IMPROVE- MENTS IN GALVANOMETERS FOR RECEIVING SIGNALS THROUGH SUBMARINE AND OTHER ELECTRIC TELEGRAPH LINES, AND FOR TESTING THEM
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by David Tunks at theOffice of the
Commissioners of Patents, with his Petition, on the 29th May 1867.
I, DAVID TUNKS, of 36, Blackburn Road, Accrington, in the County of
Lancaster, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN GALVANOMETERS FOR RECEIVING SIGNALS THROUGH SUBMARINE AND OTHER
ELECTRIC TELEGRAPH LINES, AND FOR TESTING THEM," to be as follows:-
My improvements relate principally to those kind of instruments which are
employed to receive signals from the distant station of a submarine line.
The object of the Invention is to provide an instrument for use as a gal-
vanometer that is of extreme delicacy and not liable to be easily put out of
order.
An instrument which contains all the improvements that are comprised in
this Invention consists of an electro-dynamic coil in two halves, and having its
axis horizontal; each half is a complete coil, and the two halves are juxta-
posed laterally so as to act as one coil upon a horizontal magnetic needle
which is mounted upon a vertical axis that passes freely through the division
between the coils; the said vertical axis is mounted in jewel holes that are
suitably placed on cocks which rise from the same foundation plate that
carries the coil, the lower cock passing into the interior of the coil, and the
upper cock projecting over the top of the coil. A horizontal graduated dial
plate and a pointer of aluminium enable the motions of the needle from its
normal position (parallel to the wire coils) to be noted, or its deflections to be
observed. The electric current is conveyed to the coil by means of binding

page_text: screws connected with its terminals and placed upon the base plate or foun-
dation plate of the instrument.
A peculiarity of the Invention consists in the use of a pendulum or hair
spring in connection with the said vertical axis, and thereby accomplishing
two desirable objects, first, the neutralization of the gravity of the vertical
axis and its appendages; second, it affords the utmost facility to neutralize
the directive influence of the earth's magnetism upon the magnetic needle,
and thus enables it to move freely upon the slightest impulse. The hair
spring is the ordinary hair spring used in watches or timepieces, and in its
normal condition is a flat spiral. The internal termination of the spring is
attached to a collet on the vertical axis at a suitable distance from the upper
bearing; the other end is connected to the projecting arm of a "regulator"
that works concentrically with the axis and with the spring. The consequent
deflection of the spring from its flat condition tends to neutralize the weight
of the axis, and the position of the arm of the regulator in a horizontal plane
may be such as to render the needle independent of the earth's directive
magnetic influence. If desired, a small mirror may be mounted upon the
vertical axis so as to enable the deflections to be read off upon a screen by the
aid of a suitably placed light; but this application forms no part of the present
Invention. By the use of the jewel mounting of the vertical axis in con-
junction with the hair spring and regulator arm, and in connection or not
with the above described electro-dynamic coil, as above set forth, the axes
of relays and other similar telegraphic instruments may be rendered most
sensitive to the action of the electric currents employed. By adopting this
method of mounting a magnetic needle of sufficient length and weight can be
used to utilize the whole of the electric force available in the adjacent coil.
It is not perfectly essential to the action of the apparatus that the axis of the
magnetic needle should be vertical; indeed, if it is horizontal, the axis of the
coil being vertical the hair spring need not be drawn out of its flat spiral
form, but retained in the same. In the latter case the action of the spring to
counteract the gravity of the needle axis is not employed.