New York Weather Bureau. 441 



the formation of ice, the preyailing winds are the polar winds 

 from the north; consequently they are warmed by the lake be- 

 fore they reach Ithaca, while these cold winds pass only over the 

 land to convey the heat away from Geneva. But in summer, 

 when the prevailing winds are the return current from the equa- 

 tor, those winds for Ithaca come from off the land and are not 

 cooled by the lake until after they have passed the town." Ob- 

 servations are then quoted, showing that " the influence is quite 

 manifest in winter, producing a difference of 3.3 degrees in favor 

 of Ithacja, their average being 29.4 degrees, ours 26.1 degrees. In 

 summer the difference is slight and is in their favor until the last 

 half of August. For the first half of September their average is 

 62.9 degrees, ours 63.3 degrees. For the last half theirs is 56.1 

 degrees, ours 57.6 degrees." 



^' During the whole of summer Ithaca's return current comes 

 from over a tract of land which is quite uneven in surface and 

 has a mean temperature considerably lower than Ithaca itself. 

 Duriijg the first part of the summer, until about the middle of 

 August, our return current comes, not from the lake at all, but 

 from a point of the compass too far west of south to have been 

 influenced by the lake. After the first of August we have a 

 much larger proportion of southwest winds, and then we begin 

 to feel the influence of the lake, and while the influence is in the 

 direction of cooling during the day it effects a retardation of the 

 process of cooling during the night, and thus, as I presume, 

 while the average for the twenty-four hours is greater than 

 theirs, our days are cooler and our nights are warmer than at 

 Ithaca." 



Making due allowance for the cooler exposure of the present 

 University Station at Ithaca, which is four hundred feet above 

 that referred to by Dr. Wilson, the normals given in the general 

 table of this report are in suibstantial agreement with the above 

 statements, which will also hold true of the Central Lake region 

 as a whole. 



