etc.; they show the seven colours of the spectrum; give out the seven
sounds of the natural scale; respond in a variety of ways to physical
vibration--flashing, singing, pulsing bodies, they move incessantly,
inconceivably beautiful and brilliant.[12]

The atom has--as observed so far--three proper motions, _i.e._, motions of
its own, independent of any imposed upon it from outside. It turns
incessantly upon its own axis, spinning like a top; it describes a small
circle with its axis, as though the axis of the spinning top moved in a
small circle; it has a regular pulsation, a contraction and expansion, like
the pulsation of the heart. When a force is brought to bear upon it, it
dances up and down, flings itself wildly from side to side, performs the
most astonishing and rapid gyrations, but the three fundamental motions
incessantly persist. If it be made to vibrate, as a whole, at the rate
which gives any one of the seven colors, the whorl belonging to that color
glows out brilliantly.

[Illustration]

An electric current brought to bear upon the atoms checks their proper
motions, _i.e._, renders them slower; the atoms exposed to it arrange
themselves in parallel lines, and in each line the heart-shaped depression
receives the flow, which passes out through the apex into the depression of
the next, and so on. The atoms always set themselves to the current. The
well-known division of diamagnetic and paramagnetic depends generally on
this fact, or on an analogous action on molecules, as may be seen in the
accompanying diagrams.[13]

Two atoms, positive and negative, brought near to each other, attract each
other, and then commence to revolve round each other, forming a relatively