294 Sloping Terraces of Gravel : pakt it. 



much less distance, though certainly not in the imme- 

 diate neighbourhood. The boulders found by MM. 

 Meyen and Gay on the upper plain of S. Fernando 

 (mentioned in a previous note) probably belong to this 

 same class of phenomena. 



These fringes of stratified gravel occur along all the 

 great valleys of the Cordillera, as well as along their 

 main branches ; they are strikingly developed in the 

 valleys of the Maypu, Mendoza, Aconcagua, Cachapual, 

 and according to Meyen, 1 in the Tinguirica. In the 

 valleys, however, of northern Chile, and in some on the 

 eastern flank of the Cordillera, as in the Portillo 

 Valley, where streams have never flowed, or are quite 

 insignificant in volume, the presence of a mass of 

 stratified gravel can be inferred only from the smooth 

 slightly concave form of the bottom. One naturally 

 seeks for some explanation of so general and striking a 

 phenomenon ; that the matter forming the fringes 

 along the valleys, or still filling up their entire beds, 

 has not fallen from the adjoining mountains like 

 common detritus, is evident from the complete con- 

 trast in every respect between the gravel and the piles 

 of detritus, whether seen high up the valleys on their 

 sides, or low down in front of the more precipitous 

 ravines ; that the matter has not been deposited by 

 debacles, even if we could believe in debacles having 

 rushed -down every valley, and all their branches, east- 

 ward and westward from the central pinnacles of the 

 Cordillera, we must admit from the following reasons, 

 — from the distinct stratification of the mass, — its 

 smooth upper surface, — the well-rounded and some- 

 times encrusted state of the pebbles, so different from 

 the loose debris on the mountains, — and especially from 

 the terraces preserving their uniform inclination round 

 1 ' Keise,' &c. Th. I. s. 302. 



