confidently advanced--notably by Lorentz and Larmor-- though it
was still without a positive basis. How the basis was found, in
the last decade of the nineteenth century, may be told very
briefly.

Sir William Crookes had in 1874 applied himself to the task of
creating something more nearly like a vacuum than the old
air-pumps afforded. When he had found the means of reducing the
quantity of gas in a tube until it was a million times thinner
than the atmosphere, he made the experiment of sending an
electric discharge through it, and found a very curious result.
From the cathode (the negative electric point) certain rays
proceeded which caused a green fluorescence on the glass of the
tube. Since the discharge did not consist of the atoms of the
gas, he concluded that it was a new and mysterious substance,
which he called "radiant matter." But no progress was made in the
interpretation of this strange material. The Crookes tube became
one of the toys of science--and the lamp of other investigators.

In 1895 Rontgen drew closer attention to the Crookes tube by
discovering the rays which he called X-rays, but which now bear
his name. They differ from ordinary light-waves in their length,
their irregularity, and especially their power to pass through
opaque bodies. A number of distinguished physicists now took up
the study of the effect of sending an electric discharge through
a vacuum, and the particles of "radiant matter" were soon
identified. Sir J. J. Thomson, especially, was brilliantly
successful in his interpretation. He proved that they were tiny
corpuscles, more than a thousand times smaller than the atom of
hydrogen, charged with negative electricity, and travelling at