G42 Mr. R. Beattie on the Hysteresis of Nickel and 



Consequently, the energy necessary to ionize a molecule of 

 carbonic acid would be of the same order as the energy 

 necessary to ionize a molecule of air. It would appear from 

 the relative shapes of the curves for hydrogen and carbonic 

 acid, that it requires less energy to ionize hydrogen than air 

 or carbonic acid. 



Experiments are at present being made on the conductivity 

 between electrodes of various shapes. These investigations 

 are important, as they enable us to find out whether the 

 increased conductivity is due to the motion of the positive or 

 negative ions. The results obtained with air led to the con- 

 clusion that the genesis of ions is to be attributed to the motion 

 of the negative ions, and that apparently the positive ions take 

 no part in producing new ions. 



The experiments described in this paper were made at the 

 University Observatory, Oxford ; and we must express our 

 thanks to Professor Turner for having placed some of his 

 rooms at our disposal. 



LXIY. The Hysteresis of Nickel and Cobalt in a Rotating 

 Magnetic Field. By R. Beattie, B.Sc. *■ 



SO far, the few who have worked at the subject of magnetic 

 hysteresis in a rotating magnetic field have been content 

 to experiment with iron and steel, without seeking to extend 

 their investigations to other magnetic substances exhibiting 

 hysteresis. To repair to some extent this omission, the 

 experiments about to be described were made on the hysteresis 

 in a rotating magnetic field of nickel and cobalt, the two 

 metals wdiich, next to iron, most deserve attention. 



The method employed was similar to that previously used 

 by the writer in conjunction with Mr. R. 0. Clinker f. A 

 cylindrical wooden box, B (fig. 1), with a tightly fitting lid, 

 L, was suspended by a steel wire, W, between the poles, N, S, 

 of an electromagnet which could be rotated round the vertical 

 axis OW. A brass pin driven axially into the lid of the box 

 passed loosely through a hole in a fixed support at 0, and served 

 to prevent lateral motion. The material to be examined, in 

 the form of a thin circular disk seen edgeways at D, was 

 placed in the- box and held in position by the pressure against 

 it of the lid. 



When the magnet was rotated slowly so as to avoid the pro- 

 duction of eddy-currents, the suspended system experienced 



* Communicated by the Author. 



t See < The Electrician/ Oct. 2nd, 1896. 



