CHAPTER VIII.
THE CALORE AND TANAGRO—ST. MICHAEL'S CAVE—GEOLOGY OF THE VALLEY—CAMPOSTRINA—GREAT ROCK FALLS.
Accompanied still by the Padre, I then crossed the river, and scrambled up the opposite bank, composed of deep clay and boulders, with gravel, to the mouth of St. Michael's Cave, from out of which issues that portion of the whole waters of the Calore, (as the Tanagro above this is called); that entering the limestone at Polla, at the upper end of the gorge of Campostrina, and finding its way by subterraneous channels, here debouches, and turning some primitive water-wheels at the Catalan forge, falls in a pretty succession of cascades to join the Tanagro again in its open bed. The mouth of this large cavern is probably from 50 to 80 feet above the open bed of the river opposite, and its jaws present evidence of powerful erosion. There are large stalactites within, and at about 300 feet from the mouth further entrance is barred by the water, which issues from the cavern almost clear and pellucid, while that of the river below is as white as milk, with impalpable cretaceous matter in suspension. As the water of the Calore thus divided between the subterraneous and the open channels at Polla is very muddy, and contains much calcareous
