200 CLASSICS OF MODERN SCIENCE 



"Feb. 17. — Mr. Faraday gave an account of the first two parts of 

 his researches in electricity; namely, Volta-electric induction and 

 magneto-electric induction. If two wires, A and B, be placed side by 

 side, but not in contact, and a Voltaic current be passed through A, there 

 is instantly a current produced by induction in B, in the opposite direc- 

 tion. Although the principal current in A be continued, still the sec- 

 ondary current in B is not found to accompany it, for it ceases after the 

 first moment, but when the principal current is stopped, then there is a 

 second current produced in B, in the opposite direction to that of the 

 first produced by the inductive action, or in the same direction as that 

 of the principal current. 



"If a wire, connected at both extremiities with a galvanometer, be 

 coiled in the form of a helix around a magnet, no current of electricity 

 takes place in it. This is an experiment which has been made by various 

 persons hundreds of times, in the hope of evolving electricity from mag- 

 netism, and in other cases in which the wishes of the experimenter 

 and the facts are opposed to each other, has given rise to very conflicting 

 conclusions. But if the magnet be withdrawn from or introduced into 

 such a helix, a current of electricity is produced whilst the magnet is 

 in motion, and is rendered evident by the deflection of the galvanometer. 

 If a single wire be passed by a magnetic pole, a current of electricity is 

 induced through it which can be rendered sensible." 



Before having any knowledge of the method given in the above ac- 

 count, I had succeeded in producing electrical effects in the following 

 manner, which differs from that employed by Mr. Faraday, and 

 which appears to me to develop some new and interesting facts. A 

 piece of copper wire, about thirty feet long and covered with elastic 

 varnish, was closely coiled around the middle of the soft iron arma- 

 ture of the galvanic magnet described in Vol. XIX of the American 

 Journal of Science, and which, when excited, will readily sustain be- 

 tween six hundred and seven hundred pounds. The wire was wound 

 upon itself so as to occupy only about one inch of the length of the 

 armature which is seven inches in all. The armature, thus furnished 

 with the wire, was placed in its proper position across the ends of the 

 galvanic magnet, and there fastened so that no motion could take 

 place. The two protecting ends of the helix were dipped into two 

 cups of mercury, and there connected with a distant galvanometer by 

 means of two copper wires, each about forty feet long. This arrange- 



