A photograph clearly showing that electrons are definite entities. As
electrons leave atoms they may traverse matter or pass through the air
in a straight path The illustration shows the tortuous path of electrons
resulting from collision with atoms.]
[Illustration: MAGNETIC DEFLECTION OF RADIUM RAYS
The radium rays are made to strike a screen, producing visible spots of
light. When a magnetic field is applied the rays are seen to be
deflected, as in the diagram. This can only happen if the rays carry an
electric charge, and it was by experiments of this kind that we obtained
our knowledge respecting the electric charges carried by radium rays.]
[Illustration: _Reproduced by permission of "Scientific American."_