Improvements in or connected with Magnetic Compasses for Determining a Ship's Bearings and Course.
Year: 1891

page_text: Date of Application, 12th Nov., 1891
Complete Specification Left, 12th Aug., 1892--Accepted, 1st Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in or connected with Magnetic Compasses for
Determining a Ship's Bearings and Course.
1, EDWIN BAKER, of 32, Claude Road, Cardiff, in the County of Glamorgan,
Master Mariner do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in or connected with magnetic compasses
for determining a ship's bearings and course, and the object of it is to shew at
a single glance, and simultaneously, the true, magnetic, and compass courses,
together with the true, magnetic, and compass bearings of any particular object.
It consists, speaking generally, in the combination of two representations of
compass cards, without magnetized needles together with one compass card with
magnetized needles, a shadow pin and a bearing radius.
In carrying it into effect 1 provide three cards or card-surfaces of varying
diameters so that their marked surfaces may all be read simultaneously. The
upper surface is the true card and is marked on the underneath side of the
glass top of the compass bowl. The second or middle surface is the magnetic card
and is suspended from the centre of the glass top. The third or bottom card
or surface is provided by the ordinary compass card. It is furnished with
magnetized needles resting on the central point attached to the bottom of the
compass bowl.
A radius bar is also provided. It has sight holes cut in its ends through
which the readings on the card surfaces can be noted. Diametrical lines are
fixed along these holes.
All the said surfaces and the bar are free to turn about the vertical axis of
the instrument, and suitable devices are provided by means of which the said
surfaces may be clamped to each other or either to either as may be desired.
Dated this 12th day of November 1891.
PHILLIPS & LEIGH,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in or connected with Magnetic Compasses for
Determining a Ship's Bearings and Course.
I, EDWIN BAKER, of No. 32, Claude Road, Cardiff, in the County of
Glamorgan, 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:-
14"
My invention relates to improvements in or connected with magnetic compasses
for determining a ship's bearings and course, and the object of it is to shew at
a single glance, and simultaneously, the true, magnetic and compass courses,
together with the true, magnetic and compass bearings of any particular object.
It consists in the combination of the representations of two compass cards without
magnetized needles, one compass card provided with magnetized needles, a shadow
pin and a radius bar.
The accompanying figures illustrate the construction and use of the invention.
Fig. 1 being a sectional elevation and Fig. 2 a plan.
a, b, c are three cards or card surfaces. They are necessarily of different
diameters in order that their respective markings may be read easily and without
confusion and all at the same time. The upper surface a is the true card. It
Pin17

page_text: is preferably set out on the glass top of the compass bowl. is a glass disc
suspended from the centre of the glass top. It is marked as the magnetic card.
is the ordinary compass card.
;
The glass top upon which the true card is set out is shewn as held to the
bowl d by a bezel ring e. f is a ring provided for the purpose of protecting the
edge of the central perforation in the glass top. is the shadow pin; h, the radius
bar the bearing line and a spirit level. The, latter may be dispensed with.
jis a thumb screw by means of which the magnetic card can be set to the true
card. The leeway may be marked on either side of the lubbers line inside the
bowl. is a pointer projecting from the inside of the bowl. It is commonly known
as the lubber's line. It indicates the position of the ship's head.
The invention is used as follows. The magnetic card (or suspended disc) is set
to the true card (as marked on the glass top) for the variation and the bearing
line placed to the true bearing on the true card. Then the whole top is moved
until the shadow of the pin falls on the reverse half of the bearing radius. The
lubber's line will then show the true, the magnetic and the compass course. The
difference between the true (as marked on the glass top), and the magnetic (as
marked on the suspended disc) is the variation, the deviation being the difference
between the magnetic disc and the actual compass card.
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 :-
The combination of two representations of compass cards without magnetized
needles with one compass card provided with magnetized needles, a radius bar and
shadow pin, as set forth.
Dated this 12th day of August 1892.
PHILLIPS & LEIGH,
No. 22, Southampton Buildings, Chancery Lane, W.C.,
Agents for the Applicant.