1862.] 201 



change of the insulation due to continued electrification, first published 

 by the author in a paper read before the Royal Society in 1859-60*. 

 The identity of the arrival- curve during increase arid decrease 

 shows that, 



8. "The apparent increase of resistance of the gutta percha is 

 rather due to an absorption of electricity which is again given out, 

 than to a real change in the conductivity of the material." 



The theoretical and practical conclusions on the effect of repeated 

 signals were next examined. Little change of insulation could take 

 place during the repeated signals, because the greater part of the 

 cable remained continually electrified ; and greater coincidence between 

 the experiments and the theory was therefore to be expected. 



The curve expressing the rate at which the amplitude of oscillation 

 in the received current diminishes as the number of signals increases, 

 was constructed from Professor W. Thomson's equations f ; and the 

 experimental amplitudes with 1500, 1802, and 2192 knots of cable 

 in circuit, were found to coincide in the most accurate manner with 

 this curve establishing completely the soundness of the mathemati- 

 cal theory. 



9. These results prove beyond all question that " the rate of trans- 

 mission varies as the square of the length, whether by rate of trans- 

 mission be meant that speed at which repeated signals fail to produce 

 any sensible effect, or the rate producing so great an amplitude that 

 common hand-signals can be received without confusion." 



It is also found (when small compared with the total resistance) 

 that, 



10. "The resistance of the battery and receiving instrument pro- 

 duces nearly the same effect as the addition of an equal length of sub- 

 marine cable." 



If the amplitude of oscillation in the received current caused by 

 dots at any one speed through any one straight cable were known, 

 the amplitude through any other cable at any other speed could im- 

 mediately be taken from the curve, now verified bv experiment. 



Unfortunately this one fact is wanting. The author hopes to be 

 able to supply the want in the second part of this paper. 



deen, 1859. Also paper by Professor W. Thomson and F. Jenkin, Phil. Mag. 

 1861 ; also a letter from Mr. F. C. Webb in ' The Engineer,' August 1859. 



* Published in full in Appendix to the Report of the Committee of the Board 

 of Trade on the Construction of Submarine Cables. 



t Vide Proceedings of the Royal Society, 1855. Phil. Mag. 1856. 



