1862.] 215 



current ; and consequently, when the wires were so connected that 

 the current went up one wire and down the second, up the third and 

 down the fourth, as in experiment No. 4, the magneto-electric 

 action upon No. 2 wire is counterbalanced by the magneto-electric 

 action upon No. 3, and so on ; but in experiment No. 5 the mag- 

 neto-electric current was in full force on all the wires. The result, 

 however, did not show any appreciable difference in the speed of the 

 wave, as the machine then used could not be governed with sufficient 

 accuracy. 



Experiments were made to determine the effect of applying resist- 

 ance to one end of the cable. For instance, a telegraphic instrument, 

 when applied to the cable, augments the resistance of the circuit ; 

 and when a resistance equal to half that of the cable was applied at 

 one end, the rate of the electric wave through it was decreased to 

 three-quarters. When a resistance equal to the whole of the cable 

 was added at one end, so as to double the resistance of the whole 

 circuit, the speed was reduced to about three-fifths ; and when resist- 

 ance double that of the cable was added, the speed was reduced 

 rather more than one-half. , 



Variations in the electromotive force produced no sensible varia- 

 tion in the speed of the waves. 



The second series of experiments were tried upon the Dunwich 

 and Zandvoort cable, after it was submerged, and consequently in a 

 straight line, and not, as in the previous experiment, in a coiled mass ; 

 it was therefore exposed to much less magneto -electric induction. 

 The insulation of this cable was very high indeed. 



The experiments on this cable, among other results, show that 

 doubling the length of the circuit reduced the speed nearly four 

 times. The experiments on the Mediterranean cable showed that, 

 with three times the length, the speed was reduced nearly nine times. 

 With twice the length the speed was reduced nearly four times, or 

 inversely as the square of the distance nearly. 



The mean of the experiments through 270 miles of cable are 4*76 

 revolutions of the wheel per second, or 9*52 reversals of the current 

 per second. 



In the experiments through 540 miles, or twice the length of 

 cable, the speed was 1*326 revolution of the wheel, or 2*65 reversals 

 per second. The reason why they do not follow the law of the 

 squares exactly, is probably to be attributed to the resistance of the 



