£ \m I 



in that part of the air, in which the fprig of mint had 

 grown, but died the moment it was put into the 

 other part of the fame original quantity of air ; and 

 which I had kept in the very fame expofure, but 

 without any.plant growing in it. 



This experiment I have feveral times repeated ; 

 fometimes ufing air, in which animals had breathed 

 and died ; fometimes ufing air tainted with vege- 

 table or animal putrefaction, and generally with 

 the fame fuccefs. 



Once, I let a moufe live and die in a quantity of 

 air, which had been noxious, but which had been 

 reftored by this procefs, and it lived nearly as long 

 as I conjectured it might have done in an equal quan- 

 tity of frefh air ; but, this is fo exceedingly various, 

 that it is not eafy to form any judgment from it ; 

 and in this cafe the iymptom of difficult refpration 

 feemed to begin earlier than it would have done in 

 common air. 



Since the plants that I made ufe of manifeftly 

 grow and thrive in putrid air ; fince putrid matter 

 is well known to afford proper nourishment for the 

 roots of plants ; and fince it is likewife certain that 

 they receive nourifiiment by their leaves as well as 

 by their roots, it feems to be exceedingly probable, 

 that the putrid effluvium is in fome meafure extract- 

 ed from the air, by means of the leaves of plants, and 

 therefore that they render the remainder more fit for 

 refpiration. 



Towards the end of the year fome experiments 

 of this kind did not anfwer fo well as they had done 

 before, and I had inftances of the relapfing of this 

 reftored air to its former noxious Rate. I therefore 



fufpended 



