508 Section by the Cumbre Pass, paet ii. 



balls of white crystallised carbonate of lime, of which 

 some are coated with the red oxide of iron. I have no 

 doubt, from the examination of a superincumbent 

 stratum (19), that this is a submarine lava; though in 

 Northern Chile, some of the metamorphosed sedimentary 

 beds are almost as crystalline, and of as varied com- 

 position. 



14th. Red sandstone, passing in the upper part into 

 a coarse, hard, red conglomerate, 300 feet thick, having 

 a calcareous cement, and including grains of quartz and 

 broken crystals of feldspar ; basis infusible ; the pebbles 

 consist of dull purplish porphyries, with some of quartz, 

 from the size of a nut to a man's head. This is the 

 coarsest conglomerate in this part of the Cordillera : in 

 the. middle there was a white layer not examined. 



15th. Grand thick bed, of a very hard, yellowish- 

 white rock, with a crystalline feldspathic base, including 

 large crystals of white feldspar, many little cavities 

 mostlv full of soft ferruginous matter, and numerous 

 hexagonal plates of black mica. The upper part of 

 this great bed is slightly cellular; the lower part 

 compact : the thickness varied a little in different parts. 

 Manifestly a submarine lava ; and is allied to bed 11. 



16th and 17th. Dull purplish, calcareous, fine- 

 grained, compact sandstones, which pass into coarse 

 white conglomerates with numerous particles of quartz. 



18th. Several alternations of red conglomerate, 

 purplish sandstone, and submarine lava, like that singu- 

 lar rock forming bed 13. 



19th. A very heavy, compact, greenish-black stone, 

 with a fine-grained obviously crystalline basis, contain- 

 ing a few specks of white calcareous spar, many specks 

 of the crystallised hydrous red oxide of iron, and some 

 specks of a green mineral ; there are veins and nests 

 filled with epidote : certainly a submarine lava. 



