The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

238 INTERIOR OF THE ENGLISH TELEGRAPH STATIONS.
minal on the left-hand side, and passing in the direction of the
contiguous arrow-head, leaving it by the first or upper terminal
on the same side. In this drum, when thus arranged, there is
inlaid a slip of brass, of sufficient length to allow the springs
of both these terminals to press upon it. The current now goes
on to turn-plate c, which it enters by the first or upper terminal
on the left, and comes out by the second on the same side, the
connection being exactly similar to that last described. It now
pursues its course without interruption, to the telegraph instrument, which it enters on the left-hand side of the left-hand
coil: it circulates around the coil; and, on leaving it, circulates
round the coil of the electro-magnet belonging to the alarum.
Its course is then to the upper terminal on the right-hand side
of turn-plate b, coming out by the second terminal on the same
side, and so leaving the station to continue its course to Dover
by down wire No. 1, u.
" We will now trace the course of the same up-wire 1, when
the turn-plate c is so turned that London is put in communication with Maidstone. The current pursues the same
course as before, until it arrives at the turn-plate c: it now
enters it by the upper terminal on the left side, and passing
through the box and drum, leaves it by the upper terminal on
the right side; it then descends to the left-hand side of the lefthand coil of the Mlaidstone instrument, No. 4; passes round the
coil, and continues its course to Maidstone by wire 3 down,
which becomes the No. 1 of the Mlaidstone branch at Paddock
Wood, as shown in the previous plan. But the turn-plates are
so constructed, that while they make a particular connection
for one part of the line, they provide perfectly for the part not
so immediately concerned, by putting the wires that lead to
that part in connection with the earth, and so the circuit is
complete, as far as it goes. In the present instance, the same
operation that turns 1 and 2 up-wires to Maidstone, connects
the earth with the up side of the through instrument, and the
communication is thus kept perfect between Dover and Tunbridge on the through instrument. By following with the eye,
and in the reverse direction to the arrows, the wire that comes
from the left coil of the through instrument, it is traced to the
second terminal of the turn-plate c; the connection there is
such, that the circuit is continued through the box and cylinder
to the second terminal on the opposite side: this is in connection with the lower terminal on the same side, whence a wire
descends to the comlmon earth-wire. What has here been said
of wire 1, equally holds good in respect to wire 2.
" T'urn-plate a has allowed the circuit of wire 1 up to enter