a quadrillion atoms. It is these minute and elusive particles
that modern physics sets out to master.

At first it was noticed that the atom of hydrogen was the
smallest or lightest of all, and the other atoms seemed to be
multiples of it. A Russian chemist, Mendeleeff, drew up a table
of the elements in illustration of this, grouping them in
families, which seemed to point to hydrogen as the common parent,
or ultimate constituent, of each. When newly discovered elements
fell fairly into place in this scheme the idea was somewhat
confidently advanced that the evolution of the elements was
discovered. Thus an atom of carbon seemed to be a group of 12
atoms of hydrogen, an atom of oxygen 16, an atom of sulphur 32,
an atom of copper 64, an atom of silver 108, an atom of gold 197,
and so on. But more correct measurements showed that these
figures were not quite exact, and the fraction of inexactness
killed the theory.

Long before the end of the nineteenth century students were
looking wistfully to the ether for some explanation of the
mystery. It was the veiled statue of Isis in the scientific
world, and it resolutely kept its veil in spite of all progress.
The "upper and limpid air" of the Greeks, the cosmic ocean of
Giordano Bruno, was now an established reality. It was the
vehicle that bore the terrific streams of energy from star to
planet across the immense reaches of space. As the atoms of
matter lay in it, one thought of the crystal forming in its
mother-lye, or the star forming in the nebula, and wondered
whether the atom was not in some such way condensed out of the
ether. By the last decade of the century the theory was