30 THE SCIENTIFIC PAPERS OF 



According to Faraday's definition of dialectrics, the electric 

 charge obeys the same simple law, which regulates the dispersion 

 of heat in an imperfect conductor, and which, again, is analogous 

 to Ohm's law regarding electric currents. It follows that the 

 electric charge of a Leyden arrangement is directly proportionate 

 to the lining surfaces directly to the electric force of the battery 

 (or its substitute) employed, and to the specific inductive capacity 

 of the insulating medium, but inversely proportionate to the 

 thickness of insulating coating, or if expressed by a formula, we 

 have : 



E S k 

 Q = -T in which Q, expresses the electric charge ; E, the 



electric force of the battery ; S, the metallic surface ; k, the specific 

 inductive capacity ; and d, the thickness of the coating. 



This formula is corroborated by a series of very careful experi- 

 ments by Werner Siemens upon electric cables, and it is of great 

 practical utility if combined with Ohm's formula regarding the 

 conductor. 



The following are some of the simple consequences derived from 

 the two formulae : 



1. The electric force (E) of the battery (and its substitute) has 

 no influence upon the onward velocity of the electric wave, because 

 it increases the value of P and Q equally. 



2. The time (t= -) required to charge a submerged conductor 



of a given proportion increases in the square ratio of the length 

 (1) of the conductor (in the formula for Q, the factor (S) has to 

 be expressed by I and a) which law was first arrived at by William 

 Thomson in another way, and was communicated by him to the 

 British Association in 1855, but has since been assailed by 

 Whitehouse and other electricians. 



3. It is of the first importance to make the conductor of the 

 best conducting material, and the insulating coating of the greatest 

 practical thickness, but of a material with the least specific con- 

 ductive capacity. 



4. Given the materials and the thickness of the insulating 

 coating, the rapidity of progress of the electric wave increases in 

 the simple ratio of the diameter of the conductor ; a proposition 

 differing also from the views of the promoters of the Atlantic 



