IMPROVEMENTS IN MAGNETIC COMPASSES
Year: 1875

page_text: LETTERS PATENT to George James Symons, of Camden Square,
in the County of Middlesex, for the Invention of "IMPROVEMENTS
IN MAGNETIC COMPASSES."
Sealed the 17th March 1876, and dated the 20th September 1875.
PROVISIONAL SPECIFICATION left by the said George James Symons
at the Office of the Commissioners of Patents, with his Petition,
on the 20th September 1875.
I, GEORGE JAMES SYMONS, of Camden Square, in the County of
Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN MAGNETIC COMPASSES," to be as follows:
It is not generally known, except to nautical and to scientific men,
that the compasses usually sold do not point to the true north or south
pole of the earth, or agree with the positions represented upon maps.
The fact is, the magnetic pole to which all compass needles point is not
identical with the geographical pole which is the north point of all
maps. The difference between true and magnetic north varies in

page_text: Now the object of one part of my Invention is to make compasses so
that, while the needle points to the magnetic north, the north point on
the card or dial shall always be approximately at the true north. For
this purpose I attach the needle to the card or dial at such an angle
to a line running through the north and south poles of the card as shall
correspond approximately with the difference between the magnetic and
true poles at the part of the world for which the compass is intended,
for any part of the United Kingdom an angle of 21° will be sufficiently
near.
In cases where the needle is not attached to but moves above the
card, the same correction may be obtained by attaching the needle to
an arrow or hand placed at such an angle as to shew the true north.
And in some cases I make the needle adjustable, so that it may be
corrected for different parts of the world.
For the purpose of enabling the north pole on the card or dial to be
readily seen, my Invention further consists in making an isosceles
triangle filled in with black on the card, the apex of the triangle being
at the true north while the two sides extend across the card to points at
or about S.S.E. and S.S.W. respectively.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
―filed-by-the=said-George-James-Symons-in-the Great Seal-Patent
Office on the 18th March 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
JAMES SYMONS, of Camden Square, in the County of Middlesex, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters. Patent, bearing date the Twentieth day of September, in the
year of our Lord One thousand eight hundred and seventy-five, in the
thirty-ninth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said George James Symons, Her
special licence that I, the said George James Symons, my executors,

page_text: administrators, and assigns, or such others as I, the said George James
Symons, my executors, administrators, and assigns,. should at any
time agree with and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom
of Great Britain and Ireland, the Channel Islands, and Isle of
Man, an Invention for "IMPROVEMENTS IN MAGNETIC COMPASSES," upon
the condition (amongst others) that I, the said George James Symons,
my executors or administrators, by an instrument in writing under
my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be
filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said George James Symons, do hereby
declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, reference being had to the
accompanying Drawings, that is to say :-
It is not generally known, except to nautical and to scientific men,
that the compasses usually sold do not point to the true north or south
pole of the earth, or agree with the positions represented upon maps.
The fact is, the magnetic pole to which all compass needles point is not
identical with the geographical pole which is the north point of all
maps. The difference between true and magnetic north varies in
different parts of the world; in the United Kingdom the difference
varies from 19° to 24°.
Now my Invention is intended more particularly for compasses made
so that, while the needle points to the magnetic north, the north point
on the card or dial shall always be approximately at the true north,
the needle being for this purpose attached to the card or dial at such
an angle to a line running through the north and south poles of the
card, as shall correspond approximately with the difference between the
magnetic and true poles at the part of the world for which the compass
is intended.
.
The object of my Invention is to make what I call an "unmistakeable

page_text: unmistakeably shew at a glance which is the north pole of the card.
Upon the card of-the-compass-I-make an isosceles triangle filled in with.
black, the apex of the triangle being at the true north-while-the-
two sides extend across the card to points at or about S.S.E. and S.S.W.
respectively.
'
Figure 1 is a face view (on a large scale) of one of my unmistakeable
true north compasses, and Figure 2 a section of the same taken through
the true north and south points.
The black isosceles triangle with its apex at the true north and its
base extending from the S.S.E. and S.S.W. points is clearly seen and
requires no explanation, its unmistakeableness being obvious; a is the
needle which is placed at an angle of about 19° to a line running
through the true north and south poles.
Although my Invention is intended more particularly for true north
compasses, it is also applicable to ordinary or uncorrected compasses,
the black isosceles triangle rendering the magnetic north of the card
unmistakeable. I do not, however, claim the making of compasses to
shew the true north, as I have been informed since the lodging of my
Provisional Specification that such compasses had been made before,
the same having been invented and publicly used by Mr. Bennet
Woodcroft; but what I do claim is making a black isosceles triangle
on the card of true north or other magnetic compasses as herein-before
described; so-that-the-north-pole-of-such card shall be unmistakeable..
In witness whereof, I, the said George James Symons, have
hereunto set my hand and seal, this Fourteenth day of March,
One-thousand-eight hundred and seventy-six.