TRUE VOLCANOES. 241 



of which (17,084 feet) was reached by Friedrich Parrot in 

 the ytar 1829, and by Abich and Chodzko in 1845 and 1850, 

 forms, like Chimborazo, an mi-opened dome. Its vast lava- 

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

 important character in the formation of Ararat is a lateral 

 chasm, the deeply-cut Valley of Jacob, which may be coin- 

 pal ed with the Val del Bove of Etna. In this, according to 

 Abich's observation, the inner structure of the nucleus of 

 the trachytic dome-shaped mountain, first becomes really 

 risible, as this nucleus and the upheaval of the whole of 

 Ararat are much more ancient than the lava-streams. 7 

 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, whilst 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 Pichinch'a, 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 



maximum of its oscillation, presents perpendicular bases of 15,777 fee* 

 above the surface of the sea, and of 6396 feet above the plateau in 

 which the cities of Quito, Hambato, and Nuevo Riobambaare situated; 

 bases which, combined with very accurate measurements of angles of 

 elevation, may be employed for determining distance in many topogra- 

 phical labours which are to be rapidly executed. The second of the 

 level-lines here indicated, the horizontal which bounds the lower por- 

 tion 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 below the temporary snow- 

 line, and thus the snow-fall decides as to the relative height. I have 

 heard such considerations as these upon perpetual 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 paiticular 

 individuals amongst the coloured aborigines, even when they are on 

 the lowest steps of civilization. 



1 Abich. Bulletin de la Societe de Geographic, 4me se'rie, t. i (1851), 

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

 volcano. 



VOL. V. B 



