[ 1 40 ] [Book IL 



CHAP. VI, 

 OF IGNITION AND'COMBUSTION. 



Jgnition, ivhat ; hew produced, Bunting of Phofphorus. Inflamma- 

 ble Air. Culinary Fires. Lamps, &c. //7y Flame a/cex-s. 

 y^eory of Argand's Lamp.Beji Form of Grates, Stoves, t>V. 

 C.cmbuftion produced by fame Subftanccs without a Communication, 

 n'jith the Atmofpbcre. Gun-powder, lff<r. Iron made to burn like 

 a Candle. Spontaneous Ignition. Curious Fatfs. Quantity of 

 Heat excited infuf.ng different Bodies. Scale of 'Heat '. 



IGNITION is that ftate of bodies in which the 

 matter of fire or caloric is rendered active, and 

 obvious to the fight, by the emiilion of light; in other 

 words, when both light and heat are at once emitted 

 by any body, it is faid to be ignited. Ignition does 

 not imply combuftion, as the latter indicates a change 

 or diflblution of texture in the inflammable body j 

 whereas fome of the metals, and many of the earths, 

 may be ignited without being confumed. But this 

 is a fubject which it will be neceifary to treat more 

 at large, when I come to fpeak of inflammable fub- 

 flances. 



In all cafes of ignition or inflammation the matter 

 of fire is 'detached from fome body in which it pre- 

 vioufly exiiled in a latent ftate. The fubftance with 

 which fire is moft copioufly combined, and from 

 which it is moft eafily detached, is air. If therefore 

 any fubftance can be found in nature which has a 

 greater attraction for the bafis of air than that has for 

 the matter of fire, the union of thefc two fubftances 

 will detach a quantity of the fire which had exifted in a 

 latent or combined ftate \ and ignition, and combuf- 

 tion, 



