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yet it could never be any real dis- 

 advantage in the natural fituation 

 of things, becaufe this fouled air 

 may be corrected in the atmofphere 

 by fome manner or other unknown 

 to us ; and, if not, we are, at any 

 rate, immediately out of its reach, 

 as it rifes by its being become light- 

 er. But if fuch infectious plants 

 are fliut up in fmall clofe rooms, 

 they certainly might do a material 

 injury to our constitution, and even 

 occafion death. 



It appears, by experiment 41, 

 that a plant may really foul fo much 

 air at night as fcarce to be able to 

 correct in the day. But it is to be 

 confidered, that fuch a plant, being 

 maimed by its roots being taken off, 

 and by being ihut up in a narrow 

 fpace, mull have loft fome of that 

 vigour which plants naturally have 



when 



