varied changes which occur, according as the carbon is compressed or
relieved from compression by the gentle impacts of the air set in motion
by the voice."

"The most prominent quality of carbon is its capability, under the most
minute differences of pressure, to enormously increase or decrease the
resistances of the circuit." "That the varying pressure of the black
tension-regulator (Edison's) is sufficient to cause a change in the
conducting power." Sir Frederick also said "he could not believe that
the resistance was varied by a jolting motion; could not conceive a
jolting motion producing variation and difference of pressure, and such
an instrument could not be relied on, and therefore would be practically
useless."

Sir William Thomson, in the same case, said: "The function of the carbon
is to give rise to diminished resistance by pressure; it possesses the
quality of, under slight degrees of pressure, decreasing the resistance
to the passage of the electric current;" and, also, "the jolting motion
would be a make-and-break, and the articulate sounds would be impaired.
There can be no virtue in a speaking telephone having a jolting motion."
"Delicacy of contact is a virtue; looseness of contact is a vice."
"Looseness of contact is a great virtue in Hughes' microphone;" and "the
elements which work advantages in Hughes' are detrimental to the good
working of the articulating instrument."

[Illustration: Fig. 1.]

Mr. Falconer King said: "There would be no advantage in having a jolting
motion; the jolting motion would break the circuit and be a defect in
the speaking telephone," and "you must have pressure and partially