284 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
temperature, which is apparently more eujoyable to them than a lower 
one, as they are undoubtedly more active and playful. By this means 
trout may be kept at a temperature of 70° without noticeable discom- 
fort to them, although, perhaps, 60° to 68° is a safer and surer limit, 
in view of possible accidents. The accompanying figure will illustrate 
the method in question. 
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jii 
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The great efficiency of this method of water supply over any other 
has been fully demonstated in the keeping of marine fishes at the ma- 
rine station of the Commission at Wood’s Holl, Mass. Many marine 
species require even more oxygen than the salmonidse, and thus the 
system has received substantial tests, and can be confidently recom- 
mended not only on account of the introduction of a large amount of 
air and a saving of ice and labor, but on the score of economy of water 
also, which is very often a matter of considerable importance. When 
the temperature rises above 70° it can be cooled by introducing the 
necessary amount of ice directly or by passing the water through a coil 
of pipe surrounded by ice. The retardation of the stream of water by 
the use of the very small nozzles gives it ample time to cool, and it 
can be brought down to a very low temperature. As ordinarily used 
the pipe coil has been a failure, because the water passed through it too 
rapidly to be cooled. At the Cincinnati Exhibition the water in an 
aquarium tank 18 by 18 by 48 inches was kept at a temperature of 48° 
by passing it through 70 feet of one-fourth-inch lead pipe coiled in an 
ice-chest 18 inches square, and from that through about 30 feet of rub- 
ber tubing wrapped with newspapers, passing into the tank in a one- 
sixteenth-inch stream. 
In changing trout from iced water to aquaria operated in this way it 
