In like manner the length of time that the earth has been sufficiently cool to support animal and vegetable life must be re-estimated. Until the discovery of radium it seemed definitely determined that the earth was gradually cooling, and would continue to cool, un til, like the moon, it would become too cold to support any kind of vegetable or animal life whatever. But recent estimates of the amount of radio-active matter in the earth and atmosphere, and the amount of heat constantly given off from this source, seem to indicate that the loss of heat is (for the moment) about evenly balanced by the heat given out by radio-active matter. Thus at the beginning of the new century we see the phenomenon of a single discovery in science completely overturning certain carefully worked out calculations, although not changing the great principles involved. It is but the repetition of the revolutionary changes that occur at intervals in the history of science, a simple discovery setting at naught some of the most careful calculations of a generation.
V. THE MARINE BIOLOGICAL LABORATORY AT NAPLES
THE AQUARIUM
MANY tourists who have gone to Naples within recent years will recall their visit to the aquarium there among their most pleasant experiences. It is, indeed, a place worth seeing. Any Neapolitan will direct you to the beautiful white building which it occupies in the public park close by the water's side. The park itself, statue-guarded and palm-studded, is one of the show-places of the city; and the aquarium building, standing isolated near its centre, is worthy of its surroundings. As seen from the bay, it gleams white amid the half-tropical foliage, with the circling rampart of hills, flanked by Vesuvius itself, for background. And near at hand the picturesque cactus growth scrambling over the walls gives precisely the necessary finish to the otherwise rather severe type of the architecture. The ensemble prepares one to be pleased with whatever the structure may have to show within.
It prepares one also, though in quite another way, for a surprise; for when one has crossed the threshold and narrow vestibule, while the gleam of the outside brightness still glows before his eyes, he is plunged suddenly into what seems at first glimpse a cavern of Egyptian darkness, and the contrast is nothing less than startling. To add to the effect, one sees all about him, near the walls of the cavern, weird forms of moving creatures, which seem to be floating about lazily in the air, in grottos which glow with a dim light or sparkle with varied colors. One is really looking through glass walls into tanks of water filled with marine life; but both glass and water are so transparent that it is difficult at first glimpse to realize their presence, unless a stream of water, with its attendant bubbles, is playing into the tanks. And even then the effect is most elusive; for the surface of the water, which you are looking up to from below, mirrors the contents of the tanks so perfectly that it is difficult to tell where the reality ends and the image begins, were it not that the duplicated creatures move about with their backs downward in a scene all topsy-turvy. The effect is most fantastic.
More than that, it is most beautiful as well. You are, in effect, at the bottom of the ocean—or rather, at the bottom of many oceans in one. No light comes to you except through the grottos about you—grottos haunted by weird forms of the deep, from graceful to grotesque, from almost colorless to gaudy-hued. To your dilated pupils the light itself has the weird glow of unreality. It is all like the wonders of the Arabian Nights made tangible or like a strange spectacular dream. If one were in a great diving-bell at the bottom of the veritable ocean he could hardly feel more detached from the ordinary aerial world of fact.
As one recovers his senses and begins to take definite note of things about him he sees that each one of the many grottos has a different set of occupants, and that not all of the creatures there are as unfamiliar as at first they seemed. Many of the fishes, for example, and the lobsters, crabs, and the like, are familiar enough under other conditions, but even these old acquaintances look strange under these changed circumstances. But for the rest there are multitudes of forms that one had never seen or imagined, for the sea hides a myriad of wonders which we who sail over its surface, and at most glance dimly a few feet into its depths, hardly dream of. Even though one has seen these strange creatures "preserved" in museums, he does not know them, for the alleged preservation there has retained little enough of essential faciès of the real creature, which the dead shell can no more than vaguely suggest.
Here, however, we see the real thing. Each creature lives and moves in a habitat as nearly as may be like that which it haunted when at liberty, save that tribes that live at enmity with one another are here separated, so that the active struggle for existence, which plays so large a part in the wild life of sea as well as land, is not represented. For the rest the creatures of the deep are at home in these artificial grottos, and disport themselves as if they desired no other residence. For the most part they pay no heed whatever to the human inspectors without their homelike prisons, so one may watch their activities under the most favorable conditions.
It is odd to notice how curiously sinuous are all the movements, not alone of the fish, but of a large proportion of the other forms of moving life of the waters. The curve, the line of beauty, is the symbol of their every act; there are no angles in their world. They glide hither and yon, seemingly without an effort, and always with wavy, oscillating gracefulness. The acme of this sinuosity of movement is reached with those long-drawn-out fishes the eels. Of these there are two gigantic species represented here—the conger, a dark-skinned, rather ill-favored fellow, and the beautiful Italian eel, with a velvety, leopard-spotted skin. These creatures are gracefulness itself. They are ribbon-like in tenuousness, and to casual glance they give the impression of long, narrow pennants softly waving in a gentle breeze. The great conger—five or six feet in length—has, indeed, a certain propensity to extend himself rigidly in a fishlike line and lie immovable, but the other species is always true to his colors, so to say—his form is always outlined in curves.