***Handwritten Patent text
transcribed to the best of our abilities***
William
A. Burt, Mount Vernon, Territory of Michigan
(Patented
February 25, 1836)
The
Schedule referred to in these Letters Patent and making
part
of the same, containing a description in the words of the said
William
A. Burt himself of his improvement in the instrument for
determining
the variation of the Needle, the true meridian and
the
apparent time.
Be
it known that I William A. Burt
of Mount Vernon, Macomb County, Territory of Michigan have
made an improvement, being an instrument for determining the
variation of the needle, the true meridian, and the apparent time,
which is described as follows reference being had to the annexed
drawing of the same making part of this specification. This
instrument is supposed to be attached to a circumferentor or
some similar instrument having a level in it. The arc (a) is
graduated to half degrees and works in a clamp (p) with a nonius
(g) and cleats the arc (b) to the latitude of the
place and is
secured by the clamp screw (r), which arc is also graduated to
half degrees. Upon the arc (b) is fixed a movable limb (c)
having
an opening (e) for a nonius, which limb turns on the center (d)
and moves parallel on the arc (b). Upon the movable limb (c)
is
fixed an arc (o) for bringing the arm (f) to the sun &
moon declination.
Upon the moveable limb (c) is also fixed the support
(g) upon which rests the arm (f) bearing the convex lens
(i)
for converging the rays of the sun and throwing , and throwing
them upon the plate (k) which is marked with three lines,
and upon the middle one of which the true meridian is
shown. There is also a dark glass (w) placed over the
convex lens.
Operation: First place the Instrument level,
locate
the arc (b) to the latitude of the place and clamp it adjust
the arm (f) to the sun or moon declination and also clamp
it, move the limb (c) to the hour of the day marked on the
limb (b) which will throw the sun's image upon the plate (k)
and when brought upon the centre line, will show the true
meridian. The difference between this and that shown by the
needle will be the variation, and the nonius in the limb (c)
will show the apparent time. ~ What I claim as my invention
is the before described instrument for showing the variation
of the needle by giving the true meridian, also the
apparent time.
Witnesses:
J.
H. Vanclece (?)
William A. Burt
Wm.
L. Elliot
Patented 25th of February 1836
Exd
(?) ( Rec'd
& Recorded December 31, 1838)
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