gifted a body of men--conspicuous amongst them
Sir J. J. Thomson, Sir Ernest Rutherford, Sir W. Ramsay, and Professor
Soddy--as any age could boast, with an apparatus of research as far
beyond that of any other age as the _Aquitania_ is beyond a Roman
galley. Within five years the secret was fairly mastered. Not only were
all kinds of matter reduced to a common basis, but the forces of the
universe were brought into a unity and understood as they had never been
understood before.

[Illustration: ELECTRIC DISCHARGE IN A VACUUM TUBE

The two ends, marked + and -, of a tube from which nearly all air has
been exhausted are connected to electric terminals, thus producing an
electric discharge in the vacuum tube. This discharge travels straight
along the tube, as in the upper diagram. When a magnetic field is
applied, however, the rays are deflected, as shown in the lower diagram.
The similarity of the behaviour of the electric discharge with the
radium rays (see diagram of deflection of radium rays, _post_) shows
that the two phenomena may be identified. It was by this means that the
characteristics of electrons were first discovered.]

[Illustration: THE RELATIVE SIZES OF ATOMS AND ELECTRONS

An atom is far too small to be seen. In a bubble of hydrogen gas no
larger than the letter "O" there are billions of atoms, whilst an
electron is more than a thousand times smaller than the smallest atom.
How their size is ascertained is described in the text. In this diagram
a bubble of gas is magnified to the size of the world. Adopting this
scale, _each atom_ in the bubble would then be as large as a tennis
ball.]

[Illustration: IF AN ATOM WERE MAGNIFIED TO THE SIZE OF ST. PAUL'S
CATHEDRAL, EACH ELECTRON IN THE ATOM (AS REPRESENTED BY THE CATHEDRAL)
WOULD THEN BE ABOUT THE SIZE OF A SMALL BULLET]

[Illustration: ELECTRONS STREAMING FROM THE SUN TO THE EARTH

There are strong reasons for supposing that sun-spots are huge
electronic cyclones. The sun is constantly pouring out vast streams of
electrons into space. Many of these streams encounter the earth, giving
rise to various electrical phenomena.]

Sec. 5

The Discovery of the Electron

Physicists did not take long to discover that the radiation from radium
was very like the radiation in a "Crookes tube." It was quickly
recognised, moreover, that both in the tube and in radium (and other
metals) the atoms of matter were somehow breaking down.

However, the first st