232 



MR J. C. BEATTIE ON THE 



Field. 



. Transverse Effect. 



Sign. 



Rotatory Coefficient. 



23-4 



0-08714 





1-97 



29-0 



0-09326 



- 



1-70 



35-2 



0-08958 



- 



1-35 



41-8 



0-08033 



- 



1-02 



45-0 



0-06857 



- 



0-081 



69 



Not observed. 







80-0 



0-03144 



+ 



0-21 



102-8 



0-12287 



+ 



0-63 



1100 



0-20363 



+ 



0-88 



A comparison of these results with those obtained with the original plate shows that 

 the maximum negative effect is reached with a higher field, and that the field strength 

 for which the effect vanishes is also higher. If we take the magnetic force as abscissa, 

 the transverse effect as ordinate, we may express the result by stating that the curve 

 giving the relation between the two has been moved, so that it cuts the axis at a point 

 farther along in the positive direction. 



See graph of curve giving relation between transverse effect and field strength in 

 fig. 3, where A is the curve for the plate as originally cast, B that after it was hammered, 

 C that after it was planed down. 



Finally, the dimensions of the plate were again slightly modified, and, in addition, it 



was hammered. 



Plate VI. 

 Length, . . . . . 3 -25 cm. 



Breadth, . . . . . 1-24 



Thickness, ..... 0-0657 „ 



Field. 



Transverse Effect. 



Sign. 



Rotatory Coefficient. 



49-0 



0-1075 





1-16 



66-1 



0-08014 



— 



0-64 



76-0 



0-0394 



- 



027 



85-0 



Not observed. 







123-1 



0-12246 



+ 



0-527 



134-0 



01657 



+ 



0-66 



In this instance the reversal of sign takes place with a still stronger field. An attempt 

 to further thin the plate proved abortive ; it was now so brittle that planing caused it 

 to break. 



In Plate VII. the reversal was also observed in the plate as originally made ; the effect 

 disappeared with a field strength of 43 x 138"5 c.g.s. It was then halved and the trans- 

 verse effect for both halves was observed, and was found to vanish for the same field 

 strength. Finally, one half was hammered ; the same results — negative for the weaker 

 fields, positive for the higher — were obtained, but the vanishing did not now take place 

 until a field strength 60 x 13 85 was reached. 



