Radio Broadcast - 1925, February - 113 Pages ... - VacuumTubeEra

The March of Radio 701
It might be thought that particles
as small
as the electron could be dealt with only in the
imagination,
that measurements as to their
size, velocity, quantity of electricity, etc.,
could not possibly be made. Yet this is far
from the truth. The mass of the electron,
and its size and electric charge, are known as
accurately as is. the length of a yard stick.
Measurements of the electron carried out by
independent methods agree with each other
to better than i
per cent.
Professor Millikan, when at the University
of Chicago, carried out some remarkable experiments
on electron measurements. So important
were his results regarded in the
scientific world that he was given the Nobel
Prize. Millikan sprayed oil into very small
drops, so small that they were nearly stationary
in the air, even though free to fall.
Some of the drops he used fell only one
quarter of an inch in ten seconds, so little did
the force of gravity attract them. A very
powerful microscope was required to see them;
in fact, the drops were never seen as such but
appeared like the dancing circles which appear
if one presses his eye-ball too severely. By
having these drops of oil between electrically
charged plates it was possible to make them
stop falling or even move upwards if the droplet
happened to be charged electrically. Now
if electrons were produced in the space where
the oil drops were being observed, one would
occasionally attract itself to an oil drop, which
would then immediately change its motion.
By observing the change in motion and knowing
the size of the drop (by other experiments)
the charge of a single electron could be computed.
Occasionally an oil drop suddenly
changed its motion twice as much as did the
others. This meant to the observer that two
electrons had simultaneouslv attached themselves
to the oil drop.
So by these remarkable experiments of
Millikan's the electron was almost observed
in motion. Now the electron is
being heard!
Dr. Albert W. Hull, one of the best-known research
workers of the General Electric Company,
announces that by apparatus which he
has perfected
it is possible actually to hear the
electrons which fly across a vacuum tube.
When they strike the plate of the tube they set
up oscillations which, if sufficiently amplified,
can be heard. Of course the amplification required
is enormous, so great that if it were
tried with the ordinary unshielded amplifier
outfit, the noise due to atmospheric electricity
would swamp the noise due to electron bombardment.
By working inside a metal cage,
C. FRANCIS JENKINS
A radio investigator of Washington who recently was successful in transmitting photographs by radio from
Anacostia, Maryland to Medford Hillside, Massachusetts on a wavelength of 746 meters. The photograph
shows a laboratory set up of some of the inventor's apparatus at Washington