S. E. Hip])isley — Somersetshire Coal-measures. 349 



grounds for suggesting, tliat the strata at these two places may really 

 be identical. 



This would lead to a further suggestion that the veins at Ludlows 

 above the lap, as well as the Parrington veins, may possibly be of 

 the lower series, and that the detached masses of Carboniferous 

 Limestone at Luckington and Vobster may be, comparatively speak- 

 ing, in their true places as regards the suggested lower series veins 

 at Eadstock, as far as measures above the slide are concerned. In 

 short, that the amount of the slide may be far greater than usually 

 considered, and that these masses of limestone, and the lower series 

 above them, may either have been brought down by a simple slide 

 or landslip, from their original position on the Mendips, or that there 

 is an anticlinal between Norton Hill and New Eock. The former 

 hypothesis would involve a distance moved, of, roughly, a mile or 

 more, but instances have occurred, even in the last century, of masses 

 of ground having travelled nearly four miles during landslips. — 

 Lyell's Principles, vol. ii. p. 130. 



It is not suggested that all the Eadstock measures are, as 

 suggested for those at Ludlows above the slide, equivalent to the 

 Parrington Gurney or Old Mills measures, but that the remainder are 

 in reality, as usually supposed and proved, above the red shales, but 

 beneath the Pennant, and so of the upper portion of the lower series. 



It has been remarked that the position of the Pennant gives the 

 key to the understanding of the whole district, and so it undoubtedly 

 would if we could be certain that it really was the true Pennant we 

 had selected as our starting-point ; but as it has already been shown 

 in the Kingswood district, that a Coal-measure sandstone, long con- 

 sidered to be Millstone Grit, was in reality not so, we are by no 

 means certain that sandstones, long considered to be true Pennant, 

 are so in reality, merely on account of the length of time during 

 which they have been so called. 



There are several heavy beds of sandstone which have been sources 

 of confusion as to the true Pennant (confining the term Pennant to 

 that of the Geological Survey, and including its extension down- 

 wards in the Nettlebridge and other districts) ; amongst them is a 

 bed 66 feet thick as sunk through at Old Mills, the base of it being 

 63 feet above the " Cathead " Vein there, which bed of sandstone is 

 suggested as lying between the bottom of the sinkings at Old Grove, 

 Braysdown and Grayfield and the top of the suggested true Parring- 

 ton measures ; possibly giving rise to the belief that Old Grove, etc., 

 were supra-Pennant. This bed of sandstone is also very prominent 

 at Temple Cloud, being somewhat thicker and several times repeated 

 by faults there, and has often been described as true Pennant at that 

 place, apparently principally on the grounds that it has been quarried 

 for building purposes, as its thickness is easily to be measured. 



The other sandstone beds which have done duty for Pennant need 

 not be discussed in this summary ; it is sufficient to remark that, 

 apart from the evidence afforded by organic remains, it is often 

 impossible, from lithological character alone, to be certain whether 

 a specimen is Millstone Grit, Pennant, or one of the other Coal- 



