primary has four layers, 24 turns in each, this giving a total of 96
turns. When both the parts are connected in series, this gives a
ratio of conversion of about 1:2.7, and with the primaries in
multiple, 1:5.4; but in operating with very rapidly alternating
currents this ratio does not convey even an approximate idea of the
ratio of the E.M.Fs. in the primary and secondary circuits. The coil
is held in position in the oil on wooden supports, there being about 5
centimetres thickness of oil all round. Where the oil is not specially
needed, the space is filled with pieces of wood, and for this purpose
principally the wooden box B surrounding the whole is used.
The construction here shown is, of course, not the best on general
principles, but I believe it is a good and convenient one for the
production of effects in which an excessive potential and a very small
current are needed.
In connection with the coil I use either the ordinary form of
discharger or a modified form. In the former I have introduced two
changes which secure some advantages, and which are obvious. If they
are mentioned, it is only in the hope that some experimenter may find
them of use.
[Illustration: FIG. 4.--ARRANGEMENT OF IMPROVED DISCHARGER AND
MAGNET.]
One of the changes is that the adjustable knobs A and B (Fig. 4),
of the discharger are held in jaws of brass, JJ, by spring pressure,
this allowing of turning them successively into different positions,
and so doing away with the tedious process of frequent polishing up.
The other change consists in the employment of a strong electromagnet
NS, which is placed with its axis at right angles to the line joining
the knobs A and B, and produces a strong magnetic field between them.
The pole pieces of the magnet are movable and properly formed so as to
protrude between the brass knobs, in order to make the field as
intense as possible; but to prevent the discharge from jumping to the
magnet the pole pieces are protected by a layer of mica, MM, of
sufficient thickness. s_1 s_1 and s_2 s_2 are screws for fastening the
wires. On each side one of the screws is for large and the other for
small wires. LL are screws for fixing in position the rods RR, which
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