AN IMPROVED MODE OF MAIN- TAINING THR INSULATION OF INDERAROUND TELEⱭRADUIN Winng ” TAINING THE INSULATION OF INDERGROUND TELEGRAPHIC WIRng
Year: 1873

page_text: LETTERS PATENT to Matthew Gray, of Blackheath, in the County of
Kent, Engineer, for the Invention of "AN IMPROVED MODE OF MAIN-
TAINING THR INSULATION OF INDERAROUND TELEⱭRADUIN Winng ”
TAINING THE INSULATION OF INDERGROUND TELEGRAPHIC WIRng"
PROVISIONAL SPECIFICATION left by the said Matthew Gray at the
Office of the Commissioners of Patents, with his Petition, on the
26th November 1873.
I, MATTHEW GRAY, of Blackheath, in the County of Kent, Engineer,
do hereby declare the nature of the said Invention for "AN IMPROVED
MODE OF MAINTAINING THE INSULATION OF UNDERGround TelegraphIC WIRES,”
to be as follows
The object of this Invention is to maintain the insulation of wires
covered with gutta percha or equivalent insulating materials and used
as underground telegraphic wires.
It has been found that gutta percha on becoming dry has a tendency
to shrink and deteriorate, and thereby to jeopardise the insulation of the

page_text: wires it is intended to protect. In the presence however of water the
quality of the gutta percha appears to be maintained. This I have
proved by lengthened experiments, and the maintenance of insulation
in deep-sea cables also points to the fact of the preservative character of
water.
To maintain the insulating property of the gutta percha or equivalent
covering of land wires I propose to enclose such wires in cast iron or
other pipes (which may be divided longitudinally or not), and to connect
these pipes together by flanged or other water-tight joints.
At given distances apart in the length of pipes chambers may be 1
provided (fitted with doors for entering the same) to receive the ends of
lengths of covered wires and afford facilities for joining up and testing
the same.
The line of pipes I propose to supply with water, the level of which
will be maintained above the coated wires, and for this purpose the pipes
may be connected with the street main or with elevated cisterns or their
equivalent.
To facilitate the repairing of the wires provision will be made for
running off the water from the pipes, and it will be convenient to close
the pipes at intervals, leaving only sufficient opening in the dividing
walls for the wires to pass through. This will admit of the water being
run off from any one section of the pipes when the repair of the wires
contained in that section is needed.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Matthew Gray in the Great Seal Patent
Office on the 26th May 1874.
:
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MATTHEW
GRAY, of Blackheath, in the County of Kent, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-sixth day of November, in the
year of our Lord One thousand eight hundred and seventy-three, in
the thirty-seventh year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said Matthew Gray, Her

page_text: i
At given distances apart in the length of pipes testing boxes or
chambers may be provided (fitted with doors or covers for entering the
same) to receive the ends of the lengths of covered wires and afford
facilities for leading them out to the receiving and transmitting instru-
ments for joining them up and for testing their insulation.
The line of pipes may be supplied with water (the level of which will
be maintained above the coated wires) from the street main, or from
elevated cisterns or their equivalent.
In the accompanying Drawing Fig. 1 is a longitudinal section of a
portion of a length of water-tight pipe for containing a series of insu-
Jated wires, and shewing also an interposed box or chamber for receiving
the ends of the wires intended to be joined up or to be led up to the
transmitting instruments. Fig. 2 is a plan view of Fig. 1, the cover of
the chamber being removed to shew the interior thereof.
i In these Figures A, A, are socketted pipes of cast iron fitted one into the
other, and secured by cement or otherwise. The form and proportions
of these pipes will depend upon the number of insulated wires they are
intended to receive and on the manner it may be thought best to dispose
the wires. In the Drawing they are shewn as provided to receive
twenty-one wires laid side by side, and they are made water tight so
that they may retain the water with which they are charged through
tubes a.
:
At suitable distances apart in the line of telegraphic communication
water-tight chambers are interposed between coupled lengths of pipes.
These chambers, which may be of any approved construction, are shewn
in the Drawing as composed of two flanged castings, B, B', which are
secured together by bolts and nuts, a diaphragm of elastic india-rubber C
being interposed between the flanges for the purpose to be presently
éxplained. D is a cover for closing the upper part of the chamber.
The lower division of the chamber is cast with sockets E, E¹, at its
opposite ends to receive the ends of the adjacent pipes A, A, which are
secured thereon.
The socket E is fitted with a diaphragm of elastic india-rubber F,
which diaphragm is pierced with a row of holes of such number and
diameter as will allow of the insulated wires G being threaded through
them without permitting the escape of water past the diaphragm. The
lengths of insulated wires G enter the lower division of the chamber B

page_text: at its opposite ends, and they are led up through holes made in the
diaphragm C into the upper part B¹ of the chamber, where they are
coupled up in any approved manner. At every receiving or transmitting
station there will be one of these chambers and wires will be led out
therefrom to the telegraphic instruments.
To allow for this the chamber is fitted with stuffing boxes H, through
which the wires may be led without permitting of the escape of water
from the chamber.
The object of the elastic diaphragm C is to prevent the escape of
water in quantity from the insulating box or chamber when the cover D
is removed for the purpose of inspecting and testing the wires, and
diaphragms F are interposed at convenient distances in the line of pipes
to divide the same up into sections so far as regards their capacity for
retaining water.
To facilitate the repairing of the wires taps I are fitted in the bottom
of the testing boxes or chambers, through which the water may be run
off from any section of the pipes as desired.
Having now set forth the nature of my Invention of "An Improved
Mode of Maintaining the Insulation of Underground Telegraphic
Wires," and explained the manner of carrying the same into effect, I
wish it to be understood that under the above in part recited Letters
Patent I claim enclosing telegraphic wires covered with insulating
material in pipes or channels containing water, in the manner and
for the purpose above described.
In witness whereof, I, the said Matthew Gray, have hereunto
set my hand and seal, the Twenty-third day of May, in the
year of our Lord One thousand eight hundred and seventy-
four.