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XXXI. On. the Production of Electricity by Evaporation, and 
on the electrical Neutrality of Vapour arising from electri- 
fied Still Surfaces of Liquids. By L. J. Blake, Ph.D.* 
OF the different theories as to the cause or causes of atmo- 
spheric electricity, two especially have been from time 
to time advocated. The basis of the first theory is the hypothesis 
that electricity is produced by the simple evaporation of a 
liquid. This hypothesis was first proposed by Toltaf , and 
afterwards found adherents in Pouilleti, Tait and Wanklyn§. 
Sanssureflj ConfigliachilT, Erman**, Eeichtt, Gaugainit, and 
Biess§§ attempted to overthrow it. 
The second theory rests chiefly upon the hvpothesis that 
there occurs a convection of the electricity which may be upon 
the surface of any evaporating liquid. This theory was main- 
tained by Franklin |j||, E. BecquerellflF, and De la Bive***; 
and the hypothesis itself has been experimentally tested by 
Buff f f f . The following paper is a description of an exclu- 
sively experimental investigation of these two hypotheses. 
It was carried out by means of an electrometer herein de- 
scribed. TTith the very complicated phenomena of atmo- 
spheric electricity itself, this paper has nothing directly to do; 
hence a more detailed description of the theories just stated 
is unnecessary. 
I. Production of Electricity by Evaporation. 
(a) The investigation of the first hypothesis — i. e. that 
electricity is produced simply by the change of a liquid into 
vapour — was conducted in the following manner. The mo- 
vable plate A of a Kohlrausch condenser was connected with 
* Communicated "by the Author, 
t Phil. TTans. 1782, abridged, xt. p. 274. 
% Annates de Chimie et de Physique, 1827, xxxv. p. 401, andxxxri. p. 5. 
§ Phil. Mag. [4] xxiii. p. 494; 'ZSTature," vol. xxiii. p. 340. 
II Voyages dans les Alpes, 1786, tome ii.' pp. 227 & 249. 
IF Gilbert's Arm. 1811. xliii. p. 370. 
** Ahh. der Berl. Akad. 1818, xix. p. 25. 
ft Abh. bei Begrilndung der Sachs. Ges. d. Wissenseh. 1846, p. 199. 
XX Comptes Bendus. 1854. tome xxxriii. p. 1012. 
§§ Beibungselektncitcr. 1863, ii. pp. 407 & 491. 
Illl Compare Duprez. Mem. cam. de TAcad. d. Belg. xvi. 1843. 
i]«J TraitedeVElectricite, 1836, tomeiv. p. 116; Comptes Bendus, 1856, 
tome xlii. p. 661. 
*** Traite de VElectrieite, 1858, tome iii. p. 190. 
ttt Liebir's Annalen, 1854, lxxxix. p. 203. Compare Fortschr. der 
Phys. x. p. 436. 
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