ding this chapter, give just one illustration of the
way in which all this new knowledge may prove to be as valuable
practically as it is wonderful intellectually. We saw that electrons are
shot out of atoms at a speed that may approach 160,000 miles a second.
Sir Oliver Lodge has written recently that a seventieth of a grain of
radium discharges, at a speed a thousand times that of a rifle bullet,
thirty million electrons a second. Professor Le Bon has calculated that
it would take 1,340,000 barrels of powder to give a bullet the speed of
one of these electrons. He shows that the smallest French copper
coin--smaller than a farthing--contains an energy equal to eighty
million horsepower. A few pounds of matter contain more energy than we
could extract from millions of tons of coal. Even in the atoms of
hydrogen at a temperature which we could produce in an electric furnace
the electrons spin round at a rate of nearly a hundred trillion
revolutions a second!

Every man asks at once: "Will science ever tap this energy?" If it does,
no more smoke, no mining, no transit, no bulky fuel. The energy of an
atom is of course only liberated when an atom passes from one state to
another. The stored up energy is fortunately fast bound by the electrons
being held together as has been described. If it were not so "the earth
would explode and become a gaseous nebula"! It is believed that some day
we shall be able to release, harness, and utilise atomic energy. "I am
of opinion," says Sir William Bragg, "that atom energy will supply our
future need. A thousand years may pass before we can harness the atom,
or to-morrow might see us with the reins in our hands. That is the
peculiarity of Physics--research and 'accidental' discovery go hand in
hand." Half a brick contains as much energy as a small coal-field. The
difficulties are tremendous, but, as Sir Oliver Lodge reminds us, there
was just as much scepticism at one time about the utilisation of steam
or electricity. "Is it to be supposed," he asks, "that there can be no
fresh invention, that all the discoveries have been made?" More than one
man of science encourages us to hope. Here are some remarkable words
written by Professor Soddy, one of the highest authorities on
radio-active matter, in our chief scientific weekly (_Nature_, November
6, 1919):

The prospects of the successful accomplishment of artificial
transmutation brighten almost daily. The ancients seem to have ha