To ascertain the range by firing trial volleys is, however, practicable only when the terrain near the target is visible; when the target itself is stationary; when the ground is such that the strike of the bullets can be observed; when the firing party is not under fire; and, finally, when the necessary time is available. Since all of these preliminary conditions will rarely be fulfilled, it will only in exceptional cases be possible to determine the proper elevation by this method. When this method is employed, volleys are fired either by sections or by platoons, with the same sight, at some one point of the target. For the first volley a rear sight elevation sufficiently below the proper one should be selected, so that hits on or in front of the target can be expected with certainty. This procedure is then repeated, as often as necessary, with correspondingly raised or lowered rear sight leaves, until the correct elevation is obtained. This “ranging” by trial volleys promises no result, however, if any one of the above-mentioned preliminary conditions is not fulfilled. It is advantageous to establish a bracket by firing volleys, as is done by artillery, but even with a good glass it is very difficult to observe the strike of small caliber bullets. Whether it would be advisable to adopt for this ranging a specially designed weapon, firing thin-walled shell weighing about 400 g., is a question.[141] [141] The 32 mm. _Nordenfeld_ machine gun fires a shell weighing 400 g. The older range finding instruments depend upon angle measurements at both ends of a line (up to 25 m. long). The large range finder (_Hahn_) has been adopted in the German army. (Pars. 88-98 German I. F. R.). This apparatus permits a range to be measured from one point, up to 1200 m. on low targets, and on taller targets, such as skirmishers standing, up to 1600 m. Measurements are considered sufficiently accurate when the error amounts to 2-3% up to a range of 1000 m. 3¹⁄₂-5% „ „ „ „ 2000 „ 3-3¹⁄₂% „ „ „ „ 1500 „ On the defensive the large range finders will find employment before and during the action. The men charged with the measurement of the range should be careful not to betray the position by their activity, before fire is opened. The utility of these instruments is much more restricted in an attack. However, it will often be possible, before the fire fight begins, to ascertain the range from the point selected for the first firing position, to the position to be attacked. According to Soloviev range finders failed completely in action in Manchuria. (See p. 137 supra). 6. SELECTION OF A TARGET AND TIME FOR OPENING FIRE.