583 
a few transverse lines. A porphyritic slate rock, at the point where 
the Nantel railroad crosses the turnpike road, presents similar phz- 
nomena. All these appearances, Dr. Buckland states, are consistent 
with the hypothesis of their being the effects of a glacier descending 
westward from Snowdonia through the valley of the Lyfni. Mr. 
Trimmer had previously (Oct. 1836) pointed out to the author po- 
lished and striated surfaces at the great slate-quarries near the lower 
end of this valley. The thick accumulation of unstratified gravel 
over the slate-quarries is referred by the author to northern drift. 
Valley of the Gwynant.—Between Pen-y-Gwryd and Llyn Gwy- 
nant, the rocks which have been uncovered at a few points are also 
polished, fluted and striated in lines ranging from north to south, 
parallel to the valley. A more obvious example is stated to be exhi- 
bited near Bed Gellert, about 100 yards below the bridge of Pont- 
aber-glaslyn, and a few scorings of the rock occur between Pont- 
aber-glaslyn and Bed Gellert. The trough of this valley for six or 
seven miles, from Llyn Gwynant to Bed Gellert and Pont-aber- 
glaslyn, is studded at intervals with clusters of dome-shaped hillocks, 
having had all their projections ground away by some powerful 
abrading agent. One of these masses near the turnpike gate, at the 
north-east end of Bed Gellert, is intersected by quartz veins which 
project about two inches above the surface, but preserve, as usual, 
their polished and rounded outline. 
The preceding details establish, Dr. Buckland states, the frequent 
occurrence, in the seven principal valleys of Snowdonia, of those 
phenomena which are considered by Prof. Agassiz as proofs of gla- 
cial action, and consist of obtusely rounded, dome-shaped rocks— 
furrowed, fluted, striated and polished surfaces—and the occasional 
accumulation of mounds of detritus with boulders resting on their 
surface. 
The author then proceeds to consider the remodification of glacial 
detritus by violent inundations; recalling the reader’s attention to 
the fact, that the only two cases stated in the paper of deposits re- 
sembling morains are both on the south-east side of the great moun- 
tain cham, one at Pen Tre Voelas, high up in the valley of the 
Conway, the other in a high mountain valley near Llyn Ogwyn. 
He then shows, that on that side of the chain there are no traces 
of those accumulations of far-transported materials which oecur on 
the north-west flank of Snowdonia, and consist of pebbles of granite , 
as well as other rocks derived from Anglesea, Cumberland, or Ireland, 
associated with fragments of existing species of marine shells and a 
tumultuous mass of other detritus. ‘These drifted materials are found 
high up on the flanks of the mountains; namely, on Moel Tryfan, at 
the height of 1392 feet, and at Moel Faban, more than 1000 feet above 
the valley of the Ogwyn near Bethesda*. From the former point 
they gradually descend to the plain which extends to the shore near 
* See abstracts of Mr. Trimmer’s paper, vol. i. pp. 8381, 419; also Mr. 
Trimmer’s memoir in the Transactions of the Dublin Geol. Soc., vol. i. pp. 
286, 335. | 
