1849.] 



exercised hy Trees on Climate. 



445 



flows from it. Father du Tertre relates that he often found the same 

 kind of refreshment in the horn shaped leaves of a species ofbalisier, 

 which grows on the sandy shores of Guadaloupe. I have heard many 

 of our sportsmen remark that nothing is more proper for quenching 

 thirst than the leaves of the misletoe which grows on our trees. 



The thick green leaves of plantain trees readily condense the mois- 

 ture of the atmosphere, and there is at all times within their differ- 

 ent layers a quantity of pure clear water which may be collected 

 by making an aperture in their stems. A tree of a similar charac- 

 ter exists in the Mauritius, and the first time I became aware of this 

 I received an agreeable surprise when the gardener at Pamplemoos 

 plunged his knife deep into its stem and allowed the stream of pure 

 water to spring in a jet from the wound. 



Such are in part the precautions employed by Providence, to com- 

 pensate in favor of man the inconveniences of every climate by oppos- 

 ing to the qualities of the elements contrary qualities in vegetables.* 



The facts detailed seem to establish, 



1st. That the extensive clearing of a country diminishes the quan- 

 tity of running water which flows over its surface. 



2d. That it is impossible for us to determine, at present, whether 

 this diminution is owing to a smaller annual fall of rain or to an in- 

 creased evaporation of the surface water, or to these two causes 

 combined. 



3d. That it is however shown by the authors above quoted that 

 rain oftener falls, and that more dew is deposited in well wooded 

 countries than when the country is naked; and, drawing our conclu- 

 sions from the meteorological facts collected in equinoctial regions, 

 we may presume that the extensive clearing of a country diminishes 

 the actual quantity of rain which falls upon it. 



4th. That mountains, particularly when covered with their native 

 forests, by an electric action on the atmosphere, cause clouds to 

 form around them; collect and condense the vapours of the air, and 

 equalise the fall of rain. 



5th. That the forest trees which grow on mountain summits have 

 a structure peculiarly fitting them to receive the waters of the clouds. 



6th. That lands destitute of the shelter of trees allow of more ra- 

 pid evaporation. 



* St. Pierre's Studies of Natm-e, vol. u. p. 322, ed. 1846. 



