Experimental Researches in Electricity. 19 



Proceeding to compare the magneto-electric effect pro- 

 duced upon different metals by the magnetism of the earth, 

 it was found to be in direct proportion to their conducting 

 powers, and the order in which the different metals experi- 

 mented upon is placed, is as follows, copper, zinc, tin iron, and 

 lead. That the electric currents produced are exactly pro- 

 portional to, and dependent upon, the conducting powers, 

 Faraday conceives to be established, by the perfect ventrali- 

 ty displayed when two metals, or other substances, as acid, 

 water, &c. are opposed to each other, for then the feeble cur- 

 rent, which tends to be produced in the worse conductor, 

 has its transmission favoured in the better conductor, and the 

 stronger current, tending to form in the latter, has its inten- 

 sity diminished by the obstruction of the former ; and the 

 forces of generation and obstruction are so perfectly balanc- 

 ed as to neutralise each other exactly : therefore as the 

 obstruction is inversely as the conducting powers, the ten- 

 dency to generate a current must be directly as that power 

 to produce this perfect equilibrium. 



In endeavouring to explain the phenomena of the mag- 

 netism of rotation, Messrs. Babbage and Herschell had 

 attributed them to the production, during the period, of 

 rotation in the rotating plate, of a feeble polarity, similar in 

 kind to that existing in iron. When by the adjustment of the 

 attractive and repulsive forces exerted in different positions 

 between the magnet and plate, the singular results it was 

 considered might be explained. This view, as we formerly 

 remarked, proved utterly inadequate to the explanation of 

 the phenomena, save in the single case of iron ; and Faraday 

 now thought he had devised a decisive experimental test, by 

 which it would be shewn whether the polarity developed 

 during rotation was of the same, or of an entirely different 

 nature to that present in ferruginous bodies : ee no other 

 known power," he reasoned, " has like direction with that ex- 

 erted between an electric current and a magnetic pole ; it is 



