Id 



TROPICAL AQUARIA 



and insulated from the influence of surrounding air by plenty of wool or 

 cotton batting. It contains a large body of mercury over which the gas 

 passes through a small space. As the water rises in temperature, the 

 mercury expands and so reduces this passageway, and vice versa. It 

 is a ver}' ingenious and effective device and may be obtained from 

 makers of scientific glassware at small cost. Those selling them are 

 glad to give complete instructions regarding regulation, etc. With this 

 equipment in operation one never need worry about aquarium tem- 

 perature as long as the wind cannot blow out the small pilot light. 

 The thermostat is not in itself a heater, but merely controls the source 

 of heat so as to keep a nearly uniform temperature. 



Electric light bulbs in the water are good heating units. Submarine 

 sockets are made for immersing the whole light, or the ordinary socket 

 may he used by immersing only about tv/o-thirds of the bulb. 



Shipping Tropical Fishes. It is bad policy 

 taking the risk of shipping tropical fishes when 

 the weather is not settled and warm. They 

 ma}' keep warm during the train travel, only 

 to receive a fatal chilling in delivery. To guard 

 against this some shippers have designed special 

 boxes equipped with an extra outside shell, the 

 intervening space being filled with an insulating 

 substance, ground cork being excellent for this 

 purpose. A simple expedient consists of a tin 

 can (with a tight lid) or glass jar set in a wooden 

 box, then completely covered with ground cork, 

 excelsior, papers or other substance, and the lid 

 nailed down. The top of the box should be 

 1)oldly marked, stating contents. A handle on 

 the top will help keep the top side up. 



The best method of transporting tropicals, 

 where it does not interfere with interstate laws, 

 is to get in touch with a Pullman porter and 

 have him carry them through, packed in a grip. 

 Ventilation is unnecessary. 



Fig. 60. 

 Gas Thermostat 



