IMPROVEMENTS IN MEANS FOR GOVERNING STEAM AND OTHER FLUID PRESSURE ENGINES to be as follows :
Year: 1885

page_text: I, WILLIAM CAMERON of 17, Yarborough Road, Lincoln,, in the County of
Lincoln, Mechanical Engineer do hereby declare the nature of the said inven-
tion for "IMPROVEMENTS IN MEANS FOR GOVERNING STEAM AND OTHER FLUID
PRESSURE ENGINES to be as follows :—
"
This invention relates to improvements in and applicable to steam and other
fluid pressure engines whereby better means than heretofore are provided for
governing the said engines.
In carrying out my invention I provide an improved construction of relay
cylinder valve and valve casing; the relay cylinder piston is caused to take up
a position corresponding to that of the core of a solenoid by means of a lever,
a sleeve with oblique slot and an arm and connections; the position of the core
of the solenoid is regulated to the relative position of the ports in the valve to
those in the casing so that when there is a mean current flowing through the coils
of the solenoid the core will be in its mean position and the ports in the valve will
just be on the point of opening the ports according as the core is drawn into or
forced out of the solenoid.
For this purpose I employ a solenoid into which the core is drawn against the
resistance of a spring by the action of the current in the coils of the solenoid.
Into the core is screwed a brass spindle which connects the core to the spindle of
the valve of the cylinder through a lever which is pivotted on a fulcrum cast on
a long stuffing box through which the valve spindle works.
The admission ports of the valve communicate with ports which lead into the
cylinder; the exhaust ports are at the ends of the valve casing and are covered
by the valve when in mid position. A port admits the gas steam or other fluid
under pressure which furnishes the motive power into the interior of the valve
whence it passes through one of the admission ports and is exhausted from the
[Price 1121

page_text: cylinder by one of the exhaust ports round by a passage behind the valve. By
this means the valve is nearly in equilibrium. The valve has two distinct
movements communicated to it, namely, those of translation and rotation.
The movement of translation is given to the valve by means of the solenoid core
so that the valve opens one of the ports leading to the cylinder as the core is
drawn into or forced out of the solenoid by the increase or decrease of the current.
The direction of motion of the piston is thereby governed and when combined
with the movement of rotation, the duration of that motion is also governed.
The movement of rotation is given to the valve by the motion of the piston
which is communicated to the valve through a lower spindle in a sleeve and an
arm one end of which slides on the sleeve the other end being secured to the
lower end of the piston rod; a pin is screwed into the sleeve and passes through
a slot in the spindle so that the motion received from the solenoid core is not
interfered with.
The arm is threaded on the sleeve which has an oblique groove in which travels
a set screw, screwed into the arm. The arm upon receiving the motion of the
piston rotates the sleeve to an extent equal to that which the groove is out of
the perpendicular. This motion is transmitted to the valve by the herein before
described pin. When the solenoid core has opened the valve port fully, the piston
will travel its full stroke and the angle of the oblique groove must be such that
the valve will be rotated sufficiently to close the port at that moment. i.e. when
the piston has just completed its stroke.-The motion of the piston is transmitted
to a die in a vibrating link (the position of the die determining the point of
cut off so that when a mean current is flowing in the solenoid .coil the die will
be, in the middle position), by a lever jointed to a projection on the piston rod.
The governor can be arranged to control the admission of steam by the vibrating
link or this may be replaced by any suitable form of expansion gear or the piston
rod may be coupled direct to an equilibrium throttle valve.
I can employ in place of the, herein before. described solenoid a high, spoed
centrifugal governor the governor spindle being connected thereto in sucli a,
manner that it will receive motion from the ball, arms, so that when the balls,
rise the spindle will be depressed and vice versa.
711
941
For regulating the position of the core of the solenoid, thumb screws are
employed the upper part of the core being turned down and continued through
the lower part of one of the thumb screws which, has a groove in which slides;
a pin which is carried in the prolongation of the core. By rotating the latter
thumb screw the core is also turned, as the spindle thereof which is screwed into
the core cannot turn, owing to the end of, the lever connected to the valves
spindle being placed in a slot cut in the spindle of the core which, spindle will
be lengthened or shortened according to the direction in which,the, thumb screw
is turned. If the said lever be kept, horizontal and the core spindle be lengthened.
the core will be lifted further out of the solenoid; if the spindle be shortened then
the core will be pulled further into the solenoid.
-
The other thumb screw regulates the pressure on the spring, of the solenoid.
The valve of the cylinder is operated in such a manner that the piston, in the
cylinder is caused to take up a position: corresponding to the movement of the
solenoid or the balls.
Instead of employing a high speed governor for controlling the valve, the said
governor may be replaced by a solenoid and core. The valve and casing are
essentially the same as those herein before described. except that the port is in
this case perpendicular to the axis of the valve.
The movements of the solenoid core or ball arms are communicated through
a spindle to a floating lever, the fulcrum of which, is carried on a double lever;
tbe said fulcrum acts only as a fulcrum so long as there is no motion of the piston
or that the movement of the piston is slower than or lies within the range of
travel of the spindle of the core of the solenoid. The fulcrum of the double lever
[

page_text: is carried by the stuffing box of the valve spindle the opposite ends being carried
on a set.screw screwed into the piston rod.
The action is as follows:
On the balls or the solenoid core depressing the before mentioned spindle the
valve is lifted by its lever. On the ports coming opposite each other the piston
is forced down carrying with it the ends of the double levers; this brings down
the pin on which the valve lever is hung. The end of the valve lever opposite the
valve now becomes the fulcrum of the lever and it will now turn about the said
end, the opposite end travelling through an arc sufficiently large to close the port,
thus bringing the valve back to its middle position in readiness for another
movement of the before mentioned spindle.

page_text: Improvements in Means for Governing Steam and other Fluid
Pressure Engines..
I WILLIAM CAMERON of 52 Canwick Road, Lincoln, in the county of Lincoln,
Mechanical Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement :—
This invention relates to improvements in means. for governing steam and other
fluid pressure engines and in engine governors in which a solenoidal electro
magnet hereafter called a solenoid, or an ordinary solenoid is.used, the latter
engines being employed for driving dynamo electric machines some of which
require the speed of the engine to be kept constant while others require the speed
of the engine to vary in proportion to the resistance of the circuit.
In carrying out my invention I provide an improved construction of relay
cylinder valve or valves and valve casing, the said valve or valves controlling the
supply of steam or other fluid to the ends of the power cylinder, the piston of
which operates the regulating mechanism of the engine; the relay or power
cylinder piston is caused to take up a position corresponding to that of the core
of the solenoid by means of a lever or system of levers, a sleeve with oblique slot
and an arm and connections; the position of the core of the solenoid is regulated
to suit the position of the ports in the valve relatively to those in the casing so
that when there is a mean current flowing through the coils of the solenoid the
core will be in its mean position and the ports in the valve will just be on the
point of opening the ports according as the core is drawn into or forced out of
the solenoid.
In that class of governor used in connection with engines driving dynamo
machines the speed of which is required to vary in proportion to the resistance in
the circuit, and in which a constant difference of potential is required to be
maintained, only the movement of the solenoid core from its mean position is
allowed to move the valve; the ports are in these valves oblique.
Two valves may, however, be employed the inner valve having a motion of
translation communicated by the solenoid core and the outer valve having a
rotating motion communicated by the piston of the power cylinder; the ports are
in both valves oblique. Or a valve can be employed that is actuated by a gear in
such a manner that the solenoid core moves the valve to open the ports, while the
movement of the piston of the power cylinder closes them without causing any
movement in the solenoid core.
When the governor is employed to control the speed of an engine driving a
dynamo machine employed in incandescent lighting the machine being one whose
speed varies in some proportion to the resistance in the circuit, I use a governor
the mechanism of which is arranged to allow the solenoid core to return to its
mean position without moving the valve, the core having been moved from its

page_text: mean position by an increase or decrease from the normal current. The electro
magnets forming the solenoid are wound in a shunt from the main when the
lamps are arranged in parallel.
:
The device of allowing the solenoid core to return to its mean position without
moving the valve of the power cylinder, enables the engine to run at that speed
which is required to feed the number of lamps then in circuit, the electro motive
force remaining constant. For are lighting or in any case where the lights are
arranged in series the solenoidal electro magnets may be wound to take the whole
of the current.
•
In order to enable my invention to be fully understood I will describe the saine
by reference to the accompanying drawings in which figures 1 and 3, sheet 1;
represent vertical sectional elevations of governors for steam and other fluid
pressure engines constructed according to my invention and applicable to engines
for driving dynamo electric machines which in order to maintain a constant electro
motive force do not run at a constant speed; figure 2, sheet 1, is a detached
vertical section of the solenoid and core the view being taken at right angles to
figure 1; figure 4, sheet 1, is a sectional view of a modified form of lever
connecting the valve spindle with the solenoid core; figure 5, sheet 1, is a
detached sectional view of part of the sleeve and arm and figure 6, sheet 1, is an
elevation of the same seen at right angles to figure 5; figures 1, 2 and 3, sheet 2,
are similar views to figures 1, 2 and 3, sheet 1, but illustrating arrangements of
governors suitable for maintaining a constant potential with a constant speed of
driving or a constant current; figure 4 sheet 2, is a sectional elevation of the left
hand side of figure 3 sheet 2.
Referring to figures 1 and 2 sheet 1, h, h, represent the solenoid consisting of
two electro magnets which if the engine be required for driving machinery for
incandescent lighting would be wound by a shunt wire from the main, the current
passing round both electro magnets in such a manner as to bring their poles which
are alike to one end. These poles or ends are connected by plates i, i, of magnetic
material the lower plate being insulated electrically and magnetically from the
governor stand; between the electro magnets a tube of non-magnetic material is
placed and within this tube a soft iron core called the solenoid core k, is placed:
and connected to the valve b; into the solenoid, the core k, is drawn against the
resistance of a spring 2, by the action of the current in the coils of the solenoid h, h.
Into the lower end of the core k, is screwed a brass spindle B which connects the
core to the spindle. C of the valve b, of the cylinder A through a lever k¹, which is
pivotted on a fulcrum or bracket D, cast on a long stuffing box E through which
the valve spindle C works; the lever ¹, is pivotted at 1, and has two arms F
and G carrying studs H and I on which hang two pawls m, m', engaging with
racks J and K on a lever n; which gives motion to the valve b. The two
pawls m, and m¹, are each connected by springs o and o¹, to studs, one of which is
shewn at L and which have no movement but are screwed to the bracket D of the
valve spindle stuffing box E.
The admission passages M, N formed in the tubular valve b, communicate with
oblique ports' c, c¹, which lead into the power cylinder A, the piston O, of which
actuates the regulating mechanism of the engine; d, d, are the exhaust ports.
A pipe e, admits the gas, steam or other fluid under pressure which furnishes the
motive power through a passage f, to the ends of the valve b, whence it passes
through one of the admission ports c or c', to the cylinder A and is exhausted from
the cylinder by one of the exhaust ports d, or d and through corresponding
oblique ports d³, d³, in the valve b, to its interior and then through a passage g, to
the outside of the casing. By this means the valve b, is nearly in equilibrium and
controls the admission to and exhaust from the power cylinder A
The object of the pawls m, m³, racks J and K and springs o, o', is to allow the
solenoid core k, to return to its mean position without moving the valve b. The
pawls m, and m, are in contact, with the racks J and K both at one time, only in
one position, viz, when the solenoid core k, is in.its mean position,

page_text: "
For example, supposing the solenoid core k, to be drawn down from its mean
position, by an increase of electromotive force owing to a lamp being shunted out,
the lamps being arranged in parallel, the top pawl m, would leave the rack J; the
bottom pawl m, still engaging with its rack K would transmit the movement of
the solenoid core k, to the valve b, thereby opening it, admitting fluid to the top of
the power cylinder piston O, which in moving closes the valve b, the movement
of the piston O at the same time operating the regulating appliance of the engine
so as to reduce the speed of the engine. On the speed of the engine being reduced
the electro motive force will again become normal which allows the solenoid core k,
to return to its mean position. On the return movement of the solenoid core k,
commencing, the lower pawl m², will be clear of its rack K and the upper pawl m,
will be prevented from engaging with its rack J, by the spring o¹, until the Bolenoid
core k, arrives at its mean position when both pawls m and m¹, will be again in
contact with their respective racks J and K. On the core k, rising above its mean
position owing to the fall of potential or electro motive force, the same action
takes place but with opposite pawls, the top pawl m, now moving the lever n³, to
open the valve b.
When the return takes place the bottom pawl m¹, is prevented
from engaging with its rack K by the spring o. The valve b, has two distinct
movements communicated to it, namely, those of translation and rotation.
The movement of translation is given to the valve b, by means of the solenoid
core so that the valve b, opens one of the ports leading to the cylinder A so as to
admit the fluid to one end and allow it to be exhausted from the other end of the
cylinder as the core k, is drawn into, or forced out of the solenoid h, h, by the
increase or decrease of the current, the piston moving the valve so as to close
the port. and prevent any further admission or exhaust to or from the power
cylinder until a further movement of the solenoid core in either direction has taken
place. The direction of motion of the piston O is thereby governed and when
combined with the movement of rotation the duration of that motion is also
governed.
The movement of rotation is given to the valve b, by the motion of the piston O
which is communicated to the valve through a lower valve spindle P working in a
sleeve and an arm 8, one end of which slides on the sleeve q, the other end being
secured to the lower end of the piston rod Q; a pin p, is screwed into the sleeve q,
and passes through a slot R in the valve spindle P, which allows of the vertical
movement of the valve so that the motion received from the solenoid core k, is not
interfered with.
The arm s, can slide on the sleeve q, which has an oblique groove S. (shewn
clearly in figure 6) in which travels a set screw r, screwed into the arm 8.
The action is as follows: Any movement of the solenoid core from its mean
position is communicated to the valve b, thereby opening the ports by causing
those in the valve b, to_coincide with those in the casing by a vertical movement,
this immediately causes a movement of the piston O which movement is communi-
cated to the arm 8; the arm s, upon receiving the motion of the piston O, rotates
the sleeve q, to an extent equal to that which the groove S is out of the per-
.pendicular. This motion of rotation is transmitted to the valve b, by the pin p.
This movement covers the ports in the casing thereby stopping the admission of
the fluid to and exhaust from the power cylinder A, and causing the piston O to
take a position corresponding to that taken by the solenoid core k, the movement
of the piston: O always being in a certain ratio to that of the solenoid core k.
When the solenoid core k, has opened the valve port fully the piston O will travel
its full stroke and the angle of the oblique groove S must be such that the valve b,
will be rotated sufficiently to close the port at that moment i.e. when the piston O
has just completed its stroke. The motion of the piston can be transmitted to a
die T in a vibrating link U (the position of the die T, determining the point of cut
off so that when a mean current is flowing in the solenoid coil the die T will be in t
the middle position) by a lever V jointed at W to a projection X on the piston
rod the said vibrating link. working the expansion valve of the engine. ..

page_text: The governor can be arranged to control the admission of steam by the herein-
before described vibrating link U or this may be replaced by any suitable form of
expansion gear or the piston rod may be coupled direct to an equilibrium throttle
valve.
For regulating the position of the core k, of the solenoid h, h, the compression of
the spring 2 and the position of the valve b, thumb screws 4 and 3 are employed,
the upper part of the core k, being provided with a spindle Y, sliding in the thumb
screw 4, which has a groove in which slides a pin or feather Z on the spindle or
prolongation Y of the core k. By rotating the thumb screw 4, the core will be
rotated and raised or lowered as the lower spindle B, thereof which is screwed into
the core k, cannot turn owing to the end of the lever ¹, connected to the valve
spindle C, being placed in a slot cut in the spindle B of the core which spindle will
be lengthened or shortened according to the direction in which the thumb screw 4,
is turned. If the lever, be kept horizontal and the core spindle B be lengthened,
the core k, will be lifted further out of the solenoid h, h; if the spindle be shortened
then the core will be pulled further into the solenoid. The other thumb screw 3,
between which and the core k, the spring 2 of the solenoid is placed serves to
regulate the pressure on the said spring, which balances the pull on the solenoid
core when the normal or mean current passes through the electro magnet.
The governor shewn in figure 3, sheet 1, is similar to that hereinbefore described
when referring to figure 1, sheet 1, with the exception that the herein before
described solenoid is employed in conjunction with a high speed centrifugal
governor, the governor spindle being connected thereto in such a manner that it
will receive motion from the ball arms so that when the balls rise the spindle will
be depressed and vice versa.
The valve of the cylinder is operated in such a manner that the piston in the
cylinder is caused to take up a position corresponding to the movement of the
solenoid or the balls. The movement of the centrifugal governor.is caused to com-
pensate for the movement of the solenoid core during.its return to its mean position.
In order that the return movement of the solenoid core shall cause no movement of
the valve b, I arrange the governor in the following manner: Supposing the mean
number of lamps to be in circuit and the lamps to be in parallel, a normal current is
required. If the engine be running at its mean speed the centrifugal governor being
driven by the engine will run at a corresponding speed and the governor balls B¹, B1,
will be at their mean position or mean radius, the solenoid will be in its mean position
and the valve b, will be just on the point of opening in one direction or the other.
If now some of the lamps be shunted out the electro motive force will at once rise
drawing down the solenoid core k, and moving the lever a², which is pivotted on a
link 6; the link is attached to a lever d', whose inner end is carried by the
centrifugal governor spindle C. On the solenoid core k, being drawn down, the
valve b, will be opened thereby admitting fluid to the power cylinder piston O
which on moving will close the valve b, and move the regulating appliance so as to
reduce the speed of the engine. In consequence of the engine now running at a
slower speed the centrifugal governor balls B¹, will fall from their mean radius and
take up a position corresponding to the speed at which the engine is then running.
For the same reason the potential will return to its normal allowing the solenoid
core le to return to its mean position. As the speed gradually decreases from the
mean speed the centrifugal governor balls B¹, will gradually fall from their mean
radius and the solenoid core k, will gradually rise until it arrives at its mean
position when the current will become again normal. The speed will now remain
steady until another change occurs in the number of lamps in circuit. These two
movements of the solenoid core k, and centrifugal governor in opposite directions
acting through suitable gearing serve to counteract the effect of each other on the
valve b, so that no movement of the valve occurs during tbe return of the solenoid
core to its mean position.
Figure 4, sheet 1, shews a modified arrangement of the pawls and rack
represented in the governor shewn, in, figure 1, sheet 1. It consists of two levers a

page_text: and c, pivotted at d. One end of the lever a, is connected to the solenoid core k,
and one end of the lever c, is connected to the valve spindle. Two pawls e, el, are
hung, on studs H and I carried by the lever a; the pawls engage with a rack b,
carried on the lever c, and are provided with fingers f, f'; the fingers both come in
contact with studs g, g', carried by a bracket D on the valve spindle stuffing box E
and the pawls e, e¹, are both in contact with the rack b, when the solenoid core le,
is in its mean position. The action of this gear is as follows: Supposing the
solenoid core to be drawn down by an increase of electro motive force the lever a,
will turn upon the pin d, and the pawl e¹, will leave the rack in consequence of.its
finger fresting on the stud g, which causes the end of the pawl to rise clear of
the rack b; the pawl e, still remains in contact with the rack b, and transmits the
movement of the solenoid core to the valve thereby opening it and admitting fluid
to the top of the piston of the power cylinder which in moving closes the valve
and at the same time moves the regulating appliance of the engine so as to reduce
the speed of the engine; consequently the electro motive force will again become
normal allowing the solenoid core to return to its mean position ; on the return
movement taking place the pawl e, moves over the rack whilst the pawl el, is kept
clear of it by its finger f¹, resting on the stud g¹, until the solenoid core arrives at
its mean position, thus no movement is given to the valve during the return of the
solenoid core to its mean position. On the solenoid core being forced above its
mean position owing to the fall of potential or electro motive force, a reverse
action takes place with respect to the pawls, the pawl e, being lifted clear whilst
the pawl e', moves the rack b, when the return movement of the core takes place
by reason of the quickening of the speed of the engine causing the potential to rise
towards its normal.
During this downward return the pawl e¹, moves over the rack b, the pawl e,
being kept off by its finger f, and the core will return to its mean position without
moving the valve.
Referring to figures 1 and 2, sheet 2, which shews an arrangement of governor
suitable for maintaining a constant potential with a constant speed of driving, or
a constant current, A is the power cylinder, b, the valve controlling the supply of
steam or other fluid to the cylinder by the ports cl, c, and the exhaust by the
ports d', d. The fluid is admitted to the ends of the valve in the valve casing by
the pipe e, and passage f. The exhaust passes through the port da, d³, in the valve
and thence from the interior of the valve through the passage g, to the outside of
the casing. The valve b, receives motion from the solenoid core k, and the piston O
of the power cylinder A; the movement of the solenoid core k, opens the valve,
whilst the motion it receives from the piston 0 of the power cylinder A closes it.
On a rise of potential the solenoid core is drawn down at once opening the ports
and causing the piston O to move which it continues to do until it closes the port
by moving the valve b, a distance equal to that which. the solenoid core k, had
previously moved it in the opposite direction. The movements are given to the
valve through an arrangement of differential gear arranged as follows. The
solenoid core is attached to a lever g³, whose fulcrum is on the stuffing box of the
valve spindle. On the lever g², is a stud a³, carrying a floating lever h³, one end
of which is connected to the valve spindle C; on the opposite end of the lever h³,
is attached a link a', which is secured to the lever i, by a pin at a³. The outer
end of the lever i, receives the motion of the piston O of the power cylinder A, the
other end being pivotted at a, on the valve spindle stuffing box E.
Figure 3, sheet 2, shews another arrangement for the same purpose as just
described, by reference to figure 1. The arrangement consists of a solenoid h, h,
power cylinder A, whose piston rod is connected to the expansion gear or other
regulating appliance of the engine. The controlling valve consists of two parts,
an inner valve c, moved by the solenoid core and an outer valve d, moved by an
arm 8, carried on the piston rod Q. The outer valve d, receives a rotating motion
from a sleeve q, having an oblique slot (as hereinbefore described when referring to
figure 1 sheet 1) in which a stud or projection r, on the arm 8, moves. The valve

page_text: casing is practically the same as already described and shewn in figures 1 and 3,
sheet 1. The outer valve has four ports, two communicating with each end of the
power cylinder; e', e, are the admission ports and f¹, f, are the exhaust ports; the
latter have corresponding ports in the inner valve c, by which the exhaust is adınitted
to the interior of the inner valve c, and thence through the port g, passes to the
outside of the casing. The admission ports in the outer valve d, are controlled by
the ends of the inner valve c. The ports in both valves as well as the ends of the
inner valve c, are oblique. By a suitable arrangement of the ports in the inner
valve c, the port g, may become the induction port and the ports e¹, e, the exhaust
ports; the exhaust would then pass by the passage h, through the pipe i. The
inner valve c, is coupled to the solenoid core k, by a lever g, whose fulcrum is on
a bracket D on the stuffing box E of the valve spindle C. A centrifugal governor.
can be used to replace the solenoid shewn in figures 1 and 3, sheet 2.
The governors are shewn in the annexed drawings arranged to operate the
expansion, throttle valve, or other regulating appliance by means of a lever but it
will be obvious that they can be coupled directly to the piston rod of the power
cylinder.
An ordinary solenoid can be employed in place of that shewn in the drawings.
Instead of employing solenoids in the governors hereinbefore described and
shewn in figures 1 and 3, sheet 2, the said solenoids may be replaced by centrifugal
governors.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. In a governor having a power cylinder whose piston controls the expansion
gear, throttle valve or other regulating appliance of the engine, the combination of
a tubular valve controlling the fluid to the power cylinder, a casing containing the
tubular valve with a passage arranged to bring the tubular valve practically in
equilibrium, a solenoidal electro-magnet consisting of two or more electro-magnets
with their poles which are alike at the same end arranged round a tube of non-
magnetic material in which tube is placed a soft iron core, herein called the solenoid
core substantially as hereinbefore described and represented in figures 1 and 2,
sheet 2 of the accompanying drawings.
2. The modified construction of the governor claimed in claim 1, in which a
centrifugal governor is used to replace the solenoidal electro-magnets substantially
as herein before described.
3. In a governor having a power cylinder the piston of which controls the
expansion gear, throttle valve or other regulating appliance of the engine the com-
bination of a solenoidal electro-magnet, tubular valve consisting of an inner valve
and an outer valve both having oblique ports, an arm secured to the piston having
a stud or projection sliding in a groove or slot in a sleeve and a casing containing
the tubular valves substantially as herein before described and represented in
figures 3 and 4 sheet 2 of the accompanying drawings.
4. The modified construction of the governor claimed in claim 3 in which a
centrifugal governor is used to replace the solenoidal electro-magnets substantially
as herein before described.