654 Messrs. W. Morris Jones arid J. E. Malam on the 



Such a series is reproduced in fig. 2, 

 and it will be seen that the agree- 

 ment between corresponding curves 

 is good. The figures at the head of 

 each curve give the respective scale- 

 readings. It will be seen that the 

 outer curves indicate 91^° on the 

 scale as the true transverse position. 

 The curve for this position is plotted 

 on a larger scale in fig. 3. For fields 

 below 1000 c.G.s. galvanometer de- 

 flexions were observed and the gal- 

 vanometer afterwards calibrated. It 

 will be seen that the values obtained 

 for the changes of resistance are 

 wholly negative. This result differs 

 from that of Grunmach and Heaps, 

 who obtained a few positive values for 

 fields below 1000 c.G.s. units. The 

 series of curves, however, furnishes 

 the interesting evidence that if an 

 error of setting of 2\° or even less 

 is made with the transverse posi- 

 tion as determined electrically, we 

 shall obtain the result of Grunmach 

 and Heaps. It is probable that 

 an adjustment appearing mechani- 

 cally correct may easily differ by 

 this small amount from the true 

 magnetic position, especially when 

 comparatively short lengths of wire 

 are employed. If when in a small 

 transverse field of say 400 c.G.s. 

 the specimen was rotated out of 

 position through 1°, it was found that 

 the galvanometer deflexion changed 

 from negative to positive. A series 

 of graphs of galvanometer de- 

 flexions for small fields for posi- 

 tions at intervals of 1° about the 

 transverse position further supported 

 the conclusion that a very small 

 error of setting would account for 

 the slight rise obtained by the above 

 mentioned experimenters. It may 

 be noted that in recent experiments 







Fig. 2. 









b- 



















cr 

















i 



a 





/ 







(^ 









cr 



m 



















03 













