140 PRACTICAL TROUT CULTURE. 



Even during the hottest weather, if the ice-pan 

 is kept well supplied, there is rarely need of 

 changing the water oftener than once in twelve 

 hours ; often changing is injurious to the fishes. 

 In the present age of rapid transit, every hour may 

 bring the traveler to water of entirely different 

 qualities. Rain-water should never be used, ex- 

 cept in a case of emergency. Fishes will live, and 

 sometimes thrive, in waters of entirely different 

 chemical character from those in which they were 

 born and bred ; but when confined in a can are 

 peculiarly susceptible to any change in the quality 

 of the element. 



No fear need be felt that the carbonic acid elim- 

 inated in respiration by the fishes will injure them. 

 Trout are frequently found in waters saturated 

 with this, to man, noxious gas ; and, in fact, there 

 are few of our limestone springs which are not in 

 this condition. 



We have made some experiments on the preser- 

 vation of living fishes in air-tight tanks in which a 

 large amount of air had been compressed. The 

 results have, thus far, not been in all cases favor- 

 able ; yet should this succeed, and we have not as 

 yet given up hopes of success, living fishes may 

 be shipped by express as freight or ordinary bag- 

 gage. We hope that if any one of our readers 

 should succeed in this method he will not at once 



