66 THE OCEAN WOKLD. 



by the sea was first suggested by M. Charles des Moulins of Bordeaux, 

 in 1830. The aquarium, which is charged with fresh or salt water, 

 according to the beings it is intended to contain, serves the same 

 purpose for the inhabitants of the deep which the aviary does for the 

 birds of the air cages of glass being used in place of iron wire or 

 wicker-work, and water in place of atmospheric air. 



When a globe is filled with fresh water, and with mollusks, 

 crustaceans, or fishes, it is observed, after a few days, that the water 

 loses its transparency and purity, and becomes slightly corrupt. It 

 necessarily follows that the water must be changed from time to time. 

 Changing the water, however, causes much suffering, and even death 

 to the animals. Besides, the new water does not always present the 

 same composition, the same aeration, or the same temperature with 

 that which is replaced. To obviate this defect, and taking a leaf out 

 of Nature's book, M. Moulins proposed to put into the vase a certain 

 number of aquatic plants floating or submerged duckweed, for 

 example which would apt upon the water in a direction inverse to 

 that of the animals inhabiting it. It is known that vegetables 

 .assimilate carbon, while decomposing the carbonic acid produced by 

 the respiration of animals, thus disengaging the oxygen indispensable 

 to animal life. In this simple manner was the necessary change of 

 water obviated. The same happy idea has been successfully applied 

 to salt water, and aquariums for salt-water plants and animals have 

 been proposed on a great scale. That of the Zoological Gardens of 

 Paris, in the Bois de Boulogne, inaugurated in 1861, is perhaps the 

 largest in the world. It is a solid stone building of fifty yards in 

 length by about twelve broad, presenting a range of forty reservoirs 

 of Angers slate, running north and south. The reservoirs are nearly 

 cubical, presenting in front the strong glass of Saint Gobain, which 

 permits of the interior being seen. They are lighted from above ; 

 but the light is weak, greenish, uniform, and consequently mysterious 

 and gloomy, giving a pretty exact imitation of the submarine light 

 some fathoms down. Each reservoir contains about two hundred 

 gallons of water. It is furnished with rocks disposed a little in the 

 form of an amphitheatre, and in a picturesque manner. Upon the 

 rocks various species of marine vegetables are planted. The bottom 

 is of shingle, gravel, and sand, in order to give certain animals a 

 sufficiently natural retreat. 



