12 



THE UTILITY OF FORESTS. 



BLiew . . . .66-2 degrees Fahr. 



Charkow . . . .68-1 ,, 



Szemipalatinsk . . 72-2 ,, 



Although there is a steady rise of temperature along this line, 

 reductions occur at Promenhof, Hochwald and Arvavaralji. 

 These three are situated close to extensive forests. The late 

 Mr. Blanford, while Meteorological Reporter to the Government of 

 India, drew a similar line across the gangetic plains into Assam, 

 Sylhet and Cachar, which gave data pointing to similar results. 

 They are interesting, but should be received with some caution, 

 as it is very difficult to assess the effect of other causes, such as 

 exposure to air currents and the presence of sheets of water. 



(b) The Temperature of the Soil follows that of the air overlying 

 it. The following is an abstract of observations made near the 

 50th degree northern latitude : — 



Differences of Mean Temperature of Soil between Forest 

 AND Open Ground in Degrees Fahr. 



The mean annual temperature of forest soil is decidedly lower 

 than that of soil in the open ; in summer by nearly 7 degrees, and 

 very little in winter, while spring and autumn hold intermediate 

 positions. The difference for the whole year is greatest near the 

 surface, but about the same at one foot below and beyond. It 

 decreases in spring from the surface downwards, while it increases 

 in autumn ; it is about the same in summer. 



The effect differs considerably according to species. It has 

 been found in Switzerland that the reduction produced by spruce 

 woods amounts to 4-81, that by beech to 3-01, and that by larch 



