chap. xv. Section up the Valley. 543 



here give a section of the principal beds met with in 

 crossing the entire thickness of the gypseous strata. 



First : above the porphyritic conglomerate for- 

 mation, there is a fine-grained, red, crystalline sand- 

 stone. 



Secondly : a thick mass of smooth-grained, calcareo- 

 aluminous, shaly .rock, often marked with dendritic 

 manganese, and having, where most compact, the ex- 

 ternal appearance of honestone. It is easily fusible. 

 I shall for the future, for convenience sake, call this 

 variety pseudo-honestone. Some of the varieties are 

 quite black when freshly broken, but all weather into 

 a yellowish-ash coloured, soft, earthy substance, pre- 

 cisely as is the case with the compact shaly rocks of 

 the Peuquenes range. This stratum is of the same 

 general nature with many of the beds near Los Hornos 

 in the Illapel section. In this second bed, or in the 

 underlying red sandstone (for the surface was partially 

 concealed by detritus), there was a thick mass of 

 gypsum, having the same mineralogical characters with 

 the great beds described in our sections across the 

 Cordillera. 



Thirdly: a thick stratum of fine-grained, red, 

 sedimentary matter, easily fusible into a white glass, 

 like the basis of clay stone porphyry ; but in parts 

 jaspery, in parts brecciated, and including crystalline 

 specks of carbonate of lime. In some of the jaspery 

 layers, and in some of the black siliceous slaty bands, 

 there were irregular seams of imperfect pitchstone, 

 undoubtedly of metamorphic origin, and other seams of 

 brown, crystalline limestone. Here, also, were masses, 

 externally resembling ill-preserved silicified wood. 



Fourthly and fifthly : calcareous pseudo-honestone ; 

 and a thick stratum concealed by detritus. 



Sixthly : a thinly stratified mass of bright green, 



