44 PEAK OF TENERIFFE. 



from the sides, and the depth of the crater is only 

 about 106 feet. After examining the objects that 

 presented themselves in this elevated spot, and en- 

 joying the vast prospect, the travellers commenced 

 their descent, and towards evening reached the port 

 of Orotava. 



The Peak of Teneriffe forms a pyramidal mass, 

 having a circumference at the base of more than 

 115,110 yards, and a height of 12,176 feet.* Two- 

 thirds of the mass are covered with vegetation, the 

 remaining part being steril, and occupying about 

 ten square leagues of surface. The cone is very 

 small in proportion to the size of the mountain, it 

 having a height of only 537 feet, or -^ of the whole. 

 The lower-part of the island is composed of basalt 

 and other igneous rocks of ancient formation, and is 

 separated from the more recent lavas, and the pro- 

 ducts of the present volcano, by strata x>f tufa, puz- 

 zolana, and clay. The first that occur in ascending 

 the Peak are of a black colour, altered by decom- 

 position, and sometimes porous. Their basis is 

 wacke, and has usually an irregular, but sometimes 

 a conchoidal fracture. They are divided into very 

 thin layers, and contain olivine, magnetic iron, and 

 augite. On the first elevated plain, that of Retama, 

 the basaltic deposites disappear beneath heaps of 

 ashes and pumice. Beyond this are lavas, with 

 a basis of pitch-stone and obsidian, of a blackish- 

 brown, or deep olive-green colour, and containing 



* Various measurements have been made of the height of the Peak of 

 Teneriffe ; but Humboldt, after enumerating fourteen, states that the fol- 

 lowing alone can be considered as deserving of confidence : 



Borda's, by trigonometry 1905 toises. 



Borda's, by the barometer 1976 



Lamanou's, by the same 1902 



Cordier's, by the same 1920 



The average of these four observations makes the height 1926 toises ; 

 but if the barometric measurement of Borda be rejected, as liable to ob- 

 jections particularly stated by our author, the mean of the remaining 

 measurement is 1909 toises, or 12,208 English feet. It is seen above, 

 that the height adopted by Humboldt is 1904 toises, or 12,176 English 

 feet. 



