As a rule, the observation is limited to ascertaining whether the shots are short or over. The observation of direct hits is unreliable except at very short ranges, or when palpable effects are produced in the enemy's ranks, limbers are blown up, or there are other manifest indications of the effect produced. When a target is on a height or behind a parapet, it is possible to distinguish hits on the slope of the hill or on the parapet, and to estimate correctly the error in range of the projectiles that fall short. There are no means of estimating the error in range of the projectiles that fall beyond the target, except when a battery is on an elevation and firing at a target on a plane below it; here shots striking beyond the target may be observed and the error estimated.
When several batteries are firing at the same target, and it is difficult to distinguish the individual rounds, a fire by battery will give a group of shots that may be recognized.
The observation of the fire will be facilitated by the reports of an officer or non-commissioned officer stationed some distance in advance and outside one of the flanks of the guns.
Smoke.—When the wind is across the range and blows the smoke in front of the guns, it will be difficult to correctly aim and properly observe the effects of the fire. In the case of a single battalion this inconvenience may be diminished by increasing the interval between the batteries, or may be avoided by advancing the batteries in echelon from the leeward flank so that the smoke of each windward battery will drift behind those to the leeward of it. This last measure has the disadvantage of making the leeward batteries conspicuous against the white background of smoke, and besides is not always practicable, especially when the position is on the brow of a hill. If neither of the above expedients can be adopted, and it is not possible to sufficiently increase the interval of time between the guns in each battery to permit the smoke to blow away, the fire by battery or platoon may be used, or the battalion commander may order the battalion to fire by piece, commencing on the leeward flank. When several battalions are together, as large intervals as possible should be left between them, or, if the ground permits, the battalions should be advanced in echelon from the leeward flank, in order to diminish or avoid the inconvenience of smoke drifting across the range.
When the target cannot be seen on account of smoke which hangs in front of the guns, or on account of fog, rain, or darkness, the pieces may be aimed by means of auxiliary targets.
Finding the Range.—This is the work of the battery commander. He and the range party precede the battery to the position, and as soon as the exact position of his battery is indicated by the battalion commander he observes carefully the position of the target, its nature and extent, and estimates the range by means of a map, any source available, or range-finder (all if possible), very carefully, and especially so when the fire is to be over the heads of other troops.
He estimates the ranges to other points within the field of fire which might subsequently become targets, and observes:
Nature and position of any covering mass.
Zones of ground which ought to be cannonaded.