CTLES AND ATOMS 325 



of chemistry presents a striking example in point Newton fore- 

 saw from the high refractive index of the diamond that it would 

 contain a combustible substance since so many combustible oils have 

 a high refractive power. 



As regards purely chemical relations, especially the understanding 

 of reactions and the structure of substances, the fecundity of the law 

 of Avogadro-Gerhardt is evinced at every step of the contemporary 

 path of chemistry. Starting from the laws and conceptions of 

 Lavoisier the chemistry of our .time is entirely founded on the laws 

 of Dalton and Avogadro-Gerhardt, on the doctrine of Berthollet 

 respecting the equilibria brought about in chemical actions, and on the 

 conceptions of dissociation introduced into the science by Saint-Claire 

 Deville. 



although only approximately, obtaining the coefficient of refraction from the chemical com- 

 position of a substance. For instaiice, the composition of carbon bisulphide, CS 2 = 76, 

 and from its density, 1'27, we find its coefficient of refraction to be 1'618 (because the 

 refraction equivalent = 5 + 2 x 16 = 87), which is very near the actual figure. It is evident 

 that in the above representation compounds are looked on as simple mixtures of atoms, 

 and the physical properties of a compound as referable to the properties present in 

 the elementary atoms forming it. If this representation of the presence of simple 

 atoms in compounds did not exist, then the effort to combine by a few figures a whole 

 mass of data relating to the coefficient of refraction of different substances would hardly 



