AN IMPROVED INSTRUMENT TO BE EMPLOYED IN SETTING OUT OR DRAWING GEOMETRICAL FIGURES AND MORE PARTICULARLY IN GRADUATING CIRCLES "
Year: 1883

page_text: "
LETTERS PATENT to Frances Hariott Wood of Acton Green, Chiswick in
the County of Middlesex, Spinster for an Invention of AN IMPROVED
INSTRUMENT TO BE EMPLOYED IN SETTING OUT OR DRAWING GEOMETRICAL
FIGURES AND MORE PARTICULARLY IN GRADUATING CIRCLES "
3
PROVISIONAL SPECIFICATION left by the said Frances Hariott Wood at
the Office of the Commissioners of Patents on the 26th April 1883.
FRANCES HARIOTT WOOD of Acton Green Chiswick in the County of Middlesex,
Spinster, "AN IMPROVED INSTRUMENT TO BE EMPLOYED IN SETTING OUT OR
DRAWING GEOMETRICAL FIGURES AND MORE PARTICULARLY IN
CIRCLES
D
GRADUATING
My invention consists of an instrument to be employed in setting out or drawing
geometrical figures and more particularly intended for graduating circles.
My improved instrument consists essentially of a sector having a number of
curved and radial lines thereon. The curved lines are at any required distance
apart, say 1/8th or 1/th of an inch, and are struck from the centre from which the
two sides of the sector radiate. The position on the sector of each radial line; is
such that the arc of a given graduation of the circumference of the circle of which
any one of the said curved lines forms part is a multiple of the arc contained, on
such curved line, between the radial line and one of the sides of the sector or any
given radial line thereon; for example the arc of one division of the circum-
ference of a circle graduated into five parts, as for a regular pentagon, being
(360°) 72°, the arc contained in my instrument between the side of the sector
or the given radial line and the radial line to be used in graduating the cir-
cumference of a circle into five parts will be say, '/th of 72° viz: 18°. Again
the arc of one division of the circumference of a circle graduated into 8 parts as
for a regular octagon being (3600. :) 45°, the arc contained in my instrument
between the side of the sector or the given radial line and the radial line to be
used in graduating the circumference of a circle into 8 parts will be say of 45°
[Price 6.]
=
8
=

page_text: viz 22°. In each of the curved lines before described I form one or more holes to
give passage to the point of a pencil or other like marker.
Such being the arrangement of the instrument I will now explain the manner
of using
and will suppose that it is required to draw a circle 12 inches in
diameter and graduate it into five parts so that a regular pentagon may be formed
therein. The instrument is first attached to the paper or surface on which the
circle is to be drawn by a drawing pin or other like device passed through it at
the point or centre from which the lines radiate; then the point of a pencil is
passed through a hole in the curved line which is six inches from the said centre
and a circle, which will be 12 inches in diameter, is then described by the pencil
by moving the sector a complete revolution 'on the centre. Next in order to effect
the graduation, the arc contained, (on the curved line which is six inches from the
said centre) between the side of the sector or the given radial line before described
and the radial line used in graduating the circumference of a circle into 5 parts is
taken; four times this arc will be the fifth of the circumference. The whole
circumference can thus be readily marked off by compasses or otherwise into five
equal parts and a pentagon can then be drawn with the aid of the sector itself or
any other ruler.
•
In order to make the instrument further useful I attach thereto a head or piece
at right angles to one of the sides of the sector; it can then be employed as
& T-square; but as this head might be inconvenient when drawing circles as above
explained I prefer to make it removable for which purpose it may slide in a sheath
or guide fixed to the sector, and this head may be an ordinary ruler marked off in
inches or otherwise so that it can be used separately.
"
I also make one of the sides of the sector a right angle to the third side (which
forms an extension of the arc of the sector) so that the instrument can be used as
a set-square.
I also mark off the arc of the sector in degrees so that it may be utilized for
other purposes than those above described as will be well understood.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Frances Hariott Wood in the Great Seal Patent Office on the
25th October 1883.
FRANCES HARIOTT WOOD of Acton Green, Chiswick in the County of
Middlesex, Spinster, "AN IMPROVED INSTRUMENT TO BE EMPLOYED IN SETTING
OUT OR DRAWING GEOMETRICAL FIGURES AND MORE PARTICULARLY IN GRADUATING
CIRCLES
860°
"
My invention consists of an instrument to be employed in setting out or
drawing geometrical figures and more particularly intended for graduating circles.
My improved instrument is represented in the annexed drawing and consists
essentially of a sector ABC having radial lines ab thereon, these lines being
marked off by holes c c at any required distance apart, say, half an inch as shown.
The position on the sector of each radial line a b is such that the arc of a given
graduation of the circumference of a circle struck from the centre B from which
the two sides of the sector radiate is a multiple of the arc contained between the
radial line and the side B C of the sector; for example the arc of one division of the
circumference of a circle graduated into 5 parts, as for a regular pentagon, being
=) 72°, the arc contained in my instrument between the side BC of the
sector and the radial line b to be used in graduating the circumference of a circle
into 5 parts will be say th of 72° viz 18°, that is to say, the angle b B C is 18°.
Again the arc of one division of the circumference of a circle graduated into 8 parts
as for a regular octagon being (380) 45°, the arc contained in my instrument
between the side B C of the sector and the radial line a to be used in graduating
the circumference of a circle into 8 parts will be say, of 45° viz: 221°, that is to
say, the angle a BC is 221°. Again the arc contained between the two sides
A B, BO of the sector is 30° so that twice that arc will give the side of a
hexagon.
o
360°
Such being the arrangement of the instrument I will now explain the manner
of using it and will suppose that it is required to draw a circle 12 inches in
diameter and graduate it into five parts so that a regular pentagon may be formed
therein. The instrument is first attached to the paper or surface on which the
circle is to be drawn by a drawing pin or other like device passed through it at
the point or centre B from which the lines radiate; then the point of a pencil is
passed through a hole which is six inches from the said centre, and a circle,
which will be twelve inches in diameter, is then described by the pencil by moving
the sector a complete revolution on the centre. Next in order to effect the
graduation, the arc contained, six inches from the said centre, between the side
BC of the sector and the radial line b is taken; four times this are will be the
fifth of the circumference. The whole circumference can thus be readily marked
off by compasses or otherwise into five equal parts and a pentagon can then be
drawn with the aid of the sector itself or any other ruler.
In order to make the instrument further useful I attach thereto a head or
piece E at right angles to the side BC of the sector; it can then be employed
as a T square; but as this head might be inconvenient when drawing circles as
above explained I prefer to make it removable for which purpose it may slide in
a sheath or guide F fixed to the sector and this head may be an ordinary ruler
marked off in inches or otherwise so that it can be used separately.
I also make the side BC of the sector a right angle to the third side A. O so that
the instrument can be used as a set square,

page_text: There are holes at dd placed. at such distances from the side BC as to give
respectively the 48th, 60th, 72nd, 84th, 100th, and 120th part of a circle; the position
of these holes may of course be placed to give any other required part of a circle
There are also holes at e at one degree apart, the first of them being a degree
from the side B C.
Having now described the nature of my said invention and in what manner the
same is to be performed I declare that I claim :-
The improved instrument hereinbefore described with reference to the annexed
drawing to be employed in setting out or drawing geometrical figures.
In witness whereof I the said Frances Hariott Wood have hereunto set my
hand and seal this twenty second day of October One thousand eight hundred and
eighty three.
:
F. H. WOOD (LS.)