306 TRAVELS A3I0NGST THE GREAT ANDES, chap. xyi. 



highest peak rises about 3500 feet above the apparent floor of the 

 crater in cliffs as precipitous as the steepest part of the Eigher. 



June 18. In Camp in the Valley of Collanes. Finding that we 

 Avere nearly under the highest peak, and (from such glimpses as 

 could be obtained through the clouds) that there was very little 

 chance of an ascent being effected from the inside of the crater, 

 I sent off J. -A. Carrel at 5.30 a.m., with two of the porters, to 

 examine the outside, and Louis with another to the outside of the 

 second peak. Soon after mid-day Jean-Antoine returned, and 

 reported unfavourably ; and at 4 p.m. Louis came back, saying he 

 had no view of the second summit during the whole day, but 

 thought we could go as far as he had seen.^ Determined to shift 

 camp to the north side of the mountain, outside the crater, if 

 weather would permit. Min. temp, this night was 33° "5, and on 

 the 17th, 29° Faht. 



June 19. In Camp in tlie Valley of Collanes. High wind from 

 the south-east nearly blew the tent over in the night, though it 

 was well protected by trees. At daybreak there was a hard gale, 

 and we were unable to move the camp. All the peaks of Altar 

 were clouded, and much new snow had fallen on the lower crags. 



^ They brought back rock samples from the highest points which were reached. 

 I judge, from the aneroids supplied to them, that Jean-Antoine' s party got to about 

 15,500 feet on the south side of the highest point, and Louis' to about 14,500 feet on 

 the north-west side of the second summit. In regard to the specimen broken by 

 Jean-Antoine from rock in situ Prof. Bonney says (Froc. Royal Soc, Nov. 27, 1884), — 

 "A very dark compact rock, with fairly numerous specks of a greyish felspar, and 

 with occasional minute vesicles. Under the microscope the ground-mass is found 

 to be a glass, in itself almost colourless, but so crowded with opacite as to appear 

 almost opaque with low powers ; in fact its true structure can only be seen in very 

 thin sections and with high powers. . . It is a little difficult to decide whether to 

 retain this rock in the augite-andesites, or to term it a basalt." The rock from the 

 northern peak of Altar is " a reddish-grey trachyte, studded with crystals of rather 

 glassy white felspar, roughly about "1 inch diameter, and containing some minute 

 vesicles. The ground-mass appears to be a clear glass, with numerous lath-like 

 crystallites of felspar, but is so thickly crowded with ferrite and opacite, especially 

 the former, as to be all but opaque except in the thinnest part of the section. . . The 

 rock is an augite-andesite, probably containing some hypersthene." 



