436 
which the water vapour may condense into droplets and with which 
salt-droplets may combine afterwards. 
Lenarp') believes that 7m the superficial layers of every di-electric 
liquid there is not only an electric double-layer, generated by the 
molecular forces of the liquid itself, the negative layer being situated 
on the outside, but also that these layers differ as to material. 
These differences, which vary ‘with the substances dissolved in the 
liquid (electrolytes, volatile substances, complex molecules) affect the 
thickness and the strength of the electric double-layer. 
It appears then that Lenarp reduces the problem of the origin of 
waterfall-electricity and of spray-electricity to his hypothesis regard- 
ing the specifie condition of the surface of every di-electrie liquid. 
Strictly the origin of the electrification would then be, not 
an emission of electrons, but a discharge of extremely fine droplets, 
the so-called “carriers”, which, varying with the surface condition 
of the liquid, are either very small and charged negatively, because 
they take their origin entirely from the outer negatively charged 
layer of the liquid, or they are somewhat larger and may be posi- 
tively charged, since the majority of them arise from the interior 
positive layer of the liquid. 
For further particulars we refer to LiENARD’s article itself. 
Suffice it to state that most of our results with waterfall-electricity 
are sufficiently explained by this theory. 
Not however the intensifying influence of rise of temperature 
(LENARD’s private opinion, founded on theoretical considerations, was 
that a lessening influence was to be looked for). 
Neither does this theory explain why camphor and bornylacetate 
diminish waterfall-electricity ; no more is the question of the inten- 
sifying action of the sweet substances and the colloidal substances 
settled by if. 
The results obtained before in the Utrecht Physiological Laboratory 
in experiments on spray-electricity *) are much less easy to explain 
with the aid of this theory. 
First of all pure tapwater (Utrecht Water Company) and fresh- 
distilled water (old-distilled water zs active) give no or an inappreciable 
charge in spraying. 
Secondly the intensification of the charge in consequence of addition 
1) P. Lenarp. Ueber Wasserfallelektricität. Ann. der Physik. Bd. 47—1915. 
*) H. ZwaarpemMaker. Het in overmaat geladen zijn vau reukstofhoudende 
nevels. Verslagen K. A. v. Wetensch. Deel XIX N°. 1. 
H. ZWAARDEMAKER. Specifieke reukkracht en odoroscopisch ladingsverschijnsel 
in homologe reeksen. Id. Deel XIX NO. 2. 
