MOSEL (Fr. Moselle)  , a river of France and Germany, a left-bank tributary of the Rhine . It rises at an altitude of 2411 ft. on the west flank of the Vosges, close to the Franco-German frontier, and a little N. of the Ballon d'Alsace . It flows first N.W. through the French department of Vosges, bends towards N. through that of Meurthe-et-Moselle, forms the Franco-German frontier for a short distance below Pagny, and enters Lorraine . From Sierck to Wasserbillig it forms the frontier between the Rhine Province and Luxemburg, then, turning N.E., it follows a sinuous course and reaches the Rhine at Coblenz . The principal towns on the banks of the Mosel are, in France: Remiremont, Epinal, Toul and Ponta-Mousson; in Germany: Metz, Diedenhofen, Trier (Treves) and Coblenz . The Mosel receives the waters of the Moselotte, Meurthe, Seille and Saar (its principal tributary) on the right, and the Madon, Orne and Sauer on the left . Navigation for small vessels extends downwards from Fronard, a little below Nancy, the Mosel canal affording communication from a point above Metz to the frontier . In the lower part of the valley are the vineyards from which the well-known Mosel wines are produced . The valley of the Mosel, especially the part between Trier and Kochem, is noted both for picturesque scenery and for many sites, of antiquarian interest . The length of the river is 314 m: MOSELLE-LINE, the designation of a line of French barrier forts (forts d'arret) on the upper Moselle between the fortresses of Epinal and Belfort (see these articles, also MEUSE LINE and articles referred to therein) . The purpose of this line, the separate forts of which command the relatively few lines of advance from upper Alsace through the Vosges, is to deflect a possible German invasion from Alsace either towards Belfort or towards the open gap between Epinal and Toul called the Trouee d'Epinal .