EFFECTS OF. FOEEST YEGETATIOJ^^ OK CLIMATE. 191 



diate reacli of droppings from certain trees, but this, which is 

 due to chemical action, is but a small drawback from the actual 

 sanitary blessings we have bestowed on us by the abundant 

 growth of forests in which these trees are the principal members. 

 A careful perusal of Mr. Bosisto's paper before mentioned, 

 and the learned treatise on " Air and Eain- — The beginnings 

 of a Chemical Climatology, by Kobert Angus Smith, Ph. D., 

 E.E.S., r.C.S., 1872," will, perhaps, be sufficient to show 

 that there is much which to the masses of readers and writers is 

 a kind of terra incognita, wdiich has as yet to be explored before 

 Ave can dogmatize on some of the hidden operations of Nature 

 in regard to vegetation. 



I Avill therefore now bring forward many good examples from 

 foreign countries as to the effect of " forest vegetation on climate" ; 

 and here I would remark that by " Climate" we are not to under- 

 stand exactly what popular use makes of the word. " The single 

 word ' climate,' " says a writer whom I have before quoted, 

 " expresses one of the most important relations of man to the 

 natural world around him — a relation wbich concerns humau 

 existence in its every part. But this Avord climate, taken in its 

 largest sense, comprehends within itself all those elements of 

 matter and force, the -mutual influences and actions of which 

 produce the phenomena so familiar to us under the single 

 expression." 



Dr. Daubeny (Lectures on its influence on vegetation) defines 

 "the climate of a country to be its relations to temperature, 

 light, moisture, winds, atmospheric pressure, electricity, and so 

 forth ; but assigns to its first place heat and its distribution. 

 The present object is to illustrate how one of these relations, viz., 

 moisture, is afiected by forest vegetation, the reverse of the action 

 understood by the Professor. 



If the cutting down of a forest alter the atmospherical con- 

 ditions of any spot, it may be said to affect the climate of that 

 spot, and vice versa. 



If it have any effect on the supply of water to a river, then it 

 aftects its climate in another way ; and in either case men's 

 health or the advantages of life or animal existence in such spot 

 may be affected. 



There is therefore propriety in using the expression " climate" 

 to indicate such a condition of things as existed before changes 

 that may take place. 



The late Professor Daubeny, w^hose work on Climate has just 

 been cited, gives some useful illustrations of the effects I am 

 engaged with. He quotes Boussingault's example of the Lake 

 of Yalentia in Venezuela, which has no outlet, but receives water 

 from rivers and creeks, and where, in regard to the fall of rain 

 and the humidity of the district a change was produced afi'ccting 

 the province. 



