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MUNRO'S TELEPHONIC EXPERIMENTS.


Mr. J. Munro, whose name is well known not only as a very clear writer
upon electrical subjects, but as an original investigator, has recently,
with the assistance of Mr. Benjamin Warwick, been conducting a most
interesting experimental investigation of the action of the microphone
as a telephonic transmitter, with the result of proving that metals may
advantageously be employed in the place of carbon in a transmitting
instrument, a practical development of one of the very earliest of
Professor Hughes' microphones. The fact that metallic electrodes can
practically be employed in microphonic transmitters has been denied of
late with so much assurance and in such high quarters, that Mr. Munro's
successful applications of that portion of Professor Hughes' discovery
possess an especial interest, and must to a considerable extent affect
the aspect of litigation in future contests in which the discovery of
the microphone and the invention of the carbon transmitter are vital
points at issue.

In investigating the properties of metallic conductors employed in the
construction of microphones, Mr. Munro's first experiments were made
with wires. These, in some cases, were caused by the action of a
diaphragm, to rub the one on the other in such a manner as to make the
point of contact vary (under the influence of the vibrations of the
diaphragms) on one side or other of a position of normal potential, so