96 IOWA ACADEMY OF SCIENCE 



near as possible to the place where the record of depth when 

 the lake was surveyed was 132 feet. The records of temper- 

 ature were taken by a minimum thermometer kept in a hori- 

 zontal position and weighted so as to sink readily. 



The following are records of the temperature at the bottom 

 of the lake near the center of oscillation July 13 : 



At the end of the pier at the laboratory: at surface, 68.7°; 

 at the bottom, 67.1° (six and a half feet deep). 



Half way between the pier and the hook : at the surface, 68.3° ; 

 at a depth of 5 feet, 67°; at the bottom, depth 10 feet, 67°. 

 The daily observations of the temperature of the . water at the 

 end of the pier are recorded with meteorological data in tables 

 at the end of this paper. 



The observations at the end of the pier give a surface tem- 

 perature of the water that follows the curve of maximum tem- 

 peratures of the air. The curve of maximum temperature 

 varied with the amount of sunshine. The surface temperature 

 of the water fluctuated between 64° Fahr. and 75° Fahr., often 

 in the morning toward the latter part of the month being above 

 the temperature of the air at the time, and also above the tem- 

 perature of the air during stormy weather. A day of bright 

 sunshine with little wind produced a rise of a degree or two in 

 the temperature of the surface water. In the evening the dif- 



