Dr. C. Davison — Earth-shakes in Mining Districts. 221 



Magazine.^ It disturbed a small, but elongated area, 6 miles long, 

 nearly 2 miles wide, and containing 9 square miles. Its centre is 

 half a mile north of Blisland, and the direction of its longer axis 

 E. 5° N. and W. 5° S. The shook was merely a slight tremor, of 

 intensity 4, The sound was heard by all the observers, and was 

 compared to passing trains, etc., in 33 per cent, of the records, to 

 thunder in 47, and to explosions in 20, per cent. The beginning 

 and end of the sound coincided either quite, or very nearly, with the^ 

 beginning and end of the shock. No faults are traced on the 

 Geological Survey map in the neighbourhood of the disturbed area ; 

 but, close to the centre and southern boundary of the area, are several 

 series of elvan dykes which run almost parallel to the longer axis of 

 the disturbed area. 



Camborne Eakth-Shake : June 4, 1902. 



Time of occurrence, 10.30 p.m. ; intensity, 5 ; epicentre, in lat. 50° 13"4' JN"., 

 long. 5° 16'6' W. ; number of records, 22, from 12 places, and 30 negative records 

 from 22 places. 



The area affected by this earth-shake is shown in Fig. 1. The 

 boundary, as drawn, is elliptical in form, 4J miles long, 3 miles 

 wide, and about 10 square miles in area ; the centre being about 

 one mile north-east of the centre of Camborne. It is possible,. 



uth. 



C CLTaho 



Scale ofl^vle^ 



Fig. 1. — Area of the Camborne Earth-shake. 



however, that the boundary should extend a short distance, perhaps 

 as much as half a mile, farther to the west, for there are no negative 

 records from the district immediately to the west of Camborne. The 

 direction of the longer axis is N. 24° W. and S. 24° E. 



' Geol. Mag., Dec. IV, Vol. VII, 1900, pp. 164-166. 



