214 WHAT IS PHLOGISTON ? 



subtile, elastic, and active principle, which they 

 termed phlogiston, and which was disengaged 

 during the process of combustion, producing the 

 phenomena of heat and light, or fire. Many and 

 long were the disputes of philosophers concerning 

 the nature of phlogiston. While many main- 

 tained that it was a material substance, Lavoisier 

 is supposed to have demonstrated that it was 

 only an imaginary something, invented for the 

 purpose of explaining the mystery of combustion. 

 That Stahl regarded phlogiston as the cause of 

 heat and inflammation, is evident from the name 

 he gave it, which in the Greek language signifies 

 heat or fire. 



From what is reported of Dr. Black's unpub- 

 lished Lectures on Respiration, it would seem 

 that he confounded phlogiston with the carbon 

 secreted from the lungs ; for he maintained, that 

 a portion of atmospheric air unites with phlogis- 

 ton in the lungs, and that animal heat was dis- 

 engaged during the process. (Leslie on Animal 

 Heat.) 



The celebrated Scheele supposed that heat was 

 composed of 'phlogiston and empyreal air, (oxygen,) 

 and that light was composed of phlogiston and 

 heat : while Kirwin supposed that phlogiston was 

 identical with inflammable air (hydrogen). Such 

 were the vague and contradictory opinions of 

 philosophers in regard to the nature of heat, light, 



