h of the space it occupied before it was
compressed. It is 166 times hotter. There are two sets of pipes running
from the compressor to a long upright tank called the liquefier. These
pipes pass through running water, so that the compressed air is quickly
cooled down to the temperature of the water (about 50 degrees
Fahrenheit). The pipes--at least one set of them--run the whole length
of the liquefier, and most likely are coiled. This set of pipes contains
the air to be liquefied. A second set of pipes runs to the bottom of the
liquefier, where there is a valve. By opening this valve a jet of
compressed air is allowed to play on the other set of pipes, when
intense cold is produced by the sudden expansion of the air. This cold
air rushes up around the pipe containing the air to be liquefied and
escapes at the top, thus absorbing the heat until the temperature is
reduced to 312 degrees below zero. Then the air liquefies and runs into
a receptacle, where it may be drawn off at pleasure.

It will be seen that a large part of the compressed air is wasted in
cooling the remainder sufficiently to liquefy.

The use to which liquid air may be put, advantageously, is an unsolved
problem; but no doubt it will have a place in time. All great
discoveries do. Electricity had to wait a long time for recognition; but
what a part it plays now in the everyday life of the whole civilized
world!

Curious effects are produced by this intense cold. Meat may be frozen so
hard that it will give off a musical tone when struck. Here is a pointer
for the seeker of novelties in the line of musical instruments.

Liquid air furnishes a beautiful illustration of the fact that a burning
gas jet is continually forming water as well as giving out heat and
light. If we put liquid air into a tea kettle and hold it over a gas
jet, ice will form on the bottom from the water created by the flame,
and it will freeze so hard that the flame will make no impression upon
it, other than to make the ice cake grow larger.

Although liquid air is not found in nature, and is therefore called an
artificial product, it is produced by taking advantage of natural law.
Without the intellect of man it never would have been seen upon this
earth; and the same may be said concerning many things in our world,
both animate and inanimate. The genius of man is God-like. He lifts the
veil that shrouds the mysteries of nature, and here he comes in very
touch with the mind of