20 VESSELS FOR AQUAEIA. 



of sonic kind and a plate of glass, so that the water never 

 comes in contact with the wood at all, and there is no 

 danger of its warping. Marble, soapstonc, or slate can also 

 be used for Aquarium bottoms, but they make the tanks 

 heavy, and in the case of marble, expensive. But tanks 

 made with stone bottoms will not travel well, from the 

 difficulty of screwing the iron frame to the bottom tightly, 

 without chipping it ; and if it be not screwed tight, the 

 cement will be apt to start away from the stone or glass 

 when the tank is jolted at all. The best tanks, in this 

 respect, I have seen, are some I have in which the bot- 

 tom is made of cast-iron and covered internally with glass. 



The proportions most approved of in England for the 

 form of oblong tanks are twice as long as the depth or 

 width, that is to say, forming a double cube, though, for 

 marine Aquaria, I have usually found it advantageous to 

 have the tank a little wider than these proportions, so as 

 the more nearly to imitate a rock-pool. 



When we wish to have an Aquarium of a more 

 ornamental form than an oblong, we can have it 

 octagon, like that in Plate I., Fig. 3, which is the repre- 

 sentation of one contrived by Mr. P. II. Gossc. It is con- 

 siderably wider at the top than at the bottom, so as to 

 expose as great a surface as possible to the atmosphere. 

 Again, we can make an ordinary chemist's bell-glass into a 

 vase Aquarium by inverting it and setting the knob into a 

 wooden stand, or use the glasses made for the purpose of 

 covering cake, inverting one of them, and placing it in a 

 wooden stand (as with the bell-glass), so that it can be 

 turned round for observers to view the contained objects 



