238 REACTION OF THE INTERIOR OF THE EARTH 



The volcano of Pichincha (15,890 feet), to the surprise 

 of the geologist, forms a long-drawn ridge, at one 

 extremity of which, a little higher than the rest of 

 the mountain, is situated the wide and still burning 

 crater. ( 327 ) 



Fallings in of the crater-walls, occasioned by great 

 volcanic spasms of activity, in which they are rent 

 asunder by mine-like explosions from the depths below 

 them, give rise in conical mountains to very strange and 

 contrasted forms : it has been thus in the case of the 

 Carguairazo (15,666 feet), where a fissure into "double 

 pyramids," of more or less regularity of form, took place 

 by a sudden falling in on the night of the 19th of July 

 1698 ; ( 3 - 8 ) and in that of the finer pyramids of Ilinissa, 

 (17,437 feet) ( 329 ). In a similar manner the upper por- 

 tion of crater-walls may become broken into a rude kind 

 of battlement, and subsequent commotions may leave 

 parts only of the same homogeneous mountain standing 

 as partially detached towers or peaks ; and thus at Capac- 

 Urcu, Cerro del Altar, now only 17,456 feet, two very 

 similar peaks, rising in emulation of each other, allow us 

 to conjecture the earlier primitive form of the mountain. 

 A tradition has been generally preserved among the 

 natives of the highlands of Quito, between Chambo and 

 Lican, and between the mountains of Condorasto and 

 Cuvillan, that fourteen years before the invasion of 

 Huayna Capac, son of the Inca Tupac Yupanqui, the 

 summit of the last-named volcano, after eruptions which 

 lasted uninterruptedly for seven or eight years, fell in, 

 covering the whole of the plateau on which New Rio- 

 bamba is situated with pumice and volcanic ashes. 

 Originally higher than Chimborazo, it was called in the 



