762 



TELEGRAPH, ELECTRIC. 



neous iron. Its size is that known as No. 13 

 (gauge .095) ; each strand of it is capable of sus- 

 taining a strain of 1,000 Ibs., under which it is 

 extended to the amount of one per cent. The 

 covering of this wire with the Manilla yarn, 

 like the making of the core, is performed in a 

 separate factory, specially devoted to such pur- 

 pose. Five strands of the yarn are closely 

 wound upon each iron wire from as many bob- 

 bins; each of the machines for the purpose, 

 and which are of two different patterns, being 

 capable of turning out about 140 miles of cov- 

 ered wire a day. As fast as it is thus wound, 

 the wire is passed through a hot solution of 

 tar and gutta percha, the fibrous covering be- 

 coming saturated with this ; and it is then con- 

 ducted through tanks of water, to cool this 

 coating material. 



At the Morden Wharf factory, the work of 

 closing the covered iron wires upon the core, 

 so as to complete the cable, is performed. 

 The core is received here on largo reels : 

 these are sunk in circular openings filled with 

 water ; and the coils are then for twelve hours 

 subjected to electrical tests, in order to de- 

 termine beyond a doubt the continuity of 

 the conducting wires, and the completeness of 

 their insulation. When a faulty transmission 

 of the current takes place, the difficulty is al- 

 most invariably found to consist in an imper- 

 fect joining of the ends of two lengths of wire. 

 The core having been wrapped in a padding 

 of jute, which is also saturated with a pre- 

 servative mixture, the covered iron strands are 

 closed upon it, being so wound about the core 

 that when the cable is subjected to strain this 

 shall fall first and mainly upon them ; the mech- 

 anism, expressly devised for this part of the 

 \T ork, occupies two floors of the manufactory. 

 The closing machines, below, consist essentially 

 of large wheels or tables revolving horizontally, 

 with reels of the several strands so arranged on 

 their margin as to maintain a relatively station- 

 ary position, instead of keeping their axes 

 pointed always to the centre of motion. The 

 strands, converging upward toward a small 

 opening in the ceiling, meet, and are twisted 

 round the jute-covered core. The cable, thus 

 formed entire, is conducted over grooved 

 wheels to a building the floor of which gives 

 place to huge tanks or vats, eight in number, 

 and between which platforms extend. The 

 depth of these is alike 12 feet, while four of 

 them are circular, 34 feet each in diameter, and 

 four elliptical, each 36 feet by 27. The com- 

 pleted cable is brought down from the wheels 

 overhead, and is carefully coiled away by hand 

 in these tanks, until the capacity of each about 

 140 miles is equalled. Water is kept flowing 

 into each tank over its edge, and, percolating 

 between the coils, is allowed to fill the tank to 

 the height occupied by the cable. The purpose 

 of this is to allow of a continued and thorough 

 testing of the efficiency of the protective cover- 

 ing, the ends of all the portions of cable being 

 carried into the electrician's room, and an elec- 



trical current of measured force being contin- 

 ually sent through the wires; by this means 

 the least defect in insulation can be registered 

 with unfailing accuracy, and even to its exact 

 distance and degree. 



The size of the copper or conducting wires 

 is that known as No. 18 (gauge .048) ; and the 

 weight of copper is 300 Ibs. per nautical mile, 

 against 107 Ibs. per mile in the old cable. 



The weight of the new cable completed, as 

 ascertained in air, is 35-J cwt. per mile ; that 

 of the former one having been but 20 cwt. 

 Its breaking strain is 7f tons, while that of 

 the former was only 3J tons. Its specific grav- 

 ity is very low its weight in water being 14 

 cwt. per mile, against 13.4 cwt. for the old 

 cable. This low gravity is owing to the large 

 proportion of fibrous material present ; and in 

 connection with its greatly increased strength, 

 the result gained is that the new cable is capa- 

 ble of supporting in water 11 miles of its length. 

 As, however, the greatest depth of water en- 

 countered in laying the former cable was about 

 2J nautical miles, it is not probable that the 

 present one will in any case be subjected to a 

 strain equal to its actual strength. The destruc- 

 tion of the fibrous material of the cable by 

 fishes, is believed to be guarded against by the 

 poisonous qualities of compounds with which 

 it has been saturated. 



The distance to be spanned by the cable, 

 measured at the surface of the ocean, is about 

 1,640 nautical miles. It is, however, pro- 

 posed to produce in all 2,300 miles of ca- 

 ble ; and it is expected that this entire length 

 will be finished by the end of the first week 

 of June. From the factory, the sections of 

 cable are conveyed in tanks on the hulks, 

 Amethyst and Iris, to the Great Eastern, 

 lying in the Medway. The shipping of the 

 cable was commenced January 19, 1865. On 

 board the monster steamer, which is to per- 

 form the work of laying it down, the cable 

 is in final preparation to be coiled away in 

 three immense tanks. It is expected the ex- 

 pedition will set forth about the close of the 

 month of Jane. The method of paying out 

 the cable will probably be in the main similar 

 to that before adopted; and if the rate of steam- 

 ing does not exceed seven knots an hour, the 

 object of the expedition should still be accom- 

 plished in from ten to eleven days. The 2,300 

 miles of cable, even without making allowance 

 for the twist, will contain about 16,000 miles 

 of copper wire, and 23,000 of iron wire, be- 

 sides a very much greater length of the strands 

 of fibrous material. 



Among other great lines, mainly submarine, 

 which have been projected with more or less 

 probability of future accomplishment, are, one 

 from San Francisco or Panama to the Sand- 

 wich Islands, and thence in time to China or 

 Japan; one from France to the Azores, and 

 thence to New York ; and also one to consist 

 in an extension of an existing French lino from 

 Marseilles, through Corsica and SicPy to Tri- 



