﻿I38 NEW YORK STATE MUSEUM 



the plain at Watertown was 200-250 feet, at Lafargeville about 

 350 feet, and over the plains at Chippewa Bay about 550 feet. 



Eventually the ice barrier weakened in the St Lawrence valley and 

 the Iroquois waters found a new outlet north of the Adiron- 

 dack^ which was lower (at that time) than the old outlet 'south 

 of the Adirondacks by the Mohawk valley. One point of escape 

 was the " Covey Hill gulf," precisely on the international bound- 

 ary between New York and Canada, about 4 miles northeast of 

 Clinton Mills. 1 The Covey gulf is a great V-shaped gorge in hard 

 Potsdam sandstone, leading north of east, and it carried the waters 

 of the second stage of Iroquois, or the Hypoiroquois, over to some 

 lower level in the Champlain basin. From aneroid measurements 

 it is estimated that the altitude of the head of the gulf is about 

 850 feet, or perhaps somewhat higher, but when the gulf was made 

 the district was at least 460 feet lower than it is today, and must 

 have been lower than the Rome outlet, which is now 430 feet. It 

 appears that the Covey gulf outlet was not much lower that the 

 Rome outlet, perhaps 50 feet and possibly 100 -feet. It might seem 

 as if the Covey gulf outlet represented sufficient length of time 

 for the lake waters at that level to produce recognizable features 

 along favorable stretches of the shore line, and such may yet be 

 found. Dr Gilbert has suggested that possibly the Covey gulf was 

 chiefly cut by a more ancient glacial outflow and that the Hypo- 

 iroquois may have done little work beyond clearing out the old gorge. 



As the ice front melted back this second stage of the glacial 

 waters of the Ontario basin found yet lower escape along the north 

 side of Covey hill, between the ice wall and the rock slope. This 

 third phase of the Iroquois waters must have been short-lived, with 

 rapidly falling levels, the river flow only terracing the sandstone 

 slope. It is thought that the final effect of this down-draining of 

 the glacial waters was to bring them into confluence with the oceanic 

 waters which then occupied the Champlain basin and are called 

 the Champlain (Woodworth's Hoehelagan) sea. The supposed ex- 

 tension of the sea-level waters into the Ontario basin is known as 

 Gilbert gulf. 2 



Gilbert gulf. If our present conception of the history is 

 correct the sea-level waters covered nearly . all the territory 

 comprised in our five quadrangles. On the north slope of 

 Covey hill the Champlain beaches have an altitude of at least 

 460 feet, which is the measure of the amount of land uplift in 



1 For description and illustrations of this outlet see paper by J. B. Wood- 

 worth, Ancient Water Levels. N. Y. State Mus. Bui. 84. Ebenezer Emmons 

 and G. K. Gilbert had noted the feature. 



2 Gilbert Gulf (Marine Waters in Ontario Basin). Fairchild. H. L. Geol. 

 Soc. Am. Bui. 17:712-18. 



