I'KAK OF TENERIFFK. 4.'} 



hut aqueous vapours were emitted by some of the ere- chap. mi. 

 vices, in which heat was perceptible. In fact, the E-uptto,'* 

 volcano has not been active at the summit for tliousands 

 of years, its eruptions having been from the sides, and 

 the depth of the crater is only about 106 feet. After 

 examining the objects tliat presented themselves in tliis 

 elevated spot, and enjoying the vast prospect, the 

 travellers commenced their descent, and towards evening 

 reached tlie port of Orotava. 



The Peak of TenerifFe forms a pyramidal mass having Dimension* 

 a circumference at the base of more than 116,110 yards, "^'■'^p^^'^ 

 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 637 feet, or ^^^ of 

 the whole. The lower part of the island is composed of Geological 

 basalt and other igneous rocks of ancient formation, and ''■*^'■''■" 

 is separated from the more recent lavas and the products 

 of the present volcano by strata of tufa, puzzolana, and 

 clay. The first that occur in ascending the Peak are of 

 a black colour, altered by decomposition, and sometimes 

 porous. Their basis is wacke, and has usually an irre- 

 gular, but sometimes a conchoidal fracture. They are 

 divided into very tliin layers, and contain olivine, 

 magnetic iron, and augite. On the first elevated plain, 

 that of Retama, the basaltic depositcs disappear beneath 

 heaps of ashes and pumice. Beyond this are lavas, 



" Various measurements have been made of the heij^^Iit of the 

 Peak.of Tenerifte ; but Humboldt, after enumerating- fourteen, states 

 that the followint;- alone can be considered as deservinjr 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 particularh- stated by our author, the mean of 

 the remainmg measurement is 19119 toises, or 12.20!i Engli--h feet. 

 It is seen above, that the height adopted by Humboldt is 1904 toises, 

 or 12,176 English feet. 



