122 GLACIAL GRAVELS OP MAINE. 



become longer and approach the short osar type, and are sometimes broad, 

 hke osar-plains. It should be noted that in the discontinuous systems as 

 here defined the gaps are not due to erosion subsequent to the deposition of 

 the gravel, and they are as constant and noticeable a feature as the gravels 

 themselves. As a class they are quite nearly parallel with the movements 

 of the ice during the last of the Grlacial period. This makes it probable 

 that there was a movement of the ice southwest into Penobscot Bay about 

 12 miles along the western bases of the granite hills; but thus far it is not 

 proved by evidence of the scratches. 



MOOSEHEAD LAKE SYSTEM. 



The principal branches of this important system were remarkable for 

 being very widely separated at the north. TJiey drained the glacial waters 

 of a large part of the Penobscot Valley and its tributaries, and poured 

 them into the Penobscot Bay by a single channel. Estimating the amount 

 of water by the area drained, only three or four of the osar rivers of the 

 State probably equaled this river in volume, yet a dozen or more of them 

 exceed this in the quantity of sediment they have deposited. With insig- 

 nificant exceptions, the system traverses a region of slates and schists, and 

 it is the universal law that when an osar river passed through a granite 

 region its gravels are many times as abundant as those of rivers in slate 

 regions having the same length. The tributaries of this system are all 

 easily traced; they left ridges nearly as large as those of the main river. 

 The longest one of these is the Medford-Hampden osar. 



MEDFORD HAMPDEN OSAR. 



On the north it appears to begin as a series of ridges on the south 

 shore of South Twin Lake. It passes southward as a single two-sided 

 ridge. In crossing Seboois Lake it is said to appear at certain places as 

 "horseback islands," and farther south it crosses the valley of Schotaza 

 Creek obliquely. The above statements are made on the authority of Mr. 

 Eber Ames, of Medford, and are confirmed by many others. From near 

 Schotaza Creek I have followed the system all the way to Hampden. For 

 several miles north of the Piscataquis River it is a ridge 20 to 40 feet high, 

 with arched cross section and broad base. The gravel contained many 

 cobbles and some bowlderets, all well rounded, which proves that the ridge 



