ON QUALITY OF SOIL. 



109 



directly, it lias some compensating advantages not 

 possessed by the latter. It is less exposed to par- 

 tial thaws in winter, which, by causing the snow to 

 melt, leave the ground more exposed to the inten- 

 sity of the frost ; and is likewise less influenced by 

 the violence of the south-west winds, which are often 

 so chilling in spring and autumn ; and, by blowing 

 during the season of vegetation, do more injury than 

 those from the north, which prevail most when the 

 sap of vegetables is at rest. Hence we find, that 

 the Scots fir is not only of the largest size, but best 

 as to quality of timber, in northern aspects ; and 

 even that the hard-wooded species, which require a 

 higher degree of heat to bring them to maturity, 

 grow as quickly, and attain as great a height, in a 

 north as in a south exposure, other circumstances 

 being equal. 



The elevation of the ground in which we plant is 

 a matter of much greater importance than its as- 

 pect ; and, with regard to it, the statement of the 

 following facts may be useful :— It is well known, 

 that, as we ascend in height, the temperature regu- 

 larly decreases, and this is the reason that trees, 

 which grow at the foot of a high mountain, will not 

 thrive at its top. By attending, therefore, to the 

 observations of naturalists and travellers, with re- 



