attracted by the strange light effects arising when electricity passes
through rarefied gases, because they reminded him of certain luminous
phenomena he had observed during his spiritistic investigations.
Besides this, there was the fact that light here showed itself
susceptible to the magnetic force in a way otherwise characteristic
only of certain material substances. Accordingly, everything combined
to suggest to Crookes that here, if anywhere, he was at the boundary
between the physical and the superphysical worlds. No wonder that he
threw himself into the study of these phenomena with enthusiasm.

He soon succeeded in evoking striking effects - light and heat, and
also mechanical - along the path of electricity passing invisibly
through the tube later named after him. Thus he proved for the first
time visibly, so to say, the double nature - material and supermaterial
- of electricity. What Crookes himself thought about these discoveries
in the realm of the cathode rays we may judge from the title, 'Radiant
Matter', or 'The Fourth State of Matter', which he gave to his first
publication about them. And so he was only being consistent when, in
his lectures before the Royal Institution in London, and the British
Association in Sheffield in 1879, after showing to an amazed scientific
audience the newly discovered properties of electricity, he came to the
climax of his exposition by saying: 'We have seen that in some of its
properties Radiant Matter is as material as this table, whilst in other
properties it almost assumes the character of Radiant Energy. We have
actually touched here the borderland where Matter and Force seem to
merge into one another, the shadowy realm between Known and Unknown,
which for me has always had peculiar temptations.' And in boldly
prophetic words, which time has partly justified, he added, 'I venture
to think that the greatest scientific problems of the future will find
their solution in this Borderland, and even beyond; here, it seems to