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Prof. T. G. Bonney. On the 



[Mar. 13, 



III. " Notes on trie Microscopic Structure of some Kocks from 

 the Andes of Ecuador, collected by Edward Whymper, 

 No. II. Antisana." By Professor T. G. Bonney, D.Sc, 

 F.R.S. Received February 29, 1884. 



Antisana is a much loftier and grander mountain than Pichincha ? 

 for its summit rises to an elevation of about 19,000 feet above the sea,* 

 and the upper part of the mountain (some 4,000 feet) is covered with 

 snow and glaciers. The crevasses on the latter are described by Mr, 

 Whymper as being of an enormous size, probably the largest he had 

 ever seen, and on his first attempt to ascend the peak he was pre- 

 vented from reaching the summit by chasms and cliffs of ice, among: 

 which his party, in consequence of the mists, had become entangled. 

 A second attempt proved successful, but the snowy summit of 

 Antisana is evidently not one likely to be reached by unpractised 

 mountaineers. 



The mountain is situated slightly to the south of the equator, to the 

 east-south-east of the city of Quito, and nearly due east of the town 

 of Machachi. " The extent of ground covered by Antisana," accord- 

 ing to Mr. Whymper, " is, perhaps, as great as that covered by any of 

 the Ecuadorian Andes, and more than is occupied by most of them. 

 From north to south it extends over more than 20 miles of country, 

 and not much, if at all, less from east to west. From most points 

 of view at a distance, the mountain in form appears more like a ridge 

 than a single summit. A close approach on the western side shows- 

 that this appearance is somewhat misleading, and that Antisana has 

 two principal summits, the larger and higher being an immense snowy 

 flat-topped boss, and the second (not less than 1,500 feet lower than 

 the other) a sharp peak, which is probably at all times completely 

 inaccessible." 



The lowest point to which the glaciers extend on the western side 

 is 15,294 feet; on the northern and southern they descend to about 

 the same level ; but Mr. Whymper is not able to say how far they 

 come down on the eastern side. "In that direction the most notable 

 feature of the mountain is a very extensive shoulder running out 

 from near the summit, at a height of about 17,000 feet above the sea, 

 in an east-north- east direction. It is singularly level and unbroken 

 in outline, and is entirely obscured by a snow-covered glacier, suggest- 

 ing by its form that there is an old flow of lava concealed beneath. 



" There is no trace of a crater anywhere near the summit upon any 

 side, but the snow covering the flat-topped boss, forming the higher 



* Whymper, mere, bar., 19,335 feet; Eeiss and Stubel, A, 18,885 feet. It ia 

 thus about third or fourth in order of elevation among the summits of Ecuador, being 

 about as high as Cayambe, but lower than either Cotopaxi or Chimborazo. 



