xxxiii ] 



this operation is carried on 5 whether 

 the plants mend air by abforbing, 

 as part of their nourifhment, the 

 phlogiftic matter, and leaving thus 

 the remainder of the air pure (to 

 which opinion Dr. Prieftley inclines 

 the moft) ; or whether perhaps the 

 plants pofTefs fome particular virtue 

 hitherto unknown, by which they 

 change bad air into good air, and 

 good into better, which I fufpecSted 

 to be the cafe. 



I was not long engaged in this 

 enquiry before I law a moft im- 

 portant fcene opened to my view : 

 I obferved, that plants not only have 

 a faculty to cor reel bad air in fix or 

 ten days ^ by growing in it, as the ex~ 

 periments of Dr. Prieftley indicate, 

 but that they perform this important 

 office in a compleat manner in a few 

 hours ; that this wonderful operation 

 c is 



