316 COSMOS. 



commences in the Playas, with that at the point immediately 

 at the foot of the volcano, gives 473 feet of relative per- 

 pendicular elevation. The house that we inhabited stood 

 only about 500 toises (3197 feet) from the border of the 

 Malpais. At that place there was a small perpendicular pre- 

 cipice of scarcely 12 feet high, from which the heated water 

 of the brook (Rio de San Pedro) falls down. The portion 

 of the inner structure of the soil which I could examine at 

 the precipice, showed black, horizontal, loamy strata, mixed 

 with sand (rapilli). At other points which I did not see, 

 Burkart has observed "on the perpendicular boundary of 

 the upheaved soil, where the ascent of this is difficult, a light 

 gray and not very dense (weathered) basalt, with numerous 

 grains of olivine." 9 This accurate and experienced observer 

 has, however, 10 like myself, on the spot, conceived the idea of 

 a vesicular upheaval of the surface effected by elastic va- 

 pours, in opposition to the opinion of celebrated geogno- 

 sists 11 , who ascribe the convexity, which I ascertained by 

 direct measurement, solely to the greater effusion of lava 

 at the foot of the volcano. 



The many thousand small eruptive cones (properly rather 

 of a roundish or somewhat elongated, oven-like form) which 

 cover the upheaved surface pretty uniformly, are on the 

 average 4 to 9 feet in height. They have risen almost ex- 



9 Burkart, Aufenthalt und Reisen in Mexico in den JaJiren, 1825 

 1834, Bd. i (1836), p. 227. 



10 Op. tit. sup. Bd. i, pp. 227 and 230. 



11 Poulett Scrope, Considerations on Volcanoes, p. 267; Sir Charles 

 Lyell, Principles of Geology, 1853, p. 429; Manual of Geolugy, 1855, 

 p. 580 ; Daubeny on Volcanoes, p. 337. See also " on the elevation 

 hypothesis," Dana, Geology, in the United States Exploring Expedition, 

 vol. x, p. 369. Constant Prevost, in the Comptes rendus, t. xli (1855), 

 pp. 866 876, and 918 923 : sur les eruptions et le drapeau de I'infail- 

 libilite." See also, with regard to Jorullo, Carl Pieschel's instructive 

 description of the volcanoes of Mexico, with illustrations by Dr. Gum- 

 precht, in the Zeitschrift fur Allg. Erdkunde of the Geographical Society 

 of Berlin (Bd. vi, s. 490 517); and the newly published picturesque 

 views in Pieschel's Atlas der Vulkane der Republilc Mexico, 1856, 

 tab. 13, 14, and 15. The Royal Museum of Berlin, in the department 

 of engravings and drawings, possesses a splendid and numerous col- 

 lection of representations of the Mexican volcanoes (more than 40 

 sheets), taken from nature by Moritz Kugendas. Of the most western 

 of all Mexican volcanoes, that of Colima alone, this great master has 

 furnished fifteen coloured views. 



