TERRACES OF SHINGLE. G3 



slim limbs, without any propoz'tional bulk of mus- 

 cle, these animals support so great a burden ! The 

 mule always appears to me a most surprising ani- 

 mal. That a hybrid should possess more reason, 

 memory, obstinacy, social affection, powei's of mus- 

 cular endurance, and length of life, than either of 

 its parents, seems to indicate that art has here out- 

 done nature. Of our ten animals, six were in- 

 tended for riding, and four for caiTying cargoes, 

 each taking turn about. We carried a good deal 

 of food, in case we should be snowed up, as the 

 season was rather late for passing the Portillo. 



March I9th. — We rode during this day to the 

 last, and, therefore, most elevated house in the val- 

 ley. The number of inhabitants became scanty ; 

 but wherever water could be brought on the land, 

 it was very fertile. All the main valleys in the 

 Cordillera are characterized by having, on both 

 sides, a fringe or terrace of shingle and sand, rudely 

 stratified, and generally of considerable thickness. 

 These fringes evidently once extended across the 

 valleys, and were united ; and the bottoms of the 

 valleys in northern Chile, where there are no 

 streams, are thus smoothly filled up. On these 

 fringes the roads are generally carried, for their 

 surfaces are even, and they rise with a very gentle 

 slope up the valleys : hence, also, they are easily 

 cultivated by irrigation. They may be traced up 

 to a height of between 7000 and 9000 feet, whei-e 

 they become hidden by the irregular piles of de- 

 bris. At the lower end or mouths of the valleys, 

 they are continuously united to those land-locked 

 plains (also formed of shingle) at the foot of the 

 main Cordillera, which I have described in a for- 

 mer chapter as characteristic of the scenery of 

 Chile, and which were undoubtedly deposited 

 when the sea penetrated Chile, as it now does tho 



