it is
ignited there is a sufficient amount of oxygen present to support
combustion, hence the rapid explosion which follows.

VIBRATION IN NATURE.--The physical meaning of vibration is best
illustrated by the movement of a pendulum. All agitation is vibration.
All force manifests itself in this way.

The painful brilliancy of the sun is produced by the rapid vibrations of
the rays; the twinkle of the distant star, the waves of the ocean when
ruffled by the winds; the shimmer of the moon on its crested surface;
the brain in thinking; the mouth in talking; the beating of the heart;
all, alike, obey the one grand and universal law of vibratory motion.

QUALITIES OF SOUND.--Sound is nothing but a succession of vibrations of
greater or less magnitude. Pitch is produced by the number of
vibrations; intensity by their force; and quality by the character of
the article vibrated.

Since the great telephone controversy which took place some years ago
there has been a wonderful development in the knowledge of acoustics, or
sounds. It was shown that the slightest sound would immediately set into
vibration every article of furniture in a room, and very sensitive
instruments have been devised to register the force and quality.

THE PHOTOGRAPHER'S PLATE.--It is known that the chemical action of an
object on a photographer's plate is due to vibration; each represents a
force of different intensity, hence the varying shades produced. Owing
to the different rates of vibrations caused by the different colors, the
difficulty has been to photograph them, but this has now been
accomplished. Harmony, or "being in tune," as is the common expression,
is as necessary in light, as in music.

Some chemicals will bring out or "develop," the pictures; others will
not. Colors are now photographed because invention and science have
found the harmonizing chemicals.

QUADRUPLEX TELEGRAPHY.--One of the most remarkable of all the wonders of
our age is what is known as duplex and quadruplex telegraphy. Every atom
and impulse in electricity is oscillation. The current which transmits
a telegram is designated in the science as "vibratory."

But how is it possible to transmit two or more messages over one wire at
the same time? It is by bringing into play the harmony of sounds. One
message is sent in one direction in the key of A; another message in the
other direction in B; and so any number may be sent, because the
electrical vibrations may be tun