80 F. B. TAYLOR—ORIGIN OF GORGE OF WHIRLPOOL RAPIDS. 
the south side of the Eddy basin is the correlative of the breaking of the 
Ottawa ice-dam and the end of lake Algonquin. At the upper side of 
Wintergreen flat is put, provisionally, a line of division, marking an ap- 
parent place of expansion, which may be the correlative of the closing 
of the Trent valley outlet, supposing the discharge to have passed for a - 
time in that direction, but the problems of the sections below the Cove 
are not discussed in this paper. 
RELATIONS TO OTHER INTERPRETATIONS 
This interpretation of the gorge of Niagara has gradually unfolded 
during the progress of several years’ study and field work on the history 
of the Upper Great lakes. The work on the lakes has been supple- 
mented from time to time by studies in the gorge of Niagara, not so 
thorough in detail, probably, as those made by G. K. Gilbert and J. W. 
Spencer, but thorough enough, nevertheless, to reveal the main charac- 
ters clearly. So far as known to the writer, the first suggestion that the 
volume of Niagara may have varied in consequence of a discharge of 
the upper lakes in some other direction was made by Mr Gilbert at the 
meeting of the American Association for the Advancement of Science, 
in Buffalo, New York, in August, 1886.* Following him, the writer early 
adopted a modified form of the same idea, and the subsequent work on 
the Nipissing beach and the northern outlet has been in effect a contri- 
bution to the verification of Mr Gilbert’s original hypothesis; but while 
he first suggested a northern way of discharge for the upper lakes, Mr 
Gilbert has not, unless quite recently, fully accepted the complete cor- 
relation of the gorge of the Whirlpool rapids with the activity of the 
North Bay outlet.} 
v 
*G. K. Gilbert: “‘The place of Niagara falls in geologie history.” (Abstract.) Proc. Am. Assoc. 
Ady. Sci., 1886, p. 228. The first definite suggestion that the upper lakes discharged across Nipissing 
pass at North Bay appears to have been made in “ The history of the Niagara river” referred to 
above, but apparently no attempt was made then to correlate this episode of the upper lakes with 
any particular section or feature in the gorge. 
+ In “ Niagara falls and their history’ (Nat. Geog. Monographs, vol. 1, no. 7, Sept., 1895) Mr Gil- 
bert, in speaking of the data for time measurement, on page, 234, says: ‘‘At the Whirlpool the rate 
of gorge-making was relatively very fast, because only loose material had tobe removed. Whether 
the old channel ended at the Whirlpool or extended for some distance southward on the line of the 
river is'a matter of doubt.” Ina paper on “‘ The profile of the bed of the Niagara in its gorge” 
(Abstract in Am. Geol., vol. xviii, Oct., 1896, p. 233) Mr Gilbert expresses himself in the following 
terms: ‘*The shoals at Wintergreen flat and the Whirlpool rapids are correlated with epochs when 
the discharge of the upper lakes by the Trent and Mattawa valleys left the Niagara river and falls 
too small and weak for deep excavation.” 
This generalized statement is very satisfactory, and the present paper is in effect a partial analysis 
based upon the same principles. This statement appears to leave no doubt of his acceptance of 
the correlation of the gorge of the Whirlpool rapids with the episode of Nipissing Great lake; but 
in another paper read on the same day, entitled ‘The Whirlpool-Saint Davids channel” (Abstract, 
same reference), Mr Gilbert speaks reservedly, saying that it is ‘probable that the ancient gorge 
ended two or three hundred yards above the Whirlpool, but Pohlman’s theory that it extended to 
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