Sir Charles Wheatstone (; 6 February 1802 – 19 October 1875) was an English physicist and inventor best known for his contributions to the development of the Wheatstone bridge, originally invented by Samuel Hunter Christie, which is used to measure an unknown electrical resistance, and as a major figure in the development of telegraphy. His other contributions include the English concertina, the stereoscope (a device for displaying three-dimensional images) and the Playfair cipher (an encryption technique).
Life
Charles Wheatstone was born in Westgate at. Gloucester and christened in St Mary de Lode. However some time after his death a biography confused the issue by relocating this to his grandmothers house in Barnwood, Gloucestershire. His father, W. Wheatstone, was a cobbler and music-seller in the town, but his mother descended from the lord of the manor in a nearby village and had links with London society. His father moved to 128 Pall Mall, London, four years later, becoming a teacher of the flute to royalty. Charles, the second son, stayed with his grand parents and went to a village school in Barnwood and afterwards to several institutions in London. One of them was in Kennington, and kept by a Mrs. Castlemaine, who was astonished at his rapid progress. From another he ran away, but was captured at Windsor, not far from the theatre of his practical telegraph. As a boy he was very shy and sensitive, liking to retreat into an attic, without any other company than his own thoughts.
When he was about fourteen years old he was apprenticed to his uncle and namesake, a maker and seller of musical instruments at 436 Strand, London; but he showed little taste for handicraft or business, and loved better to study books. His father encouraged him in this, and finally took him out of the uncle's charge.
At the age of fifteen, Wheatstone translated French poetry, and wrote two songs, one of which was given to his uncle, who published it without knowing it as his nephew's composition. Some lines of his on the lyre became the motto of an engraving by Bartolozzi. He often visited an old book-stall in the vicinity of Pall Mall, which was then a dilapidated and unpaved thoroughfare. Most of his pocket-money was spent in purchasing the books which had taken his fancy, whether fairy tales, history, or science.
One day, to the surprise of the bookseller, he coveted a volume on the discoveries of Volta in electricity, but not having the price, he saved his pennies and secured the volume. It was written in French, and so he was obliged to save again, until he could buy a dictionary. Then he began to read the volume, and, with the help of his elder brother, William, to repeat the experiments described in it, with a home-made battery, in the scullery behind his father's house. In constructing the battery, the boy philosophers ran short of money to procure the requisite copper-plates. They had only a few copper coins left. A happy thought occurred to Charles, who was the leading spirit in these researches, 'We must use the pennies themselves,' said he, and the battery was soon complete.
At Christchurch, Marylebone, on 12 February 1847, Wheatstone was married to Emma West. She was the daughter of a Taunton tradesman, and of handsome appearance. She died in 1866, leaving a family of five young children to his care. His domestic life was quiet and uneventful.
Though silent and reserved in public, Wheatstone was a clear and voluble talker in private, if taken on his favourite studies, and his small but active person, his plain but intelligent countenance, was full of animation. Sir Henry Taylor tells us that he once observed Wheatstone at an evening party in Oxford earnestly holding forth to Lord Palmerston on the capabilities of his telegraph. 'You don't say so!' exclaimed the statesman. 'I must get you to tell that to the Lord Chancellor.' And so saying, he fastened the electrician on Lord Westbury, and effected his escape. A reminiscence of this interview may have prompted Palmerston to remark that a time was coming when a minister might be asked in Parliament if war had broken out in India, and would reply, 'Wait a minute; I'll just telegraph to the Governor-General, and let you know.'
Wheatstone was knighted in 1868, after his completion of the automatic telegraph. He had previously been made a Chevalier of the Legion of Honour. Some thirty-four distinctions and diplomas of home or foreign societies bore witness to his scientific reputation. Since 1836 he had been a Fellow of the Royal Society, and in 1859 he was elected a foreign member of the Royal Swedish Academy of Sciences, and in 1873 a Foreign Associate of the French Academy of Sciences. The same year he was awarded the Ampere Medal by the French Society for the Encouragement of National Industry. In 1875 he was created an honorary member of the Institution of Civil Engineers. He was a D.C.L. of Oxford and an LL.D. of Cambridge.
While on a visit to Paris during the autumn of 1875, and engaged in perfecting his receiving instrument for submarine cables, he caught a cold, which produced inflammation of the lungs, an illness from which he died in Paris, on 19 October 1875 aged 73. A memorial service was held in the Anglican Chapel, Paris, and attended by a deputation of the academy. His remains were taken to his home in Park Crescent, London, (marked by a blue plaque today) and buried in Kensal Green Cemetery.
Music instruments and acoustics In September 1821, Wheatstone brought himself into public notice by exhibiting the 'Enchanted Lyre,' or 'Acoucryptophone,' at a music shop at Pall Mall and in the Adelaide Gallery. It consisted of a mimic lyre hung from the ceiling by a cord, and emitting the strains of several instruments – the piano, harp, and dulcimer. In reality it was a mere sounding box, and the cord was a steel rod that conveyed the vibrations of the music from the several instruments which were played out of sight and ear-shot. At this period Wheatstone made numerous experiments on sound and its transmission. Some of his results are preserved in Thomson's Annals of Philosophy for 1823.
He recognised that sound is propagated by waves or oscillations of the atmosphere, as light was then believed to be by undulations of the luminiferous ether. Water, and solid bodies, such as glass, or metal, or sonorous wood, convey the modulations with high velocity, and he conceived the plan of transmitting sound-signals, music, or speech to long distances by this means. He estimated that sound would travel through solid rods, and proposed to telegraph from London to Edinburgh in this way. He even called his arrangement a 'telephone.' (Robert Hooke, in his Micrographia, published in 1667, writes: 'I can assure the reader that I have, by the help of a distended wire, propagated the sound to a very considerable distance in an instant, or with as seemingly quick a motion as that of light.' Nor was it essential the wire should be straight; it might be bent into angles. This property is the basis of the mechanical or lover's telephone, said to have been known to the Chinese many centuries ago. Hooke also considered the possibility of finding a way to quicken our powers of hearing.)
A writer in the Repository of Arts for 1 September 1821, in referring to the 'Enchanted Lyre,' beholds the prospect of an opera being performed at the King's Theatre, and enjoyed at the Hanover Square Rooms, or even at the Horns Tavern, Kennington. The vibrations are to travel through underground conductors, like to gas in pipes.
And if music be capable of being thus conducted,' he observes, 'perhaps the words of speech may be susceptible of the same means of propagation. The eloquence of counsel, the debates of Parliament, instead of being read the next day only, – But we shall lose ourselves in the pursuit of this curious subject.
Besides transmitting sounds to a distance, Wheatstone devised a simple instrument for augmenting feeble sounds, to which he gave the name of 'Microphone.' It consisted of two slender rods, which conveyed the mechanical vibrations to both ears, and is quite different from the electrical microphone of Professor Hughes.
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. He also invented instruments of his own. One of the most famous was the Wheatstone concertina. It was a six sided instrument with 64 keys, logically arranged for simple chromatic fingerings. The English concertina became increasingly famous throughout his lifetime, however it didn't reach its peak of popularity until the early 20th century.
In 1827, Wheatstone introduced his 'kaleidophone', 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 Mundharmonika, creating the symphonium (or symphonion), a mouth-blown free-reed instrument with a logical layout of button keys, patented on 19 December 1829, prefiguring the bellows-blown English concertina. 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. His first course of lectures on sound were a complete failure, due to his abhorrence of public speaking. 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.
Velocity of electricity He achieved renown by a great experiment made in 1834 – the measurement of the velocity of electricity in a wire. He cut the wire at the middle, to form a gap which a spark might leap across, and connected its ends to the poles of a Leyden jar filled with electricity. Three sparks were thus produced, one at each end of the wire, and another at the middle. He mounted a tiny mirror on the works of a watch, so that it revolved at a high velocity, and observed the reflections of his three sparks in it. The points of the wire were so arranged that if the sparks were instantaneous, their reflections would appear in one straight line; but the middle one was seen to lag behind the others, because it was an instant later. The electricity had taken a certain time to travel from the ends of the wire to the middle. This time was found by measuring the amount of lag, and comparing it with the known velocity of the mirror. Having got the time, he had only to compare that with the length of half the wire, and he could find the velocity of electricity. His results gave a calculated velocity of 288,000 miles per second, i.e. faster than what we now know to be the speed of light (), but were nonetheless an interesting approximation.