Dal ton. 229 



one unit or two or more units at a time. If you have 



nothing but penny pieces to pay wages with, you must give 



either one penny, or two pennies, or three, and so on ; you 



cannot divide them. In a similar way one atom of iron 



unites with one or two atoms of sulphur, or any number 



with any number; but there are no broken atoms : and this 



is the whole of Dalton's theory. It has gone beyond the 



reach of theory — it is a fact ; but there are men who try to 



get beyond it and call it a speculation. Astronomy has to 



deal'with great masses, mechanics have small ones, chemists 



have smaller still ; but they are so far as we know atomicy 



that is, not divided in our experience. 



* Although Dalton rigidly held to the idea of atoms, he 

 by no means supposed that we had attained the indivisible 

 atom in our elements ; at least he expressly reserved this 

 point. What he speaks of is simply the ultimate particle that 

 seems to act in our chemical processes. He used atom 

 and particle.' The latest ideas of molecules entirely fit in 

 with his reasoning. Those who think otherwise cannot be 

 said to understand Dalton, and indeed, it is difficult to 

 imagine what any one means who opposes his theory, which 

 is fitted for a far greater amount of knowledge of matter 

 than any one seems by any speculations to indicate at this 

 present time. 



The consequences of Dalton's great idea soon showed 

 themselves to be that there was now one great law or theory 

 in chemistry, so that it was for the first time fit to be called 

 a science. 



It may be said distinctly that the laws which made 

 chemistry a science were first seen by Dalton and published 

 by this Society. The first announcements of them are given 

 here in his own words : — 



