hereto 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
pas 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, 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.

RIVERS.--Direction; width, depth; kind of bottom, such as mud,
sand, rocky, etc.: banks, steep or gentle, open or wooded; rapidity
of current; variations in depth at different times a