TRUE VOLCANOES. 315 



thing is lava that flows in the volcano and attains new posi- 

 tions by its fluidity, I add that that which has not. again be- 

 come fluid, but is contained in the interior of a volcanic cone, 

 may change its position. Even in the first description* of 

 my attempt to ascend the summit of Chimborazo (only pub- 

 lished in 1837, in Schumacher's Astronomische Jahrhuch), I 

 expressed this opinion in speaking of the remarkable "frag- 

 ments of augitic porphyry which I collected on the 23rd of 

 June, 1802, in loose pieces of from twelve to fourteen inches 

 diameter, upon the narrow ridge of rock leading to the sum- 

 mit at an elevation of 19,000 feet. They had small, shining 

 cells, and were porous and of a red color. The blackest of 

 them are sometimes light like pumice-stone, and as though 

 freshly altered by fire. They have not, however, flowed out 

 in streams like. lava, but \\iXNG, probably been expelled at fis- 

 sures on the declivity of the previously upheaved, bell-shaped 

 mountain." This genetic explanation might find abundant 

 support in the assumptions of Boussingault, who regards the 

 volcanic cones themselves " as an accumulation of angular 

 trachytic fragments, upheaved in a solid condition, and heap- 

 ed up without any order. As after the upheaval the broken 

 rocky masses occupy a greater space than before they were 

 shattered, great cavities remain among them, movement be- 

 ing produced by pressure and shock (the action of the volcan- 

 ic vapor force being abstracted)." I am far from doubting 

 the partial occurrence of such fragments and cavities, which 

 become filled with water in the Nevados, although the beau- 

 tiful, regular, and, for the most, perfectly perpendicular tra- 

 chytic columns of the Pico de los Ladrillos, and Tablahuma 

 on Pichindha, and, above all, over the small basin Yana- 

 Cocha on Chimborazo, appear to me to have been formed on 

 the spot. My old and valued friend, Boussingault, whose 

 chemico-geognostic and meteorological opinions I am always 

 ready to adopt, regards what is called the Yolcan de Ansan- 

 go, and what now appears to me as an eruption of fragments 

 from two small lateral craters (on the western Antisana, be- 

 low Chussulongo), as upheavals of blocksj upon long fissures. 



* Humboldt, Kkinere Schriften, bd. i., s. 161. 



f "We differ entirely with regard to the pretended stream of An- 

 tisana toward Pinantura. I regard this stream (coulee) as a recent 

 upheaval analogous to those of Calpi (Yana Urcu), Pisque, and Jorul- 

 lo. The trachytic fragments have acquired a greater thickness toward 

 the middle of the stream. Their stratum is thicker toward Pinantura 

 than at points nearer Antisana. The fragmentary condition is an ef- 

 fect of local upheaval, and in the Cordillera of the Andes earthquakes 



