sea,--that hidden half of Nature, where are to be found those wonders described by Milton at the Creation,--where, in obedience to the Divine command, "Be fruitful, multiply, and in the seas And lakes and running streams the waters fill, ... Forthwith the sounds and seas, each creek and bay, With fry innumerable swarm, and shoals Of fish, that with their fins and shining scales Glide under the green wave in sculls that oft Bank the mid sea: part single or with mate Graze the sea-weed, their pasture, and through groves Of coral stray, or sporting with quick glance Show to the sun their waved coats dropt with gold, Or in their pearly shells at ease attend Moist nutriment, or under rocks their food In jointed armor watch." But no means were at hand to pursue these unknown creatures to their unknown residences, and to observe their manners when at home. Single, withered, and often mutilated specimens of minute fish, mollusks, or radiata, in the museum, alone illustrated the mysteries of the deep sea. Fish, to be sure, could be kept for longer or shorter periods in globes of glass filled with water; but the more delicate creatures inevitably perished soon after their removal from their mysterious abodes. Such a passionate desire to "search Nature and know her secrets" finally originated the idea of the Aquarium. The term _vivarium_ was used among the ancients to signify many things,--from the dens of the wild animals which opened under the Colosseum, to an oyster-bed; and so now it may mean any collection of living creatures. Hence it could convey no distinct idea of a marine collection such as we propose to describe. The term _aqua_ was added to express the watery element; but the compound _aqua-vivarium_ was too clumsy for frequent employment, and the abbreviated word _aquarium_ has come into general use. Thus the real Aquarium is a water-garden and a menagerie combined,--and aims to show life beneath the waters, both animal and vegetable, in all the domestic security of its native home, and in all the beauty, harmony, and nice adaptation of Nature herself. It is no sudden discovery, but the growth of a long and patient research by naturalists. "What happens, when we put half a dozen gold-fish into a globe? The fishes gulp in water and expel it at the gills. As it passes through the gills, whatever free oxygen the water contains is absorbed, and carbonic acid given off in its place; and in course of time, the free oxygen of the water is exhausted, the water becomes stale, and at last poisonous, from excess of carbonic acid. If the water is not changed, the fishes come to the surface and gulp atmospheric air. But though they naturally breathe air (oxygen) as we do, yet they are formed to extract it from the water; and when compelled to take air from the surface, the gills, or lungs, soon get inflamed, and death at last puts an end to their sufferings.