NATURAL PHILOSOPHY. 165 



pany, Messrs. Whitehouse and Bright, have devoted much time to a series of 

 carefully conducted experiments, with a view of determining the influence 

 of induction, and disguised electricity in retarding the transmission of cur- 

 rents along submarine wires. An account of these experiments has been 

 officially published by the company, from which we make the following ex- 

 tracts : 



In the ordinary arrangement of the wires of the electric telegraph, where 

 they are stretched upon posts and insulated by glass and the surrounding 

 air, the current of electricity runs along as a simple stream, and with a ve- 

 locity that is almost inappreciable for ordinary distances. But when the 

 wires are inclosed in a sheath of insulating substance, like gutta percha, and 

 placed in a moist medium or a metallic envelop, the case is very different. 

 The influence of induction then comes into play as a retarding power. As 

 soon as the insulated central wire is electrically excited, that excitement 

 operates upon the adjoining layer of metal or moisture, and calls up in it 

 an electrical force of an opposite kind. Each of these forces disguises, or 

 holds fast, an equivalent portion of the other, and the electricity of the 

 central wire is thus prevented from moving freely onward as it otherwise 

 would. It is found, in short, that the submarine telegraph cable is virtually 

 a lengthened out Leyden jar, and transmits signals while being charged and 

 discharged, instead of merely by allowing a stream of the electrical influ- 

 ence to flow dynamically and evenly along it. And every time it is used it 

 has first to be filled and then emptied. In the case of a long submarine 

 wire this was found to be a task requiring considerable time, and this was 

 found, moreover, to be very much increased with an increase in the length 

 of the wire. 



In the early experiments made for the determination of the speed 

 with which the subtle influence travelled along metallic wires, hundreds of 

 thousands of miles appeared to be traversed in a second of time. But 

 when a similar examination was entered upon with telegraphic lines running 

 between London, Manchester and Glasgow, and laid under ground, and be- 

 tween London and Paris, and London and Brussels, partly under ground 

 and partly submarine, it seemed that scarcely thousands of miles were 

 passed in the same period ; indeed, the statement was made in a paper read 

 by Mr. Edward Bright, at the meeting of the British Association in J 854, 

 that the velocity of currents in ordinary use for telegraphic purposes in subterra- 

 nean conductors did not exceed one thousand miles per second. This gentle- 

 man also inferred from experiments carried on in a circuit of 480 miles of 

 underground wire, that the speed with which an electrical impulse was trans- 

 mitted varied with the energy or intensity of the current employed, and the 

 nature and conditions of the conductor used, and hence that the rate of 

 transmission might be greatly increased at will by adopting currents of a 

 different character to those which had been habitually trusted to. 



Professor Faraday had at once attributed these experimental discrepan- 

 cies to their true cause ; and Mr. Whitehouse exhibits a very beautiful and 

 convincing experimental proof that it is as Leyden jars, and by retention 

 of charge, that submarine cables act. He takes, first, fifteen miles of insu- 



