FORMER COURSES OF THE ANDROSCOGGIN RIVER 237 



These facts coupled with the character of the Androscoggin 

 valley near Gorham indicate strongly that formerly the divide 

 was along the Carter-Moriah and Mahoosuc ranges. If this were 

 the case, the upper Androscoggin had another outlet and the only 

 possible alternate course would have been through the valley now 

 occupied by the Upper Ammonoosuc to the valley of the Connecti- 

 cut at Groveton. 



The broad valley of the Upper Ammonoosuc extends eastward 

 from the Connecticut and connects with the valley of the Andros- 

 coggin by three broad, low passes. 



The most southerly of these passes {A on Fig. 3), between 

 Berlin and West Milan, is traversed by the Grand Trunk Railway 

 and its summit is less than 100 feet above the Androscoggin at 

 Berlin. Dead River, a small, sluggish stream, heads in this pass 

 and joins the Upper Ammonoosuc at West Milan. Dead River 

 appears to have been beheaded near Berlin and before that accident 

 it was undoubtedly large enough to make the broad valley which 

 it now occupies. 



The next pass to the north (B on Fig. 3) lies between West 

 Milan and Dummer. It is broad, with a summit approximately 

 100 feet above the Androscoggin. No bed rock is visible in the 

 saddle or on its slopes, and it has every appearance of being deeply 

 drift-filled. 



The third pass (C on Fig. 3) is about three miles farther north, 

 where a broad branch valley connects with the Androscoggin 

 valley by a pass approximately 100 feet above that river. This 

 pass is very broad with gentle slopes, and no bed rock is visible. 



The broad valley between Groveton and West Milan is occupied 

 by the Upper Ammonoosuc River. The narrowest part of this 

 valley is 6 miles west of West Milan, but it is probable that a lake 

 a few miles to the north marks the preglacial course of the river. 



The valley of the Upper Ammonoosuc was deeply filled by 

 glacial deposits, which have been only partially cleared out by the 

 present stream; and it is obvious that the preglacial valley was 

 much too wide to be accounted for by the erosive action of the 

 present river. The branch valley toward pass C is floored with 



