fs 46- ] 
place it hasno power to correct bad 
air, or to yield good; but, on the 
contrary, it fpreads round about it 
deleterious exhalations, which ren-= 
der the beft air even pernicious. to 
the utmoit degree. 
It will not be difficult to undere 
ftand now from what caufe all thofe 
different and contrary effects which, 
Dr. Prieftley has found in jis expe- 
riments did really depend; and why 
Mr. Sheele had conftantly found 
that the vegetation of beans always 
{poilt good air. 
Thefe gentlemen erpecied the 
good effects from the vegetation of 
the plants, as fuch. By making a 
Plant grow night and day in ordi- 
‘Wary air kept in a phial with the 
plant, the effect will depend upon - 
the greater or lefs expofure of the 
| Plant to the light. Befides, by keep- 
Re ing 
