16 Remailis on the Formation of Alluvial Deposites. 



croaeh on one another Hence they must have operated more 

 effectually in producing occasional stoppages of the river, which, 

 on regaining the mastery, has cut away the bases on either hand. 



This form of alluvium (Fig. 11) maybe distinguished as the 

 obtuse cone truncated at the base. 



After the clipping of the base, the obtuse cone becomes sub- 

 ject to a still further modification. The streams, which, in its 

 entire state, might have flowed in every direction pretty evenly 

 from its summit to its base, are diverted from their course on 

 arriving at the edges of its steep declivities. They immediately 

 begin to cut through the edges, and thus intersect the declivi- 

 ties with ravines. A very beautiful and distinct example of an 

 obtuse cone thus modified is seen in the valley of the Reuss some 

 miles above Altorf. The high road passes over it a little below 

 Amsteg. The ravines formed in its- truncated base are large 

 and verdant, and adorned, together with the other parts of the 

 cone, with fine walnut-trees and beeches. Diverging from the 

 apex, they give to the cone the appearance of being scalloped. 

 The materials carried out of one of these ravines are seen depo- 

 sited at its mouth in a very regular, but comparatively small ob- 

 tuse cone, and this cone also is dipt at its base. Another ex- 

 ample is presented in the valley of Schams. As we enter that 

 valley from the Via Mala, the high road passes under the dipt 

 base of a vast obtuse cone, and crosses the entrance (on the left 

 hand) of two or three ravines, by which it is furrowed. Look- 

 ing back upon this cone from the upper part of the valley of 

 Schams, the edges of the ravines strike the eye by their regulari- 

 ty and parallelism, and are more conspicuous than in the pre- 

 ceding case, because this cone is bare of trees. 



We may call this form (Fig. 12) the obtuse cone truncated 

 at the base, and scalloped at the edges. 



Still another form is impressed upon the alluvium of the al- 

 pine valleys from the same agency. When the valley is more 

 than usually expanded, the principal streani^ winding round the 

 base of the obtuse cone, scoops out the level alluvium on the 

 opposite side of the valley, so as to form a steep declivity ar- 

 ranged as an arc of a larger circle, parallel to the circular base 

 of the cone. A beautiful example of this presents itself a little 

 below Chamonix, the Arve flowing between the cone and the 



