IMPROVEMENTS IN THE ADJUSTMENTS OF THE MARINERS' COMPASS
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
FRANCIS MONTGOMERY MOORE 102 High St. Belfast & 23 Eden Quay Dublin,
Chronometer Maker, Watch Maker & Optician, do hereby declare the nature of
said invention for IMPROVEMENTS IN THE ADJUSTMENTS OF THE MARINERS'
COMPASS to be as follows:-
For reducing the errors of the compass by attaching the correctors to the bowl
itself inside or outside, as necessary-that is to say, by one or two adjustable iron
balls placed inside the bowl and attached thereto in such proximity to the needles
as to correct the Quadrantal errors effectually, and further, by attaching a chamber
to the bottom of the bowl to contain the magnets for adjusting the Cardinal errors
of the compass.

page_text: THE
I FRANCIS MONTGOMERY MOORE of 102 High Street Belfast and 23 Eden Quay,
Dublin Chronometer maker Watch maker and Optician do hereby declare the
nature of said invention for "IMPROVEMENTS IN THE ADJUSTMENTS OF
MARINERS' COMPASS," and in what manner the same, is to be performed, to be
particularly described and ascertained in and by the following statement :—
The objects of this invention are to more effectually control the semicircular or
cardinal errors of compasses used in iron and other ships and vessels subject to local
attraction; also to more effectually control the quadrantal errors of the compass
arising from the same cause also as a collateral result of the construction to produce
greater steadiness in the working of the card and also to greatly subdue if not
altogether obliterate the crrors usually called "heeling errors.'
"1
For correcting the semi-circular or cardinal errors of the compass I firmly attach
a chamber to the bowl so that it partakes of all its motions and in this chamber
are contained the magnets for adjusting the said cardinal errors of the compass.
For correcting-the-quadrantal-errors Lattach correctors to the bowl itself inside
(or outside as it may in some cases be necessary) such correctors being in the form
of iron balls or pieces of soft iron of other suitable form placed inside the bowl and
adjustably attached thereto in such proximity and relative position to the needles
as to effectually correct the said quadrantal errors.
And in order that this my invention may be fully understood and readily carried
into effect I will describe it with reference to the accompanying drawings of which
Figure 1 is a vertical section through the compass with its bowl and bottom
chamber. Figure 2 is a plan view with part of the card removed. Figure 3 is a
front elevation and Figure 4 a horizontal section on line y of Figure 3. Figures 5,
6, 7 and 8 are detail views. Figure 9 is a vertical section through a liquid compass.
Figure 1 is a sectional view showing part of the compass and bowl, as adapted to
outside quadrantal error correctors, and Figure 1B an end view of such a corrector.
A, Figures 1 to 3 is the compass bowl which may be of the usual form as shown,
and Ba chamber attached to the bottom of it so as to partake of all the movements
of the bowl. The bowl A is suspended by the usual gimbal arrangement C. The
compass card D is suspended on the centre E and consists of a tubular aluminium
rim d to which the annular divided paper card D is fixed and to which the ebonite
centre boss d with ebonite mounted stone centre d' is connected by means of 6
(more or less) hollow aluminium wire radial bars d³. Below these radial bars and
secured to the rim of the card frame only are two light strips & Figure 2 of
aluminium extending from one edge of the card to the other to which are suspended
two lower light aluminium brackets or bridges d³ which carry a system of needles do
for instance, three on each side of the centre.
In the chamber B Figure 1, is contained a system of magnetic correctors for the
semicircular or cardinal errors. These magnetic correctors are enclosed in brass
tubes G and are made of round steel wire of different sizes in gauge but of uniform
length. They are tempered hard, magnetized, protected from rust by oil or grease
secured and sealed in the brass tubes and being of different thicknesses possess
varied degrees of magnetic power but the brass tubes enclosing them are all of
uniform outer diameter so as to fit in any of the clamps G' as required. The two
small rings one on each side of the centre and soldered to the tubes enable the
magnets to be dropped into their proper position and to be instantly secured by the
clamp G. One end of these correctors is painted red and the other end blue to
indicate the north and south poles, Provision is made for placing them on the

page_text: inner fore or front side and on the two inner opposite sides of the chamber, the
chamber being for this purpose provided with upright guides H on which the
brackets or holders I for the magnets G can slide and be adjusted as to vertical
distance from the needles as required by means of set screws I¹ the magnets being
held in place by clamps G, or I can make a central vertical slit in each side or
chamber B to receive the bracket I if found more convenient. On the aft side of
the chamber B and at the bottom of same provision is made as shown in Figure 1
for attaching a similar magnet for the same purpose as the forward magnet.
Figures 1, 4 and 5 show the mode in which the magnets may be clamped to the
sides of the chamber and a mode for clamping a magnet to the bottom. Figure 7
shows another form of clamp and Figure 8 yet another form of clamp for readily
detaching and attaching the magnets. By the varied number strength and vertical
distance from the magnetic field of the card of these magnets any required correction
of the cardinal errors of the compass may be effected. The chamber B with its
adjustments may also be attached to the bowls of liquid or other compasses.
F, F, Figures 1 and 2 are two iron balls which by preference are hollow and
which are the correctors for the positive quadrantal errors; they are mounted on
the points of coarse-pitched screws FX Figures 1, 2 and 3 which are tapped through
bosses F1 on the two opposite sides thwartships of the bowl A with sufficient range.
to allow the balls to approach to or recede from the needles for the nicer adjustment
of this error and when adjusted they are clamped or held fast by the nuts F. In
some cases as stated I may place the correctors outside the bowl as will be. referred
to further on. I use balls of various sizes according to the amount of error to be
corrected though I may use pieces of soft iron of any other suitable form. These
balls may also be applied to liquid compasses that is to say compasses having the
card immersed in liquid and the cards being constructed with needles below the
card proper, as hereinbefore explained. In Figure 9 I have shewn a liquid compass
according to my invention. The balls F together with their adjusting screws are
in this case enclosed in brass cylinders M (one shewn in vertical cross section) and
with spherically closed inner ends, while their outer ends are open to receive the
balls and screws FX for adjustment and correction of the quadrantal errors in
the manner already described. The necessity for the cylinders to enclose the balls
will be obvious.
For correcting the negative or oblique quadrantal errors which however rarely
occur, I provide the bowl on the fore and aft side with losses F3 Figure 3 prepared
to receive screws and hollow iron balls or correctors for correcting such errors.
The card having its system of needles below the card proper and their magnetic
field being exactly opposite to that of the centre of the balls, or correctors F, the
centre of the plane of the system of needles will in the rolling and pitching of the
vessel always coincide with the centre of the balls or correctors.
In Figures 1A and 1B I. have shown the compass and bowl as adapted for outside
correctors F. The chamber A is made shallower at top and with its lower part
diminished in diameter. In this part the needles are situated opposite to the
correctors F, each of which is mounted on a bracket F* which is adjustable in a
dovetail slide part F and fixed in position by a screw F³.
If when all the foregoing adjustments have been completed it should be found
that the compass is not perfectly horizontal, I shift the eccentric adjustable weight K
in the bottom of the chamber B till an almost perfect level has been obtained. The
chamber B is closed by means of a door L to exclude any water. Obviously a
chamber for containing the cardinal error correctors might be fixed on the bowl
above the card instead of below it as here shown. In all cases it will be seen that
the centre of the length of the corrector magnets G will in all positions of the ship
in pitching or rolling coincide with the centre of the needle system of the compass
card thus tending to keep the card from oscillating and maintaining the magnetic
corrective force constant and equal. In the ordinary compass adjustments, whether
the magnet correctors are placed on the deck or in the binnacle or elsewhere apart
from the bowl the magnetic forces from the correctors must necessarily as the ship

page_text: pitches and rolls be unequal or spasmodic in their influence on the needle or needles,
and where a ship is a long time with a list or heel to either side, and on any
quadrantal course, such course having been previously corrected by chain or other
soft iron attached to the outside of the binnacle when the vessel was upright, the
heeling of the ship causes the correctors to leave the horizontal plane of the needles
and the needles in consequence to be released from the influence of the correctors
and then not only an oscillation of the card but an error of the compass at once
sets in. And so also with the cardinal courses, the correcting magnets being placed
in the usual way that is to say on the deck or attached to the binnacle, when the
ship heels from the upright position the compass is thrown to the one side of the
vertical centre of the correcting magnets so that one pole of the magnets will have
more or less power over the card than the other and hence oscillation of the card
takes place and errors of the compass enter through the ill placing of the magnets
which were intended to exclude them. Thus the errors of heel which are usually
attributed to other causes are greatly aggravated by the above false or imperfect
mode of arranging the magnets and soft iron correctors and often lead to serious
results. My construction of compass and adjustments will also greatly tend to do
away with the so called heeling error.
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:
First: A mariners compass having adjustable correctors for the quadrantal errors
attached to the bowl-itself-and-arranged in such a manner as to have their centres
always in the same horizontal plane with the needles at all-safe vertical angles of
the ship or vessel substantially as set forth.
Second: A mariners compass having adjustable correctors F for the quadrantal
error attached to the bowl itself in combination with a card having a lower system
of needles the centre of which coincides with the centres of the correctors at all safe
vertical angles of the ship substantially as set forth.
Third: A mariners compass having a chamber attached to the bowl itself said
chamber being adapted to contain adjustable correctors for the cardinal errors which
correctors have their vertical centres always parallel to the vertical centre of the
needle system and to the centre which supports the card in all safe positions of the
ship substantially as set forth.
Fourth. A mariners compass constructed as shown in the drawings.

page_text: I FRANCIS MONTGOMERY MOORE of 102 High Street, Belfast and 23 Eden Quay,
Dublin, Chronometer maker, Watch maker and Optician seek leave to amend the
specification of Letters Patent, No. 6288 of 1884, as shown in red ink in the copy
of the original specification hereunto annexed :—
On page 3 line 35 to alter the word "losses" to " bosses."
"
On page 4 line 20 after the word "that to insert the following "I do not
broadly claim to attach adjustable error correctors or intensity multipliers to the
compass bowl itself, as this was proposed for instance in Huntzingers Provisional
Specification No 2459 of 1864 and in Labadies Specification No 770 of 1869
but it will be found that by my invention two merely radially adjustable
soft iron correctors are generally sufficient for correcting the quadrantal errors
while the cardinal errors are also conveniently and rapidly corrected. But"
Line 22 after the word "having" to insert the word "radially."
Line 23 after the word "arranged" to insert the following "within the diameter
of the compass card
"
Line 26 after the word "having" to insert the word "radially"
Line 27 after the word "itself" to insert the following " and within the diameter
of the compass card"
Line 30 after the word "Third" to insert the following "In a mariners compass
the cardinal error correctors G attached to the bowl itself and also the mode of
attachment and adjustment so that they are always within the diameter of the
compass card and "
To strike out the remainder of line 30, the whole of line 31 and the word
correctors on line 32.
"
My reasons for making this amendment are as follows:-
That a clerical error requires to be corrected, and that the invention as claimed
requires to be further defined or restricted.
Thi
HOODE

page_text: In the matter of the application made by Francis Montgomery Moore for leave to
amend the Specification of Letters Patent No 6288 of 1884.
I hereby grant leave to the said Francis Montgomery Moore to amend the said
Specification in the manner proposed.

page_text: FRANCIS MONTGOMERY MOORE 102 High St. Belfast & 23 Eden Quay Dublin,
Chronometer Maker, Watch Maker & Optician, do hereby declare the nature
of said invention for IMPROVEMENTS IN THE ADJUSTMENTS OF THE MARINERS'
COMPASS to be as follows:-
For reducing the errors of the compass by attaching the correctors to the bowl
itself inside or outside, as necessary-that is to say, by one or two adjustable iron
balls placed inside the bowl and attached thereto in such proximity to the needles
as to correct the Quadrantal errors effectually and further by attaching a chamber
to the bottom of the bowl to contain the magnets for adjusting the Cardinal errors
of the compass.

page_text: I FRANCIS MONTGOMERY MOORE of 102 High Street Belfast and 23 Eden Quay,
Dublin Chronometer maker Watch maker and Optician do hereby declare the
nature of said invention for "IMPROVEMENTS IN THE ADJUSTMENTS OF THE
MARINERS' COMPASS," and in what manner the same is to be performed, to bo
particularly described and ascertained in and by the following statement:-
The objects of this invention are to more effectually control the semicircular or
cardinal errors of compasses used in iron and other ships and vessels subject to local
attraction; also to more effectually control the quadrantal errors of the compass
arising from the same cause also as a collateral result of the construction to produce
greater steadiness in the working of the card and also to greatly subdue if not
altogether obliterate the errors usually called "heeling errors."
For correcting the semi-circular or cardinal errors of the compass I firmly attach
a chamber to the bowl so that it partakes of all its motions and in this chamber
are contained the magnets for adjusting the said cardinal errors of the compass.
For correcting the quadrantal errors I attach correctors to the bowl itself inside
(or outside as it may in some cases be necessary) such correctors being in-the-form
of iron balls or pieces of soft iron of other suitable form placed inside the bowl and
adjustably attached thereto in such proximity and relative position to the needles
as to effectually correct the said quadrantal errors.
And in order that this my invention may be fully understood and readily carried
into effect I will describe it with reference to the accompanying drawings of which
Figure 1 is a vertical section through the compass with its bowl and bottom
chamber. Figure 2 is a plan view with part of the card removed. Figure 3 is a
front elevation and Figure 4 a horizontal section on line y of Figure 3. Figures 5,
6, 7 and 8 are detail views. Figure 9 is a vertical section through a liquid compass,
Figure 1 is a sectional view showing part of the compass and bowl, as adapted to
outside quadrantal error correctors, and Figure 1B an end view of such a corrector.
A, Figures 1 to 3 is the compass bowl which may be of the usual form as shown,
and B a chamber attached to the bottom of it so as to partake of all the movements
of the bowl. The bowl A is suspended by the usual gimbal arrangement C. The
compass card D is suspended on the centre E and consists of a tubular aluminium
rim d to which the annular divided paper card D is fixed and to which the ebonite
centre boss d with ebonite mounted stone centre d² is connected by means of 6
(more or less) hollow aluminium wire radial bars d'. Below these radial bars and
secured to the rim of the card frame only are two light strips d' Figure 2 of
aluminium extending from one edge of the card to the other to which are suspended
two lower light aluminium brackets or bridges d' which carry a system of needles dª
for instance, three on each side of the centre.
In the chamber B Figure 1, is contained a system of magnetic correctors for the
Bemicircular or cardinal errors. These magnetic correctors are enclosed in brass
tubes G and are made of round steel wire of different sizes in gauge but of uniform
length. They are tempered hard, magnetized, protected from rust by oil or grease
secured and sealed in the brass tubes and being of different thicknesses possess
varied degrees of magnetic power but the brass tubes enclosing them are all of
uniform outer diameter so as to fit in any of the clamps G¹ as required. The two
small rings one on each side of the centre and soldered to the tubes enable the
magnets to be dropped into their proper position and to be instantly secured by the

page_text: clamp G. One end of these correctors is painted red and the other end blue to
indicate the north and south poles. Provision is made for placing them on the
inner fore or front side and on the two inner opposite sides of the chamber, the
chamber being for this purpose provided with upright guides H on which the
brackets or holders I for the magnets G can slide and be adjusted as to vertical
distance from the needles as required by means of set screws I' the magnets being
held in place by clamps G¹, or I can make a central vertical slit in each side or
chamber B to receive the bracket I if found more convenient. On the aft side of
the chamber B and at the bottom of same provision is made as shown in Figure 1
for attaching a similar magnet for the same purpose as the forward magnet.
Figures 1, 4 and 5 show the mode in which the magnets may be clamped to the
sides of the chamber and a mode for clamping a magnet to the bottom. Figure 7
shows another form of clamp and Figure 8 yet another form of clamp for readily
detaching and attaching the magnets. By the varied number strength and vertical
distance from the magnetic field of the card of these magnets any required correction
of the cardinal errors of the compass may be effected. The chamber B with its
adjustments may also be attached to the bowls of liquid or other compasses.
F, F, Figures 1 and 2 are two iron balls which by preference are hollow and
which are the correctors for the positive quadrantal errors; they are mounted on
the points of coarse-pitched screws FX Figures 1, 2 and 3 which are tapped through
bosses F on the two opposite sides thwartships of the bowl A with sufficient range
to allow the balls to approach to or recede from the needles for the nicer adjustment
of this error and when adjusted they are clamped or held fast by the nuts F. In
some cases as stated I may place the correctors outside the bowl as will be referred
to further on. I use balls of various sizes according to the amount of error to be
corrected though I may use pieces of soft iron of any other suitable form. These
balls may also be applied to liquid compasses that is to say compasses having the
card immersed in liquid and the cards being constructed with needles below the
card proper, as herein before explained. In Figure 9 I have shewn a liquid compass
according to my invention. The balls F together with their adjusting screws are
in this case enclosed in brass cylinders M (one shewn in vertical cross section) and
with spherically closed inner ends, while their outer ends are open to receive the
balls F and screws FX for adjustment and correction of the quadrantal errors in
the manner already described. The necessity for the cylinders to enclose the balls
will be obvious.
For correcting the negative or oblique quadrantal errors which however rarely
occur, I provide the bowl on the fore and aft side with losses bosses F³ Figure 3
prepared to receive screws and hollow iron balls or correctors for correcting such
errors. The card having its system of needles below the card proper and their
magnetic field being exactly opposite to that of the centre of the balls, or correctors F,
the centre of the plane of the system of needles will in the rolling and pitching of
the vessel always coincide with the centre of the balls or correctors.
In Figures 14 and 1B I have shown the compass and bowl as adapted for outside
correctors F. The chamber A is made shallower at top and with its lower part
diminished in diameter. In this part the needles are situated opposite to the
correctors F, each of which is mounted on a bracket Fx which is adjustable in a
dovetail slide part F¹ and fixed in position by a screw F³.
If when all the foregoing adjustments have been completed it should be found
that the compass is not perfectly horizontal, I shift the eccentric adjustable weight K
in the bottom of the chamber B till an almost perfect level has been obtained. The
chamber B is closed by means of a door L to exclude any water. Obviously &
chamber for containing the cardinal error correctors might be fixed on the bowl
above the card instead of below it as here shown. In all cases it will be seen that
the centre of the length of the corrector magnets G will in all positions of the ship
in pitching or rolling coincide with the centre of the needle system of the compass
card thus tending to keep the card from oscillating and maintaining the magnetic
corrective force constant and equal. In the ordinary compass adjustments, whether

page_text: the magnet correctors are placed on the deck or in the binnacle or elsewhere apart
from the bowl the magnetic forces from the correctors must necessarily as the ship
pitches and rolls be unequal or spasmodic in their influence on the needle or needles,
and where a ship is a long time with a list or heel to either side, and on any
quadrantal course, such course having been previously corrected by chain or other
soft iron attached to the outside of the binnacle when the vessel was upright, the
heeling of the ship causes the correctors to leave the horizontal plane of the needles
and the needles in consequence to be released from the influence of the correctors
and then not only an oscillation of the card but an error of the compass at once
sets in. And so also with the cardinal courses, the correcting magnets being placed
in the usual way that is to say on the deck or attached to the binnacle, when the
ship heels from the upright position the compass is thrown to the one side of the
vertical centre of the correcting magnets so that one pole of the magnets will have
more or less power over the card than the other and hence oscillation of the card
takes place and errors of the compass enter through the ill placing of the magnets
which were intended to exclude them. Thus the errors of beel which are usually
attributed to other causes are greatly aggravated by the above false or imperfect
mode of arranging the magnets and soft iron correctors and often lead to serious
results. My construction of compass and adjustments will also greatly tend to do
away with the so called heeling error.
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 I do
not broadly claim to attach adjustable error correctors or intensity multipliers
to the compass bowl itself, as this was proposed for instance in Huntzinger's
Provisional Specification N° 2459 of 1864, and in Labadies Specification N° 770
of 1869, but it will be found that by my invention two merely radially adjustable
soft iron correctors are generally sufficient for correcting the quadrantal errors
while the cardinal errors are also conveniently and rapidly corrected. But
what I Claim is:-
First: A mariners compass having radially adjustable correctors for the quad-
rantal errors attached to the bowl itself and arranged within the diameter of the
compass card in such a manner as to have their centres always in the same
horizontal plane with the needles at all safe vertical angles of the ship or vessel
substantially as set forth.
Second: A mariners compass having radially adjustable correctors F for the
quadrantal error attached to the bowl itself and within the diameter of the
compass card in combination with a card having a lower system of needles the
centre of which coincides with the centres of the correctors at all safe vertical
angles of the ship substantially as set forth.
Third: In a mariners compass the cardinal error correctors G attached to the
bowl itself and also the mode of attachment and adjustment so that they are
always within the diameter of the compass card and A mariners-compass-having
a chamber attached to the bowl itself said chamber being adapted to contain
adjustable correctors-for-the-cardinal errors which correctors have their vertical
centres always parallel to the vertical centre of the needle system and to the
centre which supports the card in all safe positions of the ship substantially as set
forth.
Fourth: A mariners compass constructed as shown in the drawings.