When a patrol is scattered it reassembles at some place previously selected; if checked in one direction, it takes another; if cut off it returns by a detour or forces its way through. As a last resort it scatters so that at least one man may return with information. Patrols nearing their own lines should march at a walk unless pressed by the enemy. Occasionally it is advisable for the leader to conceal his patrol and continue the reconnaissance with one or two companions. Patrols far from their commands or in contact with the enemy often remain out overnight. In such cases they seek a place of concealment, proceeding thereto after nightfall or under cover. When the enemy is encountered it is very necessary to locate his main force. Information is particularly desired of his strength, whether he has infantry, cavalry, and artillery, the route and direction of his march, or the location of his camp and line of outposts. Dust clouds indicate moving bodies. Infantry raises a low, thick cloud; cavalry a high, thin cloud; artillery and wagons a broken cloud. The kind of troops, direction of march, and approximate strength may thus sometimes be roughly estimated. If from some position a body of troops can be seen marching along in column, the exact time in minutes and seconds it requires for them to pass a certain point should be noted, together with the formation they are in, thus: Infantry, column of squads, three minutes and twelve seconds; cavalry, columns of twos at a trot, one minute and twenty seconds; wagons, four-mule, five minutes. From this information the strength can be determined by the following rule: Assuming that infantry in column of squads occupy half a yard per man, cavalry in column of fours 1 yard per man, and artillery and wagons in single column 20 yards per gun, caisson, or wagon, a given point would be passed in one minute by about-- 175 infantry. 110 cavalry at a walk. 200 cavalry at a trot. 5 guns, caissons, or wagons. For troops in column of twos, take one-half of the above estimate. Patrols should always observe the country marched over, with a view to making a report on the same. The following information is always of value: =Roads.=--Direction; kind, whether dirt, gravel, macadam, etc.; width, whether suitable for column of squads, etc.; border, whether fenced with stone, barbed wire, rails, etc.; steepness in crossing hills and valleys; where they pass through defiles and along commanding heights, etc.; crossroads. =Surrounding country.=--Whether generally open and passable for infantry, cavalry, and artillery, or whether broken and impassable, due to fences, woods, crops, ravines; whether good grazing is available, etc. =Railroads.=--Single or double track, narrow or broad gauge, tunnels, bridges, cuts, direction, stations, etc. =Bridges.=--Material, wood, stone, steel, etc.; length and breadth; number and kind of piers or supports.