MOOEE ABXOEMAL SECONDAEY DEPOSITS. 48P) 



ness, has been left standing towards the roadway, and has met the 

 base of the Inferior Oolite ; and there are also two caverns in the 

 Liassic limestone which have not been explored. 



Similar conglomerates are found fringing the Carboniferous Lime- 

 stone towards East Cranmore, in the direction of Shepton llallet. 



Holwell is at the southern end of the Xunney and Whatley combs, 

 where, in this part, the Carboniferous Limestone has its greatest 

 breadth — about half a mile. The ravine continues from Cloford to 

 near Egford Bridge, the Inferior Oolite and Fullers' Earth, which 

 form the tablelands on each side, encroaching upon the limestone, 

 and narrowing its superficial breadth in this direction. At Egford 

 Bridge, although the line of the vaUey can still be traced, the Lime- 

 stones are cut off superficially by a covering of these Oolitic beds. 

 Their south-eastern exposure is about 5 miles in length. 



On looking down upon the hamlet of Holwell, its various- coloured 

 limestones give a veiy picturesque effect ; and I have no doubt that 

 the first conclusion drawn would be that everything there was Car- 

 boniferous Limestone ; but a closer examination would show this to 

 be an error. 



Passing downwards from the quarry previously mentioned, we 

 find, north of the road and parallel with it, a face of limestone-rock 

 30 feet in height by 120 feet in length, which lithologicall}^ has all 

 the aspect of Carboniferous Limestone, but in which may be detected 

 on close examination Sj)wifera Walcottii, spines of Cidarls, and 

 other remains of Liassic age. - Just below we obtain a key to the 

 solution of the difficulties attending the interpretation of the section, 

 which the facts just mentioned might otherwise have afforded. 



2. Holwell Carhoniferous Limestone and Liassic Dykes. — A road- 

 way leads into the western face of two quarry-sections, extend- 

 ing for a length of 428 feet, all of which, again, would at first 

 sight readily pass for Carboniferous Limestone. On looking at the 

 general contour of the fii^st quarry, which has a length of about 

 230 feet, it may be noticed that the quarrymen do not work it re- 

 gularly, but rather follow certain blocks or vertical courses of stone 

 into the hill, leaving irregular projecting vertical abutments, which 

 are not touched until they are found to be in the way ; and the 

 reason they assign for this is, that the limestone is of different quali- 

 ties, and their object is to extract the best. The ragged-looking 

 dykes thus left projecting from the face of the quarry may be traced 

 to the top, which is here without any capping of Secondary rock. 

 In most instances they thicken as they pass down, and one which 

 may be from 10 to 15 feet in breadth 30 feet below the surface of 

 the quarry, may be scarcely traceable, or divided into thin cracks 

 or fissures at the suiface, through which in great part the infilling 

 has taken place. 



An examination of this supposed Carboniferous-limestone quarry 

 shows that at least one-fourth of it is of Liassic age. The curious 

 phenomena here observed, and especially the thickening of the 

 dykes of more recent age downwards, are somewhat difficult to account 

 for. An analogous state of things might arise, could we suppose 



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