VOL. IX.] PHILOSOPHICAL TRANSACTIONS. 143 



by the air, and partly by a terrestrial matter. Where he refers the reader to 

 those Boylean experiments,* which make it out, that the air famishes something 

 that is necessary to produce flame: which done, he teaclies, that in nitre there 

 exist igneous particles of the air, which constitute its most active part, and by 

 which the flame of kindled nitre is produced, without any sulphur, which sub- 

 stance he will not at all admit to be found in pure nitre, being of opinion, that 

 the deflagration of nitre is made, not by any sulphureous parts of its own, but 

 by those fiery aerial parts, put into a very quick motion. Concluding upon the 

 whole, that the aerial parts of nitre are nothing else but the igneo aerial parti- 

 cles thereof, requisite to make flame, and that this aerial part of nitre is lodged 

 in the acid spirit of the same, and not in the fixed salt, which acid spirit, in his 

 opinion, is compounded of a terrene matter, that is flexile and humid, and of 

 ethereal corpuscles, that are rigid, dry, active and igneous, proceeding from the 

 air. And the igneous particles, conceived by him to be common to nitre and 

 air, he calls nitro-aerial, from whence the spirit of nitre derives its caustic and 

 corrosive nature, which he calls a potential fire, and from whence he thinks 

 also that the form of fire chiefly, if not wholly, depends. Now, forasmuch as 

 this nitro-aerial igneous spirit resides in the acid spirit of nitre, he thence infers, 

 that that nitro-aerial spirit is of a nitro-saline nature, obtaining rather the 

 nature of an acid than fixed salt. 



These things being thus by our author pre-supposed, he descends to the expli- 

 cation of the nature of fire, and makes its form and essence principally to depend 

 on the said nitro-aerial spirit put into motion; rejecting the opinion of those, 

 that will have fire producible by the subtile and briskly moved parts of any mat- 

 ter, and declaring on this occasion his dissent from those philosophers, that 

 deduce all efl^scts of nature from the same uniform matter, and the various mo- 

 difications thereof; -}- which he thinks inconsistent with the phaenomena of fire, 

 not at all, in his opinion, producible but by a certain determinate kind of parti- 

 cles, such as he calls nitro-aerial. This he endeavours to prove by divers expe- 

 riments. 



Having done with the aerial part of the spirit of nitre, he proceeds to its ter- 



* See Mr. Boyle's excellent Tracts, printed anno l672, in London, the first of which contains 

 new experiments touching the relation between flame und air, and about explosions; where among 

 many other things, is evinced the efficacy of the air in the production of flame, even without any 

 actually flaming or burning body: and where also the curious reader will meet with a fiill and very 

 instructive account of those experiments, which this author here glances at. — Note by Mr, Olden- 

 burg. 



-)• Compare herewith the considerations of the Hon. Mr. R. Boyle, about the excellency and 

 grounds of the mechanical hypotliesis. — Note by Mr. Oldenburg. 



