INTERGLACIAL EPOCHS. 307 



Yal Borlezza. It was the muddy water derived from this 

 glacier which, it will be remembered, fed the glacial lake 

 formed in the last-named valley by the ice-dam of the Camonica 

 glacier, from that portion of the glacier which dilated into the 

 lower reaches of the Yal Seriana enormous quantities of shingle, 

 gravel, and sand were carried down by the river, forming banks 

 and terraces, which are seen fringing the flanks of the valley up 

 to a great height above its present bed. These can be traced 

 down the valley beyond the mouth of the Yal Gandino, across 

 which they extend, forming a great bar, which, as viewed from 

 the road in the Yal Seriana, has all the appearance of a huge 

 moraine. One's first thought, indeed, is that this lofty bar has 

 been thrown down as the frontal moraine of an ancient glacier, 

 which may formerly have occupied the basin of Gandino. But 

 Stopanni has shown that the bar is made up of shingle, gravel, 

 and sand, the greater portion of which has come down the Yal 

 Seriana, and could not possibly have been derived from the Yal 

 Gandino. His opinion is, that the embankment was thrown 

 down by the Serio itself ; that in short it is only a portion of 

 the enormous deposits of fluvio- glacial detritus which were 

 swept down the valley when its upper reaches were occupied 

 by the ancient glacier that descended as far as the Ponte di 

 Xossa. When the glacier was at this point, says Stopanni, the 

 fluvio-glacial detritus, always strongly developed in the region 

 which a glacier approaches, extended from the Ponte di Xossa 

 until well beyond the opening of the Yal Gandino ; it rose high 

 upon the slopes of the narrow valley in which the Serio runs, 

 between the great moraine of La Selva and the mouth of the 

 Gandino basin, and thus barred the latter, and converted it into 

 a lake. My own observations enabled me to confirm these 

 views of the able Italian geologist. There can be no doubt, I 

 think, that the bar of shingle, now hardened into conglomerate, 

 which is thrown across the opening of the basin of Gandino or 

 LefY'e, is only a great cone de dejection of the Serio, formed at a 

 time when that river was enormously swollen by the water 

 escaping from melting snow and ice. The embankment pre- 



