[ i6 9 ] 



growing in it. The firft of thefe experiments was 

 made in the month of May; and they were frequently 

 repeated in that and the two following months, with- 

 out a fingle failure. 



For this purpofe I ufed the flames of different fub- 

 fiances, though I generally ufed wax - or tallow 

 candles. On the 24th of June the experiment fuc- 

 ceeded perfectly well with air in which fpirit of wine 

 had burned out, and on the 27th of the fame month 

 it fucceeded equally well with air in which brim- 

 ftone matches had burned out, an effect of which I 

 had defpaired the preceding year. 



This reiteration of air I found depended upon the 

 vegetating ftate of the plant ; for though I kept a 

 great number of the frefh leaves of mint in a fmall 

 quantity of air in which candles had burned out, 

 and changed them frequently, for a long fpace of 

 time, I could perceive no melioration in the ilate of 

 the air. 



This remarkable effect does not depend upon any 

 thing peculiar to mint, which was the plant that I 

 always made ufe of till July 1772 j for on the 16th 

 of that month, I found a quantity of this kind of 

 air to be perfectly reftored by fprigs of balm, which 

 had grown in it from the 7th of the fame montho 



That this reftoration of air was not owing to any 

 aromatic effluvia of thefe two plants, not only ap- 

 peared by the effential oil of mint having no fenfibie 

 effect of this kind; but from the equally complete 

 reftoration of this vitiated air by the plant called 

 groundfel, which is ufually ranked among the weeds, 

 and has an ofFenfive fmell. This was the refult of 

 an experiment made the 16th of July, when the 



Vol. LXI-J, Z plant 



