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Prof. J. Henry’s Contributions 
course of science. I will mention one which is somewhat 
connected with the experiments to be described in the next 
section, and which exhibits the action in a striking manner. 
This consists in causing the induction to take place through 
the partition wall of two rooms. For this purpose coil No. 1 
is suspended against the wall in one room, while a person in 
the adjoining one receives the shock, by grasping the handles 
of the helix, and approaching it to the spot opposite to which 
the coil is suspended. The effect is as if by magic, without 
a visible cause. It is best produced through a door, or thin 
wooden partition. 
52. The action at a distance affords a simple method of 
graduating the intensity of the shock in the case of its appli- 
cation to medical purposes. The helix may be suspended by 
a string passing over a pulley, and then gradually lowered 
down towards the plane of the coil, until the shocks are of 
the required intensity. At the request of a medical friend, I 
have lately administered the induced current precisely in this 
way, in a case of paralysis of a part of the nerves of the face. 
53. I may also mention that the energetic action of the 
spiral conductors enables us to imitate, in a very striking 
manner, the inductive operation of the magneto-electrical 
machine, by means of an uninterrupted galvanic current. 
For this purpose it is only necessary to arrange two coils to 
represent the two poles of a horseshoe magnet, and to cause 
two helices to revolve past them in a parallel plane. While* 
a constant current is passing through each coil, in opposite 
directions, the effect of the rotation of the helices is precisely 
the same as that of the revolving armature in the machine. 
54. - A remarkable fact should here be noted in reference to 
helix No. 4, which is connected with a subsequent part of the 
investigation. This helix is formed of copper wire, the spires 
of which are insulated by a coating of cement instead of 
thread, as in the case of the others. After being used in 
the above experiments, a small discharge from a Leyden jar 
was passed through it, and on applying it again to the coil, 
I was much surprised to find that scarcely any signs of a 
secondary current could be obtained. 
55. The discharge had destroyed the insulation in some 
part, but this was not sufficient to prevent the magnetizing of 
a bar of iron introduced into the opening at the centre. The 
effect appeared to be confined to the inductive action. The 
same accident had before happened to another coil of nearly 
the same kind. It was therrfore noted as one of some im- 
portance, An explanation was afterwards found in a peculiar 
action of the secondary current. 
