Mr Blackadder on the Constitution of Flame. S35 



but a very faint light, which is of a blue colour ; but when parti* 

 cles of carbon are presented in such a form that they can become 

 ignited, the colour of the light that is given out during their ig- 

 nition, seems to depend on the existing temperature and the sup- 

 ply of oxygen ; it is red, yellow, or white. At a certain tempe- 

 rature the charcoal that is deposited from a flame seems to unite 

 with oxygen, without the extrication of light. Thus, if the end 

 of a rod of glass, that has been blackened in the flame of a can- 

 dle, be introduced into the centre of a spirit-flame, the charcoal 

 becomes red, without undergoing any farther change ; but, on 

 withdrawing the rod from the flame, the charcoal, after becom- 

 ing black, is observed to disappear from the surface of the glass, 

 exactly in the same way that condensed aqueous vapour disap- 

 pears in dry air from a polished surface *. If the rod be made 

 to pass quickly through the air the charcoal becomes ignited ; 

 but more of it is not consumed than is observed to disappear when 

 ignition is not thus produced. The yellow light that is extricat- 

 ed, when solid vegetable or animal substances are brought into 

 contact with a blue flame, is doubtless produced by the ignition 

 of minute particles of charcoal. The yellow light given out when 

 alcoholic fluids are burned with a wick, or when minute particles 

 of various fluids are made to impinge on a blue spirit-flame, has, 

 I have reason to believe, a similar origin. — 



After the preceding part of this paper was written, a first op- 

 portunity was had of perusing the highly interesting papers on 

 Combustion, by Sir H. Davy, published about ten years ago, in 

 the Transactions of the Royal Society of London. In these pa- 

 pers the researches of that celebrated chemist are stated to be 

 unfinished, but whether he has since that period prosecuted the 

 subject, I have not had the means of ascertaining. Perhaps, with- 

 out being guilty of presumption, it may be asked. Is the evi- 

 dence hitherto adduced, in support of the following opinions con- 

 clusive ? 



" The flame of combustible bodies, in all cases, must be con- 

 sidered as the combustion of an explosive mixture of inflamma- 

 ble gas, or vapour, and air ; for it cannot be regarded as a mere 



* If it were merely carried off by the current of heated air, it might be expect- 

 ed to be similarly carried off when in the centre of a spirit flame, for the velocity 

 of the vapour is fully equal to that of the upward current of air caused by heat 

 emanating from the glass rod. 



