Davis.} 
358 
[January 18 , 
upon stratified deposits at C would simply show a late advance of 
the ice, and bear testimony to its small erosive power ; these strat- 
ified deposits, when of Alpine origin, were probably brought on 
the advancing ice, and washed from its foot. 
That the Alps have been higher than now, as the first supposi- 
tion allows, and the third and fourth suppositions require, is 
strongly indicated by their former glaciation. Elevation is now 
the main cause of the present moderate glaciation of these moun- 
tains ; former greater elevation goes far towards explaining their 
former greater glaciation. 1 The fourth supposition has the advan- 
tage over the third of placing the extension of glaciers within this 
period of elevation instead of after it, and in this it agrees with 
the first. 
As already stated, it is impossible to arrive at any quantitative 
estimate of the share that these several causes may have had in 
the result, and this want of definite conclusion is made the ground 
of complaint by some against this class of observational studies. 
W e may well say on the other hand, that considering the progress 
made toward an explanation of these phenomena in the past hun- 
dred years, we — or our younger friends — may fairly hope for a 
definite conclusion in the next; and that the unsatisfactory aspect 
of the case at present is not its proper indefiniteness, but rather the 
premature assertion of final explanations without sufficient basis. 
In looking at the north and south valleys of the Italian slope 
of the Alps, we find them in a variety of conditions : beginning 
at the west, there is the Dora Baltea, which led a vast glacier 
down from Mont Blanc to the great moraines of Ivrea, and yet is 
lakeless excepting for several small basins caught in the moraine 
(C. 13) ; the Sesia, lakeless ; the Toce (its old course to Arona) 
with Lago d’Orta ; the Ticino with Lago Maggiore, and several 
small lakes — Camobbio, Varese — between the morainal deposits; 
the small valleys of the Agno and Cassorate, of less size than 
many lakeless valleys, and yet occupied by Lago di Lugano ; the 
Adda, with Lago di Como in its branching course, and Annone, 
Pusiano and others in its terminal moraine; the Bremba and 
1 Certain geological arguments in favor of former greater elevation are pi*esented by 
Medlicott, The Alps and the Himalaya, Geol. Soc. Journ., xxiv, 1868, 34. 
