250 HENRY A. EOWLAND 



not too near and place in the liquid between the poles of a magnet and 

 attach to the galvanometer as before. 



There is a wide field for experiment in the direction indicated above, 

 for it is certainly very curious that the effect varies so much. If hydro- 

 gen were as magnetic as iron, of course acids which liberated it would 

 have no action. But it is useless to theorize blindly without further 

 experiment; and we are drawn off by other fields of research. 



In this Journal for 1886, (1. c.) Professor E. L. Nichols has investi- 

 gated the action of acids on iron in a magnetic field. He remarks that 

 the dissolving of iron in a magnetic field is the same as removing it to 

 an infinite distance and hence the amount of heat generated by the 

 reaction should differ when this takes place within or without the 

 magnetic field. Had he calculated this amount of heat due to the 

 work of withdrawing it from the field, he would probably have found 

 his method of experiment entirely too rough to show the difference, for 

 it must be very small. He has not given the data, however, for us to 

 make the calculation. The results of the experiments were inconclu- 

 sive as to whether there was greater or less heat generated in the field 

 than without. 



In the same Journal for December, 1887, he describes experiments 

 on the action of the magnet on the passive state of iron in the magnetic 

 field. In a note to this paper and in another paper in this Journal for 

 April, 1888, he describes an experiment similar to the one in this paper 

 but without our theory with regard to the action of points. Indeed 

 he states that the ends of his bars acted like zinc, while the middle was 

 like platinum, a conclusion directly opposite to ours. The reason of this 

 difference has been shown in this paper to be probably due to the cur- 

 rents set up in the liquid by the reaction of the magnet and the electric 

 currents in the liquid. 



In conclusion we may remark that our results differ from Professor 

 Nichols in this: First, we have given the exact mathematical theory 

 of the action and have confirmed it by our experiments, having studied 

 and avoided many sources of error, while Professor Nichols gives no 

 theory and does not notice the action of points. Secondly, our experi- 

 ments give a protective action to the points and ends of bars, while 

 Professor Nichols thinks the reverse holds and that these are more 

 easily dissolved than unmagnetized iron. 



