THE VALUE OF OUR FORESTS. ijj 



the amount of precipitation has for some time engaged the attention of 

 naturalists. Such an influence has been asserted, partly from theoretic 

 considerations and partly on account of the entire change presented by 

 the climatic relations of the countries in which the forests have disap- 

 peared. ... It is probable that such influence exists ; but while on 

 the one hand its consequences may be over-estimated, on the other hand 

 there is want of direct proof, inasmuch as the rain measurements have 

 been continued for too short a time, both at stations situated within 

 the woods and outside of them in the open fields. . . . 



" The commission consequently concluded that an influence of the 

 woods upon the amount of rain deposited, and especially upon the yearly 

 contribution, is probable, although direct observation does not give suffi- 

 cient evidence to determine its extent, or positively its existence." 



Dr. Rogers, of Mauritius, gives this testimony : "So late as 1864 

 the island was resorted to by invalids from India, as the * pearl ' of the 

 Indian Ocean it being then one mass of verdure. But, when the for- 

 ests were cleared to gain space for sugar-cultivation, the rainfall 

 diminished, tl^e rivers dwindled down to muddy streams, the water 

 became stagnant in cracks, crevices, and natural hollows, while the 

 equable temperature of the island entirely changed, drought was expe- 

 rienced in the midst of the ocean, and thunder-showers were rarely 

 any longer witnessed. . . . The hills were subsequently planted with 

 trees, and the rivers and streams resumed their former dimensions." 



The Island of Ascension was formerly almost a barren rock. The 

 supply of water was very scanty, derived solely from a few springs, 

 and water was often brought from the Cape of Good Hope, and even 

 from England, for the needs of the garrison. About twenty-five years 

 ago the planting of trees and shrubs and the cultivation of the soil 

 were undertaken vigorously. The water-supply has increased with the 

 progress of this work, until now it is excellent, and the garrison and 

 ships visiting the island are supplied with abundance of water and 

 vegetables of various kinds. 



Observations in France by M. Fautrat, reported to the Academy 

 of Sciences, showed that, in a dense wood of five hundred hectares, a 

 rain-gauge fixed on a tall poplar received much more water than one 

 of similar height three hundred metres beyond the borders of the 

 woods. Experiments continued during two years confirmed the first 

 results, and an instrument placed over a forest of Pimis sylvestris, at 

 twelve metres' elevation, received ten per cent, more water than one at 

 the same height in the open fields. 



But, however the case may be as to the effect of forests upon the 

 amount of rainfall, there can be no doubt that they secure a more 

 equable distribution of the rains than is usual in the open country. 

 They are also great storehouses of moisture. By their myriad leaves 

 they intercept the moisture of the passing clouds or the damp winds, 

 and convey it to the ground, or hold it within their embrace ready to 



TOL. XIX. 12 



