GEOLOGICAL TBANSFIiltS. 
107 
With respect to the fragments of granite, gneiss, and 
mica-slate, found on the shores of Santa Cruz and Orotava, 
they were probably brought in ships as ballast. They no 
more belong to the soil where they lie, than the feldsparry 
lavas of Etna, seen in the pavements of Hamburgh and other 
towns of the north. The naturalist is exposed to a thousand 
errors, if he lose sight of the changes, produced on the sur- 
face of the globe by the intercourse between nations. We 
might be led to say, that man, when expatriating himself, is 
desirous that everything should change country with him. 
Not only plants, insects, and different species of small Qua- 
drupeds', follow him across the ocean ; his active industry 
covers the shores with rocks, which he has tom from the 
soil in distant climes. 
Though it be certain, that no scientific observer has 
hitherto found at Teneriffe primitive strata, or even those 
trappean and ambiguous porphyries, which constitute the 
bases . of Etna, and of several volcanoes of the Andes, we 
must not conclude from this isolated fact, that the whole 
archipelago of the Canaries is the production of submarine 
fires. The island of Gomera contains mountains of granite 
and mica-slate; and it is, undoubtedly, in these very ancient 
rocks, that we must seek there, as well as on all other parts 
of the globe, the centre of the volcanic action. Amphibole, 
sometimes pure and forming intermediate strata, at other 
times mixed with granite, as in the basanites or basalts of the 
ancients, may, of itself, furnish all the iron contained in the 
black and stony lavas. This quantity amounts in the basalt 
of the modern mineralogists only to 020, while in amphi- 
bole it exceeds 0 30. 
Erom several well-informed persons, to whom I addressed 
myself, I learned that there are calcareous formations in the 
Great Canary, Eorteventura, and Lancerota.® I was not 
able to determine the nature of this secondary rock ; but it 
appears certain, that, the island of Teneriffe is altogether 
destitute of it; and that in its alluvial lands it exhibits 
only clayey calcareous tufa, alternating with volcanic brec- 
cia, said to contain, (near the village of La Bambla, at 
Calderas, and near Candelaria,) plants, imprints of lishes, 
* At Lancerota calcareous stone is burned to lime witli a fi/e male of 
the alhulaga, a new species of thorny and arborescent Sonchus. 
