The actual speed obtained by automatic transmission with the latter cable is as high as forty-seven (or even up to fifty) five-letter words per minute. On the previous, lighter, Atlantic cores twenty-five to twenty-eight words per minute was the usual maximum speed attainable; the former,{218} say, by average transmission and average receiving, and the latter by automatic transmission—other circumstances corresponding. Practically all submarine cables between important points—and certainly all those across the Atlantic—are now “duplexed”—a system of electrical working (instituted by Messrs. Muirhead in 1875) which enables messages to be sent in both directions at the same time. The result of this is nowadays to practically double the carrying capacity and earning power of the line, the effective speed in either direction remaining virtually the same as in “simplex” working, provided the cable is in good condition.[73] The armor of this cable (Fig. 43) is also a good example of present-day practise, each wire (usually covered with compounded tape) butting against the next; this is found to be the most durable form for a deep-sea cable.
In 1898 another French Atlantic line of a similar type to the above was laid. This involved the longest Atlantic cable-section in existence, i.e., 3,174 nautical miles, from Brest to Cape Cod, and was the first Atlantic line made and laid by Frenchmen, with the active assistance, as regards laying, of the Silvertown Company.
Recently, too, a German Atlantic cable has been laid by the Telegraph Construction Company from Emden to the Azores, and hence to New York.
The various proprietary companies here named have had duplicating lines laid for them from{219} time to time, but these it is not necessary to further allude to.
Neither has it been thought necessary to give particulars regarding the methods of construction, laying, testing or working of any of these later lines following on the pioneer undertakings, except where special novelties were introduced. For similar reasons—and seeing that the responsibility of these later lines rested with contractors—the names of their permanent staff acting for them have not been introduced.
CHAPTER XIX
ATLANTIC CABLE SYSTEMS OF TO-DAY
Connecting Links—Tariff—Revenue
AS a part of the union between the old world and the new, there are altogether fifteen cables now working across the North Atlantic Ocean ([see Fig. 45]), such as are usually termed “Atlantic cables.” Some of the Atlantic companies have special cables of their own from the landing place on the coast of Ireland to points on the Continental coasts. The figure on page 221 suggests one of the difficulties any wireless system would have to contend with in attempting at transatlantic telegraphy on a commercial basis.[74] Some of{220} these cables at each end of the corresponding main section contain more than one insulated conductor.