9o6 BULLETIN OF THE BUREAU OF FISHERIES. 



necessarily harmed by water which any chemist would pronounce unfit from a 

 sanitary standpoint. 



There must be established what may be called a fish-cultural analysis, and 

 the information this will give should cover, among other things, the reaction and 

 degree of alkalinity or acidity, hardness, total solids, sulphates, nitrates and 

 chlorides, the carbonic acid, the dissolved oxygen, nitrogen, and carbon dioxide; 

 and an ordinarj^- mineral analysis with special tests for any unusual metals 

 which there is any reason to suspect. The determinations of the atmospheric 

 gases named should be made on the perfectly fresh sample. The dissolved air is 

 the most important, and the nitrogen as important as or more so than the oxy- 

 gen. Temperature, turbidity, color, etc., are physical characters which the 

 chemist will note. Having obtained these results, not all of them can yet be 

 accurately interpreted. For the atmospheric gases one can form immediately 

 a fairly definite opinion, but as for total soUds and the minerals present, we 

 know but little of the limits of safety. Therefore it is that the final test is 

 experience itself. A long experience with fish culture and aquarium experi- 

 ments in water whose contents are accurately known ^vill ultimately lead to the 

 establishment of definite standards which will be useful to fish culture, just as 

 the long-continued chemical examination of service waters in the light of the 

 results of their usage has led to standards confessedly not well defined, but which 

 are nevertheless useful in selecting sanitary waters. 



