Explanation.—The painting is set in a small frame in the centre of a larger one.
At the back of the picture is a cogged wheel, of which the teeth move a series of pinions. In each of these latter is immovably inserted one end of a white glass rod, around which runs a spiral thread of gold (colours may be substituted), and its other end terminating in a point. These points work freely in sockets on the rim of the larger circle, equally distant, to which, consequently, they diverge.
Fig. 144.
When the cogwheel turns the pinions the glass cylinders revolve, and the spiral lines change their position continually to the vision, and, as the wheel turns to the left or right, the light seems to run up from or flow down to the picture.
XIX.—COMPLICATED TRICKS IN MECHANICAL MAGIC.
PUPPETS, MARIONETTES, FANTOCCINI, &c., &c.