C *95 ] 



fufpended my judgment concerning the efficacy of 

 plants to reftore this kind of noxious air, till I 

 mould have an opportunity of repeating my experi- 

 ments, and giving more attention to them. Ac- 

 cordingly I refumed the experiments in the fum- 

 mer of the year 1772, when I prefently had the 

 moft indifputable proof of the reiloration of putrid 

 air by vegetation; and as the fact is of fome im- 

 portance, and the fubfequent variation in the ftate 

 of this kind of air is a little remarkable ; I think 

 it neceffary to relate fome of the fads pretty cir- 

 cumilantially. 



The air, on which I made the firft. experiments, 

 was rendered exceedingly noxious by mice dying in 

 it on the 20th of June. Into a jar nearly filled 

 with one part of this air, I put a fprig of mint, 

 while I kept another part of it in a phial, in the 

 fame expofure ; and on the 27th of the fame month, 

 and not before, I made a trial of it, by introducing 

 a moufe into a glafs veffel, containing 21. ounce mea- 

 fures filled with each kind of air ; and I noted the 

 following fafts. 



When the veffel was filled with the air in which 

 the mint had grown, a very large moufe lived five 

 minutes in it, before it began to (hew any fign of 

 uneafinefs. I then took it out, and found it to be as 

 ftrong and vigorous as when it was firft put in ; 

 whereas in that air which had been kept in the 

 phial only, without a plant growing in it, a younger 

 moufe continued not longer than two or three fe- 

 conds, and was taken out quite dead. It never 

 breathed after, and was immediately motionlefs. 

 After half an hour, in which time the larger moufe 



C c 2 (which 



