1825.] of Claude-Louis Berthollet. 167 



some exploit, the plain unadorned figure of his faithful and affec- 

 tionate dog. He was no courtier before he received these 

 honours, and he remained equally simple and unassuming, and 

 not less devoted to science, after they were conferred. 



It was in 1803 that Berthollet published his work on Chemical 

 Statics. Lavoisier had established almost nothing positive or 

 precise with regard to chemical affinity, and it remained a topic 

 which few cared to assay, on account of its difficulty, until the 

 researches of Berthollet, at the Natron Lakes of Egypt, sug- 

 gested to him a train of new ideas on the subject which were 

 now published under the appropriate title of the Statique Chi- 

 mique. 



Chemists had no sooner made themselves familiar with the 

 distinctive characters by which individual substances may be 

 recognised, than the unequal energy with which two bodies act 

 upon a third became a matter of notoriety. Geoffroy, one of the 

 earUest of those who took a philosophical view of the nature of 

 combination, advanced a general theory on the subject, which 

 was eagerly embraced by the chemical world, and which his 

 successors, particularly Bergmann, contributed materially to 

 extend and to complete. According to this theory, chemical 

 affinity, or the reciprocal tendency of substances to combination, 

 is an invariable force : its intensity also is different in each indi- 

 vidual substance, and is expressible in numbers. This second 

 property was described in other words by saying that affinity is 

 elective: that is, a substance already combined with another, 

 when presented to a third, for which it possesses a still more 

 energetic affinity, separates from the former, and, by preference, 

 attaches itself exclusively to the latter. 



This hypothesis of the existence of q,n infinite number of 

 forces, all varying in their intensity, appeared to Berthollet 

 inconsistent with the ordinary simphcity of nature ; and the 

 Statique Chimique was an attempt to demonstrate that, just as 

 mider the same law of matter we see a stone fall to the earth, 

 and smoke rise from its surface, so the most opposite chemical 

 phenomena are deducible from the existence of a single active 

 principle, variously modified in its effects by a very few other 

 causes, which, like it, are equally distinct and unalterable. 



Chemical affinity he regarded, as a force, analogous in all its 

 effects, and probably indeed identical with the attraction of 

 gravitation. Like the latter, its invariable tendency is to pro- 

 duce cpmbinatiou, and its intensity is proportional to the quan- 

 tity of tl]e body in which it acts. But although it is jjrobable 

 that these two forces are ultimately of the same nature, there i;? 

 an important difference in the manner in which they are exerted. 

 Gravitation consists in the mutual attraction between two 

 masses of matter, situated at sensible distances from one 

 another. Its effects are, therefore, dependent exclusively on 



