[ *68 ] 
"Finding that candles burn very well in air in 
which plants had grown a long time, and having 
had fome reafon to think, that there was fomething 
attending vegetation, which reftored air that had 
been injured by refpiration, I thought it was pof- 
fible that the fame procefs might alfo reflore the air 
that had been injured by the burning of candles. 
Accordingly, on the 17th of Auguft, 1771, I 
put a fprig of mint into a quantity of air, in which 
a wax candle had burned out, and found that, on 
the 27th of the fame month, another candle burned 
perfectly well in it. This experiment I repeated, with- 
out the lead: variation in the event, not lefs than 
eight or ten times in the remainder of the fummer. 
Several times I divided the quantity of air in which 
the candle had burned out, into two parts, and 
putting the plant into one of them, left the other 
in the fame expofure, contained, alfo, in a glafs 
vefiel immerfed in water, but without any plant ; 
and never failed to find, that a candle would burn 
in the former, but not in the latter. I generally 
found that five or fix days were fufficient to reflore 
this air, when the plant was in its vigour ; whereas 
I have kept this kind of air in glafs veffels, immerfed in 
water many months, without being able to perceive 
that the lead alteration had been made in it. I have 
alfo tried a great variety of experiments upon it, as 
by condenfing, rarefying, expofing to the light and 
heat, &c. and throwing into it the effluvia of many 
different fubftances, but without any effect. 
Experiments made in the year 1772, abundantly 
confirmed my conclufion concerning the reffcoration 
of air, in which candles had burned out by plants 
growing 
