146 PHILOSOPHICAL TRANSACTIONS. [aNNO I674. 



any life: and by that experiment determines this matter in the negative, though 

 he denies not that there is a great affinity betwixt them. 



After this, he spends a chapter in discussing how fire is kindled and propa- 

 gated, and in what manner all fermentations are made, namely, by the pulsa- 

 tion of the Cartesian materia subtilis, whereby as by a substance that constantly 

 moves, he says, the ignited parts are put into a vehement motion. And here he 

 declares, that fire seems to him to be nothing else than a very great fermenta- 

 tion of nitro-ae rial and sulphureous parts; and concludes, that as the most vehe- 

 ment motion of the igneous particles proceeds from thence, that the sulphu- 

 reous ones pass into the particles of the nitre or air, and there hitting upon the 

 briskly agitated materia subtilis, are by the impulse of the same, together with 

 the nitro-aerial parts, found in the said substances, by an elastic impetus struck 

 out; so all the more remiss fermentations of natural things are caused hence, 

 that the said nitro-aerial particles, penetrating the salino- sulphureous mass, do 

 enter into the body of the subtile matter, by which, being put in a great agita- 

 tion, the said nitro-aerial parts are protruded together with the sulphureous 

 ones ; so that the effervescence of fire seems to him to differ from the more 

 remiss intestine motions, by which vegetables are generated or dissolved, only 

 in this; that in fire the nitro-aerial particles being closely joined with the fixed 

 salt or parts of the air, are by the impulse of the sulphureous parts and the sub- 

 tile matter carried away with violence, and put into a very swift agitation; 

 whereas in other fermentations, the sulphureous parts not being lodged so fast 

 in the embraces of the fixed salt, are by the pulsation of the nitro-aerial parts 

 and of the materia subtilis moved with more remissness. 



Next he discourses of light and colours, embracing the doctrine of Descartes, 

 making light to consist in a pulse, which by reason of the continuity of the lu- 

 minous medium is suddenly transmitted to the greater distance ; but this impulse 

 our author would have made by his nitro-aerial particles; as he is of opinion, 

 that colours are produced not from a light reflected, but from a peculiar impulse 

 of the medium, altogether different from that of light; concerning which and 

 the manner of which, the discourse itself may likewise be perused. 



To this he subjoins a chapter about lightning, which he denies to pro- 

 ceed from kindled exhalations; and having espoused the Cartesian opinion 

 of the production of thunder from the impetuous fall of the upper 

 condensed and conglaciated clouds upon the lower; he thence infers, that 

 lightning is made by his nitro-aerial particles struck out of the air, and by 

 their vehement igneous motion causing a slight and momentaneous flash 

 spreading itself over the whole hemisphere. Where he adds his thoughts about 

 the force of lightning, and its wonderful effects in melting swords without 



