. Animal activities; a first book in zoo?logy. Zoology; Animal behavior. Fig. 7.—An American Pond- weed. Another method of purifying the air in water consists in forcing a stream of air through it. This is not prac- ticable in most schoolrooms. Pouring fresh water against the side of the aquarium in such a way that many bub- bles of air are caught in the descending stream is a common and easy method. Large aquaria frequently have a constant supply of running water with a regular outflow. Such aquaria are hardly neces- sary in most schools. Small rectangular glass vessels and common battery-jar
. Animal activities; a first book in zoo?logy. Zoology; Animal behavior. Fig. 7.—An American Pond- weed. Another method of purifying the air in water consists in forcing a stream of air through it. This is not prac- ticable in most schoolrooms. Pouring fresh water against the side of the aquarium in such a way that many bub- bles of air are caught in the descending stream is a common and easy method. Large aquaria frequently have a constant supply of running water with a regular outflow. Such aquaria are hardly neces- sary in most schools. Small rectangular glass vessels and common battery-jars answer every purpose. Of course water lost by evaporation must be re- placed. With the aquatic animals mentioned here it is a good plan to depend partly on plants to change the air in the water, but in addition to this it is better to remove the greater part of the water from time to time and to replace it by a fresh supply. An easy way to accomplish this is to have all the aquaria placed on a shelf a little higher than the faucet from which water is to be supplied. A hose can be attached to the faucet for the purpose of filling the aquaria. In order to empty the vessels, it is only necessary to unscrew the hose from the faucet while it is still filled with water, being careful to keep the end of the hose in the aquarium under Fig. 8.—The Horn- wort. Fig. 9.—A Duck- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original French, Nathaniel Stowers, 1854-. New York [etc. etc. ] Longmans, Green and Co
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