274 Prof. Oersted on the Effect of a [Oct. 



Professor of Natural History, Mr. Jacobsen, Professor of Medi- 

 cine, and that very skilful chemist, Mr. Zeise, Doctor of Philoso- 

 phy. I had often made experiments by myself; but every fact 

 which I had observed was repeated in the presence of these 

 gentlemen. 



The galvanic apparatus which we employed consists of 20 

 copper troughs, the length and height of each of which was 

 12 inches ; but the breadth scarcely exceeded 2-i- inches. Every 

 trough is supplied with two plates of copper, so bent that they 

 could carry a copper rod, which supports the zinc plate in the 

 water of the next trough. The water of the troughs contained 

 .gig-th of its weight of sulphuric acid, and an equal quantity of 

 nitric acid. The portion of each zinc plate sunk in the water is 

 a square whose side is about 10 inches in length. A smaller 

 apparatus will answer provided it be strong enough to heat a 

 metallic wire red hot. 



The opposite ends of the galvanic battery were joined by a 

 metallic wire, which, for shortness sake, we shall call the vniting 

 conductor, or the niiitiiig tvire. To the effect which takes place 

 in this conductor and m the surrounding space, we shall give 

 the name of the conflict of electricity. 



Let the straight part of this wire be placed horizontally above 

 the magnetic needle, properly suspended, and parallel to it. If 

 necessary, the uniting wire is bent so as to assume a proper 

 position for the experiment. Things being in this state, the 

 needle will be moved, and the end of it next the negative side of 

 the battery will go westward. 



If the distance of the uniting wire does not exceed three- 

 quarters of an inch from the needle, the dechnation of the needle 

 makes an angle of about 45°. If the distance is increased, the 

 angle diminishes proportionally. The declination likewise varies 

 with the power of the battery. 



The uniting wire may change its place, either towards the east 

 or west, provided it continue parallel to the needle, without any 

 other change of the effect than in respect to its quantity. Hence 

 the effect cannot be ascribed to attraction ; for the same pole of 

 the magnetic needle, which approaches the uniting wire, while 

 placed on its east side, ought to recede from it when on the 

 west side, if these decHnations depended on attractions and 

 repulsions. The uniting conductor may consist of several wires, 

 or metallic ribbons, connected together. The nature of the metal 

 does not alter the effect, but merely the quantity. Wires of 

 platinum, gold, silver, brass, iron, ribbons of lead and tin, a 

 mass of mercury, were employed with equal success. The con- 

 ductor does not lose its effect, though interrupted by water, 

 unless the interruption amounts to several inches in length. 



The effect of the uniting wire passes to the needle through 

 glass, metals, wood, water, resin, stoneware, stones ; for it is 

 not taken away by interposing plates of glass, metal or wood. 



