A NEW INSTRUMENT FOR DIVIDING LINES AND DISTANCES, WHICH WILL BE USEFUL TO MATHEMATICIANS, ARCHITECTS, AND DRAFTSMEN
Year: 1811

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
JONES, of Kenton Street, Russell Square, in the County of Middlesex,
Mathematical Instrument Maker, send greeting.
WHEREAS His most Excellent Majesty King George the Third,, in and
by His Letters Patent under the Great Seal of Great Britain bearing date
.at Westminster, the Ninth day of May now last past, for Himself, His heirs
and successors, did give and grant unto me, the said Thomas Jones, His
especial license, full power, sole privilege, and authority, that I, the said
Thomas Jones, my executors, administrators, and assigns, or such others as
I the said Thomas Jones, my exécutors, administrators, 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 "A NEW INSTRUMENT FOR DIVIDING LINES AND DISTANCES,
WHICH WILL BE USEFUL TO MATHEMATICIANS, ARCHITECTS, AND DRAFTSMEN;" in
which said Letters Patent there is contained a proviso, obliging me, the said
Thomas Jones, by an Instrument in writing under my hand and seal par-
ticularly to describe and ascertain the nature of my said Invention, and in
what manner the same is to be performed, and to cause the same to be
inrolled in His Majesty's High Court of Chancery, within two calendar months
next and immediately, after the date of the said, recited Letters Patent, as in
and by the same, reference being thereto had, will more fully appear.

page_text: NOW YE, that in compliance with the said proviso, I, the said Thomas
Jones, do hereby describe and ascertain the nature of my said Invention and
the manner in which the same is to be performed by the Plan or Drawing
hereunto annexed, and as follows, that is to say :-
The said new instrument so invented by me, and which I call a sectograph,
is composed of any convenient number of small barrs (say nine) a, a, a, a, a, a,
a, a, a, of metal, or wood (but I prefer the former), each equal to each in
length, breadth, and thickness, perforated with a pin hole at each end, and one
in the middle, for the purpose of attaching them by means of pins to the three
similar barrs b, b, b, laid across them over the before-mentioned pin holes. The
three last mentioned barrs are each perforated at equal distances with as many
pin holes (say nine) as there are barrs of the first-mentioned description, and
the two setts of barrs are attached to each other by pins fitted and secured in
but not made fast in the said holes. Besides the pin holes already mentioned
the barrs a, a, a, a, a, a, a, a, a, have each a hole furnished with a dotting point.
These dotting points are for the purpose of marking or transferring the required,
divisions, angles, &., and the place for a point in each barr respectively is found
in the following manner:
All the barrs a, a, a, a, a, a, a, a, a, being placed paralell to each other draw
the diagonal line 0 to 8, and the place in the center of each barr which the
said diagonal crosses is the center of the dotting point belonging to each barr
respectively; the said pin holes are marked in the Drawing with a small white
circle (thus 0); the dotting points, with a small black circle thus (thus ).
To any convenient part of this framework (say at B) attach by a screw
or pin the graduated scale c, d. This scale has a slit which receives a pin
made fast in the middle barr b, at that part of it which will place the
scale paralell with the diagonal line 0, 8. The top of this last-mentioned pin
is screwed; a perforated square or oblong piece, which answers the double
purpose of a clamp and index, is put over this pin, over which is a female
screw e with a milled head. When the female screw is not made tight it is
obvious that all the barrs of this framework are moveable upon their
respective pins and dotting points, so that if the opposite corners 0, 8, be
pressed towards each other the corners f, g, will recede, and in this case all the
dotting points in the diagonal line 0, 8 will approach each other; and, on the
other hand, if the corners 0, 8, be drawn in an opposite direction then the
corners f, g, will approach each other and the distance between the dotting
points will be increased. The scale is graduated on one side of the slit into
inches and parts, and on the other side into degrees. As example of its
application take the following: Suppose any line is to be divided into a given

page_text: number of equal parts, say seven; place 0 on one end of the line and the seventh
dotting point over the other; then press down the whole or as many of the
intermediate points as you wish to mark: again, when a plan is to be enlarged
or reduced it is easily effected by noticing the distance of the points that are
to be transferred as indicated by the scale when applied to them, and then
making the same points to recede or approach till the required enlargement or
reduction is indicated on the scale, taking care to screw the clamp home before
moving the instrument. When angles are to be measured, place the dotting
point f on the point of the angle, the dotting point 0 on one side, and move
the dotting point 8 till it coincides with the other side of the angle, and then
the index gives the quantity. To lay down an angle, set the index to the
given quantity and clamp the instrument, and the dotting points 0, f, 8,
gives it.
It is unnecessary to say more respecting the construction of the instrument,
but it may be proper to remark, that it may be made to give a greater number
of divisions, and at the same time more minute, by intermediate dotting points
which may be attached in the following, or any other convenient manner:
Between 0 and 1 place another dotting point h, by means of the little bar i, k;
and so in like manner the dotting point C, by means of the little bar m;
and the dotting point n, by means of the bar p; and in like manner other
dotting points between the dotting points 3 and 4, and 5 and 6, and 7 and 8.
In witness whereof, I, the said Thomas Jones, have hereunto set my
hand and seal, this Eighth day of July, in this year of our Lord One
thousand eight hundred and eleven.