774 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



500 feet and consequent deltas and silting; (2) the primitive Iroquois with 

 elevation much under 440 feet; (3) the rise of Iroquois to 440 feet and 

 consequent filling of former channels, and (4) the stream erosion subsequent 

 to Iroqaois. 



LAKE IROQUOIS. 



This lake, which occupied the Ontario Basin and discharged eastward 

 past Rome, N. Y., into the Mohawk Valley, will here receive only a brief 

 notice, for the writer has given but little attention to its shores and outlet. 

 Furthermore, it lies mainly outside the district under discussion. The 

 portion of its shore from near Toronto, Ontai'io, around the western end of 

 the lake and along its southern shore attracted notice in the early days of 

 settlement. It was utilized as a trail by the red men and adopted for a high- 

 way by the early white settlers. The name Iroquois, applied by Spencer, 

 was given it because of its use as a trail by an Indian tribe of that name. 

 The beach as determined by Spencer has an altitude of but 362 feet at the 

 west end of Lake Iroquois, near Hamilton, Ontario. Spencer has found a 

 marked rise on the north shore, the altitude at Trenton, Ontario, about 140 

 miles by direct line from Hamilton, being 632 feet. The south shore shows 

 a gradual rise from Hamilton eastward to the vicinity of Rochester, its alti- 

 tude there as shown by the topographic sheet being about 435 feet, but it 

 lies so nearly at right angles with the axis of uplift from Rochester eastward 

 to the Rome outlet as to be nearly horizontal. From the Rome outlet north- 

 ward the rise is very marked, the altitude being 440 feet in the vicinity of 

 the Rome outlet and 675 feet at Adams Center, only 60 miles to the north. 

 The rise is thought by Gilbert to be even greater, for uplift was in progress 

 while the beach was forming, so that it presents a compound form north of 

 the outlet. The upper members of the compound beach join the lower 

 members upon approaching the outlet, but are thought to pass below them 

 in the part of the. lake which extended south farther than the outlet. 



Lake Iroquois was apparently held up to the level of the Rome outlet 

 by the body of ice which still occupied the St. Lawrence Valley. Upon 

 the withdi'awal of that ice the sea entered the St. Lawrence Valley and the 

 Lake Ontario Basin, there being a beach containing marine shells exposed 

 at the eastern end of the lake. This beach stands very nearly 200 feet 

 below the Rome outlet. It passes below lake level near Oswego, N. Y., as 

 determined by Gilbert. The discovery of a marine shore line at this level 



