MANAGEMENT OF AQUAEIUMS 239 



ened firmly by the top frame and clinching-bands. 

 The cement should then be pressed in firmly and 

 smoothed with the putty-knife, and when it is partly 

 dried be painted with asphaltum paint. The bottom, 

 if of wood, should be given a slight coating of liquid 

 cement to prevent warping. 



While a two-inch board may be used for the bottom 

 of an aquarium, it is more desirable to have it of 

 slate, marble or concrete. The last named is substan- 

 tial, much easier to secure and cheaper. To make a 

 concrete bottom, fashion a wooden frame of the de- 

 sired dimensions, and fill it with concrete, made of 

 three parts of sharp sand and one of cement. One- 

 half sand and half cement would possibly make a 

 harder base, but it would be more liable to crack in 

 drying unless re-inforced, than when made with the 

 proportions first given. Immediately after placing 

 the concrete in the form, large wire nails should be 

 pushed in at regular intervals around the edge of 

 the base. After the concrete has hardened the nails 

 are withdrawn, leaving holes for the bolts which are 

 to fasten the framework to the bottom. If the bot- 

 tom be of slate or marble, then bolt-holes must be 

 drilled in its surface, but it is not necessary to make 

 grooves, as the angle-iron frame can be set on the 

 surface with a thin layer of cement to prevent leak- 

 age. The frame-work is bolted to the bottom. 



If the aquarium is to contain running water, then 

 an outflow will be necessary. This may be made by 



