218 



Wisconsin Academy of Sciences, Arts and Letters. 



July, 1891. 



Depth. 



Air tern. 



Surface tern. 



Bottom tern. 



41.85 meters. 



22°.77 C. 



21.° C. 



5.4° C. 



43.5 



23.33 



23. 



5.56 



50. 



22.22 



22. 



5.28 



50.5 



25. 



22. 



5.28 



51.2 



20.55 



22. 



5.28 



56. 



21.11 



21. 



5.28 



57.75 



24.72 



21. 



5.28 



58. 



26.3 





5.28 



We notice that in August, 1890, there was a uniform temperature of 

 6.6° C. below a depth of 45 meters, and that up to 25 meters there was 

 an elevation of temperature of only one degree. In July, 1891, the bot- 

 tom temperature was 5.28° C. While we cannot compare temperatures 

 taken in August, 1890, with those taken in July, 1891, I think we may 

 fairly infer that the maximum bottom temperature in Green Lake is 

 reached in August, and that it remains nearly the same during Septem- 

 ber and October. The surface temperature is nearly the same in all the 

 deeper parts of the lake. Swimmers, in crossing the lake, claim that 

 they pass through "streaks" of different temperatures, but the ther- 

 mometer determinations show a practical uniformity of surface tem- 

 perature. 



In comparing these temperatures with those obtained by Prof, and 

 Mrs. Peckham in Pine Lake (Trans. Wis. Acad. V, 273), I notice that 

 although the surface temperatures in Pine Lake, in both July and 

 August, are higher than in Green Lake, the temperature of the deep 

 water is nearly the same. For instance, in August, 1879, at a depth of 

 18.28 meters, the bottom temperature was 7.23° C, while the surface 

 temperature at the same time was 24.44 ^ C, and in July, at a depth of 

 24.38 meters, the bottom temperature was 5.56° C, and the surface tem- 

 perature 26.12° C. Thus, at 24.38 meters, was reached very nearly the 

 minimum temperature which I found in Green Lake at 50 meters and 

 below. 



