58 Notices resfjecthig NfW Boob. 



pie forms of matter, is also manifested by the production of heat 

 and liglit, or the phenomenon of combustion, at the instant of 

 their mutual combination. But this phenomenon is not charac- 

 teristic ; for it is neither peculiar nor necessary to their action, 

 and, therefore, cannot be made t'le basis of a logical arrangement. 

 Combustion is vividly displayed in cases where none of these pri- 

 mary dissolvents is concerned. Thus some metals combine with 

 others with such vehemence as to elicit ligiit and heat; and many 

 of them, by their imion with sulphin', even in vacuo, exhibit in- 

 tense combustion. Potassium burns distinctly in cyanogen (car- 

 buretted azore\ and splendidly in sulphuretted hydrogen. For 

 other examples to the same purpose, see Combustible and Com-. 



BIJSTION. 



" " And again, the phenomenon of flame does not necessarily 

 accompanv any of the actions of oxygen, chlorine, and iodine. 

 Its production may be regulated at the pleasure of the chemist, 

 and occurs merely when the mutual combination is'Vapidly ef- 

 fected. Thus chlorine or oxygen will ynite with hydrogen, either 

 silently and darkly, or with fiery explosion, as the operator shall 

 direct. 



" Since, therefore, the cpiality of exciting or sustaining com- 

 bustion is not peculiar to these vitreo-electric elements ; since 

 it is not indispensable to tlieir action on other substances, butad-. 

 ventitious and occasional, we ))erceive the inaccuracy of that clasr 

 sification which sets these three or four bodies apart under the dc" 

 nomination of supfjurtosof combustion ; as if, forsooth, combus- 

 tion could not be supported without them, and as if the support of 

 combustion was their indefcasil)le attribute, the essential conco-. 

 niitant of their action. On the contrary, every change which 

 they can produce, by their miion with other elementary matter, 

 may be effected uitliout the phenomenon of combustion. See 

 section 5th of article Combitstion. 



" The other forty-nine elementary bodies have, with the excep- 

 tion of azote (the solitary incombustible), been grouped under 

 the generic name o'i combustibles. But in reality c(mibustion is 

 independent of the agency of all these bodies, and therefore com- 

 buslion maij be produced ivi I hout any combustible. Can this ab^r 

 surdity form a basis of chemical classification ? The decompo- 

 sition of euchlorine, as well as of the chloride and iodide of azote, 

 is accompanied with a tremendous energy of heat and light ; yet 

 no combustible is present. The same examples are fatal to the 

 theoretical part of Black's celebrated doctrine ot latent heat. 

 His facts are, however, invaluable, and not to be controverted, 

 though the hvpothetical thread used to connect them be finally 

 Hcvcvcd. 



'• To the term comluslll'lc is naturally attached the idea of the 



body 



