In 1823, his uncle, the musical instrument maker, died, and Wheatstone, with his elder brother, William, took over the business. Charles had no 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 confined his duties mostly to demonstration.