C. Davison — The Exmoor Earthquake. 5-33 



have been described by Professor Bonney and the Rev. J. F. Blake. 

 The mass which has been quarried is a lenticle of which about 

 175 x 75 ft. are clearly exposed. Its truly sedimentary character 

 has been described by Professor Bonney. Its greatest length is 

 probably not less than 700 ft. ; and there are in addition three 

 smaller lenticles a little further east, whose longer axes are from 

 100 to 200 ft. 



These great masses of quartzite can only have been portions of 

 a once continuous bed or beds, 1 from which they have been torn out 

 and carried away, as have been the innumerable masses of the 

 Cambrian quartzites in the North-West Highlands, of somewhat 

 similar form, which are piled up on the minor thrust-planes of that 

 region. Judging also from what we see in the Isle of Man, these 

 beds were probably the more massive members of an alternating- 

 series of grits and shales, the thin and flaggy bauds of grit having 

 furnished the material of the smaller lenticles. 



The complexity of structure consequent upon such movements is 

 admirably illustrated by the two regions just quoted; especially 

 where, as in the Isle of Man, movement has recurred at a later 

 period, superinducing new structures, and to some extent effacing 

 the records of the earlier episodes. 



To what extent this may have happened in Anglesey it is at present 

 impossible to say; but it seems probable that the movements which 

 have affected the schistose rocks of that island were of a very high 

 degree of intensity ; and the structural relations of the rock-masses 

 may therefore be expected to be in a corresponding degree complex 

 and deceptive. 



V. — On the Exmoor Earthquake of January 23, 1894, and 

 on its Relation to the Northern Boundary Fault of the 

 Morte Slates. 



By Charles Davison, Sc.D., F.G.S. ; 

 King Edward's High School, Birmingham. 



A SLIGHT earthquake of intensity iv, according to the Rossi- 

 Forel scale, was felt in and near Exmoor at about 9 a.m. 

 on January 23, 1894. Its interest lies, not so much in the seismic 

 phenomena presented by it, as in its connection with the northern 

 boundary fault of the Morte Slates. 



In studying this earthquake, I have been able to avail myself of 

 56 records from 48 different places, as well as of 13 other records 

 from 13 places where, so far as known, it was not perceived. The 

 names of the observers and others to whom I am indebted lor 



1 The appearances of irregular or intrusive junction figured hy Professor Blake 

 are deceptive, being due to the form of tbe present outcrop. Such discordance as 

 exists is not more than that which sometimes occurs at the margins of smaller 

 lenticles, and may be expected in any highly disturbed region. The relations of this 

 muss of quartzite' do not, 1 think, necessitate our referring its origin to causes acting 

 locally or sporadically. 



