On Rapid Periodic Variations of Terrestrial Magnetism. 



37 



occurrence. Plotting the ratios as ordinates with the periods as 

 abscissa in a diagram, the points representing different trains are 



1-2 

 10 



0-8 

 0-6 

 04 



02 



Fig. 11. 



12 

 1-0 

 OS 

 06 

 0-4 

 0-2 

 



10 20 30 40 50 T 



1-2 

 i-0 

 0-8 

 0-6 

 0-4- 



10 20 3Û vy 50 T 



10 20 30 40 50 T 



)-2 

 10 

 OS 

 0-6 

 0-4 



0-2 

 



IÛ 20 30 40 50 T 



12 

 10 

 0^8 

 06 



0-4 



0-2 



10 20 30 40 50 T 



12 

 10 

 0-8 

 06 



04- 



0-2 

 



(0 20 30 4-0 50 



