372 Progress of European Science. [Aug. 



lar arrangement of metals, acids, and conductors. This difficulty was removed 

 by a subsequent discovery of Professor Seebeck, of Berlin, only inferior in impor- 

 tance to the first, that the mere application of heat to a circuit composed of two 

 metals was competent to produce the same development of galvanic and magnetic 

 effects as those of the pile. Thus if instead of the coil of conducting wire on the 

 globe above described, each parallel were made complete in two metals, all the 

 phenomena might be represented by the application of heat only. A still farther 

 simplication has been made by Mr. Sturgeon of Woolwich, who has produced all 

 the effects of a compound metallic combination, with a rectangle of bismuth only, 

 unequally heated : a fact according wonderfully with the galvanic plate, described 

 in M. Becquerel's experiments, of a single metal acted on by saline solutions of 

 irregular composition. 



"M. Seeiseck's discovery brings us therefore," says Mr. Barlow, " a step nearer 

 to our object, by referring us to the sun as the great agent of all these phenomena, 

 and indeed only one link seems wanted to connect together the chain, and thereby 

 to reduce to simple and intelligent principles what has hitherto been considered 

 amongst the most mysterious laws of nature." 



Since the publication of Mr. Barlow's paper, Mr. Faraday has taken up the 

 subject of volt a- electric and magneto -electric induction, and although we have not 

 a full account of his experiments, the notice of them in the report of the Royal 

 Institution already prepares us for a train of highly curious results ; indeed, the 

 grand desideratum of converting magnetism into electricity seems in his skilful 

 hands on the points of attainment. 



"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 direction. Although the principal current in A be 

 continued, still the secondary 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 prin- 

 cipal current. These induced currents are so momentary that their effect on the 

 galvanometer is scarcely sensible ; but when they are passed through helices 

 containing unmagnetised steel needles, they convert them into magnets. 



If a wire connected at both extremities with a galvanometer be coiled, in the 

 form of a helix, round a magnet, no current of electricity takes place in it. This 

 is an experiment which has been made by various persons, huudreds of times, 

 in the hope of evolving electricity from magnetism, and, as in other cases in 

 which the wishes of the experimenter, and the facts, are opposed to each other, 

 lias 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 galva- 

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

 is induced through it, which can be rendered sensible," 



Thus is obtained the result so long sought after, the conversion of magnetism in- 

 to electricity ; whenever a metallic body moves near a magnet, so as to intersect 

 the magnetic curves, electricity is evolved, according to very simple laws. Similar 

 results have been obtained even with the magnetism of the earth ; on these subjects 

 Mr. Faraday had recently read a paper before the Royal Society, and he intended 

 (in February) bringing them forward experimentally at the evening meetings of 

 the Royal Institution. 



