Showing the Apparent Direction to the Eye of Lines winch are or are not Parallel to the Picture Plane.
Year: 1886

page_text: Showing the Apparent Direction to the Eye of Lines winch
are or are not Parallel to the Picture Plane.
THOMAS ROBERT ABLETT of 36 Wemyss Rd, Blackheath, in the County of Kent,
Inspector of Art Teaching. I, Thomas Robert Ablett do hereby declare the
nature of my invention for GIVING HELP IN DRAWING OBJECTS AS THEY APPEAR,
BY SHOWING THE APPARENT DIRECTION, TO THE EYE, OF LINES WHICH ARE OR
ARE NOT PARALLEL TO THE PICTURE PLANE 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 flat ring with one broad diameter. A radius or hand
is attached, at one end, to a point in the diameter which is the centre of the circle
of which the outer edge of the flat ring forms the circumference. The other end of
the radius or hand goes partly round the edge of the flat ring so as to clasp it
lightly. The radius or hand moves freely round the ring with its attachment to
the diameter acting as a pivot. A cord, which supports a small weight, is fastened
near the centre point of the diameter. This cord and weight serve as a plumb-line
when the flat ring is held in a vertical position.
In use, the flat ring is held vertically, with its diameter also vertical, on an
imaginary picture plane which is supposed to be placed between the eye and the
line to be drawn. The central line of the diameter must coincide with the
direction of the plumb-line when that hangs freely. To ascertain the direction of a
line, which is or is not parallel to the picture plane, the centre of the flat ring is
brought against one end of the line so that it can be seen through the hole at that
centre, and the radius or hand is moved until it assumes the same direction as the
line which is being examined.
The flat ring is marked out in degrees and there is a hole through the centre
of the diameter. These provisions fit the device to be used as a protractor.
Divisions are marked on the diameter & on the radius or hand to give facilities in
measuring. A nick is cut at the ends of the central line of the diameter to
show when the central line of the diameter coincides with the direction of the
plumb-line.

page_text: 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 employment of a flat ring, having one broad diameter to which are
attached a radius or hand and a plumb-line, for the purpose of giving help in
drawing objects as they appear to the eye.
2. The use of a radius or hand to show the apparent direction of a line.
3. The method of steadying the radius or hand by passing some of it partly
round the edge of the flat ring.
4. The method of attaching the plumb-line below. the centre of the diameter so
that it will be unaffected by the movement of the radius or hand.
5. The counting of the degrees, into which the flat ring is marked, downwards as
well as upwards starting from the horizontal line.
6. The hole through the centre of the diameter, which serves to show when the
end of or a point in a line coincides with the centre of the flat ring.
Dated thin 10th dow of April 1886