across the Guadarrama, through which there debouch on to Madrid the main roads from North-western Spain--those from (_a_) Valladolid and Segovia, (_b_) from Astorga, Tordesillas, and Arevalo, (_c_) from Salamanca by Avila. After this group of passes there is a long space of impracticable hills, till we come to the chief road from north to south, parallel to the Portuguese frontier: it comes down the valley of the Alagon from Salamanca, by Baños and Plasencia, on to the great Roman bridge of Alcantara, the main passage over the Middle Tagus. This is a bad road through a desolate country, but the exigencies of war caused it to be used continually by the French and English armies, whenever they had to transfer themselves from the valley of the Douro to that of the Tagus. Occasionally they employed a still worse route, a little further west, from Ciudad Rodrigo by Perales to Alcantara. When we get within the Portuguese frontier, we find a road parallel to the last, from Almeida by Guarda to Abrantes, also a difficult route, but like it in perpetual use: usually, when the French marched from Salamanca to Alcantara, Wellington moved in a corresponding way from near Almeida to Abrantes. This road runs along the basin of the Zezere, though not down in the trough of the river, but high up the hillsides above it. Spanish and Portuguese roads, as we shall see, generally avoid the river banks and run along the slopes far above them. The next great chain across the Peninsula is that which separates the barren and sandy valley of the Upper Tagus from the still more desolate and melancholy plateau of La Mancha, the basin of the Guadiana. Of all the regions of Central Spain, this is the most thinly peopled and uninviting. In the whole valley there are only two towns of any size, Ciudad Real, the capital of La Mancha, and Badajoz, the frontier fortress against Portugal. The mountains north of the Guadiana are called first the Sierra de Toledo, then the Sierra de Guadalupe, lastly on the Portuguese frontier the Sierra de San Mamed. Their peculiarity, as opposed to the other cross-ranges of the Peninsula, is that at their eastern end they do not unite directly with the mountains of Valencia, but leave a broad gap of upland, through which the roads from Madrid to Murcia and Madrid to Valencia take their way. When the Sierra de Toledo once begins roads are very few. There are practically only three--(1) Toledo by San Vincente to Merida, a most break-neck route winding among summits for forty miles; (2) Almaraz by Truxillo to Merida, the main path from Tagus to Guadiana, and the most used, though it is difficult and steep; (3) Alcantara by Albuquerque to Badajoz, a bad military road parallel to the Portuguese frontier, continuing the similar route from Salamanca to Alcantara.