128 The Evolution of Chemistry. 



tween scholastic dogma and modern verification. The 

 first turn under that young man's control let into this 

 world most of the blessings and comforts of our modern civili- 

 zation. Little did he dream of the momentous issues that 

 hung on his work. His was the first 'quantitative estimate 

 ever known to have been made in our planet the first 

 telling proof of the utter worthlessness of purely abstract 

 reasoning. He followed fixed air into and out of magnesia, 

 limestone, and the alkalies. He noted the changes caused 

 by its presence and absence. He saw plainly that these 

 changes in no way agreed with current notions about the 

 unions and vanquishments of qualities. He started other 

 able men to work in the same field, who not only verified 

 what he had done, but extended our knowledge in the same 

 direction. Priestley soon after discovered what he supposed 

 was " dephlogisticated air." We now know it as oxygen. 

 Cavendish found that Black's fixed air was a union of char- 

 coal and Priestley's new gas, and that water was a union of 

 this same gas and another combustible one then called 

 " phlogisticated air." We now know it as hydrogen. La- 

 voisier thought he saw in Priestley's " dephlogisticated air " 

 the cause of sourness in bodies, and so he called it oxygen or 

 " acid producer." Sir Humphry Davy at a later date dem- 

 onstrated that muriatic acid contains no oxygen, although 

 it is one of our most powerful mineral acids, and that La- 

 voisier was therefore in error. While the French savant 

 was evidently mistaken in this, he was certainly right in his 

 solution of the phenomena of combustion. He pointed out 

 the fact that in all ordinary combustion we have the union 

 of oxygen with some body having an affinity therefor. An 

 appreciation of this fact put an end to the phlogiston theory, 

 and established a center around which chemical facts could 

 readily crystallize. And yet how strange it even now seems ! 

 That the "burning of wood or coal and the rusting of iron 

 should be phenomena of the same kind seems scarcely 

 credible. That water is the rust of hydrogen, and choke- 

 damp that of carbon, is wonderful. The heat of our bodies, 

 the thoughts of our brains, the movements we make, hardly 

 look, to the uninitiated, as if they were all due to changes 

 in us identical in kind with those producing iron rust. 

 Yet such is the fact, and the knowledge thereof came like 

 bright sunshine into the chemical world, making clear 

 everything where before was darkness and ignorant grop- 

 ing. The human race might hunt long before it could find 



