84 ILLINOIS STATE ACADEMY OF SCIENCE 



SOME PHENOMENA IN A DYING LAKE 

 Melvin a. Brannon, President, Beloit College 



The purpose of this discussion is to bring to the atten- 

 tion of this Academy some of the salient findings asso- 

 ciated with the biological studies of a lake which is rap- 

 idly disappearing in the glacial drift regions of North 

 Dakota. The latitude and longitude of this lake are 48° 

 north and 98° west, respectively. The average annual 

 range of temperature is from 35° below zero in winter to 

 95° above zero in the summer. Ice a meter or more 

 thick forms in the winter. Winds with a velocity of 20 to 

 35 miles per hour move over the lake during many days in 

 the months of Julj^, AugTist, and September. They cause 

 a rajDid lift in vapor pressure on the water surface and 

 consequently evaporation is very high during the sum- 

 mer months. 



The territory from which Devils Lake receives its 

 water is an inland drainage basin. There is no outlet 

 from this lake other than that afforded by evaporation. 

 The result is that its specific gravity has now reached 

 a point where the water contains 1^/^% solution of the 

 salts of lime and magnesium. These salts are chiefly in 

 the form of carbonates and sulphates. 



Dr. Warren Upham made a definite study of this inland 

 drainage basin in his work on glacial lake Agassiz. The 

 following quotation from his report is of interest: 



"Through the past hundred years maximum and mini- 

 mum stages of the great Laurentian lakes have alternated 

 in cycles of about a dozen years, during which compara- 

 tively scanty average rainfall for several years was fol- 

 lowed by an unusually abundant rainfall. These fluctua- 

 tions are similar to those just noted in the rainfall of 

 North Dakota. Besides such short cycles important secu- 

 lar changes of the mean annual precipitation in this 

 State, occupying considerably longer periods, have 

 caused remarkable changes in the levels of numerous 

 lakes which have no outlet." 



''Devils Lake thus shows evidence of having attained, 

 about the year 1830, a level of sixteen feet higher than 



