122 NOTICES OF THE MEETINGS [Feb. 13, 
To make evident to the audience the relation of the electrical dis- 
charge to combustion and the fact that the terminals were themselves 
affected, the Voltaic arc was taken, first between silver and then 
between iron terminals; in ‘the first case a brilliant green coloured 
flame was produced, and in the second a reddish scintillation or spur 
fire effect, just as in the ordinary combustion of the metals. 
So with the discharge of Franklinic Electricity between the same 
two metals, a strip of silvered leather gave the bright green discharge, 
while a chain of iron gave the spur fire effect. 
The known transport of particles of the terminals from one pole to 
the other,— the different effects of different intervening media on 
induction as shewn in Faraday’s experiments,— the polar tension of 
such media, &c. were instances of the train of molecular changes 
consequent upon electrical action. 
Hitherto the polarity of the gaseous medium existing between the 
metallic or conducting terminals of the electrical circuit was only 
known as a physical polarity and not shewn to have an analogous 
chemical character with that existing in electrolytes anterior to elec- 
trolysis ; but Mr. Grove stated that in a recent communication to 
the Royal Society he had shewn that mixtures of gases having oppo- 
site electrical or chemical relations, such as oxygen and hydrogen, or 
compound gases such as carbonic oxide, were electro-chemically 
polarized or had their electro-negative and electro-positive elements 
thrown in opposite directions: thus if a silvered plate be made 
positive in such gases it is oxidized, if negative the dark spot of 
oxide is reduced ; and an experiment was shewn in which such a plate 
was thus oxidized and the spot reduced in gaseous media. 
Here, as in the other experiments, was an effect on the terminals 
and an effect of polarization of the intermedium. In the experi- 
ments hitherto shewn, solid terminals were used ; it became important 
to examine what would be the effect of liquid terminals, for instance 
water; the spark or disruptive discharge of Franklinic Electricity 
was readily obtained from its surface, but hitherto no voltaic 
battery had been found to shew a discharge at any sensible distance 
from the surface of water. 
Mr. Gassiot had procured to be constructed 500 cells of the 
nitric acid battery, the combination discovered in 1839 by Mr. 
Grove and first shewn at this Institution in the year 1840. The 
cells of this battery were all well insulated by glass stems, and as 
regards intensity of action it was probably far the most powerful 
ever seen. Mr. Gassiot had kindly lent this apparatus for the 
illustration of this evening’s discourse, and by its aid Mr. Grove 
was able to shew an experiment which he had first made when 
experimenting with Mr. Gassiot some time ago, and which produced 
the effect he had long sought for, viz. a quantitative or voltaic dis- 
charge at a sensible distance from the surface of water. The 
experiment was made as follows:—a platinum plate forming the 
anode of the battery was immersed in a capsule of distilled water, 
the temperature of which was raised. A cathode or negative 
terminal of platinum wire was now made to touch for a moment 
