DETEEMINATION OF EARTHQUAKE ORIGINS. 203 



The position from which the shock originated appears 

 therefore to have occurred very near to a place lying in 

 Long, r 15' W. and Lat. 21° 22' S. 



Fig. 31. 



23 



The actual operations which were gone through in 

 making the accompanying map were as follows. First, 

 the places with which we had to deal were represented on 

 a map in orthographical projection, the centre of pro- 



