364 EEPORT OF THE COMMISSIONER OF FISHERIES. 



flowed through the hatcheiy troughs, ponds, etc., and has gathered in 

 a waste brook at some distance below the hatchery and pond system, 

 save that the process has not been complete enough to remove all the 

 excess of nitrogen ("creek water" sample, Table IV). In fact, the 

 adjustment begins the instant the water emerges from the wells, and 

 in most cases by the time it reaches the fishes it contains somewhat 

 more oxygen and less nitrogen than at the well. The efi'ect of the 

 cleaerating process on the loss of trout fry was shown by passing the 

 "reservoir pond water" through a finely perforated metal plate with 

 a fall of about 3 feet. During a trial of nine days a trough containing 

 6,000-7,000 fry lost 645, against a loss of 2,583 in a similar trough 

 containing the same number, but supplied directly from the pond 

 without deaeration. The process, .which did not completely correct 

 the water, reduced the loss 75 per cent. Complete correction would 

 probably result from repeating the process or by sufficiently increas- 

 ing the fall. The water of hatchery well No. 1 was completely relieved 

 of its excess of nitrogen b}^ allowing it to flow drop b}^ drop down an 

 inclined wooden plank 10 feet in length. (See Table IV, p. 374.) 



Very few of the Nashua wells delivered free gas, and these only in 

 small amounts. From one of these about 500 c. c. were delivered and 

 collected during twenty days and constitute sample 2 of Table I. Only 

 air gases were present. Part of the sample was tested for methane, 

 unsaturated hydrocarbons, and carbon monoxide, without showing a 

 trace of any of these. (Dr. D. A. Morton, Syracuse, N. Y.) The 

 sample had no marked odor. The largest pond at the station, used 

 chiefly as a reservoir supply and largely spring-fed, had a soft bottom 

 from which occasional large bubbles rose. By ramming the mud with 

 a stick, large quantities of a gas about 96 per cent nitrogen (Table I) 

 could be released. Methane, which might have been expected, was 

 absent. This gas seems to be of much the same origin as that from 

 the air-bearing spring in Tennessee, though delivered in much smaller 

 quantities, and ma}^ reasonably be supposed to come from a depth 

 great enough to cause the supersaturation which existed in this pond, 

 as in all the sources of water in the vicinity. 



At the Nashua Station the gas symptoms were in evidence, but were 

 less marked than in either of the other described cases of the results 

 of supersaturated water. Exophthalmia with presence of gas appeared 

 in adult trout in ponds, and the general condition of these trout was 

 poor. This condition is believed to be secondary to the supersatura- 

 tion, which, while not sufficient to kill the adults directly by embolism, 

 causes the protrusion of the e3^e and consequent inflammation. The 

 partial or total blindness resulting keeps them from feeding properly, 

 and as they fall off in condition and become weaker they are attacked 

 by the fungus Saprolegnia. Among the deaths which resulted no 

 case of free gas Avithin the vessels was discovered. The fry showed 

 occasional gas blisters externally, and in very young fry gas was fre- 



