TRUE VOLCANOES. 319 



zon would indicate. Soon returning from Suniguaicu and 

 the Quebrada del Mestizo, we examined the long and broad 

 ridge which, striking from N.W. to S.E., unites Cotopaxi 

 with the Nevado de Quelendana. Here the blocks arranged 

 in rows are wanting, and the whole appears to be a dam- 

 like upheaval, upon the ridge of which are situated the small 

 conical mountain El Morro, and, nearer to the horse-shoe 

 shaped Quelendana, several marshes and two small lakes 

 (Lagunas de Yauricocha and de Verdecocha). The rock of 

 El Morro and of the entire linear volcanic upheaval was 

 greenish-gray porphyritic slate, separated into layers of eight 

 inches thick, which dipped very regularly toward the east at 

 60°. Nowhere was there any trace of true lava streams.* 



* It is particularly remarkable that the vast volcano of Cotopaxi, 

 which manifests an enormous activity, although, indeed, usually only 

 after long periods, and acts destructively upon the neighborhood, es- 

 pecially by the inundations which it produces, exhibits no visible va- 

 pors between its periodical eruptions, when seen either in the plateau 

 of Lactacunga or from the Paramo de Pansache. From several com- 

 parisons with other colossal volcanoes, such a phenomenon is certainly 

 not to be explained from its height of 19,180 feet, and the great tenuity 

 of the strata of air and vapor corresponding with this elevation. No 

 other Nevado of the equatorial Cordilleras shows itself so often free 

 from clouds and in such great beauty as the truncated cone of Coto- 

 paxi, that is to say, the portion which rises above the limit of perpet- 

 ual snow. The uninterrupted regularity of this ash-cone is much 

 greater than that of the ash-cone of the Peak of Teneriffe, on which a 

 narrow projecting rib of obsidian runs down like a wall. Only the up- 

 per part of the Tungurahua is said formerly to have been distinguished 

 in an almost equal degree by the regularity of its form ; but the ter- 

 rible earthquake of the 4th of February, 1797, called the Catastrophe of 

 Riobamba, has deformed the mountain cone of Tungurahua by fissures 

 and the falling in of parts and the descent of loosened wooded frag- 

 ments, as also by the accumulation of debris. At Cotopaxi, as even 

 Bouguer observed, the snow is mixed in particular spots with crumbs 

 of pumice-stone, when it forms a nearly solid mass. A slight ine- 

 quality in the mantle of snow is visible toward the northwest, where 

 two fissure-like valleys run down. Black rocky ridges ascending to 

 the summit are seen nowhere from afar, although in the eruptions of 

 the 24th of June and 9th of December, 1742, a lateral opening showed 

 itself half way up the snow-covered ash-cone. "There opened," says 

 Bouguer (Figure de la Terre, p. lxviii. ; see also La Condamine, Jour- 

 nal du Voyage a rEquateur, p. 159), "a new mouth toward the middle 

 of the part constantly covered with snow, while the flame always is- 

 sued at the top of the truncated cone." Quite at the top, close to the 

 summit, some horizontal black streaks, parallel to each other, but in- 

 terrupted, are detected. When examined with the telescope under 

 various illuminations they appeared to me to be rocky ridges. The 

 whole of this upper part is steeper, and almost close to the truncation 

 of the cone forms a wall-like ring of unequal height, which, however, 

 is not visible at a great distance with the naked eye. My description 



