long time ago.
Incidentally we gain, by the use of very high frequencies, many
advantages, such as a higher economy in the light production, the
possibility of working with one lead, the possibility of doing away
with the leading-in wire, etc.
The question is, how far can we go with frequencies? Ordinary
conductors rapidly lose the facility of transmitting electric impulses
when the frequency is greatly increased. Assume the means for the
production of impulses of very great frequency brought to the utmost
perfection, every one will naturally ask how to transmit them when the
necessity arises. In transmitting such impulses through conductors we
must remember that we have to deal with _pressure_ and _flow_, in the
ordinary interpretation of these terms. Let the pressure increase to
an enormous value, and let the flow correspondingly diminish, then
such impulses--variations merely of pressure, as it were--can no doubt
be transmitted through a wire even if their frequency be many hundreds
of millions per second. It would, of course, be out of question to
transmit such impulses through a wire immersed in a gaseous medium,
even if the wire were provided with a thick and excellent insulation
for most of the energy would be lost in molecular bombardment and
consequent heating. The end of the wire connected to the source would
be heated, and the remote end would receive but a trifling part of the
energy supplied. The prime necessity, then, if such electric impulses
are to be used, is to find means to reduce as much as possible the
dissipation.
The first thought is, employ the thinnest possible wire surrounded by
the thickest practicable insulation. The next thought is to employ
electrostatic screens. The insulation of the wire may be covered with
a thin conducting coating and the latter connected to the ground. But
this would not do, as then all the energy would pass through the
conducting coating to the ground and nothing would get to the end of
the wire. If a ground connection is made it can only be made through a
conductor offering an enormous impedance, or though a condenser of
extremely small capacity. This, however, does not do away with other
difficulties.
If the wave length of the impulses is much smaller than the length of
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