xix.] ATOMICITY. 271 



And in other substances this range of condition of formation 

 passes gradually out of our reach, but the phenomena are the 

 same in kind up to the temperature of the sun. And again, 

 when we can obtain the spectra of bodies like amorphous phos- 

 phorus we can prophesy that the relative grouping of the atoms 

 of phosphorus in this to the ordinary form will be exhibited. 



This brings us to the next point atomicity. What are the 

 associated phenomena? Lowest melting-point, simplest spec- 

 trum, lowest atomicity. Therefore we are justified, I think, 

 in assuming that atomicity may after all be but the measure of 

 the molecular groupings at work. In this way we can associate 

 various atomicities, not with moral phenomena as regards the 

 behaviour of the same molecule, but with different physical 

 states different complexities of the same substance. Thus in 

 the same substance the more complex or allotropic the molecular 

 grouping, the higher the atomicity. Hence the substances in 

 which the highest atomicities appear should, as a rule, be formed 

 and broken up at the lowest temperature. This, I am informed, 

 is really what happens in the majority of cases. 



I have ventured in these few remarks to touch upon the rela- 

 tions of the new view to modern chemical facts, because I think 

 such a discussion shows us that there are several chemical 

 regions in which the views can be tested from a chemical point 

 of view, although I have, of set purpose, dealt with them abso- 

 lutely from the physical side. One such step of the highest 

 interest has already been taken by Captain Abney. The language 

 of Professor Eoscoe, the President of the Chemical Society, in de- 

 scribing it, is so clear, and so admirably put, that it is impossible 

 for any one to improve upon it. 1 Eeferring to the work which 

 Captain Abney and Colonel Testing have done together, he says : 

 This work "is no less than a distinct physical test of the exist- 

 ence in organic compounds, of the organic radicals, and a means 

 of recognising the chemical structure of an organic compound 



1 Journal of the Chemical Society, May, 1881. 



