Vol. 62.] AN UNCONFORMITY IN THE COAL-MEASURES. 537 



Though at first sight strongly suggestive of ordinary faulting, this 

 particular section, on being carefully studied, is, we believe, more 

 reasonably explained by the effects of local irregularities as obstacles 

 in the progress of a horizontal thrust. Pebbles are here again 

 found at the actual base, as well as a little above it in the sandstone. 

 In this, and in some of the highly-disturbed and faulted sections, 

 the whole is so crushed and broken, that it is impossible in places 

 to recognize any prevailing dip. 



A few yards north of F a long extent of cliff is reached, in which, 

 except at two narrow spots, the actual unconformity is covered by 

 talus-material ; but the Mussel-Band crops out on the beach a few 

 yards from the cliff, and its perfect regularity and parallelism with 

 the Upper Sandstone show that no trace of the disturbance at F is 

 left, and that there can be scarcely any discordance of dip. Indeed, 

 the two small exposures just mentioned prove this to be the case. 

 Pebbles are there seen about a foot above the base of the Table- 

 Rocks Sandstone. 



On approaching G the Mussel-Band' dips gently northward, to 

 be soon thrown up again by a reversed fault hading in the same 

 direction, so as to abut under the unconformable sandstone, whence 

 it again dips northward at the same angle as before (see fig. 8, 

 p. 538). In this section the pebbles, which are numerous, are only 

 seen on the southern side of the fault which causes the Mussel-Band 

 to override the conglomerate formed by them ; consequently, here 

 the Mussel-Band actually overlies a bank of pebbles derived from 

 itself. 



At H the same northerly dip (with absence of pebbles at the 

 unconformity) is observable. Here are two small faults affecting 

 the lower beds, but, of course, stopping short beneath the Upper 

 Sandstone (see fig. 9, p. 538). 



Many yards of obscuring talus follow, to be succeeded by a 

 long exposure of perfectly - horizontal Table-Bocks Sandstone, 

 beneath which the lower shales dip at a regular angle of about 15° 

 to the north. Only a few pebbles are to be seen above the junction 

 along this stretch of cliff. This arrangement continues to J. Here 

 is one of the transverse stony ridges to be referred to later on 

 (see p. 546 & fig. 10, p. 539). This little ridge is followed by 

 highly- dipping shaly beds until the Mussel-Band is reached. The 

 latter exhibits a thrust-like disturbance, being sundered by a fracture 

 which causes its southern edge to rear and overtop slightly the 

 northern. Here, as elsewhere, the direction of the movement must 

 obviously have been from south to north. A fault at this place 

 restores the Lower Series of beds to horizontal ity, with the Mussel- 

 Band running parallel to the Upper Sandstone as before. At K, 

 however, the Lower Series dips sharply to a fault. This fault has 

 little effect, as on its upthrow side the Mussel-Band is once more 

 a few feet beneath the plane of the unconformity, and continues 

 regular, with a slight dip inland, for some 200 yards farther until 

 L is reached. Consideration of a second stony ridge which occurs at 

 K is deferred until later (see postea, p. 548). 



