8 Mayow 



acidity, and become to some extent nitrous. More- 

 over, steel filings if exposed to moist air, are corroded 

 just as they would be by acid fluids, and are changed 

 into aperitive crocus martis. So that apparently a 

 certain acid and nitrous spirit resides in the air. 



But when I had seriously considered the matter, 

 the acid spirit of nitre seemed to be too ponderous 

 and fixed to circulate as a whole through the very thin 

 air. Besides, the nitro-aerial salt, whatever it may be, 

 becomes food for fires, and also passes into the blood 

 of animals by means of respiration, as will be shown 

 below. But the acid spirit of nitre, being humid and 

 extremely corrosive, is fitted rather for extinguishing 

 flame and the life of animals, than for sustaining them. 



But although the spirit of nitre does not proceed 

 altogether from the air, still we must believe that 

 some part of it originates from the air. For, since 

 some part of the nitre is derived from the air, as has 

 been shown above, while the fixed salt, of which nitre 

 in part consists, proceeds from the earth, the remainder 

 of the nitre, that is to say, its acid and fiery spirit, 

 must be derived, in part at least, from the air. But 

 in order that the aerial part of the spirit of nitre may 

 be better understood, we must briefly premise the 

 following. 



First, it is, I think, to be admitted that something 

 aerial, whatever it may be, is necessary to the pro- 

 duction of any flame — a fact which the experiments of 

 Boyle have placed beyond doubt, since it is established 

 by these experiments that a lighted lamp goes out 

 much sooner in a glass that contains no air than it 

 does in the same when filled with air — a clear proof 

 that the flame enclosed in the glass goes out, not so 

 much because it is choked, as some have supposed, by 

 its own soot, as because it is deprived of its aerial 



