IGS 
7 7/ e A m e r ic <i )i (r e olog isf. 
March, 1895 
of the water as it rushes toward tlie ^\'llirlpool is [)laiiily due 
entirely to tiie eliuraeter of tliat })art of the g'or^'e. In siiort, 
the head of the old gorge of the Erigan river was a little above 
the cantilever bridge when the St. Clair outlet first opened, 
and it was there that the greater cataract of Niagara began 
its worlv. The distance from the falls to this point is a little 
less than two miles, and this represents the work of modern 
Niagara since it replaced the Krigan river. The facts seem 
to show that probably about half of this work was done dur- 
ing the progress of the simple northward uplift and before 
the great eastward elevation had begun. 
In his recent admirable paper on the "Duration of Niagara 
Falls."' Dr. Spencer has presented a more elaborate discussion 
of the development of the Niagara gorge than has ever been 
made before.* His cross-sections of the gorge are particularl}'^ 
instructive. With some slight omissions and additions I re- 
produce three of them here in 
tig. '1. It seems to me that there m^ 
can be no mistaking section (J, M^ 
which represents the Erigan gorge, ^ 
as the product of a much smaller 
stream than the greater Niagara 
which made sections D and E. 
This conclusion is still further 
)^' strengthened when we take into ac- 
count the obvious fact that the 
river in tlie Erigan gorge is much 
shallower than in the wider part 
above, probably not more than one- 
third as deep. But Prof. Spencer 
fails to offer what is, as it seems to 
me, the only true explanation of Im 
the Erigan gorge — the only expla- ■^■ 
nation whicli is perfectly correlated 
with the lake histor^Mis revealed in 
the deserted beaches. He explains 
the Erigan gorge by supposing it to have been made by the 
ureat cataract at a time when there was a sheer fall of 420 
P--^^ 
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N iaga ro-~--\. / 
:gtiSit«t^ .' 1 '.id^p J'/ 
MeiCn a-z=-.--- ^^\ 
-M 
-S?:v5\ 
*-'I)urjili()ii of Nia.siuru Falls," l)y .1. W. S[)<mi(;it. Am. 
vol. XLViir, Dt'C, 18!)4. 
uir. Sri., III. 
