Everyday Objects; Or, Picturesque Aspects of Natural History.

by W. H. Davenport Adams

It would be easy for me to develop this parallel by other and still more remarkable facts; but what I have just said will suffice to show that the line of demarcation which philosophers have, upon principle, desired to trace between the physical and moral order, has turned the mind aside from many fertile fields of research and speculation. Let us cite an example. The sun is the visible centre of light, heat, organic life; in fine, of all the movements of our material world. Yet it is but a relative focus, since the sun, with its planetary train, revolves, probably, in company with other suns or systems, around a centre as yet unknown; and as there is no reason why we should pause in this cycloidal progression, this second centre or focus of systems may revolve around a third, the third around a fourth, and so on. Thus we shall have an indeterminate series of relative centres; for the term does not exist of which we can say,—there is the beginning, or here is the end of the series.

We do not meet with the absolute in the material, any more than in the intellectual world. Truth, by its power of attraction, sets in motion all the wheels of our understanding; we seek after it eagerly, in the doubt which torments us, in the obscurity which surrounds us; we all feel the need of being enlightened by it, and warmed, and revivified; we all are in need of belief, and, at the same time, of possessing—let there be no illusion in this respect—a certainty or demonstration of what we believe.

But the truth which we think our own does not leave the mind at rest; a slight effort suffices, in fact, to teach us that the truth we accept depends upon another and remoter truth, and that the world of thought is thus carried onward in an interminable series of relative truths; unless we find it more convenient to pause here at a primary cause, as elsewhere at a primordial centre, which we may ever identify with the primary cause. But is this truth, supposed to be final, capable of satisfying equally every mind? With this question, dear reader, I close my parenthesis.

To understand clearly the variable duration of the day at all points of the terrestrial surface, let us so place ourselves as to see our planet distinctly in front. I need hardly say that this invitation is not addressed to the visual organs of the body, but to the "mind's eye, Horatio." With the former, fixed as we are on the surface of the globe, we can only see the shadows of objects standing out in relief upon it, and still, with the sun at our back, can perceive but a comparatively insignificant portion. With the second, on the contrary, we may detach ourselves from the earth, may mount afar into space, may plant ourselves on some aërial height, whence we may embrace, at a single glance, all the illuminated hemisphere of our globe: we shall have but a single shadow on the prospect,—that which our brightened planet casts behind it, and which, in four-and-twenty hours, traverses the entire surface of the globe, producing light wherever it passes.

Having completed our preparations, let us note what we perceive with our eye thus disjoined from our body,—an eye equally well adapted to fix every moving object, and to see at any distance bodies extremely small, or bodies extremely large. What a marvellous eye! And it is for us to develop its power, and freely to increase its range. What an arduous task!

The luminous envelope, the photosphere of the sun, simultaneously darts its rays in all directions, with an intensity which diminishes with the square of the distance.

Let us follow those which direct their course towards our planet.

So long as the rays do not come into collision, or strike against resistant matter, they neither warm nor enlighten. Confirming the Newtonian hypothesis of emission, they travel straight as arrows through the icy space, the shadowy ocean in which the waves of the terrestrial atmosphere are lost. But the moment they encounter a material obstacle, the rays partly penetrate it, and are partly thrown back, in such a manner as to form a series of undulations like those which the falling of a stone into a pond produces. As they recede from these repeated shocks, the rays come under that theory of undulation which Huygens promoted.[57]

Let us trace the rays of light back to their origin. These encounter first the globes nearest to the sun: the almost imperceptible asteroids, which, on account of the solar splendour, can scarcely be detected, and which, as yet, have received no baptismal names. Yonder beams illuminate other revolving globes,—Mercury, Venus, the Earth. If we here arrest our gaze, we are influenced by a vague and mournful recollection; the Earth was our place of sojourn at an epoch when thought, formerly shackled, had become free. It is thus that a seed, removed from the stem which nourished it, wanders afar to diffuse and perfect its species. Our planet, of an ochreous yellow, relieved with green and white, possesses no special privileges; it shares in the ponderated movements of the spheres; it is neither the largest, nor the smallest, nor the heaviest, nor the lightest, nor the nearest to, nor the farthest from, the sun. And shall Earth alone, of all the planets, nourish that kind of "thinking seed" which we name the human race? It seems improbable.