If an ideal line be drawn diagonally from a point so far north-west as Cape _Revellata_, near Calvi, to the point of _Araso_, far down the south-east coast near Porto Vecchio, this primary eruption may be traced in the several ranges, perpendicular to the ideal line and parallel with each other, which descending to the sea in the direction of from north-east to south-west, terminate in the principal promontories on the western coast, and form the numerous valleys which appear in succession from the Straits of Bonifacio to the Gulf of Porto.
Thus at the earliest epoch the principal axis of the island had its direction from the north-west to the south-east. The Capo Corso of those times lifted its head above the Sea of Calvi, and who can say how far the island extended at the opposite extremity? All we know is, that the group of rocky islets called the _Isole Cerbicale_, south-west of Porto Vecchio, with the _Isola du Cavallo_, and that _Di Lavazzi_ off the coast at Bonifacio; and again, the islets _Die Razzoli_ and _Budelli_ on the opposite side of the Straits, with the larger islands of _La Madaléna_ and _Caprera_, all of a similar formation with the primary Corsican range,—like detached fragments of some vast ruined structure,—appear to form the links of a chain which united Corsica with the mountain system of the north-eastern portion of the island of Sardinia.
These primitive masses are almost entirely granitic; and thus, at the epoch of its first emergence from the waters of the Mediterranean, no spark of animal or vegetable life existed in the new island.
So also one half of the masses raised by the _second_ upheaval, having the same general direction, are granitic. But, as we advance towards the north-east, the granites insensibly resolve themselves into _ophiolitic_ rocks,—a name given by French geologists to certain volcanic eruptions of the cretaceous era,—which are also found in the Morea.[21] There are but few traces remaining of this second upheaval, which evidently laid in ruins great part of the northern extremity of the former one, cutting it at right angles to the east of the Gulf of Porto. This line, ranging from the south-west to the north-east into the heart of the _Nebbio_, is broken up and destroyed through nearly its whole length.