IIIG 



field and in different positions between these two principal ones. 



The rnrient for the measurements was always normal to the field, 



the direction of wliicli is shown by the arrow in fig. 2. It was 



found (see fig. 2) thai in tlie maxim nm and minimum positions, 



R'—R 

 which were normal to each other, the val nes — - — did not differ 



/? 



much, much les.s than in the cases of graphite and bismuth. For 



these conductors in one of these principal positions I the effect is 



so much smaller than in the other one II, that Roberts ') thought 



it possible, that in position I there does not exist an effect at all. 



The small observed effect might be caused by an imperfect orienta- 



Fig. 2. 



tion in the field. In this case a small component of the effect belonging 

 to position II would be observed. For antimony the differences between 

 the results in the positions I and II are so small, that this explana- 

 tion seems not to hold. It is therefore probable, that metal crystals 

 show for a definite direction of the current, normal both to the 

 principal axis and to the field, two independent magnetic resistance 

 changes, the one when the principal axis has the direction of the 

 field, the other when it is normal to it. Other cases for intermediate 

 positions can be reduced to these. The above observations, that for 

 bismuth and graphite, i.e. for those crystals which show the greatest 

 resistance change in the field, the difference between the resistance 

 curves in the two principal positions is greatest, agree with a remark 

 of C. W. Heaps ^). Heaps, who worked with conglomerates, points out 



1) D. E. Roberts, loc. cit. p. 469. 



2) G. W. Heaps Phil. Mag, Vf 24 p. 815. 1912. 



