Improvements in Electricity Meters.
Year: 1896

page_text: Date of Application, 5th Feb., 1896
Complete Specification Left, 4th Nov., 1896-Accepted. 9th Jan.. 1897
PROVISIONAL SPECIFICATION.
Improvements in Electricity Meters.
I, GEORGE HOOKнAм, of 7 and 8 New Bartholomew Street, in the City of
Birmingham, Manufacturer, do hereby declare the nature of this invention to be
as follows:-
My invention relates to electricity meters for continuous and alternating
currents, and my object is to greatly increase the driving force actuating such
meters, and so to improve the accuracy and range of the meters while at the same
time simplifying the mechanical construction and arrangement.
The first part of my invention relates to continuous current meters of the kind
in which a motor armature is entirely immersed in mercury, and the separate
brake rotates between the poles of a permanent magnet and acts by the generation
of Foncault currents. This part of my invention consists; In a new mode of
arranging the permanent magnet circuit in such manner as to minimise the number
of air breaks in the circuit; in allowing a current to flow straight across the disc
when a disc is used by providing pole-pieces of opposing polarity on the opposite
sides of the disc; in arranging the brake magnets ou "parallel" with the motor
magnets instead of in series; in constructing the disc armature of the motor with
radial slits for the purpose of limiting the area of flow of current across the disc,
and of diminishing Foucault currents in the motor discs; in a new arrangement
of Foucault brake and the magnets operating that brake; and in the combination
of the points indicated to form a powerful and accurate continuous current meter.
The second part of my invention relates to alternating current meters in which
the motor part consists of a rotating disc or other body rotated by the inter-
action of currents caused in the disc by an electro-magnet operated by a shunt
from the alternating current to be metered, and series currents passing through
coils placed close to the disc. The brake action is obtained by means of a
permanent magnet and Foucault currents, and my invention consists; In winding
the series coils round the poles of the shunt magnet, and so permitting the said
poles to lie very close to the surface of the disc; in so shaping the ends of the
poles as to produce a long driving line or driving lines upon the disc; in rounding
the edges of the shunt magnet poles referred to so as to minimise the production of
Foucault currents at the driving part of the disc, without substantially altering
the driving force produced by the interaction of the shunt magnet current and the
series current; in correcting for the error introduced at high loads tending to
defect of registration by short circuiting the series current by means of a wire of
some pure metal such as copper or silver; in arranging the brake magnet with a
bye-pass to produce stray field chiefly by bringing the arms of the magnet close
together, and sometimes by using the cast iron base of the meter for the purpose
of dispersing the magnet field; and in the combination of the various points
herein described to produce an accurate and effective meter.
In constructing a continuous current meter by one method of carrying my
invention into effect, I arrange my permanent magnet to enclose a square or
oblong space so as to provide a considerable length of inaguet steel.
The permanent magnet is bent to form a square and a gap is left between the
opposing poles, this gap coming on the under-side of the square, which square is
lgoed vertically
A

page_text: . On the lower sides of the ends of the magnet I mount suitable pole-picces projecting
downwards. These pole-pieces spread out considerably and form in exterior
outline an arc of a circle. Each pole piece forms on its exterior surface an are of
about a quarter circle, and the same circle is struck to include the exterior edges
of both pole pieces. The interior edges of the pole pieces are shaped convex
inwardly, with a circular recess in the middle, and the edges of the lower surface
are gently rounded. Sharp edges are in fact avoided as much as possible in order
to minimise the generation of Foucault brake currents in the rotating disc.
Under the magnet poles I place a bridge-shaped cast iron bar terminating in
pole pieces similar to those described, and having the faces rounded just as
described. Between this bridge piece and the upper poles I place a dise armature
which rotates on a vertically disposed spindle. The whole of this armature and
the magnets described enclose in a vessel sometimes formed as to its circum-
ference of a glass tube and I fill this vessel with mercury.
I preferably form the armature disc of copper, and cut slits in a radial direction
towards the centre all round the circumference, leaving a sufficient part of copper
in the centre of the disc uncut. These slits I fill with any suitable non-conducting
composition and I cover both faces of the disc with non-conducting composition
leaving only the periphery of the disc free from non-conducting compound. This
periphery amalgamate-so as to get good metallic contact between the periphery
and the mercury bath in which the disc is immersed.
Above the motor pole pieces and also attached to the ends of the steel magnet I
place circular brake pole pieces which are necked to a suitable extent. Opposing
these pole pieces I arrange a cast iron or other iron bridge piece whose ends form
pole pieces corresponding in configuration to those below. In the space between I
rotate the brake disc, which may he of copper or other good conducting metal,
and I preferably mount it upon the same vertical spindle as carries the motor
:armature.
The edges of the brake pole pieces are purposely kept as sharp as possible; or,
if necessary, grooved to produce the maximum Foucault current effects in the
. brake disc. The brake pole pieces are necked to an extent sufficient to bring the
ends near magnetic saturation, so that in the event of the magnet losing power,
: the brake pole piece does not lose in the same proportion.
The vertical spindle carrying the motor dise and the brake disc is attached at its
upper part to registering wheels and dials of any usual construction. Although
I prefer, when possible, to make the brake dise of sufficient diameter to give power
enough when directly connected to the spindle, yet I sometimes mount the brake
disc on a separate spindle and gear it to the motor spindle, so that the brake disc
makes several revolutions for one revolution made by the motor spindle. By this
device I am enabled to run the motor disc or motor armature at a slow speed, and
the brake disc at a high speed.
Within the mercury, and in line with the pole pieces, I place conducting strips
as close as possible, without touching, to the periphery of the motor disc. To
these pieces I connect the wires carrying the current to be metered. The current
passes from one of these pieces through the mercury into the edge of the disc, and
it is confined in its course by the slits cut in the disc, so that it passes almost
straight across the dise through the other edge into the opposing piece. That is
the current instead of passing from the circumference of the brake disc to the
.centre and out at the centre, passes right across the disc from one side to the other,
that is twice across the radius. By this device I am enabled to increase the
diameter of the motor armature to a very considerable extent, without diminishing
the driving force, and by applying my driving force at a greater diameter, and
utilizing the poles of opposite polarities at each side of the diar, while also
limiting the area effected by the magnet poles, I am enabled to greatly increase
the torque of the notor disc. In an arrangement such as this for example I may
double the intensity of the magnet field by re-arranging the magnet circuit as
described, and 1 also double the radius and double the effect by causing the current

page_text: to flow twice across the radius. In this way for a given current it is possible for
me to give eight times the driving force to the motor disc as compared with present:
meters minus, however, a small escape of current due to part of the current flowing
through the mercury, and round by the sides of the disc instead of straight across.
In this continuous current meter I thus cause the current to flow twice across
the radius, I double the field by having opposite poles at the opposed sides of the
circumference, I limit the current to a path across the disc, by the cut armature,
and also reduce Foucault brake currents in the motor disc. I reduce the area of
the armature field and I reduce the air brake to half, and so increase the intensity.
of the field. I obtain my driving line at double the radius, and I arrange my
brake field pole pieces in parallel with the armature field pole pieces instead of in
series, and lastly, I shape my armature pole pieces so as to reduce Foucault
currents. In a meter constructed in this manner the constancy of brake field is
not so necessary as in other constructions, as in the event of fall in the magnetic
intensity of the permanent magnets, the intensity of the motor field also falls, and
by experiment I so arrange the necking down of the brake pole pieces that the
brake field falls off to a less extent than the motor field falls off. Roughly, so
that the brake field falls off at about a square root of the motor field falling off, or,
say half the percentage and so speed is rendered constant for any strength of
magnet field within wide limits. By this device I obtain a very narrow or flat
meter of small dimensions, giving great accuracy both for small and large
currents.
In this, as in other meters, the mercury friction requires to be compensated for
at high speeds, and I obtain compensation by winding a wire in series on a piece.
or part of the motor magnets.
In constructing an alternating current meter by one method of carrying my
invention into effect I arrange a rotating disc rotating on a vertical spindle, that is
the disc rotating in a horizontal plane. At one side I place an electro magnet
excited by a shunt wound bobbin fed by a shunt from the main current. This
electro magnet contains a cast iron or other iron core preferably laminated, and
bends over, terminating in pole pieces above and below the disc.
I preferably cause the terminating pole pieces to be forked both above and
below the dise, and I extend these pole pieces nearly across the radius of the disc,
that is 1 form the pole pieces to an oblong configuration, and bring them very'
close to the disc, as close as possible, without coming into actual contact with the
disc.
The pole pieces on the upper side of the disc I wind with series windings
forming two coils fairly close together. These series coils short-circuit by
means of a copper or silver wire of carefully regulated dimensions. At another
part of the disc I place the brake magnet, and this bruke magnet I arrange with
its ends or pole pieces as sharp as possible, so as to produce the maximum Foucault
current effect.
To obtain constancy in the braking effected I neck the lower pole piece of the
brake magnet, and make it as an adjustable screw.
When an alternating current is passed through the series coils of this meter, the
electro magnet is excited by the shunt current, and it produces currents in the disc
which currents inter-act with the currents produced in the series coils, and so drive
the motor disc in the manner discovered by Professor Ferraris.
By my construction of meter I obtain the electro-maguet poles very close to the
surface of the disc, and so I generate more intense induction currents in the disc,
and by my coils wound round the actual ends of the electro magnet, I obtain
alternating current coils very close to the disc and acting on a long line tending to
drive the disc.
By my construction I thus lengthen the driving line on the disc, reduce the air
space between the magnet pole pieces_und the disc, increase the area of the pole
pieces, and so strengthen the field. This I do by winding my series coils on the
pole pieces, instead of placing thein under the pole pieces as described in the

page_text: specification of a Patent already granted to me No. 20,384". I round the edges of
the pole pieces to reduce Foucault brake currents due to the series coils, but this
rounding does not affect the driving force materially. By short-circuiting the
series coils by a wire of pure metal, I reduce the current passing through the series
coils to a greater extent at low currents than at high currents, because the high
currents heat the short-circuiting wire, and by reducing its resistance, reduce the
proportional current passing at the higher currents. I thus correct for the braking
effect which increases with the higher alternating currents.
. I do not confine myself to the use of a single electro magnet with forked poles
but may use two or more magnets arranged with single poles.
Dated this 5th day of February 1896.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., Agents.
TION.
Improvements in Electricity Meters.
I, GEORGE HOOкнAм, of 7 and 8 New Bartholomew Street, in the City of
Birmingham, Manufacturer, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
My invention relates to electricity meters for continuous and alternating currents,
and my object is to greatly increase the driving force actuating such meters so as
to improve the accuracy and range of the meters while at the same time simplifying
the mechanical construction and arrangement.
The first part of my invention relates to continuous current meters of the kind
in which a motor armature is entirely immersed in mercury, and the separate
brake rotates between the poles of a permanent magnet, and acts by the generation
of Foucault currents.
This part of my invention consists in a new mode of arranging the permanent
magnet circuit in such manner as to minimise the number of air breaks in the
circuit; in allowing a current to flow straight across the disc, when a disc is used,
by providing pole-pieces of opposing polarity on the opposite sides of the disc; in
arranging the brake magnets in parallel with the motor magnets instead of in
series; in constructing the disc armature of the motor with radial slits for the
purpose of limiting the area of flow of current across the disc, and of diminishing
Foucault currents in the motor disc; in a new arrangement of Foucault brake and
the magnets operating the brake; and in the combination of the points indicated to
form a powerful and accurate continuous current meter.
The second part of my invention relates to alternating current meters in which
the motor part consists of a rotating disc or other body rotated by the inter-action
of currents caused in the disc by an electro-magnet operated by a shunt from the
alternating current to be metered, and series currents passing through coils placed
close to the disc.
The brake action is obtained by means of a permanent magnet and Foucault
currents, and my invention consists in winding the series coils round the poles of
the shunt magnet, and so permitting the said poles to lie very close to the surface
of the disc; in so shaping the ends of the poles as to produce a long driving line
or driving lines upon the disc; in rounding the edges of the shunt magnet poles
referred to so as to minimise the production of the Foucault currents at the driving
part of the disc, without substantially altering the driving force produced by the
interaction of the shunt current and the series current; in correcting for the error

page_text: introduced at high loads tending to defect of registration, by short circuiting the
Beries current by means of a wire of some pure metal such as copper or silver; and
in the combination of the various parts herein described to produce an accurate
and effective meter.
Referring to the accompanying sheets of drawings-
Figures 1 to 8 illustrate my invention as applied to a continuous current meter,
while
Figures 9 to 14 inclusive illustrate my invention as applied to an alternating
current meter.
Figure 1 is an external elevation;
Figure 2 is a vertical section;
Figure 3 is a sectional plan on the line a b Figure 2.
Figure 4 is an inverted plan and
Figure 5 is a side elevation both on a larger scale, showing the meter and brake
discs.
Figure 6 is another vertical section of the meter similar to Figure 2 but with
slight modifications of the magnet poles.
Figure 7 is an inverted plan of the magnets showing the pole pieces, and
Figure 8 is a plan of the inagnet pole pieces from above showing the magnetic
gap between the poles.
Figure 9 is a side elevation,
Figure 10 is an end elevation, and
Figure 11 is a plan.
Figures 12, 13 and 14 show clearly the polarities produced in the magaet poles
by the shunt and series currents.
In constructing a continuous current meter I arrange my permanent magnet A
to enclose a square or oblong space as shown at Figures 1 and 6 so as to provide
a considerable length of magnet steel.
The said permanent magnet is bent to form three sides of a square and pole
pieces a al complete the square leaving a suitable gap between the pole pieces which
1 fill in with non-magnetic metal so as to secure inetallic and structural continuity
but not magnetic continuity.
On the lower sides of the pole pieces a a¹ I sometimes mount additional pole
pieces e e as shown at Figure 6 which pole pieces project downwards and spread
out considerably to form in exterior outline au arc of a circle. Each such
additional pole piece forms on its exterior surface an arc of about a semi-circle,
and the same circle is struck to include the exterior edges of both pole pieces.
The are outline of the pole pieces e el is clearly shown in the inverted plan
Figure 7.
The interior edges of the pole pieces are shaped convex inwardly, with a circular
recess in the middle, and the edges of the lower surface are gently rounded.
Sharp edges are in fact avoided as much as possible in order to minimise the
generation of Foucault brake currents in the rotating disc.
In some cases I dispense with the downwardly projecting poles e e and utilize
the under surfaces of the main pole pieces a al to provide my magnetic field as
shown at Figures 1 and 2.
In all cases however under the magnet poles 1 place a bridge shaped cast iron or
other iron bar B Figures 1, 2 and 6 terminating in pole pieces b b similar to those
described and having its faces rounded as described. Between this bridge piece
and the upper poles place a disc arinature D which rotates on a vertically disposed
spindle F. The whole of this armature and the magnet poles described I enclose
in a vessel formed as to the part 1 of non-conducting material; sometimes I form
the circumferential part I of a glass tube in which case I modify the other
dispositions in a suitable manner. I may also use the upper and lower pole pieces
as is shown in the drawings to form part of the enclosing vessel.
I preferably form the armature disc D of copper and cut slits in a radial direction
towards the centre all round the circumference as shown on a larger scale at

page_text: Figure 4. leave however a sufficient part of copper in the centre of the disc
uncut. These slits I fill with any suitable non-conducting composition and I cover
both faces of the disc with non-conducting composition leaving only the periphery
of the disc free from non-conducting compound. This periphery I amalgamate so
as to get good metallic contact between the periphery and the mercury bath in which
the disc is iminersed.
Above the motor pole pieces a a¹ and attached to them in magnetic continuity L
place circular brake pole pieces c c c c', (Figures 1, 2, 3, 6 and 8) which are
necked in to a suitable extent. Opposing these pole pieces I arrange a cast iron or
other iron bridge piece C (Figures 1, 2, 3 and 6) whose ends d d form pole pieces
corresponding in configuration to those below. In the space between I rotate the
brake disc E, which may be of copper or other good conducting metal, and
I preferably mount it on the same vertical spindle F as carries the motor
armature D.
The edges of the brake pole picces are purposely kept as sharp as possible, or,
if necessary, grooved to produce the maximum Foucault current effects in the
brake disc. The brake pole pieces'c care necked to an extent sufficient to bring
the necks near magnetic saturation, so that' in the event of the magnet losing power,
the brake pole piece does not lose in the same proportion.
The vertical spindle F carrying the motor disc and the brake disc is attached
at its upper part to registering wheels and discs as O (Figure 1) of any asnal
construction.
Within the mercury, and near to the pole pieces but electrically insulated from
them, place conducting strips G Gas close as possible without touching, to the
periphery of the motor disc. To these pieces G GI connect the terminals HH
to which the wires carrying the main current to be metered are led by way of the
tubes H'H' which tubes pass through the base of the instrument. The current
passes from one of these pieces through the mercury into the edge of the motor
disc D, and it is confined in its course by the slits cut in the disc D, (slits shown at
Figure 4) so that it passes almost straight across the disc through the other edge
into the opposing piece G¹. That is, the current instead of passing from the
circumference of the brake disc to the centre and out at the centre as in former
meters, passes right across the disc from one side to the other, that is, twice across
the radius. By this device I am enabled to increase the diameter of the motor
armature to a very considerable extent, without diminishing the strength of the
field, and by applying my driving force at a greater diameter, and utilising the
poles of opposite polarities at each side of the disc, while also limiting the area
affected by the magnet poles, I am enabled to greatly increase the torque of the
motor disc. In an arrangement such as this for example I may double the intensity
of the magnet field by rearranging the magnet circuit as described, and I also
double the radius and double the effect by causing the current to flow twice across the
radius. In this way for a given current it is possible for me to give eight times
the driving force to the motor disc as compared with present meters, minus,
however, a small escape of current due to part of the current flowing through the
mercury and round by the sides of the disc instead of straight across.
In this continuous current meter I thus cause the current to flow twice across
the radius; double the field by having opposite poles at the opposed sides of the
circumference; I limit the current to a path across the disc, by the cut armature,
and also reduce Foucault brake currents in the motor disc; I reduce the area
of the armature field and I reduce the air break and at the same time greatly
increase the length of the magnet and so increase the intensity of the field. I
obtain my driving line at a longer radius, and I arrange my brake field pole pieces
in parallel with the armature field pole pieces instead of in series, and lastly I
shape my armature pole pieces so as to reduce Foucault currents.
In a meter constructed in this manner the constancy of brake field is not so
Decessary as in other constructions, as in the event of fall in the magnetic intensity
of the permanent magnets, the intensity of the motor field also falls, and by

page_text: experiment I su arrange the necking down of the brake pole pieces that the brake-
field falls off to a less extent than the motor field falls off. Roughly, so that the
brake field falls off at about the square root of the motor field falling off, or, say
half the percentage, and so speed is rendered constant for any strength of magnet.
field within wide limits.
By these devices I obtain a very narrow or flat meter of small dimensions, giving
great accuracy both for small and large currents.
In this, as in other meters, the mercury friction requires to be compensated for
at high speeds, and I obtain compensation by winding a wire in series on a piece.
or part of the motor or the brake magnets. Such a winding on the upper brake
bridge piece is shown at K, Figures 1 and 3. The connecting plates L and M
mounted adjustably on pillars rising from the main magnet pole pieces are
merely structural, and do not form part of the magnetic or electrical essentials of
the meter.
Although a disc armature and brake meter is hereinbefore described it is to be
understood that the invention may be readily carried into effect with armature
and brake of any other figure of revolution, such, for example, as a cylinder.
In constructing an alternating current meter I arrange a disc J rotating on a.
vertical spindle, that is, the disc rotating on a horizontal plane. At one side I place
an electro-magnet N excited by a shunt wound bobbin fed by a shunt from the
main current. This electro-magnet contains a cast iron or other iron core N¹
preferably laminated and bends over, terminating in pole pieces N' N' above and
below the disc. The terminating pole pieces N N are preferably forked both.
above and below the disc (see Figure 10) and I extend these pole pieces nearly
across the radius of the disc. That is, I form the pole pieces N N of an oblong
configuration, and bring them very close to the dise J as close as possible without
coming into actual contact with the disc.
The pole pieces on the upper side of the disc I wind with series windings P P¹
forming two coils fairly close together. These coils I sometimes short circuit by
means of a copper or silver wire of carefully regulated dimensions which I have
not shown upon the drawing. This I do when I desire to produce a meter which
is accurate within a very long range; for a moderate range of load, I do not.
require to do this.
At another part of the disc I place the brake magnet Q, and this brake magnet.
I arrange with its ends or pole pieces as sharp as possible, so as to produce the
maximum Foucault current effects. To obtain constancy in the braking effected
I neck the lower pole piece of the brake magnet, and make it as an adjustable
screw Qas seen more clearly at Figure 10.
When an alternating current is passed through the series coils of this meter P P1.
the electro-magnet is excited by the shunt current, and it produces currents in the
disc J which currents interact with the currents produced in the said series coils,.
and so drive the motor disc in the manner discovered by Professor Ferraris.
By my construction of meter I obtain the electro-ningnet poles N N' very close
to the surface of the disc, and so I generate more intense induction currents in the
disc J, and by my series coils P P wound round the actual ends of the electro-
magnet poles N', I obtain the alternating current coils very close to the disc and
acting on a long line tending to drive the disc.
By ny construction I thus lengthen what may be called the driving line on the
dise, reduce the air space between the magnet pole pieces and the dise, increase
the area of the pole pieces N N and so strengthen the field. All this follows
from my invention of winding the series coils P P on the pole pieces, instead of
placing them under the pole pieces between the ends of the pole pieces and the disc,.
which was the older construction.
I round the edges of the pole pieces N N³ as shown more clearly at n', n',
and n, n, of Figure 10 to reduce Foucault brake currents due to the series coils,
but this rounding does not affect the driving force materially. By short circuiting
the series coila P P by a wire of pure metal, I reduce the current passing through.

page_text: the said series coils to a greater extent at low currents than at high currents,
because the high currents heat the short circuiting wire, and by increasing its
resistance reduce the proportional current passing at the higher currents.
thus correct for the braking effect which increases with the higher alternating
currents.
Figures 12, 13 and 14 show clearly the polarities produced in the magnet pɔles
by the shunt and series currents.
[
Figure 12 is a diagrammatic side elevation of the magnet showing the shunt
coil N, the disc J and the pole pieces N' N³.
Figure 13 is a front view of the forked pole wound with series coils P P¹ and
having pole pieces N N opposed by lower pole pieces NN. This figure shows
the relative polarities when the alternating shunt current is affecting the coil N, in
this case the poles are as marked "upper North" and "lower South" N.S. or the
reverse as affected by the shunt current, upper poles are of the same kind and lower
poles of the opposite kind.
Figure 14 is a front view in every way the same as Figure 13, but the polarities
marked are there produced by the series coils P P. In this case when the left
hand pole Nis S the right hand pole N' is N, and then the lower left hand pule N
is N, while the right N³ is S. The series coils thus affect the polarities of the
forked pole pieces differently from the shunt coils. The shunt coil causes both
upper poles to be N or S and both lower to be the S or N, while the series coils
make the upper poles S and N and the lower opposing poles N and S each opposing
its opposite.
It is to be distinctly understood that the shunt and series currents are in
different phase so that the polarities rapidly succeed each other.
In the alternating current ineter I do not confine myself to the use of a single
electro-magnet with forked poles, but may use two or more magnets arranged with
single poles, nor in the continuous current meter do I limit myself to the case in
which the armature disc and brake disc rotate in separate fields. In the latter
case correction for fluid friction may be applied to the armature field in a manner
fully described by me in previous patents.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is ;-
(1.) In an electricity meter for continuous currents in which the motor armature
is immersed in mercury, the arrangement by which the passage of the current
takes place across the dise from side to side instead of from periphery to centre,
as in previous constructions, the magnetic poles being so dispused that the field is
twice cut by a radius of the disc in every revolution, each time in an opposite sense
to the last, substantially as hereinbefore set forth.
(2.) In an electricity meter for continuous currents in which the motor armature
is immersed in mercury and the armature disc and the brake disc do not rotate in
the same field arranging the brake magnetic pole pieces in parallel with the motor
magnetic pole pieces instead of in series substantially as hereinbefore set forth.
(3.) In an electricity meter for continuous currents in which the motor armature
is immersed in mercury in combination, the arrangement of the brake magnetic
pole pieces in parallel with the motor magnetic pole pieces instead of in series the
magnetic polarities at the opposite sides of the rotating armature being opposite
in kind; and the passage of the current across the armature from side to side
instead of from side to centre to increase the driving force, substantially as herein-
before described.
(4.) In an electricity meter as claimed in the preceding claim-constructing the
armature with slits the said armature being filled in at the slits, and coated on
both sides with non-conducting composition, only the periphery being left
.conducting to limit the path of the current across the disc, substantially as herein-
before described.

page_text: (5.) An electricity meter for continuous currents constructed substantially as
herein before described and illustrated at Figures 1 to 6 inclusive of the accom-
panying drawings.
(6.) In an alternating current meter in which the motor part consists of a
rotating disc or other body rotated by the interaction of currents caused in the
disc by a shunt electro-magnet and series coils placed close to the disc, winding
the series coils round the poles of the shunt magnet as herein set forth.
(7.) In an alternating current meter in which the series coils are wound round
the poles of the shunt electro-magnet as claimed in the sixth claim-shaping the
shunt magnet poles so as to produce a long driving line or driving lines upon the
disc as by making them oblong with the long axis arranged approximately radially
as herein set forth.
(8.) In an alternating current meter in which the series coils are wound round
the poles of the shunt electro-magnet, and the shunt magnet poles are shaped to
produce a long driving line or lines as claimed in Claim 7 rounding the edges of
the magnet poles to reduce the Foucault currents produced in the disc by the
series coils as herein set forth.
(9.) In alternating current meters constructed as claimed in Claims 6, 7, and 8;
short circuiting the series coils by a fine wire of copper or silver to reduce the
current passing at low loads to a greater extent than at high loads so as relatively
to increase the speed of the meter at high loads as herein set forth.
(10.) In an alternating current meter in which the series coils are wound round
the poles of the shunt electro-magnet as claimed in the sixth claim, forming the
shunt magnet poles with forked ends which produce a long driving line or lines
upon the motor disc without requiring an increase of the diameter of the said disc
as berein set forth.
(11.) An alternating current meter constructed substantially as herein before
described and illustrated at Figures 9 to 14 inclusive of the accompanying
drawing.
Dated this 4th of N
1000
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.