102 GLACIAL GRAVELS OF MAINE. 



in connection with the Katahdin system. It has not been possible thus far 

 to distinguish in these plains the gravels brought down by thfi respective 

 glacial rivers. 



The amount of sediment transported by this long osar river is ver}^ 

 great. The more noticeable features of this gravel system are the fol- 

 lowing: For most of its course the gravel takes the form of a two-sided 

 ridge (osar proper) with arched cross section. At intervals are found 

 several reaches of a low, broad ridge or plain, rather flat on top in cross 

 section, but in longitudinal section, both up and down, parallel with the 

 surfaces passed over by the system. The stratification of this plain is rather 

 horizontal or slightly arched in cross section. To this plain-like enlarge- 

 ment of the osar I have given the name broad osar, or osar-plain. In 

 places this plain enters a valley, and it then for some miles fills the bottom 

 of the valley from side to side, like a plain of valley drift, and is often 

 eroded into terraces. The broad osar in such situations is readily distin- 

 guished from valley alluvium by the more rounded shape of the pebbles 

 and by the fact that the plain soon leaves the valley and is found on the 

 hillsides where no ordinary stream could have deposited it, the pebbles and 

 all other features exactly resembling that portion of the plain found in the 

 valley. On the north it originates about 700 feet above the sea, and it ends 

 in Columbia but a few feet above high tide. Five times it leaves large 

 valleys of natural drainage and crosses hills into other valleys, besides 

 crossing many minor elevations. Its remarkable meanderings are in gen- 

 eral determined by the relief forms of the land, since it does not cross hills 

 more than about 200 feet high, measured on the north, but it does not always 

 follow the lowest passes. Reaches of fine matter alternate with coarse, 

 and where the coarsest matter appears the system generally takes the form 

 of reticulated i-idges inclosing basins. The most abundant deposits of 

 large stones and bowlders are in the granitic region of the lower Narra- 

 guagus Valley. North of Springfield there are only two places where the 

 stones are very large: One in Prentiss, at the middle of a long slope of 15 

 miles northward, and one at Macwahoc, near the middle of a southward 

 slope of more than 20 miles. Intermediate between these two points (near 

 Kingman, at the bottom of the deepest valley which the system crosses) 

 the material is unusually fine, i. e., fine sand. The gaps in this gravel system 

 are less numerous and shorter than in any other of the long systems. 



