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■place it has no power to correal: bad 

 air, or to yield good; but, on the 

 contrary, it fpreads round about it 

 deleterious exhalations, which ren- 

 der the befl air even pernicious to 

 the utmoft degree. 



It will not be difficult to under- 

 ftand now from what caufe all thofe 

 different and contrary effects which 

 Dr. Prieftley has found in his expe- 

 riments did really depend ; and why 

 Mr. Sheele had conftantly found 

 that the vegetation of beans alwavs 

 fpoiit good air. 



Thefe gentlemen expected the 

 good effects from the vegetation of 

 the plants, as fuch. By making a 

 plant grow night and day in ordi- 

 nary air kept in a phial with the 

 plant, the effect will depend upon 

 the greater or lefs expofure of the 

 plant to the light. Beiides, by keep- 

 ing 



S3 



