Evening star., 1902-08-19

channel or acrossJthe Yucatan channel or
the entrance to the Gulf of Mexico or all
three combined, she may then receive re-
ports at will of Sany suspicious circum-
stance, the apprach Of hostile fleet or any
other information necessary for effective
action.
edge of the principles involved in the use Of
wireless telegraph apparatus It is based
entirely upon the-abifity of an operator
with certain deilease apparatus, to detect
or electric pulsations, which are radiateS
in all directions with the velocity of light
on the discharge of an ordinary electric
spark; Ihese waves may perhaps be best
throwing stone into the center of a placid
and quiet pool. just how far thew travel
is unknown; it probably depends somewhat
upon the intensity Of the electric snerk. in
fact, this has been fairly wen demonstrat
ed. We are not so much interested. how
ever, in the journeys OF these waves as in
the distance from the operator at which we
can detect their presence. 1t is also a fair
ly well established fact that Hertzian
waves follow the surface of the earth and
are parallel to it.
Suppose we now erect on the surface of
the earth near the transmitting station a
vertical wire or other good Conductor Of
electricity; If insulated from the earth IT
may be utilized to transmit a current of
electricity and discharge a spark into the
air.
To Generate Electric Sparks.
For generating electric sparks the
Rhumkoff coil is ordinarily used This YOU
win probably remember as an old labora-
tory friend. An ordinary voltaic battery
is used in connection with the Rhumkofr
coil. To obtaip greater distance of trans
mission, however, a dynamo is used in
stead of a voltaic battery and a larger
induction coil than the ordinary Rhumkofr
type. In Its simpest form the battery or
dynamo Is placed in the circuit of the
| primary of the induction coil, in which
there is also placed an ordinary telegraph
make-and-break circuit key. One mole of
the secondary winding of the induction
coil is connected with the ground, and the
other pole Is connected to the transmitting
aerial wire, already alluded to.
Let us pass to the receiving station The
essential instrument of the receiving appa-
ratus Is called coherer. 1t consists of
two metal plugs, or electrodes, separated q
short distance from each other, about one
thirty-second Of an inch, placed in a glass
tube or some other tube of insulating ma
terial, with the intervening space partially
fllled with loose metal filings, usually Of
steel iron or nickel. 1t is also usual to
have these filings semi-oxidized. This in
strument was invented by Branly and not
by Marconi, as popularly supposed The
metal filings In the condition described do
not afford sufficiently good conductor to
permit an ordinary voltaic current to mass
from one electrode to the other. When
however, spark jumps across this small
interval in the coherer the metal filings ap-
pear to arrange themselves in line from one
electrode to the other sufficiently close to
give good metallic contact and thereby
complete the circuit Of a local battery al
ready connected to the electrodes It is
plain that this local battery may be made
to do certain work, such as operating an
ordinary sounder or recorder
To Establish Connection.
sWa oey+ +obI
tween the Hertzian wave coming from the
distant station, and the spark which passes
through the coherer, in order to establish
practical working apparatus At the re-
ceiving station is am aerial wire. supported
as at the transmitting station: sometimes
TO multiply effect, a number of aerial wires
are supported by masts, all of which wires
are brought together before connection is
made to the instrument; sometimes the
length of the aerial wire is Increased TO
800 or 800 feet by meaffs of a balloon
II IS natural to suppose that the effect
OF the Hertzfan waves will be increased in
proportion to the number Of conductinp
surfaces impeding their progress. II an
pears that when the wave arrives It creates
IN the wire a certain electric pulsat tion
current or effect which, passing into the
operating room, is led through the urinary
of an Induction coil and then to earth. Tt
Is curious fact that the wire is more ef-
fective it, instead of being exactly vertical.
1t fncllnes to the vertical somewhat less
than 45 degrees. 1t will be remembered
tnat at the transmitting station the poles
OF the secondary coil are practically con-
nected, one to the earth and the other to
the air. We now complete the circuit: the
electric wave passes through the air, is
caught by the vertical wire and goes to
earth, doing certain work en- route. That
work is to excite the primary of an induc-
tion coil, which In turn excites the second
ary winding of the coil connected directly
Of tha nnha hi
duces the effect described The little break
of one-thirty-second of an inch Is bridged
over, the local battery comes in play and
the sounder or recorder Is brought into op-
Grafton There are certain transformers
condensers, etc, used to magnify this ef-
feet, which 1t is not necessary for US to
discuss.
THE essential features of the apparatus
nave now been described with one eXcep-
tion. We have changed our coherer from q
non-conducting instrument to one which
readily conducts the current Of the local
battery; 1t therefore is not in condition to
repeat the work already described, and it
must be restored to its original status
before the arrival Of another Hertzian
wave can be signaled. In the same circuit
as the local battery Is what Is known as a
Taper consisting of a hammer worked
Dy an electromagnet which, every time the
circuit is closed, gently taps the coherer In
the center; this tap causes the metal filings
to drop from the positions arranged by the
SPARKS to irregular positions, thus breaking
the circuit of the local battery. Another
wave comes along. the act described Is re-
peated. and this is kept up indefinitely. The
operator, by keeping his key down Snort
and long intervals. causes the receipt OF
dots and dashes and thus the sgnificatton
OF the waves Is made complete"
Tests Between Ships.
After the shore tests are made Admiral
Bradford will ask for one and later for
two ships The shore tests will be
followed by tests for a ship at sea with
a shore station, and subsequently between
two vessels at sea-
1t Is pointed out by naval officers inter-
ested In this subject that the American
navy Is far behind European navies in the
matter OF wireless telegraphy. England
has over thirty ships equipped with the
Marconi system, and Germany's ships are
generally being fitted with wireless ap-
paratus Much attention is being devoted
to the subject IN France, where three sep
arate boards are at work, and In Italy.
where sixteen officers are devoting their
entire attention tonexprfmentatton.
In the United Statcs,5 on the other hand,
but single off1cer;sLient Hudgins. so far
has been detailed exclusively to this sub
5ect: The lack of progress along these lines
in the navy however IL not to be charged
to Admiral Bradford who believes that q