228 Mr. E. H. Hall on a new Action of 



was observed, in order to detect any indication of a change 

 in the relative potential of the two poles. 



Owing probably to the fact that the metal disk used had 

 considerable thickness, the experiment at that time failed to 

 give any positive result. Prof. Rowland now advised me, in 

 repeating this experiment, to use gold-leaf mounted on a 

 plate of glass as my metal strip. I did so, and, experimenting 

 as indicated above, succeeded on the 28th of October in ob- 

 taining, as the effect of the magnet's action, a decided de- 

 flexion of the galvanometer-needle. 



This deflexion was much too large to be attributed to the 

 direct action of the magnet on the galvanometer-needle, or to 

 any similar cause. It was, moreover, a permanent deflexion, 

 and therefore not to be accounted for by induction. The 

 effect was reversed when the magnet was reversed. It was 

 not reversed by transferring the poles of the galvanometer 

 from one end of the strip to the other. In short, the phe- 

 nomena observed were just such as we should expect to see if 

 the electric current were pressed, but not moved, toward one 

 side of the conductor. 



In regard to the direction of this pressure or tendency, as 

 dependent on the direction of the current in the gold-leaf and 

 the direction of the lines of magnetic force, the following 

 statement may be made: — If we regard an electric current as 

 a single stream flowing from the positive to the negative 

 pole, i. e. from the carbon pole of the battery through the 

 circuit to the zinc pole, in this case the phenomena observed 

 indicate that two currents, parallel and in the same direction, 

 tend to repel each other. If, on the other hand, we regard 

 the electric current as a stream flowing from the negative to 

 the positive pole, in this case the phenomena observed indicate 

 that two currents parallel and in the same direction tend to 

 attract each other. 



It is, of course, perfectly well known that two conductors, 

 bearing currents parallel and in the same direction, are drawn 

 toward each other. Whether this fact, taken in connexion 

 with what has been said above, has any bearing upon the 

 | question of the absolute direction of the electric current, it is 

 perhaps too early to decide. 



In order to make some rough quantitative experiments, a 

 new plate was prepared, consisting of a strip of gold-leaf 

 about 2 centims. wide and 9 centims. long mounted on plate- 

 glass. Good contact was ensured by pressing firmly down 

 on each end of the strip of gold-leaf a thick piece of brass 

 polished on the underside. To these pieces of brass the wires 

 from a single Bunsen cell were soldered. The portion of the 



