He had
shown that metallic plates of very slight thickness were transparent
to the cathode rays; and Professor Lenard succeeded in obtaining
plates impermeable to air, but which yet allowed the pencil of cathode
rays to pass through them.
Now if we take a Crookes tube with the extremity hermetically closed
by a metallic plate with a slit across the diameter of 1 mm. in width,
and stop this slit with a sheet of very thin aluminium, it will be
immediately noticed that the rays pass through the aluminium and pass
outside the tube. They are propagated in air at atmospheric pressure,
and they can also penetrate into an absolute vacuum. They therefore
can no longer be attributed to radiant matter, and we are led to think
that the energy brought into play in this phenomenon must have its
seat in the light-bearing ether itself.
But it is a very strange light which is thus subject to magnetic
action, which does not obey the principle of equal angles, and for
which the most various gases are already disturbed media. According to
Crookes it possesses also the singular property of carrying with it
electric charges.
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