That river, after passing Toledo, runs through a deep and long valley, walled up on either hand by lofty mountains. Those on the right bank are always capped with snow, and, ranging nearly parallel with the course of the stream, divide the valley of the Tagus from Old Castile and the Salamanca country. The highest parts are known by the names of the Sierra de Gredos, Sierra de Bejar, and Sierra de Gata; and in these sierras the Alberche, the Tietar, and the Alagon, take their rise, and, ploughing the valley in a slanting direction, fall into the Tagus. The principal mountain on the left bank is called the Sierra de Guadalupe; it extends in a southward direction from the river, and divides the upper part of La Mancha from Spanish Estremadura. The communications leading from the Salamanca country into the valley of the Tagus are neither many nor good; the principal passes are-- 1st. The rout of Horcajada, an old Roman road, which, running through Pedrahita and Villa Franca, crosses the Sierra de Gredos at Puerto de Pico, and then descends by Montbeltran to Talavera. 2d. The pass of Arenas, leading nearly parallel to, and at a short distance from, the first. 3d. The pass of Tornevecas, leading upon Placentia. 4th. The route of Bejar, which, crossing the Sierra de Bejar at the pass of Baños, descends likewise upon Placentia. 5th. The route of Payo or Gata, which crosses the Sierra de Gata by the pass of Perales, and afterwards dividing, sends one branch to Alcantara, the other to Coria and Placentia. Of these five passes the two last only are, generally speaking, practicable for artillery. The royal roads, from Toledo and Madrid to Badajos, unite near Talavera, and follow the course of the Tagus by the right bank as far Naval Moral, but then, turning to the left, cross the river at the bridge of Almaraz. Now, from Toledo, westward, to the bridge of Almaraz, a distance of above fifty miles, the left bank of the Tagus is so crowded by the rugged shoots of the Sierra de Guadalupe, that it may be broadly stated as impassable for an army, and this peculiarity of ground gives the key to the operations on both sides. For, Cuesta and Cartoajal, by reason of this impassable Sierra de Guadalupe, had no direct military communication: but Victor and Sebastiani, occupying Toledo and Talavera, could, by the royal roads above mentioned, concentrate their masses, at pleasure, on either line of operations. The rallying point of the French was Madrid, and their parallel lines of defence were the Tagus, the Alberche, and the Guadarama. The base of Cartoajal’s operations was the Sierra de Morena. Cuesta’s first line was the Tagus, and his second the Guadiana, from whence he could retreat by a flank march to Badajos, or by a direct one to the defiles of Monasterio in the Sierra Morena.