284 



G. E. STONE 



and an inch deep on the side in which to imbed the plate glass, 

 for which purpose we used regular aquarium cement. In all 

 cases we covered the rough top of the plate glass with a split 

 piece of heavy brass tubing, which makes an excellent finish. 

 All the aquaria are provided with overflows, the pipes being 

 imbedded in the cement. 



Close to the large aquarium is an apartment lined with cement 

 and covered with pudding stone for growing mosses, liverworts, 

 and ferns. This is also watered b}' a constant drip, and the plants 

 grow rapidly and remain in good condition under their favorable 

 environment. The little enclosure is constructed after the model 

 at Smith College, designed by Prof. W. F. Ganong. 



Fig. 2. Cross and longitudinal sections of cement aquaria. a,ba.ndl, different 

 thicknesses and grades of cement. 



We have never been troubled to any extent with leakage, 

 although for a few weeks magnesia from the cement ran down 

 over the stone on a lower corner of one aquarium. It has been 

 said thgct cement is not a good substance for aquaria, but we 

 have had plants and fish in ours eA^er since we constructed them, 

 and have never noticed any ill effects. Still, it would be a wise 

 precaution, on account of the magnesia and other chemicals in 

 cement, to fill and empty the aquaria once or twice before put- 

 ting in plants or fish. 



As we do not like to have too much mnning water in our 

 aquaria on account of its effect on the plants, we have made 

 some use of aerators. A de^'ice which will give a large number 

 of minute bubbles has been rather hard to find, but our experi- 

 ments have shown that if air under slight pressure is forced 

 through cylinders of wood about h inch in diameter and f inch 



