6 Experimental Researches in Electricity. 



sent with him, that could the key to the discovery but be 

 found, a rich treasure would reward the discoverer. " It ap- 

 peared very extraordinary," he remarks, " that as every elec- 

 tric current was accompanied by a corresponding intensity 

 of magnetic action at right angles to the current, good 

 conductors of electricity, when placed within the sphere 

 of this action, should not have any current induced through 

 them, or some sensible effect produced, equivalent in force to 

 such a current." These considerations, with their consequence, 

 the hope of obtaining electricity from common magnetism, 

 have stimulated me at various times to investigate experi- 

 mentally the inductive effect of electric current: the power 

 of induction herein alluded to, may be defined as that pro- 

 perty by which electrical currents induced any particular 

 state upon matter in their immediate neighbourhood, and in 

 this general sense it is employed by Faraday throughout his 

 masterly researches. 



After several experiments equally unsuccessful with his 

 former efforts, Faraday at length, in 1831, obtained decisive 

 proof of the power of a current of galvanic electricity to 

 induce upon a wire in its vicinity, a certain electrical 

 state, and in a manner very different indeed to his previous 

 expectations. It then appeared that induction took place 

 momentarily, when the contact of the conducting wire 

 with the battery was made, and again when it was broken. 

 But to render this more clear, we shall briefly detail that ex- 

 periment by which this result, and through it the large train 

 that follows it, were obtained. Two hundred and three feet 

 of copper wire in one length were coiled round a block 

 of wood ; other two hundred and three feet of similar wire 

 were interposed as a spiral between the turns of the 

 first coil, and metallic contact everywhere prevented by 

 twine. One of these helices was connected with a gal- 

 vanometer, and the other with a battery of one hundred 

 pairs of plates, four inches square, with double coppers, 



