TIME OF EARTHQUAKE : RATE OF PROPAGATION. 



291 



believed by many to be sufficiently recognisable. However that may 

 be, the beginning of the large movement is the only definite point that 

 can be reasonably correlated with the sensible earthquake wave or shock 

 as felt in its progression from place to place over the surface of the 

 affected area. 



The times of commencement of the large movement in the Indian 

 Time of com- seisinographic records of the Kangra earthquake 



meneement of large , 



movement on seis- are as follows : — 

 mograms. 



H. M. S. 



Bombay (Colaba) 1 .. 6 — 17 — 29 mean of two measurements 



Kodaikanal .. 6—21—48 



Calcutta (Alipur) . . 6—17—5-2 



and if for the present we take 6h. 9m. as a probable time for the 



beginning of the shock in the centre of the larger and more important 



Kangra epicentre, we have — 





Distance in miles from 

 centre of large epicentre. 



Seconds dur- 

 ing transit. 



Deduced rate in miles 

 per second. 



Bombay (Colaba) 

 Kodaikanal 

 Calcutta (Alipur) 



950 



1,497 



950 



509 

 768 



485 



1-87 

 1'95 

 1-96 





Mean.. 1*92 



' ... . 



Since Bombay and Calcutta are the same distance from the epi- 

 centre, we can by taking a mean of the two times of arrival at those 

 places and subtracting it from the time of arrival at Kodaikanal, obtain 

 a fresh rate of transmission which is independent of the more or less 

 guessed time at the epicentre. Thus 547 miles in 271 seconds gives a 

 rate of 2 02. Or working out the two rates independently according 

 to the time values at each of the places Bombay and Calcutta, we get 



8 of 211 and 1*93 respectively. The former rate, if continuously 



l The values given here differ slightly from those giveu in my preliminary report 

 being the final determinations as printed in the Monthly Weather fteview for April 

 1905. 



