258 THE GLACIAL LAKE AGASSIZ. 



nizing an ice-sheet and referriug the high ancient beaches of tliis basin to 

 marine submergence, the same field has also been elaborately studied 1)y 

 Spencer/ According to the glacial theory held by Gilbert, which seems to 

 me the true one, while the retiring ice-sheet still rested against the Adiron- 

 dack Mountains, and thence stretched across the St. Lawrence Valley to 

 the Laurentide highlands north of Montreal and Quebec, the glacial Lake 

 Iroquois, outflowing at Rome, formed a well-marked beach which Gilbert 

 has mapped, with determinations of its height by leveling, from the Niagara 

 River east to Rome and north to the vicinity of Watertown. The Canadian 

 portion of this beach, surrounding the western end of Lake Ontario and 

 running along its northern side to the vicinity of Belleville, has been simi- 

 larly traced by Spencer. The height of Lake Ontario is 247 feet, and that 

 of the old outlet crossing the watershed at Rome is 440 feet above the sea- 

 level. Thence the highest Iroquois beach, in its course adjacent to the 

 eastern end of Lake Ontario, has a gradual ascent of about 5 feet per mile 

 along a distance of 55 miles northward to the latitude of Watertown, where 

 the highest beach is 730 feet above the sea, showing that a differential uplift 

 of about 290 feet has taken place, in comparison with the Rome outlet. 

 From Rome westward to Rochester the beach has nearly the same height 

 with the outlet, but farther westward it descends to 385 feet above the sea 

 at Lewiston and 363 feet at Hamilton, at the western end of Lake Ontario. 

 Contintiing along the beach north of the lake, the same elevation with the 

 Rome outlet is reached near Toronto, and thence east-northeastward an 

 uplift is found, similar to that before noted east of the lake, its amount 

 near Trenton and Belleville, above Rome, being about 240 feet. 



Only two surfaces of former levels, which are supplied by the old 

 shores of Lakes Warren and Iroquois, conduct us from Chicago to Water- 

 town and the mouth of Lake Ontario. Between the level of Lake Warren, 

 at the eastern end of Lake Erie, and the latest level and highest beach of 

 Lake Iroquois, at the western end of Lake Ontario, while it outflowed at 

 Rome, there is a vertical fall of approximately 500 feet; and from the latest 

 in the series of sevei'al Iroquois beaches near Watertown, where they 



'Papers before cited; also Am. Jour. Sci. (3), Vol. XLI, pp. 12-21 aud 201-211, with maps, Jan. and 

 March, 1891. 



