354 Dr. Hopkinson and Messrs. Wilson and Lydall. [Apr. 20, 



wire ring, B is the ballistic galvanometer, Si is a reversing switch, 

 and S 2 a small switch for the purpose of short- circni ting the adjust- 

 able resistance Ei. The difference between this diagram and that in 

 fig. 1 is that R x can be suddenly inserted into the primary circuit by 

 one stroke of the reversing switch S x . In this way it is possible to 

 vary the magnetising force from one maximum through zero to any 

 desired point within the other maximum by one motion of the switch 

 Si : which operation takes but a small fraction of a second to 

 perform. 

























































































































































































































































































































































































































































































































■ 





























































































E! 

























































































































































































































































































































H 



M 









if 









































































































































































































SI 



























































1 



i 























































































































































































































































































































i 



i 

















































s 









































































































■ 



■1 



























































































































In fig. 3 the points marked x were obtained by the method in 

 fig. 1 ; the points marked • being obtained by the method in fig. 2. 

 Table I gives the values for B and H, from which these points have 



