Biography of Sir Charles Wheatstone

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Sir Charles Wheatstone was an English physicist and inventor whose work was instrumental in the development of the telegraph in Great Britain. His work in acoustics won him (1834) a professorship of experimental physics at King’s College, London, where his pioneering experiments in electricity included measuring the speed of electricity, devising an improved dynamo, and inventing two new devices to measure and regulate electrical resistance and current: the Rheostat and the Wheatstone bridge named after Wheatstone, as he was the first to put it to extensive and significant use.

Charles Wheatstone was born on 6 February 1802, at Barnwood Manor House, Barnwood, near Gloucester. His father was a music-seller in the town, who, four years later, moved to 128, Pall Mall, London, and became a teacher of the flute. He used to say, with not a little pride, that he had been engaged in assisting at the musical education of the Princess Charlotte.

Charles, the second son, went to a village school, near Gloucester, 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 well to retire 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. However, 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. Small for his age, but with a fine brow, and intelligent blue eyes, he often visited an old book-stall in the vicinity of Pall Mall, which was then a dilapidated and unpaved thoroughfare. In 1818, when aged just sixteen, Charles Wheatstone produced his first known new musical instrument, the ‘flute harmonique’, a keyed flute of some kind.

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, till 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.

In September, 1821, Wheatstone brought himself into public notice by exhibiting the ‘Enchanted Lyre,’ or ‘Aconcryptophone,’ at a father-William’s music-shop at Pall Mall and in the Adelaide Gallery. This acoustical trick featured anornate lyre suspended via a thin steel wire from the soundboardsof pianos and other instruments in the room above, and which appearedto play ‘of itself’ by sound conduction and sympathetic resonanceof its strings.

Charles Wheatstone even purported to ‘wind-up’ the Lyre when presenting the show! He speculated publicly at this time on the future transmission of music across London and of it being ‘laid on to one’s house, like gas’. Later, in 1824, he published ‘The Harmonic Diagram’, a musical theory teaching aid.

This illustration shows a demonstration of Wheatstone’s “Enhanced Lyre”, ca. 1821. Musicians played on a piano or harp in the room above the lyre, and the vibrations passed down a brass wire made the lyre appear to play by itself.

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 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 200 miles a second through solid rods, and proposed to telegraph from London to Edinburgh in this way. He even called his arrangement a ‘telephone.’ 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.

Charles and his brother William took over their uncle Charles’s musical instrument business on his death in autumn 1823, when Charles was 21 and William about 18 years of age. By 1829, Charles and his brother William had moved their business to new premises at 20 Conduit Street, near Bond Street, Regent Street and Hanover Square. Charles Wheatstone and William appear to have maintained their father and uncle’s trade in woodwind and of general musical instrument sales and manufacture.

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.

Wheatstone’s Concertina

The concertina belongs to a class of instruments known as Free Reed instruments, which also includes accordions and harmonicas. It was developed in 1829 and 1830 by Sir Charles Wheatstone after several years of building prototypes, a few of which still exist (in 1829 he patented its direct predecessor, the Symphonium, but he did not actually patent the concertina itself until 1844). He founded the firm of Wheatstone & Co to manufacture concertinas, each one expensively hand-made by highly skilled craftsmen, and at first the concertina was very much an instrument of the middle and upper class drawing room.

Its fully chromatic range was suited to classical pieces, with its fast action lending it to “party pieces” such as The Flight of the Bumble Bee. In due course other firms such as Lachenal and Jeffries were founded (several by ex-Wheatstone employees) the cost of concertinas lowered, and the instrument moved out of the drawing room and into the world of popular music. Shown on the left is the original concertina as invented by Wheatstone. You can recognise one by the 4 parallel rows of buttons and by the supports for thumb and little finger on each end. The larger baritone and bass English concertinas frequently have wrist straps as well, to help with the greater weight of the instrument.

In the 20th Century the instrument gradually fell out of favour, and one by one the makers closed or went out of business. Wheatstone’s themselves (by this time owned by Boosey & Hawkes) closed in 1968. What saved the instrument from gradually dwindling away into obscurity, as far as the UK was concerned, was the Folk Revival from the ’60s onward. Performers looking for a different sound from the ubiquitous guitar were drawn to the concertina for all its old virtues of versatility and flexibility combined with portability. In addition the concertina permitted song accompaniments that were free of the rhythmic straitjacket that the guitar in unskilled hands tends to impose upon everything. For folk and morris dance the anglo concertina and its accordion cousin the melodeon proved ideal. People started making concertinas again, many of a quality to equal anything made by the old companies.

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.

Charles Wheatsone’s refinements of Von Kempelen’s talking machine, late 1800′s

Wheatstone’s construction of von Kempelen’s speaking machine

In 1791 Wolfgang von Kempelen built a device for generating speech utterances. An improved version of the machine was built from von Kempelen’s description by Sir Charles Wheatstone. Briefly, the device was operated in the following manner. The right arm rested on the main bellows and expelled air though a vibrating reed to produce voiced sounds.” (This is illustrated in the lower half of the figure).

“The fingers of the right hand controlled the air passages for the fricatives /sh/ and /s/, as well as the ‘nostril’ openings and the reed on-off control. For vowel sounds, all the passages were closed and the reed turned on. Control of vowel resonances was effected with the left hand by suitably deforming the leather resonator at the front of the device. Unvoiced sounds were produced with the reed off, and by a turbulent flow through a suitable passage. In the original work, von Kempelen claimed that approximately 19 consonant sounds could be made passably well.

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. Wheatstone had a lifelong friendship with the scientist Michael Faraday (1791-1867), and due to Wheatstone’s intense shyness, Faraday usually delivered Charles’s lectures for him at the Royal Institution.

He achieved renown by a great experiment – the measurement of the velocity of electricity in a wire. His method was beautiful and ingenious. 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 either 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 found that the velocity of electricity was 288,000 miles a second.

He also conducted experiments in order to calculate the speed of light and produced a figure of almost 250,000 miles per second – by far the most accurate estimate of that time. Wheatstone’s device of the revolving mirror was afterwards employed by Foucault and Fizeau to measure the velocity of light. Till then, many people had considered the electric discharge to be instantaneous; but it was afterwards found that its velocity depended on the nature of the conductor, its resistance, and its electrostatic capacity. Faraday showed, for example, that its velocity in a submarine wire, coated with insulator and surrounded with water, is only 144,000 miles a second, or still less.

In 1835 Sir Charles Wheatstone read a paper on the ‘Prismatic Analysis of Electric Light’ before the British Association meeting at Dublin. He demonstrated the fact that the spectrum of the electric spark from different metals presented more or less numerous rays of definite refrangibility, producing a series of lines differing in position and colour from each other and that thus the presence of a very minute portion of any given metal might be determined. ‘We have here’, he said, ‘a mode of discriminating metallic bodies more readily than by chemical examination, and which may hereafter be employed for useful purposes’. This remark is very typical of his farsightedness into the practical utility of any known scientific fact. This suggestion has been of great service in spectrum analysis, and as applied by Bunsen, Kirchoff, and others, has led to the discovery of several new elements, such as rubidium and thallium, as well as increasing our knowledge of the heavenly bodies.

Two years later, he called attention to the value of thermo-electricity as a mode of generating a current by means of heat, and since then a variety of thermo-piles have been invented, some of which have proved of considerable advantage.

Electric Telegraph

Wheatstone abandoned his idea of transmitting intelligence by the mechanical vibration of rods, and took up the electric telegraph. In 1835 he lectured on the system of Baron Schilling, and declared that the means were already known by which an electric telegraph could be made of great service to the world. He made experiments with a plan of his own, and not only proposed to lay an experimental line across the Thames, but to establish it on the London and Birmingham Railway.

Sir Charles Wheatstone was not the ‘inventor’ of the telegraph – indeed no-one can really claim that title. The telegraph was advanced by several people starting with Stephen Gray in 1727. However, Sir Charles Wheatstone was the first person with William Cooke to develop a viable system which was made available to the public. Cooke saw the possibilities of a telegraphic system linking the major towns in the country.

But he was unknown to investors. So to get commercial support for his scheme he turned to Professor Charles Wheatstone as partner. It was in 1837 that Cooke & Wheatstone devised the first practical telegraph, which was known as the five needle system. This was an alphabetical system with five needles, controlled by five separate wires. The needles pointed to to the desired letter. It only remained for the receiving operator to note down the letters in order as received.

The five-needle telegraph, which was mainly, if not entirely, due to Wheatstone, was similar to that of Schilling, and based on the principle enunciated by Ampere – that is to say, the current was sent into the line by completing the circuit of the battery with a make and break key, and at the other end it passed through a coil of wire surrounding a magnetic needle free to turn round its centre.

According as one pole of the battery or the other was applied to the line by means of the key, the current deflected the needle to one side or the other. There were five separate circuits actuating five different needles. The latter were pivoted in rows across the middle of a dial shaped like a diamond, and having the letters of the alphabet arranged upon it in such a way that a letter was literally pointed out by the current deflecting two of the needles towards it.

To transmit a letter of the alphabet two switches were pressed which caused two needles to move and point to the appropriate letter. By pressing different combinations of switches any one of twenty letters could be transmitted. Unfortunately J, C, Q, U, X and Z had to be omitted making it difficult to send some words. Alternative methods were adopted to spell words such as “queen”, “quiz” or “axe”. Despite its shortcomings, the advantage of their equipment was that it could be used by unskilled operators.

An experimental line, with a sixth return wire, was run between the Euston terminus and Camden Town station of the London and North Western Railway on July 25, 1837. The actual distance was only one and a half mile, but spare wire had been inserted in the circuit to increase its length.

It was late in the evening before the trial took place. Mr. Cooke was in charge at Camden Town, while Mr. Robert Stephenson and other gentlemen looked on; and Wheatstone sat at his instrument in a dingy little room, lit by a tallow candle, near the booking-office at Euston. Wheatstone sent the first message, to which Cooke replied, and ‘never,’ said Wheatstone, ‘did I feel such a tumultuous sensation before, as when, all alone in the still room, I heard the needles click, and as I spelled the words, I felt all the magnitude of the invention pronounced to be practicable beyond cavil or dispute.’

In spite of this trial, however, the directors of the railway treated the ‘new-fangled’ invention with indifference, and requested its removal. In July, 1839, however, it was favoured by the Great Western Railway, and a line erected from the Paddington terminus to West Drayton station, a distance of thirteen miles. Part of the wire was laid underground at first, but subsequently all of it was raised on posts along the line. Their circuit was eventually extended to Slough in 1841, and was publicly exhibited at Paddington as a marvel of science, which could transmit fifty signals a distance of 280,000 miles in a minute. The price of admission was a shilling.

In 1840 Wheatstone had patented an alphabetical telegraph, or, ‘Wheatstone A B C instrument,’ which moved with a step-by-step motion, and showed the letters of the message upon a dial. The same principle was utilised in his type-printing telegraph, patented in 1841. This was the first apparatus which printed a telegram in type. It was worked by two circuits, and as the type revolved a hammer, actuated by the current, pressed the required letter on the paper. There is a hand generator on the front, a dial with 30 keys round the edge and a pointer. The whole thing was known as a communicator.

A separate receiver also had a single pointer. To work it one pressed the key for the letter wanted and wound the generator. The pointer would go round until it reached the key pressed and then it disconnected the generator. Pressing another key then allowed the pointer to rotate to the next letter and so on. The generator sent alternating half cycles of current to the line and the receiving pointer moved round a letter at a time, like a stepper motor, till it reached the letter being sent. It was pretty simple, robust, and needed little skill to operate. Speeds were up to about 15 words per minute.

Cooke and Wheatstone ABC Telegraph Transmitter

A rare and important ABC Telegraph Transmitter, this fine instrument is from the laboratory of one of the inventors, Professor Charles Wheatstone’s, Kings College Laboratory on the Strand England. “KCL” is stamped on the top of the base and “KCL WB” is stenciled on the bottom.. The wood screws securing the base cover are pre-1856 technology. This instrument has a 7 1/2″ diameter mahogany base supporting a spoked brass wheel on which the alphabet is printed in black lettering on its perimeter.

To operate the instrument, the sender simply rotates the wheel until the desired letter is displayed under the index arm. During rotation the instrument sends out the proper number of electric pulses to an electromagnetically controlled pointer on a remote synchronized slave receiver with a similarly lettered wheel which moves to the sender’s letter. Electric telegraphs of the 1840-50′s are of special historic importance as the earliest practical application of serial binary coded digital communication. They are one of the first bricks in the technology that led to the digital electronic “information highway” evolving today.

Advertisement for a telegraph demonstration, 1839

There were problems in insulating the iron wires which carried the signal. The wires were covered with cotton and buried in iron pipes beside the railway line. While the wires remained dry there was no problem but if they became wet the insulation failed. Nevertheless, the equipment clearly impressed the Directors of the Great Western Railway who allowed a trial to take place between Paddington and West Drayton. The trial was a partial success. The company did not accede to Cooke’s request to extend it to Bristol, but did agree an extension as far as Slough, provided railway messages were carried free of charge.

Cooke overcame the insulation problems by suspending the wires from iron posts using glass insulators. This extension was paid for by Cooke and Wheatstone and to recover some of the expense they offered the public the opportunity to send messages at a shilling (5 p) a time. Although the five needle telegraph was easy to operate it required six wires. It was soon replaced by a single needle instrument. Each letter of the alphabet was given a code of right and left needle movements, and in this way messages could be transmitted. However, this required skilled operators.

Not with standing its success, the public did not readily patronise the new invention until its utility was noised abroad by the clever capture of the murderer Tawell. Between six and seven o’clock one morning a woman named Sarah Hart was found dead in her home at Salt Hill, and a man had been observed to leave her house some time before. The police knew that she was visited from time to time by a Mr. John Tawell, from Berkhampstead, where he was much respected, and on inquiring and arriving at Slough, they found that a person answering his description had booked by a slow train for London, and entered a first-class carriage. The police telegraphed at once to Paddington, giving the particulars, and desiring his capture.

‘He is in the garb of a Quaker,’ ran the message, ‘with a brown coat on, which reaches nearly to his feet.’ There was no ‘Q’ in the alphabet of the five-needle instrument, and the clerk at Slough began to spell the word ‘Quaker’ with a ‘kwa’; but when he had got so far he was interrupted by the clerk at Paddington, who asked him to ‘repent.’ The repetition fared no better, until a boy at Paddington suggested that Slough should be allowed to finish the word. ‘Kwaker’ was understood, and as soon as Tawell stepped out on the platform at Paddington he was ‘shadowed’ by a detective, who followed him into a New Road omnibus, and arrested him in a coffee tavern.

Tawell was tried for the murder of the woman, and astounding revelations were made as to his character. Transported in 1820 for the crime of forgery, he obtained a ticket-of-leave, and started as a chemist in Sydney, where he flourished, and after fifteen years left it a rich man. Returning to England, he married a Quaker lady as his second wife. He confessed to the murder of Sarah Hart, by prussic acid, his motive being a dread of their relations becoming known. Tawell was executed, and the notoriety of the case brought the telegraph into repute. Its advantages as a rapid means of conveying intelligence and detecting criminals had been signally demonstrated, and it was soon adopted on a more extensive scale.

In 1845 Wheatstone introduced two improved forms of the apparatus, namely, the ‘single’ and the ‘double’ needle instruments, in which the signals were made by the successive deflections of the needles. Of these, the single-needle instrument, requiring only one wire, is still in use.

In 1841 a difference arose between Cooke and Wheatstone as to the shareof each in the honour of inventing the telegraph. The question was submitted to the arbitration of the famous engineer, Marc Isambard Brunel, on behalf of Cooke, and Professor Daniell, of King’s College, the inventor of the Daniell battery, on the part of Wheatstone. They awarded to Cooke the credit of having introduced the telegraph as a useful undertaking which promised to be of national importance, and to Wheatstone that of having by his researches prepared the public to receive it. They concluded with the words: ‘It is to the united labours of two gentlemen so well qualified for mutual assistance that we must attribute the rapid progress which this important invention has made during five years since they have been associated.’ The decision, however vague, pronounces the needle telegraph a joint production.

If it was mainly invented by Wheatstone, it was chiefly introduced by Cooke. Their respective shares in the undertaking might be compared to that of an author and his publisher, but for the fact that Cooke himself had a share in the actual work of invention. The introduction of the telegraph had so far advanced that, on September 2, 1845, the Electric Telegraph Company was registered, and Wheatstone, by his deed of partnership with Cooke, received a sum of L33,000 for the use of their joint inventions.

From 1836-1837 Wheatstone had thought a good deal about submarine telegraphs, and in 1840 he gave evidence before the Railway Committee of the House of Commons on the feasibility of the proposed line from Dover to Calais. He had even designed the machinery for making and laying the cable.

In the autumn of 1844, with the assistance of Mr. J. D. Llewellyn, he submerged a length of insulated wire in Swansea Bay, and signalled through it from a boat to the Mumbles Lighthouse. Next year he suggested the use of gutta-percha for the coating of the intended wire across the Channel.

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.’

In 1840 Wheatstone also brought out his magneto-electrical machine for generating continuous currents, and his chronoscope, for measuring minute intervals of time, which was used in determining the speed of a bullet or the passage of a star.

The same year he was awarded the Royal Medal of the Royal Society for his explanation of binocular vision, a research which led him to construct the stereoscope. He showed that our impression of solidity is gained by the combination in the mind of two separate pictures of an object taken by both of our eyes from different points of view. Thus, in the stereoscope, an arrangement of lenses and mirrors, two photographs of the same object taken from different points are so combined as to make the object stand out with a solid aspect.

The ‘pseudoscope’ (Wheatstone was partial to exotic forms of speech) was introduced by its professor in 1850, and is in some sort the reverse of the stereoscope, since it causes a solid object to seem hollow, and a nearer one to be farther off; thus, a bust appears to be a mask, and a tree growing outside of a window looks as if it were growing inside the room. It was eleven years later before Sir David Brewster described a binocular camera, and the first stereoscopic photographs began to be produced.

We’ve all enjoyed 3D movies and stared at 3D pictures (stereograms) on walls – well, the first real stereographer was Sir Charles Wheatstone, who made geometric 3-D drawings and a device to view them called a reflecting mirror stereoscrope in 1838. This proved that stereo perception was a result of binocular vision. Wheatstone’s actual stereoscope is preserved at the Science Museum in London.

On November 26, 1840, he exhibited his electromagnetic clock in the library of the Royal Society, and propounded a plan for distributing the correct time from a standard clock to a number of local timepieces. The circuits of these were to be electrified by a key or contact-maker actuated by the arbour of the standard, and their hands corrected by electro-magnetism.

The following January Alexander Bain took out a patent for an electromagnetic clock, and he subsequently charged Wheatstone with appropriating his ideas. It appears that Bain worked as a mechanist to Wheatstone from August to December, 1840, and he asserted that he had communicated the idea of an electric clock to Wheatstone during that period; but Wheatstone maintained that he had experimented in that direction during May. Bain further accused Wheatstone of stealing his idea of the electromagnetic printing telegraph; but Wheatstone showed that the instrument was only a modification of his own electromagnetic telegraph.

In 1843 Wheatstone communicated an important paper to the Royal Society, entitled ‘An Account of Several New Processes for Determining the Constants of a Voltaic Circuit.’ It contained an exposition of the well- known balance for measuring the electrical resistance of a conductor, which still goes by the name of Wheatstone’s Bridge or balance.

Wheatstone Bridge

The Wheatstone bridge is an electrical circuit for the precise comparison of resistances. Sir Charles Wheatstone is most famous for this device but never claimed to have invented it – however, he did more than anyone else to invent uses for it, when he “found” the description of the device in 1843. The first description of the bridge was by Samuel Hunter Christie (1784-1865), of the Royal Military Academy, who published it in the PHILOSOPHICAL TRANSACTIONS for 1833.

The Wheatstone bridge is an electrical bridge circuit used to measure resistance. It consists of a common source of electrical current (such as a battery) and a galvanometer that connects two parallel branches, conta ining four resistors, three of which are known. One parallel branch contains one known resistance and an unknown (R4 in the left example); the other parallel branch contains resistors of known resistances. In order to determine the resistance of the unknown resistor, the resistances of the other three are adjusted and balanced until the current passing through the galvanometer decreases to zero.

The method was neglected until Wheatstone brought it into notice. His paper abounds with simple and practical formula: for the calculation of currents and resistances by the law of Ohm. He introduced a unit of resistance, namely, a foot of copper wire weighing one hundred grains, and showed how it might be applied to measure the length of wire by its resistance.

He was awarded a medal for his paper by the Society. The same year he invented an apparatus which enabled the reading of a thermometer or a barometer to be registered at a distance by means of an electric contact made by the mercury.

One of Wheatstone’s most ingenious devices was the ‘Polar clock,’ exhibited at the meeting of the British Association in 1848. It is based on the fact discovered by Sir David Brewster, that the light of the sky is polarised in a plane at an angle of ninety degrees from the position of the sun. It follows that by discovering that plane of polarisation, and measuring its azimuth with respect to the north, the position of the sun, although beneath the horizon, could be determined, and the apparent solar time obtained.

The clock consisted of a spy-glass, having a nichol or double-image prism for an eye-piece, and a thin plate of selenite for an object-glass. When the tube was directed to the North Pole–that is, parallel to the earth’s axis–and the prism of the eye-piece turned until no colour was seen, the angle of turning, as shown by an index moving with the prism over a graduated limb, gave the hour of day. The device is of little service in a country where watches are reliable; but it formed part of the equipment of the North Polar expedition commanded by Captain Nares.

Wheatstone’s remarkable ingenuity was displayed in the invention of cyphers which have never been unravelled, and interpreting cypher manuscripts in the British Museum which had defied the experts. He devised a cryptograph or machine for turning a message into cypher which could only be interpreted by putting the cypher into a corresponding machine adjusted to reproduce it.

The Playfair Cipher

The Playfair cipher is a substitution cipher bearing the name of the man who popularized but not created it. This method was invented by Sir Charles Wheatstone, in around 1854, however he named his invention after his goodfriend, Lyon Playfair, the first Baron Playfair St. Andrews. Wheatstone named this method after his friend, because he was more well known to the public. Playfair was a scientist and a public figure of Victorian England. He also was “at one time or another deputy speaker of the House of Commons, Postmaster General, and President of the British Association for theAdvancement of Science”. Playfair demonstrated what he called “Wheatstone’s newly discovered symmetrical cipher”, at a dinner in January of 1854, to associates in the British Aristocracy as well as in the Foreign office. The Playfair cipher was developed for telegraph secrecy and it was the first literal digraph substitution cipher.

It was used by Britians forces in the Boer War and World War I and also by the islands of Coastwatching in Australia during World War II. This method is quite easy to understand and learn, but not that easy to break, because you would need to know the “keyword” to decipher the code. The system functions on how the letters are positioned in relationship to a 5×5 alphabet matrix. A “KEYWORD” sets the pattern of letters with the other letters entered in the cells of the matrix in alphabetical order (i and j are usually combined in one cell). For instance, suppose we use the keyword “charles” then the matrix would look like this:

Now supposing the message to be enciphered here is “the scheme really works”.

First of all the plaintext is divided into two-letter groups. If there are double letters occuring, in the message, either an ‘x’ will be used to seperate the double letters or an ‘x’ will be added to make a two-letter group combination. In our example, the phrase beomes:

Each of the above two letter combinations will have 3 possible relationships with eachother in the matrix: they can be in the same column, same row, or neither. The following rules for replacement should be used:

If the two letters are in the sme column of the matrix, use the letter below it as the cipher text (columns are cyclical).

If the two letters are in the same row of the matrix, use the letter to the right as the cipher text (rows are cyclical).

If neither the same column or row, than each are exchanged with the letter at the intersection of its own row and the other column.

For deciphering, the rules are the exact opposite.

The rapid development of the telegraph in Europe may be gathered from the fact that in 1855, the death of the Emperor Nicholas at St. Petersburg, about one o’clock in the afternoon, was announced in the House of Lords a few hours later; and as a striking proof of its further progress, it may be mentioned that the result of the Oaks of 1890 was received in New York fifteen seconds after the horses passed the winning-post.

Wheatstone’s next great invention was the automatic transmitter, in which the signals of the message are first punched out on a strip of paper, which is then passed through the sending-key, and controls the signal currents. By substituting a mechanism for the hand in sending the message, he was able to telegraph about 100 words a minute, or five times the ordinary rate. In the Postal Telegraph service this apparatus is employed for sending Press telegrams, and it has recently been so much improved, that messages are now sent from London to Bristol at a speed of 600 words a minute, and even of 400 words a minute between London and Aberdeen. On the night of April 8, 1886, when Mr. Gladstone introduced his Bill for Home Rule in Ireland, no fewer than 1,500,000 words were despatched from the central station at St. Martin’s-le-Grand by 100 Wheatstone transmitters.

Wheatstone’s Paper Tape to Store Data

In 1837, the American inventor Samuel Morse developed the first American electric telegraph, which was based on simple patterns of “dots” and “dashes” called Morse Code being transmitted over a single wire. The telegraph quickly proliferated thanks to the relative simplicity of Morse’s system. However, a problem soon arose in that operators could only transmit around ten words a minute, which meant that they couldn’t keep up with the public’s seemingly insatiable desire to send messages to each other. This was a classic example of a communications bottleneck.

Thus, in 1857, only twenty years after the invention of the telegraph, Sir Charles Wheatstone introduced the first application of paper tapes as a medium for the preparation, storage, and transmission of data. Sir Charles’ paper tape used two rows of holes to represent Morse’s dots and dashes. Outgoing messages could be prepared off-line on paper tape and transmitted later. By 1858, a Morse paper tape transmitter could operate at 100 words a minute. Unsuspectingly, Sir Charles had also provided the American public with a way to honor their heroes and generally have a jolly good time, because used paper tapes were to eventually become a key feature of so-called ticker-tape parades.

In a similar manner to Sir Charles’ telegraph tape, the designers of the early computers realized that they could record their data on a paper tape by punching rows of holes across the width of the tape. The pattern of the holes in each data row represented a single data value or character. The individual hole positions forming the data rows were referred to as “channels” or “tracks,” and the number of different characters that could be represented by each row depended on the number of channels forming the rows.

In 1859 Wheatstone was appointed by the Board of Trade to report on the subject of the Atlantic cables, and in 1864 he was one of the experts who advised the Atlantic Telegraph Company on the construction of the successful lines of 1865 and 1866.

On February 4, 1867, he published the principle of reaction in the dynamo-electric machine by a paper to the Royal Society; but Mr. C. W. Siemens had communicated the identical discovery ten days earlier, and both papers were read on the same day.

It afterwards appeared that Herr Werner Siemens, Mr. Samuel Alfred Varley, and Professor Wheatstone had independently arrived at the principle within a few months of each other. Varley patented it on December 24, 1866; Siemens called attention to it on January 17, 1867; and Wheatstone exhibited it in action at the Royal Society on the above date. But it will be seen from our life of William Siemens that Soren Hjorth, a Danish inventor, had forestalled them.

In 1870 the electric telegraph lines of the United Kingdom, worked by different companies, were transferred to the Post Office, and placed under Government control.

At Christchurch, Marylebone, on February 12, 1847, Wheatstone was married. His wife, Emma, was the daughter of J. West, a Taunton tradesman. She died in 1866, leaving a family of five young children to his care. His domestic life was quiet and uneventful.

Wheatstone was knighted 30 Jan. 1868 1868, after his completion of the automatic telegraph. He had previously (1855) 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 1873 he was appointed 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. On 2 July 1862 he was created D.C.L. by the university of Oxford, and in l864 L.L.D. by the University 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 October 19, 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, and buried in the cemetery at Kensal Green.

He left his collection of books and instruments by will to King’s College, London where they are preserved in the Wheatstone Laboratory. Wheatstone contributed to numerous scientific journals and publications. All his published papers were collected in one volume and published in 1879 by the Physical Society of London.

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