GASES DISSOLVED IN THE WATERS OF WISCONSIN LAKES. 



By EDWARD A. BIRGE, 



Secretary Wisconsin Coinmission of Fisheries. 



In the following paper I propose to sketch briefly a small part of the work on 

 lakes which the Wisconsin Geological and Natural History Survey has been 

 carrying on during the past four seasons. During 1907 and 1908 our investi- 

 gations have been aided by a grant of money from the United States Bureau 

 of Fisheries, which has enabled us to extend our field work much more than 

 would have been possible without this assistance. 



LAKE DISTRICTS OF WISCONSIN. 



The accompanying sketch map (fig. i) roughly indicates the position of 

 the lakes that have been studied. Wisconsin contains many hundreds of small 

 lakes, most of them lying in the moraines and found in hollows occasioned by 

 the melting of blocks of ice left during the glacial period. They occur in three 

 pretty well-defined districts, in the southeastern, the northeastern, and the 

 northwestern parts of the state. The water of the lakes in each district, though 

 varying much, shows a very definite general character, especially in the matter 

 of dissolved carbonates. 



The southeastern lake district, as studied by us, extends from Waupaca 

 on the north to Lake Geneva on the south, and from the lakes at Madison to 

 Lake Michigan. Nearly 50 lakes in this district have been studied by our 

 survey, and almost without exception they contain considerable quantities of 

 dissolved carbonates, represented by 30 cubic centimeters to 50 cubic centi- 

 meters or more of carbon dioxide. Most of the work has been done upon these 

 lakes. Very numerous observations have been made upon Lake Mendota at 

 Madison, the headquarters of the survey, and some hundreds of series of deter- 

 minations have been made on this lake at all seasons of the year. Much less 

 frequent observations have been made on a dozen or more other lakes in the 

 same region, giving a general picture of the annual cycle of gas changes of these 

 lakes, though not in the same detail as for Lake Mendota." 



"The diagrams accompanying this paper have been selected from a great number which have 

 resulted from the work of this survey, and are intended to illustrate some points in the distribution of 

 temperature, of the various gases, and of dissolved carbonates of hme and magnesium in the waters of 

 Wisconsin lakes. In all diagrams the vertical spaces represent the depth in meters. The horizontal 

 spaces represent either degrees centigrade in the case of temperature, or cubic centimeters of gas per 

 liter. The line marked "T" indicates the temperature; oxygen is marked "O "; nitrogen, "N "; carbon 

 dioxide, " C " ; and carbonates, " Cb." In the diagrams which show nitrogen, both "-iis gas and oxygen 

 were determined by boiUng. In those without nitrogen, the oxygen was determined by titrating 

 according to Winkler's method. The alkalinity or acidity of the water were determined by titrating 



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