The heavy field howitzer employs shell weighing 39.5 kg., containing an explosive charge of 0.85 g., and fitted with a percussion fuze either with or without delay action. This shell is designed to penetrate the roofs of splinter proofs. An earth covering 5-6 m. thick is necessary to afford protection against these projectiles. At 3000 m. a 15 cm. shell produces a crater 1 m. deep and 2.4 to 3.6 m. in diameter, _i.e._, 2 cu. m. (in made ground this crater is three times this size). The heavy field howitzer is a very effective weapon against shielded batteries. A single shell, owing to its lateral explosive effect, is capable of placing a whole battery temporarily out of action. 4. EXPEDIENTS FOR MINIMIZING THE EFFECT OF FIRE. Movements of infantry under artillery fire are unavoidable when firing lines are to be reinforced and when troops intended for the decisive attack are to be pushed closer to the enemy. Formations calculated to minimize the effect of the hostile fire must be taken up in time, since it is not always possible to make use of cover. The efficacy of the fire depends upon the accurate determination of the range and height of burst (fire for adjustment) and upon the careful observation of the subsequent fire (fire for effect).[113] The effect of this fire is considerably increased when the opponent’s infantry, against whom the fire is directed, takes up unsuitable formations (particularly broad line formations). Infantry has frequently found it advantageous to advance in small detachments moving rapidly at irregular intervals in extended order. [113] The color of uniforms exerts considerable influence on observation. According to experiments made in France, colors rank as follows as regards visibility: white (invisible at night), light blue, alizarine red, green, dark brown, gray, or yellowish brown. _Schweizer Zeitschrift für Artillerie und Genie_, 1896, I, p. 39. The following colors protect against heat, in the order named (in reverse order against cold): white, red, orange, yellow, green, blue, violet, black. The position of gray in the list depends upon the amount of white or black mixed with it. (a) Increasing the Difficulties in the Adjustment of the Hostile Fire. A battery requires about 0.8 minutes (5 to 6 rounds with percussion fuze) to secure adjustment at ranges up to 750 m. The time required for securing adjustment at the longer ranges is as follows: At 800-1500 m., on low infantry targets, 1.5 min., 6-9 rounds with perc. fuze; At 1700-2250 m., on low infantry targets, 3.7 min., 11 rounds with perc. fuze; At 2000-3000 m., on artillery targets, 4.6 min., 11 rounds with perc. fuze;