3i . PREPARING THE TANK. 



unmethodical as to mix with the gravel and pebbles of 

 one of my fresh-water tanks the empty shells of Anomia, 

 the beautiful little golden and silver-colored shells so com- 

 mon on some parts of our coast. 



Hackwork is the next thing to be attended to after we 

 have got the bottom or soil of our tank arranged to our 

 satisfaction. In a fresh-water Aquarium I do not recom- 

 mend much of it : yet if your taste, reader, leans that 

 way, be satisfied with a simple pile of stones in the centre, 

 or a cromlech, made by placing two stones on the bottom 

 at a distance from each other and laying another across 

 them — thus forming a rough arch, under which fishes may 

 retire when they are so disposed. Stones may also be 

 fastened together in the form of one or more arches by 

 means of some cement, always remembering that any me- 

 tallic or lime cement is injurious, and will be sure to taint 

 the water to the detriment of the inhabitants. The best 

 of all cements for this purpose is made by melting together 

 one part, by weight, of rough giUla-jwrcha and two parts 

 of common pitch. This cement holds well to stones and 

 does not foul the water, besides it is to a certain extent 

 flexible, thus not being liable to break on receiving any 

 sudden jar. The rock I have found to be the best for the 

 purpose of the Aquarium is either semi-crystallized quartz 

 or white feldspar, the latter of which can be obtained in 

 any quantity on New York island. It is best, perhaps, 

 when it can be done in fresh-water Aquaria, and certainly in 

 marine ones, to dispense entirely with the use of cement 

 for the purpose of uniting the rockwork. I have never 

 found it necessarv to fasten the rockwork to the bottom 



