40 The Principles of Fmit -growing. 



eastern states in May, 1895;* and most of the 

 serious disasters of untimely cold are of this kind. 

 These freezes are mostly beyond the reach of man. 

 He can only move beyond their limits. But injuri- 

 ous frosts may not only be avoided, in many cases, 

 by the selection of the location or even of the site, 

 but they may sometimes be prevented upon the very 

 '.light when they are expected. 



The chief local determinant of immunity from 

 frost 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 the 

 atmospheric fluctuations. It is, therefore, cooler in 

 summer and warmer in winter than the adjacent 

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

 the greater is this equalizing effect upon the tem- 

 perature of the shores. As between the two, great 

 depth is more important than great expanse of sur- 

 face. Lakes which are only a mile or two wide may 

 exert a very profound influence over the adjacent 



* In order to show the natural history of one of these wide-area freezes, 

 the following account is given (by E. T. Turner, Meteorologist of the Weather 

 Bureau of the Department of Agriculture of the State of New York) concern- 

 ing causes which led to the disastrous cold snap of May 13, 189.1, in New 

 York state: 



" For about a week preceding the 12th, the temperature had been very high, 

 from 80 to 85 degrees in the daytime and from 50 to 60 degrees at night. The 

 temperature of the soil must, therefore, have been considerably higher than 

 usual at that time of the year. The conditions which produced the freeze 

 were very general rather than local. About the 9th, the pressure increased and 

 the temperature fell over the western and central parts of the continent. 

 Early on the llth a large low-pressure or storm area passed eastward over 

 Canada, southerly winds flowing into it, giving the high temperature observed 

 here at noon of the llth. But after the storm center passed further to the 

 eastward we were subject to the cold westerly winds which flowed into the 

 depression from the cold high-pressure area in the west, and which continued 



