= 
PROCEEDINGS 
OF 
THE ROYAL IRISH ACADEMY. 
1846_7. ‘ No. 67: 
: May 24th, 1847. 
REV. WILLIAM HAMILTON DRUMMOND, D.D., 
Librarian, in the Chair. 
M. Donovan, Esq., continued the reading of his paper on 
the Nature of the Agency which produces the Effects called 
Galvanic, Electro-magnetic, Magneto-electric, and Thermo- 
- electric. 
The next subject to which Mr. Donovan called the atten- 
tion of the Academy was the instantaneous charge which a 
Leyden battery receives by a momentary contact with an ex- 
, tensive voltaic series. This has been always adduced as an 
i argument in support of the affirmed enormous quantity of 
. electricity which constitutes the voltaic current. Van Marum 
% charged a Leyden battery of twenty-five jars by a momentary 
connexion with a pile consisting of silver coins and zine discs, 
one inch and a half in diameter. The battery and pile were 
thus charged to the same intensity, so feebly, however, as to 
‘produce divergence in a gold leaf electrometer to the extent 
‘of five-eighths of an inch ; but the shock from the battery was 
only equivalent to half that of the pile. Facts and calcula- 
tions were adduced to show that the charge of electricity in 
this Leyden battery, when thus charged, could not have ex- 
ceeded the quantity of two or three one-inch sparks. Sir H, 
_ VOL, III. 2T 
