SITE FOE AN ORCHARD. 201 



ble-lands of our timbered regions, or the extended areas 

 of the prairie country, we shall find that the drift forma- 

 tion which covers these vast tracts, lias not been distrib- 

 uted evenly, but that there are successive rolls or swells 

 frequently recurring, which give, in some instances, con- 

 siderable variations of level. A bold ridge, of fifty feet 

 or more in hight, rises abruptly from the level prairie, 

 stretching along for miles, and affording admirable expos- 

 ures for orchard sites. Such places are observed to be 

 free from late and early frosts. In other places, there is 

 an abrupt depression of the surface, answering the same 

 purpose drawing off the cold air. These may be very 

 moderate in their extent, as the prairie sloughs, or they 

 may be small vales, the courses of the minor streams, or 

 of larger extent, the valleys of rivers, or the depressions 

 of lakes. In these latter cases, the modifying influences 

 of considerable bodies of water enter into the frost prob- 

 lem as an element of no mean value. 



It may be asked : How do these masses of water affect 

 the frost ? Science answers : By their evaporated mois- 

 ture influencing the atmosphere. This may save us from the 

 blighting influence of frost, by enveloping the frozen vege- 

 tation in a wet blanket of fog ; enabling it to be thawed 

 in the dark, as it were, by which we avoid the influence 

 of a bright sunshine, that would have destroyed the tissues 

 had they been suddenly exposed to it when frozen. An 

 equally important result is derived from the direct influ- 

 ence of the humidity of the atmosphere, which modifies 

 the temperature remarkably, as in the immediate vicinity 

 of large bodies of water. Insular sit nations especially, even 

 when low, are known to have a more genial climate in 



