LOCAL CLIMATOLOGY. 



97 



whereas Geneva is at the north end. The lakes are much the same in 

 size ; about forty-five miles long, with an average width of two or three 

 miles. Cayuga lake, however, is much the shallowest, and freezes over 

 more extensively than the Seneca. 



The point of contrast, however, is chiefly this : the one is at the south 

 end, and the other at the north end of a long and narrow valley filled 

 with a body of standing water. Now, from what has been said, we 

 should expect that the place at the south end would receive much more 

 of the warming effects of the lake in winter, and less of the cooling effects 

 in summer, for the reason that in winter, while the water is warmer than 

 the air, and is also giving out heat by the formation of ice, the winds are 

 prevailingly the polar winds from the north ; consequently they are 

 warmed by the lake before they reach the town ; — while the winds from 

 the pole (the cold winds) pass over land, and from the land to the water, 

 to convey the heat away from us. But in the summer, when the pre- 

 vailing winds are the return current from the equator, those winds for 

 Ithaca come from off the land, and have not been cooled by the lake 

 until after they have passed the town. 



WINTER. 



SUMMER. 



Month. 



Ithaca. 



Geneva. 



Month. 



Ithaca 



Geneva. 



December, 1st half . . . 



do 2d do ... 

 January, 1st do . . . 



do 2d do . . . 

 February, 1st do . . . 



do 2d do ... 



32.93 

 27.98 

 29.53 

 27.17 

 24.13 

 28.82 



30.28 

 26.69 

 24.96 

 25.40 

 23.48 

 26.03 



June, 1st half 



do 2d do 



July, 1st do 



do 2d do 



August, 1st do 



do 2d do 



63.69 

 66.77 

 69.80 

 71.47 

 68.90 

 68.37 



60.60 

 64.81 

 70.44 

 71.14 

 71.58 

 68.09 



Thus, while the influence is quite manifest in the winter, producing a 

 difference of 3°.28 in favor of Ithaca, their average for the winter being 

 29°.42, ours 26°.14. 



In the 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°.88, ours 63°.34; for the last half, theirs 56°. 08, ours 57° 61. 



During the whole of the summer their return current comes from over 

 a tract of land which is quite uneven in surface, and has a mean or 

 average temperature considerably lower than Ithaca itself During 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 compass too 

 Cab. Nat. 13 



