Year: 1885

page_text: I PHILIP MIDDLETON JUSTICE of 55 and 56 Chancery Lane in the County of
Middlesex Fellow of the Institute of Patent Agents do hereby declare the nature
of this invention to be as follows:-
This invention relates to means whereby underground lines of electrical con-
ductors can be so constructed and operated as to render them equal in efficiency
and economy of working to lines suspended on poles in the open air; and to
means whereby such lines can be made to work harmoniously when connected with
overhead lines.
In an application of even date herewith means are described for laying electrical
conductors in a conduit somewhat similar in character to that about to be described,
while in another application of the same date the manner of forming an electrical
cable such as would be employed with the present improvements is also described.
For the purpose of preventing the retarding effects of electro-static induction of
subterranean systems and for providing a suitable conduit for the protection of
such conductors, the following method has been devised. Between the conductors
and the earth (or water) in which they are deposited is interposed an insulated
metal sheath or screen. In its purpose and effects this screen differs from the
casings heretofore used. It is well known that the free electricity of the earth is
acted upon by the currents traversing underground conductors, and reacting thereon,
tends to produce a retardation or sluggishness of the said currents.
To interpose a metallic sheath or casing between such conductors and the earth
operates adversely, if at all, in preventing such retardation, if the sheath is in
contact with the earth at any point or points, since in that case the sheath becomes
also a primary conductor or medium for the deleterious charge which thus acts
directly upon the conductors enclosed by the sheath. It has been found, how-
ever, that by enclosing the insulated conductors in a sheath or screen entirely
disconnected and insulated from the ground, that retardation due to the earth's

page_text: electricity is largely diminished, the effect being, to all appearances similar to that
observed when a plate of metal is interposed between two parallel wires, or when
a metal cylinder is interposed between the primary and secondary coils of an
induction coil, the effect in both cases, being to shut off the induction of currents in
one wire by currents in the other.
When, however, a practically constant current is interposed between the earth
and the wires by using the screen as a conductor, the induced effect upon the wires
due to the proximity of the earth is entirely eliminated and retardation, due to
that cause, is completely obviated. This is attributed to the well known fact that
induction due to electro-static or to electro-dynamic causes cannot exist between
two bodies or conductors under the influence of diverse electrical action or status
when a third, which is interposed between them is constantly carrying current from
an independent source of electrical energy.
The present invention consists therefore in the combination with a conduit for
underground or similar conductors of an insulated sheath or screen enclosing the
conductors, in the combination with a sectional conduit of a sectional sheath or
screen and in the use of such screens for the purpose of interposing an active
electrical influence between the earth and the working conductors enclosed within
a cable or conduit, as will be more fully hereinafter set forth.
The conduit as described in the application referred to is formed with upper and
lower sections which after the introduction of the conductors in the lower section,
are brought together, properly secured, and filled with insulating material, blocks
of insulating material being placed in the conduit for supporting the conductors or
wires. Around these blocks and between the conductors and the outer casing is a
metallic screen made preferably in sections similar to those forming the conduit,
Between the screen and the outer casing are inserted blocks or sheets of an
insulating compound to insure the proper isolation of the screen from the ground.
The portions of the sectional sheath at the top and bottom of the conduit, are
provided with a number of perforations, which permit the escape of air and the
free circulation of the insulating compound which is introduced into the conduit
after the wires have been laid and the sections secured together. The screen may
be of sheet iron, copper or other metal, and the materials for the conduit may be
any of those commonly used.
It should here be stated that other disturbances such as induction and retardation
due to other causes than earth currents often affect seriously the rapid working of
underground, or subaqueous lines. For providing against these, special, devices are
employed such as will be hereafter described.
The insulated sheath, however, has in itself a useful and novel function, namely
the diminution or prevention of retardation caused, by the electricity of the earth.
In this respect it forms a novel and valuable adjunct to systems of this kind; when
it is allied with the active forces of a dynamic current passing through it a complete
elimination of these influences is effected.
The projecting ends of the screen are connected to wires and through them to a
battery. A current is thus caused to pass through the screens, and as no means
are employed of intercepting it, it is practically constant, unless means are, however,
devised to overcome the deleterious influences of retardation arising from the
induced reactions of the screen current upon the wires enclosed within the screen
such retardations would be more than equal to those caused by induction from the
earth itself. Therefore it will be found necessary to produce currents of opposite
polarity in wires located inside the screen to those of the screen itself. When this
is done the inductions from the screen assist instead of hindering the passage of
current in the wires which it encloses. .
With the two fold object of preventing the retardation due to the induction
between the line wires and the insulating sheath and that due to the increased
electro-static capacity of underground circuits the system above described has been
combined with that device described in the second of the before referred to appli-
cations in which a metal sheath is employed for shutting induced currents from

page_text: neighbouring conductors, so that the induced effects of the screen currents may be
taken up and neutralized by the metal sheaths enclosing each pair of the wires.
composing a group.
In this form each of the cables consist of two insulated conductors forming or
adapted to form a complete or round wire circuit and enclosed or surrounded by a
metallic sheath or jacket and an insulated metal sheath or screen interposed between
the conduit and the cables. The several features of construction here enumerated
contribute to the attainment of the desired results.
The two wire conductors operate to lessen the induction from neighboring
circuits. The metal sheaths enclosing the wires still further reduce or prevent this
induction, and by being insulated prevent retardation upon the line for the reason
that the opposite polarities in the latter neutralize the effects produced in the
sheath. The screen which encloses the cables operates to eliminate the electro-
static induction and consequent retardation due to the attractive action of the
earth's electricity which would otherwise exert itself deleteriously to the fullest
extent upon the sheaths of the individual cables, thus tending to destroy the
equilibrium effected by the currents of opposite direction within them.
A pair of separately insulated conducting wires are enclosed in a metal sheath
which is in turn enclosed by an insulated screen and by the conduit. The wires
are connected to translating devices and to a battery. The wires, however, for
some uses may be grounded separately and be supplied with current from inde-
pendent sources. In the latter case, however, these should be of opposite polarities,
that the one wire should be the working wire and the other the idle wire whose
office is to assist the former by induction.
When it is desired to operate these underground lines in connection with over-
head wires of the ordinary type suspended on poles, the underground portion of
the circuits are made completely metallic using two wires enclosed in an insulated
metallic sheath while for the aerial portions the ground is used as a part of the
circuit,
The conductors forming the leading and return wires respectively, are surrounded
by an insulated metallic sheath. The wires and sheath are carried through, say
the city, by an underground conduit at the end of which the leading wires are
grounded while the return wires are carried on to the desired point as aerial lines.
It is obvious that this disposition of wires may be made at either or both ends of
the line. The two wire portion of the line enclosed in or surrounded by the
insulated metallic screen may be advantageously enclosed in à second insulated
metallic screen. For the more effectual exclusion of the influences due to the
proximity of the earth the outer insulator may be made to carry a current as
herein before described.
A further exemplification of this method consists of a cable such as was described
in the second of the before mentioned applications consisting of a single conductor
surrounded by wrappings of insulating material and interposed metal screens,
wound with a serving of twine and laid in a trough wherein it is first supported
on blocks of insulating material to preserve it from contact with the trough, after
which the trough is filled with a hot composition preferably of the same character
as the blocks, and which when cold remain permanently viscous, or plastic. Clamps
are attached to the insulated metallic screen and are connected by wires to other
clamps which enclose an outer insulated metallic layer and with a battery complete
an insulated circuit exterior to, and insulated from, the central conductor.
When the current in the inner metallic screen has an opposite polarity to that of
the central conductor retardation due to the earth's proximity or to the condenser
action of the metal sheath is practically eliminated, first because the passage of
current in two opposite directions between the earth and the central core takes up
and dissipates the inductions from that source, while in the second place the
inductive influence upon conducting or working core of the cable produces a state
of electrical tension highly favorable to the passage of current of an opposite
direction to that of the inner screen. Such a method of working a cable is equally

page_text: applicable to sub-aqueous as to subterranean lines, but in such cases the exterior
casing must be made to conform to its requirements.
A modification of this device consists of a single metallic sheath surrounding
a single conductor both sheath and conductor being grounded and carrying currents
of opposite direction. The special advantages which this secures are that the
diameter of the cable is or may be reduced and the expense lessened and when
employed in a conduit containing the insulated metallic sheathed conductor the
effects of electro-static or exterior influences are further obviated.
The ends of the wire are grounded in the usual way and a circuit formed in
which are included signalling instruments of any kind, and a galvanic battery or
other generator of current connections are made from the ends of the insulated
metallic sheath to the ground, and a circuit thus formed, in which is included a
second battery or generator. This battery is, however, connected to the circuit
including the insulated metallic sheathing in such a manner that the current, which
it causes in the sheathing, flows in an opposite direction to that in the wire from
the line battery.
The batteries may be placed at either end of the circuits. The cable may also
be constructed in a great many ways, and is not confined to any particular form.
As for instance a simple copper wire; having a spiral wrapping of paper soaked in
paraffine and applied by means of an adhesive insulating compound or varnish;
and a further spiral wrapping of tin-foil and any suitable form of insulating and
protecting outer coating.
It will be known that such a cable or conductor as described possesses, when
used, the characteristics of a condenser. For example a positive current, flowing
in the conducting wire, produces a state of electrical tension; the sheathing of the
cable being negatively electrified. This reacts upon the conductor which becomes
positively electrified by induction. By this means the flow of current is greatly
retarded and rapid working interfered with. By this system, however, the current
in the metallic sheathing serves to maintain this state of tension, both in the outer
layer or layers of the cable, and also in the central conductor. When signals are
sent through the latter, therefore, they are accelerated rather than retarded, if
the current be in an opposite direction to that in the metal sheathing. For this
purpose it is only necessary to use such a line battery as will overcome the difference
of earth potential, as it would even be possible to transmit signals without any
battery in the working line depending entirely upon the inductive charge from the
metallic sheathing. The battery power that would be required for a round wire
circuit, is, by this means, lessened, while the retardation incident to ordinary cables
is prevented.
Cables have however been made with an insulated metal sheathing and that in
using these cables it has been proposed to pass a current through the sheathing
in the same direction as that of the signalling current. This, however, is widely
different from the nature and object of the present invention.
Dated the 90th dox of Santember 18ek

page_text: Subterranean Lines of Electrical Conductors.
I, PHILIP MIDDLETON JUSTICE of 55 and 56 Chancery Lane in the County of
Middlesex Fellow of the Institute of Patent Agents do hereby declare the nature
of this invention (a communication to me from abroad by Henry Curtis Spalding,
of Boston, Massachusetts, United States of America, Electrician) and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:—
This invention relates to means whereby underground lines of electrical con-
ductors can be constructed and operated as to render them equal in efficiency and
economy of working to lines suspended on poles in the open air and to means
whereby such lines can be made to work harmoniously when connected with
overhead lines.
In another specification of even date means are described for laying electrical
conductors in a conduit similar in character to that shown in the accompanying
drawings which form part of this specification, such conduit being shown in
Figs. 1, 2, 3, 4, 5, 6. The modifications or improvements shown in the said
figures will be hereinafter described in detail.
In another specification of even date an electrical cable is described similar in
structure to that shown enclosed in a box in Figs. 7, 8 and 9 of the said drawings.
The further improvements which form the subjects of these drawings will now be
considered in detail.
The first series of said drawings designated by the Figs. 1, 2 and 3, relate to
a method which I have discovered of preventing the retarding effects of electro-
static induction of subterranean systems and more particularly in its relation to a
conduit for the protection of such conductors. This I accomplish by interposing
between the conductors and the earth (or water) in which they are deposited an
insulated metal sheath or screen. In its purpose and effects this screen differs from
the casings heretofore used. It is well known that the free electricity of the earth
is acted upon by the currents traversing underground conductors and reacting
thereon, tends to produce a retardation or sluggishness of the said currents.
To interpose a metallic sheath or casing between such conductors and the earth
operates adversely if at all in preventing such retardation, if the sheath is in
contact with the earth at any point or points, since in that case the sheath becomes
also a primary conductor or medium for the deleterious charge which thus acts
directly upon the conductors enclosed by the sheath. I have found, however, that
by enclosing the insulated conductors in a sheath or screen entirely disconnected
and insulated from the ground, that retardation due to the earth's electricity is
largely diminished, the effect being to all appearances similar to that observed
when a plate of metal is interposed between two parallel wires, or when a metal
cylinder is interposed between the primary and secondary coils of an induction coil,
the effect in both cases being to shut off the induction of currents in one wire by
currents in the other,

page_text: When, however, a practically constant current is interposed between the earth
and the wires by using the screen as a conductor as is illustrated in Figs. 3 and 7
the induced effect upon the wires due to the proximity of the earth is entirely
eliminated, and retardation due to that cause is completely obviated. I attribute
this to the well known fact that induction due to electro-static or to electro-
dynamic causes cannot exist between two bodies or conductors under the influence
of diverse electrical action or status when a third which is interposed between them
is constantly carrying current from an independent source of electrical energy.
My present invention consists therefore in the combination with a conduit for
underground or similar conductors of an insulated sheath or screen enclosing the
conductors in the combination with a sectional conduit of a sectional sheath or
screen and in the use of such screens for the purpose of interposing an active
electrical influence between the earth and the working conductors enclosed within
a cable or conduit, as will be more fully hereinafter set forth.
Fig. 1 is an end elevation of the conduit.
Fig. 2 is a view partly in horizontal section showing parts of the sheath in plan.
Fig. 3 is a view in elevation of the conduit showing the ends of the screen
connected together by wires and a battery in circuit.
Fig. 4 is a view of the conduit wherein the enclosed wires are connected to an
overhead or "pole" line.
Figs. 5 and 6 are views in detail of the conduit in combination with doubled
wires or circuits enclosed within metallic sheaths
Figs. 7, 8 and 9 are illustrations of modifications which I employ for the same
purposes.
Fig. 10 illustrates a sheathed wire electera.
A and B represent the upper and lower sections of the conduit which after the
introduction of the conductors in the lower section are brought together, properly
secured and filled with insulating material. a, are blocks of insulating material
placed in the conduit for supporting the conductors or wires. Around the blocks a,
and between the conductors and the outer casing is the metallic screen b, b, made
preferably in sections similar to those forming the conduit. Between the screens b,
and the outer casing I insert blocks, or sheets c of an insulating compound to
insure the proper isolation of the screen b, from the ground.
The portions of the sectional sheath at the top and bottom of the conduit are
provided with a number of perforations as shown in Fig. 2, which permit the
escape of air and the free circulation of the insulating compound which is introduced
into the conduit after the wires have been laid and the sections secured together.
The screen b may be of sheet iron, copper, or other metal, and the materials for the
conduit may be any of those commonly used.
I would here state that other disturbances, such as induction and retardation
due to other causes than earth currents often affect seriously the rapid working of
underground or subaqueous lines. For providing against these I employ special
devices such as will be hereafter described.
The insulated sheath, however, as observation and experiment have led me to
conclude, has in itself a useful and novel function, namely the diminution or
prevention of retardation caused by the electricity of the earth. In this respect
it forms novel and valuable adjunct to systems of this kind, when it is allied with
the active forces of a dynamic current passing through it a complete elimination
of these influences is effected.
In Fig. 3 the projecting ends of the screen b, are connected to wires d, d¹ and
through them to the battery C. A current is thus caused to pass through the
screens, and as no means are employed of intercepting it, it is practically constant
unless means are however devised to overcome the deleterious influences of
retardation arising from the induced reactions of the screen current upon the
wires enclosed within the screen, such retardations would be more than equal to
'those caused by induction from the earth itself. Therefore it will be found
necessary to produce currents of opposite polarity in wires located inside the screen

page_text: to those of the screen itself. When this is done the inductions from the screen
assist instead of hindering the passage of current in the wires which it encloses.
With the twofold object of preventing the retardation due to the induction
between the line wires and the insulating sheath and that due to the increased
électro-static capacity of underground circuits, I have combined the system above
described with that device discussed in the second of the before referred to
specifications in which a metal sheath is employed for shutting induced currents
from neighbouring conductors, so that the induced effects of the screen currents
may be taken up and neutralized by the metal sheaths enclosing each pair of the
wires composing a group such as is shown in Fig. 5, which is an end elevation of
a conduit and its contents. In this form each of the cables consists of two insulated
conductors forming or adapted to form a complete or round wire circuit and
enclosed or surrounded by a metallic sheath or jacket and an insulated metal
sheath or screen interposed between the conduit and the cables. The several
features of construction here enumerated contribute to the attainment of the
desired results.
The two wire conductors operate to lessen the induction from neighbouring
circuits. The metal sheaths enclosing the wires still further reduce or prevent this
induction and by being insulated prevent retardation upon the line for the reason
that the opposite polarities in the latter neutralize the effects produced in the
sheath. The screen which encloses the cables operates to eliminate the electro-
static induction and consequent retardation due to the attractive action of the
earth's electricity which would otherwise exert itself deleteriously to the fullest
extent upon the sheaths of the individual cables, thus tending to destroy the
equilibrium effected by the currents of opposite direction within them.
I have illustrated this part of my invention as applied to a special form of
conduit jointly invented by Peter MoMackin and myself and described in the
first of the before mentioned specifications.
Fig. 6, illustrates one manner of working or operating such lines although I do
not confine myself thereto. In the figure is shown a pair of separately insulated
conducting wires enclosed in the metal sheath e, which is in turn enclosed by the
insulated screen b, (but which is not shown in this figure) and by the conduit A, B.
The wires are connected to translating devices D, D¹, and to the battery E. The
wires however for some uses may be grounded separately and be supplied with
current from independent sources. In the latter case however these should be of
opposite polarities, that the one wire should be the working wire and the other the
idle wire whose office is to assist the former by induction, all of which is fully set
forth in other applications.
When it is desired to operate underground lines in connection with overhead
wires of the ordinary type suspended on poles, I use the following arrangement.-
I make the underground portion of the circuits completely metallic using two
wires enclosed in an insulated metallic sheath while for the aerial portions I use
the ground as a part of the circuit. This disposition will be understood by reference
to Fig. 4 in which F represents the transmitting or receiving instruments of a
line which leads from the centre of a city for example to some distant point.
G represents the source of electrical energy. The conductors H, J forming the
leading and return wires respectively are surrounded by an insulated metallic
sheath f, such as has been described in the second specification before mentioned.
The wires and sheath are carried through the city through an underground
conduit A, B, at the end of which the wires H, are grounded while the wires J
are carried on to the desired point as aerial lines. It is obvious that this
disposition of wires may be made at either or both ends of the line. The two
wire portion of the line enclosed in or surrounded by the insulated metallic screen f
may be advantageously enclosed in a second insulated metallic screen such as that
which in Fig. 5 surrounds the entire group of wires in the conduit. For the more
effectual exclusion of the influences due to the proximity of the earth the outer
insulator may be made to carry a current as herein before described.

page_text: .
A further exemplification of this method is represented in Fig. 7 wherein a
cable such as was described in the second of the before mentioned cases consisting
of a single conductor K, surrounded by wrappings of insulating material and
interposed metal screens is wound with a serving of twine and laid in a trough L
wherein it is first supported on blocks M, of insulating material to preserve it
from contact with the trough, after which the trough is filled with a hot com-
position preferably of the same character as the blocks, and which when cold
remain permanently viscous or plastic. Clamps N N¹, are attached to the
insulated metallic screen O and are connected by the wires g, g', to the clamps P, P¹,
which enclose the insulated metallic layer Q, and with the battery R complete an
insulated circuit exterior h, and insulated from the central conductor K.
When the current in the screen O has an opposite polarity to that of the
conductor K, retardation due to the earth's proximity or to the condenser action
of the metal sheath is practically eliminated, first because the passage of current
in two opposite directions between the earth and the central core takes up and
dissipates the inductions from that source while in the second place the inductive
influence upon conducting or working core of the cable produces a state of
electrical tension highly favorable to the passage of current of an opposite
direction to that of the inner screen.
Figs. 8 and 9 are cross sections respectively of the trough or conduit L. and the
block M, and of the trough or conduit L, when filled with insulating material.
Such a method of working a cable is equally applicable to subaqueous as to
subterranean lines, but in such cases the exterior casing must be made to conform
to its requirements.
A modification of this device is shown in Fig. 10, in which a single metallic
sheath surrounds a single conductor both sheath and conductor being grounded
and carrying currents of opposite direction. The special advantages which this
secures are that the diameter of the cable is or may be reduced and the expense
lessened and when employed in a conduit containing the devices shown in
Figs. 1, 2, 3 and 4, the effects of electro-static or exterior influences are further
obviated. This part of my invention is fully illustrated in the drawing which
shows a section of cable with the proper battery and other connections. S is the
central wire or conductor of a cable, T is an insulating coating enclosing the
same, U is a metallic sheathing or layer between the insulating coating
and an
outer insulating and protective coating V.
The ends of the wire S, are grounded in the usual way and a circuit formed
in which are included signalling instruments of any kind, designated by the
letters W, W, and a galvanic battery or other generator of current P¹, N¹, con-
nections ✗ are made from the ends of the insulated metallic sheath U, to the
ground and a circuit thus formed in which is included a second battery or
generator P³, N². This battery is, however, connected to the circuit including
sheathing U, in such manner that the current which it causes in the sheathing,
flows in an opposite direction to that in the wire S, from the line battery P¹, N¹.
The batteries may be placed at either end of the circuits. The cable may also
be constructed in a great many ways, and I do not confine myself to any
particular form. In that shown S is a simple cypher wire, T is a spiral wrapping
of paper soaked in paraffine and applied by means of an adhesive insulating com-
pound or varnish; U is a spiral wrapping of tinfoil and V is any suitable form
of insulating and protective coating.
It will be known that such a cable or conductor as I have described possesses,
when used, the characteristics of a condenser. For example a positive current
flowing in the conducting wire, produces a state of electrical tension; the sheathing
of the cable being negatively electrified. This reacts upon the conductor which
becomes positively electrified by induction. By this means the flow of current is
greatly retarded and rapid working interfered with. By my system however the
current in the metallic sheathing serves to maintain this state of tension both in
the outer layer or layers of the cable, and also in the central conductor. When

page_text: signals are sent through the latter, therefore, they are accelerated rather than
retarded, if the current be in an opposite direction to that in the metal sheathing.
For this purpose it is only necessary to use such a line battery as will overcome
the difference of earth, potential, as it would even be possible to transmit signals
without any battery in the working line depending entirely upon the inductive
charge from the metallic sheathing. The battery power that would be required
for a round wire circuit, is by this means lessened, while the retardation incident
to ordinary cables is prevented.
I am aware that cables have been made with an insulated metal sheathing and
that in using these cables it has been proposed to pass a current through the
sheathing in the same direction as that of the signalling current. This however is
widely different from the nature and object of my invention.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is-
1. The combination with the conductors of an underground system of a metal
sheath or screen enclosing all of said conductors and insulated from both the
conductors and the ground, as and for the purpose set forth.
2. In an underground conduit for electrical conductors, the combination with
said conductors, of a sheath or screen interposed between the conductors and the
conduit, and insulated from both as set forth.
3. The combination with sectional conduit and the conductors contained therein,
of a sectional metallic sheath between the conduit and the group of conductors and
insulated from both as set forth.
4. The combination with a conduit composed of sections A and B, of a group of
wires contained therein, a metal sheath or screen enclosing and insulated from the
conductors, and layers or plates of insulating material b, between the screen and
the conduit as set forth.
5. In a system for the transmission of electrical signals, the combination with
one or more insulated line wires, of two insulated conductors in proximity to the
same conveying continuous currents in opposite directions, as and for the purpose
set forth.
6. In a system for the transmission of electrical signals, the combination with
one or more line wires, of two insulated conductors in proximity thereto,
connected to form a metallic circuit, and including a battery or generator, as set
forth.
7. In a system for the transmission of electrical signals, the combination with a
group of insulated wires, of two insulated metallic sheathings or screens connected
to form a metallic circuit and generator included in same circuit, as set forth.
8. In a system for the transmission of electrical signals, the combination with a
group of insulated wires, of two concentric insulated metallic sheathings, or screens
surrounding the wires and connected at the ends to form a metallic circuit, and a
battery or generator included in the circuit.
9. In an underground cable or conduit the combination with a group of wires of
two insulated metallic sheathings or screens connected to form a metallic circuit, a
battery included in said circuit in such manner as to cause the current to flow in a
sheathing or screen in a direction opposite to that of the currents in the wires
Dearest to it, as set forth.
10. In an underground system the combination with a group of cables, each
composed of two insulated conductors forming a complete or round wire circuit,
of an insulated metal sheath or screen surrounding and enclosing the cables,
substantially as set forth.
11. The combination with a group of cables each composed of two insulated
conductors forming a complete or round wire circuit and enclosed within a metallic
sheathing or wrapping of an insulated sheath or screen and an enclosing conduit or
casing all substantially as described.

page_text: 12. The combination with a group of cables each composed of two insulated
conductors forming a complete or round wire circuit and enclosed within a metallic
sheathing or wrapping of a sectional screen and a sectional enclosing conduit or
casing all substantially as herein described.
13. In a system for the transmission of electric signals, the combination with
the conductor of the working circuit and a generator and signalling instruments
connected therewith, of an insulated metallic sheathing or layer surrounding the
said conductor and a generator for producing a continuous current through the
sheathing in an opposite direction to that in the working circuit, as and for
the purpose set forth.
14. In a system for the transmission of electric signals, the combination with
the conductor of the working circuit grounded at each end and a generator and
signalling instruments connected therewith, of an insulated metallic sheathing or
layer surrounding the said conductor, connections from the ends of the sheathing
to the ground and a generator connected with the circuit so formed in such a way
as to produce therein a continuous current of opposite direction to that in the
working circuit as set forth.
15. An electric circuit composed in part of an aerial line and the ground, and in
part of two insulated conductors enclosed in a metal sheath in an insulating
conduit, the two conductors constituting respectively leading and return wires and
the return wire being grounded at the end of the conduit, substantially as and for
the purpose specified.
16. An electric circuit consisting in part of two conductors insulated from
one another and enclosed within an insulated metallic sheath, and in part of an
aerially suspended wire, the suspended wire and one of the insulated wires being
connected to earth at or beyond the same end of the said sheath, substantially as
and for the purpose herein set forth.
17. The combination with an aerial line of a two wire or metallic circuit
underground cable and two insulated metallic sheaths or screens surrounding the
same substantially as set forth.
18. In combination with a series of aerial lines of two wire or metallic circuit
underground cables connected therewith, metallic sheathings or screens surrounding
each cable, and an insulated metallic screen enclosing all of the cables, substantially
as set forth.
19. The combination of a flexible cable containing a number of insulated wires
surrounded by layers of insulating material, a sectional conduit or trough and
insulating blocks or rests for supporting the cable in the conduit as herein set
forth.
20. The combination of a flexible cable containing a number of insulated wires
surrounded by layers of insulating material, a sectional conduit or trough,
insulating blocks or rests for supporting the cable in the conduit, and a filling
of insulating material as herein described.
21. The combination of a flexible cable containing a number of insulated wires
surrounded by layers of insulating material and a metal screen or sheath, a
sectional conduit, means for supporting the cable in the conduit, and a filling of
insulating material as herein described.
D
3
C T1000
PHILIP M. JUSTICE.