4? 2 Statt cf WeMhcr m woody Countries. [Book V. 



From thefe fads, and from what is preyioufly re- 

 marked on the fubjeft of evaporation in the fecond 

 feoolc, it is plain, that trafts of land which are covered 

 with trees or luxuriant vegetables are much colder 

 than thofe where there is a lefs furface of vegetable 

 nutter, fuch grounds emitting one third more vapour, 

 according to fome experiments of Mr. Williams, than 

 the fame fpaee would if actually covered with water*. 

 Hence too, a reafon will evidently be found for that 

 amazing change of climate which a country undergoes 

 by being cleared and cultivated. America is not the 

 lame country at prefent, either with refpect to tem- 

 perature or falubrity, as when it was covered witb 

 woods; and Guiana affords a ftill more remarkable 

 inftance. Of that country, only a part has been cleared 

 from wood fmce the beginning of this century ; the 

 heat in that part is already become exceffive ; whereas,, 

 in the woody parts of the fame country, the inhabitants 

 are obliged to light a fire every night. 



It is further obferved, that the pureft fprings arc 

 generally found beneath the friendly fhelter of a 

 grove j and that in proportion as the woodlands in 

 any country are cleared, the watercourfes are dimi- 

 nifhed. 



Hence may be inferred the neceflity of preferving 

 trees about thole places whence water-fprings difcharge 

 their currents, if it is an object to preferve them j and 

 alfo of improving fmall fprings, by planting trees 

 around them, and efpecially oaks. 



And hence,- alfo, it is a fair conclufion, that in 

 this climate, where the cold certainly predominates, 

 woody fixations cannot be wholefome ; and that, 

 adjacent to houfes efpecially, the land Ihould be laid 

 open. 



* Philad. Tranf. vol. ii. p. 150. 



From 



