340 On Electrical Quantity and Intensity, [March 15, 



remained everywhere uniform, and was as high at the negative as at 

 the positive end. 



The fall of tension in electricity was always accompanied by its 

 conversion into heat ; the ignition of wire by the voltaic current, the 

 intense heat of the voltaic arc, and the heat and light of the electric 

 discharge and of the spark, were all cases of the evolution of heat con- 

 sequent on the fall of tension, and the quantity of heat evolved was 

 apparently directly proportionate to the fall of tension within a given 

 space and to the quantity of electricity passing. 



In the case of electric telegraph conductors and submarine cables, 

 it was shown, from a carefully conducted and extensive series of experi- 

 ments, that the tension falls with the most perfect regularity from the 

 positive pole of the battery to the end in connection with the earth, in 

 accordance with the law of Ohm ; and since the quantity of electricity 

 held under induction varies in the same ratio as the tension, the distri- 

 bution of the charge in a cable follows precisely the same law. It re- 

 sults from this, that if a cable with a current flowing through it be 

 divided into any number of equal sections, and the quantity in the sec- 

 tion connected with the earth be taken as unity, the quantities in all the 

 other parts, whatever their number, will be in the ratio 1, 3, 5, 7, 9, 

 11, &c. So that if a cable be divided into two halves, the quantities 

 will be in the ratio of one to three. 



The speaker stated that he had ascertained that in the voltaic 

 battery, the presence of two metals was not an essential condition — 

 the negative metal was not necessary for the formation of the electric 

 current, but only for its after detection and exhibition. A simple 

 mass of copper, iron, zinc, or any oxidisable metal, when laid on the 

 moist earth, formed a complete battery in itself, giving positive electri- 

 city to the earth, and quickly assuming a negative tension, which it 

 would communicate to any other body resting on it or in contact with 

 it, as, for instance, a length of submarine cable. If a cable thus 

 charged were afterwards removed and applied to any more electro- 

 negative metal, such as platinum, or to carbon, the charge would 

 return to the earth ; and it was found by measurement that the charge 

 thus acquired by a cable was exactly the same as if the two metals 

 had been employed simultaneously in the ordinary form of a galvanic 

 couple. If the mass of zinc were permanently connected with the 

 non-oxidisable or less oxidisable metal, and thus with the earth, the 

 tension, being constantly destroyed and as constantly renewed, would 

 form a constant current, becoming in fact a voltaic couple. If the 

 connection with the earth, instead of being made through another metal, 

 were made through any inert conducting substance or liquid, the same 

 constant current would be produced, thus forming the well-known case 

 of a voltaic battery with one metal and two liquids. 



After the conclusion of the discourse, Mr. Clark stated, with refer- 

 ence to Faraday's discovery of specific inductive capacity, that in the 

 course of some investigations conducted in conjunction with Professor 

 JIughes, they had observed that every different dielectric possessed 



