442 NEW YORK STATE MUSEUM 



and that west to the Ontario valley, was at Little Falls, the loca- 

 tion being determined by the Precambric rock mass there, 

 brought up by the Little Falls fault.^ Brigham has urged that 

 West Canada creek was, at that time, tributary to the west flow- 

 ing drainiage, which he names the Eome river, coming into the 

 valley at Oriskany by way of Hollaiud Patent.^ While the writer 

 quite coincides with this view, he is also disposed to the belief 

 that this route is comparatively modern, repreisenting a capture 

 of the upper part of the Black river drainage by a tributary of 

 the Eome river. Black creek, the main tributary of West Canada 

 creek, flows along the Precambric boundary in a northwesterly 

 course, and seems unquestionably to represent the former upper 

 portion of the Black river, as is shown in an excellent manner 

 on the new topographic map. There is heavy drift filling between, 

 but no sign of any rocky col, and the tributaries from the north- 

 east show perfect parallelism with the Black river head waters 

 comiing down from the same direction. 



Youthful character of the present drainage. During the with- 

 drawal of the Laurentide glacier from the northern Adirondacks, 

 the preglacial stream courses cut in the valley base level were 

 completely filled with glacial deposits, while at the same time the 

 irregular floor of the valley base itself was covered and evened by 

 them. After the departure of the ice, the courses of the streams 

 were determined hf the position and slope of these deposits, and 

 siome discrepancy between their present and former courses was 

 produced. The slopes of the glacial deposits in the valleys were 

 gentle, lakes occujn'ed the hollows more numerously than at pres- 

 ent, and the new streams obtained steep grades only after they 

 emerged from the hills on the slopes leading down to the Cham- 

 plain and St Lawrence valleys. Their profile was convex rather 

 than concave, and so it remains to a large extent today, while in 

 mature stream valleys the profile is concave. 



The main streams of the region are of respectable size, and their 

 slope is steep. The Saranac river from Lower Saranac lake to 

 Lake Ohamplain, in a course of about 75 miles by the river, has a 

 fall of over 1400 feet, nearly 20 feet to the mile. The Ausable, 

 from Lake Placid down, has a greater fall than the Saranac 



^U. S. Geol. Sur. 3d An. Rep't, p.362. 

 'Geol. Soc. Am. Bui. 9 :191. 



