chap. xiv. Gypseous Formation. 505 



oblique fault on another mass of the same strata [H], 

 also inclined westward, but at an angle of only about 

 30° : the complicated relation of these three masses 

 [F, G-, H] is explained by the structure of a great 

 mountain-range lying some way to the north, in which 

 a regular anticlinal axis (represented in the section by 

 dotted lines) is seeD, with the strata on its eastern side 

 again bending up and forming a distinct uniclinal axis, 

 of which the beds marked [H] form the lower part. 

 This great uniclinal line is intersected, near the Puente 

 del Inca, by the valley along which the road runs, and 

 the strata composing it will be immediately described. 

 On the south side of the road, in the space correspond- 

 ing with the mountains [E, F and G], the strata every- 

 where dip westward generally at an angle of 30°, occa- 

 sionally mounting up to 45°, but not in an unbroken 

 line, for there are several vertical faults, forming 

 separate uniclinal masses, all dipping in the same 

 direction, — a form of elevation common in the Cordil- 

 lera. We thus see that within a narrow space, the 

 gypseous strata have been upheaved and crushed to- 

 gether by a great uniclinal, anticlinal, and one lesser 

 uniclinal line [E] of elevation ; and that between these 

 three lines and the Cumbre, in the sandstones, con- 

 glomerates and porphyritic formation, there have been 

 at least two or three other great elevatory axes. 



The uniclinal axis [I] intersected near the Puente 

 del Inca 1 (of which the strata at [H] form a part) 



1 At this place, there are some hot and cold springs, the warmest 

 having a temperature, according to Lieut. Brand (' Travels,' p. 240), 

 of 91° ; they emit much gas. According to Mr. Brande, of the Royal 

 Institution, ten cubical inches contain forty-five grains of solid 

 matter, consisting chiefly of salt, gypsum, carbonate of lime, and 

 oxide of iron. The water is charged with carbonic acid and 

 sulphuretted hydrogen. These springs deposit much tufa in the 

 form of spherical balls. They burst forth, as do those of Cauquenes, 

 and probably those of Villa Vicencio, on a line of elevation. 



