CHEMISTRY AND CRYSTALLOGRAPHY— A NEW 

 SUGGESTION. 



By James Moir, M.A., D.Sc, F.C.S. 



If my readers will cast their minds backwards to the physical 

 text-books and lectures of their youth, they will recollect a. 

 certain mathematical abstraction called a particle. What exactly 

 the mathematicians meant by it, I was never able to fathom. In 

 those days Chemistry was the Cinderella of the sciences — de- 

 spised at the Universities, and as unk,nown to the so-called 

 " educated man " as Chinese — consequently no one amongst the 

 mathematicians worried about the fact that the neglected science 

 also used a similar fundamental unit of matter called a molecule, 

 or knew that Chemistry could go beyond the molecule in most 

 cases and find it made of an arrangement of atoms. 



Crystallography therefore had no possible explanation except 

 that of a geometrical arrangement of the mathematician's " par- 

 ticles " : no one knew if the " particles "' of common salt were 

 simply molecules, or much bigger aggregations of the composi- 

 tion (NaCl)x. The simple-minded were content to ascribe the 

 shapes of crystals to Divine design — like the cells of tlie honey- 

 comb, to take a more familiar case of misplaced enthusiasm. 



About six years ago a series of epoch-making papers from 

 the pen of Pope and Barlow began to appear, in which, by build- 

 ing together spheres of dififerent sizes for the difl:'erent types of 

 element, these authors succeeded in depicting the innermost 

 structure of the crystal-aggregate. Unfortunately, the pa])ers 

 are not only devoid of literary grace of any sort, but liave not 

 even the merit of ordinary scientific luciditv : most of the 

 sentences are Ciceronian in length and Kantian in obscurity ; 

 consequently the importance of the work is likely to be overlooked 

 unless another Huxley arises to interpret the scheme — which, in 

 my opinion, is just as important for science as the Darwinian one. 



The present writer is no Huxley, and must therefore be 

 content with friendly criticism, believing that Truth only grows 

 by the friction O'f mind on mind. 



The main assumption of the Pope-Barlow hypothesis is a 

 sufficiently startling one, t'/,::., that valency is a function of the size 

 of the atomic sphere : thus if the hydrogen sphere has unit volume, 

 then sodium, and chlorine, and feven iodine and caesium, have also 

 atomic spheres of much the same size as hydrogen ; whilst oxygen 

 has a sphere of volume 2, and carbon a sphere of volume 4. This 

 conception, whilst totally at variance with our knowledge of 

 valency as a series of forces varying in dircctio-n rather than in 

 magnitude, is not altogether incredible. Lately, however. Pope 

 has complicated the question by finding that silicon and oxygen 

 have nearly the same size of atomic sphere in quartz and tridy- 

 mite ; and as oxygen is certainly not tetravalent in these sub- 

 stances, silicon must be assumed to be divalent — that is, if valency 

 really depends directly on size of sphere. This conception of 

 divalent silicon seems, however, to be quite beyond belief ; and 



