CXV111 NOTES. 



( 4M ) p 319. It is particularly striking that the great volcano Cotopaxi 

 which (for the most part indeed only after long intervals of repose) manifests 

 enormous activity, especially by the devastating inundations which it causes, yet 

 in the intervals between these outbursts shows no visible smoke or vapour, as 

 seen either from the Paramo de Pansache or from the high plain of Lactagunga. 

 Comparison with other equally lofty volcanoes shows that this absence is not to 

 be explained from the rarity of the air and of the vapour at the great elevation 

 of 19,000 feet. None of the other Nevados in the equatorial Cordilleras are so 

 often seen in cloudless grandeur and beauty as the truncated cone of Cotopaxi, 

 t. e. the portion which rises above perpetual snow. . Its uninterrupted regularity 

 of form much exceeds that of the Peak of TenerifFe, in which a narrow projecting 

 wall-like ridge of obsidian runs down from the cone. The upper portion of 

 Tungurahua may have been once almost as distinguished by regularity of form as 

 Cotopaxi, but it is now greatly disfigured by the effects of the great earthquake 

 of the 4th February 1797, called the catastrophe of Eiobamba, by which it was 

 crevassed ; parts fell in, others glided down, carrying with them the forests which 

 clothed them, and large accumulations of debris were formed. On Cotopaxi, as 

 Bouguer had already remarked, there are points at which pumice and snow are 

 intermingled, and almost form one solid mass. A little unevenness in the snowy 

 mantle can be discovered on the north-west side, where two cleft-like valleys run 

 down. One does not see from a distance anything of black rocky ridges running 

 up towards the summit, although, in the eruptions of the 24th June and 9th De- 

 cember 1742, a lateral opening showed itself half-way up the snow-covered cone 

 of cinders. " II s'etoit ouvert une nouvelle bouche vers le milieu de la partie 

 continuellement neige'e, pendant que la flamme sortoit toujours par le haut du cone 

 tronque'. (Bouguer, in Figure de la Terre, p. Ixviii. Compare also La Conda- 

 mine, Journ. du Voy. a 1'Equateur, p. 159.) It is only quite near to the sum- 

 mit that one perceives some horizontal, parallel, but interrupted black streaks. 

 Looked at through the telescope under different incidences of light they appear 

 to me to be ridges of rock. This whole upper part is steeper than the rest of 

 the mountain, and forms, almost close to the truncation of the cone, a wall- 

 like annular ridge of unequal height, not, however, visible to the naked eye by 

 reason of the great distance. My description of this highest, almost perpendi- 

 cular, encircling ridge strongly drew the attention of two distinguished geolo- 

 gists, Darwin (Volcanic Islands, 1844, p. 83) and Dana (Geology of the U. S. 

 Explor. Exped., 1849, p. 356). The volcanoes of the Galapagos islands, 

 Diana's Peak in St. Helena, and Teneriffe, show analogous conformations. The 

 highest point of Cotopaxi, of which I measured the elevation by angles, is in a 

 black convexity. Perhaps it is the inner wall of a higher and more distant 



