Lives of the electricians

by William T. Jeans

Meanwhile another competitor had begun to challenge his originality. On November 26, 1840, Professor Wheatstone read a paper before the Royal Society describing his electro-magnetic telegraph clock as his own invention. He also showed the clock in action in the library. In January following he received notice from a Mr. Barwise, of St. Martin’s Lane, that he claimed to be the inventor of the clock, and shortly afterward it was stated in placards that Messrs. Barwise and Bain were the joint inventors. At first Professor Wheatstone took little notice of the attacks thus made upon his originality, but in June, 1842, he was directly charged by Mr. Bain in the public press with appropriating his inventions. In reply to that accusation, Professor Wheatstone stated that Alexander Bain was a working mechanic who had been employed by him between the months of August and December, 1840; and to the allegation that Bain communicated the invention of the clock to him in August, 1840, he answered that there was no essential difference between his telegraph clock and one of the forms of his electro-magnetic telegraph, which he had patented in January, 1840; that the former was one of the numerous and obvious applications which he had made of the principle of the telegraph, and that it only required the idea of telegraphing time to present itself and any workman of ordinary skill could put it in practice—in telegraphing messages the wheel for making and breaking the circuit was turned round by the finger of the operator, while in telegraphing time it was carried round by the arbor of a clock. He also stated that, long before the date specified, he mentioned to many of his friends how the principle of his telegraph could be applied “to enable the time of a single clock to be shown simultaneously in all the rooms of a house, or in all the houses of a town connected together by wires.” The accuracy of these statements was verified by Dr. W. A. Miller, of King’s College, and by Mr. John Martin, the eminent artist. The latter stated that Professor Wheatstone explained to him in May, 1840, his proposed application of his electric telegraph for the purpose of showing the time of a distant clock simultaneously in as many places as might be required. Mr. Martin, on hearing the explanation, said to him, “You propose to lay on time through the streets of London as we now lay on water.” Mr. F. O. Ward, a former student of King’s College, stated that Professor Wheatstone explained the matter to him on June 20, 1840. While watching the motions of the dial telegraph as he turned the wheel that made and broke the circuit, Mr. Ward remarked that if it were turned round at a uniform rate, the signals of the telegraph would indicate time, to which Professor Wheatstone replied: “Of course they would, and I have arranged a modification of the telegraphic apparatus by which one clock may be made to show time in a great many places simultaneously;” and the Professor showed him drawings of an apparatus for that purpose, in which the making and breaking of the circuit by the alternate motion of the pendulum of a clock, would produce isochronous signals on any number of dials, provided they were connected by wire. The electric clock in question has been repeatedly tried, but has not answered expectations.

Mr. Alexander Bain also accused Professor Wheatstone of appropriating his printing telegraph. He said he communicated the invention of the electric clock, together with that of the electro-magnetic printing telegraph, to Professor Wheatstone in August, 1840, before ever Professor Wheatstone did anything in the matter. To that the Professor replied that the printing apparatus was merely an addition to the electro-magnetic telegraph, of which he was undoubtedly the inventor. As to the way in which this telegraph printed the letters, he explained that for the paper disc (or dial) of the telegraph, on the circumference of which the letters were printed, he substituted a thin disc of brass, cut from the circumference to the centre so as to form twenty-four radiating arms on the extremities of which types were fixed. This type-wheel could be brought to any desired position by turning the commutator wheel. The additional parts consisted of a mechanism which, when moved by an electro-magnet caused a hammer to strike the desired type—brought opposite to it—against a cylinder, round which were rolled several sheets of thin white paper along with the alternate blackened paper used in manifold writing. By this means he obtained at once several distinct printed copies of the message transmitted. He maintained that the plan was begun and carried out solely by himself; and Mr. Edward Cowper stated, as corroborative evidence, that on June 10, 1840, he sent a note to Professor Wheatstone (who had previously told him of the contrivance by which his telegraph could be made to print), giving him information, which he had asked for, respecting the mode of preparing manifold writing paper, and the best form of type for printing on it.

It was also at the beginning of 1840 that he invented the “chronoscope,” an instrument for measuring the duration of small intervals of time. It was used for measuring the velocity of projectiles, and consisted of a clock movement set free at the moment a ball was discharged from a gun, and stopped when the ball reached the target. For this purpose a wire in an electric circuit at the gun’s mouth was broken at the instant the ball passed out of the gun; and the circuit was completed when the ball reached the target, the circuit acting on the clock movement by means of an electro-magnet. It was publicly stated in 1841 by independent witnesses that the chronoscope was capable of indicating the one 7300th part of a second; and the inventor himself stated in 1845 that with it the law of accelerated velocities had been obtained with mathematical rigour, that with it he could measure the fall of a ball from the height of an inch, and that by different arrangements which he had adopted to render the instrument applicable to different series of experiments, he intended to employ it for measuring the velocity of sound through air, water, and masses of rock, with an approximation that had never been obtained before.

In 1843 he brought before the Royal Society several methods of measuring the force of an electric current, and the paper he then read, and the methods he described, were for many years unrivalled both for simplicity and ingenuity. Speaking of electricity as an energetic source of light, of heat, of chemical action, and of mechanical power—prescient words in those days—he said it was only necessary to know the conditions under which its various effects may be most economically and energetically manifested to enable us to determine whether the high expectations formed in many quarters of some of its daily increasing practical applications are founded on reasonable hope or on fallacious conjecture. He considered that they had ample theory, but not enough of experiment to supply, except in a few cases, the numerical value of the constants which enter into various voltaic circuits; and without that knowledge accurate conclusions could not be arrived at. He explained that electro-motive force (E.M.F.) meant the cause which in a closed circuit originated an electric current; that by resistance was signified the obstacle opposed to the passage of the electric current by the bodies through which it passed; and that resistance was the inverse of what is usually called their conducting power. The principle of his methods was the use of variable instead of constant resistances, bringing thereby the currents compared to equality, and inferring from the amount of the resistances measured out between two deviations of the needle the electro-motive force and the resistances of a circuit, according to the particular conditions of the experiment. If a needle be connected with two coils of wire, and if a current be sent through one coil, the needle will be deflected to one side. If at the same time a current of the same strength be sent through the other coil, the currents will neutralize each other and the needle will remain at rest. This is what is called a differential galvanometer, and when two currents of different strength are sent through it simultaneously the needle is only affected by their difference. One form in which Professor Wheatstone used this principle has ever since been known as “the Wheatstone bridge.” It is a method by which pieces of wire of known resistance are interposed in a circuit until the current in the wire to be tested counter-balances that of the wire used as a standard of resistance; when that happens the needle indicator stands still, the wire to be tested being now of the same resistance as that of the known standard. Professor Wheatstone perceived that it was of the highest importance to have a correct standard of resistance, and one that could be easily reproduced for the purpose of comparison. He therefore adopted as a unit of resistance a copper wire one foot in length, 100 grains in weight, and ·071 of an inch in diameter. He was the first man who made a unit of resistance, and who introduced into electrical science the name of a unit and multiples of a unit; and when, nearly a quarter of a century afterward, the British Association appointed a committee on electrical standards, their reports describing about a dozen standards, paid a tribute to the originality of Professor Wheatstone as the introducer of the first unit. He was not, however, the first to use the method of measuring electrical currents or the resistance of wires, since known as the Wheatstone Bridge. In a note appended to his paper read before the Royal Society in 1843 he stated that Mr. Christie had described the same principle in the Philosophical Transactions for 1833, and added that “to Mr. Christie must therefore be attributed the first idea of this useful and accurate method of measuring resistances.” Mr. Christie, who was connected with the Royal Military Academy at Woolwich, said in his paper that the arrangement he proposed possessed many advantages; it afforded a very accurate measure of the difference of intensities of two electric currents, whether they were from the same source and were merely modified by circumstances, or had different sources; and it afforded likewise a very accurate measure of the conducting powers of different substances. Mr. Christie did not, however, succeed in drawing attention to this method, and it lay unheeded till Professor Wheatstone revived it and expounded it with matchless clearness. He at the same time devised an instrument called the Rheostat, in which a highly resisting wire was so wound round the surface of a cylinder that any length of it could be connected with a circuit by merely turning round the handle of the cylinder till the needle or galvanometer connected with it showed that the resistance of the wire on the cylinder was equal to that of the wire to be tested. As the resistance of the wire on the cylinder was accurately known beforehand, the length of it required to counterbalance the resistance of the wire in course of being tested became the measure of the latter. The wire on the cylinder may be compared to a winding measuring line; only being of high resisting power, a short length of it suffices to measure a long wire of low resistance.

Professor Wheatstone told the Royal Society in 1843 that he had employed the Rheostat and differential resistance measurer (the Wheatstone Bridge) for several years previously for the purpose of investigating the nature of electrical currents—a statement which had received a singularly generous corroboration; for in 1840 Professor Jacobi told the British Association meeting in Glasgow that Professor Wheatstone had shown him in London an instrument for regulating a galvanic current, similar in principle to one that he had laid before the St. Petersburg Academy of Sciences at the beginning of that year. Professor Jacobi, in stating that it was quite impossible that Professor Wheatstone could have had any knowledge of his similar instrument, said he must add that while he had only used his instrument for regulating the force of currents, Professor Wheatstone had founded upon it a new method of measuring those currents and of determining the different elements of them.

The Royal Society, which in 1840 had presented him with a royal medal “for the ingenious method by which he had solved the difficult question of binocular vision,” presented him with another medal in 1843, when the President, the Marquis of Northampton, said: “I now present you with this medal, one of those intrusted to the President and Council of the Royal Society by Her Most Gracious Majesty, for your paper entitled, ‘An account of several new Instruments and Processes for determining the Constants of the Voltaic Circuit.’ This is not the first time that I have had the pleasing task of acknowledging on the part of the Royal Society the great ingenuity as well as knowledge that you bring to the increase of science. You not only add to our store of knowledge, but you give to others the means of doing so too. You not only set the example of scientific pursuit, but you also facilitate it in those who may become at once your followers and your rivals. In the particular case before us you have introduced accuracy where even rough numerical data were almost wholly wanting. The improvement of such facilities in any branch of science can hardly be overstated.”

In 1845 a patent was taken out for a new form of needle telegraph, respecting the origin of which Mr. Latimer Clark relates the following incident as told to him by Mr. Greener some fifteen years after it occurred. A very high tide which occurred in 1841 caused an inundation of the Blackwall Railway, and injured the piping in which were inclosed the seven or eight wires then in use—they were then using a wire to each station; so that only one wire or two could be worked. Mr. Cooke, who was the practical engineer of the telegraph, was much concerned lest some accident might happen through the failure of the telegraph, whereby they would, he feared, be unable to communicate with the intermediate stations from the Blackwall end of the line. In view of this contingency Mr. Greener and another clerk arranged a code of signals which could be worked on one wire by simply deflecting the needle alternately, once, twice, or thrice, to the right or left; and in this way they managed to carry on communications respecting their dinners and other private matters. “Mr. Cooke, on being informed that it was still possible to telegraph, gladly availed himself of the new means of communication by one wire, and from that moment our well-known single and double-needle instrument was practically invented. If these statements be accurate the first idea of the double-needle telegraph did not originate either with Wheatstone or Cooke, but was suggested by Mr. Greener and his partner, who was at this time engaged with him on the Blackwall telegraph.”

In the popular accounts of great discoveries or inventions it is generally the falling of an apple that is said to suggest to a Newton the law of gravitation, or it is the boiling of a tea-kettle that suggests to a Watt the mechanism of the steam-engine. This has become the orthodox way of accounting for the triumphs of mind over matter in order to make them acceptable to intellectual mediocrity. Indeed, the Abbé Raynal says that the only difference between a genius and one of common capacity is that the former anticipates and explores what the latter accidentally hits upon. But, he adds, “even the man of genius himself more frequently employs the advantages that chance presents to him; it is the lapidary that gives value to the diamond which the peasant has dug up without knowing its worth.” Now it is a curious fact that while the needle telegraph was one of the few telegraphic inventions of Professor Wheatstone that was undisputed during his lifetime, the preceding account of its origin was never publicly mentioned till after his death.

Facts, however, are against its accuracy. The high tide referred to in the story occurred on November 18th, 1841, after the five-needle telegraph had been in operation on the Great Western Railway more than two years; and a few weeks’ experience of its working enabled a clerk of ordinary intelligence to tell the letters transmitted by the movement of the needles, even if the printed letters on the dial to which the needles pointed were covered over or obliterated. A minute’s examination of the five-needle instrument shows that a different combination of movements is required to represent each letter, and if these combinations be learned by a few weeks’ practice, or be written down on paper, they constitute a complete alphabet of signs. And that alphabet of signs which the five-needle instrument first taught could obviously be produced by a single needle. Thus on the five-needle instrument A is represented by the movement of the first needle to the right, and the fourth from it to the left; but it would also be represented by the movement of one needle first to the right and then four times to the left. In like manner B is represented on the five-needle instrument by the first needle moving to the right and the third from it to the left. By means of a single needle it could be represented by one movement to the right and three to the left; and so on with the other letters. Experience has suggested that the alphabet could be represented by fewer movements than those practically exhibited by the five-needle instrument; but it is obvious that a few weeks’ working of the five-needle instrument—and not a flood in the Thames—was sufficient to show that the movements of needles, without a dial or a printed alphabet, could be made to convey intelligence. This is no mere speculation. More than this was in actual operation on the Blackwall Railway; for in a contemporaneous account it is stated that the wires run all along the line inclosed in a metal tube, and the arrangement is such that whenever a particular index deviates to the right or left at the Minories Station, an index deviates to the right or left at all the other stations at the same instant. “If then,” says the contemporary writer, “a preconcerted alphabet, or key, or dictionary, or table of signals be agreed on, the relative positions of two or more index-hands will serve to convey a message. By the side of the telegraphic case a large chart is hung up, containing about a hundred sentences, instructions or questions, each of which is symbolled by a particular position of two or three index hands. Thus one position, capable of being effected by two movements of the handles, implies, ‘Will the next train wait for the next steam-boat?’ Another implies, ‘Will the steam-boat wait for the next train?’ And others: ‘How many passengers?’ ‘How many carriages?’ and various inquiries and directions relating to the engines, the ropes, the telegraphs, and the steam-boats which start from and arrive at Blackwall.” The writer added that by employing the combined simultaneous motion of three or four needles, the five-wire telegraph would afford nearly 200 signals, besides those appropriated to the alphabetic characters.

It thus appears that the idea of making the deviations of a needle represent messages or letters was not only obvious but in daily use. Yet the erroneous traditions that already envelop the infancy of this telegraph do not end here. The contemporaneous account just quoted concludes with the remark that a telegraph like that used on the Blackwall Railway and the Great Western Railway, if consisting merely of three needles and giving only twelve signs, has a power of combination fully equal to the semaphore then in use; and in recent years it has been represented by persons of authority in the telegraph world that the double-needle instrument formed the transition stage from five needles to one. Hence the single-needle instrument has generally been regarded as a gradual improvement of the parent instrument of five needles. But the fact is that both the single and double-needle instrument were minutely described in one and the same patent taken out in 1845. In that description, which would fill a chapter of this book, Professor Wheatstone was more careful to explain the advantages of the single than of the double-needle instrument. He expressly disclaimed any intention to lay down a particular signification to the signals by which the alphabet could be represented; he merely gave illustrations to show how easily a sufficient variety of signals could be obtained. At the same time he gave an alphabet of signs suitable for a single-needle instrument, and although experience has suggested a more convenient combination of signals, it is on record that within a year or two after the patent for the single and double-needle telegraphs was taken out, the single-needle instrument was tried on some of the railway lines, and the alphabet of signals used was that which the five needle instrument suggested, with slight modifications. The single needle, however, was considered deficient in rapidity; and consequently to obtain greater speed the double-needle instrument was preferred. One of the first lines to adopt it was the South Western; it soon came to be regarded as the most rapid means of telegraphing; and hence it came into general use. It maintained its supremacy in England till more expeditious instruments were invented, and then it was gradually superseded by the single-needle instrument, which was found to be more accurate and economical. Now the single-needle instrument may be seen at most railway stations and rural post offices in the United Kingdom. In this instrument the needle when moved by a current to the right hand or the left, strikes against a projecting pin placed on each side to arrest its motion; the sender by moving a handle can deflect the needle at will either to the right or the left; one deflection to the left and one to the right represents A; one to the right and three to the left B; one to the right, one to the left, another one to the right and another to the left C; one to the right and two to the left D; and so on. None of the twenty-four letters of the alphabet has more than four deflections. While E has one to the left, I has two, S three, and H four. T has one to the right, M two, O three, and Ch. four.