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And, notwithftanding the prodigious mafs of air 
that is corrupted daily by the abovementioned caufes; 
yet, if we confider the immenfe profufion of ve- 
getables upon the face of the earth, growing in 
places fuited to their nature, and confequently at 
full liberty to exert all their powers, both inhaling 
and exhaling, it can hardly be thought, but that 
it may be a fufficient counterbalance to it, and 
that the remedy is adequate to the evil. 
Dr. Franklin, who, as I have already obferved, 
faw fome of my plants in a very flourilhing ftate, 
in highly noxious air, was pleafed to exprefs very 
great fatisfaflion with the refult of the experi- 
ments. In his anfwer to the letter in which I in- 
formed him of it, he fays, 
44 That the vegetable creation fhould reftore the 
44 air which is fpoiled by the animal part of it, 
44 looks like a rational fyftem, and fee ms to be of 
44 a piece with the reft. Thus fire purifies water 
44 all the world over. It purifies it by diftillation, 
44 when it raifes it in vapours, and lets it fall in 
44 rain; and farther ftill by filtration, when, keep- 
44 ing it fluid, it fufiers that rain to percolate the 
44 earth. We knew before, that putrid animal fub- 
44 fiances were converted into fweet vegetables, 
44 when mixed with the earth, and applied- as 
44 manure; and now, it feerns, that the fame pu~ 
44 trid fubftances, mixed with the air, have a fimi- 
44 lar effect. The ftrong thriving ftate of your 
44 mint in putrid air feems to fhew that the air is- 
44 mended by taking lomething from it, and nor 
44 by adding to it.” He adds, 44 1 hope this will- 
44 give fome check to the rage of deftroying trees 
2 44 that 
