The Wheeling daily register. [volume] (Wheeling, W. Va.) 1864-1878, 1877-09-14
OCEAN CABLl 3.
How Words are Sent Under the
Water.
From Good Words.

FROM GOOu WoAue.H----
In overland lines the current traVerses
the wire suddenly, so that II the current
he sufficiently strong the Instruments VIII
be worked 1t once and no time VIII De
Lost But it is quite different In suoma
rine cables. There the current. ms slow
and varying. 1t travels along the cop
ner wire in the form of q wave or urdu-
istiop. and is received feebly at hrst, then
gradually rising to its maximum strength,
and finally diving away again rs slow y
"a il rose In the French Atlantic cable
no current can be detected by the most
delicate galyanescope at America LOT tue
first tenth of second after 1t has been
nut on at Bresl; and II takes ABOUT
half q second for the received current 10
reach its maximum value; This is owing
TO the phenomenon OF lnductioh' very
important in submarine cables, but almost
srtIrely absent In land lines. In snDha-
rine cables, IT Is well known, the copper
WIRE which conveys the current IL lnsu-
| tied from the sea water by an envelope,
usually of gutta percha. Now, the e,ec-
tricity sent into this wire induces elec-
tricity of an opposite kind to ItSefl IN Ine
sea water outside, and the attraction SET
no between these two kinds "hoids bacK
the current in the wire and re-
tards lis passage 10 the receiving
station. 1t follows, that with u
receiving instrument set to indicate
a particular strength OF current, the rate
of signaling would be very slow on long
cables compared To land lines; ana thsl
"a different form OF instrument Is requlr-
ed Tor cable work. This fact stood great
ly in the way of early cable enterprise.
Sir William then PrOiessor) Thompson
first solved the difficulty by his invention
of the "mIrror gslvanometer. ana rem
dered ut the same time the hrst Atlanllc
cable company u commercial success
Tue merit OF this receiving instrument Is
that It indicates with extreme sensibihty
All the variations of the current In the
cable, so that, instead OF having 10 "ail
uRtll each signal wave sent into lhe cable
has travelled 10 the receiving end before
sending another, u series oi waves
NAV be sent after each other In
rapid succession. These waves, en-
croaching upon each other, will coaiease
a. their bases; but If the crests remain
separate the delicate declpherer at the
other end will take cognizsnce of them,
aud make them known to the eye rs the
distinct signals OF the messenger. Inc
mirror galyaDometer is NJ once beauti-
fully simple and exqUlsitely scientific.
l. consists OF very long fine coil OF silk
covered copper wire, and In the heart OF
the coil. within a little air chamber, =
small round mirror, having four tiny
magnets cemented to its back, is hung
BY u single fiber of floss silk no thicker
than spiders line. The mirror Is OF
finn glass silvered, the magnets OF hair
spring, and both together sometimes
weigh only One-tenth OF grain. A beam
of light is thrown from lahIp upon the
mirror and reflected by it upon n white
screen or 81 ale few feet distant. where
1t forms bright spot OF light. When
there is ua current ON the instrument,
the spot OF light remains stationary ut
the zero position on the screen; but the
instant current traverses the long wire
of the coli, the suspended magnets twist
themselves horizontally out OF their form
er position, the mirror Is OF course IN
chned with them, and the beam OF hight
is detected along the screen to one side
or the other, according 10 the nature OF
the current. If n positive current, that
is to say current from the upper pole
OF the battery, gives detection to
the right oil zero, negative cur
rent, or current from the Zlnc
pole of the battery, will give detection
t. the left OF zero, and vice versa. The
a r in the little chamber surrounding the
mirror is compressed al will, so aS 10 act
like cushion and "deaden" the move
ments of tho mirror. The needle is thus
prevented from idly swinging about At
each detection, and the separate signals
are rendered abrupt and dead beat, Ms
1t Is called. At receiving station the
current coming IN from the cable has
simply TO be passed through the coil OF
the Speaker" before II Is sent INTO the
ground, and the wandering light spot
on the screen faithfully represents all
the variations To the clerk, who, look
in on, interprets these and cries
out the message word by word.
The small weight OF the mirror and mag
net which form the moving part ot this
instrument and the range To which the
minute motions OF the mirror can be
magnifed on the screen by the reflected
beam OF light, which acts as n long I'M
p4lpable hand or pointer, render the mir
ror galvanometer mslvelously sensitive
to the current, especially when compared
with other forms Of receiving instru-
ments Messages have been sent from
England to America through one Allan
tic cable aud back again TO England
through another, and there received on
the mirror galvanometer, the electric
current used being that from toy bat"
terry made out OF n lsdy's silver thimblc
a grain OF zinc, and drop OF acdusted
water.