The sun on one's back, a light background, water or snow to look over, ground that is uniform and offers no prominent points of reference, or when the air is particularly clear, as after a rain, tend to make objects appear near. A dark background, the sun in one's eyes, undulating ground to look over, or when it is cut by ravines or covered by trees or dwellings, or seen dimly at evening and in misty weather, tend to make objects appear distant. In estimating distance under the usual conditions: Men's features can be distinguished at 300 yards, head-dress at 600 yards, movement of legs and arms at 1000 yards. Infantry can readily be distinguished from cavalry at 1200 yards. Individual men become vertical lines at 1500 yards. Distinguishing between infantry and cavalry only by mode of motion at 1500 yards. A mounted man looks like a speck or dot at 2000 yards. One can perceive men and horses at 2200 yards. One can count the windows of a house at 4300 yards. By day the glittering of the sun upon the arms of troops in motion indicates the direction of their march. If the rays are perpendicular, they are moving directly toward you; if slanting from left to right downwards, they are moving towards your right, and _vice versa_; if the rays are intermittent and varied, they are moving away from you. Dust raised by cavalry forms a high light cloud, by infantry a lower and denser one, by wheeled vehicles denser still. RANGE-FINDING. The range is found by sound, by observation, by taking measurements from the map, by means of range-finders, and by trial shots. =By Sound.=--Multiply the number of seconds between burst of projectile and report of same by 370 to obtain the approximate range in yards. =By Observation.=--As indicated in the rules given above regarding the appearance of objects. =By Taking Measurements from the Maps.=--This can be done on a good topographical map on a large scale, taking care to fix thereon accurately the position of the target and also the position of the gun. =By Means of Range-finders.=--No range-finder has been adopted for our service; but several instruments are now under consideration. Whatever range-finder may be used, and with whatever care the range may be taken, errors will exist; but they may be reduced to a minimum by a good instrument and skilled observers. =Trial Shots.=--If the range be doubtful or unknown, trial shots will be used, but it must be remembered that trial shots disclose your position. Estimate the range, give the elevation indicated for it by the range table, and the necessary drift (or deflection), each unit of the deflection scale on the sight corresponding to 1/345[8] of the range, and proceed as indicated under Target Practice, page 379.