NEW METHOD OF CONSTRUCTING COMPASSES IN GENERAL SO AS TO PRE- VENT THEM BEING APFECTED BY THE MOTION OF THE SHIP IN ROUGH WEATHER, OR SUCH OTHER KINDS OF MOTION AS HITHERTO HAVE IMPEDED OR LESSENED THEIR GENERAL UTILITY, AND THAT MY NEW METHOD OF CONSTRUCTING THE VARIATION COMPASS IN PARTICULAR WILL BE BETTER ADAPTED FOR TAKING THE SUN'S AZIMUTH AND AMPLITUDE, AND THE BEARING OF DISTANT OBJECTSTHAN THOSE NOW USED
Year: 1766

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GOWIN
KNIGHT, of the British Museum, Doctor of Physick, send greeting.
WHEREAS His most Excellent Majesty King George the Third, by His
Royal Letters Patent under the Great Seal of Great Britain, bearing date
the Tenth day of June, in the sixth year of His reign, and in the year of
our Lord One thousand seven hundred and sixty-six, did give and grant
unto me, the said Gowin Knight, Ilis especial licence, full power, sole priviledge
and authority, that I, the said Gowin Knight, my exors, adñiors, and assigns,
should and might, during the term of years therein expressed, make, use,
exercise, and vend, throughout that part of His Majesty's Kingdom of Great
Britain called England, His Dominion of Wales, and Town of Berwick-upon-
Tweed, my "NEW METHOD OF CONSTRUCTING COMPASSES IN GENERAL SO AS TO PRE-
VENT THEM BEING APFECTED BY THE MOTION OF THE SHIP IN ROUGH WEATHER, OR
SUCH OTHER KINDS OF MOTION AS HITHERTO HAVE IMPEDED OR LESSENED THEIR
GENERAL UTILITY, AND THAT MY NEW METHOD OF CONSTRUCTING THE VARIATION
COMPASS IN PARTICULAR WILL BE BETTER ADAPTED FOR TAKING THE SUN'S AZIMUTH
AND AMPLITUDE, AND THE BEARING OF DISTANT OBJECTS THAN THOSE NOW USED;"
in which said recited Letters Patent is contained a proviso obliging me,
the said Gowin Knight, by writing under my hand and seal, to cause a
description of my said Invention to be inrolled in His Majesty's High
Court of Chancery within four calendar months from the date of the said
recited Letters Patent, as in and by the same. relation being thereunto had.
may more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Gowin Knight, do hereby declare that my said Invention is made and per-
formed in manner following (that is to say):-
The card and box containing it are made to oscillate in equal times, so that
the card shall always preserve a situation parrallel to the glass, and that
whether the box rolls on the inward or outward gimbol or both. This is
affected by placing the centre of gravity both of the box and of the card at
such distances from their points of suspension as to make their motions per-
fectly coincide, and by fixing a weight in the manner of a pendulum, to be
moved higher or lower by a nut and screw to the rim of the outward gimbol,
under the axis, by which the outward gimbol may be made to move in the
same time as the inward. The inward axis or gimbol is fixed to the bottom
of the box, and the body of the box with the glass fixed in it is made to take
off from the bottom. The agate is not placed in the centre of the card as
usual, but underneath, like a cup, in the place of the point, and the point is in
the centre of the card in the place of the agate cap, and screws into a cross
piece of metal in the form of a gallows, which is fixed to the needle over the
hole in its middie, so that by screwing the point higher or lower the center of
gravity of the card may be placed at such distance from the point of suspension
as shall be found necessary; the cross piece of metal into which the point is
screwed is attached to the needle by the interposition of small gimbols whereby
the tremulous motion of the point will greatly diminish the friction. The
agate is fixed to a slender stem of metal, the lower end of which is pointed,
and the stem slides into a hollow sockett in which it can turn freely on its
point. The sockett is fixt as a pedestal in the centre of the bottom of the
box, and has a slit on one side made to admit a small arm, to be screwed to
the lower part of the stem, which arm is moved backwards and forwards by
means of a small pendulum connected with it, so that whenever the box is in
motion the pendulum, arm, stem, and agate will move to and fro, and the
friction between the agate and point will be thereby greatly diminished.
In the variation compass for taking the sun's azimuth and amplitude,
and the bearing of distant objects, a reflecting mirroir is placed at each end
of the index just behind the sights, at an angle of about forty-five degrees, but
moveable at pleasure, so as to reflect the image of the graduated rim of the
card, which will then appear to the eye in a vertical position, and to be cut by
the perpendicular thread of the opposite sight, which will at the same time
cut the object in the same point if it be in the horizon; but in taking the sun's
azimuth, when its height is anything considerable, the rays of the sun are
reflected from a small polished cylander placed behind the sights, and an

page_text: opening is made in each end of the index bar. that the brass rim may be
reflected without interruption from the bar. which is slit that the shadow
of a thread underneath it may cut the graduated rim of the card.
In witness whereof, I, the said Gowin Knight, hath hereunto set my
hand and seal, the Seventh day of October, in the year of our Lord
One thousand seven hundred and sixty-six.
Inrolled the Seventh day of October, in the year of our Lord One
thousand seven hundred and sixty-six.