557 
of Edinburgh, Session 1877-78 
According to the author’s theory, the action at the receiving end 
is explained by an experiment ascribed to Page. If a bar of iron be 
surrounded by a coil of wire connected with a battery, a chink is 
heard when the connection is broken, and a feebler one when the 
connection is re-made. If the connection be made, and broken 
rapidly by attaching one end of the wire to a file and drawing the 
other along the file, a series of chinks are heard succeeding each 
other at the same intervals as the contacts are made and broken. 
It is due to the lengthening of the bar on magnetisation and the 
rearrangement of the molecules of the iron. It takes place also 
when the iron remains partially magnetised. In this case successive 
contacts increase the magnetism of the bar. In the Telephone suc- 
cessive currents pass in opposite directions through the coil. Hence 
the bar is lengthened and shortened alternately, and chinks are 
made at intervals corresponding to the intervals between successive 
waves at the sending end. Hence the sound waves at the sending 
end are reproduced at the receiving end alike in rapidity and in 
intensity. When a vibrating plate of any kind is used it increases 
the intensity of the sound, and if it be of iron the attraction will 
increase the effect. 
Since a chink is given off both when the magnetism is increased 
and diminished it might be expected that the note should be heard 
an octave higher. But since the one is more intense than the other, 
the combined effect should be to give two notes, a loud one in the 
tone of the speaker, and a feeble one an octave higher. This might 
account for the common remark that a piano sounds wiry through a 
Telephone, and that a clear lady’s voice is squeaky. But it is not 
certain that this effect is produced, for the chink is produced at 
least in part by the lengthening and shortening of the magnet. 
Either of these alone will give a chink, but when following each 
other in rapid succession they compress and rarefy the air in con- 
tact, in periods exactly agreeing with the compressions and rarefac- 
tions originated at the sending end. 
In confirmation of the supposition that the sound is produced by 
successive chinks of the material of the magnet, it was stated that 
in a very large and massive pair of Telephones made by Mr Wm. 
Bottomley, jun., when any one is speaking through one of them the 
sound is distinctly (though not articulately) heard by every one in the 
vol. ix. 4 E 
