The difficulty of hitting a target lodged in some feature of the terrain requires that the machine gun be used first of all against large targets that are visible for a short time only. When the appropriate elevation is used, a decisive effect may be confidently counted on within a short space of time; when an inappropriate elevation is used and the fire is not properly observed, only accidental hits can, as a rule, be expected, even when the fire is directed on tall, dense targets. When the fire is directed on skirmishers lying down, the effect produced is not commensurate with the amount of ammunition expended, and a slight error in the elevation used may nullify the effect entirely. A straight line of trenches, which is plainly visible, is, on the other hand, an eminently favorable target. The heating of the barrel, and the difficulty of replenishing ammunition and renewing the water in the jacket, tend to work against a participation of machine guns in a protracted fire fight. The machine gun is not at all suited for carrying on a prolonged fire action. It is very difficult to determine the relative combat value of a body of infantry as compared with that of a machine gun. One will not be far wrong in placing this value between 50 and 60 men. In experimental field firing at the Swiss Infantry Musketry School, it was demonstrated that 30-40 skirmishers almost in every case rapidly gained the upper hand over a machine gun in the open, at 900 m., but that the infantrymen had small chances of success when the position of the machine gun could not be accurately determined. In Switzerland a machine gun is considered equivalent to 50 infantrymen. Skirmishers are the most difficult target for machine guns to fight, and, at the same time, they are the most dangerous. When the fire is well observed, a good effect can, indeed, still be counted on, when the fire is directed at prone skirmishers at ranges up to 1000 m., but this is not true when the fire cannot be observed; in the last mentioned case, no effect worth mentioning is produced. =Austria.= In a field firing test (which was repeated four times) between a machine gun (gun pointer covered by a shield) and 30 infantrymen, the following results were obtained at 600 m. in 1¹⁄₂ minutes: Infantrymen 120 rounds 10 hits (9%) Machine gun 215 „ 14 „ (7%)[287] [287] Firing tests of the Army Musketry School at Bruck, a.d. Leitha, 1905. _Streffleur_, Apl. 1906, p. 524.