316 COSMOS. 



As he has acutely investigated this region thirty years after 

 myself, he insists upon the analogy which appears to him to 

 be presented by the geognostic relations of the eruption of 

 Ansango to Antisana, and those of Yana Urcu (of which I 

 made a particular plan) to Chimborazo. I was the less in- 

 clined to beheve in a direct upheaval upon fissures through- 

 out the entire linear extent of the tract of fragments at An- 

 sango, because this, as I have already repeatedly mentioned, 

 leads, at its upper extremity, to the two chasms now filled 

 with water. Non-fragmentary, wall-like upheavals of great 

 length and uniform direction are, however, not unknown to 

 me, as I have seen and described them in our hemisphere, 

 in Chinese Mongolia, in granite banks with a floetz-like bed- 

 ding.* 



Antisana had an eruptionf in the year 1580, and another 

 in the beginning of the last century, probably in 1728. Near 

 the summit of the north-northeast side, we observe a black 

 mass of rock, upon which even freshly-fallen snow does not 

 adhere. At this point a black column of smoke was seen 

 ascending for several days in the spring of 1801, at a time 



may often be produced by heaping up" (letter from M. Boussingault, 

 dated August, 1834). See p. 256. In the description of his ascent of 

 Chimborazo (December, 1831), Boussingaulfsays, "The mass of the 

 mountain consists, in my opinion, of a heap of trachytic ruins piled 

 up on each other without any order. These trachytic fragments of a 

 volcano, which are often of enormous size, are upheaved in the solid 

 state ; their edges are sharp, and nothing indicates that they had been 

 in a fused or even a softened condition. Nowhere, on any of the equa- 

 torial volcanoes, do we observe any thing that would allow us to infer 

 a lava stream. Nothing has ever been thrown out from these craters 

 Qxcept masses of mud, elastic fluids, and ignited, more or less scorified 

 trachytic blocks, which have frequently been scattered to considerable 

 distances" CHumboldt, Kkinere Schrijien, bd. i., s. 200). With regard 

 to the first origin of the opinion of the upheaval of solid masses in the 

 form of heaped-up blocks, see Acosta in the Viajes a los Andes Ecua- 

 tonales par M. Boussingault^ 1849, p. 222, 223. The movement of the 

 heaped-up fragments, induced by earth-shocks and other causes, and 

 gradual filling up of the interstices, may, according to the assumption 

 of the celebrated traveler, produce a gradual sinking of volcanic mount- 

 ain peaks. 



* Humboldt, Asie Centrale, t. ii., p. 296-301 (Gustav Rose, Mineral- 

 geognostische Reise nach dent Ural, deni Altai und dem Kasp. Mecre, bd. 

 i., s. 599). Narrow, much elongated granitic walls may have risen, 

 during the earliest foldings of the earth's crust, over fissures analogous 

 to the remarkable, still open ones, which are found at the foot of the 

 volcano of Pichincha ; as the Guaycos of the city of Quito, of 30 — 40 

 feet in width (see my Kleinere Schri/ten, bd. i., s. 24). 



t La Condamine, Mesure des trois premiers Degree du Meridien dans 

 IHemisphere Austral, 1751, p. 56. 



