164 On associated cases of Current and Static Effects. 



recently made with regard to time. That, however, does not 

 appear to me to be the case, as a few further observations on Mr. 

 Clark's recent experiments will perhaps show. When the smaller 

 battery is used, much less electricity passes into the wire in a 

 given time, than when the larger one is employed. Suppose that 

 the batteries are so different that the quantities are as 1 to 10; 

 then, though a pulse from each would take the same time for 

 transmission through the wire, still it is evident that the wire 

 would be a tenfold better conductor for the weak current than 

 for the strong one; or in other words, that a wire having only 

 one-tenth of the mass of that used for the greater current should 

 be employed for the smaller one, if the resistance for equal quan- 

 tities of electricity having different intensities is to be rendered 

 equal. 



My views connect the retardation of the transmitted current 

 with the momentary induction set up laterally by the insulated 

 and externally coated wire. The induction will be proportionate 

 to the intensity, and therefore its especial effect on the time of 

 retardation proportionately diminished with the less intense cur- 

 rent, — a result of action which will aid in rendering the time of 

 retardation of the two currents equal. 



The difference of time in the former experiments w r ith air wires, 

 and earth or water wires, very clearly depends upon the differ- 

 ence of lateral induction ; the air wire presented a retardation 

 scarcely sensible, the earth wire one amounting to nearly two 

 seconds. If the insulating layer of gutta peicha could be reduced 

 from Ol to 0*01 of an inch in thickness, and mercury could be 

 placed on the outside of that instead of water or earth, I do not 

 doubt that the time would be still more increased. Yet there is 

 every probability that in any one of these varying cases, electric 

 currents of high and of low intensity would appear at the end of 

 the same long wire after equal intervals of time. 



Mr. Clark's results may be stated thus : — A given quantity of 

 electricity at a high intensity, or a smaller quantity at a propor- 

 tionally lower intensity, will appear at the further end of the 

 same wire after the lapse of the same period of time. My 

 statement assumed the discharge of the same quantity at different 

 intensities through the same wire, and the quantities in the illus- 

 trative experiments were measured by a Leyden jar. In the 

 consideration and further development of these results, it must be 

 remembered that it is not the difference either in time, velocity, 

 or transmission of a continuous current which constitutes the 

 object in view, for that is the same both for an air wire and a 

 subterraneous wire, but it is the difference in the first appearance 

 only of the same current when wires under these different con- 

 ditions are employed. After the first appearance both wires are 



