SIR CHARLES WHEATSTONE (1802-1875), the practical founder of modern telegraphy, was born at Gloucester in February 1802, his father being a music-seller in that city. In 1806 the family removed to London. Wheatstone's education was carried on in several private schools, at which he appears to have displayed no remarkable attainments, being mainly characterized by a morbid shyness and sensitiveness that prevented him from making friends. About 1816 he was sent to his uncle, a musical instrument maker in the Strand, to learn the trade; but with his father's countenance he spent more time in reading books of all kinds than at work. For some years he continued making experiments in acoustics, following out his own ideas and devising many beautiful and ingenious arrangements. Of these the " acoucryptophone " was one of the most elegant—a light box, shaped like an ancient lyre and suspended by a metallic wire from a piano in the room above. When the instrument was played, the vibrations were transmitted silently, and became audible in the lyre, which thus appeared to play of itself. On the death of his uncle in 1823 Wheatstone and his brother took up the business; but Charles never seems to have taken a very active part in it, and he virtually retired after six years, devoting himself to experimental research, at first chiefly with regard to sound. In 1823 he published his first paper, " New Experiments on Sound," in Thomson's Annals of Philosophy, and was greatly encouraged by the appreciative translations which appeared in several Continental journals. Wheatstone's shyness still clung to him; for, although he occasionally read a paper to scientific societies when a young man, he never could become a lecturer. Hence many of his investigations were first described by Faraday in his Friday evening discourses at the Royal Institution. By 1834 Wheatstone's originality and resource in experiment were fully recognized, and he was appointed professor of experimental philosophy at King's College, London, in that year. This appointment was inaugurated by two events,—a course of eight lectures on sound, which proved no success and was not repeated, and the determination by means of a revolving mirror of the speed of electric discharge in conductors, a piece of work leading to enormously important results. The great velocity of electrical transmission suggested the possibility of utilizing it for sending messages; and, after many experiments and the practical advice and business-like co-operation of Cooke, a patent for an electric telegraph was taken out in their joint names in 1837. Wheatstone's early training in making musical instruments now bore rich fruit in the continuous designing of new instruments and pieces of mechanism. His life was uneventful except in so far as the variety of his work lent it colour. He became a fellow of the Royal Society in 1837 ; in 1847 he married ; and in 1868, after the completion of his masterpiece, the automatic telegraph, he was knighted. While in Paris perfecting a receiving instrument for submarine cables, Sir Charles Wheatstone caught cold, and died on 19th October 1875.

Wheatstone was enthusiastic in his work; and, in spite of the invincible repugnance to public speaking, he could explain his machines and describe results to his friends with animation and remarkable clearness. Owing to the cast of his mind he could only undertake work with some distinct end or definite application in view; hence he applied himself chiefly to the useful embodiment of scientific principles, and to researches designed to throw light on such subjects as the interference of mental impressions with the evidence of the senses. As a natural consequence of the nervous enthusiasm which possessed him, several researches which had been commenced, and sometimes carried to a considerable distance, were relinquished as new sources of interest presented themselves, and remained unfinished at his death. Many of his ideas were expanded and appropriated by other workers, more persevering, if less original, who carried them into effect. Wheatstone's physical investigations are described in more than thirty-six papers in various scientific journals, the more important being in the Philosophical Transactions, the Proceedings of the Royal Society, the Comptes Rendus, and the British Association Reports. They naturally divide themselves into researches on sound, light, and electricity, but extend into other branches of physics as well. But his best work by far was in the invention of complicated and delicate mechanism for various purposes, in the construction of which he employed a staff of workmen trained to the highest degree of excellence. For his insight into mechanism and his power over it he was unequalled, except perhaps by Babbage. A cryptographic machine, which changed the cipher automatically and printed a message, entirely unintelligible until translated by a duplicate instrument, was one of the most perfect examples of this. Cryptography had a great fascination for Wheatstone; ha studied it deeply at one time, and deciphered many of the MSS. in the British Museum which had defied all other interpreters. In acoustics his principal work was a research on the transmission of sound through solids (see TELEPHONE), the explanation of Chladni's figures of vibrating solids, various investigations of the principles of acoustics and the mechanism of hearing, and the invention of new musical instruments, e.g., the concertina. The kaleidophone, intended to present visibly the movements of a sonorous body, consisted of a vibrating wire, which could be varied in length, carrying a silvered bead reflecting a point of light. The motion of the bead was thus shown by persistence of the successive images on the retina, and mazy lines of light traced out its successive positions. A photometer was constructed on the same principle. In light there are a series of papers on the eye, on the physiology of vision, on binocular vision, including the invention of one of the most popular of scientific toys, the STEREOSCOPE (q.v.), and on colour. The polar clock, devised for use in place of a sun-dial, applies the fact that the plane of polarization of sky light is always 90° from the position of the sun ; hence by measuring the azimuthal angle of the plane, even when the sun is below the horizon, correct apparent solar time may be obtained. In 1835, in a paper on "The Prismatic Decomposition of Electrical Light," he proved that sparks from different metals give distinctive spectra, which could be used as a means of detecting them. This is the fundamental experiment of chemical analysis by spark spectra. But it is by his electrical work that Wheatstone will best be remembered. Much of this, such as the famous "bridge" for measuring resistances that bears his name, will be found described under ELECTRICITY (vol. viii. p. 44). He not only guided the growth of scientific telegraphy on land wires, but made the earliest experiments with submarine cables, foreseeing the practicability of this means of communication as early as 1840. For short descriptions of the "A, B, C" telegraph instrument—so popular before the introduction of the telephone—and of the automatic transmitter, by which messages may be sent at the rate of 500 words a minute, see TELEGRAPH. He also devised printing telegraph receivers of various forms, electrical chronoscopes, and many forms of electrical recording apparatus,—amongst others two sets of registering meteorological instruments, of which the earlier, described in 1842, was afterwards developed by Secchi and Van Rysselberghe (see THERMOMETER, vol. xxiii. p. 293), but the later, put forward in 1867, included metallic thermometers and was less successful.

Wheatstone's Scientific Papers were collected and published by the Physical Society of London in 1S79. The best biographical notices of him will be found in Min. Proc. Inst. C.E., vol. xlvii. p. 2S3, and Proc. Roy. Soc, vol. xxiv. p. xvi. For Wheatstone's connexion with the growth of telegraphy, see Nature, xi. p. 510, and xii. p. 30 sq.