PAPERS PRESENTED AT GENERAL SESSIONS 87 



biological questions which are of particular importance 

 in the investigations of dying lakes. 



The chemical composition of the water in Devils Lake 

 has been determined many times during the twelve years 

 that the Biological Laboratory staff has been studying 

 the life of its waters. In 1910 our chemists gave the fol- 

 lowing report : 



TONIC COMPOSITION 



Parts per million 



Calcium 4.0 



Magnesium 603.9 



Sodium 2908.8 



Bicarbonate Ion 708 . 



Carbonic Acid Ion 126 . 



Sulphuric Acid Ion 6098 . 4 



Chlorine 1177.0 



11626.1 

 HYPOTHETICAL COMBINATION 



Calcium Bicarbonate 2.4 



Magnesium Bicarbonate 846 . 9 



Magnesium Carbonate 177 . 1 



Magnesium Sulphate • 2029.9 



Sodium Sulphate 6625 . 9 



Sodium Chloride 1177.0 



10859.2 



Total residue 12429 . 



Silica 12 . 2 



Iron Oxide plus Aluminum Oxide 4.0 



Considerable quantities of organic matter and of in- 

 soluble matter were present. The water stood for a long 

 time in a warm room. It is quite possible that some of 

 the calcium bicarbonate was decomposed in this way, 

 precipitating out calcium carbonate. This may account 

 to some degree for the small amount of calcium found. 



Devils Lake is shalloAv, twenty feet being its maximum 

 depth. High winds churn the water frequently during 

 the spring, summer, and autumn. Obviously the oxygen, 

 nitrogen, and carbon dioxide would have a continual and 

 rapid vertical distribution during the open season. 

 Analysis of gases at different levels of the lake in 1911 

 gave the following readings : 



1911 Depth 



June 1 Surface 7.49 cc of 0; per liter of water — 13' level 5.76 cc 



June 29 " 5.39 14' " 4.22 " 



July 22 " 5.55 13' " 3.46 " 



July 31 " 5.46 15' " 4.64 " 



Aug. 7 " 5.40 Bottom 18' 2.14 " 



