520 



KEY. J. F. BLAKE ON THE 



a fault between the conglomerate and contorted slates ; the shore is 

 inaccessible, but there is an open cave in the proper position. The 

 importance of this section is, first, that it shows that the Ordo- 

 vician slates here seen are near the base, and that they are under- 

 lain by conglomerates • secondly, that we can compare the rocks, 

 which here correspond in character with the Ordovician elsewhere, 

 with the underlying ashy series, and see that they still remain 

 perfectly distinct ; and thirdly, that we can trace an unconformity. 

 The pebbles of the conglomerate are chiefly quartzose, such as 

 might have been derived from the underlying beds ; but they have 

 no special character which should limit them to such a source. 



A little farther east, conglomerates appear in association with the 

 slates, and then comes on again a mass of limestone, possibly faulted 

 into its present position and forming the western side of Forth 

 Llanlliana. On the east side of this bay we find another section, 

 greatly differing from the last, and introducing this new con- 

 glomerate in its place, as seen in fig. 22. On the south side, that 



Pig. 22. — View in Forth Llanlliana, looking east. 



1. Quartz-knob. 2. Purple shale. 3. Grreat conglomerate. 



4. Finer conglomerate. 5. Grey shale. /. Faults. 



is, at the base of the sequence, is seen a mass of quartzite ; above 

 this is a wedge of ashy rock getting smaller at the base — and this is 

 followed by a great band of red jasper-conglomerate, the pebbles in 

 which are very large. The series is then cut off by a fault, and 

 the rocks on the other side are broken. First comes a wedge of 

 purplish slate, apparently faulted in, then a slice which has grey 

 shales on the top, and seems to rest on a conglomerate at the inac- 

 cessible base ; then another fault, and then some similar shales lying 

 certainly on a considerable quantity of conglomerate of finer 

 character, which continues to the base of the cliff. We may safely 

 take the upper conglomerate and shale (4, 5) here to be Ordovician, 

 though the latter is not black ; but the great red conglomerate below 

 seems to be too intimately connected with the quartz-knob to belong 

 to a distinct system ; and if it does not, then we lose all sight of the 



