TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 235 



We may sum up the results as follows : — With thick plates the transverse current 

 does not change its direction for any strength of field, though in some cases a maximum 

 value is reached and passed ; nor can the change of direction be brought about by 

 planing, hammering, or modifying the dimensions of the plates. Cp. fig. 1, which gives 

 the relation between field and effect for Plate 1a, and fig. 2, which gives the same for 

 Plate II. 



With thinner plates the transverse current is positive for strong fields, negative for 

 weak ones. The field strength at which vanishing takes place is the same for the same 

 plate, so long as it is modified only in length and breadth ; but if the plate be planed 

 down, the field at which the current vanishes is stronger than in the original case. 

 Similarly, if the original plate be hammered, the field required to produce vanishing is 

 stronger : a combination of hammering and planing raises very considerably the strength 

 of the field required. From a comparison of the results, it will be seen that in different 

 plates the transverse current vanishes for different fields. Cp. fig. 3, where the three 

 curves give the relation between field strength and transverse effect for Plate Ib ; A refers 

 zo the original plate, B to the same plate hammered, C to it after planing. 



This reversal of the transverse current has already been observed by Von Ettings- 

 hausen and Nernst * in an amalgam of bismuth and tin. 



In the one certainly pure bismuth, Plate III., the ratio of the increase of resistance to 

 the square of the transverse effect, was practically constant ; this is as it should be, if in 

 diamagnetic bodies the transverse effect is, as in the magnetic metals, proportional to the 

 magnetisation I, and the increase of resistance proportional to, I 2 . If we start from this 

 and apply it to those plates in which the transverse effect vanishes, we find that our 

 facts do not tally with our assumptions. For if the transverse current be proportional 

 to the magnetisation, when the former vanishes, so must the latter and so must the 

 increase of resistance too : that is, when the transverse current vanishes, the resistance 

 of the bismuth at the same field strength must be the same as when no field is present. 

 But for Plate Ib. the following results were obtained : — 



Field Strength. 



Resistance Proportional to. 



Transverse Effect. 



o-o 



28-0 



63-0 



118-0 



147-7 



254-0 

 265-4 

 280-1 

 300-2 

 312-0 





 -0-5517 

 - 0-003 

 + 0-14253 

 + 0-22356 



That is, the transverse effect vanishes at about 63, but the resistance increase is at the same 

 field strength quite perceptible. Another effect observed in all the plates and which will 

 be later described, supports the view that the increase of resistance does not vanish with 



Sitz. bericht der kais. Akad. der Wissenschaft, ii. A.bth., 1887, Bd. 96. 



