164 PATAGONIAN EXPEDITIONS: NARRATIVE. 



collect botanical and zoological materials and rest and shoe our horses. 

 The contact of the basalt, here from two to three hundred feet thick, with 

 the underlying sedimentary rocks, determined the positions of the springs 

 of water. About the margins of the depressions and over the lower of 

 the debris-covered slopes of the escarpment were frequent exposures of 

 sedimentary deposits belonging to the Santa Cruzian beds. 



While encamped at this locality, I climbed one day to the summit of 

 the basaltic platform and travelled for a considerable distance over its 

 deeply fractured and cavernous surface. From my elevated position I 

 secured a splendid view of the surrounding country. To the eastward, 

 beyond the valley across which we had last driven, lay the great lava field 

 through which, for two hundred miles, the Rio Chico had carved its deep 

 and winding cafion. From my more elevated position I could look down 

 upon and across its broken and uneven surface, which appeared not unlike 

 that of a great sea of black water in a state of violent disturbance. Look- 

 ing southward beyond the valley of the Rios Belgrano and Chico, there 

 appeared, near the western border of this great interior lava field, a num- 

 ber of old volcanic peaks with summits already covered with snow. On 

 the west was a wide strip of open country, characterized by high rolling 

 divides separating the river valleys, over which were scattered numerous 

 glacial hills, interspersed with small lakes and broad stretches of meadow 

 lands. Such was the country that lay between the high basaltic outlier 

 on which I stood and the yet higher and noble mountain ranges, 

 whose snow-capped summits rose ever upward, until lost in the clouds on 

 the western horizon. On the north, beyond the limits of the basalt field 

 which lay at my feet, the landscape assumed the nature of an elevated 

 plain, out of which, at a distance of some fifty miles, Mt. Belgrano raised 

 its mighty mass in solitude, towering to a height of some three thousand 

 feet or more above the surrounding plain. From the nature of the coun- 

 try to the northward it was evident that we should encounter little trouble 

 for a considerable distance, while travelling in that direction. Turning to 

 my more immediate surroundings, the surface of the lava was seen to be 

 composed in places of highly vesicular, scoriaceous materials, occasionally 

 approaching in character that of a true pumice. In other places it was 

 quite hard and firm, while there were occasional nodules of a black 

 obsidian with an even luster and conchoidal fracture. There was little 

 vegetation and less of animal life. While the vegetation was, for the most 



