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equally close-a decision of this longnooted question which illustrates the ancient axiom that truth is rarely found in extremes.

One of the principal causes which modify the distribution of heat is elevation above the level of the sea. It is computed by meteorologists that the temperature of the atmosphere sinks at the rate of 1° Fahr. for every hundred yards of altitude above tide-water. Consequently whenever land rises high above the common level, a change of climate similar in its effects to increase of latitude, as regards the distribution of temperature and the consequent distribution of plants, is induced. But these effects differ greatly in different latitudes. Thus, under the equator, perpetual snow exists generally at an altitude of fifteen or sixteen thousand feet, whilst in the 70th degree of north latitude, it is found at the height of three thousand three hundred feet. Receding from the equator, these phenomena assume a more irregular character. The difference between the limits of perpetual snow on the northern and southern sides of the Himmaleh Mountains is not less than four thousand feet; and whilst these limits are at the equator nearly 30 above, they are in the frigid zone more than 10° below, the freezing point.

In reference to the effects resulting from the diminution of temperature attending the elevation of land, the following observations are made by our author:

"Whilst the flowers of spring are unfolding their petals on the plains of northern France, winter continues his icy reign upon the Alps and Pyrenees. By this beneficent appointment of nature, the torrid zone presents many habitable climates. On the great table-plain of Mexico and Guatemala, a tropical is converted into a temperate clime. As the vernal valley of Quito lies in the same latitude as the destructive coasts of French Guiana, so the interior of Africa may possess many localities gifted with the same advantages. In our own country, reference

has already been made to the marked contrast between the Atlantic Plain and the parallel mountain ridges; but it is in the geographical features of Columbia, in South America, that we find most strikingly displayed the physical phenomenon of height producing the effect of latitudea change of climate with all the conse

quent revolutions of animal and vegetable life, induced by local position. It is on the mountain slopes of from three to seven thousand feet, beyond the influence of the noxious miasmata, that man dwells in perpetual summer amid the richest vegetable productions of nature. In the mountains of Jamaica, at the height of four thousand, two hundred feet, the vegetation of the tropics gives place to that of temperate regions; and here, while thousands are cut off annually along the coast by yellow fever, a complete exemption exists. In these elevated regions, the inhabitants exhibit the ruddy glow of health which tinges the countenance in northern climes, forming a striking contrast to the pallid and sickly aspect of those that dwell below. In ascending a lofty mountain of the torrid zone, the greatest variety in vegetation is displayed. At its foot, under the burning sun, ananas and plantains flourish; the region of limes and maize and luxuriant wheat; and still oranges succeeds; then follow fields of higher, the series of plants known in the temperate zone. The mountains of temperate regions exhibit perhaps less variety, but the change is equally striking. In the ascent of the Alps, having once passed the vine-clad belt, we traverse in succession those of oaks, sweet chestnuts, and beeches, till we gain the region of the more hardy pines and stunted birches. Beyond the elevation of six thousand feet, no tree appears. Immense tracts are then covered with herbaceous vegetation, the variety in which ultimately dwindles down to mosses and lichens, which strug

gle up to the barrier of eternal snow. In the United States proper, we have at least two summits, the rocky pinnacles of which shoot up to the altitude perhaps of six thousand five hundred feet. Of these, Mount Washington, in New Hampshire, is one. Encircling the base is a heavy forest-then succeeds a belt of stunted firs-next a growth of low bushes-and still further up only moss or lichens, or lastly a naked surface, the summits of which are covered, during ten months of the year, with snow. Of the snow-capt peaks of Oregon, we possess no precise knowledge."

ished temperature in the higher reThe causes upon which this dimingions depends are-first, the perfect permeability of the atmosphere to the solar rays; and secondly, its increased capacity for caloric in proportion as it becomes more rare. As the solar rays radiate through the atmosphere almost without affecting its temperature, it

follows that the temperature of its lower regions is derived more immediately from the earth Although the atmospheric stratum immediately incumbent on the surface of the earth, owing to this rarefaction, naturally ascends, yet, as its capacity for caloric at the same time increases, it loses rapidly its sensible heat. Hence, as we ascend into the atmosphere, its temperature diminishes precisely in the ratio that its latent heat, that is, its capacity for caloric, as produced by rarefaction, increases. To explain the diminution of temperature on the summits of high mountains, no longer therefore presents any difficulties to natural philosophers. As the atmosphere is rare and diaphanous, but a small portion of the heat of the solar rays which traverse it, is retained, and as the more dense inferior strata, heated by the surface of the earth, expand, rise up, and grow cold from the circumstance alone of their rarefaction, they encounter these summits, and rob them of their caloric, which passes into a la

tent state.

It is only, however, when lands are considerably and suddenly elevated, and exposed to the action of the atmosphere laterally, that this rapid conduction of heat and rarefaction of the atmosphere can take place. When large tracts of country rise gradually, the decline of 1° of temperature for every three hundred feet of elevation, as determined either by a balloon ascension or by scaling the sides of isolated and precipitous mountains, does not by any means take place. The region of our great lakes, for example, notwithstanding it is elevated 600-800 feet above the level of the sea, so far from causing a diminution of annual temperature, produces, in consequence no doubt of the great accumulation of summer heat by the soil, an augmentation. A most striking illustration of an analogous fact is offered by the ridges and valleys of the great Himmaleh mountains of Southern Asia, where immense tracts, which theory would consign to the dreariness of perpetual congelation, are found richly clothed in vegetation and abounding in animal life. At the village of Zonching, fourteen thousand seven hundred feet above the level of the sea, in lat. 31° 36′ N., Mr. Colebrook found flocks of sheep brows ing on verdant hills; and at the village

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of Pui, at about the same elevation, there are produced, according to Captain Gerard, the most luxuriant crops of barley, wheat, and turnips, whilst a little lower the ground is covered with vineyards, groves of apricots, and many aromatic plants.

In considering the laws relative to the distribution of plants and animals over the globe, we find that they are chiefly regulated by the temperature of the atmosphere. The circumstance next in importance is the nature of soil, which has resulted from the gradual attrition of the solid materials composing the crust of the globe; but as regards the very existence of all animals, at least of the land, and all vegetables, we find this stratum of comminuted mineral substances and organic remains absolutely indispensable.

It is in tropical countries alone, beneath a vertical sun, that vegetation displays its utmost glory and magnificence. It is there, amidst eternal summer, that we find groves ever verdant, blooming, and productive. Advancing to the north or south, we soon discover forests, which, denuded of their leaves, assume during half the year the appearance of death; and still approaching the poles, we meet vegetable life under a variety of stunted forms, which are ultimately superseded by a few coarse grasses and lichens.

"The influence of temperature on the geography of plants," says Dr. Forry, "is ably pointed out by M. de Candolle. In considering its relation with the organic life of plants, it is necessary to keep in view three objects: 1. The mean temperature of the year; 2. The extreme of temperature both in regard to heat and cold; 3. The distribution of temperature among the different months of the year. The last is the most important; but in the investigation of vegetable geography, it is requisite to estimate the simultaneous influence of all physical causessoil, heat, light, and the state of the atmosphere, as regards its humidity, serenity, and variable pressure. Each plant has generally a particular climate in which it thrives best, and beyond certain limits it ceases to exist. Hence, having seen the great variations of summer and winter temperature on the same isothermal line, the absurdity of limiting a vegetable production to a certain latitude or mean annual tem

perature, is apparent. To say that the vine, the olive, and the coffee-tree, require, in order to be productive, annual temperatures of 53°.60, 60°.80, and 64°.40, is true only of the same system of climate. As the annual quantity of heat which any point of the globe receives, varies very little during a long series of years, the variable product of our harvests depends less on changes in the mean annual temperature, than in its distribution throughout the year. Thus climates in regard to vegetable productions, are strongly characterized by the variations which the temperature of months and seasons experience." Reference has already been made to the contrast in the climate of Western Europe and Eastern America, the former producing the olive and the orange in latitudes which with us are productive of ice and snow. Scarcely does a winter elapse that the Hudson river is not frozen over even in the vicinity of the city of New York; whilst Philadelphia and even Baltimore, lying on the same parallels on which flourish in Europe the olive and the orange, have their commerce often interrupted from the same cause. The Delaware, which is in the latitude of Madrid and Naples, is generally frozen over five or six weeks each winter. Even the Potomac becomes so much obstructed by ice, that all communication with the District of Columbia by this means, is suspended for weeks. Further north, we find the mouth of the St. Lawrence shut up by ice during five months of the year; and Hudson's Bay, notwithstanding it is in the same latitude as the Baltic Sea, and of thrice the extent, is so much obstructed by ice, even in the summer months, as to be comparatively of little value as a navigable basin.

Accordingly we find, that whilst the sugar-cane is cultivated in Europe as far north as latitude 36°, in a mean annual temperature of about 679, its cultivation in the United States, on account of the low winter temperature, is prevented beyond latitude 31°. In Europe, the olive ranges between latitude 360 and 44°, that is, in a mean annual temperature of 669 down to 58°, provided the mean temperature of summer is not below 71°, nor that of the coldest month below 42°, which last excludes the United States beyond latitude 35°. For the same reason,

the date, palm, and sweet orange, grow in Louisiana only to latitude 30o. That these plants would succeed, however, on the Pacific coast of our territory, on parallels corresponding to Europe, is an opinion that has for its basis the fundamental truth, that the laws of nature never vary. It has, indeed, been recently stated, on the authority of travellers, that even as high as the forty-fifth degree, the fig, citron, orange, lemon, pomegranate, and cotton plant, flourish. This, in truth, is confirmed by thermometrical observations made by Mr. Ball, of New York, at Fort Vancouver, in latitude 45° 37', situated on the Columbia River, about seventy miles in a direct line from the Pacific Ocean. During a year's observations, the lowest point is 179 of Fahr., and the whole number of days below the freezing point is only nine, all of which are noted in January. The seasons are even less contrasted than at Pensacola or New Orleans. The mean temperature of spring, summer, and autumn, are about the same as at Fort Wolcott, R. I., whilst the winter resembles that of Fort Gibson, Arkansas, "Though the latitude is nearly that of Montreal," he says, " mowing and curing hay are unnecessary; for cattle graze on fresh growing grass through the winter.

Winters on the Columbia River are remarkably mild, there being no snow, and the river being obstructed by ice but a few days during the first part of January." Here the seasons, notwithstanding five degrees farther north than the city of New York, are so mild and uniform, that the difference between the mean temperature of winter and summer is only 23°.67-a mean which is less than that of Italy or southern France, and only about two-fifths of that of Fort Snelling, Iowa, which is 569.60, notwithstanding the latter is nearly one degree further south.

Dr. Forry also points out the influence produced upon vegetable geogra phy by the unequal distribution of heat among the seasons, as illustrated in the four systems of climate demonstrated on the same parallels in the northern division of the United States; and if we extend the comparison to the Pacific coast, a fifth system, as has just been seen, may be enumerated on the same latitude. Taking the coast of New England, the region of the great lakes,

and the Pacific coast, the difference between the mean temperature of winter and spring, varies from 60.67 to 180.42; whilst in the excessive climates of the regions west of the lakes, and intermediate to them and the Atlantic, this difference ranges from 189.82 to 30°.83; and accordingly we find, as already explained, that spring and summer are confounded with each other, and that the sudden excess of heat renders the progress of vegetation almost perceptible. Not only is the vernal increase greater in excessive climates; but, as it supervenes upon a lower winter temperature, the effect produced upon the development of vegetation is in an inverse ratio. The vernal increase of 30°.83, for example, at Fort Snelling, Iowa, comes upon a mean winter temperature of 150.95, whilst at Fort Sullivan, on the coast of Maine, on the same parallel, the increase of only 17°.16 follows a winter temperature as high as 229.95.

As regards the effects of diversity of climate on the distribution of animals, our limits will not allow us to enlarge. Tropical regions, as in the vegetable creation, display animate nature in its grandest developments. Both on the land and in the sea, animals attain not only the most enormous magnitude, but exhibit the most extraordinary and diversified forms and colors in nature. Where else than amidst the profusion of vegetable exuberance teeming with animal life exhibited within the trop ics, could the elephant and rhinoceros, the ostrich and cassowary, the boa and crocodile, exist? And in illustration of the design evidenced on every hand, where but in countries so productive of animal life should we discover the ferocity of the tiger and the poison of the serpent, as wise checks upon excessive increase?

One of the most interesting problems in history is, the geographical distribution of the human family; but this subject would of itself occupy a volume. Man alone can be truly regarded as a cosmopolite. Although more readily assimilated with particular climates than any other animal, yet the inhabitants of the middle latitudes, like other animals as well as plants, in consequence of their habitual exposure to extremes of temperature and consequent greater vital energy, manifest, in the highest degree, that plia

bility of functions by which organized structures accommodate themselves to a change of physical circumstances.

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In surveying the different regions of the earth," says our author, "as it were with a coup-d'œil, the mental eye is equally struck with the dissemblances and the analogies which appear. Each climatic zone has a peculiar aspect, the physical circumstances of which mould everything with a plastic hand. Even man, endowed with those functions which constitute him a cosmopolite, becomes, in appropriating to his wants the objects which surround him, assimilated in nature. Our idea of a special climate, then, should embrace all the characteristics in the animal, vegetable, and mineral kingdoms, by which nature has distinguished one locality from another."

From remote ages, it is well known that the inhabitants of every extended locality have been marked by certain physical, moral, and intellectual peculiarities, serving no less than particularity of language, to distinguish them from all other people; but how far this result ought justly to be ascribed to the agency of the climate is still an undetermined point. But the influence of climate upon man's organization has been noticed from the earliest records of medicine. This powerful influence is apparent at once in surveying the external characters of the different nations of any quarter of the earth. In casting one's eye over our national legislature, the same diversity of physiognomy is apparent. The general countenance of each State's delegation is indeed a pretty sure criterion to judge of its comparative salubrity. We can at once distinguish the ruddy inhabitant of that mountain chain, where health and longevity walk hand in hand, where Jefferson and Madison inhaled its cheerful and invigorating breezes, from the blanched resident of our southern lowlands-those fair and inviting plains whose fragrant zephyrs are laden with poison, and the dews of whose summer evenings are replete with the seeds of mortality. As in the smiling but malarial plains of Italy,

"In florid beauty, groves and fields

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speaking of malaria in Italy, "walks hand in hand with the sources of life, sparing none; the laborer reaps his harvest but to die; or he wanders amid the luxuriance of vegetation and wealth, the ghost of a man, a sufferer from his cradle to his impending grave; aged even in childhood, and laying down in misery that life which was but one disease. He is even driven from some of the richest portions of this fertile yet unhappy country; and the traveller contemplates at a distance deserts, but deserts of vegetable wealth, which man dares not approach,-or he dies."

Macculloch gives a deplorable picture of the degeneracy produced in man by a residence of successive generations in some of the malarial districts of Italy. Young women, before the age of twenty, have often the aspect of that of fifty, while in men, the age of forty is equivalent to sixty in healthier climates. Not only does the stature become reduced, but deformities are frequent. In our own country, along the frontiers of Florida and the southern borders of Georgia, as witnessed by our author, as well as in the lowlands of our southern States generally, may be seen deplorable examples of the physical, as well as mental and moral deterioration induced by malaria. In the Pontine marshes of Italy, the residents have the appearance of walking spectres. The moral and intellectual faculties become degraded. In the Maremma of Tuscany, absolute idiotism is common. The picture drawn by Monfalcon of the moral con dition of the people in some of these pernicious districts, is truly frightful. In the catalogue of their vices, he names universal libertinism, abortion, infanticide, drunkenness, a disregard of religion, and whilst their murders are common, a large proportion are those of premeditated assassination. It is also worthy of remark, that whilst the deaths are increased and the mean du ration of life diminished, the ratios of marriages and births are augmented, it being not uncommon for one woman to have had three, four, or even five husbands.

At the same time, it is manifest that political institutions and social organization often struggle successfully against climatic agency; for heroes, men of genius, and philosophers, have

arisen both in Egypt, under the tropic, and in Scandinavia, under the polar circle.

Our author propounds the two following questions-Does the climate of a locality, in a series of years, undergo any permanent changes? Does the climate of our north-western frontier resemble that of the Eastern States on their first settlement ?

It has been much debated, whether the temperature of the crust of the earth or of the incumbent atmosphere, has undergone any perceptible changes since the earliest records, either from the efforts of man in clearing away forests, draining marshes, and cultivating the ground, or from other causes. As the earth is continually receiving heat from the sun, it follows that, if no caloric is thrown off into surrounding space, its mean temperature must be continually augmenting. It has accordingly been inferred that the increase of temperature is at the rate of 19 in eighty years; and thus the changes of climate alleged to have gradually supervened during successive ages in many countries, and particularly in the west of Europe, are attempted to be explained. But many geologists, on the other hand, maintain the doctrine, (on the supposition that the surface of the earth had a higher temperature at the period of the formation of the older rocks), of a decreasing superficial temperature as the result of radiation. It has been satisfactorily demonstrated by La Place, however, that since the days of Hipparchus, an astronomer of the Alexandrian school, who flourished about two thousand years ago, the temperature of the earth cannot have increased or decreased a single degree, as otherwise the sidereal day must have become either lengthened or shortened, which is not the case.

In regard to the former and present temperature of the earth, M. Arago arrives at the conclusion, that in Europe in general, and in France in particular, the winters were, in former ages, at least as cold as at present,an opinion founded upon the alleged fact of the congelation of rivers and seas at a very ancient period. He thinks that the conquests of agriculture, such as the opening of forests and the draining of marshes, as well as the confinement of water-courses to their chan

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