Tlie Siii-ijiid Ldhc Ahjo/Kjiiiii. — Tai/Ior. 167 
Palisades of the Minnesota shore are probably due to the same 
cause.* 
The Nipissing lieaeh is now submerged 25 feet at Duluth. 
But before tlie eastwartl uplift l)egan lake Superior had be- 
come independent and its level liad fallen 50 feet, or to the 
level of the Sault beach. It follows that when this last beach 
was formed the level of lake Superior at Duluth was relativel}'- 
75 feet lower than it is to-day. The submerged channel of 
the St. Louis river eroded 40 to 50 feet in glacial drift from 
Fond du Lac to tiie harl)or of Duluth. and probably more or 
less refilled since, points strongly to a period of tlie lake at 
the supposed Sault beach level. t 
Xiagara and Lake AUjoiKiuai. But far away fi'om lake 
Superior and the Sault there is another chronometer of the 
time since lake Algonquin lost its northern outlet. It is a part 
of the gorge of Niagara river. During the comparatively 
short life of lake Algonquin, and through all that much longer 
time while the sea filled the ancient Nipissing strait, the great 
cataract of to-day did not exist. During that time the chan- 
nel of the Niagara river was occupied by a small stream which 
drained only lake Erie. The cataract of that stream was a 
small thing compared with that of to-day. Dr. Spencer has 
called this the Erigan river, and we may appropriately call 
its cataract the Erigan fall. Its volume was about the same 
as that of the present American fall, or about three-elevenths 
of the whole stream. The great diiference in the magnitude 
of the Erigan and Niagara rivers leads one to expect that 
there would be at least some degree of difference of a corres- 
ponding kind between the gorges which their cataracts would 
make. And sucli a difference is there plainl}' enough. From 
the Horseshoe fall to a point a few rods above the cantilever 
railroad bridge there is a wide deep pool. The water in it is 
somewhat turbulent, but that is evidently not due to any fea- 
ture of the pool itself so mucli as to the powerful currents 
that invade its depths from the foot of the present cataract. 
At the cantilever bridge, however, the gorge becomes percep- 
tibly narrower and undoubtedly shallower, and the wild fury 
*Ijiiws()ii, ()|). cit.. piiii'i's Ii>7-S. 
f Mr. Warren Upliani. in TwrnU -sccund Ann. Itipl. lli'ol. and Nal. 
Hist. Survcvof Minn.. r.)r iSlK!. I'arl III. p. <")l. 
