104 GLACIAL GEAVELS OF MAINE. 



and fluviatile drift. The details are complex, and space does not permit a 

 full discussion of the problem The most probable interpretation of the 

 facts is that we have all three forms of drift represented in the Mattawam- 

 keag terraces and that the glacial river followed the route above indicated. 



Length from Mattakeunk to No. 3 Pond, about 15 miles. 



Several narrow ten-aces of water-washed gravel are found at intervals 

 in the valley of the Penobscot in Winn and Lincoln. They are found at 

 least 50 feet above the Penobscot River, and are probably sea beaches. 



KATAHDIN SYSTEM. 



This is an extensive osar system, deposited by a very large glacial 

 river which drained the region about Mount Katahdin and which was 

 remarkable for the number of its tributary branches. It is uncertain which 

 is the longest tributary of this rather inaccessible system. 



A horseback, or two-sided ridge, passes the Seboois farm, near the west 

 branch of the Seboois River in T. 6, R. 7, Penobscot County. It is known 

 to extend 3 miles northward into the forest. It passes only a few rods- 

 from the farmhouse and has been cut through at this point by a road to- 

 the depth of 12 feet. The stones are so angular that at first sight the ridge 

 appears to be a meandering lateral moraine. A more careful examination 

 shows that the finer detritus has been washed out of the mass and that the 

 stones have been slightly water polished. It is thus proved to be a form of 

 glacial gravel, the residue left after the till had been washed by gentle cur- 

 rents. The osar can be traced for several miles southward nearly parallel 

 with the west branch of the Seboois River, but it disappears near where 

 this stream enters the remarkable canyon by which the Seboois penetrates 

 the Katahdin highlands. This gorge extends from near the junction of the 

 two branches of the Seboois River almost to the junction of this river with 

 the East Branch of the Penobscot. For several miles at the north end of 

 this wild gorge the rocky hills slope steepl)'' down to the river, and there is 

 a constant succession of rapids; naturally there is but little water drift in 

 this part of the valley. Southward the valley widens here and there and 

 contains a plain of sand, gravel, cobbles, and bowlderets. In places the plain 

 is about one-foui-th of a mile wide and rides 30 or 40 feet above the present 

 bed of the river. From one to three terraces of erosion border tlie river. 

 The stones have been much more water rounded than those found in the 



