chap. x. their Marine Origin. 297 



my belief that a mountain -ridge near the Baths of Cau- 

 quenes has been upraised long subsequently to all the 

 other ranges in the neighbourhood, and that when this 

 was effected the whole face of the country must have 

 been greatly altered. In the course of ages, moreover, 

 in this and other valleys, events may have occurred like, 

 but even on a grander scale than, that described by 

 Molina, 1 when a slip during the earthquake of 1762 

 banked up for ten days the great river Lontue, which 

 then bursting its barrier ' inundated the whole country,' 

 and doubtless transported many great fragments of rock. 

 Finally, notwithstanding this one case of difficulty, I 

 cannot entertain any doubt, that these terrace-like 

 fringes, which are continuously united with the basin- 

 shaped plains at the foot of the Cordillera, have been 

 formed by the arrestment of river-borne detritus at 



1 ' Compendio de la Hist.' &c. &c. t. 1. p. 30. M, Brongniart, in 

 his report on M. Gay's labours (' Annales des Sciences,' 1833) con- 

 siders that the boulders in the Cachapual belong to the same class 

 with the erratic boulders of Europe. As the blocks which I saw are 

 not gigantic, and especially as they are not angular, and as they 

 have not been transported fairly across low spaces or wide valleys, 

 I am unwilling to class them with those, which, both in the northern 

 and southern hemisphere (' Geolog. Transac' vol. vi. p. 415), have 

 been transported by ice. It is to be hoped, that when M. Gay's long- 

 continued and admirable labours in Chile are published, more light 

 will be thrown on this subject. However, the boulders may have 

 been primarily transported ; the final position of those of porphyry, 

 which have been described as arranged at the foot of the mountain 

 in rude lines, I cannot doubt, has been due to the action of waves 

 on a beach. The valley of the Cachapual, in the part where the 

 boulders occur, bursts through the high ridge of Cauquenes, which 

 runs parallel to, but at some distance from, the Cordillera. This 

 ridge has been subjected to excessive violence ; trachytic lava has 

 burst from it, and hot springs yet flow at its base. Seeing the 

 enormous amount of denudation of solid rock in the upper and much 

 broader parts of this valley where it enters the Cordillera, and see- 

 ing to what extent the ridge of Cauquenes now protects the great 

 range, I could not help believing (as alluded to in the text) that 

 this ridge with its trachytic eruptions had been thrown up at a much 

 later period than the Cordillera. If this has been the case, the 

 boulders, after having been transported to a low level by the 

 torrents (which exhibit in every valley proofs of their power of 

 moving great fragments), may have been raised up to their present 

 height, with the land on which they rested. 



