784 Wisconsin Academy of Sciences, Arts, and Letters. 
that these affluents would help somewhat in keeping down the 
temperature of this lake. As stated above, also, the average 
depth of Lower lake is considerably less than that of Upper, 
so that the latter has a greater mass of water in proportion to 
its area. In the shallower parts of Lower lake the sun will be 
more effective in warming the water, for the light that is not 
absorbed by the water will be changed to heat when it reaches 
the bottom, and most of this heat will be absorbed by the 
stratum of water above. Where the water is deep, the light 
will pass to a much greater depth, and thus the sun’s energy 
will be distributed through a much larger quantity of water. 
In 1902, the surface water in Upper lake reached a maximum 
of 16.6° on August 4th, remained practically the same for ten 
days, and then gradually decreased. In 1903, a maximum of 
16.1° was noted on August 7th. The highest temperature noted 
for Lower lake in 1903 was 17° on August 7th. 
The transparency of the water varied somewhat. Both sum¬ 
mers it was found that a Secchi’s disk just disappeared from 
view at a depth of about 5.5 meters in July, and the water 
gradually became more transparent as the season advanced, 
reaching a maximum of nine meters about the middle of Au¬ 
gust. The lower degree of transparency early in the season was 
due to the fact that the snow on the surrounding mountains was 
melting rapidly, and as a result of this, the affluents were 
bringing large quantities of roily water into the lakes. As 
summer advanced, the streams became smaller and their waters 
were clear. 
AQUATIC VEGETATION. 
The larger aquatic plants consisted chiefly of Potamogeton. 
Three different species and one variety were found. They oc¬ 
curred in considerable abundance in both lakes. The following 
were noted: 
Potamogeton nuttallii Ch. & Schl. 
Potamogeton perfolvatus] L. 
Potamogeton perfoliaius richardsonii Bennett. 
Potamogeton praelongus Wulf. 
One or two species of Car ex were found in the pools of the 
