1882 .] 
859 
[Davis 
Serio, lakeless ; the Oglio with Lago d’Iseo and well-marked 
moraines; the Chiese and Lago d’Idro ; the Sarca, with Lago di 
Garda, the largest of all, and projecting farthest into the plain, 
with a great, lobed moraine to enclose it; the Adige (=Etsch), 
one of the largest valleys, and yet lakeless ; a great part of the 
glacier of the last named valley seems to have turned westward 
at Rovereda and joined the neighboring valley of the Sarca; 
farther east, there are no large valley-lakes. It is very evident 
from this review that no single cause for the lakes will serve ; 
and it is noticeable that all these basins, with the exception per- 
haps of Idro, are connected with the great plain by open val- 
leys, in which the alluvium or diluvium is of unknown depth, so 
that their rock basin structure is not proven though possible. 1 
The lakes are described here because the moraines are at least to 
a certain extent their effective barriers, but these have been 
strongly aided by the conditions of our first supposition and prob- 
ably equally by some modification of our fourth. 
The several north and south lakes in Central New York are 
best placed here, but are slightly different from the preceding 
examples ; the moraine that forms their barrier 2 was deposited 
by a glacial sheet that moved against instead of with the slope 
of their valleys, and in this they resemble the third subspecies of 
glacial lakes (C. 2). Cayuga lake may serve as a type of its 
companions, Skaneateles, Owasco, Seneca, and Canandaigua. 3 Its 
trough was cut by an old stream flowing from the New York 
and Pennsylvania plateau, northward into Lake Ontario, 4 at a 
time when the drainage of the region ran in channels consid- 
erably below present river levels; glacial erosion has probably 
smoothed and deepened it, but to suppose it entirely so formed 
would imply the production of a tongue of ice from the front 
1 The conclusion reached by Gastaldi (Milano, Soc. Ital. Mem., i, 1865) in reference 
to this region is that there is no morainic amphitheatre without its lake (existing or 
extinct), just as there is no lake without its enclosing morainic amphitheatre. It 
should be noted that this does not involve the question of rock-basins, since the 
extinct lakes especially referred to about Ivrea and Rivoli have their enclosing 
moraines well advanced from the mountains out on the plain. 
2 Compare Spencer, Amer. Phil. Soc , xix, 1881, 333. 
3 Oneida Lake I have not seen. 
4 Compare Carll, Second Geol. Surv. Pa., m, 1880, 330. Hall, Geol. N. Y., 4th. Distr., 
says these lakes are in “valleys of erosion.” 
