Analysis of Microseismograms. 



465 



The time- scale was such that 2'S cm. corresponds to 1 minute ; 

 hence 1 mm. corresponds to 2*14 seconds. The ordinate* 

 are tabulated in units of 0*1 mm. The breadth of the trace 

 being about 0'3 mm., it was not possible to read the values 

 accurately in the neighbourhood of acute intersections of the 

 curve with the ordinate lines, and so our readings may be 

 0'3 mm. or more in error. 



4. The main steps in the determination o£ the periods of 

 the oscillations prevailing during ] minute are set out in 

 Table I. It was found by trial that all the equations (4 / ) 

 could be well satisfied by the assumption of only two periods. 



Table I. 



i (1) 



C- ? ) 



(3) 



(4) 



(5) 



(6) 



(7) 



(8) 



t. 



y- 



a. 



Ea. 



E2«. 



E. 



y'- 



E/. 



' 00 



31 



4-21 









31 





1 



52 



- 7 



+ 4 







52 





2 



45 



-17 



+ 25 



-38 



- 1 



45 



-4 



3 



28 



+32 



-42 



+ 61 



+ 4 



29 



-1 



4 



60 



-25 



+ 36 



-48 



+ 5 



60 



+ 1 



5 



35 



+ 4 



- 6 



+ 9 



- 1 



33 



+3, 



6 



39 



+19 



-27 



+27 



-12 



38 



-3 



7 



58 



-31 



+33 



-38 



- 2 



59 



+ 2 



8 



27 



+ 14 



-11 



+ 13 



+ 6 



29 



-1 



9 



41 



+ 20 



-.20 



+24 



+ 3 



42 



+ 1 



10 



61 



-34 



+35 



-37 







59 



+ 1 



1 



27 



+ 15 



-17 



+ 21 



+ 1 



28 



— 2 



2 



42 



+ 17 



-14 



+ 10 







43 



+3 



3 



59 



-29 



+27 



-20 



+ 5 



59 



-1 



4 



30 



+ 10 



- 6 



- 3 



- 4 



29 







5 



40 



+ 23 



-30 



+41 



+ 1 



40 



+ 1 



6 



63 



-40 



+47 



-50 



+ 7 



65 



+ 1 



7 



23 



+24 



-20 



+ 21 



+ o 



22 



+ 1 



8 



47 



+ 20 



-26 



+ 29 



- 6 



4n 



-4 



9 



67 



-50 



+49 



-54 



- 6 



65 



+ 1 



20 



17 



+29 



-28 



+23 



- 4 



18 



-3 



1 



46 



+22 



-26 



+41 



+ 9 



47 



+ 3 



2 



68 • 



-55 



+69 



-88 



i- 2 



67 



-1 



3 



13 



+47 



-62 



+ 81 



- 3 



11 



+ 1 



4 



60 



— 7 



+12 



-27 



- 8, 



59 



+ 2 



5 



53 



-35 



+ 35 



-43 



- 8 



54 



-1 



6 



18 



+42 



-55 



+ 73 



- 1 



20 



-3 



7 



60 



-20 



+38 



-59 



+ 5 



61 







8 



40 



- 4 



- 4 







40 





9 



36 



+ 16 









36 





3-0 



52 











52 





Column (1) gives the abscissa?, the common difference 

 being 1 mm. or 2' 14 seconds. Column (2) gives the corre- 

 sponding ordinates y. Column (3) contains the differences 

 (a), and columns (4) and (5) the values of Ea and Wa. 



Phil. Mag. S. 6. Vol. 43. No. 255. March 1922. 2 H 



