78 REPORT ON THE SI ATE CABINET. 



make even the summers as cold at 35° of latitude as ours are at 42° or 

 43°; or, in other words, these winds make a diflfei'ence in temperature 

 equal to 8° of latitude. 



V. Situation in Heference to Inland Lakes, etc. 



These bodies of water cool the air in summer, and warm it in winter. 



Let us suppose, first, that the air is below 32°. While the lake is 

 open, the air will be warmed by contact with the water and by radiation 

 from it. It has been ascertained by experiment that one cubic foot of 

 water, in cooling 1° Fahrenheit, gives out heat enough to raise 3,080 feet 

 of air 1°, or 300 feet about 10°. 



But again : When the water becomes cold enough to freeze, and freez- 

 ing commences, the solidification gives out what is called the "heat of 

 liquefaction ;" and this, in the formation of one cubic foot of ice, is suffi- 

 cient to raise 691.922 feet of air 1°, or 34.596 feet of air 20°, or 13.854 

 feet 50°. 



Doubtless the tendency of the air, thus heated, is to rise directly 

 upward. But rather than ascend directly through the mass of colder 

 air immediately over it, it is driven by the winds ; and even when there 

 are no winds of any considerable force, it will creep along up the banks 

 of the river or lake, and the sides of the adjoining eminences, softening 

 and modifying their climate by its approach to them. 



On this point I have no statistics within my reach, except such as 

 have been derived from my own observation. January 8th, 1855, the 

 thermometer indicated 7° above at 7 a. m. in my Observatory. At a 

 private residence only a few miles west, back of the lake, it stood at 

 zero; and at Phelps, eight miles northwest, it was i-eported at 7° below; 

 and I have observed similar discrepancies in other cases. Even to the 

 east of us, and between the two lakes, Seneca and Cayuga, the tempera- 

 ture is always found to be several degrees colder when the thermometer 

 reaches a figure below zero. 



Of course, when a lake becomes entirely frozen over, or frozen out a 

 long distance from the shore, it ceases to influence the temperature in 

 the way 1 have described: in the one case, because there is no longer 

 any open surface of water; and in the other, because it is so far off, and 

 is separated from the land by a level surface along which the warm air 

 will not pass as it would if it were ascending. 



The heat thus given out by the cooling of the water and the formation 

 of ice in the autumn and early winter, would of course be returned in 



