A UMNOI<OGICAI. STUDY OF THE FINGER TAKES. 
563 
for the year and that for August not greatly below this. It follows that there is a great 
surplus of heat, potentially available for warming the lake, which is lost to the lake 
because the means for distributing it are inefficient. 
If 40,000 gram-calories represents the maximum heat budget of such a lake, this 
is little more than half the amount of heat delivered by sun and sky between April i 
and August 31. If 25,000 to 30,000 gram-calories represents a fair average for the wind- 
distributed heat, this again is less than half the heat delivered during that part of the 
warming period after the water of the lake has passed 4°. 
The following conclusions are therefore warranted : 
1. All lakes, whatever their area or depth, are on an approximate equality so far as 
their capacity for absorbing heat is concerned until their water has reached the tempera- 
ture of maximum density, or 4°, and this temperature is reached by all lakes early in the 
open season. 
2. The amount of heat absorbed after the temperature of 4° is passed, depends 
primarily on the efficiency with which the heat is carried from the surface to the deeper 
water, and this work is mainly effected by the wind. 
3. If we compare the gains of heat above 4° made by different lakes, we compare 
their wind-distributed heat, and so are able to compare the efficiency of their means of 
distribution. If the climatic and topographic conditions are similar, the efficiency of 
the means of distribution will increase with the dimensions and the depth of the lake up 
to a certain point. 
4. Since lakes reach the temperature of 4° early in the season, a comparison of their 
gains above 4° serves much the same purpose as a comparison of their annual heat budgets. 
To these statements there are several qualifications, none of which have been worked 
out quantitatively and only one of which need be stated. 
The amount of heat needed to raise the temperature of a lake from its winter con- 
dition to 4° may vary very greatly, especially in case of lakes that freeze. It is probable 
that more complete observations will show a greater proportionate range of variation in 
the amount to which lakes cool below the temperature of 4° than in the rise above 4°. 
The following table shows the facts for the lakes in question. 
Table X. — Calories per Square Centimeter op Surface Required to Raise Water of Takes 
FROM Winter Temperature to 4° and from 4° to Summer Temperature. 
Lakes. 
Calories, 
to 4®, 
1911. 
Calories, 
4® to Tm", 
1910. 
Calories, 
Tm^t0 4®, 
1912. 
Calories, 
4® to Tm®, 
1911. 
9, 600 
9, 400 
5»400 
12, 600 
6, 200 
28. 600 
28, 100 
32,900 
26. 600 
26, 000 
26.900 
26,000 
29, 700 
29*300 
25.900 
7,400 
7,000 
7; 500 
It appears, therefore, that it may require as much as a month’s supply of heat, or 
even more, to raise the temperature of the lake from its winter condition to 4°. In 
such cases as that of Skaneateles Lake in 1910, it is possible that the lake may reach 
