GEOGRAPHICAL DISTINCTIONS OF COLOR.

'Look through nature up to nature's God.'

Perhaps the most important benefit resulting to mankind from the study of the natural sciences, is the invention to which it leads of new arguments in favor of the being and benevolence of the Deity. And were this the only advantage arising from this study, it would render it well worthy the attention of the wisest and greatest of men. For every discovery which philosophers have hitherto made, whether of some new material element, or of some law or property of matter, has invariably disclosed fresh proof of the existence of an All-wise Intelligence. The chemical constitution and governing laws of a drop of water, even so far as they are now understood, may afford weapons, wherewith the weakest champion of religion might prevail against the most ingenious of the worshippers of the Goddess of Chance. Nay, were the atheist really in search of truth, no champion would be needed. The humblest flower, the meanest worm, even the dust beneath his feet, would seem to disclaim an origin in chance, and to warn him not to neglect the worship of their common Creator.

There can be no more interesting object of attention, than the examination of the evidences of design, as exhibited in parts of the intricate machinery of Nature. Physical principles, which, at first sight, or indeed after much philosophical investigation, have appeared of but limited importance, or perhaps wholly accidental or unnecessary, have, upon farther study, been found to rank among the number of most beautiful and convincing proofs of creative intelligence; have formed the most important links in the chain which holds together the material universe.

Such has been the train of thought suggested to the mind of the writer of this article, by an examination of the nature and physical relations of COLOR. This property of matter might appear to a superficial observer as one of inferior importance. He would admit that the differences of color add to the happiness of the human race, inasmuch as they give variety and beauty to material objects, and afford one of the most easy methods of distinguishing them from each other, but would probably deny that the existence of animal life is at all dependant upon color, and that it is essential to the present constitution of things. But let such an one reflect a little more upon this property—let him consider attentively all its relations—and he will doubtless change his opinion.

In travelling from the equator toward the poles, we cannot but be struck with the fact, that there exists a difference of color corresponding to a change of climate. Under the equator, the covering of the earth, that is, the vegetation, is darker than in any other part of the globe; and, as there is but little change of climate through the year, this dark covering does not give place either to the light tints of autumn, or to the snowy robe of winter. In advancing north, the foliage becomes lighter in proportion to the increase of latitude. In the temperate zone, the dark, rich robe of the tropics gives place to one of livelier hue, which, after covering the earth during a part of the year, assumes the light colors of decay, and is buried beneath the snow. Thus this change continues to keep pace with the diminution of temperature, till we enter the frigid zone, and reach the region of eternal frost.

From this difference of color in the north and south, and in summer and winter, we may deduce this general fact, that the earth adapts itself in color to the variations of temperature, presenting a dark surface to the heat of summer and the tropics, and a light one to the cold of winter and the frigid zone.

So much then for the fact. Let us now consider the design of such an arrangement. When a body contains more caloric than the air, or the other bodies by which it is surrounded, heat is given off from it in all directions, till the equilibrium is restored. Three, and perhaps more, physical operations take place in this case; radiation from the heated substance, reflection and absorption by the surrounding bodies. Now it has been proved, by repeated experiment, that these changes depend, as it regards their extent and rapidity, upon the color of the bodies. The more light-colored the heated substance is, the more slowly will it part with its superfluous caloric. Were it entirely black, the change would take place with more rapidity than in any other case. If the surrounding bodies were of a light color, a large portion of the heat radiated upon them would be reflected, and but little absorbed. Just the contrary would take place were they dark. The caloric would nearly all be absorbed, and but little reflected.

Similar to these are the phenomena of light. Bright substances reflect, and dark absorb, the rays from a luminous body. This, however, is hardly a correct method of expressing the fact intended. Philosophers believe that darkness of color is not the cause of the absorption of the luminous rays, but, on the contrary, that this absorption is the cause of the darkness. The fact in question then is this; some bodies are of such a chemical constitution, that they readily absorb light, and, as a consequence, little being reflected to the eye, they appear dark. Others, differently constituted, reflect nearly all the light that is thrown upon them, and, therefore, the lightness of their color bears proportion to such reflection.

Let us apply these facts to the explanation of the design of the geographical distinctions of color, of which we are treating. Suppose that the arrangement were different. Suppose, for instance, that the portion of the earth near the equator presented, throughout the year, a white surface to the sun. The rays of heat from that body would nearly all, upon reaching such a surface, be reflected back into the atmosphere, and would heat that part of it immediately bordering the earth, and most exposed to this reflection, to such a degree as to make the climate insupportable. The consequence would be, that a large portion of the earth would be rendered uninhabitable. But, by the existing provision, the rays of caloric pass directly through the air, heating it comparatively little, and are, for the most part, absorbed by the earth. The principle is similar in regard to light. Had the constitution of the covering of the earth in the tropics been such as to reflect the luminous rays, which are far more numerous and brilliant there than at the poles, the overpowering glare of light would alone have been sufficient to render those regions uninhabitable by any known species of animals.

Again: Let us suppose that the earth were clothed with a dark covering in the frigid zone. The few and oblique rays of heat, in that part of the globe would, after imparting but little of their caloric to the atmosphere, in their passage through it, be absorbed by the earth. The same effect would take place in regard to the rays of light, which are similarly few and feeble. It is easy to perceive the effect these things would have in darkening the polar regions, in greatly diminishing the temperature of the atmosphere, and, as a consequence, in contracting the extent of the inhabitable part of the globe. Thus we see, that by means of the snow, nay, by one, and as some would think, the least important of its properties, i. e., its color, man and his fellow animals are enabled to live in regions, the climate of which, without the instrumentality of this property, would destroy them.

After speaking of the change of color corresponding to change of latitude, it were superfluous to dwell at length upon the corresponding change of season, since the principle is precisely the same in each case. There can be no doubt but that in the temperate zone, the climate throughout the year is to a great extent equalized by this happy arrangement; that, without it, our winters would be much more rigorous, and our summers proportionably oppressive.

In passing, we might speak of another evil that would arise from snow being of a darker color. Upon a sudden change of temperature, it would melt very rapidly, and, if collected in any quantity, would occasion dreadful inundations, which would sweep and desolate the country. Such accidents occur even now in some parts of the world. How much more frequent and destructive they would be, in the case we have supposed, it is easy to conceive.

Who then can deny that we have, in the general principle which unites these phenomena, a well-attested instance of benevolent design? Who will assert that so beautiful and necessary a provision could be the result of chance?

But perhaps some one will say: 'It is true that there appears to be a happy adjustment of the color of the surface of the earth. It is true that this adjustment has an important influence in diminishing the difference of the temperatures of the polar and equatorial regions, and in rendering them both fit abodes of animals. But then, unhappily for the symmetry of the whole theory, no exception to the general principle is made in favor of the animals themselves. The inhabitants of the torrid zone, and man in a more marked and invariable manner than all the rest, are distinguished by the dark color peculiar to that part of the globe; so that they absorb the heat in an equal degree with, or perhaps greater than, the earth, since its color is even lighter than theirs. We find the same fact to exist as we advance from the equator toward the poles. The covering of the greater part of animals becomes lighter proportionally with the surface of the earth. In the frigid zone, the light color of man as well as of other animals, for instance the white bear, ermine, etc., must necessarily repel from their bodies by reflection a quantity of heat proportional to that which the atmosphere gains by reflection from the snow. This fact strikes us still more forcibly in the temperate zone, where the difference of climate, resulting from change of season, is greater than in any other part of the globe. Here our color is actually darkened by the heat of summer, in proportion to our exposure to it, and becomes lighter at the approach of winter. So that we are rendered by the heat itself more capable of absorbing it, and, consequently, of suffering from it. Surely, we cannot consider these things as evidences of design.'

But let us attentively examine these facts, and we shall find that the seeming difficulty disappears, and that the truths which gave rise to it, unite in a symmetrical whole with the others which we have mentioned, to form a cumulative and unanswerable argument in favor of the existence of a benevolent Creator.

Animal bodies do not depend for the quantity of caloric necessary to their existence upon the sun. By chemical changes, not yet well understood by philosophers, depending upon that subtle ethereal principle which we call life,[3] a sufficient quantity of animal or vital heat, as it is called, is evolved within the body itself. As this heat is constantly generated, it is necessary, in order that the body may not acquire too high a temperature, that it be as constantly conducted or radiated off. When the atmosphere contains too little caloric, its power of absorbing heat is so great as to deprive the animal body of it more rapidly than it is generated; thus producing the sensation of cold. On the contrary, when the weather is too warm, the air and other surrounding bodies, having less attraction for caloric, do not withdraw it as fast as it is generated; thus producing the feeling of heat. Perhaps, however, this is scarcely a scientific method of stating the fact in question. It is generally supposed by philosophers, that all bodies, whether in equilibrium, as it regards temperature, with surrounding substances, or not, are constantly radiating and absorbing caloric. When equally heated, the cause of their continuing so is, that they receive as much as they give off. When unequally heated, that which contains most caloric radiates more than the rest, and, of course, absorbs less than it parts with. By this means, an equilibrium of temperature is after a time brought about. Now, in cold weather, the heat which an animal body radiates is greater in quantity than the sum of what it generates itself, and absorbs from the sun and other bodies. The consequence is, it experiences the feeling of cold. In warm weather, the caloric radiated is less than that absorbed and generated; in which case, the animal suffers from heat. The vital heat of the generality of quadrupeds and other warm-blooded animals is several degrees greater in intensity than that of the atmosphere, during the warmest season in the tropics. The temperature of the human body is about ninety-eight degrees. The mean equatorial temperature Humboldt proved by repeated experiment to be eighty-one and a half degrees. It is evident, therefore, that in warm regions it is more important that the physical state and constitution of animal bodies should be adapted to the radiation of internal, than to the reflection of external heat, since the intensity of the former exceeds that of the latter.

Now we have before mentioned the fact, that the rapidity of the radiation of caloric from a heated body is in proportion to the darkness of its color. This then, taken in connection with the facts just stated, readily explains the reason why the color of animals varies with the temperature. The negroes of Africa, for example, are provided with a dark complexion, in order that the great quantity of heat which the warmth of their climate causes them to absorb, may be compensated for by an increased radiation. These unfortunate people, when they come to the north, as might be supposed, suffer at first extremely from the cold. They in time, however, become somewhat inured to it. Nature provides for them by another species of adaptation, which we cannot stop minutely to describe, but which may be proved to take place. The effect of it is to increase the evolution of animal heat, and thus to make up for the excessive radiation. Natives of high latitudes, however, are white, as has been said, and consequently their limited absorption of heat is compensated for by an equally limited radiation. We see, also, from this general principle, the design of the skin being so formed as to become tanned by exposure to the sun.

It is needless to dwell longer upon these facts. Taken in connection, they present perhaps one of the most interesting and harmonious arrangements that are to be met with in any of the departments of natural science. But it is by no means one of a few evidences of design, by which the advocate of religion may strengthen and confirm his faith. The whole universe is full of such examples. We have reason to believe, too, that we have but a very imperfect insight into the philosophy of Nature; that beyond the veil which separates the conquests of the human intellect from the vast tracts of knowledge, the possession of which yet remains to be acquired, there are myriads of beautifully-ordered systems, far surpassing in extent and grandeur any thing which the fancy of the wildest schemer has ever suggested to his mind. A few pebbles only have been gathered from the shore of the great ocean of truth. No wonder that the poet, impressed with this belief, should exclaim:

B. R. W.