, 1877-05-16
Continued from 1st page.l

snce, the results are the same. The sound
produced by the receiving instrument, is not
che sound emitted by the sending instrument,
but 10 developed by the influence OF the
vibrations Of the original sound producer on the
currents Of electricity passing along the line
from one end to the other.
In the first place it was stated that the
production Of any sound was due to the num-
Der Of vibrations per second, through which
the sound producing body moved. That q
low rate Of vibration produced a grave tone
and a high rate q high tone. That the vi
brations must be periodic or Of uniform du-
ration to produce a musical note within the
range of from 40 to 10000 vib rations per
second. and that the intensity of the tone was
directly as the energy of the vibrations.
With regard to electricity it was stated that
continuity in the conductor was essential to
the flow Of tho electric fluid that the guam
tity Of electricity was directly as to the sur.
face exposed for its development in the bat
terry, and that tension was governed by the
energy of development thai the passage of
the electric impulse through the coil of the
slectro-magnst magnetized the soft iron core
and caused II to respond also to the electro
magnetic influence by elongation and vibra.
ton.
Now in the telephone apparatus all these
physical conditions and phenomena are utilized.
First the battery with ts'poworfal combination
Of metals, carbon, and acids, whereby chemical
action is induced, heat evolved, aud electricity
developed in its two conditions. Second, the line
communicating from terminus to terminus as
the main conductor. Third, the electro mao.
net for the development of sound by vibration,
To these is added an instrument by which the
musical sounds are propagated, a description
of which is as follows Tho inventor, Profess.
aor Elisha Gray, of Chicago, constructed kew.
board of two octaves, similar in appearance TO
that of q piano. Each key Of this instrument
when pressed by the operator, or performer as
he may BIO called, sets in action a steel reed.
tuned 20 a certain definite rate of vibration,
like o tuning fork, and corresponding to its 20.
sition in the musical scale. The vibration Of
the reed is maintained by electro magnets
placed at each side of it, and which alternately
exercise an attractive force upon it. One end
Of the reed is firmly fixed in q lar while its
length is Of course free to vibrate when excited.
Thus a note ola given pitch is produced locally
aS upon on ordinary reed organ, but by the
agency of electro. magnets. Now, the next
thing to determine IS how the same vibration
can be caused in the soft iron core Of a mag.
net 100 or 200 miles distant. Another battery,
called tbs main battery, is now brought into
operation. The place of sending being for the
purpose a terminal station, q pole of the main
battery is connected with the earth. which
completes the circuit between the sending and
and receiving ends Of the line.
Professor Bell, Of Boston, has perfected an
apparatus by which not only the sound of mu.
steal notes is reproduced, but also that of the
human voice. of words spoken in ordinary con.
vsrsation. He appears to have been studying
abe subject of telephony at the same time as
Professor Gray, both gentlemen arriving at
somewhat different but equally interesting re.
suits at about the same time. But Bells
success in regard to the reproduction of the
sound of the human voice has been very marked.
Taking the invention of Reiss as a starting
point he has constructed an apparatus which,
when attached to the receiving end of the
telegraph wire, enables any person in the
apartment to hear words distinctly which are
spoken at the other end of tho line. A
trumpet-mouthed tube is set opposite an
electro magnet similar in form and arrangement
TO thai already described. Across the mouth
of the tube q diaphragm or membrane is
strained. to which is attached a light masnstised
bar of steel, which almost touches the core ends
Ofths magnet. A battery actuates the magnet
and supplies the electric fluid to the line. One
pole is to ground while the other is to the line.
At the receiving end is a single helix, with an
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