300 MIDDLEMISS : KANGRA EARTHQUAKE. 



time out, and he therefore had to admit the Dehra time inexpli- 

 cable. 1 



On the other hand the rates deduced from the times of arrival of 

 the large movement in the seismographic records at 

 Calcutta, Bombay and Kodaikanal are as we have 

 already seen far more in agreement among themselves, the extreme 

 difference of rate being only about -j* mile per second instead of nearly 

 $ mile per second. It seems, therefore, more logical to accept the mean 

 of them, namely, 1*92 miles per second, as being the best rate obtainable. 

 Whether the co-seismal lines (curves of equal time), especially near the 

 epicentre, are irregular or not in their courses round the central region 

 cannot be actually known : the number of absolutely accurate time 

 observations have been shown to be too few for such fine distinctions. 

 But it is probable that such irregularity is not great, and that the curves, 

 therefore, approximate to regular concentric circles round the epicentre. 

 It has certainly been shown that any argument against this conclusion 

 based on the markedly irregular times as recorded locally in up-country 

 stations, can have no weight because of the untrustworthy character of 

 the latter. 



II.— THE ISOSEISTS : INTENSITY AND CHARACTER OF 

 THE SHOCK. 



Following on the time and speed of the shock, the next aspect 



of the earthquake that will be considered here is 



Varying surface j£ g areas f varying surface intensity. Of these 



intensity. . 



it may be said that, whilst a systematic delineation 

 of them on the map is one of the main functions of a survey, a correct 

 appreciation of what they imply will perhaps lead us nearer to a satis- 

 factory understanding of the earthquake than may be obtained along 

 any other lines of enquiry. 



This is so because the intensity of an earthquake shock is a very 

 real .and effective quality, and in studying its effects we are led 



1 Demi-official letter to me, dated 29th September 1905. 



