Improvements in or relating to Ships' and similar Compasses.
Year: 1897

page_text: Improvements in or relating to Ships' and similar Compasses.
I, LUDWIG RELLSTAB, of 52, Lornsenstrasse, Kiel, in the Empire of Germany,
Scientist, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in ships and similar compasses, and has
particular reference to prevention or correction of deviation or deflection.
When the magnets of a deflected compass suddenly change their polarity the card
will remain in an unstable equilibrium, and will turn through an angle of 180° to
the right or to the left, when an impulse is given from left or right. If instead of
changing the polarity of the magnets that is to say instead of turning the magnetic
axis of the card, it is only a little moved, the direction of turning may be controlled.
If when say an easterly deviation arises an electromagnet is excited so that its posi-
tive pole is in the E. point of the card, the compass card will turn towards the left.
If on the contrary the compass has a westerly deviation and the electromagnet
changes its polarity, the compass card will turn to the right. In this way the devia-
tion will be counteracted if there be means for showing whether there is any deviation
and to which side such deviation takes place.
As an illustration let M indicate a magnet secured to the card and m a smaller one
pivotted in a centre pin. The latter must be removed from M so far as not to be
deflected by the latter. If a declination arises in M and m, their deflections will not
be equal as has been proved by numerous experiments. The magnet m always has a
smaller deviation than M. Such apparatus works well only when the deviating cause
and the magnet m are on opposite sides of M. It is therefore advisable to cause the
centres of rotation of M and m to coincide. The action although of different power
is the same as regards its effect, that is to say m will have a smaller deviative
than M; consequently an easterly deviation will cause a deflection of the system m
to the left relatively to M whilst a westerly deflection would cause a deflection of m
to the right.
Stronger relative deflections of m and M can be attained by placing m with its
north pole towards the south. In another arrangement both systems M and m are
in the North-South line that is to say in the magnetic meridian as long as there is
no deviation. As soon as however deviation arises and the system M turns say to the
right, the system m will turn to the left (relatively to M), and vice versa.
A complete turning (180°) of m relatively to M is impossible, for during such
turning poles of the same polarity would tend to meet and therefore would repel each
other. This turning movement may be used to make electrical contact as will be
hereinafter described.
From the above it will be clear that there may be many constructions of an
indicator of declination consisting of a compass in a compass. This indicator of
deviations is hereinafter termed a "rider," which name appears suitable because this
indicator is placed on the card and controls its movement and direction.
The influence of the electromagnet on the "rider" is diminished by placing the
electro-magnets as low as possible. This arrangement of electro-magnets has more-
over the effect of increasing the stability of the card. Whether however the

page_text: influence of the electro-magnet be useful or the reverse in making contact it must be
in any case avoided.
و
If the electro-magnet maintains the circuit closed an over-compensation may take
place; if the opposite circuit is closed by it at the wrong moment the action of the
compensation already commenced will be influenced and prevented from being com-
pleted. An arrangement of the electro-magnet so as to neutralise its action on the
rider
is not impossible. In one arrangement the poles of the electro-magnet are
everywhere equidistant from the poles of the "rider" and they therefore neutralise
each other. But in such construction considerable difficulties are met with, and in
order to attain better working of the apparatus the "rider" is also provided with
electro-magnets.
The electro-magnets of the "rider are arranged with their poles opposed to
those of the permanent magnets, near the two contacts. As already mentioned this
does not alter the direction of deflections of the "rider," but the action is opposed
to that of the electro-magnets of the card. In such construction the "rider"
becomes a compass with variable polarity, which may have either easterly and westerly
deviations the card being compelled to follow the movement of the rider. Instead of
electro-magnets simple coils may be used.
On the above principle is based the construction of a compass in which declination
is prevented. The deflection of the rider is utilised to close circuits whereby one or
several electro-magnets become operative and cause the card to turn. The declina-
tion is here counteracted by a movement in the opposite direction. The dial is
maintained having slight oscillations in its horizontal plane said oscillations being
however, reduced to a minimum and being therefore without importance for practical
use.
In the compass according to the present invention the dial consists of a card made
of say mica which is cut out in the shape of sectors between the inter-cardinal points
in order to provide room for the rider and to enable the mercury cup arranged below
the card to be in view. Centrally over the card is arranged a frame or ring of hard
rubber provided in the centre with a cap. From the edge of the frame ribs radiate
to the periphery of the card which render the whole structure more solid, and serve
to support the lateral magnets and electro-magnets. In the direction of the N-S
line on the under side of the frame are secured central magnets. On the edge of the
frame there are placed two contact studs or pins both pointing downwards.
The cap is provided at the top with a small centre pin on which the rider is
mounted.
The central magnets consist each of 8, the lateral magnets each of 4, and the outer
magnets each of 2 superposed insulated iron-plates. The manner of securing and
the shape of the magnets is however, of no particular importance in this
invention.
The electro-magnets consist of several superposed insulated plates of soft-iron.
The rider may consist of a brass cross shaped piece provided with a central cap.
On its long arm it carries 4 permanent magnets or polarity opposite to that of the
card, so that when the rider, is in place, there is a S-pole at the N-point of the
card, and a N-pole at the S-point of the card. The upper edge of the rider magnets
is in the same plane as the card when the rider is placed in position. Beneath the
rider magnets there are placed two more electro-magnets. The short transverse beam
of the rider is provided at each end with a depending contact-stud or pin one on the
west side and one on the E-side; on the right hand half of said cross beam
there are moreover provided contact plates which for convenience will hereinafter
be referred to as I and II (I being on the North and II on the South-side) and on
the left hand half an adjustable balance weight for the purpose of bringing the
rider into a horizontal position.
The box of the compass contains a large amount of lead. It is laterally
provided with two holes for the conductors a lead and a return being placed
together. The card support is of the usual constructions and may be provided
with set screws to enable the pivot pin to be correctly adjusted. The pivot pin is

page_text: preferably made of steel, nickel-steel or brass having a steel point and is mounted
loosely in the card-support on a helical spring the point being blunt in consequence
of the considerable weight of the card. Of course the centre-pin may be provided
with an agate or other point.
The mercury cup is preferably of hard rubber provided with a central hole for the
pivot pin and with 4 concentric annular recesses of the same width and, as far as
possible of equal depths in order to prevent spilling of the mercury in consequence of
the compass being violently shaken or coming into an oblique position. Each recess
is connected by a stud or conductor with a binding screw in which are screwed the
ends of the electric-conductors.
The manner of winding the electro-magnets and the action of the current resulting
therefrom will be clear from the following explanation; the electro-magnet placed
in the N-half circle is destined to counteract easterly deviation and that in the S-half
circle westerly deviation. In the former the N-pole must therefore be on the
right,hand in the latter on the left hand side, when the circuit is closed. The
electro-magnets of the rider each time that the circuit is closed, must have their
N-poles in the North their S-poles in the South. As soon as the rider is placed on
the card, its contact-plates must be between the contact points of the card. The
contact-plates on the north side of the E-W line will be referred to as "I," the
contact south of said line as "II." The circuit of the contact I is closed when an
easterly deviation arises, that at the contact II when a westerly deviation arises. In
order to explain the course of the current the leads will be called 2 and 4 and the
returns and 3. If the circuit is closed at the contact I, the current from the
conductor 2 passes through the second mercury ring to the north electro-magnet of
the rider (wound right-hand if viewed from the South), to the South electro-magnet
of the rider (right hand winding, viewed from the south) to the contact I to the
right-hand end of the north electro-magnet (left-hand winding when viewed from the
east) through the winding of the latter to the contact stud and third mercury-
ring and back through the return wire 3.
If the circuit is closed at the contact II, the current passes from the conductor 4
into the fourth mercury ring, and its contact-stud to the right hand end of the South
electro magnet (right hand winding viewed from the East), through its winding into
the contact II, through the North electro-magnet of the rider to the south electro-
magnet of the rider (through the same wires of the rider therefore as before when
closing the circuit at the contact I), into the stud and first mercury ring and back
through the wire 1. With such system of conductors it naturally follows that the
contact studs must be secured in the rider and in the dial so as to be insulated from
them and that the contact I and II must not be electrically connected with each
other except by the wire which is used on the rider. It also follows that two sources
of electricity are required, one of which is connected with the wires 2 and 3 the
other being connected with the wires 4 and 1. This peculiar electric connection is
chosen in order to have the current always circulating from the left upwards and from
the right downwards, when viewed from the south, that is to say in the same direction
as the hands of a watch. In this manner to a certain extent a so called magnetic
plate is produced, the south side of which in the whole system is directed southwards,
and the north side northwards. Thereby the magnetism of the whole system is
increased. Sinall differences in the tension and strength of the current do not have
a disturbing effect.
The strength of the current to be used depends on the thickness
of the wire used. The thicker the wire the greater may be the strength of the
current and the magnetism excited will also be stronger and the counteracting of
the deviation better; the weight in this case however will also be greater, therefore
movement will be more difficult the number of windings on the electro-magnet less, the
magnetism excited less and the counteracting of the deviation will be much slower.
If the tension of the current be low, less sparking will occur at the contacts, and
less heating, the instrument will therefore be more durable.
. It would be advisable to use silk wound copper wire of 1mm. diameter and a current of
a strength of from 3 to 3.5 amp., with the lowest tension possible. The current for

page_text: the apparatus which must be converted into one of suitable strength and tension will
preferably be supplied by the dynamos of the ship. Storage batteries or primary
batteries are not so suitable for this purpose.
When fitting up the apparatus, the wires are at first connected to the similarly.
numbered binding screws of the mercury cup the latter is placed on its support and
the pivot pin is introduced. Then the annular recesses of the cup are filled with
mercury, all to the same level, the rider is placed on the card and the latter on the
pivot pin in such a manner as to have all the points of the contact studs dipping into
the mercury rings.
The apparatus works as follows:-
In accordance with the nature of deflecting elements or the resulting force of
deflecting elements a contact will be produced. In order to produce such contact
even when the deflecting influence is small, the intermediate magnets are provided.
The rider must therefore, according to the deflecting influence, deviate to one or
to the other side upon contact being made, the card begins to turn in consequence of
one of the electro-magnets becoming excited. At the same time the electro-magnets
of the rider become operative and as the polarity of the rider is now changed, the
rider is drawn into the line of the intermediate inagnets, the contact being thus
interrupted. Then it is closed again and the same thing is repeated till the magnets
of the card are in the N-S line. The electro-magnets of the rider, must therefore
as soon as they are excited have double or more the power of that of the permanent
magnets of the rider. If in consequence of previous correction, an over-compensation
takes place, the rider is deflected to the other side. The opposite contact is effected
and thus compensation in the opposite direction is produced..
This turning of the rider may be proved in the following manner.
Let H indicate the intensity of the magnetism of the earth.
K the power of the deflecting pole of the magnet (ship magnet).
με the power of the deflecting pole of the card-magnets
k=
a=
رو
"
rider magnets (changeable polarity).
the angle of deflection of the "card from the meridian.
B="
rider
"
"
r=this distance of the pole of the ship-magnet from the compass.
l=the distance of the magnets of the rider and of the card.
The turning moment acting in the right hand direction will be marked "
in the left hand direction "_".
+
" and
If the compass has an easterly deviation then the following forces act on one of
the poles of the rider.
a) when the contact is open.
b) when the contact is closed.

page_text: .
This is the normal working of the apparatus occurring after a wrong. contact, and
acting to bring the dial' again towards the North.
The influence of the electro-magnets on the rider has not been taken into
consideration in the above calculations, because this influence is the same, whether
the right or the wrong contact has been effected and because the position of the
electro-magnets of the card is not prescribed exactly. The card will oscillate there-
fore more or less in accordance with the delicacy of the instrument about the North..
As the movements of the dial and of the rider are in the opposite directions in this
position, the deflections may be diminished so as to render the compass capable of.
being used. The disturbing influence of the inclination is not noticeable in this
apparatus.
At the contacts it is best to use platinum points. The contact-studs should be
provided at their lower ends with cutting edges in order to diminish friction in the
mercury and should be amalgamated in order to always ensure as perfect contact as
possible; if desired the contact studs may be of platinum. Too violent and unequal
movements of the card and of the rider are avoided in this construction by adding or
removing weights or by altering the dimensions of the electro-magnets. When the
apparatus is set up and in use, such violent movements are obviated by a variable
resistance or by making the pivot pin adjustable in the dial support, thus regulating.
the immersion of the contact-studs.
It would also be possible instead of providing the rider with separate electro-
magnets, to make the N.-S. beam or one portion of it, of iron and to use the rider as
an iron-core.
Instead of using two electro-magnets at the ends only one may be used, if it be
sufficiently strong. The conducting wires are loosely connected under the compass
and must leave sufficient clearance to enable the box to swing freely. It is advisable
after the mercury is poured into the recesses of the cup and the compass put in
place, to spread a thin layer of oil or glycerine over the mercury in order to prevent
the latter from becoming contaminated or oxidised. A device for lifting the card off
the pivot pin may be easily arranged. This compass is also capable of being
constructed as a fluid-compass. There would be no difficulty in making provision in
case the compass refuse to act; this would be attained by using an ordinary card or
by removing the rider. A compensation device of the kind used hitherto is not
necessary as long as the intensity of the magnetism of the earth is greater at the
point where the compass is placed, than the power of the deflecting elements.
The shape of the rider; the arrangement of the electro-magnets (coils) and magnets
may of course vary and the apparatus could by made to work with only one circuit.
For instance the dial as well as the rider may be provided each with only one contact
stud, and the mercury cup with only two annular recesses. When the contact I is
closed the current goes through the windings of the electro-magnets of the rider and
through the North electro-magnets of the dial; when the contact II is closed the
current follows the same path in the rider and through the S-electro-magnets of the
dial. The current in each case enters through the contact stud of the rider and
leaves through the contact stud of the dial. The windings of all the electro-magnets
would remain the same as hereinbefore described..
*Dated this 15th day of Fahruary 1807
BOULT & WADE,
Agents for the Applicant.

page_text: I, LUDWIG RELLSTAB, of 52 Lornsenstrasse, Kiel, in the Empire of Germany,
Scientist, 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 ships' and similar compasses, and has
particular reference to the prevention or correction of deviation or deflection.
Were the magnets of a deflected compass (Fig. 1), to suddenly change their
polarity, the card would remain in an unstable equilibrium, and would turn through
an angle of 180° to the right or to the left, on an impulse being given from left or
right. If, instead of changing the polarity of the magnets, that is to say, instead of
turning the magnetic axis of the card, it is only moved a little, the direction of
turning may be controlled. If, when, say, an easterly deviation arises, (Fig. 2), an
electromagnet is excited so that its positive pole is in the E. point of the card the
compass card will turn towards the left. If the compass has a westerly deviation,
(Fig. 3) and the electro-magnet changes its polarity, the compass card will turn to
the right. In this way the deviation may be counteracted, if there be means for
showing whether there is any deviation, and to which side such deviation takes
place.
As an illustration, let M (Fig. 4) indicate a magnet secured to the card and ma
smaller one pivotted on a centre-pin. The latter must be removed from M so far as not
to be deflected by the latter. If a declination arises in M and m their deflections will
not be equal, as has been proved by numerous experiments. The magnet m always
has a smaller deviation than M (Figs. 5 & 6); such apparatus works well only
when the deviating cause and the magnet m are on opposite sides of M. It is
therefore advisable to cause the centres of rotation of M and m to coincide,
Figs. 7 & 8 showing two examples of this construction. The action although of
different power is the same as regards its effect, that is to say m will have a smaller
deviation than M; consequently an easterly deviation would cause a deflection of
the system m to the left relatively to M, whilst a westerly deviation would cause a
deflection of m to the right.
Stronger relative deflections of m to the right can be attained by placing m with
its North-pole towards the South. In another arrangement, shown in Figs. 9 and 10,
both systems M and m are in the North-South line, that is to say, in the magnetic
meridian as long as there is no deviation, M being in a stable and m in an
unstable equilibrium. As soon however as deviation arises and the system M turns,
say, to the right, the system m will turn to the left (relatively to M), and
vice versa.
A complete turning (180°) of m relatively to M is impossible, for during such
turning, poles of M and m of the same polarity would tend to meet, and thus limit
the turning of m. Owing to the turning of both systems being unequal, it becomes
possible to produce electrical contact, as will be hereinafter described.
From the above it will be clear that there may be many constructions of an
indicator of declinations which can be made as sensitive as desired, consisting of a
compass in a compass, one compass being turned through 180° relatively to the other.
This indicator of deviations is hereinafter termed a "rider," which name appears
suitable, because this indicator is placed on the card and controls its movement and
direction.

page_text: If we imagine a compass with a rider, Figs. 9 and 10, provided also with an electro-
magnet as in Figs. 2 and 3, then of course the excited electro-magnet will influence
the rider. The arrangement may be however such that the poles of the electro-
magnet are equidistant from the poles of the rider, so that their action is balanced,
as in Fig. 11.
The influence of the electro-magnet on the "rider" is diminished by placing the
electro-magnets as low as possible. This arrangement of electro-magnets has
moreover the effect of increasing the stability of the card. Whether, however the
influence of the electro-magnet be useful, or the reverse, in making contact, it must
be in any case avoided.
As
In order to ensure proper working of the rider it is itself provided with electro-
magnets. The electro-magnets of the rider are arranged with their poles opposed
to those of the permanent inagnets of the rider, near the two contacts, and are so
strong that their magnetization is superior to that of the permanent magnets.
already mentioned, this does not alter the direction of deflections of the rider i.e. there
arises the same difference-only to a lesser degree of deflection, as shown in
Figs. 5 and 6, but it opposes the action of the electro-magnets of the card on the
permanent magnets of the rider. In such construction the rider becomes a compass
with variable polarity, which may have easterly and westerly deviations, the card
being compelled to follow the movement of the rider, owing to the action of the
magnetism of the earth on the electro-magnets of said card.
On the above principle is based the construction of a compass in which declination
is prevented. The deflection of the rider is utilised to close circuits, whereby one or
several electro-magnets, both of the card and of the rider, become operative, and
cause the card to turn. The declination is here counteracted by a movement in the
opposite direction. The dial is maintained having slight oscillations in its horizontal
plane, said oscillations being capable of being reduced to a minimum, and being then
without importance for practical use.
The compass, a construction of which will now be fully described, acts as follows:-
In accordance with the nature of the deflecting cause producing the deviation
or the resulting force of such causes, a contact will be produced. The rider must
therefore, according to the deflecting influence, deviate to one or to the other side.
Upon contact being made the card begins to turn, in consequence of one of the
electro-magnets becoming excited. At the same time the electro-magnets of
the rider become operative and as the polarity of the "rider" is now changed, the
"rider" is drawn into the direction of the magnets of the card, the contact thus
being interrupted. Then it is closed again and the same thing is repeated till the
magnets of the card are in the N-S line. The electro-magnets of the rider must
therefore, as already mentioned, as soon as they are excited become stronger than the
permanent magnets of the "rider." If, in consequence of previous correction, an
over-compensation of the card takes place, the rider is deflected to the other side.
The opposite contact is effected and thus compensation in the opposite direction is
produced.
This turning of the "rider" may be proved in the following manner :—
Let H indicate the intensity of the magnetism of the earth.
K the power of the deflecting element of the magnetism of the ship.
u the power of the deflecting pole of the card-magnets.
v=
"
"
"" "
"
"
"
rider-magnets (changeable polarity)
a=the angle of deflection of the card from the meridian.
B the angle of deflection of the "rider" from the meridian.
T = the distance of the pole of the deflecting element from the compass.
-the distance of the magnets of the "rider" and of the card.
"
The turning moment acting in the right hand direction will be indicated by +
and in the left hand direction "
-
"
"
If the compass has an E. deviation then the following forces act on the "rider,"
Figure 12.

page_text: 'In this case therefore the momentum turning the rider when a wrong contact has
been effected is greater than above. And in reality the return of the "rider" in this
case is much quicker.
When the dial under the "rider" is on the point of being over-compensated, the
following moments act on the "rider (Figure 14).
"
This is the normal working of the apparatus occurring after a wrong contact, and
acting to bring the dial again towards the North.
The influence of the electro-magnets on the rider has not been taken into
consideration in the above calculations, because this influence is the same, whether
the right or the wrong contact has been effected, and because the position of the
electro-magnets of the card is not prescribed exactly. The card will oscillate,
therefore, more or less, in accordance with the delicacy of the instrument, about the
North. As the movements of the dial, and of the rider, are in the opposite directions
in this position, the deflections may be diminished, so as to render the compass
capable of being used.
This is under an assumption that at the place where the compass it situated, the
magnetism of the earth is still stronger than the force of the deflecting elements of
the magnetism of the ship. Fig. 15 is a diagrammatic plan of the path of the
current, when only a circuit is to be used.
In case of E. deviation the contact is closed at I.
The electric current comes from the point 1, passes through the electro-magnets K
of the rider, which thus become excited, into the contact I and electro-magnet U of
the card, which thus also becomes excited and returns at the point 2.
In case of W. deviation the contact II is closed. The electric current arrives
from the point 1, passes through the electro-magnets K, contact II, into the electro-
magnet V of the card and returns at the point 2.
The points 1 and 2 are in two circular extensions of a mercury-reservoir. Into the
mercury dip contact studs, one of which projects downward from the rider and the
other from the card.
In this case U serves to turn the card to the left (opposite direction to that of
a watch-hand), V to turn the card to the right.
Description of one construction of compass.
The card is shown in Figs. 16 to 18, of which Fig. 16 is a plan, Fig. 17 a vertical

page_text: (Fig. 16).
The card consists of an
a vulcanised rubber frame E.
The cap
annular card A, connected by means of ribs with
To both are secured magnets F, H and J.
D is provided on its upper eige with a small point G (Figs. 17 and 18)
to carry the rider.
The electro-magnet U (Figs. 16-18) serves to compensate for E deviation,
therefore for turning the card in the direction opposite to that of a watch hand,
the electro-magnet V serves to compensate W deviation.
I is the contact which is closed in case of an E deviation, II the contact closed in
case of a W deviation.
The rider is shown in Fig. 19 in plan, Fig. 20 being a diagrammatic plan of the path
of the current, Fig. 21 shows the rider in vertical section on line e-f, (Fig. 19), and
Fig. 22 a similar view on line h-g (Fig. 19) at right angles to the line ef. The
rider consists of a metallic cross B (Figs. 19, 21 and 22) which is provided at the
point, of intersection of the two members, with the cap D, which lies on the centre
pin G (Figs. 17 and 18).
On the long arms of the cross (Figs. 19, 21 and 22) the rider carries permanent
magnets X of opposite polarity to that of the card, i.e. when the rider is in place, its
permanent magnets have their north-poles turned southwards, & south-poles
northwards. Beneath the rider magnets there are placed two other electro-magnets K.
The short transverse arm or bar of the rider is provided at each end with a depending
contact-stud or pin one marked 2 on the west-side, and one marked 1 on the east
side; on the right hand half of said cross bar there are, moreover, provided contact
plates I and II, I being to the North, and II on the south side, and on the left hand
half an adjustable balance weight L, for the purpose of bringing the rider into
a horizontal position (Figs. 19 and 22).
The box of the compass is shown in Fig. 23 in vertical section Fig. 24 being a plan
of the mercury-reservoir C.
m for the
The box M of the compass (Fig. 23) has two lateral passages m
conductors, a lead and a return being always placed together. The set screw N serves
to adjust exactly the card support Q. The pivot pin Ŏ is loose in the card-support on
a spring P.
The mercury cup C (Figs. 23 and 24), preferably of rubber, is provided with
a central hole for the pivot pin O, and with four concentric annular recesses C', of
the same width and, as far as possible, of equal depths, in order to prevent spilling
of the mercury in consequence of the compass being violently shaken, or coming into
an oblique position. Each recess 1b, 2b, 3b, 4b, is connected by a stud or conductor
with a binding screw C2, in which are secured the ends of the electric-
conductors 1, 2, 3, 4*.
The manner of winding the electro-magnets, and the action of the current resulting
therefrom, will be clear from the following explanation. As already mentioned, the
electro-magnet U serves to counteract easterly deviation, and the electro-magnet V,
in the S-half circle, counteracts westerly deviation. In the former the N-pole must
therefore be on the right-hand (+ on Figs. 16 and 18), in the latter on the left-hand
side (+ in Fig. 16) when the circuit is closed. The electro-magnet of the rider,
each time that the circuit is closed, must have their N-poles in the North and their
S-poles in the South (Fig. 20). The circuit at the contact I is closed when an
easterly deviation arises, that at the contact II when a westerly deviation arises,
2 and 4 are the leads, and 1* and 3* the return wires. If the circuit is closed at the
contact I, the current from the conductor 2 passes through the mercury ring 2b,
through the pin 2, to the north-electro-magnet of the rider, to the south electro-
magnet of the rider, to the contact I, to the right hand end of the north electro-
magnet U (Figs. 16 and 18), through the winding of the latter to the contact stud 3,
Fig. 18, through the mercury ring 3b, and back through the return wire 3º
(Fig. 23).
If the circuit is closed at the contact II, the current passes from the conductor 4*,

page_text: into the mercury ring 4b, (Fig. 23) to the contact stud 4 (Fig. 18), to the right
hand end of the south electro-magnets V, in Fig. 16, through its winding into the
contact II (Fig. 16), through the north electro magnet of the rider, to the south
electromagnet of the rider (Fig. 20), into the stud 1, (Fig. 22) into the mercury
ring 1b, and back through the wire 1 (Fig. 23). It follows that in the construction
two sources of electricity are required, one of which is connected with the wires 2"
and 3*, the other being connected with the wires 4 and 1°. This peculiar electric
connection is chosen in order to have the current always circulating from the left
upwards and the right downwards, when viewed from the south, that is to say in the
same direction as the hands of a clock. In this manner to a certain extent a
so-called magnetic plate is produced, the south side of which in the whole system is
directed southwards and the north side northwards. Thereby the magnetism of the
whole system is increased.
It is obvious that many different practical applications of this principle are possible.
Thus for instance, instead of electro-magnets U and V and the magnetism of the
earth for turning the card, mechanically or electrically operated means could be used,
if properly constructed, and started and switched out by a properly constructed and
properly working rider.
The compass can be constructed as a fluid compass.
The shape and construction of the rider, the number and position of permanent
and electro-magnets may be very different and the number of electric circuits is not
fixed. In the particular hereinbefore described construction two circuits were used,
as it seems that it is then easier to arrange electro-mechanical devices for turning
the card, instead of the electromagnets of the card to turn the card by means of the
magnetism of the earth. The essential point of the invention is the use of the rider
with changing polarity, therefore the use of electricity.
Having now particularly described, and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is :-
1. A compass for automatically correcting deviation comprising several rotatable
magnetic systems the magnetic axes of which can automatically alter their position
one system containing the centre or the centres of rotation of the other or others for
the purpose of indicating and automatically compensating deviations.
2. In a compass of the character described a card provided with magnets and
electro-magnets and a "rider" provided with magnets and electro-magnets
substantially as and for the purpose described.
3. The combination and arrangement of parts constituting the complete device for
automatically correcting compass deviation substantially as described and illustrated
in the accompanying drawings.
1111 1
L1005
BOULT & WADE,
Agents for the Applicant.