THE ADIRONDACK MOUNTAINS 25 



changing abruptly from a southeast to a northeast course. Instead 

 of following the broad, low valley southward from Northampton, 

 this northeast course of the river takes it across a ridge of hard 

 rock at Conklingville and into the Hudson at Luzerne. The com- 

 paratively straight course of the East Branch Sacandaga has, for 

 at least 12 or 15 miles, been determined along a fracture zone of 

 weakness. The peculiar courses of both the Hudson and Sacan- 

 daga near the border of the Adirondacks will be explained in the 

 succeeding chapter. 



West Canada creek formerly continued its southwest course into 

 the Mohawk valley, but was forced to turn sharply to the southeast 

 from Trenton Falls because of a blockade of glacial debris accumu- 

 lated there during the Ice Age. 



About one-fourth of the Adirondacks, comprising the north- 

 eastern portion together with the vicinity of Lake George, drains 

 into Lake Champlain. Before the great Ice Age, Lake George did 

 not exist but there was a division of drainage between the Hudson 

 and Champlain valleys where the " Narrows " are now located. 

 Most of the streams entering Lake Champlain are east-flowing and 

 relatively short and swift. Two notable exceptions are the Saranac 

 and Ausable rivers. 



The main branch of the Saranac begins in the large chain of 

 Saranac lakes and pursues a northeast course straight across the 

 main axis of elevation of this part of the Adirondacks. The north 

 branch of the Saranac also cuts across the main axis of elevation. 

 Prominent earth fractures have probably been influential in deter- 

 mining these courses, though the region has not yet been carefully 

 studied. 



Both the East and West branches of the Ausable river have courses 

 largely determined along fault or fracture zones of weakness, the 

 deep gorge of the West branch, known as the Wilmington notch, 

 being a notable example of such influence. The main river flows 

 through the famous Ausable chasm near its mouth, this feature 

 being explained toward the end of the next chapter. 



About one-third of the Adirondacks drains directiv into the St 

 Lawrence river by many large streams which pursue normal north- 

 westerly courses from the prominent division of drainage across the 

 region. Among the more important streams are the Chateaugay, 

 Salmon, St Regis, Raquette, Grasse, Oswegatchie and Indian rivers. 

 After emerging upon the lowlands of the St Lawrence valley, most 

 of these rivers exhibit a remarkable tendency to swing northeast- 

 ward and flow nearly parallel to the great- river for some miles 



