170 Mr. Colquhouu on the Life and Writings [Marc^, 



of t\}e profound reasoning and ingenious experiments by which 

 he endeavoured to estimate the exact amount of affinity exerted 

 in chemical combination, and the extent to which it is modified 

 or counteracted by its several rival forces, as by cohesion, by 

 expansion, by heat, sometimes favouring combination by dimi- 

 nishing cohesion, sometimes opposing it by rendering one of the 

 substances elastic, by light, by atmospheric pressure, and by the 

 slow in opposition to the rapid propagation of chemical action. 



The recently established principle of the equimultiple propor- 

 tions hi which substances combine, has contributed materially 

 to weaken the confidence with which chemists were disposed to 

 receive the conclusions of Berthollet ; and indeed it is undeni- 

 able that many of his assumptions were too vague, and too little 

 supported by ej^perimental evidence, to be admitted uncondi^ 

 tionally; that the principles by which he attempted to estimate 

 the exact amount of affinity exerted in chemical combination 

 were inconclusive ; that he placed by far too high an estimate 

 on the efficacy of mass in chemical action ; and that he made a 

 most unwarrantable generalisation when he transferred to the 

 constitution of solid bodies those laws of affinity to which he 

 had rendered it probable they are subject while in a state of 

 solution. It is not too much to expect that the final establish- 

 ment of an atomic theory, unembarrassed by arbitrary assump- 

 tions, taken in conjunction with the electro-chemical theory, 

 will conduct to a still more perspicuous conception of the laws 

 which regulate chemical combination ; and it is probable too, 

 that these views will be found to coincide with the opinions 

 entertained by Berthollet to a much greater extent, than many 

 chemists of the present day appear disposed to admit. 



The publication of the Statique Chimique involved Berthollet 

 soon afterwards in his celebrated discussion with Proust respect- 

 ing the proportions in which substances enter into combination. 

 This contest, in which the two most distinguished chemists in 

 Europe took diametrically opposite views of what may be said to 

 form the very basis of their favourite science, could not fail to 

 excite a deep sensation from its commencement ; and the extent 

 of information possessed by each, and the admirable ingenuity 

 with which each availed himself of his resources, all contributed 

 to render the controversy more and more interesting as it pro- 

 ceeded. Perhaps it is not going too far to assert, that since 

 Bergmann's enforcing the use of the balance in chemical inves- 

 tio-ations, nothing has contributed so much to the establishment 

 of the doctrine of chemical equivalents as the views respecting 

 combination which Proust on this occasion promulgated and 

 supported. As this great doctrine has rescued chemistry from 

 the domain of empyricism and uncertainty, and has elevated it 

 to the rank of a mathematical science, and as its ultimate esta- 

 blishment is owing more than is generally acknowledged tp 



