GLACIAL EROSION IN THE AAJir VALLEY 589 



described by Agassiz and others. This is seen in the great dome, which rises to a 

 height of 350 feet between the Grimsel lakes on the south and the torrent of the 

 Aar on the north. It also appears in the north wall of the gorge at this point, in 

 the roches moutonnees of the Grimsel pass, and, indeed, everywhere, save on the 

 recently weathered and frost-riven summits of the surrounding mountains. 



Attention was, however, specially directed to a series of rock basins, of which 

 several lie between the Aar glacier and the Handeck fall, a distance of about 

 7 miles. Nearly all of them are now filled with torrential debris, brought from the 

 glacier; at least they are filled up to the plane to which the rim of the original 

 basin has been cut by the powerful existing stream. 



The first of these basins extends from the front of the lower Aar glacier eastward 

 for more than a mile, and is, on the average, one-fourth of a mile wide. It is im- 

 possible to say how far westward the basin would be found to continue were the 

 glacier to disappear. It seems probable that it may extend several miles, or nearly 

 to the Abschwung, when we take account of the long existence, strong descent, 

 sturdy tributaries, and consequently vigorous work of such an ice-stream. The 

 present floor of this aggraded basin is morainic about the glacier front for a short 

 distance,- but for the most part is a fiat ground of coarse gravel and cobblestones, 

 traversed irregularly by the wandering river as it issues from its subglacial course. 

 Near the Grimsel hospice a barrier of the bed rock, powerfully glaciated and about 

 100 feet high, reaches out from the south wall of the valley to the recently cut gorge 

 which carries the stream under the north wall. Between this barrier and the 

 hospice is another floor of an aggraded basin, the Spitalboden, about one-third of 

 a mile long, followed by the rocky rim, over which the river enters the narrow 

 gorge, below the post road and north of the hospice. 



About one mile below this point the river, descending rapidly, issues from the 

 gorge upon the Ratherichsboden, an alluvial floor similar to those already described. 

 It is about one-half mile long and, like the others, marks a section of the valley in 

 which a deep and broad gouge was made by the glacier. At the northern end of 

 Ratherichsboden the river enters a V-shaped gorge between spurs which close in 

 from either side of the valley. Both of these are strongly and beautifully rounded 

 by glacial abrasion, and immediately above them Bachlisbaeh enters on the west 

 and Gerstenbach on the east. The localities here given all appear on sheets 597 

 (Guttannen) and 490 (Obergestelen) of the Swiss topographic survey, but the con- 

 touring and hachures give but a poor idea of the striking alternation of lobe like 

 basins with V-shaped gorges, which it is the object of this paper to notice. The 

 walls of the gorge below Bachlisbaeh, as of some others of the series, are glaciated 

 nearly to the bottom. 



Passing this gorge a fourth basin appears, with lofty and strongly scored slopes. 

 This basin contains but a small floor of alluvium, and indicates but slight excava- 

 tion below the level of the stream as it passes into the next constricted section. 

 This gorge, also V-shaped, with glaciated walls, leads down to the spacious basin 

 above the famous Handeck fall. The greater part of the basin is now floored with 

 wide-spreading fans, built by torrents descending from the west. Opposite Handeck 

 we have lateral spurs closing in, though not so narrowly as below Ratherichsboden. 

 Between Handeck and Guttannen, and also between Guttannen and Innertkirchen, 

 similar irregularities or alternations of glacial excavation occur, but none is so con- 

 spicuous as those already described. The last named village lies on a fine floor of 



