Vol. 60.] THE CAEENARVON EARTHQUAKE OF 1903. 233 



17. The Caernarvon Earthquake of June 19th, 1903, and its 

 Accessory Shocks. By Charles Davison, Sc.D., F.G.S. 

 (Head June 22nd, 1904./ 



[Plate XX- Map.] 

 I, Introduction. 



During the nineteenth century, the county of Caernarvon was 

 visited by at least fourteen earthquakes. Seven, if not more, of these 

 disturbances arrived from distant centres, situated near Pembroke, 

 Hereford, etc. ; but three or four were probably of local origin, 

 their epicentres being either within or not far from the boundaries 

 of Caernarvonshire. Ail of these local shocks, however, were of 

 slight intensity ; and, indeed, within the last five centuries, there 

 does not seem to have been a single indigenous earthquake that can 

 be compared either in intensity or in extent of disturbed area with 

 that which, on June 19th, 1903, was felt over nearly the whole of 

 Wales, the North- West of England, the Isle of Man, and several of 

 the eastern counties of Ireland. 



In the investigation of this earthquake, I have, as usual, been 

 assisted by a large number of correspondents, to whom my best 

 thanks are due. In various ways, I have also received timely aid 

 from Mr. Edward Greenly, F.G.S., Mr. J. D. Macdonogh of 

 Bettws-y-Coed, Mr. W. T. Davies of NantUe, and Mr. W. A. Thomas 

 of Llanfair-pwllgwyngyll. For lists of after-shocks, the value of 

 which it would be difficult to overestimate, I am indebted to 

 Mr. F. C. Carey of Bethesda, Mr. E. Davies of Bodfeirig, Mr. W. 

 T. Davies of Nantlle, Mr. TV. Hughes of. Gaerwen, Mr. W. W. Hughes 

 of Penygroes, and Mr. R. B. Jones of Clynnog. 1 



The total number of earthquakes belonging to the recent series 

 may amount to 15 or more, the first occurring on June 19th and 

 the last on June 23rd. Seven of these depend on the evidence of 

 more than one observer, and are distinguished below by letters and 

 detailed descriptions. 'The remainder are recorded on the authority 

 of one person only ; and, although I have been careful to include no 

 disturbance which did not appear to me to be of seismic origin, it 

 is advisable, I think, to follow the usual rule, and to regard their 

 character as earthquakes as not fully established. 



II. Fore-Shock. 

 (t. June 19th, about 4.25 a.m. 



Number of records, 2, from 1 place. 



A rumbling noise like thunder was heard at Griffiths Crossing, 

 near Caernarvon. 



1 The cost of the investigation was defrayed from a grant received from the 

 Government Research Fund. 



Q. J. G. S. No. 239. r 



