LECTURE I.] HISTORY OF CHEMISTRY. 5 



tion, and the phlogiston theory becomes more comprehensible 

 when we minutely study the views of the Greeks and the Romans. 

 Amongst these peoples, combustion is already looked upon as 

 consisting in the separation of the material of fire ; and Pliny 

 regarded the easy inflammability of sulphur as a proof of its 

 being largely composed of a fire material. 2 At a later date 

 sulphur was itself assumed to be the fire material ; and from 

 that view the hypothesis that all metals contained sulphur, 

 unquestionably arose. 



These few words concerning the chemical theories of the 

 ancients appear to me sufficient in order to understand Becher 

 and his follower, Stahl. Both of these based their views upon 

 those of the Greek and of the Roman philosophers ; in the 

 same way that we find so many imitators of Greek art at the 

 same period, that is, in the seventeenth century. 



A difference may, it is true, be pointed out between them ; 

 namely, that only the latter intentionally and knowingly followed 

 in the footsteps of the ancients, whilst the former declared 

 themselves to be their opponents. Thus Becher says : " A 

 good peripatetic is a bad chemist." He replaces the four 

 elements of Empedocles by three others : the verifiable, the 

 inflammable, and the mercurial earths. 3 



It is not my business here to inquire whether it was 

 Becher or Stahl who thought and wrought most with respect 

 to the phlogiston theory. Still I will not omit to draw 

 attention to the great modesty of Stahl, who wished that 

 his own services should be attributed to his teacher and friend 

 Becher : " Becheriana sunt quae profero" 4 Such examples are 

 rare. 



The adherents of the phlogiston theory regard combustion 

 as consisting in a decomposition : " only compound substances 

 can burn ; " these all contain a common principle which 

 Becher calls terra pinguis and Stahl calls Phlogiston. During 

 the combustion this principle escapes and the other constituent 

 of the substance remains behind. 



2 Kopp, Geschichte. 3, 102. 3 Ibid. I, 179. 4 Ibid. I, 188. 



