﻿GEOLOGY OF THOUSAND ISLANDS REGION I45 



hagen and Champion are the glacial channels [see footnote 

 p. 142]. The Rutland Hollow is a capacious valley cut ob- 

 liquely across the nose of the promontory, parallel in direction with 

 both higher and lower glacial channels of Black valley outflow, and 

 was undoubtedly given its form and dimensions by glacial drainage. 

 When the Black valley waters were lowered into Lake Iroquois the 

 Black river built its delta in the lake northwest of Carthage, partly 

 banked against heavy moraine. When Lake Iroquois was lowered 

 into Gilbert gulf the Black river found its ancient course obstructed 

 by the delta and moraine deposits and was compelled to follow 

 around the rock promontory in the path of the stronger shore cur- 

 rents in the lake. West of Watertown the river dropped its detritus 

 in the sea-level waters (Gilbert gulf), and when these waters were 

 lowered by the land uplift the river pursued its chance course over 

 the rock toward the retreating water body. 



To epitomize: It seems certain that the earliest drainage which 

 we can locate must have been along the weak zone of the overlap 

 of the sedimentary rocks on the Precambric, in north and north- 

 east continuation of the Black valley. Preceding the latest ice in- 

 vasion the Black river probably flowed north. Just what may have 

 occurred during the Tertiary uplift and the earlier Pleistocene we 

 do not know. It is possible that there are unsuspected elements 

 in that long history, but there is no discovered reason for any 

 preglacial southward drainage across the divide as mapped in plate 

 43. The really uncertain factor is the glaciation earlier than the 

 Wisconsin epoch. The writer is inclined to credit to glaciation 

 earlier than the Wisconsin considerable influence in producing the 

 parallelism of the rock forms and the drainage lines along the St 

 Lawrence depression; and the bluntness and roundness of the Rut- 

 land promontory ; and the cutting of the Rutland Hollow. 



Topographic features. Parallelism. The topographic ele- 

 ments of the area have a conspicuous parallelism, about northeast 

 and southwest, in accordance with the St Lawrence valley and river. 

 On the Clayton and Theresa sheets this shows clearly in the stream 

 and valley courses and in the trend of the plateaus and rock hills. 

 On the Alexandria and Grindstone sheets the parallelism appears 

 in the elongation of the rock knobs and the form of the lakes and 

 the islands in the river. This character prevails down the valley 

 far beyond our district, as shown by the river courses which instead 

 of flowing directly to the St Lawrence follow along in parallel 

 courses [pi. 43]. 



