24 VESSELS FOR AQUARIA. 



as one of the worst accidents that can happen is the 

 overstocking or crowding of the animals. The creatures I 

 have mentioned above are about the proportionate num- 

 ber that will be found in a rock-pool or a portion of a 

 pond of the size of the tank I use, that is to say, ten 

 gallons capacity ; and, indeed, in beginning to keep an 

 Aquarium, it is better to rather understock it than run 

 the risk of losing all our pets at once, as we shall be 

 most likely to do if we introduce too many at a time. 

 But when the tank has been in vigorous operation for 

 some weeks, we can carefully introduce more animals un- 

 til we have the balance of the animal and vegetable life 

 complete. Let it always be made a rule, in the stocking 

 and management of an Ai/unrium, to follow the teachings 

 of nature as nearly as possible ; for, of course, if we are 

 not guided by the discoveries of those who have gone be- 

 fore us, we shall be the more apt to fail, and have to 

 go over the same ground as they have gone over to ar- 

 rive at the goal of their knowledge and practice. 



The materials of which the tanks are usually made are, 

 in the case of circular ones, glass alone ; and in that of 

 the oblong form the sides arc composed of plates of the 

 same material, and a framp of cither wood, iron or zinc, 

 although for small tanks wood is strong enough ; yet, in 

 regard to those of over a foot long, it would not bear 

 the weight of the water unless it were made heavy and 

 unseemly, or, if it ' did bear the pressure of the con- 

 tained water whilst the tank was at rest, still, when it 

 was moved, the cement about it would be liable to start 

 from the glass in consequence of the bending of the wood 



