Glacial Erosion in Norway. 227 
higher altitudes they are best seen about glacier-falls, farther up 
the valleys. But during the Pleistocene days, the coast has been 
raised several hundred feet, at least. The form of the hummocks 
is precisely like what may be seen in southeastern Missouri and 
other States south of the line of northern drift, or are described as 
occurring 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 crys- 
talline 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 effected by drip- 
ping waters or streams. Professor 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 N orway, as the result of floating ice.’ 
The absence of transported boulders and striations upon the sur- 
face 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 exist- 
ing, now attribute to them greater power than that of removing 
soft materials, and of this power many others are sceptical, e.g., Pro- 
fessor Penck,? of the University of Vienna, who has been mis- 
quoted as having proved their great efficiency in eroding basins in 
hard rocks. To this scepticism, it seems to me that these notes 
must contribute; especially when glacial erosion is applied to the 
hypothetical excavation or modification of great lake-basins, and the 
transportation of the northern materials in the boulder clay over 
the broad plains of America, as there were no mountains of ade- 
quate height with peaks, or séracs, to supply the detritus sufficient 
to furnish the tops of the glaciers with all the boreal material of 
the drift, which “covers half a continent.” 
ie iscourse before Meeting of Scandinavian Naturalists, Copenhagen, 
* Geological Magazine, April, 1883. 
