A LIMNOLOGICAL RECONNAISSANCE 



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of the water in the lake of greater volume is lower but the 

 total quantity of heat is greater. 



The same point may be further illustrated by consider- 

 ing the temperatures reported by Dr. Tilton for Okoboji 

 in 1916 and comparing these with maximum temperatures 

 for Geneva. 



Compare first the budgets of Okoboji lake in 1919 (Table 

 19) and 1916. They are approximately 21,000 and 23,000 

 respectively" — a difference of 2000 cal. If the temperature 

 of the epilimnion is reduced to 23° they are 19,800 cal. and 

 20,800 cal., respectively — a difference of 1000 cal. in favor 

 of 1916. Yet in that year the temperature of the water 

 below 15 m. averaged more than four degrees higher than 

 in 1919 ; but as the total reduced thickness of the lake below 

 15 m. is only 240 cm. this rise in temperature represents 

 an income of only about 1,000 cal. cm.^ of the surface. 



In lake Geneva we find a summer heat-income of about 

 29,000 cal., in 1899, or, placing the temperature of the epi- 

 limnion at 23°, an income of 28,300 cal. Thus Geneva may 

 gain from 6,000 cal. to 7,000 cal. more than has been found 

 in Okoboji, assuming the correctness of Dr. Tilton's record 

 of 1916. 



Lake Geneva has been visited for so many seasons that 

 we can hardly expect to find in its temperature a much 



