200 AMEEICAN POMOLOGY. 



The frost line becomes a very important subject of in- 

 quiry in the selection of an orchard site, and in some 

 countries we find that its position may be definitely settled 

 within a limited range of elevation ; not that a certain 

 level can be indicated, above which there will always be 

 an immunity from frost, while all below will suffer, but 

 we may approximate, in certain situations, so nearly as to 

 indicate that certain sites are safe or unsafe. 



If or is it the absolute elevation alone that is to be taken 

 into the account ; in any given locality, we may assume 

 that the higher the orchard is situated above the water 

 levels, the safer it will be, and that tlie lowest depressions 

 are the most unsafe or frosty. It is not always the mere 

 elevation, but rather the relative elev.ation of the site, that 

 renders it more desirable than another in the same region. 

 There are many orchards that are situated upon a moder- 

 ate bluff, with a rapid descent of only a few feet or yards, 

 into a swale or valley of moderate extent ; these we find 

 to be uninjured, when another at a greater elevation, but 

 in a depresssd basin surrounded by higher lands, will be 

 found to have suffered from the influence of frost. In the 

 one case, the cold air could flow off rapidly into the ad- 

 joining depression, while in the other, the cold air from 

 adjoining slopes would collect, and accumulate in the situa- 

 tions desoibed. 



In the great plateaus of the world, we often find im- 

 mense tracts of land so nearly of the same level as scarce- 

 ly to afford sufiicient drainage for the surplus water ; of 

 course, we should expect to find, in such placi.>s, little va 

 riation of temperature arising from difference in elevation. 

 Sut even in such situations, whether we examine the ta- 



