pitch. Its poles swing towards and away from each other
at uniform rates, and the pitch of the magnet will depend upon its size,
thickness, and the material it is made of.

Let ten or fifteen ohms of any convenient-sized wire be wound upon the
bend of a commercial U-magnet. Let this wire be connected to a telephone
in its circuit. When the magnet is made to sound like a tuning-fork, the
pitch will be reproduced in the telephone very loudly. If another magnet
with a different pitch be allowed to vibrate near the former, the pitch
of the vibrating body will be heard in the telephone, and these show
that the changing magnetic field reacts upon the quiescent magnet, and
compels the latter to vibrate at the same rate. The action is an ether
action, the waves are ether waves, but they are relatively very long. If
the magnet makes 500 vibrations a second, the waves will be 372 miles
long, the number of times 500 is contained in 186,000 miles. Imagine the
magnet to become smaller and smaller until it was the size of an atom,
the one-fifty-millionth of an inch. Its vibratory rate would be
proportionally increased, and changes in its form will still bring about
changes in its magnetic field. But its magnetic field is practically
limitless, and the number of vibrations per second is to be reckoned
as millions of millions; the waves are correspondingly short,
small fractions of an inch. When they are as short as the
one-thirty-seven-thousandth of an inch, they are capable of affecting
the retina of the eye, and then are said to be visible as red light. If
the vibratory rate be still higher, and the corresponding waves be no
more than one-sixty-thousandth of an inch long, they affect the retina
as violet light, and between these limits there are all the waves that
produce a complete spectrum. The atoms, then, shake the ether in this
way because they all have a magnetic hold upon the ether, so that any
disturbance of their own magnetism, such as necessarily comes when they
collide, reacts upon the ether for the same reason that a large magnet
acts thus upon it when its poles approach and recede from each other. It
is not a phenomenon of mechanical impact or frictional resistance, since
neither are possible in the ether.

19. MATTER EXISTS IN SEVERAL STATES.

Molecular cohesion exists between very wide ranges. When strong, so if
one part of a body is moved the whole is moved in the same way, without
breaking continuity or the rela