Lives of the electricians

by William T. Jeans

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.