A LIMNOLOGICAL STUDY OF THE FINGER LAKES. 
565 
Seneca Lakes are compared in table xii, it will be seen that the water of Cayuga Lake 
has a higher temperature than the corresponding stratum of Seneca Lake, but the strata 
of Seneca have the greater reduced thickness and so contain more heat. 
But for the present the most important conclusion from the table lies in the general 
fact that for lakes 10 kilometers or more in length and 30 meters or more in mean 
depth, the annual gains of wind-distributed heat are on the whole independent of area 
or depth and range from something below 25,000 calories to something above 30,000 
calories. It is not asserted that in these lakes different areas and depths have no 
effect. The contrary is true, as is shown above, but in general these effects lie within 
the range of the variation due to local conditions in wind and weather. No doubt 
under exactly similar conditions the largest and deepest lake will gain most heat, but 
the effects of area and depth are such that they may be overcome by variations of 
weather. In 1910, for instance, Owasco Lake, the smallest and shallowest of the New 
York group, stands third in the amount of heat, and in 1911 Skaneateles Lake is equal 
to Seneca Lake and is much above the far larger and deeper Cayuga Lake. 
From these facts we may give a second definition for inland lakes of the first class: 
In inland lakes of the first class the wind-distributed heat, Dm(Tm® — 4), is about 25,000 
gram-calories per square centimeter of surface and usually exceeds that sum. Such 
lakes will be, under the climatic conditions of the eastern United States, 10 kilometers 
or more long and will have a mean depth of 30 meters or more. If such a lake falls 
below 25,000 calories, the deficiency will be due to exceptional conditions of topography 
or weather. If its gains rise above 30,000 calories, this result will also be exceptional. 
Further study is needed to make these statements more accurate in detail. Such 
study will show the presence and limits of the influence of area and depth within this 
class of lakes. 
In 1912 temperatures were read in Skaneateles Lake on October 18, too late for 
the maximum temperature of the upper water. The water at the bottom was 6.3°, 
much higher than in 1910 or 1911. The temperatures below the depth of 40 meters 
would be practically unaltered on October 18. If these are taken as they were found, 
and if we assume that the temperature of the water above 40 meters was the same in 
1912 as in 1910, then Tm® for 1912 would be 10.72°. If we, in like manner, assume 
for 1912 the same temperature for the upper water as in 1911, then Tm® 1912 would 
be 1 1 .33°. On the basis of the latter figures the maximum annual heat budget between 
Tm'" 1911 (1.10°) and Tm® 1912 (11.33°) would be 44,500 gram-calories. This shows 
that under favorable conditions the annual heat budget of these lakes may go as high 
as 45,000 gram-calories per square centimeter. The wind-distributed heat in 1912 
for Skaneateles Lake on these assumptions would be 29,200 gram-calories and 31,800 
gram-calories, respectively. 
distribution of HEAT. 
Distribution to thermal regions (fig. 8). — The formula for the amount of wind- 
distributed heat is Dm(Tm®-4). The product is the number of gram-calories per 
square centimeter of surface which the lake must receive that its temperature may 
