1820.] Prof. Oersted on new Electromagnetic Experiments. 375 



Article IX. 



New Electromagnetic Experiments. By Prof. Oersted. 



Since the publication of my first experiments on the magnetic 

 action of the galvanic battery, I have multiplied my researches 

 on that subject as much as a multitude of other important avo- 

 cations put it in my power. . 



The magnetic effects do not seem to depend upon the mtensity 

 of the electricity, but solely on its quantity. The discharge of 

 a strong electric battery transmitted through a metallic wire 

 produces no alteration in the position of the magnetic needle. 

 A series of interrupted electric sparks acts upon the needle by 

 the ordinary electric attractions and repulsions, but as far as can 

 be perceived, the sparks produce no electromagnetic effect. A 

 galvanic pile composed of 100 discs of two inches square each 

 metal, and of paper moistened with salt water to serve as a fluid 

 conductor, is likewise destitute of sensible effect upon the needle. 

 On the other hand we obtain the effect by a single galvanic arc 

 of zinc and copper having for a conductor a liquid possessed of 

 great conducting power ; for example, of one part sulphuric acid, 

 as much of nitric acid, and 60 parts of water. We may even 

 double the quantity of water without much diminishing the 

 effect. If the surface of the two metals is small, the effect is 

 . likewise small. But it augments in proportion as we augment 

 the surfacae. A plate of zinc, of six inches square, plunged into 

 a vessel of copper containing the liquid conductor of which I 

 have spoken, produces a considerable effect. But an arrange- 

 ment of this kind in which the zinc plate has a surface of 100 

 inches square acts upon the needle with such force that the 

 effect is very sensible at the distance of three feet, even when 

 the needle is not very moveable. I have not observed greater 

 effects from a galvanic apparatus composed of 40 similar 

 troughs ; indeed the effect seemed less great. If this observa- 

 tion, which I have not investigated expressly, is just, I shall be 

 of opinion that the small diminution of the conducting power 

 produced by increasing the number of the elements of the appa- 

 ratus weakens its electrochemical effect. 



To compare the effect of a single galvanic arc with that of an 

 apparatus composed of several arcs or elements, let us make an 

 observation. Let fig. 9 (PI. CIX), represent a galvanic arc 

 composed of a piece of zinc z, of copper c, of a metallic mreab, 

 and of a liquid conductor /. The zinc always communicates a 

 portion of its positive electricity to the water as the copper does 

 of its negative electricity. This would occasion an accumulation 

 of negative electricity in the upper part of the zinc, and ot posi- 

 tive electricity in the upper part of the copper, unless the com- 

 munication a b re-established the equilibrium by affording a free 



