ON THE ELECTRIC TELEPHONE. 
BY 
W. F. BARRETT, F.r.s.£ 
[Read November 19th, 1877.] 
The following paper does not lay claim to any originality. It 
is simply a brief description of an instrument which will probably 
play an important part in the future of the human race; 
together with an historical note of what had been accomplished 
by Reis fifteen years ago. 
The various attempts to communicate audible speech by means 
of electricity have culminated in the recent discovery by Professor 
Graham Bell of the articulating telephone. The discovery was 
not the result of chance but of long and patient endeavour. 
Every sound of the human voice is communicated from the 
speaker to the listener by means of aerial vibrations of a definite 
character. For the same sound the same wave-form is always 
reproduced. Starting from this fundamental axiom, Professor 
Bell’s first efforts were made with the view of visibly recording 
speech. A model of the human ear was constructed, to the 
tympanum of which a delicate style was attached, the movements 
of which recorded themselves on a moving slip of smoked glass. 
Thus the vowel sounds and a few simple words were readily 
recorded by this phonautograph ; which, however, differed but 
little from similar instruments previously constructed. These 
experiments revealed to Professor Bell the important point that 
the transmission of speech by electricity could onlybe accomplished 
by using what may be termed an undulatory current: that is to 
say, one that merely varied in strength without the occurrence of 
any actual interruptions which would give rise to a discontinuous 
or intermittent current. It is this principle of an unbroken 
current which distinguishes Bell’s telephone from all preceding 
efforts. The electric currents in this telephone are in simple 
proportion to the motions of the air produced by the voice, and 
further the electric waves sent to the distant extremity are (by 
a receiving arrangement precisely similar to the transmitting 
instrument), caused to reproduce motions of the air identically 
the same in character as those that gave birth to the currents. 
Thus not only is articulation heard perfectly, but moreover, the 
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