Liguria is but a narrow slip of land if we compare it with the broad plain of the Po, but it is one of the most clearly defined districts of Europe, and its inhabitants have retained many original traits. The contrast between the Podane plains and the littoral region beyond the barren Apennines is striking, but if we travel in the direction of Provence or of Tuscany the landscape changes only by degrees. The rampart of the Apennines surrounds the whole of the Gulf of {231} Genoa, and there is not a single break in it. These mountains are very different in character from the Alps, though joined to them as the branch of a tree is united to its trunk. It is not possible to tell where one chain ends and the other begins. If the main direction of the mountain is to be the criterion, the Ligurian Apennines may be said to begin at the frontier of France, near the sources of the Tinea and Vesubio; but if great height, pastures, and perennial snow are considered sufficient to constitute an Alpine region, then the Apennines only begin to the east of the Col di Tenda, for the fine summits of the Clapier, Fenêtre, and Gordalesque, to the west of that pass, attain a height of 10,000 feet. They are quite Alpine in their character, and may boast even of small glaciers, the most southerly in the mountains of Central Europe. Geologists usually draw the line where cretaceous and tertiary rocks take the place of the crystalline rocks of the Alps. But this, too, is only a conventional division, for these crystalline rocks, which constitute the crest of the Alps in the west, extend far to the east, and occasionally they break through the sedimentary formations which overlie them, and rise into summits similar to those of the Alps. Thus the granitic summits of the mountains of Spezia remind us of the mountain mass near the Col di Tenda. [Illustration: Fig. 78.—THE JUNCTION OF ALPS AND APENNINES. Scale 1 : 1,500,000] The chain of the Ligurian Apennines is by no means of uniform height, but, like that of the Alps, it consists of mountain masses separated by passes. The lowest of these passes is that to the west of Savona, named indifferently after one of the neighbouring villages, Altare, Carcara, or Cadibona. This pass is hardly more than 1,600 feet in height, and is popularly looked upon as constituting the boundary between the Alps and Apennines. The possession of this pass during war has {232} always been considered of great importance, for it commands the approaches to Genoa and the upper valleys of Piemont, and the Tanaro and Bormido, which rise near it, have often run with blood.