IMPROVEMENTS IN SOLAR COMPASSES
Year: 1874

page_text: LETTERS PATENT to William Edward Gedge, of No. 11, Wellington
Street, Strand, in the County of Middlesex, Patent Agent, for the
Invention of "IMPROVEMENTS IN SOLAR COMPASSES."-A communi-
cation from abroad by Charles Theodore Pierson, of Ramapo, in
the State of New York, and United States of America.
Sealed the 12th January 1875, and dated the 24th July 1874.
PROVISIONAL SPECIFICATION left by the said William Edward
Gedge at the Office of the Commissioners of Patents, with his
Petition, on the 24th July 1874.
I, WILLIAM EDWARD GEDGE, of No. 11, Wellington Street, Strand,
in the County of Middlesex, Patent Agent, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN SOLAR COMPASSES," a com-
munication to me from abroad by Charles Theodore Pierson, of Ramapo,
in the State of New York, and United States of America, to be as
Sallas.

page_text: The
accuracy of marine compasses, though it may also be used for any of the
purposes for which the magnetic compass is commonly used.
following is a description thereof, reference being had to the accom-
panying Drawing, which makes a part of the same, in which Figure 1
represents the face of the instrument, showing the dial and all the
improvements; Fig. 2 shows a graduated limb or are used in adjusting
the instrument for latitude; and Fig. 3 shows a modified form of the
instrument; Figures 4 and 5 are a plane view and an elevation of
the instrument, showing the manner of mounting the dials, and in
Figure 4 is shown a different form of dial and of the gnomon from that 1
shown in Figures 1, 2, and 3.
The instrument consists essentially of a dial or dials mounted in
gimbals, like an ordinary mariner's compass, in such a manner as to
rotato freely on the mounting, the dials having the points of the compass
or degrees of the circle laid out thereon, and are supplied with a 1
gnomon, which may or may not be made adjustable in the angle of
declination.
In the Drawing A is a ring dial, having the points of the compass
fully laid out upon its upper surface, and which revolvos freely on a
circular box hinge or gimbals, like a compass, sot hat the dial may always 2
maintain a perfectly level position. B is an interior dial set into the
first, and moving freely therein, and also marked with the points of the
compass. Into this interior dial two disks, which overlap each other at
the center, are cut, a portion of the dial B of a circular shape being left
at the center. One of these disks lies to the north and the other to the 2
south point of the dial B, and they are mado exactly alike in size and
shape. In one of them is placed a third dial O of paper or ivory, which
may be covered with glass, and the other is filled with a brass disk D,
supplied with a knob ‹, by means of which the dial B may be rotated on
the dial A. The dial O is marked with hour lines from the center of the 3
dial B in the manner of a sun dial, and these lines are to be laid out by
the trigonometrical formula used in the construction of horizontal sun
dials, as the ordinary geometrical formula will not be found in practico
sufficiently accurate. Each compass is preferably provided with a series
of theso hour dials O, graduated for various latitudes. For ordinary 3
purposes a separate dial for cach five degrees will give results sufficiently
accurate, but the greater number, that is to say, the less variation in
degrees of latitude between any consecutive two of the series, the greater

page_text: the degree of accuracy attained. At the center of the dial B is hinged
a.gnomon, which may be in the form shown, or in any of the ordinary
forms used in the construction of sun dials, except that it should be
pivoted. When in the form of a needle, as shown, it may have at its
base a graduated limb or arc, on which is marked the degrees of the
circle-from-one to ninety, and ninety back to one, to be used as a latitude
arc. Instead of the needle a graduated semicircle or quadrant might be
used, turning about the same center and passing down through a slit in
the dial, as shown in Fig. 3. This semicircle should be graduated in
degrees, and thus could be set to any latitude, its upper edge forming a
gnomon; E, (Fig. 5,) indicates a box hung in gimbals, and weighted to
keep dial B in a horizontal position; F, gnomon.
The operation of the device is as follows:-If only desired to be used
as a test instrument for the purpose of connecting the magnetic instru-
ment, in which case it will be sufficient to have an instrument which
can be used at the noon hour only, the form, shown in Figures Four and
Five can be used, dispensing with the hour dial, and using a non-
adjustable.gnomon, consisting of a broad plate provided with a fine slit,
through which a line of light is thrown upon the dial. The exact
moment when the sun, moon, or star is on the meridian being shown by
chronometer, the dial, which rotates freely in its mountings, should be
turned until the line of light from the slit Ģ falls upon the north point
of the dial (or, in the southern hemisphere, the south point), which will
then show the true north (or south) point. The magnetic compass can
then be corrected or compared, allowance being made for the magnetic
variation.
When used as a mariner's compass the form of instrument shown in
Figs. 1, 2, & 3, will be found more convenient, as it can be used at any
hour of the day. The gnomon should be first adjusted to the latitude of
the place when the instrument is 'to be used by means of the 'latitudo
arc, or, if preferred, by means of a separate instrument, 'laid out "in
degrees like a draftman's protractor, such as is shown in Fig. 2.
As the instrument is a true rotary sun dial, with an adjustable gnomon,
it follows that if placed with the noon mark on the meridian and the
gnomon properly adjusted, it will give the hour of the day; so conversely,
if the dial B be rotated at any hour of the day until the shadow falls
upon the line of that hour, then the noon line on the north point of the
"

page_text: dial B will be in the meridian. The outer dial A may then be turned
from the dial B a sufficient number of degrees to allow for the variations
caused by the atmospheric refraction and the variations of the compass,
also for the variation caused by the difference between solar and
mean time, the proper number of degrees being ascertained from the
nautical almanac and the instrument compared with the magnetio
compass, which may be corrected thereby.
The dial C and the plate or disk & being readily exchanged the
instrument can be used in north or south latitude; or instead of a brass
plate D another dial graduated as C may be used, which will avoid any
necessity for making the latter removable.
Instead of an hour dial laid out upon the surface of the dial Ba
simple circle marked in degrees and having its centro at the point where
the gnomon touches the plane of the dial can be used, and a table can
be readily constructed upon principles familiar to those acquainted with
the art of dialing, which will show degree of the circle on which the
shadow should fall at any hour of the day in any latitude in order to
bring the north and south points of the dial in the line of the meridian.
Such an arrangement would involve substantially the same principles as
the one described, the difference being one of notation merely. It must
therefore be regarded as coming within the limits of this Invention.
In clear weather and by day the instrument can be used as a compass,
but it is principally intended to be used as a standard by which the
latter can be corrected. The addition of the hour and the adjustable
gnomon will, it will readily be seen, vastly extend its usefulness in this
respect.
Of course many variations can be made in the construction of the
details; as instead of a gnomon casting a shadow, one marking by a
beam of light shining through a fine slit may be used, and the outer
ring may be dispensed with, the allowance for variations being made
mentally or in setting the gnomon.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Edward Gedge in the Great Scal Patent
Office on the 12th January 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
EDWARD GEDGE, of No. 11, Wellington Street, Strand, in the County of
Middlesex, Patent Agent, send grecting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fourth day of July, in the
year of our Lord One thousand eight hundred and seventy-four, in the
thirty-eighth year of Her reign, did, for Herself, Her heirs, and suc-
cessors, give and grant unto me, the said William Edward Gedge,
Her special license, that I, tho said William Edward Gedge, my
executors, administrators, and assigns, or such others as I, the said
William Edward Gedge, my executors, administrators, and 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 SOLAR COMPASSES," a com-
munication to me from abroad by Charles Theodore Pierson, of
Ramapo, in the State of New York, and United States of America,
upon the condition (amongst others) that I, the said William Edward
Gedge, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, 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 William Edward Gedge, do hereby
declaro the nature of the said Invention, and in what manner the samo
is to be performed, to be particularly described and ascertained in and
by the following statement :-
The improvements in solar compasses, the subject of this Invention,
constitute an instrument which is specially adapted for testing the
accuracy of marine compasses, though it may also be used for any of the
purposes for which the magnetic compass is commonly used. The

page_text: following is a description thereof, reference being had to the accom-
panying Sheet of Drawing which makes a part of the same, in which
Figure 1 represents the face of the instrument, showing the dial and all
of the improvements; Figure 2 shows a graduated limb or are used in
adjusting the instrument for latitude; Figure 3 shows a modified form
of the instrument; and Figures 4 and 5 are a plano view and an elevation
of the instruments, showing the manner of mounting tho dials, and in
Figure 4 is shown a different form of dial and of the gnomon from that
shown in Figures 1, 2, and 3.
The instrument consists essentially of a dial or dials mounted in
gimbals, like an ordinary mariner's compass, in such a mannor as to
rotate freely on the mounting, the dials having the points of the compass
or degrees of the circle laid out theroon, and are supplied with a
gnomon, which may or may not be made adjustable in the angle of
declination.
In the Drawing A is a ring dial, having the points of the compass
fully laid out upon its upper surface, and which rovolves freely on a
circular box hingo or gimbals, like a compass, so that the dial may always
maintain a perfectly level position. B is an interior dial set into the
first, and moving freely therein, and also marked with the points of tho
compass. Into this interior dial two disks, which overlap each other at
the center, are cut, a portion of the dial B of a circular shape being left
at the center. One of these disks lies to the north and the other to the
south point of the dial B, and they are made exactly alike in sizo and
shape. In one of them is placed a third dial O of paper or ivory, which 1
may be covered with glass, and the other is filled with a brass disk D,
supplied with a knob d, by means of which the dial B may be rotated on
the dial A. The dial O is marked with hour lines from the centre of
tho dial B in the manner of a sun dial, and these lines are to be laid out
by the trigonometrical formula used in the construction of horizontal sun;
dials, as the ordinary geometrical formula will not be found in practico
sufficiently accurate. Each compass is preferably provided with a series
of these hour dials O, graduated for various latitudes. For ordinary
purposes a separate dial for each five degrees will give results sufficiently
accurate, but the greater number, that is to say, the less variation in
degrees of latitude between any consecutive two of the series, the greater
the degree of accuracy attained. At the centre of the dial B is hinged a
gnomon, which may be in the form shown, or in any of the ordinary

page_text: forms used in the construction of sun dials, except that it should be
pivoted. When in the form of a needle, as shown, it may have at its
base or graduated limb or arc, on which is marked the degrees of the
circle from one to. ninety and ninety back to one, to be used as a latitudo
Instead of the needle a graduated semicircle or quadrant might be
used, turning about the same centre and passing down through a-slit-in
the dial, as shown in Figure 3. This semicircle should be graduated in
degrees, and thus could be set to any latitude, its upper edge forming a
gnomon; E (Figure 5) indicates a box hung in gimbals and weighted to
keep dial B in a horizontal position; F, gnomon.
The operation of the device is as follows:-If only desired to be used
as a test instrument for the purpose of correcting the magnetic instru-
ment, in which case it will be sufficient to have an instrument which
can be used at the noon hour only, the form shown in Figures 4 and 5
can bo used, dispensing with the hour dial and using a non-adjustable
gnomon, consisting of a broad plate provided with a fine slit, through
which a line of light is thrown upon the dial. The exact moment when
the sun, moon, or star is on the meridian being shown by chronometer,
the dial, which rotates freely in its mountings, should be turned until
the line of light from the slit G falls upon the north point of the
dial (or in the southern hemisphere the south point), which will then
show the true north (or south) point. The magnetic compass can then
be corrected or compared, allowance being made for the magnetic
variation.
at
When used as a mariner's compass the form of instrument shown in
Figs. 1, 2, and 3 will be found more convenient, as it can be used
any. hour of the day. The gnomon should be first adjusted to the
latitude of the place where the instrument is to be used by means of
the latitude arc, or, if preferred, by means of a separate instrument
laid out in degrees like a draftman's protractor, such as is shown in
*Figure 2.
As the instrument is a true rotary sun dial, with an adjustable gnomon,
it follows that if placed with the noon mark on the meridian and thọ
gnomon properly adjusted it will give the hour of the day; so con-
versely, if the dial B be rotated at any hour of the day until the shadow
falls upon the line of that hour, then-the noon line or the north points of
the dial B will be in the meridian. The outer dial A may then be turned

page_text: from the dial B a sufficient number of degrees to allow for the variations
caused by the atmospheric refraction and the variations of the compass,
and also for the variations caused by the difference between solar and
mean time, the proper number of degrees being ascertained from the
nautical almanac and the instrument compared with the magnetic &
compass, which may be corrected thereby.
Tho dial O and the plato or disk d being readily exchanged, the
instrument can be used in north or south latitude; or instead of a brass
plate D another dial graduated as O may be used, which will avoid any
necessity for making the latter removable.
1
Instead of an hour dial laid out upon the surface of the dial B, a
simple circlo marked in degrees, and having its centro at the point
where the gnomon touches the plane of the dial can be used, and a table
can be readily constructed upon principles familiar to those acquainted
with the art of dialing, which will show degree of the circle on which 1
the shadow should fall at any hour of the day in any latitude, in order
to bring the north and south points of the dial in the line of the
meridian. Such an arrangement would involvo substantially the samo
principles as the one described, the difference being one of notation
merely. It must therefore be regarded as coming within the limits of 2
this Invention.
In clear weather and by day the instrument can be used as a compass,
but it is principally intended to be used as a standard by which the
latter can be corrected. The addition of the hour and the adjustablo
gnomon will it will readily be seen vastly extend its usefulness in this 2
respect.
Of course many variations can be made in the construction of the
details, as instead of a gnomon casting a shadow, one marking by a beam
of light shining through a fine slit may be used, and the outer ring may
be dispended with, the allowance for variations being made mentally or in 3
setting the gnomon.
What I claim as the Invention secured to me by the herein-before in
part recited Letters Patent is,―
1st. The combination of the weighted box E hung as described, the
rotary dial plate or plates A, B, and the gnomon, adjustable or not, sub- 3
stantially as described.

page_text: 2º. The combination of a horizontal rotary dial having the points of
the compass or a portion of them laid out thereon, with the hour dial
and the gnomon, the latter being adjustable or not, substantially as
described.
... 3rd. The combination with the horizontal rotary dial of the adjustable
gnomon, substantially as described.
4th. The reversible plate D and dial C, whereby the instrument is
rendered useful in north or south latitudes, substantially as described.
5th. The improved solar compass as herein described, embodying in
its construction horizontal rotary dials, an adjustable gnomon, and a
series of interchangeable hour dials, substantially as set forth.
In witness whereof, I, the said William Edward Gedge, have herc-
unto set my hand and seal, this Thirty-first day of December,
in the year of our Lord One thousand eight hundred and seventy-
four.