THE LIBRARY. 53 



3. How they modify the temperature of a country ? 



4. Have forests any influence on the rainfall as to its 

 frequency, or its abundance and distribution, and do they 

 regulate more or less equally the flow of stream sand springs? 



.5. To what extent do they prevent the erosion of 

 mountains and lesser slopes ? 



6. Do forests draw off electricity from thunder-clouds, 

 and if they do so do they to an extent corresponding to this 

 action effect the region of the woodlands ? And 



7. What kind of influence do they exercise upon the 

 public health ? 



But with these preliminary points determined it is neces- 

 sary, he says, in order to determine the effects of forests on 

 any district.to know also the geographical position of this,its 

 geological character, its latitude.its proximity to or distance 

 from the sea, the composition of its soil, and of its subsoil, 

 and whether this may be permeable or the reverse- 

 calcareous or argilaceous all of which particulars can only 

 be determined by observation. Aud he further states thnt 

 the action of forests on the climate will be more or less 

 pronounced according to 



1. The extent, elevation, and nature of the soil and 

 subsoil. 



2. Its exposure in regard to heat or cold, and in regard 

 to the humidity or aridity of the winds. 



.*]. The "season of the year in which fellings are made ; 

 whether the kinds of trees be those with deciduous, or 

 with persistent leaves ; and the evaporation and radiation 

 going on in the different seasons. 



4. According as the season of rains be the spring, the 

 autumn, or the winter ; and 



5. The proximity of pestilential lakes, &c. 



All of these points are discussed in an exhaustive 

 manner, commencing with a permeable soil with a per- 

 meable subsoil, and a permeable soil with an impermeable 

 subsoil; and an impermeable soil with an permeable 

 subsoil, and an impermeable soil with an impermeable 

 subsoil. 



