TIME OF EARTHQUAKE : RATE OF PROPAGATION. 281 



PART II 



Chapter V. 



I.— TIME OF EARTHQUAKE : RATE OF 

 PROPAGATION. 



The determination of the exact time of the earthquake, as experi- 

 enced at the epicentre and at other places scattered 

 Difficulties. r . . 



over the felt area, i.e., the construction of co-seismal 



lines, has been beset with all the difficulties usually encountered in such 

 enquiries. 1 



The epicentral area itself, principally on account of its distance from 

 Sources of infor- ^e larger cities of Upper India, has supplied no 

 matlon - trustworthy information on this point. For the 



rest, of India, the information at my disposal has been derived from 

 two main sources, namely, (1) the earthquake forms, which express the 

 current general opinion, and (2) automatically registering instruments. 



It may here be mentioned that the time-standard use din this discus- 

 sion will be that of Madras, which is 5h. 20m. 59*2s. 

 east of Greenwich. At the date of the earthquake it 

 was the standard in use for railway and telegraph traffic, 2 and to it many 

 of the contributors to the forms referred their accounts of the shock. 

 Such was not, however, invariably the case, and a large number of 

 recorded times are local, or are unaccompanied by any reference to the 

 standard used. 



Over the greater part of provincial India the times of the recorded 



Great irregularity shock, even when referred to some standard, are so 



of recorded times. irregular (as will have been seen frem the summary 



of the earthquake forms) that at a first glance nearly all must be deemed 



1 See R. D. Oldham, Mem. O. S. of I., Volume XXIX, page 52^tmeq. 

 2 After July 1905 it was changed to so-called " Standard Indian Time " which is 

 5A. 30m. east of Greenwich. 



