British Association for the Advancement of Science. 17 
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 princi- 
ple to produce 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 be- 
fore 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 refer- 
ence to the induction of the lateral action of dif- 
ferent discharges. on each other. When the long 
? 
lines, by bending the wire, “the outer side of each 
wire only becomes luminous; when formed into : ) 
three parallel lines by a Souble 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 alone exhibits the lateral 
discharge, but the light in this case is very brilliant ; the inner 
spirals appear to increase the effect by induction. 
Prof. Henry then 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 ex- 
periment described, a copper wire, $th 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 
- the globe before mentioned, a lateral spark could be drawn 
any part of the wire, and a pistol of Volta fired, even near 
ReS aes 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; corresponding lateral sparks could be 
drawn not only from the parts of the rod between the ground and 
the ball, but, from the part above, even to the top of the rod, 
Vor. XXXIV.—No. 1. 3 
