DOCTRINE OF ELECTIVE ATTRACTIONS. 129 



different bodies, which cause them to unite. These 

 relations have their degrees and their laws. W& 

 observe their different degrees in this ; that among 

 different matters jumbled together, which have a cer- 

 tain disposition to unite, we find that one of these 

 substances always unites constantly with a certain 

 other, preferably to all the rest." He then states 

 that those which unite by preference, have " plus de 

 rapport," or, according to a phrase afterwards used, 

 more affinity. "And I have satisfied myself," he- 

 adds, "that we may deduce, from these obser- 

 vations, the following proposition, which is very 

 extensively true, though I cannot enunciate it as 

 universal, not having been able to examine all the 

 possible combinations, to assure myself that I should 

 find no exception." The proposition which he states 

 in this admirable spirit of philosophical caution, is 

 this : " In all cases where two substances, which 

 have any disposition to combine, are united; if 

 there approaches them a third, which has more 

 affinity with one of the two, this one unites with 

 the third and lets go the other." He then states 

 these affinities in the form of a Table ; placing a 

 substance at the head of each column, and other 

 substances in succession below it, according to the 

 order of their affinities for the substance which 

 stands at the head. He allows that the separation 

 is not always complete, (an imperfection which he 

 ascribes to the glutinosity of fluids and other 

 causes,) but, with such exceptions, he defends very 

 VOL. in. K 



