212 T. S. Hunt—The Decay of Rocks. 
Thus the rounded surfaces and the closed rock-basins so oftem 
observed in glaciated regions of crystalline rocks are seen to be 
ut the natural results of the process of rock-decay, which 
preceded and prepared the way for denudation. | 
§ 50. Similar views-as to glacial erosion have since been ad- 
vocated by Nathorst, and more lately by Reusch, who, in a 
memoir on the geology of Corsica, presented to the Geological 
Society of France, in November, 1882,” bas described the dis- 
integration of the granitic region of Corsica to a depth of sev- 
eral meters, giving to the surface smooth slopes instead of the 
bold escarpments seen in like rocks in Scandinavia.. He notes 
in these disintegrated rocks in Corsica enclosed balls or ellip- 
soidal masses, fresh in appearance, but like in composition and 
in structure to the enclosing rock, which, when detached, have 
been taken for erratic blocks. With this region, he contrasts 
the similar rocks near Christiania, in Norway, with hard, 
rounded surfaces, marked by glacial scratches, where it is diffi- 
cult to find any trace of superficial decay. He does not believe 
that the ice of the Glacial period removed any considerable 
portion of the hard rock, to form fiords, valleys, ete., but sup- 
oses “a profound disintegration of the Scandinavian rocks 
fore the Glacial period,” and conceives the present relief to 
“represent the surface of the unaltered syenite after the re- 
moval by the glaciers of all the decomposed part.” 
The salient rock-masses of the Norwegian coast are, like the 
fiords, arranged in a north and south direction, and this, ac- 
cording to Reusch, corresponds with that of fissures, more or 
less nearly vertical, which traverse the rock, and, as he well 
remarks, prepared the way for its disintegration in depth, the 
extent of which would depend upon differences in the nature 
of the rock. Many of the lake-basins of this region were, ac- 
cording to him, formed through the removal by glaciers of the 
ecayed material from depressions, while others are due to the 
action of moraines, serving as dykes 
§ 52. It is difficult to state more clearly the consequences 
which follow from the conception that the decomposition of 
rocks is ‘‘a necessary preliminary to glacial action and erosion, 
which removed previously softened materials.” Reusch, how- 
ever, seems, from some misconception, to regard this pre-glacial 
disintegration of the rocks as distinct from kaolinization, of 
which the crumbling of the granites in Corsica, as in other 
regions, doubtless represents an incipient stage, such as we meet 
with in depth, in regions where the superficial and more com- 
pletely decayed portions have been removed (§ 46). 
60 Bull. Soc. Géol. de France, xi, 62-67. 
