PEAK OF TENERIFFE. 5] 
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 7; of the 
whole. The lower part of the island is composed 
of basalt and other igneous rocks of ancient for- 
mation, and is separated from the more recent 
lavas and the products of the present voleano 
by strata of tufa, puzzolana, and clay. The first 
that occur in ascending the Peak are of a black co- 
lour, altered by decomposition, and sometimes po- 
_rous. Their basis is wacke, and has usually an irre- 
gular, but sometimes a conchoidal fracture. They 
are divided into very thin layers, and contain oli- 
vine, magnetic iron, and augite. On the first ele- 
vated plain, that of Retama, the basaltic deposites 
disappear beneath heaps of ashes and pumice. Be- 
yond this are lavas, with a basis of pitch-stone and 
obsidian, of a blackish-brown or deep olive-green 
colour, and containing crystals of felspar, which are 
* Various measurements have been made of the height of the 
Peak of Teneriffe ; but Humboldt, after enumerating fourteen, states 
that the following 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 objections particularly stated by our author, the mean of 
the remaining measurement is 1909 toises, or 12,208 English feet. 
~  Itis seen above, that the height adopted by Humboldt is 1904 toises, 
_ or 12,176 English feet. 
