78 PRIESTLEY. 



becomes calcined, and gains in weight precisely the 

 weight of the gas which has disappeared, the calcina- 

 tion should be ascribed to the gas, and that the repro- 

 duction of the gas by heat, or its abstraction by elec- 

 tive affinity for some other body, should be allowed to 

 have restored the metallic state by simply destroying 

 the union of the gas and the metal which had changed 

 that metal. But nothing could overcome Priestley's 

 repugnance to give up phlogiston : he adhered to it 

 while he lived; he never would believe that water 

 was formed of the two gaseous bodies whose combus- 

 tion and disappearance leaves a weight of liquid equal 

 to their joint weights ; he always imagined that water 

 was held in suspense by these gases and precipitated 

 on their disappearing. He never would believe that 

 metals owe their malleability and lustre to any cause 

 other than phlogiston, or lose their properties except 

 by oxygen taking the phlogiston from them. He 

 never would believe that combustion is anything but 

 the phlogiston leaving the inflammable body and join- 

 ing the oxygen ; or that when an acid is formed by 

 the burning, that acid contains the oxygen and the 

 combustible base. That his obstinate unbelief was 

 perfectly disinterested no one can doubt. The dis- 

 coverer of oxygen, and of the true cause of respira- 

 tion, had, of all men, the strongest interest in assent- 

 ing to a theory which was whoUy founded upon his 

 own discovery, and which made him the immediate, 

 as Black was the more remote, author of modern 

 chemical science made him the philosopher who had 

 raised the superstructure upon the foundation which 

 his predecessor had laid. 



The merit of Dr. Priestley, as a cultivator of science, 

 was the activity with which he made experiments 

 the watchful attention with which he observed every 

 phenomenon, following the minutest circumstances of 

 each process the versatility with which he prose- 

 cuted each new idea that arose from his trials his 



