PART II. 



Effects op Forests on the Humidity of the Climate. 



Chap. I. — Immediate Effects of Forests on the Humidity 

 of the Atmosphere. 



There is a wide-spread opinion that forests attract clouds and rain, 

 and a similar effect is attributed to mountains. The facts which have 

 been adduced may enable us satisfactorily to account for the pheno- 

 mena upon which the former opinion is founded ; and with the 

 explanation thus supplied we may be enabled also satisfactorily to 

 account for the latter. The phenomena referred to may be stated 

 generally to be these : forests and mountains are frequently seen 

 surmounted by clouds, stationary or passing over them, when few or 

 none are seen elsewhere in the heavens ; and, though it may be an 

 unwai'rantable conclusion that they have been attracted thither, it 

 does not excite surprise that this conclusion has been drawn from the 

 phenomena observed. In the case of forests we know, however, of 

 no kind of attraction exercised by them which could produce this 

 effect ; the effect can be accounted for satisfactorily in accordance 

 with the phenomena of vegetation which have been under consider- 

 ation ; and in these circumstances it is reasonable to conclude that 

 these supply the correct rationale of what is seen. Of this a simple 

 exposition can be given, and one not less simple can be given of the 

 similar phenomena in the case of the mountains ; and the exposition 

 of the former supplies at the same time the means of accounting for 

 the proverbial dampness of houses overshadowed by trees, or situated 

 in close proximity to woods. 



The meteorological effects of trees and forests may be apparently 

 paradoxical, and accounts of them conflicting and contradictoiy ; but 

 if instead of acting on the principle of cutting the knot we act on 

 the principle of unloosing it we may find that all facts observed and 

 reported are consistent with each other, and that many of them can 

 be accounted for satisfactorily in accordance with what is known of 

 operations patent to all. If, instead of attempting the reconciliation 



