191 EFFECTS OF FOEEST YEGETATIOJf OX CLIMATE. 



Looking to South America we find that similar conditions may" 

 be traced to those in the northern part of the continent. For 

 instance, the inhabitants of the country assured Humboldt that 

 the extreme aridity of the plains in about latitude 9°, between 

 the Orinoco and the Andes, was occasioned by a diminished fall 

 of rain, and that since the arriTal of the Spaniards the trees had 

 been destroyed. He says it is well known that in Caraccas the 

 climate was destroyed by the removal of the trees, and that 

 rain formerly abounded where now there is none, and after some 

 reasoning, adds — " It results that the desti'uction of forests, the 

 want of permanent springs, and the existence of torrents, are 

 three phenomena closely connected together." Dr. Duncan 

 shows the same results for the Deccan. The Cape de Yerds " 

 show the same connection. Many others instances are named 

 by Dr. Balfoiir, and, as we read in the JReport of the Bombay 

 Geographical Society for 1849, " thousands of similar instances 

 might be quoted." It would be unfair to omit to mention one 

 of the most remarkable of them. I allude to that of the 

 Mauritius, quoted by Yon Mueller. Dr. Rogers A'ery recently 

 issued a report " On the effects of the cutting down of forests 

 on the climate and health of Mauritius." In 1854 the island was 

 resorted to by invalids from India, as the " pearl" of the Indian 

 Ocean, it being then one m^ass of verdure. "When the forests 

 were cleared to gain space for sugar cultivation, the rainfall 

 diminished even there ; the rivers dvdndled down to muddy 

 streams ; the- water became stagnant in cracks, crevices, and 

 natural hollows, while the equable temperature of the island 

 entirely changed ; even drought was experienced in the midst of 

 the ocean, and thunderstorms were rarely any longer witnessed ; 

 the lagoons, marshes and swamps along the sea-board were 

 no longer filled with water, but gave oft' noxious gases ; 

 while the river waters became impure from various refuse. 

 After a violent inundation, in February, 1865, followed by 

 a period of complete dryness, fever of a low type set in, against 

 Avhich the remedies employed in ordinary febrile .cases proved 

 utterly valueless, pestilential malaria arose, exposed to which the 

 labourers fell on the field, and, in some instances, died within a 

 few hours afterwards." ***** Di^.. Eogers 

 very properly insists that the plateaux and highlands of Mauritius 

 must be replanted." — (Yon Mueller, Lecture, 22nd June, 1871, 

 reprinted at San Francisco.) 



Those who think the evidence afforded on the subject is not 

 suificiently scientific will hardly use that argum.ent against 

 Arago, who declares that " forests cannot fail to exercise a 

 sensible influence on the temperature of the surrounding regions. 

 The destruction of forests ought therefore to produce modifica- 

 tion of our climates." He says also : " Clearing the wood from 



