Bordering France on the east are Germany, Switzerland, and Italy. The Alps, covering Switzerland like a huge network, give to this country the appearance of an immense bastion, which, extending east, separates Germany from Italy. From Switzerland these mountains extend through and beyond the Tyrol. They separate the valley of the Danube from the valley of the Po. In Switzerland they are known as the Swiss Alps; in the Tyrol, as the Tyrolese Alps. On the north side of them are the States of Swabia, Bavaria, and Upper Austria; on the south side, Piedmont, Lombardy, and Venice. Extending south from western Switzerland to within about thirty miles of the sea, the French Alps form part of the boundary line between France and Italy; thence, turning east, they approach the Italian shore, and are here known as the Maritime Alps; still farther east, along the shores of the Gulf of Genoa, they are called the Apennines. With the exception of a few passes, this great mountain chain, almost enclosing northern Italy, forms an insurmountable barrier to the soldier. Even over the passes, especially across the higher ranges, communication was, at the time of which we write, extremely dangerous. The snow and ice, the glaciers, avalanches, frequent storms, and steep declivities, made these mountain roads hazardous and difficult for the passage of armies. The principal passes in the Swiss Alps are the St. Gothard, the Simplon, and the Great St. Bernard; in the French Alps, the Little St. Bernard, and the Mont Cenis; in the Maritime Alps, the Col di Tenda and the Col di Ormea; and in the Apennines, the Col di Cadibona and the Bochetta. Lying partly or entirely within this territory are three large rivers and their tributaries. They have their sources in or near the great chain of the Alps, and drain the tributary country. The Po rises in the French Alps, and flows east through northern Italy. The Danube rises in western Germany, and flows east through Bavaria and Austria. The Rhine rises in Switzerland, flows north into Lake Constance, thence, forming the outlet of the lake, flows west to Bâle, where it turns abruptly and flows north for the rest of its course. Early in April, 1800, an Austrian army of one hundred and twenty thousand soldiers, commanded by Marshal Kray, guarded the right bank of the upper Rhine. The right wing extended beyond Strasburg; the left, well up into the Alps east of Switzerland; and the centre, forming the greater part of Kray's army, occupied the Black Forest in the angle of the Rhine made by its change of direction at Bâle. Kray's line of communication was along several roads down the Danube to the Austrian capital.