334 COSMOS. 



tations of volcanic activity here indicated, different as they 

 are, applicable in this case ? and have the linear accumula- 

 tions of rock-detritus been upheaved upon fissures in the 

 spots where they now lie (at the foot and in the vicinity of 

 a volcano)? The two dykes of fragments, in this so slightly 

 inclined plateau, called Volcan de la Hacienda and Yana 

 Volcan, which I once considered, although only conjecturally, 

 as cooled lava-streams, now appear to me, as far as I can 

 remember, to present but little in support of the latter opi- 

 nion. In the Yolcan de Ansango, where the line of frag- 

 ments may be traced without interruption, like a river-bed, 

 to the pumice margins of two small lakes, the fall, or differ- 

 ence of level between Pinantura 1482 toises (9476 feet), and 

 Lecheyacu 1900 toises (12,150 feet), in a distance of about 

 7700 toises (49,239 feet), by no means contradicts what we 

 now believe we know of the small average angles of inclina- 

 tion of. lava-streams. Prom the difference of level of 418 

 toises (2674 feet), there is an inclination of 3 6'. A partial 

 elevation of the soil in the middle of the floor of the valley 

 would not appear to be any hindrance, because the back 

 swell of fluid masses impelled up valleys has been ob- 

 served elsewhere, for example, in the eruption of Scaptar 

 Jokul in Iceland, in 1783 (Naumann, Geognosie, Bd. i, 

 s. 160). 



The word lava indicates no peculiar mineral composition 

 of the rock ; and when Leopold von Buch says that every- 

 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 2 * 

 of my attempt to ascend the summit of Chimborazo (only 

 published in 1837, in Schumacher's Astronomisclie Jahr- 

 buch), I expressed this opinion in speaking of the remarkable 

 "fragments of augitic porphyry which 1 collected on the 

 23rd June, 1802, in loose pieces of from twelve to fourteen 

 inches in diameter, upon the narrow ridge of rock leading 

 to the summit at an elevation of 19,000 feet. They 

 had small, shining cells, and were porous and of a red 

 colour. The blackest of them are sometimes light like 

 pumice-stone, and as though freshly altered by fire. They 

 25 Humboldt, Kldnere Sclirijten, Bd. i, s. 161. 



