FORMER COURSES OF THE ANDROSCOGGIN RIVER 247 



The capture of the Mahoosuc River by the Sebago River is 

 probably not due to glacial disarrangement, but is best explained 

 as preglacial piracy by the Sebago River. 



The economic effects of these drainage changes are very impor- 

 tant. The falls at Berlin and Gorham are due to piracy; and 

 the pirate stream has not yet eroded the valley to grade. The 

 falls at Rumford, Livermore, Lewiston, Lisbon, and Brunswick 

 are due to the displacement of the river by glacial deposits. 

 These falls furnish a large amount of valuable water power and 

 there are important mills at all the places named. Prior to the 

 rearrangement of the drainage there was probably little if any 

 potential water power. When the pirate stream cut through the 

 divide it made an easy route through the mountains which is now 

 occupied by a railroad. 



