TRANSACTIONS OF THE SECTIONS. 23 
beautifully 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 considered nearly all as free electricity ; and as the insulated wire 
contains its natural quantity, the whole spark is thrown off in the form 
_ of a lateral discharge. But to explain these phenomena more fully, 
_ Professor Henry remarked, that it appeared necessary to add an 
- additional postulate to our theory of the principle of electricity,— 
- namely, a kind of momentum, or inertia, without weight ; by this he 
- would only be understood to express the classification or generaliza- 
tion of a number of facts, which would otherwise be insulated. ‘To 
illustrate this, he stated that the same quantity of electricity could be 
made to remain on the wire if gradually communicated ; but when 
thrown on in the form of a spark, it is dissipated as before described. 
_ Other facts of the same kind were mentioned ; and, also, that we could 
_ take advantage of the principle to procure a greater effect in the 
decomposition of water by ordinary electricity. The fact of a wire 
becoming luminous by a spark was noticed by the celebrated Van 
Marum more than fifty years ago ; but he ascribed it to the immense 
_ power of the great Haarlem machine. The effect, however, can be 
- produced, as before described, by a cylinder of Nairn’s construction, 
of seven inches in diameter, a globe of a foot in diameter being placed 
in connexion with the prime conductor to increase its capacity. 
Some experiments were next described, in reference to the induction 
of the lateral action of different discharges on each 
other. When the long wire is arranged in two parallel, 
but continuous lines, by bending the wire, the outer side 
of each wire only becomes luminous ; when formed into 
three parallel lines by a double bend, the middle portion 
of the wire does not become luminous, the outer sides 
only of the outer lines of wire exhibit the rays, When 
" the wire is formed into a flat spiral, the outer spiral 
e alone exhibits the lateral discharge, but the light in this 
Bat case is very brilliant; the inner spirals appear to in- 
_ erease the effect by induction. 
_ Professor Henry stated, that a metallic conductor, intimately 
- connected with the earth at one end, does not silently conduct the 
_ electricity thrown in sparks on the other end. In one experiment 
_ described, a copper-wire, one-eighth of an inch in diameter, was 
_ plunged at its lower end into the water of a deep well, so as to form 
as perfect a connexion with the earth as possible ; a small ball being 
attached to the upper end, and sparks passed on to this from the 
_ globe before mentioned, a lateral spark could be drawn from any part 
of the wire, and a pistol of Volta fired, even near the surface of the 
water. This effect was rendered still more striking, by attaching a 
ball to the middle of the perpendicular part of a lightning rod, put up 
according to the directions given by Gay-Lussac; when sparks of 
_ about an inch and a half in length were thrown on the ball, corre- 
_ sponding lateral sparks could be drawn not only from the parts of the 
