Nature of soil in vicinity of target, if possible.
Exact part of target on which to aim his guns in determining the range.
If the range be determined only by observation, it will be necessary to use trial shots.
In finding the range by trial shots it is of great importance that the object and the particular part of it to be fired at should be clearly understood. In order to avoid mistakes the captain may direct one of the officers or non-commissioned officers to rectify the aim of all the guns after they have been pointed. Care should be taken that all the guns are aimed at exactly the same point; that the exact elevation ordered by the battery commander is used, and not changed until ordered by him; and that the result of every shot is carefully observed.
The range can be more accurately and quickly found when each battery has a different target and one directly in front of it to fire at. If the target is a long line, it should be divided into as many sections as there are batteries to fire at it, and each captain should select a gun or object in the part assigned him. In such case the battalion commander can compare the elevations obtained by the several batteries, and if they agree, and the observation of the fire indicates good results, it is fair to assume that the range is correct. When several batteries are to open a long-range fire on a small target, the battalion commander generally designates the battery, and preferably that on the leeward flank, to find the range. Batteries that come into action at short distances from the enemy's line generally find the range by firing salvos at a prominent point of the target.
As a rule, percussion-shell are used to find the range, and all the guns of a battery are aimed at one point of the target; if shrapnel with percussion-fuze be used, the same principles apply.
In firing at intrenchments, however, the fire may be distributed from the first, even for obtaining the range, as the hits, as a rule, can be easily observed.
The enemy's flanks are designated, and the guns in his batteries are numbered, as he himself would designate or number them.
The firing to obtain the range should be slow and deliberate, and ample time afforded to observe each shot and make the necessary corrections.