An Improved Apparatus for correcting the Heeling Error of Ships' Compasses.
Year: 1894

page_text: Date of Application, 1st Jan., 1894-Accepted, 21st Apr., 1894
An Improved Apparatus for correcting the Heeling Error of Ships'
Compasses.
I JOHN FRANCIS STUART Lieutenant R.N. H.M.S. Hawke Mediterranean Fleet
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:-
By the use of my invention it is a simple matter to correct heeling error of ships
compasses during a voyage when the ship has appreciable motion, and this, although
highly desirable, has been hitherto impracticable.
The usual system of correction necessitates four observations, two on shore and
two on board ship; also two distinct instruments are necessary for these
observations.
By using my invention the shore observations are dispensed with, and one
observation on board ship only is necessary.
The usual system involves a knowledge of the theory of compass correction, but
by using this instrument such knowledge is unnecessary.
It is not claimed that the principal that heeling error may be corrected by
making the dip on board ship equal to the dip on shore is new, but that my
invention renders it possible to make use of this principle for correcting heeling
error both at sea and in harbour.
My invention is shown in the accompanying drawings in which Figure I. is the
plan Fig. II the side elevation and Fig. III the vertical section.
The instrument shewn in the drawings consists of a cradle A, of aluminium or
other light unmagnetic metal, supporting a magnetic dipping needle B by means
of conically recessed screws 1 in which the pivots J of the dipping needle freely
work.
The cradle carries a vertical arc C graduated in degrees, by means of which the
angle of depression of the needle may be read.
A cap D is fixed to the cradle above the centre of gravity of the instrument.
This cap rests on a pivot F passing through a hole in the bottom of the cradle.
This arrangement allows the needle to turn freely in azimuth and will therefore,
when on shore, point in the plane of the magnetic meridian and at the same time
show the correct dip at the place of observation.
The hole in the bottom of the cradle through which the pivot F passes is
sufficiently large to allow the cradle to remain steady while the ship is rolling
through an arc of about twenty degrees.
A ring of lead G gives sufficient stability to the cradle.
In order to give a means of making the plane which passes through the pivots
of the needle and the zero, or horizontal, marks Z on the graduated arc, level;
should it from any cause be out of adjustment, brackets H are attached to the
lower part of the cradle forming with the vertical arc C. four recesses into any of
which wax may be run.

page_text: The instrument is placed in the binnacle with the centre of its needle in the same
place as is usually occupied by the centre of the system of needles of the compass
card, and is allowed to steady itself in the plane of the magnetic meridian.
The heeling magnet is then raised or lowered until the needle of the instrument
shows the same degree of dip as that due to the geographical position of the ship,
as ascertained from a magnetic dip chart of the world. The heeling magnet is
then in its correct place.
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 improved instrument, constructed, arranged, and used, substantially as
described.
Dated this 19th day of April 1801