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are placed in strata on each other, like the layers 

 of the mountains of secondary formation. 



These strata, similar to those observed on the 

 brink of the ancient crater of Vesuvius at the 

 Somma, appear to be the result of successive 

 overflowings. They are formed of vitrified lava, 

 of a porphyry with base of osidian, and of pitch- 

 stone. For ages past, the peak of TenerifFe, 

 the perpendicular height of which is more than 

 nineteen hundred toises, has Beted only by late- 

 ral eruptions. The last of these eruptions is 

 that of Chahorra, which took place in 1798. 

 On beholding in the plain of Retama the enor- 

 mous quantity of substances thrown out by the 

 peak, we are astonished at the smallness of the 

 crater, from which we suppose that so much 

 ashes, pumice stone, and blocks of volcanic vi- 

 trified matter, have issued ; but Mr. Cordier, who 

 has made the longest residence of any mine- 

 ralogist in the island of Teneriffe, has furnished 

 the important observation, that the present cra- 

 ter, the caldera of the piton, is not the principal 

 opening of the volcano. This learned traveller 

 found on the northern declivity of the peak a 

 funnel of enormous dimensions, which appears to 

 have acted the principal part in the ancient 

 eruptions of the volcano of Teneriffe. 



