Tombstone epitaph., 1915-08-22


 ~I the submarine cable and - the methods used in keep Ing 1t in repair are of interest.
 Each submarine telegraph company nas in service a fleet of cable ships, tne units of which are stationed at oinerent ports for quick access to the dinerent sections of the cable. Let us Ake. for example, the cable stretching rom San Francisco to Manila, a dis Ance of l0.0l0 miles. This cable is divided into four sections-San Fran CISCO to Honolulu. Honolulu to Mid way island. Midway island to Guam. ana Guam to Manila The cable lies on the bed of the Pacific. which in places runs from three to five miles in oeptn. the latter depth being found oti the Island of Guam Sufficient slack must be paid out in laying a submarine cable to allow every part to rest on tne bottom of the ocean. however ir- regular the bottom may be.
 A cable varies in thickness and type according to its position and the na- ture of the ocean bottom in the local ny where 1t is laid. The shore end" or cable, meaning a section laid close to land. is always thicker than a sec uon out at sea Ordinarily the diam eter Of a shore section runs about 2N inches. while a section laid in deep va Ter runs about E inch in diameter. About seven strands of copper. com prising a single conductor. form the core of the cable Over this core are laid coatings of gutta percha. a layer or jVe 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 q 900 . mile.
 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 50 volts pressure at the sending end. and all that comes out at the re- ceiving end is twenty millionths am pere. Signals are transmitted simply by alternately charging and discharg ing the cable, which works much like 8 Leyden jar. One of the fastest of submarine cables transmits about 80 words a minute.
 Interruption in cable communica- tion between two stations may come from one of several causes. There is the fault caused by the teredo, a 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- ton, 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 con- pietely. from one cause or another. forming what Is known as a total break"
 Let us imagine that the cable from San Francisco to Manila Is down" as fit Is technically ex- pressed when the cable is unwork- able. In that section. 2,09s miles long. between San Francisco and Hon olulu We will assume that a series of tests based on the law of resistances has shown that the fault lies at a point 1 900 miles from San Francisco. Some times it 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 offlces-the latter by an alternate route-to keep watch on their instruments in the office for the ships call As soon as the cable ship reaches the ground" a signal. consisting of two red globes with a white diamond between. for day use. and replaced by similarly colored lamps at night. is hung in a vertical line fin front of the foremast head. This signal indicates that the ship is engaged in cablerepair work, and is therefore not under control so far as getting out of the way of other craft is concerned. A marked buoy. moored 10 a mushroom anchor. is then dropped overheard at the point where the fault fn the cable is supposed to be.
 The ship then proceeds to grapple for the cable. This is done by means os. s-.rne,. Q! 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 ts connected to an instrument known as a cynamometer. or vertical scale. RnWED TO BLOW OF FATE