B.—CHEMISTRY. 61 
able in the jostling throng of individuals inside. A surface or surface 
layer represents a sort of thin cross section which can be probed and 
examined much more readily than any part of the inside bulk. It is 
indeed only within comparatively recent years that the X-rays have 
provided a sufficiently fine probe for examining this bulk in the case 
of crystalline matter. 
The living organisms of plants and animals are full of surfaces and 
membranes. What can happen at surfaces is therefore a matter of great 
importance for the science of living things. We are bound to hold as 
long as possible to the assumption that the physico-chemical manifes- 
tations of life can be explained in terms of the potentialities of action 
inherent in electrons, atoms, and molecules. The drilled and disciplined 
soldiers of an army behave very differently from an undisciplined and 
disordered mob of the same men. ‘Thus the modes of action 
of ordered arrays and marshallings of atoms and molecules are 
of extreme interest, since such modes of action will constitute pheno- 
mena non-existent in a disordered multitude of the same atoms and 
molecules with exactly the same individual powers and potentialities 
These phenomena may be intimately connected with the phenomena of 
living matter, and as the latter evidently require the existence of surfaces 
and membranes, the idea naturally suggests itself that the special array- 
ing or ordering of individuals occurs at, and may start from, such 
surfaces. 
An essential characteristic of this ordering or arraying may consist 
in special orientation. In the chemical and physical actions occurring 
in a volume of liquid whose bulk is large compared with its surface, 
the molecules or atoms probably move towards each other with every 
sort of orientation, no special type being privileged or distinguished. 
Should, however, some special orientation be characteristic of interfaces, 
then it is clear that such interfaces will exhibit new phenomena due 
to this special sort of arraying. Moreover, if we are dealing with 
molecules which are ionised into electrically polar constituents, or which, 
if not actually dissociated, can be treated as electrically bi-polar, it 
follows that, if orientation occurs at interfaces and surfaces, then 
electrical double layers and electrical potential differences may be set 
up at such boundaries. 
In the theories of Laplace, Gauss, and Poisson the field of force 
surrounding an attracting element or molecule was regarded as essentially 
uniform in its spatial relations, 7.e. the equipotential surfaces were 
regarded as concentric spheres with the molecule as a small element at 
the centre. The only way in which the molecule could show its 
character was in affecting the intensity of this central force at a given 
distance and the rate at which the force falls off with increasing distance. 
The molecules were thought of as possessing what one might call a 
very ‘rounded and somewhat: monotonous ‘ physical’ personality or 
character as regards their fields of force. In recent years our views 
on such matters have undergone a somewhat radical transformation. 
The field of force surrounding a molecule may in reality be very 
‘irregular,’ and may be specially localised around certain active or 
‘polar’ groups Its region of sensible magnitude may be very variable 
