18 



Nowhere has this been more clearly evident than in tiie ileveldj^ment of chemistry. 

 Medicine, during the era of medical chemistry, protiably killed more of its patients 

 than it cured, and the api)lied chemistry of to-day makes greater advances in a 

 decade tlian were made during whole centuries of empiricism. 



It is scarcely more than two centuries since a few men first began to search 

 into the composition of bodies with the pure, high aim of an endeavor to extend 

 human knowledge. From this period dates the beginning of chemistry as a [)ure 

 science, and in this sense those who refer the beginning of chemistry to Lavoisier 

 do injustice to such men as Boyle, Stahl, Black, Scheele, Priestly. Cavendish and 

 many others. 



Tliese men worked with the same spirit and purpose, and often in the face of 

 far greater ditticulties tlian those which later workers were compelled to face. 

 These were the real pioneers of pure chemistry. 



In tiie hands of the.se workers we find for the first time in the science one of 

 the best and higliest characteristics of any pure science, the proposal, develop- 

 ment and general acceptance of an important theory — a theory which coordinated 

 and ex|)laiued from one point of view many and diverse |)henomena — a theory 

 conceived in a pure philosophical spirit — one step in the constant endeavor of the 

 highest minds to tear away from before our eyes the things which are fortuitous 

 and misleading and to get a little closer to the realities which lie at the basis of 

 all material existence. I refer, of course, to the theory of phlogiston. 



In outward appearance ordinary combustion is of the nature of a decompo- 

 sition and this view of the phenomena was held from the earliest times. Build- 

 ing, as every founder of a theory must, on the best knowledge which was pos- 

 sessed, and recognizing the close connection between the oxidation of metals and 

 ordinary combustion the chemists of this time proposed the theory that all bodies 

 capable of combustion or oxidation contain a common substance or principle 

 called phlogiston, and that combustion consists in the escape of the ])hlogist<)n 

 leaving behind that with which it was combined. 



In accordance with this view, wood, charcoal and similar substances are rich 

 in phlogiston and mostly disappear in burning. Metals are composed of phlogis- 

 ton and the metallic calex or what we now know as the oxide — the metal being 

 considered compound and the oxide as one of its parts. 



At the time when the theory was projiosed and developed it gave a (piite satis- 

 factory explanation of most of the phenomena then known> It served as a means 

 of bringing together under one i)oint of view very many and diverse facts and of 

 coordinating them all under a system which was clear and intelligible. As new 

 facts were discovered they were explained and systematized as far as possil>le in 



