564 
bulletin of the bureau of fisheries. 
4° so late that the whole season of later warming may be thrown over into the period 
when days are long and winds are light. Thus there might be a correspondingly small 
amount of wind-distributed heat. As a matter of fact, this result did not happen in 
the case cited, since Skaneateles Lake gained its full quota of heat in 1911 and this will 
usually be the case. 
The last heat gained by a lake is in the epilimnion and therefore is near the surface — 
in the New York lakes not below 15 meters. The wind velocity from mid-July on through 
August is not essentially less than it is during the preceding six weeks. The surface is 
still receiving a great amount of heat, and the increasing length of the night adds to the 
chances of distribution. Thus in general a lake gains by the middle of August all of the 
heat that the wind can get into its depths; and whether a lake starts to accumulate its 
wind-distributed heat two weeks or so earlier or later makes little if any difference in 
the general result. In any case the heat is supplied to the deeper water of the lake early 
in the season before the velocity of the wind has greatly fallen. 
Table XI. — Calories per Square Centimeter of Surface Needed to Raise Water of Lakes 
FROM 4° TO Summer Temperature, or the Amount of Wind-Distributed Heat. 
Lakes. 
Dm. 
meters. 
Tm"-4. 
X910. 
Calories. 
rm ^ 4 , 
I9II. 
Calories. 
Tm“-4. 
1912. 
Calories. 
38.8 
54-5 
30-5 
29-3 
88.6 
43-5 
33- 1 
7. 07 
5 * 26 
8.17 
9 - 59 
3-71 
6. 10 
7.90 
27,400 
28,600 
24, 900 
28, 100 
32.900 
26, 700 
25.900 
5-99 
4. 94 
7. 48 
8.86 
3-35 
6. 84 
7.42 
23, 200 
26, 900 
22, 800 
26,000 
29, 700 
29, 700 
23 I 500 
Owasco 
9 - 93 
29,000 
(“) 
26,000 
Green (Wis.) 
7.96 
“ See p. 565. 
Table xi shows that Keuka Lake has the smallest amount of wind-distributed 
heat in both years and Seneca Lake the largest. So far as the former lake is concerned, 
it seems probable that this will be the regular condition, the narrowness of the lake 
and its steeper banks reducing the influence of the wind. It is not so certain that the 
result in Seneca Lake will be confirmed by further study, although this conclusion 
seems probable. No two lakes can be more nearly equal in area or similar in topo- 
graphical condition than are Seneca and Cayuga Lakes. But three factors contribute 
to give Seneca an advantage in gaining heat during the early part of the season — 
steeper slopes, greater depth, and greater volume. The result of these was that Seneca 
Lake absorbed more heat into its deeper water than did Cayuga in 1910. The water 
of Seneca Lake below 30 meters received i ,600 calories per square centimeter of the sur- 
face of the lake more than the corresponding water of Cayuga, and in 1911 the excess 
was about 300 calories. 
The steeper sides of Seneca Lake give it an advantage in distributing heat to the 
deeper water, since the large shoal areas at the north end of Cayuga Lake tend to keep 
the return currents near the surface; but the chief advantage of Seneca Lake is in the 
greater reduced thickness (p. 566) of its several strata. If the results for Cayuga and 
