SECOND RECORD OF OSCILLATIONS IN LAKE LEVEL 35 
weeks of the session (June 26-July 2 and July 10-16). Four 
rainfalls caused marked elevations in the surface of the lake. 
One occurred in the night of June 28-29, when a heavy rain 
raised the surface 1.75 inches. On July 2 the surface was raised 
.4 inch, on July 19 it was raised .5 inch and on July 24, .6 inch. 
In each case the graph shows the presence of large storm waves. 
Slight fluctuations that seem due to oscillations in the level 
of the lake at the point of observation are noted in the graph 
for June 30 and for July 2, each amounting to .06 inch, when 
waves were small, each oscillation varying through a period of 
ten hours. On July 19 there was a rise in the level of the 
lake of about .06 inch for about six hours at the point of ob- 
servation, and then a return to the former level without a corre- 
sponding depression. This was accompanied by high waves, 
when a strong wind shifted from southeast to northwest. In a 
similar manner on the night of July 23-24 there was an oscilla- 
tion when there were large waves preceding a thunderstorm. 
The wind had been in the southwest the day preceding the storm. 
Of changes in direction during the storm there is no record. 
During the night of July 23-24 the wind gauge recorded an 
average velocity of 9.1 miles per hour. This was the only in- 
stance during the time that the wind gauge was used that there 
was any relation to be detected between wind velocity and the 
oscillations in the lake. During that time the wind was almost 
constantly from the southwest. Generally when the wind gauge 
near the laboratory (and about sixty feet above the lake) re- 
corded a velocity of about four miles per hour the wind out in 
the center of the lake was strong enough to raise large waves 
on which white caps were nearly ready to appear. 
CIRCULATION IN THE LAKE, AND THE TEMPERATURE. 
Changes in the circulation of water at the end of the pier were 
noticeable, and these followed tl^e direction and velocity of the 
wind. They were of two types: When the wind blew strongly 
toward the laboratory from the lake not only were floating ob- 
jects tossed up on the beach but the warm water at the surface 
was pushed in and down, SO' that often when the wind was pro- 
longed the water at the bottom was at the same temperature as 
that at the surface at the end of the pier where the water was 
