CHAP. XIII. THEORY OF AGASSIZ CONFIRMED. 259 



cited, has, during a late visit to Lochaber, in 1861, observed 

 marjy facts higlily confirmatory of the hypothesis of glacier- 

 lakes which, as I have already stated, was originally advanced 

 by Mr. Agassiz. In the first place, he found much superficial 

 scoring and polishing of rocks, and accumulation of boulders 

 at those points where signs of glacial action ought to appear, 

 if ice had once dammed up the waters of the glens in which 

 the "roads" occur. Ben ISTevis may have sent down its 

 glaciers from the south, and Glen Arkeg from the north, for 

 the mountains at the head of the last-mentioned glen are 

 3000 feet high, and may, together with other tributary glens, 

 have helped to choke up the great Caledonian valley with ice, 

 so as to block up for a time the mouths of the Spean, Eoy, 

 and Gluoy. The temporary conversion of these glens into 

 glacier-lakes is the more conceivable, because the hills at 

 their upper ends not being lofty nor of great extent, they 

 may not have been filled with ice at a time when great 

 glaciers were generated in other adjoining and much higher 

 regions. 



2dly. The shelves, says Mr. Jamieson, are more precisely 

 defined and unbroken than an}' of the raised beaches or ac- 

 knowledged ancient coast-lines visible on the west of Scotland, 

 as in Argyleshire, for example. 



3dly. At the level of the lower shelf in Glen Eoy, at points 

 where torrents now cut channels through the shelf as they 

 descend the hill-side, there are small delta-like extensions of 

 the shelf, perfectly preserved, as if the materials, whether fine 

 or coarse, had originally settled there in a placid lake, and 

 had not been acted upon by tidal currents, mingling them 

 with the sediment of other streams. These deltas are too 

 entire to allow us to suppose that they have at any time since 

 their origin been exposed to the waves of the sea. 



4thly. The alluvium on the '• cols" or watersheds, before 

 alluded to. is such as would have been formed if the waters 



