328 LAVOISIER. 



which the authors of the experiments and original 

 framers of the theory had given. As regards the latter 

 doctrine, the obscurity of Mr. Cavendish's language, 

 even of Mr. Watt's though in a much less degree, has 

 been observed upon already. But we need only con- 

 sider Dr. Priestley's view of the air he had discovered, 

 and the name he gave it, in order to be satisfied how 

 confused were the notions derived from the phlogistic 

 theory, and how they obscured his naturally acute 

 vision. When he called it dephlogisticated air, he in- 

 tended to say that air, the atmosphere, parts with 

 phlogiston, and the residue is oxygen gas. But then 

 if phlogiston be added, it should again become com- 

 mon air. Now he held the calcination of metals to be 

 the evolution of phlogiston, therefore this operation 

 should have restored the gas to the state of common 

 air. But, instead of that, the gas was absorbed alto- 

 gether. Again : the residue, when common air is de- 

 prived of the dephlogisticated portion, is another air 

 which he called phlogisticated, because it contained 

 more phlogiston than the common air. But how by 

 this theory could the union of such a phlogisticated 

 air with a dephlogisticated air make the common air ? 

 By the hypothesis, that air with phlogiston added is 

 azote, with phlogiston subtracted is oxygen gas. 

 Therefore mixing the two, you should have produced, 

 not the air that had been phlogisticated in making the 

 one, dephlogisticated in making the other, but double 

 the quantity operated upon.* Such was the load of 

 absurdity and contradiction under which the favourite 

 hypothesis of the day placed Priestley entirely, Caven- 

 dish to a great degree, Watt in some sort ; such was 

 the weight of prejudice against which Lavoisier had to 

 contend ; such was the maze of error from which he 

 boldly broke loose and extricated chemical science. 

 It is his glory that he first effected this emancipation ; 



* If common air (a) Phlog. = ox. gas, and com. air (a) -f- Phlog. 

 = azote ; Ox. gas -\- azote = not a, as it ought to be, but 2 a. 



