An Improved Scientific Optical Toy.
Year: 1898

page_text: Date of Application, 22nd Jan., 1898-Accepted, 12th Mar., 1898
COMPLETE SPECIFICATION.:
An Improved Scientific Optical Toy.
I, GEORGE HENRY MACSWINNEY, of No. 12, Temple Court, King Street, Sydney
in the Colony of New South Wales, Doctor of Medicine, do hereby declare the
nature of this invention, and in what manner the same is to be performed to he
particularly described, and ascertained in and by the following statement :-
This invention relates to a scientific optical toy, so constructed that an optical
illusion is obtained in a very simple manner, at the same time illustrating a peculiar
property, which light possess, namely diffraction. In order that this invention may
be more fully understood reference will now be made to the accompanying sheet
of drawings which forms part of this specification and in which ;-
Figure 1 is a diagrammatic view of this invention.
Figure 2 is a sectional elevation looking from the rear inwards.
Figure 3 is an enlarged front end elevation.
Figure 4 is a sectional elevation of a modification in the construction.
In all figures similar letters are used to denote similar parts.
A is a tube constructed of any suitable material having secured near the end a
dise B, this disc fits the tube tightly, and has in the centre, an opening C, preferably
square. At the back of the disc B, and across the opening C, I secure a piece of
feather D, by means of two daubs of wax E, E. In placing the feather in position,
care must be taken so that the centre rib F, divides the opening C into equal parts,
thus the side ribs will remain natural and undisturbed (see Figure 2). To protect
the feather two pieces of glass may be used, one in front of the disc, and one
behind it; no great care need be exercised in choosing a feather, as almost any
feather will serve the purpose. In the modification shewn in Figure 4, a square
box G, may take the place of the tube A, one end H, of the box G being open, the
other end having the eye piece J, which may be either circular or square, in this
case the feather D would be placed against the inside of the box at the back of the
eye piece.
The use of this scientific optical toy is to produce an effect, although an illusion,
similar to the Roentgen rays-when the hand, pencil, pipe or other object is viewed
through this toy against the light; this toy is also useful scientifically to illustrate
the peculiar property of light, namely, diffraction, the best illusion is obtained by
viewing the fingers of the hand widely separated, as it appears to make the flesh
translucent, shewing the bones dark and opaque.
This peculiar optical illusion is caused by the rays of light from the object-
say a finger, passing through the small interstices of the feather ribs, those
passing through the interstices on one side of the central rib, crossing those
which pass through on the other side, and as there a great number of interstices
visible at one time, many images are produced on the retina of the eye, and where
the images overlap a dark image will be produced apparently representing the bone
of the finger, the side images which do not cross will represent the flesh of the finger,
and appear translucent.