IMPROVEMENTS IN PROVING ELECTRIC CONDUCTORS, & IN THE APPARATUS CONNECTED THERE WITH." PROAL SP
Year: 1859

page_text: LETTERS PATENT to Cromwell Fleetwood Varley, of No. 4, Fortess
Terrace, Kentish Town, & Cornelius John Varley, of No. 7, York
Place, Kentish Town, St. Pancras, Middlesex, for the Invention of
"IMPROVEMENTS IN PROVING ELECTRIC CONDUCTORS, & IN THE APPARATUS
CONNECTED THERE WITH."
PROVISIONAL SPECIFICATION left by the said Cromwell Fleetwood Var-
ley and Cornelius John Varley at the Office of the Commissioners of
Patents, with their Petition, on the 23rd June 1859.
We CROMWELL FLEETWOOD VARLEY of No. 4 Fortess Terrace Kentish
Town & CORNELIUS JOHN VARLEY No. 7 York Place Kentish Town
St. Pancras Middlesex do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN PROVING ELECTRIC CONDUCTORS & IN THE APPARATUS
CONNECTED THEREWITH" to be as follows
The chief object of our Invention is to find out the locality of defects in the
insulation of a conductor or imperfect continuity of the latter without remo-
ving the covering or the insulator; or cutting the conductor for testing. We
generally first ascertain approximately the locality of the fault by the following
new method For example suppose the defective conductor to be a cable in
the maker's stores & under water we pass the current from a voltaic battery
through the two wires of a differential galvanometer in opposite directions one
pole of the battery being connected with the earth or water & the two ends
of the wires from the differential galvanometer connected with the two ends
17861-1.

page_text: of the conductor whose insulation is defective the current from the battery
divides & goes round the galvanometer in opposite directions & entering
both ends of the cable escapes at the defect in the insulator if this defect is
equidistant from the two ends the resistance will be equal the currents round
the galvanometer will be equal & the needle will stand at zero If the
fault be not in the middle the resistance will be unequal, the shorter route will
allow the passage of more electricity than the other & the needle will be
deflected we now introduce a rheostat into the shorter circuit & introduce
so much resistance as shall make the two portions equal in resistance having
noted this & the resistance of the whole conductor, the following formula will
show very nearly the exact locality of the defect

page_text: nating currents are applied to one end only of the cable the other end of the
cable is insulated, the currents then run along the conductor to the fault &
there escape our probes then show by the existence or non-existence of cur-
rents in their coils on which side of the fault they are. Having traced out
the locality of the fault a Spanish windlass is made or the cable is cut at the
spot, repair'd, & spliced as usual. Thus by a single cut or splice the fault
is removed. Hitherto to find such a fault it has been necessary to cut &
splice the cable in many places before the locality of the fault was traced out.
A splice takes from two to ten hours to make & frequently wastes from
twenty to thirty feet or more of cable; besides causing great delay & expense,
& injury to the cable. When the defect is a break in the conductor we first
pass powerful currents from an induction coil or coils these currents leap
across the break in the conductor & there & there only produce great heat
which melts the insulator & so causes defective insulation at this spot, this
effected we proceed as in the former case. When the defect is a very small
one giving great resistance the induction coil is used to burn it open & thus
admit the water & give free vent to the electricity we then proceed as before.
When the conductor under examination is simply a wire coated with an insu-
lator & the conductor is broken we apply currents of considerable tension to
one end of the wire & place an insulated conductor of electricity such as metal
tubes, foil, or place a portion of the wire under examination in a basin of
water insulated. The charge entering the wire acts by electric induction on the
outer tube, foil, or water, which latter acts the part of the outer coating of a
Leyden jar, this outer coating is connected with one of two conductors that are
very near each other in a highly exhausted receiver The other conductor is
connected with the earth, The induced electricity will then be seen to pass
between the two conductors This outer covering is then moved along the
insulated conductor & the moment it has passed the fault, where the inside
tension terminates the light in the vacuum ceases & indicates that the defect
has been passed or we use any of the well known instruments for indicating
the presence of small portions of electricity When it is desirable not to damp
the insulated wire containing a defect in the insulation we put the whole coil
into a large receiver & exhaust to a nearly perfect vacuum then on causing
currents to enter one end of the wire they escape at the defect through the
rarified air to the pump plate & thus indicate at once by their luminosity the
exact locality of the fault.
For the purpose of making the exhaustions it became requisite to have a
pump that cou'd absolutely be always depended on for readily producing
a sufficiently perfect vacuum, & as the ordinary air-pumps do not give such s

page_text: vacuum for these tests, & are always liable to become leaky, We have con-
structed the following which gives with certainty the required vacuum & is
very little liable to derangement by use.
The peculiarities of this pump are, that mercury is used above the piston,
the valves, & the joints, to keep all air-tight & which by filling the space
below the piston on its descent perfectly excludes all the air & moisture
hence it is able to pump out condensable vapour a circumstance that greatly
promotes the exhausting power. The valves are lifted mechanically & the
whole so arranged that all is easily comeatable for cleaning.
In testing for a defect when out at sea great difficulty is experienced from
the motion of the ship, & the feebleness of the currents. We obviate much of
this by supporting the galvanometer or indicator on a table of the following
construction On the point at the top of a very heavy pendulum whose
vibrations are rapid, we mount a heavy table on its center of gravity this is
so connected by a spring or springs to the pendulum that it maintains a
position the mean between all the vibrations, on this table we mount our
galvanometer.
When an astatic galvanometer is used of slow oscillation we alternate the
connections of the galvanometer with the probes at such a rate as to cause
many or all of the alternating currents from the probe to pass round the
galvanometer in one direction & thus amplify the deflections At sea or at a
distance this is done by clocks or pendula one at the end of the conductor to
alternate or intermit the currents The other with the probe to reverse the
connections between the probe & its galvanometer These clocks or pendula
do not keep exactly the same time & thus a series of currents are caused to
flow in the same direction round the galvanometer & so amplify the
deflection, & as the pendula do not keep quite the same time the galvanometer
slowly oscillates from side to side. At sea we prefer the reflecting gal-
vanometer & generally use two exactly alike in construction but connected
in reversed directions so that the swinging affects both mirrors alike while
currents are indicated by the approaching to or receeding from each other of
the two reflected spots These needles are made more or less astatic by
bringing a large magnet near to them to neutralize the earth's magnetism; or
any other suitable means are adopted When a conductor is broken & we
wish to ascertain the approximate distanco of the break without burning open
the insulator or where this cannot be done we measure the distance by the
amount of induction in the following new way A rheostat or bobbins of
resistance are prepared free from magnetic induction or retardation this we
effect by winding the rheostat with two or more wires or a doubled wire &

page_text: cause the currents to flow in opposite directions round them an equal number
of times this removes the momentary irregularity of their resistance. We
prepare also a series of induction plates whose action is similar to that of
extensive Leyden jars of known & suitable dimensions These induction plates
are added to the coils of the rheostat so as to give them induction corre-
sponding in amount to that of an equal length of cable The following
example will explain their use Suppose a wire broken in the gutta percha
& thereby insulating perfectly, by passing the current of a battery round the
wires of a differential galvanometer as much resistance & corresponding
induction surface are added as shall produce equilibrium This measures with
tolerable precision the amount of induction or charge & discharge of the cable
& consequently the distance of the leak in the conductor This can also be
used to test the locality of a defect which gives great resistance but not
complete insulation as before assumed As these induction plates are bulky.
we prefer winding our differential galvanometer with many wires, we then
connect the cable to one wire, but the rheostat to many, in this case
the resistance of the latter is increased in proportion while the surface of the
induction plates is reduced & render'd less cumbersome & expensive.
Our clocks or pendula used for alternating &c. the currents, are sometimes
arranged to send the intermittent currents for a few minutes, then disconnect
the wire or put it to earth or both for testing; thus enabling us after finding
the particular wire & the locality of the fault, to test. the insulation & con-
ductivity of the remainder of the wire
We do not confine ourselves to the exact form of apparatus described nor
to their application to any particular kind of conductor These probes may
also be used for picking out of a number of wires the one sought without
injuring the insulation of any of them This is of particular use in tunnels
We sometimes test our wire by exhausting it then letting in water or
acidulated water &c. to the exhausted wire & lastly the pressure of the
atmosphere this finds out many small faults otherwise not visible.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Cromwell Fleetwood Varley and Cornelius John Varley in the
Great Seal Patent Office on the 22nd December 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME we СROM-
WELL FLEETWOOD VARLEY of No. 4 Fortess Terrace Kentish Town and
CORNELIUS JOHN VARLEY of No. 7 York Place Kentish Town St. Pancras
Middlesex send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria by Her Letters
Patent bearing date the Twenty-third day of June in the year of our Lord One
thousand eight hundred and fifty-nine in the twenty-third year of Her reign
did for Herself Her heirs and successors, give and grant unto us the said
Cromwell Fleetwood Varley and Cornelius John Varley Her special licence that
we the said Cromwell Fleetwood Varley & Cornelius John Varley our execu-
tors administrators and assigns, or such others as we the said Cromwell Fleet-
wood Varley and Cornelius John Varley our executors administrators and
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 "IMPROVE-
MENTS IN PROVING ELECTRIC CONDUCTORS AND IN THE APPARATUS CONNECTED THERE-
WITH
upon the condition (amongst others) that we the said Cromwell
Fleetwood Varley and Cornelius John Varley our executors or administrators
by an instrument in writing under our or one of our or their or one of their
hands and seals 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 immediately after the date of the said Letters Patent
33
NOW KNOW YE that I the said Cromwell Fleetwood Varley on behalf of
myself and of the said Cornelius John Varley now deceased do hereby declare
the nature of our said Invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement and accompanying Drawings that is to say
The chief object of our Invention is to find out the locality of defects in
the insulation of a conductor or imperfect continuity of the latter without
removing the covering or the insulator, or cutting the conductor for testing
We generally first ascertain approximately the locality of the fault by the
following method. For example (vide Fig. 1) suppose the defective con-
ductor to be a cable in the maker's stores and under water we pass the
current from a voltaic battery C Z through the two wires of a differential
galvanometer in opposite directions one pole of the battery being connected
to the earth or water, and the two ends of the wires from the differential
galvanometer connected with the two ends of the conductor at S S whose
insulation is defective the current from the battery divides and goes round
the galvanometer in opposite directions and entering both ends of the cable
escapes at the defect in the insulator. If the defect is equidistant from the
two ends i. e. at B the resistance will be equal, the currents round the galva-
g

page_text: nometer will be equal, and the needle will stand at zero. If the fault be not
in the middle of the cable but located at the resistance will be unequal the
shorter route y will allow the passage of more electricity than the other
and the needle will be deflected. We now introduce a rheostat r into the
shorter circuit y and add so much resistance as shall make the two routes
indicated by the arrows equal in resistance, having noted this and the
resistance of the whole conductor the following formula will show very nearly
If the fault be not
nometer will be equal, and the needle will stand at zero.
in the middle of the cable but located at the resistance will be unequal the
shorter route y will allow the passage of more electricity than the other
and the needle will be deflected. We now introduce a rheostat r into the
shorter circuit y and add so much resistance as shall make the two routes
indicated by the arrows equal in resistance, having noted this and the
resistance of the whole conductor the following formula will show very nearly
the exact locality of the defect.
Resistance of the whole conductor = S
then
"
of longer portion
= x
x + y = S
"
of shorter portion
= y
a = y +r
of rheostat
= ↑
S
T
"
2
=y
The peculiarity of this mode of testing is that the ever varying resistance
of a damp fault does not affect the result. The arrows indicate the supposed
direction of a negative current for ease of explanation N.B. as a negative
current both attracts moisture to the fault and keeps the metallic surface in
an unoxidised state it is nearly always the best current to use for testing,
A positive current causes the resistance at / frequently to vary very much
owing to its oxydising action. This operation is not always used especially
when the cable is short.
Having ascertained the approximate locality the actual spot is found by
our second improvement which we call probes vide Figs. 2, 3, and 4.
Fig. 2 is a side view of one of our forms of probes containing a portion of
a cable under test Figs. 3 and 4 are end views and sections a represents
a portion of cable containing five wires, the five conducting wires being
covered with gutta percha hemp and iron as usual, 6 a saddle-shaped piece
of soft iron wrapper with insulated copper wire c, d Figs. 2 and 3 flat bars
or plates of iron fitting against the flat surfaces of 6 at e. e these should be
fitted accurately, ƒ and g the two ends of the wire coil c, h. Figs. 3 and 4
shows a protecting lining for the wire c. Fig. 4 shows another form of probe
in which two saddles of iron b. b. are used fitting against each other united
by hinges the pin at one side being withdrawn to open or to close them
securely when re-inserted. When a current of electricity is flowing through
a conductor it produces magnetic influence or rays throughout the length
and outside of the conductor We apply outside the cable a. a our probes
consisting of coils of wire, iron bars or horse-shoes wrapped with wire as
above described to be acted on by the magnetic power of the current in the

page_text: conductor. Every time a current runs through the conductor or ceases to
flow or is reversed, the magnetism in the probe is disturbed generating
weak electric currents in the coils c of the probes. These weak currents are
rendered visible by a delicate galvanometer which is included in the circuit.
We generally employ a reversing apparatus similar in principle to that first
invented and patented by Cromwell Fleetwood Varley in 1854 for working
printing telegraphs We cause alternating or intermitting currents to enter
one end of the cable and escape at the leak or we cause currents to enter
both ends but at different rates of alternation or intermission, in the latter
case on applying our probes outside the conductor we see immediately by
the speed of the deflections on which side of the fault the probe is. The
probe or probes are then moved along the cable towards the leak until by the
varying speed of the deflections we discern that the fault has been passed.
When the intermittent or alternating currents are applied to one end only of
the cable, the other end is insulated the currents then run along the conductor
to the fault and there escape Our probes then show by the existence or
non-existence of currents in their coils on which side of the fault they are
Having traced out the locality of the fault a Spanish windlass is made or the
cable is cut at the spot repaired and spliced as usual. Thus by a single cut
or splice the fault is removed Hitherto to find such a fault it has been
necessary to cut and splice the cable in many places before the locality of the
fault was traced out A splice takes from 2 to 10 hours to make and fre-
quently wastes from 20 to 30 or more feet of cable besides causing great
delay expense and injury. When the currents are feeble we apply many
probes extending over 12 or 20 feet of the cable their combined action gives
greater deflection to the galvanometer. One foot length of probe is generally
sufficient with moderate battery power, but when the cable exceeds 10 or
20 miles in length we use greater length of probe. Many other forms of
probe may be used to effect this purpose. It is not absolutely necessary to
complete the iron circuit by the pieced Figs. 2 and 3, but so doing increases the
power considerably. We generally use a reflecting galvanometer for showing
the currents generated in the probe coils c and we have made the following
improvement in the galvanometer, we make the reflector of hardened
steel magnetised this reduces the weight of it which is considerable when a
silvered glass is used with a magnet attached to it. When the defect is a
break in the conductor we first pass powerful currents from an induction
coil or coils, these currents leap across the break in the conductor and
there and there only produce great heat which melts the insulator and so
causes defective insulation at the spot. This effected we proceed as in the

page_text: former case.
When the defect is very small and so offers much resistance to
the passuge of a current through it, the induction coil is used to burn it open
and so admit the water and give free vent to the electricity. We then apply
the probes and discover the locality and proceed as before described.
When the conductor under examination is simply a wire coated with an
insulator and the conductor is broken but insulation sound we apply currents
of considerable tension to one end of the wire and place an insulated con-
ductor of electricity, such as metal tubes foil or place a portion of the wire
under examination in a basin of wated insulated, the charge entering the wire
acts by electric induction on the outer tube, foil or water these latter act the
part of the outer coating of a Leyden jar these tubes foil or water are con-
nected with any apparatus suitable for indicating the presence of statical
electricity of low tension or they are connected with one of two conductors that
are very near each other in a highly exhausted receiver as Fig. 5 or 6 the
other conductor is connected with the earth, the induced electricity will then
be seen to pass between the two conductors in the vacuum. This outer
covering is then moved along the insulated conductor and the moment it has
passed the fault where the inside tention terminates the external electric
indications cease and show that the fault has been passed.
When it is desirable not to damp the insulated wire containing a defect in
its insulation we sometimes put the whole coil into a large receiver and exhaust
to a nearly perfect vacuum then on causing currents to enter one end of
the wire they escape at the defect through the rarified air to the pump plate.
and thus indicate at once by their luminosity the exact locality of the fault.
For the purpose of making the exhaustions it became needful to have a
pump that may always be depended on to produce a sufficiently good vacuum
We have constructed one that will give the required vacuum and is very little
liable to derangement by use and its parts are easily comeatable for cleaning
or adjusting. The peculiarities of this pump are that it has a perfectly open
and free passage from the receiver to the barrel when the piston is rising and
the same passage is perfectly closed when the piston descends without any valve
mercury being used to effect that purpose. The same liquid metal is placed
at bottom of the barrel, above the pistons, the valves, and joints or fittings, to
keep all air-tight. Sufficient mercury is allowed to leak back through
openings made for this purpose at every rise of the pistons and valves in
order that at every passage or escape of air there may be some mercury to
follow out also and so secure the total expulsion of all air.
For the sake of using mercury every part of the pump is made of iron,
glass, or other suitable material. Figs. 7, 8, 9 and 10 show its construction

page_text: and action a. a the barrel b and c the upper and lower portions of the
piston capable of sliding to or from each other d and e two upper valves
these four are all conical f the piston rod 6 the piston g. 9 two lifting
rods which slide through the piston but are jointed to the plunger c at h. h,
iia circular spring to make the rods slide with friction, jj the long
narrow passage from the barrel a up to the receiver or pump plate 32 inches
or more in height, the weight of this column always balances the atmospheric
pressure and so keeps the passage closed without any other valve.
j
In Fig. 8 the piston 6 is nearly up when it began to rise it lifted the plunger c
just enough to leave room for the mercury to flow down from the tubej into
the space and so leave the passage j open, air from the receiver then freely
follows the piston when the piston begins to descend its first act is to push
the plunger o into the mercury k and spread it above the hole ; and close it up
On the farther descent of the piston the mercury rises in ; till it balances the
pressure. The piston leaves a vacuum behind it so the air below more readily
rushes past the valve (which is an iron flap and under mercury) into the
vacant space and is followed by some of the mercury. Every crevice below
the piston is filled with mercury so there is nothing left to expand when the
piston again rises, The top of the piston is well flooded with mercury; On its
rising the cone of the valve a dips first in the middle and the mercury
gradually rises to the circumference and drives all the air before it past the
margin of the valve, at this instant the upper valve e floats a limited way in
the mercury which is all round and over it, so it causes a perfect exclusion of
air and leaves nothing but mercury above the piston The pistou 6 when up
at the top has lifted both the valve d and the valve e whose play is limited by
stops nn, on its redescending the valve e first rests on its seat and as the
piston and valve d descend they leave a vacuum between d and e which causes
what air adheres to the mercury to expand into the space between d and e on
the further descent of the piston the valve d rests on its seat shutting off from
the piston any so expanded air and thus the further descent of the piston leaves
a very complete vacuum behind it to receive the air and mercury from below
which rushes past the piston on its nearing the bottom, the mercury driving all
air (and moisture when there is any) before it through the valve 2. m. When
the
pump is double-barrelled each barrel has a separate tubular passage jj,
32 or more inches high.
Fig. 9 shows the spring ring ii in top of the piston 6 to act against the
rods 9, 9, the flap valve having enough play under its screw head, m
entrance from the under margin of 6 to the valve 1.
Fig. 10 the plunger c, hh screws which fasten the pins of the rods g. 9.

page_text: Fig. 11 the mode of checking the ascending mercury at any required height,
a conical valve o is kept down by a weight p when the mercury rises high
enough to float this weight the valve o checks or slackens its farther progress.
This is not generally necessary.
When a conductor is broken and we wish to ascertain the approximate
distance of the break without burning open the insulator or where this cannot
be done we measure the distance by the amount of induction in the following
way. A rheostat or bobbins of resistance are prepared free from magnetic
induction or retardation this we effect by winding the rheostat with two or
more wires or a doubled wire and cause the currents to flow in opposite
directions round them an equal number of times This removes the momentary
irregularity of their resistance arising from magnetic induction We prepare
also a series of induction plates whose action is similar to that of extensive
Leyden jars of known and suitable dimensions these induction plates are
added to the coils of the rheostat so as to give them induction corresponding
in amount to that of an equal length of cable The following example will
explain their use.
Suppose a wire broken in the gutta percha and thereby insulating perfectly,
by passing the current of a battery round the wires of a differential galvano-
meter as much resistance and corresponding induction surface are added as
shall produce equilibrium. This measures with tolerable precision the amount
of induction or charge and discharge of the cable and consequently the
distance of the leak in the conductor This can also be used to test the
locality of a defect which gives great resistance but not complete insulation
as before assumed. As these induction plates are bulky we prefer winding
our differential galvanometer with many wires, say 11, We then connect the
cable to one wire, but the rheostat to 10, in one continuous circuit, the
resistance of the latter is increased in proportion i.e. 10 times while the
surface of the induction plates is reduced to one-tenth and thus rendered less
cumbersome and expensive. On making and breaking contact if the inductive
absorption of the cable tested be 10 times as great as that in our induction
plates while the resistance of the induction plate circuit is 10 ten times as
great as the cable wire, the electricity rushing in to charge the cable will be 10
times as great as that into the induction plates but as the latter circuit is of
10 times the resistance of the cable the time of the chargings will be equal.
Lastly as the smaller charge or current circulates 10 times as often round
the differential galvanometer coil as does the cable charge or current, but in
an opposite direction, they exactly neutralise each other and the needle

page_text: remains at zero. Thus the inductive charge is measured and the distance of
the defect shown.
In testing for a defect in a cable with the probes when out at sea great
difficulty is experienced from the motion of the ship and the feebleness of the
currents we obviate much of this by supporting the galvanometer or indicator
on our sea table of the following construction Fig. 12 explains the principle
on which they are constructed a. a tho table, having at its centre of gravity
a point b by which it stands in a cup c this table when truly balanced will
neither be twisted nor thrown out of its horizontal position by any motion of
the ship. The table is retained in the horizontal position by means of short
quickly oscillating pendula d. d. of which there are 3, 4 or more, the
pendula d. d are suspended from an imaginary plane or circle coinciding with
and equidistant from the centre of gravity 6 of the table these pendula hang
somewhat like scale pans below their beam From the pendula d. d are
springing connections e e, e. e, the pendula being free to move in any direction,
these springs bring and keep the table in the horizontal position. Any motion
sets them oscillating rapidly and as their springs are feeble compared with
the inertia of the table no motion of the latter is perceptible Thus we get
a steady table at sea. The pendula are as near as possible alike in time of
oscillation and are connected by a light frame (not shown in the Drawing
but easily understood) which merely secures their simultaneous action "It
must be borne in mind that cables are never repaired in rough seas when
such a table could not be used."
We propose where necessary to attach gyrascopes to the table which may
be kept in motion by a train of wheels f is a terminal with platina wire
insulated from the table and dipping into the ring cup g which is insulated
from the post on top of which is the cup c these cups c and g are
partially filled with mercury. The currents from our probe travel as shown
by arrows viz. up the post h. Through the cup c the point and the terminal
i to the galvanometer ; back again through the terminal and platina wire f
to the circular trough g and thence to the other end of the probe coil. k a
lamp with a shade to hide it from the screen m, its light after entering the
galvanometer is thrown back by the reflector to the screen m on which it
forms an image or spot of light.
We prefer using two galvanometers wound in opposite directions and
throwing two images near each other on the screen and thus when a current
is passing their oscillations due to the current cause the little reflected images
to approach or recced thus the oscillations caused by the electric currents are

page_text: meters much more sensitive.
readily distinguished from those caused by the motion of the vessel, n. n
adjusting magnets to neutralize the earth's action and so make the galvano-
When we do not use reflecting galvanometers
we use an ordinary astatic one but as one impulse is seldom sufficient we
reverse the connections of the galvanometer with the probe as often as we
reverse the battery connections with the cable and thus cause the alternate
currents of the probe to circulate round the galvanometer in one direction,
their combined action giving a larger deflection. These reversals are pro-
duced by any of the well known commutators When using such an instru-
ment at sea we propose to station a clock beating half-seconds on shore at
that end of the cable to make the reversals and also a clock on board beating
not quite half seconds and thus there will be a given number of currents sent
round the galvanometer in one direction, then a pause followed by a reversal
in the direction of the currents then the slow oscillation of the needle from
side to side will show the existence of currents
The modus operandi at sea Suppose the cable broken we first by testing
get an approximation to the locality,-clocks with the reversing apparatus
are then attached to one or both ends of the cable, we prefer the latter, in
this case the clocks are constructed to send reverse or alternating currents
from their batteries to the cable at unequal intervals say the one reverses the
current at every half second and the other at every second.
The ship is sent as near as possible to the estimated spot to grapple for the
cable when this is found and brought up it is often very taut The sea table &c.
if lifted on to its post and adjusted the probes are then applied outside the cable
when by the speed of the oscillations of its needle it is seen on which side
of the break the ship is-The cable with buoy attached is then lowered and
the ship proceeds in the direction of the fault, grapples again and applies the
probes, this operation is repeated till the fault has been passed which is shown
by the oscillations coinciding with the other clock The value of this will be
apparent since to splice a heavy cable takes from 8 to 12 hours and con-
sumes much cable.
When the cable contains a defect but has not parted it may be under-run
and the probes applied throughout this operation, when the passage of the
fault through them will be instantly indicated. These probes are also useful
in tunnels on lines and elsewhere to indicate the position of faults without
cutting the conductor. When there is no iron covering nor iron near the
conductor an astatic needle in a case is applied to the outside of it as shown
in Fig. 13 a side view and 14 a top view 15 the astatic needle separate,
and thus by the deflection of the needle the passage of a current is indicated

page_text: or if preferred two batteries whose like poles are connected with the earth
are attached to each end of the defective wire,-these cause currents to flow
from each end towards the defect and there escape
On applying the needle
the case the needle is
or rather on placing the wire into the grove in
deflected and indicates the direction of the current On passing the fault the
direction of the current will have changed and the needle will be deflected in
the opposite direction. This apparatus enables us to pick out of a number of
lines the one under test and then to trace out its fault without cutting either
the insulating covering or the conductor,-this is of much service in tunnels
or street work where the copper wire is not covered with iron.
Where the conductor to be tested is not covered with any insulating
medium for example a telegraph wire suspended in the air I adopt the fol-
lowing plan of tracing out what in telegraphic phraseology is called an earth
or a contact when the same cannot be readily discovered in the ordinary
manner by the cyo An astatic or very sensitive galvanometer is wound
with thick copper wire about No. 14 guage the two ends of this galvanometer
wire are connected to the line wire to be tested as shown in Fig. 16 from
10 to 60 yards apart any current passing along the line divides one part of
it traversing the galvanometer the remainder continuing through the line.
In this way the direction of the passing currents are readily detected If
now a line have a leak (make earth) and this be not visible to the eye in the
usual way connect the line at each end to a battery so that similar currents
(say positive ones) enter the line and escape at the leak as shown Fig. 17 on
applying the galvanometer the direction of the current will be indicated This
will show on which side of the fault the galvanometer has been applied In
this way the exact spot can be readily traced out. The strength of the current
traversing the galvanometer is shown by the formula
i, current traversing the line before the galvanometer is applied R, resistance
of the line included between the terminals of the galvanometer wire a and b
Fig 16, resistance of galvanometer, 1 current traversing the galvanometer
(or loop) circuit.
Claims We do not confine ourselves to the precise forms described as the
same effect may be produced by various other modifications.
We claim generally the means of discovering faults in telegraph cables or
conductors covered with insulating media without removing or damaging the
external covering or insulating medium.

page_text: We claim the mode of testing for the locality of faults described in Fig. 1
whereby we are enabled to indicate almost the exact locality of a leak even
when the resistance of the fault itself varies very much under the operation of
testing and which variation would have given erroneous indications by the
hitherto known processes.
The general arrangement of the probes as shown in Figs. 2, 3 and 4.
We claim the pump shown in Figs. 7, 8, 9 and 10. also the measuring the
distance of a fault in telegraphic cables by the inductive charge and discharge
by means of differential galvanometers and resistance coils to each of which
latter are attached induction plates to give them an inductive charge cor-
responding to an equal amount of cable.
We claim the sea table Fig. 12 which may be used for other purposes than
those described.
The mode of tracing out defects as shown in Fig. 13, 14 and 15 and also
that in Fig. 16 and 17.
In witness whereof I the said Cromwell Fleetwood Varley have
hereunto set my hand and seal this Twenty-second day of December
in the year of our Lord One thousand eight hundred and fifty-nine.
CROMWELL FLEETWOOD VARLEY. (L.S.)