394 ^'''''^ American Geologist. june, isos 
regard the hypothesis of glacial dams as "a result of logical reasoning". 
The doctrine in favor of glacial dams is certainly no stronger and no 
more ably supported by distingviishe'd opinions than was the question 
of glacial excavation of lake basins, which my investigations, in spite 
of the opposition at the time, have aided in dispelling. The change of 
opinion which has taken place in this great subject gives me confidence 
in not accepting the hypothesis of glacial dams based upon evidence 
which, although often plausible, recedes on being approached. 
The first point in question is the hypothesis of the termination of 
deserted beaches against moraines. To reiterate, there are three notable 
examples where glacial dams have been theoretically located, nam.ely 
at North Adams, New York, at Crittenden, New York, and at Cleve- 
land, Ohio. At both Crittenden and Cleveland Mr. Leverett announced 
what he considered the termination of the beaches against moraines, 
which, if the facts were correct, would become very strong evidence. 
But in the case of North Adams I found the continuation of the Iro- 
quois beach beyond that point, a fact since recognized by the author 
of the dam. Prof. Gilbert. Mr. Leverett's conclusions as to the ter- 
mination of the Forest beach at Crittenden have since been set aside 
l^y Prof. Fairchild's discovery of its extension farther eastward without 
finding its termination. Again, at Cleveland Mr. Upham found that 
the beach extended beyond the morainic termination, and suggested 
that it probably reached ten miles farther. Thus when beaches have not 
been traced to their terminations against moraines, in the best known 
localities where such phenomena have been described, and failed of 
establishment, it seems illogical to cite such as a diagnosis of glacial 
dams; — the more so as contradictory evidence is suggested in the ter- 
races farther east. Although I recognize the important contributions 
towards the final history of the Great lakes by those who use the 
glacial dam as a working hypothesis, yet the evidence so far adduced 
as to the location of the ice barriers themselves can only lead to the 
verdict of "not proven". 
In 'my paper referred to I have mentioned terraces upon the southern 
side of the Adirondack mountains, — I may also add upon the southern 
and eastern sides of the White and Green mountains, — as occurring 
at hundreds of feet above the low lands, and having the same character- 
istics as the terraces upon the northern side of the mountains, which 
last have been regarded by some as originating in glacial dams. Al- 
though the observations extend over hundreds of miles and are of as 
much importance as the beaches about the western end of the lakes, 
they have been left unexplained by the advocates of trlacial dams. Yet 
for several years I have thrown down the challenge for their elucidation. 
"Faith", says my critic, "in the harmony of the universe inspires con- 
fidence that the features of debatable origin, in which Dr. Spencer has 
taken refuge as a defense against glacial dams (page 117) and which 
have as yet received less attention than they merit, will some time 
be found consistent with tbe already well established facts and prin- 
ciples of geology, among which facts it seems safe to include glacial 
