Correspondence — Strata of Mendip Hills. 



567 



It appeared that along the Luckington and Yobster side of the 

 Mendip Hills, the abnormal inverted or apparently discordant junc- 

 tion of the disturbed Coal-measures at their foot, with the limestones 

 of the range, is traceable for about five miles, two of the three out- 

 lying, and, as I could gather, inverted patches of limestone being 

 situated at distances from the junction of somewhat more than a 

 mile and a little less than three-quarters of a mile respectively. 

 The hypothesis that these outliers were portions of underlying lime- 

 stones brought to the surface by faulting, having been set aside by 

 the fact of the outliers' non-continuance in depth, the author favoured 

 the idea of inversion instead. 



That such am amount of inversion as Mr. M'Murtrie suggested is 

 by no means an impossibility I can well conceive, having seen, in 

 the case of a narrow and much compressed anticlinal ridge, on the 

 confines of Afghanistan, a strong band of hard limestone with a 

 great thickness of overlying sandstones and clays, so completely in- 

 verted that this limestone band could be traced curving upwards and 

 outwards from its place on the flank of the anticlinal, until found to 

 rest for nearly half a mile with completely inverted horizontality 

 upon the likewise inverted sandstones and clays, the whole of the 

 rocks being well exposed, and the inverted limestone capping spurs 

 from the anticlinal range, thus : — 





A. Limestones. B. Sandstones and Clays. c. d. Inversions of varying -width 

 up to above \ mile or nearer half a mile English. 



In the country where this occurs nearly all the boundaries of 

 numerous parallel anticlinal ridges are lines of abnormal vertical or 

 inverted junction of the two groups represented above, these ridges 

 having lengths sometimes exceeding fifty miles, and the only places 

 where the rocks are found in their, so to speak, natural or normal 

 order being where the beds fold over the terminations of the anti- 

 clinal axes. 



Such lines of abnormal junction or inversion are also known to 

 exist for greatly longer continuous distances on the flanks of the 

 Himalayas and the Alps. 1 



But admitting inversion in the case of the Luckington and Vobster 



1 See paper on the Alps and Himalayas, by H. B. Medlicott, Esq., Quart. Journ. 

 Geol. Soc. 1868, vol. xxiv. p. 34, and a paper On Some Points in the Stratigraphical 

 Structure of the Panjab, op. eit. 1874, vol. xxx. p. 61. 



