408 



Notes on the Influence 



[No. 36, 



standing the severity and length of the winter, thus continues ; 

 indeed in some parts of the island, the crops in particular have 

 been remarkably good, having had plenty of rain at the proper 

 season. Ey comparing with each other the quantities of rain 

 which have fallen during the last seven years, it will be seen how 

 greatly the amount varies from year to year. Many years must 

 therefore elapse before sufficient data can be obtained from which 

 to deduce a correct average of the annual amount. The quantity 

 is perhaps double of what it was in the beginning of the present 

 century. The cause of this increase is doubtless the plantations 

 of trees which have been formed since that period on the high 

 grounds. These plantations appear to have performed another 

 piece of good service to the island. Eormerly heavy floods caused 

 by sudden torrents of rain, were almost periodical and often very 

 destructive. Eor the last nine or ten years none have occur- 

 red. If the cause of these rauis was electrical disturbance, the 

 trees may, by their conducting powers, have controlled the ten- 

 dency.* 



K possessed of the foregoing information, alone, doubts might 

 arise as to whether the extent of vegetation in such countries 

 were not rather the consequence than the cause of the abundance 

 of water, but the observations of other scientific men support the 

 belief that a mutual reaction goes on between these two physical 

 agents, and that the presence of trees greatly adds to the supply 

 of water and feeds the running streams ; and that so soon as man, 

 to supply his wants, has thinned or removed the trees which clothe 

 the hill sides of the district he inhabits, the rain diminishes or 

 rapidly runs off, its rivers dry up, and the previous fertility of its 

 lands completely disappears. As an instance of the consequence 

 of the hill sides being denuded, an intelligent officer has stated 

 that when he first went to Dapoolie, the hills were clothed with 

 trees and shrubs ; they now show nothing but bare rock and earth 

 black and red. The climate is, now, considerably hotter and 

 drier, and streams which then ran in May are now dried up in 

 December.! 



■Humboldt after leaving the town of Caraccas remarks that ma- 



* St. Helena Almanac, 1848, p. 5. 



f Surgeon Dimcan in Bombay Times. 18.'19. 



