y deed "not debarred
from studying the internal mechanism of a molecule," nor, perhaps, from
taking it to pieces. In 1895 came the {70} discovery of the X-rays by
Roentgen in Germany, to be followed in a year by Becquerel's discovery
of spontaneous radio-activity, and in a couple of years by the
remarkable further discovery, made by Madame Curie, of what was termed
"radium," a substance that went on producing heat _de novo_, keeping
itself permanently at a higher temperature than its surroundings, and
spontaneously producing electricity.

This in itself was a new fact of extraordinary interest. For long,
discussion had been waged between two departments of scientific
inquirers. The geologists and biologists had demanded hundreds, and
perhaps thousands, of millions of years to allow for the developments
with which they were concerned. The physicists, led by Lord Kelvin,
refused to admit the demand, claiming that it could be proved
mathematically that it was impossible that the sun could have been
giving out heat at its present rate for more than a hundred million
years, at the very outside. The appearance of radium robbed this
argument of its cogency. It is true that an examination of the sun's
spectrum has not, as yet, revealed any radium lines, but it is well
known that helium, a transformation product of radium, is present in it.

And this modification of our views as to the {71} probable age of our
solar system was far from being the only result of this latest
discovery. Investigations which followed into radio-activity led the
Cambridge professors, Larmor and Thomson, to conclude that electricity
existed in small particles, which were called "electrons."[1] These
seem to be the ingredients of which atoms are made. A molecule is
composed of two or more atoms. That of hydrogen, for example, has two;
that of water three; and so on up to a thousand or more.

Molecules are very small. If a drop of water were magnified to the
size of the globe, the molecules would be seen to be less than the size
of a cricket ball!

Atoms are much smaller. "The atoms in a drop of water outnumber the
drops in an Atlantic Ocean." Electrons are much smaller still--about
"a thousand-million-million times smaller than atoms."[2]

Within the atom thousands or tens of thousands of these electrons are
moving in orderly arrangement, at terrific speed, round and about one
another. The amount of energy required to build up a molec