658 THE POPULAR SCIENCE MONTHLY. 



a glass, filled and inverted it under water, and lifted it inverted 

 so that it remained full on the surface of the water. Then he made the 

 new gas pass through a tube and rise under the glass ; the ascending 

 bubbles soon filled the vessel with the pure gas. Thus he had oxygen 

 collected in a glass of roater; he held the microcosm in his grasp, and 

 could investigate its properties. Almost at the same time the gas was 

 discovered by the Swede Scheele, who prepared it by heatiug oxide of 

 manganese. This was but one step, however ; the substance that was 

 to initiate a. new era in the world was discovered but not yet recog- 

 nized. As yet an error SAvayed the mind of man. 



The phenomenon of combustion which, at the present time, is as- 

 cribed to the chemical union of oxygen with combustible bodies, was 

 at that time explained as due to the escape of an unknown Jire-siibsta?ice 

 called phlogiston. The products of combustion wer-3 said to be dephlo- 

 gisticated. That substance was thought to escape from the burning 

 body during the act of combustion ; and yet experience demonstrated 

 that the result of the combustion, such as, for example, the rusts of 

 lead, zinc, and copper, had more weight than the original metals. In 

 reply to this, it was maintained that the phlogiston possessed negative 

 weight (that it buoyed up the substances on account of its levity). 

 Thus error begat error. At length the mystery was solved by Lavoi- 

 sier. He distinctly recognized the nature of oxygen as that of a 

 simple body, and asserted that combustion was the combination of a 

 substance with oxygen. This introduced the element into chemistry, 

 a conception which formed at once the basis of an exact science. 

 Priestley was the Copernicus of Chemistry, Lavoisier became its 

 Kepler. 



An immense number of familiar facts now easily clustered around 

 this fundamental conception ; and the so-called antiphlogistic system 

 sprang into life, a system which has prevailed up to this day, although 

 its name is no longer in use, there being no purpose in maintaining a 

 term that would perpetuate the memory of an error. 



The system met with the fate of that of Copernicus ; after a pro- 

 tracted struggle it came out victorious, the tenet of every naturalist 

 now living. Oxygen being the most frequently-occurring substance, 

 entering into combinations with all bodies, forming eight-ninths of the 

 weight of water, and over one-half the mass of our globe, and being 

 the conspicuous element ever present in the phenomena of combustion 

 and respiration it was eminently the substance to establish the new 

 system everywhere. More than half the science of chemistry is taken 

 up by oxygen and its compounds. Priestley and Scheele, its discover- 

 ers, remained to the ends of their lives enemies to the new theory. 

 On the 16th of Floreal, in the year II. of the French Republic, Lavoi- 

 sier was compelled to lay his head under the guillotine. 



The composition of water was discovered by Cavendish. This 

 completed the antiphlogistic system. Water consists of two gases, 



