20 THE PKlXCirLES OF 



animals, which form part of the food of our fish. The fish, 

 it is true, cat the animals, bat they leave still the cdnfenfy 

 that cover the glass, and prevent an unobstructed view of 

 the habits of our pels. These plants are the natural food 

 of certain genera of snails, and the principal business of the 

 latter, when they are introduced into a foul tank, is to go 

 to work and remove the conferva from the glass, for our 

 special benefit. There is one species of snail, called by con- 

 chologists Lymmm stagnate, that will not perform its duty 

 of cleaning the glass, but prefers, like a drone in the 

 hive, to eat our more tender plants ; but my readers will 

 be. glad to learn that this mischievous mollusc is not found 

 in our country. 



The great difference between a fish-globe and an Aqua- 

 rium is, that in the one, we keep fish only, whilst, in the 

 other we cultivate many beautiful and wonderful plants 

 and animals which would not flourish if we changed the 

 water often. This is a great desideratum, as changing 

 the water endangers, to a certain extent, our carpets by 

 the spilling ; and then again, in an Aquarium, the fish are 

 not always subjected to continual excitement as they arc in 

 a fish-globe, where they must, as most likely everybody 

 has observed, come to the surface to breathe, unless we 

 change the water continually. This is an unnatural action 

 in the fish, that is seldom or never seen in a pond or 

 river. We can change the water continually, by having 

 a jet in the form of a fountain, and where we can have 

 this contrivance, as we can in the city of New York, fish 

 will generally thrive without the use of plants ; but, then, 

 we lose the beautiful sight of the preen foliage. There 



