IMPROVEMENTS IN ELECTRICAL CONDUCTORS FOR TELEGRAPHIC COMMUNICATION
Year: 1854

page_text: PROVISIONAL SPECIFICATION left by William Thomson, William John
Macquorn Rankine, and John Thomson at the Office of the Commis-
sioners of Patents, with their Petition, on the 4th December 1854.
We, WILLIAM THOMSON, Professor of Natural Philosophy in the University
and College of Glasgow, WILLIAM JOHN MACQUORN RANKINE, of Fifty-nine,
Saint Vincent Street, Glasgow, Civil Engineer, and JOHN THOMSON, of Fifty-
nine, Saint Vincent Street, Glasgow, Civil Engineer, do hereby declare the
nature of our said Invention for "IMPROVEMENTS IN ELECTRICAL CONDUCTORS FOR
TELEGRAPHIC COMMUNICATION" to be as follows:-
According to the usual construction of electrical conductors for telegraphic
communication which are intended to be laid under ground or under water,
one conducting wire of copper (or other metal possessing a good conducting
power for electricity) is provided for the transmission of each independent
electric current. Each such conducting wire is insulated by being coated
with gutta percha in the following manner :-Gutta percha, being purified and
maintained in a soft state in the usual manner, is contained in a strong metal
box or receiver, provided with a piston; each wire to be coated passes into such
box through a hole just large enough to let the wire pass easily, and issues
from the box through the centre of a hole of the diameter of the gutta percha
coating; the soft gutta percha being compressed by the piston, issues from
tlic second hole in the form of a cylindrical cord, containing and carrying

page_text: along with it the conducting wire, which thus issues from the box coated with
gutta percha. By treating the cylindrical cord thus formed in the same
manner in which the original wire was treated, it may, if required, be pro-
vided with a second coating of gutta percha external to the first. Conducting
wires thus prepared are employed either singly or twisted into compound
cords, one coated conducting wire for each independent current, and are
protected in various ways; the way best suited for submarine purposes being
to surround them first with a covering of hemp, and, secondly, with a casing
of spirally-wound strong iron wires, so as to form an iron wire cable, containing
in its interior the coated conducting wire or wires. Such is the ordinary
construction of electrical conductors for telegraphic communication which are
laid under ground or under water, which construction is extensively known
and practised.
When a conducting wire of a given sectional area, coated and laid as above
stated, is employed to produce signals at a given distance, the time required
for the production of each signal includes the time lost in producing a statical
electric charge of a certain intensity at the outer and inner surfaces of the
coating, whereby the conducting wire is insulated; for until such statical
electric charge is produced, the electric current in the wire cannot produce
its full, effect in acting on the apparatus whereby signals are made. The time
lost from this cause is the greater, the smaller the wire and the thinner its
insulating coating; and the less, the larger the wire and the thicker it's insu
lating coating. Such loss-of-time-also increases -very-rapidly-with-increased
length of the conducting wire, and for lines of telegraphic communication
extending to very long distances may be so great as seriously to impair the
efficiency of the telegraph unless counteracted: Now, one of the means of
counteracting the effect of great length of conductor in causing such loss
of time is to increase greatly the sectional area of the conducting wire; but
by such increase of sectional area the stiffness of the conducting wire would be
increased at the same time, so as to increase the risk of its being damaged.or
broken by being bent, wound, coiled, or twisted. By employing; however, a
strand, cord, or rope, consisting of several smaller wires in contact with each
other, and with or without hempen or other cores, a sectional area equal sto
that of a larger wire may be obtained, combined with sufficient Hexibility to
prevent danger of breaking, or damage of the conducting wires by their being
bent, wound, coiled, or twisted; and even supposing a partial breakage to
occur, such a strand, cord, or rope also affords security against the evil effects of
such breakage; for so long as the whole of the wires of which it is composed are
not broken across at one spot, the communication will continue to be efficient.

page_text: The nature of our Invention consists in providing for each independent
electric current in electrical conductors for telegraphic communication a strand,
cord, or rope, consisting of several conducting wires in contact with each
other, with or without hempen or other-cores, instead of a single.conducting
wire for each independent electric current, as formerly practised; such strands,
cords, or ropes being coated with gutta percha or other insulating material,
and protected either singly or in compound cords by iron cables or otherwise,
in a manner similar to that now known and practised with respect to single
conducting wires for each independent current; and the object of this Inven-
tion is to obtain increased sectional area of conducting wires and increased
security against interruption of the communication, combined with increased
flexibility, or any one or more of these advantages separately or combined.