Mr. Bowman on Silurian Rocks west of Abergele. 197 



bank, where a trial for copper is now carrying on, this limestone rests on a bed of 

 very fine blue loamy clay (b, woodcut), which in its turn rests upon a blue clay- 

 slate (a). At this spot is the fault represented in the section. 



On the north side of the fault the dip of the strata is a little east of north, and 

 at an angle of about thirty degrees with the horizon, which is conformable with the 

 general incHnation of the hmestone ; but on the south side the dip is south-west, 

 and at a much less angle. In the trial level, and also in the lower portion of the 

 dingle southwards, nothing is seen but the hard blue clay-slate, fine-grained and 

 slightly micaceous, and containing, in the planes of stratification, here and there, a 

 layer of small shells and obscure marks of vertical cleavage, similar to that which I 

 have found in a coarser and harder clay-slate in the quarries of Nantglyn and Cyflfyl- 

 liog on the high plateau between the rivers Clwyd and Conway, and fifteen to twenty 

 miles south-east of the present locahty. I saw here none of the cleavage lines, some- 

 times straight, sometimes curved, which I observed on the flagstones at the above 

 quarries. These lines are merely superficial, and are only observed by their mica- 

 ceous or nacreous lustre. The transverse strise on the large Orthoceras are very 

 seldom found in the coarse flags at Nantglyn ; the medial longitudinal line is a 

 depression ; the specimens, which taper abruptly about the middle, are from two to 

 eight inches long and two inches across at the broad end. 



The rill in Ffernant dingle discharges itself into Melin y Person brook, which 

 runs eastward into the Dulas. The red marly conglomerate is succeeded on the 

 south by a light greyish brown alluvium with blue slate pebbles, forming the sur- 

 face south from Melin y Person brook. I then entered upon the slate or schistose 

 rocks, which rise above the pretty village of Bettws Abergele on the south, show- 

 ing great contortions and a nearly perpendicular stratification (as distinguished 

 from cleavage) ; but a little further south the beds are variously inclined, both as 

 to angle and the direction of the dip, showing considerable disruptive forces, ap- 

 parently operating at different periods. On the height, to the left or east of the 

 road, is a very hard fine-grained greywacke rock, enclosing detached joints of 

 small Crinoidea. It has a cleavage sometimes approaching to columnar, like that 

 of many traps or green-stones, separating the mass into large triangular or wedge- 

 shaped pieces. Still further south, in a quarry on the right, the greywacke again 

 occurs, and, in addition to this cleavage, it shows a distinct parallel stratification 

 with a considerable dip to the south-east. The beds are each three to four feet 

 thick, and above or upon them rest four other thin seams of the same, each from 

 nine inches to a foot thick, alternating with seams of breccia of about equal thick- 

 ness. The paste of the breccia is the same greywacke just described, with minute 

 encrinital joints and other organic remains ; while the imbedded material is a 

 dark glossy clay-slate, mostly in angular fragments, and without any fossils. 



