LACS DANS LE PAYS DE GALLES

valions on the glacier between the Mârjelen-see and Ihe ridge beyond the Bettenhorn, and I was surprised to find tbat a lai*ge pail of the ice-cliff I had walked along had broken away, and was floating about the lake in a prodigious number of white icebei^, some of them bearing stones and boulders, like the bergs in a liitle fiord of an Arclic Océan. — As they melt thèse bergs discharge Iheiroccasional freights over the bottom of the lake. The day aller, while eojoying the scène, one of Ihem becoming topheavy from the more rapid melting of the ice below the water , roUed completely over with a great roaring noise of displaced waters pouriog down ils sides , calling to mind the descriptions by Arctic voyagers of the turmoil caused by the occasional complète reversai of the great icebergs of the Atlantic that bave travelled from the coasts of Greeih land.

^« R. 16. In still weather many boulders may be seen scaltered oTer

*" dVclues" '^* ^he bottom of the Lakes of Llanberis; and since visiting Ihe Alelsih

glacier I bave often thought , that an épisode , in the glacial history

of the Pass may hâve heen that thèse blocks of stone ivere scattered by kebfrp

broken from a glacier that descended into the lake, like the cliff of ice tbat mnr overlooks the Mâijelen-see.

The érosion of such hoUows by ice also seems strictly analogous to Ihat which scooped ont the more perfect rock-basins, not only of the lakes and pools in ordinary glacier-valleys (such as Ihose of Cwm-glas on Snowdon, and of Llyn Cywîon above Nant Francon)*, but also of those that lie on high passes and watersheds , like ihe Todten-see , between the Grîmsel and the Valley of the Rhône ; oi again^ on high surfaces , like the tarns on some of the rough tablelands between Ffestiniog, Nant Gwynant, and the river Conwy; or, on the once mammillated but now half-weatherwom surfaces of gneiss y where a network of pools, tarns, and lakes by the score, may be seen from the sharp peakof Suilven, for instance, in Sutberiand , the basins of many of which were seemingly scooped eut, when , like the north of Greenland , the land , ail save the roughe^t crags, was covered by a vast sheet of thick ice that descended below the présent level of the sea. The producing cause of thèse pe-

^ D. A. Illustration : Passage de Llanberis^

culiar hollows thati hâve seen in Wales and Swilzerland, was probably an immense weigbt of super-incumbent ice pressing and grinding downwards and otUwards, over high^ flat, and sometimes broad watersheds and table-lands , during that period of intensest cold that produced the glaciers of Wales , and the great original extension of the glaciers of Switzerland.

R. 17. The graduai destruction of ice-worn surfaces is also a point S"«w^" of considérable interest and importance, for, though thèse signs **"**' must endure for many âges, still they are haslening to decay. When the tuif and glacier débris is lifled, though the underlying surfaces of cleaved slate often retain a perfect ice-polish , yet , after long exposure , the smoothness and finer markings disappear ; and though the gênerai rounded form remains^ the surface becomesroughened, and the highly-inclined cleavage planes présent on their edges a slightly serrated aspect. The deeper flutings , however , oflen last for a long time ; but even thèse at lenglh vanish , though it is not until long after this bas been eifected that the gênerai rounded form of the roches moutonnées is entirely obliterated.

Phenomena of the same gênerai nature are observable in the igneous and other uncleaved rocks over which a glacier bas passed. The original poUshed surface, on exposure, becomes roughened by atmospheric disintegration ; but the gênerai form long remains to attest its glaciel origin , and in no case is there any danger of the Gxperienced eye confounding this with those forms in gneiss produced by spherical décomposition, about which so much bas been written. Finally, in the long lapse of time, air, water, and repeated frosts do their work, the rock splits at its joints , crumbles', masses fall off, and by degress it assumes an irregular and craggy outline , altogether distinct from the glaciated surface produced by the longcontinued passage [of ice ; and thus it happens that on the very summit of some tower-like crag, the sides of which bave been rent by the frosts of untold winters, the student of glacial phenomena sometimes finds yet intact the writing of the glacier ; v^hile below on its sides ail trace of the ice-Qood bas long since disappeared. Thèse things may seem almost incredible to those who are unaccustomed to read the records of many terrestrial révolutions in the rocks; but, nevertheless , of thèse extinct glaciers it istrue, that