HISTORY OF THE ATOMIC THEORY. 183 



the chemists of the period, by understanding definite pro- 

 portion, and learning to reason in the spirit of the atomic 

 theory. 



William Higgins made an advance on Bryan Higgins in this 

 theory of sulphur and heat, and he was a man evidently of an 

 acute mind. But he was destined to find Emerson's saying true, 

 that we often find in the sayings of great men our own rejected 

 ideas. He was heir to the common opinion that atoms existed, 

 and the opinion of Dr. Higgins that they united and formed 

 molecules of compound bodies. He applied the reasoning 

 further, and said that they must then unite in numbers of one 

 or two, or three, and that there could be no intermediate 

 combination, as there were no intermediate division of 

 atoms. He applied this reason in two or three cases. These 

 cases, such as nitric acid, are so clear and beautiful, that 

 we can only be surprised that the general law was not 

 seized on. They are the first clear and satisfactory reasons 

 given for saturation, and for definite proportion in general. 

 Higgins was therefore the first man who used the idea of 

 atoms with such force as to be serviceable in chemistry. He 

 used the idea of ultimate particles and the molecular state of 

 bodies to illustrate saturation, and definite and multiple pro- 

 portion, and gave us therefore the fundamental ideas of 

 stoechiometry as they exists in chemical science, from which 

 everything else might have easily flowed. 



He had seen the right road, but dared not go farther. 

 But we must take his own apology, ** Est quoddam prodire 

 tenus, si non datur ultra." It is something to have gone thus 

 far, if he had no power to go beyond it. 



Like Dr. Higgins, and the most of the chemists of last 

 century, he assumed certain forces of attraction, and endea- 

 voured to give comparative values to the forces of combination. 

 These numbers representing affinity misled Higgins. Had he 

 seen any general law, he would have seen that weights repre- 



