802 MODIFICATIONS OF ASPECTS OF ORGANIC NATURE 



rays which strike on the needle-shaped leaves of an adjacent wood 

 of ordinary acreage, made up of such trees as the spruce or the 

 larch ; and the vapour which is thus set free into the entire cir- 

 cumambient atmosphere alike of glacier and of wood, acts most 

 potently in several ways in the direction of saving the glacier from 

 wasting. 



On the other hand, great as the influence of the evaporating 

 power of trees and forests may be shown to be in some directions, 

 it is possible enough to overrate it as regards such more than 

 localised matters as the increase of the rainfall. 



*It is,' says Dr. Brandis ('Ocean Highways,' Oct. 1872, p. 204), 'a widely spread 

 notion, entertained by many writers who are competent to judge, that forests increase 

 the rainfall, and that the denudation of a country in a warm climate diminishes its 

 moisture. Much of what is known regarding the history and the present state of the 

 countries round the Mediterranean seems to support this theory, but it has not yet 

 been established by conclusive evidence.' 



The important point seems to be that in mountains this influence 

 may count for something considerable, whilst in the plains, how- 

 soever well wooded, trees can act only as do other good radiators in 

 the way of precipitating, not wind-borne moving vapour, but simply 

 dew. 



Mr. N. A. Dalzell, in the Report on the Sind Forest for 1859- 

 1860, observes (par. 31): — 



* Although it would be too hardy an assertion to say that the existence of forests in 

 Sind causes any increase in the fall of rain, they certainly do so on the summits and 

 tops of mountains;' and par. 35 : *In enumerating the benefits derived from forests, 

 I make here no use of the fact that forests attract rain-clouds, because I do not think 

 it applicable to plains, and because it is not yet clear that causes are not mistaken for 

 effects, that is, whether it is the rain produces forests, or forests which produce rain ; 

 and certainly no inhabitant of Sind would consider it legitimate to decide that because 

 a country is covered with wood, therefore it is wet.' 



It is satisfactory to be able to add that the result of Professor 

 Ebermayer's prolonged observations in Bavaria has brought him 

 to the same conclusions as those of Dr. Dalzell, carried on in the 

 very alien surroundings of Sind. Dr. Ebermayer's words on this 

 subject, used in summing up the results of his researches, are 

 (1. c, p. 202) : — 



'Auf Grund unserer Untersuchungen, glauben wir daher besuchtigt zu sein an- 

 nehmen zu dtlrfen, dass in Ebenen von gleichern allgemeinen Charakter der Einfluss 

 des Waldes auf die Regenmenge jedenfalls sehr gering ist, und dass er auch auf die 

 procentische Regenvertheilung keine Einwirkung hat. Mit der Erhebung iiber die 

 Meeresoberflache nimmt die Bedeutung des Waldes beziiglich seines Einflusses auf 



