Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/928

 ward to any distance ; and with a very slight pitch or slope it would slide forward along the incline." To this let me add that if the floor on the margin of the heap of grain was undulating, the stream of grain would take the course of such undulations. The want, therefore, of much slope in a country, and the absence of any great mountain-range, are of very little moment " to the movement of land-ice, provided we have snow enough" 1.

As the ice reaches the coast it naturally takes the lowest level. Accordingly it there forks out into glaciers or ice-rivers, by which means the overflow of this great ice-lake is sent off to the sea. The length and breadth of these glaciers varies according to the breadth or length of the interspace between the islands down which it flows 2. If the land projects a considerable way into the great ice-lake, then the glacier is a long one ; if the contrary is the case, then it is hardly distinguished from the great interior ice-field, and, as in the case of the great glacier of Humboldt in Smith's Sound, the interior ice may be said to discharge itself almost without a glacier. The face of Humboldt's glacier is in breadth about sixty miles. This, therefore, I take to be the interspace between the nearest elevated skirting land on either side. It thus appears that, between the inland ice and the glacier, the difference is one solely of degree, not of kind, though, for the sake of clearness of description, a nominal distinction has been drawn. The glacier, as I have said, will usually flow to the lowest elevation. Accordingly it may take a valley and gradually advance until it reaches the sea. In the course of ages this valley will be grooved down until it deepens to the sea-level. The sea will then enter it, and the glacier-bed of former times will become one of those fjords which indent the coast of Greenland and other northern countries often for many miles ; or these may be much more speedily produced by depression of the land, such as I shall show is at present going on. By force of the sea the glacier proper will then be limited to the land, and its old bed become a deep inlet of the sea, hollowed out and grooved by the icebergs which pass outwards, until in the course of time, by the action of a force which I shall presently describe (§ 4), the fjords get filled up and choked again with icebergs, in all probability again to become the bed of some future glacier stream 3. Where there is no fjord at hand, or where these defluents are not sufficient to draw off the surplus supply of ice, the " inland ice " will "boil " over the cliff's, overflowing its basin, and appear as hanging glaciers, whence every now and again huge masses of ice (the aerial

1 Quart. Journ. Geol. Soc. xxiv. 1865, p. 166.

2 Properly speaking, according to the ordinary nomenclature, the whole of the ice, from the " neve " downwards, should be called " glacier ; " but as we have not yet penetrated sufficiently far into the interior to observe where the "neve" ends and the " glacier " begins, I have for the sake of distinctness adopted the above arbitrary nomenclature.

3 The origin of fjords is more fully developed in a memoir by the author on " The formation of Fjords, Canons, Benches, &c," in Proc. Roy. Geog. Soc. vol. xiv. 1869 ; Journal, vol. xxxix. ; and in his " Das Innere der Vancouver Insel," Petermann's ' Geographische Mittheilungen,' 1869, pp. 94, 96.