[ i6* 3 



As the iron is reduced to a calx by this procefs, 

 I once concluded, that it is phlogifton that fixed air 

 wants, to make it common air j and, for any thing 

 I yet know, this may be the cafe, though I am ig- 

 norant of the method of combining them -, and when 

 I calcined a quantity of lead in fixed air, in the. man- 

 ner which will be defcribed hereafter, it did not feem 

 to have been lefs foluble in water than it was before. 



n. 



On Air in which a candle, or erimstone, 

 has burned out. 



It is well known that flame cannot fubfift long 

 without change of air, fo that the common air is 

 necerTary to it, except in the cafe of fubftances, into 

 the compofition of which nitre enters ; for thefe will 

 burn in vacuo, in fixed air, and even under water, 

 as is evident in fome rockets, which are made for 

 this purpofe. The quantity of air which even a 

 fmall flame requires to keep it burning is prodi- 

 gious. It is generally faid, that an ordinary candle 

 confumes, as it is called, about a gallon in a 

 minute. Considering this amazing confumption 

 of air, by fires of all kinds, volcano's, &c. it be- 

 comes a great object of philofophical inquiry, to as- 

 certain what change is made in the conftitution of 

 the air by flame, and to difcover what provifion there 

 is in nature for remedying the injury which the at- 

 mofphere receives by this means. Some of the fol- 

 lowing experiments will, perhaps, be thought to 

 throw a little light upon the Subject. 



The 



