Improved Method of and Instrument for Taking Observations from Heavenly Bodies, especially applicable for Navigation Purposes.
Year: 1893

page_text: Date of Application, 23rd June, 1893
Complete Specification Left, 17th Feb., 1894-Accepted, 2nd June, 1894
Improved Method of and Instrument for Taking Observations
from Heavenly Bodies, especially applicable for Navigation
Purposes.
A communication from RICHARD WADE JENKINS, of Bowhill Estate,
Nawalapitiya, Ceylon, Tea Planter.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention to be as
follows:-
This invention relates to an improved method of and instrument for taking
observations of heavenly bodies and has for its object among other purposes to
facilitate the ascertainment of the true or astronomical north, latitude, longitude
(local time), solar time and the course of a ship.
Before describing the method and instrument constituting this invention I will
describe the fundamental principles upon which the invention is based.
As is well known the earth is immersed from pole to pole in the parallel rays of
the sun in consequence of which and the convexity of the earth's surface vertical
stiles cast shadows in almost every direction, which feature if sought to be
employed as data upon which to base astronomical calculations is still further
complicated by the sun's ever-varying declination.
In considering how to avoid the difficulties attendant upon the employment of
data such as before mentioned the inventor imagined that if the earth were cut in
two through any meridian, and one-half were removed, a circular plane would be
left upon which all vertical stiles would at every instant cast parallel shadows.
To mechanically avail himself of this theory, the inventor proceeds as follows;-
A disc, hereinafter also termed the "solar compass," assumed to represent the
before mentioned circular plane, is pivotted on pins or between centres (mounted in
an adjustable semi-circular graduated arc) in the same plane as its surface and a
vertical gnomon is erected at its centre. At every sunrise and sunset the shadow
of this gnomon falls to opposite parts of the circumference of the solar compass.
Assuming the pivots to be the north (N.) and south (S.) poles, 90 degrees from
each is the east (E.) and west (W.) and 23 degrees marked on the northern and
southern sides of the east and west points respectively indicate the sun's north and
south declination.
To produce imaginary sunrise and sunset the disc or "solar compass" is tilted so
that its plane bisects the sun. When the disc is turned in azimuth so that the
shadow of the central gnomon falls on the sun's declination for the day and hour
(reversed N. for S., and S. for N.) the axis must be in the meridian provided it is
also inclined parallel to the earth's axis. If the semi-circular graduated arc be
not adjusted to the latitude, the meridian being known, and the disc's axis be set in
the meridian, the latitude may be found by the same means with equal accuracy.
Therefore if there is produced imaginary or artificial sunrise and sunset on the
disc or solar compass-adjusted as directed-at any instant and place the shadow
of the vertical gnomon falling on the sun's declination will necessitate the poles of
the instrument being truly north and south.
It is always sunrise or sunset somewhere and when the disc or solar compass is
made to bisect the sun as directed, its plane is the same or parallel to the horizon
of those places at which the leaning gnomon would be vertical.
The semi-circular graduated arc may be adjustably mounted in the upper end of

page_text: a standard or pillar to the foot or lower end of which is secured a compass card
whose north point is directly and permanently under the north point of the solar
compass, and the standard is mounted in a preferably heavy base so that it and the
parts carried by it may be turned in azimuth; the heavy base for use on ships may
be supported in suitable gimbals, so as to keep it always level and the standard
vertical, but otherwise the base is not free to move, that is to say it cannot be
turned in a horizontal plane.
Just outside the compass card at the lower end of the standard is marked a line
which when the instrument is mounted on a ship points to the ship's head so that
when the solar compass is turned in order to find the sun at the proper declination
the ship's course may be ascertained by comparing the mariner's compass with the
before-mentioned line.
In order that the instrument may indicate longitude (local time) a second and
preferably smaller disc or dial is rigidly secured to the "north" (or interchangeably
to the "south") end of the graduated arc with its plane at a right angle to that of
the solar compass. This dial is marked with the hours &c. and degrees of arc and
a pointer or index secured to or adapted to move with the solar compass indicates
on said dial the sun's angular clevation and local time whenever the solar compass
is adjusted to bisect the sun.
Although a single central gnomon may be used as before described yet it is
preferred to use two gnomons cach carrying a lens whose focal distance is
preferably the diameter of the solar compass. These gnomons are mounted on a
bar pivotted centrally to the centre of the solar compass and capable of being
turned round the cast and west arc of 48 degrees corresponding to the sun's
declination. Thus, by adjusting either of these gnomons (east, or west, morning
or evening) to the sun's declination, at any time the other is automatically
adjusted to the same degree in the opposite hemisphere. At the instant that the
focal image of either lens falls on a spot marked to receive it on the opposite
gnomon the plane of the solar compass bisects the sun.
The solar compass may be several feet in diameter, or if constructed with the
mathematical accuracy of say a theodolite it may be proportionately smaller.
Verniers may be employed where found most convenient for dividing the degrees
of latitude, declination and sun's altitude.
The instrument after being set up level on land, or when at sea, maintained level
by its gimbals is used in the following manner;-
It is first roughly adjusted to the magnetic north and the known latitude of the
place, then the cast or west gnomon is adjusted accurately (according as it may be
fore or after noon) to the degree corresponding to the sun's declination for the day
and hour. The adjusted gnomon is then directed to the sun, by turning the
standard in azimuth until the focal image falls on the proper point on the opposite
gnomon. At that instant the axis of the solar compass will be in the meridian,
and in consequence will point due north and south, thus checking the variations
and irregularities of the ship's ordinary magnetic compass. At the same instant
the dial will indicate the local time &c. &c. and as before described, when used on
a ship the ship's course, all by the same adjustment and all of which may be read
off at one inspection.
The before described instrument may be modified without departing from the
spirit of the invention for instance instead of using complete dials or discs, rings
may be employed as the central parts do not affect the working of the instrument,
and moreover the principle involved in the apparatus though, as herein described
specially applicable for taking observations from the sun, is also available for the
moon, stars and other heavenly bodies.
Dated thie 21et dor of June 1802
W. P. THOMPSON & BOULT,
Of London, Nottingham, Liverpool, and Manchester,
Agents for the Applicant.

page_text: Improved Method of and Instrument for Taking Observations
from Heavenly Bodies, especially applicable for Navigation
Purposes.
A communication from RICHARD
WADE JENKINS, of Bowhill Estate,
Nawalapitiya, Ceylon, Tea Planter.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of the said invention and in
what manner the same is to be performed, to be particularly described aud
ascertained in and by the following statement:-
This invention relates to an improved method of and instrument for taking
observations of heavenly bodies and has for its object among other purposes to
facilitate the ascertainment of the true or astronomical north, latitude, longitude
(local time), solar time and the course of a ship.
Before describing the method and instrument constituting this invention I will
describe the fundamental principles upon which the invention is based.
As is well-known the earth is immersed from pole to pole in the parallel rays
of the sun, but in consequence of the convexity of the earth's surface vertical
stiles cast shadows in almost every direction, which feature if sought to be employed
as data upon which to base astronomical calculations is still further complicated by
the sun's ever-varying declination.
In considering how to avoid the difficulties attendant upon the employment of
data such as before mentioned, the inventor imagined that if the earth were cut in
two through any meridian, and one-half were removed, a circular plane would be
left upon which all vertical stiles would at every instant cast parallel shadows.
To mechanically avail himself of this theory, the inventor proceeds as follows;-
A disc, hereinafter also termed the "solar compass," or solar compass disc, assumed
to represent the before mentioned circular plane, is pivotted on pins or between
centres (mounted in an adjustable semi-circular graduated are hereinafter referred
to as the "latitude arc ") in or about the same plane as its surface, and a vertical
gnomon is erected at its centre or on a radial arm, (or, as hereinafter described,
two adjustable gnomons are arranged at diametrically opposite points of the solar
compass). At every sunrise and sunset the shadow of this gnomon falls to opposite
parts of the circumference of the solar compass. Assuming the pivots to be the
north (N.) and south (S.) poles, 90 degrees from each is the east (E.) and west (W.)
and 23 degrees marked on the northern and southern sides of the east and west
points respectively indicate the sun's north and south declination.
To produce imaginary sunrise and sunset the disc or solar compass is tilted so
that its plane bisects the sun. When the disc is turned in azimuth so that the
shadow of the central gnomon falls on the sun's declination for the day and hour
(reversed N. for S., and S. for N.) its axis must be in the meridian, provided it is
also inclined parallel to the earth's axis. If the latitude-arc be not adjusted to the
latitude, the meridian being known, and the disc's axis be set in the meridian, the
latitude may be found with equal accuracy.
Therefore, if there is produced imaginary or artifical sunrise or sunset on the
disc or solar compass-adjusted as directed-at any instant and place the shadow
of the vertical gnomon falling on the sun's declination will necessitate the poles of
the instrument being truly north and south.
The latitude arc may be adjustably mounted in the upper end of a standard or
pillar to the foot or lower end of which is secured a compass-card whose north point
is directly and permanently under the north point of the solar-compass, and the
standard is mounted in a preferably heavy base so that it, and the parts carried by
it, may be turned in azimuth; the heavy base for use on ships may be supported

page_text: in suitable gimbals or equivalent so as to keep it always level and the standard
vertical, but otherwise the base is not free to move, that is to say it cannot be
turned in a horizonal plane.
Just outside the circumference of the compass card (at the lower end of the
standard) is marked on the heavy base, a line which, when the instrument is
mounted on a ship, points to the ship's head, so that when the solar compass is
turned in order to find the sun at the proper declination the ship's course may be
ascertained by comparing the mariner's compass with the before-mentioned line.
In order that the instrument may indicate longitude (local-time) a semi-circular
dial of convenient size is rigidly secured to the "north" (or interchangeably to the
"south") end of the latitude-are, with its plane at a right angle to that of the
solar compass. This dial is marked with the hours &c., and degrees of arc, and a
pointer or index secured to or adapted to move with the solar compass indicates on
said dial the sun's distance from the meridian and local-time whenever the solar
compass is adjusted, and made to bisect the sun.
Although a single central gnomon may be used, as before described, yet it is
preferred to use two gnomons each carrying a lens (which "lenses" are hereinafter
also referred to as the " gnomons") whose focal distance is the diameter of the
solar compass. These gnomons or lens-carriers or the lenses themselves are mounted
on a bar pivotted centrally to the centre of the solar compass and capable of being
turned round the east and west arc of 48 degrees corresponding to the sun's
declination. Thus, by adjusting either of these gnomons (east, or west, morning or
evening) to the sun's declination, at any time, the other is automatically adjusted
to the same degree in the opposite hemisphere. At the instant that the focal
image of either lens falls on a spot marked to receive it on the opposite gnomon
the plane of the solar compass bisects the sun.
The solar compass may be several feet in diameter, or if constructed with
the mathematical accuracy of say a theodolite it may be proportionately smaller.
Verniers may be employed where found most convenient for dividing the degrees
of latitude, declination and sun's position.
The instrument after being set up level on land, or when at sea, maintained level
by its gimbals or equivalent is used in the following manuer ;-
It is first roughly adjusted to the magnetic north and accurately to the known
latitude of the place, then the east or west gnomon is adjusted accurately (according
as it may be fore or after noon) to the degree corresponding to the sun's declination
for the day and hour. The adjusted gnomon is then directed to the sun, and the
standard turned in azimuth until the focal image falls on the proper point on the
opposite gnomon. At that instant the axis of the solar compass will be in
the meridian, and in consequence will point due north and south, thus checking the
variations and irregularities of the ship's ordinary magnetic compass. At the same
instant the dial will indicate the local time &c. &c. and as before described, when
used on a ship the ship's course, all by the same adjustment, and all of which may
be read off at one inspection.
The before described instrument may be modified without departing from the
spirit of the invention, for instance instead of using complete dials or discs, rings
may be employed, as the central parts do not affect the working of the instrument,
and moreover the principle involved in the apparatus though herein described as
specially applicable for taking observations from the sun is also available for the
moon, stars, and other heavenly bodies.
In the accompanying drawings
Figures 1 and 2 are two elevations of the instrument taken at right angles to each
other.
Figure 3 is an underside or back view of the solar compass and its directly
connected parts detached from the latitude arc.
Figure 4 is an elevation of one of the gnomons and its vernier.
In Figure 1 the solar compass is represented as in the same plane as the latitude
arc as it would be when adjusted at the equator at noon, and in Figure 2 it is shown

page_text: with its index slightly out of perpendicularity with the latitude arc as it would be
when adjusted at about 5.15 at the same place.
Like letters indicate like parts throughout the drawings.
In the Provisional Specification the instrument was described as comprising the
following princinal parts ri-
2. A neavy base.
3. A standard.
4. A mariner's compass card.
5. A graduated semi-circular arc.
6. The solar-compass or solar-compass disc.
7. Cross bar, with gnomons, leuses, and verniers.
8. The local-time dial.
9. The index-hand, or pointer.
These several parts are constructed of metal or other firm and durable material,
and the verniers, graduations, centres and circles are mathematically correct and
true; and all the parts are accurately fitted together so that no wobbling, looseness
or shakiness may be anywhere perceptible; and the "base" is arranged to maintain
a constant level, and the "standard a true and constant vertical position. In the
complete working instrument a few aids in the shape of adjusting screws, clamps,
arms, verniers &c. will be useful, and may be considered to be necessary accessories,
and these are hereinafter more fully described while further and more particularly
describing each of the above mentioned parts of the instrument, which though
recording so many valuable data (when so easily adjusted, as directed) is of
extremely simple construction.
1. The gimbals. These, their casing, and their supports being of any ordinary
construction are not shown in the accompanying drawings, it being considered
sufficient to show merely the knife edges or trunnions A' of the base A, which are
supported in the gimbals. The strength, size and height of the gimbals and their
fittings should be adapted to the size of the base of each instrument, and the size
(diameter &c.) of the base will depend, generally, on the diameter of the solar-
compass disc.
2. The base. In diameter, the base A. should not, as a rule, be much, or any,
smaller than the solar-compass disc B, that no danger be run of the instrument being
at all top-heavy. The base A should fit in, and be attached to, the inner ring of
the gimbals by strong knife edges or trunnions A', at about from one or, for large
instruments, to two inches, below its surface, and it should be several inches (or
even feet) in depth (according to the size of the instrument) and well weighted at
the bottom. The hole A' (shown in dotted lines in Figures 1 and 2) in, and
through, its centre should be perfectly central and true, and extend through the
whole depth or thickness of the base, and this hole should be uniform through its
whole length and in size be commensurate with that of the whole instrument, and of
the standard C-large in diameter for a large instrument, and smaller for a more
delicately made one. The prolongation or pintle C¹ of the standard C which this
hole is intended to accommodate, should fill and fiti t truly, passing through it to
beyond the bottom of the base A where the pintle C should be provided with large
washers D D' and nuts C' screwed on tight, but leaving the standard and pintle a
fiee and smooth horizontal motion. The washer D is let into and rigidly secured
to the body of the base, as shown in dotted lines in Figure 1, and the washer D' of
the same size as D immediately below it, is free to revolve with the standard C and
pintle C in order to ensure smoothness of motion. This washer D' should be held
in place by one or more nuts C' screwed on to the threaded end of the standard
pintle C¹.
For instruments to be used on land any convenient and suitable fixed or portable
stand or support, to carry the latitude arc E may be substituted for the before
described base A, and provided with two spirit levels or equivalent one at right
augles to the other.

page_text: It
3. The standard. Preferably this should be short so that the centre of gravity
of the parts it carries and supports, does not fall outside its own vertical axis.
should be of larger diameter than the pintle C¹ fitting into the base A. It may be
plain, square, or ornamental. Its pintle C should pass centrally through the
mariner's-compass card F which is preferably secured to the under surface of the
standard, so that it may be supported and be rotated by the standard slightly above
and out of contact with the top surface of the base A. As a means of readily
turning the standard C and its directly connected parts to right and left in azimuth,
at least one light but strong metallic lever-arm, or bar C³, should be firmly
attached to it near the bottom, (passing just over the mariner's-compass-card F)
and reaching to the circumference of the base A over the edge of which it may
slightly lap as shown in Figure 1 and there be furnished with a clamping screw C₁
to hold it in any desired position. At its head, the standard in shape is preferably
spread out and flat, with a grooved top, curved (top and bottom) to correspond
with the chord or part of the latitude-arc E the groove C³ accommodates. This
groove C³ should extend throughout the whole length of the top, and be deep and
wide enough to carry the latitude arc E for about 30 (thirty) of its degrees
in length so as to afford ample support to it. As this flat top cannot be allowed to
project much above the inner edge of the latitude-arc E, or-what is the same
thing the said aic E cannot be sunk very deeply in the groove C³ beyond its own
width (so as not to interfere with the midday position of the solar-compass B and
its gnomons G G¹) the latitude-arc E itself (for this reason) should be somewhat
broader than would otherwise be necessary in order that its graduations El may bo
read through an opening C in one side of the said flat top of the standard C.
This opening C should be sufficiently large to accommodate a fixed vernier C7 on
its bottom edge to divide the degrees of the latitude-arc. Strong clamping-
screws H should be fitted in the back of the standard C to press against and
firmly hold the latitude-arc E in its place, in the grooved head of the standard C.
It is essential that this part be well and efficiently made and fitted, the bottom of
the groove corresponding with the outer edge of the latitude-arc, so that no
wobbling be possible. Also, the upper, or top, part of the said groove C should on
its front side be made with a slightly projecting inner flange, or rim C³ shown in
dotted lines in Figure 2 so that the latitude-arc E, when carried in the said groove
at any angle, cannot move, or tilt, forwards or backwards, or fall out of the groove.
The width of the groove C³ should be somewhat larger than the thickness of the
latitude-arc E so that a metal plate H can be accommodated in the groove
between the ends of the clamping-screws H and adjacent face of the latitude arc E
to distribute the pressure of the screws H over the surface of the latitude-arc and
prevent the latter from being damaged by the screws. Further it is necessary to
provide for the ready, easy and smooth adjusting of the latitude-arc E to any
degree of latitude (after having temporarily loosened the clamping-screws H).
To facilitate this movement the outer edge of the latitude-arc E may be milled or
finely toothed as at E so that it may be operated upon by two correspondingly
milled or toothed pinions I I. These wheels or pinions I may be carried in
bearings C provided on the flat head of the standard C the handle 12 of one say
to be worked with the right hand preferably on the front side (or cast) and the
handle I of the other say I' to be worked with the left hand on the back (or west)
side of the flat head of the standard C. Each pinion or adjusting wheel I I¹ is
fixed on a short horizontal shaft 13 one end of which is short so as not to project
beyond the outer face of the bearing at one side but projecting far enough at the
other side to receive one of the before-mentioned milled or other wheels or
heads I².
I
This last-described part of the instrument, though constituting an efficient
apparatus, may be replaced by any other of different construction adapted to hold
firmly and turn smoothly the latitude-are E, without departing from the spirit of
the invention. In practice it has been found that this is one of the most important
parts of the instrument for it is essential that the latitude-arc E be firmly and

page_text: truly supported at any degree of latitude desired, so that the centre of the solar
compass B above shall be always directly over, or in the same plane, as the vertical
axis of the standard C. As an alternative of the last described adjusting device
the outer edge of the latitude arc E may be formed smooth and an ordinary
theodolite tangent screw used for fine adjustment, the clamp H H¹ being retained
as before.
4. The mariner's compass card. This compass card F in sheet metal or other
suitable material is secured in any convenient manner as by rivets or screws to the
bottom of the standard C so as to be slightly above the top service of the base A,
the pintle C of the standard passing centrally through F, and it should turn in a
horizontal plane smoothly over the face of the base. It may be somewhat smaller
in diameter than the base A in order to give room for a conspicuous line (not
represented on the accompanying drawings) to be marked on the base corresponding
to the ship's head, or keel, by means of which line the ship's course &c. can be read
off the said card. Being attached to the standard C the north and south line of
compass card F should be secured in the same vertical plane as the line joining the
north and south poles of the solar-compass B and arms of the latitude-arc E above.
When mounted in gimbals on board ship the variations of the magnetic compass,
in any part of the world, can, by comparing it with the solar compass be read and
recorded at every observation made with the instrument. It may here be remarked
that the mid-point between the sides of the ship, or right over the keel, is naturally
the right place to fix this or any other such instrument, but should masts or funnels
interfere as they often do, there can be no objection to the instrument being fixed
anywhere on board, or to be made movable and clear of these obstructions to the
rays of the sun &c.
"
5. The latitude arc. This are E is a strong metallic arc slightly larger than a
semi-circle (much resembling the "brazen-meridians" usually seen on terrestrial
and celestial globes) and it varies in strength and dimensions according to the size
of the instrument. For a small solar compass, say of one foot in diameter, a
convenient size for this " arc would be from say three to five eighths of an inch in
thickness and two inches broad. This breadth is more than is absolutely necessary for
strength, but as already mentioned in describing the groove C in the head of the
standard C it is for the purpose of its sinking low enough in that groove to give
the clamping screws H a good holding surface, as well as to afford room for the
opening C in the front side of the standard sufficiently low down to expose the
graduations E' to view against the vernier C', and generally because this part should
be made strong and firm. Any dimensions that provide for these contingencies and
afford sufficient stability and strength will however suffice. The opening C should
be long enough for a vernier to extend over say fifteen degrees of the arc E, and
wide enough to afford an ample view of the graduations. The groove in this case
would be about two and one-eighth inches deep, the extra one-eighth being allowed
for the rim C (Fig. 2) engaging with the arc's inner edge.
The latitude-arc E is of course graduated from 0° degrees at its lowest, or central
point, along each quadrant to 90° (degrees) at each end. At each of these
90° points it is drilled in its inner edge or otherwise provided with bearings to
receive the poles or pivots of the solar-compass B.
6. The solar compass. This compass or disc B, the essence of the invention,
requires to be skilfully constructed and correctly graduated, centred, and fitted,
and the two gnomons G G¹ must be alike and truly facing each other with the
focus of each lens in the same plane. In theory the solar compass B is merely a
plane, but inasmuch as a thin disc of metal is apt to warp and twist, and thus not
to present a true plane or circle, this 'disc may be made any convenient thickness to
obviate this tendency, so as to ensure a perfect plane and true circular outline.
In theory, too, it should be swung on pivots or pins whose common axis should be
flush with the surface of B but as the sun's rays do not diverge, and all parallel
planes receive his rays simultaneously, this, too, may be disregarded in practice, and
the disc be hung on pivots or pins B¹ Figure 3 of sufficient strength fixed midway

page_text: between its upper and lower surfaces, so that it may be evenly balanced. It is not
desirable however that the thickness should be at all greater than is necessary to
ensure a perfect plane and circle. In diameter it should be somewhat smaller than
the diameter of the inner edge of the latitude-arc E so as to allow ample room for
its manipulation and to carry its gnomons G G¹ clear of the head of the standard C
at noon. It may receive round the parts of its pivots B¹ left exposed, collars or
bosses to keep it tight and true in its place between the ends of the latitude-arc E.
Fitted on one of the ends of the latitude-arc E may be a pinion K shaft K' and
hand-wheel or equivalent K' to work on a wheel B* secured on the pivot B' of the
solar-compass B, for facilitating the adjustment of the solar compass disc B as will
be well understood. This adjusting mechanism may however be dispensed with and
the solar-compass be adjusted by hand, as if it be properly fitted to the latitude arc,
and tightened say by means of collars, it will rest at any required inclination to
which it may be adjusted. Ninety degrees of arc from each of the north and south
points of suspension (or poles) of the solar compass disc B are the "east" and
"west" points which are duly marked close to the circumference leaving however
space for the verniers; and, within concentric arcs, from each of these points
towards north and south, the degrees of arc must be marked as at B³ corresponding
to the sun's north and south declination, say up to twenty-five degrees on each side
of the east and west points. These degrees of are must be set out with
mathematical accuracy so that cach mark-if joined to its corresponding mark or
degree on the diametrically opposite side of the disc B, and in the opposite
hemisphere, shall pass truly through the centre of said disc, where (in theory) the
vertical axis of the central gnomon would be.
The vertical gnomons G G' carry lenses G and verniers G³, and are fixed to or
form part of a horizontal bar G which is pivotted centrally to the solar-compass
disc B (preferably at its underside) with a free motion in azimuth to the extent of
the sun's declination, or say fifty degrees of arc. To support this bar G and to
steady its motion, it may be guided between plates G³ (one near each end) and the
underside or back of the solar-compass B, the plates G being secured to B by
means of blocks or feet G which are of substantially the same thickness as the
bar G, and by which the further movement of the bar G₁ is prevented beyond its
twenty-five degree limits in either direction. The bar G and its directly
connected
parts may be clamped in any desired position by means of the screws G.
66
"
"
7. The gnomons, lenses, verniers &c. The swinging cross-bar G' just described
passing under or at the back of the solar-compass-disc B may be bent upwards at
right angles, at the circumference of the disc B at each of its ends to act as
gnomons vertical to the plane of said disc. Their purpose is to cause the sun to "rise
or set upon the solar compass disc B at any instant, precisely as he rises and sets
at the same instant on any such parallel plane on the earth's surface; and also at
his corresponding degree of declination, or as he would "rise" and "set" on the
already supposed plane of the earth's centre (one-half the hemisphere having been
removed). This effect on the solar-compass-disc B could indeed be produced
without their aid, by merely tilting the disc towards the sun till it projected a
shadow of only its own thickness as a straight line, but for the necessity of also
accurately determining the sun's declination on the plane of the disc. The simplest
way to determine this, as already stated, would be my means of a centrally-fixed
vertical gnomon, but in practice and for the convenience of employing "verniers
to divide the degrees of arc, it is preferable to use circumferential gnomous as
indicated in the drawings, each carrying a small lens G' for this purpose, cach lens
being of the same focal length, namely, the, diameter of the solar-compass disc B.
These lenses G2 should he carried with their centres at the same height above the
surface of the solar-compass, and this height need not exceed one inch. They
should truly face each other and be crossed at their centres by intersecting lines or
wires upon whose point of intersection the focal image of each is to be received
when properly adjusted to the sun's declination and turned towards him. It is
only by their means indeed that the direction of the true "north" is ascertained
"
"

page_text: because the final adjustment necessary to bring their axes in the same plane as the
centres of the sun and the solar-compass disc B of necessity causes the said disc B
(and the mariners compass F below it) to indicate the true astronomical north, the
ship's course, and also by comparison the variations of the magnetic compass; and
the local solar-time. These lenses G² as shown in Figures 2 and 4 should be
carried in circular or square frames, on the upturned vertical ends of the cross-
bar G. Any other optical or mechanical device may here be used for this purpose,
and notably either short or long telescopes for either night or day work, the
gnomons, in that case being so constructed as to carry such a telescope steadily
directed across the centre of the solar compass disc B preferably by means of
separate and transferable longer gnomons that can be screwed on to the end of the
cross-bar G just where it bends upwards behind the vernier G³ of the more
permanent gnomons. In other words, the lenses may be removable and a telescope
be used in their place, in the same plane and direction (when thought convenient)
but as a rule the lenses will be found sufficient even for the stars, as, by removing
the distant one and using only the one near the eye, a star can be brought into the
same plane as the solar disc B, by means of the cross-wires g g'.
Just where the vertical part of the bar G' or gnomon G meets or touches the
surface of the solar-compass-disc B it carries the verniers G to divide as before
described the declination degrees, moving with it smoothly over the circumference
of the disc B, close to the graduations B3 in the usual way.
8. The local time dial. This dial L as shown in Figure 2 is substantially a half-
disc of convenient size, with a diameter conveniently the same as that of the
solar-compass disc B; it is slightly larger than a half-disc so as to afford room for
the two hours marked "XII" at the two poles. The north "pole” as indicated in
the drawings (or in latitudes where more convenient the south pole) of the solar-
compass disc B is adjacent to the dial L and a line passing through the north and
Bouth poles of B bisects the line joining the two hours marked XII. The dial L
may conveniently be secured to the latitude-arc E by means of screws L' or
equivalent passing through a tongue or projection L' formed in part with L and
screwing into the latitude-arc E at its inner edge; other means may however be
employed for securing L to E.
The dial L round its extreme outer circumference has a space L' left along
which the vernier L of the index or dial hand L travels contiguously with a
concentric circle along and around which the degrees of are are marked as
at L which graduations the vernier L is intended to divide. These should be
marked from 0° at each noon (or the two hours of XII) to 90° at the top or
hour VI (which arrangement will indicate the sun's distance from the meridian at
any time of the day after sun-rise and before sunset) and thus more accurately
determine the true solar-time. Within an inner concentric circle (close to the last
named graduations) are marked as at L' Figure 2 the hours and minutes of time,
as on a clock face, with this difference that the hour "VI" is at the top, and there
are two "XII's" one at each end of the horizontal line joining the two poles, the
intervening hours being marked in in accordance with these positions. This arrange-
ment of the hours and the "index" is sufficient to indicate all the hours between
sunrise and sunset anywhere in the world.
The local-time-dial instead of being a half-disc centered on to the pole of the
solar compass may, without departing from the spirit of the invention, be a half-
circle arching equatorially over the solar-compass, from east to west, (or in some
other such position between the two poles) the dial in this position, or positions, being
kept fixed at right angles to the solar compass by its two ends being firmly secured
to the east and west points of a ring held at right angles to the plane of the
latitude arc.
This supporting circle, or ring, would, therefore, be in the same
plane as the solar compass at six o'clock and itself be kept in position by being
screwed, or otherwise secured to both ends of the latitude arc's outside edge,
co.ucident with the two 90 degree marks. The index hand would, in this modifi-
cation of the instrument, also have to be shifted from its polar position to the centre
B

page_text: or near the centre, of the solar compass, always however on its north or south line,
or meridian, but carrying its vernier and passing over the hours and degrees as
before, (the ring dial being the same as the disc-dial without its central parts). As
this central position of the index hand might somewhat interfere with the sun's
focal image the polar position of the time-dial is preferred. This objection,
however, would not obtain if the index-hand were slightly away from the centre,
or if fixed at the centre-it were bent so as to allow the focal rays from the
lens to pass unimpeded, that its end may pass back to its own vertical plane above
the bend.
9. The index or pointer. This pointer L' is substantially similar to an ordinary
clock minute-hand and through its lower part the pole of the solar-compass B
passes, a length of the hand or lug L Figs. 1 and 3 being left to bend underneath
the solar-compass B where it may be secured as by screws or equivalent L' thus
causing the hand L' itself to firmly stand vertical to the solar-compass disc B and
parallel and close to the time-dial L over the face of which it moves like the hand
of a clock. Where it crosses the time hours L' it is reduced to a narrow strip,
which passing beyond the hours to the circle of degrees of arc, to the outer
circumference of the dial, there carries on its end the before mentioned
vernier L'.
66
"
"
Regarding the instrument as a whole it only remains to say that the larger the
diameter of the solar-compass the greater will be the accuracy of its records.
"Arago
the eminent French astronomer, demonstrates the truth of this fact in
his "Popular Astronomy" vol. I chap. VI in these words "The value of a degree,
a minute a second, will be double on a circle of double the diameter, and these
values would be triple on a circle whose radius was triple, and so on.
That the
advantages of circles of large dimensions are considerable is thus proved." But of
course a limit is necessarily put to this, as to all other things, in practice, and the
use of verniers renders the use of instruments of colossal size quite unnecessary.
A two-foot "solar-compass constructed and mounted as before described will
probably be found large enough, but the relative dimensions and the construction
of the various parts may be modified without departing from the spirit of the
invention, for instance, as will be obvious, instead of the gnomons carrying cross-
lined lenses as in the example illustrated they may be provided with cross wires or
metallic plates with cross slits in them, and moreover the solar-compass disc B
instead of being in the form of a solid disc may be formed of one or more rings or
parts of rings.
"
MODE OF USING THE INSTRUMENT.
1st. Set the east or west, gnomon G (according as it may be fore- or after-noon)
by means of the appropriate verniers G³ and scale B³ to the declination of the sun,
moon or other selected heavenly body, as nearly as this can be ascertained from
the almanack and the ship's chronometer. (The error of this adjustment will be
the error of the instrument.)
2nd. Set the latitude-arc E to the known latitude of the place of observation by
means of the adjusting pinion I¹ in the head of the standard C and clamp by means
of the screws H.
3rd. Incline the solar-compass disc B towards the sun, or other heavenly body
selected, till by the shadow of its thickness (as projected on the hand or other
object) or in any other convenient manner, it is seen to apparently bisect the
selected body.
4th. Turn the standard C by its horizontal arm C³ in azimuth till the adjusted
lens G throws its focal image on to the centre of the opposite lens G² as indicated
by the intersecting lines 9 g. At that instant the instrument will indicate
automatically
1. The astronomical north and the meridian, on the solar-compass disc B and
on the mariner's card F (without any reference to table or calculations,
beyond the usual correction for refractionl

page_text: 2. The ship's course, on the mariners' card F.
3. The variation and error of the magnetic compass (by comparison).
4. The local solar-time on the dial L.
5. The longitude (by calculation).
If it be required to find the latitude (the true north being known) set the
gnomon G and tilt the solar-compass disc to the sun (or other desired heavenly
body) as before and (while keeping the N. and S. line of the solar compass to the
north, or in the meridian) bring the focal image of the adjusted lens G² on to
the opposite lens as before, by means of the adjusting pinions I' in the head of the
standard C, and clamp.
Through the opening C in the standard C can then be read the latitude thus
automatically recorded without any calculation whatever beyond the usual
correction for refraction; and the other records may also be read as before.
When the latitude arc is set or adjusted to the place of observation, in carrying
the solar-compass guomous, time dial and index hand with it, these parts are each
made to correspond in position with the natural phenomena to which they
particularly refer.
The before described instrument while especially applicable for navigating
purposes is also very useful on land as a sun dial or for explorers as a whole or in
part, for example, the upper portion without the standard C and latitude arc E
may be used as a simple sun dial.
The before described apparatus may be modified without departing from the
spirit of the invention for example, instead of the before described gimbals I may
use any other efficient and convenient means for maintaining the instrument (from
the mariner's compass card F upwards) in a truly vertical position long enough to
be read when in use.
In the following claims I have employed the words "one adjustment" by which
I wish it understood that I mean "one adjustment" of the instrument as a whole,
this adjustment comprising a series of adjustments of the various individual parts
of the device.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondent and in what manner the
same is to be performed I declare that what I claim is :-
1. Ascertaining the true "astronomical north" the meridian of the place of
observation a ship's course the variation and error of the magnetic compass the
local solar time and facilitating the ascertainment of the longitude by one adjustment
of the same instrument.
2. Ascertaining the true "astronomical north" the meridian of the place of
observation a ship's course the variation or error of the magnetic compass the
local solar time or facilitating the ascertainment of the longitude by one adjustment
of the same instrument.
3. Ascertaining the true "astronomical north" the meridian of the place of
observation a ship's course the variation and error of the magnetic compass the
local time and facilitating the ascertainment of the longitude by one adjustment and
ascertaining the latitude by another adjustment of the same instrument.
4. Ascertaining the true "astronomical north" the meridian and latitude of the
place of observation a ship's course the variation and error of the magnetic
compass the local time and facilitating the ascertainment of the longitude by means
of an instrument comprising a disc such as B capable of being adjusted on an axis
extending diametrically across it and of being turned in azimuth one or more
gnomons or a telescope a latitude arc E mariner's compass card F dial such
as L and pointer such as L' substantially as described and illustrated in the
accompanying drawings.
5. Ascertaining the true "astronomical north" the meridian of the place of
observation a ship's course the variation and error of the magnetic compass the
local solar time and facilitating the ascertainment of the longitude (I) By so

page_text: adjusting the plane of the disc or other circle that it shall be parallel to any
circular offing or plane on the earth's surface in the same latitude upon which the
sun is at that instant either rising or setting the position of the sun on the horizon
as seen from such plane or offing being indicated theoretically by the shadow of a
single stile or gnomon when properly adjusted falling upon a corresponding degree
of declination in the opposite hemisphere of the said disc but practically by a
circumferentially-adjusted gnomon or telescope casting the sun's focal image upon
the centre of a directly opposite similar gnomon in a plane parallel to that of the
said disc. (II) By a solar time-dial so adjusted that its plane shall so far as the
sun or heavenly body is concerned always be the same as or coincident with
the plane of the equator or other parallel of latitude and in consequence be also
always in the same plane as the sun's diurnal path the sun's progress along his
path minute by minute and other divisions of arc and of time being followed by an
index hand and vernier over the fixed face of the said dial. (III) By recording the
ship's course as determined by the aforesaid solar compass gnomons and other parts
so as to be read in the language of the mariner's compass by bearings and points so
that it may easily and instantly be compared with the reading of the ship's ordinary
compass the variation deviation and errors of which are thus detected and corrected
substantially as described.
6. Ascertaining the true solar time on land by means of a solar compass-disc
swinging declination bar and gnomons a time-dial and index-band combined and
suitably set to the latitude substantially as described.
7. In an instrument such as described the combination with a standard C
adjustable about a constantly-vertical axis of a latitude arc such as E adjustable
therein a disc or solar compass disc such as B adjustable in the latitude arc
a mariner's compass card a dial such as L L' L' secured to the latitude arc
a pointer such as L L secured to and one or more gnomons or a telescope
adjustable on the solar compass substantially as described and illustrated in the
accompanying drawings.
8. Ascertaining the true astronomical north by means of a solar compass disc
upon the surface or plane of which the sun or other heavenly body is made
to "rise "
and "set"artificially capable of being turned on its poles and in
azimuth so as to bring the centres of circumferentially-set gnomons or lenses
or a telescope into the same plane as the centres of the said heavenly body and the
plane of the disc whereby the true "astronomical north or the meridian of the
place of observation can be automatically indicated on the instrument substantially
as described.
"
9. The combination and arrangement of parts constituting the complete instrument
substantially as described and illustrated in the accompanying drawings.
Dated this 15th day of February 1894.
W. P. THOMPSON & BOULT,
Agents for the Applicant.