IMPROVEMENTS IN MAGNETIC COMPASSES
Year: 1876

page_text: LETTERS PATENT to Francis Barker, of Clerkenwell, in the County of Mid
dlesex, for the Invention of "IMPROVEMENTS IN MAGNETIC COMPASSES."
PROVISIONAL SPECIFICATION left by the said Francis Barker at the Office
of the Commissioners of Patents on the 30th May 1870.
FRANCIS BARKER, of Clerkenwell, in the County of Middlesex.
IN MAGNETIC COMPASSES."
"IMPROVEMENTS
My Invention relates to an improved pocket compass, which may be used either
as a mariner's floating compass, or as a needle or land compass at pleasure, the
floating card being for this purpose made removable from the compass needle.
The card is also made adjustable relatively to the needle, so that it may be made
to indicate the true north in any part of the world.
For use as a needle compass a glass or other transparent dial is provided beneath
the needle, the said dial also serving as the back of the compass box. It is marked
with the points of the compass and is surrounded by a bevelled rim divided and
figured as in ordinary compass circles.
By placing the compass on a nap or chart the compass bearing or direction of
any point may be read off with greater ease than by ordinary compasses.
To enable the compass bearings of any place on the map or chart which is beyond
the reach of the compass to be readily ascertained a fine cord is attached at the
under side of the glass dial to the centre or pin on which the needle is poised, the
said pin being itself fixed in the glass dial.
The compass needle is constructed of round steel wire, which I find retains when
hardened more magnetisin than ordinary needles, and in order to compensate the
magnetic dip at different parts of the world sliding brass weights are applied to
the needle, said weights being adjustable in order to keep the needle horizontal.
The compass box is fitted with a glass cover, which is readily removed to give
access to the interior for adjusting the needle, detaching the compass card, or
other purpose. The bezel which holds the glass is fitted to revolve, and is provided
with an index mark or pointer, so that when in use as a needle compass the
variation may be read off in degrees on a graduated circle beneath.
The Invention also comprises an improvement more particularly applicable to
the compass card known as Singer's Patent. This improvement consists in marking
the N point in black color on a white or blank space on the black ground of the
Singer compass card, and marking the S point in a white letter on a black ground
on the white half of the card.

page_text: thread M, which is attached to the centre of a little button R fitting in a socket in
the centre of the base of the pin C. The thread can be wound on this button
when not in use. In lieu of the thread 1 may use a rod fitted or applied to the
same centre to which one of its edges would be radial. The needle D is made of
round steel wire pointed at both ends, and is preferably electro-gilt. It carries one
or more sliding brass weights N, by adjusting which the needle may be so balanced
as to compensate for the magnetic dip. The glass cover O of the case is made
removable to give access to the interior, and its bezel, which can be turned round or
adjusted in the case A, carries a pointer P for reading off the variation on the
circle I. Referring to Figure 4 it will be seen that the N is marked in black on a
white space (preferably of the shape shown) in the black half of the card, and the
Sin white on a black ground of similar shape in the white half.
Having described the nature of the said Invention, and the manner of performing
the sanic, I declare that what I claim as the Invention to be protected by the
herein-before in part recited Letters Patent is―
1st. Making the compass card removable from the needle as shown and described
to adapt the instrument for use as a needle compass or floating card compass at will.
2nd. The combination with a transparent bottom to the compass case of a
bevelled circle of degrees above, and a cord or other device radiating from the
centre for ascertaining the compass bearing of any point on a chart or map outside
the compass, as herein described.
3rd. In combination an adjustable bezel carrying an index or pointer, and a circle
of degrees below, on which the pointer indicates the amount of variation, as
described.
4th. Making the magnetic needle of round steel wire with conical points, as
shown and described.
5th. The improvement in the Singer compass card, as shown and described.
In witness whereof, I, the said Francis Barker, have hereunto set my hand and
seal, this Twenty-ninth day of November, in the year of our Lord One
thousand eight hundred and seventy-six.
FRANCIS BARKER. (L.S.)
FRANCIS BARKER. (L.S.)