The morning news. [volume] (Savannah, Ga.) 1887-1900, 1898-02-26

Electrician Dodd, who has a cabin on the
main deck which is equipped with the va
rious electrical appliances necessary for
the purpose. The efficiency of the electri-
cal department is, OF course, of prime i'm
portance on a cable ship.
The cable Is usually broken so that the
copper conductor is freely exposed to the
salt water, and in such cases the locating
of a break or imperfection may be COM
paratively easy matter, unless there OBJ
tain certain adverse conditions which il
is not necessary TO mention here. In MAX
ing the test the operator whether he be
on the ship or at one of the cable sta
tons on shore, sends an electric current
INFO one end of the cable and lets it flow
out into the sea at the other end. The
current as ever schoolboy knows, exper-
fences a certain resistance in It's passage,
and the amount of this resistance is pro-
portional to the length of the conductor
through which it flows. So, leaving out
of consideration in this instance any dis
turbing causes, it is obvious that if a cable
IS broken in the middle the resistance TO
the current OF electricity will be only half
as much as If the current flowed through
the whole length of the conductor.
The amount of resistance is measured
by an electrical unit, the ohm In the
testing apparatus are coils of wire care
ohms resistance 10 a current flowing
through them. The test consists an bal
incing the coils of known resistance in
the apparatus against the unknown re
sistance offered by the cable conduct tor
in somewhat analogous way to that by
which one obtains the weight OF an I'M
known substance by balancing it against
known weight. OF course in perfecting
the test, there are various corrections to
h.ao or f,I nd 4 fHf,,,f 49, I
times there occur breaks or faults in the
cable which it is very hard TO locate,
but in most cases the trouble can be 10.
Called by ascertaining the resistance be-
tween the testing point and the seat of
the trouble.
All cables. whether in operation or stor-
ed ready for use, are tested regularly,
whether any trouble is suspected or not
The Atlantic cables are tested weekly, and
a careful record kept of the amount of
resistance of each test. so that when a
break occurs II is at once known how much
resistance per miie the cable had been Of
fering before the break occurred, and di-
Vidins the total resistance of the cable by
the resistance Der mile from the testing to
the breaks shows the number of miles be-
tween those two points. The distance be-
ing obtained, it then only remains for the
NAVIGATOR TO refer 10 his cable charts in
OTueF 10 KNOW 10 what point IN the ocean
he must direct his ship. This method of
locaiizaton is generally very accurate
Rarely is there an error of more than
two miles. and often ii is less than one
mile.
Breaks in the cable are due to a variety
of causes. The most common one in shoal
water is the tearing of the cable by the
anchor of some vessel The caple is Of
ten damaged, too. by chatting on rocks and
by an iceberg grounding on top of it. In
deep water these causes are not operative
and the breaks are usually due to decay
There is some reason to suppose that in
South American ATTITUDES the swordhsh
cuts the cable in two. but this is not
known. Faults are oeeasioned i'm shallow
water nv submarine insects eating into the
gutta percha afterAhe wire armor has de-
cayed, but there is a good deal of mystery
surrounding the causes of decay in mid
ocean. Some noted scientists have stated
that seismic, disturbances sometimes make
trouble, but Capt Trott entirely objects
to the theory.