Improvements in and connected with Nautical Protractors.
Year: 1893

page_text: Date of Application, 19th July, 1893
Complete Specification Left, 30th Mar., 1894-Accepted, 5th May,
1894
Improvements in and connected with Nautical Protractors.
I, JAMES BAXTER MURRAY, of 28 Herriet Street, Pollokshields, Glasgow,
Master Mariner, do hereby declare the nature of this invention to be as follows
This invention relates to an instrument or protractor for use by mariners when
coasting.
The invention is designed to overcome the difficulties of finding a ship's correct
position and true course, the error of the compass, deviation etc., under certain
circumstances while coasting, especially when celestial observations cannot be
obtained and also to obviate mistakes which are liable to be made in finding a
vessel's position by cross bearings etc., when correcting the bearings for error of
compass, before applying the same to the chart.
Mistakes of this nature are liable to occur even with the most careful navigator,
when hurried and anxious, resulting in ship's position being erroneously placed with
Such
the not infrequent consequence of subsequent stranding and total loss.
mistakes are usually attributed to errors of judgement in estimating distances,
currents, indraughts, etc., which could easily be detected, from time to time, by the
frequent use of the new instrument.
The improved protractor consists of a plain brass ring which is cut or made
with a thin flange around its periphery. Extending diametrically across the ring
is a bar or rod which at one side is extended for a short distance beyond the ring so
as to form a projecting arm. Fitted on the bar and at the centre of the ring is a
pivot to which three movable and radiating arms are connected. These arms are
capable of turning in one plane round the pivot as a common centre. Each of the
arms are or may be bevelled on one or both edges and the three movable ones are
provided with hinged sights and pinching screws for clamping them in any desired
position on the ring. One edge of each of the arms leads in a straight line,
through the centre of the instrument. The arms are, preferably, made of thin
brass with a backing of boxwood or like material. The boxwood enables the arms
to be made very light and also gives a suitable surface to move over the chart.
The arms, which are arranged one on top of the other, are held to the ring by
means of metal strips which grip the flange, or, if so desired, the arms may be made
with grooves or recesses which grip on the flange. By making the arms with a
boxwood or like backing and the ring with a flange the arms and ring can be laid
perfectly flat on the surface of the chart.
With this instrument, which is provided with a sight pin at its centre, horizontal
bearings are taken, from the centre sight along the bevelled edges, past the hinged
sights on the arms to the shore objects.
A simple skeleton frame or stand consisting, preferably, of two cross pieces of
wood and parallel end pieces, is provided for holding the protractor in position
when taking bearings. To prevent the protractor being turned round, on its
stand, two small catches are provided on the stand. These catches preferably
consist of a small piece of metal fixed in position and a small movable or hinged
clamping piece.
The protractor with its stand is preferably placed upon the compass glass when
it is desired to take observations.
When using the instrument it is so placed on the compass glass that the cross
bar and extension is exactly in line with or parallel to the centre line of the ship
taken from bow to stern. The movable arms are then manipulated so as to sight

page_text: three prominent objects on the shore, such as lighthouses, points of land, mountain
peaks etc., that can be recognised on the chart. When this has been done the arms
are clamped in position and the instrument then removed and placed on the chart
in the usual way.
When properly placed on the chart the centre of the instrument
represents the true position of the ship and a line drawn along the extension of
the diametrical arm gives its true course. The error and deviation of the compass
can be found simultaneously with the ship's true position without calculations,
observations, inspection of tables, trouble or loss of time.
If the instrument is used from time to time and the time of taking each set of
bearings noted, especially when navigating on coasts imperfectly surveyed, it will be
absolutely impossible for a vessel to run into danger unknown to the master,
providing the weather is favourable for discerning conspicuous objects on shore, as
he has thus a means of finding the distance from the land, the speed of the ship,
checking the courses steered, detecting set of currents, indraughts etc.
It is not necessary to always place the instrument upon the compass as it can be
secured in any other convenient and suitable position.
As it is not necessary to know the value of the angles protracted no degrees
or points of the compass need be marked on the ring the arms being simply
marked A, B, C, D to distinguish one from the other.
Dated this 18th day of July 1892
H. D. FITZPATRICK,
70, Wellington Street, Glasgow, Agent.
Improvements in and connected with Nautical Protractors.
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 :-
This invention relates to an instrument or protractor for use by mariners when
coasting.
This invention is designed to overcome the difficulty of finding a ship's correct
position and true course, the error of the compass, deviation, etc., under certain
circumstances while coasting, especially when celestial observations cannot be
obtained and also to obviate mistakes which are liable to be made in finding a
vessel's position by cross bearings, etc., when correcting the bearings for error of
compass, before applying the same to the chart.
Mistakes of this nature are liable to occur even with the most careful
navigator, when hurried and anxious, resulting in ship's position being erroneously
placed with the not infrequent consequence of subsequent stranding and total loss.
Such mistakes are usually attributed to errors of judgment in estimating
distances, currents, indraughts, etc., which could easily be detected from time
to time, by the frequent use of the new instrument.
And in order that my said invention may be properly understood I have
hereunto appended an explanatory sheet of drawings, whereon,
Fig. 1 is a plan view of the instrument.
Fig. 2 is a side elevation.
Fig. 3 is a side elevation of the stand.
Fig. 4 is a plan and Fig. 5 a side elevation of the counterpoise.
Figs. 6 and 7 are views of the hinged sights.
Referring to the drawings whereon the same reference letters wherever
repeated indicate the same parts.
The improved protractor consists of a plain brass ring a which is cut or

page_text: น.
made with a thin flange b around its periphery. Extending diametrically across
the ring is a bar or rod c, which, at one side, is extended for a short distance.
Fitted on the bar and at the
beyond the ring so as to form a projecting arm
centre of the ring is a pivot e to which three movable and radiating arms f, g,
are connected. These arms are capable of turning in one plane round the pivot.
as a common centre. Each of the arms are or may be bevelled on one or both
edges and the three movable ones are provided with hinged sights i,,, and
pinching screws j for clamping them in any desired position on the ring. One
edge of each of the arms leads, as shown, in a straight line through the centre.
of the instrument. The arms are, preferably, made of thin brass with a backing
of box-wood or like material. The box-wood enables the arms to be made very
light and also gives a suitable surface to move over the chart. The arms which
are arranged one on top of the other are held to the ring by means of metal
strips which grip the flange, or, if so desired, the arms may be made with grooves
or recesses which grip on the flange. By making the arms with a box-wood or
like backing and the ring with a Hange the arms and ring can be laid perfectly
flat on the surface of the chart.
A removable counterpoise k (see also Figs. 4 and 5) is provided for balancing
the instrument on the horizontal plane when protracting angles from the top of
the compass.
This counterpoise has an arm, made with a forked end k' which.
fits on pivot e, and also a pinching screw k³ for clamping it, at any desired position.
to the flanged ring a. kis a metal strip attached to the underside of the counter-
poise and which grips the flange 6 of the ring in the same manner as the strips on
the arms.
Figs. 6 and 7 show one of the hinged sights to a larger scale, Fig. 6 represents
the sight as folded down and Fig. 7 as standing up.
With this instrument, which is provided with a sight pin at its centre,.
horizontal bearings are taken, from the centre sight along the bevelled edges,
past the hinged sights on the arms to the shore objects.
A simple skeleton frame or stand m consisting preferably of two cross pieces of
wood m², m³, and parallel end pieces m³, m² is provided for holding the protractor
in position when taking bearings. To prevent the protractor being turned round,
on its stand, two small catches n, n', o, o' are provided on the end pieces. These
catches preferably consist of a small piece of metal n or o fixed in position and a
small movable or hinged clamping piece n¹ or o¹.
The protractor with its stand is preferably placed upon the compass glass when.
it is desired to take observations. p is a screw for clamping it in position.
When using the instrument it is so placed on the compass glass that the cross
bar c and extension d is exactly in line with or parallel to the centre line of the
ship taken from bow to stern.
On the drawing, S, H, represents the ships head. The movable arms are then
manipulated so as to sight three prominent objects on the shore, such as light-
houses, points of land, mountain peaks etc., that can be recognised on the chart..
When this has been done the arms are clamped in position and the instrument
then removed and placed on the chart in the usual way. When properly placed
on the chart the centre of the instrument represents the true position of the ship.
and a line drawn along the extension of the diametrical arm gives its true course.
The error and deviation of the compass can be found simultaneously with the
ship's true position without calculations, observations, inspection of tables, trouble
or loss of time.
If the instrument is used from time to time and the time of taking each set of
bearings noted, especially when navigating on coasts imperfectly surveyed, it will
be absolutely impossible for a vessel to run into danger unknown to the master,
providing the weather is favourable for discerning conspicuous objects on shore,
as he has thus a means of finding the distance from the land, the speed of the ship,
checking the courses steered, detecting set of currents, indraughts, etc.
It is not necessary to always place the instrument upon the compass as it can be

page_text: secured in any other convenient and suitable position. In this case the stand may
if desired be dispensed with.
As it is not necessary to know the value of the angles protracted no degrees or
points of the compass need be marked on the ring the arms being simply
marked A, B, C, D, to distinguish one from the other.
I am aware that protractors with three movable arms have been heretofore made
and used but they give a vessel's position only whereas my instrument in addition
to this gives the true cause, error and deviation of compass simultaneously with
the ship's position.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
consider novel and desire to claim is :-
1. A nautical protractor consisting of a ring a, to which one fixed arm & and
three movable arins f, g, h are secured, substantially as hereinbefore described and
shown on the drawings annexed and for the purpose set forth.
2. The combination with the nautical protractor hereinbefore described of the
stand m, substantially as set forth.
3. The general arrangement and combination of parts of the improved nautical
protractor, substantially as hereinbefore described and shown on the drawings
annexed.
Dated this 28th day of March 1894.
H. D. FITZPATRICK,
70, Wellington Street, Glasgow, Agent.