S-i6 REPORT OF THE COMMISSIONER OF FISHERIES. 



tributes a veiy small part to the total atmospheric balk, is extremely 

 soluble. 



Ignoring- its minor constituents and regarding the argon group of 

 gases with the nitrogen, the atmosphere is apj^roximately made up of 

 79 parts of nitrogen gas and 21 parts of ox3"gen gas by volume. The 

 carbon dioxid present has no particular connection with the gas dis- 

 ease and will not be referred to further. A\'hen water is exposed to 

 the atmosphere it absorbs these two gases until a state of equilibrium 

 is reached, when no further change takes place and these gases, if the 

 temperature and pressure remain constant, are neither further absorbed 

 nor given off by the water. The latter is then said to bo saturated 

 with air. If now any change takes place in the temperature of the 

 water, or in the pressure which it sustains, either a further absorption 

 will occur or some of the aii" will l)c given off from the water. These 

 changes, especialh' under artificial conditions, may occur rapidly, and 

 the adjustment to an equilibrium ma}' not keep pace; therefore, at 

 at any given time water may fall short of saturation and air be pass- 

 ing into it, or it ma}' be supersaturated and air be passing awa}' from 

 it, assuming of course in either case that it is not protected from con- 

 tact with the atmosphere. In other words, water may hold in solution 

 an excess or a dcticienc}* of air, or an excess or deficiency of either 

 one of the air gases, nitrogen or ox3^gen, independentl}' of the other. 

 The rapidit}' with which water supersaturated or infrasaturated with 

 air will become saturated, or in equilibrium, will depend upon the 

 area of its contact with the atmosphere. It therefore follows that 

 water only moderately exposed to the atmosphere, as in tanks or most 

 containers, may remain for a considerable time either above or below 

 the saturation point. But the tendeuc}" is constantly toward the 

 equilibrium of the saturation point, which will ahva3's finall}' be 

 reached. 



The actual amounts of nitrogen and of ox3-gen Avhich water will 

 absorb from the atmosphere have been determined by analyses of air- 

 saturated water. Authorities differ somewhat in the results. The 

 figures cited here and in the tables give the highest values. One liter 

 of pure water at 0^ C. , the freezing point, and at a pressure of 760 

 mm. of mercur}', the standard atmospheric pressure, will absorb 19.53 

 c. c. of nitrogen from the atmosphere (Pettersson and Sonden) and 

 10.18 c. c. of oxygen (Winkler); at 20^ C. and 760 mm., 12.8 c. c. 

 nitrogen (Dittmar), and 6.35 c. c. of oxygen (Winkler). Pure sea 

 water takes up somewhat less. These figures are taken from Comey's 

 Dictionary' of Solubilities. 



RESPIRATORY PROCESSES AND MECHANISM IN FISHES. 



To understand the effect of supersaturated water upon fishes it is 

 necessarv to consider the respiratorv processes and the mechanism by 



