360 NOTICES OF THE MEETINGS [Feb. 3, 
get the discharge by carrying or convection, and by disruption, as 
in the spark. 
In the year 1852, Mr. Grove communicated at an Evening 
Meeting of the Members of the Royal Institution, his researches on 
the disruptive discharge, shewing by the oxidation and reduction of 
the terminal surfaces, a state of chemical polarity in the gaseous 
intervening medium, antecedent to the discharge, the discharge 
consisting of a subversion of this polarity attended with intense 
local heat, and a transmission of minute particles of the terminals 
between which it took place.* 
In what may be termed Pneumatic Electricity, or the electrical 
effects produced on and by gases, there seems some reason to believe 
that the molecules conduct, or in other words that at indefinitely 
minute spaces, electricity can pass without the phenomena of dis- 
ruptive discharge: for instance in the gas battery, either the mole- 
cules must conduct, or the gases must by contact with the platinum 
be brought into a liquid state. 
The effects of rarefaction on gases (as by the air-pump) tends to 
render the disruptive discharge more facile, and to enable electricity 
of the same degree of intensity to pass across much larger spaces 
than it would when transmitted across gases in a dense state. 
The next enquiry is whether the effect of rarefaction by heat is 
the same as that by mechanical attenuation; and heated gas was 
shewn by Mr. Grove to facilitate the disruptive discharge of elec- 
tricity : so strikingly was this evidenced with flame, that when the 
flame of a spirit lamp was held near the terminal point of the coil 
apparatus of Ruhmkorff, (the coatings of a Leyden phial being con- 
nected with the secondary coil, and the terminals being separated to 
a distance far beyond that at which the spark would pass in cold 
air), the spark darted to and along the margin of the flame, and 
could be curved or twisted about in any direction, at the will of the 
experimenter, giving a striking illustration of the crooked form of 
lightning, and of the probable reason why it does not pass in straight 
lines, the temperature of the air being different at different points of 
its passage, and much of this variation of temperature being in all 
probability occasioned by the mechanical effect on the air of the 
discharge itself. 
No amount of rarefaction has hitherto shewn any thing like 
conduction in gases at ordinary temperatures; but on the other hand 
flame does give distinct evidence of conduction without disruptive 
discharge, and an experiment was made demonstrating this. 
Is this effect of flame due simply to its consisting of highly heated 
gas? or is it due to the chemical action taking place throughout the 
whole structure of the flame? 
When closely approximated metals are brought to the point of 
visible ignition, signs, but very feeble signs of transmission of elec- 
tricity take place. M. E. Becquerel has recently published some 
* Phil. Trans. 1852, p. 87. 
