Improvements connected with Mariners' Compasses.
Year: 1894

page_text: Date of Application, 23rd Nov., 1804
Complete Specification Left, 23rd Sept., 1895-Accepted, 22nd Feb., 1896
PROVISIONAL SPECIFICATION.
Improvements connected with Mariners' Compasses.
We, ARTHUR WEMYSS HORSBRUGH of 16 Leinster Square in the County
of London Gentleman and JOHN HODGSON LEE of 23 South Eaton Place in the
said county retired Lieutenant R.N. do hereby declare the nature of this invention
to be as follows:-
The object of our invention is to provide a compass which shall be free from error,
or deviation, by local attraction, or disturbing influences.
According to our invention there is placed around the compass, in a horizontal
plane, a ring of iron, or several such rings, the said ring, or rings being
capable of being turned in a horizontal plaue, or of being otherwise adjusted,
if required.
This ring, or these rings, is, or are, wound with conductors, such for instance as
copper wires of low resistance, the windings being in one direction round one half
of the ring and in the other direction round the other half. The wires, or
conductors, are connected in such a way that current flows in the opposite
windings; the said current being either that of the earth, by the continuations
of the coils being led to earth (by being led into the sea from the ship for
instance) or the current being derived from a battery, or electric generator of any
description.
The ring, or rings, wound as aforesaid, is or are polarized by the passage of the
electric curient through the windings described. The exact position of its or their
poles can be marked on the ring or rings or inside the compass-bowl in which case
the bowl is to revolve with the ring or rings and when by revolving the ring or
rings the compass needle is brought to coincide with the diameter between the ring
poles the true pole is indicated.
The compass may be used as an ordinary compass or as a standard compass by
which the direction of the true pole can be ascertained and the error of other
compasses be corrected by comparison therewith on any course, or bearing.
Dated this 23rd day of November 1894.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
Improvешения соднесocu WIVн магде
We, ARTHUR WEMYSS HORSBRUGI, of 16 Leinster Square, in the County of
London, Gentleman and JOHN HODGSON LEE, late of 23 South Eaton Place, but
now of 257 High Holborn, in the said county, retired Lieutenant, R.N. 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 :-
The object of our invention is to provide a mariners compass which shall be free
from error, or deviation, by local attraction, or disturbing influences, and to enable
the compass to be corrected and the true north, and a ships position to be ascertained

page_text: by direct magnetic observation, in place of by astronomical sights; the meridian
being capable of being taken when no other observation than magnetic measurements
can be made.
The principle involved in this invention is the direct adjustment of the magnetic
forces present so as to obtain a magnetic field in which the lines of force of both
polarities are equally distributed over equal areas and have the centre of their axes
of attraction coinciding with the centre of this magnetic field.
According to our invention there is placed around the compass, in a horizontal
plane, a ring of iron, or several such rings, the said ring or rings, being capable of
being turned in a horizontal plane, or of being adjusted to any desired angle for the
purpose of taking the meridian.
This ring, or these rings, is, or are, wound with conductors, such for instance as
copper wires of low resistance, the windings being in one direction round one half
of the ring and in the other direction round the other half of the ring. The wires
or conductors, are connected in such a way that a current may be allowed to pass
through the opposed windings; the said current being either that of the earth, by
the continuations of the coils being led to earth (by being led into the sea from the
ship for instance) or the current being derived from a battery, or electric generator
of any description.
The ring, or rings, wound as aforesaid is, or are, polarized by the passage of the
electric current through the windings described, thus producing two foci of
attraction cach of which has a special affinity for the different polarities of the
compass needle.
The positions of these foci are determined by the strength of the
current traversing each of the coils and provided the resistances of these coils are
equal to one another the passage of the current through them produces an equal
quantity of free magnetism round each coil, because the potential of the current is
equally divided between the coils. Any force, however, which interferes with the
accurate division of the current displaces the foci of attraction from their normal
positions or those positions which they would occupy if the current was equally
distributed between both coils and as the potential of the curre it is expended on
the production of free magnetism, the amount of free magnetism thus produced is
affected by the intensity and the polarity of the free magnetism surrounding the
path of the current. The electric resistance of the coils, and consequently the
equal distribution of the current, is therefore dependent on the intensity and polarity
of the terrestrial magnetism and the magnetism from other sources which is free to
affect the coils and the potential of the current may therefore produce a larger or
smaller amount of free magnetism according as the field of force through which this
potential is expended is favourable or unfavourable to the work of the current.
A larger force or quantity of free magnetism is produced by a given current when
the polarity of that magnetism is of contrary phase to the polarity surrounding the
path of the current than when the character of the exterior force through which
the current does its work is of similar phase to the free magnetism produced by.
the passage of the current. This is due to the well known law of attraction and
repulsion, polarities of similar phase repelling one another, while polarities of
contrary phase attract one another, and the work done by the current may be
assisted by the attraction of exterior magnetism or retarded and diminished by
repulsion from the same sources, much after the same manner that the distance
covered by a ship during given time is greater or less according to the direction
and force of the currents affecting her.
The coils on the ring being so arranged that the path of the current traverses
every maguetic stress in the horizontal plane by which the position of the compass
needle can be affected, while at the same time the work done by the potential of
the current is divided equally by the length of the wire or conductor into the
production of opposite polarities: it follows that there must be some position
on the ring for the foci of attraction in which the amounts of free magnetism
of contrary phase produced by the passage of the current are exactly equal to
one another, and these points constitute the true poles of the ring.
The exact

page_text: position of its, or their, poles can be marked on the ring, or rings, or inside the
compass bowl, in which case the bowl is to be made to rotate with the ring, or
rings, and when by rotating the ring or rings, the compass needle is brought to
coincide with the diameter between the ring poles the true pole is indicated.
Practically the best position for placing the index mark of the poles is found to
be at an angle of forty-five degrees from that diameter of the ring on which the
division between the opposed coils is situated, a magnet or magnets being so
placed as to retain the needle in this position in the manner hereinafter described.
The compass may be used as an ordinary compass or as a standard compass
by which the direction of the true pole can be ascertained and the error of
other compasses be corrected by comparison therewith on any course or bearing
but when magnets are used in the bottom of the bowl as hereinafter shewn,
these must be removed when it is desired to use the instrument as an ordinary
compass.
Up to a certain strength, depending on the number of turns in the coils, the
current need only be sufficient to provide for the work it has to do. This work
is the creation, or production of a field of force which has an equal number of
lines of force on both sides of the ring. If a magnet be placed near the ring
the intensity of that field of force next it is increased, and the work of the
current is used to equalize the lines of intensity on the other side of the ring.
But as there is a limit to the quantity of work a current can do, it is evident
that the strength or power of producing magnetism in the quantities required
may not be sufficient to effect this equalization. This source of local attraction
may also be too Etrong to be overcome by the additional force supplied by turning
the ring so as to utilize the stresses of terrestrial magnetism. A strong current is
therefore necessary but here a fresh difficulty is presented in the Arago, or
Foucault currents, which are set up in the interior of the iron and prevent au
accurate adjustment of the needle. These currents can be provided for either by
connecting up the iron of the ring to the wire by which the current returns to
the battery, or source of electric potential, or by placing another conductor,
insulated from the iron, round the periphery of the ring and in close contact with
the insulation of the coils. By the first method the Arago or Foucault currents
are utilized to assist the potential of the current, and by the second method the
Arago or Foucault currents produce, in the insulated conductor, a series of currents
of similar strength, and of opposite phase, which, travelling in the opposite direction,
neutralize the effect of the Arago or Foucault currents and assist in an equal
distribution of the magnetic field of the ring. Both methods are useful and effective,
but we consider the second one to be the more reliable for an equal distribution of
the magnetic field while a combination of both would probably be best. By these
means the neutral zones of the ring are eliminated and the strength of the current
which can be used, is greatly increased.
The direction in which the current passes round the ring produces two different
magnetic fields. Let the ends of the coils be joined at one side of the ring, and
the ends of the coils at the other side be called A and B. Then the current
may pass either from A to B or from B to A. One of these directions will give
a magnetic field in which the position of the polarities on the ring with regard
to the polarities of terrestrial magnetism is such, that the polarities of the ling
are of similar phase as the polarities of the earth. The other direct on
in which the current may be passed round the ring gives a magnetic field
which has polarities opposed to or of contrary phase to the polarities of the
earth's magnetismi. The first of these directions gives a magnetic field in
which the direction of the needle enclosed by it coincides with the direction
of any other needle subject only to terrestrial magnetism. The other, in which
the polarities of the ring are of contrary phase to the terrestrial magnetism,
gives a reversal of the poles of the enclosed needle. When the second phase of
the current is used then the zero point of the ring, or the place where the coils are
equally divided, lies in a line which coincides with the meridian, or terrestrial axis.

page_text: This point being marked, whenever the needle lies opposite it, the current being
passed at the same moment, through the windings ou the ring then the needle lies
in the true meridian and is unaffected by the current. But if the direction in
which the current passes through the ring coils be not such as will produce
polarities in opposition to the polarities of terrestrial magnetism, then the zero
point of the ring will be on the magnetic meridian.
All the effect of reversing the direction of the current may be produced by
simply turning the ring round because if the direction of the current be maintained
the same as it passes through the ring then, when one side of the ring producing
a south seeking polarity is opposed to a south seeking polarity of terrestrial
magnetism the needle will lie on the true meridian: but by turning the ring round
while the current is passing, the south seeking polarity of the ring is brought
opposite to the north seeking polarity of the earth and the needle lies in the
magnetic meridian. In practice it is found easier to maintain the direction of
the current constant, and to mark one side of the ring as southerly, or northerly,
as the case may be.
The needle ought to lie in the centre of the horizontal plane of the ring, or
cylinder, and should be exactly half way between the top and bottom of ring, or
cylinder. By raising, or depressing the needle from this mid section plane we
obtain different directions varying with the height of the needle.
In practice also it has been found easier to reverse the reading of the card, when
the true or geographical direction is required by placing the north seeking end of
the magnet or magnets under the south point of the card. Thus we obtain a direct
and actual reading of the true direction without further calculation. For the
measurement of the total error of the locality another card may be provided in
which the polarities of the needle or needles are arranged in the usual manner and
which can be used when the magnetic meridian is required.
To obviate the necessity of marking the ring poles, and also to maintain the
reversed card in an approximate position, magnets turning with the ring may be
introduced into the bottom of the compass bowl. When two such inagnets having
their south seeking polarities opposite to one another are placed in such a position
that they turn with the ring on the same centre then the natural position of the
compass needle suspended above them is at an angle of 45° to the line of their
longitudinal axis. When no current is passing the needle lies wholly under the
influence of these magnets, but whenever the current passes through the coils the
field of force is changed and the needle swings in response to this change. If how-
ever the magnets be placed at an angle of 45° to the true north then no swing takes
place when the current passes provided the direction be such as to cause the
needle to lie on meridian while the position assumed by the needle remains the same
after the current has stopped. Consequently if it be known that the current is
passing in the right direction it may safely be assumed that the needle lies on the
meridian, when its position is unaffected by passing the current. This obviates the
necessity for marks on the ring though it is better in practice to provide such
marks so as to approximate the true direction more rapidly.
The needle is rendered steadier, and less liable to large swings, by introducing a 4
contact breaker into the circuit. This is due to the fact that a contrary current
passes in the copper ing (used for the elimination or correction of Arago or
Foucault currents) whenever the current is made and interrupted.
In order to ensure that the current is passing it is advantageous to introduce an
electric bell into the circuit. This serves a double purpose as it indicates when 5
the current is passing and also acts as a contact breaker.
An ordinary contact button may be used in order to allow of the current being
passed when required.
In order to have a constant current not liable to any breakdown from loss of
battery power, the current produced by the friction of the ship against the salt 5
water may be used with advantage. This may be achieved by fastening a large
copper plate on each side of the ship and connecting the two sides by an insulated

page_text: wire. Or the bow and stern of the ship may be provided with such plates and
connections.
An instrument constructed in accordance with our invention is shewn in vertical
section in Figure 1 and plan with card and cover J removed in Figure 2 of the
accompanying drawing. It consists of an ordinary compass bowl A swung on
gimbals B and gimbal ring B' in the usual manner and contained in a box C say
of wood. Inside this bowl A is another bowl A2, which carries the aforesaid iron
rings D (of which four are shewn) and coils E E³, and is free to be revolved upon,
and independently of the outer bowl A. To facilitate its movement it is shewn as
being mounted on rollers a and as having lugs a³ to be grasped by the user. In the
bottom of the inner bowl A' are placed two bar magnets F F which are adjusted
to the requirements of the ring D and coils E E³, and secured firmly in position
by the clamps f. On the edge of the box C is placed the button 9 for making
contact for completing the circuit through the coils E E, which are led up to it.
The other extremities of the coils E Es are fixed to sliding contacts H which
enable the current to be passed from the battery N into the coils E E² whatever
may be the relative position of the bowls. The "point stem I rests on the
bottom of outer bowl A and passes through the centre of inner bowl A' to cirry
the point on which the card turns. Over the ring coils E E, and magnets F F,
is placed a brass cover J, and an ordinary four needle, or any suitable card i, is
suspended on the point. The ship's head is shewn by a strip of brass 1 fastened to
the "point stern I and passing to the edge of the card where a small brass
pillar m, takes the place of the lubber line in an ordinary compass. By this
instrument a very close approximation of the actual position of the terrestrial axis
can be obtained very readily.
"
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. In combination with the mariner's compass means for obtaining a magnetic
field in which the lines of force of both polarities are equally distributed over
equal areas and have the centre of their axes of attraction coinciding with the
centre of this magnetic field substantially as hereinbefore described.
2. In combination with the mariners compass an adjustable horizontal iron
ring, or adjustable horizontal iron rings, wound with conductors in reverse
directions, and connected to earth or to a source of electricity, substantially as and
for the purposes hereinbefore described.
3. A mariners compass and adjuncts consisting of an arrangement and com-
bination of parts as hereinbefore described and illustrated by the accompanying
drawings for the purposes explained.
Dated this 23rd day of September 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.