70 OLDHAM. THE CACIIAR EARTHQUAKE OF 10TH JANUARY 1869. 



(and practically the portion lost would be small), then, in the alteration 

 of the angle of emergence from 20° to 45°, the amount of horizontal 

 velocity lost, or the amount of slips, would be 



940—342=598 

 and the proportion of this to the whole would be 



598: 940 



that is, about two- thirds of the whole velocity ; so that to increase the 

 angle of emergence from 20° to 45°, the whole of the vertical velocity 

 must have been transmitted, but only one- third of the horizontal, or 

 allowing for loss of vertical velocity in transmission, about three-quarters 

 of the horizontal velocity must disappear by slippage. 



This may seen to some rather a wild hypothesis, but I see no other 

 way of explaining the abnormally high angle of emergence at Silchar. 

 There is, however, confirmatory evidence at the station itself; about 

 half a mile to the east of the Police guard stand the church and 

 cutcherry ; both were cracked, and though neither of them give very 

 exact indications of the angle of emergence, yet they show it to have 

 been much lower here than at the Police guard, not more than 30°. 

 Thus at two places only half a mile apart the angle of emergence differs 

 by at least 15°. This difference may be explained by referring to the 

 map, plate A. Remembering that the shock was coming from the 

 north, or nearly so, it will be seen that, after passing under the river, it 

 had to travel twice as far to reach the church, as was necessary to reach 

 the Police guard ; and consequently in the former case the upper clays 

 were able to take up a larger proportion of the horizontal component by 

 which means the angle of emergence was decreased. 



That this slipping of the deeper seated clays under the surface beds 

 took place, is also suggested by the distribution of the earth fissures. As 

 explained in chapter IV, they are caused by the momentum impressed on 

 the clays by the earthquake-wave, and it is there shown that, provided 

 sufficient motion was impressed on the clays, fissures would be formed 

 whether the shock was travelling towards or away from the river. An 

 inspection of the map will show that while almost the whole extent of the 

 ( 70 ) 



