ACTION OF A MAGNET ox CHEMICAL ACTION 243 



furthermore pitted on the ends in a remarkable manner. On Prof. 

 Remsen's signifying that he had abandoned the field for the present, 

 we set to work to illustrate the matter in another manner by means 

 of the electric currents produced from the change in the electrochemical 

 nature of the points and hollows of the iron. 



The first experiments were conducted as follows: Two bits of iron 

 or steel wire about 1 mm. in diameter and 10 mm. long were imbedded 

 side by side in insulating material, and each was attached to an insulated 

 wire. One of them was filed to a sharp point, which was exposed by 

 cutting away a little of the insulation, while the other was laid bare on 

 a portion of the side. The connecting wires were laid to a reflecting 

 galvanometer, and the whole arrangement was placed in a small beaker 

 held closely between the poles of a large electromagnet, the iron wires 

 being in the direction of the lines of force. When there was acid or 

 any other substance acting upon iron in the beaker, there was always a 

 deflection of the galvanometer due to the slightly different action on 

 the two poles. When the magnet was excited the phenomena were 

 various. When dilute nitric acid was placed in the beaker and the 

 magnet excited, there was always a strong throw of the needle at the 

 moment of making circuit, in the same direction as if the sharp pointed 

 pole had been replaced by copper and the other by zinc. This throw 

 did not usually result in a permanent deflection, but the needle slowly 

 returned toward its starting point and nearly always passed it and 

 produced a reversed deflection. This latter effect was disregarded for 

 the time being, and attention was directed to the laws that governed 

 the apparent ' protective throw,' since the reversal was so long delayed 

 as to be quite evidently due to after effects and not to the immediate 

 action of the magnet. 



With nitric acid this throw was always present in greater or less 

 degree, and sometimes remained for some minutes as a temporary 

 deflection, the time varying from this down to a few seconds. The 

 throw was independent of direction of current through the magnet, and 

 apparently varied in amount with the strength of acid and with the 

 amount of deflection due to the original difference between the poles. 

 This latter fact simply means that the effect produced by the magnet 

 is more noticeable as the action on the iron becomes freer. 



When a pair of little plates exposed in the middle were substituted 

 for the wires, or when the exposed point of the latter was filed to a 

 flat surface, the protective throw disappeared, though it is to be noted 

 that the deflection often gradually reversed in direction when the cur- 



