332 COSMOS. 



cienda, de Santa Lucia, and del Cuvillan. Their declivities 

 are everywhere very rugged and steep, even at the extremi- 

 ties. In their present state they consist of conchoidal and 

 usually sharp-edged fragments of a black basaltic rock, with- 

 out olivine or hornblende, but containing a few small white 

 crystals of felspar. The fundamental mass has frequently a 

 lustre like that of pitch stone, and contains an admixture 

 of obsidian, which was especially recognizable in very 

 large quantity, and more distinctly, in the so-called Cueva de 

 Antisana, the elevation of which we found to be 15,942 feet. 

 This is not a true cavern, but a shed formed by blocks of 

 rock which had fallen against and mutually supported each 

 other, and which preserved the mountain cowherds and also 

 ourselves during a fearful hailstorm. The Cueva lies somewhat 

 to the north of the Yolcan de la Hacienda. In the two 

 narrow dykes, which have the appearance of cooled lava- 

 streams, the tables and blocks appear in part inflated like 

 cinders or even spongy at the edges, and in part weathered 

 and mixed with earthy detritus. 



Analogous but more complicated phenomena are presented 

 by another also band-like mass of rocks. On the eastern 

 declivity of the Antisana, probably about 1280 feet per- 

 pendicularly below the plain of the Hacienda in the direction 

 of Pinantura and Pintac, there lie two small round lakes, of 

 which the more northern is called Ansango, and the southern 

 Lecheyacu. The former has an insular rock, and is sur- 

 rounded by rolled pumice-stone, a very important point. 

 Each of these lakes marks the commencement of a valley ; the 

 two valleys unite, and their enlarged continuation bears the 

 name of Volcan de Ansango, because from the margins of 

 the two lakes narrow lines of rock debris, exactly like 

 the two dykes of the plateau which we have described above, 

 do not, indeed, fill up the valley, but rise in its midsb like 

 dams to a height of 213 and 266 feet. A glance at the local 

 plan which I published in the " Geographical and Physical 

 Atlas" of my American travels (pi. 26), will illustrate these 

 conditions. The blocks are again partly sharp-edged, and 

 partly scorified and even burnt like coke at the edges. It is 

 a basaltic, black, fundamental mass, with sparingly scattered 

 glassy felspar ; some fragments are blackish brown and of a 

 dull pitch stone-like lustre. Basaltic as the fundamental mass 



