PROFESSOR WHEATSTONE.
CHAPTER I.
“Talent may follow and improve; emulation and industry may polish and refine; but genius alone can break those barriers that restrain the throng of mankind in the common track of life.”—Roscoe.
The saying is as old as Lucretius that time by degrees suggests every discovery, and skill evolves it into the regions of light and celebrity; thus in the various arts we see different inventions proceed from different minds, until they reach the highest point of excellence. The electric telegraph is sometimes mentioned as one of the latest illustrations of this theory of evolution. One of its first inventors, Steinheil, defined telegraphic communication, in its most general sense, as the method employed by one individual to render himself intelligible to others; and regarding it in that light as synonymous with intercourse, declared that it was no human discovery, but one of the most wonderful gifts of nature. In man, he said, this gift of nature has attained an astonishing development in the form of speech and writing; and as writing redeems the passing sounds from fleeting time, so in like manner are the remotest distances to be annihilated and thoughts to be interchanged with those far away; “the means of accomplishing this do not lie directly within our reach, but by patient observance of the powers and the phenomena of nature, we render these subservient to us and make them the bearers of our thoughts; and it is this task which in the ordinary acceptation of the word is termed telegraphic communication.” Such was the philosophic view of the nature of the electric telegraph propounded by Steinheil in 1838 when it was in nonage, and later writers have not hesitated to say that the idea of using the transmission of electricity to communicate signals is so obvious as hardly to deserve the name of an invention. But the fact is that this “idea” was in existence for two centuries before it could be turned to good account, because the one thing wanting in order to utilise it was an invention.
In 1617, Strada, in one of his prolusions published at Rome, mentioned the possibility of one friend communicating with another at a great distance by means of a loadstone so influencing a needle on a dial containing the letters of the alphabet as to make it point to the letters intended to form the communication. The same idea was recorded in 1669 by Sir Thomas Browne, who stated that this conceit was widespread throughout the world, and that credulous and vulgar auditors readily believed it, while the more judicious and distinctive heads did not altogether reject it. “The conceit,” he said, “is excellent, and if the effect would follow, somewhat divine: it is pretended that from the sympathy of two needles touched with the same loadstone and placed in the centre of two rings with letters described round about them, one friend keeping one and another the other, and agreeing upon the hour wherein they will communicate, at what distance of place soever, when one needle shall be removed unto another letter, the other, by wonderful sympathy, will move unto the same.” Dr. Johnson, in his Life of Sir Thomas Browne, says that “he appears indeed to have been willing to pay labour for truth. Having heard a flying rumour of sympathetic needles, by which, suspended over a circular alphabet, distant friends or lovers might correspond, he procured two such alphabets to be made, touched his needles with the same magnet, and placed them upon proper spindles; the result was that when he moved one of his needles, the other, instead of taking by sympathy the same direction, ‘stood like the pillars of Hercules.’ That it continued motionless will be easily believed; and most men would have been content to believe it without the labour of so hopeless an experiment.”
The prevalence of this “idea” on the Continent is shown by the following passage which appeared in a book of Mathematical Recreations by Schwenter, published in 1660:
“If Claudius were at Paris and Johannes at Rome, and one wished to convey some information to the other, each must be provided with a magnetic needle so strongly touched with the magnet that it may be able to move the other from Rome to Paris. Now suppose that Johannes and Claudius had each a compass divided into an alphabet according to the number of letters, and always communicating with each other at six o’clock in the evening; then (after the needle had turned round three and a half times from the sign which Claudius had given to Johannes), if Claudius wished to say to Johannes—‘Come to me,’ he might make his needle stand still, or move it till it came to c, then to o, then to m, and so forth. If now the needle of Johannes’ compass moved at the same time to the same letters, he could easily write down the words of Claudius and understand his meaning. This is a pretty invention; but I do not believe a magnet of such power could be found in the world.”
Addison, in the Spectator of 1711, called attention to the “idea” of Strada, and like Dr. Johnson spoke of it as a chimera. It thus appears that the two greatest intellects in England in the eighteenth century, the former adorning its opening and the latter its closing years, treated with supreme contempt the “idea” that intelligence could be communicated to a distance by magnetised needles pointing to the letters of the alphabet on a dial. Yet in the next century this “idea” became an accomplished fact, and Charles Wheatstone did more than any other man to make it an every day occurrence. Hence his name in England has been most prominently associated with the invention of the electric telegraph. Many able men had tried to solve the problem before him, but had not succeeded. Yet that which our wisest forefathers regarded as chimerical, and scientists of different nations laboured for in vain, we are now told was so obvious and simple as scarcely to deserve the name of an invention.
The electric telegraph claims a long pedigree. One of the first attempts to transmit signals through a wire by means of electricity was made in 1727 by Stephen Gray, a pensioner of the Charterhouse. He connected a glass tube with the end of a wire 700 feet long, and by rubbing the tube the wire became so electrified as to attract light bodies at the other end. He also discovered that a wire loop should not be used to fasten up his conductor, because such a loop not being an insulator the electricity escapes through it. His observations were written down by the Secretary to the Royal Society the day before his death. He stated that “there may be found a way to collect a greater quantity of electrical fire, and consequently to increase the force of that power, which by several of these experiments seems to be of the same nature with that of thunder and lightning.” Similar experiments were made a few years afterwards by Winkler of Leipsig, Lemonnier of Paris, and Watson in London, Franklin at Philadelphia, and De Luc at the Lake of Geneva.
In 1753 a definite scheme of telegraphic communication was published. In the Scots Magazine for February appeared a letter from a Renfrew correspondent, who signed himself C. M., on “An Expeditious Method of Conveying Intelligence.” This writer said: “Let a set of wires equal in number to the letters of the alphabet be extended horizontally between two given places; at the end of these wires let balls be suspended against a glass sheet, and the wires striking the glass, these balls would drop upon an alphabet arranged upon the table, and thus by a spelling method, communication could be made of words.”
In a book published in 1792, Mr. Arthur Young, who travelled in France in 1787, stated that “a very ingenious and inventive mechanic,” M. Lomond, had made a remarkable discovery in electricity: “You write two or three words on a paper; he takes it with him into a room and turns a machine inclosed in a cylindrical case, at the top of which is an electrometer, a small fine pith ball; a wire connects with a similar cylinder and electrometer in a distant apartment; and his wife by remarking the corresponding motions of the ball, writes down the words they indicate; from which it appears that he has formed an alphabet of motions. As the length of the wire makes no difference in the effect, a correspondence might be carried on at any distance. Whatever the use may be, the invention is beautiful.”
Twenty years after the publication of the letter of C.M. in the Scots Magazine, Le Sage of Geneva endeavoured to work a telegraph by means of twenty-four wires with a pair of pith balls attached to each, thus representing the letters of the alphabet. By the use of frictional electricity any of the balls at one end of the wire could be moved by the operator at the other end, but it was found difficult to get the balls after being electrified to resume their respective places. To overcome this difficulty, and also to produce the requisite number of signals with fewer wires, experiments were afterwards made by different men on the Continent, and notably by Ronalds in England. This experimenter erected a wire eight miles long in his garden at Hammersmith, and laboured for seven years to solve the problem of telegraphy with frictional electricity. He used a dial containing letters and figures, and the collapsing or diverging of a pith ball was to correspond with the desired letter. He offered this telegraph to the Government, who informed him in reply, that “telegraphs of any kind are now wholly useless, and no other than the one now in use will be adopted.” In a book which he wrote in 1823 he described a complete system of telegraph, and expressed the hope that he would see the day when the King at Brighton would be able to communicate by telegraph with his ministers in London. Both his plan and his book were neglected, but his wishes for the success of the telegraph were abundantly fulfilled. In 1874 Mr. Gladstone conferred on him the honour of knighthood in recognition of his early efforts in connection with the telegraph. He died shortly afterwards at the patriarchal age of ninety-one.
The discovery of the Voltaic pile, described in a previous chapter, gave a fresh impulse to electricians, and eventually supplied the requisite kind of electricity for working a practical telegraph. So great was the sensation excited among the learned by the discovery of the Voltaic pile, that in 1801 Napoleon called Volta from Pavia to Paris, and attended a meeting of the Institute to hear the theory of the pile explained by its discoverer. There and then Napoleon caused a gold medal to be voted to Volta, and afterwards gave him a valuable present of money. Indeed it is said that the pile excited the enthusiasm of Napoleon more than any other scientific discovery. Volta was made a member of the French Institute in 1802, and in the same year was born the man whose name was destined to be for ever associated with one of the most useful applications of Voltaic electricity—the electric telegraph.
Charles Wheatstone was born at Gloucester in February 1802. His father was a music-seller in that town; and on removing afterwards to London he became a teacher of the flute, and was accustomed to boast that he had been engaged in connection with the musical education of the Princess Charlotte. His son, Charles, was educated at a private school in his native city. It is said that he early showed an aptitude for mathematics and physics; but not much is known of his youthful career. On his removal to London he became a manufacturer of musical instruments, the scientific principles of which formed with him the subject of profound studies. His practical ingenuity was displayed in the application of the scientific principles he discovered to new purposes, to the construction of philosophical toys and the improvement of musical instruments. “In 1823,” says a friend of his who wrote a notice of him in the Proceedings of the Royal Society, “at the age of twenty-one, we find him in conjunction with his brother, long since deceased, engaged in the manufacture and sale of musical instruments in London.” But there is unquestionable evidence of his having obtained distinction in London by his ingenuity at the age of nineteen.
Of his first notable achievement in London the following curious account was given in September, 1821, in the leading literary journal of that time: “We have been much gratified,” said the writer, “with an exhibition in Pall Mall of an instrument under the denomination of the enchanted lyre, the invention of a Mr. Wheatstone. The exhibition room presents a work of handsome construction in the form of an ancient lyre suspended from the ceiling. Its horns terminate in mouths resembling bugles. Its centre is covered on both sides with plates of a bright metallic lustre, and there is an ornamented keyhole, like that of a timepiece, which admits of its being wound up, but which is evidently a mere ruse, as the instrument certainly does not utter melodious sounds in consequence of that operation. Round it there is a slight hoop-rail, perhaps five feet in diameter, which is supported by equally slight fixtures in the floor. The inventor disclaims mechanism altogether (though he winds up the machine) and asserts that the performance of the enchanted lyre is entirely the result of a new combination of powers. Be that as it may, its execution is both brilliant and beautiful. The music seems to proceed from it; the tones are very sweet; the expression soft or powerful, and the whole really charming. We listened to Steibelt’s battle-piece with unfeigned pleasure, and were equally delighted with several other compositions of simple melody and of more difficult harmony. Mr. Wheatstone professes to be able to give a concert, producing by the same means an imitation of various wind and stringed instruments; the lovers of music will have a treat in hearing the enchanted lyre go through a half hour’s entertainment.”
Another contemporary account is more prescient, if not amusing. On the 1st of September, 1821, it was reported in the Repository of Arts that “Under the appellation of the enchanted lyre Mr. Wheatstone has opened an exhibition at his music shop in Pall Mall, which has excited considerable sensation among the votaries of the art. The form of a lyre of large dimensions is suspended from the ceiling apparently by a cord of the thickness of a goose-quill. The lyre has no strings or wires, but these are represented by a set of metal or steel rods, and it is surrounded by a small fence. The company being assembled, Mr. Wheatstone applies a key to a small aperture, and gives a few turns representative of the act of winding up, and music is instantly heard, and apparently from the belly of the lyre. The sceptical he invites to stoop under the fence, and hold their ears close to the belly of the lyre; and they, including ourselves, are compelled to admit that the sound appears to be within the instrument; but while making this admission, the attentive auditor is instantly convinced that the music is not the effect of mechanism (a fact indeed which Mr. Wheatstone not only concedes, but openly avows, even in his notice). It is quite obvious that the music is produced by a skilful player, or perhaps two, upon one or more instruments. The music seems to proceed from a combination of harp, pianoforte, and dulcimer; it certainly at times partakes of the character of these three instruments; and in point of tone, the difference sometimes is considerably in favour of the lyre; the piano and forte appear more marked, the crescendo is extremely effective, and the forte in the lower notes is inconceivably powerful in vibration. The performance lasts an hour: various pieces of difficult execution are played with precision, rapidity, and proper expression.”
“It is evident that some acoustical illusion, effected through a secret channel of some sort or other, is the cause of our hearing the sound in the belly of the lyre.... How then is sound thus conducted so as to deceive completely our sense of hearing? This seems to be the only question that can suggest itself on witnessing this singular experiment; it is a secret upon which Mr. Wheatstone rests the interest and merit of this invention; and to this question, no one, as far as we can learn, has yet been able to return an answer that could solve every difficulty. It is really a very ingenious invention, which the proprietor as yet wishes to keep a secret. It may be proper to add that Mr. Wheatstone represents the present exhibition to be an application of a general principle for conducting sound, which principle he professes himself to be capable of carrying to a much greater extent. According to his statement, it is equally applicable to wind instruments; and the same means by which the sound is conducted into the lyre will, when employed on a larger scale, enable him to convey in a similar manner the combined strains of a whole orchestra. This promised extension of the principle of conducting musical sounds from one place to another gives rise to some curious reflections on the progress which our age is constantly making in discoveries and contrivances of every description. Who knows but by this means the music of an opera performed at the King’s Theatre may ere long be simultaneously enjoyed at Hanover Square Rooms, the City of London Tavern, and even at the Horns Tavern at Kennington, the sound travelling, like gas, through snug conductors, from the main laboratory of harmony in the Haymarket to distant parts of the metropolis; with this advantage, that in its progress it is not subject to any diminution? What a prospect for the art, to have music ‘laid on’ at probably one-tenth the expense of what we can get it ourselves! And if music be capable of being thus conducted, perhaps words of speech may be susceptible of the same means of propagation. The eloquence of counsel, the debates in Parliament, instead of being read the next day only—But we really shall lose ourselves in the pursuit of this curious subject.”
It has been said that the death of mystery is the grave of interest. Nevertheless, Charles Wheatstone did not keep secret the means by which this mysterious music was produced. In 1823 he contributed a paper to Thomson’s Annals of Philosophy in which he described the remarkably simple and original experiments that led him to the invention of this apparatus, and explained how molecular vibrations produced sound. With reference to phonic vibrations in linear conductors he said: “In my first experiments on this subject I placed a tuning-fork at the extremity of a glass or metallic rod five feet in length communicating with a sounding-board. The sound was heard as instantly as when the fork was in immediate contact, and it immediately ceased when the rod was removed from the sounding-board or the fork from the rod. From this it is evident that vibrations inaudible in their transmission, being multiplied by meeting with a sonorous body, become very sensibly heard. Pursuing my investigations on this subject, I discovered means of transmitting, through rods of much greater length, and of very inconsiderable thickness, the sounds of all musical instruments dependent on the vibrations of solid bodies and of many descriptions of wind instruments. One of the practical applications of this discovery has been exhibited in London for about two years under the appellation of the ‘Enchanted Lyre.’ So perfect was the illusion in this instance from the intense vibratory state of the reciprocating instrument and from the interception of the sounds of the distant exciting one, that it was universally imagined to be one of the highest efforts of ingenuity in musical mechanism.” It is a noteworthy evidence of the interest evoked by this article that it was reproduced in the leading French and German publications of that year.
This “Enchanted Lyre” has since been described by Mr. W. H. Preece as the first telephone. It was exhibited, he says, “to delighted crowds at the Adelaide Gallery; it was often used by Prof. Faraday, and has frequently since been produced by Prof. Tyndall at the Royal Institution. A large special box was placed in one of the cellars of the Institution, and a light rod of deal rested upon it. No sound was heard in the theatre until a light tray or other sounding-box was placed on the rod, whereupon its music pealed forth over the whole place. The vibrations of the musical box, with all their complexity and beauty, are imparted to the rod of wood and are thence given up to the sounding-box. The sounding-box impresses them upon the air, and the air conveys them to the ear, whence they are transmitted to the brain, imparting those agreeable sensations called music.”
Wheatstone’s invention of the Enchanted Lyre or the “first telephone” was no accidental discovery or lucky idea: it was the result of a profound and original investigation of the scientific principles of sound. He discovered and demonstrated by numerous experiments that sound was produced by the vibrations of the atmosphere; and in 1823 when he announced for the first time that “the loudness of sound is dependent on the excursions of the vibrations, volume or fulness of sound on the number of the coexciting particles put in motion,” he stated that he had just seen Fresnel’s paper, in which the same conclusions were arrived at with respect to light as he (Wheatstone) had proved with respect to sound. He added that “the important discoveries of Dr. Thos. Young have recently re-established the vibratory theory of light, and new facts are every day augmenting its probability. The new views in acoustical science which I have opened will, I presume, give additional confirmation to the opinions of these eminent philosophers.” Prophetic words!
The analogy between sound and light as results of wave-motions in air or ether is now part of the alphabet of science. Charles Wheatstone made an independent discovery of the principles of sound; but in this he was partly anticipated by Young. Nor was he alone in the original and practical experiments by which he demonstrated their accuracy. At the time he made these experiments (he was then only twenty years old), he thought he was the first who had indicated the phenomena of sound in that way; but Professor Oerstead, of Copenhagen, on seeing him perform these experiments, informed him of some similar ones he had previously made.
In the middle of the year 1827 he invented a small instrument consisting of a steel rod on the top of which a glass silvered bead was placed. By concentrating on it an intense light and making the rod to vibrate, beautiful forms were created. In this respect this philosophical toy resembled the Kaleidoscope which Brewster invented; and it was therefore called the kaleidophone. There is, however, no similarity between the construction or mode of action of the two instruments. In 1828 he devised the terpsiphone which made music by the reciprocal vibrations of columns of air. In 1833 he contributed to the Royal Society a paper on acoustic or Chladni figures, so called because Chladni in 1787 showed that by strewing sand on vibrating surfaces, and then throwing the particles into vibration by means of a violin bow, beautiful and varied symmetrical figures could be produced. Wheatstone showed that all the figures of vibrating surfaces result from very simple modes of vibration, oscillating isochronously, and superposed upon each other, the figures varying with the component modes of vibration, the number of the superpositions, and the angles at which they are superposed.
As indicating the variety of subjects that engaged his attention about the same time, a fact recorded by a friend may be quoted here. At one period Wheatstone’s attention was for a time directed to problems of mental philosophy, and especially to the quasi-mechanical solution of them which was hoped for by the followers of Gall and Spurzheim; he was an active member of the London Phrenological Society, then presided over by Dr. Elliotson, and in January 1832 he read a paper at one of the meetings on dreaming and somnambulism, which was published in extenso in the Lancet of that date. This paper is remarkable like all his writings for the extreme clearness with which known facts are stated and the deductions based upon them.
Another subject which occupied his attention for some years was the construction of speaking-machines, upon which he made certain improvements, and of which he wrote a short and interesting history. He declared in 1837 that the advantages which would result from the completion of a speaking-machine rendered the subject worthy of the attention of philosophers and mechanicians; and he endorsed a remark of Sir D. Brewster that before another century was complete a talking and singing machine would doubtless be numbered among the conquests of science.
In a paper which he communicated to the Journal of the Royal Institution in 1831 “On the Transmission of Musical Sounds through solid Linear conductors and on their subsequent Reciprocation,” he gave an account of some experiments that evolved a principle now found to be next in importance to that of the telegraph. He said: “I believe that previous to the experiments which I commenced in 1820, none had been made on the transmission of the modulated sounds of musical instruments, nor had it been shown that sonorous undulations, propagated through solid linear conductors of considerable length, were capable of exciting in surfaces with which they were in connection a quantity of vibratory motion sufficient to be powerfully audible when communicated through the air. The first experiments of this kind which I made were publicly exhibited in 1821; and on June 30th, 1823, a paper of mine was read by M. Arago at the Academy of Sciences, in which I mentioned these experiments, and a variety of others relating to the passage of sound through rectilinear and bent conductors. I propose in the present instance to give a more complete detail of these experiments.” He then proceeds to give an account of the experiments he had made during the intervening ten years, and concludes by saying: “As the velocity of sound is much greater in solid substances than in air, it is not improbable that the transmission of sound through solid conductors, and its subsequent reciprocation, may hereafter be applied to many useful purposes. Sound travels through the air at the rate of 1,142 feet in a second of time, but it is communicated through iron, wire, glass, or wood with a velocity of about 18,000 feet per second, so that it would travel a distance of 200 miles in less than a minute.... Should any conducting substance be rendered perfectly equal in density so as to allow the undulations to proceed with uniform velocity without any interference, it would be easy to transmit sounds through such conductors from Aberdeen to London, as it is now to communicate from one chamber to another. The transmission to distant places of a multiplication of musical performances are objects of far less importance than the conveyance of the articulations of speech. I have found by experiment that all these articulations, as well as the musical inflections of the voice, may be perfectly, though feebly, transmitted to any of the previously described reciprocating instruments, by connecting the conductor either immediately with some part of the neck or head contiguous to the larynx, or with a sounding-board, to which the mouth of the singer or speaker is closely applied.” Nearly half a century elapsed before these observations found their full application in the telephone and microphone.
It may be here noted that in a paper on experiments in audition published in 1827 Wheatstone said: “The great intensity with which sound is transmitted by solid rods at the same time that its diffusion is prevented, affords a ready means of augmenting the loudness of external sounds and of constructing an instrument which, from its rendering audible the weakest sounds, may with propriety be named the microphone.” It is said that that was the first time the word microphone was ever used; and it was the name given in 1878 to an instrument which has since come into general use as the complement of the telephone, the microphone being the best adapted for sending spoken messages by electric wire, and the telephone the best for receiving them.
Concurrently with these scientific studies, his practical powers as an inventor were being advantageously exercised in the improvement of musical instruments, old and new. In a communication to the Royal Institution in February, 1828, he gave an account of a Javanese musical instrument called the Génder, which was brought to England by the late Sir S. Raffles, and in which “the resonances of unisonant columns of air” were used to augment the sounds of the vibrations of metallic plates. A hollow bamboo of a certain length was placed perpendicularly under each metallic plate which, being struck and made to vibrate, produced a deep, rich tone by the resonance of the column of air within the bamboo. He then stated that, though other rude Asiatic and African instruments made use of the same principle, he did not know of its being used in any European instrument; and he therefore promised to publish soon an account of several methods which he had devised for utilising the resonance of columns of air. About two months afterwards his attention was called to a newly-invented German instrument which made use of that principle. It was called the Mund Harmonica; and, as the name implies, music was produced in it by placing the mouth over some small metallic tongues or springs and blowing upon them so as to cause them to vibrate; “these vibrations produced so many impulses upon the current of air and thus caused sound.” This instrument is now best known as a child’s toy. It was soon improved in Germany into a primitive kind of accordion, in which keys were placed over the metallic tongues, and the requisite current of air to vibrate them when the keys were opened was produced by compressing a kind of bellows, which formed the body of the instrument. This was the most simple form of wind instrument; and Charles Wheatstone soon increased its range and facilitated its manipulation. His improvements consisted in the employment of two parallel rows of finger studs or keys on each end, and in so placing them with respect to their distances and positions as that they might, singly, be progressively and alternately touched or pressed down by the first or second fingers of each hand without the fingers interfering with the adjacent studs, and yet be placed so near together as that any two adjacent studs might be simultaneously pressed down when required by the same finger; the peculiarity and novelty of this arrangement consisted in this, that whereas in the ordinary keyed wind musical instrument then in use the fingering was effected by a motion sideways of the hands and fingers, in the new arrangement that mode of fingering was rendered entirely inapplicable: and he made available a motion not previously employed, namely, the ascending and descending motions of the fingers. By this method of arranging the studs he was able to bring the keys much nearer together than had been done previously, and the instrument was made more portable. He also introduced two additional rows of finger studs on each end of the instrument for the purpose of introducing semitones when required. In other words, he invented the concertina, the first patent for which was dated June 19th, 1829, under the title of improvements in the construction of wind-musical instruments.
The accordion, (said to have been invented at Vienna by Damian in 1829,) is described by the best musical authorities as little more than a toy in comparison with the concertina. Indeed, the concertina is one of the few musical instruments distinguished for sweetness and compass, that is known to be the exclusive invention of one man. Music intended for the oboe, flute, and violin, can be played on it; while the only other instruments upon which music written for the concertina can be played, are the organ and harmonium. Nothing, says Dr. Grove, but the last-named instruments can produce at once the extended harmonies, the sostenuto and the staccato combined, of which the concertina is capable. The origin of the organ is lost in the myths of antiquity, and it has been the subject of improvements during the last 500 years. The harmonium is an evolution of the present century, and has been brought to its present state by the combined improvements of several musical men, including Charles Wheatstone. But of the concertina he was the sole inventor; and if it be true that the unknown man (or rather men) who invented the fiddle was a greater genius than the inventor of the steam-engine, surely the invention of the concertina was no mean achievement. Certainly it was not an instant achievement. Its perfection appeared to be a work of time; for in 1844 he took out another patent for improvements, consisting of (1) the arrangement of the touches or finger-stops which regulate the opening of the various valves covering the apertures in which the springs or tongues vibrate; (2) a mode of obtaining a different degree of loudness for each side of the concertina independently by applying a partition to divide the bellows into two parts; (3) a mode of arranging and constructing the cavities in which the tongues or spirals are placed, by which a bass concertina may be made of more portable dimensions than by the mode of arrangement usually adopted in the treble concertina; (4) a mode of constructing concertinas whereby the same tone or spring is made to sound whether the wind be driven into or out of the bellows, namely, by means of a double passage valve applied to each tongue separately; (5) a mode of varying at pleasure the pitch of the concertina by apparatus capable of altering the effective length of its tongues or springs; (6) an arrangement of the lever or support of the key or apparatus for admitting the wind to act upon the tongue of the concertina; (7) a mode of applying apparatus to sting a tongue or spring into vibration in addition to the wind on that tongue; and (8) of modifying or ameliorating the tone of a freely vibrating tongue or spring by means of the resonance of a column of air in a tube tuned in unison with it, the tube being so placed that the free air shall intervene between its open end and the tongue or spring.
In connection with this subject, it should be added that he made important improvements in the harmonium when it might be said to be in its infancy. Without going into details, suffice it to say that at the Great Exhibition of 1851 he exhibited the portable harmonium, which the jury on musical instruments described as quite original in all its mechanical parts. It had a compass of five octaves, and although the keyboard was of the same extent as in the larger harmoniums, the instrument could be instantly folded up so as to occupy less than half its height and length. The jury, in awarding the inventor a prize medal, said the portable harmonium was peculiarly constructed for producing expression, and might either be used by itself for the performance of music written for the organ or harmonium, or for taking violin, flute, or violoncello solos or parts—its capabilities of expression giving it great advantages in imitating these instruments.
In 1834 he was appointed Professor of Experimental Physics in King’s College, London; and as such he delivered in the following year a course of eight lectures on Sound; but while retaining the professorship, he soon discontinued lecturing because of his invincible distrust of his own powers as a speaker.
About the same time he gave to the world what, in order of time, might be described as the first fruits of his studies in electricity, and what, in point of originality, many electricians have described as his most brilliant discovery. In 1831 Professor Faraday told the Royal Institution of the method by which the silent philosopher proposed to ascertain the velocity of the electric spark; and in 1834 he himself contributed to the Philosophical Transactions “An account of some experiments to measure the velocity of electricity and the duration of the electric light.” It has been repeatedly said that this one experiment was enough to render his name immortal in the annals of science. The velocity of electricity is so great that it was believed there was no means on earth capable of measuring it. This desideratum Professor Wheatstone supplied. He devised means by which a small mirror was made to revolve at the immensely rapid rate of 800 times in a second, and in front of it placed half a mile of insulated copper wire, on the ends and in the middle of which were fixed brass balls intended to interrupt a current of electricity sent through the wire. On connecting the ends of the wire with a Leyden jar, he saw three sparks—one was at each end as the electricity left the jar, the other was at the brass balls in the middle of the wire. The one end of the wire was connected with the inner coating of the jar charged with positive electricity, while the other end of the wire was attached to the outer coating, which had negative electricity, so that at the moment of contact the electricity passed from each end of the wire in order to find an equilibrium. The middle of the wire, however, was cut, and had a small brass ball at each end, distant one-tenth of an inch; and when the two currents of electricity reached that interruption the middle spark was produced. These sparks were reflected by the rapidly revolving mirror; and he had the wire so arranged that if the three sparks were simultaneous, the mirror would show them in parallel straight lines. But they evidently were not simultaneous, for the middle one appeared a little later than the other two; the revolving mirror had in the interval moved round a minute distance, thus showing the reflection of the middle spark behind the others. The interval between the sparks was found to be the one millionth part of a second, and their appearance on the mirror, as it revolved, supplied data as to the rate at which the current moved, from which it was easily calculated that the velocity of electricity is 288,000 miles a second. Thus, it was said, he forced the lightning to tell how fast it was going. This experiment, which was originally made in his lecture-room at King’s College, and with the result of which he was much delighted, instantly spread his name throughout the civilised world as the discoverer of one of Nature’s greatest secrets.[6] The original apparatus used for that purpose was also used at the Royal Institution in 1856, to illustrate the instantaneous duration of a spark. It was ascertained that the duration of a spark does not exceed the twenty-fifth thousandth part of a second; it was explained that a cannon ball, if illuminated in its flight by a flash of lightning, would, in consequence of the momentary duration of the light, appear to be stationary; and that even the wings of an insect moving 10,000 times in a second would seem at rest.
With regard to the scientific value of the revolving mirror, M. Dumas said in 1875: “This admirable method enabled Arago to trace with a certain hand the plan of a fundamental experiment which should decide whether light is a body emanating from the sun and stars, or the undulating movement excited by them. Executed by the accomplished experimentalist, it proved that the theory of emission was wrong. This method has then furnished to the philosophy of the sciences the certain basis on which rest our ideas of the nature of force, and especially that of light. By means of this or some other analogous artifice, we can even measure the speed of light by experiments purely terrestrial, which, pursued by an able physicist, have guided the measure of distance between the earth and the sun.”
Professor Wheatstone himself suggested that the velocity of light might be measured in the same way as electricity. In July, 1835, he told the Royal Society that he proposed to extend his experiments on the velocity of electricity to measure the velocity of light in its passage through a limited portion of the terrestrial atmosphere. It may be added that the complete solution of the velocity of light by the revolving mirror, although the subject of elaborate experiments by Arago, was facilitated by some improvements made in the apparatus by later experimenters.
The mirror has been used in different ways for the measurement of light. In 1850, Arago gave a description of his attempts to determine its velocity, but failing eyesight prevented him carrying out his full design. The subject was, however, taken up by M. Fizeau and M. Foucault, who employed steam power instead of clockwork to give motion to the mirror. By Foucault’s method a beam of light was reflected from a revolving mirror to a fixed concave mirror, and before it was reflected back again the revolving mirror had moved a sufficient space to enable him to compute therefrom the velocity of light. Fizeau’s method was simpler. He made a toothed wheel revolve with great rapidity, while a beam of light passed through one of the open spaces between the teeth, and fell upon a reflecting mirror at a considerable distance away. If the wheel were at rest, the beam would be reflected back through the same space by which it had entered; but the wheel being in rapid motion, the reflected beam would either fall on the next tooth which would prevent it passing through, or if the motion were increased, it would get through the next opening. A variety of tests like these has given the velocity of light as about 187,000 miles per second.
Professor Wheatstone also rendered memorable service in connection with the development of spectrum analysis. In a paper which he communicated to the Dublin meeting of the British Association in 1835, on “The Prismatic Analysis of Electric Light,” he expounded a discovery which has since led to useful results. Most metals, such as iron, copper, and platinum, when exposed to the gas flame, impart no colour; for that purpose they must be subjected to a higher temperature; and Professor Wheatstone found that the best way of attaining the requisite temperature was by the use of the electric spark. He found that a single electric discharge passed through a gold wire at once dissipated the metal into vapour. He also showed that by looking through a prism at the spark proceeding from two metallic poles, the spectra seen contained bright lines which differed according to the kind of metal employed. “These differences,” he said, “are so obvious that any one metal may instantly be distinguished from others by the appearance of its spark, and we have here a mode of discriminating metallic bodies more ready than chemical examination, and which may hereafter be employed for useful purposes.” Hofmann has well said that “within this fact a new mode of distinguishing bodies from each other lay folded, like the tree within the seed, awaiting evolution. The new line of research thus opened by Wheatstone with reference to bright lines produced by electric discharges, was pursued in a variety of directions by several observers. Foucault (1849), Masson (1851-55), Angström (1853), Alter (1854-55), Secchi (1855), Plückar (1858-59), Bunsen and Kirchhoff (1860), were successively engaged in this inquiry. It would exceed the limits of this sketch to minutely describe the phenomena presented by the spectra of the known metals, or to dwell on the infinitely minute quantities of substances found to be capable of producing the effect. The extreme delicacy of the new process is now a familiar fact; and it is equally well known that in using this method, the presence of one metal scarcely interferes with that of another. It would be out of place here to do more than simply mention the astronomical applications of spectrum analysis; such as, for example, the determination by its means of the composition of the solar atmosphere, in which M. Kirchhoff has proved, with a degree of probability approaching to certainty, the presence of several metals well known on this earth; amongst others potassium, sodium, calcium, iron, nickel, chromium, &c.” This delicate test has made it possible to detect the presence of the two hundred millionth part of a grain (in weight) of sodium, while by revealing bright lines not referable to any known body it has been the means of discovering five new metals—cæsium and rubidium by Professor Bunsen in 1860, thallium by Mr. Crookes in 1861, indium by Professors Richter and Reich in 1864, and gallium by M. Lecoq in 1875.
The year 1836 was distinguished in the history of electricity by the discovery of the constant battery of Professor Daniell. Early in that year Professor Daniell, of King’s College, announced in a letter to Faraday, that he had been led to the construction of a voltaic arrangement which furnished a constant current of electricity for any length of time, and had thus been able to remove one of the greatest difficulties which had hitherto obstructed those who had endeavoured to measure and compare different voltaic phenomena. This constant battery, which he improved in the spring of the same year, is still in general use. In it the zinc is placed in a semi-saturated solution of sulphate of zinc, and the copper in a saturated solution of sulphate of copper, the two solutions being separated by a porous earthenware partition. This battery furnishes a constant supply of electricity for weeks together.
Early in 1837 Professor Wheatstone publicly called attention to the capability of the thermo-electric pile as a source of electricity. Seebeck of Berlin discovered in 1822 that when different metals are soldered together and their junction heated, a current of electricity is generated; and Nobili and Melloni contrived on that principle the thermo-multiplier, an apparatus which indicates the effects of heat by the deflections of a needle on a scale, like a thermometer, the needle being moved by the electricity produced by the heat. But this means of producing electricity was better known for its delicacy than for its strength till Professor Wheatstone made some experiments—probably the first made in England—for the purpose of showing how the thermo-electric pile could be utilised as a source of electricity. In his account of these experiments he stated that “the Cav. Antinori, director of the Museum at Florence, having heard that Professor Linari, of the University of Siena, had succeeded in obtaining the electric spark from the torpedo by means of an electro-dynamic helix and a temporary magnet, conceived that a spark might be obtained by applying the same means to a thermo-electric pile. Appealing to experiments, his anticipations were fully realised. No account of the original investigations of Antinori had reached England in April, 1837; but Professor Linari, to whom he early communicated the results, published certain experiments and observations of his own on the subject in L’Indicatore Sanese for December 13, 1836.” The interesting nature of these experiments induced Professor Wheatstone to attempt to verify the principal results. For that purpose he used a thermo-electric pile consisting of 33 elements of bismuth and antimony formed into a cylindrical bundle ¾ of an inch in diameter, and 1⅕ in length. The poles of this pile were connected by means of two thick wires with a spiral of copper ribbon 50 feet in length and 1½ inch broad, the coils being well insulated by brown paper and silk. One face of the pile was heated by means of a red-hot iron brought within a short distance of it, and the other face was kept cool by contact with ice. Two short wires formed the communication between the poles of the pile and the spiral, and the contact was broken, when required, in a cup of mercury (a non-conductor) between one extremity of the spiral and one of these wires. Whenever contact was thus broken a small but distinct spark was seen. He added that Professors Daniell, Henry, and Bache assisted in the experiments, and were all equally satisfied of the reality of the appearance. At another trial the spark was obtained from the same spiral connected with a small pile of fifty elements, on which occasion Dr. Faraday and Professor Johnson were present, and verified the fact. By connecting two such piles together, so that similar poles of each were connected with the same wire, the spark was seen still brighter. He concluded by stating that such experiments supplied a link that was wanting in the chain of experimental evidence tending to prove that electricity, from sources however varied, is similar in its nature and in its effects; and that the effect thus obtained from the electric current originating in the thermo-electric pile might no doubt be easily exalted by those who had the requisite apparatus at their disposal, till it equalled the effect of an ordinary voltaic pile.
As Professor Wheatstone was not accustomed to write articles or to deliver lectures, it is not an easy matter to measure the extent of his knowledge at any particular time; but one more incident may be mentioned as indicating the range of his studies on electricity about this time. Between 1830 and 1835 William Snow Harris wrote several articles in the Nautical Magazine on the utility of fixing lightning conductors in ships. It was a popular impression then that pointed metal rods attracted lightning. Snow Harris contended, on the contrary, that damage to ships occurred not where good conductors were, but where they were not, and that such conductors could no more attract lightning than a watercourse could be said to attract water, which necessarily flowed through it at the time of heavy rains. He afterwards prepared a list of 220 ships of the British Navy which were struck and damaged by lightning between 1792 and 1846. In June, 1839, a committee of the Admiralty consulted Professor Wheatstone and Professor Faraday as to the safety of the continuous conductors advocated by Snow Harris. To that committee Professor Wheatstone stated that “it has been proved beyond all doubt that electricity follows the best conducting path which is open to it; and that when it finds a metallic road sufficient to conduct it completely, it never flies to surrounding bodies greatly inferior in conducting power. The experiments of M. de Romas, made in France, with the electrical kite, immediately after Franklin’s first attempt, might satisfy the most timid in this respect. Imagine, writes he to the Abbé Nollet, ‘that you see sheets of fire nine or ten feet long and an inch broad, which made as much or more noise than reports of a pistol. In less than an hour I had certainly thirty sheets of these dimensions, without counting a thousand others of seven feet and under. But what gives me the greatest satisfaction in this new spectacle is that the largest sheets were spontaneous, and notwithstanding the abundance of fire which formed them, they constantly followed the nearest conducting body. This constancy gave me so much security that I did not fear to excite this fire with my discharger, even when the storm was violent; and when the glass branches of the instrument were only two feet long I conducted wherever I pleased, without feeling the smallest shock in my hand, sheets of fire six or seven feet long, with the same facility as those of only six or seven inches.’ The wire of the kite was insulated, and the sparks were drawn by a metallic conductor held in the hand by means of an insulating handle, and communicating with the ground by a chain. The human body is known not to be one of the worst conductors; yet, because it was two feet further than a far more perfect one, it received none of the discharge, even though the conducting path were an interrupted one. The phenomenon to which the name of lateral explosion has been generally given was first observed by Henly, more than half a century ago, and has been subsequently experimented upon by Priestly, Cavallo, and more recently by Biot.” The committee attached the greatest weight to the opinion of Professor Wheatstone, which Faraday supported, and which was eventually adopted. Experiment and experience confirmed its accuracy.
At the time when he had attained such a recognised position as an electrician he was making progress in another field of electrical study in which he was destined to gain still greater eminence and to obtain more extensive and permanent results.