I have before alluded to the invention by my father of a system of
physiological symbols for representing the action of the vocal organs,
and I had been invited by the Boston Board of Education to conduct a
series of experiments with the system in the Boston school for the deaf
and dumb. It is well known that deaf mutes are dumb merely because they
are deaf, and that there is no defect in their vocal organs to
incapacitate them from utterance. Hence it was thought that my father's
system of pictorial symbols, popularly known as visible speech, might
prove a means whereby we could teach the deaf and dumb to use their
vocal organs and to speak. The great success of these experiments urged
upon me the advisability of devising method of exhibiting the vibrations
of sound optically, for use in teaching the deaf and dumb. For some time
I carried on experiments with the manometric capsule of Koeenig and with
the phonautograph of Leon Scott. The scientific apparatus in the
Institute of Technology in Boston was freely placed at my disposal for
these experiments, and it happened that at that time a student of the
Institute of Technology, Mr. Maurey, had invented an improvement upon
the phonautograph. He had succeeded in vibrating by the voice a stylus
of wood about a foot in length, which was attached to the membrane of
the phonautograph, and in this way he had been enabled to obtain
enlarged tracings upon a plane surface of smoked glass. With this
apparatus I succeeded in producing very beautiful tracings of the
vibrations of the air for vowel sounds. Some of these tracings are shown
in Fig. 4. I was much struck with this improved form of apparatus, and
it occurred to me that there was a remarkable likeness between the
manner in which this piece of wood was vibrated by the membrane of the
phonautograph and the manner in which the _ossiculo_ [small bones] of
the human ear were moved by the tympanic membrane. I determined
therefore, to construct a phonautograph modelled still more closely
upon the mechanism of the human ear, and for this purpose I sought the
assistance of a distinguished aurist in Boston, Dr. Clarence J. Blake.
He suggested the use of the human ear itself as a phonautograph, instead
of making an artificial imitation of it. The idea was novel and struck
me accordingly, and I requested my friend to prepare a specimen for me,
which he did. The apparatus, as finally constructed, is shown in Fig. 5.
The _stapes_ [inmos