FINGER LAKES OF NEW YORK. 



223 



Table 8. — Amount op Heat in Summer Heat Income and Work Necessary to Distribute It. 



INoTE. — Expressed in units per square centimeter of the depth in question; not (as in other tables) in units per square centimeter 



of the lake surface.] 



ABSORPTION OF SUN'S ENERGY. 



Observations were made in 1918 on Seneca, Cayuga, and Canandaigua Lakes in 

 order to ascertain the rate at which the energy of the sun's rays is absorbed by the 

 water of the lakes. The instrument is described in another paper (Birge, 192 1), 

 and the description will not be repeated. It consists of a receiver containing 20 sma41 

 thermal couples which can be lowered into the lake to any desired depth and alternately 

 exposed to the sun and covered. The electrical effect of the sun's radiation on the ther- 

 mal couples is proportional to the energy in its rays, and the resulting electrical cur- 

 rents are measured by the deflections caused in a d'Arsonval galvanometer. The 

 galvanometer is kept on shore and is connected with the receiver by an insulated cable 

 100 m. long. 



The observations on the three lakes afford excellent illustrations of the results 

 obtainable by this instrument, and also of the difficulties which necessarily attend 

 observations of the kind if made in the course of a short visit, when ever}^ opportunity 

 must be fully used. The general results from each lake are clear and unmistakable, 

 but in each case the details are affected by special conditions of sky or water. 



A part of the observations on Seneca Lake is given in Table 9 in order to show the 

 nature of the data. 



