The undoubted effect of the third and last upheaval was the almost entire destruction of the southern portion of the first; and it was at this time the island received its present form. It occurred in a direction from north to south. So long as the masses of this last eruption have not come in contact with the masses of previous upheavals, their direction remains regular, as is shown by the mountain-chain of Cape Corso. But it had to burst its way through the towering masses of the southern ridge with a fearful shock; it broke them up, altering its direction, and sustaining interruption at many points, as is shown by the openings of the valleys, which lead from the interior to the plain of the east coast, and have become the beds of the streams that flow into the sea on this side--the Bevinco, the Golo, the Tavignano, the Fiumorbo, and others. The rock strata of this third upheaval are primitive ophiolitic and primitive calcareous, covered at various places by secondary formations. The primitive masses, which occupy, therefore, the south and west of the island, consist almost entirely of granite. At their extremities they include some layers of gneiss and slate. The granite is almost everywhere covered--a clear proof that it was elevated at a period antecedent to that during which the covering masses were forming in the bosom of the ocean, to be deposited in horizontal strata on the crystalline granite masses. Strata of porphyry and eurite pierce the granite; a decided porphyritic formation crowns Mounts Cinto, Vagliorba, and Perturato, the highest summits of Niolo, overlying the granite. From two to three feet of mighty greenstone penetrate these porphyritic rocks. The intermediary masses occupy the whole of Cape Corso, and the east of the island. They consist of bluish gray limestone, huge masses of talc, stalactites, serpentine, euphotides, quartz, felspar, and porphyries. The tertiary formations appear only in isolated strips, as at San Fiorenzo, Volpajola, Aleria, and Bonifazio. They exhibit numerous fossils of marine animals of subordinate species--sea-urchins, polypi, and many other petrifactions in the limestone layers. In regard to the plains of the east coast of Corsica, as the plains Biguglia, Mariana, and Aleria, they are diluvial deposits of the period when the floods destroyed vast numbers of animal species. Among the diluvial fossils in the neighbourhood of Bastia, the head of a lagomys has been found--a small hare without tail, existing at the present day in Siberia. There is no volcano in Corsica; but traces of extinct volcanoes may be seen near Porto Vecchio, Aleria, Balistro, San Manza, and at other points.