NATURAL PHILOSOPHY. 157 



Valencia. The mean times of transmission were 0.25 s and 0.24% 

 indicating an increase of speed with an increase of electro- 

 motive power. And, so far as the experiments on these 4 days 

 are concerned, we might infer that on the complete metallic cir- 

 cuit formed by the 2 cables, the time for transmitting the signals 

 through about 3,475 kilometers, or 2,160 statute miles, was not far 

 from "0.29 s for a battery of 3 cells, 0.26 s for one of 4 cells, and 

 0.215s for one of 10 cells. 



On the other hand, the average transmission time for signals 

 sent by a current induced in a single cable by means of a " con- 

 denser," with a battery of 10 cells, was 0.31 s on the 25th, and 

 0.34 s on the 28th of October; the mean interval on these 2 days 

 being 0.328 8 . Each of the condensers used possessed an elec- 

 trostatic capacity of about 20 farads ; so that with a tension of 10 

 cells or 8.4 volts, their capacity would not be far from 168 farads, 

 or equal to that of about 590 miles of cable, or, in other words, a 

 little more than one-quarter the capacity of one whole cable. 



Results of recorded signals give 0.26 s as the transmission time 

 through one cable with earth return, when the ground connection 

 was made with the zinc, and 0.27 s when it was made with the 

 middle of the battery, the former corresponding to the use of 4 

 cells at one statign only, the latter to 2 cells at each station. 



The velocity of signals made by closing and interrupting the 

 circuit is next considered, the conclusion being that in general a 

 longer time was required for the transmission of signals after an 

 interval of 10 seconds than after an interval of 5 seconds. In 

 those cases where no earth-connection existed, and the signals 

 were alternately positive and negative, the cable was meanwhile 

 assuming its electrical equilibrium, so that a positive signal was 

 transmitted more rapidly through the conductor when it was 

 affected with a larger amount of negative electricity, and a nega- 

 tive signal more rapidly through a conductor containing more 

 positive electricity. This affords new testimony to the erroneous 

 character of the supposition that the conductor must be charged 

 through any portion of its length, in order to transmit a signal 

 beyond that portion. 



As showing the continued existence of currents (doubtless en- 

 gaged in establishing equilibrium) during the intervals between 

 the signals, it may be of interest to mention that on one occasion 

 when the 2 cables had been joined at Heart's Content, without bat- 

 tery, and while the Valencia battery had been temporarily discon- 

 nected, signals from Newfoundland were distinctly received. 

 They were weak, and the deflections of the needle were scarcely 

 one-fifth as large as usual, yet they were none the less distinct, 

 and a complete set of signals, 10 in number, at proper intervals, 

 and preceded by a " rattle," was recognized at Valencia. No 

 other record of them was made, than the fact of their transmission 

 by alteration of the make-circuit and break-circuit signals, although 

 no battery had been connected with the cable for several minutes. 



A series of experiments was made for the purpose of ascertain- 

 ing the effect of changes in the electro-motive force upon the 

 speed of the signals, and whether these signals could by the 

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