ts
by concentrating the voice on the listener's ear.

What is a Stethoscope?

An instrument used by physicians for ascertaining the action of the
lungs, judging by the sound of their motion whether they are healthy
or not.

Describe the Audiphone.

It is a fan-shaped instrument to help deaf people, and is made of
flexible carbonized rubber. Fine silk cords attached to the upper edge
bend it over, and are fastened by a wedge in a handle. The top edge of
this fan rests upon the upper teeth, and the sound waves strike its
surface; the vibrations are thus conveyed by the teeth and the bones
of the face to the acoustic nerve in the ear.

Describe the Telephone.

It is an instrument by which conversation may be carried on at a
distance, and is composed of three parts--a thin disk of soft metal, a
small coil or bobbin of silk-covered copper wire, and a small bar
magnet about four inches long. The bobbin is placed on one pole of the
magnet, so that the wire is as it were steeped in the magnetic space
round the pole. The metal disk is placed face close to the pole and
bobbin, so that when it vibrates in front of the pole a series of wave
currents will be set up in the coil of wire on the bobbin. The whole
is encased in wood, and a mouth-piece is provided for speaking against
the disk. The coil of wire on the bobbin is of course connected by its
two ends into the circuit of a telegraph line.

Who invented the Telephone?

It was invented, almost simultaneously, by Alex. Graham Bell, a
native of Scotland, and Professor of Vocal Physiology in the Boston
University, and Elisha Gray, of Chicago.

What is a Phonograph?

It is an instrument for recording the vibrations of sounds, and
consists of a revolving cylinder covered with tin-foil. To this
cylinder is attached a mouth-piece, fitted with a thin plate or disk,
on the outer side of which, next to the cylinder, is a needle or
point. The cylinder runs on a screw, so that the whole length of it,
from end to end, may pass under the point. On speaking into the
mouth-piece the voice causes the disk to vibrate, and the point to
trace marks corresponding to these vibrations on the tin-foil. By
turning the cylinder so that the point again passes into the marks in
the tin-foil, the sounds that entered at the mouth-piece can be
reproduced at any time.

By whom was the phonograph invented?

By Thomas A. Edison, who was born in Ohio in 1847. Mr. Edison is the
invent