THE AQTJAEIUM. 



"iC 



other live, is because water is simply a vehicle for holding in 

 solution the oxygen which is necessary to animal life. And 

 the greater the stirface of water exposed to the air, the more 

 oxygen will it absorb in proportion to its bulk. 



An aquarium of the shape and size of Fig. 1, which would 

 present to the air a surface of water of 32 square inches, 



would hardly supply the oxygen 



ajn^ necessary for the health of three 



small fish ; while one like Pig. 2, 

 having a superficial measurement 

 of 64 square inches, would hold 

 comfortably six small fish; but 

 one of the shape and size of 

 Fig. 3, presenting a surface of 

 128 square inches, would supply 

 sufficient oxygen for twelve fish. 

 piQ 2. -^d yet all three aquaria would 



contain exactly the same quantity 

 of water, viz., 512 cubic inches. 



I have kept twenty-six small minnows for a week in an 

 ordinary soup-plate, a little more than half -full of water, and 

 then only one of them died. At the present time one pike 

 (9in. long), twenty very small roach (about l^in. long), nine 

 perch (from 2^in. to 3in. long), and one large water newt 



r 



16 iiL. 



Fig. 3. 



(Triton cristatus) are living in perfect health in an aquarium 

 21in. by 13fin., but which contains water only 2in. deep- 

 sufficient to cover the dorsal fin of the biggest fish as he 

 swims just clear of the bottom. And these fish live in this 

 comparatively small quantity of water in apparently the 

 best of health, not only because the water is very shallow in 



B 2 



