Dr. C. Davison — Earth-shakes in Mining Districts. 219 



are marked with parallel striations and grooves, as if portions of clay 

 had moved over each other. It is difficult to resist the conclusion' 

 that the clay has not been deposited in the fissures by water, but has 

 been introduced by pressure when in a partially consolidated con- 

 dition. An ice-sheet pushing forward clayey morainic material 

 might have conceivably produced the efi'ect, but I hesitate to pro- 

 nounce a definite opinion on such a limited section, 



W. C. Lucy remarks ^ that clay containing quartz pebbles is 

 scattered "nearly all over the Cotteswold range," sometimes up to 

 a thickness of 3 feet, and often filling pockets in the oolite. 



The boulders and some of the gravels and clays found in the 

 Evenlode valley between Shipton and Moreton tend to confirm the 

 evidence of the Tangley section by suggesting the agency of ice, at 

 least as far south as Tangley, at lower levels. 



Since writing the above, I have referred to Mr. David's paper ^ 

 " On the Evidence of Glacial Action in South Brecknockshire and 

 East Glamorganshire." He describes the shattering of rocks by 

 ice-action, and states that " boulder-clay has been forced into the 

 shattered strata to a depth of 12 feet at least." 



I trust that these notes will attract to the district the attention of 

 those who have made a special study of glacial phenomena. 



VI. — On Earth-Shakes in Mining Districts. 

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



THE term ' earth-shake ' has been applied to local disturbances 

 of the earth which owe their origin, either in part or wholly, 

 to artificial causes. Typical examples of earth-shakes are those 

 which are occasionally felt at Sunderland and other places on the 

 magnesian limestone of the Durham coast, and which have been 

 attributed by Prof. Lebour to rock-falls in underground channels, 

 enlarged no doubt by pumping in connection with the local water- 

 suppl3^^ Other examples are the shocks frequently felt in mining 

 districts, and either caused or precipitated by mining operations. 

 Earth-shakes of this class have occurred in the Ehondda Valley in 

 Glamorganshire on June 22, 1889, April 11 and May 2, 1894, and 

 October 16, 1896 ; in the neighbourhood of Camborne on June 4 and 

 10, 1902; at Pendleton, near Manchester, on February 27, 1899, 

 and April 7, 1900; at Kilsyth in Stirlingshire on February 16, 1898, 

 and in various other districts. 



The last group of earth-shakes are found to possess certain features 

 in common : — 



(1) The disturbed area is small, from one to five miles in diameter ; 

 and, as a rule, the boundary is approximately circular in form. 



^ Ibid., vol, vii, pp. 50-61. 



2 Quart. Journ. Geol. See, 1883, p. 39. 



^ "On the Breccia-gashes of the Dui-ham Coast and some Eecent Earth-shakes 

 at Sunderland," North of England lust, of Min. Eng. Trans., vol, xxxiii, 1884, 

 pp. 165-174; "On some Eecent Earthquakes on the Durham Coast and their 

 probable Cause," Geol. Mag., Vol. II, 1885, pp. 513-515. 



