[274] The 25 barreled _mitrailleuse_, cal. 13 mm., fired volleys at the rate of 125 rounds per minute. Its fire was considered equivalent to that of 50 needle guns; its weight was 1,485 kg., each of its four horses pulling 371 kg.; its maximum range was 3,000 m. Its most favorable, practical range 500-1,500 m.--A glaring defect of the gun was that fire pauses occurred whenever cartridges were fed into the slot and that the lateral spread of its cone of dispersion was extremely small. [275] Battle of Gravelotte. _Gen. St. W._, pp. 705-712, 723 and 781. The employment of three Gatling guns in rear of the park wall of Yoré, during the defense of the plateau of Auvours. (_Revue d’artillerie_, 1900, p. 297; _Gen. St. W._, IV, p. 817). The situation changed entirely when a practicable, smokeless powder was invented, and Hiram Maxim, an American, succeeded in utilizing the energy of the recoil (a factor neglected up to that time, although annoying to the marksman) for opening the breech, inserting a fresh cartridge into the chamber, closing the breech, and automatically firing the piece.[276] Through this invention it became possible to fire a maximum of 900 and an average of 500 rounds per minute, from a single barrel moving laterally back and forth. The desire to obtain a still greater rate of fire was checked effectively, because of the fact that with such an increase the danger of jamming increased and the use of infantry ammunition was precluded. The water in the jacket continues to be a decided drawback to this type of gun, for it is not always easily procured, impairs the mechanism by freezing, makes it difficult to change barrels, and constitutes a considerable weight. If cooling the barrel by means of water were to be dispensed with, the accuracy of the piece would rapidly diminish, and, after 1000 rounds of continuous fire, bullets would tumble even at short ranges. At the present time water is still the most effective means of cooling the barrel.[277] [276] Of the other types the following may here be mentioned: _Hotchkiss_ (France), insufficient cooling of the barrel by air; _Schwarzlose_ (Austria), machine gun model 7, a very simple weapon which has only a single spring. [277] In the _Colt_ Machine Gun, which is not water-cooled, after 500 rounds had been fired, a cartridge inserted into the piece exploded in seven seconds, and cartridges placed in the chamber a quarter of an hour later exploded in 20 seconds.