IMPROVEMENTS IN THE MAGNETIC NEEDLE AND MARINERS' COMPASSES
Year: 1850

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
MORTIMER, of Hanover Square, in the County of Middlesex, Esquire, send
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Seventh day of
December, One thousand eight hundred and fifty, in the fourteenth year
of Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said John Mortimer, my exors, admors, and assigns, Her especial
licence, full power, sole privilege and authority, that I, the said John
Mortimer, my exors, admors, and assigns, or such others as I, the said John
Mortimer, my exors, adiñors, or assigns; should at any time agree with, and
no others, from time to time and at all times during the term of years therein
expressed, should and lawfully might make, use, exercise, and vend, within
England, Wales, and the Town of Berwick-upon-Tweed, my Invention of
"IMPROVEMENTS IN THE MAGNETIC NEEDLE AND MARINERS' COMPASSES ;" in which
said Letters Patent is contained a proviso that I, the said John Mortimer,
shall cause a particular description of the nature of my said Invention, and in
what manner the same is to be performed, by an instrument in writing under
my hand and seal, to be inrolled in Her Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said
in part recited Letters Patent, as in and by the same, reference being there-
unto had, will more fully and at large appear..

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
John Mortimer, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, are fully described and
ascertained in and by the following statement thereof, reference being had to
the Drawing hereunto annexed, and to the figures and letters marked thereon
(that is to say)-
My Invention consists of improvements in magnetic needles and in
mariners' compasses.
And in order that my Invention may be most fully understood and readily
carried into effect, I will proceed to describe the means pursued by me.
DESCRIPTION OF THE DRAWING.
Figure 1 shows the plan of the card of a mariner's compass; Figure 2
shews a section of the same; and Figure 3 shews an under side view of the
card and needle. By these views it will be seen that the needle, in place of
proceeding across the card, as heretofore, that is, having as much of the needle
on one side of the axis of motion as the other, I cause the axis to be near one
end, the chief portion of the needle being on one side of the axis, and in order
to balance the needle and card I apply a portion of brass or other metal
not magnetic, as is shewn; by this arrangement I find the magnetic. needle of
a mariner's compass comes more quickly to rest, and I also find that the
action of a needle is better. The Drawing shews the south pole of the magnet
most distant from the axis of motion; this, however, may be varied; and
I recommend the use of two compasses, the one having the south pole most
distant from the axis of motion, and the other having the north pole most
distant from its axis..
Figure 4 shows a plan of another mariner's compass, and Figure 5, a
section thereof, which, in place of having the axis of the needle coincident with
the axis of the card, the axis of the needle is carried by a slide, which can be
moved in a groove to any point on the card (or hemisphere) representing the
latitude of the place of observation; and if such instrument be fitted to sights,
which may place the pivot on which the needle traverses and the centre
or pole of a card in a direct line with the meridian, then, by adjusting the
index hand to the direction that the needle takes; the variation of it will be at
once shewn, as, for instance, in Figure 4, supposing the latitude to be 40° N.,
and the groove to be placed in a direct line with the terrestrial pole, and the
axis of the needle set to 40°, the declination there appears to be 16. is a
magnetic needle, suitably mounted on an axis, and on which axis a pointer k
turns, so as to be set in the line of the needle, and thus as it were extend the

page_text: length of needle, so as to show more exactly the point on the graduated
scale to which the end of the needle points. are dots on the pointer k to
show when the point of the pointer k and the point of the needle are in the
same line.
Figure 6 shows a dipping needle with a peculiar mode of suspending the
frame thereof, by which means it will at all times hang vertical. a is the loop
by which the instrument is suspended, it is connected to the ball 6 by two
points or axes c opposite each other, and the ball is attached to the frame e by
means of two other points f, f, or axes, as shewn, by which an universal joint is
obtained to a dipping needle. The joint itself is not new, but its combination
with a dipping needle is what constitutes the novelty of this part of my
Invention.
Having thus described the nature of my Invention, and the manner of
performing the same, I would have it understood that I do not confine myself
to the details so long as the peculiar character of any part of my Invention be
retained; but what I claim is,
First, the means of suspending the needles of mariners' compasses.
Secondly, I claim the construction of mariners' compasses, described in
respect to Figures 4 and 5.
And, thirdly, I claim the mode of suspending dipping compasses.
In witness whereof, I, the said John Mortimer, have hereunto set my
hand and seal, this Seventh day of June, in the year of our Lord One
thousand eight hundred and fifty-one.
Enrolled the Seventh day of June, in the year of our Lord One thousand
eight hundred and fifty-one.