174 Dr. C. Davison — British Earthquakes, 1893-99. 



JSarth-ShaJces in Mining Districts. 



Under this heading are included several shocks which, it is 

 possible, may be of artificial origin, and, if so, ought to be regarded 

 as spurious earthquakes. Formerly, I should have so considered 

 them, but another explanation has recently occurred to me ; and, if 

 it be correct, it will be evident that they are partly artificial and 

 partly natural in their origin. It thei'efore seems desirable to 

 consider them separately. 



Bhondda Valley. — The shocks referred to are frequently felt in 

 the Khondda Valley in Glamorganshire. One occurred on June 22, 

 1889,^ and there have been at least three others within the period 

 embraced by this paper, on April 11 and May 2, 1891, and 

 October 16, 1896. Judging, however, from the expressions used 

 by several of my correspondents, it is probable that these are the 

 dates of only the more important movements. 



The shock which occurred on April 11, 1894, at about 2.40 a.m., 

 is described as one of the severest recently felt in the district ; and 

 making every allowance for exaggeration in the accounts,- there can 

 be no doubt as to its intensity. At one or two places it cannot have 

 been less than 5, that is to say, it must have been the strongest 

 shock considered in this paper. Two loud reports, like those of 

 cannon, were heard in quick succession, and at the same moments, 

 or immediately afterwards, sharp vibrations were felt. They seem to 

 have been almost equally distinct underground, for in several pits 

 the miners rushed to the bottom of the shaft, thinking that a violent 

 explosion had occurred. Notwithstanding the strength of the shock, 

 however, the disturbed area was very small. So far as I have been 

 able to ascertain, its boundary is almost exactly circular, about 5 

 miles in diameter, and with its centre ^ mile east of Forth. 



The second shock took place about noon on May 2, 1894, and 

 seems to have originated in the same district. At the surface it 

 must have been much slighter than the preceding shock ; but 

 underground it produced similar effects, miners in the same pits 

 again leaving their work to escape from what appeared to be an 

 explosion. 



On October 16, 1896, the district affected was a very small one, 

 not more than a mile in diameter, including Ystrad - y - fodwg, 

 Pentre, Ton, and Gelli. At about 11 p.m. a loud boom, like the 

 muffled sound of blasting, was heard, followed by a brief shaking. 

 The sensation is described by most as like that experienced in 

 a room immediately beneath another in which a heavy article of 

 furniture had fallen. Miners at work rushed from one pit to 



1 Geol. Mag., Vol. VIII, 1891, p. 371. 



2 Houses are said to have rocked like cradles, etc. " Sir," said Dr. Johnson, 

 when Boswell told him of the earthquake of Sept. 14, 1777, " it ■will be much 

 exaggerated in public talk: for, in the first place, the common people do not 

 accurately adapt their words to their thought : they do not mean to lie : but, taking 

 no pains to be exact, they give you very false accounts. A great part of their 

 language is proverbial. If anything rocks at all, they say it rocks like a cradle : 

 and in this way they go on." 



