FINGER LAKES OF NEW YORK. 



229 



used as the basis of larger conclusions and when in computing the results all radiation 

 is assumed to be direct, the effect of the direct rays of the sun in warming the lake is 

 placed at a maximum. In the preceding paragraph all radiation is supposed to come 

 directly from the sun. In fact at Madison about 16 per cent of the total radiation 



FE c 

 Fig. 3.— Work curves of Scncca Lake, mean temperature. The vertical axis shows depth; the horizontal axis shows gram centi- 

 meters of work per meter of depth and square centimeters of surface of lake. OCC, curve of direct work. About 145 g. cm, 

 of work, for instance, are necessary' to carry the heat of the 9 to 10 m. stratum from the surface and put it in place. BDE, 

 curve of distributed work, derived from OCC, showing the amount of work done in each i m. stratum. The area OBEFO 

 (distributed work) is equal to the area OCCFO (direct work). ODD shows the contribution of the sun in distributing the 

 sun's energy. The area ODDBO gives the contribution of the sun. and that of the wind is represented by the area ODEFO. 

 (See Table i5, p. 235.) 



received April i to August 31 comes during cloudy hours, and about 16 per cent more 

 comes from the sky during sunny hours. The direct sun, therefore, supplies only about 

 two-thirds of the radiant energy received by the lake. It may be assumed that during 

 cloudy hours equal areas of sky supply equal amounts of energy to a surface normal to 

 the rays. On this basis, and allowing for reflection from water surface, the mean path of 



