.
The needle, in passing rapidly in contact with the recorded waves, was
vibrated up and down, causing corresponding vibrations of the diaphragm.
In this way sound-waves similar to those caused by the original sounds
would be set up in the air, thus reproducing the original speech.

The modern phonograph operates in a precisely similar way, the only
difference being in details of refinement. Instead of tin-foil, a wax
cylinder is employed, the record being cut thereon by a cutting-tool
attached to a diaphragm, while the reproduction is effected by means of
a blunt stylus similarly attached.

The cutting-tool and stylus are devices made of sapphire, a gem next in
hardness to a diamond, and they have to be cut and formed to an exact
nicety by means of diamond dust, most of the work being performed under
high-powered microscopes. The minute proportions of these devices will
be apparent by a glance at the accompanying illustrations, in which the
object on the left represents a common pin, and the objects on the right
the cutting-tool and reproducing stylus, all actual sizes.

In the next illustration (Fig. 4) there is shown in the upper sketch,
greatly magnified, the cutting or recording tool in the act of forming
the record, being vibrated rapidly by the diaphragm; and in the lower
sketch, similarly enlarged, a representation of the stylus travelling
over the record thus made, in the act of effecting a reproduction.

From the late summer of 1878 and to the fall of 1887 Edison was
intensely busy on the electric light, electric railway, and other
problems, and virtually gave no attention to the phonograph. Hence,
just prior to the latter-named period the instrument was still in its
tin-foil age; but he then began to devote serious attention to the
development of an improved type that should be of greater commercial
importance. The practical results are too well known to call for further
comment. That his efforts were not limited in extent may be inferred
from the fact that since the fall of 1887 to the present writing he has
been granted in the United States one hundred and four patents relating
to the phonograph and its accessories.

Interesting as the numerous inventions are, it would be a work of
supererogation to digest all these patents in the present pages, as they
represent not only the inception but also the gradual development and
growth of the wax-record type of phonograph from its infancy to the
present perfe