Bodies of Water 45 



in which the winter temperature is too low for the grow- 

 ing of fruits. 



The chief local determinant of immunity from frost 

 (aside from latitude and altitude) is proximity to bodies 

 of water. These bodies act as equalizers of temperature. 

 The water holds latent heat, and it does not respond 

 quickly to atmospheric fluctuations. Therefore, it is 

 cooler in summer and warmer in winter than the adjacent 

 land. The larger and deeper the body of water, the greater 

 is this equalizing effect on the temperature of the shores, 

 other things being equal. As between the two, great 

 depth is more important than great expanse of surface. 

 Lakes only a mile or two wide may exert a very profound 

 influence over the adjacent land if they are very deep. 

 The distance to which the protecting influence of the 

 water may extend is determined very largely by the con- 

 formation of the shore lands. As a rule, there are distinct 

 slopes toward the water, and it is rare that the effect of 

 the water on the temperature extends much beyond the 

 crest of the elevation. When the elevation is 300 feet or 

 more, in the northeastern states, the region of immunity 

 from frost ordinarily does not extend more than two- 

 thirds of the distance to the summit. Along the central 

 New York lakes, when the slopes are steep, the area of 

 the tender fruits, as grapes, does not reach more than 

 }4 mile or one mile. The famous Chautauqua grape-belt 

 is confined to a strip about 2 to 3 miles wide lying against 

 Lake Erie, and reaching an elevation at its landward mar- 

 gin of less than 200 feet. Along the eastern shore of Lake 

 Michigan, the peach area extends from 1 or 2 miles to 15 

 or 20, depending on the conformation of the surface. Along 

 the lower Hudson River the area of the tender fruits does 

 not depart, as a rule, more than a mile or two from the 



