IMPROVEMENTS IN TESTING INSULATED CONDUCTORS
Year: 1860

page_text: LETTERS PATENT to Edward Orange Wildman Whitehouse, of Brighton,
in the County of Sussex, Electrician, for the Invention of "IMPROVEMENTS
IN TESTING INSULATED CONDUCTORS."
Sealed the 22nd February 1861, and dated the 23rd August 1860..
PROVISIONAL SPECIFICATION left by the said Edward Orange Wildman
Whitehouse at the Office of the Commissioners of Patents, with his
Petition, on the 23rd August 1860.
I, EDWARD ORANGE WILDMAN WHITEHOUSE, of Brighton, in the County of
Sussex, Electrician, .do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN TESTING INSULATED CONDUCTORS," to be as follows:-
This Invention relates to an improved system or mode of testing insulated
conductors or telegraph cables, and is specially applicable to the testing in
detail of minute portions of any length of such insulated conductor or cable;
the object of the Invention being to detect and render evident the most minute
loss or escape of the current at any particular spot, and to separate such loss
or escape from the aggregate loss upon the rest of the conductor or cable.
In carrying out this Invention, it is proposed on the escape or exit of [the
current through the insulating material of the conductor or cable at the spot to
be examined, to prevent it passing direct to earth, and to pass it to earth thro' a

page_text: sensitive galvanometer, by which the amount of such loss is measured, instead
of measuring the whole force of the entering current. This system or mode
of testing conductors or cables is particularly applicable to the careful exami-
nation and testing of the joints made at intervals during the construction of a
length of cable.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Edward Orange Wildman Whitehouse in the Great Seal
Patent Office on the 23rd February 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
ORANGE WILDMAN WHITEHOUSE, of Brighton, in the County of Sussex,
Electrician, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-third day of August,.in the year of our Lord
One thousand eight hundred and sixty, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Edward Orange Wildman Whitehouse, Her special license that I,
the said Edward Orange Wildman Whitehouse, my executors, administrators,
and assigns, or such others as I, the said Edward Orange Wildman White-
house, my executors, administrators, or assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN TESTING INSULATED
CONDUCTORS," upon the condition (amongst others) that I, the Edward Orange
Wildman Whitehouse, by an instrument in writing under. my hand and seal,
should particularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and: cause the same to be
filed in the Great Seal Patent Office within-six calendar months next.and im-
mediately after the date of the said Letters Patent..
NOW KNOW YE, that I; the said Edward-Orange-Wildman Whitehouse,
do hereby declare the nature of my said Invention, and in what, manner the
same is to be performed, to be particularly described and ascertained in
and by the following statement, reference being had to. the accompanying
Drawings and to the letters and figures marked thereon, that is to say :—1
'
In the testing of insulated conductors for submarine electric, telegraph cables,

page_text: the mode of procedure has hitherto been to place battery and galvanometer in
circuit between the earth and one end of the cable, the bulk of the cable being
immersed in a tank in contact with earth, while the other end is free and
insulated. The amount of current passing through the instrument has been
regarded as the measure of the "loss" by defective insulation. Or, the current
thus passing has been compared with that passing through a known and
measurable resistance by means of some rheostatic arrangement, and thus the
resistance of the cable, as it is termed, has been determined..
During the manufacture of submarine electric telegraph cables, as mile after
mile is added to the length previously made, great care has always been
required to make a sound "joint," as it is called, in the insulating covering at
the point of junction; and it, has been the invariable practice, 1 believe, after
such joint has been made and before it is allowed to be covered with the
outer iron wires of the cable to test it by immersion in a pail or trough of
water, in connexion with the earth, careful observation being made at the time
to detect if any increase become apparant in the current entering the cable.
So long as the entire length of cable under examination does not exceed a
few miles, the detection of a very slight degree of fault at a "joint" is quite
possible, and even comparatively easy; but on examining lengths of cable
approaching to or exceeding one hundred miles, where the minute increase of
loss due to the joint, is merged in the largeness of the total amount of leakage,
it becomes impossible with the utmost care and delicacy in this mode of testing,
to determine whether the joint in question (which may be eight or ten inches
in length) give fifty or one hundred times, or even one thousand times as much
loss as an equal length of perfect cable should do. A degree of imperfection
which must thus inevitably pass undetected may ultimately most seriously
endanger the safety of the whole cable. This is more particularly the case in
long cables, where at the same time the greatest amount of property is at
stake; for it is demonstrable that while on the one hand the longer the cable
the greater is the necessity for the highest attainable degree of insulation, on
the other, it is precisely under these conditions that it has been heretofore im
possible, by the accredited mode of testing, to detect degrees of imperfection at
the joint, which yet would sooner or later entail the certain destruction of the
cable.
..
. By the improvements now to be described, it becomes as easy to detect and
measure the slightest appreciable loss upon a joint made in. a cable one thousand
miles in length, as it would be if the joint in question were a short specimen
detached for the purpose of testing.

page_text: ..An examination of the simple plan of the circuits annexed, will show that the
principle of my Invention is; to separate the current lost at the joint from the
sum of that lost upon the rest of the cable, and to examine it by the use of a
separate instrument: This is most simply effected by insulating the trough or
reservoir into which the joint is plunged for testing and conveying the current
(so caught) through a very sensitive galvanometer to earth.
Figure 1 of the accompanying Sheet of Drawings represents a Diagram of the
circuits in the old mode of testing. B is the battery, one pole being connected
with the earth by the wire and earth plate E, the other pole being attached to
the galvanometer G, through which the current passes to the cable C, the
joint J of which to be tested is immersed in the reservoir R, which is connected
with earth by an earth plate and wire E'. c is the free insulated end of the
cable:
Figure 2 annexed, is a plan of the circuit for the simplest form of testing;
adopting this improved principle; B, the battery; C, the cable in contact with
earth; c, the free and insulated end of the cable; E, E', earth wires; R;
reservoir containing water, mercury; or other conducting fluid.; J, joint;
G, galvanometer..
Figure 3 is a plan of the circuits, inverting the direction of the .current,
which will now pass from the insulated reservoir to the cable through the joint,
and thence out by the conductor through a galvanometer to earth....
Figure 4 is a plan of the circuits in which the earth wires may be joined
across direct from the insulated reservoir through the galvanometer to the
battery, instead of being carried to earth plates, as usual. In all these the
principle is, that of testing the loss at the joint, or part examined; separately
from that existing on the rest of the cable.
If it be desired to test in other well known ways; as for example, by the
differential method, by resistance cables or rhæostats, by Wheatstone's bridge,
or by electric tension, or in any other method, the plan' of the circuit will, of
course, quoad hoc; be correspondingly altered in detail, as will be well under-
stood by electricians; but whatever be the mode adopted, the improvement in
which my Invention consists, and which is equally applicable to all, is essentially
the examination of the loss (or escape of electricity) at the suspected part as it
were separately from the rest of the cable by such arrangement of the circuit
and instruments as shall permit of such examination apart from the aggregate
of the loss existing upon the rest of the cable.
A less perfect mode of applying the same principle, but still. a manifest
improvement upon the present mode of testing joints, would be by the use of a

page_text: wetted cloth or damp sand, or some similar material with which to surround
the joint, this would be then laid upon an insulated slab instead of the trough,
the connexions and circuit remaining as before.
In witness whereof, I, the said Edward Orange Wildman Whitehouse,
have hereunto set my hand and seal, this Twenty-third day of February,
One thousand eight hundred and sixty-one.
WILDMAN WHITEHOUSE. (L.S.)