1835.] TERRACES OF SHINGLE. 9*9 



for their madrinas saves infinite trouble. If several large troops are 

 turned into one field to graze, in the morning the muleteers have 

 only to lead the madrinas a little apart, and tinkle their bells ; and 

 although there may be two or three hundred together, each mule 

 immediately knows the bell of its own madrina, and comes to her. 

 It is nearly impossible to lose an old mule ; for if detained for several 

 hours by force, she will, by the power of smell, like a dog, track out 

 her companions, or rather the madrina, for, according to the muleteer, 

 she is the chief object of affection. The feeling, however, is not of 

 an individual nature ; for I believe I am right in saying that any 

 animal with a bell will serve as a madrina. In a troop each animal 

 carries on a level road, a cargo weighing 416 pounds (more than 29 stone), 

 but in a mountainous country 100 pounds less ; yet with what delicate 

 slim limbs, without any proportional bulk of muscle, these animals 

 support so great a burden! The mule always appears to me a most 

 surprising animal. That a hybrid should possess more reason, memory, 

 obstinacy, social affection, powers of muscular endurance, and length 

 of life, than either of its parents, seems to indicate that art has here 

 outdone nature. Of our ten animals, six were intended for riding, 

 and four for carrying 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 igt/t. We rode during this day to the last, and therefore 

 most elevated house in the valley. 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 7,000 and 

 9,000 feet, where they become hidden by the irregular piles of debris. 

 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 former chapter as 

 characteristic of the scenery of Chile, and which were undoubtedly de- 

 posited when the sea penetrated Chile.as it now does the more southern 

 coasts. No one fact in the geology of South America interested me 

 more than these terraces of rudely-stratified shingle. They precisely 

 resemble in composition the matter which the torrents in each valley 

 would deposit, if they were checked in their course by any cause, such 

 as entering a lake or arm of the sea; but the torrents, instead of 

 depositing matter, are now steadily at work wearing away both the 

 solid rock and these alluvial deposits, along the whole line of every 

 main valley and side valley. It is impossible here to give the reasons, 

 but I am convinced that the shingle terraces were accumulated during 



