Improvements in Sextants and similar Instruments.
Year: 1893

page_text: Date of Application, 23rd May, 1893
Complete Specification Left, 20th Feb., 1894-Accepted, 7th Apr., 1894
PROVISIONAL SPECIFICATION.
Improvements in Sextants and similar Instruments.
I, JAMES BAXTER MURRAY, of 28 Herriet Street, Pollokshields, Glasgow,
Master Mariner, do hereby declare the nature of this invention to be as follows:-
Hitherto it has generally been necessary to have the sea horizon visible to the
observer, or to use the surface of a liquid as an artificial horizon, when ascer-
taining the altitude of any celestial or terrestrial object by means of such
astronomical instruments as sextants, quadrants, octants etc.; and, on land, it has
been impossible, with such instruments, to measure the depression or-a-small angle
of elevation of any visible object with the artificial horizon; it has also been
practically impossible to obtain, by means of such appliances, the altitude of
objects having a greater angle of elevation than 70°, or thereabouts.
The present invention has for its object to enable an observer, whether on land
or sea, either by day or by night, to measure the altitude or depression of an
object without the aid of any horizon whether natural or artificial. As no horizon is
used with the improved instrument, which I prefer to term an "angleometer,"
when taking altitudes, it is not necessary to make the usual allowances for
"dip."
The invention will be found of great service to shipmasters when sailing
through fogs, or under other conditions where a sea horizon is not visible, although
the sun, moon, cr stars may be. plainly visible overhead, as it will enable observa,
tions to be accurately taken in such circumstances.
The invention consists in attaching to the telescope holder, sight vane, or other
suitable part of a sextant, quadrant, octant, reflecting circle or like instrument a
device for determing the horizontal plane. The device consists of a balance fork
or ring which has a slot in it for vertical adjustment. This balance fork or ring
is secured to one end of a lever by means of a pinching screw which passes
through the slot and enters a tapped hole in the end of the lever. The method
of securing the ring or fork is such that it can be turned to right or left as
desired.
The lever is fulcrumed, at its centre of gravity, in centres, knife edges, or
screw sockets, carried in or made part of a bent arm or equivalent which is
secured by a thumb or pinching screw, preferably, to the telescope holder. A
small weight is fitted or attached to or made one with one end of the lever to
counterbalance the weight of the fork or ring at the other end so that the lever
with its attachments is balanced on its fulcrum. Attached at right angles to or
made one with the lever, at its centre of gravity, is a pendulum or plummet,
which, as the lever is balanced, always hangs truly vertical. As this lever is at
right angles to the pendulum it is always held truly horizontal, no matter how the
sextant, or other instrument to which the device is attached is moved about.
The lower end or bob of the pendulum passes through a slot in a cross bar
fitted on the astronomical instrument or to the arm and can be clamped in position
when so desired by means of a pinching screw, or equivalent, working in a hole in
the cross bar.
Stretched across the prongs of the fork, or across the horizontal diameter of the
ring, is a wire, cord, or equivalent which is or may be secured in place by passing
it, at either side, through holes in the prongs or in the ring and securing the
ends by binding screws.

page_text: This cord, wire, or thread is fitted in a truly horizontal plane, and when the
pendulum of the device is truly vertical should be exactly in line and coincide
with a wire or thread which is fitted on the horizon glass frame in such manner
that it exactly bisects in a horizontal plane, the line of sight through the telescope.
The wire or thread of the horizon glass is, or may be, held at each side by
means of pivotted arms attached to the horizon glass frame. The ends of the wire
or thread may be secured by passing them through holes, or slots, or resting
them in nicks in the arms and then fixing them tightly in place by means of
small binding screws. By having the arms pivotted the wire or thread can be
raised or lowered as desired. Instead of having a wire or thread, a horizontal
line may be scratched across the horizon glass for the same purpose.
The device is so arranged that the balance lever is always in a truly horizontal
position and parallel with the line of sight, when the pendulum is hanging
vertical.
To adjust the device the sextant or other instrument is held so that the line
of sight is at right angles to the pendulum which of course hangs truly vertical.
When this has been done the pendulum is clamped in position and the balance
fork or ring is then raised or lowered which is done by slackening the pinching
screw sufficiently to admit of the fork or ring being moved the length of its slot
until the horizontal wire in it is exactly in line and coincides with the horizontal
wire of the horizon glass frame. When this adjustment has been effected the
pinching screw can be unclamped and the instrument is then ready for taking
observations.
With this instrument to find the altitudes during a dense fog with no horizon
but with a moderately bright sun overhead, bring the sun down in the usual way
then hold the instrument so that the horizontal wire in balance fork or ring
coincides with the horizontal wire of the horizon glass. Now turn the tangent
screw of the verner with the left hand whilst the instrument is held by the right
until the lower edge of the sun's disc touches the horizontal line on the horizon
glass. Then clamp the verner in position and read off altitude in the usual way.
When holding the instrument the body of the observer acts as gimballs in
accordance with the motion of the vessel.
When angles of altitude are taken in this manner the height of observer's eye
is not considered and therefore there will be no correction for "dip."
It is advisable when placing the instrument in the box to clamp the pinching
screw of the pendulum so as to keep the parts in position.
The fulcrum centres are made as fine as possible so as to give the least
possible friction.
If so desired the device may be fitted with a vertical wire as well as a horizontal
In this case, of course, the horizon glass would have a vertical wire or
thread also.
one.
The device may be modified in form with departing from the principal of the
invention.
With my invention, the instrument is always ready for use, and the attachment
does not require to be taken off when the instrument is placed in the box.
The attachment does not interfere with the sun's altitude being taken in the
usual way.
The attachment can, at any time, be taken off the sextant or other instrument
by merely unscrewing the thumb screw on the telescope holder.
The device, whilst very simple, is thoroughly efficient.
Dated this 22nd day of May 1893.
H. D. FITZPATRICK,
70, Wellington Street, Glasgow, Agent.

page_text: Improvements in Sextants and similar Instruments.
I, JAMES BAXTER MURRAY, of 28 Herriet Street, Pollokshields, Glasgow,
Master Mariner, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
Hitherto it has generally been necessary to have the sea horizon visible to the
observer, or to use-the-surface of a liquid as an artificial horizon, when ascertaining
the altitude of any celestial or terrestrial object by means of such astronomical-
instruments as sextants, quadrants, octants etc.; and, on land it has been impossible,
with such instruments, to measure the depression or a small angle of elevation of
any visible object with the artificial horizon, it has also been practically impossible
to obtain by means of such appliances the altitude of objects having a greater
angle of elevation than 70° or thereabouts.
The present invention has for its object to enable an observer, whether on land
or sea, either by day or by night, to measure the altitude or depression of any
object without the aid of any horizon whether natural or artificial. As no horizon
is used with the improved instrument which I prefer to term an "angleometer,"
when taking altitudes, it is not necessary to make the usual allowance for dip.
The invention will be found of great service to shipmasters when sailing through
fogs or under other conditions where a sea horizon is not visible, although the sun;
moon, or stars may be plainly visible overhead, as it will enable observations to be
accurately taken in such circumstances.
.
The invention consists in attaching to the telescope holder, sight vane, or other
suitable part of a sextant, quadrant, octant, reflecting circle or like instrument a
device for determining the horizontal plane. The device consists of a balance, fork
or ring which has a slot in it for vertical adjustment. This balance fork or ring is
secured to one end of a lever by means of a pinching screw which passes through
the slot and enters a tapped hole in the end of the lever. The method of securing
the ring or fork is such that it can be turned to right or left as desired.
The lever is fulcrumed, at its centre of gravity, in centres, knife edges, or screw
sockets, carried in or made part of a bent arm or equivalent which is secured by a
thumb or pinching screw, preferably to the telescope holder. A small weight is
fitted or attached to or made one with one end of the lever to counter balance the
weight of the fork or ring at the other end so that the lever with its attachments is
balanced on its fulcrum. Attached at right angles to or made one with the lever
at its centre of gravity, is a pendulum or plummet, which, as the lever is balanced
always hangs truly vertical.
As this lever is at right angles to the pendulum it is always held truly horizontal,
no matter how the sextant or other instrument, to which the device is attached, is
moved about.
The lower end or bob of the pendulum may work inside a fixed box containing
oil or other fluid or it may pass through a slot in a cross bar fitted on the
astronomical instrument or to the arm. It can be clamped in position when so
desired by means of a pinching screw or equivalent.
Stretched across the prongs of the fork, or across the horizontal diameter of the
ring, is a wire, cord, or equivalent which is or may be secured in place by passing
it, at either side, through holes in the prongs or in the ring and securing the ends
by binding screws.

page_text: This cord, wire, or thread is fitted in a truly horizontal plane, and when the
pendulum of the device is truly vertical should be exactly in line and coincide with
a wire or thread which is fitted on the horizon glass frame in such a manner that it
exactly bisects in a horizontal plane, the line of sight through the telescope. The
wire or thread of the horizon glass is, or may be held, at each side, by means of
pivotted arms attached to the horizon glass frame. The ends of the wire or. thread
may be secured by passing them through holes, or slots, or resting them in nicks in
the arms and then fixing them tightly in place by means of small binding screws.
By having the arms pivotted the wire or thread can be raised or lowered as desired.
Instead of having a wire or thread, a horizontal line may be scratched across the
horizon glass for the same purpose.
The device is so arranged that the balance lever is always in a truly horizontal
position and parallel with the line of sight, when the pendulum is hanging
vertical.
And in order that my said invention may be properly understood I have hereunto
appended an explanatory sheet of drawings whereon:-
Fig. 1 shows a sextant with the "angleometer" attachment secured thereto.
Fig. 2 is a side view of the balance fork.
Fig. 3 is a part longitudinal section and Fig. 4 a front view of a special form of
telescope which can be used with the instrument.
Fig. 5 is a side view of the horizon glass.
Fig. 6 is a side view and Fig. 7 a vertical section of the oil box with pendulum.
Fig. 8 shows a slightly modified construction of the device.
Referring to the drawings whereon the same reference numerals wherever
repeated indicate the same or similar parts.
1 is the balance fork, which, as shown at Fig. 2, has a slot 2 in it for vertical
adjustment. 3 is the horizontal wire or cord which is secured in place by passing
its ends through holes in the prongs of the fork and then securing them by binding
screws 4.
The balance fork is secured to the end of the horizontal lever 5 by means of the
screw 6 which, as aforesaid, passes through the slot and enters a tapped hole in
the end of the lever. The fulcrum centres 7 of the lever 5 are preferably made of
platinoid and work in platinoid concave sockets in the vertical complement 8 of the
horizontal arm 9. The lever 5 which may be bent downwards as shown, has the
small counter balance weight 10 at its lower extremity.
The
The horizontal arm 9 is secured, as shown, by the pinching screw 11 to the
telescope holder 12. 13 is the plummet or pendulum. This pendulum, which, as
shown, is preferably made with a broadened base and with tapered sides works
within the hollow quadrantal shaped box 14 secured rigidly to the forked bar 8.
This box has, or may have, compartments 15, 16, in it, and the compartment 16
may be partially filled with oil or other liquid 17. Very little liquid is required as
the pendulum nearly fills up the entire space within the compartment 16.
reason for having the compartment 15 is to permit the liquid to run into it through
the opening or slit 19, when the instrument is laid down on its side, instead of
through the slot 20 at the top of the compartment 16 as would otherwise be the
case. The dividing partition 18 prevents the liquid escaping from the com-
partment 15 through the slot 20 should the sextant be turned upside down.
The pendulum may be provided with stop pins 21 if so desired.
22 is the clamping screw for securing the pendulum.
As will be seen at Fig. 5 a horizontal wire or thread 23 is or may be fitted
across the horizon glass 26 and be secured to the two pivotted arms 24 attached
to the frame 25.
27 is the telescope of the sextant and 28 the verner.
To adjust the device, the sextant or other instrument is held so that the line of
sight is exactly at right angles to the pendulum 13 which, of course, hangs truly
vertical. When this has been done the nendulum is clamped in position by the

page_text: screw 22 and the balance fork or ring 1 is then raised or lowered, which can be
done by slackening the pinching screw 6 sufficiently to admit of the fork or ring
being moved the length of its slot, until the horizontal wire 3 in it is exactly in line
and coincides with the horizontal wire 23 of the horizon glass frame. When this
adjustment has been effected the pinching screw 22 can be unclamped and the
instrument is then ready for taking observations.
With this instrument to find the altitude during a dense fog with no horizon but
with a moderately bright sun overhead, bring the sun down in the usual way then
hold the instrument so that the horizontal wire in balance fork or ring coincides
with the horizontal wire of the horizon glass. Now turn the tangent screw of the
verner with the left hand whilst the instrument is held up by the right until the
lower edge of the sun's disc touches the horizontal line on the horizon glass. Then
clamp the verner in position and read off altitude in the usual way.
When holding the instrument the body of the observer acts as gimbals in
accordance with the motion of the vessel.
-When-angles.of altitude_are_ taken in this manner the height of observer's eye
is not considered and therefore there will be no correction for "dip."-
In the modified arrangement shown at Fig. 8 the pendulum is not inclosed in a
box and its bob 13 is or may be made of quadrantal or like shape and be hollow.
The interior of the bob may be filled with a heavy metal such as lead or mercury
or with a combination of these two metals. The pendulum can, in this case, be
clamped in position by the thumb screw 22, the shank of which passes through a
longitudinal slot cut in the horizontally bent lower part 8" of the long branch of
the forked vertical complement 8 and enters a tapped hole in the bob of the
pendulum. 29 represents the line of sight passing through the wires 3, and 23.
The screw 11 can be used for vertical adjustment.
In lieu of fitting the wire 23 on the horizon glass frame it can be fitted in a
special form of telescope. The telescope, which is shown at Figs. 3 and 4, consists
of a tube 30 with a ring 30" fitted in an adjustable piece 31 at one end, and with
an adjustable sight 32 at the other end. Fitted in the ring 30" is the horizontal
wire, 23ª, which bisects the line of sight. The adjustable sight 32 can be moved
so as to suit the eye of the observer.
If desired the wire 23" may be fitted at or near the inner end of the adjustable
piece 31.
It is advisable when placing the instrument in the box to clamp the pinching
screw of the pendulum so as to keep the parts in position.
The fulcrum centres are made as fine as possible so as to give the least possible
friction.
If so desired the device may be fitted with a vertical wire as well as a horizontal
In this case, of course, the horizon glass would have a vertical wire or
thread also.
one.
The device may be modified in form without departing from the principle of the
invention.
With my invention, the instrument is always ready for use, and the attachment
does not require to be taken off when the instrument is placed in the box.
The attachment does not interfere with the sun's altitude being taken in the
usual way.
The attachment can, at any time, be taken off the sextant or other instrument by
merely unscrewing the thumb screw on the telescope holder.
The device whilst very simple is thoroughly efficient.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I consider novel and desire to claim is :-
1. The combination with a sextant, quadrant, or similar instrument, of a device
for determining the horizontal plane of the observer's line of sight, substantially
as hereinbefore set forth.

page_text: 2. The combination of the horizontal lever 5, adjustable balance fork or ring I
with its wire or equivalent 3 and the pendulum or its equivalent 13, substantially
as hereinbefore described with reference to the drawings annexed.
Dated this 19th day of February 1894.
H. D. FITZPATRICK,
70, Wellington Street, Glasgow, Agent.