The times. [volume] (Washington [D.C.]) 1897-1901, 1899-04-30
WIRELESS TELEGRAPHY.
Four Recognized Methods of Send
Ing Electric Air siEnnIa.


to au extended and animated discussion of
other systems of wireless tclegraphy.
AT the present time there are at least four
Clearly recognized methods OF sending e,ec-
trio signals without metallic connections
between stations. Mr.. Preece tried what
is called induction He laid a mile of
wire along the ground on the mainland,
and another mile of wire, parallel with the
first. on an island a mile away. A message
sent through one circuit was caught by
induction" in the second very much as
telephone message was at one time over
heard by users CT a parallel telephone wire,
Although Dir. Lodge and some others think
that this system may yet be developed
further. Mr.. Preece himself has practically
abandoned 1t as unsatisfactory and I'M
promising.
Secondly. there is what is known as the
Hertz wave method. BY wsll-known APP
paratus-an induction cola stream OF
sparks is produced a. gap In an electric
circuit Electro magnetic waves are
thrown out sidewise from the gap. These
can be picked up at a moderate distance
by means OF one of the many sensitive de-
vices well known to expert electricians.
Marconi uses a bit of mechanism called
the ''coherer." which was invented by
Branley. He connects coherer a local
battery and an ordinary telegraph.c sound
er with short wires, and whenever Hertz
waves from distance fall on the coherer,
the latter permits the local current to pass
and actuate the sounder. The only origi-
nal part of Marconi's work. apparently,
was the addition to the coherer OF an au-
tomato Taper. which caused the parti-
cles of metallic dust in the coherer to fall
apart and break the connection when no
waves were coming from space to affect it.
Thirdly, there is what is called the Con-
duction' method. 1t has been proposed to
drop a wire from the transmitting station
into the earth or sea. and a similar wire
from the receiving station to the
same conducting medium, and let
the message go through this AS
yet this plan has been tried only imper-
fectly, and on small scale. Silvanus p
Thompson once offered to the British gov
eminent to establish communication be-
tween London and the Cape of Good Hope
in this manner, If he could have $50, goo
with which to procure and install the nee
essary instruments.
Fourthly. an important modification OF
the last mentioned plan has been suggest
ed by Mr. Tesla, who has experimental
with all of these systems. and who has
gone rather further into the theories in
volved than many others whose names are
often heard in connection with wireless
| telegraphy. In lecture which he deiiv-
| cred in st. Louis in February. 1893. Mr..
| Tesla roughly outlined plan that should
utilize the earth. but should supplement
| the apparatus which produced his current
with short conductor that ran up a pole
into the air for a short distance and terrni-
mated in fiat metal plate. This plate
would correspond TO the Leyden jar, or
condenser" of the laboratory. The quail
ty OF the current sent into the earth would
be affected in certain ways by such an at
| tachment.
| The nature of the influence thus exerted
| may be inferred from one of Mr.. Tesla
| most famous inventions, the Tesla coil"
| This consists Of a condenser and an Undue
| ton coil in combination. An induction coil,
| it will be remembered, is made of two
| carefully insulated coils of wire, one short
| and coarse, and the other long and fine
| II current is sent through the coarse
wire, or primary circuit" it induces an
other, possessing less quantity but higher
| pressure, in the fine wire or Secondary
circuit. Now, Mr.. Tesa's scheme was to
| take a condenser, pour his current into
| this first, fill it to overflowing, and then
let the escape lead to the primary circuit
| of an induction coil. The current in the
secondary would then possess new charac-
teristics. 1t would be made up of abrupt
vibrations of almost uncomfortable frequen
cy and penetrating power. In the produc-
| ton of x-rays and many other kinds of
electrical work, the Tesla coil has been
found to be an exceedingly valuable in
| strument.
OF course, since the St Louis lecture
was delivered Mr.. Tesla has perfected sew
eral other devices, notably his "oseillator.'
which increases the possibilities of -'poten-
tial, voltage" pressure" or whatever
else one may choose to call the penetrat-
| inc ftp af oil 9Th
instruments which he has invented EN-
crease the efficiency of the scheme out
| lined more than six years ago, but they
do not alter or add essentially to the prin-
| ciple.
1t is a singular fact that when Marconi
first began to work with Hertz waves he
did not use any vertical wire running up
a pole and terminating in a metallic plate.
But as soon as he added that feature to
his equipment. he was delighted to find
that he had improved its working quail
ties. In a paper which he read before the
Institute of Electrical Engineers in Lon
don last month, Marconi said: with
other forms of Hert2ian transmitters and
receivers. / find it quite impossible to OBJ
| tain any results if hill mountain or
| large metallic object interyenes in any
way between the two stations. When the
vertical wire system is employed. il be-
comes easy to telegraph between posi-
tons screened from each other by hill
or the curvature of the earth.
am rather doubtful as to the correct ex-
PLANTATION of this effect. as there can b.
very little doubt as to the complete opac-
ity of hill three miles thick, or. say
several miles of sea water. way out oil
the difficulty may be arrived az, II we sup
pose that the electrical oscillations a-e
| transmitted to the earth by the earth wire
from the induction cold, travel along the
face of the. earth, reach the earth wire OF
the reacting instrument, and by travelling
up this wire to the coherer bring about its
action"
If this explanation be approximately
correct. it would seem possible, net to say
probable. that two sets of vibrations arr
excited. one at the spark gap. traversine
the ether. and the other sent down into
the earth. The former may be discerniblt
at a short distance but the latter at
much greater one. Thus Marconi appear:
to be producing a double result, and to b,
discovering the fact gradually. The edect
which is produced at the greater distance
looks very much like that which Mr. Tesla
contemplated in his st. Louis lecture NOR,
than six years ago. In view of the printed
record, which anyone may find for himself
il is strange that Mr.. Tesla when cues
toned on the subject. speaks as graciously
as he does about Marconi He cannot b;
persuaded into uttering uncomplimentary
imputations or interpretations. If any in
justice has been done, he evidently trust:
to time TO rectify and the innate homes q
of the scientific world to set things right
In discussing the value of a vertical wire
or an elevated station, The London Tele.
graph remarked few days ago: DIR
Slaby. of the Technical High School. a
Charlottenburg. near Berlin. last yeal
| made an Interesting sarias of inrnst in.n ion.