In encamping troops in winter-quarters, it is sometimes necessary to scatter them over a considerable extent of ground, in order to facilitate their subsistence. In such a case, the arrangement of guards requires the utmost care. A chain of advanced posts should be placed several miles' distance from the line of camp; these posts should be supported by other and larger detachments in their rear, and concentrated on fewer points; and the whole country around should be continually reconnoitered by patrols of cavalry. The manner in which Napoleon quartered and wintered his army on the Passarge, in 1806-7, furnishes a useful lesson to military men, both in the matters of encampment and subsistence. An immense army of men were here quartered and subsisted, in a most rigorous climate, with a not over fertile soil, in the midst of hostile nations, and in the very face of a most powerful enemy. A Roman army invariably encamped in the same order, its troops being always drawn up in the same battle array. A Roman staff-officer who marked out an encampment, performed nothing more than a mechanical operation; he had no occasion for much genius or experience. The form of the camps was a square. In later times, they sometimes, in imitation of the Greeks, made them circular, or adapted them to the ground. The camp was always surrounded with a ditch and rampart, and divided into two parts by a broad street, and into subdivisions by cross-streets and alleys. Each tent was calculated to hold ten privates and a petty officer. In the middle ages, the form of the camp did not differ very essentially from that of the Romans, the variation consisting principally in the interior arrangements, these arrangements being made to correspond to the existing mode of forming a line of battle. The details of this system may be found in the military work of Machiavelli. The art of fixing a camp in modern times is the same as taking up a line of battle on the same position. Of all the projectile machines must be in play and favorably placed. The position must neither be commanded, out-fronted, nor surrounded; but on the contrary ought, as far as possible, to command and out-front the enemy's position. But even in the same position there are numerous modes of arranging an encampment, or of forming a line of battle, and to select the best of these modes requires great experience, _coup d'oeil_, and genius. In relation to this point Napoleon makes the following remarks:--