ecting these adjustments;
but considerable skill was required to obtain good results, and great
difficulty was experienced in meeting the variations in the wax-like
cylinders, due to the warping under atmospheric changes. Consequently,
with the early types of commercial phonographs, it was first necessary
to shave off the blank accurately before a record was formed thereon,
in order that an absolutely true surface might be presented. To overcome
these troubles, the very ingenious suggestion was then made and adopted,
of connecting the recording and reproducing styluses to their respective
diaphragms through the instrumentality of a compensating weight,
which acted practically as a fixed support under the very rapid sound
vibrations, but which yielded readily to distortions or variations
in the wax-like cylinders. By reason of this improvement, it became
possible to do away with all adjustments, the mass of the compensating
weight causing the recorder to engage the blank automatically to the
required depth, and to maintain the reproducing stylus always with the
desired pressure on the record when formed. These automatic adjustments
were maintained even though the blank or record might be so much out of
true as an eighth of an inch, equal to more than two hundred times the
maximum depth of the record groove.

Another improvement that followed along the lines adopted by Edison for
the commercial development of the phonograph was making the recording
and reproducing styluses of sapphire, an extremely hard, non-oxidizable
jewel, so that those tiny instruments would always retain their true
form and effectively resist wear. Of course, in this work many other
things were done that may still be found on the perfected phonograph
as it stands to-day, and many other suggestions were made which were
contemporaneously adopted, but which were later abandoned. For the
curious-minded, reference is made to the records in the Patent Office,
which will show that up to 1893 Edison had obtained upward of sixty-five
patents in this art, from which his line of thought can be very closely
traced. The phonograph of to-day, except for the perfection of its
mechanical features, in its beauty of manufacture and design, and in
small details, may be considered identical with the machine of 1889,
with the exception that with the latter the rotation of the record
cylinder was effected by an electric motor.

Its essential use as then contemplated was