290 MIDDLEMISS : KANGRA EARTHQUAKE. 



With the above exception, it becomes evident that the earthquake- 



Regnlar radial form tim °- records , though untrustworthy in detail 

 progression of the (especially in the more outlying towns and districts) 



° lk ' when considered as a whole, and when special 



credence is given to important centres where many substantiated obser- 

 vations agree with each other, contain nothing to discredit the regular 

 radial progression outwards of the shock from the epicentral region 

 towards the circumference of the felt area. And these finally are in 

 agreement with the few specially trustworthy automatically recorded 

 times provided by the seismographs (see p. 291). 



(2) Special Instrumental Records. 

 These are derived primarily from the seismographs of the Milne 

 Seismo 1 d ^ e * n ^ e meteorological observatories of Bombay 

 maguetograph re- (Colaba), Kodaikanal in the Palni Hills and Calcutta 

 oords * (Alipur), and secondarily from magnetographs in the 



observatcries at Bombay (Colaba), Dehra Dun, Barrackpore and 

 Toungoo. 



If recent criticisms of seismographic records is to be trusted (as to 

 which specialists in this branch of science can alone speak with parti- 

 cular knowledge), the Milne seismograph trace, which is very small and 

 often blurred 1 cannot be trusted to show all those minute sub-divisions 

 of regularly recurring period and amplitude which the larger forms 

 working with a large natural period of swing, register b}' means of a 

 needle point on smoked paper, and which give an open or large time- 

 scale diagram. 2 



The so-called preliminary tremors as seen in long-distance seismo- 

 grams written by th,e Milne instrument, are, however, fairly well 

 differentiated from the large movement which follows. The splitting 

 of the preliminary tremors into two groups, first and second, is also 



1 It depends on a reflected spot of light impinging on sensitised paper, and this it 

 appears may not always bo bright and sharp. 



2 See " Publications of the Earthquake Investigation Committee in Foreigu 

 Languages " No. 24, p. 26, also " La Science Seismologique," by Le Comto de Mon- 

 tessus de Ballore, p. 40. 



