REPLANTING FOLLOWED BY HUMIDITY. 117 



entering into new and inorganic combinations, and that the element 

 will finally disappear from the globe." I do not know anything of 

 the facts or the reasonings on which this opinion rests. 



If it be necessary, in considering the effects of forests on the 

 humidity of the climate, to take into account cases in which the 

 extensive destruction of forests does not appear to have powerfully 

 aflfected the quantity of the rainfall over a wide expanse of country, 

 it is no less necessary to take into account other cases in which the 

 extensive destruction of forests does appear to have been followed by 

 a marked desiccation of land, and aridity of climate. They are facts 

 perfectly compatible with each other, and the establishment of either 

 is neither a disproof of the other, nor does it invalidate the testimony 

 on which it is received, though it may prompt to a more strict 

 scrutiny of what is said, and of the credibility of this, than might 

 otherwise have been given to it. Let it suffice here to state that the 

 objections to which such statements are open are these, first, that 

 they are vague and general, and, second, that they relate to effects 

 which may have been otherwise produced than in accordance with the 

 supposition advanced ; and what is considered the cause may have 

 been in reality the effect, for anything to the contrary advanced in 

 the statements made. 



Sect. III. — Cases in ivhich the Destruction of Trees has been followed 



hy Desiccation, and the Replanting of Trees followed by 



the Restoration of Humidity, 



In treating of the Hydrology of South Africa, in a separate 

 volume already referred to, I had occasion to cite St. Helena as a 

 South African Island supplying illustrations of corresponding effects 

 produced on the climate both by the destruction of trees and by 

 extensive sylviculture. 



From a note appended by Emsmau to his German translation of 

 a work on meteorology in relation to cosmical phenomena by Foissac,* 

 it appears that in the beginning of the sixteenth century the forests 

 of St. Helena must have been extensive, for it is stated by him, on 

 the authority of the introductory chapters in Beatson's St. Helena, 

 that it was the goats which destroyed the beautiful forests which, 



* Meteorologie mit RUcksight auf die Leiiere vom Kosmos. Deuich von 

 A. U. Emsman, Leipzig, lb59. 



