THE ISOSEISTS. 323 



The accompanying sounds were generally heard before and during 

 the shock and were of the nature of rushing wind or a railway train in 

 motion. Many agree that the shocks died away gradually as they had 

 begun. 



It is clear from the above that either a continuous series of vibra- 

 „ . tions with distinct maxima and minima, or a 



Conclusion. 



preliminary set of milder, followed by 2 or 3 separate 

 sets of stronger vibrations which died away, represent the case for this 

 area. The variations recorded in detail may be either subjective, or 

 have resulted from the diverse surface conditions. 



A few overturned objects noted by Mr. Simpson give us certain in- 

 formation regarding the wave elements at this place. 



Overturned objects. m -, r _. _. 



Iney are as follows : — In Dehra Dun cantonment 

 3 chimneys of the Imperial Cadet Corps new quarters, measuring 3 feet 

 by 3 feet by 10 feet were not overturned though cracked at the base. 



From West's formula f=g- already used (see p. 35) the acceleration 



y 



of the wave particle cannot have been as great as 9 feet per second. 

 But at Raj pur (a short distance away) one of two gate pillars, 22 inches 

 by 22 inches by 8 feet was overturned. Using the above .formula again 

 we get /=7 feet per second per second, and as one was overturned and 

 the other not, it is likely that the value 7 is about correct. In millime- 

 tres this gives 2,100 which according to Omori, is equivalent to Rossi 

 Forel scale IX. 



At Landour in No. 7 Barracks 20 chimneys 20 inches square by 7 feet 

 high were fractured at the base and one was leaning. This gives /=less 

 than 11 feet per second. At Prospect Point a looking-glass at a height 

 of 4 feet 6 inches on a wall was projected 3 feet 6 inches horizontally, 

 which gives v = 6J feet per second as the horizontal velocity with which 

 it left the wall. 



ISOSEISTS NOS. VI- VII, IV-V AND II-III. 



The area circumscribed within the two grouped isoseists" VI -VII and 



Only shown on those of all that follow are only shown on the west , 



south and east of the epicentral tracts, inasmuch as 



y2 



