in Europe and North America. 339 
feet above the sea, and 1929 feet deep; and its bottom is there- 
fore 1229 feet below the level of the sea. On the borders of 
these lakes the rounded rocks and the well known glacier- 
stranded boulders, high on the mountain-sides, attest that these 
deep valleys were filled to the brim by a vast system of glaciers 
that flowed southerly from the snow-shed that runs from the 
eastern side of Monte Rosa, by the Rheinwald-horn, to the top 
of the valley of the Adda,—a system of glaciers so large that, 
hike that of Aosta and Ivrea, further west, they protruded 
their ends and deposited their moraines far south on the plains 
of Piedmont and Lombardy. 
The glacier of Ivrea, when it escaped from the valley of the 
Doire, deposited a moraine at its side, east o 
Ivrea, rising in mere débris 1500 feet above the plain, and 
Spreading out eastward in a succession of fan-shaped ridges 
miles in width. The vastness of this mass gives a fair idea 
of the huge size of the glacier, and of the great length of time 
it must have endured; and just as this glacier hollowed out 
the little rock-basins in which lie the tarns that nestle among the 
arge roches moutonnées between the town and the moraine,” so, 
deep as the hollows of the great lakes of Maggiore and Como 
are, I believe they also were scooped out by the grinding power 
of long-enduring ice, where, under favorable circumstances, the 
aciers were confined between the mountains, and therefore 
thicker than the glacier of Ivrea where it debouched on the 
plam. Diagrams illustrative of this subject should be drawn on 
4 true scale; otherwise, height, depth, and steepness being ex- 
aggerated, the argument becomes vitiated. I have not the data 
Xt giving an actual outline of the bottom of the Lago Mag- 
lore; but a line drawn from the upper end of the lake to the 
Tequired depth near the Borromean Islands gives an angle only 
of about 3° in a distance of about 25 miles, and from thence to 
the lower end of the lake (12 or 13 miles) of about 5°. T 
depths of Maggiore and Como do not, in my opinion, militate 
against my view; for, if the theory be true, depth is a mere 
lake begins; and where the ice was on the largest scale near the 
Borromean Islands, there the lake is deepest. ; 
Summary with regard to the Alpine Lakes,—And now, in re- 
viewing the subject of the origin of the lakes of Switzerland and 
North Italy, I would remark— 
___? There are other well known lakes dammed up by the moraine of this great 
