VESSELS FOR AQUARIA. 25 



— and again, it might, if it were not well seasoned, warp, 

 and so rain the tank. Mahogany is the only wood that 

 can be used with any safety for this purpose, as it is 

 well seasoned in the forest before we get it. I have a 

 tank made of thick mahogany which has been in use some 

 months, aud does not yet show any signs of warping, as it 

 was very carefully made. I have, in some cases, made use 

 of black walnut for small tanks, that is to say, those of 

 fifteen inches in length ; and they have stood very well ; 

 though I cannot recommend wooden tanks of any kind 

 or size. Zinc is certainly superior to wood for Aquarium 

 frames ; but, still, there are objections to it : for if it be 

 ornamental and portable, it is so brittle a metal in the 

 cast state that any ordinary sized tank, having a frame 

 made of it, would not bear any great pressure of water ; 

 while, if it were made with sheet malleable metal, though 

 it would not break, it would be apt to bend, and so start 

 the cement. Zinc is the metal most used in England for 

 small Aquaria, as it is a cheap material ; but I cannot 

 recommend it for the purpose, and there is no reason why 

 we should use it in preference to iron. 



Iron is by far the best substance for the frame of an 

 Aquarium, as it is cheap, strong, durable, and can easily 

 be made ornamental and thin enough to be comparatively 

 light, without endangering its strength at all. I have some 

 tanks that are made entirely of iron and glass, which are 

 extremely durable, but rather heavy, though that, as I 

 have said before, is not necessary. The bottom can be 

 made of a slab of some well seasoned wood, as maho- 

 gany or white pine, and covered internally with cement 



