16 ~—sC British Association for the Advancement of Science. 
into it, by the force of the blows, like so many wedges, thereby 
weakening the strength of the iron. 
Electricity.—Prof. Henry then made a communication respect- 
ing the Lateral Discharge in common Electricity. 
The primary object of these investigations was to detect, if 
possible, an inductive action in common electricity, analogous to 
that discovered in a current of galvanism. For this purpose an 
analysis was instituted, of the phenomena known in ordinary 
electricity by the name of the lateral discharge. Prof. Henry 
“was induced to commence with this from some remarks by Dr. 
Roget on the subject. The method of studying the lateral spark 
consisted in catching it on the knob of a small Leyden phial, and 
presenting this to an electrometer. The result of the analyses 
‘Was in accordance with an opinion of Biot, that the lateral dis- 
charge is due only to the escape of the small quantity of redun- 
dant electricity which always exists on one or the other side ofa 
jar, and not to the whole discharge. ‘The Professor then stated — 
several consequences which would flow from this; namely, that — 
we could increase or diminish the lateral action, by the several 
means which would affect the quantity of redundant, or as it 
may be called, free electricity, such as an increase of the thick- — 
ness of the glass, or by substituting for the small knob of the jar _ 
a large ball. But the arrangement which produces the greatest 
effect, is that of a long fine copper wire insulated, parallel to the — 
horizon, and terminated at each end by a small ball. When — 
sparks are thrown on this from a globe of about a foot in diame- 
ter, the wire, at each discharge, becomes beautifwly luminous 
from one end to the other, even if it be a hundred feet long ; rays 
are given off on all sides perpendicular to the axis of the wire. — , 
In this arrangement the electricity of the globe may be consid- 
ered nearly all as free electricity ; and as the insulated wire com> ’ 
tains its natural quantity, the whole spark is thrown off in the 
form of a lateral discharge. But to explain this phenomenon 
more fully, Prof. Henry remarked, that it appeared necessary t0 
add an additional postulate to our theory of the principle of ele¢- 
tricity,—namely, a kind of momentum, or inertia, without weight} _ 
by this he would only be understood to express the classification — 
_,or generalization of a number of facts, which would otherwise — 
be insulated. — To illustrate this, he stated that the same quantity 
of e city could be made to remain on the wire if gradually 
Ee 
Bs 
