The Ordway new era., 1915-08-13

SN most before the smoke OF
SM battle has cleared away,
A1 the submarine cable and
| ~ the methods used In keep
Ing 1t In repair are of interest.
Each submarine telegraph company
mas In service a fleet of cable ships.
the units of which are stationed at
dfnerent ports for quick access to the
different sections OF the cable. Let US
take, Tor example, the cable stretching
from San Francisco to Manila, a dis
lance OF 10.O10 miles. This cable is
divided into four sections-San Fran
cisco to Honolulu. Honolulu to Mid.
way island, Midway island to Guam.
and Guam to Manila. The cable lies
on the bed of the Pacific, which In
places runs from three to five miles In
depth. the latter depth being found OF
the island Of Guam. Sufficient slack
must be paid out in laying submarine
cable to allow every part to rest on
the bottom Of the ocean, however ir-
regular the bottom may be.
A cable varies In thickness and type
according to Its position and the ma.
ture Of the ocean bottom In the local
ity where It is laid. The shore end"
OF cable, meaning section laid close
to land. Is always thicker than a sec
ton out at sea. Ordinarily the diam
eter OF shore section runs about T2A
inches. while section laid in deep wa
ter runs about X inch in diameter.
About seven strands of copper. com.
prising single conductor. form the
core of the cable. Over this core are
laid coatings of gitta percha. layer
OF 1ute or oakum. and an envelope Of
composition rubber. Over this some
strands Of Strengthening wires are
wound on. and tarry rope and tape are
wound about the whole. The average
cost of cable complete is about 81 900
a mile.
A surprisingly small amount of cur
rent is required for operating a sub
marine cable. One OF the hardest
worked of the Atlantic cables requires
only 30 volts pressure at the sending
end. and all that comes out at the re-
cetvfng end is twenty-millionths am.
pere. Signals are transmitted simply
by alternately charging and discharg-
ing the cable. which works much like
Leyden jar. One Of the fastest OF
submarine cables transmits Abssst so
words a minute.
Interruption In cable communities
ton between two stations may come
from one Of several causes. There is
the fault" caused by the teredo, sub
marine boring animal that penetrates
the protective coatings in an effort to
get at the core. Then the shore end
of cable, in spite Of special protec.
tion. does not always withstand the
rolling and friction OF the tides, and
besides this. there is the risk that the
cable may be fouled, or lifted by a
ships anchor. A cable may part COM
pletely. from one cause or another.
forming what is known a. a total
break"
Let US imagine that the cable
from San Francisco to Manila Is
down." as 1t is technically et.
pressed when the cable is unwork.
able. in that section. zoos miles
long. between San Francisco and Hon.
oluiu We will assume that series OF
tests based on the law of resistances
has shown that the fault lies at point
1000 miles from San Francisco. Some
times 1t is possible by testing to locate
the position Of the fault within one
tenth mile. but the average is about
FIVE miles. Before the cable ship sails
for the ground" as the location Of
the break. or fault, is called. the ships
electricians will have made their own
tests and advised both the San Fran.
cisco and Honolulu ofices-the latter
by an alternate route-to keep watch
on their instruments in the office for
ship reaches the ground" a signal.
consisting of two red globes with
white diamond between, for day use,
and replaced by similarly colored
lamps at night, is hung in a vertical
line in front of the foremast head.
This signal indicates that the ship is
engaged In cable-repair work, and is
therefore not under control so far as
getting out of the way of other craft
is concerned. A marked buoy, moored
to a mushroom anchor. is then dropped
overheard at the point where the fault
in the cable is supposed to be.
The ship then proceeds to grapple
for the cable. This is done by means
of a grapnel, OF which there are many
kinds, all studded with prongs calcu.
lated to catch anything they encoun-
ter. To this grapnel is attached
steel hawser, the inboard end OF which
is connected to an instrument known
as a cynamometer. or vertical scale.