[ xxxvi ] 



and even the mqft poifonous plants 

 perform this office in common with 

 the mildejl and the mqft falutary ; 

 that the moft part of leaves pour 

 out the great eft quantity of this dephlo- 

 gifticated air from their under fur face, 

 principally thofe of lofty trees ; that 

 young leaves, not yet come to their 

 full perfections yield dephlogifticated 

 air lefs in quantity, and of an in- 

 ferior quality \ than what is produced 

 by full-grown and old leaves ; that 

 fome plants elaborate dephlogifticated 

 air better than others y that fome 

 of the aquatic plants feem to ex cell 

 in this operation ; that all plants 

 contaminate the furrounding air by 

 night, and even in the day-time 

 in ffjaded places ; that, however, 

 fome of thofe which are inferior to 

 none in yielding beneficial air in 

 the fun-Jhine^ furpafs others in the 



power 



