FINGER LAKES OF NEW YORK. 



233 



mates which will show the general situation and in our almost complete ignorance of 

 the subject, such statements are not without value. 



We take, therefore, as the summer heat income of Seneca Lake 34,000 cal./cm.' 

 of surface. Of this sum, 32,400 cal. are found below i m.; 28,000 cal. below 5 m. ; 

 and 21,900 cal. below 10 m. These figures are based on the calories found per square 

 centimeter of the depth in question, and not those per square centimeter of the 

 surface. In computing the relative work of sun and wind these figures must be 

 used, since the sun's radiation which passes through the shallow water is absorbed by 

 the bottom of the lake. 



The distribution of this heat, attributing all work to the wind, requires about 

 2,874 g- cm. of work per square centimeter of the lake's surface. This work is distrib- 

 uted (fig. 3) at the rate of about 290 g. cm./cm.^ of the surface at the surface; 270 

 g. cm./cm." at i m. depth; 202 g. cm./cm.- at 5 m. ; and 125 g. cm./cm.^ at 10 m. In 

 the upper 5 m. there is done about 45 per cent of the total work; about 33 per cent 

 in the 5 to 10 m. stratum, both of which are within reach of the direct influence of the 

 sun; about 20 per cent more of the work comes in the 10 to 15 m. stratum. 



Applying the experience gained from observations on Lake Mendota, it may fairly 

 be assumed that Seneca Lake receives about 65,000 cal./cm.- of surface during the 

 period of the summer heat income. The lake loses, therefore, about one-half of the 

 incident heat. 



If we apply the mean sun data of Table 12 to this gross income, the sun delivers 

 during this period about 13,400 cal. to the depth of i m. ; 3,000 to 5 m. ; and 450 to 

 10 m. These numbers are, respectively, 41 per cent, 11 per cent, and 1.9 per cent of 

 the quantity of heat which passes through these levels. (See Table 7 for quantity of 

 heat.) 



The work attributed to the wind at these depths would be diminished by the aid 

 of the sun in the same ratio that the heat delivered by the sun bears to the total amount 

 of heat passing through those levels. Computed on this basis, the sun does all of the 

 work of distributing heat at the surface, 41 per cent at i m. depth, 11 per cent at 5 m., 

 etc. These quantities may be plotted as on figure 3 (p. 229) and the points connected 

 by a curve. Then the area ODBO is proportional to the total work done by the sun 

 under the conditions assumed. This area may be measured with a planimeter. It is 

 equal to about 16 per cent of the area representing the total work. The part of it 

 below I m. is about 10.9 per cent of the work done below i m. of depth. 



This represents the maximum possible aid which, under the conditions assumed, 

 the sun can give in the distribution of heat, for it assumes that the entire loss of inci- 

 dent radiation by the lake, amounting to one-half of that received, falls on the wind- 

 placed heat and that no loss falls on the sun-placed heat. This assumption is evidently 

 not correct. If, instead, we assume that the sun-placed heat suffers equal losses mth 

 that distributed by the wind, the aid of the sun will be reduced to about S per cent 

 of the total work done and to about 5.5 per cent of the work done below i m. 



Probably the assumption of equal losses is unfair to the sun. A great part of the 

 lost heat is in that which is absorbed by the thin stratum at the surface and is used in 

 evaporation, lost to the air at once or during the following night, etc. Almost all of 

 the heat in the longer waves of the spectrum is absorbed by a much thinner layer of 



