30 INDIRECT UTILITY OF FORESTS. 



Scotch pine woods ; on the other hand, during January 

 spruce woods moderate the extremes of cold twice as much as 

 heech or Scotch pine woods. This is due to the dense foHage 

 of beech in summer and its leafless condition in winter ; 

 while the leaf canopy of Scotch pine woods is always much 

 thinner than that of spruce woods. The range of difference 

 is greatest in the case of beech woods. 



The above data indicate that forests situated immediately 

 to the north and south of the 50° northern latitude reduce 

 the temperature of the air in their interior, which effect 

 communicates itself to the surrounding country owing to the 

 continuous interchange of air between the two. The actual 

 effect, it was thought, might be even somewhat greater than 

 the above data show, because many of the outside stations 

 were situated so close to the edge of the forest that their 

 temperature was already somewhat affected by an interchange 

 of the air. This was indicated by the fact that greater 

 differences of temperature were observed in those cases 

 where the outside stations were situated at a great distance 

 from the edge of the forest. With the view of arriving at 

 more final results on this point, a commencement was made 

 in Austria to establish a system of so-called radial stations, 

 that is to sa}^, several series of points of observation which 

 commence in the centre of a considerable block of forest and 

 are placed in various directions, at fixed intervals, from the 

 centre and gradually into the open country surrounding the 

 forest. In this way, it has been ascertained that the effect of 

 forests on the temperature of the air in the adjoining open 

 country is very limited. 



Dr. Woeikof, late Director of the Meteorological Institute 

 at St. Petersburg, has published several series of figures, with 

 the view of illustrating the effect of extensive forest areas on 

 the temperature of the surrounding countr3^ He gives the 

 mean temperature of July for various series of places, each 

 series being situated as near as possible on the same degree 

 of latitude, after having reduced the data to the same latitude 



