121.92 45 7.22

10 ...... 480 (Bottom) 146.30 44.5 6.94

11 ...... 500 152.40 44 6.67

12 ...... 600 182.88 43 6.11

13 ...... 772 (Bottom) 235.30 41 5.00

14 ...... 1506 (Bottom) 459.02 39.2 4.00

It will be seen from the foregoing numbers that the
temperature of the water decreases with increasing depth to
about 700 or 800 feet (213 or 244 meters), and below this
depth it remains sensibly the same down to 1506 feet (459
meters). This constant temperature which prevails at all
depths below say 250 meters is about 4 degrees Cent. (39.2
Fah.). This is precisely what might have been expected; for it
is a well established physical property of fresh water,
that it attains its maximum density at the above-indicated
temperature. In other words, a mass of fresh water at the
temperature of 4 deg. Cent. has a greater weight under a
given volume (that is, a cubic unit of it is heavier at this
temperature) than it is at any temperature either higher or
lower. Hence, when the ice-cold water of the snow-fed streams
of spring and summer reaches the Lake, it naturally tends to
sink as soon as its temperature rises to 4 deg. Cent.; and,
conversely, when winter sets in, as soon as the summer-heated
surface water is cooled to 4 deg., it tends to sink. Any
further rise of temperature of the surface water during the
warm season, or fall of temperature during the cold season,
alike produces expansion, and thus causes it to float on
the heavier water below; so that water at 4 deg. Cent.,
perpetually remains at the bottom, while the varying
temperature of the seasons and the penetration of the solar
heat only influence a surface stratum of about 250 meters in
thickness. It is evident that the continual outflow of water
from its shallow outlet cannot disturb the mass of liquid
occupying the deeper portions of the Lake. It thus results
that the temperature of the surface stratum of such bodies of
fresh water for a certain depth fluctuates with the climate
and with the seasons; but at the bottom of deep lakes it
undergoes little or no change throughout the year, and
approaches to that which corresponds to t