126 GLACIAL GKAVELS OF MAINE. 



tlie ice still remained over the Moosehead region to the north, the glacial 

 streams would bring down well-polished sediment, while, when the ice had 

 melted over the Piscataquis Valley, this rounded sediment, as it was poured 

 out by the glacial streams on the steep slopes in Blanchard, would l3e 

 transported by the swift Piscataquis River and deposited on the more gentle 

 slopes in Abbott. In this way we may account for valley drift containing 

 stones having the shapes of the glacial gravels. Of course the stones woiild 

 be somewhat rounded while being transported by the river, but these stones 

 are roiuider than I find in the beds of even the swift streams that come 

 down from Mount Katahdin. With respect to the ice they were frontal 

 matter. 



From Abbott a line of ridges and teiTaces of unmistakable glacial 

 gravel, interrupted by several short gaps, is found on the south side of the 

 Piscataquis River, extending eastward through Guilford and Sangerville. 

 It then turns southeastward and follows the valley of Black Brook (a 

 stream flowing northwest into the Piscataquis River) past Dover South 

 Mills to the "Notch" in the northeastern part of Garland. All the way 

 from Abbott to the Notch the ridges are in general broad and plain-like, 

 some of them 50 and even 70 feet high, and are separated by frequent 

 gaps. Near Dover South Mills there are two parallel ridges for nearly a 

 half mile, which inclose a deep elongated basin. This enlargement of the 

 system about two-thirds of the distance up the slope closel}' corresponds 

 to the plexus of reticulated ridges in Prentiss, also on a northward slope. 



The Notch is a remarkably low pass which forms a natural gateway 

 through the range of rather high hills which border the Piscataquis Valley 

 on the south. The top of the pass is less than 100 feet above the Piscata- 

 quis River at the mouth of Black Brook. Approaching the Notch from the 

 northwest, many ridges and irregular terraces and mounds of glacial sand 

 and gravel are seen along the south flanks of the main ridge. Part, if not 

 all, of these are due to irregular erosion, by springs and streams, of a plain 

 of rather fine sand and gravel which was laid down at the side of the main 

 ridge of coarse gravel and cobbles. As a whole, this plain appears to cor- 

 respond to what I have termed the broad osar. In this case an osar was 

 first formed. Subsequently the channel became enlarged, not on both 

 sides, as usually happens, but almost wholly at the south side — the side 

 away from the glacial flow. In this broad channel was deposited a plain of 



