IROQUOIS WATER NORTH OF ADIRONDACKS 219 



Although the beaches had been found east of Watertown, as at Pitcairn, 

 Professor Fairchild drew a glacial dam, as presented on his map, 3 right 

 over them, but later he has abandoned this theory, and finds that the 

 Iroquois Beach continues farther eastward. 4 Thus he confirms my early 

 hypothesis of open water north of the Adirondacks, although one time I 

 regarded it as marine. 



On personally making the investigation of the Mohawk outlet of Lake 

 Iroquois, the terraces were observed higher than its water plane. This 

 fact threw a new light on the shorelines north of the Adirondacks, and 

 seemed to justify the correlation of the beaches and terraces occurring 

 there with those of the Mohawk, as well as indicating that there were 

 also lower ones corresponding to the Iroquois level. I then zigzagged at 

 proper elevations and found the repetition of the terraces or beaches ex- 

 tending to the northeastern angle of the Adirondacks plateau. The 

 marine deposits were also studied. All the measurements bearing on the 

 deformation have been triangulated, with the results that shorelines of 

 the region of northern New York and beyond the Saint Lawrence are 

 now explainable in a manner not previously understood. 



Iroquois Shore and higher Terraces in the Mohawk Valley 



Southeast of Lake Ontario, the Iroquois Beach sweeps around an em- 

 bayment now well known as the Eome outlet of Lake Iroquois. An out- 

 let of the Ontario basin along this route was mentioned by Professor 

 Newberry 5 as early as 1871, if not before. This was long prior to the 

 first investigation of Lake Iroquois. 



At Eome the embayment is 2 or 3 miles wide, with the floor covered 

 by the delta deposits brought down by the Upper Mohawk. This gradu- 

 ally narrows to a valley, which is still a mile wide at Herkimer, 27 miles 

 distant in a direct line, and 12 miles south of the latitude of Eome. Six 

 miles farther east, at Little Falls, the valley contracts to little more than 

 a quarter of a mile, and here the river passes through a rock-walled 

 channel ; but a mile and a half below the valley abruptly broadens out. 

 At Little Falls the rapids descend 40 feet over an ancient rocky divide 

 between two preglacial valleys, now deeply filled with drift, including 

 interglacial clays, which are covered with the shore and delta deposits of 

 Lake Iroquois. The modern Mohawk Eiver, below Eome, appears to be 

 flowing contrariwise to the direction of the ancient rock-bound valley, 

 but in doing so it is simply coursing its way over the plains and delta 



•Twentieth Ann. Kept. State Geological Survey of New York. 1002. 

 4 New York State Museum Bulletin No. 158, 1012, pp. :?2-.'<r>. 

 6 Geology of Ohio, 1871. 



XVI— Bull. Gbol. Soc. Am., Vol. 24, 1912 



