AN INSTRUMENT INVENTED BY US FOR MEASURING STANDING TIMBER
Year: 1767

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, JOHN
DUNCOMBE, of Ludlow, in the County of Salop, Mathematician, sendeth
greeting.
WHEREAS His present Majesty, by His Royal Letters Patent, bearing
date on or about the Eighteenth day of May last, in the seventh year of His
reign, was graciously pleased to grant to me, the said John Duncombe and
Joseph Polile, of Ludlow aforesaid, Engraver, our executors, admors, &
assigns, the sole making and vending "AN INSTRUMENT INVENTED BY US FOR
MEASURING STANDING TIMBER," within that part of His Majesty's Kingdom
of Great Britain called England, Dominion of Wales, and Town of Berwick-
upon-Tweed, and also in His Majesty's Colonies and Plantations abroad, for
the term of fourteen years.
NOW KNOW YE, that I, the said John Duncombe, in compliance with
and performance of a proviso or condition in such Letters Patent contained,
do hereby describe and ascertain the nature of the said Invention, in manner
following (that is to say):-
This machine or instrument is founded upon that branch of the mathematicks
called plane trigonometry, and consists of divers members or parts, videlicit:
_First, a semicircle, which is divided into two equal parts or quadrants;

page_text: these quadrants or parts are each divided into ninety degrees, &c., beginning
at the middle of the semicircle, and upon the diameter thereof hangs a
plummet, in order to fix the instrument perpendicular, which may otherwise
be done by a bubble. There is also a chord parallel to the diameter, and
likewise a radius which passes through the diameter and chord at right angles.
Secondly, upon a center on the radius hangs an altimetrian; between the
chord and diameter a small semicircle is fixed thereto, and a screw to confine
it in any position. This altimetrian is divided from the center both ways,
each into forty equal parts, which are again divided and subdivided; the small
semicircle is divided into degrees, &c. (the centre thereof being ninety
degrees); the radius-from-the-center-of-the-diameter-to-the-center of the
altimetrian is divided into twenty equal parts, which are again divided and
subdivided, corresponding with the divisions upon the altimetrian. There is
also a Nonins on the radius which cuts the degrees, &c., upon the small semi-
circle of the altimetrian. Thirdly, on the back of the instrument a sliding
stock is confined to the axis-that-moves-concentrically parallel to an index on
the opposite side, it being confined thereto. This index is divided into forty-five
equal parts, &c., corresponding with the former divisions, and has also a
Nonins which cuts the degrees, &c., upon the semicircle of the instrument.
There is also a groove in the radius that slides across the axis by means of
a screw working between the chord and semicircle of the instrument.
Fourthly, upon the stock is a sliding piece that always works at right angles
with the altimetrian by means of a groove therein. To the shank of the
sliding piece is annexed a moveable limb, which is divided into twenty-five
parts, &c., as before; and likewise upon the axis on the right hand of the
instrument is a center, on which an index with telescope sights works
horizontally, &c. Upon the moveable limb of the sliding piece there are
also two small semicircles; which are each divided from the center each way
into degrees, &c., in order to keep the sights always in a parallel position.
The use of this.instrument is for measuring standing timber, surveying of land,;
levelling, mineing, engineering, measuring altitudes, declivities, and distances,
and for the solution of all cases in plane trigonometry. N.B.-Notwith-
standing the nature and present form of the instrument is here particularly
described, yet the several divisions thereon may be augmented or diminished to
any other number or numbers, and the instrument be made in any other form
or manner whatsoever,, provided it be still agreeable to the principle aforesaid,
videlicet, that of plane, trigonometry; and the said John Duncombe doth,
hereby aver and declare that the particulars above set forth, together with the

page_text: Drafts, Plans, and the references thereto hereto annexed, contain a full, true,
and perfect description of the said Invention.
In witness whereof, I, the said John Duncombe, have hereunto set my
hand and seal, this Fifteenth day of September, in the seventh year of
the reign of our Sovereign Lord George the Third, by the grace of
God of Great Britain, France, and Ireland King, Defender of the
Faith, &c., and in the year of our Lord One thousand seven hundred
and sixty-seven