It includes two regions of widely differing physical characteristics: the
northern, continental; the southern, peninsular. The peninsula is slightly
larger than the continental portion: together their area is about 91,200
square miles.

*Continental Italy.* The continental portion of Italy consists of the
southern watershed of the Alps and the northern watershed of the
Apennines, with the intervening lowland plain, drained, for the most part,
by the river Po and its numerous tributaries. On the north, the Alps
extend in an irregular crescent of over 1200 miles from the Mediterranean
to the Adriatic. They rise abruptly on the Italian side, but their
northern slope is gradual, with easy passes leading over the divide to the
southern plain. Thus they invite rather than deter immigration from
central Europe. East and west continental Italy measures around 320 miles;
its width from north to south does not exceed seventy miles.

*The peninsula.* The southern portion of Italy consists of a long, narrow
peninsula, running northwest and southeast between the Mediterranean and
Adriatic seas, and terminating in two promontories, which form the toe and
heel of the "Italian boot." The length of the peninsula is 650 miles; its
breadth is nowhere more than 125 miles. In striking contrast to the plains
of the Po, southern Italy is traversed throughout by the parallel ridges
of the Apennines, which give it an endless diversity of hill and valley.
The average height of these mountains, which form a sort of vertebrate
system for the peninsula (_Apennino dorso Italia dividitur_, Livy xxxvi,
15), is about 4,000 feet, and even their highest peaks (9,500 feet) are
below the line of perpetual snow. The Apennine chain is highest on its
eastern side where it approaches closely to the Adriatic, leaving only a
narrow strip of coast land, intersected by numerous short mountain
torrents. On the west the mountains are lower and recede further from the
sea, leaving the wide lowland areas of Etruria, Latium and Campania. On
this side, too, are rivers of considerable length, navigable for small
craft; the Volturnus and Liris, the Tiber and the Arno, whose valleys link
the coast with the highlands of the interior.

*The **coast-line**.* In comparison with Greece, Italy presents a striking
regularity of coast-line. Throughout its length of over 2000 miles it has
remarkably few deep bays or good harbors, and these few are almost all on
the southern and w