NATURAL PHILOSOPHY. 167 



A careful examination was made of the influence each wire exerted upon its 

 neighbor, in setting up slight charges of an opposite kind of electricity in- 

 ductively, and it was found that the inductive influence thus exerted was only a 

 ten-thousandth part of that ichich was transmitted along either of the wires, 166 

 miles long. The results were attained by passing currents in various direc- 

 tions and in various ways along three wires simultaneously, and by estimat- 

 ing the differences of power in each, by their diverse capabilities of magneti- 

 zing soft iron bars. 



By 1855 the scientific corps had provided themselves with much more com- 

 plete and perfect instruments for pursuing these inquiries ; and the construc- 

 tion of new telegraph lines had also furnished them with better opportunities 

 of making their experiments. It was soon found that a magneto-electrical 

 current took a second and a half to discharge itself, when it moved through 

 1,146 miles of wire, in consequence of the retarding power of induction in 

 this extended medium. This was a rate of speed not at all compatible with 

 any profitable employment of a trans-atlantic telegraph for commercial pur- 

 poses, and the next step was to devise some remedy for this inductive ob- 

 stacle. The first thing done was to send different kinds of electricity along 

 the wire in succession, in the hope that each transmission of one kind would 

 clear away the residue of the other which had immediately preceded it. 

 The result was a complete success. Although the same wire and the same 

 magneto-electric combination were employed which had before demanded a 

 second and a half for the completion of a single discharge, seven and eight 

 currents now readily recorded themselves in a single second. When, posi- 

 tive followed negative, and negative followed positive, in exactly equal pro- 

 portions, the electrical equilibrium of the wire was continually restored as 

 fast as it was disturbed, each current clearing away the inductive influence 

 .which the other had left behind it. It was proved, moreover, in the course 

 of these experiments, that successive charges of electrical influence, either 

 of the same kind or of alternate opposite kinds, may be travelling along 

 lengthened conducting wires simultaneously, the one following the other 

 like successive waves upon the sea. Alternate positive and negative signals 

 were sent along 900 miles of wire, at the rate of eight signals in each 

 second, and two signals arrived at the end of the wire after the acts of 

 transmission had been discontinued. In another experiment by the use of a 

 wire 1,020 miles long, three signals of a single-stroke bell were distinctly 

 heard after the movement of the hand which originated the current had 

 ceased. This, therefore, indicated a way in which the rapidity of trans- 

 mitting electrical currents along a submarine wire could be increased ; it 

 was necessary only to employ opposite kinds, positive and negative alter- 

 nately. 



The next point to be investigated was the ratio in which increase of dis- 

 tance in a gutta percha covered telegraph wire augments the difficulties of 

 rapid transmission. It had been supposed that the available force was di- 

 minished in the ratio of the square of the distance traversed, that is, that 

 a current which has traversed 600 miles has only a thirty-sixth part of the 

 working force of a precisely similar current which has travelled only 100 



