.SYA' WILLIAM .SY/;.J//-:.V\, /--.A'..s. 29 



in the spring of l.s.V., part of which I have laid upon the 

 table. 



Tliu electrical condition of the submerged conductor is a subject 

 of the greatest interest, upon which electricians are still divided, 

 and, treated mathematically, involves problems of the highest 

 order, such as only Professor William Thomson and a few others 

 can hope to deal with effectually. The important point is, how- 

 ever, to arrive, first of all, at a clear understanding of the laws 

 of nature upon which those calculations should be based, and 

 tln'M' laws when rightly interpreted, are always extremely simple. 



The submerged (or underground) line wire may in the first 

 place be considered in the light of a mere conductor, following 

 Ohm's law, which as is well known, is to the effect that the 

 amount of electricity passing in a given time depends upon the 

 sectional area of the conductor, upon the electric force (intensity) 

 of the battery, upon the specific conducting power of the material, 

 and inversely upon the length of the conductor. It is expressed 

 by the following formula : 



E a c 



I , in which P signifies the quantity of electricity 



passing ; E, the electric force of the battery, or its substitute ; 

 a, the sectional area of the conductor ; c, the speci6c conducting 

 power ; and 1, the length of the conductor. 



In the next place the cable has to be considered in the light of 

 a Leyden jar of extraordinary length, formed of gutta-percha, 

 with the conductor for an inner, and the sheathing (or moisture) 

 for an outer metallic coating. This Leyden arrangement has to 

 be charged to a certain degree before the electric current can 

 make itself felt at the further extremity, but the supply of 

 electricity being limited at every point by the resistance offered 

 by the conductor, according to Ohm's law, it follows that the 

 entire cable can be charged only in a progressive manner, as 

 though it consisted of a series of Leyden jars charging the one 

 into the other until it reaches the last, which djscharges itself 

 through the receiving instrument into the earth. The amount of 

 impediment thus offered to the progress of the electric current 

 depends evidently upon the capacity of the Leyden arrangement, 

 which capacity should be reduced to a minimum for a given size 

 of conductor. 



