Page:The American Boy's Handy Book edition 1.djvu/87

outside of the glass a coat of green paint on all but one side, leave that clean and transparent to serve as a window, through which may be observed the interior and its occupants. The rockery or arch that is to occupy the centre of the aquarium should be cemented together with marine cement. Although this is not absolutely necessary, it is the best plan, and prevents many accidents. The following receipt I cull from the Scientific American:

Cement for Marine Aquaria.—Take 10 parts, by measure, litharge, 10 parts plaster-of-Paris, 10 parts dry white sand, 1 part finely powdered resin, and mix them when wanted for use into a pretty stiff putty with boiled linseed oil. This will stick to wood, stone, metal or glass, and hardens under water. It resists the action of salt water. It is better not to use the tank until three days after it has been cemented.

The arch may be built out of clean cinders or ragged and irregular stones; an old oyster-shell with its rough side uppermost can be used as a top-piece. To make the arch steady and not liable to upset, the bottom should be composed of rather large flat stones.

Cover the bottom of the aquarium to a depth of an inch or more with sand from the beach. Procure the salt water from the ocean itself, and if possible obtain the supply some distance from shore. In no case must you dip the water for your aquarium up from the mouth of a fresh-water stream or muddy creek. If the tank is narrow and deep, fill only about one-third of it. Let the water stand in the aquarium for several days before introducing the plants. Select the bright algæ or seaweeds that you find attached to small pebbles; the stones will of course sink to the bottom of your aquarium and keep the plants in an upright and stationary position. After all is arranged to your satisfaction, choose a place for the location of your tank where there will be light enough to plainly see its contents