Collecting and Rearing Insects 
645 
•outside. (Bicycle-tape is good.) Place an oblong strip of glass 8£ X1 inch 
across the inside of each corner. Fill the space, thus formed, with cement. 
Fig. 812. —Battery-jar aquarium. (After Jenkins and Kellogg.) 
Fill in the grooves of the bottom board with cement before pressing down 
the panes of glass. Where the glass sides join the bottom board use cement 
carefully both inside and out, filling all the cracks. 
The cement should be made according to the following formula: 
White sand. .. . 
Plaster of Paris. 
Litharge. ...... 
Powdered resin. 
Make into a stiff paste with boiled linseed-oil. Use as little oil as possible 
and take proper care in mixing. Leave for several days to harden the 
cement. Then fill slowly and pour off the water several times before using. 
Place an inch and a half of sand on the bottom of the box. This sand 
should be previously baked or boiled to rid it of bacteria. Its main purpose 
is as an anchorage for growing plants. Over this place a layer of variously 
sized pebbles treated in the same way. These form hiding-places for the 
aquatic fauna. Fill with water to the depth of five or six inches. Stock 
with water-plants, the streams or ponds of the neighborhood to determine 
the kind. Watercress, water-crowfoot, Potamogeton, Chara, and eel- 
grass are good kinds. Parrot’s-feather can usually be obtained at nurseries. 
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