Mr. J. J. Waterston on Chemical Notation* 515 



may remain in the jar in consequence of the vanishing attractive 

 force which the coatings exert upon each other, as is found by 

 experiment. 



Windsor Villas, Plymouth, 

 November 1, 1863. 



LXXIII. On Chemical Notation. By J. J. Waterston, Esq, 

 To the Editors of the Philosophical Magazine and Journal, 



Gentlemen, 



IN your last Number, Mr. Odling has remarked on my com- 

 munication advocating the vapour-density system of chemi- 

 cal notation. I have been in the habit of using it in arranging 

 the thermo-molecular facts of chemistry in a convenient form for 

 easy reference ; and finding that it enabled the mind to grasp 

 easily rather complicated molecular relations which could not 

 be done with any other without tedious verbal accompaniment, 

 I endeavoured some ten or fifteen years ago to bring it to the 

 notice either of the Royal Society or British Association ; I forget 

 which. The attempt was unavailing, as indeed it is likely to be 

 in the present case, if some professional chemist of eminence 

 does not take it up in a magnanimous spirit. I did not trouble 

 myself further on the subject, because I felt that, as chemical 

 science progressed, it would be certain to be adopted in regular 

 course as the natural symbolic language — indeed that it would be 

 impossible to get on without it — and that it would be better 

 that the suggestion should come from within the schools. But 

 years have passed on, and the chance of this seemed becoming 

 less by degrees, until I was incited to make another effort by 

 Mr. Odling' s lecture, in which it appeared as if the school of 

 chemists to which he belongs had permanently adopted an im- 

 proper system, and were actually making mistakes in con- 

 sequence. 



The vapour-density system (or, for shortness, let us call it' 

 the V.D. system) is founded on the bulk of all molecules in 

 the gaseous state being equal. This, according to Mr. Odling, 

 is an extremely recognized fact among chemists*. "Let chemi- 



* At p. 513 of Dr. Graham's second volume the following occurs : — 

 "3. The system (of notation)*of Gerhardt, based, like that of Berzelius, on 

 the hypothesis that all simple gases contain equal number of atoms in equal 

 volumes." See also p. 512, vol. ii. This, I presume, is concurred in by 

 Mr. Odling and the school ; so that we are to understand that they are agreed 

 that (1) it is &fact that all simple or compound gases and vapours contain 

 equal number of molecules in equal volumes ; and (2) that the system of 

 notation they adopt is based on the hypothesis that the simple gases contain 

 equal number of atoms in. equal volumes. 



