1862.] RAMSAY GLACIAL OEI&IN OF LAKES. 199 



rally in the same set of rocks as the other two lakes, is 700 feet above 

 the sea, and 1929 feet deep ; and its bottom is therefore 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 (Nos. 6 and 7 of the Map, PI. YIII.) that 

 flowed southerly from the snow-shed that runs from the eastern side 

 of Monte Eosa, by the Eheinwald-horn, to the top of the vaUey of 

 the Adda, — a system of glaciers so large that, like that of Aosta and 

 Ivrea (No. 8 of the Map), further west, they protruded their ends and 

 deposited their moraines far south on the plains of Piedmont and 

 Lombardy. 



The glacier of Ivrea {No. 8 on the Map), when it escaped from the 

 valley of the Doire, deposited a moraine at its side, east of the town 

 of Ivrea, rising in mere debris 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 large roches moutonnees be- 

 tween 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 

 favourable circumstances, the glaciers were confined between the 

 mountains, and therefore thicker than the glacier of Ivrea where it 

 debouched on the plain. Diagrams illustrative of this subject should 

 be drawn on a true scale ; otherwise, height, depth, and steepness 

 being exaggerated, the argument becomes vitiated. I have not the 

 data for giving an actual outhne of the bottom of the Lago Mag- 

 giore ; but a line drawn from the upper end of the lake to the 

 required 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) o/ about 5°. The depths of 

 Maggiore and Como do not, in my opinion, militate against my 

 view ; for, if the theory be true, depth is a mere indicator of time 

 and vertical pressure in a narrow space. It is interesting, and 

 confirmatory of this view, that the deepest part of the Lago Mag- 

 giore is just at the point where the enormous glacier of the Yal 

 d'Ossola joined the great ice-stream that was formed by the united 

 glacier-drainage of the valleys above Bellinzona and Locarno. "Where 

 these glaciers united, there the 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 Lahes. — And now, in reviewing 

 the subject of the origin of the lakes of Switzerland and North Italy, 

 I would remark — 



1st. That each of the great lakes (see Map) lies in an area once 

 covered by a vast glacier. There is, therefore, a connexion between 

 them which can scarcely be accidental. 



* There are other well-known lakes dammed up by the moraine of this great 

 glackr. 



