Birge—On the Evidence for Temperature Seiches. 1009 
corded. I shall, therefore use these in my discussion, espe¬ 
cially as Wedderburn’s illustrations are almost wholly taken 
from them. 
The diagram of temperature movements which Wedderburn 
gives ( ? 07, p. 421) is not easily read. I have, therefore, 
platted on a different scheme and a larger scale his observa¬ 
tions from noon of Aug. 14 to noon of Aug. 21, (Plate LXVI). 
This period includes three of the five major movements of 
the thermocline which came in August, and also includes the 
swing that looks to me most nearly as I suppose a great seiche 
would appear. The rise of temperature in the hypolimnion, 
shown in the center of the diagram (Aug. 17), is that chosen 
for special illustration and discussion by Wedderburn. It 
seems to me plain that this great swing of the isotherms was 
not a seiche, as defined by Watson. Examination of the dia¬ 
gram will show that during Aug. 16 the wind was constantly 
from the southwest, off shore, and the isotherms steadily rose 
as the warmer surface water was blown away, until in the 
afternoon the epilimnion practically disappeared. At 4 a. 
m. of Aug. 17 the wind shifted to east and then to north¬ 
east and blew from that quarter for nearly 20 hours. Under its 
influence the warm surface water returned to fill the end of 
the lake, crowding down the hypolimnion. After some ten 
hours of this wind, the filling extended out to the yacht and 
caused a sudden and great rise of temperature. Then as the 
northeast wind dropped and was followed by calms and south¬ 
west breezes, the displaced hypolimnion swung back toward 
its normal position and the isotherms rose with it. This is 
my reading of the movement, nor can I see ground for a differ¬ 
ent interpretation. It is certainly clear that the movement 
was by no means independent of conditions in the epilimnion 
but, on the contrary, was directly associated with changes of 
wind which must shift the epilimnion and so tend to cause 
the movement of temperature in the hypolimnion. These 
forces also seem wholly adequate to effect it and there is no 
need of supposing a seiche in order to explain it, 
If this temperature change was caused by an on-shore wind, 
it is obvious that the sudden downward sweep of the isotherms. 
