256 The American Geologist. April, is% 
ever, were attributed to glacial lakes and the efficiency of the glacier to 
act as a dam for waters of such magnitude was never questioned. The 
marine hypothesis was held for other reasons. In the first season's 
work 1 thought I discovered a rather sudden break in the ancient water 
planes at Petoskey ; and there is in fact a change of gradient near that 
place, although, as I have since found, it does not appear so conspicu- 
ously anywhere else on that parallel. Another error, as it now appears, 
was the assumption that the highest beach of tiie north end of Green 
Bay is continuous with that back of Marquette. The interval of dis 
tance was too great for the inference of continuity. I entertain no 
doubt now that the beach at the former place was made after the with 
drawal of an ice-dam which held up the water at the latter. 
To my mind the disproof of the northward straits from lake Superior 
greatly weakens the marine hypothesis, and it strengthens the glacial 
hypothesis correspondingly. I was still further impressed with the 
easy possibility of an ice dam for lake Algonquin, when I visited the 
deep narrow valley of the Ottawa river. In short, by the past season's 
explorations, the relation between my two working hypotheses is com- 
pletely reversed. The primary presumption is now strongly in favor of 
the ice barrier, while the marine hypothesis has fallen far behind, 
almost out of sight. A small residue of facts in the basin of lake 
Temiscamang still suggests the possibility of a short, shallow marine 
invasion of the Great Lakes. But this possibility is remote and will 
probably vanish on more complete investigation. If lake Algonquin was 
glacial, there is little reason left to suppose that lakes Iroquois and 
Agassiz were not the same. 
The acceptance of these views necessitates a radical revision of two 
or three of my earlier papers, especially with reference to certain names 
used in them. What I called the " Chippewa " beach (Am. Jour. Sci., 
April, 1895) is in reality the northern extension of the Algonquin beach, 
and the term "Chippewa " so used will therefore be dropped. The 
terms "First" and "Second," as applied to two supposed similar 
stages of lake Algonquin (Am. Geologist, Feb. and March, 1895), will 
also be dropped, the name " lake Algonquin " remaining as previously 
used by Prof. Spencer. It becomes necessary also to find some appro- 
priate name for the waters which made the Nipissing beach, and it 
seems very desirable to use the word Nipissing. The three upper lakes 
at this period were three separate bodies of water just as they are to-day. 
Hence, in place of the name " Second Lake Algonquin " I have adopted 
the name " Nipissing Great Lakes," and so we may speak of the Nipis- 
sing beach of the Nipissing Great Lakes, just as we do of the Algonquin 
beach of lake Algonquin and the Iroquois beach of lake Iroquois. The 
facts gathered and recorded in the papers already published are not af- 
fected in any way by this change of hypothesis, except that they are 
put in better order by it. 
The lake history is now so far worked out that I can state without 
fear of contradiction that there are only two great, strongly developed 
shore lines which mark critical lake stages for the whole area of the 
