572 
BULLETIN OF THE BUREAU OF FISHERIES. 
a depth greater than the t umber stated an amount of heat equal to one maximum 
day’s supply in summer. 
Nor is this all. The upper lo meters contain from 45 to 65 per cent or more of the 
heat absorbed. This region is that in which nocturnal cooling, the action of waves, and 
the direet penetration of the sun aid in distributing the heat. At depths where these 
agencies cease to act the influence of the wind declines very rapidly. 
It is worth while to call attention to the fact that the distribution of heat is strikingly 
similar in each year and that the two years show marked differences. 
Figure 8 (p. 566) shows in graphic form the results for 1910 in the case of Owasco 
Lake and Seneca and Cayuga Lakes, respectively the largest and deepest and the smallest 
and shallowest of the lakes. The greater quantity of heat in Seneca Lake was due 
almost wholly to the greater amount distributed to the hypolimnion, that in the epilim- 
nion and thermocline being about equal in both lakes. It thus appears that in general 
the distribution of heat is independent of the area or depth of the lakes, in the case of 
lakes of the first class. The mean of observations made in Green Lake, Wisconsin, 
during 10 or 12 years falls midway between the results for Cayuga Lake in 1910 and 
I9ii,and shows that this lake also belongs to lakes of the first class. The curve of 
heat distribution for Canadice Lake is added to show the facts for a smaller lake. 
HEAT SUPPLY OF THE SMALLER LAKES. 
We must now consider the heat supply of the two smaller lakes, of which we have 
hydrographic surveys, Canadice and Otisco. We are unable to discuss their annual 
heat budget, as no winter observations have been made on them, but the amount of 
wind-distributed heat can easily be ascertained. It will be remembered that Otisco 
Lake has an available length of about 7.33 kilometers and a mean breadth of 0.93 kilo- 
meters; its maximum depth is 20.1 meters, and its mean depth 11.2 meters. The 
corresponding figures for Canadice Lake are: Length, 5.12 kilometers; mean breadth, 
0.51 kilometers; maximum depth, 25.4 meters; mean depth, 16.4 meters. The ratio 
^^is about O.S3 in Otisco, which is not far from the mean of that in case of the six 
Dmx 
m 
deeper lakes. In Canadice Lake — — = 0.64, a number nearlv one-third higher than 
Dmx 
the mean of the other lakes and about 16 per cent greater than the highest one. This 
fact is of great influence on the heat supply of Canadice Lake. 
Both lakes are small and shallow as compared with those which have been discussed. 
Their mean temperature is correspondingly high (Otisco, 19.2°; Canadice, 15.8°). Both 
temperatures, and especially that of Otisco, are much above that of the deeper lakes. 
The mean depth, however, is so small that the total amount of wind-distributed heat. 
Dm (Tm®-4), is much smaller. In Canadice this sum is 19,400 gram-calories per square 
centimeter of surface, and in Otisco Lake the amount is still smaller, 17,000 gram- 
calories. It appears therefore that Canadice Lake accumulates about 80 per cent as 
much heat per unit of surface as the larger lakes and Otisco Lake about 65 per cent 
as much. 
