1895.] Geology and Paleontology. 571 
dammed lake. Mr. Upham, on the other hand, ascribes nearly all 
submergence to ice-dammed lakes, and admits none as marine except 
that which is proved by fossils. As often happens in such cases, the ` 
probability is that the truth lies between these wide extremes. Ice 
dams have played an important part, but not to the exclusion of marine 
submergence even at high levels. On the other hand, marine invasion 
is not available as an explanation for some of the most important areas 
of submergence.” 
' Mr. Taylor’s views of the subject under discussion are summarized 
in the following chronological conspectus, taken from the last paper of 
his series, from which it will be seen that they are of the medium 
character referred to above : 
“ As its maximum the great Laurentide glacier covered the whole 
area of the Great Lakes. By a correlation of the abandoned shore 
lines, moraines and outlets, and the gorges, recently submerged shores 
and rivers of this region the following order of events is made out for 
the post-glacial history of the Great Lakes. They are set down in 
seven principal stages with transitions or critical stages between. 
“1. Glacial, ice-dammed lakes. Outlets at Fort Wayne, Chicago 
and other places. Beaches correlated with moraines in Ohio. Glacial 
lakes fall by stages as outlets change on withdrawal of the glacier- 
dams. Land relatively high in the north but slowly subsiding. 
“ First transition: By withdrawal of glacier the Niagara river is 
opened and the upper lakes become united. 
“II. First Niagara lakes. First epoch of Niagara Falls begins at 
Lewiston. For a short time glacial Lake Iroquois receives the water 
from Niagara. Shore lines of lower levels of this glacial lake washed 
over and obliterated by later marine invasion. Gradual depression of 
land continues at north, finally opening Nipissing outlet. 
“ Second transition.—First two-outlet climax. Marked by the Algon- 
quin Beach. (Possible subdivision here for Trent river outlet). 
Gradual northward depression continues. First epoch of Niagara 
Falls closes at the Whirlpool. Epoch of Erigan Fall begins. 
“III. First Lake Algonquin. Outlet eastward over Ni ipissing 
pass. 
“ Third transition: Gradual northward depression continues. Nip- 
issing outlet brought down to sea level. Lakes become marine. 
“IV. Warren Gulf (rising stage). Marine waters fill the three 
upper lakes, the Ontario, St. Lawrence, and Winnipeg basins. 
“ Fourth transition: Marine climax. Marked by the Chippewa 
Beach. Northward depression eeases and gradual elevation begins, 
