242 THE CAERNARVON EARTHQUAKE OF 1903. [Aug. I904, 



neighbourhood. One of them occurred between five and six hours 

 before the great displacement, the next four within little more than 

 an hour afterwards, and the sixth two days later. The last two, if 

 they were connected with the Aber-Dinlle Fault, originated in foci 

 quite close to the surface. 



If we may assume the disturbances of the second class to have 

 been of seismic origin, then small sudden creeps, rather than slips, 

 affected other portions of the fault, one of them occurring at the 

 south-western end of the principal focus, two at the north-eastern 

 end, and five in the central region. If, however, the originating 

 fault were submarine, the weakness of the tremors resulting from 

 the central and southern slips may be partly due to the greater 

 distance of the foci. 



Denoting slips at the north-eastern end, centre, and south-western 

 end, by the letters n, c, and s, and using capital letters for those 

 perceived by several or many observers, the distribution of the 

 different slips in time may be represented as follows : — 



June 19th 21st 22nd 23rd 



N, principal focus, s, X, X. X. //, c, N, n, c, X, c, c, c. 



Thus, as in the Japanese earthquake of 18U1 and the Inverness 

 earthquake of 1901, seismic action towards the close of the series 

 was withdrawn from the lateral margins of the principal focus and 

 was ultimately confined to its central region. 



EXPLANATION OF PLATE XX. 



Map of the area affected by the principal Caernarvon earthquake of June 19th, 

 19(Jo. on the scale of 30 miles to the inch. 



Discussion. 



The President observed that the Author's first paper read before 

 the Society discussed the movements of scree-material. Subse- 

 quently the Society had welcomed several papers on earthquakes 

 from his pen : and it was interesting to find that these very different 

 subjects were both dealt with in the present paper. The Aber- 

 Dinlle Fault, so far as he recollected, brought rocks of very different 

 degrees of hardness into apposition along some parts of its course. 



