TEACHING THE JUDGMENT, AT SIGHT, OF THE SIZE OF ANGLES OR THE NUMBER OF DEGREES CONTAINED BY THEM
Year: 1885

page_text: OI Angies.
THOMAS ROBERT ABLETT of 36 Wemyss Rd, Blackheath, in the County of
Kent, Inspector of Art Teaching. I Thomas Robert Ablett do hereby declare thé
nature of my said invention for TEACHING THE JUDGMENT, AT SIGHT, OF THE
SIZE OF ANGLES OR THE NUMBER OF DEGREES CONTAINED BY THEM, to be as
follows:-
-
My invention consists of a disc of wood or other material with one diameter
marked on it. One radius of this diameter is strongly made out & the other is
faintly made out. A pin or pivot is placed in the centre of the disc to hold a strip.
of metal or other material. This strip is so fashioned that a lower edge of it will
coincide with one radius of the aforesaid diameter at the same time that an upper
edge will coincide with the radius of the same diameter. Thus placed these two
edges of the strip form a continuous straight line coinciding with the diameter
aforesaid. The strip when revolved forms by means of its edges, aforesaid, equal
opposite angles with the aforesaid diameter.
One edge of the strip is marked out strongly (with paint or other material) &
the other edge is marked faintly to correspond, each one, with a radius of the
aforesaid diameter. At the back of the disc the circumference has divisions on it
which enable the edges of the strip to be placed at any given distance from the
aforesaid diameter so as to form angles with it of a required number of degrees.

page_text: THOMAS ROBERT ABLETT of 36 Wemyss Rd, in Blackheath Village, in the
County of Kent, England, Inspector of Art Teaching. I, Thomas Robert Ablett
do hereby declare the nature of my invention for TEACHING THE JUDGMENT, AT
SIGHT, OF THE SIZE OF ANGLES OR THE NUMBER OF DEGREES CONTAINED BY THEM,
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
My invention consists of a disc of stout cardboard or other material. On one
face of the disc (marked A in drawings) a diameter D E is drawn so that one half
of it is a thick line & the other half a thin line. A strip of metal FG revolves on
a pin fixed in the centre of the aforesaid diameter D E. This strip of metal F G 1
is so made that the opposite edges .X & Y can be placed to coincide with the
diameter D E at one and the same time and thus to form a continuous straight line
with it. When the strip of metal F G is revolved the edge X forms, with that half
of the diameter marked S E, an angle equal to the angle formed by the edge Y
and that half of the diameter marked S D. The bend in the middle of the strip of 1
metal serves to make the apex of each angle come as near as possible to the centre
of the diameter. The extremities of the strip of metal pass round & clasp the edge
of the disc as shown in the side elevation C. One extremity G is pointed as shown
at G and the other is rounded as shown at F1 on the reverse face of the disc B
(see drawings). The reverse face of the disc B has its circumference marked off
into certain divisions which indicate degrees. These markings enable the teacher
to place the edges of the metal strip F G in such a way as to make any required
angle with the diameter D E. HI is a band attached to the disc and it is clasped
by the teacher when the disc is being shown to the pupils.
.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The shape of the strip of metal or moveable diameter FG. This shape causes
the opposite edges of this moveable diameter (marked X & Y on the drawings) to
form part of one straight line which runs, when continued, through the centre of
the fixed diameter.
2. One half of the fixed diameter D E is thickened in order to call special
attention to one of the two angles, which are formed by the diametera.

page_text: 3. The use of two diameters or intersecting lines, one marked on the disc and
one consisting of a strip of metal.
4. The bending of both ends of the strip of metal or moveable diameter F G
round the edges of the disc. The pointing of the end shown at G₁ so that the
edge X of the moveable diameter will make an angle with E S equal to that which
the point at G marks on the reverse side of the disc B.
5. The employment of a strap H I to support the disc on the hand of the
teacher.