h second, and the ear drum, being
flexible, will respond and will vibrate at the same rate. The
vibration of the ear drum will be transmitted by the three bones and
the fluid to the fibers of the auditory nerves. The impulses imparted
to the auditory nerve reach the brain and in some unknown way are
translated into sound.

278. Care of the Ear. Most catarrhal troubles are accompanied by an
oversupply of mucus which frequently clogs up the Eustachian tube and
produces deafness. For the same reason, colds and sore throat
sometimes induce temporary deafness.

The wax of the ear is essential for flexibility of the ear drum; if an
extra amount accumulates, it can be got rid of by bathing the ear in
hot water, since the heat will melt the wax. The wax should never be
picked out with pin or sharp object except by a physician, lest injury
be done to the tympanic membrane.

279. The Phonograph. The invention of the phonograph by Edison in
1878 marked a new era in the popularity and dissemination of music. Up
to that time, household music was limited to those who were rich
enough to possess a real musical instrument, and who in addition had
the understanding and the skill to use the instrument. The invention
of the phonograph has brought music to thousands of homes possessed
of neither wealth nor skill. That the music reproduced by a phonograph
is not always of the highest order does not, in the least, detract
from the interest and wonder of the instrument. It can reproduce what
it is called upon to reproduce, and if human nature demands the
commonplace, the instrument will be made to satisfy the demand. On the
other hand, speeches of famous men, national songs, magnificent opera
selections, and other pleasing and instructive productions can be
reproduced fairly accurately. In this way the phonograph, perhaps more
than any other recent invention, can carry to the "shut-ins" a lively
glimpse of the outside world and its doings.

[Illustration: FIG. 195.--A vibrating tuning fork traces a curved line
on smoked glass.]

The phonograph consists of a cylinder or disk of wax upon which the
vibrations of a sensitive diaphragm are recorded by means of a fine
metal point. The action of the pointer in reporting the vibrations of
a diaphragm is easily understood by reference to a tuning fork. Fasten
a stiff bristle to a tuning fork by means of wax, allowing the end of
the point to rest lightly upon a piece of smoked glass. If the glass