New COMPASS FOR NAVIGATION, AND OTHER PURPOSES
Year: 1824

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
GRAYDON, of the City of Bath, Esquire, Captain in the Royal Engineers, send
greeting..
WHEREAS His most Excellent Majesty King George the Fourth, by
His Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Fifth day of August, in the fifth year of His reign, did,
for Himself, His heirs and successors, give and grant unto me, the said
George Graydon, His especial licence that I, the said George Graydon,
my executors, administrators, and assigns, or such others as I, the said George
Graydon, my executors, administrators, or assigns, should at any time agree with,
and no others, from time to time and at all times during the term of years
therein expressed. should and lawfully might make, use, exercise, and vend,
within England, Wales, and the Town of Berwick-upon-Tweed, my Invention
of "A New COMPASS FOR NAVIGATION, AND OTHER PURPOSES," in which said
Letters Patent there is contained a proviso, that if I, the said George
Graydon, shall not particularly describe and ascertain the nature of my said
Invention, and in what manner the same is to be performed, by an instrument
in writing under my hand and seal, and cause the same to be enrolled in His
Majesty's High Court of Chancery within six calendar months next and
immediately after the date of the said in part recited Letters Patent, that
[Prise 8d.1

page_text: then the said Letters Patent, and all liberties and advantages whatsoever
thereby granted, shall utterly cease. determine, and become void, as in and by
the same, reference being thereunto had. will more fully and at large appear.
NOW KNOW YE, that, in compliance with the said proviso, 1, the said
George Graydon, do hereby declare the nature of my said Invention, by the
following description thereof, and the manner in which the same is to be
performed and carried into effect, by the Drawing which is hereunto annexed,
reference being thereunto had, and to the letters and figures marked thereon,
as follows (that is to say):-
My Invention of A New Compass for Navigation and other Purposes consists
of an instrument or compass, which I have denominated a Celestial Compass,
from the circumstance of its being adapted to obtain data for determining the
latitude or longitude at sea by means of the heavenly bodies, and at a time
when the horizon is obscured, and also of finding the azimuth of the sun or
a star at any time when these objects are visible. The celestial compass is
adapted to be used at sea or on land in place of the ordinary magnetic com-
pass, and will be found particularly serviceable in high northern or southern
latitudes, where the directive power of the magnetic needle becomes almost
useless from it's feeble and uncertain action. The celestial compass also furnishes
the means of detecting or ascertaining the variation of the magnetic needle by
inspection so long as the heavenly bodies are visible. I will first describe, with
reference to the Figures upon the annexed Drawing, a convenient mode of
construction for the celestial compass, and will describe such modifications of
it's parts as will render it applicable to the various purposes for which it is
intended, and I will afterwards give such examples of the mode of adjusting
and using the compass as will enable persons conversant with operations of a
similar nature to employ the same.
Figure 1, upon the annexed Drawing, represents a perspective view of the
celestial compass mounted in gimbols, as it would be used at sea for the
purposes of navigation. This Figure represents the instrument about one
third of the real size: but the dimensions are not important, as they would
vary according to circumstances. A, B, represents the face or dial plate of
the instrument, as I will denominate it. This plate is screwed or otherwise
fixed upon the upper part of a box or case C, of a hemispherical form,
the object of which will be herein-after explained. The hemisphere C
is suspended upon pivots or axes at c, which work freely through holes
formed in a metal ring D. and this ring is suspended upon pivots or axes
at d, being situated at right angles with the pivots c. before mentioned.
The pivots d are adapted to turn in holes or sockets formed in adjustable

page_text: bearings at the upper part of the two standards or supports E, E, and the feet
or bases of the said standards are screwed down upon a circular plate of metal
F, G, which is capable of revolving upon an axis in the centre thereof
affixed to the stationary platform or board H, I. The plate F, G, has the
cardinal points marked upon it in the ordinary manner of magnetic compasses,
and is divided into degrees near it's outer diameter, being provided with a
vernier I, affixed to the platform before mentioned. K, L, represents a heavy
plate of metal which is suspended from the pivots or axes c by two brackets or
open arms, one only of which arms is seen in the Figure at M, the other being
obscured by the hemisphere C. The plate K, L, is situated considerably
below the centre of gravity or axis upon which the hemisphere C and ring
D are suspended, and thus tends always to maintain the instrument in a plane
parallel to the horizon or nearly so, in the same manner as the ordinary ships'
compass which is at present in use. The plate K, L, has an arm or limb
rising up from it at K, the upper part of which is provided with a vernier k,
adapted to read off the degrees upon a graduated arc g, h, which is engraved
on the side of the hemisphere C. The under surface of the plate K, L, is
provided with two plain mirrors or reflecting surfaces m, m, which are situated
in a frame affixed perpendicular to the plate K, L, but in such position that
the reflecting surfaces form a salient angle with each other. These mirrors,
by reflecting the horizon from two different parts, furnish the means
of adjusting the instrument into an horizontal position, or proving whether it
preserves the horizontal position, when in use; for example, when any two
parts of the horizon are reflected in the mirrors m, m, if the instrument is
moved until the images of the said two parts appear upon the mirrors in
one straight line, that line being at the same time parallel to the edges of
the mirrors, will indicate that the plate K, L, to which they are affixed,
is horizontal. The dial plate A, B, before mentioned, is provided with
two pillars or axes o, p, which are capable of revolving. steadily in tubes
or sockets in a direction perpendicular to the surface of the dial plate.
The lower parts of the pillars o, p, are furnished with limbs and verniers
g and r, adapted to read against the divisions or degrees upon the divided
arcs Q, R, and the upper parts of the pillars o, p, are formed to a square
fork or open frame, and are each provided with reflecting glasses or mirrors
O and P, which are adapted to turn upon small axes or pivots passing
through the sides of the said open frames in a direction parallel to the face of
the dial plate A, B. The outermost ends of the said small axes are each
provided with a limb s, t, carrying the graduated arcs or- sectors S and T,
which are furnished with verniers and w to read off the divisions with
.
accuracy. The reflecting mirror
is only partially
silvered, and the

page_text: remaining portion is left transparent; at the same time the mirror P is
silvered over it's whole surface. This last-mentioned mirror is mounted in a
small interior frame, which is adapted to turn on secondary pivots in the
frames, which is connected by the pivot or small axes aforesaid with the
limb t. By this means the mirror P has the liberty of motion in both
directions horizontally as well as a motion vertically upon it's pillar or
axis p.
These motions become necessary in making observations, with
those stars which have a considerable degree of declination. The secondary
motion of the mirror P is effected by a small racked or worm wheel z, which
has a screw engaging with it, furnished with a micrometer or divided head n,
by which the angle or extent of side inclination may be determined. In some
cases I mount the mirror O in a double frame, and provide it with a screw
and micrometer head, in a similar manner to the mirror P, as above described.
The pivots or axes c, upon which the hemisphere is suspended, project some
distance through the ring D, and are furnished with small screw caps, which
may be screwed on or off for the purpose of giving the hemisphere a slight
motion endways or in the direction of its axes, in order to adjust it into a
proper position to balance correctly in it's gimbols after the indexes have been
placed properly for making an observation. The hemisphere C contains a
weight or counterpoise within it, so situated, that the centre of gravity of the
whole mechanism which is mounted upon the dial plate should fall as nearly as
possible in the centre of the said hemisphere; but as this centre will be
slightly disturbed by the moving of the indexes and mirrors upon their axes
upon the dial plate, its adjustment or equilibrium may be restored by screwing
up or down the small spherical weight Z, which is tapped upon a wire
projecting out from the centre of the dial plate. W represents a short
telescope, which is supported by a pillar rising from the dial plate; it's axis is
placed correctly in a line with the centre of the two mirrors O and P, such
line being parallel to the dial plate A, B, and in a line over the centre thereof,
so that the reflected images of the sun, moon, or stars, when they fall on the
mirrors, may be viewed through the telescope, to ascertain when the coin-
cidence of the images takes place. Note, in this construction of the instru-
ment the graduated ares Q and R must be divided and marked with half
degrees or with twenty-four hours in the circle, in consequence of reflecting
glasses or mirrors being used; and the arcs of declination S and T must also
be graduated into half degrees; but the arc of elevation g, h, upon the
hemisphere C, as well as the circle upon the plate F, G, may be divided into
whole degrees.
The dial plate A, B, with its appendages, as represented in Figure 1,
emoved from the homienhore Cond aimbole
and mat ho nood

page_text: in the hand by having a handle screwed or otherwise fixed to the under
side of the dial plate, for the convenience of holding it by, in making
observations.
I shall now proceed to explain the manner in which the celestial compass
is to be adjusted for use, giving one example of using it, to explain, for
instance, how the same is to be applied for the purpose of ascertaining the
moon's meridian, distance, and declination, as data for determining the latitude
or longitude, and I will then point out in a general manner what deduction
or allowances are to be made in the use of this instrument for errors and
variations, by which means persons sufficiently conversant with the use of
astronomical instruments will be enabled to employ it in the various cases to
which it may be found applicable. Suppose the celestial compass to be in the
position represented by Figure I upon the annexed Drawing; the instrument
is turned round upon the axis or pivot of the plate F, G, until the axes d, d,
and consequently the line A, B, upon the dial plate is found, by the aid of the
common magnetic needle or any other convenient manner, to be somewhere
near the plane of the meridian, the surface of the dial plate being inclined to
coincide with the plane of the equator by means of the arc of altitude g, h,
upon the hemisphere C, being set by it's vernier k, to the latitude of the
place, at which point it is secured by a clamping screw, such as seen at k,
applied in the usual manner. The divided arc T is set by it's vernier w to
the angle of declination of any known star which is to be found in the tables
such as are used for astronomical purposes. After this the limb and vernier r
is set to such division upon the arc R as will correspond with the meridian
distance of the same star, which is found by calculation from the tables in the
usual manner. This being done, the adjusting screw seen at V, Figure 1, is
moved either way until the reflected image of the star, when viewed through
the telescope W, appears to be in the centre of the mirror P, in which
situation the line A, B, upon the dial plate, as well as the axis of the telescope,
will be situated in the plane of the true meridian. The divided arc S is now
moved until the reflected image of the moon, when viewed through the
telescope W, is made to appear upon the horizontal centre line of the partially
silvered mirror O; at which time the limb and vernier q is moved until the
image of the moon, when viewed through the telescope, is brought to coincide
with the reflected image of the star in the mirror P, which will be seen above
the silvered portion of the mirror O. These operations being gone through,
the moon's meridian distance will be read off upon the divided arc Q, by the
vernier q, and her declination will be read off. upon the divided arc S by the
vernier v, which, after making the usual corrections for errors in altitude, and

page_text: for parallax and refraction, the true positions will be given. With respect
to this latter correction for parallax and refraction of the declination, it may be
necessary to give some general data as a guide for the observer to construct his
tables by. These may be deduced by astronomical calculation resulting from
the relative positions between the vertical and declination circles at the time of
observation, and the regular proportion which, in each latitude, the error or
correction for declination bears to the error or correction for altitude, which
error or correction for altitude is supposed to be known: for instance, in
latitude 20, the correction for declination is about 3 of the correction for altitude:
in latitude 51 it is about 4. and in latitude 60 about -
Tables may
therefore be calculated for any latitude, by which the required correction for
declination may be found by inspection. The true declination being thus
obtained, the longitude may be readily determined by means of the moon's
right ascention or angular distance from any known star.
Figure 2 upon the annexed Drawing shews a modification of construction in
part of the instrument, which will render it particularly applicable to be used
by day when the sun is visible. In this modification the reflecting glasses are
dispensed with, in lieu of which the direct light of the sun is made to fall
upon a pair of cross wires, so as to direct their shadow upon a semi-transparent
surface, furnished with cross lines in a direction of about 45° degrees to the
wires before inentioned, and the coincidence of the shadow of the cross wires
with the intersection of the lines upon the semi-transparent surface will de-
termine the required position. This apparatus consists of a dial plate A, B,
which is adapted to fit into and be screwed to the hemisphere C. being occa-
sionally substituted in place of the dial plate A, B, with it's reflecting glasses
and appendages, as herein-before described by reference to the Figure 1.
The dial plate A, B, shewn in Figure 2, is divided into twenty-four hours
upon it's surface, and it has also a circle of degrees graduated upon it. The
said dial plate is provided with an hour index or hand E, which is formed
to a vernier at one of it's extremities to read against the degrees upon the
dial plate. F represents a hand or index which indicates the minutes.
The
two hands E and F are connected together by wheelwork beneath the dial plate
in the same manner that the hour and minute hauds of ordinary clocks and
watches are connected, but with the wheels and pinions so proportioned that
the minute hand F, when turned round by means of the milled head f, in the
centre or otherwise, will perform twenty-four revolutions for one revolution
of the hour hand E. P represents a small frame or square. which is mounted
so as to admit of being turned round when required upon the stationary pin or
axis, which passes through the centre of the dial plate and the two hands.

page_text: The frame P is adapted to receive a piece of ivory or other opaque or semi-
transparent substance 9. having cross lines or wires intersecting each other
upon its surface. The hour hand E has near one of it's extremities a small
pillar or tube o projecting up from it, and into this tube a small round rod s is
adapted to slide, having a square frame O at it's uppermost extremity furnished
with cross wires, as represented in the Drawing, Figure 2. The round rod s
is graduated and numbered with tangents to the angles of elevation and de-
pression above and below the level of the intersection of the cross lines upon
the surface q, and it is provided with a vernier scale, formed on the side of the
pillar o, to read against the divisions on the round rod. It is also furnished with
a clamping piece and micrometer screw, as shewn in the Figure, to move it up
or down with a slow motion. Y represents a balance weight, which is for the
purpose of keeping the instrument in balance, as above mentioned, with
reference to the Figure 1, and z represents the small spherical counter-
balance to restore the equilibrium, in case it should be destroyed by the
setting of the indexes in their proper positions for making an observation. I
sometimes provide that part of the instrument (which is represented in
Figure 2) with a watch movement, adapted to give motion to the hour and
minute hands, or indexes E and F, in the same manner as motion is given to
the hands of an ordinary watch, but with the wheelwork so proportioned that
the hour hand E shall perform only one half a revolution in twelve hours, and
the minute hand F shall perform twenty-four revolutions during one entire
revolution of the hour hand E. The instrument when so constructed and
placed with it's dial-plate A, B, in the hemisphere C, shewn in Figure 1
(instead of the dial plate, with it's appendages, which is there represented),
forms a very complete compass for steering a ship by means of the motions of
the heavenly bodies, instead of steering by the magnetic needle. This is found
to be an important application of the celestial compass, particularly in navi-
gating a ship in high northern or southern latitudes. The manner of using
the celestial compass for this purpose, in steering by the sun, would be as
follows: Suppose the platform H, I. (as represented in Figure 1 upon the
annexed Drawing) to be screwed down upon the binnacle or other convenient
part of a ship, in such a position that the line H, I, which is drawn upon the
said platform, may coincide exactly in a longitudinal direction with a line
immediately over or otherwise parallel to the vessel's keel; in this situation
the compass plate F, G, which has the instrument mounted upon it, as afore-
said; is to be turned round upon it's axes until the zero of the vernier at. I is
brought to coincide with the point or degree upon the compass plate, which
will-indicate the course desired to be steered; for instance, in the Figure !

page_text: upon the Drawing. the compass plate F. G. is represented as set proper for
steering a course due north: now, if the hemisphere (be elevated upon its
axis or pivots c until the divisions upon the arc g. h. are brought to read
against the vernier k at the degree of latitude of the place where the vessel is
sailing, it will be evident that the dial plate A. B. will be situated parallel to
the equator, or perpendicular to the earth's polar axis. In this situation, if the
hands or indexes E. F. (see Figure 2) be set to the apparent time, say three
hours, or forty-five degrees from the meridian, for example as shewn in the
said Figure. the person who steers the vessel has only to keep her upon such a
course that the shadow at the point of intersection of the cross wires in the
frame may fall upon the surface q in such position that the said point of
intersection may continually coincide with the perpendicular mark or wire
upon the surface q, and the vessel will proceed in a true northern direction.
as indicated by the points upon the compass plate F. G.
Figure 3 upon the annexed Drawing represents a modification in the con-
struction of the celestial compass or instrument which renders it particularly
applicable to the purposes of taking bearings on land. or for laying down
angles in surveying by means of the heavenly bodies, without using a
magnetic needle. In this mode of construction the instrument may either
be used as a portable instrument. being held in the hand, or it may be
mounted upon a small tripod stand in the manner of levels or theodolites.
The instrument consists of an index or dial plate A. B. which is divided into
twenty-four hours, and is also graduated with a circle of degrees. This dial
plate is mounted upon pivots or axes, which pass through holes or bearings in
a metal ring D. so as to admit of vibrating thereupon. and the degree of angle
at which it may have been placed is determined by an are or sector g, h, which
is graduated with degrees, and is adapted to read off against the divisions upon
a vernier affixed to the ring D. The dial plate A. B. is furnished with an
index or hour hand E. one extremity of which hand is formed to a vernier to
read off against the degrees upon the dial plate. The hand E has also a small
pillar or tube o rising up from it. into which tube a small graduated rod s
slides, and is formed at the upper extremity to a flat plate or disc O, having a
small sight or aperture through it. P represents a small square of ivory, or
other semi-transparent or opaque material. having cross lines or wires upon it's
surface. It is fixed so as to admit of being turned round when desired upon a
pin in the centre of the dial plate. The ring D has a groove or circular
channel turned out in it's face. into which channel a second ring F, G, is
inserted, with liberty of turning round freely therein. The ring F, G, is pro-
vided with a vernier adapted to read off against the degrees upon the ring D,

page_text: and it has two sights W. r, screwed upon it, which project up therefrom, and
have slits or apertures formed in them, provided with perpendicular wires
or hairs for observing any object by. The sights W, , have joints in them at
about the middle of their length for enabling them to be folded down into a
compact form for the convenience of carriage. The outer circumference of
the ring D is cut with a screw, and is adapted to have a box screwed over it,
30 as to form a cover for the instrument when not in use. The said box also
serves to screw on beneath the plate D in the manner of ordinary box sextants,
so as to serve for holding the instrument by when used in the hand. This
instrument, may be used, if desired, with reflecting glasses or mirrors, as
described for Figure 1: but for simplicity and portability it is more convenient
without them.
I will explain the manner of adjusting this compass for use. giving one
example of using it. for instance, the method of ascertaining the bearing of
any object on land by the aid of the heavenly bodies, and without employing
the magnetic needle. In making use of the celestial compass on land, in
order to find the bearing of any object, the index or hour hand E, Figure 3,
upon the annexed Drawing, is to be set to the apparent time. suppose three
hours, or forty-five degrees from the noon hour line A. B. and the dial plate
A. B, is to be inclined upon it's pivots or axis c. in the ring D, until the divided
arc g; h, reads off against the vernier k. the degree corresponding with the
latitude of the place. The small rod is now to be raised out of the tube o
until the divisions upon it are brought to correspond with the tangent of the
angle of the sun's declination. This being effected. the instrument is to be
held up in the hand, and moved about until the speck of light which passes
through the small aperture in the disc O (from the sun for instance) is made to
fall upon the intersection of the cross wires upon the tablet P. at which time
the surface of the ring D will be situated truly horizontal, and the line A, B,
upon the dial plate, and the north and south line upon the ring D, D, will be
situated in the plane of the true meridian. The ring F, G. and sights W, w,
are now to be turned round until the object (the bearing of which is described
to be ascertained).. when viewed through the slits or apertures in the said
sights, appears to be intersected by the perpendicular wires in the said slits or
apertures, in which situation the true bearing of the object may be ascertained
by inspection of the vernier I, by reading off against the circle of degrees upon
the ring D. In some cases it would be found very convenient to have a small
reflecting mirror fixed at about the part w. Figure 3, on the inside of that
sight which is turned towards the object, in order that the coincidence of the
speck of light aforesaid. with the cross wires upon the tablet P, might be

page_text: observed distinctly by reflection, at the same time that the observer might
have his eye placed to the sights for viewing the object. The said small
reflector should be fixed so as to admit of being moved in order to adjust it to
a position for reflecting the image of the cross wires in a proper direction.
I have now described. with reference to the annexed Drawing. my said
Invention of A New Compass for Navigation and other Purposes, and have
explained, by way of example, the manner of using the same. sufficiently to
enable persons conversant with operations of a similar nature to practice the
Invention and whereas I have been obliged. in order that the nature of my
said Invention might be clearly understood, to introduce and describe in this my
Specification many parts and apparatus which have been heretofore used in
compasses and other instruments of a like nature. I do hereby declare that
I make no claim to the parts of the compass or instrument which I have above
described in their separate or uncombined state. but I confine my present
claim of Invention to the new arrangement and combinations of the said parts
which has been herein-before described, so as to form a new compass for
navigation and other purposes, which will be found in many cases to possess
considerable advantages over such compasses as have been heretofore used.
observing always that the form and proportions of the various parts may be
varied according to the discretion of the workmen employed in constructing
the same. The materials of which the whole may be made may also be
varied according to the circumstances of the case, without departing from the
intent and object of the Invention, as herein-before described and set forth.
In witness whereof, I. the said George Graydon. have hereunto set my
hand and seal, this Fifth day of February. in the year of our Lord
One thousand sight hundred and twenty five
Inrolled the same Fifth day of February, in the year above written.