PHLOGISTIC THEORY. 267 



iv as to take into account the quantities of the elements which combined ; 

 but this leads us into a new train of investigation, which was, indeed, 

 a natural sequel to the researches of Geoftroy and Bergman. 



In 1803, however, a chemist of great eminence, Berthollet, published 

 a work (Essai de Statique Chimique], the tendency of which appeared 

 to be to throw the subject back into the condition in which it had been 

 before Geoffroy. For Berthollet maintained that the rules of chemical 

 combination were not definite, and dependent on the nature of the 

 substances alone, but indefinite, depending on the quantity present, and 

 other circumstances. Proust answered him, and as Berzelius says, 4 

 " Berthollet defended himself with an acuteness wnich makes the reader 

 hesitate in his judgment ; but the great mass of facts finally decided 

 the point' in favor of Proust." Before, however, we trace the result of 

 these researches, we must consider Chemistry as extending her inqui- 

 ries to combustion as well as mixture, to airs as well as fluids and solids, 

 and to weight as well as quality. These three steps we shall now 

 briefly treat of. 



CHAPTEPt IV. 



DOCTRINE OF ACIDIFICATION AND COMBUSTION. PHLOGISTIC THEORY. 



PUBLICATION of the Theory by Beccher and Stahlli will be 

 -L recollected that we are tracing the history of the progress only of 

 Chemistry, not of its errors ; that we are concerned with doctrines 

 only so far as they are true, and have remained part of the received 

 system of chemical truths. The Phlogistic Theory was deposed and 

 succeeded by the Theory of Oxygen. But this circumstance must 

 not lead us to overlook the really sound and permanent part of the 

 opinions which the founders of the phlogistic theory tafcght. They 

 brought together, as processes of the same kind, a number of changes 

 which at first appeared to have nothing in common ; as acidification, 

 combustion, respiration. Now this classification is true; and its 

 importance remains undiminished, whatever are the explanations 

 which we adopt of the processes themselves. 



The two chemists to whom are to be ascribed the merit of this step, 

 and the establishment of the phlogistic theory which they connected 



4 Chem, t iii. p. 23. 



