Improvements in Apparatus for Determining a Ship's Bearings and Course.
Year: 1890

page_text: Date of Application, 29th Sept., 1890
Complete Specification Left, 3rd Mar., 1891-Accepted, 23rd May, 1891
PROVISIONAL SPECIFICATION.
[Communicated from abroad by EDWIN BAKER, on board S. S. Fedele Primavesi,
Port Said, Egypt.]
Improvements in Apparatus for Determining a Ship's Bearings and
Course.
I, HENRY HARINGTON LEIGH, Fel. Inst. P.A., Assoc. Mem. Inst. C.E.,
practising as Phillips & Leigh, at 22, Southampton Buildings, Chancery Lane,
in the County of Middlesex, Engineer and Patent Agent, do hereby declare the
nature of this invention, to be as follows:-
This invention relates to improvements in apparatus for determining a ship's
bearings or course, and the object of it is to shew at a single glance, and simul-
taneously, the true, magnetic, and compass courses, together with the true,
magnetic, and compass bearings of any particular object.
In carrying it into effect, I provide three ordinary compass cards of different
diameters, so that as the larger of the three is at the bottom and the smaller at the
top, all of them can be read at once. The top one is the true card; the middle one,
the magnetic card; and the bottom one, the compass card.
A. bar underlies the bottom card, and the three cards and it are all pivotted on a
common centre upon which they can all turn independently of each other. A right
line is led from the pivot outwards beyond the periphery to indicate the direction
of the ship's head, and a second one from the pivot to the end of the bar to serve
as a line for taking bearings.
A shadow pin is provided at the said end of the bar. A central sight is
provided.
The devices above described are, preferably, of metal and are mounted upon
gimbals.
DL: aail a
1000
COMPLETE SPECIFICATION.
Improvements in Apparatus for Determining a Ship's Bearings and
Course.
I, HENRY HARINGTON LEIGH, Fel. Inst. P.A., Assoc. M. Inst. C.E.,
practising as Phillips & Leigh at No. 22, Southampton Buildings, Chancery
Lane in the County of Middlesex, Patent Agent and Engineer, 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 improvements in course or bearing cards, and the object
of it is to shew at a single glance, the true, magnetic, and compass courses simul-
taneously, together with the true magnetic and compass bearings of any particular
object.
In order that my invention, and the means by which it is to be carried into
practical effect, may be thoroughly understood, I will now describe them in detail,
referring in so doing to the accompanying drawings which are to be taken as part
of this Specification and read therewith.
Finlan

page_text: .
Fig. 3 is a side elevation of a simpler type of the invention than that illustrated
in the preceding figures.
Fig. 4 is a sectional side elevation of a modification of the construction illustrated
in Fig. 1, to the extent of replacing the box and suspension device by a simple
flat base.
Like parts are throughout the figures marked with the same reference letter.
A, A are the gimbals by which the device is supported in the case A'.
a, a are lines to indicate the lee-way as affecting the ship's course.
B is the base plate from which hangs a central spindle 6 having at its extremity
a balance weight b. C is a shadow pin fixed upon the top of the spindle b.
D is the compass card, E is the magnetic card, and F is the true card. All
these three cards are marked like ordinary compass cards without magnets but of
decreasing diameters, the compass card being the larger of the three so that the
points upon all are equally visible. The cards are concentric, and can each be
turned freely about the common axis of the instrument.
G is a clamping screw adapted to clamp the true card F to the magnetic card E.
H is a clamping screw adapted to clamp the magnetic card E to the compass
card D; and I is a third clamping screw adapted to clamp the compass card D to
the base plate B. Instead of three clamping screws, I may use one only adapted
to clamp all three cards. I do not confine myself to any particular type of
clamping screw or clamping device but may make use of any adapted to discharge
the functions described above.
J is the bearing radius. It is a metal bar with sight-holes at each end through
which the cards beneath can be read, and the diametrical reading lines j, j stretched
across said holes. It is free to turn about the axis of the instrument.
Referring to Figs. 3 and 4, B¹ is a strong card replacing the base plate B. The
case A is discarded as already explained.
The following general directions for the use of my invention will illustrate
its scope and practical utility.
The complete instrument in the box is useful to find the errors of a ship's
compass at sea,
and is so constructed as to illustrate the effects of variation and
deviation upon a ship's course.
It also illustrates the effects of variation and deviation upon every bearing of
any object taken by the ship's compass: it is a course and bearing corrector.
It will illustrate all calculations containing variation, deviation and leeway;
checking their correct application and obviating error by placing the whole
operation graphically before the eye.
The instrument is used thus:-
Place the box in a convenient place parallel with the keel of the ship, set the
outer or compass card to the course you are steering, clamp with the top screw;
set the middle or magnetic card to the inner or true card for the variation, clamp
with the bottom screw; set the bearing line to the sun's true bearing (as per
azimuth tables) on the true card, and turn the true and magnetic cards clamped
together until the shadow of the centre pin falls on the reverse half of the bearing
line, clamp with the middle screw the difference between the magnetic and the
compass cards is the deviation.
Being now set for variation and deviation, the bearing line placed to the ship's
head shews the true magnetic and compass course you are steering; placed to port
or starboard of the ship's head corresponding with the leeway, it shews the true
magnetic and compass course through the water: no leeway, then the course steered
is the course made through the water.
Set as above the bearing line placed over any point on the compass card corre-
sponding with any bearing taken by the ship's compass shews the true magnetic
and compass bearing at once placed over a magnetic bearing taken from a
magnetic chart, it shews what that bearing would be by the ship's compass.
Figs. 3 and 4 are cheap modifications of the above to hang up in vessels' chart

page_text: rooms, and can be used to shew the deviation when the ship's compass is fitted with
a shadow pin or other method of obtaining a reliable bearing of the sun.
They can be used for all the other uses of the complete instrument and serve to
indicate to the officer in charge what course to steer.
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
claim is :
1. The combination of three compass cards independently adjustable with
reference to each other about a common axis, as set forth.
2. The combination of three compass cards independently adjustable about a
common axis, a bearing radius, and a shadow pin, as set forth.
3. The combination of three compass cards independently adjustable about a
common axis, a bearing radius, and a shadow pin, the whole gimbal-mounted on
a suitable base plate in a suitable case, as set forth.
4. The general arrangement and construction of the aforesaid apparatus, as
set forth.
1001
PHILLIPS & LEIGH.