THE ELECTRIC TELEGRAPH. 



It may be asked whether, if deposited, an electric current could 

 be transmitted through it so as to produce telegraphic signals ? 



There can be only two reasons for doubting this -first, the 

 length of the conducting wire, and, secondly, the inductive effects 

 of the water upon the cable. 



The intensity of the current transmitted by a battery of given 

 power upon a wire, is in the direct ratio of the conducting power 

 of the wire and the magnitude of its transverse section, and in the 

 inverse ratio of its length. A length so great as 1500 or 1600 

 miles, would of course considerably attenuate the current. 



But it will be recollected that, in the experiments described in 

 Chap. I. par. 9, made by M. Leverrier and myself, messages were 

 transmitted over a space of 1000 miles of wire without inter- 

 mediate battery power, and with a terminal battery of very 

 limited power. In that case 336 miles of the wire upon which 

 the current was transmitted were iron, a very indifferent con- 

 ductor, and the remaining 746 miles were copper wire of extremely 

 small diameter. It is certain, therefore, that by reason of the 

 inferior conducting power of the one part, and of the very small 

 transverse section of the other part, this length of 1082 miles 

 offered a much greater resistance to the transmission of the 

 current than would 1600 miles of copper wire, such as is usually 

 selected for submarine cables. 



But independent of these considerations, nothing would be 

 easier than to give the copper wire enclosed in the cable such a 

 thickness, and to apply to it such batteries, as would ensure the 

 transmission of a current of sufficient intensity. 



The effects of the recoil currents produced by the inductive 

 action of the water upon the cable, cannot be so certainly appre- 

 ciated with our present knowledge and experience ; but although 

 the effects of these are sensible in the cases of the submarine and 

 underground wires already laid down, they have not produced 

 any obstruction to the efficient performance of the telegraphs, and 

 the managers of the Magnetic Telegraph Company, which works 

 well several hundred miles of wire partly subaqueous and partly 

 underground, assure me that no inconvenience or obstruction 

 whatever is found to arise from this cause. If no other objection 

 were raised against the project of a Transatlantic cable save this, 

 it may be safely pronounced that there would be nothing to be 

 apprehended which the resources of science and art would not 

 easily surmount. 



It does not appear, therefore, that any part of the great 



problem of subatlantic telegraphy remains to be solved, except 



that which is involved in the financial view of the question. If 



it be undertaken as a commercial enterprise with a view to a 



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