IMPROVEMENTS IN APPARATUS FOR REGULATING ELECTRIC LAMPS AND FOR MEASURING ELECTRICAL CURRENTS AND ELECTRICAL ENERGY >
Year: 1882

page_text: LETTERS PATENT to Andrew Gray of Glasgow in the County of Lanark
North Britain Assistant to the Professor of Natural Philosophy in the
University of Glasgow and Thomas Gray also of Glasgow aforesaid
Electrician for an Invention of "IMPROVEMENTS IN APPARATUS FOR
REGULATING ELECTRIC LAMPS AND FOR MEASURING ELECTRICAL CURRENTS
AND ELECTRICAL ENERGY
>
PROVISIONAL SPECIFICATION left by the said Andrew Gray and Thomas
Gray at the Office of the Commissioners of Patents on the 20th July 1882.
ANDREW GRAY, of Glasgow, in the County of Lanark, North Britain, Assistant
to the Professor of Natural Philosophy in the University of Glasgow, and THOMAS
GRAY, also of Glasgow, aforesaid, Electrician, "IMPROVEMENTS IN APPARATUS FOR
REGULATING ELECTRIC LAMPS AND FOR MEASURING ELECTRICAL CURRENTS AND
ELECTRICAL ENERGY."' "
This invention relates to apparatus for regulating electric lamps and for the
measurement of electric currents and electrical energy.
To regulate the feed of the carbons in an electric lamp we use a hollow dru
formned by a single hollow cylinder or having a hollow space between two coaxial
cylinders of different diameters or the hollow space within which is divided into
two or more cellular spaces by partitions properly placed. These cellular spaces
are partially filled with a suitable liquid and communicate with one another by
small apertures in the partitions. When this drum is moved round in any
direction by the action of a turning couple which may be supplied by the carbons
and their holders in an electric lamp the liquid applies an opposite couple resisting
the motion.
If the magnitude of the turning couple be less than a certain value depending
on the amount and density of the liquid contained in the cellular spaces the wheel
will be turned round by the couple until the liquid by being accumulated in one
side of-the drum opposes an equal and opposite couple.

page_text: The motion thereafter becomes uniform or nearly so and depends on the rate of
loss of head of the liquid by flow through the aperture.
Combined with this in the application to an Electric Lamp we use an apparatus
as hereinafter described for further controlling the motion of the carbons according
to the amount of current flowing so as to keep the carbons constantly as nearly
as may be at the desired distance apart.
One convenient form of this apparatus which may be used either by itself or in
combination with other apparatus for controlling the motion of the carbons depends
on an application of the principle of a similar instrument to that known as
"Barlows Wheel," which is a metallic disc which can be rotated round an axis
through its centre, by the action of a properly placed magnet or magnets on a
current of electricity passing between the centre and circumference of the disc.
We so modify this instrument by multiplying the number of discs, and arranging
the currents through them and the magnets as to obtain the power necessary to
separate the carbons, when the circuit is first closed, and thereafter to control
according to the strength of the current the rate of motion of the carbons.
Instead of "Barlow's Wheel," we may use any other convenient form of
electrical controlling apparatus. We place the apparatus employed either in the
main circuit or in a derived circuit as we find convenient.
A modification of electrical regulator for the speed of the mechanism which we
use consists of a small coil with or without a core of soft iron which is rotated
with sufficient speed by a train of wheel works between the poles of an electro
magnet excited by the current.
Another application of the hollow drum containing liquid as hereinbefore
described is in combination with a modified form of "Barlow's Wheel" to form two
instruments which are or may be used in connection with the lamp herein before
described or in connection with other lamps or apparatus for generating or
utilizing electric energy.
The form of "Barlow's Wheel" which we use consists of one metallic disc or a
series of metallic dises on the same or on a separate axis, the first of which is
electrically connected with the second by a cylinder pivoted on an axis parallel to
the axes of the discs, and the second electrically connected to the third at their
centres, the third electrically connected to the fourth at the circumference by a
cylinder on the same axis as the first cylinder or on a separate axis, and so on
according to the number of discs. The turning couple is obtained by placing
round each arrangement of two discs and a cylinder, a fixed coil of convenient form
and dimensions whose plane is at right angles to the planes of the discs placed so
as to produce by the mutual action of the currents flowing in it, and in the discs, a
couple tending to rotate the discs.
When the current is made to flow through the coils and axes of this arrangement
in any manner the turning couple is a function of the current depending on the
flow of the current in the coils and disc.
For the current meter the coil or coils are made of low electrical resistance and
the whole current or a known part of the current is sent through the disc or discs
and coil or coils. A counter connected by gearing and graduated scale registers
the amount of electricity which has flowed through in any time during which it
was in action.
In the energy meter the coil surrounding the disc is of sufficiently high
resistance to give a force proportional to the difference of potential between the
extremities of the coil. The whole or a known proportion of the current in the
main circuit is sent through the disc while the high resistance coil is put on as a
shunt in the circuit. The motion at any instant varies more or less with the
product of the difference of potentials between the two ends of the coil, and the
whole current in the circuit and by a properly arranged counting apparatus, the
whole energy used in any time in any part of the circuit can be measured.
For measuring the difference of potentials between any two points in an electric
circuit we use a galvanometer of the form hereinafter described. The coil of this

page_text: galvanometer is composed of several thin copper or German silver wires each
covered with insulating material. These wires are twisted together so as to form
a stranded rope. These wires may alternatively be all joined together in series, or
any number may be joined in series, and these opposed with regard to their effect
on the needle to the remainder also joined in series. By varying the proportions
of the parts thus opposed various powers are given to the instrument and at the
same time its resistance to the current, passing through it, maintained constant.
The wires forming the rope are arranged in suitable groups and all the members of
each group joined in series. The terminals of each group are connected to suitable
studs or contact pieces which may be connected together so as to give any desired
power to the instrument.
The range of the instrument may be extended by combining with it a subsidiary
coil of very low resistance and of much lower power than can be obtained with
the main coil above described. This subsidiary coil, when very low power is
required is joined in series with the main coil, which is then so joined that the
current passing through it, produces no effect on the needle. When this low power
is not required this subsidiary coil need not be included in the circuit.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Andrew Gray and Thomas Gray in the Great Seal Patent Office on
the 19th January 1883.
ANDREW GRAY, of Glasgow, in the County of Lanark, North Britain, Assistant
to the Professor of Natural Philosophy in the University of Glasgow and THOMAS
GRAY also of Glasgow, aforesaid, Electrician' "IMPROVEMENTS IN APPARATUS FOR
REGULATING ELECTRIC LAMPS AND FOR MEASURING ELECTRICAL CURRENTS AND
ELECTRICAL ENERGY
"
Our said Invention relates to apparatus for regulating electric lamps and for the
measurement of electric currents and electrical energy.
To regulate the feed of the carbons in an electric lamp we use a hollow dram
formed by a single hollow cylinder or having a hollow space between two coaxial
cylinders of different dinmeters or the hollow space within which is divided into
two or more cellular spaces by partitions properly placed.-These cellular spaces
are partially filled with a suitable liquid and communicate with one another by
small apertures in the partitions. When this drum is moved round in any direction
by the action of a turning couple which may be supplied by the carbons and their
holders in an electric lamp the liquid applies an opposite couple resisting the
motion.
If the magnitude of the turning couple be less than a certain value dependin
on the amount and density of the liquid contained in the cellular spaces the wheel
will be turned round by the couple until the liquid by being accumulated in one
side of the drum opposes an equal and opposite couple.
The motion thereafter becomes uniform or nearly so and depends on the rate of
loss of head of the liquid by flow through the aperture.
Combined with this in the application to an Electric Lamp, we use an apparatus
as hereinafter described for further controlling the motion of the carbons according
to the amount of current flowing so as to keep the carbons constantly, as nearly
as may be, at the desired distance apart.
One convenient form of this apparatus which may be used either by itself or in
combination with other apparatus for controlling the motion of the carbons depends
on an application of the principle of a similar instrument to that known as "Barlows
Wheel," which is a metallic disc which can be rotated round an axis through its
centre, by the action of a properly placed magnet or magnets on a current of
electricity passing between the centre and circumference of the disc.-We so
modify this instrument by multiplying the number of discs and arranging the
currents through them and the magnets as to obtain the power necessary to
separate the carbons, when the circuit is first closed and thereafter to control
according to the strength of the current the rate of motion of the carbons.
Instead of "Barlows Wheel," we may use any other convenient form of electrical
controlling apparatus. We place the apparatus employed either in the main circuit
or in a derived circuit as we find convenient.
A modification of electrical regulator for the speed of the mechanism which we
use, consists of a small coil with or without a core of soft iron, which is rotated
with sufficient speed by a train of wheels, works between the poles of an electro
magnet excited by the current.
Another application of the hollow drum containing liquid as herein before
described is in combination with a modified form of "Barlows Wheel," to form two
instruments which are or may be used in connection with the lamp herein before
described or in connection with other lamps or apparatus for generating or
utilizing electric energy.
The form of "Barlows Wheel" which we use consists of one metallic disc or a

page_text: series of metallic discs on the same or on a separate axis, the first of which is
electrically connected with the second at the circumference by a cylinder pivoted
on an axis parallel to the axes of the discs, and the second electrically connected
to the third at their centres, the third electrically connected to the fourth at the
circumference by a cylinder on the saine axis as the first cylinder or on a separate
axis, and so on according to the number of discs.-The turning couple is obtained
by placing round each. arrangement of two discs and a cylinder, a fixed coil of
convenient form and dimensions whose plane is at right angles to the planes of the
discs placed so as to produce by the mutual action of the currents flowing in it,
and in the discs, a couple tending to rotate the discs.
When the current is made to flow through the coils and axes of this arrangement
in any manner the turning couple is a function of the current depending on the
flow of the current in the coils and disc.
For the current meter the coil or coils are made of low electrical resistance and
the whole current or a known part of the current is sent through the disc or discs
and coil or coils. A counter connected by gearing and graduated scale registers
the amount of electricity which has flowed through in any time during which it
was in action.
In the energy meter the coil surrounding the disc is of sufficiently high resistance
to give a force proportional to the difference of potential between the extremities
of the coil. The whole or a known proportion of the current in the main circuit is
sent through the disc while the high resistance coil is put on as a shunt in the
circuit. The motion at any instant varies more or less with the product of the
difference of potentials between the two ends of the coil, and the whole current in
the circuit and by a properly arranged counting apparatus, the whole energy used
in in any time in any part of the circuit can be measured.
For measuring the difference of potentials between any two points in an electric
circuit we use a galvanometer of the form hereinafter described. The coil of this
galvanometer is composed of several thin, copper or German silver wires each
covered with insulating material.-These wires are twisted together so as to form a
stranded rope.
These wires may alternatively be all joined together in series or
any number may be joined in series, and these opposed with regard to their effect
on the needle to the remainder also joined in series. By varying the proportions
of the parts thus opposed, various powers are given to the instrument and at the
same time its resistance to the current, passing through it, maintained constant.
The wires forming the rope are arranged in suitable groups and all the members of
each group joined in series.-The terminals of each group are connected to suitable
studs or contact pieces which may be connected together so as to give any desired
power to the instrument.
The range of the Instrument may be extended by combining with it a subsidiary
coil of very low resistance and of much lower power than can be obtained with the
main coil above described. This subsidiary coil, when' very low power is required
is joined in series with the main coil, which is then so joined that the current
passing through it, produces no effect on the needle. When this low power is
not required this subsidiary coil need not be included in the circuit.
And in order that our said Invention may be properly understood we now
proceed more particularly to set forth the system, mode or manner in or under
which the same is or may be used or practically carried into effect, reference being
had to the accompanying drawings and to the letters and Figures marked thereon
that is to say :-
Figure 1, is an elevation partly in section of mechanism for controlling the
motion of carbons in an arc lamp constructed according to and constituting part of
our present Invention.
Figure 2, is a plan of the same.
Figure 3, is a plan of a modified form of mechanism for attaining the same
results, with the carbous and their carriers omitted.
Figure 4, is a vertical section taken on line A, B, Figure 3.

page_text: Figure 5, is a side elevation of a current meter constructed according to and
constituting another part of our present Invention.
Figures 6, and 7, are respectively front and end elevations of a coil constructed
as an alternative of a part of the before mentioned mechanism.
Figures 8, 9, and 10, are respectively plan, end elevation and side elevation of a
potential galvanometer constructed according to and constituting another part of
our present Invention.
Figure 11, is a diagramatic view of a modified form of a commutating apparatus
for the potential galvanometer last referred to above constructed according to and
.constituting part of our present Invention.
The lamp represented at Figures 1, and 2, Sheets 1, and 2, is suitable for being
used with strong currents of electricity and is regulated by the electro magnetic
action between the currents flowing along a radius of each of two (as shewn) or
more metallic discs a, and a properly situated permanent or (as shewn) an electro
magnet b, and as hereinafter more fully described. The discs a, are mounted on
the same axis c, as or an axis geared with that of the hollow drum d, (hereinafter
more particularly described with reference to Figure 5, of the accompanying
drawings) and the discs have their planes parallel. The current is sent into the
discs e, either by causing their lower edges to dip into cups of mercury e, or by
means of brushes properly arranged to make contact on the edges of the discs a,
and are connected together metallically at their centres by their axis c.-To
prevent the current spreading in the discs a, they may be cut into segments in the
manner shewn at Figures 1, and 5; the whole of these segments remaining con-
nected at the centre. The electro-magnet b, is made in three pieces (as shewn
more particularly at Figure 2) connected together at one end so as to form a
compound magnet, consisting of three straight flat electro magnets with soft iron
cores set with their planes parallel and with their cores fixed at one end to a
common end plate of iron. The coils of these magnets are so joined in circuit
that the polarity induced by the current in the two side magnets, is of the opposite
name to that of the central magnet. They are of the same length and have pole
pieces f, at their extremities made so as to give two pairs of opposing faces parallel
to the planes of the magnets b, and sufficiently far apart to allow the discs a, to be
introduced freely between them.-The magnets are made sufficiently broad to give
pole faces long enough to cover nearly all the available radial space in the discs a,
in which the current is at any time Howing.-The discs a, are placed between the
opposing faces of the magnets b, in such a manner that the vertical radius joining
the mercury cup e, and the centre of the disc a, is parallel to a plane which may
bisect the pair of pole faces along their lengths. The magnet b, can be moved,
that is to say drawn to a greater distance from the radius of the disc in which the
current is flowing until the plane through its poles is at such distance from the
vertical radius of the disc a, as to give the requisite force.-We may suppose the
current from the generator to pass by one of the cups of mercury e, from one of
the terminals of the generator to the disc a, then along a radial space in that disc
to the centre and to the other disc along the axis c, along the other disc a, to the
second cup of mercury e, then to pass to the electro magnet coils, thence through
the lamp carbons g, and h, to the other terminals of the generator or otherwise so
that the whole or a convenient portion of the current may pass through the electro-
magnet coils, discs, and carbons.-In order that the lamp may be used with other
lamps in circuit, a high resistance coil is wound round the outside of the electro-
magnet coils, which is joined up so as to act as a shunt on the arc.
The electro-magnetic action between the magnetic field and the current in the
discs a, causes them to turn round until the turning couple is balanced by the
opposite couple due to difference of levels of the liquid i, in the two sides of the
hollow drum d, and the resultant couple given by the carbons and their holders j,
and k. This drum is shewn in Figure 1, Sheet 1-The hollow space l, in it, is the
annular space between two coaxial cylinders m, and d.-This space is divided into

page_text: compartments by partitions o, all inclined at the same angle to the radius as shewn
and each partition is pierced at its outer end with a small orifice p.
In consequence of this difference of levels, the liquid flows through the orifices p,
in the partition o, of the drum d, and the discs a, turn round slowly in obedience
5 to the resultant of the electro-magnetic and gravitational action. The electro-
magnetic action tends in the first place to separate the carbons g, and h, until this
action is counterbalanced by the gravitation of the carbon holders j, and k, and
carbons g, and h, while the drum d, prevents any great sudden change in the
Jength of the arc from taking place; thus insuring steadiness of the light. At the
same time, if by any accident the current ceases to flow, the difference of the
weight of the carbons g, and h, and their holders j, and k, is sufficient to turn
the drum d, so as to close the arc. To facilitate rapid adjustment of the arc we
may in some cases use an electro-magnet placed immediately above the upper
carbon holder j, and moved up and down along with it.-A convenient arrange-
ment for such a magnet is to make half the soft iron core of the magnet coil fast
within the upper half of the coil and to attach the other half of the core to the
carbon holder j, the whole to be so adjusted that when the current passes, the
carbon holder is suddenly lifted through a fixed distance and held there until
the current ceases to pass, when it is again lowered.
In connection with this drum we may use as an alternative of the discs a,
herein before described, any other convenient form of electro-motor such for
example as a small ring of the form known as the Gramme ring as shewn at
Figures 3, and 4, of the accompanying drawings. The Gramme ring G, is rotated
with sufficient speed by a wheel q, and pinion r, similar to that herein before
described with reference to Figures 1, and 2, of the accompanying drawings, or by
a train of wheels, between the poles 8, and t, of the electro-magnet, which is excited
by the current passed into the Gramme ring by the brushes u.- -The working of
this modification is in all other respects similar to the mechanism herein before
described with reference to Figures 1, and 2, of the accompanying drawings.
The instrument, which we call a current meter and that which we call an energy
meter, consists in its elementary form of one or more pairs of discs similar to those
described above with reference to Figures 1, and 2, Sheets 1, and 2, in connection
with an Electric lamp.-These discs of each pair are connected together at their
outer edges either by a metallic cylinder rolling on the edges of the discs or the
edges of the discs may dip into cups of mercury which are in metallic connection,
or each disc may be made up of sections insulated from one another and each pair
of corresponding sections in the two discs connected together by means of strips of
metal fixed to their outer ends.
The magnetic field by the action of which on the current in the discs, they are
made to revolve, is produced by means of a suitable coil of wire or in the case of
the current meter copper strip placed round the discs with its plane at right angles
to their plane in the most suitable position for producing the necessary turning
couple. Such an arrangement is adapted for application to the measurement of
very powerful currents.
In order to obtain greater power than is possible by the use of the arrangement
above described we use in the current meter a modification of the above arrange-
ment in which the magnetic field is produced by a permanent magnet as shewn in
Figure 5, Sheet 3.-The disc a, is shewn cut into sectors by slits, these slits being
closed at the edge of the disc with insulating material and the whole turned
smooth. As in the case of the lamp herein before described the disc is shewn
dipping a short distance into a cup of mercury.-By means of the permanent
magnet a much more intense magnetic field can be obtained at the sector of the
disc in which the current is flowing at any instant.-The discs are turned by electro-
magnetic action between the magnetic field and the current, and are controlled by
the drum d, as herein before described. This arrangement is fitted with any
counting apparatus adapted to register according to the flow of the liquid through
he orifices in the partitions of the drum d.

page_text: In order to virtually multiply to any extent in a convenient manner the number
of pairs of discs, we use the arrangement (represented on a reduced scale at
Figures 6, and 7, which are detached views of this particular part of the mechanism)
and in which the electrical action is precisely the same. A drum is made of wood
or some other insulating material or of metal covered if necessary with insulating 5
material. Wound round, this drum are coils v, of wire or copper strip the medial
plane of each of which is radial and passes through the axis w, of the drum.
The ends of the wire forming each coil are connected to commutator bars x, placed
parallel to the axis w, of the drum on a cylindrical surface of small radius coaxial
with the drum.-The cylinder carries a sufficient number of these coils v, sym- 1
metrically arranged round the drum to give an action nearly enough constant and
continuous for our purpose."
The electro-magnetic action on the current in the coils v, of the drum by which
a couple tending to rotate the drum is given, is produced by one or more stationary
coils y, of wire or copper strip placed round outside the drum so that the plane of
this coil or coils y, is always nearly in the most advantageous position for acting
on the current in the coil or coils y, on the drum, which are in circuit at any
time.
In the current meter the stationary coil or coils y, and the coils v, on the drum
are to be made of thick copper wire or copper strip so as to have a low electrical
resistance.
In the current meter the whole or a known fraction of the current passes through
the stationary coil or coils and thence by means of the mercury cups or other
metallic contacts such as those hereinbeforé described, through the coil on the
drum, the ends of which are in contact with the mercury or with the contact
rollers 2.
In this instrument whether movable discs or coils wound on a movable drum
are employed, we may use for producing the. necessary magnetic field at the discs
or coils, an electro-magnet or electro magnets, through the coils of which the whole
or a known portion of the current to be measured, flows.-These electro-magnets
have cores of soft iron of sufficient magnitude to render the magnetization within
necessary limits proportional to the current in their coils.
In this instrument when fixed and movable coils are used the total quantity of
electricity which has flowed through it in any time, is nearly in simple proportion
to the total angle through which the drum has turned in that time, hence a simple
counting apparatus suffices to measure the total quantity of electricity in Coulombs,
or other unit adopted.
The Instrument herein before described, when fitted with fixed coils, and movable
discs or coils, is suitable for the measurement of either continuous or alternating
currents.
In the Instrument which we call an energy meter either stationary coil or
coils y, or a coil or coils v, (of a similar form to those shewn in connection with
our current meter in Figures 5, 6, and 7, Sheet 3), ou the drum (preferably the
former), are to have a high resistance say over Five thousand olims, but it is
essential that either one or other of the two sets of coils should be of low resistance
and the other set of high resistance.
In both the current and energy meters the currents may be sent through the
coils on the drum by making the commutator x, Figures 6 and 7, to roll on
friction rollers 2, of good conducting material, the axles a', of the rollers z, being
placed in metallic connection with the circuit in any convenient manner, the guide
rollers b', being insulated; or the ends of the commutator bars, at each end of the
drum may be bent out from the cylinder in which the bars x, are placed so as all
to project radially in a plane at right angles to the axis of that cylinder.-The
spaces between the bars are filled with insulating material and the whole turned in
a lathe so as to form a smooth flange. The lower edge of each flange thus formed
is made to dip into a cup of mercury.
In the energy meter the whole or a known fraction of the current is made to pass

page_text: through the low resistance coil while the ends of the high resistance coil or coils
provided in the place of one of the sets of coils in the drawing, Figure 6, and 7,
Sheet 3, are in metallic connection with two points in the external circuit of the
generator. The current in this high resistance coil having a certain relation to the
difference of potential between these two points and the current in the movable
low resistance coil being either the whole or a known fraction of the current
Blowing in the circuit, the couple turning the drum at any instant bears a certain
relation to the rate at which energy is being given out in the external circuit
between these two points. With a counting apparatus, the total quantity of energy
given out in any time may be determined.
We may use in this Instrument when it is employed for measuring the energy
given out in the external circuit of a generator the difference of potentials between
the poles of which is nearly constant instead of the fixed high resistance coil above
referred to, a high resistance coil wound round a core of soft iron for producing
the magnetic field tending to turn the drum. This forms an electro-magnet which
is placed relatively to the movable coils, in a similar position to that of the
permanent magnets hereinbefore referred to with reference to the current meter.
The hollow drum d, shewn in Figure 5 Sheet 3, in connection with one form of
our Current meter, having internal partitions, and containing liquid all as hereinafter
described is used in the form there shewn or in a modified form for regulating an
Electric Lamp and the different forms of current and energy meters hereinbefore
described. When used with the current meter or the energy meters, it is mounted
on the same axis c, as.the discs or the drum carrying coils, or on a separate axis
geared to the axis of the discs or of the drum carrying coils, by suitable wheelwork;
or this drum d, may be suspended from the axle of the discs a, or of the drum
carrying the coils v, or from an axle in gear with the axle of the discs or drum
carrying the coils it by a cord or cords passing round the hollow drum d, or round.
pulleys fixed to the axis of this drum d.
-
The drum d, used in the current meter and in the energy meter is like the drum
hereinbefore described except that the central cylinder m, is or may be greatly
reduced or may be omitted altogether, thus giving the whole cylinder for the hollow
space.
When the current is caused to flow in the coils of any one of the arrangements
above described, the drum carrying the coils is turned round until the turning
couple is balanced by an equal and opposite couple produced by the liquid in the
hollow drum d.
The liquid then flowing through the orifices p, in the partitions o, allows the
drum to turn round at a rate which at each instant bears a certain relation to the
difference of levels of the liquid on the two sides of the drum, and therefore having
a certain relation to the electro-magnetic action between the coils v, on the drum
and the stationary coil or coils y.
:
1
For measuring the difference of electric potentials producing currents through
our lamp circuit or for testing our current meter or for the measurement of
differences of electric potentials generally, we use a high resistance galvanometer
represented at Figures 8, 9, and 10, Sheet 1, which consists of a coil or coils of
insulated wire, made up as hereinafter described, with a magnetic needle c',
suspended or pivoted at its centre and carrying a light index d', free to turn in a
horizontal plane over a scale e', on which the position of the index at any instant
can be observed. The coil f¹, is made up of. a compound wire formed by, twisting
in a regular manner the requisite number of single insulated wires into a, cable.-.
The wires forming the strands of this cable are then to be connected to the
plates g, and h, in the following manner;--the outside end of a separate wire to
each of the plates marked 1, in the row h¹, the inside ends of the same wires to
the plates marked 1, in the row g¹, next the outside end of a separate wire is
connected to each of the plates marked 2, in row h¹, the, inside ends of these wires
to the outside ends of other two wires and the inside ends of these to the plates.
marked 2,.in row g¹, thus forming two groups of two in series. In a precisely

page_text: similar manner two groups of four each are connected to the plates marked 4, in
the rows h¹, and y¹, and so on for any number of pairs of groups, each pair of
groups consisting of a greater number of wires than that preceding. In the above
description each pair of groups after the first, consists of double the number of
wires of that which immediately precedes, but any other ratio which is convenient
for the purpose in view may be taken.-The whole of these groups may be put in
series by connecting the plates in row h¹, with the respectively opposite plates in
row g¹, and this gives the greatest sensibility.-Any pair of groups may be made
to have no electro-magnetic effect upon the needle by connecting the two plates in
row g, belonging to that group together and the right hand plate in row h',
belonging to that group with the left hand plate in the same row, belonging to the
next group.
Another method of making the connection is shewn in diagram in Figure 11,
Sheet 3. In this case the ends of each group are connected to two plates or
springs, fixed to the side of a plug j', and these plugs metallically connected to
each other by means of springs or plates k¹.-By turning any plug j', the group
attached to it has its electro-magnetic effect on the magnetic needle reversed. A
proper stop arrangement is made in this case to prevent the plug making more than
about one-half turn in either direction.
The range of sensibility of the instrument may be increased by placing another
coil of low resistance of a smaller number of turns on the same bobbin, the ratio of
the sensibility of the instrument when this coil acts alone to the sensibility
thereof when any one of the other coils acts, is determined experimentally. This
coil may be made of so low a resistance that it can, without materially altering
the total resistance be left out of circuit when the compound wire is being used.
Having now described and particularly ascertained the nature of our said
Improvements and the system, mode or manner in or under which the said
Improvements are carried out in Electrical apparatus we would observe in con-
clusion that we do not limit ourselves to the precise details hereinbefore described
and shewn upon the accompanying Drawings as the same may be varied without
departing from the essential features of our Improvements and in particular we
would point out that in the apparatus for measuring currents and energy it is not
essential that the drum d, be used, as any mechanically equivalent apparatus may
be substituted therefor, but what we do consider to be novel and original and
therefore claim as the Improvements secured to us by the hereinbefore in part
recited Letters Patent is :-
1
First. The combination with a motor of a hollow regulating drum divided into
compartments by partitions pierced by orifices and containing liquid for separating
and regulating the motion towards one another of the carbons in an electric lamp,
substantially as herein before described.
Second. The application in apparatus of the character herein set forth of a
hollow cylinder divided into compartments by partitions which are pierced by
orifices and containing liquid for the purpose of producing a slow rotatory motion
bearing a nearly constant relation to the motive force or turning couple substantially
as hereinbefore described.
Third The combination of the before mentioned divided drum with an arrange-
ment of discs and coils or of movable coils and fixed coils, or of discs or coils and
magnets for the measurement of the quantity of electricity which has passed
through an electric circuit in an interval of time substantially as herein before
described.
Fourth. The combination of the before mentioned drum with a system of
movable discs or coils and fixed coils of high resistance with or without soft iron
cores also with movable coils of high resistance and fixed coils of low resistance
with or without soft iron cores for the measurement of the amount of energy given
out in an electric circuit in any given time substantially as herein before
described
Fifth. The construction of a galvanometer for the measurement of electric

page_text: potentials wherein the coil is formed of a cable of wires regularly twisted together
so that an electric current passing through any one strand of the cable, will produce
practically the same effect that the same current would produce when passed
through any other strand and so that the sensibility of the instrument may be
varied as required, while the electrical resistance of the coil of the instrument is
maintained constant substantially as herein before described.
In witness whereof, We the said Andrew Gray and Thomas Gray have
hereunto set our hands and seals this Eighteenth day of January, in the
year of Our Lord One thousand eight hundred and eighty three.
TY