EN ANGLETERRE
R. 1. Between Ihe Snowdon range and Ihe Menai Slraits, Ihe coun- "•"* try descends to the sea in a séries of undulations, in great part (/^^^,a /f«/#i.) covered by Drifl , through which weatherworn bosses of rock protrude, oflen with rounded outlines, the smoothness of whicb bas been much destroyed by almospheric influences.
Passing from Caernarvon lowards Llanberis , when we reach Ibe marsbes near Cwm-y-glo* , the Drift disappears from the valley^ the rocks stand ont more boldly, and by and by, on bolh shores of Llyn Padarn * the experienced eye bas no difficulty in distinguishing clear évidences of glacial action; for the rocks where unwearthered , are round and mammillated, and Iheir smootbed surfaces are somelimes grooved , the striations running north-west in the direction of the valIey and of the ienglh of the Iake. Many beautiful instances of this occur by the sides of Llyn Padarn , and one obvions
Tlie striation of the rocks, and most of the moraines meutioned in the foUowing pagres , are marked on the map. A few passages near the close of this memoir are extracted from other papers written by myself for the Journal of the Geological Society, the Edinburgh Philosophical Journal , and the Catalogue of rock spedmens in the Muséum of Pratical Geology.
' D. A. Extrait de : Peaks^ Passes, and Glaciers. A Séries of excursions by members of the Alpine-Club. Edited by Sohu Bail, M. R. I. A., F. L. S., prc»ident of the Alpine- Club, 1859, 2« vol., p. 419 à 474. The old Glaciers of Switzerland and North Wales, par A. C. BWBM179 F. R. S. and G. S. (paragraphes R.).
**D. A. Illustration : lac et passage de Llanberis.
' The Valley of Coal , or more probably, of Light. Lying in the Lower Silurien rocks. this valley bas nothiog to do wilh the Coal-measures of the geologist ; though I once found certain insane miners sinkin^ for coal in the black Silurian slaty shales of the district.
* Padarn, a Welsh saint; Padam's Lake.
example may be seen in a little rounded islet, near the loiver enl of the lake, close by the railway. With a liltle search, numerous like exaraples are found on the rocky slopes many hundreds of fe».t above the level of the lake , and on thèse ail the slriœ nin northwesterly. On the map I bave traced them in forty-six places , ovrr a space nearly two miles in breadlh , between the northern slop»of Bryn-mawr * and Clegyr ", the lake lying between. Here and ther-, on the side of Clegyr next the lake, little patches of moraine maWr lie amid the rocks , while beyond its north-eastern slope, (here L< a broad expanse of Drift stretching towards Nant Francon.
The same is the case by the sides of Llyn Péris , both low aiji
high; — as, on the unbroken surfaces of rock araid the great slaW
quarries, below Elidyr-fach ; on the opposite slopes of Cwm Ael-
hir ' ; and far obove to the very summits of Pen Carreg-y-frân * au !
Derlwyn • ; — where indeed the striations fairly cross Ihe \raler5-
hed , and strike nearly westward , in a manner comparable to th^
change of direction of the groovings on the summit of the ri Le
below the Betlenhorn , that divides the valley of the great Alets. b
Biocpmhc. glacier from that of the Rhône. Blocks of felspathic porphyry, thaï
bave traveUed from the higher mountains of Snowdon , lie scatter.^l
about; and on the very summit of the ridge near Derlwyn, odo
stands perched on the crags , i a manner at once suggesting thaï il
was deposited by ice where it now stands*.
surfticefi A beautiful glaciated mrface of hard Cambrian grit may be secn
Hie» et iiTiéei. jjy ^^^ jjgjjj of thc road , near the Coppermine, above Uyn Péris*,
close to the small oclagonal building marked f office ;» on the On)nance map , where the striations running down the valley ait' as fresh as if the ice had but lately disappeared. Other rounded surfaces slip into the lake ; others form mounds of rock above th'road ; and ûnally, often decayed ^ they pass far up among the Caïubrian grits, to the very summit of Pen Carreg-y-frân. On the opp."
< Big HilL
* Craggy Rocks.
' Eye-brow Valley.
* Crow-rock HUl.
" Oak-copse.
*D. A. Illustration : bloc perché près Derlwyn, au col (passage) de Uanberis.
* Peri8 , a Welsh saint.
site slopes, at the raoulh of Cwm Dudodyn, the rounded forms are also apparent, but the finer glacial markings bave oflen disappeared from tbe softer surfaces of the slate. Up tbe Pass , every step beyond Llyn Péris , the évidences of a **"*"
et
vanisbed glacier become more and more apparent. Erratic boulders a^ém^^ errauqaei. mingled with smaller moraine mcUler^ lie by the roadside and up among the rocks , by the experienced observer, easily distinguished from more modem blocks and talus that lie belovsr the weathered cliffs. On both sides of the valley, the rocks, strewn with blocks, frequently présent the well-known moutonnée form , more or less Roches moutonnées. perfect ; and this is especially obvions towards the turnpike gâte , and near Pont-y-gromlech *, where bosses of felspathic porphyry rise like little hills in the middle of the valley, something like miniatures of that behind the Grimsel. Though their sides bave been scarred by tbe winters' frosts , their summits , roughened by the weather, still retain the familiar largely mammillated form imprcsscd on them of old by the grinding ice ; and while the tourist, who sees something in scenery beyond mère external form , is often puzzled to account for the numerous blocks, that, perched on precarious points, seem as if they ought to hâve taken a ûnal bound into the lowrer valley, the well-pleased eye of the geologist versed in ice , at once detects that they were let gently down where they lie by the melting of the diminishing glacier *.
Further up the valley, behind Blaen-y-nant', a brook descends Moaines. from the hollow of Cwm-glas'. A little way up its banks a goodsized moraine f afterwards to be more parlicularly noticed , bas been eut through by the stream , and bends up both its banks. Above this , going up the Pass , the ground on the right is ail covered with moraine débris y and nearly opposite the great fallen blocks of slone , miscalled a Cromlech , a huge mound Worthy the name of a hill rises in the valley between the road and the upper side of the entrance to Gwm-glas. So large are some of the angular blocks with biocs angoiew.
' Cromlech Bridge.
* D. A. Illustration : roches moutonnées et blocs perchés sur lé col (passage) de Llanberis.
* « The Houth of the Valley, » where the house stands. » The Grcy Valley.
which il is studded , thaï for some time I was doublful if Ihe biii did nol chiefly consist of a solid mass of felspathic porphyry, bul the mixed nature of its fragments, ils form, and posîlion, afler many a visit, forced noe to the conclusion ihat it is ihe relies of o large moraine, shed from tbe upper side of a glacier thaï once de^cended from Cwm-glas , and abutted on the opposite side of iho Pass.
Below Pont-y-gromlech , Ihere are other traces of moraines, auJ several erratic blocks — one of them of greenstone — lie perched on the rounded rock of felspar porphyry. The slriaiions on its surface are almost ail weathered away, but such as are traceable XrevÀ towards Llyn Péris , and, as is frequently the case, tbe more bioken side of the roche moutonnée aiso faces down tbe valley. Opp«jsite^ above the bridge, on the Snowdon side of the valley, a grrjt dark wall of rock rises abruptly from the broken lower slojK^i , about a quarter of a mile from the road. From the bottom of the Pass it looks almost inaccessible, but half way up there is a rotfjft tenace i at the foot of a greenstone dyke that forms in part tbe tO'X» of the cliff. The slope of the précipice is about 68° towards ib^* Roche polio Pass, and in one place especially the wall of rock is polished, and profondémeui sméc. rf^^îp/j/ striatcd îu at least six principal deep grooves, whicb sloj»:
down the valley (not down the hill) al an angle of i2**. Sonie uf
Ihem , are deeply graven, from two lo two and a half feel wide.
and twelve or eighteen inches deep , and they run so symmetricaiK
along an almost vertical wall of rock, thaï the idea is at once su^'-
gested to the mind, that they were formed by the long-coDlinutiJ
pressure of a glacier so large , that il filled the valley to a far grealcr
elevation than the grooves, and by reason of the huge superincuni-
bent mass of ice , a middie slratum , as it were , of the glacier nas
jammed against its bounding vvalls so powerfuUy, that by help if
the grinding of imprisoned stones, in fime, it wore oui tbe dtx\
furrows still so perfect.
Roches nouionuée», To thc vcry top of thc Pass the same kind of évidences , bolh .^i
p«rhé«*dan"^ moraine débris and striation , continue unabated , especially on *b:
!• piui élevée du pai-AigfAer slopcs on the north-eastern side of the valley, wbere abvu'
^^^' the modem shiugle and broken cliflfls that overlook the brook, nu-
merous roches moutonnées remain, still parlially unweathervd .
SNOWDON (montagne). 565
hère and there dotled with blocs perchés. By Ihe road at the twelflh mileslone a good instance occurs o{si roche moutonnée^ easily seen by Ihose who are satisfied with roadside geology. Its curving outlines are perfect on the top, but at the sides it bas been shattered bv the weather.
Close by Ihe waler-shed atGorphwysfa*, siriaiions in the rocks still run nortb-westerly in the direction of the Pass , b'ke those that must now be forming at the snowshed of the Upper-Aar and other {placiers. Once fairly across the watershed , where the valley widens, ihey rapidly curve round >vith Ihe average slope of the ground , some passing in the direction of Nanl-y-gwryd *, towards Capel Curig^, and others down NantGwynant*.
R. 2. Thus far some of the more obvions glacial phenomena in snowdon (montafnii>). Ihe Pass of Llanberis* can scarcely fail to strike the most hasty observer, and if we ascend some of the tributary valleys that run upwards into the heart of Snowdon , they become stili more impressive.
This mountain , the highest and noblest in Ihe district, is bounded on three sides by valleys, which in ail respects are usurpassed in geological inlerest and wild beauty, by any in Ihe Norlh Wales. On the north-east lie Ihe bare crags of the narrow Pass of Llanberis , on the east the sofler beauties of Nant Gwvnant, and on the west Ihe long drift'covei'ed slopes of the broad dépression that runs from Llyn Cwellyn' to Beddgelert. In the midst of thèse, the mountain rises in a tall peak 3574 feet (1088 mètres) above the sea, its base being formed mostly of old lava beds of felspathic porphyry, and the topmost thousand feet chiefly of stmtiPied felspathic ashes. In thèse rocks six vast hollows bave been scooped out by time, forming the wild upland valleys of Cwm-glasbach ", Cwm-glas,
* The «Resling-place,» after the long ascent from Llanberis, Beddgelert, or Capel Curig.
* ■ Fathom Valley, » or of the lenght of a man. The meaning is obscure. ' Curig, a man's name. Curig*s Chapel.
•While Valley, or literally, Whatevale Valley.
* D. A. niustration : roches moutonnées et blocs perchés sur les hauteurs du passage de Llanberis.
* Cwellyn , properly Cawellyfij a basket , hamper, or creel. So called from the fishingcreels once used in the lake.
* LitUe Grey Valley.
