1012 Wisconsin Academy of Sciences, Arts, and Letters. 
main factor in temperature changes in the hypolimnion, the 
temperature phenomena must he clearly analyzed and it must 
be shown which of them are due to the immediate influence 
of wind, which to irregular movements of the hypolimnion, 
and which to stationary waves or seiches. 
There remain to he considered the movement of midnight 
Aug. 19-20 and also that of Aug. 11, which though of smaller 
amount is a similar case and open to similar explanation. 
Wedderburn does not refer to these movements of the isotherms, 
although they appear more like temperature seiches than any 
of the other swings of temperature in August. This is es¬ 
pecially clear in the movement of Aug. 19-20. Reference 
to the diagram will show that on Aug. 19 a northeast 
wind began at 2 a. m. and caused a slight hut obvious 
descent of the isotherms at 6 and 8 a. m. After 10 a. m. 
there was little, or no wind recorded during the day; at 8 p. 
m. it was northeast again, followed by light southwest breezes 
and calm during the night. Between 6 and 8 p. m. began a 
rapid descent of the isotherms, culminating at midnight. They 
remained about stationary during four hours, or more, then 
swung back to their former position, and later, on Aug. 22, 
to a still higher level under the influence of a southwest wind. 
In this case there is plainly an on-shore wind associated 
with the rise of deep water temperatures. It is plain also that 
the rise is greater than would have been expected from the 
amount of wind and that it came later than in the other oases. 
Thus the descent of the isotherms seems not wholly but to 
some degree independent of the movements of the epilimnion 
and their rise is practically independent of the wind. It is 
also to he noted that the 45° isotherm began to move 
downward some four hours before the 50° isotherm. The 
question is not one of association of these movements with an 
on-shore wind, hut of the adequacy of the wind to produce so 
great a swing of the isotherms, which, with a much smaller 
amount of wind than on Aug. 17, is a swing of the same gen¬ 
eral order of magnitude as that. 
I believe that this movement was a secondary effect of that 
of Aug. 17 and that it was directly caused by underwater cur- 
