to e.vpla'm the Phancffiena of ComluJI'ion. 203 



Inquiries as to frame any particular theory on the fubjeft of 

 combullinn. 



In referring back to the earher periods of the hiflory of 

 chemiftry, we (hall find that Becherwas the firft philofopher 

 who withdrew that fciencefrom the contra(5led limits of phar- 

 macy and alchemy, and laitl the foundation of the doftrine 

 of phlogiRon. 



G, Erneft Stnhl,, whofe genius was formed for ihe bigheft 

 improvement of fcience, fucceeded him ; and it is to this phi- 

 lofopher that we are indebted for the firft pofitive attempt to 

 explain the phaen'^jmena, and to exhibit a regular theory of 

 combufiion. 



The do6lrine of phlogifton, as expounded by this cele- 

 brated chemift, is too well known to require being defcribed* 

 at any confidcrable length. 



It proceeded on the airumplion, that there was only one 

 fubfiance in nature capable of combufiion, which he there- 

 fore called phlogifion ; and he held, that all bodies that were 

 inflammable owed their combufiibility only to the prefcnce of 

 this principle. Combufiion^ therefore, he confidcred merely 

 as its feparation in the form of light and heat; and fuch bo- 

 dies as were not infiammable were thought to be devoid of 

 it: for d'jring the conibuilion of fubfiances he taught that 

 their phloiiiiton flies ofi", and the incombufiible pnrts of them 

 alone; remain behind. Thus, if iron be expoicd to a fuffi- 

 cientlv firong heat it vvill undergo conibufiiion, a complete 

 alteration will take place in its confiituent parts, and a refi- 

 duum will be found left of an incombufiible nature. 



Stabl explained thefe phaenomena in the following way: 

 Iron he confidered as a peculiar earth united to a centain 

 proportion of phloeifiou ; when it was made to undergo corn- 

 bullion, the phlotrifloB which formed a part of it, and to 

 which it alone owed its combufiibilitv, mode its efcape, and 

 there was left behind only the bafe, \vliich wasf found to 

 be no longer inflammable. Now, as this feparation was al- 

 ways attended with the cmifllon of light and heat, phlogifion 

 was confidered only as heat and light comhined with fonie. 

 other fpecies of rnatter in a peculiar and unknown way. 



Thisdoclrine w'as confidered as deriving much lupport from 

 the hti, that a body, after having undergone condMifiion, 

 (i.e. by the difllipation of its phlogifion in llie form of light and 

 heal,) was converted into a bodv that was no longer condiul- 

 tible, but which .might again have it» combufiibility refinred 

 by the addition of any inflammable matter. Thus, in the 

 example before adduced, if, after the iron has undergone the 



proccis' 



