Omaha daily bee., 1899-11-03
The FIELD OF ELECTRICITY
1xpert Analysis Of the Marconi System Of
Wireless Telegraphy.
RIVALS FOR THE ITALIANS HONOR
Aluminium Wire Coming Into Use ns
a substitute for Copper-Comipg
Train Light Casts Its
shadow before.

III lut IOpulhT SClc0Ce MOntnly lOE ANU- |
vember, Prof John Trowbridge of Harvard
university discusses the method OF COM
munication which is now so closely asso-
ciated with Marconi's name. Prof. Trow
bridge is so well known for his own re-
searches into electrical phenomena and for |
the caution which characterzes his state
ments about such matters that his utter |
anoes will command confidence as well as |
respect. .....
One Of the most interesting features Of the |
article in question is its explanation of the |
function of the vertical wire with which |
Marooni so greatly enhanced the efficiency |
OF his apparatus In the first experiments
with Hertz wave telegraphy 1t was supposed
that vibrations which conveyed the mes
sage from one station to the other proceeded
only from the spark gap" of the induction
coil-an interval OF few inches between
two brass knobs. But Prof. Trowbrldge
points out that the vibrations extend up
the vertical wire and pass out into space
horizontally from its whole length The
vibrations are not apparent to the eye.
The wire does not move But the electro
magnetic impulses travel along the metal
and then are thrown off in concentrc cir
cles into the ether-a series of ripples like
those proceeding from a stone dropped into
the middle Of pond. Each wave Is
continuous affair from the bottom to the
top of the wire.
So, too. at the receiving end, 1t Is not
merely the tiny "coherer" that picks up
the waves. but the entire piece of wire at
tached thereto Its vertical position and
length render 1t peculiarly susceptible to
the incoming disturbance OF the ether. The
vibrations, thus caught, are conveyed along
uyire To 10 influence
device very much as the engineers hand
does a valve in a steampipe. The current
of local battery, flowing through short
circuit at the receiving station, is thus
enabled to actuate "sounder" and the
message is licked off as in ordinary teleg
raphy.
Focusing the Waves.
When one recognizes that the source from
which the waves proceed is not the spark
gap alone, but the vertical wire also, he
perceives that 1t Is practically impossible to
catch and focus them as the rays OF search
light are concentrated. There has been
some attempt at that sort of thing, but II
Prof. Trowbrdge is correct such efforts
are futile These vibrations which go out
directly from the spark gap can thus be
focused, but not those from the wire. The
use of a parabolic mirror therefore, would
seem to be unavailing, either in increasing
the range of the transmitter or in insuring
secrecy. That electro magnetic waves are
thrown off laterally along the entire yerti-
cal wire has been demonstrated afresh at
the jefferson laboratory. Prof. Trowbridge
places sensitive plates so that the wire can
pierce them at the center and then sprinkles
iron filings on them When the induction
coil is put into operation and electro-mag-
netic waves are sent up the wire they COM
pei the iron filings to arrange themselves in
concentric circles around the wire. The ar
rangement of the latter Is then recorded by
photography. This effect can be secured at
any part CT the wire.
The only method of which Prof. Trow-
bridge can conceive for extending the dis
tance to which messages can be sent by the
Marconi system is one that would intensity
the shock given to the wire by the spark
There is a close analogy between the be-
havior CT electromagnetic waves and sount
waves To be sure, the latter are enor
mously slower and less frequent than tn,
former. And sound Is transmitted only b.
matter. 1t will not go through vacuum
But Hertz waves are propagated by tha
attenuated medium which is supposed t.
fill interstellar space, the ether. However
there are many points of resemblance be
tween them
For instance, il a piano string is strucl
feeby the note which 1t emits will be audi
BILE at only a short distance. But the NOR
vigorous and more abrupt the stroke tn
further the sound will travel. "A spar
always proceeds from the gap opened in a
ordinary electric circuit whenever brea
is made And simultaneously a few wave
are communicated to the surrounding ether
They may be very feeble, but they ar
generated at least. The suddenness OF tn
stoppage OF the current has something t
do with the force OF these waves. Henc
electricians have sought for means OF In
terruption which should give the most con
spicuous effects. The old induction CO
yields a more intense eurrent than can
obtained otherwise and modern attachment
to 1t impart a peculiar sharpness to th
break Now Prof. Trowbridge thinks tht
only by developing this method further ca
the range Of wireless telegraphy be e,
tended. The instrument known as rela
by means OF which messages transmitted /
the Morse system can be repeated and thu
sent beyond the station at which they a.
first received, is not applicable to the Ma
conf plan.
The possibility of maintaining secrecy
communication is considered briefly by Il
Harvard expert. He deems 1t credible tn
some day the frequency OF the waves VI
be SO controlled that only receiving II
strument attuned to this rate will respol
and no other receiver VIII De sensitive
given transmtter. Marconi and othe
have talked of this good deal and wi
differences OF opinion have been express
witbing the last two years about the feas
bility of achieving the result But fro
the way in which Prof. Trowbridge spea
1t Is to be inferred that as yet the th
has not actually been done Thus far me
OF the experiments made with Hertz wa
telegraphy have aimed to enlarge, not
limit its scope.
Other Claimants.
view of the number OF inventors W
now claim to have discovered the one perf'
method of transmitting signals throu
space on the wings OF the ether. con
papers assertion that wireless telegrap
is in the air" would seem to be justin
An Oklahoma man claims to have a syst
OF great simplicity, by means of which
can talk with towns sixty miles acr
country. Ducretet the French experiment
prophesies that transatlantic cables
soon be abandoned in favor of his syste
which will carry wireless messages fr
Paris to New York He needs only
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