432 TRANSACTIONS OF SECTION B. 
It is to the advantage of the hypothesis formulated by Batlow and Popé 
that the elements are represented as of constant valency in so far as their 
1elative volume spheres of influence are concerned—the compound in which 
the higher valency is manifest being derived from that of lower valency by 
the opening out of the close packed arrangement and the insertion of certain 
new elements ; but the fact that in such cases the volume is altered not in one 
direction alone in the crystalline structure but proportionately in all direc- 
tions would seem to show that the volume sphere of atomic influence does 
actually change ; the change is one, however, which affects all the atoms in 
the complex proportionately. 
At present, unfortunately, our methods of treating the problems of 
valency are such that we cannot in any way give expression to the energy 
side of the phenomena. 
Of late there has been talk of electrons in this connexion but what is 
said is little more than superficial paraphrase, in the advanced scientific 
slang of the day, of the ideas which have long been current. When, follow- 
ing Odling, we represent valency by dashes written after the elementary 
symbol, we give clear expression by means of a simple convention to certain 
ideas that are well understood by all among us who are versed in the facts; 
to speak of electrons and use dots instead of dashes may serve to mislead the 
unwary, who hang on the lips of authority, into a belief that we have 
arrived at an explanation of the phenomena, but those who know that we 
have reached only the let-it-be-granted stage, who feel that the electron is 
possibly but a figment of the imagination,* will remain satisfied with a 
symbolic system which has served us so long and so well as a means of giving 
simple expression to facts which we do not pretend to explain. Not a few 
of us who listened to the discussion of the nature of the atom at Leicester 
could not but feel that the physicists knew nothing of its structure and 
were wildly waving hands in the air in the endeavour to grasp at an 
interpretation which would permit of mathematical interpretation being 
given to the facts. Until the credentials of the electron are placed on a 
higher plane of practical politics, until they are placed on a practical plane, 
we may well rest content with our present condition and admit frankly that 
our knowledge is insufficient to enable us even to venture on an explanation 
of valency. 
In 1885 and again in 1888, I ventured to call in question the interpreta- 
tion of valency which Helmholtz had given in the Faraday lecture in 1881. 
On the present occasion, I would insist still more emphatically on the in- 
sufficiency of the atomic charge hypothesis; especially that it affords no 
satisfactory explanation of variable valency and of those fine shades of 
difference which are manifest, especially in the case of nitrogen, when the 
radicle attached to the dominant element is varied. In 1885 I discussed this 
question with reference to the nature of electrolytes and questioned the con- 
clusion Helmholtz arrived at that electrolytes belong to the class of typical 
compounds the constituents of which are united by atomic affinities, not to 
the class of molecular aggregates. The opinion I then ventured to give was 
as follows :— 
‘The current belief among physicists would appear to be that primarily the 
dissolved electrolyte—the acid or the salt—is decomposed almost exclusively. 
We are commonly told that sulphuric acid is added to water to make it conduct, 
1 In my opinion the experimental evidence is in no way satisfactory. It appears 
to me to be desirable that in studying the phenomena of electric discharge in 
gases, especially in vapours of complex substances, the horrible pitfalls should be 
taken into account with which the field of work is studded ; unless every precaution 
to secure purity—precautions such as Baker and Dewar have taught us to use—be 
taken at every step, the conclusions based on all such observations must be open 
to grave doubt, 
