﻿86 M. Dumas' s Remarks on Affinity. 



of motion as naturally result from that force, but also that they 

 are moved by certain active principles, such as is that of gravity, 

 and that which causes fermentation and the cohesion of bodies. " 



I will conclude these quotations by a few lines in which New- 

 ton states the true philosophy of science : — 



" To tell us that every species of things is endowed with an 

 occult specific quality, by which it acts and produces manifest 

 effects, is to tell us nothing ; but to derive two or three general 

 principles of motion from phenomena, and afterwards to tell us 

 how the properties and actions of all corporeal things follow from 

 those manifest principles, would be a great step in philosophy, 

 though the causes of those things were not yet discovered; and 

 therefore I scruple not to propose the principles of motion above 

 mentioned, they being of very general extent, and leave their 

 causes to be found out." 



Without solving the question propounded by Newton, Ber- 

 thollet subsequently discovered one at any rate of the general 

 principles of motion, the application of which to the fundamental 

 reactions of salts upon each other, of acids and of bases on salts, 

 constitutes what are known as Berthollet's laivs. 



If, for instance, we mix nitrate of lime and sulphate of soda, 

 both in aqueous solution, sulphate of lime is deposited and ni- 

 trate of soda remains in solution. 



Berthollet justly ascribes the exchange of the base and of the 

 acid which has taken place, not to more energetic affinities, but 

 to the deficient solubility of sulphate of lime. He shows that, in 

 general, when two saline solutions are mixed, and one of the 

 four salts capable of being formed is insoluble, this one is formed, 

 deposited, and thus determines the production of the corre- 

 sponding complementary salt. 



Berthollet assigns the greater cohesion of the insoluble salt 

 as the cause which determines its formation ; but if we en- 

 deavour to define by what signs he ascertains whether the cohe- 

 sion of a salt is greater or less, we are forced to accept solubility 

 and insolubility themselves as the only indications of the weak- 

 ness or the intensity of the cohesion. Thus, in the statement of 

 Berthollet's laws, we have long been content to say that, in the 

 mixture of two saline solutions, if the possible insoluble salt is 

 formed and is deposited it is because it is insoluble. 



I have shown, however, that Newton with wonderful precision 

 had indicated the greater or less force of union of the parts as 

 one of the determining causes of fluidity or of fixity ; for what 

 Berthollet calls cohesion consists really in a diminution of volume, 

 in an increase of density, as my investigations on atomic vo- 

 lumes prove. 



If, for instance, we compare magnesia, lime, strontia, and 



