HISTORY OF VERMONT. 93 



hy the air which was collected in it, amounted 

 to sixty one grains. The quantity of air there- 

 JTore, estimated by its bulk, which was emitted 

 from the limb of the tree, was to the quantity 

 of water thrown off from the same limb, as six- 

 ty one to sixteen. Making the calculation m 

 the same manner as before, this will give four- 

 teen thousand seven hundred and seventy four 

 gallons, as the quantity of air, thrown off in 

 twelve hours, from one acre of land, thus cov- 

 ered with trees. The purity and salubrity of 

 this air is as remarkable as the quantity of it. 

 It has been found that an animal will live five 

 times as long in this kind of air, as in common 

 air of the best qualityc The purity of the at= 

 mosphere, is constantly impaired by the respira- 

 tion of animals, by combustion, the putrefaction 

 of bodies, and by various other causes. In such 

 ways, the air over large and populous citi'es, is 

 so greatly and constantly corrupted, that it would 

 soon become unwholesome and noxious to the 

 inhabitants, if it was not removed, or purified. 

 Nature has made abundant provision' for this 

 purpose, in the immense quantities of air, which 

 new countries supply. The trees and vegeta- 

 bles perpetually produce it, in large quantities, 

 and in the purest state ; and the winds carry it 

 from one country to another, where it is n.03t 

 wanted. 



Heat. The principle by which these ope- 

 rations are carried on, and which seems to have 

 the greatest effect in vegetation, is heat. Dif- 

 ferent vegetables require different degreei of 

 heat, or different climates, to give them their 

 greatest degree of increase, and perfecuoa. 



roL. I. M 



