MLbeet.] CHICAGO TO NIAGARA FALLS. 455 



and the Artemisia gravel, deposits likewise of great extent and con- 

 taining material of distant origin, but not yet satisfactorily interpreted. 



From Hamilton, at the bead of Lake Ontario, the train runs eastward 

 over a broad escarpment of red Medina shales (Upper Silurian) super- 

 ficially sheeted with till and clay similar to the Champlain. At the 

 left lies Lake Ontario; at the right the plain rises to the foot of an 

 escarpment several hundred feet in height, which is capped by Niagara 

 limestone. The plain is contoured by an old shore line of Lake Ontario, 

 known as the Iroquois beach. In the city of Hamilton at the head 

 of the lake this beach takes the form of an immense free spit or 

 embankment more than 100 feet in height. At other points it appears 

 as a low barrier of sand and shingle, and yet at other points as a low 

 bluff undermined by the waves. Since the date of the Iroquois beach 

 the lake water has also stood at a level lower than the present, and 

 during the period of low water the small streams which traverse the 

 plain opened valleys in the lacustrine clay. These valleys are now 

 partly occupied by lake water, being marked by small bays, to each of 

 which a small stream is tributary. 



Leaving the littoral plain, the train climbs the escarpment, SO as to 

 approach Niagara falls on the plain constituted by the upper surface 

 of Niagara limestone. 



NIAGARA FALLS. ».«. 



By (J. K. Gilbert. 



The Niagara river flows northward from Lake Erie to Lake Ontario. 

 The region is floored by Paleozoic strata, which dip at a low angle 

 toward the south or upstream. Two limestones are of physiographic 

 importance, the ( 'orniferous and the Niagara. Beneath the Cdrniferous 

 and above the Niagara are several hundred feet of shaly beds (Onondaga 

 salt group), yielding readily to erosive agencies. Beneath the Niagara 

 limestone are feebly resistant beds, known as the Niagara shale, the 

 Clinton beds, and the .Medina shale. As a result of this alternation of 

 hard and soft strata the district consists topographically of two sloping 

 plateaus, each limited toward the north (downstream) by an escarp- 

 ment. The Coruiferous escarpment, lying near Lake Erie, is relatively 

 low; the Niagara escarpment is about 200 feet high and faces toward 

 Lake Ontario. Lake Erie rests on the Coruiferous plateau, and the 

 Corniferous limestone determines the height of its water surface. 

 Across this limestone the river Hows with a rapid current. In the 

 region of shales beyond it travels more slowly and spreads out broadly. 

 It traverses the plateau of Niagara limestone in a narrow canyon, at 

 theSiead of which is a cataract. The passage through the canyon is 



