to have occurred about 
 that period, are ascribed to the excessive use of gun- 
 powder in war. In this misnamed publication, many 
 equally philosophical explanations of meteorological 
 phenomena may be found. Not only rain, but the 
 Aurora Borealis, thunder and lightning, and other 
 phenomena, are considered results of the explosions 
 of gunpowder. 
 
390 ON Tl'lE CAUSES AND PRINCIPLES 
 
 Supposing that the aggregate amount of heat com- 
 municated to the earth, and of moisture evaporated 
 from the surface of the land and water, to be the same 
 in each year, it is obvious, that the aggregate amount 
 of moisture annually returned to the earth in the vari- 
 ous forms of rain, snow, hail, and dew, must also be 
 equal. Hence, wet and dry seasons, which, according 
 as they happen in summer or in winter, produce un- 
 usual coldness, or unusual warmth for the time of the 
 year, may be regarded as mere local peculiarities, oc- 
 casioned principally by differences in the direction and 
 force of the wind, during the corresponding seasons 
 of different years. Thus, winds which produce wet 
 weather in one clim.ate, are found to occasion dry 
 weather in another. And if different kinds of wea- 
 ther, simultaneously occurring in different countries, 
 and chmates, could be adjusted against each other, 
 according as they deviate from the mean, it is not 
 unlikely, but that the annual aggregate of weather 
 prevailing over the earth's surface, would turn out to 
 be always the same, or very nearly so. Upon similar 
 principles, it is not improbable, that, by means of some 
 compensating causes, not yet understood, each climate, 
 within a limited, and perhaps somewhat irregular period 
 of time, receives its average proportions of wet and 
 dry weather. 
 
 I am disposed to think, that the alterations conti- 
 nually in progress on the earth's surface, particularly 
 those of draining the soil, and of clearing and plant- 
 ing forests, together with the extension of land in 
 certain quarters, and its diminution in others, are the 
 principal causes of that irregular variety in the wea- 
 
OF METEOROLOGICAL PHENOMENA. 391 
 
 ther of different years, and in the corresponding sea- 
 sons of different years. Though such local causes at 
 first affect only the weight, hygrometric condition, 
 and temperature of the atmosphere immediately in- 
 cumbent, still, by modifying and altering the direction 
 and force of the winds, they ultimately give birth to 
 general and widely extended results. And the effects 
 produced in one year, or in one season of the year, 
 have an influence in diversifying the meteorological 
 character of those that follow. I am also inclined to 
 think, that the weather in different years has a con- 
 stant tendency to assimilate; and that, provided there 
 were no such changes as those above-mentioned in 
 progress, the weather, in corresponding seasons of the 
 year, would ultimately become exactly alike. If these 
 opinions be correct, it is obvious, that, as changes are 
 continually going on with unequal degrees of rapidity, 
 on different parts of the earth's surface, the causes 
 which disturb the uniformity of the weather in different 
 years, must be ever-varying. Hence, cycles, or an 
 exact periodical recurrence of the same kind of wea- 
 ther, after any given number of years, need never be 
 expected to take place. And as the unusual magni- 
 tude of any particular wave, is occasioned by the union 
 and coalescing of smaller undulations ; so summers 
 and winters remarkable for heat or cold, or any other 
 peculiarity, may result, at irregular intervals, from the 
 accidental co-operation of a favourable combination of 
 antecedent, and existing circumstances, for producing 
 the effect. 
 
CHAPTER X. 
 
 OF RARE AND IMPERFECTLY UNDERSTOOD METEOROLOGICAL 
 PHENOMENA. 
 
 We now come to treat of several atmospheric phe- 
 nomena, some of which are but little, and others not 
 at all understood. The following is a list of them in 
 the order in which they are to be considered : — 1st, 
 The Ignis Fatuus. 2d, Falling Stars. 3d, Fireballs 
 and Meteoric Stones. 4th, Dry Fogs. 5th, Halos, 
 Mocksuns and Mockmoons. 6th, The Mirage and 
 Unusual Refractions. And, 7th, The Aurora Bo- 
 realis. 
 
 Of the Ignis Fatuus. — The meteor denominated 
 Ignis Fatuus, is also known by the more familiar epi- 
 thets of Will-o'-the-Wisp, and Jack-o'-the- Lantern. 
 This meteor makes its appearance on very dark still 
 nights, over boggy or marshy ground. It usually pre- 
 sents the appearance of a pale taper-looking flame ; 
 sometimes apparently at rest on the surface of the 
 bog, but more frequently moving about from place to 
 place, at the height of five or six feet above the ground. 
 At times it becomes invisible, and shortly thereafter 
 re-appears in the same, or some other place not very 
 distant. It is said, but I question the truth of the 
 statement, that it retires upon being approached, so 
 that, even though followed, it can never be overtaken. 
 Owing to this circumstance, together with that of the 
 
OF METEOROLOGICAL PHENOMENA. 393 
 
 marshy soil over which it makes its appearance, the 
 ignorant have ascribed to it an imaginary existence, 
 possessing the mischievous disposition of wishing to 
 mislead travellers into dangerous boggy ground. 
 
 Though this meteor is certainly within the reach 
 of examination, I am not aware that its nature has 
 ever been chemically investigated, or even that it 
 has been subjected to close inspection. Combustion 
 consists, in most cases, of the chemical combination 
 of a combustible substance, with the oxygen of the 
 air, attended, in consequence of the condensation 
 which thereupon ensues, by the evolution of heat and 
 light. It is known that certain substances take fire 
 at very low temperatures. Thus phosphorus under- 
 goes a very slow combustion upon exposure to the 
 atmosphere at ordinary temperatures, and its combus- 
 tion becomes more rapid according as the warmth 
 increases. From analogy, it has been supposed that 
 the ignis-fatuus is an example of combustion at a low 
 temperature, consisting merely of the chemical com- 
 bustion of the oxygen of the air, with streams of some 
 imknown phosphoric fluid issuing under peculiarly 
 favourable circumstances, in a concentrated form, 
 from boggy ground 5 and resulting from animal or 
 vegetable matter, in an unknown stage of decomposi- 
 tion. According to this hypothesis, its extinction in 
 one locality, and reappearance in another, together 
 with its flitting about from place to place without be- 
 ing wholly extinguished, depends upon the streams of 
 the phosphoric fluid ceasing to be sufficiently concen- 
 trated to support combustion at one place, and be- 
 coming sufficiently concentrated to do so at another. 
 
 3d 
 
394 ON THE CAUSES AND PRINCIPLES 
 
 It must be confessed, however, that the nature of this 
 phenomenon is involved in much mystery; and were 
 it only to gratify curiosity, demands investigation. 
 
 Of Falling Stars. — This meteor makes its appear- 
 ance on rare occasions in all kinds of clear weather, 
 but particularly during frost, and when there is little 
 wind. It is seldom visible for more than one or two 
 seconds, and is never seen but at considerable alti- 
 tudes in the atmosphere. It exhibits a rapid pro- 
 gressive motion, its course being usually somewhat 
 inchned downwards from the horizontal, and hence 
 the name Falling Star. 
 
 The principal hypothesis advanced to explain this 
 meteor, is that it results from a stream of combustible 
 gaseous matter rising up from the earth, and taking 
 fire at an altitude where the atmosphere becomes suf- 
 ficiently dry, and free of aqueous vapour, to admit of 
 its combustion. The direction of its motion is sup- 
 posed to result from the conjoint influence of the 
 tendency of the combustible fluid to ascend, with the 
 horizontal movement of the atmospheric current. 
 When the stream of combustible matter reaches the 
 requisite altitude it takes fire, and combustion is pro- 
 pagated backwards against the wind, and somewhat 
 inchned downwards in the course of the ascendinsf 
 stream of combustible matter. Its extinction is sup- 
 posed to be owing to the increasing amount of aque- 
 ous vapour as it descends in the atmosphere. 
 
 The preceding hypothesis is exceedingly unsatis- 
 factory. It is impossible that any stream of gaseous 
 matter could rise from the earth to the altitude where 
 this meteor usually makes its appearance, without 
 
OF METEOROLOGICAL PHENOMENA. 395 
 
 being completely intermixed with the atmosphere, and 
 dissipated by the wind, even in the stillest weather 
 that ever occurs. What is called a falling star, may 
 therefore, be regarded as a phenomenon, which has 
 hitherto frustrated all attempts at explanation. 
 
 Of Fireballs and Meteoric Stones. — No meteor- 
 ological phenomenon is more incomprehensible than 
 Fireballs, and the descent of Meteoric Stones. Fire- 
 balls present the appearance of globular bodies in a 
 state of intense ignition, and moving with great velo- 
 city, apparently in a horizontal direction, at a great 
 altitude above the surface of the earth. Their ex- 
 tinction is said to be attended with an explosion re- 
 sembling thunder, which is more or less loud, accord- 
 ing to the distance of the observer from the place 
 where it occurs. The explosion is immediately fol- 
 lowed by the descent of what are called aerolites, or 
 meteoric stones, which are of all different magnitudes, 
 from the weight of a few grains, to that of perhaps a 
 hundred pounds. These products of fiery meteors, 
 though somewhat rare, appear to have fallen at inter- 
 vals in all ages and climates, for nearly tw^o thousand 
 years past, and probably also, had records of them 
 been kept, in all anterior times. All those that have 
 been examined present a similar structure and appear- 
 ance. Upon being chemically analyzed, their ele- 
 mentary constituents are found to be nearly alike; and 
 their specific gravity, relative to that of water, varies 
 only from about 3.6 to 3.7. By way of sample, we 
 subjoin the analysis by Vauquelin, of one of three 
 stones which fell in France, in the commune of Char- 
 
396 
 
 ON THE CAUSES AND PRINCIPLES 
 
 sonville, in the department of the Loiret, and neigh- 
 bourhood of Orleans : — 
 
 Silica, 
 
 38.4 
 
 Alumine, .... 
 
 3.6 
 
 Lime, ° . 
 
 4,2 
 
 Magnesia, .... 
 
 13.6 
 
 Iron, .... 
 
 25.8 
 
 Nickel, .... 
 
 6. 
 
 Manganese, 
 
 0.6 
 
 Sulphur, . . . 
 
 3. 
 
 Chrome, .... 
 
 1.3 
 
 98.7 
 
 The fall of the stones above analyzed, occurred on 
 the 23d of November, 1810, about half-past one 
 o'clock, P.M., and was accompanied by a series of 
 detonations and reverberations, which lasted some 
 minutes. The detonations are said to have been as 
 loud at Orleans, Montargis, Salbri, Vierzon, and 
 Blois, as at the place where the stones fell ; and con- 
 siderable alarm was excited, from the apprehension 
 that they were occasioned by the blowing up of a 
 powder magazine. These stones were precipitated 
 perpendicularly. No luminous meteor, or visible 
 fireball, preceded their descent, — a circumstance 
 probably owing to the influence of the intense light 
 of the sun, in obscuring one that was comparatively 
 feeble. One of them took the ground at Montelle, 
 but was never discovered ; and of the other two, one 
 fell at Villenoi, and the other at Moulin-Brule, all of 
 which places are within the distance of a mile. One 
 of the stones weighed about twenty pounds, and made 
 
OF METEOROLOGICAL PHENOMENA. 397 
 
 a hole in the ground just large enough for its admis- 
 sion in a perpendicular direction, driving up the earth 
 to the height of eight or ten feet. It was taken out 
 half an hour after, when it was still so hot that it 
 could scarcely be held in the hand, and it had a strong 
 smell of gunpowder which it retained till it was quite 
 cold. The second formed a similar hole three feet 
 deep, weighed forty pounds, and lay fourteen hours 
 in the ground before it was extracted, when it was 
 quite cool. Both these stones were shapeless masses, 
 irregularly rounded at the projections. The day on 
 which they fell was remarkably calm and serene, and 
 not a cloud appeared above the horizon. 
 
 A variety of hypotheses have been advanced, in 
 order to account for the origin of meteoric stones. 
 According to one of these, meteoric stones are mis- 
 siles projected from volcanoes in the moon. This 
 extravagant hypothesis is countenanced by calcula- 
 tions of La Place, Poisson, Dr Flutton, and others, 
 by which it has been demonstrated, that a heavy 
 body, projected with a velocity of 6000 feet in a 
 second, may be driven beyond the sphere of the 
 moon's attraction into that of the earth. 
 
 The greatest initial velocity ever communicated to 
 a ball by gunpowder, is little more than 2000 feet 
 per second ; and owing to the resistance of the at- 
 mosphere, the velocity of the ball rapidly diminishes 
 as it recedes from the mouth of the gun. Now, it 
 can hardly be supposed, that volcanic action could 
 ever communicate to stones, a greater initial velocity 
 than gunpowder confined in the barrel of a gun, can 
 be made to communicate to a ball. And the attrac- 
 
398 ON THE CAUSES AND PRINCIPLES 
 
 tion of the moon, even upon the supposition that it is 
 not surrounded by an atmosphere, may be supposed 
 to diminish the initial velocity of stones projected 
 from lunar volcanoes as rapidly, as the resistance of 
 the air diminishes the velocity of balls projected from 
 a gun. Hence, to conclude that stones are projected 
 from lunar volcanoes with such inconceivably greater 
 force and velocity, as to enable them to pass through 
 the space of 6000 feet in a second, in direct opposi- 
 tion to the moon's attraction, is an extravagant con- 
 ception, refuted by all analogous facts with which we 
 are acquainted. And a hypothesis which rests upon 
 such a basis, must be regarded as fanciful and ima- 
 ginary, and altogether unworthy of attention. 
 
 Another hypothesis much more extravagant than 
 the preceding, is, that meteoric stones are small cen- 
 tral fragments of a large planet, that once revolved 
 round the sun between the orbits of Mars and Jupiter, 
 but which is supposed to have exploded in some for- 
 mer age. According to this hypothesis, the four 
 small planets denominated Juno, Pallas, Ceres, and 
 Vesta, are four large fragments of the exploded 
 planet. And meteoric stones, which have been oc- 
 casionally falhng on the earth's surface from time im- 
 memorial, are small central fragments, projected with 
 such force as to be driven beyond the attractive in- 
 fluence of the large ones ; and which, since the time 
 of the explosion, have been wandering about through 
 space, and occasionally falling upon the other plane- 
 tary bodies of the solar system, when they accidentally 
 happened in their peregrinations, to come within the 
 sphere of their attraction. 
 
OF METEOROLOGICAL PHENOMENA. 399 
 
 This hypothesis consists of an improbable supposi- 
 tion, founded upon another improbable one. The 
 arguments adduced to show that the explosion of a 
 large planet gave birth to the above-mentioned four 
 small ones, are somewhat analogous, and nearly as 
 unsatisfactory, as those by which Bufion endeavoured 
 to support his wild theory, that the whole planetary 
 system consists of fragments struck off from the sun, 
 at one and the same time, by the collision of a comet. 
 This opinion BufFon conceives is proven by the fact, 
 that all the planets, as well as their satellites, revolve 
 round the sun nearly in the same plane, and in the 
 same direction, viz., from west to east, round their 
 axes, as well as in their orbits. The author of the 
 hypothesis we are considering, ridicules the one first 
 noticed as being romantic. But it is certainly more 
 romantic, to suppose the existence of a volcanic force 
 so great as to explode a planet, so that its parts could 
 never afterwards reunite by the force of attraction, 
 than to suppose that stones could be projected from 
 a lunar volcano, with a velocity of 6000 feet in a 
 second. 
 
 But admitting, for the sake of argument, that a 
 planet did explode several thousand years ago, (though 
 that is a very unlikely circumstance,) and that small 
 central fragments, in consequence of being projected 
 with great force, were driven beyond the sphere of at- 
 traction of the large ones, which have kept pretty near- 
 ly in their former orbit, it is an exceedingly extrava- 
 gant idea, to fancy that meteoric stones, which have 
 been falling at recorded intervals for nearly 2000 years 
 back, can be small detached portions of the exploded 
 
400 ON THE CAUSES AND PRINCIPLES 
 
 planet flying about yet, and falling upon the earth as 
 numerously as ever. When the extremely small at- 
 tractive force of the earth, relative to that of the sun 
 is considered, one would suppose, that if those small 
 fraojments ceased to revolve round the sun in orbits, 
 according to the ordinary principles of other plane- 
 tary bodies, they must all very soon have fallen into 
 the sun by the force of its attraction, and that none 
 of them could have struck the earth, unless, in the 
 course of its annual revolution, it had accidentally 
 been in a proper position for intercepting some of 
 them in their descent towards the sun. But to sup- 
 pose that small fragments of the exploded planet 
 should have deviated so far, and yet so slowly, and ir- 
 regularly, from their original orbit, as to continue fall- 
 ing upon the earth at intervals for such a length of 
 time, is a hypothesis too chimerical and extravagant 
 to gain any belief. 
 
 Another hypothesis is, that meteoric stones are 
 thrown up by terrestrial volcanoes. If it is thereby 
 meant, that the stones are thrown up in the same 
 solid state as they descend, the hypothesis is dis- 
 proved by the fact of their having fallen at many 
 hundred miles' distance from any volcano ; and at 
 times when no eruptions in the nearest volcanoes 
 had occurred for a great number of years previous. 
 
 The following hypothesis by Playfair is more plau- 
 sible than any of the preceding. And as it is given 
 with less pretension to accuracy than any of the 
 others, we subjoin it in his own language : — 
 
 *' In the absence of all analogous appearances, it 
 is perhaps unphilosophical to offer any explanation 
 
OF METEOROLOGICAL PHENOMENA. 401 
 
 of the meteoric stones. We would only suggest as 
 a mere possibility, that gaseous substances may be 
 thrown up into the air, from the numerous volcanoes 
 on the earth's surface, and may carry with them cer- 
 tain elements of metallic and stony bodies from the 
 mineral regions ; these, while floating about in the 
 atmosphere, may sometimes be collected in consider- 
 able quantities into one place, where being subjected 
 to electric or galvanic action, they are united into a 
 solid mass. The fact that many of these stones have 
 fallen during thunderstorms, seems to limit the place 
 of their formation to the atmosphere of the earth." 
 
 That aerolites originate in the higher regions of 
 the atmosphere, seems probable from the following 
 facts : — 1st, They never exceed a moderate magni- 
 tude. 2d, They are uniformly preceded by, and ori- 
 ginate out of a fiery meteor, which is seen moving 
 horizontally with great rapidity, and sometimes for a 
 very great distance, in the higher regions of the air. 
 3d, However far the fiery meteors supposed to give 
 birth to meteoric stones may travel horizontally in the 
 higher regions of the air, they always explode, and 
 are extinguished at a considerable altitude ; and yet 
 that altitude is so limited, that the explosion is usually 
 heard at the earth's surface. 
 
 Upon the supposition that aerolites originate in 
 the higher regions of the terrestrial atmosphere, it is 
 certain that the metallic and earthy substances of which 
 they are composed must exist in the gaseous state, in 
 the elevated regions where they are formed. That 
 the substances of which meteoric stones are composed 
 are derived from the subjacent earth, seems probable 
 
 3 E 
 
402 ON THE CAUSES AND PRINCIPLES 
 
 from the fact, that the relative proportions of their 
 several constituents, bear a general relation to those 
 in which these constituents are found, as component 
 parts of the crust of the earth. Thus silica, which is 
 the most abundant element in meteoric stones, is also 
 the most abundant element in the strata composing 
 the crust of the earth. And iron, which is the second 
 most abundant element in meteoric stones, is also a 
 very abundant element in the terrestrial strata. On 
 the other hand, chrome and maganese, which are the 
 least abundant elements in meteoric stones, form but 
 a very small proportion of the crust of the earth. 
 
 The first difficulty in explaining the phenomena 
 exhibited by aerolites, is to show how the metallic 
 substances of which they are composed get translated 
 into the elevated regions of the atmosphere. So far 
 as chemical analysis may be depended upon, no such 
 substances are to be found in the air within twenty 
 thousand feet of the level of the sea. And the fact, 
 that fireballs which give birth to meteoric stones, are 
 never seen in the atmosphere near the earth's surface, 
 so far confirms the results of chemical analysis, that 
 the elementary constituents of meteoric stones do not 
 exist in the lower aerial strata. Recent chemical in- 
 vestigations have demonstrated, that, besides the 
 metals, all the earthy substances contained in mete- 
 oric stones, are compounds, with the exception of 
 sulphur, and consist of different metallic bodies, united 
 with a greater or less proportion of oxygen. And 
 though chemical analysis has hitherto failed in de- 
 composing metals, it is by no means improbable that 
 they also are compounds. 
 
OF METEOROLOGICAL PHENOMENA. 403 
 
 Now, unless it be supposed that the elements of 
 meteoric stones constantly exist in the gaseous state, 
 either intermixed with the air in its more elevated re- 
 gions, or that they form a separate and specifically 
 lighter atmosphere beyond the boundaries of that with 
 which we are acquainted, it is obvious, that, before 
 ascending, they must first be volatilized, and con- 
 verted into the gaseous state. And as a great degree 
 of heat is necessary to produce such an effect. Play- 
 fair's suggestion, that the elements of meteoric stones 
 may be carried up into the atmosphere by means of 
 volcanic agency, may be regarded as not only a mere 
 possibility, but as a hypothesis by no means improb- 
 able. 
 
 Another difficulty attending the phenomenon of 
 fireballs, is to account for the great horizontal velocity 
 with which they always appear to move. It is pre- 
 sumable that the intense ignition to which they seem 
 subjected, is owing to the heat and light evolved dur- 
 ing the condensation of the materials of which the 
 meteoric stones are composed. And it is possible 
 that the rapid horizontal motion of fireballs, may be 
 owing to the progressive propagation of the chemical 
 combination, and condensation of those materials; and 
 this may result from the affinity of the substances 
 undergoing combustion and condensation, for those 
 that remain uncondensed. The nature of the explo- 
 sion upon which the extinction of the meteor, and 
 the descent of the meteoric stones ensues, has hither- 
 to received no explanation. Indeed, owing to the 
 unattainable elevation at which fireballs make their 
 appearance, all the knowledge we need ever ex- 
 
404 ON THE CAUSES AND PRINCIPLES 
 
 pect to obtain concerning their nature and origin, is 
 limited to very doubtful conjectures. Fireballs, and 
 the descent of meteoric stones, may, therefore, be 
 regarded as phenomena which do not admit of being 
 satisfactorily accounted for. 
 
 Of Dry Fogs. — Another meteor, which, if the de- 
 scription given of it be correct, (but which is very 
 doubtful,) has never received any satisfactory explan- 
 ation, is what is called Dry Fogs. We subjoin the 
 description given of this meteor by Dr Prout in his 
 Bridgewater Treatise, together with part of the com- 
 mentary thereupon, which we consider the only un- 
 philosophical passage in that deservedly popular work. 
 
 *' In the year 1782, and still more in the year fol- 
 lowing, a remarkable haze of this kind extended over 
 the whole of Europe. Seen in mass, this haze was 
 of a pale blue colour. It was thickest at noon, when 
 the sun appeared through it of a red colour. Rain 
 did not in the least degree affect it. This haze is 
 said to have possessed drying properties, and to have 
 occasionally yielded a strong and peculiar odour. It 
 is also said to have deposited in some places a viscid 
 liquid, of an acrid taste, and of an unpleasant smell. 
 About the same time, there were in Calabria and in 
 Iceland, terrible earthquakes, accompanied by volcanic 
 eruptions. These earthquakes and eruptions were 
 supposed to have been connected with the haze. In- 
 deed it has been generally remarked, that such a con- 
 dition of the atmosphere has been usually preceded 
 by an earthquake, either in the same, or in some ad- 
 joining country. The dispersion of this haze in the 
 summer of 1783, was attended by severe thunder- 
 
OF METEOrx-OLOGICAL PHENOMENA. 405 
 
 storms. As might be expected, the general state of 
 health has, for the most part, been deranged during 
 the continuance of these phenomena. Simultaneously 
 there have been epidemic diseases of various kinds. 
 Thus in the above mentioned years, 1782 and 1783, 
 an epidemic catarrh, or influenza, prevailed through- 
 out Europe; affecting not only mankind, but likewise 
 other animals. 
 
 " The nature of the matter thus diffused through 
 the atmosphere is quite unknown. It may at differ- 
 ent times be not less various than the character of 
 the epidemics to which it gives origin." 
 
 I am inclined to think that the preceding descrip- 
 tion of a dry fog is exceedingly exaggerated, and incor- 
 rect ; and I suspect must have been extracted by Dr 
 Prout from some very inauthentic source. Many old 
 people are still alive who must recollect the phenom- 
 ena, if they were so remarkable, as they are said in 
 the above extract to have been. But what convinces 
 me that the description is inaccurate, is, that though 
 it is only 52 years since this dry fog occurred, I never 
 heard it mentioned by any person who had witnessed 
 it ; and never saw it noticed by any author till I read 
 it in the Bridgewater Treatise. At all events, there 
 is no satisfactory evidence adduced, that the epidemic 
 catarrh which prevailed in 1782 and 1783, was pro- 
 duced by the dry fog. Judging from the fact, that 
 influenza frequently becomes epidemic in seasons 
 when no dry fogs make their appearance ; and except 
 in the above instance, is never recorded, so far as I 
 am aware, to have been accompanied with a dry fog, 
 it is presumable, that they have no connection. Influ- 
 
406 ON THE CAUSES AND PRINCIPLES 
 
 enza is usually supposed to be produced by exposure 
 of the body to great and sudden, and sometimes, to 
 frequently repeated changes of temperature. In this 
 climate, it generally occurs during east or north-east 
 winds, in the months of April and May ; and when 
 the sky for the season of the year, is on an average 
 clearer, and freer of clouds than usual. In the above 
 circumstances, the vicissitudes of temperature to which 
 the body is exposed, are usually greater than at any 
 other season of the year. When exposed to the sun, 
 and sheltered from the breeze, the heat is then felt to 
 be very considerable. But during night, or when ex- 
 posed to the breeze, and sheltered from the sun dur- 
 ing day, the dry atmosphere, by promoting evapora- 
 tion, rapidly extracts the heat from the body, and pro- 
 duces the feeling of cold. The vicissitudes in the 
 atmospheric temperature are farther augmented, by al- 
 ternate changes in the direction of the wind, from 
 south-west to north-east, and the contrary. Such 
 changes of wind are of frequent occurrence, in this 
 climate, during April and May ; and are attended by 
 a greater and more sudden alteration of temperature, 
 than at any other period of the year. In seasons re- 
 markable for the above combination of circumstances, 
 influenza is apt to become epidemic. 
 
 From the great numbers seized about the same 
 time with this epidemic, it has been conceived by 
 some to be infectious. But from the fact of its fol- 
 lowing no progressive route traceable on a map, and 
 frequently becoming simultaneously epidemic, not 
 only in one, but in a number of neighbouring, and 
 sometimes even in distant countries j and from its 
 
OF METEOROLOGICAL PHENOMENA. 407 
 
 affecting the most sequestered and thinly peopled 
 districts, equally with those where the population is 
 densest, and the thoroughfare greatest ; the appear- 
 ances of infection have, with more propriety, been 
 ascribed to the circumstance of great numbers being 
 exposed to the same causes of disease. 
 
 At Philadelphia, in the beginning of December, 
 1831, a remarkably prevalent epidemic of this kind 
 occurred, which was said to be produced by an un- 
 usually sudden and great change of temperature. The 
 following is an extract of a letter from a relative of 
 mine, describing its effects : — 
 
 " Philadelphia, 10th December, 1831 The win- 
 ter has set in here so suddenly, that firewood has 
 risen, in a few days, from 6 to 12 dollars a cord. To- 
 day and yesterday are milder than it has been, and the 
 ice in the Delaware is still moving during part of 
 every tide. There never were so many bad colds 
 before in this place as now. It is supposed by some 
 that 50,000 people are confined to the house with 
 them. The banks and other public offices find the 
 utmost difficulty to get along from so many of their 
 hands being confined at home. Out of a class of 
 medical students, which consists of 100, only 16 are 
 attending the lectures ; and it is said that the legisla- 
 ture of New Jersey have adjourned on the same 
 account." 
 
 Dr Prout, following up his notion of different epi- 
 demic diseases being produced by the presence of 
 foreign materials in the atmosphere, ascribes the ap- 
 pearance of that malignant and infectious species of 
 Asiatic cholera in this island in 1831 and 1832, and 
 
408 ON THE CAUSES AND PRINCIPLES 
 
 which originated in India in 1817, to a cause of this 
 kind. In proof of which, he says, " On a particu- 
 lar day, the ninth of February, 1832, the weight of 
 the air suddenly appeared to rise above the usual 
 standard." And it retained its augmented weight 
 during the whole time his experiments were carried 
 on, viz. for about six weeks thereafter. In explana- 
 tion, he says, " There seems to be only one rational 
 mode of explaining this increased weight of the air 
 at London, in February, 1832; which is by admitting 
 the diffusion of some gaseous body through the lower 
 regions of the atmosphere of this city, considerably 
 heavier than the air it displaced. About the ninth of 
 February the wind, which had previously been west, 
 veered round to the east, and remained chiefly in that 
 quarter till the end of the month. Now, precisely 
 on this change of the wind, the first cases of epidemic 
 cholera were reported in London, and from that time 
 the disease continued to spread. That the epidemic 
 cholera was the effect of the peculiar condition of the 
 atmosphere, is more, perhaps, than can be safely 
 maintained ; but reasons which have been advanced 
 elsewhere lead the writer of this treatise to beheve, 
 that the virulent disease, termed Cholera, was owing 
 to the same matter which produced the additional 
 weight of the air." 
 
 Whether the increased weight of the air, which Dr 
 Prout alludes to in the above quotation, was owing to a 
 diminution in the amount of its aqueous vapour, or to 
 increased atmospheric pressure, or to some other cause, 
 may be left undetermined. But hardly any person will 
 beheve that epidemic cholera in London, or in any 
 
OF METEOROLOGICAL PHENOMENA. 409 
 
 other part of Europe, was spread by the wind, or pro- 
 duced by any other means, than those by which other 
 infectious diseases are communicated. Indeed, if I 
 recollect right, the first case of cholera in London was 
 traced to a vessel which had just arrived from Sunder- 
 land, or Newcastle, where the disease then was. It 
 would be deviating unwarrantably from our subject to 
 enter into any lengthened digression on this point. 
 We will only therefore add, that owing to the short- 
 ness of the interval between imbibing the infection by 
 communication with the sick, and the symptoms of 
 disease ; and to the circumstance of the disease never 
 appearing in any instance, but where such communi- 
 cation with the sick, as is known in other infectious 
 epidemics to be capable of communicating infection, 
 had previously occurred ; there never perhaps appear- 
 ed any distemper on the face of the earth, of which 
 there was such innumerable and incontestable evidence 
 of its being communicated from man to man by in- 
 fection ; and by infection alone. And that the di- 
 rection of the wind, or the condition of the atmo- 
 sphere, (except within the apartments or dwellings of 
 persons labouring under the disease, or in places where 
 individuals suffering under the premonitory symptoms 
 had previously been,) had no influence in spreading 
 it whatever, was equally satisfactorily demonstrated.* 
 
 * In this island, by far the greatest number of persons who were 
 seized with cholera, had either previously visited, or lived in the 
 same house with a cholera patient. Many were infected (as is the 
 case with dysentery,) by visiting the necessaries, which persons 
 labouring under the premonitory symptoms of this distemper fre- 
 quented. Infection was also communicated by tlie clothes and 
 
 3f 
 
410 ON THE CAUSES AND PRINCIPLES 
 
 Of Halos^ Parhelia, or Mocksuns, and Mock- 
 onoons. — In very high latitudes, and sometimes in 
 temperate latitudes during cold weather, what are 
 called Halos, and Parhelia, or Mocksuns, and Mock- 
 moons, are on rare occasions seen. A halo consists 
 sometimes of one, and sometimes of two concentric 
 circles of coloured or refracted light, such as that of 
 a rainbow, the one forming an angle of about 23i de- 
 grees, the other an angle of about 47 degrees with 
 the sun, or moon. In different parts of these concen- 
 tric circles, and chiefly in opposite points at a similar 
 altitude with the. sun, bright spots of unrefracted hght 
 are seen, which have, received the names of mock- 
 suns, or mockmoons, according as the light is receiv- 
 ed from the sun or from the moon, during the appear- 
 ance of the halo. From these bright spots diverging 
 horns, or small segments of an external circle of re- 
 fracted light, has on some occasions been seen. 
 Sometimes the parhelia have conical tails of coloured 
 
 bedding of persons who had died of the disease. And in some very 
 rare instances, there is reason to suspect, (though this point is not 
 altogether certain,) that infection was communicated by persons 
 who had been visiting the sick, to others who had had no known 
 communication with them ; and this too, without the persons who 
 transported the infection, (perhaps on their clothes,) ever being 
 seized with the disease. I am inclined to think, that the external 
 atmosphere, even in the densest parts of cities, or in the neigh- 
 bourhood of cholera hospitals, never became so strongly impreg- 
 nated with the infectious effluvia, as to communicate disease in one 
 single instance. Similar observations are probably applicable to 
 all other infectious diseases communicated by means of effluvia 
 diffused through the atmosphere, and emanating originally from 
 the lungs, skin, or discharges of patients labouring under like dis- 
 eases. 
 
OF METEOROLOGICAL PHENOMENA. 411 
 
 light, turned away, like the tail of a comet, from the 
 true sun. 
 
 A variety of theories have been advanced in order 
 to explain the nature of a halo. In these it seems to 
 be generally agreed, that the phenomenon is produc- 
 ed by the sun or moon's light, being refracted by nu- 
 merous small, and perhaps primary crystals of snow, 
 or frozen vapour, of similar configuration, floating in 
 the air. The quantity of these crystals though con- 
 siderable, is not conceived to be so great as to dark- 
 en the air, or obscure the light of the sun to any very 
 palpable extent. Now it is obvious that if these 
 crystals be all of the same determinate configuration, 
 they will all float in a still, or nearly still atmosphere, 
 in a similar position, viz. with their bases, or heaviest 
 sides undermost ; and consequently, will all refract 
 the light of the sun in the same degree. Hence the 
 reason, that the halo or coloured circle of refracted 
 light, always appears at the same distance from the 
 sun. 
 
 Parheha, or mocksuns, and mockmoons, have 
 been supposed to be produced by numbers of those 
 floating crystals of snow or frozen vapour, being ar- 
 ranged in such a manner at particular points, that the 
 sun or moon's light is transmitted in a concentrated, 
 instead of a refracted form. This opinion is in all 
 hkelihood erroneous. Indeed, the circumstance of 
 parhelia always making their appearance at the same 
 points of the halo relative to the position of the sun, 
 demonstrates that they are not produced by any acci- 
 dental, or difl"erent arrangement of the floating crys- 
 tals, from what exists in other parts of the atmosphere. 
 
412 ON THE CAUSES AND PRINCIPLES 
 
 The phenomenon probably depends upon some un- 
 explained influence of frozen crystals in polarizing 
 light. The number of theories however advanced 
 in order to explain this, and the preceding phenom- 
 ena, and which all differ more or less from each other, 
 show that they are by no means perfectly understood. 
 
 As the phenomena of halos, and mocksuns, and 
 mockmoons, are more connected with the science 
 of optics, than with that of meteorology, it would be 
 digressing too far from our subject, to enter into any 
 detailed account of the various and somewhat obscure 
 theories, which have been advanced in order to explain 
 them. 
 
 Of the MiragCi and Unusual Refractions. — This 
 is another subject that has been slightly adverted to 
 in meteorological writings, but which more strictly 
 belongs to the science of optics. 
 
 Refraction of the line of vision is famiharly exem- 
 plified in the following experiment. Let a shilling 
 be placed in the bottom of an empty basin situated 
 on the floor, and let a person stand just so far dis- 
 tant from it, as to be unable to see the shilling. If 
 water be then slowly poured into the basin, the shil- 
 ling though it does not change its real position, grad- 
 ually comes more and more into the view of the spec- 
 tator. This is owing to the line of vision being re- 
 fracted somewhat downwards at the surface of the 
 water ; or, speaking more correctly, to the rays of 
 light reflected by the shilling, being refracted down- 
 wards towards the horizontal, upon emerging from the 
 surface of the water. 
 
 Different substances appear to have different powers 
 
01' METEOROLOGICAL PHENOMENA. 413 
 
 in refracting light, and each substance, by having its 
 density increased, has its refracting power thereby 
 augmented. Aqueous vapour, in an imperfectly dis- 
 solved state, (such as when it exists in the state of 
 haze or mist,) seems to have more power in refracting 
 light than air; and both air and mist, (provided the 
 latter be not so dense as to obscure the view of dis- 
 tant objects,) have their powers of refracting light 
 augmented by increase of density. Besides, the op- 
 tical illusion produced by the refracting power of im- 
 perfectly dissolved aqueous vapour, is farther assisted 
 by the circumstance of the colour of the light reflected 
 by the haze being so similar to that of water, as to be 
 indistinguishable from it. Hence vessels sailing on 
 water, when seen refracted by haze or mist, appear as 
 if saihng through the air; and distant objects, raised 
 by the refraction of aqueous vapour above their actual 
 level in the horizon, appear as if surrounded by water. 
 And it need hardly be remarked, that every object 
 appears to the spectator, to be in the direction in 
 which the rays of light reflected, or emanating from 
 it, enter the eye. Of course, if the rays of light be 
 refracted before entering the eye of the spectator, the 
 object appears not in the direction in which it actually 
 is, but in the direction in which the refracted rays 
 emanating from it enter the eye. 
 
 The phenomena of the mirage, and of unusual re- 
 fractions in general, are explained according to the 
 preceding principles, either by supposing that the 
 atmospheric strata, near the earth's surface, are un- 
 equally heated, and therefore unequal in density; or 
 by supposing, that they contain unequal proportions 
 
4-14 ON THE CAUSES AND PRINCIPLES 
 
 of mist or imperfectly dissolved moisture. Supposing 
 the atmospheric strata, within a few yards of the sur- 
 face of the earth, to be free of haze, while imme- 
 diately above that altitude, there is a slight degree of 
 haze arising from moisture not thoroughly dissolved, 
 but not so dense as to obscure the view of distant 
 objects. In this case, a distant object, viewed along a 
 level surface, such as a vessel at sea, will appear in its 
 natural position, while, owing to the refracting power 
 of the undissolved moisture above, another figure of 
 the vessel will appear as if sailing in the air, and will 
 seem to be diminished or increased in height, or in 
 different degrees distorted, or even inverted, accord- 
 ing as the different strata, and portions of the mist by 
 which the rays of light emanating from the vessel are 
 refracted, increase or diminish in densitv, Accordingr 
 to similar principles with that of the image of a vessel 
 saiHng in the air, distant objects are sometimes seen 
 on land by means of the refractive power of imper- 
 fectly dissolved aqueous vapour, when slight eminences 
 intervene between the object viewed and the spec- 
 tator. 
 
 In Egypt, and in neighbouring level sandy deserts, 
 the mirage sometimes assumes the appearance of a 
 sheet of water inundating the ground near the hori- 
 zon. This effect is supposed to be owing to re- 
 fractions, produced partly by the influence of the 
 rarefaction of the atmosphere being greatest near the 
 heated ground, and diminishing upwards, and partly 
 to the unequal proportions of imperfectly dissolved 
 moisture, which these various atmospheric strata con- 
 tain. 
 
OF METEOROLOGICAL PHENOMENA. 415 
 
 Of the Aurora Borealis, or Northern Lights. — 
 This phenomenon makes its most brilHant appearances 
 in high latitudes, and during the cold season of the 
 year. When seen in this climate, it usually presents 
 the appearance of a faint illumination of the northern 
 parts of the sky, somewhat resembling the departure 
 of twilight; and frequently, though not always, seems 
 to emanate from a dark cloud near the northern ho- 
 rizon. Sometimes it presents the appearance of 
 arches of striated light, commonly called Streamers, 
 of about the breadth of a rainbow, originating near 
 the northern horizon, and stretching across the sky, 
 in a southern direction, to the zenith, and sometimes 
 much beyond it. These streaks are sometimes ob- 
 served gradually vanishing, and again in the same, or 
 some other place, suddenly bursting out, as if some 
 luminous matter were rushing from the north towards 
 the south, in the higher regions of the atmosphere. 
 The other more equally diffused portions of the me- 
 teor, which present the appearance of a faint light in 
 the sky, are subject to constant variations in bright- 
 ness; sometimes gradually disappearing in one quar- 
 ter, while they are becoming more vivid in another. 
 When the meteor becomes remarkably bright, the 
 expanse of light in the sky, is sometimes seen to 
 spread and contract, in consecutive flashes, with such 
 rapidity, as to maintain a visible waving and undula- 
 tory movement. Sometimes when this meteor is 
 seen to expand very suddenly over the zenith, par- 
 ticularly in dry, clear, cold weather, a hissing, rushing 
 noise is heard. The variation of the needle is also 
 affected by it, its north pole being usually somewhat 
 
41G ON THE CAUSES AND PRINCIPLES 
 
 diverted from its regular position, towards where the 
 meteor is brightest. 
 
 The altitude of this meteor above the surface of 
 the earth, has been variously estimated by different 
 individuals. Bergman, from a mean of thirty com- 
 putations, makes the height of this phenomenon to 
 be 468 English miles. Boscovich calculated the 
 height of an aurora borealis, observed on the 16th 
 December, 1737, by the Marquis of Poleni, to have 
 been 825 miles. Mairan supposed the far greater 
 number of aurorfe to be at least 600 miles above the 
 surface of the earth. Euler assigned them an eleva- 
 tion of several thousands of miles ; and Dr Blagden 
 limits their height to about 100. 
 
 Various theories have been advanced to explain 
 this phenomenon. According to Kirwan, it is owing 
 to the combustion of hydrogen gas, which he^supposes 
 to exist in great quantity in the higher regions of the 
 atmosphere, and which, he conceives, is set on fire by 
 electricity. This theory is founded upon no evidence 
 whatever, and is disproved by various facts. Air ob- 
 tained at the height of 22,960 feet has been analyzed 
 by Gay Lussac, and hydrogen has not been detected 
 to be one of its elements, save as a constituent of 
 aqueous vapour. And even the proportion of aqueous 
 vapour, contained in the atmosphere, has been found 
 to decrease so rapidly upon ascending perpendicularly, 
 that at the height of 22,960 feet, its mean amount, 
 relative to the other ingredients of the atmosphere, is 
 only about one-eighth part of what it is at the surface 
 of the earth. 
 
 The supposition that hydrogen gas exists in quan- 
 
OF METEOROLOGICAL PHENOMENA. 417 
 
 tity in the higher regions of the atmosphere, is far- 
 ther disproved by the fact, that hydrogen, as well as 
 all other gaseous substances, when in free communi- 
 cation with the air, or with each other, have a tend- 
 ency to intermix together so completely, that each 
 proportion of space contains an equal amount of each 
 of them. Thus if two glass globes, the one above 
 the other, and communicating by a stopcock, be sev- 
 erally filled with different gases, and the stopcock 
 turned, so that they are allowed to communicate, they 
 gradually and completely intermix, even though the 
 specifically lighter gas be contained in the upper 
 globe. For instance, suppose the upper globe be 
 filled with hydrogen, the lightest of all gases, and the 
 lower one filled with common air ; if the stopcock be 
 turned so as to allow them to communicate, they be- 
 come in a short time so completely intermixed, that 
 each globe is found to contain an equal proportion of 
 hydrogen, intermixed with an equal proportion of com- 
 mon air. Now, reasoning from the analogy of the 
 above experiment, it must be inferred, that hydrogen 
 does not exist either as a separate gas beyond the 
 boundaries of the atmosphere with which we are ac- 
 quainted, nor as a large constituent of the more ele- 
 vated aerial strata. Even supposing that by some 
 means or other a stratum of hydrogen was suddenly 
 spread over the summit of the atmosphere, it must 
 be inferred according to the same analogy, that it 
 would very soon be intermixed so completely with the 
 subjacent aerial strata, that each proportion of space 
 would contain an equal quantity of it, relative to the 
 proportions of the other atmospheric elements. When 
 
 3g 
 
4 18 ON THE CAUSES AND PRINCIPLES 
 
 these observations are considered in conjunction with 
 the fact, that hydrogen, except as an element of 
 aqueous vapour, does not exist as a constituent of the 
 atmosphere lower than the altitude of 22,960 feet, 
 which is the greatest height ever reached by man, it 
 may be inferred that it does not exist above that 
 elevation. 
 
 We will only farther remark, that if Kirwan's 
 theory was correct, it is presumable, that the pheno- 
 menon of the aurora would be of equally frequent oc- 
 currence, and equally brilliant, in intertropical cli- 
 mates, as it is in high latitudes. This, however, is 
 not the fact. The aurora, at least in its more bril- 
 liant exhibitions, is confined almost exclusively to very 
 high latitudes; and in intertropical climates it is wholly 
 unknown. 
 
 According to Dr Halley, the aurora is owing to 
 the circulation of the magnetic effluvia of the earth 
 from one pole to the other. And Beccaria, who sup- 
 posed that the electric fluid circulated in a similar 
 manner from pole to pole, conceived that the aurora 
 was produced in certain states of the atmospherej 
 when the circulation of the electric fluid becomes less 
 elevated than usual. Both these theories have been 
 disproved by the observations of Mr Forster, by which 
 it appears, that the columns of the aurora shoot up 
 towards the zenith from the southern polar regions, in 
 the same manner as they do from the northern. 
 
 A modification of the theory last mentioned, is, that 
 the aurora is produced by the passage of the electric 
 fluids, in the higher regions of the atmosphere, from 
 the polar towards the equatorial latitudes. Accord- 
 
OF METEOROLOGICAL PHENOMENA. 419 
 
 ing to this theory, electricity is constantly circulating 
 through the terrestrial strata from the equatorial to 
 the polar regions. It is then supposed to ascend 
 from the earth, and return in the higher regions of 
 the atmosphere to the equatorial latitudes, where its 
 circuit is completed by again descending to the earth. 
 This theory is free from the objections urged against 
 the others, and is supported by the analogy of certain 
 electric phenomena that can be artificially exhibited. 
 '* Thus, if a glass tube, resembling a Florence flask in 
 size and shape, be exhausted of air by means of a 
 stopcock and syringe fixed to its mouth, and be then 
 excited by friction, it will appear filled with a pale 
 light, resembling the aurora borealis, which will go 
 and come at intervals, sending forth brilliant flashes, 
 exactly as this meteor does in the heavens. If either 
 end of the flask be presented to the conductor of an 
 electrical machine, the other being held in the hand, 
 a constant stream of pale light will be transmitted 
 through it proceeding from the conductor. Mr Can- 
 ton also contrived to exhibit an imitation of the aurora 
 borealis, by means of electricity transmitted through 
 the Torricellian vacuum formed in a glass tube, about 
 three feet long, and hermetically sealed. When one 
 end of the tube is held in the hand, and the other ap- 
 phed to the conductor of an electrical machine, the 
 whole tube is illuminated from end to end, and will 
 continue luminous for a considerable time after it has 
 been removed from the conductor. If after this, it 
 be drawn through the hand either way, the light will 
 be uncommonly intense, extending without the least 
 interruption from one hand to the other, even through- 
 
420 ON THE CAUSES AND I'lllNCIPLES 
 
 out its whole length. By this operation, however, 
 a great part of the electricity is discharged ; never- 
 theless the tube will flash at intervals, if held at one 
 extremity and kept quite still, but if it be grasped by 
 the other hand at the same time in a different place, 
 strong flashes of light will hardly ever fail to dart 
 from one end to the other, which will continue for 
 twenty-four hours, and longer, without any fresh ex- 
 citation. An arched double barometer, of a consider- 
 able height, exhibits these phenomena in a still more 
 striking manner." 
 
 The striking analogy between the luminous ap- 
 pearances exhibited in the preceding experiments, 
 and that of the aurora borealis, affords strong grounds 
 for believing, that this phenomenon is produced by 
 the passage of electricity, through the elevated and 
 highly rarefied strata of the atmosphere, from the polar 
 towards the equatorial regions. This opinion is far- 
 ther confirmed by the circumstance of the magnetic 
 needle being affected by a brilhant aurora, in the 
 same manner as it is by the approach of a thunder- 
 cloud. And when it is considered, that coldness 
 and dryness are favourable to the accumulation of 
 electricity in bodies, the hypothesis under considera- 
 tion is also supported by the fact of this phenomenon, 
 only making its appearance in high latitudes, and in 
 winter, rather than in summer. 
 
 Upon the preceding theory it may be remarked, 
 that neither electricity nor any other fluid can set it- 
 self in motion ; and though set in motion, could not 
 continue to pervade either the earth or the atmo- 
 sphere, or any other obstructing medium, without the 
 
OF METEOROLOGICAL PHENOMENA. 421 
 
 agency of some force, or propelling power to maintain 
 the motion. The principal defect therefore in the 
 above theory, is, that no explanation is given how the 
 circulation of electricity originates, and is maintained 
 in the manner described ; or how the aurora in this 
 climate, should be visible only on rare occasions. 
 
 In what follows, we do not pretend wholly to sup- 
 ply what is wanting to render the above theory satis- 
 factory ; but we will endeavour to throw out some hy- 
 pothetical suggestions, which, to a hmited extent, will 
 obviate objections, and may ultimately lead to a tho- 
 rough explanation of the whole phenomena. 
 
 According to the principle we formerly advanced 
 when treating of the cause of thunder in the fifth chap- 
 ter, viz., that heat and electricity are mutually repel- 
 lent ; the capacity of any body for electricity increases 
 as its temperature sinks, and diminishes as its tem- 
 perature rises. In the former case, it becomes un- 
 dercharged, and attracts electricity ; in the latter, it 
 becomes surcharged, and gives off electricity. Agree- 
 ably to this principle, the capacity of the atmosphere, 
 and the subjacent terrestrial strata for electricity, and 
 the amount of it therein contained, increases from 
 the equatorial to the polar regions. Now, all that is 
 necessary in order to account for the origin and main- 
 tenance of an electric current, such as that which has 
 been conceived to exist in order to explain the pheno- 
 menon of the aurora, is to show how any portion of 
 the earth or atmosphere in the direction of the elec- 
 tric current, should have a tendency to become un- 
 dercharged with electricity, so that the electric fluids 
 
422 ON THE CAUSES AND PllINCirLES 
 
 should be attracted in the supposed direction of the 
 current. 
 
 When treating of winds, it was stated, that their 
 most general cause, is the gradual diminution in the 
 mean annual temperature of the atmosphere, from the 
 equatorial towards the polar regions. And, if the 
 mean for the whole earth be estimated, that the pre- 
 vailing direction of the wind in the upper half of the 
 atmosphere, is from the equatorial towards the polar 
 latitudes, while the prevailing direction in the lower 
 half, is from the polar towards the equatorial. Now, 
 as the prevailing wind in the upper half of the atmo- 
 sphere from the equatorial towards the polar regions, 
 is becoming gradually colder, it may be conceived to 
 be constantly more or less undercharged with electri- 
 city, in consequence of its electric capacity increasing 
 faster than it is supphed by the non-conducting, or 
 rather the very slow-conducting dense atmospheric 
 strata underneath. Hence, an electric current in the 
 higher regions of the atmosphere, from the polar to- 
 wards the equatorial regions, ought to be produced, 
 by the tendency of electricity to diffuse itself equally 
 among bodies, according to their several affinities for 
 it. The aerial particles, as their temperature gets re- 
 duced in their progress northwards in the higher re- 
 gions of the atmosphere, have their capacity for elec- 
 tricity thereby increased. Consequently, the mutual 
 repulsion of the particles of electricity accumulated in 
 the polar latitudes of the earth and atmosphere, gives 
 rise to an electric current towards the equatorial lati- 
 tudes. And the reason why the visible, and concen- 
 trated portion of this electric current, is restricted to 
 
OF METEOROLOGICx\L PHENOMENA. 423 
 
 great altitudes in the atmosphere, may be owing, to 
 the increasing power of the air in conducting electri- 
 city as its density diminishes. Near the earth's sur- 
 face, the density of the air is so great, that electricity 
 can only pass through it very slowly: whereas, at great 
 altitudes, its density is so much reduced, that electri- 
 city may pass through it with considerable facility. 
 
 The abstraction of a portion of the electricity from 
 the elevated regions of the atmosphere above the polar 
 regions, must cause electricity to ascend from the sub- 
 jacent terrestrial strata, in order to compensate for 
 the deficiency of electricity created by the electric 
 current towards the south, which we have supposed 
 to give rise to the aurora. Upon similar principles, 
 the passage of electricity in the polar regions from 
 the earth to the higher regions of the atmosphere, 
 must cause the earth in these latitudes to be un- 
 dercharged with electricity, relative to its capacity 
 for it. Hence, an electric current through the ter- 
 restrial strata from the equatorial to the polar regions 
 will be produced. And this in its turn, will create a 
 deficiency of electricity in the terrestrial strata of the 
 equatorial regions. The reduction of temperature 
 which the atmosphere undergoes, and the consequent 
 increased electric capacity which it acquires, in as- 
 cending from the earth's surface, upon the approach 
 of the sun to the zenith, and which we supposed in the 
 fourth chapter to be the chief cause of the rainy sea- 
 son in intertropical climates, enables us to understand 
 how the electric current is completed, in accordance 
 with the theory of the aurora boreahs, which we are 
 now endeavouring to elucidate. The electric current 
 
424 ON THE CAUSES AND PRINCIPLES 
 
 in the higher regions of the atmosphere from the 
 polar to the equatorial latitudes, upon reaching the 
 intertropical zone where the atmosphere is ascending, 
 will be attracted downwards towards the earth, by the 
 increasing capacity of the atmosphere, and also of 
 aqueous vapour, for electricity, as their temperature is 
 reduced in rising from the heated surface of the earth. 
 And this descending electric current, is possibly one 
 of the sources whence the clouds in intertropical 
 climates, are supplied during the rainy season with 
 electricity. 
 
 Thus we see that the force or propelling powerwhich 
 originates, and maintains the electric current before 
 described, may be owing to attraction exerted upon 
 electricity by the increasing capacity of the atmo- 
 sphere for it, as its temperature gets reduced upon 
 rising from the earth's surface in intertropical climates; 
 and as its temperature gets farther reduced, in its 
 progress from the equatorial to the polar latitudes, in 
 the higher regions of the atmosphere. Hence the 
 current of electricity so produced moves in an oppo- 
 site direction to that of the atmospheric current, and 
 only does so, when the wind blows from a warm to- 
 wards a cold climate. 
 
 It may be objected to the view which we have given 
 of the electrical current, that it ought to present a 
 luminous appearance in rising from the polar latitudes 
 of the earth to the higher regions of the incumbent 
 atmosphere, in the same manner as it does in its pass- 
 age in the higher regions of the air from the polar to 
 the equatorial latitudes. In answer to this objection 
 it may be remarked, that owing to the increasing non- 
 
OF METEOROLOGICAL PHENOMENA. 426 
 
 conducting power of the air, as its density augments 
 in descending towards the earth's surface, the current 
 of electricity is probably more concentrated in its 
 passage to the equatorial latitudes in the higher at- 
 mospheric regions, than it is when rising in polar lati- 
 tudes from the subjacent earth, to those elevated 
 aerial strata. And hence, it may present a luminous 
 appearance in the former circumstances, and not in 
 the latter. Air is a non-conductor of electricity, and 
 the denser, the drier, and the colder it is, the strong- 
 er do its non-conducting properties become. No 
 substance however is possessed of such perfect non- 
 conducting properties, as altogether to prevent the 
 passage of electricity from one body to another, when 
 the latter is electrically undercharged relative to the 
 former. It is not improbable but the electric current 
 in the higher regions of the atmosphere, is supplied 
 with electricity in high latitudes, from a very large 
 extent of the earth's surface. And the great extent 
 of terrestrial surface from which it is supplied may 
 compensate for the slowness, and smallness of the 
 supply from any given portion thereof. Supposing 
 that electricity ascends from every part of the earth's 
 surface within the Arctic circle, we would have the 
 ascending current of electricity diffused over a circle 
 of the earth's surface, the diameter of which would 
 be no less than 3266i English miles. Whereas, the 
 portion of the higher atmospheric strata, into which 
 the current of electricity in its progress towards the 
 equatorial regions is subsequently concentrated, may 
 not exceed a few miles in perpendicular depth, and 
 perhaps not so much. 
 
 3h 
 
426 ON THE CAUSES AND PRINCirLES 
 
 In like manner, the reason why the aurora becomes 
 less brilhant as it recedes from the polar latitudes, 
 until it becomes altogether invisible, is probably owing 
 principally to the circumstance of the electric current 
 becoming diffused over a larger circumference, as it 
 diverges from the polar circles towards the equatorial 
 regions; and partly, perhaps, to the increasing tem- 
 perature, on receding from the polar regions, aug- 
 menting the conducting power of the atmosphere; and 
 thereby giving less obstruction to the electric cur- 
 rent; and consequently causing less electric accumu- 
 lation. 
 
 The sudden extension and bursting out of the au- 
 rora at particular places, and thereafter its becoming 
 gradually less vivid, may be owing to the obstruction 
 given to the electric current by the non-conducting 
 properties of a cold, dry atmosphere. In such cir- 
 cumstances, it may be easily conceived that the elec- 
 tric fluids may, for a time, accumulate in high lati- 
 tudes, till the increasing repellent power, mutually 
 subsisting among the particles of electricity, enables 
 them at length to force a passage from some project- 
 ing point through the obstructing medium. This is 
 somewhat analogous to the manner in which portions 
 of electricity accumulating in a thundercloud are dis- 
 charged at intervals, by forcing a passage from a de- 
 pendent part of the cloud to the earth, through the 
 non-conducting atmosphere. 
 
 The extreme elevation assigned to the aurora by 
 Bergman, Boscovich, Euler, and others, which we 
 formerly mentioned, I conceive, to be erroneous. In- 
 deed the remarkable discrepancy between their esti- 
 
OF METEOROLOGICAL PHENOMENA. 427 
 
 mates, such as Euler supposing its elevation to be 
 several thousand miles, and Blagden only 100, shows 
 that the principles upon which the estimates are made, 
 are not to be relied upon. Besides, as electricity 
 meets with no obstruction whatever in passing through 
 an entire vacuum, the irregular, and frequently inter- 
 rupted movements, and sudden burstings forth of this 
 meteor from particular projecting points, do not admit 
 of any explanation, unless the phenomena presented, 
 are the result of movements of the electric fluids with- 
 in the Hmits assigned to the atmosphere, by which the 
 earth is surrounded. 
 
 The hissing or whizzing noise which sometimes, 
 and especially in high latitudes, accompanies the sud- 
 den bursts or eruptions of the aurora, I am disposed 
 to ascribe, not as is usually done to the distant phe- 
 nomena, but to the corresponding, and simultaneous 
 movement of the electric fluids in the air around the 
 spectator. The particles of electricity are mutually 
 repellent. Of course, when a current of electricity 
 in the higher regions of the air, suddenly supervenes 
 the place where the observer is situated, all the elec- 
 tricity contained in the atmosphere underneath the 
 electric current, is repelled towards the earth; and 
 the whizzing or crackling noise heard, I conceive is 
 produced by the passage of repelled electricity from 
 one aerial particle to another. When the air is fully 
 saturated with electricity, and when, from great cold- 
 ness, dryness, and density, its non-conducting power 
 is strongest, the whizzing noise should be loudest. 
 And in opposite circumstances, the proportion of re- 
 pelled electricity may be so smaU in quantity, or may 
 
428 ON THE CAUSES AND PRINCIPLES 
 
 pass SO easily to the earth, as to occasion no audible 
 sound whatever. 
 
 Supposing the perpendicular height of the aurora 
 to be only thirty or forty miles above the level of the 
 sea, which is probably much nearer the truth than the 
 previously stated estimates, it is obvious, that the hiss- 
 ing or crackling noise above alluded to, is not pro- 
 duced by what is occurring either at that, or any 
 greater elevation, for the two following reasons. 
 
 1. Sound emitted by a sonorous body is less 
 audible, according as the air around it becomes more 
 rarefied. And when a body is surrounded by a per-, 
 feet vacuum, its susceptibility of communicating sound 
 ceases entirely. Of course, no sound audible at the 
 earth's surface, can be produced by the vibratory 
 movements of matter existing beyond the boundaries 
 of the atmosphere. And even at the height of thirty 
 or forty miles above the level of the sea, the air must 
 be so rarefied, that, were all the artillery on earth 
 simultaneously discharged at that altitude, no audible 
 sound could reach the earth's surface. 
 
 2. It has been ascertained that sound travels at 
 the rate of 1142 feet in a second, or about an Eng- 
 lish mile in four and a half seconds. Consequently, 
 before sound produced at the height of 30 or 40 
 miles could reach the earth's surface, two or three 
 minutes would elapse. Now, the fact which dis- 
 proves the hypothesis that the hissing noise is pro- 
 duced at the height of 30 or 40 miles, is, that it is 
 heard exactly at the same instant, that the rushing 
 extension of the meteor towards the south is seen. 
 Indeed, so simultaneously is the extension of the 
 
OF METEOROLOGICAL PHENOMENA. 429 
 
 meteor towards, or over the zenith seen, and the 
 whizzing sound heard, and so distinct is the sound 
 from every other, that no person can observe the con- 
 comitance without being impressed with the behef, 
 that the sound is produced by the influence of the 
 meteor. The only hypothesis, therefore, by which 
 the two phenomena can be connected, is that which 
 we have advanced, viz. to suppose that the whizzing 
 sound is produced by a movement of repelled electri- 
 city in the air immediately surrounding the spectator, 
 corresponding to, and produced by that in the higher 
 regions of the atmosphere, which we conceive to be 
 the cause of the aurora. 
 
 The fact of the aurora being visible only on rare 
 occasions, may be owing to the electric current being 
 sufficiently strong only under such a favourable com- 
 bination of circumstances, as rarely occurs in this cli- 
 mate. And the chief of these circumstances, accord- 
 ing to the hypothesis under consideration, is probably 
 a rapid decrease from the polar to the equatorial 
 latitudes, in the amount of electricity contained in the 
 higher strata of the atmosphere, relative to their elec- 
 tric capacity; and which may be occasioned by a strong 
 wind from the south, in the upper regions of the air. 
 This may possibly be assisted by an unusual accumu- 
 lation of electricity in the atmosphere in polar lati- 
 tudes, relative to the atmospheric capacity in those 
 regions for electricity ; and which may be occasioned 
 by a rapid rise of temperature, subsequent to an un- 
 usual degree of atmospheric dryness, coldness, and 
 stillness. Such are all the hypothetical suggestions 
 which we mean at present to advance, in order to 
 
430 ON THE CAUSES AND PRINCIPLES, &C. 
 
 explain the phenomena presented by the aurora bo- 
 realis. 
 
 We have now concluded our survey of the causes 
 and principles of meteorological phenomena. In a 
 variety of instances, the views and explanations ad- 
 vanced are new ; but how far they are entitled to the 
 character of being true, it is not for me to decide. 
 When different explanations have been given of phe- 
 nomena by different individuals, their relative degrees 
 of probability, or improbability, have been impartially 
 weighed and appreciated ; and where opinions how- 
 ever universally received by meteorologists, appeared 
 to be erroneous, we have not failed to call them in 
 question. On various occasions, when meteorologi- 
 cal facts have obtruded themselves, of which the ex- 
 planation was either defective, or altogether wanting, 
 we have either endeavoured, on the spur of the mo- 
 ment, to supply the deficiency, or admitted our in- 
 competence to do so. Many of the explanations 
 given may be objected to on account of their hypo- 
 thetical character. But be it recollected, that to con- 
 ceive and construct an hypothesis, by which unex- 
 plained phenomena may be accounted for in accord- 
 ance with the analogies of nature, is always the first 
 step towards discovery ; and even though, from some 
 oversight, it may turn out upon examination to be 
 erroneous, the attempt to refute it sometimes reveals 
 the truth. 
 
 END OF THE METEOROLOGICAL TREATISE. 
 
A SUMMARY 
 
 OF THE 
 
 MORE IMPORTANT INFORMATION, 
 
 COLLECTED FROM VARIOUS SOURCES, RELATIVE 
 
 TO 
 
 MARSH FEVERS; 
 
 OBSERVATIONS ON THE VARIOUS MEASURES RECOMMENDED FOR 
 THE PREVENTION OF THIS CLASS OF EPIDEMICS. 
 
ON MAKSH FEVERS. 
 
 Prefatory Observations. — Chemical science has 
 hitherto afforded no information regarding the nature 
 of infectious effluvia. Neither the tainted atmo- 
 sphere of a fever-hospital, nor of a city infected with 
 the plague where hundreds are dying daily, nor the 
 noxious air from putrid marshes, nor that which is 
 contained in apartments where persons have died of 
 infectious diseases, has ever yet been found by che- 
 mical analysis, to contain any substance deleterious to 
 human life, and to the presence of which the pheno- 
 menon of infection might be referred. Experiments 
 with a view to such discoveries, and particularly to 
 ascertain the nature of marsh miasma, have been 
 often made, but uniformly without success. " M. 
 Julia, who has paid considerable attention to chemical 
 analysis, has sixty times subjected to trial the air of 
 the marshes of Cercle, near Narbonne ; of the pond 
 of Pudre, near Sigean ; of Salces and Salanque, in 
 Roussillon; of Capestang, not far from Beziers ; and 
 of the different marshes on the coast of Cette ;" and 
 has constantly obtained the like results, which differed 
 in no respects from the ordinary ingredients of atmo- 
 spheric air. Various opinions, I am aware, have, on 
 
 3i 
 
434 ON MARSH FEVERS. 
 
 this subject, been promulgated. By some, marsh mi- 
 asmata have been supposed to consist of azote ; by 
 others of carbonic acid gas ; some say hydrogen ; 
 others carburetted hydrogen ; and others sulphuretted 
 hydrogen. From such discordant opinions, it may 
 with reason be inferred, that nothing hitherto has 
 been discovered relative to this point, except that 
 chemical analysis is as yet too imperfect to determine 
 the composition of marsh miasmata, (and, it may be 
 added, of other infectious effluvia,) or even to detect 
 their presence. The fact, however, which demon- 
 strates that the above conclusions are erroneous, is, 
 that all those substances of which miasmata are said 
 to consist, have often been evolved by artificial means 
 in the laboratory of the chemist, without, in any one 
 instance, producing disease. 
 
 The sense of smell is equally at fault in discover- 
 ing the nature, or the presence of infectious effluvia. 
 Certain marshes are observed to emit offensive odours; 
 but others, where no such smells can be perceived, 
 are known to be equally productive of the same spe- 
 cies of fever. And in seaports, in the very focus 
 where the yellow fever, the most deadly of all this 
 class of diseases, has made its irruption, the olfactory 
 nerves give to man no intimation of danger. Hence 
 it may be concluded, that odoriferous particles are 
 different from those which originate marsh fevers. In 
 like manner, the presence of the various kinds of 
 effluvia which communicate small-pox, measles, hoop- 
 ing-cough, scarlet fever, &c. to a healthy person in- 
 troduced into the presence of the sick, cannot be dis- 
 covered by the sense of smell. And it is said that 
 
ON MARSH FEVERS. 435 
 
 expurgators at Lazarettoes, have been known to be 
 suddenly seized with the plague upon opening bales 
 of goods from infected places, when no other evi- 
 dence of the presence of the deadly instrument of 
 communication could be detected. Finally, I have 
 heard it stated that some practitioners could recognise 
 the smell peculiar to the fever-ward of an hospital, 
 and likewise that of an apartment where a patient 
 labouring under Asiatic cholera was lying. But even 
 in these cases, it is doubtful whether that which is 
 perceived be the odour of morbid perspiratory secre- 
 tions, or of the pecuhar effluvia which generate typhus 
 and cholera. 
 
 From these observations it is obvious, that all the 
 knowledge we possess regarding the origin of epidem- 
 ics, and of the mode in which they are propagated, 
 and of the means by which they may be prevented, 
 or avoided, is founded upon inferences deduced from 
 observing the locahties, the coincidences, and other 
 circumstances in which they make their appearance, 
 contrasted with those in which immunity from their 
 influence is maintained. And in order to connect 
 and explain these, as well as all the other phenomena 
 which the history of such diseases reveal, we are 
 forced to believe in the existence of material instru- 
 ments of communication susceptible of atmospheric 
 diffusion, to which the names of effluvia and miasmata 
 have been assigned ; but of the nature or composi- 
 tion of which, it is probable that mankind are for ever 
 destined to remain ignorant. 
 
 Epidemic diseases may be divided into three 
 classes : — 
 
436 ON MARSH FEVERS. 
 
 l6-^. Those which originate exclusively in endemic 
 causes, such as a miasma engendered by the soil 
 operated upon by heat and moisture, or some pecu- 
 liarity in the water, or in the manner of living of the 
 mass of the people. Marsh fevers may be given as 
 an example of the former, and the Goitres of Swit- 
 zerland as an example of the latter. 
 
 2d. Those which arise from atmospheric causes, 
 such as great, sudden, and sometimes frequently re- 
 peated transitions from heat to cold, or from dryness 
 to dampness, or the opposite. To this class belong 
 cattarh and influenza ; and likewise coughs and all 
 slight inflammatory diseases arising from catching 
 cold. 
 
 3d. Those whose origin is unknown, but which are 
 kept alive, and propagated from man to man, by means 
 of infectious effluvia generated during disease. To 
 this class belong small-pox, measles, scarlet fever, 
 typhus fever, plague, Asiatic cholera, &c. 
 
 The first of the above classes, viz. marsh fevers, 
 goitres, &c. exhibit the distinguishing characteristics 
 of non-contagion, viz. restriction to the localities which 
 give them birth, and making their appearance simul- 
 taneously in all places similarly circumstanced with 
 regard to soil, heat, and moisture, or other local 
 causes ; however distant from each other, or however 
 secluded from human intercourse. 
 
 The second class, viz. catarrh and influenza, &c, 
 also exhibit peculiar attributes, which are likewise in- 
 dicative of non-contagion. They may be distinguished 
 from the first class, by not being restricted to certain 
 localities J and from the third class, from the following 
 
ON MARSH FEVERS. 437 
 
 circumstances. Isf, From their never spreading and 
 travelling progressively from town to town, and from 
 district to district, with the slow progress of pilgrims, 
 vagrants, armies, or caravans. 20^, From their re- 
 specting neither non-intercourse, nor frequent inter- 
 course. 3d, From their showing no preference either 
 for thickly or for thinly peopled districts, nor for the 
 usual tracks of commercial intercourse, such as h'loh- 
 ways, navigable rivers, and canals. 4^A, From their 
 indiscriminately and simultaneously invading all places 
 and countries, however distant or secluded from each 
 other, where those sudden or successive atmospheric 
 vicissitudes which produce them, have occurred. 
 
 The third class, viz. small-pox, typhus fever, 
 plague, Asiatic cholera, &c. differ from the two pre- 
 ceding classes, by presenting the strongly marked, and 
 never to be mistaken features of infection; the chief 
 of which are the following: — 1^^, Attacking succes- 
 sively those, or more frequently a portion only of 
 those, who, by proximity of dwelling, and commu- 
 nication with the diseased, are most exposed to infec- 
 tion; such as the different members of the same family, 
 and inhabitants of the same tenement, particularly 
 those who attend the sick, or frequently enter, and 
 perhaps sleep in the apartment in which they lie. 2(/, 
 Spreading from one house to another according as 
 their inmates have visited, or have had communica- 
 tion with persons from infected dwellings, or have 
 received body clothes, or bedding, previously used by 
 infected persons. 3f/, Spreading from town to town, 
 and breaking out upon, or immediately subsequent to, 
 the arrival of ships, troops, or individuals, from in- 
 
438 ON MARSH FEVERS. 
 
 fected places; those usually being the first attacked 
 who had recently visited the seat of infection, and 
 there imbibed the poison. 4ifA, Travelling progres- 
 sively from one country to another, (like the Asiatic 
 cholera, without regard to the direction or velocity 
 of the wind,) along the leading thoroughfares of com- 
 merce, whether by sea or land, and whether by high- 
 ways, navigable rivers, or canals: following the march 
 of armies; and making their irruption not simultane- 
 ously in distant localities similarly circumstanced, but 
 consecutively, so that their path, interspersed with 
 occasional leaps over an intermediate village, can be 
 traced on a map, and the successive dates of their 
 appearance at each town and village on their way, 
 may be chronologically recorded. 
 
 It is only of the first of these classes of epidemics 
 that we mean now to treat, and in doing so, we will 
 confine ourselves exclusively to marsh fevers, partly 
 in consequence of the great mortality resulting from 
 them, which, according to Bancroft, exceeds that of 
 all diseases incident to mankind;* and partly because 
 the facts concerning them, and the laws that regulate 
 their appearance and disappearance, are most interest- 
 ing, and best established. Without farther preface, 
 we will proceed to give 
 
 A SUMMARY OF THE MORE IMPORTANT INFORMATION, COL- 
 LECTED FROM VARIOUS SOURCES, RELATIVE TO MARSH 
 fevers; WITH OBSERVATIONS ON THE VARIOUS MEASURES 
 RECOMMENDED FOR THE PREVENTION OF THIS CLASS OF 
 EPIDEMICS. 
 
 * See Bancroft's Essay on Yellow Fever, p. 490. 
 
ON MARSH FEVERS. 439 
 
 It has long been observed, that the insalubrity of 
 warm climates, bears a general relation to the marshi- 
 ness of the soil, and to the degree of heat to which 
 that soil is exposed. All level low-lying countries, 
 such as are frequently found on the banks, and near 
 the mouths of rivers; and particularly those which are 
 liable to be inundated during rainy weather, and after- 
 wards, from want of a sufficient declivity, retain a 
 swampy character, are, when much subjected to solar 
 heat, the most productive of disease. Mr Annesley, 
 in his work on the prevalent diseases of India, and of 
 warm climates generally, refers the different sources 
 of miasma, or malaria, to the following heads: — Isf, 
 Marsh lands, and the low grounds along the banks, 
 and at the mouths of rivers; 2d, The low, dense, 
 luxuriant copsewood, called Jungles in the East; 3g?, 
 Forests, situated in valleys; 4:th, Rice-grounds; 5th, 
 Canals and ditches, pools, and lagoons. To these 
 we may add clay soils, and such as are rich with vege- 
 tative nutriment, particularly if allowed to lie fallow, 
 or to remain uncultivated and unploughed. Wharves 
 likewise, particularly when composed of rich alluvial 
 depositions, and constructed so as to encroach upon 
 the bed of a river, seem, when under the influence of 
 a vertical sun, to yield miasmata possessing the strong- 
 est morbific powers.* 
 
 The diseases which such localities generate, are 
 chiefly of the febrile kind, varying in degrees of ma- 
 
 * Peat-bogs or moors do not appear to generate marsh miasmata, 
 nor their attendant class of diseases. This is supposed to be owing 
 to their antiseptic quality, enabling them to retard the decompo- 
 sition of vegetable and animal substances. 
 
440 ON MARSH FEVERS. 
 
 lignity from the fever and ague or intermittent, to (be 
 deadly yellow fever. In Batavia in the island of Java, 
 vegetative life presents itself in its greatest luxuriance 
 and variety ; " but the atmosphere is continually in- 
 fected with deleterious vapours which rise from the 
 surrounding swamps and morasses ; and the trees 
 with which the quays and streets are crowded, impede 
 the free circulation of the air, and retain the putrid 
 effluvia, which otherwise would in some degree be 
 dissipated. Here fevers are continually raging, and 
 of strangers who come to settle, three out of five are 
 reckoned to die the first year." The Pontine marshes 
 in Italy near Rome, are proverbially productive of 
 miasmata which occasion fevers ; and I have been 
 told that in many parts of the United States of Ame- 
 rica, particularly near the banks of the Ohio ; and in 
 many other districts where a large proportion of the 
 lands possess a swampy character, autumnal sickness 
 is every year so general, that it may be said in some 
 degree, less or more, to aff"ect the whole population. 
 
 Indeed, in all warm chmates without exception, 
 wherever morasses and pools of stagnant water exist, 
 or wherever inundations of rivers leave vegetable or 
 animal substances to putrefy in moist muddy soils, ex- 
 posed to the burning heat of a vertical sun, fevers, 
 sickness, and unhealthiness of climate, are never-fail- 
 ing attendants. But the fact which most satisfacto- 
 rily proves such soils operated upon by heat to be the 
 cause of disease, is, that no sooner are the marshes, 
 and the pools of stagnant water impregnated with ve- 
 getable and animal substances removed, than the fe- 
 vers and sickness ascribed to them in a great mea- 
 
ON MARSH FEVERS. 441 
 
 sure disappear, and the climate becomes more salu- 
 brious. Calcutta, which is situated in the midst of a 
 flat and marshy country, was, at its first establishment 
 as a European colony, almost as destructive to human 
 life by reason of the insalubrity of its atmosphere, as 
 Batavia. By clearing away part of the trees and 
 jungle, and by draining some of the most offensive 
 marshes in the neighbourhood of the city, and filling 
 up many of the tanks in the streets, the climate, though 
 still very trying and dangerous to the constitution, 
 particularly of new-comers, is said to have become 
 much less so than it was. In the United States of 
 America it is observed, that gradually as the lands are 
 getting: drained, cleared of woods, and cultivated, so 
 in proportion are the agues and autumnal fevers be- 
 coming less frequent, and less virulent. And in the 
 county of Essex in England, and also in Cambridge- 
 shire, Lincolnshire, and the East Riding of York- 
 shire, agues and intermittent fevers, which were for- 
 merly very prevalent, have become, since the soil has 
 been better drained and cultivated, comparatively rare. 
 " Violent fevers," says Dr Bancroft, " which were 
 considered as pestilential, formerly prevailed very of- 
 ten in the summer and autumn at Bourdeaux, and 
 frequently compelled the parliament to remove to 
 other places. The Cardinal de Sourdis, having form- 
 ed a just opinion of the cause of these fevers, under- 
 took to drain a very offensive marsh, which then ex- 
 isted on the west of the city. Accordingly, two great 
 canals were dug by his orders, and at his expense, to 
 convey the stagnant water into the river, and a fine 
 causeway being erected over the infected spot, and 
 
 3k 
 
442 ON MARSH FEVERS. 
 
 planted with rows of elm trees, the plague, so called, 
 ceased to appear." 
 
 That heat is an auxiliary in the formation of mor- 
 bific marsh miasmata, is proved by innumerable facts. 
 In cold latitudes where the greatest summer heat is 
 inconsiderable, the inhabitants of swampy soils are but 
 little disturbed with marsh fevers. In climates where 
 the difference between the summer and winter tem- 
 perature is considerable, marsh fevers seldom or never 
 make their appearance till the heat of summer begins 
 to be oppressive. At first they are not only less fre- 
 quent, but their symptoms are in general comparative- 
 ly mild ; but it is observed, that as the heat of sum- 
 mer advances, and particularly in those years when the 
 heat becomes unusually great, the fevers increase not 
 only in frequency, but also in virulence and malignity 
 of character. Gradually, however, as the temperature 
 declines, marsh fevers again become not only less fre- 
 quent, but milder and less dangerous, till at length, 
 upon the accession of frost or cold weather, they en- 
 tirely disappear. 
 
 The corresponding seasons of different years vary 
 extremely in their productiveness of marsh fevers. 
 In general much rain in the end of spring, and during 
 the first half of summer, followed by excessive heat 
 and drought, give rise to the greatest prevalence, and 
 the most malignant kinds of marsh fever. In such 
 seasons the yellow fever becomes epidemic in many 
 places, chiefly seaports, where in ordinary years it is 
 unknown. 
 
 To the preceding rule there are exceptions, which 
 depend upon differences in respect to the dryness of 
 
ON MARSH FEVERS. 443 
 
 the soil of different places. In order to promote the 
 putrefaction of vegetable substances, moisture, and 
 air, as well as heat, are required. *' Accordingly," 
 says Bancroft, " it is found, on the west coast of Af- 
 rica, and in some of the West Indian islands, which 
 are liable to long droughts, as Barbadoes, and more 
 particularly Antigua, that marsh fevers occur very sel- 
 dom in those dry seasons j but that they become very 
 prevalent whenever these droughts are suddenly ter- 
 minated by frequent rains." On the other hand 
 superfluity of moisture, such as results during inun- 
 dations, retards the putrefaction of vegetables, and 
 the disengagement of miasmata, principally, it is sup- 
 posed, by secluding them from the action of the air. 
 Accordingly it is observed, that the vapours arising 
 from marshes are innoxious, until so much of the 
 water has been evaporated, as to expose the surface 
 of the soil to the atmosphere. And in hke manner, 
 in certain low tropical countries, such as the Dutch 
 and French colonies on the coast of Guiana, viz, 
 Surinam, Berbice, Demerara, and Essequibo, as well 
 as at Cayenne, and the adjoining settlements, the in- 
 habitants are most healthy during the rainy season 
 when the lands are overflown ; and fevers are rarely 
 seen among them, until the prevalence of dry weather 
 has so far caused the water to evaporate, as to leave 
 the surface of the ground uncovered in many places. 
 In such countries, fevers only prevail in the latter part 
 of the dry seasons. 
 
 In places where, from declivity, draining, or other 
 causes, the soil, when exposed to solar influence, soon 
 becomes exhausted of moisture, great heat accom- 
 
444 ON MARSH FEVERS. 
 
 panied with occasional showers is most favourable to 
 the production of miasma and fever. In short, it is 
 when the soil is exposed to the action of the sun and 
 air, and in the state of mud, or rather perhaps be- 
 tween that state and absolute dryness, that deleterious 
 miasmata are most copiously exhaled. And in differ- 
 ent localities, all the variations observable relative to 
 the season of the year, and to different years, when 
 marsh fevers become most prevalent and malignant, 
 are regulated by the different degrees of heat and 
 moisture, requisite to bring the soil to the most fa- 
 vourable state for the exhalation of miasma. 
 
 The period of the year when marsh fevers become 
 most prevalent, is usually sometime after the annual 
 atmospheric temperature has passed its maximum. 
 The number who died daily of the malignant yellow 
 fever at Barcelona in 1821, increased till about the 
 middle of October, but after that period, the fever 
 rapidly subsided. In the seaports of the United 
 States, the yellow fever never makes its appearance, 
 till after the temperature in the shade has remained 
 for several days at or above 80 degrees of Fahren- 
 heit ; and at such times, a thermometer sheltered 
 from currents of air, and exposed, like the ground, to 
 the sun, would stand between 130 and 160 degrees. 
 
 That inundations of rivers when succeeded by heat 
 are causes of malaria, is proved by many facts. Mac- 
 culloch tells us that in Egypt the season of fever com- 
 mences with the subsidence of the Nile. At Bas- 
 sorah the same effects, and to a highly destructive 
 degree, are produced after the overflowings of the 
 Euphrates. At Rome, immediately after an inunda- 
 
 I 
 
ON MARSH FEVERS. 445 
 
 tion of the Tiber in 1695, they were visited with a 
 destructive fever. And similar fevers arise in various 
 places on the banks of the Don, the Danube, and the 
 Rhone, when inundations of these rivers are succeed- 
 ed by heat. Inundations of salt water occasioned by 
 high tides are, in Mr Annesley's opinion, no less 
 productive of miasmata in intertropical climates, than 
 those which arise from fresh water floods. 
 
 It has been supposed that a moist heated air is 
 sufficient of itself to occasion marsh fevers, without 
 the aid of any undetected materials being diff'used 
 throughout the atmosphere, which they call miasmata. 
 This supposition however is disproved by many facts. 
 Marsh fevers never originate at sea in warm climates, 
 even during the rainy season when the air is damp 
 to saturation, unless the ships have previously touch- 
 ed at unhealthy places where such diseases prevail, 
 and where the poison is imbibed which subsequently 
 gives rise to morbid coporeal action. Neither do 
 marsh fevers make their appearance on shore in warm 
 climates during the rainy season, except in the vicinity 
 of marshes and other suspicious soils. And no soon- 
 er are the marshes drained, though the heat and mois- 
 ture of the atmosphere during the rainy season remain 
 as great as ever, than the fevers cease to appear. 
 
 Another fact of importance connected with marsh 
 fevers, and which seems to be completely established, 
 is that persons become less liable to be affected by 
 them, and if affected, the symptoms are usually less 
 severe, and less dangerous, according to the length 
 of time that they have been exposed to the influence 
 of warm climates, and particularly to such as are most 
 
446 ON MARSH FEVERS. 
 
 productive of marsh miasmata. It is accordingly 
 universally admitted, that persons who go from a cold 
 to a warm climate, are much more liable to be affect- 
 ed by fever, and that too with more malignant symp- 
 toms, during the first year of their residence, than 
 ever afterwards. In the seaports of the United 
 States of America, when the autumnal fevers appear, 
 it has been observed, that strangers and new-comers, 
 particularly those who have recently left a cold cli- 
 mate, are the first to be attacked ; and while the 
 natives, and the strangers whose constitutions have 
 been long seasoned to the influence of warm and 
 marshy countries, are merely aff'ected with mild inter- 
 mittent and remittent fevers, the same disease attacks 
 new-comers from cold latitudes, with all the malignant 
 symptoms of the deadly yellow fever. 
 
 In the 60th number of the Quarterly Review, I 
 find it stated, that " the countrymen who come down 
 in the harvest time into the Campagna, Modena, 
 Ferrara, Bresse, &c. where the rice-grounds and 
 marshy districts are principally situated, are most 
 frequently attacked with the fever, even when the 
 season was considered favourable by the natives. A 
 similar observation was made at Walcheren ; it was 
 also remarked that strangers were variously affected 
 according to the district whence they came. Thus it 
 was found that those of the British troops who were 
 natives of mountainous countries, and dry soils, were 
 more frequently affected than the natives of flat and 
 moist districts. General Monnet, who commanded 
 the French troops in Flushing during the whole of 
 the seven years it was in their possession, recom- 
 
ON MARSH FEVERS. 447 
 
 mended that they should not be frequently changed ; 
 for when it was the custom to send battalions from 
 Bergen-op-Zoom every fourth night, in succession to 
 work on the lines of Flushing, these men never failed, 
 on their return to be taken ill in great numbers. 
 General Monnet, therefore, advised that a stationary 
 garrison should be retained in Walcheren, in order 
 that it might be habituated to the air ; and he adduc- 
 ed an instance of a French regiment which suffered 
 only one half the sickness and mortality in the second 
 year of its being there, which it experienced during 
 the first half-year, and it scarcely suffered at all in the 
 third." 
 
 In conformity with the same analogy, it is noticed, 
 that those whose constitutions from birth, or long re- 
 sidence, have become habituated to the influence of 
 warm and marshy climates, are less hable to be af- 
 fected by marsh fevers upon removing to a colder la- 
 titude, than the natives of the country to which they 
 have emigrated. Thus, in the West Indies, and also 
 in the United States of America, it has been observed 
 that negroes recently imported from the warmer cli- 
 mate of Africa, and even their descendants, are less 
 liable to suffer from marsh fevers, than the natives 
 of America, or of the West Indies. 
 
 But though it is completely established that per- 
 sons become less liable to be affected by marsh fevers, 
 and if affected, that the symptoms are usually less se- 
 vere, and less dangerous, according as their constitu- 
 tions have become more habituated to marsh effluvia 
 by long residence in warm swampy climates, still the 
 reason why it is so, is not understood. From various 
 
448 ON MARSH FEVERS. 
 
 analogies, I am disposed to think, thattiiis, as well as 
 several phenomena presented by infectious epidemics, 
 principally depend upon an unexplained property pe- 
 culiar to the nervous system, of being more suscep- 
 tible of impressions, and of exciting proportionally 
 stronger corporeal action, according as it has been less 
 habituated to such, or similar impressions ; and vice 
 versa, of being less susceptible of impressions, and 
 these consequently only capable of exciting propor- 
 tionally feebler corporeal action, according as it has 
 been more habituated to such, or similar impressions. 
 Thus, a person of weak constitution can be brought 
 by the long use of opium, to stand a dose, without 
 experiencing any great inconvenience, which would 
 destroy several strong men unaccustomed to it. Again, 
 upon entering an apartment impregnated with candle 
 smoke, or any other odour, our sense of smell imme- 
 diately communicates the fact ; but after remaining a 
 short time exposed to its influence, we become alto- 
 gether unconscious of its presence. It appears also 
 that the less accustomed the olfactory nerve has pre- 
 viously been to any odour, the more sensitive it is to 
 its impression j and vice versa. Thus, I have been 
 informed by a friend, upon whose veracity I can de- 
 pend, that in Gottingen in Sweden, where wood only 
 is used as fuel, that a person newly arrived from Eng- 
 land can be detected by the smell of coal emanating 
 from his clothes, and which must have been deposited 
 upon them when in this country. Now, in this island 
 where coal is generally used as fuel, and where our 
 sense of smell must be frequently exposed to its in- 
 fluence, we are totally unconscious of its odour. Upon 
 
ON MARSH FEVERS. 449 
 
 analogous principles I conceive, that a small portion 
 of marsh miasma imbibed by a person newly arrived 
 from a cold latitude, and who has previously been al- 
 together unaccustomed to such an emanation, will pro- 
 duce a much stronger influence upon his nervous 
 system, and through its agency, may be expected to 
 produce more virulent morbid action in his corporeal 
 frame, than upon a person whose nerves have long, or 
 frequently, been exposed to similar impressions. 
 
 Upon similar principles, infectious epidemics, (that 
 is, diseases which are communicable from man to 
 man through the instrumentality of some unperceived 
 effluvium emanating from the lungs, or skin, or other 
 discharges of patients, labouring under them,) are 
 most infectious, and most deadly, upon their first 
 breaking out; and this is particularly the case af- 
 ter a long disappearance of the same disease. On 
 the other hand, all infectious epidemics become 
 milder in their symptoms, less deadly, and seemingly 
 less infectious, according as they are of more fre- 
 quent occurrence, and according as they continue 
 for a longer time in the same place. Thus, in that 
 malignant and infectious species of Asiatic cholera 
 which originated in India in 1817, and in the course 
 of seventeen years travelled over the greater part of 
 the earth, it was observed, that the number of deaths 
 relative to recoveries were similar, and always much 
 greater at its first appearance in every town or district 
 which it visited ; and that the proportion of deaths 
 gradually became less, the longer the disease con- 
 tinued in any place, until it entirely disappeared. It 
 might be supposed that these effects should be as- 
 
 3l 
 
450 ON MARSH FEVERS. 
 
 cribed, partly to the increasing care to avoid infection, 
 after the disease had shown its deadly nature ; and 
 partly to the circumstance of the most susceptible per- 
 sons, and whose constitutions might also be the least 
 capable of withstanding the disease, being apt to be 
 the first infected. But every person who witnessed 
 the epidemic, and saw the number of miserable 
 drunken objects who escaped infection, and the little 
 care taken to avoid infection upon the decline of the 
 epidemic, must come to the conclusion, that the 
 above results were principally owing to the circum- 
 stance of the nervous systems of those exposed to the 
 infectious effluvium, having become in some degree 
 habituated to it, and on this account less liable to be 
 excited to morbid action thereby. Analogous facts 
 support this conclusion. For instance, it is observed 
 that nurses, and medical attendants, upon their first 
 introduction to the fever wards of an hospital, are ex- 
 ceedingly liable to be infected with fever. But if 
 they exercise caution in exposing themselves to the in- 
 fectious effluvium emanating from the patients' lungs, 
 and skin, for some time after their first introduction 
 to the hospital, their nervous systems become by habit 
 so insensible to its influence, that no morbid corporeal 
 action can be thereby thereafter excited; and they are 
 consequently seldom or never subsequently attacked 
 with the disease. Were it not for this providential 
 arrangement, it would be almost impossible to pro- 
 cure persons to attend upon those who had the mis- 
 fortune to be attacked with any infectious epidemic. 
 
 The progressive travefling propensity of infectious 
 epidemics, and their incapacity to return over the 
 
ON MARSH FEVERS. 451 
 
 same ground which they have previously traversed, ex- 
 cept in a very hmited degree, can only be explained 
 upon the same principle. After remaining in one 
 place for a short time, the nerves of the persons most 
 exposed to the noxious effluvium become so insensible 
 to its influence, that it ceases to communicate dis- 
 ease ; or if disease be communicated in rare instances, 
 it usually appears in a milder form, and it is seldom 
 propagated farther. Thus, it was observed, that the 
 Black Death which traversed the earth in the 13th 
 century ; and the infectious cholera in the present 
 century, (and the same remark is probably more or 
 less applicable to all infectious diseases,) became gra- 
 dually milder after remaining in any place for a short 
 time ; and that they travelled onwards from one 
 town, and from one country to another, and seldom or 
 never returned, (except in a very limited degree,) to 
 any place which they had previously visited. 
 
 Farther, it is by no means improbable, that habit 
 exerts different degrees of influence in diminishing the 
 deleterious consequences of diff'erent kinds of infec- 
 tious effluvia, according as they are more or less akin 
 to such as mankind are constantly, or frequently ex- 
 posed. This may be the reason why certain epi- 
 demics present a more general, and more permanent 
 infectious character than others ; and why they re- 
 main longer in the same locality. 
 
 The non-liabihty of persons to be infected a second 
 time, (except in extremely rare instances,) with such 
 diseases, as small-pox, measles, and scarlet fever, &c.; 
 and the reason why a second attack of such infectious 
 distempers, as the plague, Asiatic cholera, &c., is 
 
452 ON MARSH FEVERS. 
 
 usually observed to be less virulent than the first, pro- 
 bably depends upon the same principle, viz., a gra- 
 dually increasing insensibility of the nervous system 
 to be acted upon by any exciting cause, according as 
 it has been more exposed to its influence. The optic 
 nerve presents phenomena somewhat analogous. By 
 continued exposure for a short time to a very strong 
 light, this nerve becomes insensible to the influence 
 of light, and incurable blindness is the consequence. 
 Such a misfortune has sometimes befallen persons 
 with naturally weak eyes, who persisted in viewing a 
 partial eclipse of the sun for a considerable time, with- 
 out the protection of a smoked glass. Inferior, and 
 less permanent degrees of insensibility to light, are 
 experienced by too long exposure to strong light. 
 And every person must have observed, that, in pass- 
 ing from the light of day into a darkened room, 
 (meaning thereby an apartment into which very little 
 light is admitted,) it takes some time before the eyes 
 become so sensitive to a small quantity of light, as to 
 make surrounding objects visible. 
 
 Finally, it is not improbable that the gradual re- 
 covery of a patient labouring under an infectious dis- 
 ease, (and possibly of many other diseases not infec- 
 tious,) depends upon the same peculiar property of 
 the nervous system, viz., that of becoming gradually 
 insensible to the exciting cause of disease, and con- 
 sequently less capable of prolonging the morbid cor- 
 poreal action, according as it becomes more habitu- 
 ated to it. Without the aid of some such hypothesis, 
 it is difficult to comprehend how a person should re- 
 cover from an infectious distemper, exposed as he 
 
ON MARSH FEVERS. 453 
 
 must always be to an effluvium emanating from his 
 own person so deleterious in its nature, as to be cap- 
 able of communicating a like disease to a healthy per- 
 son, introduced for a short time into the same apart- 
 ment. If this hypothesis regarding the manner in 
 which many diseases work their own cure be correct, 
 all violent remedies which in any degree weaken the 
 patient, are to be suspected of doing harm instead of 
 good. By unnecessarily reducing the strength of the 
 patient, his body is rendered less capable of with- 
 standing the virulence of the disease, till such time as 
 the growing insensibility of the nervous system to its 
 exciting cause, performs the natural cure. 
 
 Upon this point we will only farther remark, that 
 when a nerve has become insensible to any exciting 
 cause by continued exposure to its influence, some 
 change in its physical constitution must have taken 
 place. But in what that change consists we are totally 
 ignorant. We will now return from this digression 
 to our subject. 
 
 No climate yet discovered is too hot for the exist- 
 ence of marsh fevers. Indeed it is generally admitted, 
 that if other circumstances be equally favourable, the 
 hotter the climate is, the more prevalent are fevers ; 
 and the more malignant their symptoms. To this 
 conclusion it might be objected, that in latitudes con- 
 siderably distant from the equator, such as those in 
 which New York, Philadelphia, and Charleston lie, 
 the autumnal fevers which attack the natives, fre- 
 quently manifest a more malignant character, than 
 they do in warmer intertropical climates. This effect, 
 however, is to be ascribed to the circumstance of con- 
 
454 ON MARSH -FEVERS. 
 
 tinued warmth, exerting a stronger influence than that 
 which is temporary, in conferring power on the hu- 
 man constitution to resist the evils which heat occa- 
 sions. The average annual temperature at Phila- 
 delphia is much lower than it is near the equator, but 
 then the heat is less uniform. The summer is about 
 as warm, while the winter is much colder, and accord- 
 ingly, its inhabitants are comparatively only half sea- 
 soned to the influence of a warm climate. 
 
 The reason why the most malignant species of 
 marsh fever, viz., yellow fever, is principally confined 
 to towns, seems owing to a combination of causes : — 
 Istf To the greater warmth in towns, — their tempera- 
 ture being usually 3 or 4 degrees higher than that of 
 the surrounding country. 2d, To their inhabitants 
 living more intemperately than those of the country. 
 And 3c?, To the greater number of residents unha- 
 bituated to the climate. 
 
 Though marsh fevers vary considerably in their 
 symptoms in different seasons, and in different climates, 
 and have received different appellations, they never- 
 theless seem to be essentially the same disease, vary- 
 ing only in degrees of malignity with the temperature of 
 the climate, the quantity of miasma, the duration and 
 constancy of exposure to its deleterious influence, and 
 the different degrees of unsuitableness in the human 
 constitution to resist the evils which miasmata create. 
 The accuracy of this opinion rests not merely on the 
 similarity of circumstances which originate all marsh 
 fevers, and which increase or diminish their virulence, 
 and terminate their existence, (for they all simultane- 
 ously cease upon the accession of frost and cold wea- 
 
ON MARSH FEVERS. 455 
 
 ther;) but also upon their making their appearance 
 at the same time and place, and running into each 
 other by insensible gradations. " Never," says Dr 
 Rush of Philadelphia, " has the unity of our autumnal 
 fever been more clearly demonstrated, than in our 
 present epidemic. Its four principle grades, viz., the 
 intermittent, the mild remittent, the inflammatory 
 bilious fever, and the malignant yellow fever, have all 
 run into each other in many instances." 
 
 Though it be now universally admitted, that marsh 
 miasmata are material substances capable of com- 
 municating diseases to the human frame, yet from the 
 mass of evidence adduced by Bancroft, and other 
 writers, it appears to be completely established, that 
 those diseases are not in themselves infectious. From 
 their never appearing but in the same localities, and 
 in such only where there is an obvious, or a suspected 
 cause in the vicinity ; and from their never spreading 
 from those localities, nor being communicated onwards 
 in a progressive manner to places at a distance, where 
 there is no local cause for their appearance j it is 
 reasonable to infer, that the human body, when la- 
 bouring under such diseases, does not generate within 
 itself, or at all events, does not propagate around a 
 corresponding effluvium to that which produces the 
 disease. And from the same facts it is reasonable 
 farther to infer, that marsh effluvia either do not de- 
 posit themselves on clothing, or on articles of mer- 
 chandise ; or if they so deposit themselves, that they 
 do not continue to retain their poisonous quality, so 
 as to be transferable from one place to another in the 
 
456 ON MARSH FEVERS. 
 
 ordinary routine of human intercourse, or of mercan- 
 tile transactions. 
 
 As the non-contagiousness of marsh fevers, and 
 particularly of the yellow fever, has been repeatedly 
 called in question, and as it is of most essential im- 
 portance to ascertain the truth as to this point, not 
 only in regard to the precautions necessary in attend- 
 ing the sick, and in separating them from the healthy; 
 but also to determine the propriety of enforcing quar- 
 antine regulations relative to these diseases ; it may 
 not be amiss to introduce a very limited selection of 
 evidence, in support of the opinion above advanced. 
 
 " What may be considered," says Dr John Hun- 
 ter, " as an experimentum crucis to prove the non- 
 existence of contagion, is, when the sick leave their 
 usual residence, and go to other places which are 
 healthy, without spreading the disease. This," he 
 adds, ** constantly happens in the remittent fevers of 
 the West Indies," among which he includes the yel- 
 low fever. 
 
 " It seems highly probable," says Dr Bancroft, 
 " that in many cases the miasmata producing yellow 
 fever in seaport towns of the West Indies, and the 
 United States of America, arise from the soil im- 
 mediately around, and, perhaps, sometimes under, the 
 very houses, wharves, &c. where they are imbibed by 
 the persons in whom that fever afterwards appears. 
 Accordingly we find that in New York, Philadelphia, 
 Baltimore, Norfolk, and Charleston, this fever always 
 begins, and often continues exclusively in the low 
 streets immediately adjoining the harbours and wharves 
 of these towns, except in the cases of some individ- 
 
ON MARSH FEVERS. 457 
 
 uals, who, after having imbibed the noxious exhala- 
 tions of the wharves and low streets in question, by 
 residence or employment in or near them, happen to 
 fall sick in other situations." And in another passage 
 he says : " One fact, which decidedly proves the yel- 
 low fever to be destitute of any contagious power, is 
 that of its never havings been communicated to others 
 by any one of the many thousands, who, in the West 
 Indies, as well as at Charleston, Norfolk, Baltimore, 
 Philadelphia, New York, &c. were removed beyond 
 the reach of marsh miasmata, whilst labouring under 
 the disease, or after having imbibed its poison ; though 
 in many of these, the disease appeared in its worst 
 forms, and proved mortal." 
 
 " The impossibility," says Bancroft in another pass- 
 age, " of spreading the disease in situations remote 
 from marsh miasmata has been attested, not merely 
 by persons who believed it not to be contagious, but 
 by one of the strongest assertors of the contrary 
 opinion, by the very person who appears to have first 
 misled Dr Rush, and others on this subject, (I mean 
 Dr Lining of Charleston,) more than half a century 
 ago. His words are these, " Although the infection 
 was spread with celerity through the town, yet, if any 
 from the country received it in town, and sickened on 
 their return home, the infection spread no farther, 
 not even so much as to one in the same house." 
 
 The manifesto of 15 physicians assembled at Bar- 
 celona respecting the cause of the deadly yellow fever 
 of that city in 1821, presented to the Cortes, is equal- 
 ly satisfactory. Two of the conclusions to which 
 they came after the most minute inquiry were : That 
 
 3 M 
 
458 ON MARSH FEVERS. 
 
 the disease was indigenous, and not contagious ; and 
 that the sanatary measures adopted by the govern- 
 ment were precarious, wholly useless, and even pre- 
 judicial, if we except that of emigration. And one of 
 the numerous facts as related by Dr M'Lean, upon 
 which the preceding conclusions were founded, is, 
 that "those who leftBarcelonetta, with all their effects, 
 without submitting to the purifications enjoined by 
 the contagionists, did not carry the disease to any of 
 the healthy points to which they were destined ; and 
 if a few of them sickened, the causes having been ap- 
 plied at Barcelonetta, none of their companions or 
 attendants were affected, who had not anteriorly been 
 in the focus of infection." 
 
 In Philadelphia the non-contagiousness of yellow 
 fever is so firmly believed, that after the sick who are 
 labouring under this disease have been removed from 
 the seat of contagion, (which as a means of cure is a 
 common practice,) it is not unusual for acquaintances 
 to visit them without the slightest apprehension of 
 danger, and it has never been known that any evil 
 consequences therefrom resulted. 
 
 The most conclusive evidence however upon this 
 subject, is to be found in the official reports, made to 
 the constituted authorities of the various towns in 
 the United States, where the yellow fever has appear- 
 ed. Dr Miller, in his report to the governor of 
 New York, says : " Many who had contracted the 
 disease in New York, died of it at Boston, Albany, 
 and other cities at a distance ; many likewise at 
 Greenwich, Brooklyn, and other villages, in the neigh- 
 bourhood. In no instance did these victims of the 
 
ON MARSH FEVERS. 459 
 
 epidemic communicate contagion." And in another 
 passage he says, " No communication of the disease 
 was ever observed in yellow fever hospitals, situated 
 at a small distance from the cities to which they be- 
 long. No exception to this has ever occurred in any 
 of the numerous seasons of this pestilence at our 
 hospital at Bellevue, the marine hospital at Staten 
 island, that of Philadelphia, or any other in the United 
 States ; provided the malignant air of the city had 
 been avoided." Without quoting other reports, it 
 may be stated, that in every instance, after the fullest 
 and most rigid investigation, the result has been to 
 demonstrate in the most satisfactory manner, that the 
 yellow fever, and other inferior degrees of marsh fever, 
 are not communicable.* 
 
 Upon the preceding evidence we will only remark, 
 that the incapacity of an epidemic to spread or travel 
 from certain districts where it appears either constantly 
 throughout the year, or periodically during a portion 
 of the year, or only in certain favourable years, is the 
 only infallible criterion of its being non-contagious. 
 It is this species of evidence that has settled the 
 question with regard to yellow fever. The broadly 
 asserted fact, that those who have been affected with 
 this malady when removed, according to common cus- 
 tom, to yellow fever hospitals, or to the houses of re- 
 latives at a distance from the source of the miasma, 
 have never been known to communicate the disease 
 to attendants who avoided visiting the infected dis- 
 trict, extinguishes all other kinds of opposing evi- 
 
 * For farther evidence we refer to Bancroft's essay on Yellow 
 Fever. 
 
460 ON MARSH FEVERS. 
 
 dence. Such an assertion, unlike other facts rela- 
 tive to contagion, admits of no evasion or misrepre- 
 sentation. It is open to the scrutiny, and if untrue, 
 to the contradiction, not of individuals, but of thou- 
 sands of individuals in New York, Philadelphia, and 
 the other cities where the disease appears. 
 
 Another fact that seems to be completely esta- 
 blished, and which it is of most essential importance 
 should be known by all those who have occasion to 
 visit countries where marsh fevers prevail, is, that the 
 liability of being affected is much greater during night, 
 than it is during day. " It is related," says Bancroft, 
 " by Dr James Lind, that in a voyage to the coast of 
 Guinea, performed in the year 1766, by the Phoenix 
 ship of war, of 40 guns, the officers and ship's com- 
 pany were perfectly healthy, till, on their return home, 
 they touched at the island of St Thomas. Here the 
 captain unfortunately went on shore, to spend a few 
 days in a house belonging to the Portuguese governor 
 of that island. This happened during the rainy or 
 sickly season. In the same house were lodged the 
 captain's brother, the surgeon, some midshipmen, and 
 the captain's servants. But, in a few days after their 
 being on shore, the captain, his brother, the surgeon, 
 and every one, to the number of seven, who had slept 
 in that house, were taken ill ; and all of them died 
 except one, who returned to England in a very ill 
 state of health. The ship lay at anchor there twenty- 
 seven days, during which time three midshipmen, five 
 men, and a boy, remained on shore, for twelve nights, 
 to guard the water casks, under pretence that the 
 islanders would steal them ; all of whom were like- 
 
ON MARSH FEVERS. 461 
 
 wise taken ill, and two of them only escaped with life. 
 At that island, only those who slept on shore were 
 taken ill. And none of those w^io slept on shore 
 escaped the sickness, and of them only three survived 
 it." — The extract proceeds, but I only here insert 
 the substance of it, viz. " That in another similar 
 voyage the next year, the same vessel touched at the 
 same island during the sickly season, where she lost 
 eight men out of ten, who had imprudently remained 
 all night on shore. The rest of the ship's company, 
 who always returned to the ship before night, though 
 they spent the greater part of the day on shore, con- 
 tinued in perfect health." 
 
 Dr Trotter, late physician to the royal navy, says : 
 " In a voyage down the coast of Guinea, in the As- 
 sistance, in the year 1762, we had scarcely a man in- 
 disposed. We wooded and watered at the island of 
 St Thomas, and with a view to expedition, a tent was 
 erected on shore, in which the people employed on 
 these services were lodged during the night. On the 
 middle passage, every man who slept on shore died, 
 and the rest of the ship's company remained remark- 
 ably healthy." 
 
 Dr John Clark relates, that a Danish ship in 1768 
 having anchored at North Island, near the straits 
 of Sunda, twelve of the crew were sent on shore to 
 fill water, where they only remained two nights. 
 Every one of them were seized with a fever of which 
 none recovered ; but, although the ship went out to 
 sea, none except the twelve who slept on shore were 
 attacked with the complaint. 
 
 It may be remarked, that the preceding facts, as 
 
462 ON MARSH FEVERS. 
 
 well as many similar ones, which, for the sake of bre- 
 vity, we omit, strongly corroborate the opinion that 
 marsh fevers are not contagious. In each of the cases 
 related, the portion of the ship's company who had 
 not slept on shore communicated freely with those 
 who had, both after, and immediately previous to their 
 falling sick, and yet none of them were infected. 
 
 In farther proof of the danger to be apprehended 
 from exposure to night air in marshy countries, I may 
 mention, that it has long been observed in Rome, 
 (and strangers are usually warned of the danger,) that 
 those who, to avoid the heat of the day, travel, during 
 the sickly season, through the Pontine marshes be- 
 tween Rome and Naples by night, though it only 
 takes six or eight hours to pass through them, are ex- 
 ceedingly apt to be immediately thereafter affected 
 with fever. 
 
 From the preceding and such like facts, some have 
 imagined that it is the act of sleeping, and not of re- 
 maining exposed to night air, that is dangerous. It is 
 possible that the relaxation of the system during sleep, 
 may, to a limited extent, diminish the. power of the 
 body in resisting the noxious influence of miasma ; 
 but this alone will not explain the phenomena. It has 
 repeatedly occurred that individuals who happened to 
 stop late on shore, even though they did not sleep 
 there, were soon after attacked with fever; while those 
 who returned to their ship uporr the approach of even- 
 ing escaped. Nor is there any evidence, that those 
 who avoided sleep while passing through the Pontine 
 marshes by night, were less liable to be afterwards af- 
 fected with fever, than those who slept. And in cor- 
 
ON MARSH FEVERS. 463 
 
 roboration of the same opinion, I have been told by 
 persons who resided long in New York and Philadel- 
 phia, that it was in both these towns the general be- 
 lief, founded upon common observation, that when the 
 yellow fever was raging, little danger was to be ap- 
 prehended by perambulating the streets of the in- 
 fected district during the heat of the day, but great 
 danger at night. 
 
 Though the risk incurred by visiting a marshy dis- 
 trict be unquestionably much diminished during day, 
 still it is not altogether annihilated. In Philadelphia 
 and New York, cases of infection have been known 
 to result from persons entering, and remaining for a 
 short time in unventilated houses and stores in the 
 sickly part of these towns, even during the hottest 
 period of the day. And one of the last times the yel- 
 low fever broke out in Philadelphia, the persons first 
 attacked were a few coopers employed during the day 
 at a particular part of the wharf, where the poisonous 
 miasma must have been issuing from the soil in a very 
 concentrated form. The facts of this case were pub- 
 lished in an official report, but I only learned the sub- 
 stance of it from a relative of my own who then re- 
 sided at Philadelphia. As the facts here alluded to 
 tend to show, that the danger arising from marsh mi- 
 asma increases with the duration of exposure, and 
 probably with the amount inhaled, it may not be amiss 
 to state them. They are as follow : — " Part of the 
 coopers had been employed in the dangerous spot the 
 whole day, and one or more of them were there only 
 part of the day, and the master had merely visited 
 them, and that only for very short spaces of time, at 
 
404 ON MARSH FEVERS. 
 
 intervals during tlie day. Those who laboured there 
 the whole day all died ; those who had been there 
 only a part of the day after a severe illness recovered; 
 and the master of the workmen was only affected with 
 nausea, vomiting, and the other incipient symptoms 
 of the yellow fever for about two hours." 
 
 I have only met with one fact to corroborate the 
 preceding opinion, and it does so only indirectly. It 
 is a statement by Dr Bancroft, (page 384,) to the fol- 
 lowing effect, that " as the fever receded from the 
 low ground, and malignant atmosphere of Water 
 Street, it became more and more mild and manage- 
 able, till its evanescent shades in Second Street were 
 in many instances, much lighter than the common re- 
 mittent of the country." The inference I draw from 
 this quotation is, that the miasma became more and 
 more diluted with the atmosphere as the distance 
 from the source of emanation increased ; and that the 
 malignity of the fever depended upon the amount of 
 the poisonous miasma actually inhaled, without its 
 making much difference whether the inhalation of it 
 was continued for one hour in a more, or for several 
 hours, in a proportionally less concentrated form. 
 
 From a variety of well authenticated facts, some of 
 which we will quote, it appears that a few feet of per- 
 pendicular elevation has a remarkable influence in di- 
 minishing the danger arising from marsh miasmata. 
 
 It is related by Dr Hunter, that, in Spanish Town, 
 in Jamaica, the difference in the healthiness of the 
 ground-floor of the barracks, and of that immediately 
 above it, was so great, that of a similar proportion of 
 inmates, it was found, upon investigation, that three 
 
ON MARSH FEVERS. 405 
 
 of those who slept in the former were attacked with 
 fever, for one who slept in the latter. A similar case 
 occurred at St Anne's barracks in Barbadoes. It 
 was there likewise ascertained, that about three in the 
 lower floor took the yellow fever, for one in the floor 
 immediately above it. The testimony of Dr Fergu- 
 son, one of the principal medical officers of the army 
 in St Domingo in the late war, is to the same effect. 
 He remarked, that two-thirds more men were taken 
 ill on the ground-floors, than in the upper stories. 
 
 Dr James Clark relates the following instance com- 
 municated to him by Professor Brera, whilst attending 
 the clinical wards of the hospital at Padua. The wall 
 of that w'mg of the building where these wards are 
 situated, is washed by a branch of the sluggish Brenta, 
 and it frequently happened that the windows of them, 
 (which were about sixteen feet above the surface of 
 the water,) having been carelessly left open, until too 
 late an hour, several of the patients were attacked 
 with intermittent fevers, in some instances of the per- 
 nicious kind. This never occurred in the women's 
 wards, which are immediately over those of the men, 
 though there is no reason to believe that more care 
 was taken in shutting the windows of those, than of 
 the former. It was also remarked at Walcheren, that 
 those who slept in the upper stories of houses were 
 less liable to the disease, and had it in a milder form, 
 than those who slept on the ground-floors. The tes- 
 timony of the natives was likewise in favour of this 
 observation. 
 
 The greatest height in the atmosphere to which 
 marsh miasmata ascend, or rather the height at which 
 
 3 N 
 
4GG ON MARSH FEVERS. 
 
 the quantity existing becomes so small as to be incap- 
 able of communicating disease, can hardly be'said to be 
 ascertained. It probably increases with the heat of the 
 climate, and of the season of the year, and also with the 
 stillness and density of the atmosphere, and the quan- 
 tity of miasma generated, and the extent of its source 
 underneath. " On this subject, the Baron de Hum- 
 boldt has observed, that the farm of Encero, situated 
 above Vera Cruz, is a stranger to the insalubrity 
 which reigns over the whole coast; the elevation of 
 this farm is 3045 feet, and it forms the highest limit 
 of the yellow fever. M. Rigaud de FIsle has also 
 endeavoured, by some observations made in the neigh- 
 bourhood of Rome, to fix the point at which the marsh 
 efHuvia are innoxious; this he considers to vary from 
 6S2 to 1006 feet above the level of the situation 
 whence they emanate." 
 
 In order to account for a variety of the facts which we 
 have related, it has been usually conceived, that marsh 
 miasmata are specifically heavier than common air. 
 Hence upon their assuming the gaseous form, though 
 they tend like odours and other aeriform substances, 
 and probably by means of the same unknown force, 
 to diffuse themselves equally throughout the atmo- 
 sphere, yet their greater specific gravity counteracting 
 this tendency, not only prevents their rising above a 
 limited altitude, but causes the greatest proportion to 
 float near the surface of the ground, and restricts 
 their greatest accumulations, and the increased dan- 
 ger thence arising chiefly to hollows and low-lying 
 places. 
 
 The preceding hypothesis, so far as it goes, is 
 
ON MARSH FEVERS. 407 
 
 probably correct ; but it requires additional assistance 
 to explain all the phenomena. During day, as has 
 been previously stated, little or no more danger is to 
 be apprehended from miasmata in low, than in ele- 
 vated situations; and upon the accession of frost and 
 cold weather, whether during night or day, danger in 
 all situations ceases. In explanation of the former 
 of these facts, it can hardly be supposed that a 
 greater amount of miasma is generated during night 
 than during day. Indeed, there is a sufficiency of 
 indirect evidence to prove that the reverse is the case. 
 For instance, 1^^^, Marsh fevers are common to 
 marshy districts in all hot climates, and if other cir- 
 cumstances be equally favourable, their frequency and 
 malignity is proportional to the degree of warmth : 
 on the contrary, in similar situations in very cold lati- 
 tudes, such fevers are altogether unknown. 2^/, In 
 temperate climates, marsh fevers never make their 
 appearance till the summer heat is considerable, and 
 they are observed to increase in frequency and viru- 
 lence as the temperature rises ; and subsequently to 
 become milder, and of less frequent occurrence, as 
 the temperature declines, until they entirely disap- 
 pear. 3d, In every instance where bodies are known 
 to be capable of assuming the gaseous form, an in- 
 crease of heat promotes their volatilization ; whereas, 
 an increase of cold not only retards it, but, if carried 
 to a sufficient extent, prevents it altogether. These 
 reasons induce me to think, that the amount of mias- 
 ma volatilized in a given time, increases like the quan- 
 tity of water evaporated, with the temperature of the 
 source from whence it emanates ; and consequently 
 
468 ON MARSH FEVERS. 
 
 must be neater durino; the beat of day, than it is 
 during the cbillness of night, and will increase as the 
 temperature of the season advances, and diminish as 
 it again decHnes. 
 
 In accounting for the greater habihty of being af- 
 fected with marsh fevers arising from the greater 
 accumulation of miasmata during night than during 
 day, the dissipating influence of the sun is usually 
 referred to, without any explanation of the manner in 
 which the effect is produced. We will, therefore, 
 supply this deficiency, by pointing out the mode in 
 which the solar heat must promote the intermixture 
 and dilution of miasma with the atmosphere, for it is 
 probably to this circumstance that the beneficial in- 
 fluence of the sun is to be ascribed. 
 
 During day, the surface of the ground, where it is 
 exposed to the sun's rays, becomes warmer than the 
 atmosphere; and this superior temperature being 
 communicated to the stratum of air in immediate 
 contact with it, diminishes its specific gravity, and 
 causes it to ascend. Thus the sun, even during the 
 stillest weather, by promoting the intermixture of the 
 various atmospheric strata, is a constant source of 
 ventilation; for agreeably to aerostatic principles, the 
 warmer and lighter atmospheric particles underneath, 
 must be continually ascending during day, while the 
 colder and heavier particles from the upper strata of 
 the atmosphere, must be simultaneously descending 
 to supply their place. Besides, miasma generated 
 during day, by partaking of the solar warmth which 
 is then communicated to the surface of the ground, 
 will be thereby rendered specifically lighter. Both 
 
ON MARSH FEVERS. 469 
 
 which circumstances co-operating with the diffusive 
 tendency of miasma, will accelerate that intermixture 
 and dilution of it with the atmosphere, which may 
 reasonably be supposed to render it harmless, and in- 
 capable of communicating disease. 
 
 During night, particularly when there is little or no 
 wind, and the sky is clear of clouds, the above cir- 
 cumstances, which promote ventilation, and the dis- 
 sipation of miasma, are reversed. The surface of 
 the ground, as has been proved by the observations 
 of Dr Wells, then becomes colder than the lower 
 atmosph'eric strata ; and this coldness being commu- 
 nicated upwards, the temperature of the air during 
 serene nights, has been found to increase to the 
 height of 220 feet, and how much higher is un- 
 known, as observations have not been extended far- 
 ther. Hence, during night, the various atmospheric 
 strata, unlike what takes place during day, become 
 specifically heavier according to their proximity to 
 the surface of the ground; and instead of tending 
 to intermix with each other, are enabled, even in op- 
 position to the agitating influence of any slow pro- 
 gressive motion over a slightly uneven surface, to re- 
 tain their relative positions during the whole of the 
 night. Besides, the specific quantity of whatever 
 miasma is exhaled during night will be increased, by 
 its partaking of the then superior coldness of the 
 earth's surface. And this circumstance, which is the 
 reverse of v/hat happens during day, will co-operate 
 with the greater specific gravity of miasma in coun- 
 teracting its tendency to diffuse itself upwards through 
 
470 ON MARSH FEVERS. 
 
 the atmosphere, and consequently, will favour its ac- 
 cumulation near the ground during" night. 
 
 Though the influence of the preceding circum- 
 stances go a considerable length towards accounting 
 for the greater liability of being affected with marsh 
 fevers during night, than during day, still, the ex- 
 planations thereby afforded are not altogether satis- 
 factory. If heat diminishes the specific gravity of 
 miasma only to the same extent as it does that of air, it 
 is difficult to conceive how the solar warmth should be 
 able, in opposition to the greater gravity of miasma, 
 to prevent all accumulation of it near the surface of 
 the ground during day, so as effectually to destroy 
 the liability of being then affected by fever ; or why, 
 upon the return of night, its accumulation near the 
 surface of the ground should so quickly re-appear. 
 Nor does it explain why, upon the sudden acces- 
 sion of frost and cold weather, the previously ex- 
 haled miasma should so suddenly disappear. 
 
 After reflecting upon these difficulties, and upon 
 the various phenomena connected with this subject, 
 I am inclined to think that to explain them satisfac- 
 torily, requires us to suppose, in addition to the ex- 
 planatory circumstances already stated, that the spe- 
 cific heat of miasmata is greater than that of common 
 air; and accordingly, that with equal increments and 
 decrements of temperature, the specific gravity of the 
 former, will decrease and increase more than that of 
 the latter. By the aid of this supposition, the pre- 
 viously mentioned explanatory circumstances, which 
 of themselves barely account for some of the phe- 
 nomena, and for others not at all, become much more 
 
ON MARSH FEVERS. 471 
 
 efficient. Nor is this hypothesis by any means ex- 
 travagant. For, in the first place, all the knowledge 
 or ideas we possess regarding the existence, the hab- 
 itudes, the movements, and the effects of miasms, are 
 merely conjectural inferences, deduced in order to 
 account (as this is intended to do,) for certain phe- 
 nomena otherwise inexplicable. In the second place, 
 all bodies, whether simple or compound, that have 
 been examined, differ in their specific heat ; and 
 though there be a general tendency towards a relation 
 between the specific gravity, and the specific heat of 
 bodies, yet, the departures from this relation are so 
 numerous, so irregular, and in many instances, so 
 great, that to suppose an additional departure there- 
 from to account for phenomena, which in order to an 
 explanation, point that way, is far from being an ex- 
 travagant conjecture. The specific heat of miasms 
 can only differ from that of air by being greater or 
 less ; and as we cannot ascertain which is greatest or 
 least by direct observation and experiment, we are 
 left to determine this point by considering which of 
 the two suppositions harmonize best with the phe- 
 nomena, and accordingly which will explain them most 
 satisfactorily. 
 
 Agreeably to the hypothesis that the specific heat 
 of miasma is greater than that of common air, the 
 following effects ought to be produced. 
 
 1. As temperature rises, the difference between 
 the specific gravity of miasma and air, (supposing the 
 former to be the heaviest,) will diminish, and of 
 course, will exert lest influence in counteracting the 
 ascension of miasma, while acting in obedience to its 
 
47"2 ON :\IARSII FKVEUS. 
 
 tendency to diffuse itself equally, (upwards as well as 
 horizontally,) throughout the atmosphere. On the 
 contrary, as temperature sinks, the difference between 
 the specific gravity of miasma and air will increase ; 
 and of course, will exert a proportionally augmented 
 influence in counteracting its tendency to diffuse it- 
 self upwards through the atmosphere. 
 
 2. As the temperature of the air rises, its capacity 
 for containing miasma, whether it exist in a state of 
 solution, or of mere suspension and mixture there- 
 with, will increase, just upon the same principle as 
 the capacity of the air for humidity, (which has also a 
 greater specific heat than air,) increases with its tem- 
 perature. 
 
 The conjoint operation of these two circumstances, 
 satisfactorily explain the principal difficulties attend- 
 ing the phenomena of marsh miasmata. The in- 
 creasing coldness as we rise above the earth's surface, 
 operating upon the greater specific heat of miasmata, 
 explains the reason, why the altitude to which they 
 ascend is limited; and why at greater heights, marsh 
 fevers are unknown. Though the temperature of 
 miasms be reduced only in the same degree as the 
 particles of air at a similar elevation, still, this reduc- 
 tion of temperature increases the specific gravity of 
 the former, more than that of the latter: and hence, 
 the tendency of miasms to diffuse themselves upwards, 
 must obviously be at length counteracted by the in- 
 creasing coldness, just as the ascension of aqueous 
 vapour is counteracted, and limited, by the same 
 cause. 
 
 The reason why marsh fevers do not appear in 
 
ON MARSH FEVERS. 473 
 
 winter, or in high latitudes; and why they cease in 
 temperate dimates, upon the accession of frost and 
 cold weather, is evidently explicable upon the same 
 principle as the phenomenon above explained. In 
 consequence of the superior specific heat of miasms, 
 the coldness in high latitudes, or during winter, will 
 increase their specific gravity so much more than it 
 does that of air, as to prevent their assuming the 
 gaseous state, in which alone they are supposed capa- 
 ble of occasioning fevers. In like manner, in tem- 
 perate latitudes, upon the accession of frost or cold 
 weather, the farther volatilization of miasma will not 
 only be prevented, but that which has been previously 
 exhaled and diffused throughout the atmosphere, will 
 be precipitated to the ground; and hence, the fevers 
 which in the aeriform state they occasioned, must 
 thereafter disappear. 
 
 The greater liability of being affected by marsh 
 fevers during night than during day, likewise admits 
 of a much more satisfactory explanation, by the as- 
 sistance of the hypothesis above advanced, than it 
 does without it. During the heat of day, the specific 
 gravity of miasms and air being more nearly approxi- 
 mated than during the chilness of night, the same 
 amount of exhaled miasma will rise not only to a 
 greater altitude than it would otherwise do, but will 
 diffuse itself more equally amongst the higher and 
 lower atmospheric strata; and thus, by being diluted 
 with the intermixture of a larger proportion of air, 
 will become less dangerous. On the contrary, the 
 coldness during night, by increasing the specific grav- 
 ity of miasma more than that of air, will cause a 
 
 3o 
 
474 ON MARSH FEVERS. 
 
 gradual precipitation of the former towards the earth's 
 surface, upon the same principle, as aqueous vapour 
 is precipitated in like circumstances in the form of 
 mist. Hence, the miasma that ascended during the 
 warmth of the previous day, by becoming specifically 
 too heavy to float during night in the higher and rarer 
 regions of the atmosphere, will descend; and instead 
 of being equally diff'used amidst the higher and lower 
 regions of the air, will accumulate in greatest propor- 
 tion amongst its inferior and denser strata; and thus 
 increase the danger to be there apprehended. 
 
 The increasing virulence and frequency of marsh 
 fevers as the summer heat advances, and their subse- 
 quent diminution in malignity and frequency as the 
 temperature again declines, also harmonizes with what 
 might be anticipated from the greater capacity of air 
 for miasms as its temperature rises, an effect which 
 must result, like in the analogous case of humidity, 
 from the specific heat of miasms being greater than 
 that of air. Owing to this circumstance, the amount 
 of deleterious miasma capable of floating in a given 
 bulk of air, and the danger to be thence apprehended, 
 will increase as the summer heat advances, and de- 
 crease as it again declines. And upon the same prin- 
 ciple, if other circumstances be equally favourable, 
 the amount of miasma floating in the atmosphere, and 
 the insalubrity of the climate thence arising, will be 
 proportional to its warmth. 
 
 Thus we see that the various phenomena presented 
 by marsh fevers, are in strict accordance with what 
 might be expected to result from the specific heat of 
 the miasma, which occasions them, being greater than 
 
ON MARSH FEVERS. 475 
 
 that of air; and that the difficulties attending their 
 solution, by aid of this supposition disappear. The 
 correctness of the hypothesis is farther confirmed by 
 considering what would result from a contrary suppo- 
 sition, viz. the specific heat of miasms being less than 
 that of air. In this case, miasms would diff"use them- 
 selves upwards through the atmosphere with greatest 
 facility during^ the chilness of night, and again de- 
 scend and accumulate in greatest proportion amongst 
 its inferior and denser strata, during the heat of day; 
 and the amount capable of floating in the atmosphere, 
 instead of increasing should diminish with the warmth 
 of the climate, and of the season of the year. Hence, 
 contrary to what is known from experience to be the 
 fact, the liability of being aff"ected with marsh fevers 
 should be greater during day than during night; and 
 should decrease as the warmth of the climate and of 
 the season of the year advances. And were it not 
 unnecessary to illustrate this point farther, it could in 
 like manner be shown, that all the other phenomena 
 which ought to result upon the supposition of the 
 specific heat of miasma being less than that of air, 
 would be directly the reverse of what are actually pre- 
 sented. 
 
 That marsh miasmata are susceptible of being trans- 
 ported by aerial currents, particularly when their velo- 
 city is moderate, so as to communicate disease at a 
 distance from their source of exhalation, is completely 
 ascertained. Dr Lind, speaking of the unfortunate 
 attempt to make a settlement at the island of Balam- 
 bangan, near Borneo, where scarcely one in ten of 
 those sent thither survived the first six months, says : 
 
476 ON MARSH FEVERS. 
 
 *' From October till April, during the north-east mon- 
 soon, the wind comes from the sea, and the settlement 
 is perfectly healthy; but from April till October, dur- 
 ing the south-west monsoon, the wind blows over the 
 marshes, both of this island and Borneo, and produces 
 fevers of the most malignant nature, which frequently 
 cut off the stoutest men in 12 or 14 hours." 
 
 Regarding the distance from the source of emana- 
 tion, to which marsh miasmata diffuse themselves ho- 
 rizontally in such abundance as to communicate dis- 
 ease, either in still weather, or by the aid of aerial 
 currents, medical opinions vary extremely. Bancroft 
 supposes the distance very limited, viz. not farther 
 than from one-fourth to half a mile, even in the most 
 favourable circumstances. Macculloch, on the other 
 hand, conceives, that by means of aerial currents, they 
 may travel hundreds of miles without much dilution 
 with the atmosphere. He supposes, for instance, that 
 easterly winds in spring give rise to agues in Eng- 
 land, in consequence of their transporting the malaria 
 of Holland thither ; and a similar opinion is advanced 
 by a writer in the Seventy-second number of the Ed- 
 inburgh Review. Before hazarding an opinion upon 
 this subject, we will quote a limited selection of facts: 
 
 *' According to Sir Gilbert Blane, not only the 
 crews of the ships in the road of Flushing were en- 
 tirely free from the endemic of Walcheren, but also 
 the guard-ships which were stationed in the narrow 
 channel between Flushing and Beveland, the width 
 of which is about 6000 feet ; and although some of 
 the ships lay much nearer to one shore than to the 
 other, there was no instance of any of the men or 
 
OK MARSH FEVERS. 477 
 
 officers being taken ill with the same disorder, as that 
 with which the troops on shore were affected ; whilst 
 ships at the distance of 3000 feet, and even farther 
 from swampy shores in the West Indies, were affected 
 by the noxious exhalations ; and the same thing is 
 said to occur in the India ships in the channel lead- 
 ing to Calcutta." It need hardly be stated, that the 
 object of the writer of the preceding extract from the 
 Quarterly Review, is to prove, that deleterious exha- 
 lations in genera], possess more morbific and malig- 
 nant qualities, in proportion to the warmth of the 
 chmate in which they are engendered. The argu- 
 ment itself, so far as regards the object of the writer, 
 is entitled to little consideration. A more extended 
 horizontal diffusion may obviously arise from the 
 greater abundance of miasma j but stronger morbific 
 properties appertaining thereto, is no more indicated 
 by a greater, than it would be by a less diffusive ten- 
 dency. We know that marsh fevers are more malig- 
 nant and fatal in warm than they are in cold climates; 
 but whether this be owing to stronger morbific pro- 
 perties in the miasmata, or to their greater abundance, 
 or to the united influence of both these causes oper- 
 ating, in conjunction with the greater heat of the cli- 
 mate, upon the human constitution, it is impossible, 
 in the present state of science, to determine. But to 
 proceed with our statement of facts. 
 
 In Philadelphia, the yellow fever seldom or never 
 spreads farther than the low part of the town, being 
 chiefly restricted to Water-street, and others immedi- 
 ately contiguous to the wharves and banks of the 
 river, where the miasms which occasion the disease 
 
478 ON MARSH FEVERS. 
 
 are supposed to be engendered. In New York the 
 same thing has been observed. The seat of the 
 fever is there hkewise confined to a corresponding 
 locahty in the lower portion of the city ; and the 
 mere avoidance of that district during the sickly 
 season, is said to afford perfect security against the 
 disease. 
 
 It may likewise be briefly stated, without quoting 
 the facts individually as related by medical authors, 
 that it has been often observed with regard to fleets 
 anchored on sickly coasts, that the crews of the ves- 
 sels nearest the shore were affected with sickness, 
 while those only a cable length or two farther off", re- 
 mained perfectly free from disease. In such cases 
 it has also been found, that the sickly ships upon 
 removing a httle farther from the shore, became 
 healthv. 
 
 In the town of Kingston, in the island of Jamaica, 
 the sickly season commences about the beginning of 
 August, after the usual sea breeze from the east has 
 died away, and continues till November, when the sea 
 breeze again recovers its ascendancy. The sickness 
 during this period is with good reason ascribed to the 
 exhalations from marshes about five miles to the west 
 of the town ; for it is observed, that it is only when 
 the land breeze blows from that direction, and it gen- 
 erally does so only very gently, that sickness prevails. 
 It is also remarked, that the part of the town which 
 is farthest removed from the marshes, is the health- 
 iest. In this instance, it appears that marsh miasma, 
 aided by an extremely gentle breeze, which is chiefly 
 perceptible in the morning, communicates disease at 
 
ON MARSH FEVERS. 479 
 
 a distance of five miles from the source from whence 
 it emanates. 
 
 From the case of Rome we cannot draw any satis- 
 factory conclusion. No marshes exist within a dozen 
 miles of that city ; but it has been usually believed, 
 that the soil of the surrounding country, and even the 
 stagnant water, and filth within the city itself, engen- 
 der deleterious miasms. 
 
 From the preceding facts and others of a similar 
 kind related by medical authors, we may draw the fol- 
 lowing conclusions : — 
 
 1. In perfectly still weather, marsh miasma is most 
 abundant above the source of exhalation ; and the 
 amount diff"used horizontally gradually decreases, so 
 that at the distance of little more than half a mile 
 from its source, and frequently much nearer, it be- 
 comes so diluted with the atmosphere, as to be in- 
 capable of communicating disease. 
 
 2. When there is any wind, no danger is to be 
 apprehended from miasmata, except to the leeward of 
 their source of emanation : but in this direction, par- 
 ticularly during night, and when the breeze is very 
 gentle, miasmata may be conveyed to a distance of 
 five miles in such a concentrated state as to commu- 
 nicate disease. 
 
 It need hardly be remarked, that the inferred limits 
 above stated, are merely approximations to the truth 
 so far as has been determined by observation. It is 
 obvious, however, that the distance to which mias- 
 ma may diffuse itself horizontally during still wea- 
 ther ; or to which it may be transported by means 
 of aerial currents, in a sufliciently concentrated state 
 
480 ON MARSH FEVERS. 
 
 to communicate disease, will vary with circumstances ; 
 such as, the extent of the source of exhalation, 
 and the amount exhaled in a given time ; the ele- 
 vation of the source of exhalation relative to that 
 of the surrounding country ; and the degree of ob- 
 struction, which trees, houses, rising grounds, or 
 other inequalities of surface, present to its diffusion. 
 In Philadelphia, New York, and other towns, the 
 diffusion of miasma in such a concentrated state as 
 to communicate disease, is limited by a combination 
 of the above causes ; such as, the smallness of the 
 source of exhalation, and of course the smallness of 
 the amount exhaled ; the comparative lowness of the 
 parts of these cities where it is engendered j and the 
 interruption which the houses present to its spread- 
 ing horizontally. The distance of diffusion will also 
 vary with the weather. During day, provided the 
 sun's rays are not obstructed by clouds, the mias- 
 mata will be rapidly dissipated, as has been already 
 explained, even above the source of exhalation. But 
 in cloudy weather, when the sun's rays are obstructed, 
 and little heat is communicated to the earth's surface, 
 and to the lower atmospheric strata, miasmata, with- 
 out much dilution, may diffuse themselves horizon- 
 tally, in still weather, or may be transported by the 
 wind to a considerable distance even during day. Dur- 
 ing night, however, when the lower atmospheric strata 
 become colder and specifically heavier according to 
 their proximity to the surface of the ground, the dis- 
 tance of diffusion and transportation, and the danger 
 thence arising, will be always greater than it is dur- 
 ing day. 
 
ON MARSH FEVERS. 481 
 
 Macculloch's idea of miasmata being transported 
 for hundreds of miles in such a concentrated state as 
 to communicate disease, I regard as an extravagant 
 conjecture unsupported by any thing hke satisfactory 
 evidence. If such were true, distance from marshes, 
 contrary to what is known from experience to be the 
 fact, would afford httle or no protection from the dan- 
 ger thence arising. Even supposing, agreeably to 
 Macculloch's notion, that the same identical portion 
 of air is transported for hundreds of miles without in- 
 termixture with other portions, (which, judging from 
 the obvious effect of unevenness on the surface of 
 the ground in producing intermixture, is extremely 
 improbable,) still the diffusive tendency of miasma 
 itself, must be continually operating in promoting di- 
 lution during its progress. Besides, the circumstance 
 of the deleterious influence of miasma being so ex- 
 tremely circumscribed in the hottest climates, as it 
 appears to be from some of the facts we have stated, 
 leads me to think, that in addition" to the effect of 
 coldness in precipitating miasmata from the atmo- 
 sphere, there must be some extensive chemical agency 
 constantly at work in decomposing them, totally in- 
 com.patible with their distant transportation in any con- 
 centrated, or dangerous form. We know that all ex- 
 cess of carbonic acid gas formed during combustion 
 and respiration, beyond the proportion natural to the 
 atmosphere ; and that all odoriferous particles, as well 
 as all known gaseous substances engendered during 
 the decomposition of vegetable and animal matter, are 
 soon precipitated by means of some unknown chemi- 
 cal agency ; and that they never are transported by 
 
 3p 
 
482 ON MARSH FEVERS. 
 
 aerial currents beyond a very limited distance. Hence, 
 judging from analogy, it is presumable, that miasmata 
 assume the aerial form only for a hmited time j and 
 thereafter return to the earth to undergo that peculiar 
 succession of changes, which in the course of their 
 chemical revolution they are destined to perform. 
 
 Strong winds or hurricanes are said to diminish the 
 danger arising from marsh miasmata, not only during 
 their continuance, but even, as is believed, for some 
 time thereafter. The island of Bourbon is usually 
 visited by one or two hurricanes in the course of each 
 year. They happen between the months of Decem- 
 ber and March, which, as the island is in the southern 
 hemisphere, corresponds to the sickly period, in 
 warm climates, in the northern hemisphere, between 
 July and October. The salubrity of this island is 
 ascribed in a great measure to these periodic storms; 
 for it is observed by the inhabitants, that the want of 
 them is invariably succeeded by unwholesome sea- 
 sons. 
 
 The influence of strong winds and hurricanes in 
 diminishing the danger arising from marsh miasmata 
 during their continuance, is obviously owing to the 
 copious dilution of these, and all other noxious va- 
 pours with the atmosphere, which they occasion. In 
 proportion to the rapidity with which the air passes 
 over the exhaling marshes, so must the amount of 
 miasma, which it thence receives, be smaller. And 
 even this diminished amount, will undergo more co- 
 pious dilution, according as an increased velocity of 
 the aerial current over the uneven surface of the 
 ground, has a stronger influence in promoting the in- 
 
ON MARSH FEVERS. 483- 
 
 termixture of the higher and lower atmospheric strata. 
 The efficacy of hurricanes in promoting healthiness 
 for some time thereafter, probably results from their 
 sweeping away, not only all deleterious miasmata that 
 may have been previously exhaled, but also by means 
 of the force with which they impinge upon the ex- 
 haling surfaces, all that is about to assume the aerial 
 form. 
 
 Another fact of importance is the influence of a' 
 screen, whether it be a forest, a stone wall, or any 
 other intercepting body, in sheltering places to lee- 
 ward from the pernicious effects of marsh miasmata. 
 The following facts will illustrate this point. 
 
 In Rome, one side of a street is said to be sickly, 
 in consequence of being exposed to the external 
 miasmata brought thither by the wind, or by its own 
 diff'usive tendency ; while the opposite side of the 
 same street, by means of the shelter it receives from 
 the first line of buildings, is comparatively healthy. I 
 have also been informed by a medical gentleman who 
 resided for some time in Rome, that the part of the 
 city where the Jews principally reside, which is the 
 lowest lying, the closest built, and in every respect 
 the worst ventilated district, is notwithstanding the 
 healthiest during the sickly season : and the reason 
 assigned, is the shelter from the external miasma 
 which this district receives from the intervening build- 
 ings. 
 
 In one of the West India islands, I forget which, 
 the inmates of a barracks were very liable to be affect- 
 ed with fevers when the wind blew from a certain di- 
 rection, in which lay swampy lands. As a measure of 
 
484 ON MARSH FEVERS. 
 
 prevention, the windows that looked towards the 
 marshes were built up, and the unhealthiness of the 
 barracks was thereafter in a great measure removed. 
 
 M. Rigaud de Tlsle relates that near Saint Ste- 
 phano, on Mount Argentel, in the midst of an un- 
 healthy country, a convent is situated which was fam- 
 ed for the salubrity of its air, so long as it was sur- 
 rounded with woods, but since the cutting of these 
 it has become unhealthy. At Velletri near the Pon- 
 tine marshes, the cutting of an intermediate wood oc- 
 casioned, immediately and for three successive years, 
 fevers and other diseases, which committed great 
 ravages : the same eifect was observed to result from 
 a similar cause, near Campo Salino ; and also in 
 many other places. 
 
 In explanation of the preceding facts it may be re- 
 marked, that the benefit arising from such apparently 
 inadequate means of protection, is principally to be 
 ascribed to the great specific gravity of miasmata. 
 Hence their tendency to attach themselves to solid 
 bodies, such as trees, that they meet with in their 
 progress ; and hence likewise, the proximity to the 
 ground at which they float, and their consequent in- 
 abihty to surmount any perpendicular obstacle, such 
 as a stone wall, at the only time they are concentrated 
 and dangerous, viz., during night. 
 
 Regarding the channel through which marsh mias- 
 ma make its injurious impression on the animal frame, 
 nothing has been ascertained. Mr Annesley thinks, 
 (and his opinion is probably correct,) that it acts 
 chiefly through the medium of the air passages of the 
 lunjrs : but whether the material cause is absorbed. 
 
ON MARSH FEVERS. 485 
 
 or operates on the nervous system only, he does not 
 attempt to determine, though he thinks it probable 
 that it may operate in both modes. 
 
 In conformity with what is known of many other 
 absorbed poisons, a certain time elapses, which varies 
 in different constitutions, between the period of in- 
 haling the deleterious miasma, and the appearance 
 of disease. This fact has been completely demon- 
 strated in those cases, (one or two of which we for- 
 merly quoted,) in which vessels having touched at 
 unhealthy islands, those of the crew who slept on 
 shore, and them only, were all subsequently, and suc- 
 cessively at different intervals after exposure to infec- 
 tion, attacked with fever. In general, the most ma- 
 lignant fevers make their appearance soonest after 
 infection. In malignant cases, the interval between 
 infection and the appearance of disease, may vary 
 from 10 hours to a fortnight; but in intermittents, and 
 mild remittents, though they likewise may appear 
 soon after infection, it has been supposed, that the 
 poisonous miasma which occasions them, particularly 
 if imbibed upon the approach of cold weather, may 
 lurk in the body for several months, and at length 
 develop itself in the form of disease. Bancroft (p. 
 241.), after quoting several remarkable facts in proof 
 of this latter circumstance related by Dr John Hunter, 
 says: " Extraordinary as these facts appeared to be 
 when first made known, the fullest confirmation of them 
 has been since produced by the late expedition to Zea- 
 land ; in which it has been indisputably ascertained, 
 that considerable numbers, both of officers and sol- 
 diers, who were employed on that service, and who 
 
486 ON MARSH FEVERS. 
 
 escaped the sickness, whilst at Walcheren, and other 
 parts of Zealand, were attacked with intermitting 
 fevers, and some of them as late as six, seven, eight, 
 and even nine months, after being brought back to 
 this country ; though care was taken to place them 
 generally in situations remote from all the known 
 sources of marsh miasmata. 
 
 The proportion of mankind who die of marsh fe- 
 vers, and of other diseases arising from marsh mias- 
 ma, though much diminished in later times in conse- 
 quence of better draining, is still very great. Mac- 
 culloch states, (though the estimate is probably far 
 beyond the truth,) that it has been rudely computed, 
 that more than half the natural mortality of the hu- 
 man race is owing to marsh fever and its conse- 
 quences. Nor is this great mortality the only evil 
 arising from marsh miasma. According to medical 
 authors, the inhabitants of districts most exposed to 
 its influence, present an unhealthy and unhappy ap- 
 pearance. Even the powers of the mind seem to be 
 thereby impaired. *' It is an observation," says Mac- 
 culloch, *' as old as physic itself, that inferiority of 
 the intellectual faculties is the inheritance of those 
 who reside in marshy countries, and in a dense, foggy 
 atmosphere." 
 
 Yellow fever, according to Bancroft, seldom de- 
 stroys life in less than three or four days ; but gener- 
 ally, though it may terminate fatally, this does not hap- 
 pen till between the 7th and the 15th day. In some 
 of the most virulent kinds of this fever, however, 
 death ensues within 24 hours of the time of attack. 
 Dr Lind, as formerly stated, relates, that in the island 
 
ON MARSH FEVERS. 487 
 
 of Balambangan, in the East Indies, the fevers are 
 so maHojnant as to kill the stoutest men in twelve or 
 fourteen hours. 
 
 Of those who are seized with yellow fever, not 
 above one-half, on an average, recover ; and unlike 
 what happens in the case of small-pox, measles, &c. 
 the same individual may be attacked many times in 
 the course of a hfetime. The persons most liable to 
 this malady are males of a muscular and plethoric 
 habit of body, between the age of 15 and 30, and 
 particularly those who have recently arrived from a 
 colder latitude. The aged, and the valetudinary, 
 according to Bancroft, are not so apt to be attacked, 
 as the vigorous, and the robust. Women are said to 
 be less liable than men, and children less than either. 
 
 Treatment of Patients. — With a view to curing 
 yellow fever, and all inferior degrees of marsh fe- 
 ver, the most important rule to be observed, and 
 which, with slight modification, is susceptible of an 
 extended application to all diseases arising from an 
 infected atmosphere, is to remove the patient as soon 
 as possible from the seat of contagion. The fatigue 
 unavoidable in doing so, instead of being hurtful, 
 even when the patient is reduced to a state of great 
 weakness, is thought so beneficial, that Dr Jackson 
 recommends the motion of a carriage as a means of 
 cure. It is reasonable to conceive a priori, that to 
 allow a patient to remain exposed to the influence of 
 the miasma which originated his illness, and which is 
 capable of communicating a similar disease to a 
 healthy person, is neither the most favourable locality 
 for effecting a cure, nor that in which he is likely to 
 
488 ON MARSH FEVERS. 
 
 receive the most suitable attendance. This point, 
 however, has been set at rest, and the truth of what 
 might have been anticipated confirmed, by the benefit 
 observed to result from the practice of removal. In 
 New York and Philadelphia, it has been ascertained, 
 that of those who are removed to hospitals, or to the 
 houses of relatives at a distance from the seat of in- 
 fection, a greater proportion recover, than of those 
 who remain where the disease was contracted. And 
 even when death ensues after removal, the disease is 
 observed, on an average, to take a longer period to 
 destroy life. 
 
 Regarding the proper mode of curing the more 
 malignant species of marsh fever, commonly called 
 yellow fever, the opinions of different physicians, so 
 far as medicine is concerned, are at antipodes. Ac- 
 cording to the writer of the article on Medicine in 
 Brewster's Encyclopaedia, some practitioners in the 
 same situation, and during the same epidemic, carry 
 the depleting system to an unheard-of length, while 
 others ply stimulants and tonics with no less eagerness 
 and confidence. Upon such opposite extremes in 
 medical practice, it need hardly be remarked, that 
 instead of being both right, they ought to be sus- 
 pected of being both wrong ; and by way of getting 
 at the truth, it might be well to inquire, not which 
 system does most good, but which does least harm. 
 
 The cold affusion repeated again and again during 
 the progress of the disease, preceded by copious 
 bleeding, and followed by blistering, injections, pur- 
 gatives, and warm fomentations, (as if the cure de- 
 pended upon the number and strength of the reme- 
 
ON MARSH FEVERS. 489 
 
 dies,) is recommended by Dr M*Lean. It is need- 
 less to inquire whether or not such rough treatment 
 ever performed miraculous cures, for in the history of 
 medicine, evidence of that kind is seldom wanting ; 
 but judging from the circumstance of its never hav- 
 ing become general, as well as a priori^ from its 
 greater hkelihood to injure a man in health, than 
 recover one in disease, its propriety is more than 
 questionable. 
 
 Patients are to Doctors subjects, 
 Fit for experiments and projects ; 
 Which though ailing by the bye, 
 They seldom on themselves do try. 
 'Tis hence a leech proves better far, 
 Than fifty armed men of war ; 
 For he by lance and purging skill, 
 Can more than sword by hundreds kill. 
 
 HUDIBEAS. 
 
 I am inclined to think, that in diseases where death 
 or recovery soon ensues, violent and unnatural reme- 
 dies are frequently believed to cure, for no better 
 reason, than that they do not invariably kill. A con- 
 siderable proportion of those attacked with yellow 
 fever recover ; and it is ever difficult to determine, 
 whether this result be in consequence, or in spite of 
 medical treatment. In all dangerous and rapid dis- 
 eases where no certain remedy has been discovered, 
 nor any uniform mode of treatment adopted, the 
 safest practice undoubtedly is, to do little or nothing 
 more than sooth the feelings, calm the fears, and gra- 
 tify the taste and desires of the sick. And in yellow 
 fever, all perhaps that should be done, beyond removal 
 
 3 Q 
 
490 ON MARSH FEVERS. 
 
 from the seat of contagion, is to regulate the amount 
 of covering agreeably to the patient's sensation of 
 heat and cold ; to minister to his excessive thirst and 
 lonmns for fresh air ; and trust the rest to the cau- 
 tious, well-timed, and ever salutary efforts of nature. 
 
 In the cure of the less virulent kinds of marsh 
 fever, viz. intermittents, and mild remittents, the in- 
 variable recommendation by medical authors of Peru- 
 vian bark administered during the intermission and 
 remission of disease, and even during a state of con- 
 valescence, is satisfactory evidence of its propriety 
 and utihty. It is hkewise an undisputed observation, 
 that when the general health of a patient, originally 
 from a cold latitude, continues long impaired after a 
 fever, recovery is best perfected by returning to his 
 native climate. 
 
 Preventive Measures. — Though marsh fevers be 
 now happily almost unknown in Great Britain, they 
 still prevail in our East and West India settlements. 
 And if we reflect on the numbers of our fellow-country- 
 men, and even of our friends and relatives, that have 
 occasion, in the pursuits of merchandise or of plea- 
 sure, to visit these or other countries where such dis- 
 eases prevail; and whose lives are so often sacrificed 
 to their ignorance of the means of preserving them, 
 which such facts as we have quoted in the previous 
 pages reveal, the importance of the subject, inde- 
 pendent of the collateral information which it com- 
 municates, relative to the means of guarding against 
 all pestilential diseases, appears. We will, therefore, 
 before taking leave of our subject, briefly state, though 
 in some cases it be partly to recapitulate, the means 
 
ON MARSH FEVERS, 491 
 
 found useful in destroying the deleterious properties 
 of malaria soils ; and the personal precautions neces- 
 sary in order to avoid their baneful influence. Of 
 these preventive measures, some, as will obviously 
 appear, cannot be accomplished without the aid of 
 public funds, and legislative enactment; while others 
 are within the power of every one to adopt for himself. 
 The former are properly objects that demand the 
 interference of local and municipal governments ; 
 the latter require merely the exercise of individual 
 prudence. Of the former class, the first we will men- 
 tion is embankment. 
 
 The swampy character of a large proportion of the 
 low-lying alluvial formations contiguous to the banks 
 of rivers, and along the sea-coast, is partly, and some- 
 times wholly, produced by inundations during rainy 
 weather, or high tides, to which they are periodically 
 subject. Wherever this is the case, embankment is 
 usually recommended as an obvious and efficient cor- 
 rective of the pernicious qualities of the soil. The 
 efficacy of this remedy, however, as we will subse- 
 quently have occasion to show, is more apparent in 
 its immediate, than in its ultimate tendency; and its 
 propriety can be better determined by the observation 
 of local circumstances, than by general speculation. 
 
 When the swampy character of the soil is owing to 
 its power of retaining moisture, whether received in 
 the form of rain, or during inundations, draining, 
 where the level admits of it, is the proper remedy. 
 This corrective is with propriety in most cases left to 
 private speculation, for it fortunately happens, that 
 draining is the best means of fitting swampy soils for 
 
492 ON MARSH FEVERS. 
 
 purposes of husbandry; and the proprietor who there- 
 by consults his own interest, simultaneously promotes 
 the health of the community. The almost total dis- 
 appearance of intermittents from our bills of mortality, 
 is in a great measure to be ascribed to better draining, 
 executed wholly for individual benefit, and at private 
 expense. In the United States of America, a pro- 
 gressive tendency towards a similar result is likewise 
 observed to keep pace with the increase of population, 
 the consequent rise in the value of land, and its more 
 extensive cultivation.* 
 
 The benefit of draining is not confined to the coun- 
 try : it is equally beneficial in towns. Its object be- 
 ing nothing more than to dry the soil, its efficacy is 
 greatly assisted by paving and sweeping the streets. 
 By these auxiliary means, all filth and stagnant water 
 are not only removed; but the rain which falls, in- 
 stead of soaking into the ground, is conveyed imme- 
 diately into the common sewers. 
 
 In those towns where yellow fever frequently makes 
 its appearance, and where the source from whence the 
 miasma which occasions the disease emanates, is, as 
 
 * It need hardly be remarked, that the drainage of swamps 
 should never be attempted during the sickly season ; for such 
 would not only be certain death to the labourers employed, but 
 by reducing the swamps to the state of drying mud, (in which 
 condition they are most productive of dangerous exhalations,) the 
 sickness would in the first instance be thei'eby increased. The 
 most fitting time for such operations is the middle of the day, and 
 the coldest period of the year. Those employed should be natives, 
 or long residents, who have become accustomed to the climate : 
 they should likewise be well clothed and fed ; and never worked 
 so long as to feel exhausted or fatigued. 
 
ON MARSH TEVERS. 493 
 
 frequently happens, very limited, it is proper, in addi- 
 tion to the corrective measures above stated, to ex- 
 amine the nature of the soil, with a view to the re- 
 moval of that part of it at least, which is nearest the 
 surface, provided its character be suspicious. Soils 
 are in general to be suspected of possessing delete- 
 rious quahties in proportion to their vegetative fer- 
 tility, and their power of retaining moisture. Of 
 course, in making a change, the rule to be observed, 
 is to substitute that which is less fertile, and has a 
 less retentive power in respect of water, for that which 
 has greater fertility, and has a greater retentive power. 
 According to Kirwan, soils that abound in the argil- 
 laceous principle, (that is, clay soils, or those in which 
 clay predominates,) are the most retentive; and those 
 that abound in the coarse sihcious principle, (that is, 
 sandy and gravelly soils,) the least; and calcareous or 
 chalky soils are intermediate between the two. By 
 the experiments of Bergman it appears, that argill 
 takes up 2*5 times its weight of water when saturated 
 so as to let none drop. 
 
 Magnesia, ...... 1"05 
 
 Chalk, 0-5 
 
 Silicious Sand, ..... 0*25 
 
 By this statement it appears, that Silicious Sand, 
 which by itself is perfectly barren, has only ^^th part 
 of the retentive power in respect of water that argill 
 has. And hence the propriety of substituting sand 
 or gravel for clay, and for loams in which clay pre- 
 dominates. This recommendation is so far in con- 
 formity with the observations of Linnaeus. That great 
 
494 ON MARSH FEVERS. 
 
 naturalist observed, that intermittent fevers were most 
 prevalent in clay soils: and Bancroft thinks that this 
 is owing to their power in retaining moisture. 
 
 The preceding observations, so far as regards the 
 nature of the soil, point out the safest situations for 
 the encampment of armies in warm unhealthy chmates; 
 also for the building of hospitals, as well as private 
 residences. And where the nature of the soil and 
 other circumstances are equal, the more elevated the 
 situation the better. 
 
 When, owing to the lowness of the land, the drain- 
 ing of swamps is impracticable, the most obvious re- 
 medy is to fill them up. In towns likewise the filling 
 up of hollows, and the maintenance of proper levels 
 with a view to draining, and dryness in general, is of 
 essential importance to the health of their inhabitants. 
 
 The submerging of swamps where draining is im- 
 possible, has been also recommended. Moisture is 
 in all cases necessary to vegetation ; and different 
 vegetable productions require soils that are very dif- 
 ferent from each other in this particular ; but com- 
 plete submersion seems about equally destructive to 
 vegetation with the total absence of moisture. Soils 
 subjected to solar influence are usually supposed to 
 be most productive of miasmata, when in the state of 
 mud, or between that state and dryness. Hence, 
 drainage of swamps, which, in the first instance, 
 would reduce them to this state, is particularly to be 
 avoided during the warm and sickly season. And 
 hence the propriety of submersion, when the heat of 
 the sun during this period has a tendency to reduce 
 them to this state. The efficacy of submersion in 
 
ON MARSH FEVERS. 495 
 
 preventing the exhalation of miasmata, is conceived 
 by Beecher, to be owing to the great quantity of 
 fluid opposing the decomposition of animal and vege- 
 table substances. 
 
 Another recommendation is to prevent the stagna- 
 tion of water in marshes, by directing the course of 
 rivers through them. *' Empedocles is said to have 
 delivered the Salentini from the dangerous exhala- 
 tions to which they were subjected, by conducting 
 into their marshes two neighbouring rivers, which 
 cleared them of their stagnant water ; and the air be- 
 ing no longer tainted, the diseases to which they had 
 been previously liable ceased." 
 
 This subject acquires additional importance by con- 
 templating the property, common in a greater or less 
 degree to all rivers, of raising the level of their beds 
 while traversing flat countries in their approach to the 
 ocean. The cause of this property of rivers is ob- 
 vious. The earthy materials with which their waters 
 become impregnated during the higher and more 
 rapid parts of their course, and particularly during in- 
 undations, are deposited as their basins expand, and 
 their currents diminish in rapidity. Upon this point, 
 by way of authority, we will insert a short extract from 
 Baron Cuvier's Theory of the Earth. 
 
 " M. de Prony," says Cuvier,* " having been di- 
 rected by government to investigate the remedies that 
 might be applied to the devastations occasioned by 
 the floods of the Po, ascertained that this river, since 
 the period when it was shut in by dikes, has so greatly 
 raised the level of its bottom, that the surface of its 
 
 * Page 128. 
 
496 ON MARSH FEVERS. 
 
 waters is now higher than the roofs of the houses in 
 Ferrara. At the same time, its alluvial depositions 
 have advanced so rapidly into the sea, that, by com- 
 paring old charts with the present state, the shore is 
 found to have gained more than six thousand fathoms 
 since 1604, giving an average of a hundred and fifty, 
 or a hundred and eighty, and in some places two hun- 
 dred feet yearly. The Adige and the Po, are at the 
 present day higher than the whole tract of land that 
 lies between them ; and it is only by opening new 
 channels for them in the low grounds, which they have 
 formerly deposited, that the disasters which they now 
 threaten may be averted. 
 
 " The same causes have produced the same effects 
 along the branches of the Rhine and the Meuse ; and 
 thus the richest districts of Holland, have continually 
 the frightful view of their rivers, held up by embank- 
 ments, at a height of from twenty to thirty feet above 
 the level of the land." 
 
 From the preceding facts and others of a similar 
 kind, considered in conjunction with the circumstance 
 of all such hollow intermediate lands, as those above 
 alluded to, being unhealthy 5 the propriety in certain 
 cases of opening new channels for rivers through low- 
 lying marshy districts, only determinable by local sur- 
 vey, becomes apparent. Rivers are the great drains 
 into which all minor ones empty themselves ; and by 
 which the superfluous water beyond what is necessary 
 for vegetation, is returned to its parent ocean. But 
 when the surface of the water in those great drains 
 becomes higher than that of the adjoining country, 
 drainage of the soil becomes impossible, except by 
 
ON MARSH FEVERS. 497 
 
 such expensive and inefficient methods, as digging 
 reservoirs, and hfting the waters they receive over 
 river embankments by means of marsh-mills, and other 
 mechanical contrivances. 
 
 Besides, there is reason to think, that the marshi- 
 ness of many districts, is partly owing to the greater 
 elevation of the surface of the embanked rivers which 
 traverse them. Springs issuing from the ground are 
 ever owing to the absorption of water at a higher le- 
 vel, and which is sometimes conveyed by subterrane- 
 ous channels to great distances from its source of in- 
 troduction, before appearing at the surface. In like 
 manner, wherever the elevated beds of rivers are in 
 any degree permeable to moisture, portions of water 
 may be expected to find its way by subterranean 
 channels, so as to appear at the surface, and occasion 
 marshiness of soil, at considerable distances from its 
 source of introduction. 
 
 Such considerations show that the utility of em- 
 banking rivers is very questionable, unless the deep- 
 ening process can be made to counteract their ten- 
 dency to raise the level of their beds. Unembanked 
 rivers uniformly direct their course along the lowest 
 level, and thereby act not only as natural drains, but, 
 if requisite, afford the greatest facility for additional 
 artificial draining. Besides, the subsequent advan- 
 tages resulting from inundations, unless they happen 
 when crops are on the ground, in general more than 
 compensate for their temporary inconvenience. While 
 their alluvial depositions leave everywhere a fertile 
 soil, they gradually fill up hollows, and raise the level 
 of low-lying plains, so as eventually to prepare the 
 
 3 R 
 
498 ON MARSH FEVERS. 
 
 land for being permanently freed from that marshi- 
 ness, and unhealthiness, which they at first promoted. 
 By embankments these advantages are not only lost, 
 but evils in a national point of view result. Gradually 
 as the beds of embanked rivers are raised by succes- 
 sive depositions above the level of the surrounding 
 country, drainage of the soil becomes not only more 
 necessary, and more difficult ; but the lives and pro- 
 perty of a people so protected from inundation, are 
 ever at the mercy of an enemy. 
 
 Another preventive measure is by legal enactment 
 to discourage or prohibit, within a limited distance of 
 towns, the cultivation of articles, such as rice, and the 
 preparation of others, such as steeping hemp and flax, 
 which are generally admitted to be productive of mal- 
 aria. This might be considered an invasion of the 
 right of private property ; but it ought to be recol- 
 lected, that the application of property to purposes 
 injurious to health, deteriorates the property of others. 
 Of two evils the least ought to be preferred. Health 
 and household property are certainly objects as worthy 
 of legal protection, as the value of land. Perhaps in 
 agricultural districts, where there are few houses, pro- 
 hibitions of this kind are inexpedient ; but in the 
 neighbourhood of towns, where the advantage in- 
 creases with the amount of property, and the number 
 of those whose health is to be protected, the propriety 
 of prohibiting any mode of cultivation, preparation, 
 or deposition of articles injurious to health, is un- 
 questionable. 
 
 A counterpart to the preceding recommendation is 
 by premiums, if necessary, to encourage within a 
 
ON MARSH FEVERS. 499 
 
 limited distance (say a couple of miles,) of towns, the 
 cultivation of such articles, as correct the pernicious 
 qualities of the soil. To this class sugar-cane, and 
 such other vegetable productions as require much 
 nourishment, are thought to belong. This opinion is 
 founded upon Dr Jackson's theory of the source of 
 miasmata. He conceives, that these deleterious 
 emanations chiefly consist of the excess of vegetative 
 nutriment afforded by the soil, beyond what the plants 
 covering its surface can make use of in the way of 
 growth ; and hence the reason that marsh fevers are 
 most prevalent and virulent in warm climates; and in 
 soils, and seasons, most productive of luxuriant vege- 
 tation. This theory I may observe is by no means 
 established ; but it is nevertheless so much in unison 
 with the leading phenomena attending marsh fevers, 
 as to warrant the adoption of the above recommenda- 
 tion as a measure of precaution. 
 
 It has been uniformly observed, that constant culti- 
 vation and cropping of the hnd, and extracting from 
 it as much produce as possible, has a powerful ten- 
 dency in correcting its deleterious properties. On the 
 contrary, allowing it to lie fallow, or to remain uncul- 
 tivated or unploughed, has an opposite effect. With 
 a view therefore to promote the salubrity of warm 
 climates, particularly in the neighbourhood of towns, 
 these observations are worthy of attention. 
 
 In towns where the source of the miasma which 
 occasions disease is external, building a high wall, or 
 planting a belting of trees in the intermediate space, 
 may obviously, from facts previously mentioned, be 
 serviceable. But wherever the source of disease is 
 
500 ON MARSH FEVERS. 
 
 within a town, widening, paving, draining, and sweep- 
 ing the streets, and building them in straight hnes ; 
 and in general by removing every obstruction to the 
 free circulation of air, such as trees and ramparts ; and 
 by police regulations prohibiting and removing depots 
 of filth, and decomposing vegetable and animal mate- 
 rials, also stagnant water, mud, and rich soil on or 
 near the surface of the ground, particularly from 
 wharves, banks of rivers, and low-lying places, are the 
 most advisable preventive remedies. 
 
 Most of the precautionary measures within the 
 power of individuals to adopt for themselves, and 
 which we are now to enumerate, are obvious inferences 
 from the facts previously quoted. Persons who wish 
 to preserve health in warm sickly climates, particularly 
 those recently arrived from cold latitudes, should avoid 
 the night air, never venturing out of their houses dur- 
 ing the sickly season for an hour or two after sunrise, 
 nor remaining out after sunset. Elevated situations, 
 as far distant as convenient from wharves, and marshy 
 low-lying districts, especially those visited by sickness 
 in previous years, should be selected for dwellings, 
 and places of business. Sitting and sleeping apart- 
 ments should never be on the ground flat, but as high 
 above it as possible ; and the windows should never 
 be opened from sunset till an hour or two after sun- 
 rise, and not at all when the wind blows from the 
 marshy district.* In general, when the wind blows 
 
 * The recommendation given in the text, to keep the window 
 shut at night during the sickly season in warm, swampy climates, 
 is not applicable to the climate of Britain, nor to that of countries 
 where marsh fevers are unknown. Mankind spend nearly one- 
 
ON MARSH FEVERS. 501 
 
 over marshes, exposure to it ought to be avoided, 
 particularly during night, and for an hour or two after 
 sunrise ; and also during day, provided the weather 
 be cloudy, or foggy. When exposure to night air, 
 
 third of their lives in bed. And as breathing fresh air essentially 
 contributes to promote health and strength, the air of bed-rooms 
 is particularly worthy of attention. 
 
 I made a lengthened series of thermometric observations con- 
 ducted during all seasons of the year, partly to ascertain how far 
 the air within a bed-room 12 feet square, with a northern exposure, 
 underwent vicissitudes of temperature corresponding to those of 
 the external atmosphere, the upper part of the window being open, 
 by day and night, nearly two inches during winter, and about four 
 inches during summer. The door of the apartment was kept open 
 during day, but shut during night. The results of the observa- 
 tions, so far as applicable to the point under consideration, were as 
 follow : — 
 
 1. The diurnal range of temperature within the bed-room was 
 greatly less than that of the external atmosphere. When the di- 
 urnal range of temperature exhibited by a thermometer suspended 
 outside of the window, was, on very rare occasions, as much as 
 from 15 to 20 degrees, the range exhibited by a thermometer sus- 
 pended inside of the bed-room, did not exceed five or six degrees. 
 And when the diurnal range of temperature exhibited by the ex- 
 ternal thermometer, was about the mean, viz. from 7 to 8 degrees, 
 the range of temperature, inside of the bed-room, did not exceed 
 2 degrees, and seldom was so much. 
 
 2. From my time of going to bed to that of rising, (the former 
 varying, perhaps, from midnight to two o'clock in the morning, 
 and the latter from 7 to 9 o'clock, a.m.) the thermometer inside 
 of the bed-room varied, on rare occasions, as much as two degrees; 
 more frequently it did not vary above one degree ; and more fre- 
 quently still it did not vary so much as one degree. And these 
 variations almost always consisted of an augmentation of temper- 
 ature, which I ascribed partly to the influence of the heat evolved 
 by a person in warming a room ; for the thermometer, outside of 
 
502 ON MARSH FEVERS. 
 
 or to winds blowing over marshes is unavoidable, the 
 shorter the duration of exposure, the safer. 
 
 It is said that gauze frames fitted to the windows 
 of houses much exposed to malaria, will arrest its pro- 
 gress ; and likewise that sleeping under a mosquito 
 net, in an infected place, will protect a person from 
 the noxious influence of the atmosphere. These points 
 have not been satisfactorily established; but when the 
 efficacy of trees in robbing a current of air of its dele- 
 terious vapours is considered, it seems by no means 
 improbable, that a gauze frame may have the effect 
 above ascribed to it ; and likewise that a mosquito 
 net, or even that a muslin or silk handkerchief 
 
 the window, varied from one to eight degrees in the same time ; 
 and the variations were as often downwards as upwards. 
 
 3. The temperature in the bed-room was always considerably 
 higher during night than that of the external atmosphere. Hence 
 no injury can result during night from the intrusion of damp air; 
 for however damp the external air may be, it becomes compara- 
 tively dry, hygrometrically speaking, upon entering the bed-room, 
 in consequence of the augmentation of temperature which it then 
 undergoes. 
 
 Now, as catching cold principally results from sudden and great 
 variations of temperature, I infer from the preceding facts, that 
 there is no risk of catching cold from sleeping with the bed-room 
 window open one inch during winter, and two or three inches 
 during summer, or perhaps considerably more. And from the air 
 within the bed-room being thereby kept fresh and wholesome, and 
 all respiratory and perspiratory vapours and gases allowed more 
 freely to escape, I also infer that great benefit results not only to 
 those in health, but also, and in a more especial manner, to the 
 sick and the valetudinary from this practice. To insure perfect 
 safety, it may be advisable, when the wind blows directly in at the 
 window, or when the bed-stead is near the window, that a bed- 
 curtain intervene between the window and the person in bed. 
 
 
ON MARSH FEVERS. 503 
 
 thrown over the face when asleep, may intercept the 
 miasma during respiration, though it does not obstruct 
 the passage of air. It is said hkewise that the inha- 
 bitants of infected districts, are rendered less liable 
 to the influence of malaria by being clothed in wool, 
 living well, and keeping their houses warm and dry; 
 and also, that when travellers are obliged to pass the 
 night in malaria districts, the danger they run is much 
 diminished, by keeping the air of their sleeping and 
 sitting apartments dry and warm by means of a fire, 
 so as to assimilate their corporeal warmth, and the 
 temperature and hygrometric dryness of the atmo- 
 spere by which they are immediately surrounded dur- 
 ing night, to what they are during day. 
 
 Those who visit malaria districts merely on excur- 
 sions of pleasure, and who usually can select their 
 own time, ought to avoid doing so during the sickly 
 season, viz., summer and autumn. And those who 
 go to reside permanently in such climates, ought to 
 study if possible to arrive there soon after the sickly 
 season has ceased, in order that they may be some- 
 what habituated to the climate before it returns ; re- 
 collecting, that the danger is much greater, and pre- 
 cautions proportionally more necessary, the first year 
 of residence, than the second ; and more the second, 
 than the third. 
 
 When the yellow fever breaks out in a town, no 
 precautions will aff"ord complete security, except emi- 
 gration to a healthy spot during its continuance. And 
 as the sickly season is of short duration, and the seat 
 of disease, particularly in towns, is usually so ex- 
 tremely circumscribed, that ten minutes' walk will 
 
504 ON MARSH FEVERS. 
 
 transport a person from the place of greatest danger, 
 to one of perfect safety, it is folly to neglect such a 
 simple and efficient means of prevention. 
 
 Ships of war, in touching at unhealthy climates 
 during the sickly season, should lie at anchor as far 
 as convenient from the land, particularly when the 
 wind blows from that direction; and none of the crew 
 ought ever to be permitted to sleep on shore, or re- 
 main there after sunset. When the wind blows from 
 the land, especially during foggy or cloudy weather, 
 and also during night or early in the morning, those 
 of the crew who are not required on deck, ought to 
 avoid exposure to the breeze, by going below. 
 
 Those who reside in malaria districts, should be 
 particularly careful to avoid excessive fatigue, or long 
 fasting, during the sickly season. Dr John Hunter 
 observes, that if persons are exposed to the exhalations 
 of marshes, when fatigued by hard labour and long 
 fasting, the poison gains admission more readily into 
 the body, and produces immediately the worst kind 
 of fever. It is in this way, (he adds,) that soldiers 
 suffer so much in actual service in the West Indies : 
 the few cases of fever which proved fatal in twenty- 
 four hours, that came under his inspection, were all 
 contracted in that manner. Indeed, there is reason 
 to believe, that every thing which reduces the vigour 
 of the constitution, such as intemperance, debauchery, 
 and irregularity in living; or obstructs the perspiration, 
 such as damp feet, and exposure to cold, or rain, par- 
 ticularly after being much heated, either by exercise, or 
 the sun's rays, has a similar effect with hard labour 
 and long fasting, in rendering the body more hable to 
 
ON MARSH FEVERS. 505 
 
 be affected by marsh miasma. And, judging from 
 the rapidity with which yellow fever, and other infe- 
 rior degrees of marsh fever, have been observed to 
 follow intemperance, fatigue, exposure to cold, and 
 wet, &c. there are grounds for believing, that though 
 a portion of the poison be introduced into the system, 
 it may frequently be overcome, and got quit of, by 
 the strength of the constitution, without producing 
 disease; but if in such circumstances the body be 
 exposed to any debilitating cause whatever, disease, 
 which might otherwise have been averted, may be 
 immediately brought on. Hence, with regard to regi- 
 men, it may be laid down as a general rule, that the 
 avoidance of whatever reduces the vigour of the con- 
 stitution either permanently or temporarily; and the 
 adherence to that mode of hving, which each person 
 has found best calculated to promote his own individ- 
 ual health and strength, are, during the sickly season, 
 and when exposure to marsh emanations, and other 
 infectious effluvia, is unavoidable, the most likely 
 means of preventing marsh fevers, as well as all other 
 diseases. 
 
 Bleeding, laxative medicines, and spare diet, have 
 been recommended to new-comers from cold latitudes, 
 by way of assimilating their constitutions to that of 
 natives, and of those who by long residence have be- 
 come habituated to the climate. I very much doubt 
 the propriety of the former part of this recommenda- 
 tion. We know little or nothing regarding those 
 alterations in the constitution produced by long resi- 
 dence, which render the body less liable to the dis- 
 eases of warm climates. The visible changes, (and 
 
 3s 
 
-500 ON MARSH FEVERS. 
 
 it is probable that those that are invisible correspond 
 with them,) are an increased sallowness or darkness 
 in the complexion, (supposed to arise from an aug- 
 mented secretion of bile,) an enlargement in the 
 caliber of the external blood-vessels; and a diminution 
 in the amount of muscular fibre, and of fat. But 
 bleeding and laxative medicines, I should suppose, 
 instead of accelerating, will rather retard these; and 
 possibly whatever other changes are effected in the 
 constitution by long residence in a warm climate. 
 Besides, by reducing the vigour of the constitution, 
 they would probably have much the same effect as 
 hard labour, long fasting, exposure to cold after being 
 heated, or sudden exhaustion arising from any cause, 
 in affording more easy admission to the poisonous 
 miasma. 
 
 The latter part of the recommendation, viz. spare 
 diet, being less artificial, and more in accordance with 
 the dictates of nature, seems to be less objectionable. 
 Judging from the circumstance of the muscular and 
 robust being most liable to yellow fever, under-eating 
 is probably less dangerous than over-eating; and a 
 cooling diet preferable to one that is heating. These 
 in reality are only Nature's prescription, and she, in 
 all cases of uncertainty, is the safest physician. Ap- 
 petite prescribes to a person newly arrived from a 
 cold climate, the essentials of a spare and cooling diet, 
 viz., an increase in the amount of liquid, and a dimi- 
 nution in that of solid food ; and so far, and no far- 
 ther, spare diet may be recommended. 
 
 Dr Chisholme recommends the wearing of flannel 
 next the skin in warm climates, with a view to keep- 
 
ON MARSH FEVERS. 507 
 
 ing the body in an equable degree of warmth. And 
 when the security thereby afforded against all vicissi- 
 tudes of temperature is considered ; and particularly 
 the supposed effect of the sudden transition from the 
 heat of the day to the coolness of night, in rendering 
 the body more apt to imbibe the poison, the recom- 
 mendation is probably judicious. Upon this point, 
 however, it may be remarked, that the sensations of 
 heat and cold seem to have been given with a view to 
 teach us instinctively to protect our corporeal frame 
 from injury, arising from extreme, or unwholesome 
 temperatures. And it is now universally admitted, 
 that the temperature which is most agreeable, is also 
 the most wholesome, not only to those in health, but 
 likewise to patients labouring under any disease what- 
 ever. Now, as the atmosphere in warm climates is 
 more frequently felt disagreeably warm than disagree- 
 ably cold, especially by new-comers from colder lati- 
 tudes, it is reasonable to think, that if flannel is worn 
 at all, it ought to be of the thinnest kind ; and the 
 outer garments ought on the same account to be also 
 thin and cool. 
 
 Finally, It has been ascertained that substances, 
 according as their colour is whiter, and their surface 
 smoother, are better reflectors of heat ; and when 
 temperature is on the increase, absorb in a given 
 time a smaller proportion of it, and consequently, in 
 such circumstances, are the slowest in becoming 
 warm; while on the other hand, they are proportionally 
 worse radiators of heat, and accordingly, are the 
 slowest of becoming cold when temperature is on the 
 decrease. Hence, the lighter the colour, and the 
 
508 
 
 ON MARSH FEVERS. 
 
 smoother the outer surface of the external garments, 
 the more ehgible they are in all climates for preserv- 
 ing the body in an equable degree of warmth, both 
 during the diurnal and the annual variations of tem- 
 perature; and whether circumstances require exposure 
 to the heat of the sun, or afford the protecting in- 
 fluence of the shade. 
 
 END OF THE ESSAY ON MARSH FEVERS. 
 
AN EXPOSITION 
 
 ERRONEOUS NATURE OF MR OWEN'S PLAN 
 
 AMELIORATING THE CONDITION OF MANKIND, 
 
 ACCOMPANIED WITH 
 
 OBSEEVATIONS ON THE MEASURES AND POLICY CALCULATED TO 
 PROMOTE THAT DESIRABLE OBJECT. 
 
AN EXPOSITION OF THE ERRONEOUS NATURE OF MR OWEN's 
 PLAN FOR AMELIORATING THE CONDITION OF MANKIND, 
 ACCOMPANIED WITH OBSERVATIONS ON THE MEASURES AND 
 POLICY CALCULATED TO PROMOTE THAT DESIRABLE OBJECT. 
 
 To ameliorate the condition of our fellow-men, or 
 in Other words, to increase their happiness and dimi- 
 nish their misery, as far as lies in our power, is the 
 duty of every member of society. The proposer of a 
 plan which has only this object in view, is certainly 
 entitled to a hearing, if not to our gratitude, for his 
 philanthropy. But when its adoption requires great, 
 and immediate sacrifices of comfort, and important al- 
 terations in our habits, and manner of living ; it is not 
 to be expected, unless he can clearly prove, that it 
 would immediately, or ultimately, be attended with 
 great advantage, that mankind will make any change. 
 And if he persists in recommending it, after it has 
 been often, and clearly demonstrated, that its adop- 
 tion is impracticable ; and if practicable, would be at- 
 tended with injury instead of benefit to society, he has 
 no claim to expect that mankind will regard him in 
 any better light, than as an enthusiastic, well-mean- 
 ing, but strangely infatuated visionary. 
 
 In the following paper, I purpose to commence 
 with a summary of Mr Owen's plan, a knowledge of 
 
512 REVIEW OF 
 
 which I have principally obtained from his own report 
 on the subject to the county gentlemen of Lanark- 
 shire. I will then examine the various items of which 
 it consists ; and endeavour to prove, that, separately 
 considered, they are calculated to injure, and not to 
 benefit society. And will conclude by showing, that, 
 in its remote consequences, the universal adoption of 
 his plan would ultimately spread, and greatly increase 
 ignorance, poverty, and crime, instead of producing 
 (as Mr Owen tells us) " incomprehensible know- 
 ledge, and incalculable wealth, even until it became 
 so abundant that any farther increase to it, would be 
 considered useless, and not to be desired." It may 
 be likewise here premised, that, when treating of the 
 last department of our subject, we will take the oppor- 
 tunity of reviewing a variety of the measures which 
 have been proposed for ameliorating the condition of 
 mankind ; and will endeavour to discriminate between 
 those that are, and those that are not, calculated to 
 further this desirable object. 
 
 First, then, for the summary of Mr Owen's plan. 
 
 Mr Owen proposes to erect buildings in the form 
 of parallelograms, which he says is the best form, cap- 
 able of containing each, from 300 individuals as a 
 minimum, to 2000 as a maximum ; but from 800 to 
 1200 he considers the most desirable number for 
 forming into agricultural villages. These buildings 
 are to be erected as near as possible to the centre of 
 the land belonging to them ; and are to contain the 
 sleeping, dining, and cooking apartments of the villa- 
 gers ; as well as the store-rooms, and granaries for 
 holding their redundant wealth. Also an inn for the 
 
MR Owen's system. 513 
 
 accommodation of travellers ; an infirmary for the dis- 
 eased ; and in the centre of the parallelogram, a 
 church and two schools ; one for the education of in- 
 fants from two to six, and the other, for children from 
 six to twelve years of age. The workshops for carry- 
 ing on the manufactures of the different necessary, 
 and ornamental articles for the use of the villagers, are 
 to be placed at some distance from the parallelograms, 
 under a plantation. Each parallelogram is to have 
 attached or belonging to it, from 150 to 3000 acres of 
 arable land ; but generally from 800 to 1500 acres, 
 that is, from half an acre, to an acre and a half, for 
 each individual, less or more in proportion as it is 
 reckoned most advisable, to hoard up their redun- 
 dant, or unconsumed wealth, in manufactured goods, 
 or in agricultural produce. And each association, 
 generally speaking, is to create for itself, a full supply 
 of the necessaries, conveniences, and comforts of life. 
 The education of the young is not to be conducted 
 through the medium of books, but systematically by 
 means of sensible signs ; and all is to be produced 
 by the knowledge of some new science, which he 
 absurdly supposes he has discovered ; and which he 
 calls, a knowledge of the science of the influence of 
 circumstances over human nature. The present mode 
 of promoting education by exciting emulation from 
 hope of reward or dread of punishment, he says is not 
 only productive of all the bad, but destructive of all 
 the good qualities in human nature. In his system 
 of education therefore, these are to be superseded by 
 a knowledge of the science of the influence of cir- 
 cumstances over mankind. 
 
 3t 
 
514 REVIEW OF 
 
 The villagers, to save the trouble of separate cook- 
 ing establishments, are to take their meals all to- 
 gether at the same time and place. And their dress 
 is to be loose, and similar to that of the Romans, or 
 Highlanders. 
 
 One of the first measures which Mr Owen pro- 
 poses, in order to let prosperity loose on the country, 
 (to use his own words,) is to abolish the use of gold 
 and silver as a circulating medium ; and to erect hu- 
 man labour into a standard of value, in order to pre- 
 vent the rise and fall in the price of commodities, 
 which are to be bartered according to the quantity of 
 labour contained in each. Spade husbandry is to be 
 substituted for the plough and harrow. The minute 
 divisions, and sub-divisions of labour, by way of en- 
 larging the minds of his villagers, are to give place 
 to the plan of every man producing an article com- 
 pleted by himself. And they are all to work by turns 
 at different trades, in order to prevent the bad effects 
 upon health, by remaining always in the same posi- 
 tion, and employment ; as well as to give every one 
 his just share of the agreeable, and disagreeable oc- 
 cupations. And finally, the government of each 
 parallelogram is to be a committee, consisting of all 
 the persons between the ages of 35 and 45. 
 
 Such are the outlines of Mr Owen's new plan of 
 society, " by the adoption of which," he says, " the 
 vicious, the idle, and the pauper, shall be made virtu- 
 ous, industrious, and independent." He offers to 
 " exchange their poverty for wealth ; their ignorance 
 for knowledge; their divisions for union;" and he 
 
MR Owen's system. 515 
 
 farther adds, that " he has promised far less than will 
 be realized." 
 
 We will now examine the various items of which 
 the plan consists ; and endeavour to show, that separ- 
 ately considered, they are calculated to injure, and not 
 to benefit society. 
 
 I mean to pass over the parallelogram form of Mr 
 Owen's villages, which he says is better than any 
 other, without assigning a reason, according ^to; his 
 usual custom, why it is so. Also the size of the 
 farms, with only observing, that the largest, viz. 3000 
 acres of arable land, would be rather inconvenient 
 for cultivation, in consequence of the distance be- 
 tween the dwellings of the labourers, and its remote 
 parts. 
 
 We shall also pass over a variety of the less im- 
 portant inconsistencies,* and proceed to inquire into 
 
 * Some of the inconsistencies alluded to in the text, are as fol- 
 low : — Mr Owen, in one part of his report states, " that each as- 
 sociation, generally speaking, is to create for itself a full supply of 
 all the necessaries, comforts, and conveniences of life." This can 
 only be accomplished, by each parallelogram having labourers en- 
 gaged at all different employments. At another part he says, 
 " the villagers are to take their meals all together, at the same 
 time and place;" at another part, he says, " that at meals, the 
 villagers will all be clean, well dressed, intelligent, and possessing 
 benevolent dispositions, all of which combined, will give a proper 
 zest to the entertainment;" and at another part, " that they are 
 all to work by turns at diiferent trades, in order to give each his 
 just share of the agreeable, and disagreeable employments." 
 
 But how incompatible are these different parts of his plan with 
 each othex'. How can those, who are digging the remote parts of 
 a farm of 3000 acres of arable land, take their meals at the same 
 time and place, with those who are working in the inuuediate vi- 
 
516 REVIEW OF 
 
 the nature of his system of education, which is con- 
 sidered the only part of his plan not totally irrational. 
 
 Mr Owen tells us that the success of his arrange- 
 ments, will depend upon the manner in which the 
 infants and children shall be trained, and educated, 
 in his two schools ; *' for," says he, " men are, and 
 ever will be, what they are, and shall be, in infancy 
 and childhood." 
 
 The fundamental principle in his essays on the 
 formation of human character, and which pervades 
 almost every page of his writings, is that the character 
 of man is entirely dependent upon education ; that 
 it is formed by his predecessors for him, and that 
 therefore he may be made to acquire any character 
 they choose. Here Mr Owen's error originates in 
 not perceiving, that man has received a character from 
 the hand of nature, which cannot be eradicated ; 
 though, as every body knows, it may be operated 
 upon to a hmited extent by his predecessors. Man, 
 like every other animal, is born with the instinctive 
 principle of acting towards his own gratification, ac- 
 cording as his reason directs. This principle, which 
 
 cinity of their eating apartments ? Or how is it possible, that men 
 engaged at all different kinds of dirty employments can appear 
 clean, and well-dressed at every meal ? Then again, what a num- 
 ber of suits of clothes must each individual possess, in order to be 
 able to equip himself for each kind of employment. Or, if an ex- 
 tensive wardrobe be deemed unnecessary, how unsuitable would 
 the dress of one trade be for that of another ! Then how impossible 
 would it be for each person, to qualify himself for working in ro- 
 tation at each different trade, and employment ! How unsuitable 
 to the limited capacity of man, and the short term of his earthly 
 existence ! 
 
 I 
 
MR Owen's system. 517 
 
 is the source of all actions good and bad, is influenced 
 by circumstances, which it is frequently impossible 
 for man altogether to control, or even to predict. Pro- 
 vidence foreseeing, that the principle of acting with 
 a. view to our own gratification, if left unrestrained, 
 must lead to confusion, has wisely provided a check 
 to its abuse. In man accordingly vindictive princi- 
 ples are implanted, which not only excite him to resist 
 aggression, but to punish the aggressor ; and this is 
 the check which nature has prescribed in order to 
 control, and direct the selfishness of mankind, so as 
 to prevent one from trespassing upon the rights of 
 another. Selfishness thus restrained, excites us to 
 pursue our own happiness according as reason and 
 experience direct, without abridging that of others. 
 Human laws with punishments annexed to their 
 violation, are founded upon the same principle ; and 
 beneficially supersede in society the exercise of vin- 
 dictive feelings, which is found in some measure 
 destructive to human happiness. Laws are useful in 
 protecting the rights of individuals; and in producing 
 confidence in the transactions between man and man. 
 They exist in every civilized nation, and are absolute- 
 ly necessary for the maintenance of peace and order 
 in society. Mr Owen, however, going upon his 
 erroneous principle, that mankind have no character 
 but what they are taught, considers all the natural 
 checks to the tendency of man to encroach upon the 
 rights of his neighbour, as useless, and unnecessary. 
 He tells us, that " those laws which enact punishments 
 for a very great variety of actions, which are designat- 
 ed crimes, are palpably absurd, and unjust." But let 
 
o 
 
 18 REVIEW OF 
 
 US hear the substance of Mr Owen's plan of teaching 
 mankind in order to prevent crimes. 
 
 In his essays on the formation of human character, 
 he says, " That each child at two years of age, on his 
 entrance into the play-ground, is to be told in lan- 
 guage which he can understand, that he is never to 
 injure his play-fellows ; but, on the contrary, he is to 
 contribute all in his power to make them happy. 
 This simple precept will effectually supersede all the 
 errors which have hitherto kept the world in igno- 
 rance." By this I understand, that Mr Owen means, 
 if what he says has any meaning, that this simple pre- 
 cept, (which is very good so far as it goes,) will ef- 
 fectually supersede all the laws and measures which 
 are adopted for preventing crimes. But Mr Owen 
 goes on to say, in the same unintelligible strain, *' Thus, 
 by merely attending to the evidence of our senses 
 respecting human nature, and disregarding the wild, 
 inconsistent, and absurd theories, in which man has 
 been hitherto trained in all parts of the earth, we shall 
 accomplish with ease and certainty, the supposed 
 Herculean labour of forming a rational character in 
 man, and that too, chiefly before the child commences 
 the ordinary course of education." 
 
 The inadequacy of the proposed means to accom- 
 plish the end of preventing crimes, is too obvious to 
 require comment. But it may be observed, that the 
 propriety of inculcating good moral precepts on the 
 minds of youth, is by no means new. The efficacy 
 of moral precepts in conjunction with good example, 
 has been admitted to a limited extent, and their pro- 
 priety recommended by every moralist from the days 
 
MR Owen's system. 519 
 
 of Solomon to the present time. To take measures 
 in order to increase the difficulties of committing 
 crimes, and to remove the temptations to commit 
 them so far as is practicable, but which is very limited, 
 is also obviously proper. In addition however to 
 these, the adoption of measures in order to counter- 
 act the temptation to commit crimes by the dread of 
 punishment, is not to be overlooked. This, as I 
 have already shown, is the means which nature points 
 out ; and nature always employs the simplest, and 
 the most efficient means for accomplishing her ends. 
 The innate disposition to resist aggression, and to 
 punish the aggressor, is the principle which nature 
 has implanted within us to teach morality j and which 
 imperceptibly tends to beget moral habits among man- 
 kind. Laws are found to be efficacious in prevent- 
 ing crimes, because they are in accordance with na- 
 ture's plan. Good example, and moral precepts, are 
 but aids to nature's directions ; and when their effi- 
 cacy is compared with the simple, and effective plans 
 of nature, they are found to sink into total insignifi- 
 cance. Man is a being whose actions are governed 
 by selfish motives, and when these tempt him to en- 
 croach upon the rights of his fellow-creature, they re- 
 quire counteractives which operate upon his selfish 
 consideration of future consequences, with at least 
 equal power. To adopt therefore with Mr Owen, 
 a moral precept of man's invention, in the hope that 
 it will altogether prevent crimes j and to abandon the 
 instinctive principle of resisting aggression, and pun- 
 ishing the aggressor, and every thing in accordance 
 therewith ; would be to disregard the dictates of na- 
 
,520 REVIEW OF 
 
 ture, and experience ; and to betray the- grossest ig- 
 norance of the influence of motives, in exciting, and 
 in restraining human actions. 
 
 But let us inquire farther into the method of teach- 
 ing, and what the children are to be taught. 
 
 In his essays on the formation of human character, 
 he says, " The precept that was given to the child 
 of two years old, on coming into the play-ground, 
 * that he must endeavour to make his companions 
 happy,' is to be renewed and enforced on his entrance 
 into the school. And in addition to the knowledge 
 of the principle and practice of the above-mentioned 
 precept, the boys and girls are to be taught in the 
 school to read well ; and to understand what they 
 read ; to write expeditiously a good legible hand ; 
 and to learn correctly so that they may comprehend, 
 and use with facility the fundamental rules of arith- 
 metic. The girls are to be taught also to sew, cut 
 out, and make up useful family garments ; and after 
 acquiring a sufficient knowledge of these, they are to 
 attend in rotation the public kitchen and eating-rooms; 
 to learn to prepare wholesome food in an economical 
 manner, and to keep a house neat and well-arranged." 
 In another part of the same work he has the common 
 sense to recommend, that the national plan for the 
 formation of character should include all the modern 
 improvements in education, without regard to the 
 system of any one individual. All this is good enough, 
 but it contains nothing new. When these ideas were 
 published, Mr Owen's original views seem to have 
 been only in their infancy. In his subsequent writ- 
 ings, however, we find that he has got into his head 
 
MR Owen's system. 521 
 
 peculiar notions on education, which we shall hear 
 from himself. " Children," he tells us, *' are to be 
 trained systematically to acquire useful knowledge by 
 means of sensible signs, whereby their powers of re- 
 flection and judgment, may be habituated to draw ac- 
 curate conclusions from the facts presented to them. 
 Teaching by sensible signs is founded in nature, and 
 will supersede the present defective and tiresome sys- 
 tem of book-learnincr." 
 
 Upon visiting New Lanark, in May, 1825, I found 
 exhibited there an expensive system of education, 
 partly established, and partly in preparation, in accord- 
 ance with the preceding description of teaching by 
 means of sensible signs, the leading features of which 
 I will now describe, and what is new will criticise. 
 
 Children, before being learned to read their native 
 language, were taught from the mouth of a teacher, 
 geography, natural history, botany, and general 
 history. Geography was taught with the aid of 
 globes and maps, as it is everywhere else. Natural 
 history with the usual assistance of miniature pic- 
 tures of the different animals : a familiar anecdote be- 
 ing told by the teacher concerning each, in order to 
 give the child a knowledge of the nature of the ani- 
 mal. Botany was taught by means of painted repre- 
 sentations of plants, which, where the plants them- 
 selves cannot be conveniently exhibited, is a usual 
 substitute. General history was taught by means of 
 striped paintings, filled up with small pictures con- 
 sisting of groups of human figures, which were in- 
 tended to represent historical incidents ; and nations 
 were distinguished from each other by stripes of dif- 
 
 3u 
 
5-2:1 REVIEW or 
 
 ferent colours. Reading was taught according to the 
 Lancasterian system ; though I was infornned, Mr 
 Owen preferred DufiePs. Dancing and singing were 
 taught similarly to the common methods. 
 
 The first thing that is new in this system of edu- 
 cation, is deferring to teach children to read, till they 
 have first acquired a knowledge of geography, na- 
 tural history, botany, and general history. This al- 
 teration in the order of education, appears to be 
 inferior to the ordinary arrangement. By the time 
 children are capable of learning geography and bo- 
 tany, they are quite able to learn to read, and, as is 
 proved by experience, of doing so in as short time, 
 and with as little labour, as they are at any after pe- 
 riod of life. One advantage of learning to read first, 
 is, that it reduces the cost of education. Children so 
 taught give comparatively little trouble to a teacher 
 in afterwards learning geography, natural history, or 
 any thing else. By the aid of a book, lessons may be 
 prescribed, and they thereby in a great measure teach 
 themselves. The familiar anecdote which is told by 
 a teacher, in order to give a child some idea of the 
 natural history of an animal, can be as intelligibly told 
 by a book ; and with this additional advantage, that 
 while the child is gaining a knowledge of the nature 
 of the animal, it may also be learning to read. 
 
 It is sometimes contended by those who are in fa- 
 vour of deferring the teaching of children to read, 
 that as knowledge consists only in the possession 
 of ideas, of which words are merely the signs, chil- 
 dren should first be taught ideas, and then language 
 to express them. But let it be recollected, that Ian- 
 
MR Owen's system. 523 
 
 guage either spoken, or written, is the instrument of 
 communicating ideas ; and that without it, we have 
 ahnost no means of teaching. Those who wish first 
 to teach children ideas seem to think, that they ac- 
 quire none hut what they are taught by their fellow- 
 creatures ; whereas, they are constantly acquiring 
 ideas for themselves, from the time they come into the 
 world. Even the names of things, with the things 
 themselves, and words expressing ideas, with the 
 ideas themselves, from hearing them appHed, become 
 in early life gradually and imperceptibly so closely 
 associated, that language either spoken, or written, 
 (when they have learned to read,) immediately sug- 
 gests the idea, and the idea the language. 
 
 It is imagined by some that teaching by means of 
 sensible signs, even in learning to read, is proper so 
 far as it can be introduced, in order that children may 
 learn to understand what they read ; and, to use Mr 
 Owen's language, " that their powers of reflection 
 and judgment, may be habituated to draw accurate 
 conclusions from facts presented to them." Thus 
 the miniature figure or picture of a horse is to be at- 
 tached to the word horse, in order that the child may 
 have an idea what the word horse means ; a table to 
 the word table ; a chair to the word chair, &c. But 
 how very limited must such a system be ! A few 
 names of things is all that can be so described. Be- 
 sides, children, who are apt to understand every de- 
 scription in the literal meaning, and just as it is re- 
 presented, instead of being able to form just concep- 
 tions, or draw accurate conclusions from such pictures 
 being presented to then;, provided they had not pre- 
 
5l24 REVIEW OF 
 
 viously acquired correct notions of what a horse, a 
 table, or a chair meant, would be led to form most er- 
 roneous ideas concerning these, as well as concerning 
 the shape, colour, and size, of all other objects. This 
 would partly arise from imperfections in the arts of 
 drawing and painting ; and partly in consequence of 
 the miniature size in which all the laqxer objects of 
 nature, would necessarily have to be delineated. What 
 kind of accurate idea could a child form of the bulk, 
 and strength of an elephant, from the picture of one 
 the size of a mouse ? Or of the height of a moun- 
 tain 27,000 feet high, from a conical drawing twelve 
 inches in length ? Or what correct ideas of nations 
 could it form, from large pictures divided into stripes 
 of different colours ^ Neither man nor beast is left 
 to derive a knowledge of external objects from such 
 imperfect sources. We are born with faculties which 
 instinctively take cognizance, and form ideas of ob- 
 jects, and their qualities, from the actual things them- 
 selves; and not from imperfect representations. Long 
 before a child can begin to learn to read, it knows the 
 name, and appearance of all common objects. It 
 knows what the words horse, chair, and table mean, 
 as soon as spoken, or as soon as it can read the word, 
 without the explanation of miniature pictures. And 
 hence the reason, that a child taught by means of 
 sensible signs, can form ideas of objects, and draw 
 conclusions, in no degree more accurately, than one 
 taught upon the old plan, without any such assistance. 
 The only other new part of Mr Owen's system of 
 education, is his teaching of general history by means 
 of large paintings, which, contain a confused assem- 
 
MR Owen's system. 525 
 
 blage of small pictures. Different nations are repre- 
 sented by stripes of different colours. And the dates 
 being marked on the margin, the periods of the com- 
 mencement, the increase, the decrease, and the ex- 
 tinction of nations, which are almost the only points 
 they describe intelligibly, are represented by the com- 
 mencement of the coloured stripe ; its increase, and 
 decrease in breadth ; and its extinction. A few other 
 disconnected historical events in the form of small 
 pictures are introduced, but these being necessarily 
 represented in an extremely imperfect manner for 
 conveying instruction ; and having no printed key or 
 explanation, require the aid of an interpreter in order 
 to be understood. Printed chronological tables of 
 remarkable events, seem to be superior to such paint- 
 ed ones in several respects. They are much easier 
 understood, and the information obtained from them 
 is therefore less liable to error ; they are more easily 
 referred to ; more portable ; and less expensive. 
 
 Besides, what is useful in the study of history is 
 not only totally omitted in Mr Owen's historical maps, 
 but it is impossible that it can be intelligibly repre- 
 sented in any such way. To know that a number of 
 disconnected events have taken place in the world, 
 is of very little importance. The useful departments 
 of history consist in tracing the chain of causes and 
 consequences in the rise, progress, and decline of 
 nations ; in exhibiting the effects of the policy of 
 different governments ; and in pointing out the influ- 
 ence of laws, institutions, beliefs, customs, and man- 
 ners upon the character of mankind in different ages 
 and nations. By acquiring such historical knowledge. 
 
.5i2() iiRviEW OF 
 
 tlie reasoning powers of man are improved; a thorough 
 and extended acquaintance with human nature is ob- 
 tained ; and the welfare of mankind is essentially 
 promoted. History should teach us to anticipate the 
 future by a knowledge of the past. It should teach 
 statesmen to avoid the errors of their predecessors, 
 and to adopt a line of policy, and to frame laws and in- 
 stitutions, calculated to promote individual, and na- 
 tional wealth. It should teach mankind religious toler- 
 ation, and to renounce all beliefs but such as are conso- 
 nant to reason and common sense. And by freeing us 
 from prejudices, which seem to be naturally in favour 
 of our own customs and manners, should pave the 
 way for the adoption of those which are most favour- 
 able to human happiness. Such are some of the 
 useful purposes which historical knowledge should 
 promote : but the painted historical narratives, ex- 
 hibited at New Lanark, can answer no such ends. 
 They are better fitted for show, than use. As instru- 
 ments of communicating historical information, they 
 are found, when carefully examined, to be extremely 
 defective, and unintelligible. Only a very few dis- 
 connected incidents, such as battles, murders, and 
 deaths, can be represented by them ; and these so 
 very imperfectly, that their causes and effects are not 
 only left unnoticed ; but even who the parties repre- 
 sented in the picture are, is unintelligible, without the 
 verbal explanation of a teacher. 
 
 Signs, or hieroglyphics on blank maps, represent- 
 ing the different kinds of religion, and the diversified 
 forms of government established in diiferent parts of 
 the world, is another of Mr Owen's useless applica- 
 
MR Owen's systeim. 5'21 
 
 tions of bis intended general system of teaching by 
 means of sensible signs. Where the English lan- 
 guage is spoken, the word Christian, or Mahometan, 
 is more generally understood, and is as easily inserted 
 on a blank map of Europe, as a painted figure of a 
 cross, or of a crescent, which are among the most in- 
 tellio-ible of this class of sensible signs. 
 
 Man, very soon after he comes into the world, be- 
 gins to acquire a knowledge of surrounding objects 
 by means of material instruments adapted for the pur- 
 pose. And by hearing language spoken, he imper- 
 ceptibly acquires a knowledge of its meaning, and 
 learns to apply it himself. Words are the usual signs 
 whereby mankind communicate their ideas ; and all 
 other signs of ideas, which might vary in every differ- 
 ent seminary, according to the taste of the teacher, 
 are never used in after life. Teaching; indiscrimin- 
 ately by means of sensible signs, maybe useful in the 
 education of the dumb, who have no bettter means of 
 receiving instruction. But with those who possess 
 the faculties of hearing, and of speech ; and so long 
 as mankind converse by means of words, and not 
 signs ; and so long as histories are printed, and not 
 painted ; it is surely most advisable to teach children 
 to understand, and to practise the method they must 
 afterwards adopt. 
 
 The only point in this system of education which 
 merits consideration, is the influence which graphic 
 description, or picture delineations of historical facts, 
 or occurrences of any kind, have in assisting the 
 memory. Facts so represented, whether exactly re- 
 sembling the things themselves or not, on account of 
 
5*28 REVIEW OF 
 
 the mental associations thereby Ibrmed, are known to 
 have some httle effect, in leaving a more lasting im- 
 pression upon the memory, than simple narrative. 
 Mnemonical systems, or arts of memory, have all 
 been formed upon the effect observed in assisting 
 memory, by means of mental associations of ideas, 
 with time, place, and real, or imaginative pictures. 
 But these, like Mr Owen's painted narratives, when 
 applied to the retention of general knowledge, or the 
 cultivation of our reasoning faculties, have all been 
 found to have either no effect at all, or one that was 
 extremely limited and imperfect in its application. 
 Hence the reason why none of those who have at- 
 tempted to take advantage of mnemonical systems, 
 have ever been observed to possess more practical 
 knowledge, or stronger reasoning faculties, than their 
 fellow men. And hence the reason why no greater 
 prodigies of learning and genius have appeared at 
 New Lanark, than have appeared at Old Lanark. 
 
 Though I have attempted to show that Mr Owen's 
 historical maps are of little or no value, I do not 
 mean to say that every thing of that kind is useless. 
 The plates in Thomson's Atlas of the comparative 
 heights of mountains, and lengths of rivers, and maps 
 representing the different animals inhabiting their na- 
 tive quarters of the world, and pictures representing 
 the costumes of different nations, convey to the mind 
 at a glance, an interesting, and at the same time, a 
 clearly intelligible description. Pictures are found 
 to be important aids to descriptions in correcting our 
 notions of places, animals, objects, and scenes of 
 every kind which we have not seen. And hence they 
 
MR Owen's system. 5'29 
 
 have been employed by natural historians, anatomists, 
 botanists, travellers, and descriptive writers, and teach- 
 ers of every kind. Even painted historical narratives, 
 though perhaps first used by Mr Owen in the educa- 
 tion of children, are not his invention. This mode 
 of transmittin(y a knowledf^e of remarkable events 
 accordin.o' to Dr Robertson, seems to have been em- 
 ployed by very rude nations, who had no better 
 method, prior to the invention of writing. But when 
 this art was introduced, it superseded the use of 
 painted narratives, just as a more useful, more con- 
 venient, or cheaper method of communicating and 
 transmitting knowledge, as well as of doing every 
 thing else, will always supersede that which is less so. 
 
 For the purpose of encouraging assiduity and at- 
 tention on the part of pupils, the excitement of emu- 
 lation by means of rewards, and more honourable 
 situations, has been effectively had recourse to. But 
 Mr Owen, without showing how, says " that the 
 present mode of education, of exciting emulation by 
 hope of reward and dread of punishment, is not only 
 productive of all the bad, but destructive of aU the 
 good qualities in human nature, and in his system of 
 education," he again tells us, without showing how, 
 that " rewards and punishments are to be superseded 
 by a knowledge of the science of the influence of 
 circumstances over human nature." 
 
 Every person of ordinary information knows that 
 rewards and punishments, particularly the former, have 
 influence in accelerating the education of children, 
 by making them attentive and studious ; and that the 
 practical adoption of rewards and punishments is 
 
 3x 
 
530 REVIEW OF 
 
 founded upon the knowledge of that influence. But 
 Mr Owen proposes to do away with these, which are 
 amongst the most eff'ectual means yet discovered, for 
 accelerating' education. 
 
 But let us next hear the eff'ects of his mode of 
 tuition. 
 
 Mr Owen says, that by his system of education 
 *' by means of sensible signs, infants and children 
 will acquire more real knowledge in one day, than 
 they can acquire by the old system of books in many 
 months, also the best habits and dispositions, &c. 
 And by the time they are twelve years of age, they 
 will have acquired a knowledge of all the arts and 
 sciences of which the present age are possessed; and 
 having acquired a knowledge of the science of the 
 influence of circumstances over mankind, they will 
 be entitled to the name of rational beings." 
 
 Such a hyperbolical description refutes itself. Suf- 
 fice it to say, that though Mr Owen frequently through- 
 out his writings treats the rest of mankind as irrational 
 beings, merely because they have not been educated 
 according to his system; yet after giving it a careful 
 examination, it is difficult to perceive any good rea- 
 son, why his rational beings of twelve years of age, 
 can be any thing else than children after all. And 
 instead of having acquired a knowledge of all the arts 
 and sciences of which the present age are possessed, 
 they are unable to speak or write two sentences to- 
 gether, on any subject, either sensibly or grammati- 
 cally. And of this no better evidence need be adduced, 
 than that composition, which, after reading, writing, 
 and arithmetic, is the most useful part of education 
 
MR Owen's system. 531 
 
 for improving the mental faculties, is totally overlooked 
 in Mr Owen's system. 
 
 The dress of the villagers is to be loose, and similar 
 to that of the ancient Romans, or modern Highland- 
 ers. Mr Owen says, *' the Romans and Highlanders 
 appear to be the only two nations, who adopted a 
 national dress on account of its utihty, without, how- 
 ever, neglecting to render it highly becoming, and 
 ornamental." But is not the dress of every nation 
 useful, and at the same time partly ornamental ? And 
 in what does the superior utility of the Highland garb 
 over that of other civilized nations consist? In sup- 
 port of the cold uncomfortable dress of the High- 
 landers, Mr Owen seems to think that clothing is of 
 no permanent use in keeping the body warm. "Ad- 
 ditional clothing," says he, " makes one feel warmer 
 at first, but that the body soon becomes proportionally 
 unable to resist the cold, and one soon feels as cold 
 with the additional clothing, as though it had never 
 been put on." That habit has in this case some 
 effect must be admitted. But that clothing, and ad- 
 ditional clothing, does not assist mankind in resisting 
 the effects of cold, and in rendering changes of tem- 
 perature less felt, is contrary to universal experience, 
 and to the practice of all nations founded thereupon. 
 The human frame is possessed of an internal active 
 power of producing, or rather of collecting and evolv- 
 ing caloric, which, by the body's being placed in a 
 cooler atmospheric temperature, than the corporeal 
 heat necessary for the support of life, is getting con- 
 stantly abstracted. The body has the power upon 
 demand, of increasing its production of heat, and of 
 
6d'2 REVIEW OF 
 
 retention thereof, to a certain extent, but not to one 
 that is unHmited. When the abstraction of heat ber 
 comes greater than the power of production, the tem- 
 perature of tfie surface of our bodies is gradually re- 
 duced below what is necessary for the support of life, 
 and health ; and if continued, disease, and death 
 would soon be the consequence. 
 
 It is ascertained that the degree of heat which is 
 most agreeable, is also that which is most healthful ; 
 and in proportion as either heat or cold become dis- 
 agreeable, so do they become unwholesome, and in- 
 jurious, not only to those who enjoy health, but to 
 such as labour under disease whatsoever be its nature. 
 A certain degree of bodily temperature, varying in 
 different kinds of animals, seems necessary for life; 
 and the sensations of heat and cold appear to be im- 
 planted in man, and animals, in order to direct them 
 instinctively towards the preservation of their exist- 
 ence. It is also ascertained that not only different 
 men, but the same men, at different periods of life, 
 and in different states of health, as well as when under- 
 going different degrees of bodily exertion, require dif- 
 ferent degrees of clothing. Thus the aged, the infirm, 
 and those whose occupations preclude bodily activity, 
 require more clothing than the young, the vigorous, 
 and the actively employed. And hence the adoption 
 of a uniform, cold, or warm dress, as Mr Owen 
 directs, would be to oppose the dictates and warnings 
 of nature; and which, in proportion as it diminished 
 bodily comfort, would tend to injure the health and 
 happiness of mankind. 
 
 Mr Owen seems even to go the length of indirectly 
 
MR owen's system. 533 
 
 recommending the propriety of going naked, or at 
 least approves of much bodily exposure, for the main- 
 tenance of virtue, and sexual delicacy. " Sexual 
 delicacy and virtue," says he, " will be found much 
 higher in nations, among whom the person from in- 
 fancy is the most exposed, than among those people 
 who exclude from sight, every part of the body, ex- 
 cept the eyes." This leads me to consider in what 
 sexual delicacy consists. Sexual delicacy appears to 
 be a sentiment, which manifests its existence, by in- 
 ducing us to screen our nakedness from observation. 
 Its intention is to protect the virtue and chastity of 
 youthful innocence. And nature, we may rest as- 
 sured, teaches us in this, as in every other instance, 
 to take the simplest and the best means for producing 
 the effect. When the natural guardians of our moral 
 sentiments are removed, those feelings soon become 
 depraved, or altogether lost. Hence the reason why 
 improper pictures, scenes, or theatrical representa- 
 tions, soon blunt this youthful feeling. And I will 
 venture to add, without the proof of ocular observa- 
 tion, that where total nakedness exists, if such a 
 nation is any where to be found, the sentiment under 
 consideration is as httle or no more felt, than it is by 
 the beasts of the field. 
 
 Having now considered Mr Owen's measures for 
 the acquirement of incomprehensible wisdom, and the 
 production of an unlimited increase of happiness and 
 morality, we will next examine his three grand mea- 
 sures for the advancement of national prosperity, and 
 the production of incalculable wealth, even until it 
 become so abundant, that any farther increase to 
 
534 REVIEW OF 
 
 it will be considered useless, and not to be de- 
 sired. 
 
 The first measure whereby Mr Owen proposes to 
 let prosperity loose on the country, (to use his own 
 words,) is the abolition of the use of gold and silver 
 as a circulating medium, and the erection of human 
 labour into a standard of value, thereby preventing 
 the rise and fall in the price of commodities, which 
 are to be bartered according to the quantity of labour 
 contained in each. 
 
 Mr Owen says, " that gold and silver have already 
 been found unable to perform the task that ignorance 
 assigned them, for, in 1797, government were obliged 
 to enact that bank of England paper should become 
 the legal standard of value; a striking proof," says he, 
 " that society may make any artificial substance, whe- 
 ther possessing intrinsic worth or not, a legal stand- 
 ard of value." And he farther adds, '* that any at- 
 tempt of the bank to resume cash payments, will prove 
 as vain as to try to restore a full grown bird to the 
 shell in which it was hatched, or to make the clothes 
 of an infant cover a giant ; for the improvements in 
 society have equally outgrown the late system of cash 
 payments." 
 
 The exchangeable value of gold and silver, I need 
 hardly remark, is dependent upon the value of the 
 amount of labour requisite to produce them. Thus, 
 the value of the amount of labour requisite to produce 
 a guinea, is, generally speaking, exactly equal to the 
 value of the amount of labour requisite to produce a 
 guinea's worth of cotton, sugar, or of any other com- 
 modity. If a plan was found out for producing gold 
 
MR Owen's system. 535 
 
 with one half the labour it takes at present j or, if 
 the currency was alloyed with a base metal, so that 
 it only contained one-half its previous amount of 
 gold, (as has been done by some of our former kings 
 when they wished to reduce the real amount of their 
 debts one half, though the nominal amount remained 
 as before,) a guinea would only possess one-half its 
 previous value ; and would only purchase one-half of 
 its previous amount of cotton, sugar, or any other 
 commodity ; the labour of producing these articles 
 remaining as before. Or, vice versa, the amount of 
 labour requisite to produce cotton, sugar, &c., being 
 reduced one-half, while that of producing gold re- 
 mained unchanged, a guinea would purchase twice 
 the amount of cotton, sugar, &c., which it previ- 
 ously did. Labour, therefore, is the cause of value ; 
 and a guinea, or gold, contains the labour in it 
 equal to its value. Bank-notes are only valuable, 
 in proportion as the issuers of them are bound to 
 give something valuable for them, upon their being 
 presented for that purpose ; or according as it is 
 likely that something valuable may immediately, or 
 ultimately be obtained for them. The case alluded 
 to by Mr Owen of the bank of England being ab- 
 solved from payment of their notes in specie, was 
 merely a temporary measure. And the bank has since 
 resumed cash payments, which Mr Owen, with all his 
 knowledge of the science of the influence of circum- 
 stances over human nature, said, " was as impossible 
 as to restore a full grown bird to the shell in which 
 it was hatched, or to make the clothes of an infant 
 
5J30 ltI::VIEW OF 
 
 cover a giant ;• for tlie improvements in society had 
 equally outgrown the late system of cash payments." 
 
 In reality there is no invariable standard of value 
 in existence. In exchange, labour as well as gold, 
 and every other article, rises and falls according to 
 the supply and demand. But that gold and silver are 
 well qualified for a circulating medium, or for being a 
 standard or measure of value, if you choose so to 
 speak, has been most satisfactorily acknowledged 
 among all nations, by their universal adoption of them. 
 And though Mr Owen says they have been found 
 unable to perform the task that ignorance assigned 
 them, nothing has yet been discovered that could so 
 well answer the purpose. Though bank-notes of dif- 
 ferent amounts are generally used in this country, still 
 it must be recollected, that their value depends upon 
 their being the representatives of gold ; and upon re- 
 sponsible persons being bound to pay them in such, 
 when presented for payment. 
 
 The use of a circulating medium is to render the 
 exchange of commodities, or buying and selling, easy. 
 By being possessed of a portion of the circulating 
 medium, gold and silver, we can go wherever we 
 choose, and purchase whatever we want, from who- 
 ever has it for sale. But if all circulating mediums 
 were abolished, and the bartering of commodities ac- 
 cording to the quantity of labour contained in each 
 introduced, as Mr Owen proposes, we would not only 
 have to find out a person who had the article we 
 wished to purchase, but one who was desirous of ex- 
 changing the article we wanted, for that which we had 
 to give for it. How much more inconvenient would 
 
MR Owen's system. 537 
 
 such a system be than the present one of a gold and 
 silver currency ! and how much more tardy and doubly 
 difficult the transactions of merchandise ! Without a 
 circulating medium, or common measure of value, in- 
 tercourse with foreign nations, and even travelling 
 beyond the limits of our own parallelogram, would be 
 attended with extreme difficulty. Who could carry 
 with him food and every thing else he required, or a 
 sufficient supply of articles to exchange for every 
 thing he wanted ? Even though he had a supply of 
 exchangeable articles, if he had not food also, he 
 might starve before he could fall in with a person, who 
 would barter provisions for any of the articles he had to 
 give for them. 
 
 The next measure by which Mr Owen proposes to 
 enrich the country, is to cultivate the soil with the 
 spade, instead of the plough and harrow. 
 
 Owing to my ignorance of agriculture, I am unable to 
 state the difference of productiveness, and of expense, 
 attending these two methods of cultivation. But if 
 we take into consideration the knowledge of spade 
 husbandry that exists, (for it is no new discovery,) 
 and the interest that every one has to adopt the most 
 profitable mode of cultivation, we are warranted in 
 drawing the conclusion, that the superiority of pro- 
 duction by the spade cultivation, does not compensate 
 for the saving of labour by the plough. Or, in other 
 words, that the surplus produce gained by means of 
 the spade plan, would not support the additional num- 
 ber of labourers thereby requisite. That this is by 
 no means doubtful, is evident from the universal use 
 of the plough ; whereas, if it were in the least degree 
 
 3 Y 
 
<538 REVIEW OF 
 
 uncertain which plan was the most profitable, both 
 would be in general use. But let us hear what Mr 
 Owen says. After telling us most liberally, according 
 to his usual custom, of the immense, and miraculous 
 advantages that would result from spade cultivation, 
 he says, " that the present race of farmers are not 
 qualified to take advantage of it, because they have 
 not a knowledge of the science of the influence of cir- 
 cumstances over human nature." But how a know- 
 ledge of this science (which seems to be his constant 
 loop-hole in cases of difficult explanation,) would qua- 
 lify farmers to cultivate the soil, he leaves the reader 
 to discover. 
 
 The next important measure which Mr Owen pro- 
 poses, for the benefit of mankind, is to abolish the 
 minute divisions, and sub-divisions of labour ; and 
 to make every man, by way of enlarging his under- 
 standing, produce an article completed by himself. 
 He also proposes that every one should change his 
 employment alternately, in order that each might 
 have an equal share of the agreeable and disagreeable, 
 the healthy and unhealthy occupations. 
 
 It need hardly be remarked, that these measures, 
 like those which we have already considered, would 
 tend to impoverish, instead of enriching society. 
 Every means whereby an article can be produced at 
 less expense of labour, is a saving of that portion of 
 labour to the community, which may be used, if re- 
 quired, in some other beneficial way, such as, in the 
 production of some other useful article. And in like 
 manner, every means whereby a given amount of any 
 manufactured article can be produced by fewer work- 
 
MR OWEN*S SYSTEM. 539 
 
 men, is a saving to the community of the labour of 
 the workmen thereby rendered superfluous. Practice 
 at one trade, or in any particular department thereof, 
 gives facility and expedition in working ; and on this 
 account the sub-dividing plan, by which a man's hand 
 is always engaged at the same occupation, is found to 
 be the most productive, and that which brings manu- 
 factured articles cheapest to market. Hence the rea- 
 son that as nations advance in wealth, (that is, in the 
 means of producing the necessaries and luxuries of 
 life,) minute divisions, and sub-divisions of labour, 
 (as are exemplified in the cotton mills formerly under 
 Mr Owen's superintendence at New Lanark,) are 
 more and more introduced into manufacturing estab- 
 lishments. 
 
 Mr Owen's additional proposal, that each person 
 should work in succession at every different trade, 
 would still farther diminish the productive power of 
 society. The facility and expedition acquired by 
 each individual continuing at the same occupation, 
 would in this case not only be lost, but the time, la- 
 bour, and study, spent in gaining a knowledge of each 
 trade, so as to be able to work at them ; and the in- 
 feriority of the workmanship, would increase with 
 the number of occupations which each individual had 
 to learn, and practise. Such a system might make 
 the villagers Jacks of all trades, but as the proverb 
 farther tells us, they could be masters of none. 
 
 Notwithstanding the obvious nature of the fore- 
 going remarks, Mr Owen, in his usual strain of unin- 
 telligible declamation, says, that " minute divisions of 
 labour, and division of interest, are only other terms 
 
540 REVIEW OF 
 
 for poverty, ignorance, waste of every kind, universal 
 opposition throughout society, crime, misery, and 
 great bodily and mental imbecihty ;" and he farther 
 adds, that " these things are plain and obvious to 
 every capacity." But how a minute division of labour 
 is only another term for poverty, ignorance, waste of 
 every kind. Sec. ; must be left to those, who are skil- 
 ful in interpretation to explain. 
 
 The government of each parallelogram is also quite 
 original. It is to consist of a committee of all the 
 persons between the ages of 35 and 45 ; and their 
 business is to plan the operations of the villagers. 
 Thus it appears, that all the persons in the prime of 
 life, and who, on that account, are ablest to work, are 
 to have all the rest that is going. How much better 
 would it be to leave this less laborious duty to persons 
 of more advanced age, rather than doom those to 
 perpetual toil, whose bodies, in consequence of age 
 and other infirmities, were becoming unfit for action, 
 and required rest. No mention is made of laws. 
 Indeed what could be the use of laws, which, on ac- 
 count of having no penalties attached to their viola- 
 tion, they had no means of enforcing. Such a go- 
 vernment would be powerful in point of numbers, but 
 without power in every other respect. 
 
 It is somewhat amusing to notice the numerous and 
 inconceivable effects, which a knowledge of the sci- 
 ence of the influence of circumstances over human 
 nature, is to produce, besides those already men- 
 tioned. " It is to put an end to wars ; it is to 
 create new mental powers j" (phrenologists would 
 then have to discover a few more organs,) " it is to 
 
MR Owen's system. 541 
 
 supersede," what Mr Owen calls " the present truly 
 irrational system of individual rewards and punish- 
 ments J it is to dispel ignorance, to prevent crime, to 
 put an end to misery, and to open a new era to the 
 human race, in which real happiness will commence, 
 and perpetually go on increasing through each suc- 
 ceeding generation. And although the characters of 
 the present generation have been formed under exist- 
 ing circumstances, which," he says, " are altogether 
 unfavourable to happiness, yet having acquired a know- 
 ledge of this science, they will be placed in circum- 
 stances so agreeable to human nature, and so well 
 adapted to all the acknowledged ends of human life, 
 that those objects of anxious desire, so ardently 
 sought for through past ages, shall be secured to 
 every one, with the certainty of a mathematical pro- 
 cedure." 
 
 Such are some of the effects which Mr Owen says 
 " will be produced by a knowledge of the science of 
 the influence of circumstances over human nature ; 
 and a knowledge by which these can be controlled, 
 so as to direct mankind," to use Mr Owen's own 
 words, "to the production of universal good or uni- 
 versal evil." " Society," he goes on to say, " are at 
 present governed by circumstances ; whereas, by his 
 system, society would govern circumstances. Char- 
 acter is formed for, and not by the individual. Chil- 
 dren from birth are continually subjected to impressions 
 derived from external circumstances, which impres- 
 sions, when combined with their natural qualities, do 
 truly determine the character of the individual through 
 
542 REVIEW OF 
 
 every period of life ;" * and he says, " from a know- 
 ledge of the science so often named, man will be able 
 to form good or bad characters, which will continue 
 through hfe, by the education and impressions which 
 are made upon infants ; for men are, and ever will be, 
 what they are, and shall be, in infancy and childhood;" 
 and he farther adds, *' all the bad qualities will be pre- 
 vented, by excluding all notions of reward, punish- 
 ment, and emulation, from the education of children.'* 
 It would be tedious to examine particularly every 
 idea contained in these quotations. But why does 
 not Mr Owen explain this science ; and how a know- 
 ledge of it would be productive of so many benefi- 
 cial effects to the human race? If Mr Owen means 
 any thing at all by a knowledge of the science of the 
 influence of circumstances over human nature, it is 
 only what is called in common language, a knowledge 
 of human nature. That the character of man, or the 
 manifestations of his character, are very much affected, 
 and influenced by external circumstances, from his 
 earhest years to the end of his days, is known and 
 observed by every one. Laws for the prevention of 
 crime and the protection of virtue and property, are 
 founded upon a knowledge of the circumstances that 
 influence human conduct. Punishments annexed to 
 the breaking of laws, and a vigilant pohce for the de- 
 tection of criminals, in order that punishment may 
 follow, are measures invented by human wisdom, and 
 
 * The sentence immediately preceding the asterisk, is unobjec- 
 tionable ; but in what follows, Mr Owen again deviates into his 
 erroneous notions. 
 
MR Owen's system. 543 
 
 found by experience to be well calculated to modify 
 or alter circumstances, so as partly to counteract the 
 temptation to crime, and to restrain man from tres- 
 passing upon the rights of his neighbour, by making 
 it for his interest so to do. In like manner, rewards 
 and marks of distinction for inventions, or good ser- 
 vices, produce circumstances, that are known and 
 observed to operate upon the innate faculties or char- 
 acter of man, so as to stimulate him to act in a way 
 that is considered beneficial to his fellow-creatures ; 
 and when apphed to the education of children, is in- 
 tended to induce them to study in order to benefit 
 themselves. Even the beneficial effects produced by 
 religion upon the morals of mankind, are chiefly, if 
 not wholly, dependent upon the circumstance of its 
 holding out the hope of reward to the virtuous, and 
 the dread of punishment to the wicked, thereby con- 
 trolling circumstances, so as to make it appear to be 
 the interest of man to be virtuous. Thus while Mr 
 Owen intends to control circumstances, he proposes 
 the abolition of rewards and punishments, the most 
 effectual means yet discovered for the purpose, with- 
 out giving us any idea of what he intends to sub- 
 stitute. 
 
 To suppose that character, or the manifestations of 
 character, is no way affected or influenced by external 
 circumstances after the age of childhood, is but one 
 of Mr Owen's numerous and obvious errors. Till 
 this period of life, man displays almost only his ori- 
 ginal or natural character, derived from his organiza- 
 tion, which is even then only partially formed. It is 
 chiefly subsequent to this period of life, and not till 
 
544 REVIEW OF 
 
 man comes in contact with man ; not till he is under 
 the necessity of pushing his way in the world, and of 
 providing for himself, when being more seriously ex- 
 cited to action, and more exposed to temptation than 
 in infancy and childhood, that external circumstances 
 have most eflfect upon his character. Besides, the 
 powerful influence of habit upon character, which 
 arises from a continuance of the same circumstances, 
 at so young an age as that of childhood, can hardly 
 be said to exist. 
 
 That education has some effect in the formation of 
 character, must be admitted ; but that it thereupon 
 wholly depends, as Mr Owen supposes, is evidently 
 erroneous. Certain passions and propensities, inde- 
 pendent of education and external circumstances, are 
 implanted in man by the hand of nature. The strength 
 of these, arising from difference of organization, varies 
 in different individuals; and to these differences, the 
 diversity of character, must be partly, if not princi- 
 pally ascribed. Among the inferior animals, striking- 
 differences of character exist, which can be referred 
 only to difference of organization. We never find 
 the character of a sheep, existing in the shape of a 
 tiger; nor the character of a tiger, in that of a sheep; 
 nor by any training or education can their characters 
 be assimilated, which would be the case, if such dif- 
 ferences depended solely upon training, and not upon 
 structure. As it is with different animals, so is it 
 with different men, though not to the same extent ; 
 they are differently formed, and therefore possess dif- 
 ferent characters. No education can make the cow- 
 ardly, brave; or the stupid, wise, beyond a hmited 
 
MR Owen's system. 545 
 
 extent. No education can give the dull, submissive, 
 patient, phlegmatic temper, the violent, commanding, 
 and impatient character of the choleric. Nature has 
 formed them opposites, and no education, nor cir- 
 cumstances, can make them altogether assimilate. 
 
 The only original idea of Mr Owen's, that is de- 
 serving of a moment's consideration, is that of in- 
 creasing the national wealth, by all men acting in 
 miion for the interest of the whole, instead of each 
 individual acting, as at present, for his own private 
 benefit. Or in other words, that with the same amount 
 of labour, more of the necessaries, comforts, and luxu- 
 ries of life, would be produced by mankind acting in 
 union for the interest of the whole, than what is pro- 
 duced, by each individual acting separately for him- 
 self. 
 
 To show that this would not be the case, it may 
 be observed, that all the actions of mankind spring 
 from some motive or other; and that the stronger the 
 motive, the greater, and the more constant, will be 
 the exertion. Self-interest is naturally a stronger mo- 
 tive for industry, than the interest of another, or than 
 the common interest of the community. A man's 
 mental and bodily powers, are called more into action, 
 when his private interest is the motive, than when his 
 private interest is so much divided and diminished, as 
 it would be, by being combined with the private inter- 
 est of every other member of society. Hence the 
 reason, why piece-work, or payment for the work done, 
 wherever it can be adopted, is always found the most 
 productive plan of employing labourers, and the most 
 advantageous to the employer. And hence also the 
 
 3z 
 
540 REVIEW OF 
 
 reason, why Mr Owen's system of all acting in union 
 for the common interest, would not be so productive 
 as the present plan of each acting separately for him- 
 self. 
 
 The waste, besides, under a system where all the 
 wealth or produce of the community was common 
 property, would also be greater. A man would not 
 have the same inducement to economize, where his 
 economy would be of no more advantage to himself, 
 than it was to every other member of the community, 
 as he- would have, if the whole advantage of his eco- 
 nomy was gained by himself. The system would, 
 besides, be unfair, and would consequently be pro- 
 ductive of discontent, and disagreement. It would 
 be unjust that the ingenious, the industrious, and the 
 frugal, should not have advantages over those who 
 had no invention, the lazy, and the extravagant. Jus- 
 tice requires, that in proportion to the superior use- 
 fulness of the former over the latter, as members of 
 society, they ought to be rewarded. In short, a sys- 
 tem founded upon the principle, that every man would 
 exert himself to the utmost of his abihty for the com- 
 mon benefit, without possessing the means within 
 itself of rewarding every one according to his exer- 
 tions, and general usefulness ; and without the power 
 of compelling a man to work if he was lazy, and hap- 
 pened not to be inclined ; or of inflicting punishment 
 upon any one who injured, or acted unjustly towards 
 the other members of the community; might suit the 
 condition of some imaginary beings, but is not adapted 
 to the nature of man. 
 
 In the present natural system of society, every 
 
MR Owen's system. 547 
 
 thing is so admirably adapted to answer the end for 
 which it was intended, and so well calculated for the 
 promotion of the common welfare, that when every 
 one acts for his own individual benefit, instead of act- 
 ing in opposition to the interest of the community, 
 as Mr Owen supposes, he is acting in union with 
 them in the most effective way for their interest. In 
 proportion, generally speaking, as a man's labour is 
 profitable to himself, so is it beneficial to the com- 
 munity. If any article of consumption becomes 
 scarce, the person who most speedily supplies the de- 
 mand, while he benefits the community by furnishing 
 them with the article they want, enriches himself, by 
 obtaining an amount of profit or remuneration, pro- 
 portional to the demand for the article and its scarci- 
 ty. Thus it is, that private benefit goes along with 
 public benefit ; and that when a man is acting with 
 the intention of only promoting his own individual ad- 
 vantage, he is acting in perfect union with the rest of 
 the community for the interest of the whole. Hence 
 the reason why every article of ordinary consumption, 
 can always be got to purchase with but trifling varia- 
 tions in price. And hence the reason, why under the 
 present natural system, which Mr Owen is pleased to 
 call " Old Society," a government consisting of a 
 committee of all the persons between the ages of 35 
 and 45, whose business is to direct the operations of 
 the community, lest any article should become scarce, 
 is found to be totally unnecessary. 
 
 We will now make some observations on the re- 
 mote consequences of Mr Owen's plan, and en- 
 deavour to show that, if universally adopted, instead 
 
.548 REVIEW OF 
 
 of diffusing knowledge, wealth, and good morals 
 among mankind, it would tend to spread, and greatly 
 increase ignorance, poverty, and crime. 
 
 It is difficult to perceive any permanent advantage 
 that would either immediately, or ultimately be con- 
 ferred on society, by the universal adoption of Mr 
 Owen's plan, even though freed from many of its un- 
 natural absurdities and impossibilities, while the dis- 
 advantages are both numerous and obvious. 
 
 It proposes to abolish punishment, reward, and 
 emulation. The first of these has its origin in the 
 vindictive principles of our nature, wisely and bene- 
 ficially implanted in man, in order to restrain the im- 
 proper direction of our selfish feelings. Its abolition 
 could only tend to increase the commission of crimes, 
 by removing the restraint, while the disposition and 
 temptation to commit them, remained as great as be- 
 fore. To maintain order in society, and check the 
 commission of crimes, punishments seem to be un- 
 fortunately, but absolutely necessary. Like every 
 thing else, however, (as was the case with the laws of 
 Draco,) it may be overdone. That kind and degree 
 of punishment is best, which, with least severity, has 
 the greatest effect in preventing the commission of 
 crime. In advancing the education of children, its 
 indiscriminate application is at best but doubtful. 
 Slow progress commonly arises more from a want of 
 natural aptitude of apprehension, and capacity for re- 
 ceiving instruction, than from inattention. To inflict 
 chastisement under such circumstances, is but to 
 punish the child for its misfortune, and for what it 
 cannot help. Nevertheless, in the education of chil- 
 
MR Owen's system. 549 
 
 dren, as well as in the moral government of society, 
 punishment of some kind or other is useful, if not 
 absolutely necessary, in order to restrain impropriety 
 of conduct. The utility of rewards is universally 
 acknowledged, and therefore universally adopted. 
 Emulation, which consists in a wish to be considered 
 superior, if not in itself a distinct innate principle, 
 arises naturally and involuntarily in man, and other 
 animals, out of a perception of the superiority and 
 inferiority which they either possess, or suppose they 
 possess, relatively to each other. This principle, 
 which Mr Owen considers so destructive to human 
 happiness, and notions of which he recommends to be 
 so scrupulously excluded from the education of chil- 
 dren, is, when properly directed, one of the most ef- 
 fective means for exciting mankind, at every period 
 of life to cultivate their mental faculties, and to ac- 
 quire bodily accomplishments ; and, in short, is won- 
 derfully calculated to encourage general industry, and 
 the performance of virtuous actions of every kind. 
 There is no doubt that a spirit of emulation or ambi- 
 tion, by the adoption of suitable means, may be either 
 damped, or encouraged : and that it may, in some 
 instances, proceed to an injurious extent, must be also 
 admitted. But its effects upon the whole are decid- 
 edly beneficial. 
 
 Man, like every other animal, is formed with a 
 combination of instruments and faculties, admirably 
 fitted for the kind of life he is destined to lead. 
 Even self-interest, the ruling principle of our nature, 
 and to which in an extended sense* all our actions 
 * Self-interest, in the extended sense here and in other passages 
 
550 REVIEW OF 
 
 can be traced, is found upon examination to minister to 
 the advancement of public good, and general pro- 
 sperity. For man to attempt therefore by any system, 
 wholly to eradicate or destroy the innate principles of 
 the human constitution ; and thereby to improve upon 
 the works of his Creator, would, even if possible, 
 only tend, in all probability, to destroy his moral hap- 
 piness, and to injure his worldly condition. But to 
 try to root out what Mr Owen considers the bad 
 qualities of our nature, (but which can ail be shown 
 to be ultimately productive of good,) by such feeble 
 and inadequate means, as the exclusion of all notions 
 of reward, punishment, and emulation, from the edu- 
 cation of children under twelve years of age ; or even 
 by any means whatsoever, is just as vain, useless, and 
 unprofitable, as it would be, to endeavour to direct 
 the winds, or to control the tides. 
 
 The distribution of the population into parallelo- 
 grams at equal distances over a country, according to 
 Mr Owen's system, besides being productive of in- 
 justice and disagreement, in consequence of the un- 
 equal fertility of the soil, would also tend to impover- 
 ish mankind. The wealth of a nation is promoted by 
 every improvement in the arts, and every arrangement 
 
 alluded to, means the disposition to gratify all our desires and 
 feelings, without regard to whether such gratification is, or is not 
 intentionally directed, so as to joroiuote the happiness of others, 
 provided (which is always the case,) that such is attended with our 
 own personal gratification. Even those affections which may be 
 called generous or benevolent, such as love, friendship, and pity, 
 excite us to action only in proportion to the amount of pleasure 
 enjoyed, or the amount of evil avoided, by immediate, or antici- 
 pated feeling. 
 
MR Owen's system. 551 
 
 of society, whereby the necessaries, comforts, and 
 luxuries, of life, are supplied with less labour and ex- 
 pense. According to the present system of society, 
 every individual in pursuing his own interest, fixes his 
 residence where he can most easily find employment; 
 or where he sees the best prospect of bettering his 
 condition. Hence mankind arrange themselves, in 
 the most favourable way for promoting the wealth of 
 nations. Villages, towns, and cities, arise without 
 human foresight or direction, in the most suitable 
 situations for diminishing the labour of mankind, in 
 conducting their commercial transactions. Manufac- 
 tures, when neither stimulated nor restricted by the 
 ignorance of statesmen, naturally fix their seat, and 
 prosper, where the greatest local advantages are pos- 
 sessed ; and commerce takes its direction through 
 those channels, by which the interchange of commo- 
 dities, throughout the world, can be conducted, and 
 the desires of man gratified, with the least labour and 
 expense. Governments in reality have got no more to 
 do in contriving the most perfect distribution of popu- 
 lation, than to allow every individual instinctively to 
 pursue his own interest. And it is evident that 
 every forced arrangement of population, (such as 
 the parellelogram distribution proposed by Mr Owen,) 
 in proportion as it deviated from that which was na- 
 tural, would diminish instead of increasing, the wealth 
 and productive power of mankind. 
 
 An extended survey of the existing arrangement of 
 society, presents a scene of universal harmony. It 
 resembles a machine, the diff'erent parts of which are 
 not only admirably fitted to each other; but being 
 
552 REVIEW OF 
 
 possessed of an inherent power of mutual self-adjusf- 
 ment, every injury which the mechanism can receive, 
 is soon repaired without the aid or direction of human 
 skill. By each individual acting for himself, every 
 comfort and convenience can be procured on the 
 cheapest possible terms ; every improvement is adopt- 
 ed ; and mutual interest and accommodation are 
 thereby so wonderfully maintained, that we can tra- 
 verse the earth with ease, safety, and expedition, and 
 scarcely know we are from home. 
 
 But under Mr Owen's system, where no law ex- 
 isted to check abuse; no reward for merit; almost 
 no motive to excite exertion ; nor mutual interest to 
 induce man to accommodate his fellow-creature ; a 
 scene of idleness and discord would be presented, 
 and the symmetry of the machine would be destroyed. 
 Consider how difficult it would be to travel or mer- 
 chandise without a circulating medium ! How weak 
 would be the motive or inducement to roam abroad, 
 under a system where commerce must cease, in con- 
 sequence of each parallelogram producing all that it 
 required, generally speaking, within itself! How lit- 
 tle to gratify the curiosity of man, delighting in novel- 
 ty and variety, where nothing was to be seen, but the 
 dull, unpleasing uniformity of endless parallelograms! 
 How narrowed would become the field of fame ! How 
 discouraging to the cultivation of genius ! And, com- 
 pared with the present state, how insipid the life of 
 man, confined as it were to spend his days within 
 the narrow precincts of a parallelogram, instead of 
 having the world for his stage, and the human race 
 for his audience. 
 
MP. Owen's system. 563 
 
 Under Mr Owen's system, where the means and 
 motives for travelling would be in a great measure 
 destroyed, man by losing intercourse with the inhab- 
 itants of the rest of the world beyond his own paral- 
 lelogram, would also lose a knowledge of their opin- 
 ions, manners, customs, and religious notions. Such 
 a loss would inevitably subject the human mind to 
 every kind of narrow prejudice. For of ail things 
 known, travelling, and general intercourse with the 
 world, have the greatest influence in promoting liber- 
 ality of sentiment ; and in dispelling the bigoted ig- 
 norance and superstition, which characterize the na- 
 tives of all remote and insulated nations. 
 
 The language spoken by the inhabitants of the 
 different parallelograms, from want of intercourse, 
 (for it is this principally that assimilates them,) would 
 also gradually diversify in accentuation, pronunciation, 
 and subsequently in spelling, till the language of one 
 parallelogram, became unintelligible in every other. 
 And instead of having one language spoken all over 
 Great Britain and Ireland, we should have as many 
 different dialects as parallelograms. 
 
 Knowledge under such a system could hardly be 
 expected to advance j for instead of the whole world 
 reaping the benefit of an invention, or improvement 
 in any of the arts and sciences, without regard to 
 where it originated, as in the present state of things, 
 it would likely be confined to the particular parallelo- 
 gram in which it was discovered. It is even reason- 
 able to suppose, that under such a system, knowledge 
 would be retrograde. It is by no means likely, that 
 every parallelogram would produce men both qualified 
 
 4a 
 
554 IIEVIEW OF 
 
 and inclined, to keep up the present state of know- 
 ledge in all its departments. But it is highly proba- 
 ble, that from want of encouragement given to men 
 of genius, which the system strictly forbids, all learn- 
 ing and study would be gradually abandoned. The 
 human species under such a system, from having no 
 hope of advancement, or of bettering their condition, 
 to stimulate them to exertion, would sink into a state 
 of indolence, ignorance, and stupidity. And from 
 want of exercising, and thereby of improving their 
 mental faculties, would probably degenerate in the 
 course of a few generations, into beings possessed 
 comparatively of weak reasoning powers, whose ac-- 
 tions would be governed more by instinct and super- 
 stition, than by reason and experience. 
 
 The moral influence upon society which the sepa- 
 ration of children from their parents at two years of 
 age, when they commence their education ; and the 
 effects of the mutual independence that must after- 
 wards subsist between children and parents, under 
 Mr Owen's joint-stock system, may likewise be con- 
 sidered. 
 
 In the present state of society, parents are bound 
 by law to support their children according to ability; 
 and they, in their turn, to support their parents when 
 they happen to require such assistance. This recip- 
 rocal obligation, however, does not exist merely be- 
 cause it is regarded as useful to society, and on this 
 account enforced by statutory enactment; but because 
 it is felt by mankind generally to be a duty, in the 
 performance of which they experience pleasure, and 
 in the neglect of which they suffer pain. The law. 
 
MR Owen's system. 555 
 
 in this case, properly encroaches upon individual 
 rights, in order to enforce what the feelings common 
 to man, in every age and nation, point out as an act 
 of duty. And so invariably is our individual duty, 
 and public utility connected, that the performance of 
 whatever the common sense of mankind declares to 
 be our duty, is ever found to be practically useful. 
 
 Providence, in order that virtue should in some 
 degree receive its reward, and vice its punishment, 
 has so organized the human frame, that the exercise 
 of every benevolent affection, and the performance of 
 every virtuous action, not only gains us the good will 
 of others, but is accompanied internally with pleasing 
 sensations. And on the contrary, that the indulgence 
 of every malevolent feeling, while it sinks us in the 
 estimation of others, occasions pain and uneasiness to 
 ourselves. The knowledge of this equitable ordina- 
 tion, every moralist ought to inculcate. It teaches 
 man, in order to promote his own happiness, to cher- 
 ish benevolent affections towards his fellow-creature, 
 and to control and restrain those of an opposite char- 
 acter. It is in accordance with this wise provision in 
 the animal economy, that the parent's anxiety, and 
 care for the welfare of his child, becomes one of the 
 sources of his happiness. 
 
 It would be out of place here to inquire metaphy- 
 sically, whether parental and filial affections originate 
 in internal organization exclusively adapted to these 
 purposes, or in the influence of necessarily habitual 
 proximity, and other circumstances, operating upon 
 our reasoning faculties. It must, however, be admit- 
 ted, that separation and mutual independence, not 
 
666 REVIEW 01' 
 
 only weaken those feelings, but beget mutual indiffer- 
 ence towards each other's welfare ; and, on the con- 
 trary, that habitual intercourse and association, and 
 mutual dependence, and exchange of services, create 
 and cherish, not only these affections, but every other 
 friendly and benevolent feeling implanted in man. 
 
 Legislative wisdom is displayed, not in attempting 
 to modify and alter human nature so as to suit ideal 
 states of society, but in adapting laws and institutions 
 to accord with human nature. It is only by such 
 means that the happiness of mankind will ever be pro- 
 moted. Feelings are the sources in which pleasure 
 and pain originate. They are the forces that impel 
 to action; and the direction of the impulse, guided 
 by reason and experience, is ever towards their grati- 
 fication. So wonderfully, however, are human feel- 
 ings adapted to our social condition, that while they 
 instinctively impel us towards their own exclusive 
 gratification, they are secretly and simultaneously di- 
 recting us to use the means, by which the moral hap- 
 piness of others, and the prosperity of society, may 
 be best promoted. And laws, institutions, and forms 
 of government, which do not harmonize with the ag- 
 gregate influence of human feelings throughout society, 
 will ever be more or less inefficient, prejudicial, and 
 productive of discontent. 
 
 To separate children from their parents at so early 
 an age as two years ; and for children and parents to 
 become mutually independent thereafter, according 
 to any arrangement of joint-stock property, is in op- 
 position to the dictates of nature; and evil instead of 
 good would therefrom result. Such would not only 
 
MR Owen's system. 557 
 
 lessen the number of our sources of enjoyment ; but 
 by severing those hnks, and weakening those affec- 
 tions, that connect the interest, and mutual well- 
 wishes of a family, would reduce man to a friendless 
 state of existence, in which, though he might feel an 
 independent indifference towards all mankind, yet the 
 feelings of all mankind would stand in the same rela- 
 tion towards him. Would our condition be amelior- 
 ated by such a change? Would we be better attended 
 in the hour of helplessness and distress, by the hand 
 of a stranger who cared not for us, than by that of a 
 relative? No: the condition of mankind will never 
 be ameliorated by such means. Let us remain as we 
 are. The present is the natural state of society, and 
 that which is most conducive to domestic happiness. 
 It harmonizes with the feelings common to our na- 
 ture, because it originates in, and is maintained by, 
 their aggregate influence. It interweaves the affec- 
 tions, and connects the interest of successive genera- 
 tions. Parents and children living together as one 
 family, feel mutually concerned in advancing each 
 other's prosperity. The former feel pleasure in edu- 
 cating, and thereby promoting the future welfare of 
 their children; and they, in their turn, impressed with 
 a sense of gratitude and affection, find it a pleasing 
 duty to assist and comfort their aged parents. 
 
 There is only one other general view of the remote 
 consequences, that would result from the adoption of 
 Mr Owen's plan for ameliorating the condition of 
 mankind, deserving of consideration; but which alone 
 is sufficient to show its unfitness, for being productive 
 of any ultimate beneficial effects; and enough to prove, 
 
558 REVIEW OF 
 
 that it, as well as all other systems of equality, would 
 necessarily deteriorate the condition, and thereby 
 impair the happiness of society. The remote con- 
 sequences alluded to, are those that result from 
 the principles, which, in different states of society, 
 and under different laws and regulations, determine 
 the degree of force with which population presses 
 upon the means of subsistence. As this subject re- 
 veals the only means whereby the condition of man- 
 kind can be permanently ameliorated, it is of more 
 importance that it should be understood, than any of 
 those which we have been examining. And as the 
 opinions of Malthus, the author of the greater part 
 of the views in question, have been opposed, misre- 
 presented, and treated with ridicule and contempt, by 
 individuals who have neither read his works, nor know 
 what his opinions are; we will consider this depart- 
 ment of our subject at greater length, than would have 
 otherwise been necessary. 
 
 The following are some of the leading principles, 
 from which the greater part of the Malthusian doc- 
 trines may be deduced. 
 
 1. The procreative principle implanted in the hu- 
 man species, is stronger than what is necessary to 
 support a stationary population, provided the means 
 of subsistence can be easily procured by the mass of 
 the people j and accordingly, in such circumstances, 
 population tends to increase. Malthus says: "Popu- 
 lation invariably increases, where the means of sub- 
 sistence increase, unless prevented by some very 
 powerful and obvious checks." 
 
 2. The average condition of mankind where the 
 
MR Owen's system. 559 
 
 land is all previously cultivated, and the population 
 employed, is lowered, at least so far as food is con- 
 cerned, by every addition to their numbers. And the 
 augmenting difficulty which the mass of the people 
 experience in procuring the means of subsistence, as 
 their condition sinks, gradually retards, and at length 
 arrests the increase of population. 
 
 3. The fear entertained by individuals of making 
 their condition worse by marrying, together with the 
 hope of making it better by remaining single, in some 
 cases prevents marriages altogether, and in others 
 makes them later in life of being contracted ; both of 
 which circumstances, by diminishing the number of 
 children born, check the increase of population, and 
 prevent its pressing so hard as it would otherwise do 
 upon the means of subsistence. 
 
 That the procreative principle implanted in the 
 human species, is stronger than what is necessary to 
 support a stationary population, provided the means 
 of subsistence can be easily procured by the mass of 
 the people; and accordingly, that in such circum- 
 stances population tends to increase, is a proposition 
 that scarcely requires proof. Unless this had been 
 the case, the earth could never have been replenished 
 with inhabitants. Emigration from old-peopled states 
 to a newly-discovered country, must have diminished 
 the population of the former, as much as it increased 
 that of the latter. And colonization of distant un- 
 inhabited parts of the earth, could have served no 
 purpose, but that of weakening the parent state, by 
 withdrawing a portion of its inhabitants, without the 
 possibility of filling up the deficiency thereby occa- 
 
5G0 REVIEW OF 
 
 sioned. But that the opposite is tlie f;jct, is demon- 
 strated by the growth of colonies. Since America 
 was discovered by Columbus in 1492, various portions 
 of that vast continent have been colonized by emi- 
 grants from the different states of Europe ; and the 
 procreative principle has in three centuries and a 
 half, conferred on that large portion of the globe, a 
 European population.* And this has taken place, 
 while, owing to improvements in machinery and hus- 
 bandry, and the cultivation of waste lands, the exten- 
 sion of manufactures, the more general employment, 
 and the greater production and diffusion of wealth 
 throughout society, all acting and reacting as instru- 
 ments, whereby the means of subsistence can be more 
 easily procured by the mass of the people, the popu- 
 lation of all the countries of Europe has been simul- 
 taneously increasing.t 
 
 * Malthus says : " In the northern states of America, the popu- 
 lation was found to double itself, for several successive periods, 
 every twenty-five years." 
 
 t According to statistical estimates, the aggregate amount of 
 the population of Europe, which is wholly composed of old-peopled 
 states, has increased twent^^-eight or twenty-nine millions from the 
 year 1815, to the beginning of 1829. This augmentation is prin- 
 cipally to be ascribed to the increased means of supporting a larger 
 population, arising from the causes mentioned above in the text. 
 It may also in part be owing to the cessation of war, to vaccina- 
 tion, to more effective means being taken to prevent the spread of 
 contagious diseases, and to the removal of those causes in which 
 they originate; all of which tend to lengthen the average duration 
 of human life, and accordingly promote the tendency to augmenta- 
 tion without proportionally increasing the moral restraints that 
 check population. In so far as these causes are contributing to 
 increase the population of Europe, they must be proportionally 
 
MR Owen's system. 561 
 
 In support of the doctrine that population tends to 
 increase under favourable circumstances, Malthus 
 says : *' The actual increase of the population of the 
 various nations of the earth may be advanced. Do 
 we not see that whenever the resources of any coun- 
 try increase, so as to create a great demand for labour, 
 and give the lower classes a greater command over 
 the necessaries of life, the population of such country, 
 though it might before have been stationary, or pro- 
 ceeding very slowly, begins immediately to make a 
 start forwards ? And do we not see in those few 
 countries, or districts of countries, where the pressure 
 arising from the difficulty of procuring the necessaries 
 and conveniences of life, is almost entirely removed ; 
 and where, in consequence, the checks to early mar- 
 riages are very few, and large families are maintained 
 with perfect facility, the rate at which the population 
 increases is always the greatest ?" 
 
 That the average condition of mankind, where the 
 land is all previously cultivated, and the population 
 employed, is lowered, at least so far as food is con- 
 cerned, by every addition to their numbers ; and that 
 the augmenting difficulty which the mass of the peo- 
 ple experience in procuring the means of subsistence 
 as their condition sinks, gradually retards, and at 
 length arrests the increase of population, is a doctrine 
 that is equally incontrovertible. The greater the 
 number among whom the produce of the soil is to be 
 divided, the smaller must be the portion allotted to 
 each. The price of food, like that of every other 
 
 tending to deteriorate the average condition of its inhabitants, at 
 least so far as food is concerned. 
 
 4 B 
 
562 REVIEW OF 
 
 article, rises with its scarcity and the number of pur- 
 chasers ; and the wages of labour, with the value of 
 its productions, sink with the increase of labourers. 
 An increase of population thus deteriorates the con- 
 dition of the industrious classes, which constitute the 
 mass of every community, by lowering wages, and 
 raising the price of food relatively to each other. 
 
 By statements made by Dr Villerme on the com- 
 parative mortality of the wealthy and indigent classes 
 in Paris, it appears that poverty shortens the average 
 duration of life. During the five years from 1817 to 
 1821, though the annual mortality for the whole of 
 Paris varied in the different years, the relative mor- 
 tality in the different arrondissements, as noted below, 
 underwent little or no alteration : — 
 
 In the 1st Arrondissement the mortality was 1 in 58 
 
 2 1 — 62 
 
 3 1 — 60 
 
 4 . 1 — 58 
 
 5 1 — 53 
 
 6 1 — 54 
 
 7 1 — 52 
 
 8 1 — 43 
 
 9 1—44 
 
 _ 10 1—50 
 
 11 — . 1—51 
 
 _ 12 = ^ 1 — 43 * 
 
 Upon examination, it was found that local influ- 
 ences could not be assigned for the above results. 
 
 * The proportions here given are from the deaths au domicile^ 
 and supply an average for the whole of 1 in 51 ; but when the 
 mortality in the hospitals (which are chiefly supplied from the 
 poorer districts) is added, the ratio is increased to 1 in 32. 
 
MR Owen's system. 563 
 
 The ratio of mortality was as great in the spots most 
 sheltered from northerly winds, and most open to the 
 sun, as it was in those placed in precisely opposite 
 circumstances. Nor did the water account for the 
 fact. 
 
 Neither could the density of the population be as- 
 signed as the cause of the results. Upon examina- 
 tion it was found, that in the 8th arrondissement, the 
 mean space allotted to each individual was 48 square 
 metres ; and in the 12th, 36 square metres ; while 
 the mean space for each individual in the 7th and 4th 
 arrondissements, was only 10 and 6 square metres 
 respectively. If density of population had been the 
 cause of the difference in the ratio of mortality, the 
 mean duration of hfe should have been shortest in 
 the 7th and 4th arrondissements ; whereas, by the 
 above table, in these two districts, the annual mor- 
 tality relative to the population, is considerably less 
 than the average j while in the 8th and 12th it is the 
 greatest. 
 
 Upon farther comparison it was found, that (with 
 the single exception of the eleventh, which could not 
 be well accounted for,) the annual mortality increased 
 with the poverty of the different arrondissements. 
 Those districts being reckoned the poorest, in which 
 the greatest number of untaxed houses were found. 
 Poverty, therefore, in some way or other shortens the 
 average duration of human life. And hence one rea- 
 son, why the augmenting difficulty which the mass of 
 the people experience in procuring the means of sub- 
 sistence as their condition sinks, gradually retards, 
 and at length arrests the increase of population. 
 
5(j4 REVIEW OF 
 
 " The wages of labour," says Malthus, " sink as 
 population advances, till they are just sufficient to 
 maintain a stationary population. In a country where 
 the wages of labour estimated in food are low, and 
 that food is relatively of a very low value, both with 
 regard to domestic and foreign manufactures, the con- 
 dition of the labouring classes must be the worst pos- 
 sible. Poland, and some parts of Russia, Siberia, 
 and European Turkey, afford instances of this kind. 
 In Poland, the population seems to be almost sta- 
 tionary, or very slowly progressive ; and the popu- 
 lation and produce are both scanty compared with the 
 extent of territory. Yet, here, corn is in abundance, 
 and great quantities are yearly exported. But it is 
 neither the power of a country to produce food, nor 
 even what it actually produces, that hmits and regu- 
 lates the progress of population, but the quantity 
 which, in the actual state of things, is awarded to the 
 labourer. The demand for labour in Poland is very 
 small, and the condition of the lower classes of so- 
 ciety is extremely miserable. The misery of Poland 
 arises from the little encouragement given to industry 
 of any kind, owing to the state of property, and the 
 servile condition of the mass of the people. The 
 population of Poland is composed of boors and large 
 landed proprietors ; the produce of the soil which is 
 worked by the former, all belongs to the latter." It 
 need hardly be remarked, that, in the above case, the 
 exported corn serves merely to supply the proprietors 
 of the soil with articles of foreign growth and manu- 
 facture, and does not employ the labouring classes in 
 Poland 5 and consequently does not increase their 
 
MR Owen's system. 565 
 
 means of purchasing food, and the other necessaries 
 of life. 
 
 " Population," says Malthus, in another passage, 
 " is necessarily limited by the means of subsistence, 
 and can never increase beyond the lowest nourishment 
 capable of supporting life. It is of no consequence 
 whether a country export corn or not, the population 
 must still be regulated by the real wages of labour, 
 and must come to a stand when the necessaries which 
 these wages command, are not sufficient under the 
 actual habits of the people, to encourage an increase 
 of numbers." 
 
 The checks which keep population on a level with 
 the means of subsistence, or rather, in consequence 
 of their joint agency, which keep down population, 
 so that the average condition of mankind is raised 
 considerably above that limit, are classed by Malthus 
 under two general heads : the positive, and, the pre- 
 ventive. " The positive checks to population include 
 every cause which destroys life, such as mortality 
 arising from old age, or infirmity ; or which contri- 
 butes to shorten its natural duration, such as accidents, 
 unwholesome occupations, severe labour, exposure to 
 the seasons, extreme poverty, bad nursing of children, 
 infanticide, great towns, excesses of all kinds, the 
 whole train of common diseases and epidemics, wars, 
 pestilence, plague, and famine. The preventive 
 check to population is peculiar to man, and arises 
 from his being endowed with reason, which enables 
 him to calculate the distant consequences of mar- 
 riage."* The procreative principles implanted in 
 
 * Malthus says: "The checks to population are all resolvable 
 
5G() REVIEW OF 
 
 every species of animal, like the reproductive proper- 
 ties of every kind of vegetable, are sufficiently power- 
 ful to cause them to increase and multiply. Hence 
 they go on multiplying unless restrained by obvious 
 causes, till the positive checks, viz., the augmenting 
 inability to obtain a sufficiency of nourishment, grad- 
 ually retards, and at length puts a stop to all farther 
 increase. Animals and plants therefore increase and 
 multiply, till their number is exactly on a level with 
 the means of subsistence, that is, till the quantity of 
 nutriment which they can severally obtain, is reduced 
 to the lowest amount capable of supporting life, and 
 perpetuating the several species, without increase or 
 diminution in their numbers. Malthus from a shght 
 verbal oversight somewhat fails in elucidating his 
 subject, by always seeming to regard population as 
 being on a level with the means of subsistence in any 
 country, at the point where population becomes sta- 
 tionary. But to reason in analogy with the principles 
 which regulate the number of animals and vegetables, 
 
 into moral restraint, vice and misery, or the fear of misery. Of 
 the preventive checks, that which is not followed by irregular 
 gratification, may properly be termed moral restraint. Infanticide, 
 promiscuous intercourse to such a degree as to prevent the birth 
 of children, unnatural passions, violations of the marriage bed, and 
 improper arts to conceal the consequences of irregular connection, 
 clearly come under the head of vice. 
 
 " Of the positive checks, those which appear to arise unavoid- 
 ably from the laws of nature, may be called exclusively misery ; 
 and those which we obviously bring upon ourselves, such as wars, 
 excesses, and many others which it is in our power to avoid, are of 
 a mixed nature. They are brought upon us by vice, and their 
 consequences are misery." 
 
MR Owen's system. 567 
 
 where their farther increase is restrained only by na- 
 tural causes, or as Malthus calls them, positive 
 checks, population can never be said to be on a level 
 with the means of subsistence, till the whole com- 
 munity be reduced to Hve upon the poorest and small- 
 est amount of food capable of supporting life, and 
 perpetuating the species, without increase or diminu- 
 tion in number. Now, owing to the human species 
 being able to calculate the distant consequences of 
 marriage, and of sexual intercourse, population never 
 increases in any natural state of society, till the whole 
 community be reduced to this condition, which, in 
 point of wretchedness and poverty, is the lowest in 
 which they can possibly exist. This leads us to the 
 consideration of the third principle, viz., the preven- 
 tive check to population, the effect of which is to 
 limit, and arrest the increase of population, so that 
 the mass of the people can at all times command a 
 greater amount of food and other necessaries, than is 
 absolutely requisite for the support of life, and the 
 perpetuation of the species. 
 
 That the fear entertained by individuals of making 
 their condition worse by marrying, together with the 
 hope of making it better by remaining single, in some 
 cases prevents marriages altogether, and in others 
 makes them later in life of being contracted ; and that 
 both these circumstances diminish the number of 
 births, and thereby prevent population from pressing 
 so hard as it would otherwise do on the means of sub- 
 sistence, is a doctrine that Malthus has established 
 beyond all controversy. If this was not the case, the 
 whole population would be married by the time they 
 
568 REVIEW OF 
 
 are 18 or 20 years of age ; whereas, we find that of 
 the females who reach maturity, a large proportion 
 die without ever having been married, and without 
 contributing towards the perpetuation of the species. 
 We will only select one statistical estimate in support 
 of the truth of the principle under consideration, 
 and refer to the original work,* where numberless 
 others may be found. The proportion of annual 
 deaths to the whole population on an average through- 
 out the whole of Norway, is only as 1 to 48, while 
 the marriages are as 1 to 130. In Holland, however, 
 the annual mortality is 1 in 23, while the annual 
 marriages are 1 in 64. By comparing the propor- 
 tion of deaths and marriages in Holland, with that in 
 Norway, we see how much they mutually depend upon 
 each other. Similar comparisons hold good every 
 where. Deaths, by producing vacant livings, and by 
 diminishing the number of consumers of food, and 
 thereby improving the condition of those who remain 
 alive, prepare the way for marriages ; and hence it is 
 found, that the longer the average duration of hfe is 
 in any country, provided the population be stationary, 
 the fewer are the matrimonial engagements relative 
 to the population, or the later they are of being con- 
 tracted ; and the larger is the proportion of females 
 who die unmarried ; and vice versa. 
 
 In like manner, supposing population stationary, 
 whatever tends to increase the average duration of 
 human life, such as vaccination, or in warm climates, 
 the extinction of marsh fevers by the draining of 
 
 * Malthus on Population. 
 
MR Owen's system. 569 
 
 marshy lands, diminishes the chance which females 
 have of getting married, and begets customs and ha- 
 oits among the mass of the people favourable to the 
 exercise of the preventive check to population, and 
 of course unfavourable to early marriages.* Upon 
 similar principles, the chance which females have of 
 getting married, is greater in countries where popu- 
 lation is rapidly increasing, such as in the United 
 States of America, and also in cities and districts of 
 countries similarly circumstanced, than in those where 
 the population is stationary, or very nearly so. 
 
 Supposing the mean duration of human life the 
 same, it is obvious from the preceding observations, 
 that the average condition of the mass of the people 
 at the point where population becomes stationary, 
 must be raised more or less above that at which popu- 
 lation is on a level with the means of subsistence, 
 according as the preventive check is more or less 
 effective in preventing and delaying marriages. In 
 order, therefore, to ameliorate the condition of man- 
 kind, our endeavours ought to be chiefly directed to 
 the introduction of such laws and arrangements into 
 our civil institutions, as are calculated to beget pro- 
 spective prudential habits among the mass of the 
 people, whereby the preventive check may be ren- 
 
 * That the influence of the preventive check in limiting popu- 
 lation, by preventing and delaying marriages, increases with the 
 average duration of life, is demonstrated by the fact, (and many 
 others may be found in Malthus' works,) that the population of 
 Norway, where the mean duration of life is 48 years, is as sta- 
 tionary, without any aid either from emigration or war, as it is 
 in Holland, where the mean duration of life is only 23 years. 
 
 4c 
 
570 REVIEW OF 
 
 dered more efficient in limiting population. *' In 
 most countries," says Malthus, " among the lower 
 classes of people, there appears to be something like 
 a standard of wretchedness, a point below which they 
 will not continue to marry and propagate their species. 
 This standard is different in different countries, and 
 is formed by various concurring circumstances of soil, 
 climate, government, degree of knowledge, and civil- 
 ization, &c. the principal circumstances which con- 
 tribute to raise it, are liberty, security of property, the 
 spread of knowledge, and a taste for the conveniences 
 and comforts of life. Those which contribute prin- 
 cipally to lower it, are despotism and ignorance. In 
 an attempt to better the condition of the lower classes 
 of society, our object should be to raise this standard 
 as high as possible, by cultivating a spirit of inde- 
 pendence, a decent pride, and a taste for cleanliness 
 and comfort among the poor." * 
 
 In accordance with the preceding recommenda- 
 tions, Malthus, in another passage, says: *' Of all the 
 plans which have been proposed for ameliorating the 
 condition of the labouring classes, by increasing their 
 
 * The circumstance of Earl Grey's Reform Bill limiting the 
 elective franchise to ten- pound rented householders — a rank which 
 even the lowest class of labourers, by the exercise of industry and 
 economy, may easily attain — may have some slight influence in 
 begetting prudential habits among the lower orders. The elective 
 franchise is now sufficiently extensive for all the purposes of good 
 government ; and were it only for the above reason, it ought not 
 to be extended farther. The present constituency are at least|.as 
 competent to select proper representatives as any lower constitu- 
 ency, and less liable to be bribed, or to be deceived by demagogues 
 and unworthy persons. 
 
MR owen's system. 571 
 
 prudence and foresight, that of saving banks, as far 
 as they go, is the best. By giving to each individual 
 the full and entire benefit of his own industry and 
 prudence, is the best plan for promoting such habits." 
 
 In like manner, with a view still farther to promote 
 a spirit of independence and prudential habits among 
 the mass of the people, life insurances, and friendly 
 societies, which, for a small monthly or yearly contri- 
 bution, confer a subsequent right to receive assistance 
 in case of need, are worthy of support. Such insti- 
 tutions ought to receive every protection and security 
 which cheap laws, and the power of government can 
 enforce. And as the first duty of every member of 
 society, is to free the community as far as possible 
 from any chance, that he or his family shall ever be- 
 come a burden to them, tradesmen who connect 
 themselves with such institutions, should be regarded 
 as better members of society, and more eligible for 
 employment, than those who do not. 
 
 On the other hand, poor laws, in so far as they 
 beget imprudent habits in contracting marriages, by 
 affording rehef and support to the poor and improvi- 
 dent, so do they ultimately tend to lower the average 
 condition of a people. Upon this point, Malthus 
 says : " The effect of the Enghsh poor laws may 
 perhaps be to alleviate the intensity of individual mis- 
 fortune, which benefit is counterbalanced by their 
 spreading poverty over a much larger surface. 
 
 "It is impossible to raise the condition of the 
 poorest class by giving them poor's rates, without 
 lowering the condition of those classes above them 
 who maintain their independence, without applying 
 
•572 REVIEW OF 
 
 for parish assistance. If there is only a fixed amount 
 of food for a given population, if by enabling the 
 lowest class to purchase a better share of that food 
 by parish assistance, than what they would be able to 
 procure without assistance, it is evident that the re- 
 mainder of the food for the rest of the population 
 must be proportionally less, and of course thereby 
 raised in price to the disadvantage of all those classes 
 who do not receive parish aid. The price of corn in 
 a scarcity, will depend much more upon the obstinacy 
 with which the same degree of consumption is per- 
 severed in, than on the degree of the actual deficiency. 
 " An increase in the price of provisions will arise, 
 either from an increase of population faster than the 
 means of subsistence, or from a different distribution 
 of the money of the society. The poor laws tend to 
 depress the general condition of the poor in these 
 two ways. Their first obvious tendency is to increase 
 population, without increasing the food for its sup- 
 port. A poor man may marry with little or no 
 prospect of being able to support a family without 
 parish assistance. They may be said, therefore, to 
 create the poor which they maintain ; and as the pro- 
 visions of the country must in consequence of the in- 
 creased population, be distributed to every man in 
 smaller proportions, it is evident that the labour of 
 those who are not supported by parish assistance, will 
 purchase a smaller quantity of provisions than before, 
 and consequently more of them be driven to apply 
 for assistance." In another passage Malthus says : 
 *' Already above one-fourth of the population of Eng- 
 
MR OWEN*S SYSTEM. 573 
 
 land and Wales, are regularly dependent upon parish 
 relief." 
 
 The above opinions are legitimate inferences from 
 the principles which regulate population. Yet Mal- 
 thus, to whom the science of political economy is 
 more indebted for advancement than to any other man 
 save Dr Adam Smith, has been characterized, as well 
 as all his followers, as uncharitable and hard-hearted, 
 for advocating, and believing in the great political 
 truths which he has revealed. 
 
 The opponents of the Malthusian doctrines cry out, 
 compare the state of Ireland where no poor laws exist, 
 with that of England where there are poor laws. The 
 difference, however, in the condition of England and 
 Ireland, is totally independent of the existence, or 
 the absence of poor laws. In society, we see that the 
 conduct of one man is much more regulated by a re- 
 gard to consequences, than that of another. As it is 
 with individuals, so is it with nations. The Irish, 
 compared to either the English or the Scotch, are, 
 from their physical constitution, a light-hearted, and 
 an improvident people. Their conduct is compara- 
 tively but little influenced by a calculation of future 
 consequences. And hence the preventive checks to 
 population, viz., the hope of improving their condi- 
 tion by remaining for a time single, and the fear of 
 making it worse by entering into the state of mar- 
 riage, have less influence with equal worldly prospects 
 in preventing and delaying marriages in Ireland, than 
 what they have in England or Scotland. And hence, 
 from this cause alone, the average condition of the 
 mass of the people, at the point where the conjoint 
 
574 REVIEW OF 
 
 influence of the preventive and positive checks render 
 population stationary, is lower in Ireland, than what 
 it is in either of the other two countries. 
 
 Again, the average wealth or condition of a nation, 
 is determined by the aggregate produce of land and 
 labour, relative to the population. The larger the 
 former is in reference to the latter, the higher is the 
 average condition of the people. Husbandry, in its 
 present improved state, cannot employ one-half of the 
 population which the produce of the soil, if properly 
 cultivated, is capable of supporting. Hence, in coun- 
 tries merely or chiefly agricultural, such as Poland 
 and Ireland, the population is only half employed ; 
 whereas, in countries such as England and Scotland, 
 where agriculture and manufactures are equally pros- 
 perous, the population is wholly employed. A half 
 idle population produce little, when compared with an 
 industrious people, aided by the power of machinery. 
 And where little is produced, there is little to divide. 
 Hence, in every old-peopled state, the average con- 
 dition of the population is higher where manufactures 
 are established, (and the more they are aided by ma- 
 chinery the higher it is,) than in those that are merely, 
 or chiefly agricultural. Though the average condi- 
 tion in relation to food be nearly the same in both, in 
 relation to all the other necessaries and comforts of 
 life, it is very different. Besides, in England, and in 
 free countries generally, where commerce and manu- 
 factures are flourishing, the number of those reduced 
 to the ranks of poverty are smaller in proportion to 
 the better classes, than in countries merely or chiefly 
 agricultural, such as Poland and Ireland. The more 
 
MR Owen's system. 575 
 
 numerous gradations in the scale of society in the 
 former, present greater facilities, and excite a more 
 general desire of rising in the world, than in the latter. 
 And as the desire of rising in the world increases like 
 every other, with the facility, and the more immediate 
 prospect of gratification, the preventive checks to po- 
 pulation become more efficient, and consequently the 
 standard of subsistence is raised higher, in England 
 than in Ireland. 
 
 Finally, Ireland is inhabited by a physically con- 
 stituted disorderly race of people, and their natural 
 character is rendered more turbulent by bad govern- 
 ment, and particularly by the unwise support of an 
 expensive church establishment, the doctrines of 
 which are disliked by nine-tenths of the population. 
 The consequence is, that a considerable proportion 
 of the lands in Ireland, are owned by persons who find 
 it safer, and more comfortable to reside, and spend 
 their incomes in England. The former thus becomes 
 a country that exports a considerable proportion of 
 her produce, in the shape of rent, to be consumed in 
 the latter. And this is another reason why Ireland 
 presents to the eye of the traveller, a general appear- 
 ance of poverty in comparison with England. 
 
 It is unquestionable that poor laws, such as those 
 of England, which confer a legal claim upon the poor 
 when unemployed to demand assistance from the rich, 
 and to have their wages made up to a legal standard 
 when they happen to sink below it, not only open the 
 door to fraud and imposition, but convert the funds 
 destined for the support of the poor into the wages of 
 labour. And it is equally unquestionable, that if 
 
570 REVIEW OF 
 
 administered in their intentional spirit, by encourag- 
 ing idleness and improvidence, they would naturally 
 tend to diminish the influence of the preventive 
 checks to population, and spread rather than mitigate 
 the evils they were intended to remedy. But on 
 the other hand, the disposition of a community to 
 protect themselves from the evils occasioned by 
 bad laws, gradually gives rise to correctives in their 
 administration. Thus the dislike to be confined in 
 the parish workhouse, in order to receive relief, has 
 been found in some parts of England, to be a salutary 
 check to the mischief which its laws create. And in 
 like manner, the obligation of each parish to support 
 only its own poor, has formed so strong an induce- 
 ment to wealthy proprietors to rid themselves of poor 
 tenantry, by destroying their cottages, and preventing 
 them from being domiciliated upon their estates, that 
 the encouragement to population, which the English 
 poor laws have been supposed to produce, has been in 
 some degree balanced, and in some cases more than 
 balanced, particularly in country parishes, by the 
 counteractives to which they have given rise. And 
 while the professed object of the laws has been to 
 relieve and assist the poor, their practical application, 
 by forcing them from the country to seek shelter in 
 the over-crowded, and unwholesome portions of large 
 towns, has often been to distress and destroy them. 
 
 Such are some of the causes of the difference in the 
 average condition of the people in England and Ire- 
 land, independent of poor laws j and such are some 
 of the reasons, why the English poor laws in their 
 practical operation, have in many cases produced 
 
MR OWEN S SYSTEM. 577 
 
 results in reference to population, totally at variance 
 with the natural tendency of such laws, if administer- 
 ed in their true spirit. 
 
 It is a self-evident proposition, that poor laws do 
 not increase the aggregate wealth of a nation ; they 
 merely transfer a part of that wealth from the rich to 
 the poor. Such laws benefit one portion of the com- 
 munity at the expense of another. They directly in- 
 fringe upon the right of private property ; and are, 
 abstractly considered, unjust. The circumstance of 
 birth, confers on no man a claim to be supported by the 
 produce of the soil, which is owned, and cultivated by 
 his fellow-creatures. The procreative principle im- 
 planted in the human species, is stronger than what is 
 necessaiy to support a stationary population; and un- 
 less restrained by the fear of consequences, would in- 
 evitably increase population, till the whole community 
 were reduced to live upon the lowest amount of food 
 capable of supporting life. In like manner, unless the 
 right of private property was respected, all the benefits 
 derived from the social state would be lost; a system 
 of equality would be established ; and the whole com- 
 munity would also in this case be soon reduced by 
 procreation, to the lowest possible condition. 
 
 Malthus says : " There are two decisive arguments 
 against systems of equahty ; one is the unsuitableness 
 of a state of equality, both according to experience 
 and theory, to the production of those stimulants to 
 exertion which can alone overcome the natural indo- 
 lence of man, and prompt him to the proper cultiva- 
 tion of the earth, and the fabrication of those con- 
 
 4d 
 
.-578 REVIEW OF 
 
 veniences and comforts, which are necessary to his 
 happiness. 
 
 *' The other is the inevitable and necessary poverty 
 and misery, in which every system of equahty must 
 shortly terminate, from the acknowledged tendency of 
 the human race to increase faster than the means of 
 subsistence, unless such increase be prevented by 
 means infinitely more cruel than those which result 
 from the laws of private property, and the moral obh- 
 gation imposed upon every man by the commands 
 of God and nature, to support his own children." 
 " Man," says Malthus, in another passage, " has only 
 a conditional right to subsistence, and only if he be 
 possessed of property, or if his labour purchase food." 
 If a man prefers present enjoyment, to attempting to 
 insure himself against poverty at a future time, he has 
 no claim upon the property of those who by their 
 industry, good fortune, good management, and eco- 
 nomy, have acquired and preserved it. It is unjust 
 that the man who chooses to marry and get a family, 
 before he sees any prospect of providing for them, or 
 perhaps with poverty staring him in the face, should 
 have a legal right to support himself and family at the 
 expense of those who have acted more providently. 
 And it is at least equally unjust, that a man and his 
 family, who have spent and enjoyed the whole pro- 
 duce of their labour in the early, or past portion of 
 their existence, should have a legal claim upon the 
 produce of the industry of the man and his family, 
 who have saved, and laid past a part of theirs, in 
 order to support their respectability, and inde- 
 pendence, and enjoy it at a future period of their 
 
MR owen's system. 579 
 
 lives. Justice requires that the rightful owner should 
 have the free disposal of his property, unincumbered 
 by any legal claim on the part of persons who have 
 never been of any service to him, and with whom he 
 is totally unconnected. 
 
 But then it may be said, that human laws have not 
 rigid justice so much for their basis as public advan- 
 tage, and that the avowed object of poor laws, is to 
 do a slight injustice or evil, that a great benefit may 
 result to society. The objects which poor laws have 
 in view, are : — 
 
 1. To endeavour at a trifling expense to the rich, 
 which they can well spare, to raise the condition of 
 the lower orders of society, and secure them from 
 want and starvation, when thrown out of employment 
 during those fluctuations of trade, which it is fre- 
 quently impossible to foresee or prevent j and which 
 are, and probably always will be, but too little pro- 
 vided for by the lower orders. 
 
 2. To equalize the burden according to the means 
 of bearing it ; for when the support of the poor is left 
 to private benevolence, some give, and some do not. 
 
 3. To do away with public begging, which has a 
 demoralizing and degrading influence upon society. 
 It is farther contended that the cost of maintaining 
 the poor in that way, is greater than by means of a poor 
 tax ; and their numbers, even according to Malthu- 
 sian doctrines, are in consequence thereby more en- 
 couraged. Besides, when the poor are left to subsist 
 by begging, their labour is lost to the community, 
 which ought not to be the case under a properly and 
 judiciously administered poor tax. 
 
580 REVIEW OF 
 
 It is obvious from the preceding statement of the 
 objects which poor laws have in view, that if tolerated 
 at all, their administration would require to be put 
 under severe and strict regulations. In order to pre- 
 vent the assistance given to the poor having any very 
 pernicious influence in begetting improvident habits, 
 and thereby increasing population, the condition of 
 those who receive aid, should be decidedly worse than 
 that of the lowest class of labourers, who maintain 
 their independence, and live by the fruits of their own 
 industry. In order to prevent fraud and imposition, 
 (and it cannot be altogether prevented otherwise,) 
 those who receive aid should be under the necessity 
 of residing within the parish vi'orkhouse. And that 
 their labour might not be lost to the community, they 
 ought to be under the obligation to work according to 
 ability, at any occupation which overseers might di- 
 rect ; and the proceeds of their labour, should be ap- 
 plied to defraying the expenses attending such estab- 
 lishments. 
 
 It is evident that by such regulations, the strongest 
 objections to poor laws would be obviated.* But af- 
 ter all it is doubtful, whether, under the best system, 
 and the best administration of poor laws that ever will 
 be devised, the advantages gained are a sufficient com- 
 pensation for the disadvantages, remote as well as im- 
 mediate, to which they give birth. 
 
 * By tlie Poor Law Amendment Bill, (for which it is supposed 
 the nation is indebted to Lord Brougham,) the chief defects in the 
 English system of poor laws will be remedied. Even what may 
 be thought the illiberal enactments of that bill, are well calculated 
 to produce the salutary results which they have in view, and which 
 could not be accomplished by any other means. 
 
MR Owen's system. 581 
 
 It is always to be feared that any legal provision for 
 tlie poor, will, in the estimation of the public, lessen 
 the obligation of a family to support their aged pa- 
 rents ; and this of itself, in a social point of view, is 
 calculated in a serious manner to diminish the agg-re- 
 gate happiness of mankind. What a forlorn prospect 
 it would be for a labouring man to be separated from 
 his relatives, and forced to submit to the regulations 
 of a poor's house, in order to obtain the necessaries 
 of life in his old age ! And how preferable is that 
 state of society, which necessarily results from the 
 absence of poor laws, where the aged parent is sup- 
 ported by, and resides with the family, which, during 
 the early period of life he has himself clothed, fed, 
 and educated ; in whose presence he feels so much 
 happiness ; and in whose prosperity and welfare he 
 takes so deep an interest ! 
 
 Besides, even the best-arranged system of poor 
 laws, is liable to many disadvantages, as well as 
 abuses. It is a tax upon the community, and like all 
 unnecessary or exorbitant taxation, infringes accord- 
 ing to its amount, upon the right of every man to en- 
 joy the fruits of his labour, with as little diminution 
 as is consistent with the support of good but cheap 
 government, and the maintenance of order in society. 
 And not to mention the unequal, the vexatious, and 
 arbitrary methods adopted in levying the money for 
 the support of the poor, a considerable amount of it 
 is wasted ; and like every other fund raised for a spe- 
 cial purpose, is always more or less hable to be mis- 
 applied. Thus, a considerable proportion of the 
 money levied goes to support surveyors, assessors. 
 
582 REVIEW OF 
 
 and others connected with the administration of the 
 poor laws ; and other proportions are spent in litiga- 
 tion. In both cases, so much wealth is lost to the 
 community, without the poor receiving any direct be- 
 nefit therefrom. 
 
 Finally^ The existence of any legal provision for 
 the poor, however meagre, has more or less influence 
 in counteracting and discouraging prudential habits 
 among a people, which, if no poor laws existed, would 
 show themselves in the more extensive establishment, 
 and more general support of saving banks, friendly 
 societies, and life insurances. 
 
 It might be thought that the influence of the pre- 
 ventive checks to population, is restricted exclusively 
 to the lower orders. This, however, is not the fact. 
 *' In England," says Malthus, " the preventive check 
 to population operates in a considerable degree. 
 Those among the higher classes, who live principally 
 in towns, often want the inclination to marry, from the 
 facility with which they can indulge themselves in 
 illicit intercourse with the sex. And others are de- 
 terred from marrying, by the idea of the expenses 
 they must retrench, and the pleasures of which they 
 must deprive themselves, on the supposition of having 
 a family. The sons of tradesmen and farmers are ex- 
 horted not to marry, and generally find it necessary to 
 comply with this advice, till they are settled in busi- 
 ness or a farm, which may enable them to support a 
 family. Among clerks in counting-houses, and the 
 competitors for all kinds of mercantile and professional 
 employment, it is probable, that the preventive check 
 to population, prevails more than in any other depart- 
 
MR Owen's system. 583 
 
 ment of society. Perhaps men-servants are under the 
 strongest restraints ; for, if they marry, they lose their 
 present employments, and know of no other to betake 
 themselves to." 
 
 Under the present system of society, which by 
 every one working for his own individual advantage, 
 is productive of such an immense variety of ranks 
 and degrees of wealth, it might be supposed that po- 
 verty must press harder upon the lower orders, ac- 
 cording as their numbers relative to those of the bet- 
 ter classes become reduced, just as the pressure on 
 the foundation increases with the height of the pyra- 
 mid, and the narrowness of its base. This, however, 
 is not the case. On the contrary, the preventive 
 checks to population seem to operate more power- 
 fully upon the middle, than upon the lower ranks of 
 society. The labouring classes being at the bottom 
 of the scale already, have no room to sink; and hence 
 they are deterred comparatively in a slight degree 
 from entering into the married state, by the fear of 
 making their condition worse. But while the hope 
 of rising exerts upon the middle classes, at least equal 
 force to what it does upon the labouring population, 
 in preventing and delaying matrimonial engagements, 
 the fear of thereby rendering their condition worse, 
 and of sinking below the rank of their family and ac- 
 quaintances, operates with fourfold influence. 
 
 The condition of the lower orders appears to be 
 actually ameliorated, according as the wealthier classes 
 of society relatively increase in numbers. In propor- 
 tion as the lower orders relative to the other classes 
 are few in number, so is the opportunity and the 
 
584 REVIEW or 
 
 prospect of rising in the world increased, and accord- 
 ingly the preventive checks to population become 
 more efficient. And it will be found to result there- 
 from as a general law, that the aggregate condition of 
 the labouring classes in any country, (food, clothing, 
 lodging, and other comforts all included in the esti- 
 mate,) rises according as their number is few, when 
 compared with the aggregate wealth and amount of 
 the whole population. Besides, in years of scarcity, 
 and in times of commercial difficulty, which are never 
 foreseen, and too little provided for, the accumulation 
 of wealth in the hands of a portion of the community, 
 by affording the means of charity, becomes a blessing 
 to the poor, and some security against starvation. 
 
 Emigration, according to Malthusian principles, is 
 merely a temporary expedient, which, as it does not 
 diminish the population permanently relative to the 
 means of subsistence, is not calculated to have any 
 lasting influence in ameliorating the condition of a 
 nation. The power of the reproductive principles 
 implanted in the human species, so far exceeds what 
 is necessary to maintain a stationary population, even 
 in those countries where the average duration of life 
 is the shortest, that any continued systematic plan of 
 emigration, by lessening the efficacy of the preventive 
 checks, would almost proportionally encourage an in- 
 crease of population, and consequently could have no 
 permanent influence in raising the average condition 
 of a people. On the contrary, emigration, conducted 
 at the public expense, tends to impoverish a nation in 
 two ways. First, the cost of it is defrayed out of the 
 pockets of those who remain. And second, it with- 
 
MR Owen's system. 585 
 
 draws the enterprizing, and those who, from being in 
 the prime and vigour of hfe, are best fitted for labour, 
 (for such only emigrate,) while it leaves the women 
 and children, and all the unproductive classes, such 
 as clergy and lawyers, and those who, from age and 
 infirmity, are unable to work, and consequently who 
 contribute nothing towards the wealth and productive 
 power of a nation. Public liberty requires, that every 
 individual should possess the privilege of emigrating 
 without hinderance to wheresoever he chooses, pro- 
 vided he does so at his own expense. But the means 
 of emigration should never be supplied from the pub- 
 lic purse, except perhaps when large bodies of work- 
 men, concentrated in particular districts, are suddenly 
 thrown out of employment by improvements in ma- 
 chinery, or by unforeseen political or commercial vi- 
 cissitudes. And even in such cases, its propriety is 
 questionable. Workmen thrown out of employment 
 soon find out other means of supporting themselves ; 
 and before any plan of emigration can be arranged 
 and carried into effect ; and even before such an ex- 
 pedient is thought of, the evil which suggested it, has 
 usually in a great measure subsided. 
 
 Upon this subject it may be farther remarked, that 
 to prevent disputes between nations arising from the 
 misconduct of emigrants and persons abroad, every 
 man ought to be subject to the laws of the country in 
 which he happens to be, and to them alone ; nor 
 should the parent state have any right to interfere in 
 his behalf. 
 
 Infanticide, according to Malthus, has no influence 
 in keeping down population, so as to raise their aver- 
 
 4 E 
 
586 REVIEW OF 
 
 age condition. In lact it appears to have a contrary 
 tendency. Owing to the protection afforded by feel- 
 ings of parental affection, the number of children de- 
 stroyed where infanticide is allowed, does not com- 
 pensate for the additional number born, in conse- 
 quence of the preventive checks to population being 
 thereby in a considerable degree removed. It is ac- 
 cordingly found, that in countries, such as China, 
 where this barbarous custom is permitted, population 
 presses harder upon the means of subsistence, and 
 the condition of the people is more wretched, and the 
 shortening of life occasioned by poverty greater, than 
 in those where it is not. Hence it is consistent not 
 only with moral propriety, but also with political ex- 
 pediency, that infanticide is prohibited amongst all 
 civihzed nations. 
 
 It is a popular, though in my opinion an erroneous 
 belief, that the condition of mankind would be ame- 
 liorated, by supplying them with education, and reli- 
 gious instruction, at the public expense. That the 
 former should be accomplished by taxing the com- 
 munity, or burdening the land, for the support of a 
 national system of education, and endowed schools j 
 and the latter, by making similar provision for sup- 
 porting an estabhshed religion, and endowed churches. 
 
 National systems of education supported at the 
 public expense, are but systems of equality so far as 
 education is concerned. It is the duty of every man 
 to educate his family at his own expense ; and in so 
 doing, he not only receives remuneration in propor- 
 tion to the interest he takes in promoting their future 
 welfare, but he gains a prospective advantage in being 
 
MR Owen's system. 587 
 
 more likely to obtain assistance from them, if disease, 
 or misfortune, should in his old age, render it neces- 
 sary. The expense of educating a family, is one of 
 the circumstances which deteriorate a man's condition 
 in the married state ; and consequently is one of the 
 items which have an influence in preventing and de- 
 laying marriages, and in diminishing the pressure of 
 population upon the means of subsistence. Besides, 
 it is not just that the man who has no family, should 
 be taxed for the education of those with whom he is 
 unconnected, and from whom he never received, nor 
 expects to receive any benefit. 
 
 A national system of education is liable to other 
 disadvantages. It begets a system of patronage and 
 corruption in the appointment of teachers ; it in- 
 creases the expense of education to the community ; 
 by establishing one uniform system it prevents all im- 
 provement both in the art of teaching, and in the 
 course of study; and deprives the nation of the bene- 
 fit which they would derive from the ingenuity, and 
 industry of teachers, competing individually for public 
 favour. 
 
 The right of appointing teachers to national, and 
 endowed schools in general, must always be vested in 
 some patron, or patrons. And for every living, the 
 emoluments of which are higher than the wages ob- 
 tained by a common workman, there always will be 
 more than the requisite number of applicants. This 
 gives rise to an endless system of canvassing, and 
 various ways of exercising influence. From the im- 
 possibility of patrons serving every applicant, much 
 ill-will and opposition throughout society is excited j 
 
588 REVIEW OF 
 
 and teachers are frequently selected more in conse- 
 quence of influence exerted in their favour, than for 
 any merit which they themselves possess. All these 
 evils are avoided by having no national system of 
 education, no endowed schools, and no patrons but 
 the pubhc, for whose favour teachers ought to be 
 allowed freely to compete with each other upon equal 
 terms ; and be remunerated for their individual exer- 
 tions, and public usefulness, exclusively by those who 
 employ them. 
 
 That a national and endowed system of education 
 would be more expensive to the community, than one 
 of free competition among teachers, may be inferred 
 from the fact, that all government, as well as endowed 
 and chartered establishments, are uniformly conducted 
 with less economy, and with less advantage to the 
 public, than those which are set up for private benefit 
 upon principles of free competition. And the best 
 proof of this being the case is, that whenever the 
 trade is opened to the free competition of private in- 
 dividuals, the trade of the government or chartered 
 company falls to the ground. Besides, monopolies, 
 and chartered companies with exclusive trading privi- 
 leges, are ever observed to arrest improvement and in- 
 genuity in conducting mercantile affairs ; and become 
 means whereby the articles they supply are raised ex- 
 orbitantly in price to the consumer. 
 
 Again, seminaries established by law, are ever apt 
 to be erected in unsuitable localities for educating the 
 community at a cheap rate. The caprice, or the 
 private interest of a patron, or influential person, who 
 has ground to feu, may determine the site of the law- 
 
MR Owen's system. 589 
 
 established school, without regard to the accommoda- 
 tion of those who are to be educated. And it may be 
 here observed, that endowed seminaries, and charity 
 schools founded upon the bequests of benevolent 
 persons, are usually so inconveniently situated, that 
 they exhibit remarkable examples of the misapplica- 
 tion of the wealth and resources of a nation ; and in- 
 stead of affording cheap education to the poor, they 
 merely create sinecure births for lazy teachers. In 
 proof of these opinions we find nineteen munificently 
 endowed colleges at Oxford, the population of which 
 is less than 20,000. And in many rural districts, 
 such as at Dollar in Scotland, where there is a very 
 limited population to educate, we find an extensively 
 endowed seminary, the patronage of which is intrust- 
 ed exclusively to the minister and elders of the parish. 
 What would be thought of the policy of a law, re- 
 quiring that the whole produce of the soil, and the 
 manufactures of England, should be sent to Oxford 
 and Cambridge for sale ? And yet it would not be 
 more absurd, than that the youths of England should 
 require, at an extravagant expense, to be sent to 
 Oxford or Cambridge, in order to receive a college 
 education. 
 
 Again, the course of study in endowed schools, is 
 frequently any thing but what is useful to the pupils 
 in after life. Thus we find that one-half of the time 
 devoted for education by the present system, is spent 
 in studying the dead languages, Latin and Greek,* 
 a knowledge of which, since they ceased to be spoken, 
 
 * At Glasgow, the study of Latin occupies six years ; four 
 years in the Higli -school, and two in the college. 
 
590 REVIEW OF 
 
 and since all the works of any value in these languages 
 have been translated, is actually of no use to mankind. 
 
 But endowed schools, and such as are patronised 
 by magistrates and other municipal rulers, besides per- 
 petuating absurd courses of study, actually increase 
 the expense of education, and smother competition. 
 And instead of fostering education, have practically 
 the effect of counteracting and retarding it. Thus 
 in Glasgow, what is called the High-school, is patron- 
 ised, and the teachers are appointed, by the magis- 
 trates and council. A pension of £50 a-year to each 
 of the teachers, numerous premiums annually given 
 to the most deserving of the pupils, and school ac- 
 commodation, are all provided at the expense of the 
 town's funds. In this school, boys are taught Latin 
 for four years upon such a wretched principle, that at 
 the end of that time, they are unable to speak or write 
 the language ; and are even incapable of translating 
 a sentence out of a common Latin author, without 
 the aid of a dictionary ; while in the same time, and 
 with as little labour if properly directed, they might 
 master half a dozen of the living languages. 
 
 It might be supposed that endowing teachers out 
 of the public purse, would have a proportional effect 
 in reducing the fees exacted from the pupils. This, 
 however, is seldom or never the case. In fact, it is 
 generally the reverse. The fees in the High-school 
 above noticed, are 12^. 6d. for a quarter of a year's 
 instruction, — six weeks of a vacation annually being 
 charged at the same rate. It might be thought that 
 such high fees, would give rise to opposing schools, 
 supported upon independent principles by teachers 
 
MR OWEN*S SYSTEM. 591 
 
 themselves. But such is the baneful influence of the 
 patronage of local authorities, that the patronised 
 school becomes the fashionable one ; and is thereby 
 so much raised in public estimation, that it crushes, 
 and altogether prevents competition.* 
 
 In hke manner, granting to certain colleges, the 
 exclusive privilege of conferring licenses to practice 
 surgery and medicine, upon the production of tickets 
 certifying that a previous attendance of the prescribed 
 classes in these endowed colleges has been complied 
 with ; and also conferring upon such institutions, the 
 exclusive right of granting degrees, the possession of 
 which confers a higher rank, in respect to professional 
 knowledge, in the estimation of the public, destroys 
 all free competition in teaching. In consequence of 
 the monopoly thereby created, professors are enabled 
 to exact exorbitant fees from the students, in addition 
 to the annual income arising from college property 
 and grants from government, which is also divided 
 among the professors. Thus, in the college of Glas- 
 gow, a fee of three guineas is exacted from each 
 
 * Those who call themselves the Reformed Town Council, (by 
 way it is supposed of increasing their patronage,) have recently 
 appointed similarly endowed teachers, in other branches of educa- 
 tion, to this High-school. In reality, it is only the families of the 
 better classes of citizens, that can afford to receive instruction at 
 this seminary. And as the town's funds, which are intrusted by 
 law to the management of the town council, equally belong to all 
 citizens, the taking a portion of them to endow additional teachers 
 in this school, besides being a gross act of injustice to teachers 
 who compete for public favour upon independent principles, is 
 neither more nor less than I'obbing the poor, in order to teach the 
 families of the rich. 
 
69'2 REVIEW OF 
 
 student for two hours' instruction a-day, during six 
 months, in a numerously attended class ; when as 
 good instruction, provided no endowed colleges ex- 
 isted, would be afforded the public by the free com- 
 petition of teachers, for one-fifth, or possibly one- 
 tenth part of that sum. 
 
 That all should be educated is not of such essen- 
 tial importance to the happiness of society ; nor are 
 the advantages of education so much overlooked, as 
 to require that this commodity should be exclusively 
 provided for by law and taxation. Education becomes 
 of less value to each individual, according as the num- 
 ber educated is greater. And reasoning from the ac- 
 knowledged influence of free trade, in determining 
 the proper supply, and the true value, of every other 
 useful commodity, it may be inferred, that if educa- 
 tion were neither restrained, nor encouraged by law, 
 but left to free competition among teachers acting in- 
 dividually for their own advantage, it would be sup- 
 plied at the cheapest rate, and to the extent that is 
 most useful to the community at large. In the pre- 
 sent state of society, the supply of education, like that 
 of every other commodity, may safely be left to be 
 regulated by the demand. And free trade in teach- 
 ing, as in every other department of merchandise, is 
 that which invariably furnishes the best article at the 
 cheapest price. 
 
 If no endowed colleges or seminaries existed, we 
 should find schools erected, (just hke shops for the 
 sale of commodities,) in the most convenient locah- 
 ties for supplying education to the public. And in- 
 stead of indolent, careless, overpaid teachers, which 
 
MR Owen's system. 593 
 
 the system of patronage, endowments, and appoint- 
 ments for life create ; we should have industrious, 
 careful teachers, freely competing with each other for 
 pubhc favour, and remunerated according to their re- 
 spective degrees of usefulness. And, instead of slow 
 methods of communicating instruction, and absurd 
 courses of study being perpetuated ; the pubhc, act- 
 ing upon the mercantile principle, of purchasing the 
 best article at the cheapest price, would soon be 
 found to patronise only such teachers as were most 
 useful in accelerating education, and in communicat- 
 ing the greatest amount of valuable information in a 
 given time. Under such a system of free competi- 
 tion, instead of education being confined within the 
 walls of endowed and misplaced seminaries, (where 
 the fees, and the courses of study are seldom or never 
 altered, except disadvantageoiisly, so far as the public 
 interest is concerned,) it would be brought to every 
 man's door. And teachers, who are ever the best 
 judges of each other's merit, and whose mutual in- 
 terest creates the strongest stimulant to mutual ex- 
 ertion and confidence, would be found combining 
 with each other, with a view to afford valuable courses 
 of instruction. And where the poverty of certain dis- 
 tricts rendered cheapness of essential importance, the 
 same room or hall, would be found as well fitted for 
 giving instruction in every department of science, as 
 separate halls for each department. Under such a 
 free trade system, the teaching of dead languages, 
 for want of pupils, would soon cease ; and courses 
 of study, in exact proportion as they were found 
 
 4f 
 
594 REVIEW OF 
 
 useful in after life, would be patronised by, and sup- 
 plied to the public* 
 
 To tax the community, or burden the land, in 
 order to endow churches, and support an estabhshed 
 
 * Notwithstanding the obvious nature of the observations in 
 the text above, Lord Brougham has recently proposed a series of 
 resolutions in the House of Lords, explanatory of his vievi's relative 
 to the establishment of a national system of education. In his 
 speech introductory to the resolutions, he shows how apt funds 
 bequeathed for charitable purposes, [are to be wasted and mis- 
 applied ; and how inefficacious bequests for educating the poor, 
 have usually been for accomplishing the objects which the testators 
 had in view. " I would just refer," says Lord Brougham, " to a 
 few instances, in order to show what large sums of money were 
 squandered much worse than uselessly, in the distribution of the 
 funds of several endowed schools. The funds for endowed schools 
 in Middlesex, were, in 1819, £31,000 a-year, and the number of 
 children educated at them did not exceed 2,260. The funds for 
 a similar purpose in London, amounted to £84,000 a-year, and the 
 number of children was not more than 1,630. In St Paul's, (a 
 day school,) the regular charge for each pupil was from £15 to 
 £20, besides other items, which made it amount to a larger sum." 
 In June, 1835, Mr D. W. Harvey made a motion in the House of 
 Commons, for the appointment of a select committee to inquire 
 into the state of the public charities in England and Wales. He 
 stated " that a previous commission, appointed for a similar pur- 
 pose, had produced twenty-four reports, averaging each 800 pages, 
 without any beneficial consequence resulting." He farther men- 
 tioned, " that by returns of the money which had been actually 
 advanced by the Treasury, it appeared that the expense of that 
 commission had not been less than £210,000; and taking the 
 printing, &c. into account, it might be said, in round numbers, 
 that the commission had cost the country £250,000." He adds: 
 " So great was the mismanagement, and, above all, the profligate 
 plunder of the property belonging to the poor, as testified in these 
 reports, that it presented a monument of the incapacity of our 
 
MR Owen's system. ,595 
 
 religion, is at least as objectionable and impolitic, as 
 it is to tax the community for the support of a na- 
 tional system of education ; and the objections to the 
 one, are in general applicable to the other. Religion 
 
 courts to do them justice." The information communicated in 
 the speeches of Lord Brougham and Mr D. W. Harvey demon- 
 strates, that property set aside, or bequeathed for any special pur- 
 pose, has a natural tendency to beget corrupt patronage, fraud, 
 and plunder, in its application. When this circumstance is con- 
 sidered, in conjunction with the trouble and expense of collecting 
 school-rates ; and of supporting commissions for looking after the 
 funds, keeping teachers at their duty, and preventing the patronage 
 created from becoming a political engine for party purposes, (which 
 are all avoided and rendered unnecessary by the free trade plan;) 
 it may be inferred, that the establishment of a national system of 
 education, and the endowment of schools in general, besides pro- 
 ducing other evils, would saddle the country with a source of po- 
 litical discord, and a load of unnecessary taxation. And there is 
 little doubt, but that it would ultimately tend to impoverish the 
 nation, by causing education to absorb a much larger proportion 
 of the produce of land and labour, than it would do if left to volun- 
 tary teachers, competing freely with each other, and acting sever- 
 ally for their own individual advantage. 
 
 Lord Brougham admits that the education of the people by 
 means of unendowed schools, is rapidly extending ; and he speaks 
 as if he thought, that the voluntary schools set up merely for pri- 
 vate advantage, and which have already done so much for educa- 
 tion, should not be inconsiderately interfered with. Notwithstand- 
 ing, in his national system, he goes the length of proposing, that 
 what he calls Normal schools for teaching teachers, should be sup- 
 ported at the public expense ; and of course, that additional taxa- 
 tion in some form or other should be imposed for that purpose. 
 The art of teaching is not more difficult to learn, than that of other 
 trades for the supply of the necessaries and luxuries of life. It is 
 likewise equally susceptible of improvement. But improvement in 
 the art of teaching is certainly more likely to go on under a free 
 
596 REVIEW OF 
 
 is a matter between God and man, with which human 
 laws, having for their object the security of personal 
 rights and property, have nothing to do whatever. 
 Mankind are at the expense of supporting govern- 
 ments for the purpose, not of deteriorating, but of 
 ameliorating their condition ; for the purpose, not of 
 diminishing their natural rights, which entitle each in- 
 dividual to pursue his own happiness according as his 
 reason directs, so long as he does not encroach upon 
 the rights of his neighbour, but in order that those na- 
 tural privileges may be better secured. Every man 
 has by nature the right of examining the evidence 
 upon which any religion is founded ; and of express- 
 ing his opinion thereupon, either in speech or writ- 
 system, which permits teachers to exercise their own judgment and 
 ingenuity in the matter ; and where, from increased public patron- 
 age, they may expect to be remunerated for their ingenuity and 
 skill ; than under a national system of education, which supposes 
 the adherence to one uniform plan, and gives no encouragement 
 to ingenuity and attentive zeal on the part of teachers. To pro- 
 vide pi'oper food, clothing, and house accommodation, is of in- 
 finitely greater importance to the comfort and happiness of man- 
 kind, than to provide education. But what would be thought of 
 a proposal to establish schools at the public expense, for teaching 
 farmers to cultivate the soil ; others for teaching bakers to bake 
 bread ; and others for teaching brewers to make malt liquors ? 
 And what would be thought of a proposal to tax the community 
 for the support of schools, to teach manufacturers to make cloths 
 of different descriptions ; and tailors and milliners, how to fashion 
 them into suitable habiliments for human beings to wear? Or 
 what would Lord Brougham think of a proposal to tax the com- 
 munity, or burden the land, for the support of schools to teach 
 clergymen sound doctrine; and, which in the opinion of many is 
 paramount to all other considerations, the proper method of com- 
 municating religious instruction to the people? 
 
MR Owen's system. 597 
 
 ing. And every man has also the right of worship- 
 ping his Creator, according to the form which he 
 thinks most acceptable. The existence of an estab- 
 lished church supported at the pubHc expense, is at 
 variance with these rights. To tax a man for the 
 support of a religion in which he does not believe, is 
 a gross act of injustice ; and to tax one sect of 
 Christians for the support of a particular form of wor- 
 ship from which they dissent, is equally unjust. 
 Church property, as well as all public property, be- 
 longs equally to all members of the community ; and 
 any partial application of such property for the bene- 
 fit of a particular class of the community, is an act of 
 injustice towards all the other classes. In short, it 
 would not be more unfair to build the dwelling-houses 
 of only one sect at the public expense, than it is to 
 build, or endow the churches of only one sect at the 
 public expense. 
 
 Nor is the majority of a community, or the govern- 
 ment acting by their authority, entitled to tax a dis- 
 senting minority to support an established church. 
 They have a right to enforce universal submission 
 only to such laws, as would be rendered nugatory, if 
 a dissenting minority were permitted to resist. But 
 no majority of a community are entitled to force uni- 
 versal compliance with laws, where the preservation 
 of their rights, does not require such comphance. It 
 is obvious that the majority of a community, or the 
 government appointed by them, are entitled to force 
 universal compliance with criminal laws ; for if a dis- 
 senting minority were allowed to violate them with 
 impunity, the rights of the majority, by whose author- 
 
598 REVIEW OF 
 
 ity such laws were made, could not be thereby pro- 
 tected. It is different however with the religious 
 rights of mankind. In this particular, the natural 
 rights of all may be perfectly maintained, without the 
 compliance of one party with the will of another. | 
 Both the majority and the minority can enjoy their 
 respective religions, and practise their own forms of 
 worship, without in the least degree invading the 
 rights of each other. And therefore, in accordance 
 with the equitable principle of every man paying only 
 for what he himself uses, or gains some advantage 
 from, no majority of the community however great, 
 nor any government acting by their authority, have a 
 right directly or indirectly to tax any minority how- 
 ever small, for the support of any church or form of 
 worship, from which they dissent. 
 
 One of the arguments advanced by the advocates 
 of church establishments, is, that an established 
 church acts like a cheap police in maintaining order 
 in society. Such an ill-founded argument hardly 
 deserves an answer. Religion supported upon equit- 
 able voluntary principles, always contributes to main- 
 tain order. But law-established religion, besides be- 
 ing inimical to public liberty, has frequently been a 
 cause of wars and massacres, and of every degree of 
 persecution and intolerance. Even at present in our 
 own country, where the liberality and good sense of 
 the mass of the people enforce toleration, (for it 
 unfortunately appears to be the fact, that clergy as a 
 body, are always more or less disposed to be intolerant 
 if they have the power,) law-established religion, which 
 supposes the injustice of taxing the whole, for the 
 
MR Owen's system. 599 
 
 benefit of only a portion of the community, creates, 
 and ever will create, discord and animosity through- 
 out society. And the estabhshed church of Ireland, 
 instead of being a cheap substitute for a police, is 
 not only a most expensive burden itself, but renders 
 a strong police, and the presence of a standing army 
 absolutely necessary, in order to keep down the ten- 
 dency to tumult and insurrection, which its existence 
 creates. 
 
 Another argument in favour of church establish- 
 ments, is, that their existence is necessary for the 
 support of religion. Those who advance this opinion 
 may be reminded, that Christianity originally took 
 root, and spread, without being supported by law, 
 or established churches. In the United States of 
 America, religion flourishes without the assistance of 
 a church establishment, and seems to exert a salutary 
 influence upon the moral happiness of mankind, 
 totally free from every disadvantage. This is the 
 natural result of religion left to grow, and spread of 
 itself, without the aid of government, and church 
 establishments. In that country, where a nation is 
 presented rising to wealth and greatness, with a rapid- 
 ity unexampled in ancient or modern history, the 
 Protestant and the Catholic, and all other sectarians, 
 live in perfect harmony with each other. It is be- 
 cause there is no established religion, and no favour- 
 ed sect. There the law recognises no man in his 
 religious capacity ; and each sect, at their own ex- 
 pense, build and support their own churches j and 
 without molestation enjoy their own religion, and 
 practise their own form of worship, without being 
 
600 REVIEW OF 
 
 taxed directly or indirectly for the support of any 
 other.* 
 
 To man, but to none of the inferior races of ani- 
 mals, is the foreknowledge given, that existence in 
 this world must soon terminate. But man revoltsjat 
 the prospect of annihilation, and desires to perpetuate 
 his existence. This desire, co-operating with the 
 prospect of mortality, has gained a ready and willing 
 belief, for all the various religions that have appeared 
 on earth ; and which severally hold out the prospect 
 of eternal hfe and happiness, upon conditions favour- 
 able to morality. And such is the influence of pre- 
 conceived opinions, and such the prejudice in favour 
 of believing, and practising, that which we have been 
 accustomed without examination to consider true, and 
 
 * It is worthy of being remarked, that though the population 
 of the United States be composed of persons, or the descendants 
 of persons, originally professing all different religions, and belong- 
 ing to every different sect ; the different creeds and forms of wor- 
 ship of the mass of the people, are gradually assimilating to the 
 Presbyterian form established in Scotland, with the difference of 
 being unconnected with the state, and freed from patronage. From 
 a recent survey it also appears, that in Ireland, the Presbyterians, 
 who, in that country, are a dissenting body, are increasing in a 
 much more rapid ratio than the Catholics ; while the number of 
 Episcopalians, notwithstanding their being supported by an enor- 
 mously endowed church establishment, seems to remain almost 
 stationary. From these facts it may be inferred, that the Presby- 
 terian form of Christianity, on account perhaps of its being the 
 simplest, and cheapest of all religious forms of worship ; and like- 
 wise from its being the freest from superstitious reverence, and 
 empty mummery, is that which would spread itself over Great 
 Britain and Ireland, were it not for the existence of endowed 
 church establishments. 
 
MR owen's system. 601 
 
 best, that the rehgion of the mass of the people, in 
 every age and nation, is the same as that of their fore- 
 fathers. Our rehgious faith is therefore in a great 
 measure determined by the place of our nativity, a 
 circumstance over which we have no control. Hav- 
 ing been born and brought up in Britain, a Christian 
 country, we are Christians. But had we been born 
 in Turkey, we would have been followers of Maho- 
 met. 
 
 Birth and education determine not only the parti- 
 cular religion which we profess, but even, though not 
 so certainly, the peculiar sect with which we ever af- 
 terwards remain connected. Thus, the mass of those 
 who are born and brought up among Cathohcs, re- 
 main Catholics ; and those who are born and brought 
 up among Protestants, remain Protestants. In like 
 manner, those who are born and brought up, whether 
 among Methodists, Quakers, Seceders, Presbyterians, 
 or Episcopalians, for the most part remain ever after- 
 wards, attached to the faith, and form of worship in 
 which they have been bred. 
 
 These facts ought to teach us to exercise unlimited 
 toleration, towards those who diflfer from us in religi- 
 ous behef ; and show how presumptuous it is in us to 
 declare the religion of our neighbour untrue, or his 
 form of worship unacceptable to his Creator, because 
 ours happens to be different. Had our birth and edu- 
 cation been the same as that of our neighbour, and 
 our neighbour's the same as ours, the creeds which 
 we severally and exclusively believe, and the forms of 
 worship to which we are severally attached, would 
 have been reversed. No man is responsible for the 
 
 4g 
 
002 REVIEW OF 
 
 belief, or form of worship of another ; and therefore, 
 no man is entitled to use coercive measures, in order 
 to make his own practice in these particulars, a rule 
 for others. While we severally maintain the right of 
 exercising our own judgment upon religious subjects, 
 and of practising any form of worship which we ap- 
 prove; let us at the same time be sure, that in thought, 
 word, and deed, we grant to our neighbour, the same 
 right which we claim for ourselves ; and thus obey the 
 greatest of all moral precepts, " Do unto others as 
 you wish to be done by." If governments would 
 merely confine themselves to protecting all sects in 
 the exercise of their own pecuhar forms of worship, 
 and prevent one from encroaching on the rights of 
 another, we may rest assured, that religion will serve 
 all the wise and benevolent purposes for which its in- 
 troduction on earth was intended. And no sincere 
 Christian will ever believe that those principles in hu- 
 man nature, which, without almost any thing approach- 
 ing to evidence, have gained credit for the grossest 
 and most improbable superstitious notions that hu- 
 man ingenuity could devise, are not sufficiently power- 
 ful to perpetuate the religious faith in which he be- 
 lieves. 
 
 Besides the injustice of church estabUshments, and 
 the ill-will and disturbance in society which their ex- 
 istence creates, they are objectionable in consequence 
 of being more expensive than voluntary churches, re- 
 lative to the amount of religious instruction which 
 they afford; and hence, by absorbing an unnecessarily 
 large proportion of the resources of a nation, they 
 tend to lower the average condition of the people. 
 
MR Owen's system. 603 
 
 In Ireland, we have a renniarkable instance of the 
 wasteful expenditure of the public money, in support- 
 ing an established church. About £3,000,000 an- 
 nually are set aside for the support of this useless 
 establishment, while, by the recent report of the com- 
 missioners to parliament, the number of Episcopalians, 
 including men, women, and children, therefrom re- 
 ceiving religious instruction, is only 853,000. Nor 
 is it any answer to this objection, that a large propor- 
 tion of the funds for supporting church establishments, 
 consists partly of property bequeathed in perpetuity 
 by religious persons ; and partly of a portion of the 
 rent of land, called tithes, set aside by law in ancient 
 times for that purpose, and which now has no proper 
 owner but the church. The wealth of a community 
 consists of the produce of land and labour ; and its 
 sum total in any given country, without deviating far 
 from the truth, may be valued at a certain annual 
 amount. Now, if a larger proportion of this produce 
 of land and labour be permanently set aside in order 
 to support a church establishment, than what would 
 provide an equal amount of religious instruction, to 
 the same portion of the population by means of vo- 
 luntary churches, the community are to that extent 
 impoverished. The larger the proportion of the pro- 
 duce of land and labour annually set aside for the sup- 
 port of religion is, the smaller must be the propor- 
 tions set aside for supplying the other wants of man- 
 kind. 
 
 Discontent never results from permitting every in- 
 dividual to act according to his own will, so long as he 
 does not encroach upon the rights of others. And 
 
(104 REVIEW OF 
 
 general contentment is more likely to result from laws 
 and institutions, which allow every man to spend his 
 income how and where he chooses, and with as little 
 diminution in the form of taxation as possible ; than 
 from such as deprive him of what he considers an un- 
 necessarily large proportion of his income in the shape 
 of taxes, and especially if the revenue therefrom ac- 
 cruing be applied partly, or principally, to purposes 
 from which he receives no gratification, and derives 
 no benefit. The public are ever the best judges of 
 their own wants, and if left to themselves, will make 
 provision for them upon the principle, both with re- 
 spect to cost and quality, which is most satisfactory to 
 themselves. Now, religious instruction, and places 
 adapted for worship, are desires which the pubhc wish 
 to gratify. And, as the tastes and notions of indi- 
 viduals vary with regard to the value of the various 
 necessaries, luxuries, and enjoyments of life ; so do 
 they vary with regard to the value of church accom- 
 modation, and the kind of religious instruction. Each 
 individual has a natural right to spend his income ac- 
 cording to his own taste. And hence, it would not 
 be a more unjust and impohtic infringement upon the 
 natural privileges of mankind, nor a more tyrannical 
 and uncalled for usurpation of the individual rights of 
 a people, for government to determine what propor- 
 tion of income each man should set aside for purchas- 
 ing the different kinds of food and clothing ; and 
 what other proportions, for travelling expenses, house 
 accommodation, and medical attendance ; than it is 
 for government to determine what proportion of the 
 income of individuals, or, (which is a concealed 
 
MR Owen's system. 605 
 
 method of doing the same thing,) to determine what 
 proportion of the aggregate income of the community, 
 should be set aside for the purpose of providing either 
 education, or rehgious instruction to the people. 
 
 The right of entailing lands, or of bequeathing pro- 
 perty in perpetuity, whether for the purpose of en- 
 dowing churches or seminaries, or supporting charit- 
 able institutions, besides being disadvantageous in 
 various other respects, tends to lower the average 
 condition of the community. Every man should have 
 the fullest right of giving away his property during 
 his Hfe, or of bequeathing it at his death, to whomso- 
 ever he chooses. But to fix the application of pro- 
 perty in all time coming, is an infringement upon the 
 rights of posterity. If all the lands in the country 
 were entailed, and these entails could not be broken, 
 the whole population, with the exception of the heirs 
 to such entails, would be thereby deprived of all right 
 to hold property in land. Now as the land constitutes 
 a large proportion of the whole property in the coun- 
 try ; and as individual wealth consists in being pos- 
 sessed of a portion of the property in the country ; 
 the difficulty of acquiring wealth, or even of gaining 
 more than an average livelihood, bv means of indus- 
 try, economy, and good management, increases, ac- 
 cording as the proportion of land and other property 
 held in entail, becomes greater. In like manner, 
 the greater the amount of property bequeathed in 
 perpetuity, or set aside by law, for the support of 
 churches, schools, or charitable institutions, the less 
 can be held by, and be at the disposal of private in- 
 dividuals, and of course the greater is the difficulty of 
 
606 REVIEW OF 
 
 acquiring wealth, or of gaining more than an average 
 livehhood, by the exercise of economy, and welLdi- 
 rected industry. 
 
 It has been already stated, that the desire of rising 
 in the world increases, like every other, with the facil- 
 ity and the more immediate prospect of gratification. 
 Hence whatever diminishes a man's chance of rising 
 in the world, whether it be entails, bequests in per- 
 petuity, heavy taxation, or any other cause, is unfa- 
 vourable to the exercise of prudential habits in con- 
 tracting marriages, and therefore tends to deteriorate 
 the average condition of a people. 
 
 Abstractly considered, there is something ridiculous 
 in the existence of hereditary owners of land, who, as 
 if they were fatuous persons, are deprived of the right 
 of selhng, or otherwise disposing of their property. 
 And as neither virtue, wisdom, nor the possession of 
 knowledge, are hereditary, to defend the right of en- 
 tailing property, upon the principle, that it is neces- 
 sary in order to support a hereditary peerage, and a 
 hereditary legislative body, is something like saying, 
 that one absurdity requires to be supported in order 
 to perpetuate another. When it is considered that a 
 large proportion of the hereditary peerage, and other 
 owners of entailed estates, notwithstanding their im- 
 mense annual revenues, are deep in debt ; and that 
 it is chiefly through their influence, and for the pur- 
 pose of providing for the junior branches of their fa- 
 mihes, that the country continues to be burdened 
 with expensive church, and military, and naval estab- 
 lishments, the absurdity of permitting entails and 
 their natural concomitants to exist, becomes apparent. 
 
MR Owen's system. 607 
 
 An elective peerage kept up to a certain fixed num- 
 ber, and appointed by tiie king with the consent of 
 his ministers, and liable to be denuded of nobility 
 only upon ceasing to be able to pay their debts, is in 
 theory, and would be found in practice, greatly su- 
 perior as a legislative body, to one that is hereditary. 
 Such a nobility might be expected to set a good ex- 
 ample to their inferiors in rank ; and none of those 
 unseemly spectacles, which the present state of the 
 law produces, viz., noblemen with immense incomes 
 running into debt, and in the character of legally 
 protected swindlers defrauding honest tradesmen of 
 payment of their accounts, would be presented. The 
 natural rights of every generation are the same ; and 
 no laws ought to be allowed to exist, which in the 
 slightest degree infringe upon the rights of posterity. 
 Laws and institutions which afford the greatest facility 
 to the acquirement of wealth and property, not only 
 encourage the exercise of prudential habits in con- 
 tracting marriages, but by promoting industry and 
 economy, increase both the aggregate, and the average 
 individual wealth of a nation. In order that each in- 
 dividual should possess his just right of acquiring 
 wealth, and of being fully recompensed for his in- 
 dustry and ingenuity, it is necessary that every one 
 should possess the uncontrolled privilege of spending 
 his property, and that no right of entailing or be- 
 queathing property in perpetuity should be permitted. 
 If such were the case, the ultimate consequence would 
 be, that the middle classes of society, which are both 
 the happiest, and the most moral portion of the popu- 
 lation, would be greatly increased in numbers ; and 
 
008 REVIEW OF 
 
 property would never accumulate in the hands of 
 single individuals to such a monstrous extent, nor be 
 so apt to get into the possession of unworthy persons, 
 as under the present laws. Upon this point I will 
 only add, that instead of being an injury, I conceive 
 it would be a public benefit, not only that the right of 
 entailing property should cease, but that all property 
 bequeathed in perpetuity, as well as all church pro- 
 perty upon the death of incumbents, and which of 
 course belongs to no living individual, should be se- 
 questrated, and applied to defray the expenses of go- 
 vernment. 
 
 Unnecessarily heavy taxation, whereby the people 
 are robbed of a portion of their income, is another 
 means by which the difficulty of acquiring wealth, or 
 of gaining more than an average livelihood is in- 
 creased ; and which, by discouraging the exercise of 
 prudential habits, deteriorates the average condition 
 of society. It is the natural right of every man to 
 enjoy the fruits of his industry, with the least possible 
 diminution in the shape of taxation, consistent with 
 the support of good government, and an effective ad- 
 ministration of the laws. Hence, that form of govern- 
 ment, and that code of laws, are the best, which at 
 the least expense, afford the greatest security to per- 
 sons and property.* 
 
 * Representative forms of government, the members of which 
 are elected by ballot, with publicity given to all their procedure, 
 afford the best practical security, that economical management 
 will be adhered to, and that the public money will not be misap- 
 plied. In addition, however, to these precautions, it is advisable, 
 that those who have charge of the public funds and the patronage 
 
MR Owen's system. 609 
 
 National debts, which render heavy taxation neces- 
 sary in order to pay the interest of them, are palpable 
 infringements upon the rights of posterity. Borrow- 
 ing money and converting it into a transferable stock, 
 bearing interest, and using it for government pur- 
 poses, is neither more nor less, than one generation 
 borrowing and spending money, and leaving those 
 that succeed to pay the interest thereof, or the prin- 
 cipal, according as they find it convenient. The rea- 
 son assigned in defence of this conduct immediately 
 subsequent to the Revolution in 1688, when the debt 
 of Great Britain commenced, was, that the wars aris- 
 ing out of the Revolution were carried on as much 
 for the benefit of succeeding generations, as for that 
 which then existed ; and it was therefore supposed 
 to be fair, that succeeding generations should pay part 
 of the expense. A similar argument can be brought 
 forward in defence of contracting debt during every 
 war. Succeeding generations may be supposed to 
 be benefited by their ancestors resisting aggression 
 and invasion. All such arguments, however, are evi- 
 dently absurd and unjust. Are succeeding genera- 
 tions to be burdened and incapacitated from defend- 
 ing themselves by being encumbered with the debts 
 of their ancestors ? Is the industry of their labour to 
 be thus mortgaged ? Or are they bound, upon any 
 
 in burghs, should not be permitted to remain too long in office, — 
 a circumstance which is uniformly observed to have a corrupting 
 influence. This is best provided against by a burgh constitution, 
 which prohibits town-councillors from being elected to serve for 
 more than three j^ears at a time ; and, upon going out of office in 
 rotation, from being eligible for at least a corresponding period. 
 
 4h 
 
010 REVIEW OF 
 
 principle of justice, to pay the taxes and war expenses 
 of previous generations as well as their own ? Cer- 
 tainly not. The natural rights of every generation 
 are the same ; and in order thereto, each generation 
 ought to be as unincumbered with debt as that which 
 preceded it. The son is not bound for the debts of 
 his father, or of his grandfather, when they happen to 
 die without leaving property to pay their debts ; and 
 yet he might have been benefited by some specula- 
 tion of theirs, had it succeeded. If the descendants 
 were responsible for the debts of their ancestors, the 
 produce of our labour might not have belonged to us. 
 And a profligate parent, instead of supporting his fa- 
 mily, might live at their expense before they were 
 born. Upon the same principle, the government ex- 
 penses of one generation might be thrown upon the 
 next. No taxes might be raised at all. One loan 
 after another might be contracted for, to pay the in- 
 terest of what had been previously borrowed, and to 
 defray all the current expenses of government. 
 
 From these observations, it is evidently a settled 
 point, that can stand neither examination nor discus- 
 sion, that a nation is under no obligation whatever, 
 except as a matter of expediency, to pay either the 
 principal, or the interest of debt, contracted before 
 their time. The only principle upon which govern- 
 ments have any right, on a pressing emergency, (such 
 as the unexpected breaking out of war,) to contract 
 debt, is that of annuities terminable in thirty, or at 
 most in forty years, which would throw the burden of 
 payment, upon what may be called the generation 
 that contracted it. 
 
MR OWEN*S SYSTEM. 611 
 
 As the sudden cancelling of the national debt would 
 occasion almost universal bankruptcy, and much in- 
 dividual suffering, chiefly among the mercantile classes, 
 vi'ho had very little to say in its contraction ; it might 
 be expedient, that individual holders of stock should 
 be paid in full. But all stock held by corporations, 
 and other public bodies, and all investments in stock 
 for the support of public institutions, (the sum total 
 of which is supposed to include three-fourths of the 
 debt,) should be immediately cancelled. And if any 
 private property is to be made available for the pay- 
 ment of the portion of the debt held by private in- 
 dividuals, it ought certainly to be the entailed estates 
 of the nobihty upon the demise of present incum- 
 bents, and of those whose ancestors had a share in 
 the management of national affairs, during the period 
 when the debt was contracted.* 
 
 * It has been suggested, and in all probability correctly, that if 
 government were to pass an act, declaratory of the illegality of 
 contracting for future loans, on any other principle than that of 
 terminable annuities ; and were at the same time to impose taxes, 
 estimated to raise an annual revenue of £5,000,000, to be applied 
 exclusively and inviolably in all time coming to the liquidation of 
 the national debt ; the additional security thereby given to funded 
 property, and the amount of capital thereby thrown into the mar- 
 ket, would, in the course of two years, so lower the common rate 
 of interest, and, in particular, the rate at which government could 
 borrow, that the whole of the three per cent, consols might be 
 converted into a stock bearing interest of two per cent. This, in 
 reality, would reduce the interest of the debt nine millions annually, 
 viz., from £27,000,000 to £18,000,000. It is obvious that the 
 adoption of such a measure would cause stocks to rise rapidly. 
 And it is certainly proper that the country, and not the fund- 
 holders, should get the benefit thereof. If, therefore, such a mea- 
 
61*2 REVIEW OF 
 
 As the population in any country is regulated, much 
 more by the amount of food which the wages of the 
 mass of the people can command, than by the amount 
 of the other necessaries and luxuries of life, every im- 
 provement in machinery, by which the amount of 
 manufactures with the same labour is increased, and 
 by which their price relative to that of food is reduc- 
 ed, augments the aggregate wealth of the nation, and 
 raises the average condition of the people. Though 
 improvements in machinery may, for a time, deterior- 
 ate the condition of the labourers thereby thrown out of 
 employment, even their condition, so soon as they 
 have got into other avocations, is improved as much 
 as that of the other members of the community. 
 While the average condition of a people in reference 
 to the quantity of food they can severally command, 
 remains unchanged by improvements in machinery ; 
 in relation to the amount of the other necessaries and 
 luxuries of life thereby reduced in price, it is amelior- 
 ated. Hence the reason, that the average condition 
 of a labouring man in a civilized country, where 
 human industry and manufacturing skill are assisted 
 by machinery, is superior to that of a chief of a savage 
 tribe. The former by means of his wages can com- 
 mand as much food as the latter ; and a much greater 
 amount of all the other comforts, conveniences, and 
 luxuries of life. 
 
 In like manner, by assimilating and adopting de- 
 
 sure were adopted, it ought to be simultaneously enacted, that 
 government should be entitled to pay off the debt at the price of 
 stocks on the day on which the measure was first proposed in 
 parliament. 
 
MR owen's system. 613 
 
 cimal divisions as far as possible for weights, measures, 
 and coins, throughout the kingdom ; and even by 
 extending the assimilation, by arrangements for that 
 purpose with the governments of other countries, with 
 which we carry on commercial intercourse ; the labour 
 of supplying ourselves with the necessaries and luxu- 
 ries of life, whether produced at home or abroad, 
 would be diminished. Hence the wealth of the na- 
 tion would be thereby increased, and the average 
 condition of the people raised, just as it is by im- 
 provements in machinery. 
 
 Upon similar principles, every improvement in our 
 civil institutions, whereby a smaller number of persons 
 can perform all the work, in any particular depart- 
 ment, that is required, operates like improvements 
 in machinery, in increasing the amount of useful arti- 
 cles produced relative to the population ; and accord- 
 ingly raises the average condition of a people. Thus 
 by arranging, simplifying, and improving our code of 
 laws, and by assimilating them throughout the king- 
 dom, instead of having different laws, and different 
 sets of law-functionaries for England, Scotland, and 
 Ireland, a smaller number of lawyers would suffice for 
 all the business required of them. In like manner, 
 passports, and alien laws, which place foreigners on a 
 different footing from natives, should be for ever abol- 
 ished ; and Britain ought to set the example to other 
 countries. Such institutions and regulations, are 
 but relics of ignorance and despotism. They give 
 rise to fees and perquisites, which support a class of 
 persons, whose business, instead of being of any use 
 to mankind, merely obstructs commercial intercourse, 
 
614 REVIEW OF 
 
 and occasions unnecessary expense, trouble, and waste 
 of time to travellers. Of course, the superfluous hands 
 thrown idle by such and similar reformations, in order 
 to support themselves, would have to direct their at- 
 tention to the production of articles useful to man- 
 kind. Hence the average condition of the people 
 would be raised, by a greater amount of useful articles, 
 relative to the population, being thereby produced ; 
 and which, in reference to the price of food, would be 
 sold, or divided amongst them at a lower rate. 
 
 In like manner, war, independent of the additional 
 taxation necessary for its support, deteriorates the 
 average condition of a people, according as it with- 
 draws a greater or less proportion of the labouring 
 classes from productive avocations, to such as yield 
 nothing useful to mankind. When it first breaks out, 
 a demand for labourers, which raises the price of la- 
 bour, and of all articles thereby produced, takes place. 
 But though the condition of the labouring classes, as 
 well as that of those who hold stocks of manufactured 
 goods thereby raised in price, may at first be apparent- 
 ly improved, this effect is merely temporary ; and re- 
 sults only when the war happens to be with a nation 
 with whom we carry on so little trade, that the num- 
 ber of labourers thrown idle by the suspension of 
 commercial intercourse with them, is less than those 
 that receive employment in avocations connected with 
 the support of war. Though the trade of certain 
 places, and the condition of certain classes of artificers, 
 may during its continuance be somewhat improved ; 
 the trade of other places, and of other classes of la- 
 bourers, is more than proportionally injured. Upon 
 
MR OWEN*S SYSTEM. 615 
 
 the whole, its effects are decidedly prejudicial. It di- 
 minishes the aggregate production of useful articles 
 relative to the population ; and in proportion as it 
 does so, it lessens their aggregate wealth, and dete- 
 riorates their average condition. 
 
 Peace, on the other hand, independent of the bene- 
 fit resulting from the reduction of taxation which it 
 permits, is favourable to national wealth, and individ- 
 ual prosperity. The transition from a state of war to 
 that of peace, operates much in the same manner as 
 improvements in machinery. The number of labour- 
 ers thereby turned from the unproductive avocations 
 of war, to the productive departments of manufactur- 
 ing industry, lowers wages, and the price of all manu- 
 factured goods. But though the condition of the 
 labouring classes, and of those who hold stocks of 
 manufactured goods, may at first be thereby injured ; 
 still as its effect is to increase the aggregate produc- 
 tion of useful articles, relative to the population, it 
 ultimately increases the aggregate wealth, and raises 
 the average condition of a people. 
 
 Discriminating duties upon foreign articles, accord- 
 ing as they are imported in foreign or British ships, 
 is a contemptible device for favouring the home ship- 
 ping interest, which foreign governments can easily 
 see through, and easily counteract. The result of 
 such a selfish policy when met by counteractives, is, 
 that vessels can only get a cargo in one direction : 
 they sail to foreign ports empty, with the chance of 
 getting a cargo home. This, by requiring a greater 
 number of seamen, and of ships, to do the same 
 amount of work, increases the freight j and conse- 
 
616 REVIEW OF 
 
 quently injures the condition of both nations, by rais- 
 ing the prices of the articles which they severally im- 
 port. For the benefit of all nations who carry on 
 commercial intercourse with each other, a reciprocal 
 understanding should exist, that all ships, with their 
 cargoes, should be permitted to enter ports, and to 
 load and unload, on a footing of perfect equality, with- 
 out regard to where they were built, or where their 
 owners reside, or whether navigated by natives or 
 foreigners. 
 
 As free competition is that which invariably pro- 
 duces the best article at the cheapest price, monopo- 
 lies, and exclusive trading privileges of every kind, 
 should be abolished. Our tastes are different ; and 
 each individual is the proper judge of what he wishes 
 to purchase for his own use. Of course, when two 
 articles are offered for sale at the same price, a man's 
 condition is certainly better, (and a similar remark is 
 applicable to the condition of a nation,) when he is 
 permitted to purchase the article which he hkes best, 
 without regard to where he gets it, than if he was pre- 
 vented by retaliatory prohibitions, or discriminating 
 duties, from so doing. Hence, free trade, which is 
 the means of supplying both the individual, and the 
 aggregate wants of a nation at the cheapest price, 
 should be permitted to the fullest extent, without 
 regard to the restrictions of foreign countries, which 
 we cannot, and should never attempt to control. 
 
 To the preceding rule there is one exception, and 
 it is of a temporary nature. When a country is 
 supplied from abroad with a particular species of 
 goods, (for example with cotton goods,) which it 
 
MR Owen's system. 617 
 
 possesses every local advantage for manufacturing 
 within itself, that the country from whence it is sup- 
 plied enjoys ; it is good policy to encourage the 
 establishment of such manufacture at home. Ow- 
 ing, however, to the want of knowledge, and facilities 
 for manufacturing, the cost of producing an article 
 is greater at first, (its quahty being taken into ac- 
 count,) than ever afterwards ; and this, in most cases, 
 prevents the establishment of such manufactures. 
 Now, the only means whereby this disadvantage can 
 be overcome, is either to prohibit the importation of 
 the same article from abroad, (which is the policy at 
 present adopted by France towards us, in reference to 
 cotton manufactures,) or to protect the home manu- 
 facturer by such a high duty on the foreign article, as 
 enables him to compete profitably in the home mar- 
 ket, with the foreign manufacturer. By such policy, 
 a permanent saving is gained, for a temporary loss. 
 When the manufacture is fully established, and the 
 requisite skill acquired, ail prohibitions and protecting 
 duties may cease ; for the country will then, and ever 
 afterwards, supply itself at a cheaper rate than it can 
 be supplied by the foreign country. This result 
 arises from the saving of expense that necessarily 
 attends the freight, carriage, insurance, and agency 
 commissions, unavoidable in the transportation of 
 goods from one country to another. 
 
 In countries merely or chiefly agricultural, and 
 which labour under no local disadvantages for manu- 
 facturing, the policy above recommended is exceed- 
 ingly advantageous, and wonderfully calculated to raise 
 the average condition of their inhabitants. By sup- 
 
 4i 
 
618 iievip:w of 
 
 porting a manufacturing population at home instead 
 of abroad, which, with the cultivators of the soil, be- 
 come mutual and never-failing customers to each 
 other, even during periods of war and political dis- 
 cord, it raises the value of land. By affording con- 
 stant employment to a population, which, in the 
 present improved state of husbandry, could only be 
 half employed in cultivating the ground, it operates 
 like improvements in machinery, in increasing the ag- 
 gregate production of useful articles relative to the 
 population. And hence it augments the aggregate 
 wealth, and raises the average condition of a people. 
 
 In a country which labours under local disadvan- 
 tages, which permanently disqualify it from supplying 
 itself with any particular species of manufactured 
 goods, at so low a price as it can be supplied by a fo- 
 reign country, the policy under consideration is inju- 
 dicious. Under such disadvantages, to attempt to 
 establish a manufacture by prohibitions or protecting 
 duties, and to persist in such a system of policy, is 
 merely to throw away money uselessly, to the extent 
 of the difference between the cost of supplying itself 
 with the prohibited article, and being supphed with it 
 from the foreign country without prohibition or pro« 
 tecting duty. 
 
 In the United States of America, the duties upon 
 imports, which were originally had recourse to only 
 for financial purposes, have had the effect of prema- 
 turely fostering their own manufactures. So long as 
 that country remains only very partially peopled, and 
 the price of labour consequently continues high, it 
 would have been more conducive to their national 
 
MR OWEN*S SYSTEM. 619 
 
 prosperity, had the portion of the population, at pre- 
 sent engaged in the manufacture of articles which 
 they could import at a cheaper rate from Europe, 
 been employed in clearing the ground, and cultivat- 
 ing food, and articles for exportation, such as cotton, 
 tobacco, &c. Ultimately, however, when the States 
 become so populous that the price of labour sinks as 
 low, or nearly as low as it is in Europe ; and other 
 avocations, besides those they have, are required in 
 order to employ the people ; the having recourse to 
 protecting duties for the purpose of establishing the 
 cotton and woollen manufactures within their own ter- 
 ritories, and which, by raising the raw materials them- 
 selves, they possess the greatest advantages for sup- 
 porting, would be good policy. 
 
 When taxes or duties on articles of consumption 
 are necessary for financial purposes, they ought to be 
 shifted, or altered relatively to each other, as little as 
 possible. The consumption of any manufactured 
 article is regulated, not so much by its individual va- 
 lue in use, as by its value in reference to that of other 
 articles which can be used as substitutes. By reducing 
 the duty on any article, for instance on silk, the con- 
 sumption of silk goods will be increased ; but then 
 the consumption of cotton goods will be proportion- 
 ally diminished. Trades which are upon the increase 
 usually pay more than the average rate of profit ; 
 while trades that are upon the decrease, usually pay 
 less. By taking off the duty on silk, the manufacture 
 of silk goods would be increased, and for a time would 
 pay more than the average rate of profit ; but the 
 manufacture of cotton goods would be proportionally 
 
(y20 REVIEW OF 
 
 diminished, and, for a time, would pay less than the 
 average rate of profit. Nor is the benefit which the 
 country, in such circumstances, derives from the en- 
 couragement given to the production of silk goods, a 
 sufl[icient compensation for the loss sustained by the 
 discouragement given to the production of cotton 
 goods. Suitable manufacturing establishments, per- 
 sons employed at fixed salaries, and workmen trained 
 to the trade, exist to the extent required to continue 
 the previous supply of cotton goods ; whereas estab- 
 lishments require to be enlarged, more persons at fixed 
 salaries employed, and additional workmen trained to 
 the trade, in order to produce an additional supply of 
 silk goods. The buildings and machinery fitted up 
 for the manufacture of cotton goods are partly ren- 
 dered useless ; and the labour of the persons employ- 
 ed at fixed salaries, and the acquired skill of the 
 workmen are partly lost to the community, by the al- 
 teration of duties ; while nothing in lieu thereof is 
 gained. Hence, it may be laid down as a maxim in 
 commercial policy, that every alteration or shifting of 
 duties from one article to another, for a time dimi- 
 nishes the aggregate wealth, and lowers the average 
 condition of a people. 
 
 When capital is paying a less rate of profit in one 
 department of merchandise than in others, it is soon 
 turned from the less into the more profitable channel. 
 And so is it with labourers. When wages are lower 
 in one trade than in another, (the comparative skill 
 required, and other circumstances being taken into 
 account,) the workmen soon change from the one to 
 the other, till an equality of wages is restored. Com- 
 
MR Owen's system. 621 
 
 plaints from interested parties relative to the distress 
 which certain trades experience, in consequence of 
 taxation, when the same system of taxation has been 
 permanent for a length of time, are absurd, and should 
 never be listened to by government. The only rule 
 that should be kept in view in this department of le- 
 gislation, is, that those duties are the best which are 
 collected with least trouble and expense relative to 
 the amount of revenue ; and which are least liable to 
 give rise to smuggling, and fraudulent evasion of pay- 
 ment. Trade soon accommodates itself to any per- 
 manent system of taxation, but never to one that is 
 constantly fluctuating. And the worst Ministry for a 
 mercantile country, such as Great Britain, is one that 
 is continually shifting, and altering the relative pro- 
 portions of duties upon articles of commerce, in order 
 to please deputations of interested applicants. 
 
 A good harvest operates like a sudden diminution 
 of population, in raising the average condition of a 
 people. By lowering the price of provisions, a small- 
 er proportion of the income of individuals is absorbed 
 in purchasing them ; and of course a larger propor- 
 tion is left to buy clothing, and other manufactured 
 commodities. Hence a good harvest not only lowers 
 the price of food, but by increasing the consumption 
 of manufactures, augments the demand for labour, 
 raises the wages of the labourer, and for a time ame- 
 liorates the general condition of society. On the 
 other hand, a bad harvest operates like an increase of 
 population, without a corresponding augmentation of 
 the means of subsistence, in deteriorating the con- 
 dition of a people. By raising the price of provisions, 
 
622 REVIEW OF 
 
 an unusually large proportion of the income of in- 
 dividuals is absorbed in purchasing them; and of 
 course, a proportionally smaller amount is left to buy 
 clothing, and all other necessaries, and luxuries. 
 Hence a bad harvest not only raises the price of food, 
 but by diminishing the consumption of manufactures, 
 lessens the demand for labour, lowers the wages of 
 the labourer, and for a time deteriorates the general 
 condition of the community. 
 
 In reference to population, a good and a bad har- 
 vest produce opposite results. The former by pro- 
 ducing a temporary effect in ameliorating the condi- 
 tion of society, encourages marriages, and an increase 
 of population ; whereas, the latter, by deteriorating 
 the condition of society, prevents and delays marriages, 
 and tends to diminish population. Good and bad 
 harvests, in these respects, balance each other. They 
 are circumstances which produce no permanent influ- 
 ence in either deteriorating, or improving the condi- 
 tion of society. But an improvement in husbandry, 
 such as better draining, which permanently increases 
 the productiveness of the soil, relative to the number 
 of hands employed in cultivating it, operates like im- 
 provements in machinery, in bettering the condition 
 of the community. By leaving an amount of spare 
 labourers, whose industry, in order to support them- 
 selves, is soon directed to productive avocations, the 
 quantity of useful articles produced, relative to the 
 population, is augmented. And hence the aggregate 
 wealth of the nation is permanently increased, and 
 the average condition of the people ameliorated. 
 
 It is generally believed that the average condition 
 
MR Owen's system. 623 
 
 of the people in this country, would be permanently 
 and greatly ameliorated by free-trade in corn. There 
 can be little doubt, however, that the extent of the 
 anticipated amelioration has been much over-estimat- 
 ed. That a temporary improvement might therefrom 
 result, after trade had recovered from the shock pro- 
 duced by the alteration in the value of commodities, 
 is not improbable ; but it is presumable, that little or 
 no permanent amelioration of condition would be 
 thereby effected. Supposing that upon the repeal of 
 the corn laws, a reduction in the average price of 
 all sorts of grain took place to the extent that is anti- 
 cipated, viz. from 8 to 15 shillings a quarter, without 
 any immediate reduction in the wages of the opera- 
 tives taking place, it is obvious, according to Mal- 
 thusian principles, that this amehoration in their 
 condition, would increase the number of marriages. 
 This in a few years would augment the number of 
 consumers of provisions, and ultimately the number 
 of labourers, so much, that their wages would be able 
 to command as little food, as they were before the 
 repeal of the corn laws. 
 
 Those who argue for the repeal of the corn laws 
 on the principle, that the reduction of the wages of 
 labour which would thereupon ensue, would enable 
 us to extend our foreign trade, forget that the mass of 
 foreign nations are interested in establishing manu- 
 factures in their own countries ; and that a slight in- 
 crease to their protecting duties, would extinguish all 
 prospect of a repeal of the corn laws, having any in- 
 fluence in increasing our foreign trade with such na- 
 tions. The system of protecting duties established 
 
G24 REVIEW OF 
 
 on the continent of Europe, has already had the ef- 
 fect of enabhng them to supply themselves with vari- 
 ous kinds of manufactured commodities, at a cheaper 
 rate, than they could now be sent from this country, 
 from which they were formerly supplied. And there 
 is reason to believe, that if peace continues, and es- 
 pecially if the British system of banking, by which 
 capital and credit are rendered available for mercan- 
 tile purposes, and which is so much wanted on the 
 continent, was generally introduced there, it is pro- 
 bable, that a large proportion of the goods which we 
 at present send thither, would ere long be superseded 
 by the supply afforded by their own manufacturing 
 establishments. And this result may be expected to 
 take place, whether the corn laws be repealed or not. 
 The wealth of a nation consists in the aggregate 
 produce of its own land and labour ; and the greater 
 its amount relative to the population, the higher is 
 the average condition of the people. If the whole 
 population are as constantly employed at present, as 
 they would be after the repeal of the corn laws, any 
 increase of wealth that could therefrom result, would 
 be owing to a small extent of the most inferior soils 
 ceasing to be cultivated. The industry of a portion 
 of the labourers now engaged in cultivating such soils, 
 by being directed to other avocations, might be able 
 to purchase as much food from abroad, as would be 
 sufficient to support the whole of them. Of course 
 the residue of the labourers, in order to obtain a 
 livelihood, would have to direct their industry to the 
 production of other useful articles ; and the aggregate 
 amount of these would be the sum total of the in- 
 
MR Owen's system. . 625 
 
 creased wealth, which the nation could gain by the 
 repeal of the corn laws. 
 
 Foreign trade is merely an exchange of a portion 
 of the commodities which different countries severally 
 produce. It accommodates the taste of mankind for 
 variety, by affording an additional choice of commo- 
 dities for sale. And according as home or foreign 
 articles, at their respective prices, are more or less 
 preferred, so are they said to be more or less wanted, 
 or in demand. In the long run, the aggregate ex- 
 ports and imports are equivalents in the countries 
 from which they are exported ; and merely become 
 enhanced in value by changing their respective places. 
 The merchant is the party that effects the transfer, 
 and gains the profit, which, after deducting the ex- 
 pense, arises out of the enhancement of value conse- 
 quent to the transfer. Foreign trade is thus limited 
 by the wants of the respective nations which carry it 
 on ; and these wants are regulated by the relative 
 value which the respective nations put upon the arti- 
 cles which they have to exchange. The price or ex- 
 changeable value of every article sinks as the supply 
 increases, provided the demand be not proportionally 
 increased. Consequently there is a limit beyond 
 which, if the exchange of commodities goes on, in 
 place of being profitable to the merchant who effects 
 the transfer, it is attended with loss. In this case, 
 trade is said to be overdone, and tends to decrease. 
 On the contrary, when the transfer of goods, or of 
 any particular species thereof, from one country to 
 another, pays the merchant who effects it more than 
 
 4k 
 
()2G REVIEW OF 
 
 the ordinary rate of profit, it is said to be underdone, 
 and tends to increase. 
 
 Thus we see foreign trade is limited, and naturally 
 tends to adjust itself, to the extent that is best calcu- 
 lated for supplying the wants of the respective nations 
 that carry it on. While some articles are paying more 
 than the ordinary rate of profit, others are paying less ; 
 and the merchant who merely looks to his own in- 
 terest, regulates the supply of the various transferable 
 articles as nearly as possible to the extent that is most 
 desirable, and most advantageous for both nations. 
 
 Now, when it is considered that the wealth of a 
 nation consists in the possession of articles useful to 
 mankind, and that it increases according as the amount 
 of useful articles relative to the population becomes 
 greater ; it is obvious, that the value of foreign trade 
 increases according as the amount of imports becomes 
 greater, relative to the amount of exports. And hence 
 the reason, that trading with a country, where, in con- 
 sequence of manufacturing skill, articles of consump- 
 tion are cheap, is more beneficial than trading with 
 one where they are dear. If the wages of labour were 
 lowered by a repeal of the corn laws, the price of all 
 our manufactures thereby produced, would be propor- 
 tionally lowered by the competition of our own mer- 
 chants and manufacturers, not only in the home, but 
 also in the foreign market. The result would be, 
 that so far as our export trade was concerned, foreign 
 countries would gain all the advantage of the reduc- 
 tion of wages produced by the repeal of the corn laws. 
 For instance, in exchange for a similar amount of 
 cotton, or of wheat from America, we would have to 
 
MR Owen's system. 627 
 
 send a larger amount of cutlery and hardware, (and so 
 of every other exchangeable commodity,) after the 
 repeal of the corn laws, than we do at present. 
 
 The anticipated benefit which we would derive from 
 the repeal of the corn laws, depends upon the pro- 
 duce of a smaller number of our labourers engaged in 
 manufacturing avocations, being able to purchase and 
 bring home a greater amount of corn from abroad, 
 than the same number of labourers, directed to the 
 cultivation of inferior soils at home, could produce. 
 M'CuUoch, in his notes and supplemental disserta- 
 tions to his edition of Dr Adam Smith's Wealth of 
 Nations, states, that, in the event of the ports being- 
 thrown open, if the price dechned eight shilhngs a- 
 quarter, the loss which the nation, or the consumers 
 of grain in Britain annually sustain by the present 
 corn laws, is no less than £19,200,000. If the price 
 declined ten shillings a-quarter, then the annual loss 
 to Britain by the corn laws is £24,000,000. And, if 
 the price declined fifteen shillings a-quarter, he says, 
 that " the annual loss occasioned by the corn laws to 
 the consumers, cannot amount to less than the enor- 
 mous sum of thirty-six-millions." By the tables ap- 
 pended to his dissertation on the corn laws, it ap- 
 pears, that the amount of all the kinds of grain, meal, 
 and flour imported into Britain for 15 years previous 
 to 1826, exclusive of what was received from Ireland, 
 and, after deducting what was again exported, does 
 not average half a million of quarters annually. The 
 greatest quantity imported in one year was in 1819, 
 which, after the exclusion and deduction above stated, 
 amounted only to 3,431,584 quarters. 
 
028 REVIEW OF 
 
 Supposing the com laws were repealed, all the sav- 
 ing resulting to the country therefrom, would be in 
 the reduced value of the amount of grain which we 
 afterwards annually imported. This is evident from 
 considering, that what we subsequently raised at 
 home, would continue to be raised with the same 
 amount of labour, and would require the same num- 
 ber of labourers as before. Now, estimating the 
 average value of all kinds of grain imported to be two 
 pounds sterling a-quarter, there is reason to think, 
 that though we were to get all the grain for nothing, 
 that we ever will import in any one year after the re- 
 peal of the corn laws, it would neither be worth 
 £36,000,000, nor £24,000,000, nor even £19,200,000, 
 which are the respective sums that M'Culloch says 
 would be saved by the repeal of the corn laws, accord- 
 ing as a dechne in prices equal to fifteen, ten, or only 
 eight shillings a-quarter, was thereby occasioned. 
 M'Culloch states, that the quantity of the different 
 sorts of grain annually consumed in the United King- 
 dom, has been estimated to be at least 48,000,000 of 
 quarters. Now, his opinions, to be correct, relative 
 to the amount of saving under consideration, would 
 require, that, after the repeal of the corn laws, the 
 whole 48,000,000 of quarters consumed in Great 
 Britain and Ireland, should be imported from abroad 
 at the reduction in price which he mentions, instead 
 of being almost wholly raised at home. But there is 
 nothing more certain, than that, though the corn laws 
 were repealed, nearly as great an amount of grain 
 would continue to be raised at home as at present ; 
 and therefore no very great additional quantity would 
 
MR Owen's system, 6*29 
 
 be imported from abroad. The only difference would 
 be, that in consequence of being able to receive sup- 
 plies from abroad, lower than the present home price, 
 the price of home-raised grain would sink to a similar 
 level. But this difference of price, which, according 
 to M'Culloch's estimate, would be gained to the 
 country, would be lost to the landlords ; for they 
 would have to let their farms at a corresponding re- 
 duction of rent. M'Culloch's notion that not above 
 a fourth part of what he considers the saving that 
 would accrue to the consumers of grain, would be lost 
 to the landlord in the shape of rent, is obviously falla- 
 cious from considering, that almost the whole of the 
 lands at present in cultivation would continue to be 
 cultivated, after the repeal of the corn laws, at a re- 
 duction of rent exactly proportional to the reduced 
 value of grain. And it is also an error to suppose, 
 that the reduction in the price of all necessaries and 
 luxuries, would be reduced by the repeal of the corn 
 laws, in the same proportion as the landlord's rents. 
 
 Again, while M'Culloch supposes that the repeal 
 of the corn laws would reduce wages, and the price 
 of manufactured commodities, as much as the price 
 of corn, he overlooks the fact, that we would in this 
 case, have to export a correspondingly larger propor- 
 tion of manufactured articles in return for the grain, 
 cotton, sugar, wines, timber, and other foreign articles 
 that we imported. The same principles that regulate 
 foreign trade at present, would continue to do so 
 after the repeal of the corn laws. If British manu- 
 factures were reduced in price in the home market 
 by the repeal of the corn laws, they would be corres- 
 
G30 REVIEW OF 
 
 pondingly reduced in the foreign market. For other- 
 wise, capital would soon get turned from supplying 
 the home market, into the more profitable trade of 
 supplying the foreign market; and so would continue, 
 till an equality in the profits of capital invested in the 
 home and foreign trade, was re-established. Hence 
 another reason, why the repeal of the corn laws would 
 not be attended with the benefit to this country which 
 M'Culloch supposes. 
 
 The policy hitherto adopted by governments in the 
 mutual arrangement of tariff's, has always been to get 
 the duties on imports reduced as low as possible ; 
 while little or no attention is paid to the duty upon 
 exports. But if any policy is required in the matter, 
 the reverse ought to be the case. As taxes upon 
 articles of consumption are always in the end paid by 
 the consumer, it is obvious, that taxes upon imports 
 are paid by ourselves ; whereas taxes upon exports, 
 are paid by the consumers of them in foreign coun- 
 tries. Now if there is any article which we export 
 to a foreign country, which they must have, and 
 which they cannot get from any other quarter, it is 
 obvious, that by taxing this article before it is export- 
 ed, we make the foreign country pay a portion of our 
 taxation. On the same principle, by prohibiting 
 foreign vessels, and foreign manufactures from enter- 
 ing the ports of our colonies, we might make our 
 colonies pay a portion of our taxation, by taxing 
 our exports thither. But we would thereby injure 
 the condition of the colonies in a greater degree, than 
 we benefited ourselves. 
 
 In like manner, if upon the repeal of the corn laws. 
 
MR Owen's system. 631 
 
 we were to tax all our exports, so as to raise them in 
 the foreign market to the same price as at present, 
 foreign nations would be made to pay taxes upon 
 what we exported them, equivalent to the difference 
 in the price of such articles in the home market, be- 
 fore and after the repeal of the corn laws. Such a 
 line of poHcy however, would in all probability be soon 
 met by retaliatory counteractives, which might teach 
 us the propriety of resorting to the system of recipro- 
 city. For instance, the United States of America, 
 by way of retaliation, might tax all the tobacco, flour, 
 &c., which they export to this country. And if they 
 Vv'ere to tax all the cotton which they export to Britain, 
 while they allowed it to be shipped to all the other 
 countries of Europe free of taxation, they would seri- 
 ously injure our cotton manufactures, and would pro- 
 bably destroy, at least for a time, all our foreign trade 
 in cotton goods. It might be thought that we are 
 protected against the adoption of such a measure on 
 the part of the United States, by the circumstance, 
 that it would injure themselves as much, if not more, 
 than it injured us. For in the first place, they would 
 not be able to dispose of the whole of their surplus 
 cotton ; and in the second place, by encouraging the 
 growth of cotton in other quarters of the globe, it 
 would tend to render us independent of them in fu- 
 ture. It is perhaps however just as well for both 
 parties, that neither of them provokes the other to 
 retaliate, by commencing such a selfish line of policy. 
 I am disposed to think, that if the corn laws were 
 repealed, the price of corn in foreign markets would 
 so advance, that the reduction which v^'ould take place 
 
032 REVIEW OF 
 
 in Great Britain, would be much less than is generally 
 supposed. If, however, the reduction was as great as 
 has been generally estimated, an immediate repeal of 
 the corn laws would be attended with very serious evils 
 in a national point of view, and very great injustice to 
 individuals. Thus all leases of farms would have to 
 be annulled, or otherwise the farming interest would 
 be ruined. Again, the value of land would sink so 
 much in price, that landlords who had borrowed money 
 upon their estates, to half or two-thirds of their value, 
 would be thereby deprived of their right to the other 
 proportion ; and a similar remark is applicable to those 
 who have borrowed money upon household property or 
 machinery. Again, as the wages of labour would ul- 
 timately fall proportionally to that of food, the value 
 of the annual aggregate produce of land and labour 
 estimated in pounds sterling, after the repeal of the 
 corn laws, would be considerably reduced ; and con- 
 sequently, the interest of the national debt, and all 
 fixed salaries, which in pounds sterling remained as 
 before, would absorb a larger proportion of the aggre- 
 gate produce of land and labour than they do at pre- 
 sent, and accordingly would be felt as a proportionally 
 heavier burden.* 
 
 * The obvious fact stated in the sentence immediately preceding 
 the asterisk M'CulIoch denies. He conceives that the £19,200,000 
 annually, (supposing that to be the aggregate reduction in the 
 price of the whole grain consumed in Britain, after the repeal of 
 the corn laws,) would be a saving to the consumers of it, which 
 would enable them to pay that additional amount of taxes, without 
 their condition being more reduced than they are at present by 
 the existence of the corn laws. His error here lies in forgetting, 
 what he admits in other passages, that the wages and income of 
 
MR OWEN*S SYSTEM. 633 
 
 It may be said that these evils might be obviated, 
 by simultaneously reducing the size of the sovereign, 
 and of the other coinage, proportionally to the reduc- 
 tion in the value of grain, and the wages of labour. 
 But then it is impossible to anticipate correctly the 
 extent of reduction in the price of grain and the wages 
 of labour, that would either immediately or ultimately 
 follow the repeal of the corn laws. And even though 
 this could be done, still that is not all the information 
 required. Though the price of articles of home 
 manufacture, so far as workmen's wages constituted a 
 part thereof, might fall in proportion to the reduction 
 of wages, it does not follow that the interest of capi- 
 tal, and the profit of the manufacturer, which also con- 
 stitute a part of the price of every manufactured arti- 
 cle, should also fall in an equal proportion. Besides, 
 the price of all articles raised abroad, such as cotton, 
 silk, sugar, wines, tea, coffee, &c., would not be 
 in the slightest degree affected, by the reduction in 
 the workmen's wages, expected to result from the 
 repeal of the corn laws. Hence it is obvious, that any 
 reduction in the weight of the sovereign proportional 
 to the reduction in the value of grain, even supposing 
 that could be correctly anticipated, (which is impossi- 
 ble,) would be a gross act of injustice towards all who 
 had money lent. And consequently, the anticipation 
 of such a measure being adopted, would produce great 
 commercial calamity, by occasioning a run upon the 
 banks for gold and silver of the present weight, in 
 order to hoard it ; and also by the annihilation of 
 
 the consumers of grain, would ultimately be reduced in proportion 
 to the reduction in the price of grain. 
 
 4l 
 
6:34 REVIEW OF 
 
 credit, and the calling up of all lent money, to which 
 it would give rise. In short, a government that would 
 for a moment entertain the idea of tampering with the 
 currency under any circumstances whatever, would 
 show their utter incompetence to legislate for a com- 
 mercial country. 
 
 Lastly, owing to the measures adopted by foreign 
 governments in order to foster, and establish manu- 
 factures in their own countries, by means of protecting 
 duties; and which, as we formerly explained, is wise 
 policy where the countries labour under no local dis- 
 advantages for manufacturing, it is probable, that the 
 price of grain in foreign countries will gradually assi- 
 milate to what it is in Great Britain. In the abstract, I 
 am favourable to free trade in grain, as well as in every 
 other commodity, on the principle, that, Hke a slight 
 improvement in the machinery for husbandry, without 
 any diminution in the supply of grain, it might dis- 
 engage a few, and only a few workmen, whose industry 
 might be directed to the production of some other 
 useful article. Nevertheless, when the evils above 
 enumerated, which in our artificial state of credit and 
 taxation, would attend the immediate repeal of the 
 corn laws, are considered in conjunction with the 
 prospect of a gradual assimilation in the price of grain 
 at home and abroad, I am disposed to think, that if 
 any repeal of the corn laws is to take place, it ought 
 to be a prospective and gradual measure, such as a 
 reduction of one-third of the duty, (supposing it first 
 to be converted into a fixed amount,) to come into 
 operation ten years hence; another third, twenty years 
 hence; and a total repeal not to take place sooner 
 
MR Owen's system. 635 
 
 than thirty years from the present period. Of course 
 it would have to be also enacted, that farmers who had 
 leases with more than ten years to run, were entitled 
 to have them shortened to that period, if they gave 
 sufficiently early notice to their landlords. By the 
 adoption of a gradual measure of this kind, public 
 clamour would be somewhat put down; and the re- 
 peal of the corn laws would probably be effected 
 without doing injustice to any party ; and actually 
 without producing any material change in the price of 
 grain. 
 
 We have thus, at considerable length, inquired into 
 the influence of various measures and kinds of policy, 
 in determining the aggregate wealth, and the average 
 condition of a people. The conclusion to which we 
 come, is, that the condition of mankind in any coun- 
 try, can be permanently ameliorated only by means 
 calculated to increase the amount of food, or of the 
 other necessaries and comforts of life, relative to the 
 population. In order to further these desirable ob- 
 jects, measures and policy which contribute to render 
 the preventive checks more efficacious in restraining 
 population, as well as those which increase the annual 
 produce of land and labour relative to the population, 
 should be adopted ; while measures and policy calcu- 
 lated to produce contrary effects, should be avoided. 
 What these measures and kinds of policy are, has 
 been sufficiently pointed out, and explained in the 
 preceding pages. Upon this subject we will only 
 farther remark, that as ignorance and crime are in- 
 variably found to increase with the poverty of the 
 lower orders of society, the means which are most 
 
63G REVIEW OF 
 
 calculated for ameliorating the average condition of a 
 people, are also best adapted for raising their intellec- 
 tual and moral character. 
 
 It is almost unnecessary to apply any of the pre- 
 ceding observations, except for the sake of form, to 
 Mr Owen's system. In a state of society such as he 
 proposes, where all property was held in common, and 
 where every one had a right to draw upon the public 
 stores according to his wants, the preventive checks 
 to population which raise the average condition of 
 mankind by limiting their numbers, could have no in- 
 fluence. Under this, as well as under all other sys- 
 tems of equality, where individual exertion and pru- 
 dence, and the sacrifice of immediate inclination, hold 
 out no prospect of individual benefit, there could be 
 no stimulant to industry ; no personal providence nor 
 economy ; no thinking before marriage how they were 
 to provide for a wife and family; no hope of bettering 
 their condition by remaining single ; and no fear of 
 making it worse by entering into the state of marriage. 
 Hence the number of inhabitants in each parallelo- 
 gram would rapidly increase, and soon exceed the 
 limits assigned it. What is to be done with the sur- 
 plus population ? Perhaps it may be said, form new 
 parallelograms. But when the whole land is occupied, 
 what then is to be done ? Nothing farther can be 
 done. The land itself cannot be increased, and its 
 productiveness cannot be indefinitely increased. In 
 the vegetable world, plants, by means of the repro- 
 ductive principles with which they are endowed, in- 
 crease and multiply till the soil is capable of support- 
 ing no more. In hke manner, the lower animals, if 
 
MR owen's system. 637 
 
 left to the freedom of their own will, multiply till want 
 or scarcity of food, checks their farther tendency to 
 increase. And so would it be with the human species 
 under any system of equahty such as Mr Owen's, 
 which, instead of equalizing wealth, by destroying the 
 influence of the preventive checks to population, 
 would equalize and increase poverty. In such cir- 
 cumstances, instead of a few being reduced to poverty, 
 population would inevitably increase, till the whole 
 community were restricted to the smallest amount of 
 nourishment capable of supporting life, and perpetu- 
 ating the species. And in years of scarcity, uni- 
 versal starvation and incapacity to assist each other, 
 would reduce the condition of man to the lowest pos- 
 sible state of degradation and misery. 
 
 Under the present system of society, which, by every 
 one working for his own individual interest, is produc- 
 tive of such an immense variety of ranks and degrees 
 of wealth, a very limited number, consisting of only 
 the poorest class, are reduced to the lowest subsist- 
 ence, which in this country at least, is considerably 
 above the starving point. As population increases, 
 the preventive checks gradually act with augmenting 
 efficacy, till in conjunction with the positive checks, 
 all tendency to increase is arrested, and population 
 becomes stationary. Indeed so mild, silent, and un- 
 seen, and so equal to all classes of society, are the 
 preventive checks in their operation, that their influ- 
 ence, though seemingly as apparent as the sun at 
 noon-day when pointed out, was never tiU recently 
 detected. 
 
 Though joint-stock societies have been known to 
 
638 REVIEW OF 
 
 exist, and for a time to prosper in half-peopled coun- 
 tries, such as America, where labour is high paid; 
 yet their regulations have all been much wiser, and 
 infinitely better adapted for insuring success, than 
 those which Mr Owen proposes. Such joint-stock 
 societies have generally, if not always, been composed 
 of persons belonging to the same religious sect, driven 
 by persecution from their native country. By an 
 arrangement of Providence, the members of such per- 
 secuted sects, receive some compensation for the in- 
 justice dealt them by their fellow-men, by becoming 
 mutually attached, and more amicably disposed to- 
 wards each other. And it is invariably observed, that 
 ultimately, when the persecution to which they were 
 once subject has long ceased, and passed into obli- 
 vion, the bond of union which kept them together is 
 broken, and the association dissolves by the mutual 
 consent of its members. 
 
 Supposing it possible that Mr Owen's system could 
 go on till population was checked by starvation, it is 
 evident that at this point selfishness must get the 
 upper hand, and the strong' would oppress the weak 
 in order to save themselves from starvation. War 
 originating in the same cause, would take place be- 
 tween the occupiers of the different^ parallelograms ; 
 and all the malignant feelings in human nature being 
 thereby excited, slaughter, rapine, and devastation, 
 would spread around, till some mighty revolution 
 shivered to pieces this visionary fabric, and left man 
 to provide for himself, and to reap the fruits of his 
 own industry, which Providence has ordained to be 
 not merely the most natural system, and that which is 
 
MR Owen's system. 6.39 
 
 most conducive to human happiness, but the only 
 state in which society can permanently exist. 
 
 There are some borrowed maxims to be met with 
 prefixed to Mr Owen's plan, which are calculated 
 beforehand to give it something like a plausible ap- 
 pearance ; such as, 1st. That labour, properly direct- 
 ed, is the source of all wealth. 2d. That, when pro- 
 perly directed, a man's labour is of far more value to 
 the community, than the expense necessary to main- 
 tain him in considerable comfort. 3d. That the di- 
 rect effect of every addition to scientific, or mechani- 
 cal and chemical pov/er, is to increase wealth. These, 
 and some such others, are borrowed truths that every 
 person knows. And though Mr Owen prefixes them 
 to every promulgation of his plan, and a person 
 might thereby be led to conceive that they were its 
 fundamental principles, they are subsequently entirely 
 lost sight of, and form no part of them. Indeed, his 
 system is generally diametrically opposed to such 
 maxims. For instance, that a man should work al- 
 ternately at each trade ; or that the divisions and sub- 
 divisions of labour should be abohshedj or that spade 
 husbandry should again be introduced, instead of that 
 by the plough and harrow ; or that gold and silver as 
 a circulating medium should be done away with, and 
 the old system of barter resorted to in its place ; is 
 surely neither directing a man's labour properly, nor 
 taking advantage of the scientific and mechanical 
 knowledge possessed by mankind, for promoting the 
 increase of wealth. 
 
 The cleanness of the establishment, and the exter- 
 nal appearance of comfort in the dwellings of the 
 
040 REVIEW OF 
 
 work-people at New Lanark, which, combined with 
 the beauty of the scenery, attracts the visiter's atten- 
 tion, are also quite distinct from Mr Owen's plan. 
 They merely show, (an example worthy of imitation,) 
 the influence of a master over his workers in a se- 
 questered part of a country, when directed towards 
 these objects. 
 
 Upon reviewing Mr Owen's system, we are struck 
 with its numerous glaring absurdities and impossibili- 
 ties ; with the inadequacy of the means for accom- 
 plishing the proposed ends ; and with the palpable 
 ignorance of human nature, and of the doctrines of 
 political economy, which it everywhere displays. 
 Something analogous to it may be adapted upon a 
 limited scale to the state of criminals confined to 
 hard labour, or to the forlorn submissive condition of 
 paupers and slaves under the subjection of an arbi- 
 trary master ; but it is utterly destitute of every thing 
 calculated to promote the liberty, independence, 
 wealth, and happiness of mankind at large. Even 
 his system of education,* which is considered the 
 
 * It is to be lamented that the bigotry of the age still retards 
 and increases the expense of the initiatory department of educa- 
 tion, viz, learning to read, by compelling teachers to use as school- 
 books, only religious works, and such as contain select specimens 
 of English composition in prose and verse. Children can neither 
 understand, nor receive improvement from the moral lessons which 
 works of this description inculcate ; nor can they form the slight- 
 est appreciation of the beauties they contain. In fact, the reading 
 of them is felt by children as a disagreeable act of drudgery. 
 
 Reading is simply combining together, upon inspection, letters 
 or characters which have severally a determinate force or sound, 
 so as to form words. And learning to read, is merely learning 
 
MR Owen's system. 641 
 
 only part of his plan not totally irrational, seems more 
 calculated to attract the attention of a superficial 
 observer, than to stand the test of close examination. 
 Its great expense, compared with its utility, precludes 
 all chance of its being generally adopted ; and it may 
 be safely predicted, that it never will be found in a 
 single instance, productive of any of those great ad- 
 vantages, which its admirers expect. Similar obser- 
 vations are apphcable to the Infant school systems of 
 education, at present so much in repute. They are 
 chiefly remarkable for the introduction of a systematic 
 plan of clapping hands, and other things equally fri- 
 volous and unimportant. 
 
 Notwithstanding the imperfect nature of Mr Owen's 
 plan, he is so certain of its being adopted, that he 
 says " a longer continuance of the existing arrange- 
 ments is impossible, that every body cries something 
 must be done, and that his system will be adopted, in 
 spite of all that prejudices in favour of old estabhshed 
 customs can do." Disregarding his sanguine expec- 
 tations, which are quite of a piece with the rest of 
 his notions, let. it be, in conclusion, observed, that 
 it may be within the boundary of possibihty, but is 
 barely within that of probability, that a man who has 
 
 the art of doing this with rapidity, — a thing which can only be 
 acquired by practice. Now, the obvious means of accelerating 
 this department of education, is to use as school-books, only such 
 as children experience pleasure in reading, and which they would 
 have an inclination to read whenever they were at leisure. Ro- 
 binson Crusoe has been recommended by a man of genius, as a 
 book in every respect fitted for amusing, and instructing the minds 
 of children. This, therefore, or others of a similar nature, should 
 only be used as school-books in teaching children to read. 
 
 4 M 
 
{]-i'2 REVIEW OF MR OWEN's SYSTEM. 
 
 been inventing nothing all his days, but theories for 
 the amelioration of his species that are absurd and 
 incapable of being reduced to practice, will ever pro- 
 duce one that is rational, and at the same time prac- 
 ticable. 
 
APPENDIX. 
 
 The annexed map, on which are delineated Humboldt's iso- 
 thermal lines, and the table of temperatures of the principal 
 places contained within the isothermal zones, which are sever- 
 ally bounded by them, are taken from the article Meteorology 
 in the Encyclopaedia Metropolitana. The map and table of 
 temperatures, are referred to at page 249 of our treatise on 
 the Causes and Principles of Meteorological Phenomena. 
 
 On the map, the number inserted at both extremities of 
 each of the isothermal lines, is the mean annual temperature 
 in degrees of Fahrenheit for all places along the isothermal 
 line; and the lines are severally denominated, and distin- 
 guished from each other, by that mean temperature. Thus 
 the isothermal line with 32° marked at both its extremities, 
 is denominated the isothermal line of 32 degrees ; and so of 
 all the others. 
 
 The isothermal lines exhibit a sameness in the mean annual 
 temperature at the tropic of Cancer, whether it be land or 
 water. Thus the isothermal line of 77° has almost no curve 
 whatever, and coincides nearly with the tropic of Cancer, 
 from which, on the map, it can hardly be distinguished; 
 whereas, the other isothermal lines become more curved as 
 they recede farther towards the north. The reasons why it 
 is so, we have endeavoured to explain in our meteorological 
 treatise, beginning at page 251. 
 
(i4-J: APPENDIX. 
 
 According to Playfair a sameness in the mean annual tem- 
 perature, whether it be land or water, occurs about the 30th 
 parallel of latitude ; and nearer the equator than that parallel, 
 the mean annual temperature increases upon receding from 
 the ocean, a fact which we have explained at page 255. In 
 our chapter on Temperature, we have ^.dhered to Playfair's 
 statement in preference to that of Humboldt, principally be- 
 cause fixing upon the parallel that coincides with the tropic 
 of Cancer, as being that at which the mean annual tempera- 
 ture is uniform, whether it be land or water, looks more like 
 modifying facts to support a theory, than the other. 
 
 The more northerly isothermal lines also exhibit a lower 
 mean annual temperature for the latitude in America, than 
 on the old continent. Thus the extremity of the isothermal 
 line of 32° in America, is nearly 5 degrees of latitude lower 
 than the other extremity in Asia. The reasons why it is so, 
 we have attempted to explain in our meteorological treatise, 
 beginning at page 256. 
 
APPENDIX. 
 
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GLASGOW: 
 
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