100 IOWA ACADEMY OF SCIENCE 



proximately half an inch are thought due to waves caused as a 

 steamer made a landing and left, as these lines were made in the 

 daytime and at hours when the steamer was due. 



July 15. There was a strong southeast wind till the rain began to 

 fall; then the wind shifted and blew hard from the southwest at about 

 3:30 P. M. The precipitation amounted to one and one-half inches, 

 but the gauge recorded a rise of only half an inch, the difference 

 being due apparently to the strong wind. 



July 16. The pronounced rhythm is not due to the effects of the 

 storm because the line is straight from midnight to daybreak and 

 straight again Friday night. It is possible the rhythm is due to 

 changing winds of which there is no exact record. 



July 17. There was heavy precipitation and changing winds of 

 which there is no record, excepting as the heavy precipitation raiser! 

 the pen above the revolving cylinder of the gauge (1 and 5-16 in.) 

 Apparently there was a fall of 3-32 inch at eleven o'clock A. M., just 

 before the rain came. 



July 19-25. The graph is characterized by a constant and almost 

 uniform lowering of the level of the lake due to evaporation, equalized 

 by a somewhat strong northwest wind on the 24th, when the line traced 

 became almost horizontal. The remainder of the week the wind was 

 light and the barometric gradient zero. 



July 26. The rise was due to precipitation. 



July 28. The marked rise of three-tenths of an inch was due to the 

 wind which then began to blow from the northwest. 



July 30. The rise was due to precipitation. 



SUMMARY. 



Tidal effects were almost zero, barometric effects too small to 

 be detected without magnification, and intake and outflow about 

 equal. Wind effects were noticeable, and when strong wind 

 was not prolonged, were quickly compensated by movement in 

 the lake. The wind directed the circulation in the lake. The 

 division of the lake water in epilimnion, thermocline, and hypo- 

 limnion was pronounced, even after strong winds. Evaporation 

 amounted to about two-tenths inch per twenty-four hours. Rain- 

 fall caused an immediate rise in the hydrograph. 



