THE TELEPHONE AND HOW IT WORKS. 567 



or pulsation passes for each letter, and the final ' op ' we have tried to 

 represent shows the stoppage of the needle at the letters as words 

 were spelled out. 



" It must not be understood that the sounds of those various in- 

 struments are actually heard in the telephone. What happens is, that 

 the currents stealing along the telephone-wire by induction produce 

 vibrations in the diaphragm of that instrument, the little metal mem- 

 brane working on the magnet in ready response to every current set 

 up the latter. When it is remembered that the principle of the tele- 

 phone is that the sound-caused vibrations in the filmy diaphragm at 

 one end create similar but magnetically-caused vibrations in the dia- 

 phragm at the other end, and so reproduce the sound, it will be obvi- 

 ous why the rapid roll of the ABC currents, or the swift sending of 

 the fast-speed transmitter, when brought by induction into the tele- 

 phone-wire, cause disturbances in the sound-vibrations, and thereby 

 cripple the instrument. One instrument of either kind named would 

 have a certain effect, but one Morse would not have any greatly preju- 

 dicial effect. But a number of Morses going together, such as were 

 heard in our experiments, would combine to be nearly as bad as one 

 A B C or fast-speed Morse. So delicate is the diaphragm to sound 

 (and necessarily so) that, in all experiments with the telephone itself? 

 every sound from without broke in, giving an effect like the well- 

 known ' murmur of the shell.' " 



" Joining up our wire now to a more distant station at some miles 

 along the railway, and having on its poles a number of what are 

 known as 'heavy' circuits, the pot-boiling sound assumed even more 

 marked characteristics. The A B C no longer affected us ; but a num- 

 ber of Morse instruments were in full gear, and the fast-speed trans- 

 mitter was also at work. While we were listening, the circuit to 

 which we were joined began to work, and the effect was literally elec- 

 trical. Hitherto we had only borrowed currents or, seeing they 

 were so unwelcome, we might call them currents thrust upon us 

 and the sounds, though sharp and incessant, were gentle and rather 

 low. But, when the strong current was set up in the wire itself, the 

 listener who held one of our telephones nearly jumped from the floor 

 when an angry ' pit-pat, ^pit-pat, pit-pat-pit ' assailed his ear, causing 

 him to drop the instrument as if he had been shot. It was a result 

 none of us had expected, for it did not seem possible that the delicate 

 metal diaphragm and the little magnet of the telephone could produce 

 a sound so intense. Of course, it was only intense when the ear was 

 held close to the orifice of the instrument. Held in the hand away 

 from the ear, the telephone now made a first-rate ' sounder,' and we 

 could tell without difficulty not only the signals that were passing, 

 but found in it a more comfortable tone than that given by tfee Morse 

 sounder in common use. 



" Other experiments of a like character led to results so similar 



