great liking for the commercial part, but his ingenuity found a vent in
making improvements on the existing instruments, and in devising
philosophical toys. At the end of six years he retired from the
undertaking.

In 1827, Wheatstone introduced his 'kaleidoscope,' a device for
rendering the vibrations of a sounding body apparent to the eye. It
consists of a metal rod, carrying at its end a silvered bead, which
reflects a 'spot' of light. As the rod vibrates the spot is seen to
describe complicated figures in the air, like a spark whirled about in
the darkness. His photometer was probably suggested by this appliance.
It enables two lights to be compared by the relative brightness of their
reflections in a silvered bead, which describes a narrow ellipse, so as
to draw the spots into parallel lines.

In 1828, Wheatstone improved the German wind instrument, called the MUND
HARMONICA, till it became the popular concertina, patented on June 19,
1829 The portable harmonium is another of his inventions, which gained a
prize medal at the Great Exhibition of 1851. He also improved the
speaking machine of De Kempelen, and endorsed the opinion of Sir David
Brewster, that before the end of this century a singing and talking
apparatus would be among the conquests of science.

In 1834, Wheatstone, who had won a name for himself, was appointed to
the Chair of Experimental Physics in King's College, London, But his
first course of lectures on Sound were a complete failure, owing to an
invincible repugnance to public speaking, and a distrust of his powers
in that direction. In the rostrum he was tongue-tied and incapable,
sometimes turning his back on the audience and mumbling to the diagrams
on the wall. In the laboratory he felt himself at home, and ever after