70 Report of Chemistry and Experimental Philosop/ii/. [Feb. I, 

 nieut auimxod, wliicb is ii perpendicular sec- j ^ 



tion of it in the direction of its breadth, ccee 

 being u trough of copper 3 inches high, 4 

 inches long, and \ inch wide ; zz, a plate of 

 zinc, keptiu its place by two pieces of cork 

 II ; offJJ'z, a brass wire about a fiuarter of n 

 linediaiucler ; ah, a l)rass wire as small as 

 possible, but capable of sustaining the ap- 

 paratus ; and cac, a linen thread for attach- 

 ing the wire to the apparatus. The troiiprh 

 contains the usual conducting fluid. The 

 uniting wire of this apparatus will attract 

 the north pole of the needle when it is placed 

 on the left side of the plane cffffz, regarded 

 in the direction /z. On the same siile, the 

 south pole will be repelled. On the other 

 side of tills plane, the north will be repelled 

 and the south pole attrarted. In effecting 

 this, we must not place the needle above^, 

 nor below/z or/c. If, instead of presenting 

 a small moveable needle to the uniting wire, 

 we present to one of the extremities^/, one 

 of the poles of a strong magnet, the attrac- 

 tion or repulsion (indicated by the needle) 

 will cause the galvanic apparatus to revolve 

 round the prolonged axis of the wire ah. 



If we substitute, in place of the conduct- 

 ing wire, a large ribbon of copper of the 

 same breadth as the plate of zinc, a feebler 

 effect only is produced. The effect is on the 

 other hand increased by making the conduc- 

 tor very short. 



This figure represents the perpendicular 





section of this arrangement in the direction 

 of the breadth of the trough ; and the annexed 

 is a perspective view of it, in which ahcdef 

 represent the conducting plate, andezsj/the 

 plate of zinc. Here the north pole of the 

 needle will be attracted towards the plane of 

 ahc, and the south pole will be repelled from 

 the same plane ; cdf will have contrary 



effects. In this appiir.uus the extremities 

 act like the poles of the needle, but it is only 

 the faces of the extremities, and not the in- 

 termediate parts that have this analogy. 



A moveable galvanic apparatus may also 

 be made of two philes, one of copper and 

 one of zinc, twisted into spirals, and su.s- 

 pended in the conducting fluid. This appa- 

 ratus is more moveable, but greater prec^iu- 

 tious are necessary to avoid deceptions when 

 expcrinienis are made with it. 



I have not yet discovered a method of ma- 

 king a galvanic apparatus direct itself to- 

 wards the poles of tbe earth. For such a 

 purpose the apparatus would require to be 

 much more moveable. 



In repeating the interesting experiments 

 of M. Oersted, Sib Humphry Davy found, 

 that the uniting wire of platinum was mag- 

 netic from its power of attracting iron 

 filings. This wire was also found to com- 

 municate permanent magnetism to steel bars 

 transversely attached to it, or placed trans> 

 versely at some distance from it; while the 

 same bars, when placed parallel to the wire, 

 had only a temporary magnetism when in 

 the vicinity of the ap|)aratus. 



The most important fact, however, in Sir 

 Humphry Davy's experiments, is, that when 

 the electricity from a Leyden battery is pas- 

 sed through a wire or through air, the wire 

 and air and the surrounding space became 

 magnetic, so that bars of steel made tan- 

 gents or sines or circles round the wire, all 

 became magnets, the north pole of one being 

 opposite to the south pole of the other. By 

 means of a powerful Leyden battery, Sir 

 Humphry has made magnets at the distance 

 of fourteen inches from the wire. He has 

 also been able to attract and repel bars 

 placed in the voltaic circuit by the common 

 magnet. 



Jlr. Ampere commuBicated to the Aca- 

 demy of Sciences three memoirs,on the 18th 

 and 25th of September, and the 30tb of Oc- 

 tober, ISiJO. The following are the princi- 

 pal conclusions deduced from the second 

 memoir. 



1. "The two electric currents attract one 

 another when they move parallel and in the 

 same direction, and they repel one another 

 when they move parallel and in oppocite di- 

 rections. 



2. It follows, therefore, that when the 

 metallic wires through which these currents 

 are transmitted, can only turn in parallel 

 planks, each of the two currents tends to 



bring 



