Action of a Magnet on Chemical Action. 41 



it is to be noted that the deflection often gradually reversed 

 in direction when the current was sent through the magnet ; 

 i. e., only the latter part of the previous phenomenon appeared 

 under these circumstances. 



When the poles, instead of being placed in the field along the 

 lines of force, were held firmly perpendicular to them, the pro- 

 tective throw disappeared completely, though as before there 

 was a slight reverse after-effect. 



Some of Professor Remsen's experiments on the corrosion 

 of a wire in strong nitric acid were repeated with the same 

 results as he obtained, viz : the wire was eaten away to the 

 general dumb-bell form, though the protected ends instead 

 of being club-shaped were perceptibly hollowed. When the 

 wire thus exposed was filed to a sharp point the extreme 

 point was very perfectly protected, while there was a slight 

 tendency to hollow the sides of the cone, and the remainder 

 of the wire was as in the previous experiments. In both 

 cases the bars were steel and showed near the ends curious 

 corrugations, the metal being left here and there in sharp 

 ridges and points. In one case the cylinder was eaten away 

 on sides and ends so that a ridge of almost knife-like sharpness 

 was left projecting from the periphery of the ends. 



These were the principal phenomena observed with nitric 

 acid. Since this acid is the only one which attacks iron freely 

 in the cold, in Prof. Remsen's experiment, this was the one to 

 which experiments were in the main confined. With the 

 present method, however, it was possible to trace the effect of 

 the magnet whenever there was the slightest action on the iron, 

 and consequently a large number of substances, some of which 

 hardly produce any action, could be used with not a little facility. 



In thus extending the experiments some difficulties had to 

 be encountered. In many cases the action on the iron was so 

 irregular that it was only after numerous experiments under 

 widely varying conditions that the effect of the magnet could 

 be definitely determined. Frequently the direction of the 

 original action would be reversed in the course of a series of ex- 

 periments without any apparent cause, but in such case the 

 direction of the effect due to the magnet remained always un- 

 changed, uniformly showing protection of the point so long as 

 the wires remained parallel to the hues of force. When, how- 

 ever, the original action and the magnetic effect coincided in 

 direction, the repetition of the latter showed a decided ten- 

 dency to increase the former. 



When using solutions of various salts more or less freely pre- 

 cipitated by the iron, it frequently happened that the normal 

 protective throw was nearly or quite absent, but showed itself 

 when the magnet circuit was broken as a violent throw in the 

 reverse direction, showing that the combination had been act- 



