THE POSITION AND EXTENT OF THE SEISMIC VERTICAL. 63 



importance cannot be attached to any deductions drawn from this building-, 

 which I have noticed here chiefly because of its being- a curious instance 

 of how misleading what is apparently the clearest evidence may be. 



From Sylhet I have drawings of cracks in the church tower, which 

 give a direction of wave- path between N. 26° E. and N. 35° E., the true 

 direction being probably N. 30° E. though the rocking of the tower 

 might produce a difference between the true and the apparent direction 

 of the emergence. 



At Yeddo some chimneys were overthrown in a direction N. 30° 

 E., and though their shape may to a slight degree have modified the 

 direction of their fall, it could not introduce any very grave error. The 

 cracks in the native hospital seem to give a much more easterly direc- 

 tion, as much as N. 60° E., but fissures are a much less trustworthy 

 source of information than the overthrow of simple bodies. 



At Silchar the direction as given by different bodies varies from 

 N. 12° 30' E. to N. 12° W. ; the latter is that given by the verandah 

 pillars of the native hospital, and is very probably modified by the effects 

 of the heavy thatched roof ; but at the same time it must be borne in 

 mind that the same structure of the ground which gives rise to the 

 formation of earth fissures will also to a certain extent modify the 

 direction of the wave-path in the neighbourhood of the river. 



Proceeding to the actual determination of the position of the seismic 

 vertical, the first step will be to tabulate the direction of wave-path as 

 observed at the various stations. 



N. 12° 30' E. 

 N. 3° 20' E. 

 N. 6° W. 



to N. 10° W. 



N. 12° W. 



N. 26° E. 



N. 35° E. 



Mean N. 30° E. 



( 63 ) 





Class I, 



Silchar — 





Mr. Stewart's tomb 



... 



Mr. Hunter's tomb 



... 



Infantry hospital 



... 



Church tower 



... 



Sylhet— 





Church tower 



••• 



