A more interesting piece of apparatus is illustrated in Fig. 35. The
construction is the same as before, only instead of the lamp filament
a small platinum wire p, sealed in a stem s, and bent above it in a
circle, is connected to the copper wire w, which is joined to an
inside coating C. A small stem s_1 is provided with a needle, on the
point of which is arranged to rotate very freely a very light fan of
mica v. To prevent the fan from falling out, a thin stem of glass g is
bent properly and fastened to the aluminium tube. When the glass tube
is held anywhere in the electrostatic field the platinum wire becomes
incandescent, and the mica vanes are rotated very fast.
Intense phosphorescence may be excited in a bulb by merely connecting
it to a plate within the field, and the plate need not be any larger
than an ordinary lamp shade. The phosphorescence excited with these
currents is incomparably more powerful than with ordinary apparatus. A
small phosphorescent bulb, when attached to a wire connected to a
coil, emits sufficient light to allow reading ordinary print at a
distance of five to six paces. It was of interest to see how some of
the phosphorescent bulbs of Professor Crookes would behave with these
currents, and he has had the kindness to lend me a few for the
occasion. The effects produced are magnificent, especially by the
sulphide of calcium and sulphide of zinc. From the disruptive
discharge coil they glow intensely merely by holding them in the hand
and connecting the body to the terminal of the coil.
To whatever results investigations of this kind may lead, their chief
interest lies for the present in the possibilities they offer for the
production of an efficient illuminating device. In no branch of
electric industry is an advance more desired than in the manufacture
of light. Every thinker, when considering the barbarous methods
employed, the deplorable losses incurred in our best systems of light
production, must have asked himself, What is likely to be the light of
the future? Is it to be an incandescent solid, as in the present lamp,
or an incandescent gas, or a phosphorescent body, or something like a
burner, but incomparably more efficient?
There is little chance to perfect a gas burner; not, perhaps, because
human ingenuity has been bent upon that problem for centuries without
a radical departure having been made--though this argument is not
devoid of force-but because in a burner the higher vibrations can
never be reached except by passing through all the low ones. For how
is a flame produced unless by a fall of lifted weights? Such process
cannot be maintained without renewal, and renewal is repeated passing
from low to high vibrations. One way only seems to be open to improve
a burner, and that is by trying to reach higher degrees of
incandescence. Higher incandescence is equivalent to a quicker
vibration; that means more light from the same material, and that,
again, means more economy. In this direction some improvements have
been made, but the progress is hampered by many limitations.
Discarding, then, the burner, there remain the three ways first
mentioned, which are essentially electrical.
Suppose the light of the immediate future to be a solid rendered
incandescent by electricity. Would it not seem that it is better to
employ a small button than a frail filament? From many considerations
it certainly must be concluded that a button is capable of a higher
economy, assuming, of course, the difficulties connected with the
operation of such a lamp to be effectively overcome. But to light such
a lamp we require a high potential; and to get this economically we
must use high frequencies.
Such considerations apply even more to the production of light by the
incandescence of a gas, or by phosphorescence. In all cases we require
high frequencies and high potentials. These thoughts occurred to me a
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
the wire, then corresponding short waves will be sent up in the
conducting coating, and it will be more or less the same as though the
coating were directly connected to earth. It is therefore necessary to
cut up the coating in sections much shorter than the wave length. Such
an arrangement does not still afford a perfect screen, but it is ten
thousand times better than none. I think it preferable to cut up the
conducting coating in small sections, even if the current waves be
much longer than the coating.
If a wire were provided with a perfect electrostatic screen, it would
be the same as though all objects were removed from it at infinite
distance. The capacity would then be reduced to the capacity of the
wire itself, which would be very small. It would then be possible to
send over the wire current vibrations of very high frequencies at
enormous distance without affecting greatly the character of the
vibrations. A perfect screen is of course out of the question, but I
believe that with a screen such as I have just described telephony
could be rendered practicable across the Atlantic. According to my
ideas, the gutta-percha covered wire should be provided with a third
conducting coating subdivided in sections. On the top of this should
be again placed a layer of gutta-percha and other insulation, and on
the top of the whole the armor. But such cables will not be
constructed, for ere long intelligence--transmitted without
wires--will throb through the earth like a pulse through a living
organism. The wonder is that, with the present state of knowledge and
the experiences gained, no attempt is being made to disturb the
electrostatic or magnetic condition of the earth, and transmit, if
nothing else, intelligence.
It has been my chief aim in presenting these results to point out
phenomena or features of novelty, and to advance ideas which I am
hopeful will serve as starting points of new departures. It has been
my chief desire this evening to entertain you with some novel
experiments. Your applause, so frequently and generously accorded, has
told me that I have succeeded.
In conclusion, let me thank you most heartily for your kindness and
attention, and assure you that the honor I have had in addressing such
a distinguished audience, the pleasure I have had in presenting these
results to a gathering of so many able men--and among them also some
of those in whose work for many years past I have found enlightenment
and constant pleasure--I shall never forget.
[Transcriber's note: Corrected the following typesetting errors:
1) 'preceived' to 'perceived', page 16.
2) 'disharging' to 'discharging', page 30.
3) 'park' to 'spark', page 33.
4) 'pssition' to 'position', page 50.
5) 'to th opposite side' to 'to the opposite side', page 56.
6) 's resses' to 'stresses', page 147.]