[ J 97 ] 



but not exceedingly well, thefe eleven days; on which 

 account, I had deferred making the trial fo long. 

 This reftored air was afTecled by a mixture of ni- 

 trous air, almoft as much as common air. 



As this putrid air was thus ealily refiored to a 

 considerable degree of fitnefs for refpi ration, by 

 plants growing in it, I was in hopes that by the 

 fame means it might in time be fo much more 

 perfectly refiored, that a candle would burn in 

 it ; and for this purpofe I kept plants growing 

 in the jars which contained this air till the 

 middle of Auguft following, but did not take fuffi- 

 cient care to pull out all the old and rotten leaves. 

 The plants, however, had grown* and looked fo 

 well upon the whole, that I had no doubt but that 

 the air muft cpnitantly have been in a mending 

 flate ; when I was exceedingly fnrprized to find, 

 on the 24th of that month, that though the air in 

 one of the jars had not grown worie, it was no 

 better, and that the air in the other jar was fo much 

 worfe than it had been, that a moufe would have 

 d-ied in it in a few feconds. It alfo made no effer- 

 vefcence with nitrous air, as it had done before. 



Sufpecting that the fame plant might be capable 

 of refloring 'putrid air to a certain degree only 9, 

 or that plants might have a contrary tendency in 

 fome ftages of their growth, I withdrew the old 

 plant, and put a frefh one in its place ; and found 

 that, after {even days, the air was refiored to its 

 former wholefome ftate. This fact I. confider as a. 

 very remarkable one, and well deferving of a far- 

 ther investigation, as it may throw more light upon 

 the principles of vegetation. It is not, however,, 

 7 - a finsie: 



