On the Leicester Earthquake of August 4, 1893. 87 



that they are approximately so, and that their accordance in all 

 general respects is such that they support each other and warrant 

 the conclusions drawn from them. 



I have again to acknowledge my deep indebtedness to the late 

 lamented Professor Hertz for the very able advice he at all times so 

 readily gave me while I was engaged on the above work under him 

 at the University of Bonn during the session 1892 93. 



;< On the Leicester Earthquake of August 4, 1893." By CHARLES 

 DAVISON, M.A., F.G.S., Mathematical Master at King 

 Edward's High School, Birmingham. Communicated by 

 Professor J. H. PoYNTiNG, F.R.S. Received February 28, 

 Read May 10, 1894. 



On August 4, 1893, at 6.41 P.M. (G.M.T.), an earthquake shock was 

 felt throughout the whole of Leicestershire and Rutland, and in parts 

 also of the adjoining counties of Lincoln, Nottingham, Derby, Staf- 

 ford, Warwick and Northampton. The disturbed area, therefore, 

 lies entirely within the land. It is also one over which villages and 

 country houses are for the most part closely scattered, and it has 

 thus been possible to obtain a large number of careful and detailed 

 accounts. I have received altogether 391 records from 298 places 

 where the earthquake was observed, and 103 others from 97 places 

 where, so far as known, no trace of it was perceived.* 



My inquiries were carried out on the supposition that tectonic 

 earthquakes are, as a rule, mere incidents in the gradual develop- 

 ment of faults, that the shock is caused by the friction which results 

 from one rock-mass slipping slightly but heavily over and against 

 the other, the accompanying sound and tremulous motion being due 

 to the exceedingly small and rapid vibrations which proceed chiefly 

 from the margins of the fault-surface over which the slip takes 

 place. f 



The interpretation of the evidence collected rests on the following 

 principles : 



(1.) The direction of the fault is parallel, or nearly so, to that of 

 the longer axis of the disturbed area, or of an isoseismal line. 

 (2.) The intensity of the shock increases in both directions from the 

 fault-line until a maximum is reached, and then decreases, so that 



* The expenses of the inquiry were defrayed by part of a grant which I had the 

 honour to receive from the Government Eesearch Fund. I regret that I am unable 

 to acknowledge in detail the valuable and courteous assistance rendered by my 

 numerous correspondents. 



f " On the Nature and Origin of Earthquake-sounds," ' Geol. Mag.,' vol. 9, 1892, 

 pp. 206218. 



VOL. LVII. H 



