Ch. XXIX.] PEAK OF TEXERIFFE. 645 



The crater of Vesuvius in 1822 was 2000 feet deep; and, if it 

 were a lialf-submerged cone like St. Paul, the excavating power of 

 the ocean might, in conjunction with a gradual upheaving force, give 

 rise to a large caldera. Whatever, therefore, may have been the 

 nature of the forces, igneous or aqueous, which have shaped out the 

 Yal del Bove on Etna, or the deep abyss called the Caldera in the 

 north of Palma, we may well conceive that some craters may have 

 been enlarged into calderas by the denuding power of the ocean, 

 whenever considerable oscillations in the relative level of land and sea 

 have occurred. 



Peak of Teneriffe.— The accompanying view of the Peak, taken 

 from sketches made by M. Hartung and myself during our visit to 

 Teneriffe in 1854, will show the manner in which that lofty cone is 

 encircled on more than two sides by what I consider as the ruins of 

 an older cone, chiefly formed by eruptions from a summit which has 

 disappeared. That ancient culminating point from which one or 

 more craters probably poured forth their lavas and ejectamenta may 

 not have been placed precisely where the present peak now rises, and 

 may not have had the same form, but its position was probably not 

 materially different. The great wall or semicircular range of preci- 

 pices, c, c, surrounding the atrium, b, b, is obviously analogous to the 

 walls of a Caldera like that of Palma ; but here the cliffs are insig- 

 nificant in dimensions when compared to those in Palma, being in 

 general no more than 500 feet high and rarely exceeding 1000 feet. 

 The plain or atrium, b, b, figs. 704 and 705, lying at the base of the 

 cliffs, is here called Las Canadas, and is covered with sand and pum- 

 ice thrown out from the Peak or from craters on its flanks. Copious 

 streams of lava, d, d, have also flowed down from lateral openings, 

 especially from a crater called the Chahorra, /, fig. 705, which is not 

 seen in the view, fig. 704, as it is hidden by the Peak. The last 

 eruption was as late as the year 1798. 



Fig. 705. 



Section through part of Teneriffe, from X.E. to S.W. On a true scale ; as given in 

 Von Buch's ll Canary Islands." 



a. Peak of Teneriffe. d. Modern lavas. 



b. The Canadas or atrium. '/ Cone and crater of Chahorra. 



c. Cliff bounding the atrium. 



To what extent the lavas, d, d, figs. 704 and 705, may have nar- 

 rowed the circus or atrium, b, or taken away from the height of the 

 cliff, c, no geologist can determine for want of sections ; but should 

 the Peak and the Chahorra continue to be active volcanoes for ao-es, 

 the new cone, a, might become united with the old one, and the lava 



