38 
IOWA ACADEMY OF SCIENCE Yol. XXIV, 1917 
July 26 seem also to mark the presence of water with different 
temperatures, but not of the extent of that mentioned above. 
The graph gives a thickness of only five to seven meters for 
the epilimnion July 18, and a thickness of only two meters and 
of one meter for the thermocline. The graph for July 26 gives a 
thickness of seven and a half meters for the epilimnion and of 
three and a half for the thermocline. Doubtless these increased 
in the next three weeks. 
•Pig. lc. Graph of maximum and minimum temperature on the porch of 
the cottage at the Lakeside Laboratory during the session of 1916, June 18- 
July 26. 
SURFACE TEMPERATURE. 
The temperature of the surface at the pier rose steadily almost 
daily from 62.5° Fahr. on June 18 to 78.5° Fahr. on July 10, and 
then varied between 78.5° and 83.5° ; so that for bathing the wa- 
ter was generally above 78.5° Fahr. 
Fig. Id. Graph of the relative humidity on the porch of the cottage at 
the Lakeside Laboratory, June 18-July 26, 1916, from observations at 7 
a. m., 12 m. and 7 p. m. 
METEOROLOGY. 
The maximum temperature of the air on the cottage porch 
ranged from 64° Fahr. (June 21) to 93.4° Fahr. (July 23), at 
which time it was ten degrees below the temperature reported 
