The subterranean fermentation of which Tuscany is the scene is no doubt due in a large measure to the changes which have taken place in the relative proportions of land and sea. Several isolated hills rise near the coast like islands from the sea, and these have evidently been joined to the mainland by the alluvial deposits brought down by the rivers. The Monti Serra (3,000 feet), to the east of Pisa, between the Arno and the Serchio, are almost insulated even now, for they are surrounded by swamps, and the level of the Lake of Bientina, at their eastern foot, is scarcely thirty feet above that of the Me­di­ter­ra­nean. The heights along the coast to the south of Leghorn are not quite so isolated, but the lowland which connects them with the table-land of the interior is only of small elevation. The promontory, however, whose extremities are occupied by the towns of Populonia and Piombino (653 feet), is joined to the mainland only by a low plain of sand. The most perfect type of these ancient islands is presented to us in the superb Monte Argentaro, at the southern extremity of the Tuscan littoral, which rises boldly from the sea to a height of 2,085 feet, and is attached to the mainland by two narrow strips of land covered with pine-trees, enclosing a lake of regular shape: in the midst of it, on a fragment of the ancient beach, is built the town of Orbetello. This lake, which looks almost as if it were the work of a generation of giants, has been converted into an eel-pond, and millions of fish are caught in it every year. Towards the west of this mountain, in the direction of Corsica, lie the islands of Giglio and Monte Cristo (2,062 feet) and the rock of Formica. The island of Elba, farther north, forms a small world of its own.

The rivers of Tuscany have wrought great changes in the plains through which they flow, and along the sea-coast. Their labour has been facilitated by the nature of the soil which they traverse. The least rain converts the barren hill-slopes into a semi-fluid paste, which is carried by the rivers down to the sea. The mouth of the Arno has thus been pushed forward to the extent of seven miles in the course of a few centuries. In former times the Serchio and the Arno united before they flowed into the sea, but the Pisans diverted the former river to the {243} north, in order to rid themselves of its unwelcome deposits. Pisa, in the time of Strabo, stood at a distance of only twenty Olympian stadia from the Tyrrhenian Sea, and when the cascina of San Rossore was built, towards the close of the eleventh century, its walls were close to the beach, which is now at a distance of three miles. Extensive plains intersected by dunes, or tomboli, and partly covered with forests of pines, have been added to the land in the course of centuries. These sandy wastes have become the home of large herds of horses and half-wild cattle, and the camel has been acclimatised there, it is said, since the Crusades. These changes in the coast-line may not, however, be due exclusively to the agency of the rivers, for there exists evidence of an upheaval of the land. The building stone known at Leghorn as panchina is clearly of marine origin, and the shells which enter into its composition are still met with in the Tyrrhenian Sea.

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Fig. 84.—MONTE ARGENTARO.

From the French Chart. Scale 1 : 168,000.

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Fig. 85.—VAL DI CHIANA.

From the Austrian Staff Map. Scale 1 : 218,000.