that it is liable to have rock-rubbish dumped on its surface. Moreover, the course of such valley-glaciers is so short as a rule, and their rate of flow so comparatively rapid, that conspicuous lateral moraines cannot be accumulated. It is further noteworthy that Norwegian glaciers do not form prominent terminal moraines, and these are composed chiefly of water-worn gravel and blunted and subangular stones. Sharply angular blocks and fragments do not predominate as in the end-moraines of Alpine glaciers. In a word, the Norwegian terminal moraines appear to consist mainly of infraglacial and fluvio-glacial detritus, which the ice builds up into low mounds and ridges. But if superficial moraines are sparingly developed, the same is not the case with ground-moraines. These are seen not only under the glacier-tongues in valleys, but they are conspicuous likewise under the bordering ice-walls of the plateau-sheets. Everywhere, also, from the margin of these sheets, as from the valley-glaciers, flow streams and torrents of turbid.

water.

The phenomena exhibited by the Scandinavian icefields are exemplified on a much larger scale in Greenland. There, as in Norway, superficial moraines are entirely wanting, except where the ice-sheet protrudes long tongues into mountain-valleys and fiords. Where the ice-sheet terminates upon land ground-moraines are conspicuous. Nansen, for example, tells us that at Austmannatjern, where he left the inland ice after his famous traverse, enormous accumulations of mo

raine were seen. These were of true infraglacial origin, consisting largely of blunted and striated stones, which could only have been transported by the ice as ground-moraine. No Nunatakkr occurred within the mer de glace near this place, and not a vestige of surface-moraine was visible. Dr. Hoist, Dr. Drygalski, and others have referred to the appearance of ground-moraines in Greenland, and the phenomena in question have also been described by Professor Chamberlin. The latter shows that the tongues of ice proceeding from the local ice-caps and from the great inland ice are crowded towards their base with ground-moraine, the lower strata of the ice for a thickness of 50 to 70 feet above the bottom showing layers and irregular sheets of clay, mud, sand, stones, and boulders, all of which are of infraglacial origin, while the upper and much thicker mass of ice is free from such inclusions. It is not necessary to enter into greater detail, but it may be added that in Greenland as in Norway turbid water escapes in large volume from the "inland ice."

Reflecting upon the facts thus briefly recapitulated, we must conclude that glaciers are powerful agents of erosion. Not only do they grind, smooth, and polish rock-surfaces, as everyone admits, but they also quarry their beds. The stones and boulders of the groundmoraines are derived directly from below by the ice itself. In the case of Alpine glaciers, no doubt débris may occasionally be introduced to the ground-moraine from above; but this descent of superficial detritus

cannot take place in the plateau-sheets of Scandinavia, nor in the local ice-caps of the great "inland ice" of Greenland. In some way or other, rocks underlying a glacier are liable to disruption and displacement; and such, we cannot doubt, is the chief source of the stones and grit and clay of ground-moraines generally. There is direct evidence, indeed, to show that glaciers not only abrade and smooth, but rupture the rocks over which they flow. Professor Heim refers to an observation of Von Escher on the Zmutt Glacier, underneath which were seen projecting reefs of schist glaciated atop, which had been fractured and sundered by the glacier. Again, Professor Simony has described the appearance presented on the bed of one of the Dachstein Glaciers (Karls-Eisfeld) during the temporary retreat of the ice. What struck him most was not so much the smoothed and polished surfaces as the broken and disrupted masses, the shattering being most marked in places where the rockledges faced the direction of the ice-flow. The prevailing character of the erosion, Professor Simony remarks, is that of a continuous rock-shattering. On the north side of the glacier, where the surface had become depressed for 40 to 60 feet, the exposed rocks showed polishing in only a few places, glacial pressure having resulted rather in a wholesale superficial shattering, and in the production of a rubble of angular fragments.

Similar phenomena have been observed by MM. Penck, Brückner, and Baltzer at the Uebergossenen

Alm. During the past thirty years this glacier has retreated for two or three hundred yards. Its deserted bed is traversed by a belt of hornblendeslate, which, like the adjacent rock-masses, is well glaciated and sprinkled with large striated blocks of gneiss. In some places, however, the hornblendeslate, after having been smoothed and polished, has been broken up, and débris, consisting of smaller and larger fragments and blocks, polished on one side only, are found incorporated in ground-moraine a little further down. This is a clear case of infraglacial quarrying. Another good opportunity of studying the results of modern glacial action has been afforded by the retreat of the Lower Grindelwald Glacier. The lowering of its surface has exposed two rock-terraces. One of these is well glaciated, showing roches moutonnées with conspicuous Stoss and Lee-Seiten. Between the mammillated rocks stretch several shallow rock-basins, some of them being filled with water. One of these, according to Professor Penck, measured 26 feet in breadth, 42 feet in length, and 3 feet in depth, and was smooth and ice-worn from end to end. Both terraces are trenched by the deep gully of the Lütschine, the upper portions of the rocky walls being conspicuously striated and fluted, while here and there they present the shattered surfaces which are equally characteristic of glacial action.

Professor Brückner has in like manner described the broken and ruptured rocks and smoothed surfaces which appear side by side upon the bed of a glacier.

Thus at the Mazellferner he saw resting upon the jagged projecting out-crops of certain rocks a block, many cubic metres in size, enclosed in ground-moraine, along with which it had travelled over the cracked and shattered rock-ledges. The ground-moraine was squeezed in between the disjointed masses. · In another place, where the bed-rock was well smoothed and striated, he observed an irregular rough cavity or hollow, from which a slab of rock had evidently been extracted. In the recently deserted beds of the Obersalzbachkees (Hohe Tauern) and the Hornkees (Zillerthal) he noticed that the rocks were jointed in a direction approximately parallel to their upper surface-a structure which has favoured their rupture and displacement. Here and there, in the midst of a well smoothed area, rough cavities indicated whence slabs had been removed; and now and again the detached fragments themselves were detected. Many such loose slabs were observed by the same geologist on the bed of the Stampflkees. On one side they exhibited the parallel striation characteristic of rock which has been glaciated in situ, while the other sides were rough and irregular, and showed no trace of abrasion. That fragments of this character are not more frequently extruded at the lower end of a glacier is readily understood when we remember that they could not travel far below ice without losing their rough surfaces, and becoming more or less glaciated all over.

Professor Chamberlin has recorded the occurrence