1 02 SHAFFNER ON COMMUNICATION WITH AMERICA [May 14, 1 860. 



On an air line of that length the transmission would be instan- 

 taneous, and on such lines the art of telegraphy is but a question of 

 mechanism. On a telegraph line constructed through the air, 

 perfectly insulated, and traversing an even and favourable tem- 

 perature, a thousand words can be transmitted in one minute by the 

 aid of mechanism. The ordinary manipulation, however, is with 

 the hand, by the opening and closing of a given metallic circuit 

 charged with electricity. The maximum transmission in this 

 manner may be considered at about forty words per minute. The 

 speed of transmission of the electric force through submarine cables 

 depends upon the conductibility of the metal, its insulation, and 

 length of circuit. I have good authority for saying that experiments, 

 instituted in England with No. 16 copper wire, have proved that 

 the electric current requires one-third of a second for the first 600 

 miles, and one second for 1000 miles. According to this progression, 

 the time required to transmit an electrical impulse 2000 miles 

 would be about nine seconds. This delay or hindrance is called 

 "retardation." The cable becomes a Leyden jar, and the current 

 transmitted is, more or less, held in suspension until discharged by 

 some contrivance. It is owing to this suspension or retardation, 

 and the irregularity of its time, that long submarine telegraphs 

 cannot be made effective for commercial purposes. 



Circuits of the Northern Route. — The electric circuits of the North 

 Atlantic telegraph will be short — the longest about 600 miles, and 

 cables can be laid capable of transmitting at least twenty words per 

 minute. It will be a financial question that will determine the 

 capacity of the cables for the commercial telegraphy. Between 

 Scotland and the Faroes, and between the Faroes and Iceland, cables 

 can be laid that can equal the working of a double line of cables 

 across the other sections of the route, or perhaps it may be found 

 best to construct them for the short sections with two wires for 

 telegraphing, and on the other sections with three or more con- 

 ducting wires. If either one of the sections fail, the whole are not 

 lost, and another cable can be promptly submerged. 



The Seas. — The depths of the seas are but little known. A few 

 soundings were taken on the route last autumn. The water between 

 Scotland and the Faroe Islands, and thence to Iceland, is not very 

 deep, not exceeding, perhaps, 1000 fathoms, and there can be no 

 doubt but that the bottom is very deep mud. The soundings taken 

 last fall between Iceland and Greenland proved the bottom in that 

 sea to be deep mud. The greatest depth of water was 1540 

 fathoms. The mud brought from the bottom has been examined 

 by Professor Ehrenberg, of Berlin, and he says that he found 



