APPARATUS FOR GENERATING PROVISIONAL SPECIFICATION
Year: 1883

page_text: LETTERS PATENT to Sir William Thomson, Knight, of Glasgow College,
Doctor of Laws and Professor of Natural Philosophy in the University and
College of Glasgow in the County of Lanark, North Britain, for an Invention
of "APPARATUS FOR
GENERATING
PROVISIONAL SPECIFICATION left by the said Sir William Thomson at
the Office of the Commissioners of Patents on the 28th September 1883.
Sir WILLIAM THOMSON Knight, of Glasgow College, Doctor of Laws and
Professor of Natural Philosophy in the University and College of Glasgow, in the
County of Lanark, North Britain, "APPARATUS FOR GENERATING, REGULATING,
MEASURING, RECORDING AND INTEGRATING ELECTRIC CURRENTS,"
This Invention relates to Improved apparatus for generating, regulating,
measuring, recording and integrating electric currents.
With respect to the improved apparatus for generating electric currents for
dynamos such as those of Siemens, Gramme, Siemens-Alteneck and others having
a soft iron armature core in the shape of a figure of revolution, 1 use fine soft iron
wires of square section wound continuously and spirally but as nearly as may be in
coaxal circles, with the successive strands mutually insulated by strong thin paper
riband, and with the neighbouring circles kept from contact by a very fine knife, or
by a circular edge of thin sheet metal or paper during the winding, and if need be
prevented from afterwards coming into contact by the insertion of solid distance
pieces, or by a solidifying cement, such as Plaster of Paris, or putty pressed in
when still plastic.
For the toroidal helix of a Pacinotti, or Gramme ring, I use square or rectangular
copper wire, wound in one or other of two ways; or in suitable intermediate
combinations, according as high potential and small current, or comparatively low
potential and strong current, is to be produced.

page_text: For a high potential dynamo, before winding on the wire I cut it into proper
lengths for the separate double coils hereinafter described, and I wind each length,
beginning from its two ends, on two flat bobbins each containing nearly all of the
half length in one plane.-The ends of the wire must be well enough secured, by
bending them into holes in the bobbin cores, to allow the wire to be laid in its
place in the armature, under a strong pull direct from the bobbin.—Suitable
bobbins of strong thin riband paper, of about the same breadth as the diameter of
the wire, are prepared to be wound on between the successive turns of the wire.
To commence the winding, the soft iron toroidal core, coated with insulating
material, is held securely fixed by clamps conveniently placed not to impede the
process. A pair of the wire bobbins is taken, and the wire between them is
stretched tightly across the inner rim of the soft iron toroid with a few degrees of
obliquity. One of the bobbins is then clamped or held tightly by hand while the
winding is commenced from the other. The winding from each bobbin of wire is
to be performed altogether in one plane, and simultaneously with it a riband of
paper is to be wound between its turns from one of the prepared bobbins of
paper. The interior bed for the wire is smoothed by a very acute little wedge
of wood, cut obliquely and placed so as to receive the wire, where it begins to
leave the core near the end of the first turn to mount on the initial oblique portion
of wire and begin the second turn.-A plane guiding check of metal is fixed
temporarily to the core in proper position for the first coil and the wire in being
wound on, is pressed firmly against it.-The winding may be done simply by hand
but I prefer to do it by an apparatus which I have designed for the purpose, in
which the bobbin is pivoted on a crank pin, and carried round with the leverage
afforded by a handle projecting as far beyond the crank pin as is consistent with-its
being carried round inside the aperture of the toroid.-The crank turns round a
collar temporarily placed on the toroid beside the place where the coil is to be
wound on. The turning of the bobbin on the crank pin is resisted by a great force
of friction, or the crank pin and lever may be held fixed, while the toroid,
temporarily supported on bearings, is turning round an axis, tangential to its
circular axis. When the first coil is completed, its outer end is secured from
motion relatively to the ring by lashing. The plane face of the coil next which
the second coil is to be wound, is then coated with strong fine paper or with thin
mica, and a removeable distance-piece of exceedingly thin sheet metal is placed
against the outer half of the face, to prepare nearly enough a plane in the proper
direction, to receive one face of the second coil.-The second coil is then wound on
as was the first but contrary wards, and its outer end lashed securely.-The free
face of the second coil is then coated with fine paper or mica, and the proper plane
for the third coil is made up by a metal distance-piece. The third and fourth coils
are then wound on by a similar process; and so on by a repetition of similar
processes until the whole ring is covered; the clamps holding the armature being
shifted from time to time, to hold it firmly without impeding the winding-The
original guiding check might be removed safely, when the first six or eight coils
are on; but it may be left in position until the covering is so nearly completed
that the completion of the winding comes to be impeded by it.-The circumference
of the ring must be accurately divided into equal parts beforehand, and the exact
position for each coil marked, so that the covering when completed may be quite
uniform. When the winding of the coils is completed, the metal distance pieces
must be removed, and fine silk thread wound round and round through the
aperture of the ring, and into the wedge-shaped spaces, left vacant by the removal
of the distance-pieces. After this is done the outer ends of the coils are to be
unlashed, and, while still kept as much as possible under tension, are to be securely
soldered or brazed together in order.
For large current and comparatively small potential, I place the square copper
wire on the core in successive layers; each forming a closed toroidal helix with its
ends soldered together. After having made the first layer close to the core, I coat
it with very thin paper, and wind on the second layer over it; the wire of the

page_text: second layer resting on the wire of the first, and not across the spaces between the
wire of the first, and so on with successive layers.-The whole number of layers
may for example be four or five or six.-I prevent contacts between the consecutive
turns of cach layer, by distance-pieces of paper or mica at the inner circumference
of the toroid where they are closest, and by putty or other solidifying cement
elsewhere. I arrange the solderings at places on the toroidal beds of the successive
layers, nearest to points at equal distances on the inner circumference of the toroid.
The winding, now described, greatly diminishes the induction of local currents,
which would take place in a single conductor of cross-sectional area, equal to the
sum of the areas of the several helices which by my arrangement are joined to act
in parallels, with very little loss of space by insulating material.-The winding
has also the advantage of avoiding the difficulty of bending such a heavy single
conductor, as would be equal to the compound helix.
For the number of commutator bars, I choose a multiple of the number of layers,
in order that the mechanical connection between the ends of each layer, may be
secured by the additional soldering hereinafter described. I cut away a little of
each of the paper coatings, so as to uncover a short length of the wire below it,
at each point of its length nearest to a point of attachment of an electrode leading
inwards to the commutator bars.-The joined ends of the several layers are placed
at an equi-distant set of these points.-The wire of each layer is soldered to the
wire of the layer below, over a short length of each of the bared places.-I make
the electrodes, which lead to the commutator bars, of thick sheet copper cut concave
to fit over a convenient length of the outermost layer of the compound toroidal
helix, to which it is soldered.-These plates when fixed in their places lie approxi-
mately in planes projecting inwards towards the axis of the armature.-I make
their inner edges straight and parallel to the axis and I border them with stout
copper pins for making the connections with the ends of the commutator bars.―
When very large collecting surface is desired, I make each commutator bar double
with holes or hollows in the ends of its two halves next one another which ara
placed on, or in connection with the pins projecting from the inner edges of the
plate electrodes herein before described, and secured by solder.-The ends of the
commutator bars are held securely fixed by metal rims from which they are insulated
electrically, by woody fibre or other suitable strong solid insulator.-When so great
a collecting surface is not required, I connect and secure in position in the manner
herein before described, the inner and outer ends of a single set of commutator bars
placed as usual on a cylinder.
I attach the arinature to the axle which is to bear it, by two discs of gun-metal
with bevelled rims, bolted firmly together so as to clamp it by pressing obliquely
inwards and outwards against it, according to lines of pressure lying in conical
surfaces at angles for example, of between 10° and 30° to the axis. The bevel
surfaces are insulated from the helix of the armature by woody insulite or other
strong enough insulator.-The discs may be slotted radially to check the induction
of local currents in them.-The pins for the inner connections of the commutator
bars project through holes made for them in the gun-metal discs.
I support the collecting brushes on a single brush frame, whether the commutator
bars are single or double.-This brush frame I support by a collar or collars on the
turning axle, or else on pivots fine enough to let it turn easily in either direction,
and I apply a stop to prevent it from being carried round by the friction and
hesion between the commutator bars and the brushes., I place counter stops on
the brush holders so that in the event of the machine being accidentally or
intentionally turned backwards at any time, they shall lift the brushes off the
commutator bars in the act of checking the backward motion, which the brush
frame takes with the rest of the machine, and so save the brushes from damage.-
Or I divide the brush into separate parts mutually insulated each contributing a
conducting are to the main electrode. Each of these conducting arcs is arranged
to break circuit, except through a parallel arc of comparatively high resistance,
through which the current is allowed to flow when it is in the wrong direction.―

page_text: An electro-motive force produced by this secondary are or ares, remakes the circuit
through the larger conducting are by means of an automatic make-break similar
to that described in tny Specification N° 3032, A.D. 1881, when the current is in
the right direction.-When the machine is to work in either direction with two
sets of brushes suited respectively to the two directions, I arrange the stops and
counter stops so as to take one set of brushes off contact of the commutator bars
at the right time to prevent it from damage; and to bring the other set into
contact automatically if the reverse motion of the armature is continued. I alter
by hand or automatically the position of the stop or stops from time to time
according to the varying strength of the current in the use of the machine, so
that the brush frame shall take the position suited to minimize heating in the
contacts, and in short circuited portions of the helix-For this purpose I attach
a pair of small brushes, insulated from the rest of the circuit, to the brush frame,
in such positions as to touch the commutator bars on the two sides of the middle
of the contact area of one of the main brushes.-These brushes are put in circuit
with an indicating galvanometer or electro-magnetic controller.-When the galvano-
meter needle is been to be deflected to one side or other, the brush frame is shifted
by hand in one direction or the other until the needle is brought to zero; or the
same result is obtained automatically by an electro-magnetic controller acting on
the brush-frame stop.-This may be an arc joining the two brushes formed into a
solenoid fixed to the brush-frame, which is acted on by a fixed steel magnet, or by
an electro-magnet, so as to apply the force required to bring the brush frame into
its proper position.-The form of electro-magnetic controller described in my
Provisional Specification N° 2028 A.D. 1883, with reference to the hydraulic
oozing integrator is also suitable for this purpose, and in accordance with details
hereinafter described with reference to the potential regulator I apply it so as to
cause water to flow into or out of a bucket according as the electric current is in
one direction or the contrary.-This bucket is supported on a counterpoised lever,
by which the brush-frame stop is brought to such a position that the electric current
to be annulled, is nil or nearly enough so, for practical purposes.
As an alternative method, instead of a pair of auxiliary brushes, I sometimes
divide the main working brush into two parts or into three parts mutually
insulated; and I use two parts on two sides of the middle to give electro-magnetic
action when there is any difference of potential between them, by which the
requisite adjustment is produced.-The mode of doing this which I prefer is to join
these two brushes by an are the electro-magnetic force of which produces the
desired regulation, while a conductor, from the middle of it, is led away to one of
the main electrodes of the dynamo, or is joined to the electrode from the middle
brush, to produce the whole nain, when the brush is divided into three parts.
For a sufficiently important dynamo I adjust the two main brushes each
independently by the manner which has been explained.
To start and stop the dynamo, I use a pulley driven by a belt.-This pulley I
arrange to be clamped by a solid conical piece pressed into a hollow cone on one
side of the pulley; or by two such fittings, one on each side of the pulley.-The
clamping is done by a spring wholly borne on the axis, and rotating with the
machine when the machine runs. To stop the machine 1 use a fork and lever, or
equivalent mechanism by which the clamping force of the spring is balanced and
the conical fitting or fittings left free. The fork acts on a collar which rotates
with, and stops with the machine. Thus the frictional rubbing under the heavy
force during the operation of the fork, ceases as soon as the machine stops and is
null while the machine is running. The pulley runs loose on the shaft when the
machine is stopped by the fork. To start the machine the relieving force of the
fork is annulled, and the spring is allowed to clamp the conical fittings with a
mod-rate and safe but sufficient force.
To allow the abundant use of oil of the most suitable kind on the bearings of the
dynamo, and countershafting and engine connected with it, and to prevent any of
the said oil from reaching the commutator bars, or any other part of the machine

page_text: where it is not wanted, or from being scattered or dropped anywhere in the
neighbourhood, I use on each side of each bearing a centrifugal disc and a fixed
canal round it, by which all the oil escaping from the bearings is thrown
off by centrifugal force, and allowed to run down to the lowest point of the
canal, whence it is drained by a pipe into an oil sink, provided with a filter of
flannel or other suitable material. For oil supply I use a large vessel, preferably
of glass or furnished with a glass visual gauge, that it may be casy to see how
much is in it at any time, and large enough to hold at least a twenty-four hours'
supply. A tube with stop-cock lots oil flow from the supply bottle through small
branch tubes to all the bearings.-Each branch tube ends in a fine hole through
which the oil passes freely, so as to give three or four drops or more per minute,
falling into a cone or wide passage leading to the bearing-The place of the
dropping from each branch should be easily seen, so that the person in charge may
readily see at any time, that there is no failure in the oil supply.-Once a day
filtered oil from the sink should be lifted up or pumped up and replaced in the
supply bottle, unless in cases in which it is worth while to pump it up continuously.—
In a large establishment I do this by a single pump for all the dynamos and for all
the bearings of counter shafting and of engines and for all parts of the engines,
requiring a dropping or continuous supply of oil. This pump draws up filtered oil,
freed from water as well as solid particles which may have got mixed with it in
any part of the mechanism or engine, whether gas engine or steam engine, and
replaces it in serviceable condition in the reservoir-Oil passing from the bearings,
slides, cylinders or other parts of the dynamos and connected mechanism, is guarded
as much as possible from being scattered or dropped about anywhere, and is led
away by drain tubes to a sink where it is purified by settlement and filtration. —
The attendant must replenish daily or weekly the supply reservoir, to make up for
whatever oil may be lost through any imperfection of the drainage and purifying
arrangements, or by decomposition in the mechanism or by evaporation.
For the field magnets I use cylindrical electro-magnets having pole pieces of soft
iron so arranged as to give an effective magnetic field for a toroidal armaturo
extending over somewhat more than three fourths of the sectional circumference of
the toroid. The iron cores with their pole pieces form, together with iron end-
plates, the main framework of the machine.
For exciting the electro-magnet I use a conductor of copper or other suitable
material in the form of flat thin strip with insulation consisting of a riband of very
thin strong parchinentized paper.
I construct a suitable number of flat spirals by winding this conducting strip on
a temporary core with an insulating layer of paper between the consecutive turns
and immerse each coil in a hot mixture of melted resin and beeswax which soaks
into the paper and helps when cold to consolidate the whole.-The exciting con-
ductor of the electro-inagnets is constituted of these spirals, as many as possible of
them being placed upon the iron cores.- -By removing the pole pieces or the end
plates, the spirals may be easily slipped on to the cores one by one and then joined
properly in series, care being taken that they are insulated from the iron core and
from each other, which may conveniently be accomplished by covering the iron
core with paper and varnish, and by placing, between each pair of spirals, a paper
washer of the same diameter as the spiral itself. This form of electro-magnetic
solenoid may also be used advantageously in many arrangements, where motions
are effected by electro-magnetic action.-It has the following important advan-
tages: a convenient arrangement of wheelwork is easily made by which such
spirals may be constructed speedily and accurately and at very slight expense.-
The insulating material may be exceedingly thin consistently with safety, because
of the smallness of the difference of potentials to be insulated by it and because the
process of winding the double riband of copper and paper causes no injurious strain
on the insulating material. The ratio, of the space occupied by the insulation,
to that occupied by the copper, being thus reduced to a minimum, the solenoid
is proportionally more effective than it could be if made on any of the ordinary plans.

page_text: As an alternative, instead of electro-magnets I sometimes use bars, or bundles
of bars of very hard steel magnetised in situ.-In this case I prefer that the main
framework of the machine shall not be dependent for any structural strength on
the steel magnets. For this purpose I support the soft iron pole pieces in proper
position by means of columns of brass or other non-magnetic metal of tubular or
U-formed section, firmly secured to the iron end plates, and of such dimensions
that the framework so constituted shall be strong enough independently of the
steel magnets. Within the cavities of each of these columns is placed the bar or
bundle of bars constituting the magnets.
The bar or bars, to form each magnet, are placed in position and are then
magnetised. This I effect by winding round cach temporarily several layers of a
flexible insulated conductor, and a powerful current is sent through it momentarily
to give a very great magnetising force.-By means of one or of several such
successive applications of magnetising force, the whole magnetism that the steel
magnets can keep in their actual position is given to them in that position.―
Should the magnetism become impaired to any serious extent either through
lapse of time or by any accidental disturbance, it may be renewed with great ease
at any time by repeating the process by which the original magnetisation was
effected. In some cases it may be found convenient to allow the magnetising
coils to remain permanently in position.
In a system of electric lighting by incandescent lamps the economy greatly
depends upon the condition that the difference of potential between the two main
conductors shall be kept within a very narrow range of variation.-The range
allowed by the Board of Trade,-five per cent above or below the normal value, is
too much to do justice to incandescent lamps.-Hence I have designed the regulator
now to be described to confine the range of the difference of potentials between
the electric mains, within much closer limits than the Board of Trade ten per cent.
In an electric light installation for a house or establishment, not including great
distances I regulate the potential to the required degree by placing in the circuit
resistances so as to never allow the potential to rise above the proper highest
amount. This I effect automatically as follows :—A bucket containing mercury is
suspended by means of a spiral spring and bas its interior in communication by
means of a flexible india rubber tube with the interior of a fixed cylindrical vessel
or well, also containing mercury-A spiral row of holes, each inclined to the
vertical at about 45°, is bored through the side of the well and in each hole is
fitted, mercury-tight, a copper or iron wire having one end always covered with
mercury in the inclined hole, and the other end connected to one of a corresponding
number of conducting arcs (resistance coils).-The other ends of these resistance
coils are brought together to a terminal to which is connected one side of a cut
which is made in one of the mains.-The other side of the cut is connected to the
mercury in the interior of the well by a copper wire passing through the bottom.-
Thus as the mercury rises in the well one after another of the resistance coils is
put in multiple are into the circuit of one of the mains.
The length and effective rigidity of the spiral spring supporting the bucket must
be so adjusted, that if the bucket be displaced vertically up or down, it shall remain
at rest in the position in which it is placed.-The free level of the mercury in the
well depends upon the position of the suspended bucket.―Thus a raising or a
lowering of the bucket, by placing in or removing from the circuit a certain
number of the conducting arcs effects the regulation.
I do this automatically,-raising the mercury-bucket when the potential is too
small, and letting it down when the potential is too great, by application of
electro-magnetic force for example, on the following plan:-An electro-magnetic
balance like that described in my Provisional Specification N°. 2028, A.D. 1883,
but instead of a thick metal coil in circuit with one of the mains, having a fine
wire coil with its ends connected to the two electric mains, acts on two small pipes
connected by fine india rubber tubes respectively, with a fixed reservoir and a
moveable water bucket, so that when the potential is too small water runs through

page_text: the first pipe and falls into the water bucket, and when the potential is too great
water runs out of the bucket through the second pipe; and when the potential is
right or nearly so both flows are stopped.-The water bucket is attached to one
end of a lever, of which the other end presses the mercury bucket up or down
when the water bucket goes down or up.-The outflow pipe of the water bucket
is actuated by a rod lying along the lever, or in the axis of a tube constituting
the lever, and having its end in or nearly in the fulcrum-axis of the lever.-This
rod is pivoted so that it can be turned round a longitudinal axis.-A crank arm on
the outer end of the rod acts on the outflow pipe so as to lift it or lower it.—A
second crank is attached to the inner end of the rod, so placed as to lie as
nearly as may be in the fulcrum-axis of the lever when the rod and cranks are
in the middle of their special range. The end of the second mentioned crank is
acted on by one end of a connecting rod, of which the other end is jointed to the
electro-magnetic balance.
To compensate the effect of change of temperature in changing the resistance of
the electro-magnetic coil of the instrument I use a mercury thermometer with so
much mercury in it as to fill the tube at ordinary temperatures, and with a
chamber into which the mercury is expelled from the tube when the temperature
rises, and from which it runs back into the tube when the temperature falls.―This
thermometer I support, after the manner of a common balance, on knife edges or
by other equivalent menus; and I connect it with the moveable part of the
electromagnetic balance, so that when the current through the coil becomes
lessened by elevation of temperature, the diminished electro-magnetic force shall
be supplemented by a force from the thermometric balance, and the resultant
controlling effect on the regulating appliance, shall be independent of the
temperature or nearly enough so for practical purposes, and shall depend wholly,
or nearly enough so, on the difference of potentials to be regulated.
For a long range tangent galvanometer, I make the electro-magnetic deflector,
a pair of equal and similar coils or simple circuits, or branch conductors fixed
symmetrically beside one another in a horizontal plane and an astatic pair of
needles hung on a silk fibre so as to be free to turn round a vertical axis
symmetrically situated between the two conductors, which for brevity shall -bo
called the central vertical.
The current to be measured passes in contrary directions round the two circuits,
or in parallel directions through the two branch conductors and the resultant
effect conspires on the two needles to turn their planes towards the vertical plane
cutting the two conductors symmetrically, which for brevity I shall call the
"traverse."--Four fixed bar magnets, or electro-magnetic coils, or a pair of
equivalently acting horse-shoe magnets, (which for brevity I call the "directive.
magnets," urge the astatic system towards the vertical plane of symmetry,
perpendicular to the traverse.-For brevity the vertical plane, in which the needles
rest under the influence of the directive magnets alone, shall be called the "zero
plane." The strength of the current to be measured, is equal to the constant of
the instrument multiplied into the tangent of the angle between the zero plane
and the plane in which the needles rest under the combined influence of the
directive inagnets and the current through the coils.
The constant of the instrument, is adjusted to its proper value by increasing or
diminishing the distances between the directive magnets and the needles.-To do
this in the simplest manner I make the directive magnets in the shape of round
bars of hardened steel, with screw threads cut on them; and I support them in
brass nuts attached to the frame of the instrument with a spring arrangement to
give steadiness to each screw in its nut.-By turning one or more of the magnets
in its nut the required adjustment is made; or two horse shoe magnets may be
used, each mounted on a sliding frame, which by a screw is moved so as to bring
the magnet nearer to or farther from the needles.-The zero plane is adjusted to
exact perpendicularity to the traverse by turning slightly the whole system of
directive magnets, or one or more of them round the central vertical; the test of.

page_text: the perpendicularity being, equality of the deflection on two sides of the zero
plane, produced by equal currents in contrary directions.-To enable this
adjustment to be easily effected, the wooden base carrying the glass cover is made
in two parts, one of which, carrying the system of adjustment magnets or a part
of it, is made to turn relatively to the other, which carries the conductors, the
suspension of the needle or needles, and a scale or scales as hereinafter described.
Or instead of this method I sometimes support the lower pair of magnets each in
a wedge or sector of wood, by means of the brass steadying nut herein before
described. Each of these wedges or sectors is placed in a slot so as to be capable
of a slight azimuthal motion about a vertical axis through the centre of the
needles, and when the zero adjustments have been made the sectors are fixed in
position in the slots by filling pieces or wedges.- When electro-magnetic coils are
used, instead of bar magnets, to give the requisite directive influence, the constant
of the instrument might still be adjusted to the proper value by shifting the coils to
greater or less distances from the needles, but it is in most cases more easily done
by increasing or diminishing the quantity of wire in the coils. To afford
convenience for doing this the bobbius carrying the coils are so mounted that
without dismounting them each can be turned round its axis so as to wind on or
off as much wire as is needed to obtain the desired constant.-The adjustment of
the zero plane is still performed by turning slightly the directive system round
the central vertical.
I use a horizontal circular scale, of divisions proportional to tangents of angles
from its middle engraved on a glass mirror, or printed on paper pasted on the
mirror, to facilitate avoidance of parallactic error, for reading the deflections of a
pointer attached to the frame which carries the pair of astatic needles.-This
circular scale is so mounted as to be independently adjustable, so that when the
magnetic zero plane is adjusted. to be exactly perpendicular to the traverse, the
zero of the scale shall be exactly under the end of the pointer.-When it is desired
to be able to take readings by either end of the pointer, I use two circular scales
one for each end, and adjust each independently; because I find that the two ends
of the pointer cannot generally be trusted to as being exactly in a straight line
through the central vertical.
The pair of deflector coils or branch conductors may be each circular, or of any
other shape. When very strong currents, as for instance thousands of amperes, are
to be measured, I prefer to make them crescent shaped, and to let the wholo
current divide itself between the two, as nearly equally as may be.-I use different
pairs of coils or of branch conductors, adjustible so that their traverses may all be
brought into exact coincidence, to give different grades suitable for giving good
sensibility through different parts of a long range, in one instrument and with one
astatic pair of needles.
To connect the clectro-magnetic coil or effective conductor into the circuit
whose current is to bo tested I use strong copper bars bent at right angles and
brazed or soldered to the electro-magnetic conductor, or cast in one piece with it so
as to project out horizontally from the instrument and downwards, into mercury
contained in shallow copper bottomed pans; the bottoms of these pans being
connected to the ends of the main electrodes.-When it is desired to be able to
throw the galvanometer out of the circuit, without stopping the main current, I
place one of the before mentioned pans of mercury over the other, and I make the
lower pan much broader than is necessary for the galvanometer connection and
connect a piece of copper to the upper electrode, so as to project downwards from
it towards the free surface of mercury in this pan. To throw the galvanometer
out of circuit I press down the upper electrode which is sufficiently flexible, till the
projecting piece on it dips into the mercury below. This short circuits the
galvanometer and nearly annuls the current through it.-To quite annul the
current 1 press the electrode still farther down till the pan of mercury carried by
it becomes separated from the upper fixed galvanometer electrode.-By pressing
down still farther the upper main electrode, the lower copper pan is pressed down

page_text: by permission of sufficient flexibility of the lower main electrode, till the connection
between the main electrodes and the electro magnetic coil is wholly broken.
In some cases I effect the required breakings and makings of connection by
lowering and raising the levels of the mercury in the several pans by means of
moveable buckets and flexible connecting pipes or by taking out or putting in
mercury in any convenient way, without moving or bending the pans or electrodes.
In cases of fixed establishments when a conveniently accessible portion of the
electric circuit is straight and the current through it to be measured is not more
than a few hundred amperes, I use an astatic pair of needles above and below the
straight line of the current.-For this purpose I cut a slot in the conductor
allowing the lower needle to be passed down through it and leaving space enough
for the stem, connecting the two needles, to turn in it in the use of the
instrument. Or when it is not convenient to cut a slot I connect the two needles
by a frame of non-magnetic material which may be a fork or open arc, or may be
a closed rectangle with the two vertical sides of silk fibre, or of fine thread.―This
frame, at first open, is put in position round the conductor, and then joined; the
silk fibre suspension being completed before or after the closing of the frame.-
I prefer this closed frame to an open arc or fork, which can easily be made of
aluminium light enough to bear the two needles, because the closed frame is better
adapted to keep the distance between the two needles as nearly constant as is
necessary for practically perfect accuracy, but in some cases the fork may be
preferred as more convenient.
For stronger currents I divide the main conductor symmetrically, so as to give
two horizontal passages gently curved on the two sides of a space which at its
broadest may conveniently be about twenty inches broad.-In the centre of this
space I fix a closed case with glass.cover containing an astatic pair of needles with
pointer and scale or scales and magnetic directive system of four screw bar inagnets
as explained above.-In these circumstances the traverse is the plane through
the centres of the needles, perpendicular to the electric stream line.-The per-
pendicularity of the zero plane of the magnetic directive system to the traverse, is
most easily adjusted by turning the case slightly in either direction till the
equality of deflections by currents in opposite directions is obtained.-This form of
galvanometer is an extreme case of that of the two crescent shaped coils from
which we may imagine it obtained by enlarging to infinity the two outer curves of
the crescents.
For an automatic make-break appliance, suitable for use in connection with the
long range recorder and integrator hereinafter described, or to act as a safety
break I use the mercury-bucket and well arrangement hereinbefore described in
connection with my improved potential regulator and slow extinguisher. For this
purpose the well is simply arranged so that when the mercury in it rises to a
certain level it shall make contact with mercury remaining in an inclined or
vertical tube in the bottom of which is fixed a wire serving for electrode.-A hard
steel bar magnet, or a bar of soft iron, suspended vertically by the supporting
spiral spring, carries attached to its lower end the mercury bucket in flexible
communication with the mercury well.-A solenoid is fixed surrounding the iron
bar or magnet and coaxal with it, and the requisite motion is given to the mercury
bucket by electro-magnetic action due to a current through the solenoid.
As an alternative apparatus to attain the objects described above in connection
with the mercury bucket and well make-break and safety break, I sometimes use
a shallow canal of mercury, the bottom of the canal being concave or consisting of
two planes inclined at a small angle upward on the two sides of the middle line.―
The bottom of this canal which must be of insulating material may be of varnished
paper coating a bed of iron or of other thin insulating material with iron as close
to it below as possible.-The mercury in this canal is put in communication with
the main circuit through two deeper cups at its two ends.-Steel magnets or an
electro-magnet are so placed as to produce a magnetic field with vertical lines of
force crossing the mercury of the canal.-When the main current augments to.

page_text: such a degree that it is desirable the circuit should be broken, this result is
obtained by the transverse electro-magnetic force acting on the mercury and
driving it to one side. The force increases in simple proportion to the strength of
the current through the circuit when a steel magnet is used: but greater
sensitiveness may be given to the arrangement by using an electro-magnet so
related to the circuit 'that the strength shall increase in the circumstances in which
it becomes desirable that the circuit should be broken.
As an improved slow extinguisher I use an adaptation of the mercury bucket
and well herein before described in connection with my improved potential
regulator to effect by quickly lifting or lowering the bucket by hand and leaving
it, the operation performed by the hollow ball or vessel partially filled with
mercury rolling down an inclined channel as described with reference to the slow
extinguisher of my Provisional Specification No. 2028, A.D. 1883.
For a potential gauge to give convenient indications of a potential kept, as in
the Board of Trade requirement for electric lighting, always within five per cent
above or below a prescribed definite amount, I use a galvanometer with coil or
coils of fine german silver wire and a system of directive magnets so arranged that
the needle or astatic pair of needles shall rest in a plane perpendicular to the
traverse when the potential is at its prescribed value, and that the percentage of
that value by which the potential deviates from it in excess or defect at any time,
shall be shewn by round numbers of scale divisions. When a single needle is
used I make the directive system of four screw magnets in horizontal lines
perpendicular to one another through the centre of the needle with dissimilar poles
next the needle in each of the two lines.
As an alternative plan the pair of magnets in the traverse may be placed with
similar poles next the needle and may in this case be much weaker magnets than
those placed perpendicular to the traverse.-In adjusting, the two magnets of each
pair should be kept at approximately equal distances from the needle.-The pair
in the traverse is to be adjusted to cause the needle to rest perpendicular to the
traverse, when the potential is at the prescribed value. The pair perpendicular to
the traverse is to be adjusted to cause the proper number of scale divisions of
deflection to be produced by a stated per-centage deviation above or below the
prescribed amount.
For large differences of potential for example more than 200 or 300 volts, the
following form of gauge founded on the principles of electrostatic force may be
used with the advantage of simplicity and of avoiding the expense of the great
length of fine wire in the resistance coils required for gauging large differences of
potential by the electro-magnetic method.
A moveable plate is arranged to constitute one plate of an air condenser, in such
a manner that the permitted motion to and fro augments and diminishes the
capacity of the condenser, by increasing or diminishing the di-electric area, without
altering the thickness of the space or spaces of air concerned.-Of the two bodies
whose difference of potential is to be measured, one is connected with the moveable
plate or plates, and the other with the fixed plate or plates.-The square root of
the magnitude of the force required to prevent the moveable plate from moving in
the direction which would augment the capacity of the condenser, is proportional
to the required difference of potential which is thus guaged by the measurement
of the force in question.
As an alternative form of the electro-static volt guage I support the moveable
plate referred to above, on a floater and guide the motion by means of a double
jointed frame according to the plan hereinbefore described in connection with the
recorder and integrator
For electric current recorder and integrator I use a long riband of paper pulled
slowly by clock-work, to receive a curve record marked on it by a glass or metal
tubular pen, moved transversely to distances from a zero line simply proportional
to the strength of the current; also to actuate frictionally an integrating wheel on
the following plan.-The wheel is chiefly supported by resting with its rim on the

page_text: paper and it is guided by a horizontal axle pivoted on bearings belonging to a frame
called for brevity, the wheel frame which is pivoted so as to be free to turn round
the vertical through the point of contact of the rim of the wheel and the paper,
which for brevity will be called the main vertical-The wheel frame is actuated
by a connecting rod in such a manner that a point of it in the plane through the
axis of the wheel and the main vertical is moved to distances from the plane
through the main vertical and parallel to the paper's motion, simply proportional
to the strength of the current. Thus when there is no current the wheel does not
turn because the direction of motion of the paper is then parallel to its axis. But
when the axis of the wheel is carried through any angle from this zero position,
the wheel is caused to rotate with a velocity equal to the tangential component of
the velocity of the paper, because, the surface of the paper being frictionally
isotropic, the relative motion of the wheel and paper must be parallel to the axis
of the wheel except in so far as a slight error is introduced through the pivoting of
the axis of the wheel being not perfectly frictionless.-Now the component velocity
of the paper in the direction of the tangent to the rim of the wheel at the point of
contact is equal to its whole velocity multiplied by the sine of the angle of
displacement of the wheel frame from its zero position.-Hence the velocity of the
wheel is always proportional to the strength of the current and the whole anglo
that it turns through, shewn on divisions on its circumference by an index attached
to the wheel frame, is the required integral.-The motion of the paper may
conveniently be made so slow and the wheel so large that no counting train of
wheels is needed, for most practical cases.--Thus for a private house one hundred
equal divisions of the circumference may conveniently be made to correspond to
shillings or francs of the amount chargeable, so that once a quarter or once a
month the inspector may be able to render the account from merely looking at the
wheel, with however the check afforded by the curve record in case of possible
doubt as to a complete revolution of the wheel. The curve record is also valuable
both to the supplier and user of the electricity as a true indicator of how the
account shewn at any time by the wheel has been run up and as a trustworthy
witness to be referred to in case of doubt as to anything having failed to act or
having acted wrongly in the recording or integrating apparatus.
To produce the motions in simple proportion to changes of strength of the
current required to actuate the pen, and the integrator, when the current to be
measured is continuous I use an electro magnetic solenoid pulling one end of a long
bar inagnet of well hardened steel mounted horizontally so as to be free to move
in the direction of its length.-For this purpose I support the weight of the
magnet on water, or, to prevent freezing and to diminish loss by evaporation, on a
inixture of glycerine and water, by a floater of thin sheet copper, and I guide the
motion by a double rectangular frame of which one extreme edge is mounted so as
to be free to turn round a horizontal axis, and the other extreme edge is pivoted
on a cross bar rigidly connected with the magnet.-Other mechanical and electro-
magnetic modes of obtaining an equivalent result may be preferable in some cases.
-To cause the bar to take dispacements in simple proportion to the magnetic
force and to return to its zero position when freed from electro-magnetic force,
use a single spiral spring pulling the bar in the direction opposite to that of the
electro-magnetic force. The proper sensibility is adjusted by lengthening or
shortening the effective parts of this spring by a screw arrangement as described in
my Provisional Specification N° 2028 A.D. 1883.
The solenoid which pulls the bar inagnet hercinbefore described, has its aperture
of diameter somewhat larger than the diameter of the bar, and is fixed round one
end of the bar coaxal with it. The current to be measured is sent through the
solenoid in such a direction as to draw the magnet inwards in order that demag-
Detisation of the steel such as might be produced by a current in the opposite
direction may be avoided.-The length of the solenoid ought to be sufficient to
allow all or nearly all of the free polarity of the end of the magnet concerned to
lie within the solenoid through the whole range of the motion allowed to the

page_text: magnet. When the solenoid is uniform I find that the force pulling the bar
augments more with equal additions to the strength of the current, the stronger
is the current. To cause the additions to the displacement, produced by equal
additions to the current to be nearly enough equal for practical purposes, through
the whole used range, I sometimes attach several little transverse bars to the
spring which pulls against the electro-magnetic force, and I place fixed stops in
such positions that one after another of these bars is stopped as the moveable end
of the spring is pulled further and further.-I estimate that two of these bars will
suffice to give a good practical result. The position of the first stop will be
found by experiment, and then with a farther increase of the current a second
experiment will determine the position of the second stop.-A current galvano-
meter must be used in the circuit for making these experiments, and a large
surface Daniell's battery or other convenient constant enough source to produce
the desired currents.
Instead of the spiral spring I sometimes use a pendulum to cause the bar
to return to its zero position when freed from electro-magnetic force.-This I
effect by connecting the pendulum weight to the end of the bar by a fine
thread pulling horizontally and in this case I am enabled to adjust for the
inequalities in the pulling force of the solenoid on the bar, by placing pins or
a curved cheek, like one cheek of the cycloidal pendulum so that the effective
length of the pendulum cord shall be shortened by the proper amount to make
the necessary correction in the pulling force of the horizontal thread attached to
the pendulum.
The object of causing the additions to the displacement produced by equal
additions to the current to be equal, may be helped or may be wholly attained
by winding the solenoid less or more densely in some parts of its length than in
others.
The steel bar magnet carries on its upper side a point on which is balanced a
connecting rod one end of which carries a pin or a ring by which it moves the
integrator frame by means of a ring or pin attached to this frame.-The steel bar
magnet also carries a little frame on knife edges to one end of which is fixed a
glass or metal pen, carrying a sufficient supply of dissolved aniline to trace the
recording curve for several months.-This frame is balanced so that the pen presses
on the paper with a very small definite approximately constant force, which I find
need not exceed a deci-gramme.
Instead of a straight bar magnet, one bent to a circular are may also be used
especially when more of compactness is desired for the apparatus than the long
straight bar allows.-The bar, if circular, may be supported and balanced so as to
be free to move round a vertical axis through the centre of the circle.-With this
form of magnet the solenoid should be not straight but its axis should be circular
to correspond to the magnet.
To obtain greater power and compactness the bar magnet may be bent into the
form of the letter Z, but with its two ends in the form of arcs of a circle, having
its centre in an axis about which the bar magnet is fice to move. This allows.
electro-magnetic solenoids to be used pulling the two ends of the magnet so as to
give conspiring effects.-I support it by silk thread or metallic wire so as to bear
the whole or nearly the whole of its weight and guide it against horizontal motions
by a pivot or pin and collar or vertical knife edges.
I also use as an alternative method which is available either for continuous or
for alternate currents the following apparatus:-A circular coil of fine wire is
mounted with its plane vertical in such a manner as to be free to move in a
horizontal direction perpendicular to its plane.-To do this I support the weight
of the coil on a floater, and guide it by a double jointed frame as herein before
described. To give the proper adjusting force I use a spiral spring pulling in the
direction opposite to that of the electro-magnetic force or two spiral springs pulling
against one another, which also serve for the electrodes of the coil joining its ends
to two fixed terminals-These terminals are put in connection with the two electric

page_text: mains. The moving coil, thus constituted an electro-magnet, is urged by another
electro-magnet composed of a pair of coils through which the current to be measured
passes. These coils are arranged to give as nearly as may be an equally effective
field of force for the moving coil throughout the whole range of its motion.―This
may be done by making the fixed coils flat and very broad but I prefer to do it by
making these coils less broad, and not flat but of the curvilineal shape.-This is
easily done by first making the coils flat and then slipping the different turns
relatively to one another so that the edges of the riband lie on the curve, being
concave towards the field in which the moving coil moves.-I find by theory that
if the overall diameters of the coils were infinite in comparison with their other
dimensions, an exact uniformity of field would be given by making the curves
exactly circular-The circular form will in practice with such proportions render
the uniformity of the field perfect enough or nearly perfect enough for practical
purposes.
In winding the riband coils four spaces are left to allow two bars supporting the
fine wire coil to pass freely through them.
In case of failure of the automatic action of the integrating wheel, the curve
recorder gives a curve whose area, found by any of the known practical methods,
shews the amount of the account against the user.-I supply with the instrument
when desired a special integrator for integrating the curve, constructed on the same
plan as the integrator which works automatically in the regular action of the
instrument. For this purpose I use a wheel frame and integrating wheel on the
same plan as that hereinbefore described.-The pivots of the vertical axis of the
integrator frame are supported on bearings attaclied to a horizontal bar pivoted on
the moveable edge of a double jointed frame like that hereinbefore described for
guiding the steel magnet of the apparatus.-The fixed axis of this jointed frame is
fixed properly on a table, and the riband of paper carrying the curve is placed
firmly on the paper with its zero line in such a position that the integrating wheel
rests with its rim on it and that its direction is perpendicular to that of the
parallel axes of the guiding frame. A tracing point fixed to the wheel frame is
then carried over the curve to as great a length as the jointed frame allows.―Thus
the area of part of the curve is obtained on the integrating wheel. The paper is
then shifted to allow a fresh portion to be operated on, and so the whole integration
is effected.
When the amount of current to be integrated and recorded is liable from the
needs of the users to vary between very wide limits, so as to be at times beyond
the range of a single recorder such as that described above I use a double or triple
or multiple instrument on the same plan, constituted as follows, which I term a
"long range recorder and integrator"-Two or more sets of the electro-magnetic
mechanism of the apparatus hereinbefore described are so connected by a con-
venient automatic make-break, that so long as the amount of the current to be
integrated is less than a certain limit it all passes through the solenoid of the one
set of electro-magnetic mechanism and is recorded by it, and when the current to
be integrated is above this limit it is caused to divide itself through the solenoid of
the second electro-magnetic mechanism. Thus while part of the current is still
recorded by the first mechanism, the excess of the whole above this part is recorded
by the second mechanism.-The clock work is arranged to drive the paper wheel
for each of the recording mechanisms.
Although I have described my Invention under several heads I would have it
understood that they are not to be considered as separate disconnected Inventions
but only as integral parts of one Invention each being new and all being adjuncts
depending one upon the other and producing the best result when used in
combination And I will not in my final Specification lay claim to any or cither
of such parts when used independently of the others or other of thein or their
equivalents but only as a whole to be worked and used in combination

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Sir William Thomson in the Patent Office on the 27th March
1884.
Sir WILLIAM THOMSON, Knight, of Glasgow College, Doctor of Laws and
Professor of Natural Philosophy in the University and College of Glasgow in the
County of Lanark, North Britain APPARATUS FOR GENERATING, REGULATING,
MEASURING, RECORDING AND INTEGRATING ELECTRIC CURRENTS
"
"
My said Invention relates to improved apparatus for generating régulating,
measuring, recording and integrating electric currents.
With respect to the improved apparatus for generating electric currents, for
dynamos such as those of Siemens, Gramme, Siemens-Alteneck and others having
a soft iron armature core in the shape of a figure of revolution, I use fine soft iron
wires of square section wound continuously and spirally, but as nearly as may be
in coaxal circles, with the successive strands mutually insulated by strong thin
paper ribaud, and with the neighbouring circles kept from contact by a very fine
knife, or by a circular edge of thin sheet metal or paper, during the winding, and
if need be prevented from afterwards coming into contact, by the insertion of solid
distance pieces, or by a solidifying cement such as Plaster of Paris, or putty,
pressed in when plastic.
For the toroidal helix of a Pacinotti or Gramme ring, I use square or rectangular
copper wire wound in one or other of two ways, or in suitable intermediate
combinations according as high potential and small current, or comparatively low
potential and strong current, is to be produced.
For a high potential dynamo, before winding on the wire, I cut it into proper
lengths for the separate double coils hereinafter described, and I wind each length
beginning from its two ends, on two flat bobbins each containing nearly all of the
half length in one plane.-The ends of the wire must be well enough secured by
bending them into holes in the bobbin cores, to allow the wire to be laid in its
place in the armature under a strong pull direct from the bobbin.-Suitable
bobbins of strong thin riband paper, of about the same breadth as the diameter
of the wire, are prepared to be wound on between the successive turns of
the wire.
To commence the winding the soft iron toroidal core coated with insulating
material, is held securely fixed by clamps conveniently placed not to impede the
process. A pair of the wire bobbins is taken, and the wire between them is
stretched tightly across the inner rim of the soft iron toroid, with a few degrees
of obliquity. One of the bobbins is then clamped or held tightly by hand, while
the winding is commenced from the other.-The winding from each bobbin of wire
is to be performed altogether in one plane, and simultaneously with it a riband
of paper is to be wound between its turns from one of the prepared bobbins of
paper. The interior bed for the wire is smoothed by a very acute little wedge
of wood cut obliquely and placed so as to receive the wire, where it begins to
leave the core near the end of the first turn to mount on the initial oblique
portion of wire and begin the second turn.-A plane guiding check of metal is
fixed temporarily to the core in proper position for the first coil and the wire in
being wound on, is pressed firmly against it.-The winding may be done simply
by hand, but I prefer to do it by an apparatus which I have designed for the
purpose, in which the bobbin is pivoted on a crank pin, and carried round with
the leverage afforded by a handle projecting as far beyond the crank pin, as is
consistent with its being carried round inside the aperture of the toroid.-The

page_text: crank turns round a collar temporarily placed on the toroid beside the place where
the coil is to be wound on.-The turning of the bobbin on the crank pin is resisted
by a great force of friction, or the crank pin and lever may be held fixed, while
the toroid, temporarily supported on bearings, is turning round an axis tangential
to its circular axis.-When the first coil is completed, its outer end is secured from
motion relatively to the ring by lashing. The plane face of the coil next which
the second coil is to be wound, is then coated with strong fine paper or with thin
mica, and a removeable distance-piece of exceedingly thin sheet metal is placed
against the outer half of the face, to prepare nearly enough a plane in the proper
direction to receive one face of the second coil.-The second coil is then wound on
as was the first but contrary-wards, and its outer end lashed securely.-The free
face of the second coil is then coated with fine paper or mica, and the proper plane
for the third coil is made up by a metal distance-piece. The third and fourth coils
are then wound on by a similar process, and so on by a repetition of similar
processes until the whole ring is covered; the clamps holding the armature being
shifted from time to time to hold it firmly without impeding the winding.-The
original guiding check might be removed safely when the first six or eight coils
are on, but it may be left in position until the covering is so nearly completed
that the completion of the winding comes to be impeded by it.-The circumference
of the ring must be accurately divided into equal parts beforehand, and the exact
position for each coil marked, so that the covering when completed may be quite
uniform. When the winding of the coils is completed, the metal distance pieces
must be removed, and fine silk thread wound round and round through the
aperture of the ring, and into the wedge-shaped spaces left vacant by the removal
of the distance-pieces.-After this is done the outer ends of the coils are to be
unlashed, and while still kept as much as possible under tension, are to be securely
soldered or brazed together in order.
For large current and comparatively small potential, I place the square copper
wire on the core in successive layers, each forming a closed toroidal helix with its
ends soldered together. After having made the first layer close to the core, I coat
it with very thin paper, and wind on the second layer over it, the wire of the
second layer resting on the wire of the first and not across the spaces between
the wire of the first, and so on with successive layers.-The whole number of
layers may for example be four or five or six.-I prevent contacts between the
consecutive turns of each layer, by distance-pieces of paper or mica at the inner
circumference of the toroid, where they are closest, and by putty or other
solidifying cement elsewhere.-I arrange the solderings at places on the toroidal
beds of the successive layers nearest to points at equal distances on the inner
circumference of the toroid.
The winding now described, greatly diminishes the induction of local currents,
which would take place in a single conductor of cross-sectional area, equal to the
sum of the areas of the several helices, which by my arrangement are joined to act
in parallels with very little loss of space by insulating material.-The winding has
also the advantage of avoiding the difficulty of bending such a heavy single
conductor as would be equal to the compound helix.
For the number of commutator bars, I choose a multiple of the number of layers,
in order that the mechanical connection between tho ends of each layer may bo
secured by the additional solderings hereinafter described. I cut away a little of
each of the paper coatings so as to uncover a short length of the wire below it, at
each point of its length nearest to a point of attachment of an electrode leading
inwards to the commutator bars. The joined ends of the several layers are placed
at an equi-distant set of these points. The wire of each layer is soldered to the
wire of the layer below, over a short length of each of the bared places.-I make
the electrodes, which lead to the commutator bars, of thick sheet copper, cut
concave to fit over a convenient length of the outermost layer of the compound
toroidal helix, to which it is soldered.-These plates when fixed in their places, lie
approximately in planes projecting inwards towards the axis of the armature.—I

page_text: make their inner edges straight and parallel to the axis, and I border them with
stout copper pins for making the connections with the ends of the commutator
bars. When very large collecting surface is desired I make each commutator bar
double, with holes or hollows in the ends of its two halves next one another, which
are placed on, or in connection with the pins projecting from the inner edges of
the plate-electrodes herein before described, and secured by solder. The ends of
the commutator bars are held securely fixed by metal, rims, from which they are
insulated electrically by woody fibre or other suitable strong solid insulator.-
When so great a collecting surface is not required, I connect and secure in position
in the manner herein before described, the inner and outer ends of a single set of
commutator bars placed as usual on a cylinder.
I attach the armature to the axle which is to bear it, by two discs of gun-metal
with bevelled rims, bolted firmly together, so as to clamp it by pressing obliquely
inwards and outwards against it, according to lines of pressure lying in conical
surfaces at angles for example of between 10° and 30° to the axis.-The bevel
surfaces are insulated from the helix of the armature by woody insulite or other
strong enough insulator.-The discs may be slotted radially to check the induction
of local currents in them.-The pins for the inner connections of the commutator
bars project through holes made for them in the gun-metal discs.
I support the collecting brushes on a single brush-frame whether the commutator
bars are single or double.-This brush-frame I support by a collar or collars on the
turning axle, or else on pivots fine enough to let it turn easily in either direction,
and I apply a stop to prevent it from being carried round by the friction and
hesion between the commutator bars and the brushes.-I place counter-stops on
the brush-holders, so that in the event of the machine being accidentally or
intentionally turned backwards at any time, they shall lift the brushes off the
commutator bars in the act of checking the backward motion which the brush-
frame takes with the rest of the machine, and so same the brushes from damage.-
Or I divide the brush into separate parts mutually insulated, each contributing a
conducting-arc to the main electrode, and Each of these conducting-arcs is arranged
to break circuit, except through a parallel arc of comparatively high resistance,
through which the current is allowed to flow when it is in the wrong direction.―
An electro-motive force produced by this secondary arc or arcs, re-makes the
circuit through the larger conducting arc by means of an automatic make-break
similar to that described in my Specification No 3032, A. D. 1881, when the current
is in the right direction.-When the machine is to work in either direction, with
two sets of brushes suited respectively to the two directions, I arrange the stops,
and counter-stops so as to take one set of brushes off contact of the commutator-
bars, at the right time to prevent it from damage, and to bring the other set into
contact automatically, if the reverse motion of the armature is continued.-I alter
by hand or automatically the position of the stop or stops from time to time,
according to the varying strength of the current in the use of the machine, so that
the brush-frame shall take the position suited to minimize heating in the contacts
and in short-circuited portions of the helix-For this purpose I attach a pair of
small brushes, insulated from the rest of the circuit, to the brush-frame, in such
positions as to touch the commutator-bars on the two sides of the middle of the
contact-area of one of the main brushes.-These brushes are put in circuit with an
indicating galvanometer or electro-magnetic controller. When the galvanometer
needle is seen to be deflected to one side or other, the brush-frame is shifted by
hand in one direction or the other until the needle is brought to zero, or the same
result is obtained automatically by an electro-magnetic controller acting on the
brush-frame stop. This may be an arc joining the two brushes, formed into a
solenoid fixed to the brush-frame, which is acted on by a fixed steel magnet or by
an electro-magnet, so as to apply the force required to bring the brush-frame into
its proper position.-The form of electro-magnetic controller described in my
Specification N° 2028 A.D. 1883 with reference to the hydraulic oozing integrator
is also suitable for this purpose, and, in accordance with details hereinafter

page_text: described with reference to the potential regulator, I apply it so as to cause water
to flow into or out of a bucket according as the electric current is in one direction
or the contrary. This bucket is supported on a counterpoised lever by which the
brush-frame stop is brought to such a position that the electric current to be
annulled is nil or nearly enough so for practical purposes.
As an alternative method, instead of a pair of auxiliary brushes, I sometimes
divide the main working brush into two parts or into three parts mutually
insulated; and I use two parts on two sides of the middle to give the electro-
magnetic action, when there is any difference of potential between them, by which
the requisite adjustment is produced.-The mode of doing this which I prefer is to
join these two brushes by an arc, the electro-magnetic force of which produces the
desired regulation, while a conductor from the middle of it is led away to one of
the main electrodes of the dynamo, or is joined to the electrode from the middle
brush to produco the whole main when the brush is divided into three parts.
For a sufficiently important dynamo I adjust the two main brushes each
independently in the manner which has been explained.
To start and stop the dynamo, I use a belt pulley which I arrange to be clamped
by a solid conical piece pressed into a hollow cone on one side of the pulley, or by
two such fittings one on each side of the pulley.-The clamping is done by a
spring wholly borne on the axis and rotating with the dynamo when the dynamo
runs. To stop the dynamo I use a fork and lever or equivalent mechanism, by
which the clamping force of the spring is balanced, and the conical fitting or
fittings left free. The fork acts on a collar which rotates with and stops with the
dynamo. Thus the frictional rubbing under the heavy force during the operation
of the fork, ceases as soon as the dynamo stops, and is null while it is running.
The pulley runs loose on the shaft when the dynamo is stopped by the fork.-To
start the dynamo the relieving force of the fork is annulled and the spring is allowed
to clamp the conical fittings with a moderate and safe but sufficient force.
To allow the abuudant use of oil of the most suitable kind on the bearings of
the dynamo, and counter shafting and engine connected with it, and to prevent any
of the said oil from reaching the commutator bars or any other parts of the
dynamo where it is not wanted, or from being scattered or dropped anywhere in
the neighbourhood, I use on each side of each bearing a centrifugal dise and a fixed
canal round it, by which all the oil escaping from the bearings is thrown off by
centrifugal force, and allowed to run down to the lowest point of the canal, whence
it is drained by a pipe into an oil sink provided with a filter of Hanuel or other
suitable material. For oil supply I use a large vessel preferably of glass, or
furnished with a glass visual gauge so that it may be easy to see how much oil is
in it at any time, and large enough to hold at least a twenty-four hour's supply.—
A tube with stopcock permits the oil to flow from the supply bottle through small
branch tubes to all the bearings.-Each branch tube ends in a tine holo through
which the oil passes freely, so as to give three or four drops or more per minute
falling into a cone or wide passage leading to the bearing-The placo of the
dropping from each branch should be easily seen, so that the person in charge may
readily see at any time that there is no failure in the oil supply-Once a day
filtered oil from the oil sink should be lifted up or pumped up and replaced in the
supply bottle, unless in cases in which it is worth while to pump it up continuously.
-In a large establishment I do this by a single pump for all the dynamos and for
all the bearings of the counter shafting and of the engines and other machinery,
requiring a dropping or continuous supply of oil. This pump draws up filtered
oil, freed from water as well as solid particles which may have got mixed with it
in any part of the mechanism or engine, whether gas engine or steam engine, and
replaces it in a serviceable condition in the reservoir.-Oil passing from the
bearings, slides, cylinders, or other parts of the dynamos and connected mechanism,
is guarded as much as possible from being scattered or dropped about anywhere,
and is led away by drain tubes to a sink where it is purified by settlement and
filtration. The attendant must replenish, daily or weekly the supply reservoir to

page_text: make up for whatever oil may be lost through any imperfection of the drainage
and purifying arrangements, or by decomposition in the mechanism, or by
evaporation.
For the field inagnets I use cylindrical electro-magnets, having pole pieces of soft
iron so arranged as to give an effective magnetic field for a toroidal armature,
extending over somewhat more than three fourths of the sectional circumference of
the toroid. The iron cores with their pole-pieces form together with the iron end
plates the main framework of the machine."
.
For exciting the electro-magnet I use a conductor of copper or other suitable
material in the form of flat thin strip with insulation consisting of a riband of
very thin strong parchmentised paper.
I construct a suitable number of flat spirals by winding this conducting strip
on a temporary core with an insulating layer of the paper between the consecutive
turns, and immerse cach coil in a hot mixture of melted resin and bees wax, which
soaks into the paper and helps when cold to consolidate the whole.-The exciting
conductor of the electro-magnets is constituted of these spirals, as many of them
as possible being placed upon the iron cores.-By removing the pole-pieces or the
end plates, the spirals may be easily slipped on to the cores one by one, and then
joined properly in series; care being taken that they are insulated from the iron
core and from each other, which may conveniently be accomplished by covering
the iron core with paper and varnish, and by placing between each pair of spirals
a paper washer of the same diameter as the spiral itself. This form of electro-
magnetic solenoid may also be used advantageously in many arrangements where
motions are effected by electro-magnetic action.-It has the following important
advantagea convenient arrangement of wheel-work is easily made by which
such spirals may be constructed speedily, and accurately, and at very slight
expense. The insulating material may be exceedingly thin, consistently with
safety, because of the smallness of the difference of potentials to be insulated by it,
and because the process of winding the double ribaud of copper and paper causes
no injurious strain on the insulating material.—The ratio of the space occupied by
the insulation to that occupied by the copper being thus reduced to a minimum,
the solenoid is proportionally more effective than it could be if made on any of the
ordinary plans.
As an alternative, instead of electro-magnets, I sometimes use bars or bundles
of bars of very hard steel magnetized in situ.-In this case I prefer that the main
framework of the machine shall not be dependent for any structural strength on
the steel magnets. For this purpose the soft iron pole-pieces are supported in
proper position, by means of columns of brass or other non-magnetic metal of
tubular or U-formed section, firmly secured to the iron end plates and of such
dimensions that the framework so constituted shall be strong enough independently
of the steel magnets. Within the cavities of each of these columns is placed the
bar or bundle of bars constituting the magnets.
The bar or bars to form each magnet is or are placed in position, and is or are
then magnetised. This I effect by winding round each, temporarily, several layers
of a Hexible insulated conductor, and a powerful current is sent through it
momentarily to give a very great magnetising force.-By means of one or of
several such successive applications of inagnetising force, the whole magnetism
that the steel magnets can keep in their actual position, is given to them in that
position. Should the magnetism become impaired to any serious extent, either
through the lapse of time or by any accidental disturbance, it may be renewed
with great ease at any time by repeating the process by which the original
magnetisation was effected.-In some cases it may be found convenient to allow
the magnetising coils to remain permanently in position.
A dynamo embodying the improvements described in the preceding paragraphs
of this Specification, is shewn by Figures 1, and 2 of the annexed Drawings.
Figure 1, is a transverse section and Figure 2, a plan partly in horizontal section.-

page_text: In the machine the axis of rotation is vertical, but in some cases I prefer to
construct the machine with the axis horizontal.
The main framework is constituted by the two circular end plates a³, and 6º,
bolted firmly together by the iron pole-pieces c, and the four hollow columns do,
made of any sufficiently strong non-magnetic metal.-The lower end plate 6º, has
on its upper surface a short hollow pillar e, to serve as a footstep bearing for the
shaft, of the machine, while the upper end plate aº, has on its upper surface
two pillars go, which support a cross bar ³, carrying the upper bearing of the
shaft f-The cross-bar ho, must be so secured to the pillars go, as to be easily
removeable for the purpose of putting on the belt.-A ready way of doing this is
shewn in the Drawings.-The cross-bar h, has two slots one of them being shewn
in plan on Figure 2 which, when the nuts are loosened, allow the bar to be rotated
about the shaft sufficiently to permit of the belt being placed in position on
the belt pulley º.
The core of the armature which is in the form of a toroid constructed of square
soft iron wire in the manner herein before described is shewn at j.
The winding, shewn in section at ko, may be according to either of the methods
herein before described. To facilitate the winding for a "high potential" ariuature,
I use one or other of the two processes of winding herein before described for that
purpose.
The commutator bars 1º, are placed together in the usual manner so as to form a
cylinder, surrounding the shaft fo, and insulated from it and the disc m.-Slips n³,
of copper, equal in number to the commutator bars 18, serve as electrodes leading
from the armature to the said commutator bars.-Each slip nº, has fixed to its
inner end a round copper bar o³, rising through a hole in the upper disc m³, and
there soldered to a slip of copper connecting it to the corresponding commutator
bar. The electrodes nº, are of three different lengths regularly alternating, thus
allowing the holes in the disc mº, through which the pins o, pass, to be disposed
on three concentric circles so as not to unduly weaken the disc m.-The slips of
copper connecting the pins oº, to the cominutator bars may be integral parts of the
commutator bars as shewn.-In cases where the dimensions of the machine render
it advisable to have a greater commutating surface than is obtainable by one
commutating cylinder above the armature, I construct a similar commutating
cylinder below the armature, as indicated by the dotted lines in that position on
Figure 1, and make connection between it and the electrodes no, by prolonging the
pins o, downwards through the disc p.-The commutator bars 1º, are secured at
their lower ends by the insulated ring q, of metal or other suitable material or by
a serving of strong silk cord; the upper ends are held by the washer, by means
of an annular projection from it as shewn.-This washer 79, which is insulated
from the commutator bars 19, is fixed on the screw nut 8, and helps to secure that
the whole commutating cylinder 18, shall be rigidly fixed to and revolve with tho
shaft fo
The armature is supported and fixed to the shaft fo, by the two discs m³, and pº,
of gun-metal or other suitable material; having bevilled edges which press the
armature obliquely upwards and downwards.-The lower disc pº, is supported by
an annular projection to on the shaft f, to which it is keyed or otherwise securely
fixed. The upper disc mo, is also keyed to the shaft and is pressed down by the
nuts, screwed on the shaft, and the collar u, keyed to the shaft f, thus providing
the necessary frictional force between the bevilled edges of the upper and lower
discs and the armature, which, together with that due to the weight of the armature
resting on the lower disc, ensures that the armature shall rotate rigidly with the
shaft The nut 8, and the collar uº, may be of any suitable strong insulating
material so as to insulate the commutator bars from the shaft f⁹.
The brush-frame, the arrangement for its support, and the electro-magnetic and
other apparatus with their connections for regulating its position, are not shewn in
he Drawings. These details have already been described in extenso in a preceding

page_text: paragraph, and their application to the machine exhibited is obvious.-The form of
brush used may be any of those described in my Specification No 5668 A.D. 1881.
The belt pulley as arranged for conveniently stopping and starting the dymmo
is constructed as follows.-The steel disc v, firmly secured to the shaft fo, by the
collars w³, and x, carries on its outer edge a ring y, having its edge cone-shaped
as shewn, and is slightly cupped so as to act as a spring pressing the ring y, into a
conical bed on the loose pulley -An iron disc, having a cone-shaped edge
fitting into a conical bed on the pulley, is secured to the shaft fo, above the
pulley 2º, so that the effect of the pressure of the spring disc, is to pass the
pully, up and eventually clamp it between the two conical surfaces of the ring y³,
and the disc, both of which rotato with the shaft f-At a10, is shewn in section.
the arms of a lever arrangement, by which the pressure of the spring disc vº, may
be counterbalanced when the ring y, is pulled down, and the pulley iº, allowed to
fall away from the disc c, until stopped by the collar ³, when it is free to rotato
without communicating its motion to the shaft fo-To start the dynamo the
relieving force of the spring has simply to be annulled.
The oil supply to the bearings of the dynamo is upon the method hereinbefore
described, and the arrangements for intercepting and carrying off the waste oil are
indicated in the Drawing, Figure 1.-Three centrifugal discs 610, with their
corresponding fixed canals clo, are placed at proper positions on the shaft, and
branch tubes are fitted to each canal to carry off the waste oil;-that from the
lowest of the three, being led from the bottom of the footstep bearing c³, by means
of a hole bored through the end plate 6º.
I have hereinbefore described various methods of constructing tho field magnets
for my dynamo.-In the machine shewn in Figures 1, and 2, I have illustrated one
of the plans in which the pole pieces c, are of soft iron, while the exciting magnets
are bars or bundles of bars of liard steel.-The soft iron pole-pieces cº, are so shaped
as to give an effective field extending over more than three-fourths of the sectional
circumference of the toroid.-The four columns d³, are of the section shewn in
Figure 2, and permit the steel for the magnets to be readily placed in position from
the outside. After the steel for the magnets has been placed in position, a
sufficient length of flexible conductor is temporarily coiled upon each column, and
a powerful magnetising current sent momentarily through it, thus giving to the
magnets in situ all the magnetism which they are capable of retaining. Should
the magnetism of the steel bars become diminished through lapse of time or from
any other circumstance, it can be readily restored by a repetition of the original
process.
As regards this part of my Invention the important and novel features are,-
First The mode of making an armature core of soft iron wire of rectangular
section described above with referenco to Figures 1, and 2, of the accompanying
Drawings.
Second-The winding of an uninsulated copper wire and paper riband in
alternate layers in separated pairs of coils on a toroid by aid of guiding checks
in the manner described; and the subsequent introduction of solid separators or
solidifying cement into the interstices, to secure the mutual fixity, and the mutual
insulation of the coils, all as described above with reference to the mode of winding
for high potential.
Third The mode of winding on the conductor in successive layers each
constituting in itself a complete toroidal helix with mutual insulation between the
different parts except where they are soldered together and connected to the
electrodes leading to the commutator bars, as described above with reference to
the mode of winding for large currents and comparatively small potential.
Fourth-The mode of mounting the toroidal armature by clamping it between
two plates or dises by means of bolts or otherwise, as described with reference to
the Drawings; and the electrodes leading from the inner side of the toroidal ring
symmetrically inwards between these plates, and the symmetrical arrangement o
double connections which this structure allows.

page_text: Fifth The supporting of the brush-frame by means of collars on the main
turning shaft for the purposes herein before described.
Sixth The application of an adjustable stop to prevent the brush-frame from
flying round with the shaft and commutating cylinder, and causing it to rest in
its proper position when the machine is at work, while leaving it free to move in
the reverse direction in case of the motion of the armature being reversed at any
time.
Seventh-The safety apparatus for removing the brushes from contact with the
commutator bars, in case of the motion of the armature being reversed.
Eighth The automatic adjustment of the position of the brush-frame so as to
annul the current, by the electro-magnetic action of the circuit between the small
auxiliary brushes, in the manner and for the purpose described above.
Ninth The mode of making the exciting solenoids for the electro-magnets of
ribbon, copper, and paper, described above.
Tenth The use of hard steel magnetised bars in place of soft iron cores between
the pole-picces and end plates;-these being strongly enough connected by columns
of non-magnetic material ;-and the use of removeable electro-magnetic solenoids
to magnetise the steel bars or to re-magnetise them at any time in the manner
described.
Eleventh The oiling arrangements by which a superabundance of oil is kept
dropping on each bearing of the dynamo or on each bearing and upon each sliding
piece of the engine or other motor connected with it, without waste of oil, in the
manner described.
Twelfth The mechanical auxiliary apparatus for winding wire on a toroid as
described above.
In a system of electric lighting by incandescent lamps, the economy greatly
depends upon the condition that the difference of potential between the two main
conductors shall be kept within a very narrow range of variation.-The range
allowed by the Board of Trade--five per cent above or below the normal value-
is too much to do justice to incandescent lamps.-Henco I have designed the
regulator now to be described, to confine the range of the difference of potentials
between the electric mains, within much closer limits then the Board of Trade ten
per cent range.
In an electric light installation for a house or establishment, not including great
distances, I regulate the potential to the required degree by placing in the circuit
resistances so as to never allow the potential to rise above the proper highest
amount. This I effect automatically as follows:-a bucket containing mercury is
suspended by means of a spiral spring, and has its interior in communication by
means of a flexible india rubber tube or by a glass or iron syphon with the interior
of a fixed cylindrical vessel or well also containing inercury.-A spiral row of holes
cach inclined to the vertical at about 45°, is bored through the side of the well,
and in each hole is fitted mercury-tight, a copper or iron wire having one end
always covered with mercury in the inclined hole, and the other end connected
to one of a corresponding number of conducting arcs (resistance coils).-The other
ends of these resistance coils are brought together to a terininal which is connected
with one side of a cut which is made in one of the mains.-The other side of the
cut is connected to the mercury in the interior of the well by a copper wire passing
through the bottom.-Thus as the inercury rises in the well, one after another
of the resistance coils is put, in multiple arc, into the circuit of one of the mains.
The length and effective rigidity of the spiral spring supporting the bucket, must
be so adjusted that if the bucket be displaced vertically up or down, it shall remain
at rest in the position in which it is placed. The free level of the mercury in the
well depends upon the position of the suspended bucket, and thus a raising or
a lowering of the bucket, by placing in or removing from the circuit a certain
number of the conducting arcs, effects the regulation.
I do this automatically, raising the mercury-bucket when the potential is too
small and letting it down when the potential is too great by application of electro

page_text: magnetic force, for example on one or other of the two following plans which for
brevity I shall refer to as the "Hydraulic" and "Direct" methods.
In the "Hydraulic method," an electro-magnetic balance, like that described in
my Specification N° 2028 A.D. 1883, but having, instead of a thick metal coil in
circuit with one of the mains, a fine-wire coil with its ends connected to the two
electric mains, acts on two small pipes connected by fine india-rubber tubes
respectively with a fixed reservoir and a moveable water-bucket, so that when the
potential is too small water runs through the first pipe and falls into the water-
bucket, and when the potential is too great water runs out of the bucket through
the second pipe, and when the potential is right or nearly so both flows are
stopped. The water-bucket is attached to one end of a lever, of which the other
end presses the mercury-bucket up or down, when the water-bucket goes down or
up. The outflow pipe of the water-bucket is actuated by a rod lying along the
lever or in the axis of a tube constituting the lever, and having its end in or nearly
in the fulcrum-axis of the lever. This rod is pivotted so that it can be turned
round a longitudinal axis. A crank arm on the outer end of the rod acts on the
outflow pipe so as to lift it or lower it. A second crank is attached to the inner
end of the rod, so placed as to lie as nearly as may be in the fulcrum-axis of the
lever, when the rod and cranks are in the middle of their spiral range. The end of
the second-inentioned crank is acted on by one end of a connecting rod of which
the other end is jointed to the electro-magnetic balance. To compensate the effect
of change of temperature in changing the resistance of the electro-magnetic coils of
the instrument, when this method of moving the mercury-bucket is adopted, I use
a mercury thermometer, with so much mercury in it as to fill the tube at the
ordinary temperature, and with a chamber into which the mercury is expelled from
the tube when the temperature rises, and from which it runs back into the tubo
when the temperature falls.-This thermometer I support after the manner of a
common balance, on knife-edges or by other equivalent means, and I connect it
with the moveable part of the electro-magnetic balance, so that when the current
through the coil becomes lessened by elevation of temperature, the diminished
electro-magnetic force shall be supplemented by a force from the thermometric
balance, and the resultant controlling effect on the regulating appliance shall be
independent of the temperature or nearly enough so for practical purposes, and
shall depend wholly, or nearly enough so on the difference of potential to be
regulated.
When the electric activity of the circuit suffices, I prefer to use the "Direct"
method in which the lifting and lowering of the mercury-bucket is effected by
direct electro-magnetic action. For this purpose the moveable coil is in the form
of a short solenoid placed with its axis vertical and supported by a cylindrical
floater fixed to the upper mouth of the solenoid. The magnetic field for this
moveable solenoid is produced by a coil placed with its axis vertical, within a
vertical iron cylinder, and having for its core an iron pillar standing up from and
being continuous or in magnetic connection with the iron bottom of the cylinder.
A thick iron disc is fixed to and in magnetic connection with the top of this iron
pillar, and is of such a diameter as to leave between its edge and a corresponding
annular projection from the lip of the outer cylinder, an annular space wide enough
to permit of the moveable solenoid moving freely up and down through it.-The
vertical depth of this annular space, is so small in proportion to the length of the
solenoid, that the resultant force experienced by the solenoid is practically uniform
for the permitted range of motion.-The iron outer cylinder is prolonged upwards
by thin copper or other non-magnetic metal, and is filled with oil in which the
floater carrying the solenoid is borne; the weight being so adjusted that throughout
the range of effective motion of the solenoid, the floater is entirely below the
surface of the oil-A properly placed stop prevents the floater rising above the
surface of the oil when the electro-magnetic force is nil, or too little to overcome
the floatational force.-When this method of moving the mercury-bucket is
adopted, there is no need for other apparatus to effect a temperature compensation,

page_text: since the expansion of the oil by heat developed in the coils, or by rise of
atmospheric temperature affords a ready means of doing this. As the temperature
of the oil increases its floatational force diminishes, and therefore a smaller electro-
magnetic downward pull will balance it.-The weight and floatational force are
adjusted by experiment, so as to make a temperature compensation sufficiently
exact for practical purposes.-In cases in which the weight of the solenoid and
floater borne by the oil is too great, the compensation would be overdone: and in
such cases a portion of the weight is supported by a thread pulled upwards by a
weighted lever.
An instrument designed to carry out the details of the potential regulator
herein before described, is shewn in Figures 3, and 4 of the annexed Drawings.-
The mercury-bucket do, is suspended from the fixed support e¹0 by means of the
spiral spring 10-To permit of the various necessary adjustments hereinafter
described, this spring f16, has its upper end carried by the screw threads of the
screwed bar go, which is supported by the framework in such a manner, that it
may be moved vertically up and down by the nut h¹0, screwing on it, and may
also be turned by the milled head 10, so as to screw into the spring f10, without
itself becoming thereby displaced vertically.-The well 10, which, with the
bucket do, may be of any convenient material not acted upon by mercury, such as
wood, porcelain, or other like material, is fixed on the support e¹0 and has its
interior in communication with that of the bucket 10, by means of a syphon tube,
or as in the arrangement shewn, by the flexible india-rubber tube 10, connecting
the fixed tubes 10, and m¹0, fixed respectively in the bottoms of the well, and
of the bucket d¹º-The wall of the well, has a series of perforations, placed at
equal distances apart on a spiral line passing, in this case, once round the
circumference. These perforations are cylindrical, of any convenient diameter,
and do not pass straight through but are inclined.upwards towards the inside of
the well, so that their axes make an angle of about 45° to the vertical.—Within
the outer end of each is fixed mercury-tight a stout copper wire n¹º-Thus is
constituted the mercury well 10, with its spiral row of inclined holes on its
interior surface, the bottom of each hole being the end of a copper. wire.-
These wires no, are connected each to a conducting arc (or resistance coil), as
shewn diagraminatically at oo, while the other ends of the conducting arcs are
brought together, to a fixed terminal p-At 91%, is shewn a thick copper wire
fixed in the bottom of the well 10, so that its end surface is in contact with the
mercury within the well -This wire q, and the terminal 210, form the
terminals of the instrument.-The inclined holes herein before described always
retain sufficient mercury to fill them, so that as the free level of the mercury in the
well rises and falls, contact is made and broken successively for the conducting
ares or resistance coils o¹º, between two surfaces of mercury.
In the use of this instrument, one of the "mains" of the circuit to be regulated
is cut, and the two ends connected respectively to the terminals po, and q¹-
Then, the bucket and well being properly supplied with mercury, the bucket is
raised or lowered diminishing or increasing the resistance in the circuit according
as the difference of potentials is below or above the normal value.
To effect this automatically according to the "Hydraulic" method herein before
described for actuating the mercury bucket I use the apparatus shewn diagram-
matically at Figures 5, 6, 7, and S.-The lever 10, is supported after the manner
of an ordinary balance, by means of the cross bar 810, resting on kuife-edges.-To
one end of this lever 10, is suspended a bucket 10, containing water, while the
other end presses the mercury-bucket 10, up or lets it down, as the water
bucket 10, goes down or up.-A rod 10, having two cranks w10, and 1°, is carried
by the lever 10, and pivotted so that it can turn about a longitudinal axis.-The
crank wl, attached to its inner end is placed so as to lic, as nearly as may be, in
the axis of the lever 10, when the rod is in the middle of the range of its own
turning; and is actuated by a flexible cord or by a connecting rod yio, attached to
the moveable part of the electro-magnetic arrangement hereinbefore referred to..

page_text: The crank, attached to the outer end of the rod v10, raises or lowers the outflow
tube 10, of the water bucket to, by means of the thread all; this outflow tube 10,
being rendered sufficiently flexible by reason of the india rubber connecting
piece A prolongation c", of the crank 10, serves to counterpoise the rod vlo
with its two cranks, and also by means of the connecting thread ", to raise or
lower the outflow pipe el, of the fixed water cistern fil; this outflow pipe el,
being, as in the other herein before described, rendered sufficiently flexible by
means of the india-rubber connecting piece g". The outflow pipe el, from the
cistern, discharges into the bucket t10, while the outflow tube 10, from the bucket
discharges into a waste trough "The free level of the water in the cistern f¹¹,
is arranged, by any of the well known methods, to be kept at an approximately
constant height above the bottom.
The action of the instrument is as follows:--when the difference of potential
between the "mains" is below the normal value, the electro-inagnetic controlling
apparatus pulls up the crank 2010, raising the outflow pipe 10, of the water
bucket to, thus preventing outflow from it and lowering the outflow tube c¹¹,
causing water to flow from the cistern f¹¹, into the bucket t-This increase to
the weight of water in the bucket t¹0, disturbs the equilibrium of the lever 10, and
causes it to press upward on the connection to the mercury bucket u10, and thereby
produces the necessary regulation.-When the difference of potential between the
"mains" rises abovo the normal amount, the motions hereinbefore described are
reversed; the outflow from the cistern is stopped, that from the water-bucket
started, and the mercury-bucket is depressed to produce the necessary regulation.
The compensating thermometer herein before described for supplementing any
diminution of the electro magnetic controlling force due to heating of the fine wire
coils is shewn at Figure 8.
The method of actuating the mercury bucket, by direct electro-magnetic action,
and which I havo referred to as the "Direct" method, will be understood by
reference to Figure 9, which is a vertical section of the appliance.-The moveable
coil, is seen attached to the bottom of the floater which is borne by the
liquid. The field of magnetic force in which this coil moves, is produced by the
fixed coil, with an iron core 1, having at its upper end the iron disc m¹³,
continuous with it, and at its lower end being in magnetic connection or, as shewn,
continuous with the iron bottom n¹³, of the iron cylinder o¹³ -The poles of tho
magnetic field are thus the circular edge of the disc m13, and the annular
projection 22, on the inside of the iron cylinder o-Tho sheet copper pro-
longation 9, of the iron cylinder o¹³, permits of the surface of the oil being
sufliciently high to be above the floater, throughout its permitted range of
motion. A properly placed stop, not shewn in the drawing, prevents the said
floater, 12, under any circumstances, from rising beyond a certain limit.-The
electro-magnetic action produced by this arrangement of coils is transmitted to the
mercury bucket through the cord or connecting rod 13, by any convenient method.
In regard to this part of my Invention the important and novel features are,-
First The arrangement of a suspended bucket containing mercury in
communication by a flexible tube or otherwise, with a well also containing
mercury, combined with the adjustments and connections; and the two methods of
actuating the mercury bucket herein before described as the " Hydraulic" and
'Direct methods with reference to Figures 5, 6, 7, and 9, of the annexed
Drawings.
"
Second The plan of temperature compensation for change of resistance in the
electro-magnetic coils of the potential regulator, as herein before described with
reference to Figure 8, of the accompanying Drawings.
For an automatic make-break appliance, suitable for use in connection with tho
long range recorder and integrator hereinafter described, or to act as a safety break,
I use the mercury-bucket-and-well arrangement hereinbefore described in connection
with my improved pontential regulator. For the simpler purpose the well is
arranged so that, when the mercury in it rises to a certain level, it makes contact

page_text: with mercury remaining in an inclined or vertical tube, in the bottom of which
is fixed a wire serving for an electrode.-A hard steel bar-magnet, or a bar of soft
iron, suspended vertically by the supporting spiral spring, carries attached to its
lower end the mercury-bucket in communication with the mercury well by means
of a flexible tube or a siphon of glass or iron tube.-A solenoid is fixed surrounding
the iron bar or magnet and coaxal with it, and the requisite motion is given to the
mercury-bucket by electro-magnetic action, between the solenoid and the soft iron
bar or steel magnet, due to a current through the solenoid.
The details for adapting the mercury-bucket-and-well herein before described in
connection with the Potential Regulator, for use as an automatic make-break and
as a safety-break, will be readily understood by reference to Figures 3, and 4, of
the accompanying Drawings.-For an automatic make-break, the mercury well,
instead of having a spiral row of holes has only one inclined or vertical hole or
tube and the iron or copper wire fitted in it is of considerable thickness.-The
electro-magnetic controlling force may be obtained by means of a solenoid
surrounding a steel bar-magnet or bar of soft iron suspended vertically from the
spring and bearing at its lower end the mercury-bracket, or by any other
convenient arrangement.-The current is made or broken by raising or lowering
the mercury-bucket, so that the level of the mercury in the well is above or below
the level of the mouth of the hole or tube. When the current flowing in the
solenoid falls below a certain limit, the electro-magnetic force is overpowered by a
spiral spring pulling down the mercury bucket, and so breaking circuit.
For a safety-break the arrangement is similar, only the whole current flowing in
the circuit passes through the well and the solenoid, and tho solenoid is arranged to
pull down the mercury-bucket and so break circuit when the amount of current
passing through it exceeds the limit of safety.-In this case the circuit may
conveniently be re-made by hand.
As an alternative apparatus to attain the objects herein before described, in
connection with the mercury-bucket-and-well make-break and safety-break,
I sometimes use a shallow canal of mercury, the bottom of the canal being concave
whether curved or consisting of two planes inclined at a small angle upward on the
two sides of the middle line.-The bottom of this canal, which must be of insulating
material, may be of varnished paper coating a bed of iron, or of other thin insulating
material with iron as close to it below as possible. The mercury in this canal is
put in communication with the main circuit through two deeper cups at its two
ends. Steel magnets or an electro-magnet are so placed as to produce a magnetic
field with vertical lines of force crossing the mercury of the canal.-When the
main current augments to such a degree that it is desirable the circuit should be
broken, this result is obtained by the transverse electro-magnetic force acting on
the mercury and driving it to one side and throwing a portion of it out of the
canal, thereby breaking the circuit.-The force increases in simple proportion to
the strength of the current through the circuit when a steel magnet is used; but
greater sensitiveness may be given to the arrangement by using an electro-magnet,
so related to the circuit that the strength shall increase in the circumstances in
which it becomes desirable that the circuit should be broken.
As an alternative I also sometimes use an arrangement placed in the circuit of
one of the mains, whereby an electro-magnetic action due to the current itself
effects the desired purpose, without, or with, the aid of an electro-magnet or
permanent magnet;-The two forms of this appliance are shewn on Sheet 4 of the
Drawings; Figures 10, 11, 12, 13, and 14, illustrating the form when no magnet
of any kind is used, and Figure 15, when a permanent magnet is used.-The full
Drawings of the simpler form with no magnet, will enable both modifications to be
readily understood. These Drawings represent the said instrument at Figure 10,
in front elevation, at Figure 11, in plan, at Figure 12, in end elevation, and at
Figures 13, and 14, in transverse sections taken respectively on the lines A, B,
and C, D.-A tube 812, of paper or thin vulcanized fibre has its one end stopped
with a copper bar t¹², and its other end by a disc ¹² of copper, these two being

page_text: connected by a sufficient quantity of mercury 12, within the tube to form to form
a continuous conductor between them.-A bar of copper w, of suitable form and
shape is secured outside the tube s12, and is in metallic connection with the
disc Thus the two electrodes of the appliance are t¹ and w, and in practice
these are suitably connected to each side of a cut in one of the mains of the circuit
to be controlled. A cut in the side of the tube s pernits the ejectment of a
portion of the mercury, in the action of the instrument to break the current.
In Figure 14, which is a cross-section, is illustrated the combination of a
permanent magnet with this appliance.-The one conductor x, is a round insulated
copper bar, which is surrounded by a permanent steel magnet y2, as shewn.-Tho
mercury portion of the circuit 2, is connected to the copper portion 12, at one of
its ends, and passes between the poles of the magnet as shewn. The electrodes are
the free ends of the fixed (1) and movable (1) portions of the circuit in the
appliance.
As an improved slow extinguisher, I use an adaptation of the mercury-bucket-
and-well herein before described in connection with my improved potential regulator,
to effect, by quickly lifting or lowering the bucket by hand and leaving it, the
operation performed by the hollow ball or vessel, partially filled with mercury,
rolling down an inclined channel as described in my Specification N° 2028
A.D. 1883.
-
The mercury bucket - and well arrangement is similar to that herein before
described in connection with the potential-regulator, and shewn in Figures 3, and 4,
of the annexed drawings but with the alterations hereinafter indicated.-The hole
at the summit of the spiral is of increased diameter, and the conducting are joining
it to the terminal corresponding to po, is a bar of copper equal in cross sectional
area to one of the "mains."-Thus, when the free level of the mercury in the
well is above the level of the upper end of the highest hole, metallic connection is
established between the terminals of the instrument, by all the conducting arcs in
parellels, one of these being of infinitely small resistance. The number of holes in
the spiral, and therefore the number of conducting arcs, is chosen so as to give the
necessary gradation in the extinguishing of the lamps, for the purpose described in
connection with the slow-extinguisher of my Specification N° 2028 A.D. 1883.—
The capacity of the mercury-bucket is so related to the capacity of the well, that
it, with the connecting tube, is capable of holding all or nearly all of the mercury
used, and hence when the mercury-bucket is at its lowest position, the free level of
the mercury in the well, is situated somewhere in the tube entering the well at the
bottom, or at any rate is below the level of the upper end of the hole at the bottom
of the spiral. The period of time to which the extinguishing extends, is that
required to allow the mercury in the well to flow into the bucket, and may be
made longer or shorter by decreasing or increasing the diameter of the connecting
tube.
A cut is made in one of the "mains" for the circuit of lamps to be extinguished,
and the two terminals of the instrument, corresponding to pio, and q¹º, are joined
to these two ends. To extinguish the lamps or to re-excite them, the mercury-
bucket is depressed, or raised, by hand through a given distance, and left; the
amount of displacement being fixed by stops properly placed.
As regards this part of my Invention the important and novel fenture consists
io,—
The use of the mercury-bucket-and-well referred to above in connection with
my improved potential regulator, with the modifications adapting it to act as an
automatic make-break, as a safety-break, and as a slow extinguisher, together
with the appliances described in connection with Figures 10, 11, 12, 13, 14, and 15,
as alternatives for a safety-break.
For a long range tangent galvanometer I make the electro-magnetic deflector a
pair of equal and similar coils or simple circuits, or of branch conductors, fixed
symmetrically beside one another in a horizontal plane, and an astatic pair of
needles hung on a silk fibre, so as to be free to turn round a vertical axis,

page_text: symmetrically situated between the two conductors, which for brevity thall be
called the "central vertical."
The current to be measured passes in contrary directions round the two circuits,
or in parallel directions through the two branch conductors, and the resultant
effect conspires on the two needles to turn their planes towards the vertical
plane cutting the two conductors symmetrically, which for brevity I shall call the
traverse." Four fixed bar magnets or electro-magnetic coils or
a pair of
equivalently acting horse-shoe magnets, which for brevity I call the "directive
magnets," urge the astatic system towards the vertical plane of symmetry
perpendicular to the "traverse."--For brevity the vertical plane in which the
needles rest under the influence of the directive magnets alone shall be called the
"zero plane."-The strength of the current to be measured is equal to the constant
of the instrument multiplied into the tangent of the angle between the zero plane,
and the plane in which the needles rest under the combined influence of the
directive magnets and the current through the coils.
The constant of the instrument is adjusted to its proper value by increasing or
diminishing the magnetic force produced on the needles by the controlling
magnets. To do this in the simplest manner, I make the directive magnets in the
shape of round bars of hardened steel, with screw threads cut on them, and I
support them in brass nuts attached to the frame of the instrument with a spring
arrangement (explained with reference to Figures 19, to 22,) to give steadiness to
each screw in its nut.-By turning one or more of the magnets in its nut the
required adjustment is made.-I also use as an alternative method two pairs of
vertical magnets mounted on two coaxal vertical cylinders, of which one bears the
other, with freedom to turn it into and clamp it in any relative position, while the
former may be turned round the vertical of the fibre on which the needles hang.
The zero plane is adjusted to exact perpendicularity to the "traverse," by.
turning slightly the whole system of directive magnets round this "central
vertical"; the test of the perpendicularity being, equality of the deflection on two
sides of the zero plane, produced by equal currents in contrary directions.
When electro-magnetic coils are used instead of bar magnets to give the requisite
directive influence, the constant of the instrument might still be adjusted to the
proper value by shifting the coils to greater or less distances from the needles, but
it is in most cases more easily done by increasing or diminishing the quantity of
wire in the coils, and it may be varied at any time by adding more or less
resistance externally to the wire of the coils.-The adjustment of the zero plane is
still performed by turning slightly the directive system round the " central
vertical."
I use a horizontal circular scale of divisions proportional to tangents of angles
from its middle, engraved on a glass mirror or printed on paper pasted on the
mirror, to facilitate avoidance of parallactic error for reading the deflections of a
pointer attached to the frame which carries the pair of astatic needles.-This
circular scale is so mounted as to be independently adjustable so that when the
magnetic zero-plane is adjusted to be exactly perpendicular to the " traverse," the
zero of the scale shall be exactly under the end of the pointer.-When it is desired
to be able to take readings by either end of the pointer, I use two circular scales
one for each end, and adjust each independently;--because I find that the two
ends of the pointer cannot generally be trusted to as being exactly in a straight
line through the "central vertical."
The pair of deflector coils or conductors may be each circular, or of any other
shape. When very strong currents, as for instance thousands of amperes, are to be
measured, I prefer to make the deflectors crescent shaped, or of a central deflector
bar and two side bars all joined at one end, and to let the whole current divide
itself between them as nearly equally as may be.-I use different pairs of coils or
of branch conductors, adjustable so that their "traverses" may all be brought into
exact coincidence, to give different grades suitable for giving good sensibility.

page_text: through different parts of a long range, in one instrument and with one astatic
pair of needles.
To correct the electro-magnetic coil or effective conductor, into the circuit whose
current is to be tested, I use strong copper bars bent at right angles and brazed or
soldered to the electro-magnetic conductor or cast in one piece with it, so as to
project out horizontally from the instrument, and downwards into mercury
contained in shallow copper bottomed pans;-the bottoms of these pans being
connected to the ends of the main electrodes.-Or I use mercury pans rigidly fixed
to the instrument, and downward projections of the electrodes of the circuit
dipping into these pans.-When it is desired to be able to throw the galvanometer
out of the circuit without stopping the main current, I place one of the before
mentioned pans of mercury over the other, and I make the lower pan much
broader than is necessary for the galvanometer connection and connect a piece of
copper to the upper main electrode, so as to project downwards from it towards
the free surface of mercury in this pan-To throw the galvanometer out of
the circuit, I press down the upper electrode which is sufficiently flexible, till tho
projecting piece on it dips into the mercury below.-This short-circuits the
galvanometer, and nearly annuls the current through it.-To quite annul the
current, I press the electrode still further down till the pan of mercury carried by
it becomes separated from the upper fixed galvanometer electrode. By pressing
down still farther the upper main electrode, the lower copper pan is pressed down
by permission of sufficient flexibility of the lower main electrode, till the connection
between the main electrodes and the electro-magnetic coil is wholly broken.
In some cases I effect the required breakings and makings of connection by
lowering and raising the levels of the mercury in the several pans by means of
moveable buckets and flexible connecting pipes, or by taking out or putting in
mercury in any convenient way without moving or bending the pans or electrodes.
In the diagrams Figures 16, to 22 (inclusive) of the annexed drawings is
exhibited the construction of the long range tangent galvanometer.-The branch
conductor, in the form of a circle having its centre in the "central vertical," and
the branch conductor 1, in the form of an ellipse within the circle of j", having
its longer axis in the zero plane, and its shorter axis in the "traverse," are each of
copper about 5 centimetres broad and twelve millimetres thick.-The inner branch
conductor 1, lies wholly within ¹¹, and is also of an elliptic form, having its longer
axis in the zero plane, and its shorter axis in the "traverse."-It is of copper about
5 centimetres broad by 2 millimetres thick.-The three branch conductors j, k,
and, are situated in the same plane, and are metallically connected together
at m", while they are insulated from each other at the opposite points n", o,
and p-The electrodes, as hereinbefore described, project one from each branch
conductor, at n, oll, and pl, and are so placed that the portion of each conductor
influencing the system of needles is symmetrical on each side of the zero plane.-
I also sometimes place an electrode at ml, where the branch conductors are joined
together. The four electrodes so constituted I shall hereafter designate as m",
no, and Two equal and similar circles q", ql, of strip copper, joined
together so that the current to be measured passes in contrary directions round
them, are placed so that their axes lie in the traverse"; the one being above the
plane of the upper edges of the branch conductors, and the other below the plane
of the lower edges. Electrodes on the plan hereinbefore described are placed
conveniently for .connecting these coils in the circuit when the current to be
measured is within the grade to which they are adapted.
11
An astatic pair of needles 11, 11, is carried by a suitable framework, and is
suspended by a silk fibre according to the improved safety method described in my
Specification No 2028 A.D. 1883. The needles 71, 71, are placed one above, and
one below, the branch conductors; being one within each of the coils q", q".
The directive system of magnets consists of four screw bar magnets s", {" u¹¹
and v, placed with their unlike poles toward the needles.-The upper pair 8,

page_text: and ", have a common axis which is coincident with the intersection of the zero
plane with a horizontal plane above the branch conductors; while the lower
pair u, and v, are similarly placed in the intersection of the zero plane, with a
horizontal plane below the branch conductors.-The magnets are supported in the
manner hereinbefore described, so as to permit of the adjustments necessary in the
use of the instrument.-A steady-nut of the kind referred to for carrying the screwed
bar magnets is shewn in detail in Figures 19, to 22.-It consists of a brass cylinder w₁,
having fixed in its intérior the screwed nut ", to fit the thread on the screwed bar
magnet s.-A transverse cut is made in the wall of the cylinder wll, on one side,
and by means of this opening the free ends of the spring y, are permitted to press
on the screwed magnet 8", within the cylinder, and to press it firmly into the
screwed bed of the nut -The spring y", is conveniently fitted in a slot on the
circumference of the cylinder w-Two narrow webs 11, on the exterior of the
cylinder w, prevent it, when in position, taking rotation about a longitudinal axis
on account of friction between the interior nut a¹¹, and the magnet, when the
magnet is turned to screw it out or in.
The alternative method of constituting the directive system of magnets, by
supporting them in vertical positions upon two vertical coaxal cylinders, will be
readily understood by reference to Figures 23, and 24, of the annexed drawings
which are respectively a plan and sectional elevation.-The arrangement shown is
adapted for a potential galvanometer, where the coils and system of needles would
occupy the space in the interior of the inner cylinder, but the necessary changes to
adapt this to the long-range straight-bar tangent galvanometer for strong currents
are obvious consisting in cutting away parts of the cylinders to allow the conducting
bars to pass through them.-The outer cylinder 2 is supported on the bottom
of a cylindrical cavity in the base of the instruinent, by means of its lower edge.
which is rounded and rests on two V, grooves, and on a plane surface placed
120° apart. A projecting ledge on the inner cylinder 2, Las, cut in its lower
surface, a circular V-groove.-This cylinder t, is supported by three rounded feet
fixed to the outer cylinder s¹², two of which are in the circular V-groove, while the
third is on the flat surface.-Each cylinder carries two hard steel magnets u¹², u¹,
fixed diametrically opposite each other.-The inner cylinder carries on the uppor
surface of its ledge a circular degree-scale ;-and two pointers, one fixed to the
outer cylinder and the other to the base of the instrument, are conveniently placed
for reading degrees on this scale. The two pairs of directive magnets u, may
thus be moved azimuthally to any desired relative position, while the geometrical-
slide method of supporting the cylinders ensures the motion being strictly
azimuthal about the "central vertical."-Three binding screws 12, 1, 12, fixed
on the outer cylinder, are available for clamping the two cylinders together at
the three points in which the rounded feet support the inner cylinder.-The
pointer attached to the outer cylinder reads degrees on the scale according to the
relative position of the pairs of magnets on which position depends the magnitude
of the controlling power, which may be anything from very nearly zero to a
maximum. When the cylinders are clamped together the whole system of magnets
may be turned in azimuth, in order to adjust the zero, without altering the
sensibility. Two perforations in the base of the instrument permit the insertion
of two lever bars, by which the zero adjustment may be effected without removing
the glass cover.
The scales which are shewn dotted in position at Figure 16, are capable
of a slight motion about the "central vertical," for the adjustments hereinbefore
described.
For the first grade of measurement, indicating about one hundred amperes per
division of the scale, the electrodes used are those of ", and o; that is the
direction of the current is as indicated by the arrows in Figure 16;-For the
second grade, indicating about ten amperes per division, the current to be measured
is sent through the branch conductors, and ", or ", and "; that is the
electrodes are o¹¹, and p¹¹, or m¹¹, and p¹¹.—For the third grade of measurement

page_text: =
the current is sent through the circles q", and in this case the indication given
'may be about one ampere division of the scale.
The adjustments to secure that for each grade integral numbers of amperes shall
be indicated for each division of the scale, are as follows:-
For the first grade, by moving the magnets nearer to or further from the
needles, or by altering azimuthally the relative positions of the magnets.
For the second grade by bending the branch conductor ¹¹.
For the third grade by filing the edges of the copper ribbon, or by boring
holes in its centre line so as to increase or diminish the force on the needles.
"
"
The adjustment to cause the three traverses to lie in a common plane is as
follows:-
The "traverse" for the first grade is accurately determined in the construction
of the instrument.
"
The traverse for the second grade is made coincident with that of the first
grade, by a translation to one side or another of the branch conductor 1, which,
on account of its thinness, has a certain degree of flexibility.
To cause the "traverse" of the third, to agree with both those of the second
and the first, the three branch conductors j", ", and ", fixed relatively to each
other, are to be turned slightly on the base of the instrument, to which is attached
the double coil q, q, used for the third grade of measurement.
Methods have been herein before described by which the parts or the whole
of the system of directive magnets may be moved round the central vertical;
thus providing means for adjusting the magnetic zero plane to be perpendicular
to the common plane of the three " traverses," and for adjusting the sensibility
of the instrument.
In cases of fixed establishments, when a conveniently accessible portion of the
electric circuit is straight, and the current through it to be measured is not too
great, I use an estatic pair of needles above and below the straight line of the
current. For this purpose I cut a slot or pierce a hole in the conductor, allowing
the lower needle to be passed down through it and leaving space enough for the
stem connecting the two needles to turn in it in the use of the instrument.-Or
when it is not convenient to pierce the conductor I connect the two needles by
a frame of non-magnetic material, which may be a fork or open arc, or may be
a closed rectangle with the two vertical sides of silk fibre or of fine silk thread.-
This frame, at first open, is put in position round the conductor and then joined ;
the silk fibre suspension being completed before or after the closing of the frame.-
I prefer this closed frame to an open arc or to a fork either of which can easily
be made of aluminium light enough to bear the two needles, because the closed
frame is better adapted to keep the distance between the two needles as nearly
constant as is necessary for practically perfect accuracy, but in some cases the fork
inay be preferred as more convenient.
"
For stronger currents I divide the main conductor syminetrically, so as to give
two horizontal passages gently curved on the two sides of a space which, at its
broadest, may conveniently be about ten inches broad.-In the centre of this space
I fix a closed case with glass cover, containing an astatic pair of needles with pointer
and scale or scales, and magnetic directive system according to any of the methods
herein before described.-lu these circumstances the " traverse is the plane
through the centres of the needles perpendicular to the electric stream-line.-The
perpendicularity of the zero plane of the magnetic directive system to the
traverse," is most easily adjusted by turning the case slightly in either direction,
till the equality of the deflections by currents in opposite directions is obtained.-
This form of galvanometer is an extreme case of that of the two crescent shaped
'coils, from which we may imagine it obtained by enlarging to infinity the two
outer curves of the crescents; or is a similar form to what that of Figure 16, would
become if the current to be measured were made to enter at the clectrode m¹¹, and
'divide along the two limbs of either of the branch conductors ", " ";—the pairs
of electrodes in these cases being respectively m" n", m" o", and m" p".

page_text: As regards this part of my Invention the important and novel features are,
First Tangent galvanometer with a pair of deflector conductors, or a single
straight deflector conductor, in a horizontal plane, and astatic pair of needles above
and below the plane.
Second A number of such pairs of deflector conductors all mounted in one
instrument to give a graded galvanometer with a single pair of astatic needles.
Third The screw bar magnet and steady nut for adjustment.
Fourth-The four bar magnets and the method of supporting them on vertical
cylinders or the electro-magnetic coils, or the two horse-shoe magnets for controlling
an astatic pair of needles.
Fifth The adjustment of the pairs of coils for the graded galvanometer to make
their "traverses" coincide as explained above.
Sixth The adjustable mounting of the directive electro-magnetic coils, to allow
their zero plane to be adjusted to exact perpendicularity to the "traverse" when
electro-magnetic coils are used instead of steel magnets for the directive system.
Seventh-The independent adjustable mounting of the circular scale of tangents,
or of the two circular scales of tangents to allow its zero or their zeros to be
adjusted to the ends of the pointer when the zero plane of the directive system is
exactly perpendicular to the " traverse."
"
Eight In a galvanometer for strong currents the making and breaking of
connection with the galvanometer by stiff electrodes projecting downwards from
the instrument into moveable pans of mercury connected with the main electrodes.
For a potential gauge to give convenient indications of a potential kept, as in
the Board of Trade requirement for electric lighting, always within 5 per cent
above or below a prescribed definite amount, I use a galvanometer with a coil or
coils of fine Gerinan silver wire, and a system of directive magnets so arranged that
the needle or astatic pair of needles, shall rest in a plane perpendicular to the
traverse" when the potential is at its prescribed value ;-and that the per centage
of that value, by which the potential deviates from it in excess or defect at any
time, shall be shewn by round numbers of scale divisions.-When a single needle
is used I make the directive system of four screw magnets in horizontal lines
perpendicular to one another through the centre of the ucedle, with dissimilar
poles next the needle in each of the two lines. As an alternative plan the pair
of magnets in the " traverse may be placed with similar poles next the needle,
and may in this case be much weaker magnets than those placed perpendicular to
the "travorse."-In adjusting either of these systems of directive magnets the two
magnets of each pair should be kept at as nearly as possible equal distances from
the needle. The pair in the "traverse" is to be adjusted to cause the needle to
rest perpendicular to the "traverse when the potential is at the prescribed
value. The pair perpendicular to the "traverse is to be adjusted to cause the
proper number of scale divisions of deflection to be produced by a stated per
centage deviation above or below the prescribed amount.-I also sometimes support
the directive maguets in vertical positions on coaxal cylinders as hereinbefore
described in connection with the long range tangent galvanometer.
13
"
"
As an alternative forma of potential gauge for use at sea, which may also be used
on land, and is available as a safety controller to prevent overincaudescence of the
lamps, I use two coils of fine wire one fixed and the other moveable, or a pair of
fixed coils and a pair of moveable coils in one plane connected so that the current
passes through them in opposite directions, in order to avoid disturbance from
terrestrial magnetism or other external magnetic force. The proportions and
relative positions of these fixed and moveable coils, are decided according to
the conditions necessary for obtaining an approximately uniform field of force
throughout the permitted range of motion, as explained in connection with
the Idiostatic Gauge (Figures 39, 40, and 41,) of my Specification N° 2028
A.D. 1883.-The moveable coil or coils is or are attached to a hollow body
pivoted on a horizontal axis, (or when used on board ships or vessels an axis
parallel to the ship's deck, or supported on gimbals so as to remain always

page_text: approximately horizontal) having bouyancy enough to support itself and the coils
in petroleum oil at ordinary temperatures.-This pivoted body is actuated by a
spring, preferably a spiral like that of Brequet's metallic thermometer, which is
adjusted by experiment to produce to torque balancing the electro-magnetic
repulsion between the fixed and moveable coils, when an electric current passes
through them; and varying with temperature to such a degree that the coils shall
balance in the same position, under the influence of the greater or less current
corresponding to lower or higher temperatures, with the same difference of potentials
between the terminals of the coils.--A pointer attached to the moveable body
marks on.a scale graduated by experiment, the number of volts of difference of
potential between the terminals.
When used as a safety controller. the moveable body carries a contact piece,
preferably a staple of copper wire with its tips amalgamated, and with amalgamated
discs of copper fixed perpendicularly to the arms of the staple at short distances,
for example one tenth of an inch, from the tips.-The tips are, by the motion of
the moveable body, brought to dip into two cups of mercury, when the potential
exceeds the permissable limit, and are held in contact with the mercury, by the
capillary attraction of the mercury on the discs, until a sufficient force is applied
to the moveable body to withdraw the staple out of the mercury cups. Or the
moveable body acts upon a pivoted tumbler controlled by a spring, so as to push it
over its position of unstable equilibrium when the potential reaches the permissable
limit, and let it fall against a contact piece.-By either of these means a definite
amount of resistance is suddenly thrown into the circuit of the exciting electro-
magnet of the dynamo, or a shunt is thrown upon this circuit so as to suddenly
diminish the force of the field enough to reduce the potentials of the lamps to a
safe degree. If this sudden drop reduce the incandescence too inuch, the engineer
in charge alters the resistance so as to bring up the incandescence to the proper
degree, of which he judges by the potential gauge herein before described, or by
any other convenient potential gauge, or by the appearance of his pilot lamp or of
the other lamps in the engine room.
I sometimes make the potential gauge to consist of only one fixed and one
moveable coil, which are of small diameter and are shaped like small toroids, or
anchor rings. In this case the instrument is not immersed in oil. The moveable
coil is fixed to one end of an ordinary balance beam, supported horizontally on
knife edges, which carries a counterpoise at the other end, and a pointer for reading
the indications on a properly placed scale; also a dash pot to annul the oscillations
of the balance beam when the instrument is in use. The coils consist each of a
comparatively short length of very fine silk covered copper wire, say Nutuber 60
Birmingham Wire Gauge. A suitable length of fine insulated german-silver wire,
to bring up the resistance to several thousand ohms, is wound upon the base or
part of the base of the instrument (which for this purpose is preferably round) in
the following manner, so as to exert no direct electro-magnetic force on the
moveable coil. The whole length of wire necessary, is divided into an even number
of parts each of equal length.-The winding on of this wire is in one direction,
until all of the first part is laid on, then the direction of winding is reversed, and
the second part is wound on in an opposite direction to that of the first.-This
mode of winding is continued for the remaining parts of the wire, reversing the
direction of winding in passing from one part to the succeeding part, until all the
german-silver wire is wound on the base of the instrument in equal lengths, which
are laid on alternately in the one direction and the other.
I also sometimes use this mode of winding for the resistance coils of the long
range potential galvanometer of my Specification N° 2028 A.D. 1883.
The Board of Trade potential gauge is shewn in Figures 25, 26, and 27,
respectively in side elevation, end elevation, and in plan.-Two fine wire coils are
shewn at a, and 61, with a needle suspended between them by a silk fibre,
according to the safety method described in the Specification tiled in pursuance of

page_text: Letters Patent granted to me the said Sir William Thomson N° 2028 A.D. 1883
in connection with the potential galvanometer.
The system of directive magnets illustrated consists of four bar magnets
c12, 12, 12, and 12, screwed, and carried in brass steady nuts similar to those
herein before described with reference to Figures 19, to 22, these steady nuts being
properly fixed in the wooden block g12, forming the body of the instrument.-The
axes of the four magnets and of the needle are in one horizontal plane.-The
two magnets e, f, which have a common axis coincident with that of the needle,
when the needle rests in a plane parallel to that of the coils a¹², 612, are placed
with dissimilar poles next the needle, and serve to produce an adjustment of the
sensibility, for instance to give one volt to the division, or two volts to the division,
or ten volts to the division, or other convenient round numbers.-The other two
magnets c, and 1, have their axes in a plane passing through the centre of the
needle, and perpendicular to the plane in which the axes of the magnets e¹², f¹³,
lie, and are placed with like poles towards the needle.-These, which may be much
weaker magnets th in the others, serve to adjust the zero of the pointer h¹².
The system of directive magnets according to which the bar-magnets are
supported vertically, has been already described with reference to Figures 23
and 24.
In using this Instrument, I sometimes cause the zero to be at one end of the
scale, so that when the potential is at the prescribed definite amount, the pointer h¹³,
is at the centre mark of the scale of tangents.-The deviations are thus more
easily observed on account of the large size of the divisions.
The alternative type of potential gauge adapted for use either on sea or land,
and available also as a safety potential controller will be readily understood by
reference to Figures 28, and 29, these being respectively partly front and side
elevations and partly sections. The two fixed coils m³, ms, are secured to the
framework n, in such positions that the two planes containing them intersect in a
line coincident with or vertically below the axis of the two V grooves 01, 01-
The moveable coil p, is carried by a light framework q pivoted by means of
knife edges, 214, resting on the two V grooves 01, 0, carrying also a
counterpoise 814, and the floater t-The whole instrument is immersed in a vessel
filled with oil to such a height that no part of the moveable body, except a very
delicate pointer, cuts the surface of the oil, and the weights of the moveable body
are so distributed, that its centre of gravity is accurately in the axis of the
permitted motion, that is the line joining the places of contact between the knife
edges, and the V grooves o, o-The two arms of the framework q", q",
are insulated from each other and serve as electrodes for the moveable coil p
For this purpose they have two amalgamated copper plates u, u, dipping
respectively into mercury contained within the two vessels 2014, cl, which serve as
the electrodes of the instrument. It will be observed that the contacts thus
provided, are very approximately in the line of the axis of the permitted motion.
The spiral controlling spring after the manner of Bregnet's metallic thermometer,
and the pointer and scale, are not shewn on the Drawings as their application to
the instrument is obvious.
I also sometimes use an instrument, constructed similarly to that hereinbefore
last described, but adapted to gauge currents instead of potentials.
The methods hereinbefore fully described, for adapting this instrument for use as
a safety potential controller, are sufficiently obvious to render drawings of them
unnecessary.
So also with respect to the idiostatic potential gauge on a somewhat similar plan
to that of the foregoing, but pivoted horizontally and not immersed in oil, and
having only one fixed and one moveable coil and these of small size, the description
herein before given is sufficiently detailed and clear to render drawings unnecessary.
As regards this part of my Invention the important and novel feature consists in
The use of two magnetic forces at right angles to one another, separately
adjustable so as to fulfil respectively the two conditions stated; and of the

page_text: electro-magnetic arrangement of coils (being a modification of those described with
reference to Figures 39, 40, and 41, of my Specification N° 2028 A.D. 1883)
combined with a floater and the whole immersed in oil, for a potential or current
gauge and safety potential controller as herein before described; also the method
herein before described, of winding german-silver wire for use as a shunt or shunts
or resistance coil or coils, in or on the base of the instrument with which it is or
they are to be used, so as to exert no direct electro-magnetic force on the needle or
other moveable magnetic or electro-magnetic body.
For large differences of potential, for example more than 200 or 300 volts, the
following improved forms of gauge, founded on the principles of electrostatic force,
may be used with the advantage of simplicity, and of avoiding the expense of the
great length of fine wire in the resistance coils required for gauging large differences
of potential by the electro-magnetic method.
A moveable piece of metal is arranged to constitute one conductor of an air
condenser, in such a manner that the permitted motion to and fro augments and
diminishes the capacity of the condenser, by increasing or diminishing the di-electric
area without altering the thickness of the space or spaces of air concerned.-Of
the two points of a circuit whose difference of potentials is to be measured, one is
connected with the moveable piece or pieces of metal and the other with the fixed
plate or plates of the condenser.-The square root of the magnitude of the force
required to prevent the moveable body from moving in the direction which would
augment the capacity of the condenser is proportional to the required difference
of potentials, which is thus gauged by the measurement of the force in question.
For large enough differences of potentials, I reduce the moveable conductor of the
air condenser to a ring, moving perpendicularly to its plane towards or from a
globular or round-ended fixed conductor of smaller diameter.
Two forms of the electrostatic volt gauge are represented at Figures 30, and 31,
of the annexed drawings.-The instrument shewn in sectional elevation at Figure 30,
is suitable for gauging ordinary differences of potential, and consists of a balanced
lever a, pivoted on knife edged supports and carrying pivoted on one end of it
the brass cylinder 614, constituting the moveable plate of the condenser, and ou
the other end a scale pan c-The fixed plate consists of two brass cylinders d, e¹³,
in metallic connection, and fixed in any convenient manner on the stand, which
is of insulating material such as wood.-The three cylinders b¹, and d, e, are
coaxal when the balanced lever a14, is horizontal.-The weights of the balanced
lever a, with the scale pan c, and cylinder 614, carried by it, are so disposed that
the lever a rests in horizontal equilibrium when there are no weights in the scale
pan, and no electrostatic force between the fixed and moveable cylinders; also the
centre of gravity is sufficiently far below the knife edge supports to give just the
desired sensibility.
One of the two points in the circuit whose difference of potentials is to be
measured is connected to one of the V groove supports g1, of the balanced beams a",
and thence through the steel knife edge and balanced lever a¹, to the cylinder 614;
while the other point is placed in metallic connection with the two cylinders d¹, e¹-
The square root of the weight required to be placed in the scale pan c¹, to keep the
balanced beam a", in horizontal equilibrium measures directly the difference of
potentials.
The modified form of this instrument which I use for gauging large differences
of potentials, is shewn at Figure 31, by a sectional elevation. It is similar in
every respect to the instrument herein before last described with reference to
Figure 30, except in the form of the fixed and moveable conductors. In the
instrument shewn at Figure 31, the moveable conductor is reduced to a ring h
carried by the lever while the fixed conductor takes the form of a round-
ended cylinder j, supported on the stand ", by means of a glass-stem The
method of using this instrument is of course exactly the same as that described
with reference to the instrument shewn in Figure 30.

page_text: As regards this part of my invention the important and novel feature consists in,
The use of the potential gauge giving by electrostatic force a similar result to
that obtained by the instrument represented at Figures 25, 26, and 27, for cases in
which the potential is so great that the amount of fine insulated wire required to
give the result by electro-magnetic force is too costly.
arc,
To standardise the Board of Trade, and other potential gauges hereinbefore
described as giving their indications by electro-magnetic action, or for the purpose
of obtaining experimentally the adjustment of the magnetic controllers for
potential or current galvanometers, which corresponds to any definite number or
numeric of divisions on the galvanometer scale per volt, I use a new form of
Daniell's Battery, which is shewn at Figure 32, in transverse section. It consists
of a shallow rectangular tray a10, of sheet copper, which may be about 15 centimetres
square, with vertical sides about 5 centimetres high.-These sid-s for electrical
reasons, enamelled or painted, to prevent contact between them and the liquid of
the cell. Within this tray is placed a zinc plate &G, about 3 millimetres thick and
14 centimetres square, supported firmly in notches of four wooden blocks cl, cia,
resting securely in the four corners of the tray.-The zinc plate b₁o, is supported
in a position slightly inclined to the horizontal, to prevent bubbles of gas from
lodging on its lower side.-In the centre of the zinc plate is a hole about one
centimetre diameter, through which the stem of the filler 6, long enough to reach
the bottom of the tray, passes, which is used to pour into the bottom of the tray a
measured quantity of a saturated solution of Sulphate of copper.-The tube of the
filler is very fine, and the capacity of the wide part is sufficient to hold the whole
amount of copper solution, which is poured quickly into the filler, and flows slowly
out of it in the course of about a minute, so as to spread slowly over the bottom
of the cell. The wide part of the filler is flat, so as to let it rest stably on the
top of the zinc plate. To set up in action this cell, a solution of Sulphate of zinc
of 102 specific gravity is poured into the tray so as to fill it as high up as the
zine plate b, and by means of the filler, a concentrated solution of Sulphate of
copper, sufficient in quantity to make a layer half a centimetre deep, is poured in
along the bottom of the tray a¹-The difference of potentials between the
terminals of this cell, while it is being employed to maintain a current through
about 250 ohms, I find to be approximately 108 volts.
For an electric current recorder and integrator, I use a long riband of paper,
pulled slowly by clock-work, to receive a curve-record marked on it by a glass or
inetal tubular pen moved transversely to distances from a zero line simply
proportional to the strength of the current;-also to actuate frictionally an
integrating wheel on the following plan.-The wheel is chiefly supported by
resting with its rim on the paper, and it is guided by a horizontal axle pivoted
on bearings belonging to a frame called for brevity the "wheel-frame" which is
pivoted, so as to be free to turn round the vertical through the point of contact
of the rim of the wheel and the paper, which for brevity will be called the "main
vertical." The "wheel-frame" is actuated by a connecting rod, in such a manner
that a point of it in the plane through the axis of the wheel and the "main
vertical," is moved to distances from the plane through the "main vertical" and
pallel to the paper's motion, simply proportional to the strength of the current.-
Thus when there is no current, the wheel does not turn because the direction of
motion of the paper is then parallel to its axis.-But when the axis of the wheel
is carried through any angle from this zero position, the wheel is caused to rotate
with a velocity equal to the tangential component of the velocity of the paper;
because, the surface of the paper being frictionally isotropic, the relative motion of
the wheel and paper, must be parallel to the axis of the wheel, except in so far as
a slight error is introduced through the pivoting of the axis of the wheel being
not perfectly frictionless.-Now the component velocity of the paper, in the
direction of the tangent to the rim of the wheel, at the point of contact, is equal
to its whole velocity, multiplied by the sine of the angle of displacement of the
"wheel-frame" from its zero position.-Hence the velocity of the wheel is always

page_text: "
proportional to the strength of the current, and the whole angle that it turns
through, shewn on divisions of its circumference by an index attached to the
wheel-frame," is the required integral. The motion of the paper may be
conveniently inade so slow, and the wheel so large, that no counting train of wheels
is needed for most practical cases. Thus for a private house, one hundred equal
divisions of the circumference may conveniently be made to correspond to shillings
or francs of the amount chargeable ;-so that once a quarter or once a month the
inspector may be able to render the account, from merely looking at the wheel;-
with however the check afforded by the curve-record, in case of possible doubt as
to a complete revolution of the wheel.-The curve-record is also valuable both to
the supplier and user of the electricity, as a true indicator of how the account
shewn at any time by the wheel has been run up, and as a trustworthy witness to
be referred to in case of doubt as to anything having failed to act or having acted
wrongly, in the recording or integrating apparatus.
To produce the notions in simple proportion to changes of strength of the current
required to actuate the pen and the integrator, when the current to be measured
is continuous I use an electro-magnetic solenoid pulling one end of a long bar
magnet of well hardened steel, or two parallel solenoids pulling the two ends of a
horse-shoe magnet, mounted horizontally so as to be free to move in the direction
of its length or of its parallel arms. For this purpose I support the weight of the
magnet on water, or to prevent freezing and to diminish loss by evaporation on a
mixture of glycerine and water, by a floater of thin sheet copper; and I guide the
motion by a double rectangular frame, of which one extreme edge is mounted so
as to be free to turn round a horizontal axis, and the other extreme edge is pivoted
on a cross bar rigidly connected with the magnet.-Instead of this method of
supporting the moveable magnet, I sometimes prefer to support it simply by means
of fine threads or wires attached to fixed points. Other mechanical and electro-
magnetic modes of obtaining an equivalent result may be preferable in some cases,
as for instance the electro-magnetic arrangement herein before described as the
Direct" method for moving the mercury-bucket of my mercury-bucket-and-well
regulator. To cause the bar to take displacements in simple proportion to the
electro-magnetic force, and to return to its zero position when freed from that
force, I sometimes use a single spiral spring pulling the bar in the direction opposito
to that of the electro-magnetic force. The proper sensibility is adjusted by
lengthening or shortening the effective parts of this spring by a screw arrangement
such as is described in my Specification No. 2028 A.D. 1883.-But in many cases
the gravity of the magnet itself suffices.
"
The solenoids which pull the magnet herein before described have their apertures
of a diameter somewhat larger than the sectional diameter of the magnet, and are
fixed round the two ends of the horse-shoe.-The current to be measured is sent
through the solenoids in such a direction as to draw the magnet inwards in order
that demagnetization of the steel, such as might be produced by a current in the
opposite direction, may be avoided. The length of the solenoids ought to be
sufficient to allow all or nearly all of the free polarity of each end of the magnet
concerned, to lie within the solenoid through the whole range of the motion
allowed to the magnet. When the solenoids are uniform, I find that the force
pulling the magnet augments more, with equal additions to the strength of the
current, the stronger the current becomes.-To cause the additions to the displace-
ment, produced by equal additions to the current, to be nearly enough equal for
.practical purposes through the whole used range, I sometimes attach several little
transverse bars to a spiral spring pulling against the electro-magnetic force, and I
place fixed stops in such positions that one after another of these bars is stopped,
as the moveable end of the spring is pulled further and further.-1 estimate that
two of these bars will suffice to give a good practical result.-The position of the
first stop will be found by experiment, and then with a farther increase of the
current a second experiment will determine the position of the second stop.-A
'current galvanometer must be used in the circuit for making these experiments, and

page_text: a large-surface Daniell's Battery, or other convenient constant enough source
produce the desired currents.
The object of causing the additions to the displacement produced by equal
additions to the current to be equal, may be helped or may be wholly attained by
winding the solenoid less or more densely in some parts of its length than in
others.
The steel magnet carries on its upper side a point on which is balanced a
connecting rod, one end of which carries a pin or a ring by which it moves tho
integrator-frame by means of a ring or pin attached to this frame.-The steel
inagnet also carries a little frame on knife edges, to one end of which is fixed a
glass or metal pen carrying a sufficient supply of dissolved aniline to trace the
recording curve for several months.-This frame is balanced so that the pen presses.
on the paper with a very small definite and approximately constant force, which I
find need not exceed a decigramme
Instead of a straight bar magnet, or a horse-shoe magnet with straight parallel
branches, a bar-magnet bent to a circular arc may also be used, especially when
more of compactness is desired for the apparatus than the long straight bar allows.―
The bar, if circular, may be supported and balanced so as to be free to move round
a vertical axis through the centre of the circle.-With this form of magnet the
solenoid should be not straight but its axis should be circular to correspond to the
magnet.
To obtain greater power and compactness, the bar magnet may be bent into the.
form of the letter Z, but with its two ends in the form of arcs of a circle, having its
centre in an axis about which the bar magnet is free to move.--This allows electro-
magnetic solenoids to be used pulling the two ends of the magnet so as to give
conspiring effects.-I support it by silk thread or metallic wire so as to bear the
whole or nearly the whole of its weight and guide it against horizontal motions by
a pivot, or pin and collar, or vertical knife edges.
I also use as an alternative method, which is available either for continuous or
for alternate currents, the following apparatus.-A circular coil of fine wire, or of
thick wire or of copper ribbon, is mounted with its plane vertical in such a manner.
as to be free to move in a horizontal direction perpendicular to its plane. To do
may be hung
this I support the weight of the coil on a floater.-The coil itself
from the floater, and may be wholly or partially submerged under the liquid,
provided the liquid be of non-conducting material.-Heavy paraffine or petroleum
of the least volatile quality is suitable. To give the proper adjusting force I use a
fine thread passing horizontally to a pulley under the liquid, and upwards to a
buoyed weight, or downwards to a sinker ;-or I use a spiral spring pulling in the
direction opposite to that of the electro-magnetic force; or two spiral springs which
also serve for the electrodes of the coil, joining its ends to two fixed terminals.―.
These terminals are put in connection with the two electric mains. Or I support
the moveable coil on an approximately vertical balance arın above the line of knife
edges, with a counterpoise below insufficient to give it stability in this position.―
When the moveable coil is of thick conductor it is joined into the circuit through
slips of copper dipping into cups of mercury arranged as nearly as possible in line
with the knife edges.-I attach a floater to the balance above the line of kuife
edges, so that when the whole is submerged under oil the moveable coil is
sufficiently stable above the line of knife edges.-A bar carried by the balance arm
and projecting above the oil gives by a connecting rod or cord the proper deflection
to the integrating wheel to correspond to the strength of current to be integrated.
-The moving coil thus constituted an electro magnet, is urged by another electro
magnet composed of a single coil or of a pair of coils through which the current to
be measured passes.-These coils may be arranged to give as nearly as may be, an
equally effective field of force for the moving coil throughout the whole range of
its motion. This may be done by making the fixed coils flat and very broad but I
prefer to do it by making these coils less broad and not flat but of the curvilineal
shape shewn in the Drawings.-This is easily done by first making the coils flat

page_text: and then slipping the different turns relatively to one another, so that the edges of
the ribbon lie on the curve shewn in the drawing, being concave towards the field
in which the moving coil moves.-I find by theory that if the overall diameters.
of the coils were infinite in comparison with their other dimensions, an exact
uniformity of field would be given by making the curves exactly circular.-The
circular form will in practice, with such proportions as those shewn in the Drawings
render the uniformity of the field perfect enough or nearly perfect enough for
practical purposes. If the fixed coils be of fine wire the proper shape is given to
them by winding them on properly shaped bobbins.-The main line in which the
current to be integrated flows is in circuit with the moveable coil, and a branch
current between the two mains flows through the fixed coils, or vice versa,
according to which of the coils are made of fine conductor and which of thick.
In case of failure of the automatic action of the integrating wheel, the curve
recorder gives
a curve whose area, found by any of the known practical methods,
shews the amount of the account against the user.-I supply with the instrument
when desired a special integrator for integrating the curve, constructed on the same
plan as the integrator and which works automatically in the regular action of the
instrument. For this purpose I use a wheel-frame and integrating wheel on the
same plan as that described above.-The pivots of the vertical axis of the integrator
frame are supported on bearings attached to a horizontal bar, pivoted on the
moveable edge of a double jointed frame like that described above for guiding the
steel magnet of the apparatus.-The fixed axis of this jointed frame is fixed
properly on a table and the ribbon of paper carrying the curve is placed firmly on
the table with its zero line in such a position, that the integrating wheel rests with
its rim on it, and that its direction is perpendicular to that of the parallel axes of
the guiding frame.-A tracing point fixed to the wheel-frame, is then carried over
the curve to as great a length as the jointed frame allows. Thus the area of part
of the curve is obtained on the integrating wheel. The paper is then shifted to
allow a fresh portion to be operated on and so the whole integration is effected.
When the amount of current to be integrated and recorded is liable, from the
needs of the users, to vary between very wide limits so as to be at times beyond
the range of a single recorder such as that described above, I use a double, or
triple, or multiple instrument on the same plan, constituted as follows and which I
terin a long-range recorder and integrator.-Two or more sets of the electro-
magnetic mechanism of the apparatus described above are so connected by a
convenient automatic make-break, that so long as the amount of the current to be
integrated is less than a certain limit it all passes through the solenoid or solenoids
of the one set of electro-magnetic mechanism, and is recorded by it; and when the
current to be integrated is above this limit it is caused to divide it-elf through the
solenoid or solenoids of the second electro-magnetic mechanism. Thus while part
of the current is still recorded by the first mechanism, the excess of the whole
above this part is recorded by the second mechanism.-The clockwork is arranged
to drive the paper wheel for each of the recording mechanisms.
A form of the current recorder and integrator suitable for recording and
integrating continuous currents is represented respectively in front elevation and
end section at Figures 33, and 34.-The long bar magnet al, actuated by the
solenoid 3, is suspended by the cords c¹³, attached to the arms d¹³, (or by any
convenient arrangement) from the floater e13, floating freely in water or other
suitable liquid contained in the reservoir 13-The motion of the magnet to and
fro is caused to take place in a vertical plane passing through the axis of the
solenoid, by the double jointed frame g³, having one end pivoted on an axis fixed
to the frame of the instrument, and the other end pivoted on an axis fixed to the
bar magnet a-The bar-magnet carries pivoted on a needle-point the connecting
rod 3, which transmits the motion of the magnet a³, to the frame ¹³, carrying
the integrating wheel j³, (hereinafter more particularly described) by means of a
needle point on the rod h¹³, acting on the cup 3, fixed mouth down on the wheel-
frame The magnet 3, carries the light frame pivotted on
an axis

page_text: perpendicular to the axis of the magnet.-This frame 13, carries at one end the
glass or metal pen m³, for recording by tracing an ink line on paper, and is
counterpoised at 13, so that the end bearing the pen is a little the heavier and.
causes the pen to press lightly on the paper.
A suitable arrangement of wheel-work driven by a weight or a spring, gives a
slow uniform rotation to the axle of the drum 03, which draws the paper with the
necessary tension across the flat brass recording table p¹³, situated below the line of
motion of the pen.
The wheel-frame ³, carrying the integrating wheel ¹³, is pivoted so as to be
capable of notion, with as little friction as possible, about a vertical axis herein-
before called the "main-vertical," passing through the axis of the drum o¹³, and the
shape of the integrating wheel 1, is such that the point of contact between it and
the drum o13, is in this same vertical axis.
A spring q, which, for the purposes of adjustment, is fixed at one end to the
frame-work of the instrument according to the method hereinbefore described with
reference to my mercury-bucket-and-well regulator, or as described in my
Specification N° 2028 A.D. 1883 in connection with the potential regulator, has its
other end attached to the bar magnet als, and supplies a force tending to bring the
bar magnet back to its zero position when deflected from it by reason of a current
flowing through the solenoid 613-The transverse bars for compensating the
unequal additions made to the force exerted on the magnet a¹³, by the solenoid 613,
are secured to the spring q¹³, and proper stops are fitted for them to abut against.
When the pendulum method of compensation is adopted I sometimes suspend
the pendulum from a pin fixed in one of the vertical limbs of the guiding frame gl³,
which is made broad enough to receive the pins or curved cheeks.
The modifications necessary to adapt this instrument to record and integrate
either continuous currents or the currents from alternate current machines aro
represented respectively in front elevation and horizontal section at Figures 35,
and 36. The bar magnet of the last described instrument is replaced by the fine
wire coil 13, carried by the bar 813, suspended from the floater 13-This coil 13 is
in the form of a toroid and is placed so as to be within the toroidal space formed
by the two coils -These coils n¹³, are made of riband copper, capable of
bearing the greatest current or currents to be measured without heating, and are
properly secured to the stand of the instrument., The guiding ³, guides the
motion of the bar s13, carrying the coil 13, the remaining parts of the instrument
being exactly similar to those already described.
J
The modifications of the instrument consequent on using bar magnets of horse-
shoe, curved, or Z shaped form, and of supporting the moveable magnets by
methods other than those shewn and hereinbefore described in connection with
Figures 33, and 34, have already been fully described;-as also the method by
which the integrating wheel herein before described as a part of the recorder and
integrator, may be used as a simple integrating wheel for measuring the area of
any space bounded by curved lines
As regards this part of any Invention the important and novel features are,
First A straight or curved bar or horse-shoe magnet actuated by a solenoid or
solenoids and floated or supported on a vertical axis with adjuncts adjusted to
produce motions in simple proportions to the strength of the current through the
solenoid or solenoids for the purpose of recording by a curve or of integrating the
current.
Second-The integrating wheel acting automatically in the manner described.
Third-The modification of the said apparatus adapted to integrate a curve by
hand.
Fourth-The fine wire electro-magnet coil connected to two fixed terminals and
floated or otherwise supported so as to permit of motion parallel to itself in the
approximately uniform field of force produced by flat or curved sided coils through
which the current to be measured passes, for the purpose either of measuring or of
recording and integrating the current.

page_text: Fifth The long-range recorder-integrator in which the current when too strong
for one, divides itself between the conductors of two or more recording and
integrating mechanisms.
Sixth The Z shaped bar adapted to allow the use of electro-magnetic positive
pull on each pole.
Seventh The supporting of part of the weight of the Z bar or equivalent in
electro-magnetic apparatus by thread or wire and guiding by a pivot or knife edges
or equivalent so as to give great freedom to move round a vertical axis at the same
time preventing any other motion.
For an electrometer to be used as a potential gauge, in cases where electrostatic
force suffices, my quadrant electrometer, with bililar suspension and sulphuric acid
connection between the needle and one of the pairs of fixed quadrants as described
in my book entitled "Electrostatics and Magnetism" Sections 344 to 357 may be
used; but for this purpose I prefer an improved form of that instrument, the
improvement consisting in the needle being hung by fine platinum or other wires
so that the Sulphuric Acid connection is dispensed with, and convenient means
being afforded of varying the force to suit the circumstances.-The instrument
thus improved I use as a balance-measuring instrument by finding the torsion
required to bring the needle to a stated position when the greatest accuracy is
wanted. But the same instrument serves as an inspectional potential gauge by
leaving the torsion head untouched and reading off the potential by the position of
the needle on a specially graduated scale.-This scale may be graduated either by
comparison with the long range electro-magnetic potential meter herein before
described in connection with Figures 43, to 45, (inclusive) of my Specification
N° 2028 A.D. 1883; or by aid of the torsion head of the electrometer itself used as
a balance instrument. To prevent the fine suspension wire from being broken
when the instrument is carried about, I use the ring and pin safety guard described
in connection with Figures 43, to 45, (inclusive) of my Specification N° 2028
A.D. 1883.
As regards this part of my Invention the important and novel feature is,
For gauging and measuring the difference of potentials between any two points
of an electric circuit, the improved electrometer substantially as hereinbefore
described.
When any of the forms of regulator hereinbefore described are used for current,
instead of potential, in order to prevent overheating in the resistance coils I make
them of metallic riband preferably German-silver or Iron and wind them on the
outside of a metal can (preferably copper) containing water, and covered by a lid
with a steam pipe to carry off waste steam or to give surface enough to condense
it and let it run back as liquid into the can, in cases in which the evaporation is
so great as to make the lid necessary or useful.-The outside of the can is coated
with thin strong insulating material such as thin paper laid on several times round,
and consolidated by shellac Varnish. In places where there is a sufficiently
abundant and convenient water supply, I keep the can cool by a flow of water
through it.
As regards this part of my Invention the important and novel feature is,
The resistance coils for use with current regulators substantially as hereinbefore
described.
Instead of the jointed arrangement to prevent lateral motion, or any deviation
from strictly horizontal motion hereinbefore described in connection with the
current recorder and integrator and illustrated at Figures 33, and 34, of the
annexed Drawings I sometimes effect this by an alternative method.-I use a
wheel pivoted on a vertical shaft, and two straight horizontal rails presenting
vertical planes, that is to say one rail on each side of the wheel and at such a
distance apart that the wheel cannot touch both rails simultaneously. These rails
are attached to the moveable magnet or body of the recorder and integrator and
the axis of the wheel is fixed; or vice versa, the bearings of the wheel are attached
to the moveable magnet or body and tho rails fixed.-If the moveable body

page_text: diverges, by more than a very small distance from its proper line of motion, the
wheel rolls on one or other of the rails, and prevents any greater deviation from
the proper line of motion taking place.
The last mentioned arrangement besides being applicable to the magnet or
moveable body of the recorder and integrator is also applicable to the moveable
magnet or body of a potential meter or of a regulator or controller.
As regards this part of my Invention the important and novel feature is,
The alternative arrangement of apparatus for preventing lateral motion or
deviation from strictly horizontal motion in current recorders and integrators,
potential meters, or in a regulator or controller, and consisting of the pivoted wheel
on vertical axis and pair of rails operating as hereinbefore described.
Having now described and particularly ascertained the nature of my said
Invention, and the system, mode, or manner in or under which the same is, or miny
be used, or carried into practical effect, I observe in conclusion that I have pointed
out what are the important and novel features of my Invention under the several
heads above described, and I would have it understood that those features of my
Invention, while they are new as applied, are only claimed as used respectively in
combination with the others or other of them, or their equivalents, and forming
the several new and useful combinations which constitute respectively my improved
apparatus (1,) for generating and (2,) for regulating (3,) for measuring and (4)
for recording and integrating, electric currents substantially as described, and such
combinations are not disconnected Inventions but are used as parts of a whole
which I claim as my entire invention and from which the best results aro obtained
by using conjointly all the said combinations.
In witness whereof I, the said Sir William Thomson, have hereunto set my
hand and Seal this Twenty-fourth day of March in the year of Our Lord One
Thousand Eight Hundred and Eighty-four.
WITTAN THOMSON (LS)