2 F. B. TAYLOR—-ORIGIN OF GORGE OF WHIRLPOOL RAPIDS. 
observation, even the extreme differences of width and especially of 
depth in the gorge are not in themselves particularly striking. The 
width and depth in the different sections had to be made known accu- 
rately before their import could be clearly perceivable, and this was not 
possible until the gorge had been surveyed and mapped and some attempt 
had been made to ascertain its depth by soundings or by some other 
method of safe inference. Not so, however, with the Greatlakes. Their 
changes are represented by phenomena of large magnitude. Their epi- 
sodes are generally clearly defined and separated, and there is little 
lability of mistaking the import of their characters. 
The four outlets —The cataract draws its power from Erie, Huron, Michi- 
gan, and Superior, the four great lakes above it. During the retreat of the 
last ice-sheet, when lake Huron was perhaps half uncovered, the waters 
of glacial lake Warren fell away and lake Erie was left independent of 
its three larger neighbors to the north, and has remained so ever since. 
It is the changes of these three that have most affected the history of 
Niagara. he relief of the boundary or rim of the watershed of the 
three upper lakes is such that with ashght amount of tilting this way or 
that, one or another of four different outlets, according to the direction of 
tilting, may become the way of discharge.* Only one of these, which is 
the present outlet at Port Huron through the Saint Clair and Detroit 
rivers and lake Hrie, conducts the water to Niagara. One of the others, 
situated at Chicago and lacking only a few feet of being active at the 
present time, would carry the water to the Mississippi;+ but this outlet 
has not been active since modern Niagara began its career. Another 
outlet that was probably active for a short time since Niagara began is at 
Balsam lake, in Ontario, and carried the water down the Trent valley to 
the basin of lake Ontario.{ The remaining outlet, situated at North 
Bay, Ontario, about 70 miles northeast of the north end of Georgian 
bay, appears to have been active for a relatively long time.§ By this 
*F.B. Taylor: ‘tA short history of the Great Lakes,’ being chapter x in ‘‘ Studies in Indiana 
geography,” edited by Prof. C. R. Dryer. (Inland Publishing Co., Terre Haute, Indiana, 1897.) 
7 Frank Leverett: ‘“‘ Pleistocene features and deposits of the Chicago area.” Chicago Academy 
of Science, Bull. no. ii, May, 1897. : 
F. B. Taylor: ‘Correlation of Erie-Huron beaches with outlets and moraines in southeastern 
Michigan.” Bull. Geol. Soc. Am., vol. 8. 1897. 
tJ. W. Spencer: ‘‘ Notes on the origin and history of the Great Lakes of North America,” (Ab- 
stract) Proc. Am, Assoc, Ady. Sci. 1888, p. 199; ‘‘ Deformation of the Algonquin beach, and birth 
of lake Huron,” Am. Jour. Sei., iii, vol. xli, 1891, p. 19. i 
G. K. Gilbert: “‘The Algonquin river,” (Abstract) Am. Geol., vol. xviii, Oct., 1896, p. 231. 
2G. K. Gilbert: ‘The history of the Niagara river.” Sixth Ann, Rept. Com’rs of State Reserva- 
tion at Niagara, Albany, 1890, pp. 72-73. Same in Rept. of the Smithsonian Inst., 1890. 
F. B. Taylor: ‘The ancient strait at Nipissing,” Bull. Geol. Soc. Am., vol. 5, 1894. Same in Am. 
Geologist, vol. xiii, March, 1894, p. 220; ‘‘ A reconnaissance of the abandoned shorelines of the south 
coast of lake Superior,’ Am. Geologist, vol. xili, June, 1894, p. 370; ‘‘ The second lake Algonquin,” 
Am. Geologist, vol. xv, Feb. and March, 1895, with *‘ Preliminary notes on studies of the Great 
Lakes made in 1895,” Am. Geologist, vol. xvii, April, 1896, p. 253-257; ‘“‘A short history of the Great 
Lakes,”’ as above. 2 
x 
