Page:Popular Science Monthly Volume 5.djvu/709

Rh which quickly develop microscopic vegetation or confervæ upon the sides of the aquarium, and upon the rocks within it. This vegetation, although unobtrusive, performs all the work done by the more conspicuous plants of the fresh-water aquarium. The credit of inventing the aquarium proper has generally been given to Madame Power, before alluded to, who, in the year 1832 and thereabouts, while studying the marine animals on the coast of Sicily, brought into use the "water-cage" to facilitate her investigations. But Mr. W. Alford Lloyd, the present Curator of the Crystal Palace Aquarium, London, who is one of the highest authorities on the subject, contradicts that view. In an article published in Science Gossip, several years ago, he says that the introduction into the "water-cage" of "plants for the avowed purpose stated beforehand, of preserving the purity of the sea-water, and of sustaining the animals in health, is due to Mrs. Thynne, who experimented in London, in 1846, on living madrepores." Madame Power, it appears, was in the habit of changing the water in her cages. It would seem, therefore, that while to Madame Power belongs the credit of furnishing the clew to the scientific value of the aquarium, to Mrs. Thynne belongs that of inventing the aquarium itself.

Some interesting facts, not wholly of a zoological nature, have been observed through the aquarium. Thus it was ascertained that objects through the medium of water appear shorter than they really are. At the distance of a few feet, a fish, or other object, appears about one-fifth shorter than it is. Mr. Lloyd, through Science Gossip, has made known some curious effects of electricity on fish. A friend of his had a large fresh-water garden-aquarium. One day, during a thunder-storm, a house, about 200 feet from the aquarium, was struck by lightning. At the moment of the flash, all the fish in the aquarium, forty-three in number, of various kinds, were suddenly suspended perpendicularly, heads downward, with their tails at the surface of the water, in which position they feebly and vainly endeavored to swim to the bottom of the tank. "The manner in which the eels were almost jerked out of their hiding-places, in the sand at the bottom of the tank, was very remarkable. In less than half an hour forty-one were dead, strongly curved, almost in the form of semicircles, and fast decomposing; but two gradually recovered, by being placed in running water. It is well known that when fish become sick and die, under ordinary circumstances, they turn belly upward, horizontally, instead of having nose downward, as in this case."

These facts sufficiently indicate the utility of the aquarium, and the necessity for having one at Central Park. As an indication of the interest commanded by the subject in England, it may be mentioned that Mr. Kent has begun a series of lectures at Manchester, to show how it subserves the purposes of scientific instruction. The first lecture was delivered on the last Friday in June to a fairly numerous