Wheeling register. [volume] (Wheeling, W. Va.) 1878-1935, 1899-10-05
and reliable than those used by Cal
zecchi, Brandy and others.

I IA9AtAJ 80 A4
| other by about one-thirtieth of an inch,
the gap between them being partially
| filed with a mixture of nickel and sill
yer filings. These materials have been
| found to be the most sensitive and re-
liable after a long series of expert
ments.
So much for the coherer. The rest of
the receiving apparatus is perfectly easy
to understand. In circuit with the CO.
herer is a single dry cell and "a tele-
graphic relay of the ordinary type. This
| relay is used to close the circuit of a
local battery, which works a Morse
writing instrument and also an electric
bell hammer. The hammer strikes the
coherer a smart tap to restore 1t to its
normal high resistance after it has re-
ceived an impulse from the distant
transmitter.
To protect the coherer from the too
powerful effects of the local transmit
ter the whole receiver is inclosed in a
metallic box.
To receive a message all that is nee
essary is to connect the vertical line,
either directly or through a small in
duction coil, to one end of the coherer,
the other end of it being connected to
earth.
| DISTANCES so FAR COVERED.
The chief factor in determining the
distance of transmission possible is the
height of the vertical wire. Mr.. Mar
conf finds that by doubling the height
the distance becomes quadrupled. That
is, assuming 20 feet will give one mile,
40 feet will give four miles, 80 feet six
teen miles, and so on. There are, Of
| course, other factors, such as the sensi-
tiyeness of the coherer and the adjust
ment of the apparatus generally, but ap-
parently they are not so marked in their
effects.
Why this vertical wire is necessary
i for long distance is not certain. 1t has
been suggested that the earth's curva-
ture may have something to do with
it. Compare this, however, with Mr..
Marconi's results in the English naval
maneuvers last summer, when, with
$50 feet of wire at each end, he sue
ceeded in te~legraphing rs miles. To do
this the a must have passed
through a "hill' of water 35 miles long
and 700 feet high.
More probably the vertical wire is
necessary because it's use lengthens the
waves and propagates them in a plane
vertical to the surface Of the earth, and
they are, therefore, less likely to be alb
sorbed by it. The fact that the waves
are heightened of course causes them
to be more penetrative and capable of
affecting a receiver at a greater dis
lance.
SPEED OF TRANSMISSION.
Of the working of a wireless tele-
graph station there is not much to say,
as it is essentially the same as that of
any other telegraph Office. At present
the speed of transmission is rather less;
it does not ordinarily exceed about ff-
teen words a minute, but this will, of
course, increase with time.
A call is indicated by s bell which is
switched off during the reception of a
message. AS before stated, the tele-
grams are printed in dots and dashes on
an ordinary Morse mixer, the operator
having merely to read them from the
tape.
The key used is of a slightly different
form from the usual Morse key, the
back contact being used to connect the
vertical wire to the receiver, so that
no changing over from the transmitter
to the receiver is necessary after send
ing a message.
KEEPING MESSAGES UNDER CON-
troll.
In a recent issue of Pearson's Maya
zine are the following points about the
Mareoni system, which will prove of in
terest:
One Of the peculiarities of the Mar
conf system is that the electric waves
set up by the transmitter radiate out
into space in all directions. Thus, if
you place a transmitter in the middle of
a park and put four receivers north,
south, east and west, then each of them
viii receive the same message. If the
system comes into general use, it will,
OF course, be necessary to find some ar
rangements by means Of which one
special receiver shall respond only to
4 special transmitter; otherwise one
would never know whether a message
was really intended for enc or not.
Mr.. Mareoni has found a means of pre-
venting messages affecting instruments for
which they are not intended. BY means
of refiectors it is possible TO project the
electric waves in an almost parallel beam
which will not reflect any receiver placed
out of the line of propagation This would
enable several forts or hilltops or islands
to communicate with each other without
any fear of an enemy tapping or inter-
fering with the signals.