Dr. C. Davison — The Penzance Earthquake. 487 



its presence has already been anticipated.^ There appears to be 

 a very close resemblance in the characters of this zone atBeddington 

 and those of the corresponding zone in the coast sections near 

 Margate, so well described by Dr. Rowe.- With hardly an exception 

 the same characteristic fossils enumerated by Dr. Rowe and a definite 

 sponge bed are present in both. 



Hitherto the highest Chalk in this part of the county has been 

 considered to belong to the zone of Micraster cor-anguinum, and in 

 the third volume on the Cretaceous Rocks of Britain, lately issued, 

 it is stated (p. 179) that in the eastern part of Surrey the zone 

 of Marsiipiles is either concealed beneath the Eocene or more 

 probably was removed from the summit of a low anticlinal flexure, 

 formed and eroded before the deposition of the Tertiaries.^ Professor 

 Barrels included the Purley beds of Caleb Evans in the zone of 

 Ilarsupites, but no specimens of this crinoid have ever been found 

 in them, and it is probable that there is a considerable thickness 

 of Chalk between them and the Chalk of the Beddington ridge in 

 which this fossil abounds. 



IV. — The Penzance Earthquake of March 3, 1904. 



By Chakles Davisox, Sc.D., F.G.S. 



DURING the last fifteen years slight earthquakes have occurred 

 in Cornwall on eight occasions, the dates being Oct. 7, 1889 ; 

 Mar. 26, 1891 ; May 16 and 17, 1892; Jan. 26, 1896; and Mar. 29, 

 April 1 and 2, 1898. The Pembroke earthquakes of Aug. 18, 1892 

 (0.24 and 1.40 a.m.), and Nov. 2, 1893, and the Hereford earthquake 

 of Dec. 17, 1896, were also felt in the county. Local earth-shakes, 

 probably connected with mining, operations, occur occasionally, as 

 on June 4 and 10, 1902. Under the same heading should perhaps 

 be included the shock of Aug. 27, 1895, near Blisland, which I was 

 led to class as seismic on account of its very elongated, though 

 small, disturbed area.* 



The Penzance earthquake of March 3, 1904, occurred at about 

 1.5 p.m.^ Isoseismal lines of intensities 5 and 4 are represented on 

 the accompanying map, and these show at a glance that the 

 epicentre was submarine. Little more than half of each curve 

 traverses the land, and the form of the remaining portions over the 

 sea-area can only be conjectured from their trend before leaving the 

 land. If, however, the isoseismal 5 be completed, the centre of 

 the curve must be close to a point (indicated by a cross on the map) 

 in lat. 50° 4-2' N., long. 5° 27-6' W., or about 3i miles south of 

 Marazion. This curve is 13^ miles long, and probably 10 miles 



1 Journ. Roy. Micros. Soc, 1904, p. 7. 



2 Proc. Geol. Assoc, vol. xvi (1900), pp. 294-301. 



■^ Terrain cretace superieiu- de I'Angleterre et de I'lrlande, 1876, p. 139. 



* Geol. Mag., Dec. IV, Vol. VII (1900), pp. 164-5. 



5 The foUomng accoixnt is based ou 76 records from 46 places, and 13 negative 

 -records from 12 places. The cost of the inquiry was defrayed from a grant received 

 from the Government Research Fund. 



