IMPROVEMENTS IN ARTIFICIAL HORIZONS FOR QUADRANTS, SEXTANTS, OCTANTS. AND OTHER NAUTICAL AND SURVEYING INSTRUMENTS
Year: 1882

page_text: LETTERS PATENT to William Edward Gedge, of N° 11 Wellington Street,
Strand, London, in the County of Middlesex, Patent Agent, for an Invention of
"IMPROVEMENTS IN ARTIFICIAL HORIZONS FOR QUADRANTS, SEXTANTS, OCTANTS.
AND OTHER NAUTICAL AND SURVEYING INSTRUMENTS" a communication to
him from abroad by Solon Pattee, a Citizen of the United States, residing in
the City and County of San Francisco, State of California, one of the United
States of America
PROVISIONAL SPECIFICATION left by the said William Edward Gedge at
the Office of the Commissioners of Patents on the 20th December 1882.
WILLIAM EDWARD GEDGE, of N° 11, Wellington Street, Strand, London, in the
County of Middlesex, Patent Agent, "IMPROVEMENTS IN ARTIFICIAL HORIZONS.
FOR QUADRANTS, SEXTANTS, OCTANTS AND OTHER NAUTICAL AND SURVEYING
INSTRUMENTS' A Communication to me from abroad by Solon Pattee, a Citizen of
the United States, residing in the City and County of San Francisco, State of
California, one of the United States of America,
My invention relates to a means of determining the true horizon in sextants,
octants and like instruments when taking observations under conditions where the
natural, horizon, or any fixed distant object, is not available.
And my invention consists in suspending a pendulum within an enclosing case
to protect it from outside disturbances, and then attaching the case to the frame of
the instrument in front of the eye piece or sight tube and in such relation to a
reflector that the true vertical position of the pendulum, and the consequent true
vertical position of the instrument, is indicated to the observer by the reflected.
image of the end of the pendulum.
The reflector is so adjusted with respect to the line of sight through the said
eye piece or sight tube and to the position of the pendulum, that when the
instrument is brought to the true vertical à reflected image of the pendulum shall
coincide with the line of sight and be visible to the observer, at the eye piece
My invention consists also in suspending the pendulum within a sealed tube or
case containing a suitable non-congealable liquid by which the natural vibrations of

page_text: the pendulum, produced by motions of the vessel upon which the instrument is
used or from the unsteadiness of the operator; are counteracted or modified and a
more definite image of the pendulum is given in the reflector.
.
The following description explains the nature of the said invention or
improvements and the manner of constructing, applying, and operating or using
the same.
1. The pendulum is suspended within a case of cylindrical or other suitable
shape, and from the pointed ends of. two screws that pass through the outside of
the case, at the upper end, and take into small holes on opposite sides of the
pendulum so as to give it a free motion upon such points of suspension.
2. The pendulum is hollow to permit rays of light entering through the opening
in the top of the case to pass through the pendulum and out through the bottom
lense.
The pendulum thus mounted and suspended is held in the line of these openings,
and the centre line or axis of the bottom aperture coincides with the centre of two
openings in the top and bottom respectively of the case when the pendulum
occupies a true vertical position
To attach the case to an instrument, a brace having one-end secured to the side
of the case at the lower end has its free end inserted through a loop to be provided
on top of the horizon frame.
'
A milled head screw passes through the top of the loop to hold.the brace.
A reflecting surface, either of black or colored glass or of a prism, is mounted in
a frame and is attached by a hinge joint to a brace that is secured to the lower
part of the pendulum case.
A curved arm extends downwards and forward in position to support the lower
end of the reflector frame
The end of this arm is screw threaded and passes through a slot in an ear or lug
on the reflector frame, and by means of binding nuts, one on each side of the ear,
accurate adjustment is had of the reflector to an angle of 45 degrees with the face
of the lower end of the case.
A reflector is mounted over the top of the pendulum case to reflect artificial
lights as from a lantern, or otherwise, from the side down into the case.
This reflector.can be turned over the top of the case to direct rays of light down
through the opening.
A stop is fixed upon the underside of the mirror frame to strike against the top
of the case. When the mirror is brought over the top this stop limits the movement
and regulates its adjustment.
When applied and adjusted for use this artificial horizon is attached to the loop
on top of the horizon frame in upright position and secured by screws.
A diaphragm is inserted and secured in place in the end of the pendulum tube to
close one half of its aperture and present an edge extending diametrically, across it.,
The reflected image of this edge is made to coincide either with a line drawn
across the face of the reflector or with a horizontal line on the unsilvered portion
of the horizon glass; the true position of the instrument is thus determined
At such time of operation the image of the sun is brought down in the usual-
way of the instrument to cut the same horizontal line on the reflecting portion of
the horizon glass.
'
When it is required to find the altitude of a star at night, the upper reflector is
placed at such an angle as to reflect artificial light from a lantern at the side, down
through the case:
To overcome the vibrations of the pendulum, due to the unsteadiness of the
hand or the motion of, the vessel, I fill the pendulum case with some suitable
transparent fluid confined within it by means of two caps
Alcohol, glycerine or any other sufficiently transparent fluid that will not congeal
can be employed for this purpose
The effect of this fluid upon the pendulum can be greatly increased by fixing to
the outer sides of the pendulum two thin metallic flanges or wings, which extend

page_text: from end to end and in line with the points of suspension but out of contact with
the inner surface of the case. Or the case can be made of elliptical form at the
base or lower portion in order to give a larger body of fluid at and around the
lower end of the pendulum in a direction fore and aft.
This body of fluid surrounding the pendulum permits a free swinging movement.
but checks the tendency of the pendulum to vibrate while the instrument is in the
hand.
I use a telescope of the kind usually employed in sextants or octants to give a
better defined image of the sun, or a star, than with the unaided sight, excepting
that upon its forward end is placed a cap containing a bisected or half lense of a
focal distance equal to the distance between the object end of the telescope and a
point in the centre of the inclined reflector.
This cap is placed in such position that the half lense is opposite the unsilvered
portion of the horizon glass while the reflected object is seen unobstructed through'
the open space of the cap.
By such means the image of the sun in the glass and the image of the diaphragm
in the reflector can be distinctly seen at the same time
- I also provide an attachment for use upon and with the horizon glass to give on
the reflecting surface of its glass an indicating line to take the place of the
ordinary horizontal fixed line drawn across the surface of the reflecting portion of
the horizon glass.
The horizon frame is fixed by a stud to the instrument. The glass of this
attachment has a plain or unsilvered part and a silvered part or reflecting surface
to which the image of the sun is brought down; it is also provided with a small
clamp bar with a slot in it, and a pointer or blade to present a straight edge and
of proper length to project across, and over, the face of the mirror.
On the head of this blade a lug fits and slides up and down in the slot of the
clamping bar.
3
"A binding screw takes into this lug from the outside of the bar and through a
spring plate on the top, over the slot, clamps the bar at the desired point higher or
lower on the surface of the horizon mirror.
This device gives an adjustable line or mark on the horizon glass, instead of a
fixed line

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Edward Gedge in the Great Seal Patent Office on. the
4th June 1883.
WILLIAM EDWARD GEDGE of No. 11 Wellington Street, Strand, London, in the
County of Middlesex, Patent Agent, " IMPROVEMENTS IN ARTIFICIAL HORIZONS
FOR QUADRANTS, SEXTANTS OCTANTS AND OTHER NAUTICAL AND SURVEYING
INSTRUMENTS A communication to me from abroad by Solon Pattee a Citizen of
the United States residing in the City and County of San Francisco, State of
California, one of the United States of America..
My Invention relates to a means of determining the true horizon in sextants
octants and like instruments when taking observations under conditions where the
natural horizon or any fixed distant object is not available.
And my Invention consists in suspending a pendulum within an enclosing case
to protect it from outside disturbances and then attaching the case to the frame of
the instrument in front of its sight tube or eye piece and in such relation to a
reflector, also placed in front of the eye piece, that the true vertical position of the
pendulum and the consequent true vertical position of the instrument is indicated
to the observer by a reflected image of the end of the pendulum seen in the
reflector.
M
The adjustment of this reflector with respect to the line of sight through the said
eye piece and to the position of the pendulum is such that when the instrument is
brought to the true vertical a reflected image of the end of the pendulum shall
coincide with the line of sight and be visible to the observer at the eye
piece.
My invention consists also in suspending the pendulum within a sealed tube or
case containing a suitable uncongealable liquid by which natural vibrations of the
pendulum produced by notions of the vessel when the instrument is used on
ship board, or from the unsteadiness of the operator when used in other situations;
are counteracted or modified and a more definite image of the pendulum is given in
the reflector.
The following description explains the nature of my said Invention or improve-
ment and the manner of constructing applying and operating it
In the Drawings hereinafter referred to:-
Figure 1-represents my invention as applied to a sextant
Figure 2-is a separate view of the device attached to the horizon frame of an
instrument
Figures 3-4-5-5 6 and 7 are detail views of the separate parts, of which fig: 3
is the pendulum tube and parts, fig: 4 a vertical section through the tube
and its case.
Figures 5 and 5 and 6 the case in detail; and fig: 7the inclined reflector.
Figure 8-shows the detail parts of the cap and half lense for a sight tube or
telescopic eye piece.
Figures 9, 10 and 11 are detail views of an attachment which I apply to the
mirror of the horizon frame to give an adjustable register mark upon its face
The pendulum A, is suspended within a case B, of cylindrical or other suitable
shape and from the pointed ends of two screws d, d, these pass through the outside
of the case at the upper end and take into small holes on opposite sides of the
pendulum to give free points of oscillation.
I prefer to make the said case of a short section of metal tube, and close both
ends by screw caps, so that the pendulum is entirely isolated from outside
disturbances.
The top cap E, has a central opening covered by a plain flat glass, burnised into

page_text: the cap or fixed so as to be water tight, and the lower cap F, holds a plano-convex-
lense f
The pendulum is hollow to permit rays of light entering through the top opening
to pass down through the centre of the pendulum and out at the bottom lense. In
order to define the centre of the aperture through the pendulum, a diaphragm C
(figures 3 and 4) formed of a small cap having a half-moon opening in the end, is
secured in the end to close one half of its aperture and present an edge extending
diametrically across it...
Thus mounted and suspended the center or axis of the pendulum will coincide
with the center of the opening through the case when it occupies a true vertical
position.
To attach the case B to an instrument, a brace (9) having one end fixed to the
side of the case at the lower end, has its free end inserted through a loop h, to be
provided on top of the horizon frame X, and a milled head screw (I) passes through
the top of the loop to bind against and hold the brace.
Beneath the case B a reflecting surface L, either of black or colored glass, or of
a prism, is inserted in a frame L₁, that is attached by a hinge joint m to a brace N.
The brace is secured to the lower part of the pendulum case, at which point also a
curved arm, P, is fixed by screw p to support the lower end of the reflector
frame.
The screw threaded end of this arm passes through a slot in a lug, s, on the
reflector frame and two binding nuts T, T, on the arm P, one upon and the other
under the lug, secure an adjustment of the hinged frame L' to an angle of 45° with
the bottom face of the pendulum case.. A reflector W, figures 1, 2, 4 and 5, is
mounted over the top of the pendulum to reflect artificial lights as from a lantern
or otherwise down into the case.
1
j
This reflector is turned over the top of the case for use at night or where
sufficient natural light cannot be had.
A stop w fixed on the under side of the mirror frame W₁, is arranged to strike
the top of the case and to so regulate the position of the mirror that its centre
shall be brought directly over the center of the case aperture.
The frame Wis hinged at W2 to a ring W³ that encircles while it is free to
revolve on the upper part of the pendulum case.
}
To apply and adjust this "Artificial Horizon" for use it is attached to the loop h
on the horizon frame and secured by the screw (I) as illustrated in figure 1. of
the drawing, and the reflector L, is adjusted, to the required angle by turning thể
nüts T, T,
"
.
The rays of light passing down through the pendulum case then produce a
reflected image of the end of the pendulum in the reflector, which image is visible
to the observer at the eye piece, and by changing the position of the instrument
the reflected edge of the diaphragm C, is made to coincide with a line drawn across
the face of the reflector L, or with a horizontal line on the unsilvered part of the
horizon glass, at which time the instrument will have the required vertical position:
The image of the sun is then thrown in the usual way by the instrument to cut
the horizontal line on the reflecting portion of the horizon glass.
To find the altitude of a star at night, the upper reflector W, is set at an angle to
throw rays of light from some suitable source, as a lantern, down through the case.
The telescopic syphon Y is of the kind usually employed in sextants or octants
to give a better defined image of the sun, or a star than is possible with the unaided
sight, but upon its forward end is fitted a cap Y', figures 1 and 8, holding a bisected
or half lense Y2 of a focal distance equal to the distance between the object end of
the telescope and a point on the centre of the inclined reflector.
The half lense is set opposite the unsilvered portion of the horizon glass, while
the reflected image in the silvered portion of the horizon glass is seen through the
half opening in the cap. The image of the sun in the glass and of the pendulum
end in the reflector are distinctly seen at the same time.

page_text: To give an accurate adjustment of the parts of the device to an instrument;
I employ a moveable indicating line or edge on the horizon glass to take the place
of the ordinary fixed horizontal line across the surface of the reflecting portion of
the glass.
. This attachment is illustrated in figs: 9, 10 and 11, where the X, is the horizon
frame and the stud by which it is fixed to the instrument, R, is the plain and R
the silvered or reflecting surface, S, is a narrow clamp with a slot s¹ to receive the
head of a thin blade or pointer s². The edge of this blade extends across the
face of the reflector R¹, and can be moved up and down under the clamp that holds
its head 3. A binding screw t' taking into the head from the outside of the
clamp, and through a spring t2 placed over the slot, serves to hold the blade at any
point of adjustment, higher or lower.
While not essential to the practical working of my invention this movable
indicating line is of advantage in adjusting the "Artificial Horizon to an instru-
ment. When first applied this adjustment is made as follows:-
•
After attaching the pendulum case to the horizon frame, the image of the
pendulum seen in the inclined reflector is made to agree with the distant horizon
by simply changing the inclination of the reflector until the line on its surface
coincides with the horizon seen by the observer at the eye piece.
This position of the reflector is then secured by tightening the binding nuts T, T,
and at the same time if necessary the line or mark on the horizon glass R¹. is
adjusted to agree with the line of the reflector L. While the instrument holds the
same position.
This sets the instrument to the dip or inclination of the horizon and it is then
ready for use at all times in foggy weather or at night, or under conditions when
a horizon cannot be had..
. The reflector L is made somewhat narrower than the aperture through the plain
portion of the glass R, in order to permit the distant horizon to be seen at the
same time with the reflected image of the pendulum from the eye piece to effect
this adjustment.
A novel mode of overcoming such vibrations of the pendulum in its case that are
due to the unsteadiness of the hand or the motion of the vessel, and which is also
an important feature of my present invention, consists in filling the pendulum case
with some suitably transparent fluid
This body of fluid surrounding the pendulum presents a free swinging movement
but checks all tendency to vibrate
Alcohol, glycerine or any other sufficiently transparent and practically uncon-
gealable fluid can be employed for this purpose.
This effect of the fluid can be greatly increased by fixing to the outer sides of
the pendulum two thin metal flanges or rings from end to end and in line with the
points of suspension but out of contact with the sides of the surrounding case. Or
the case can be made of elliptical form at the base in order to give a larger body
of fluid at and around the lower end of the pendulum in a direction fore and aft.
This improved device is also of value for service on land in many situations and
for all purposes where a true horizontal is to be determined.
f
I do not claim as my Invention the use of a pendulum to determine the position
of a sextant, octant or other instrument, but I claim the use of a pendulum enclosed
within a case or tube by which the disturbing effects of the wind and air currents
are removed and the movements of the pendulum are produced by force of gravity
alone. And I also claim immersing such an enclosed pendulum in transparent fluid
to prevent vibrations due to the unsteadiness of the instrument
Having now described and ascertained the nature of the said Invention Commu
nicated to me as aforesaid and the manner in which the same is or may be
performed, I would have it understood that what-
AE
Claim as secured to me by, the herein before in part recited Letters Patent is —
Firstly: The use of an inclined reflector combined with a hollow case or tube

page_text: containing a pendulum free to swing therein on points of suspension, said case or
tube having apertures through the top and bottom for transmission of light, and
pendulum with a supporting brace to hold it in an upright position above the reflector,
whereby the movements and position of the pendulum are made visible to an
observer in front of said reflector substantially as herein described and shown.
Secondly The use in combination, of a pendulum suspended in a sealed tube or
hollow case having openings in top and bottom for the transmission of light, and an
inclined reflector arranged with relation to the said openings and to the line of
sight through an eye piece or sight tube whereby the end of the pendulum is
visible to the observer and its position determined substantially as herein described
and shown.
Thirdly The use in a sealed hollow case or tube having apertures in top and
bottom for the transmission of light and containing a pendulum that is free to
oscillate in line with the said apertures, of a transparent liquid to surround the
pendulum for preventing or modifying vibrations due to external disturbances,
substantially as herein described and shown.
Fourthly The hollow pendulum case or tube having apertures in top and bottom
for transmission of light, adapted to hold a body of transparent liquid, the
suspended pendulum free to oscillate in line with the said aperture and the brace
for securing the case to the frame of an instrument, as herein described and shown.
Fifthly The use in combination with the pendulum case or enclosing tube
having apertures in top and bottom for the transmission of light, and containing a
suspended pendulum free to oscillate in line with said apertures, of the adjustable
reflector over the top of the said tube for directing rays of light from the side down
through the said tube.
Sixthly-In a sextant, octant or quadrant, the use in combination with the
enclosed suspended pendulum, and the inclined reflector, arranged with relation to
the horizon mirror of the instrument as described, of the cap for the telescopic eye
piece, containing a bisected lense substantially as described and shown.
In Witness whereof I the said William Edward Gedge have hereunto set
my hand and seal this Fourth day of June in the year of our Lord one
thousand Eight hundred and Eighty three
WE GEDGE (L.S.)