The evening times., 1899-05-31
WIRELESS TELEaRAPHY.
A Method Radically Differing From
MarcOnf's Plan.

|
A system of wireless telegraphy differ
ing in principle from that of Marconi is at
tracing attention just now in the world Of
science. The essential fact which is utiliz-
ed in the new method was discovered by
| Hertz in 1887, and has since been devel-
oped more fully by other investigators.
Ordinary white light when analyzed by a
| prism Is broken up into spectrum OF vari-
| Gus colors. each one representing vibra-
tions of the ether at different rate from
| those of the others. The violet rays have
a much shorter wave length than the red
ones. By photography and other Eeans it
has been ascertained that in addition to
| the waves which produce visible colors
| and the visible effect which is called
light there are others which are shorter
| than the violet waves, and some that are
much longer than the red ones.
What are called the ultra violet" rays.
| because they proceed from a region in the
| spectrum beyond the visible violet, possess
| relation to electricity. One of their char
| acteristics is that If they are projected
upon an electrified object they will assist
in discharging the store of electricity
thereon. Here is another popularity: Sup
pose that narrow gap is created in cir
cult through which an electric current has
been flowing; that the wires on each side
the knobs have been so near each other
! that the current can leap across, in
shower of tiny sparks. Now, if the dis
| tance be increased n trifle, just enough to
! check the flow Of sparks across the gap.
| and then a beam of ultraviolet radiance
| be made 10 fall upon the knobs, the How Is
restored, and the sparks will again begin
| to leap from one terminal to the other with
almost incalculable frequency.
Prof Zickler, of Brunn, Moravia, has
perfected a method of signaling with ul-
tra-violet rays, in which he employs ap-
paratus operating on the principle just in
dicated AT the sending station he uses
an electric light of the arc pattern, mas
much as the electric arc Is particularly
rich in ultraviolet rays. The light from
the lamp is concentrated by means OF a
concave mirror, as in the case OF search
light, and is projected in slender, COM
pact beam. A lens used in the front of the
lamp to assist in the work of concentration
is made of a specially selected material, Il
kind of quartz, which will not filter out OF
the light the invisible ultraviolet rays.
Immediately ahead Of the lens Is placed
movable screen of glass, that has also been
chosen carefully because it will obstruct
these ultra violet rays. although it will not
interfere with the visible radiance from the
arc.
system of telegraphy knows that the ope-
rator alternately closes and opens an cleo
tric circuit by bringing one terminal IN
contact with the other and then withdraw
ing ii. The length Of time during which
a contact lasts and the size OF the space
between the contacts can be varied enough
TO constitute full alphabet. In the Zick-
Ter system the letters are formed after the
Morse code or any other that may be pre-
ferred simply by removing the glass screen
from in front of the lamp and then restor-
ing it. The interruptions of the invisible
radiance effected in this way are of such
lengths and are so spaced as to fall into
an Ineligible scheme. Instead of open
ing and closing a key" as in ordinary
telegraphy the operator uses a convenient
device for altering the position Of the glass
screen in front Of his arc light.
AT the receiving station a bit of appa-
ratus is used in which a suitable lens
catches the pencil of parallel rays and TO-
cuses them. Just inside the box in whose
front this lens is set there are two termi
mails of an electric circuit brought near to
each other. but without touching. One of
the terminals is a small globe coated with
platinum foil. The other is a round, fiat
plate having a polished surface, SO as to
serve as a reflector as well as an electrode.
1t not only helps to complete circuit for
the flow of current through wires in the
station, but it also catches the focused in
coming ultra violet rays, so that they fall
In a tiny spot on the centre Of the disk.
The disk is set at such an angle that
the rays are reflected onto the globular ter
minal. Both. then feel the influence of the
ultraviolet rays, and are enabled to de-
velop a stream of sparks that would not
otherwise flow. The sparkling is not the
important feature Of the performance,
though But the flow of the current thus
promoted may be made to affect other in
struments in the circuit, such as sound
er" or telephone or bell. And when, by
the interposition Of the obstructing screen
at the sending station, the arrival of ul-
ira violet rays at the receiving end is stop
ped the flow of the local current ceases,
too The apparatus here described can be
made to give signals by any Of the ap-
proved systems.
1t should be noticed that this plan Diff
fers from the photographic method Of sig
mailing with a sunbeam thrown from mir
ror in this important respect: The latter
plan deals with visible light, which is COM
pletely extinguished and restored. Anyone
near the receiving station can see the
flashes and interruptions and if versed in
the code can read the messages being
transmitted. But in Prof. Zickler's system
the luminous rays of the arc light continue
to shine steadily. No one sees any fuct-
uation in their brilliancy. All that is in
terrupted and restored is a beam of abso-
lutely invisible radiance. which can be de-
tected only by a suitable receiver.
The receiver, too, must be suitably p'ac-
ed. Unless the beam from the sending sta
ton falls upon the lens Of the receiving
apparatus its signals cannot be read. The
system guarantees perfect secrecy, there
fore, something that even the Marconi
method does not now seem to promise.
The electromagnetic waves which Marconi
uses are generated in such a manner that
they spread in all directions and can be
picked up by anyone who has a receiving
instrument of the right sort
Searchlights have been made which
throw a beam for a distance of thirty or
forty miles, and an interval of ninety or q
hundred miles has been spanned by the
Chicago Fair protector, which was removed
to Mount Lowe, in California, and trans
ferred to the vicinity of San Francisco dur
ing the war with Spain. Presumably the
invisible rays can be detected as far away
as the luminous ones. And it is conceiv-
able that with improved apparatus this
system can be worked successfully for
more than a hundred miles. 1t is a costly
system, however, and available only for
service in which it is feasible to lay out
large sums OF money for the original in
stallation.
Thus far Prof. Zickler has covered only
about mile with his successful expert
ments. This must not be regarded as any
indication of the limitations to which the
plan is subject. Although Marconi has had
a line working for year or SO between
the Isle Of Wight and Bournemouth, eigh-
teen miles away, and expects soon to have
another working across the English Chan