1849.] 



exercised 'By Trees on Climate, 



411 



of, as to diminished fertility of the soil from the removal of belts of 

 wooded country ; the rationale of this is most evident.* 



The climate of Eio de Janiero has been very much modified by 

 the clearing away of the forests in the neighbourhood. Previous 

 to this the seasons could scarcely be divided into wet and dry as 

 they are at present. Then rain fell nearly all the year round, and 

 thunder storms were not only more frequent but more violent. 

 So much has the moisture been reduced that the supply of water 

 for the city has been considerably diminished, and the Government 

 has in consequence forbidden the further destruction of the for- 

 ests." Gardner's Travels in Brazils. 



Another author remarks that the whole of the eastern front of 

 the range (of mountains in Penang) has within a few years been 

 denuded of its forests, and representations have been often made to 

 the local authorities at Penang, urging the necessity of reserving 

 the jungles, on the summits and higher slopes^ but hitherto with- 

 out effect. * * But climate concerns the whole community and 

 its protection from injury is one of the duties of Government. 

 In Germany and France there are special laws and departments 

 for the preservation and extension of forests. 



It is not necessary to cite Humboldt or Boussingault to prove 

 the great influence in tropical regions of forests, and, especially, of 

 mountain forests, in attracting and condensing clouds, diminishing 

 local temperature and increasing humidity. But if the forests had 

 no other effect than to protect the clay soil^ of the mountains from 

 the action of the sun's rays this alone ought to be sufficient to en- 

 sure their careful preservation. It is in this soil that the waters 

 which supply all the streams of the island, and wliich percolate 

 downward to the lower lands, are enclosed. These m.ountains are 

 in fact great natural reservoirs, elevated in mid air and exposing 

 the most extended surfaces possible, which are covered to a small 

 depth with a sponge of porous decomposed rock for the absorption 

 and retention of water. In ordinary seasons, when there is a con- 

 siderable fall of rain, the importance of preventing the contents of 

 these reservoirs from being dissipated may not be so obvious. But 

 it may now be considered as a well established fact that tlie 

 eastern Archipelago is subject to periodical droughts, althougli the 



* Ecport from Dr. Gibson, dated Qtli March, 1846, 

 YOt. XT. xo,*Xxxvi. ^ 1 



