Let the River Marne be used as a base from which this topography can be determined. The Marne rises near Langres, which is the northwest angle of that pentagon of fortresses (Belfort, Epinal, Langres, Dijon, and Besancon), which incloses an almost impregnable recuperative ground for exhausted armies. From Langres the Marne flows almost north by west for about fifty miles through a hilly and wooded country, then, taking a more westerly course, it flows for approximately seventy-five miles almost northwest, across the Plain of Champagne, past Vitry-le-Francois and Chalons, thence almost due westward through the Plateau of Sezanne, by Epernay, Chateau Thierry, La Ferte-sous-Jouarre, and Meaux to join the Seine just south of Paris. In the neighborhood of Meaux, three small tributaries flow into the Marne--the Ourcq from the north, and the Grand Morin and Petit Morin from the east. The Marshes of St. Gond, ten miles long from east to west and a couple of miles across, lie toward the eastern borders of the Plateau of Sezanne, and form the source of the Petit Morin, which has been deepened in the reclamation of the marsh country. Once more considering the source of the Marne, near Langres, it will be noted that the River Meuse rises near by, flowing north by east to Toul, and then north-northwest past Verdun to Sedan, where it turns due north, flowing through the Ardennes country to Namur, in Belgium. To the east of the Meuse lies the difficult forest clad hill barrier, known as the Hills of the Meuse; to the east extends (as far as Triaucourt) the craggy and broken wooded country of the Argonne, a natural barrier which stretches southward in a chain of lakes and forests. West of this impassible country of the Meuse and the Argonne lies the plain of Champagne-Pouilleuse, which is almost a steppe, bare and open, only slightly undulating, overgrown with heath, and studded here and there by small copses of planted firs, naught but a small portion of the whole being under cultivation. Between the Forest of the Argonne and this great plain, which is over a hundred miles long from north to south and forty miles in width, lies a short stretch of miniature foothills, with upland meadows here and there, but crossed in every direction by small ravines filled with shrubs and low second-growth timber. Here lies the source of the Aisne, a river destined to live in history; and on the farther side begins the great plain. On the west of the plain of Champagne rises, 300 feet, with a curious clifflike suddenness, the Plateau of Sezanne. The effect is as though a geological fault had driven the original plateau from north to south throughout its entire length, and then as though there had been a general subsidence of the plain, giving rise to the clifflike formations known as Les Falaises de Champagne, at the foot of which runs the road from La Fere-Champenoise to Rheims.