IMPROVEMENTS IN MARINE COMPASSES; AND IN APPARATUS APPLICABLE THERETO
Year: 1855

page_text: LETTERS PATENT to Andrew Small, of Glasgow, in the County of Lanark,
North Britain, Ship Chandler, for the Invention of "IMPROVEMENTS IN
PROVISIONAL SPECIFICATION left by the said Andrew Small at the
Office of the Commissioners of Patents, with his Petition, on the 17th
December. 1855.
I, ANDREW SMALL, of Glasgow, in the County of Lanark, North Britain, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN MARINE
COMPASSES; AND IN APPARATUS APPLICABLE THERETO," to be as follows:-
This Invention relates to the application to mariners' compasses or to dumb
compass cards of certain improved contrivances, designed for ascertaining the
error or deviation, of the compass needles at all times when a celestial object is
visible, and without requiring a sight of the horizon. When the said con-
trivances are applied to the compass-needle itself, the needle is supported in a
ring or frame fitted into the ordinary compass bowl, and capable of being
turned round for the purpose of adjusting the details, carried by it. These
details, consist, in the first place,, of a "true meridian" circle, which is capable
of adjustment in a vertical plane, and is graduated or marked with degrees of
latitude, or altitude. At right angles to this meridian circle is rivetted to it an
equatorial circle, which turns, upon centres fixed to the ring, adjustable in
the compass bowl. The equatorial circle is graduated or marked with the
hours of the day, as counting from noon in either direction. On centres,
carried by the meridian circle at points 90 degrees from the intersection and
attachment of the equatorial circle, is a third circle, capable of being set round

page_text: to the hours marked upon the equatorial circle, and formed with slits round its
four quarters. On one of the centres carrying the third circle is also carried a
small segment of a circle, which is not slit, but is marked instead with a centre
line. The centre last referred to is pierced externally to receive a stile for
throwing a shadow of the sun upon the segment. In using these contrivances,
the ring or frame carrying the circles is shifted round until the meridian circle
is brought into the north and south line, as actually shewn by the compass
needle. The equatorial circle is then set to the latitude of the place, and the
third or slit ring is set to the hour of the day. If the sun is shining, a stile is
set in the uppermost of the centres, or other place fitted to receive it, which
carry the third ring, with which ring the segment is adjusted to coincide; the
whole frame with the circles is then again shifted round until the shadow of
the stile is thrown upon the centre line of the segment, and the error of the
compass needle will be accurately shewn by the angular distance of the true
meridian circle from the north and south points on the compass card.
If the sun is visible, but not sufficiently clear to throw a shadow, it may be
viewed through the slits in the third circle, the apparatus being turned round
until it can be so viewed. In adapting these contrivances to a dumb compass
card, the card is fixed inside the frame carrying the circles, and the whole is
suspended upon gimbals, or upon centres athwart ship, and also in a fore
and aft direction, by which the whole is kept in a horizontal position.
I use
In addition to the method of finding the error of the compass, my Invention
consists in the mode of correcting it by magnets. For this purpose
two segmental magnets attached, when required, to the true meridian circle,
and capable of being moved by hand in a circular direction on the meridian
circle, in a line with either their longer or shorter axis. When these magnets
are used for the correcting compass, two only are necessary; but when used
for a common steering compass, two circles are used and four magnets, the
meridian circle being always placed in a line parallel to the ship's keel, and
the other circle, which is at right angles to the meridian, will then be trans-
verse to the keels; the magnets on each are all moveable, the same as on the
compass for finding the error, herein-before described, those on the meridian
circle adjusting for north und south, and those on the one at right angles to it
adjusting for the east and west courses. These circles are graduated with a
scale of equal parts, to shew the elevation of the magnets when the adjustment
is made, the magnets being then fixed by clamp screws. There is also a
pointer and graduated segmental scale attached for shewing the inclination of
the ship.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed'
by the said Andrew Small in the Great Seal Patent Office on the
16th June 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANDREW
SMALL, of Glasgow, in the County of Lanark, North Britain, Ship Chandler,
send greeting.
our
:
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of December, in the year of
Lord One thousand eight hundred and fifty-five, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Andrew Small, Her special license that I, the said Andrew Small, my.
executors, administrators, and assigns, or such others as I, the said Andrew.
Small, my executors, administrators, or assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise, .and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN MARINE COM-
PASSES, AND IN APPARATUS APPLICABLE THERETO," upon the condition (amongst
others) that I, the said Andrew Small, by an instrument in writing under
my hand and seal, should particularly describe and ascertain the nature of
the said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Andrew Small, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement in writing, reference being had to the accompanying Drawings, and
to the letters and figures marked thereon, that is to say :-
My said Invention relates to the application to mariners' compasses or to
dumb compass cards or rings of certain improved contrivances, designed for
ascertaining the error or deviation of the compass needles at all times when a
celestial object is visible, and without requiring a sight of the horizon. When
the said contrivances are applied to the compass needle itself, the needle is
supported in a ring or frame fitted into the ordinary compass bowl, and capable
of being turned round for the purpose of adjusting the details carried by it.
These details consist, in the first place, of a "true meridian" circle, which is
capable of adjustment in a vertical plane, and is graduated or marked with

page_text: degrees of latitude or altitude. At right angles to. this meridian circle is
riveted to it an "equatorial" circle, which turns upon centres fixed to the ring,
adjustable in the compass bowl. The equatorial circle is graduated or marked
with the hours of the day, as counting from noon in either direction. On
centres, carried by the meridian circle at points 90 degrees from the intersec-
tion and attachment of the equatorial circle, is a third circle, capable of being
set round to the hours marked upon the equatorial circle, and formed with
slits round its four quarters. On one of the centres carrying the third circle is
also carried a small segment of a circle, which is not slit, but is marked
instead with a centre line. The centre last referred to is pierced externally to
receive a stile for 'throwing a shadow of the sun upon the segment. In using
these contrivances, the ring or frame carrying the circles is shifted round until
the meridian circle is brought into the north and south line, as actually shown
by the compass needle. The equatorial circle is then set to the latitude of the
place, and the third or slit ring set to the hour of the day. If the sun is
shining, a stile is set in the uppermost of the centres (or other place fitted to
receive it), which carry the third ring, with which ring the segment is adjusted
to coincide. The whole frame with the circles is then again shifted round
until the shadow of the stile is thrown upon the centre line of the segment,
and the error of the compass needle will be accurately shewn by the angular
distance of the true meridian circle from the north and south points on the
compass card. If the sun is visible, but not sufficiently clear to throw a
shadow, it may be viewed through the slits in the third circle, the apparatus
being turned round until it can be so viewed. In adapting these contrivances
to a dumb compass card or ring, the card or ring is fixed inside the frame
carrying the circles, or the degrees of the compass may be marked on the
frame itself, and the whole is suspended upon gimbals, or upon centres athwart
ship, and also in a fore and aft direction, by which the whole is kept in a hori-
zontal position.
In addition to the arrangements for finding the error of the compass, this
Invention also comprehends a mode of correcting the error by means of mag-
nets. For this purpose, two curved or segmental magnets are attached, 'when'
required, to the true meridian circle, being capable of adjustment by hand in a
circular direction on the meridian circle, in the line of either their longer or
shorter axis. When these magnets are used for the correcting compass, two
only are necessary; but when used for a' common' steering compass; two circles
and four magnets are used, the meridian circle being always placed in a line
parallel to the ship's keel, whilst the other circle, which is at right angles to
'the' meridian, will cross the keel transversely. The several magnets are made

page_text: capable of adjustment, as in the case of the correcting compass, those on the
meridian circle being adjusted for north and south courses, and those on the
other, circle for east and west courses. 'These circles are graduated: with scales
of equal parts, to show the position of the magnets when adjusted. Instead of
having two or more adjustable magnets in this way; a single magnēt may be
used; such magnet being placed úpón a pivot: on. the meridian. circle, so as to
be adjusted by being turned round more or less: In addition; a pointer or
pendulum with a graduated segmental; scale is adapted to the binnacle or com-
pass box, to show the inclination of the ship.
And in order that my said Invention may be properly understood,. I have
hereunto appended; and shall now proceed to 'describe, a Sheet of explanatory;
Drawings; Figure 1 on such Sheet of Drawings being an elevation, and
Figure 2a plan, of a compass as fitted with my improved arrangements for
ascertaining and correcting the error thereof:
The card A; the outer bowl B; and the gimbal ring: arrangement C for sus
pending the whole, may be constructed according to .aný of the plans in use:
Upon or within the upper edge or rim of the compass bowl B is placed a ring
or horizontal circle D, graduated to degrees of the circle,' and capable of
adjustment round the compass. This ring answers the purpose of what is
termed a dumb compass card, that is to say, 'a card marked with the points.or
degrees of the compass, and capable of being adjusted in any required. position:
When this ring D is adjusted it may be fixed by the pinching screw E.. To
the ring D is attached by the studs or pivot joints' F. an equatorial ring:G;
which has rivetted to itself at right angles a."true meridian"". ring, H; the
studs F also serve to carry the inner bowl. containing the compass card. and
needle. The equatorial ring G is graduated with the hours from noon, running
in either direction from the meridian circle. The meridian circle H. is marked
with degrees of latitude or altitude, and it may also be slit on each side. for
taking the bearings of lights or headlands. A moveable hour circle I is jointed
to the ring H, at points corresponding to the 'poles, and can be set round to
any hour, as marked upon the equatorial circle G. This circle I is slit along
its centre line, so that objects can be viewed through it. A segment J, having
a centre line marked upon it, is centred upon the stud K, which connects the
circle I to the circle H; and when an observation, is to be made by means of a
shadow, instead of by viewing the object through the slits in the circle I, this
segment J is brought.over the circle I, and a stile L is fixed in a socket made to
receive it in the stud K. A socket is also formed in the segment J to receive
the stile, as at M, when from the circumstances of any particular case the
shadow of the stile, if placed at L, cannot be made to fall on the segment J.

page_text: In proceeding to ascertain the error: of the compass by means of the herein-,
before described contrivances, the "dumb compass" circle D is set round until
the meridian circle H is brought into the north and south line, shown by the
compass needle. The equatorial circle G is then set to the latitude of the
place, and the hour circle I is set to the hour of the day, as marked upon
the circle G.. The ring D, carrying the circles G, H, I, is then shifted round
until the sun either casts a shadow from the stile. on the centre line of the seg-
ment J, placed immediately over the ring I, or is seen through the slits in the
latter. When this is done, the compass deviation will be shown by the angular
distance of the "true meridian" circle H from the north and south line,
shown by the compass needle. The true course of the ship will also be shown,
by the dumb compass, by the crossing or cutting of the lubber's point on
the outer bowl. A small magnet S, N, Figure 1, may be centred upon the
stud K. of the ring H, for the purpose of correcting the needle's deviation;
when this has been ascertained, the correction being effected by setting round
this magnet more or less..
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried
into effect, I may observe, in conclusion, that I do not confine or restrict
myself to the precise details or arrangements which I have had occasion
to describe or refer to, as many variations may be made therefrom without
deviating from the principles or main features of my Invention; but what I
consider to be novel and original, and therefore claim as the Invention
secured to me by the herein-before in part recited Letters Patent, is,-
First, the application and use in mariners' compasses, and the general and
detailed arrangement and construction of dumb compass rings, and equatorial
meridian and hour circles, for the purpose of ascertaining the error or deviation
of the compass needle, as herein-before described.
Second, the systems or modes of correcting the error or deviation of the
needle in mariners' compasses by means of adjustable magnets placed upon
circles or rings encompassing the card, as herein-before described.
In witness whereof, I, the said Andrew Small, have hereunto set my
hand and seal, this Fourteenth day of June, One thousand eight
hundred and fifty-six.
:
ANDREW SMALL.
(L.S.)