222 Dr. C. Davison — Earth-ahakes in Mining Districts. 



The shock consisted of one prominent vibration, like that produced 

 by the fall of a heavy weight, followed by a tremulous motion lasting 

 for one or two seconds. The sound was heard by all the observers. 

 In 15 per cent, of the records it was compared to passing vehicles, 

 etc., in 8 per cent, to thunder, in 31 to loads of stones falling, in 



15 to the fall of a heavy body, in 23 to explosions, and in 8 per cent, 

 to miscellaneous sounds ; three out of every four comparisons being 

 to types of brief duration. In nearly every case the terminal epochs 

 of the sound coincided with those of the shock. 



If the earth-shake were due to fault-slipping, the fault must run 

 from about N. 24° W. to S. 24° E. and pass a short distance, between 

 half a mile and a mile, to the north-east of Camborne. As to the 

 hade of the originating fault there is no evidence furnished by the 

 earth-shake. Of the three faults shown on the map (Fig. 1) the 

 more westerly one closely satisfies the assigned conditions. It is 

 the ' great cross course ' of the Dolcoath Mine, and passes thi-ough 

 a point about f of a mile north-east of Camborne in a direction from 

 N. 33° W. to S. 33° E., heaving the Dolcoath Lode 140 yards to the 

 south. The hade of the fault, as Mr. H. P. Vivian kindly informs 

 me, is practically zero. 



Barnsley Earth-Shake : October 25, 1903. 



Time of occurrence, 11.5 p.m.; intensity, 7; epicentre, in lat. 53° 31-3' N., 

 long. 1° 28'2' "W. ; number of records, 13, from 9 places, and 12 negative records 

 from 10 places. 



As in the two preceding shocks, the disturbed area (Fig. 2) is 

 elliptical in form. It is 5| miles long, 3J miles wide, and contains 



16 square miles. Its centre is almost coincident with the village of 

 Worsborough, and the direction of its longer axis is N. 38° W. and 

 S. 38° E. 



The intensity of the shock was 7 at Worsborough and Hoyland, 

 6 at Worsborough Bridge and Barnsley, and from these places it 

 died away rapidly towards the boundar3^ The shock consisted of 

 a single series of vibrations lasting from 3 to 5 seconds. The sound 

 was also of brief duration, being compared either to the fall of 

 a heavy body or to thunder. In the pit at Worsborough it was 

 mistaken for that of an explosion. 



As will be seen from the map, there are several faults which are 

 parallel, or nearly so, to the longer axis of the disturbed area. The 

 faults are indicated by broken lines, except one, which is in part 

 continuous. This fault hades to the north-east, its direction in the 

 central portion of the disturbed area is N. 41° W. and S. 41° E., and 

 its course at the surface is on the south-west side of the epicentre. 

 It thus satisfies the observed conditions, and satisfies them more 

 closely than any other fault. 



The curved line on the map (Fig, 2) represents the outcrop of 

 the Barnsley Coal-bed within the disturbed area. At the Barrow 

 colliery, which is the nearest to Worsborough, the depth of the 

 bed is about 100 yards. Mr. E. Richardson, the manager of the 

 colliery, kindly informs me that practically the whole of the coal in 



