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and allowed it, though being unstable, to flow against a metallic 
dise even from some distance, we discovered a very strong charge, 
which, of course, under the experimental conditions (overpressure 
of two atmospheres), was invariably a positive charge. While the 
cloud diffuses after the flow is arrested, the charge is left behind on 
the electroscope. The surrounding air is evidently not more conduct- 
ive than it would be without a vapour. Also the drops creeping 
down the disc appear to be charged, the charge being under the 
experimental conditions invariably positive. 
The literature contains previous reports of vapours disposed to 
condense in the shape of drops round the positive ions as their 
nuclei ?). We know now that in the cases here referred to, which 
were few and far between, the experimenter used substances of 
some olfactory quality. This induced us to examine all odorous sub- 
stances at our disposition with a view to their electrical effect. 
First of all we examined the odorous solids at band, as I felt 
inclined to generally identify the phenomenon observed by us with 
the so called odoroscopic phenomenon *). Then our researches were 
extended to odorous liquids in aqueous solution. Seemingly insoluble 
substances were mixed with water in a separator; the fluid was 
subsequently filtered and the filtrate sprayed under an overpressure 
of two atmospheres into an inconstant vapour *). 
Electrification was detected with: acetaldehyd, acetone, ether, 
ethyl-alcohol, ethylbisulfid, ethylbromid, ethylbutyrate, ethylmelonic 
acid, allylsulfid, ammoniac, amylacetate, amylalcohol, amylbutyrate, 
1) Cf. H. KAMERLINGH ONNEs and W. H Keesom, Enc. d. meth. Wissenschaft 
V. 10, p. 910, note 937, which brings up the literature to 1912. 
2) The odoroscopic phenomenon has been discovered by VENTURI. was named 
after him, studied again by PrÉvosr and extensively inveStigated by LrkGEOrs. 
(Arch. de physiol. 1868 t. I p. 35). VAN DER MENSBRUGGHE (mém couronnées 
par l'acad. royale de Belgique t. 34 1870) correlated it with a lowering of the 
surface tension. MARCELIN (Ann. de phys. t. IX, p. 14 1914) found that by covering 
the evaporation and consequently the movement was stopped. A satisfactory method 
to obtain a perfectly pure, fat-free water surface has been suggested by RÖNTGEN. 
For the theory see Lord RAYLEIGH Sc. papers. Vol. 3, p.p. 347 and 383. 
3) The phenomenon of electrification affords a very sensitive reagent to find out 
whether any part of an odorous substance dissolves or not; in this respect it is 
comparable to the olfactory sense. Therefore, the vessels must be kept perfectly 
clean and control tests with pure water must continually be inserted. The amount 
of electricity conveyed by the vapour to the electroscope is astonishingly great, 
much greater than the electricity generated by the splashing of water (LENARD). 
A full discussion of electrification through transformation of liquid surfaces into 
gases was brought forward by A. Becker in Jahrb. der Radioactiv. u. Electron. 
3d. II, p. 42. 1912. 
