238 



From December 3 to noon of the 20th the lake was covered with ice. During 

 this period the surface temperature varied from 33° to 34^° and the bottom from 

 35° to 36°. 



At 5:00 P. M. of the 20th, ten hours after the ice started to move in a body 

 from the lake, the surface showed 352°, ^ g^io of 25°; the bottom 375°, another 

 gain of 22°, and in the shallow water, fifty feet from south shore, where it had 

 been 32°, 33°, 33° on the 7, 8 and 9th respectively, it was now 43°, a gain of 10°. 



The next day surface and bottom both registered 37° degrees at the twenty- 

 five-foot station. 



The results of these observations are embodied in the accompanying profile 

 chart, in which it has been attempted to show the absolute and relative move- 

 ments of the air, surface, and bottom of lake at a depth of twenty-five feet. 



/& 2D 



Temperatures from September 23 to December 23. Broken line, temperature of air; 

 dotted line, temperature of water 25 feet below surface on the bottom; continuous line, tem- 

 perature of water at the surface at the same place. 



