On Eapid Periodic Variations of Terrestrial Magnetism. 



9 



applied "end on," so that for the same distance of the deflector, 

 the deflection must be made twice as large as in the case of the Y- 

 instrument to insure the same sensibility. The distance of the 

 deflecting magnet from the needle of the instrument was 127 cm., 

 so that 1 mm. on the record corresponds to 0*15 T. 



The gradual creeping of the luminous spot is also observed in 

 this case. Hence the same remark applies as to the accuracy of 

 tlie records. 



Fig. 3, A. 



1—4 — h-f- 



5 loom 



H 1— ^H 1 1 1 



n 



CM 



7=î 



Ü 



ma 



(2 



CE 



lï 



m 



