50 
THE FIEST TELEPHONE. 
less strongly than before against tlie spring, thereby making a 
less complete contact than before ; and, by thus partially inter- 
rupting the passage of the current, caused the current to flow 
less freely. The sound-waves which entered the air would in this 
fashion throw the electric current, which flowed through the 
point of variable contact, into undulations in strength. Eeis 
himself termed the contact-part of his Telephone an ‘'inter- 
ruptor.” That it was not intended to operate as an abrupt 
make-and-break arrangement, as some persons have erroneously 
fancied is evident ; firstly, because the inventor introduced deli- 
cate springs to give a following-contact (like that in Blake’s 
well-known “ transmitter ”), and so prevent abrupt breaks from 
occurring ; secondly, because abrupt breaks would have violated 
the fundamental principle to which he refers in the sentence 
immediately preceding his description of the instrument shewn 
to the Frankfort Society, namely that of creating tones whose 
curves were like the undulatoiy curves imparted at the trans- 
mitting end of the instrument ; thirdly, because (in another 
article) he described his instruments as opening and closing the 
circuit in proportion to the sound-wave ; which obviously an 
abrupt “ break-and-make apparatus without a spring-contact 
could not possibly do. The mechanism which Eeis thus invented 
— and which is substantially alike in all his instruments- — might 
be appropriately described as the combination of a tympanum 
with an electric current-regulator ; the essential principle of the 
electric current-regulator being the employment of a loose or 
imperfect contact between the two parts of the conducting 
system ; those parts being so arranged that the vibrations of the 
tympanum would alter the degree of contact, or occasion an 
approach and recession of the atoms of the two surfaces, and so 
vary the resistance offered at the point of contact to the flow of 
the current. 
The particular form of the instrument shewn at Frankfort 
