in Magnetism and Electricity \ 101 



a commutator, instead of that from a magneto-electric machine. 

 He also found that an alternating current meets with less resist- 

 ance when transmitted through an electrolyte than does the 

 direct current from the same voltaic battery, and rightly conjec- 

 tured that the non-appearance of the gases liberated by the 

 alternating current was due to their recombination on the surface 

 of the electrodes. Moreover De la Rive, in common with many 

 other physicists, has maintained that the transmission of the 

 current, and the electrolyzation of the liquid in contact with the 

 electrodes, are inseparably connected. I do not, however, find 

 that any one has yet given a direct proof, or one free from am- 

 biguity, that the transmission of a current of so low an intensity 

 as that used in Faraday's experiment is dependent upon the elec- 

 trolyzation of the liquid through which such current is trans- 

 mitted. Hence it is that up to the present time the absolute 

 generality of the law of definite electrolysis has been doubted 

 by some philosophers, and has never acquired more than a high 

 degree of probability with others. 



175. Returning to the phenomena exhibited by the conduc- 

 tors when in contact with the terrestrial bed : — It has been shown 

 that all the effects of resistance and conduction produced by the 

 naked and tape-covered coils immersed in the tub of fresh water 

 were identical with those exhibited when these same coils were 

 immersed in the canal (113, 143), (131, 144), (129, 147), (119, 

 150). We have also seen that the current from the 2^-inch 

 machine, which would not heat thin wire when the conductors 

 were coiled up separately in the canal or in the tub of fresh 

 watery would nevertheless melt four inches of this wire at N 

 when the coils were immersed in the tub of salt water at a dis- 

 tance of 3 inches apart (151). Hence it seemed highly probable 

 that similar differences of resistance to the passage of the cur- 

 rent would also be found between the fresh and salt water in con- 

 tact with the terrestrial bed. 



176. Two of the copper-rope conductors used in the canal 

 experiments were therefore extended separately in the sea, on the 

 coast of Lancashire, in about one fathom of water. On trans- 

 mitting the current from the 2^-inch machine through the ex- 

 tended conductors, the same quantity of thin wire (four inches) 

 was melted at N as when the conductors were coiled up sepa- 

 rately in the tub of salt water (151). 



177. But when the submerged conductors were placed in 

 connexion with the single Grove's cell, the current which 

 made three-quarters of an inch of thin wire red-hot at N when 

 the double coil was immersed in the tub of salt water (152) was 



