84. Prof. J. D. Forbes on the Repulsion of 
of the horseshoe were adjusted by moving it on the pasteboard 
shelf until simultaneous contact of the two limbs with the fixed 
Wires was obtained on moving the graduated head of the torsion 
wire A from right to left. The completion of the current was 
effected without much difficulty by gently pressing the rough 
extremities of the wires into contact by the help of the torsion 
head. 
I found it convenient to increase the tension of the current 
by introducing into the cireuit an ordinary electrodynamic coil 
of stout wire, with or without a core of iron wires. 
So far from finding anything like repulsion of the moveable 
horseshoe on the continuation of the circuit, I soon observed 
that attraction took place, resisting the force of twist of the 
platinum wire exerted through a considerable are, when it tended 
to produce separation. This attraction continued to subsist even 
after the current was withdrawn. 
With a horseshoe composed of two straight limbs, a and 4, of 
bismuth, the connexion c being of copper, a still more decided 
attraction was the result; and it continued to subsist after with- 
drawing the current of electricity, even if only one of the poles 
touched the horseshoe. 
When the terminals P, M were somewhat flatly rounded (as 
in fig. 6a), and the extremities of the horseshoe also carefully 
rounded and polished, I was unable to obtain electrical contact 
by the pressure due to mere torsion. ‘The current did not pass 
until the extremities were touched with nitrate of mercury and 
wiped dry, when it passed readily ; and a marked adhesion took 
place while the current lasted, and for some time after it stopped. 
While the electricity passed, a fizzing noise was audible from the 
extremities of the wires. This might possibly be due to an in- 
sensible vibration. It thus appears that the irregularitics of 
surface of the wires at the points of contact im the first form of 
the experiment was favourable to the electrical propagaticn, as 
it is in the case of ordinary frictional electricity. 
A current from a very powerful Ritchie’s mduction coil, ex- 
cited by four pairs of Grove’s, was next passed through the ap- 
paratus last described. Distinct adhesion took place of the ends 
in contact, opposing a force amounting to 90° or more of tor- 
sion. It continued while the current passed, and for some time 
after. By and by they separated through the effect of torsion. 
This experiment was very instructive. If it commenced when 
the terminations were a little apart, the high-tension electricity 
passed readily in the form of sparks from P and N to the horse- 
shoe—the horseshoe steadily approaching—the sparks getting 
shorter and finally vanishing at both contacts, the attraction 
continuing and facilitating electrical contact. Apparently the 
