1821.] Repiirf of Chemislry and Expcrimeniiil- Phihsophij. 



m 



\s depressed, wbeii the wire is situated on 

 the west side, Rnd raised vvheu it is situated 

 OD the eaai side. 



4. If the uniting wire is placed at right 

 angles to the magnetic meri(linu,the needle 

 remains at rest, whether U is placed above or 

 below the nailing wire ; excepting in the 

 case when it is very near the pole of the 

 needle, and then the pole will be raised, if 

 the negative electricitj' enters from the west 

 and depres-ed when it enters from tlie east. 



5. VVhen the uniting wire is placed verti- 

 cally, and receives the negative electricity 

 at its upper end, if it is opposite the pole of 

 the needle, it will turn to the east, but if it 

 is opposite a poinc between the pole and the 

 centre of the needle, it will turn to the west. 

 When the negative electricity enters at the 

 lower end, the phenomena are reversed. 



6. If the uniting wire is bent into the form 

 of Z, so as to form two parallel legs, it at- 

 tracts or repels the poles of the needle ac- 

 cording to certain circumstances of position. 

 If we place the wire opposite one of the 

 poles of the needle, the plane of the legs 

 being perpendicular to the magnetic meri- 

 di.Di, tlie negative electricity entering by the 

 east leg, and the positive by the west leg, 

 the pole win be repelled to the east or to the 

 west, according to the situation of the plane 

 of the legs. But if the negative electricity 

 enters by the west leg, and the positive by the 

 «ast leg, the pole will be attracted. If the 

 plane of the leg is perpendicular to the mag- 

 netic meridian, and opposite a point situated 

 between the extremity and the centre of the 

 neadle, all these eftects will ba inverted. 



The nature of the uniting wire has no n- 

 flueoce on the above phenomena. Wires of 

 platina, gold, silver, brass, iron, plates of 

 lead and tin, and even mercury, may be em- 

 ployed with the same success. Several wires 

 twisted together, or metallic ribbons, may 

 also be used. The uniting wire does not 

 lose its effect when interrupted by water, 

 unless^when the interruption amounts to se- 

 veral inches in length. 



The action of the uniting wire upon the 

 needle may be transmitted without any di- 

 ininutiou of its effect, through glass, melaLs, 

 wood, water, rosin, earthen- ware and stones. 

 Even when these various substances are in- 

 terposed at the same time, they scarcely 

 seem to diminish the effect. A disc of tlie 

 electropborus, plates of porpliyry, a stone- 

 ware vessel full of water, were interposed 

 with as little effect, and the influence of the 

 uniting wire continued the same when the 

 needle was shut up in a brass box filled with 

 water. As the ordinary galvanic and elec- 

 trical influence has never been transmitted 

 Ihrougii these sub-^mice?, the efi'ects which 

 take place in the contlici; of eicctricity are 

 'totally different from tliose whicli belong to 

 ele<;lrical attractions audrepubiious. 



Needles of brass, glass and gum lac, 

 were nubstituted in place of the magnetic 

 needle ; but they were not influenced by the 

 «ciioD of the uniting wire. 



In extending his electro-magnetic re- 

 searches, M. Oersted has obtained several 

 additional results of a very interesting nature. 



He found that the electro-magnetic eft'ects 

 do aot depend upon the intensity of the elec- 

 tricity, but solely on its quantity. A plate 

 of zinc of six inches square, immersed into 

 a vessel of copper containing the dilute acid, 

 produces a considerable electro-magnetic 

 effect ; but when the plate has 100 square 

 inches of surface, it acts upon the needle 

 with such force, that the effect upon it is 

 sensible at the distance of three feet. The 

 effect is diminished rather than increased, 

 when forty troughs, similar to this single 

 one, are united in one battery. M. Oersted 

 found, that the discharge of a strong electric 

 batter}-, transmitted through a metallic wire, 

 produced no deviation in the needle ; neither 

 did a series of uninterrupted sparks produca 

 any other enect than the ordinarj' attrac- 

 tions and repulsions. A galvanic pile of 100 

 discs of two inches square each, and paper 

 moistened with salt-water, is also destitute 

 or any sensible effect. 



In comparing the effect of a single gal- 

 vanic arc with that of an apparatus com- 

 posed of several, M. Oersted supposes the 

 annexed figure to represent a galvanic arc 



composed of one piece of zinc «, a. piece of 

 copper c, a metallic wire a b, and a fluid 

 conductor /. The zinc always communi- 

 cates a portion of its positive electricity to 

 the water, as t^he copper does of its negative 

 electricity, which would protluce an accu- 

 mulation of negative electricity in the upper 

 part of the zinc, and of positive electricity 

 in the upper part of the copper, and the 

 communication by ah did not re-establish 

 the equilibrium by presenting a free passage 

 to the negative electricity from s to c, and 

 of the positive electricity from c to s. The 

 wire ah, therefore, receives che negative 

 electricity of the zinc, apd the positive elec- 

 tricity of the copper; whereas a wire which 

 forms a con-munication between the two 

 poles of a battery, receives positive electri- 

 city from the pole of the zinc, and negative 

 from that of the copper. 



" If we attend to this distinction," says 

 M. Oprsted, " we may, with a single gal- 

 vanic arc, arranged as I have described, re- 

 peat all the experiments which I had before 

 made with a compound galvanic apparatus. 

 One great advantage of this plan is, that we 

 may form the arc sufficiently light to be sus- 

 pended by a small metallic wire, so as to 

 revolve roiind the axisof the wire prolonged; 

 and ill tiiisway we may examine the action 

 of a magnet on the galvanic arc. 



" for this purpose I employed the arrange- 

 ment. 



