THE ATOMIC VIEW OF NATURE. 397 



through Newton. But who could compare the state of 

 chemistry at the present day with that of astronomy in 

 the age of Laplace ? There, every step had tended to 

 show that the one Newtonian formula sufficed to com- 

 prehend all cosmic phenomena ; here, the simplification 

 introduced by Dalton has had to give way to a series 

 of modifications which have rendered the atomic theory 

 one of the most complicated machineries ever introduced 

 into science. Let us review in brief the fate of Dalton's 

 hypothesis during the century which followed. Quite in 

 the early years of the atomic theory, Wollaston propheti- n. 

 cally foretold that if once an accurate knowledge were prophecy, 

 gained of the relative weights of elementary atoms, philo- 

 sophers would not rest satisfied with the determination 

 of mere numbers, but would have to gain a geometrical 

 conception of how the elementary particles were placed 

 in space. Van't Hoff s ' La Chimie dans 1'Espace ' pub- 

 lished at Rotterdam in 1875 was the first practical reali- 

 sation of this prophecy. Many stages had to be gone 

 through before this latest phase of the atomic view was 

 attained. Had it been the case that every elementary sub- 

 stance combines with any other substance only in one 

 fixed numerical proportion, no necessity would have ex- 

 isted to look upon the atomic numbers as anything else 

 than equivalents. But it was found that though the 

 combining numbers were fixed they were not always the 

 same ; it was found that if a substance combined in two 

 or more proportions with any other, the larger proportions 

 were always exact multiples of the smallest proportion. 

 And this the rule or law of multiple proportions was 



