OP THE DEPTH OF THE SEISMIC FOCUS. 67 



At Shillong the only building- of which I have any drawings or 

 notes is the magazine, which, like that at Yeddo, is a small rectangular 

 building with a low-crowned roof and a sort of porch or ante-room 

 attached, the buildings were unsuited for seismometry, and give no indi- 

 cations of any value. 



At Teriaghat, a small village at the foot of the hills on the way 

 up to Cherrapoonjee, the dak bungalow was cracked ; it is a small four- 

 roomed building of rubble masonry, and the cracks show an angle of 

 emergence of about 30°, which would give a depth of focus of 42 "7 

 miles. 



At Sylhet the church tower was cracked severely, and from the 

 cracks the angle of emergence is deduced as 38°, which would give 

 a depth of focus of 68 miles ; this, however, is manifestly far too great, 

 the obliquity of the cracks having been increased by the form of the 

 tower, which would swing as an inverted pendulum and so alter the 

 direction of the cracks considerably. 



From Asalu and Kochela sketches of cracked and overthrown build- 

 ings have been communicated by Major Godwin-Austen. That from 

 Asalu is of a guard-house severely cracked, but the cracks are 

 evidently chiefly due to, or certainly very much modified by, the push 

 of the heavy thatched roof of the building ; while at Kochela the build- 

 ing, a disused sawmill, was almost completely overthrown, and the small 

 portions left standing do not give any indication of the angle of 

 emergence, though they seem to show that it was small. 



Before proceeding to the discussion of the data at the remaining 

 station, Silchar, it will be advisable to sum up what has been said so far. 

 As will have been noticed, there are but two stations from which observ- 

 ations of any value have been obtained, but as the results obtained at 

 these two stations confirm each other, their accuracy is certainly probable, 

 though a greater number of observations would have been desirable. 

 The altitudes of these two stations above the level of the sea I have not 

 been able to obtain with accuracy, but they are Yeddo and Teriaghat, 



( 67 ) 



