PREGLACIAL LAND SURFACE AND SOILS. 267 



basins they may have been filled with peat. In the valleys there would be 

 much stream wash — silts, sands, and gravels. I have never given up hope 

 that somewhere portions of these preglacial soils, peats, or lake sediments 

 were enabled to survive beneath the rough ridings of the ice-sheet in masses 

 sufficiently large to contain characteristic fossils and be recognizable. So 

 far as yet discovered, the onl}^ bodies of preglacial soil that failed to 

 be incorporated with the drift of the ice-sheet were contained in small 

 depressions of the rock. They consist mainly of rock weathered in situ, 

 and plainl 3^ underlie the glacial drift. They are much the oldest of the 

 superficial deposits of Maine. The largest of the depressions of this kind 

 in which the primeval soils are preserved were in argillitic and quartzitic 

 schists, and Avere less than 7 feet in diameter, unless certain narrow east- 

 west ravines in sedimentary rock that open out from the gorge of the 

 Seboois River not far from Blount Katahdin be also of this kind. The pro- 

 jecting tongues left by the unequal weathering of the fine-grained schists 

 were thin and easily broken. Hence these rocks were reduced by the 

 glacier to such an even or gently undulating surface that their glaciation 

 may well be termed planing. The mica- and other coarse schists yield fewer 

 areas of preglacial weathering, and these only from 1 to 3 feet in diameter. 

 The laminse are thicker and vary much in hardness. The glaciated rock 

 often shows undulations a few inches wide and from 1 to 3 inches high, so 

 that the surface has a ribbed appearance, as of corduroy. The projecting 

 ribs are rather parallel to the strike of the laminse. of schists, and more often 

 are transverse to the glaciation. Where the furrows between the ridges are 

 very large they have sometimes been described as grooves gouged out of 

 the rock by a single bowlder. Where they happen to be parallel with the 

 glaciation it is difficult to decide the question of their origin; but where 

 they are parallel with the lamination of the rock and transverse to the 

 glaciation, as they usually are, they must be regarded as due to the condi- 

 tion of the weathered rock as the ice began to act upon it. The ridges are 

 the projecting edges of the harder layers which the glacier was not able to 

 plane off to a flat surface, although removing the weakened rock and leaving 

 the surface of both the ridges and the hollows thoroughly polished In 

 other words, in these cases the signs of the surface of preglacial weathering 

 were not entirely obliterated. 



The granites and syenitic granites are glaciated in still more irregular 



