230 COSMOS. 



(17,084 feet) was reached by Friedrich Parrot in the year 

 1829, and by Abich and Chodzko in 1845 and 1850, forms, 

 like Chimborazo, an unopened dome. Its vast lava streams 

 . have burst forth far below the snow-line. A more import- 

 ant character in the formation of Ararat is a lateral chasm, 

 the deeply-cut valley of Jacob, which may be compared with 

 the Val del Bove of ^tna. In this, according to Abich's ob- 

 servation, the inner structure of the nucleus of the trachytic 

 dome-shaped mountain first becomes really visible, as this nu- 

 cleus and the upheaval of the* whole of Ararat are much more 

 ancient than the lava streams.* The Kasbegk and Tschegem, 

 which have broken out upon the same principal Caucasian 

 mountain ridge (E.S.E. W.N.W.) as the Elburuz (19,716 

 feet), are also cones without craters at their summits, while 

 the colossal Elburuz bears a crater-lake upon its summit. 



As conical and dome-like forms are by far the most fre- 

 quent in all regions of the earth, the isolated occurrence of 

 the long ridge of the volcano of Pichincha, in the group of 

 volcanoes of Quito, becomes all the more remarkable. I 

 have occupied myself long and carefully with the study of 

 its structure, and, besides its profile view, founded upon nu- 

 merous angular measurements, have also published a topo- 

 graphical sketch of its transverse valleys. | Pichincha forms 

 a wall of black trachytic rock (composed of augite and oli- 

 goclase) more than nine miles in length, elevated upon a fis- 

 sure in the most western Cordilleras, near the South Sea, 

 but without the axis of the high mountain ridge coinciding 



angles of elevation, may be employed for determining distance in 

 many topographical labors which are to be rapidly executed. The 

 second of the level lines here indicated, the horizontal, which bounds 

 the lower portion of a single occasional snow-fall, is decisive as to the 

 relative height of the mountain domes, which do not reach into the 

 region of perpetual snow. Of a long chain of such mountains, which 

 have been erroneously supposed to be of equal height, many are be- 

 low the temporary snow-line, and thus the snow-fall decides as to the 

 relative height. I have heard such considerations as these upon per- 

 petual and accidental snow limits from the mouths of rough country 

 people and herdsmen in the mountains of Quito, where the Sierras 

 Nevadas are often close together, although they are not connected by 

 the same line of perpetual snow. Grandeur of nature sharpens the 

 perceptive faculties in particular individuals among the colored abo- 

 rigines, even when they are on the lowest steps of civilization. 



* Abich, Bulletin de la SocitU de Geographic, 4me serie, t. i. (1851), 

 p. 517, with a very beautiful representation of the form of the old vol- 

 cano. 



t Humboldt, Vues de Cordilleres, p. 295, pi. Ixi., and Atlas de la 

 Re/at. Hist, dn Voyage, pi. 27. 



