TRUE VOLCANOES. 335 



they were forced out through lateral fissures of the volcano, 

 as the word reventazon would indicate. Soon returning 

 from Suuiguaicu and the Quebrada del Vi estizo. we examined 

 the long and broad ridge which, striking from N.W. to S.E., 

 unites Cotopaxi with the Nevado de Quelenclaila. Here the 

 blocks arranged in rows are wanting, and the whole appears to 

 be a darn-like upheaval, upon the ridge of which are situated 

 the small conical mountain el Morro and, nearer to the horse- 

 shoe shaped Quelendaria, seA r eral 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 towards the 

 east at 60. Nowhere was there any trace of true lava- 

 streams? . 



30 It is particularly remarkable that the vast volcano of Coto- 

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

 only after long periods, and acts destructively upon the neighbour- 

 hood, especially by the inundations which it produces, exhibits no 

 visible vapours between its periodical eruptions, when seen either in the 

 plateau of Lactacunga, or from the Paramo de Pansache. From several 

 comparisons 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 vapour 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 trun- 

 cated cone of Cotopaxi, that is to say the portion which rises above 

 the limit of perpetual snow. The uninterrupted regularity of this 

 ash-cone is much greater than that of the ash-cone of the Peak of 

 Teueriffe, on which a narrow projecting rib of obsidian runs down 

 like a wall. Only the upper part of the Tungurahua is said for- 

 merly to have been distinguished in an almost equal degree by the 

 regularity of its form, but the terrible earthquake of the 4th Feb- 

 ruary, 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 fragments, as also by the accu- 

 mulation of debris. At Cotopaxi, as even Bouguer observed, the 

 enow is mixed in particular spots with crumbs of pumice-stoue, 

 when it forms a nearly solid mass. A slight inequality in the 

 mantle of snow is visible towards the north-west, whei-e 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 

 Juno and 9th December, 1742, a lateral opening showed itself halfway 

 up the snow-covered ash-cone. " There opened," says Bouguer (Fiyui't. 

 de la Terre, p. Ixviii ; see also La Condarniue, Journal du Voyage a 

 I'EquatcUr, p. 159), " a new mouth towards the middle of the paii 



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