GLACIAL EEOSION. 95 



by the fall of ice as it dashes from one frost-cracked rock to another. One of these 

 great ice-aval auches I witnessed from the other side of the valley, fully a mile distant. 

 Thoiisands of tons must have fallen at this time, but as the ice fell from rock to rock, it 

 was converted into what, seen at the distance, appeared to be white dust. There are no 

 considerable streams from the upper glacier, but from the rapidly melting glacier below 

 the fall the volume of water laden with mud is large. As this glacier is not ploughing 

 up, but levelling down the inequalities of its bed of loose material, we cannot suppose 

 that the mud comes from any other than the dirt upon and within the ice, and that 

 obtained by the dripping water as it levels the terminal moraine. This is only one of 

 the examples everywhere to be seen shewing the erroneous estimate of glacier-erosion, 

 when based upon the amount of mud carried down by the streams flowing from the 

 glaciers ; for the debris is brought upon their surfaces by other than grinding action, and, 

 as far as observation goes, it is not derived from beneath them, at least, to any great 

 extent. 



Although I have seen some of the sharp angles of the rocks at 2,000 feet above the 

 fjords along the sides of the valleys, somewhat rounded and scratched, yet the inequali- 

 ties of the faces have not been removed by erosion of any kind. At numerous places in 

 Norway, as well as in other countries, hummocks of rock rise above or out of the glaciers, 

 as the ice flows around them at lower levels, these channels having been deepened, not 

 by glaciers, but by subglacial streams. 



Nowhere are the roches moutonnées so abundant as on the coast of Norway. In their 

 more perfect form, they are not extensively developed along the coast at more than 250 feet 

 above the sea. At higher altitudes they are best seen about glacier-falls, farther \\p the 

 valleys. But during the Pleistocene days, the coast has been raised several hundred feet, 

 at least. The form of the hvxmmocks is precisely like what may be seen in south-eastern 

 Missouri and other States south of the line of northern drift, or are described as occuring in 

 Ceylon, Brazil and other tropical countries, to which only are added the scratches. The 

 forms of these hummocks must be principally attributed to the atmospheric erosion of the 

 crystalline rocks where the debris has been swept away by currents or by ice. We see 

 them more frequently swept clean upon the coasts of either cold or warm countries than 

 in the interior, where the currents are only those from rain or local glaciers, for even the 

 sweeping beneath the glaciers is principally efiected by dripping waters or streams. Prof. 

 Kjerulf, of the University of Christiania, than whom there is no better authority, regards 

 the production of hummocks and their glaciation up to a height of 600 feet upon the coast 

 of Norway, as the result of floating ice. ' 



The absence of transported boulders and striations upon the siirface of many parts of 

 the high plateaus of Norway is doubtless, in part, attributable to the ability of ice to flow 

 around loose obstacles, and the frequent want of higher ridges to furnish material by their 

 debris falling upon the ice to work through the mass afterwards. 



The faith in glaciers, as great erosive agents, has been so severely shaken that few 

 geologists, who personally study those still existing, now attribute to them greater power 

 than that of removing soft materials, and of this power many others are sceptical, e.g. 

 Prof. Penck,^ of the University of Vienna, who has been misquoted as having proved their 



' Discourse before Meeting of Scandinavian Naturalists, Copenhagen, 1873. 

 ' Geological Magazine, April, 1883. 



