Vol. 58.] HANGING VALLEYS IN THE ALPS AND HIMALAYAS. 715 
by ice,’ but the ice which formed it must have come down the 
valley now occupied by the icefall. Therefore, Why the icefall ? 
Why was the barrier not degraded ? 
Mr. Harker, in his admirable description of the glaciation of 
Skye, alludes to the weight of the ice and the grinding of the 
ground-moraine. A great deal of excavating work has been. 
attributed to ground-moraine; but, as a matter of fact, there is very 
little material at the bottom of the ice. Most of it is carried en- 
glacially in an ice-sheet, and not between the ice and the valley- 
floor. 
In many places it is possible to study the relative action of ice 
and running water, occupying the same valley and working side by 
side. Fig. 2 in Pi. XL, for instance, which is from a photograph 
taken in Hornsund Bay (Spitsbergen), shows a gorge cut down by the 
water running under the ice, and the ice moulding itself down into 
the gorge. The gorges which terminate many of the glaciers of 
Switzerland have been thus produced ; the gorge at the end of the 
Aleisch Glacier has been cut down by the subglacial river, and the 
same phenomenon is well seen at the end of the Mer de Glace and 
elsewhere. 
The question of the excavation of lake-basins by ice I must 
leave to another occasion, though Prof. Davis considers that they 
are intimately bound up with the origin of the hanging valleys. 
I hope, however, to have shown that, so far as the districts 
described above are concerned, there is no proof that the over- 
deepening of the main valley, and the consequent production of 
‘hanging’ lateral valleys, has been the result of ice-excavation, 
and that the marked occurrence of these valleys in glaciated districts 
can possibly be accounted for in quite another way. 
EXPLANATION OF PLATES XXXVI-XL. 
Puate XXXVI. 
Map and longitudinal section of the Valle Leventina, together with sections 
of the chief hanging valleys to which allusion is made. The map shows the 
various characteristics on which emphasis is laid in the text. The sections are 
all drawn to the true scale of 1: 50,000, except that across the Jongri Plateau 
which is on the scale of 1: 100,000. The asterisks denote the lower ter- 
mine‘ions of the hanging valleys. 
Piatt XXXVIT. 
Fig. 1 shows the river-gorge of Monte Piottino and the old river-level above 
on the right, which exactly corresponds with the mouth of the Val 
Piumogna. 
Fig, 2 illustrates the overlapping character of the profiles below Faido. 
Puatr XXXVITII. 
Photograph of the gorge of La Foos, from the edge of the Val Piora, 
looking down into the Valle Leventina. 
1 *Glacial Erosion in France, Switzerland, & Norway’ Proc. Boston Soe. 
Nat. Hist. vol. xxix (1900) pp. 273-822. 
