436 
of vast masses of detritus, apparently derived from the valleys 
of the Severn and the Dee, and containing also numerous 
angular fragments of granite from Ravenglass and elsewhere, 
we proceeded up the vale of Llangollen, and observed the 
polished and grooved condition of the slate rocks. We saw 
also a curious fluted surface in a slate rock near the village of 
Llangollen; but this being on one of the divisions of stratifi- 
cation, was evidently owing to mechanical causes, by a hori- 
zontal sliding of one bed of the rock on the other — in a hand 
specimen the grooving bears a resemblance to glacial flutings, 
but when viewed in situ the difference is very obvious. In 
the vicinity of Pentre Violas and Yspytty Evan, vast masses 
of detritus are formed into rounded knolls and hills of consi- 
derable magnitude, and have the appearance of moraines 
modified by the action of water. About a mile from Llyn 
Ogwin, where the river Llugwy turns to the south-east, 
there is a series of mounds of earth and gravel covered at 
their summits with hundreds of large blocks of stone, and 
these, Dr. Buckland states, approach nearer to the condition 
of moraines undisturbed since their deposition by a glacier, 
than any other mounds of detritus which he has seen in 
North Wales. The stream from the lakes at Capel Curig 
falls into the Llugwy, near a lofty mound resembling a ter- 
minal moraine, and below this junction the rocks are rounded, 
grooved, and polished. Near Llyn Ogwin a great number 
of rocks are worn into bosses or dome-like shapes ; the sur- 
face is in most instances much abraded or weather-worn, 
notwithstanding which the deep groovings may be traced, and 
the former existence of a polished surface is evidenced by the 
extreme smoothness and curved contour of the veins of 
quartz, which project from half an inch to one or two inches, 
and thus form an index to the amount of abrasion. 
I may here observe, that the scenery of this district is 
5uch as to merit especial notice, and will amply repay the 
