And this is only the beginning of the wonders that were done with
"ordinary matter," quite apart from radium and its revelations, to which
we will come presently. Most people have heard of "atomic energy," and
the extraordinary things that might be accomplished if we could harness
this energy and turn it to human use. A deeper and more wonderful source
of this energy has been discovered in the last twenty years, but it is
well to realise that the atoms themselves have stupendous energy. The
atoms of matter are vibrating or gyrating with extraordinary vigour. The
piece of cold iron you hold in your hand, the bit of brick you pick up,
or the penny you take from your pocket is a colossal reservoir of
energy, since it consists of trillions of moving atoms. To realise the
total energy, of course, we should have to witness a transformation such
as we do in atoms of radio-active elements, about which we shall have
something to say presently.
If we put a grain of indigo in a glass of water, or a grain of musk in a
perfectly still room, we soon realise that molecules travel. Similarly,
the fact that gases spread until they fill every "empty" available space
shows definitely that they consist of small particles travelling at
great speed. The physicist brings his refined methods to bear on these
things, and he measures the energy and velocity of these infinitely
minute molecules. He tells us that molecules of oxygen, at the
temperature of melting ice, travel at the rate of about 500 yards a
second--more than a quarter of a mile a second. Molecules of hydrogen
travel at four times that speed, or three times the speed with which a
bullet leaves a rifle. Each molecule of the air, which seems so still in
the house on a summer's day, is really travelling faster than a rifle
bullet does at the beginning of its journey. It collides with another
molecule every twenty-thousandth of an inch of its journey. It is turned
from its course 5,000,000,000 times in every second by collisions. If we
could stop the molecules of hydrogen gas, and utilise their energy, as
we utilise the energy of steam or the energy of the water at Niagara, we
should find enough in every gramme of gas (about two-thousandths of a
pound) to raise a third of a ton to a height of forty inches.
I have used for comparison the speed of a rifle bullet, and in an
earlier generation people would have thought it impossible even to
estimate this. It is, of course, easy. We put two screens in the path of
the bullet, one near the rifle and the other some distance away. We
connect them electrically and use a fine time-recording machine, and the
bullet itself registers the time it takes to travel from the first to
the second screen.
Now this is very simple and superficial work in comparison with the
system of exact and minute measurements which the physicist and chemist
use. In one of his interesting works Mr. Charles R. Gibson gives a
photograph of two exactly equal pieces of paper in the opposite pans of
a fine balance. A single word has been written in pencil on one of these
papers, and that little scraping of lead has been enough to bring down
the scale! The spectroscope will detect a quantity of matter four
million times smaller even than this; and the electroscope is a million
times still more sensitive than the spectroscope. We have a
heat-measuring instrument, the bolometer, which makes the best
thermometer seem Early Victorian. It records the millionth of a degree
of temperature. It is such instruments, multiplied by the score,
which enable us to do the fine work recorded in these pages.
[Illustration: _Reproduced from "The Forces of Nature" (Messrs.
Macmillan)._