IMPROVEMENTS IN APPARATUS CONNECTED WITH SUBMARINE TELEGRAPHY
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Henry Gardner at the Office of the
Commissioners of Patents on the 21st October 1876. A communication from
abroad by Le Comte Emilio de Siccardi, of Turin, in the Kingdom of Italy,
HENRY GARDNER, of the Firm of Robertson, Brooman, and Company, of 166,
Fleet Street, in the City of London, Patent Agents. "IMPROVEMENTS IN APPARATUS
CONNECTED WITH SUBMARINE TELEGRAPHY." A cominunication from abroad by
Le Comte Emilio de Siccardi, of Turin, in the Kingdom of Italy.
"
"
The object of this Invention is, firstly, to obtain by the mere influence of the
very feeble currents provided by submarine cables contacts ensuring the closing of
the circuit of a local pile; secondly, to apply the Morse system to submarine
telegraphy in order to obtain printed Morse signals instead of signals thrown by the
mirror of "Thomson's" galvanometer. For this purpose the ordinary mirror gal-
vanometer is transformed into a relay (relai) galvanometer, the distinctive feature
in which consists in the employment of mercury to establish the contact intended
to close the circuit of the local pile.
The following description will enable the apparatus employed to be under-
stood:-At the centre of a circular plate of wood is mounted upon a copper foot
a galvanometer bobbin. The wire in the bobbin is of a very small diameter, and is
twisted a sufficient number of turns upon the bobbin to obtain a resistance of from
3,500 to 4,000 ohms. The current from the line passes through the spirals of the
galvanometer, and then goes to earth. In the line of the axis of the bobbin, and
at their ends, are placed two bronze supports, the bases of which are adjusted in a
groove of a cross piece, also of bronze. The supports slide with gentle friction in
their grooves, so that their position may be regulated as desired. Each support
carries an arm, in the opening of which is placed the movable system of the
apparatus. This system is composed essentially of a little axis of aluminum with
points of steel pivotting between the platinum points of two screws. Upon this
axis is fixed a very light magnetized needle, provided upon one of its ends with
two sharpened platinum points. These points are situated opposite to the extremity
of a tube, also of platinum, electrically isolated from the metallic mass of the
apparatus and filled with mercury. It is between these points of platinum and the
little drop of mercury that the projection of the orifice of the tube occurs, which
established the contact intended to close the circuit of the local pile. The tube is
screwed into a support, which enables it to be easily brought into a convenient position.

page_text: The amplitude of the oscillations of the needle is limited by two screws with
ivory points. The axis of each magnetized needle is crossed by a little rod of
aluminum bent into a right angle at its middle, and dipping by the flattened
extremity of its vertical part into a silver cup filled with water. This arrange-
ment is for the purpose of preventing any oscillation of the magnetized needle other
than that provoked by the emission of a line current. Two permanent magnets
mounted upon heavy bronze feet are placed on each side of the galvanometer. They
are approached or separated at will. Each of them serves, firstly, to call back the
neighbouring needle to its original position after each deviation; secondly, to regulate
the influence of the line current upon that needle; thirdly, to neutralize the influence
of the terrestrial poles which do not fail to act upon the inagnetized needles of the
apparatus.
The action of the apparatus is as follows
-When it is desired to use the
apparatus the supports are moved one towards the other, so as to introduce the two
systems pivotting from 15 to 20 millemetres in the interior of the bobbin. The
latter must be sufficiently long that the needles thus approached towards one
another may not be reciprocally influenced. The exterior magnets are suitably
placed so that their antagonistic force upon the magnetized needles may be in
relation to the force of the line current. A pole of the local pile is then united with
two isolated tubes, and the second pole with the metallic mass of the apparatus,
and consequently with the two magnetized needles. These needles are placed so
that their poles of contrary denominations are opposite to one another, so that under
the influence of any line current they always deviate in opposite directions. It
will now be understood that by the emission of a current in one direction one
needle arrives into contact with the mercury, so as to close the local current,
becoming a printing receiver, the other needle remaining in repose; by the emission
in the contrary direction the needle which has just made contact remains in repose,
and the second needle closes in its turn the local circuit.
Originally the local pile was arranged with two different circuits, each comprising
a tube and an armature of a printing receiver; the two armatures acted inde-
pendently and inscribed one of the points to the right and the other to the left of the
same band of paper according to the direction of the line current, printed despatches
were thus printed in the same manner as they are read on the graduated scale of
"Thomson's galvanometer," but this system presents several difficulties in its
application.
"
It is well known that when several currents are sent successively through a
submarine cable in the same direction, as must be done for certain letters, these
currents gradually diminish in strength. It is known also that the "Varley
condensator preserves during these emissions, and up to the passage of an in-
verse current, a charge which prevents the mirror of the Thomson galvanometer
from returning to zero. In the present apparatus these defects would be very
injurious, 1stly, because the successive currents in the same direction would become
too feeble to produce the deviations of the needles; or 2ndly, because under the
permanent charge of the line resulting from their emission there would be pro-
duced an adherence of the needle to the mercury probably too strong to be overcome
by the exterior magnets. To avoid these difficulties use is made of a manipulator
sending the currents alternately in opposite directions, and which always closes the
same local circuit. This manipulator has the general form of a "Morse"
key but
differs from it by the following addition:-The touch or cross piece is provided
with a catch acting upon a ratchet, upon the axis of which is placed an inverter.
The latter is composed of three little copper wheels of the same diameter; the
middle wheel communicates with the earth by a friction spring, and the lateral
wheels with the metallic mass of the manipulator by two other ffriction springs.
These wheels have an equal number of teeth at their circumference, the breadth of
which is only one quarter of a step or turn (pas). The teeth of the middle wheel
have intervals separating the teeth of the lateral wheels. Two springs communi-
cating each with a pole of the pile of the line rub at the circumference of the three

page_text: wheels. When the touch of the manipulator is lowered the inverter makes a half
turn and the friction springs put the one, a pole of the pile (zine for example) in
communication with the middle wheel, that is to say, with the earth, the other,
the second pole of the pile, in communication with a lateral wheel, that is to say,
with the metallic mass of the manipulator, and consequently with the line.
When
the touch is lowered again these effects are reversed. The currents of a same pile
can then be sent on the line by reversing them continually, which avoids all
remanent charges.
It will be now understood that it will be no longer possible to print despatches
so that they can be read in the same manner as those obtained upon the graduated
scale of Thomson. It is also necessary to observe that upon submarine lines one
absolutely cannot, as one can in aerial lines, obtain currents of a duration variable
at will suitable for the impression of points or strokes as in a "Morse" receiver. It
is for this reason that it becomes indispensible with the present instrument to make
a little change in the Morse alphabet.
The points of the alphabet are always represented by points spaced a certain
amount (. ..), and the strokes by two points a little less separated (.. ....).
The slight inconveniences which may result from this new manipulation differing
so little from that used up to the present time will be largely compensated for by
the advantages possessed henceforth of producing in submarine cables all the effects
possible with a contact closing a local circuit. One could for example obtain trans
lation, and perhaps even make use of the "Hughes" apparatus.