might have a much lower speed and go so much nearer the sun
that it was seriously deflected in its course, as we see in the case of
comet visitors. But if for some reason or other the lump of matter found
itself inside the solar system without the endowment of high velocity it
would certainly be absorbed. Just so an electron can pass through an
atom with or without serious deviation from its line of motion, provided
that motion is rapid enough. Only recently have we been able to exert
electric forces of sufficient strength to set an electron in motion with
the speed it must have if it is to maintain an individual existence Now
we can gather electrons at will, dragging them from the interior of
solid bodies, and hurl them with tremendous speed like a stream of
projectiles. Since in the open air the speed is soon lost by innumerable
collisions with the air-molecules, the effect can only be studied
satisfactorily in a glass bulb from which the air has been evacuated.
Crookes made great improvements in air-pumps during an investigation on
thallium, and consequently was able to obtain the high vacuum required
for the experiment with the electron streams. It was afterwards found by
Roentgen that when an electron stream in an evacuated bulb was directed
upon a target placed within the bulb, a remarkable radiation issued
from the target. Thus arose the so-called X or Roentgen rays. As you all
know they have for many years played a most important part in surgery
and medicine. You may have heard that during the war they were also used
to examine the interior of aeroplane constructions and to look for flaws
invisible from without. Although X-Rays are of the same nature as light
rays they can penetrate where light rays cannot, passing in greater or
less degree through materials which are opaque to visible light and
allowing us to examine the interior which is hidden from the eye.

Every electric discharge is essentially a hurried rush of electrons.
When we rub two bodies together and they become electrified we have in
some way or other torn electrons from one of the bodies and piled them
on the other. The former becomes the positively charged body and the
latter the negative. A film of moisture stops this action. When wool is
spun in factories it tends to become in certain stages of the process
too dry and too free from grease; the yarn then becomes electrified as
it passes over the leather rollers, and when the machine tries to spi