Birge—Heat Budgets of American and European Lakes. 171 
contains 1 liter, this sum gives the number of large calories 
necessary to raise a column of water, whose base is 1 sq. cm., 
and whose height is the maximum depth of the lake, from 0° 
to the temperature at the time of observation. This method was 
later modified by employing the mean temperature of each 10 in. 
section of the column of water instead of the temperature of the 
ends of the section. The unit of 'area was altered to the sq. 
dm., thus multiplying the number of calories in the result by 
100 and escaping the necessity of using fractions of a calorie. 
This method permits a study of the gain and loss of heat in 
any one lake, but it does not permit a comparison of different 
lakes. 
If the method is applied to the New York lakes, the following 
results will be reached; 'which should be compared with those 
of Table A. 
TABLE 1 
ANNUAL HEAT BUDGETS OF NEW YORK LAKES, COMPUTED BY FOREL’S 
METHOD 
Calories 
Calories 
Gain, 
Lake 
Winter, 1911 
Summer 
cal. 
Cayuga . 
30,100 
(1910) 92,000 
(1911) 86,400 
61,900 
56,300 
Seneca . 
62,600 
(1910) 120,400 
(1911) 109,300 
57,800 
46,700 
Owasco .. 
3,500 
(1910) 59,700 
(1911) 53,900 
56,200 
50,400 
*Green (Wis.) . 
16,200 
(1910) 68,600 
(1911) 67,100 
52,400 
50,900 
The method can also be applied to measure the gains of heat 
above 4°, and the result for 1910 will be as follows: 
TABLE 2 
SUMMER HEAT-INCOME OF NEW YORK LAKES, COMPUTED BY FOREL’S 
METHOD 
Lake 
Calories, 1910 
Lake 
Calories, 1910 
Canadice .... 
25,000 
Otisco... 
27,000 
Canandaigua. 
40,100 
Owasco. 
39,700 
Cayuga . 
40,000 
Seneca. 
44,500 
■*Grfifvn fWis.l . 
39,800 
Skaneateles. 
39,200 
* This Wisconsin lake is smaller than the New York lakes, but of the same type. It 
is constantly used in comparison with them in Birge and Juday ’14. 
