156 GLACIAL GKAVELS OF MAINE. 



I find no signs of any glacial streams that could have deposited the last- 

 named plain except that delta branch of the Hartland system which radiated 

 southeast from the "Kingdom;" neither could I trace this system farther 

 south than the delta-plains in northern Appletou. 



SUMMARY. 



The Hartland-Montville osar river must have deposited its gravels late 

 in the osar period, or, like the Katahdin and other osars, it would have 

 deposited gravels all the waj^ to the sea. At this time the sea stood at or 

 near the contour of 230 feet, and the delta-plains of Liberty and Appleton 

 do not extend much below that elevation. In the Sebasticook Valley, for 

 about 20 miles, from Hartland to Unity, the system traverses a region that 

 was at one time submerged in the sea, as is proved without a shadow of 

 doubt by the great numbers of marine fossils found in the sedimentary 

 clays which partly or wholly overlie the glacial gravel. But at the time 

 when the delta-plains in Liberty, Appleton, Searsmont, and Montville were 

 being laid down, the Sebasticook Valley must have been covered by ice, as 

 is proved by the great size of the glacial streams by which only could so 

 large plains be deposited. The glacial waters of the Sebasticook region 

 then j^oured southward through the Hogback Mountain Pass over a divide 

 not far from 200 feet above the level of the osar at Unity Pond. Into the 

 north end of this pass two glacial rivers flowed from the north, one from 

 Unity and Hartland, the other from Freedom. At the south end of the 

 pass the system received another tributary, while from the enlarged chan- 

 nel or glacial lake at that point two delta branches diverged, one flowing 

 south and the other southwest, and they emptied into the sea at points 

 about 10 miles distant from each other. The narrow delta-plains in Liberty 

 and Appleton are in a level region, where, if the glacial river had flowed 

 into the open sea, they ought to have spread out in fan shape. That they 

 remained so long and narrow is an indication that they were not deposited 

 in the open sea, but in bays of the sea which extended back into the ice. 

 The question whether a stratum of floating ice was over these plains will 

 be considered elsewhere. The plain northwest of North Searsmont is more 

 broadly fan-shaped. Its northern end extends across the valley of Greorges 

 River, and the delta was probably deposited in the open sea. 



Did the two glacial rivers, which diverged from the south end of the 



