548 Royal Society : — 



or, the last terms being contracted into one, 



[«*(X-«) + /3'=(Y-/3)](X- m Z)(Y-«Z) 1 



+ [,3(X-«)-«(Y-/3)] [«(X->»Z)*-/9(¥-»Z)*] \ 



This is the very form of the equation given by Mr. Cayley, and 

 putting in evidence, as he remarks, both the directing lines, as 

 also the cubic curve, if Z = 0. 



This solution will, I hope, in some measure serve to increase 

 the interest of this investigation as illustrating the theory of skew 

 surfaces in general, and making it more accessible to scholars. 



LXXIII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 490.] 

 June 19, 1862. — Major- General Sabine, President, in the Chair. 

 f j^HE following communication was read : — 



■*■ " On the Relative Speed of the Electric Wave through Subma- 

 rine Cables of different lengths, and a unit of Speed for comparing 

 Electric Cables by bisecting the Electric Wave." By Cromwell F. 

 Yarley, Esq. 



The present paper gives the results of some experiments which 

 were undertaken to determine, first, the relative speed of the elec- 

 tric wave through cables of various lengths ; secondly, the retarding 

 effect of the iron covering of the cable ; and thirdly, methods for the 

 increase of the speed of the electric wave. 



"When a long submarine cable or subterranean wire is connected at 

 one end through a galvanometer to the earth, and the other end is 

 connected with a battery, a current flows through it, deflecting the 

 galvanometer-needle. 



If the needle be made very light and small, so as to have but a 

 small amount of inertia, and the cable be long, the current will be 

 seen to arrive after the lapse of a short but appreciable interval of 

 time, and will gradually augment in intensity approaching to, but 

 never attaining, the maximum. 



Professor Thomson has investigated this subject mathematically, 

 and arrived at the conclusion that in submarine cables of different 

 lengths the speed is inversely as the square of the distance. 



Through the Atlantic Cable, the conducting wire of which weighed 

 93 lbs. to the statute mile, and the length of which was rather more 

 than 2300 statute miles, the electric current did not show itself on 

 Thomson's sensitive reflecting galvanometer until more than one 

 second after contact had been made with the battery at the other end. 



In experiments made by the author in 1854 upon 1600 miles of 

 wire between London and Manchester, connected up in one continuous 

 circuit, the current was not visible upon the chemical recording 

 instruments then in use until after the lapse of about three seconds. 



These experiments were repeated by Professor Faraday ; and he 

 has made known the results. 



