Birge—On the Evidence for Temperature Seiches. 1007 
hypolimnion on the lee side of the lake and raising it on the 
windward side, furnishes the conditions for starting a seiche. 
But as the wind declines or ceases and the liypolimnion swings 
hack toward its former position, does it continue its movement, 
rising above the normal at the lee side of the lake, and then 
falling so as to start a series of pendular oscillations ? Or is 
the return so slow and the hypolimnion so loaded by the 
epilimnion that movement practically ceases when the iso¬ 
therms have returned to the horizontal position ? If the first 
question is answered in the affirmative, then what are the 
extent and influence of such pendular oscillations? These 
questions are to be answered on the basis of observation. If 
periodic movements of considerable magnitude can be shown 
which, started by the wind, are thenceforward independent of 
the wind and of the movements of the epilimnion, then the 
case is proved. 
I must confess that I find the evidence adduced by the Loch 
Hess observers insufficient to prove their case. Heither Watson 
nor Wedderburn seems to have carefully discriminated move¬ 
ments directly associated with wind from those which are pos¬ 
sibly independent of it. All movements of the surface of the 
hypolimnion are apparently referred to indiscriminately as 
seiches. Even the greatest temperature changes are listed as. 
seiches, which, if they were such, would involve a vertical 
swing of the water amounting to 200 feet, or more. An ampli¬ 
tude of 100 feet is said by Wedderburn to be quite ordinary. 
Many of the movements in July, 1904, as well as all of those' 
of August, seem to be regarded as seiches. Certainly there' 
must have been some movements which were correlated with, 
the wind, and it would seem that Watson and Wedderburn 
should analyze the complex movements of temperature in and! 
below the thermocline and should point out which are due to 
seiches and which are of other types. Yet no attempt is made 
to do this and I cannot see that either author furnishes any 
criterion by which to discriminate temperature changes due 
to a seiche from those due to other movements of the hypolim¬ 
nion. 
