316 REACTION OF THE INTERIOR OF THE EARTH 



valued friend Boussingault, whose chemico-geological 

 and meteorological views I always delight in sharing in, 

 regards what is called the Volcano of Ansango, and 

 which I now look upon rather as an eruption of frag- 

 ments from two small lateral craters (on the west side 

 of Antisana, not far from Chussulongo), as an elevation 

 or upheaval of blocks ( 45 ) over long fissures. Having 

 examined this region, with much sagacity, thirty years 

 after me, he lays much stress on the analogy which the 

 geological relations of the eruption of Ansango to Anti- 

 sana appeared to him to present with those of Yana 

 Urcu (of which I had made a special topographical 

 plan) to Chimborazo. I was myself less inclined to 

 believe in an elevation over fissures situated imme- 

 diately below the whole linear extent of the Ansango 

 series of fragments, because, as I have said, they can 

 be traced up to two orifices now filled with water. 

 Unfragmentary wall-like elevations of great length and 

 uniform direction are not unknown to me, having seen 

 and described such in Chinese Tartary, consisting of 

 horizontal banks of granite. ( 451 ) 



Antisana had a fiery eruption ( 452 ) in 1590, and 

 another in the beginning of the last century, probably 

 in 1728. Near the summit, on the N.N.E. side, there 

 is remarked a black mass of rock on which even fresh 

 fallen snow does not remain. For several days in the 

 spring of 1801, at a time when the summit was on all 

 sides perfectly free from clouds, a column of black 

 smoke was seen to ascend from this point. On the 

 18th of March 1802, Bonpland, Carlos Montufar, and 

 I, arrived on a rocky ridge covered with pumice and 

 black basaltic scoriae, in the region of perpetual snow, at 



