yune 20, 1878] 



NATURE 



2C9 



are shown, s represents the source of sound, which I have 

 shown on the black board, u represents the battery, and T 

 the telephone. Now the battery is another remarkable speci- 



FlG. 2. 



men of scientific manufacture. Three little glass tumblers are 

 taken ; at the bottom of each a coil of copper wire is coiled 

 spirally. The copper wire is covered with a little sulphate of 

 copper. The tumbler is then filled with moistened clay, and 

 upon the top of the clay is placed a piece of scrap zinc. The 

 three cells are placed in a cigar-box. s is what is called the box- 

 transmitter. The tube-transmitter is shown on this diagram. 



^AA..^^^^ -^.-^ S-^ 



Fig. 3. 



A is a glass tube [about two inches long, and one quarter inch 

 in diameter, inside which several pieces of mercurised carbon 

 are inserted, touching each other with a pressure regulated by 

 a screw fixed to each end. In that drawing there are six pieces 

 of carbon, acting in this little transmitter ; here (pointing) there 

 are seven or eight, but that makes little difference, and the size 

 of the carbon appears to be of little consequence. He has 

 produced effects with carbon not larger than a pin's head. We 

 shall show this by and by, but rather than disturb the order of 

 these researches, I think it advisable in the next place to show 

 you how this principle has been carried a little farther to pro- 

 duce what he calls the "microphone." This apparatus, drawn 

 upon the board, is extremely sensitive. It will give evidence 

 of nearly every sound ; but in the microphone itself, which I 

 have here, this extreme sensitiveness is carried to a still fiurther 

 extent. In point of fact, this is a microphone; but in this 

 particular instance the pressure bearing between the two 

 carbons is regulated by a spring fixed in this way, and it is 

 so regulated that the transmitter is independent of any position 

 in which it may be held. It is free to be moved in any direc- 

 tion in consequence of the pressure of the spring, but in one 

 form of instrument this spring is dispensed with, and the 

 pressure between the carbons is reduced to its greatest sensi- 

 tiveness by making the two arms of this lever as short as pos- 

 sible. In the first machine he used, a piece of carbon was fixed 

 on the top of an upright board, and a smaller piece was fixed 

 down below. A cup-shaped hole was made in the upper piece 

 of carbon, and a similar one in the bottom piece. Resting in 

 these holes was a lozenge-shaped piece of carbon ; and this 

 lozenge-shaped piece of carbon rests with the greatest nicety 

 upon its lower support, and is just in that position of equili- 

 brium that the slightest atmospheric disturbance produces the 

 effects which we are now about to show you. I think it 

 desirable to tell you that you must not to-night expect distinct 

 articulation. We have made a violent effort to make these 

 experiments evident to you all. (Illustrations were given of 

 speaking, singing, &c., &c.) 



Now, the effects you have just heard have been produced by a 

 transmitter similar to that drawn on the board. We will now 

 repeat the effects with the machine on the table ; and in order 

 that you may judge of the effect — for Prof. Hughes desires 

 that you should see there is no deception — we will connect this 

 up, and use his old friend the clock to make its ticks,* if it will, 

 evident over the whole room. One of the greatest effects which 

 this instrument produces is to render evident the tramp of a fly ; 

 and we have some nice little captives with which we will demon- 

 strate that effect at the close of the meeting. (Illustration with 

 clock.) To show that that is not due to the clock itself. Prof. 

 Hughes will lift up the clock, when all traces of sound will have 

 disappeared, and on putting it down again the sounds will be 

 produced ; so that the sound you hear is the sound of that clock 

 which has been magnified. (This was so.) 



Now, we have here a common quill pen, and Prof. Hughes 

 will do as they do on the stage, pretend to write a letter ; and I 

 have no doubt if you listen attentively you will hear the scratch- 

 ing of his pen. (Illustrated.) 



There are some peculiarities in this apparatus that are very 

 striking. In the first place, though the sounds produced are 

 very great, they do not interfere with each other. If you have 

 a friend at the other end speaking to you, you can hear his 

 voice distinctly working through your voice ; and the result is 

 you get a duplex action. Two or three persons can talk to each 

 other without impediment or confusion. 



Yet another point is, that the articulation is absolutely perfect. 



One of the great difficulties, both in the telephone and the 

 phonograph, is getting the sibilant sounds reproduced — such as 

 "s," and '•c,"and "sh," &c., which are produced by such 

 extremely minute variations of the sonorous vibrations that they 

 are lost in those instruments. Thus, if through the telephone you 

 ask a person to "waltz," it will come out "walk," and names like 

 my own, with the sound of "s" in it, would come out " Pree," 

 not " Preece." In this transmitter one of its chief peculiarities 

 is the fact that all sounds are faithfully reproduced ; and it tends 

 very much to upset the notion — Helmholtz's theory — that vowel 

 sounds and other sounds are due to the superposition of waves 

 upon waves of tones and over-tones. This apparatus shows 

 almost unquestionably all these different properties ; all these 

 effects of intonation are due to differences in the form of the 

 curve sent. Another peculiarity is this. I have told you that 

 all in this room, every one's body while I am speaking, is alive 

 with sound. If you take this transmitter and place it in front 

 of your mouth, or put it on your forehead, or on the top of 

 your head, or put it into your pocket, or upon your breast, it 

 will still transmit sounds to distant places. Put it in a room, it 

 does not matter where, it will reproduce the sounds. Put it 

 anywhere in a drawing-room where there is a piano, you will 

 hear the sounds of the piano faithfully reproduced. It is as 

 you see a marvellously rough affair. You may throw it up, kick 

 it about, or do what you like with it, it will always act. Here 

 is the identical box that Prof. Hughes made two or three months 

 ago. It has never been touched, it has been always at work, 

 and never needs repair. 



These are some of the peculiarities of his instrument, and I 

 daresay some of you would-like to know a little about its theory. 

 We have here two points in contact, and those two points in 

 contact complete an electrical circuit. The electric current that 

 flows through that circuit depends for its strength entirely upon 

 the obstacles or resistance in that circuit to the flow of the 

 current ; an alteration in any shape or form in the resistance of 

 that circuit will result in the increase or decrease of the strength 

 of the current flowing, and upon this diagram I have made a 

 rough attempt to give you an idea of what occurs. 



\J^JjJjjjjJ^jj 



Fl5. 4. 



You must not conceive these round balls are molecules them- 

 selves, they are merely meant to represent the sphere of action 

 of each molecule. In a normal state the molecules rest against 

 each other, as shown by the upper hne. When fi-om any cause 

 pressure is increased, they are contracted, as shown in the second 

 line ; when from any cause the pressure is decreased they ex- 

 pand, in the form shown on the other line. While I speak to 

 you, the air of this room is thrown into vibration, the mass of 

 air being subdivided into molecules in compression and mole- 

 cules in extension. In a long wire these successions of com- 

 pressions and extensions compensate each other ; but when we 

 break up a body into infinitely small parts, when we make less 

 contact between tv.o bodies, as shown there, and isolate the 



