358 Wisconsin Academy of Sciences , Arts , and Letters. 
TABLE 8. 
Comparison of Lake Geneva and Green Lake, 1913. 
Geneva 
Green 
Summer heat-income, cal. 
26695. 
,17.50 
2336.6 
23005. 
20.15 
27316. 
12.25 
Mean temperature, C°. 
Total work, g. cm.. 
2022.6 
21886. 
18.85 
Calories 0 m.-20 m. 
Mean temperature, 0 m.-20 m. 
Calories below 20 m. 
3690. 
5450. 
Work, 20 m. and below, g. cm. 
RT. 0 m.-20 m., meters. 
500.6 
14.3 
5.5 
476.5 
14.7 
18.4 
RT. 20 ra. to bottom, m. 
By summer heat-income is meant the quantity of heat gained by the lake above 4°. See Birge ’15, p. 2. 
The quantity of heat and of work is stated in this table, as well as elsewhere, in units per sq. cm. of the surfaoe 
of the lake. 
The heat income in each lake is about the same; Green 
lake having an amount somewhat greater and accumulated 
with the expenditure of decidedly less work. This is the 
customary relation of the lakes. The amount of work done in 
warming the water of the two lakes at depths below 20 m. 
is closely alike. This might be expected, since lakes of the 
same size and form ought to be able to furnish about the 
same amount of work to distribute heat at such a depth. 
The amount of heat distributed by the work is, however, 
very different, lake Geneva securing from 500 g. cm. of 
work only about two-thirds as much heat as Green lake 
gets from 476 g. cm. This is because the shallower lake in¬ 
volves a higher temperature, and the rise of temperature in¬ 
volves an increase of thermal resistance which exceeds the 
increase of work due to the greater depth of Green lake. 
This, however, does not tell the whole story; for in this 
statement the units of work and heat are referred to a unit of 
area at the surface of the lake. If they are referred to a unit 
of area at the 20 m. level the disadvantage of the shallower 
lake becomes more apparent. The area of lake Geneva at 
20 m. is 50.7% of that at the surface, and that of Green lake 
is 61.0%. If the figures for work and heat are divided by 
these numbers the result is: 
TABLE 9. 
Geneva 
Green 
Heat per sq. cm. of area at 20 m., cal. 
7280 
8930 
Work at 20 m., g. cm. 
990 
780 
