102 w. UPHAM—NIAGARA GORGE AND SAINT DAVIDS CHANNEL. 
masses of the Niagara limestone, rolled about by the power of the water- 
fall, have worn the river bed toa maximum depth of nearly 200 feet be- 
neath the water surface. 
The narrowness of the gorge along the Whirlpool rapids is therefore 
attributed to the conditions of the river erosion here indicated, rather 
than to decrease of the volume of the river (which several geologists have 
thought probable or certain) by diversion of the water of the upper lakes 
to flow from lake Huron eastward. Studies of the glacial lake Agassiz 
and of the Laurentian glacial lakes convince me that the progress of the 
epeirogenic uplift of the northern United States and Canada from the 
Champlain depression was too rapid to. accord with the hypothesis of 
any outflow from lake Huron toward the east during the long time that 
would be required for the Niagara river, while thus diminished, to erode 
the gorge along the Whirlpool rapids. 
The explanations here given to account for the variation in the width 
of the Niagara gorge, and for its partly very rapid and partly very deep 
and gently flowing river, with the relation of this gorge to the Saint 
Davids channel and the upper continuation of that channel by a ra- 
vine, accord mainly with Dr Julius Pohlman’s discussion of the Niagara 
history; but his conclusion that the age of the river and of Postglacial 
time has been only about 3,000 years is here regarded as probably less 
acceptable than a higher estimate. The present writer thinks that the 
Niagara gorge implies for the Postglacial period, in harmony with Pro- 
fessor N. H. Winchell’s discussion of the recession of the falls of Saint 
Anthony, a duration between 5,000 and 10,000 years. 
NIAGARA GoRGE 
PHYSICAL FEATURES IN GENERAL 
A gorge about 63 miles long, extending southward from the Niagara 
limestone escarpment at Lewiston and Queenstown to the apex of the 
Horseshoe falls, has been eroded by the river since the withdrawal of the 
border of the continental ice-sheet from this district. The width of the 
gorge at its top varies mainly from 1,000 to 1,500 feet, but is ohly 650 
to 800 feet for three-fourths of a mile along the upper part of the Whirl- 
pool rapids and at the railway bridges. The depth from the brink of the 
gorge to the river is mainly about 300 feet, but is decreased above the 
rapids to about 225 feet. To this depth, however, must be added that of 
the river itself, making the whole depth of the gorge to the bottom of 
the water somewhat more than 400 feet at its northern end, at the Whirl- 
pool, and between the railway bridges and the falls. 
The sides of the gorge through all their length, excepting at the Foster 
‘N 
