208 



NATURE 



\yu7ie 20, 1878 



CQabled to-night to bring before you the results of his labours, 

 and they have been labours indeed. For months and months he 

 has been working and straining at the ideas which at last he has 

 •elaborated into the microphone. 



Now the chief characteristic of the apparatus I am going to 

 introduce to you to-night is its great homeliness, its uncouth 

 roughness, and its absurd simplicity. With common nails, with 

 small pieces of wood, with halfpenny money-boxes, with plain 

 sealing-wax, with the ordinary apparatus which every child has 

 at its command, he has been able to attack nature in her strong- 

 hold — to ask her questions and receive back answers, and lay 

 bare to us facts and thoughts which, though they have existed 

 from time immemorial, are brought to light now for the first 

 time. 



Now, let us in the first place ask ourselves this question : 

 What is sound ? It is a very difficult question to answer in the 

 short time at my disposal ; but it is necessary that I should first 

 say something to you about the nature of sound, and then say 

 something about the nature of electricity, and show you how the 

 one can be converted into the other. 



Now, what is sound? While I am speaking to you I am 

 setting the air in this room into vibration. The air of this room 

 is composed of an infinite number of infinitely small molecules ; 

 every molecule is set in motion, and vibrates to and fro, back- 

 wards and forwards, like the bob of a pendulum, and between 

 my mouth and every one of the ears in this hall there is a rapid 

 but short excursion to and fro of every single molecule that 

 comprises the atmosphere of this room ; and it is the impinging 

 of these molecules against the drum of the ear that produces 

 that sensation called sound. But more than that, not only is 

 the air of this room in this marvellous state of motion, but every 

 piece of wood, every wall, every picture, everything in this 

 hall at this moment, is almost, I may say, alive, trembling away, 

 moving backwards and forwards, forming what are called sono- 

 rous vibrations. If the sound be loud enough, and the note 

 deep enough, we can distinctly feel these vibrations. Sound is 

 therefore the vibration in particular periods and particular phases 

 of matter. 



Now what is electricity ? Faraday, the greatest electrician 

 perhaps that ever lived, was asked that question, and he said the 

 more he studied electricity, the more he unravelled its mysteries, 

 the more mystified he became as to its cause and its origin ; 

 therefore it seems an act of impudence on my part or the part of 

 any one else to attempt to answer the question. What is electri- 

 city? But great strides have been made since the days of 

 Faraday ; we know a greal: deal mer* now of the internal mole- 

 cular action of bodies ; we know that light, and heat, and 

 sound are the mere action of those molecules of which matter 

 is composed, and we feel sure, from the facts brought to our 

 notice by the delicate apparatus of the present day, that electri- 

 city is simply a mode of motion, nothing more or less than the 

 simple play of the molecules of matter. The truth of this will 

 be made evident to-night by the wonderful connection which 

 exists between sound — which we know to be a mere mode of 

 vibration — and electricity, which will reproduce to us the 

 effects of sound. To make this evident to us we must have 

 a detector which will render apparent to us any electrical 

 action that shall result in sound, and it fortunately happens 

 that this marvellous telephone is an instrument of such ex- 

 treme delicacy that it has made us acquainted with currents 

 of electricity hitherto unknown, though their presence has been 

 suspected. The telephone which Prof. Hughes has employed 

 in his researches is as simple in its construction as all his other 

 apparatus. It consists of two rough pieces of board clamped 

 together. There is half the coil of an electro-magnet that 

 probably has been in his possession since his early experiments 

 to judge from its appearance. The magnet is a piece of steel 

 rod that has been magnetized. The wire used, and which he 

 has found extremely useful, is wire that was originally made 

 for very different purposes, viz., for ladies' bonnets, and in front 

 of this is placed a piece of ferrotype iron, well-known by those 

 who have experimented with the telephone. 



But what is the source of sound ? It was necessary in making 

 these experiments that he should have a source of sound. 

 His source of sound was a small mantelpiece clock of 

 French manufacture, which cost originally three or four francs. 

 It has been in use many years, and has been in many parts 

 of the world. It is repaired with great lumps of sealing- 

 wax, but nevertheless it has, or ought to have, a pendulum, 

 which gives a succession of beat?, and those beats form a 



source of sound. Now, with this source of sound, and his 

 beautiful scientific apparatus or detector, he started upon one 

 of Sir Wm. Thomson's discoveries, viz., that wires alter their 

 electrical condition when they are placed under strain. He 

 took a piece of wire, applied weight to it, connected the clock 

 with it, and heard nothing. He was not disconcerted, he 

 applied weight after weight till he reached the breaking strain 

 of the wire, and at the moment when the wire broke, he heard 

 a rush or sound which he thought was an indication of what he 

 was searching for, so he took the two ends of his wire and laid 

 them together, placed his source of sound above them, and to 

 his intense delight heard — what imagination perhaps assisted 

 him in believing to be — a tick. He thought he was on the right 

 track, and he then manufactured with a flat piece of brass for a 

 lever, a pin for an axle, sealing wax for cement, and black wax 

 for solder, and the uncovered bonnet wire for binding, a little 

 apparatus which enabled him to apply constant pressure to the 

 thing he was experimenting upon ; in fact, by this means, he 

 was enabled to produce what electricians call a "bad joint." 

 To his intense delight he found that with this bad joint he was 

 able to obtain sonorous effects. But this contrivance, simple as 

 it a ■•pears, was a great deal too elaborate and complicated for 

 his purpose, so he took two little nails — the little bright nails 

 so much used in France — laid them side by side, not touching 

 each other, and bringing the ends of the wire in contact with 

 them, and laying between, or across them, a third and similar 

 nail, he was able to reproduce, almost perfectly, the sound of 

 the clock, and more than that he began to get indications of the 

 sound or tone of the voice. He then useti chains ; he took my 

 gold chain and put it beneath his little compressor, and with 

 that we were able to speak with great ease. From that he tried 

 filings, and found with matter in a finely divided state, that -he 

 was able to reproduce all effects of sound. At last he made 

 little glass tubes about two inches long, filling them with white 

 bronze powder which artists use, which is a mixture of zinc 

 and tin, and he was able to exactly reproduce the tones of 

 the voice. But in his experiments with carbon he was able to 

 make what may be called quite an independent discovery. The 

 carbon he experimented with was the common carbon used by 

 artists in sketching their drawings, and this cai-bon he found to 

 be a non-conductor of electricity. The idea struck him that 

 this non-conductor of electricity might be made a conductor, 

 and by various processes he at last arrived at a plan of boiling 

 or heating this carbon in quicksilver. Carbon so heated in an 

 atmosphere of quicksilver itself becomes permeated through and 

 through with quicksilver, and by that means we get the mercury 

 subdivided into an infinitely fine state. Probably mercury in 

 this state as closely approaches the molecular as anything can do. 



Fig. I. 



There is no apparent indication of mercury"under the micro- 

 scope, and yet we know that the carbon has been mercurised, 

 because it is converted from a complete insulator into a con- 

 ductor, and it has a metallic ring when it falls. Now then, 

 having by these processes arrived at a substance which is remark- 

 ably sensitive to all the variations of the sound of the human 

 voice, his next task was to construct these things into such a 

 form as to make them telephonic transmitters. For that purpose 

 he brought to his aid a very cheap kind of apparatus, a half- 

 penny money-box ;- inside this he placed his carbon transmitter, 

 and as this discovery is not fenced in by fear of the patent or 

 any other law, I am quite sure you will be glad to know how 

 to make a Hughes transmitter. First he takes a piece of quarter- 

 inch board about two inches long and one inch broad, and he raises 

 upon that two thin brass bearings with a hole worked through 

 by means of a pin for the support of the axis. He then takes 

 a piece of carbon which has been mercurized about two inches 

 long, which has a pin cemented to it near its centre, and which 

 acts as an axis, and makes it into a lever. On the board he 

 places a small piece of carbon, similarly treated, and upon this 

 rests another similar sized piece of caibon, the two being con- 

 nected by a piece of paper. 



This is the end of one wire, and that the end of another 

 wire; and on this diagram the arrangements of the circuit 



