The following passage is from a good book, Villa and Zapata, by Frank McLynn. I hope such passage will be allowed to be posted, because the book is worth recommending and the passage offers good information on military history.
The basis of the machine gun was a series of parallel barrels, six in some models, ten in others, which were revolved round a fixed axis by a crank, and usually fed automatically from a drum mounted above the barrels; early models fired up to 100 rounds a minute, later one up to 1,000. the Gatling gun was first used significantly in battle at Tel-el-Kebir in 1882, when six Gatlings manned by thirty British sailors were said to have accounted for half Arabi Pashas 12,000 Egyptian dead. However the Gatlin was not a self-firing gun of the type that continue to fire as long as the trigger was pressed. It was Hiram Maxim who introduced a method of gelatinizing nitrocellulose, which allowed the burning speed of powder to be accurately controlled. Maxim worked out a method enabling him to use the recoil automatically to eject the first round, pull another round into position, then fire the second round. The recoil from this second round repeated the cycle, which continue as long as the trigger was pressed, the rate of fire being adjustable up to 600 rounds a minute.
[John Moses] Browning used the energy of escaping muzzle gases to operate his weapon, then developed the improved recoil-operated mechanism. [Colonel Isaac Newton] Lewis had a gas-operated gun, charged from a flat drum magazine and this became the preferred method of combat in the aerial dogfights of the First World War. Machine-guns had featured prominently in the terrible trench-warfare battle of the Russo-Japanese War of 1904-5 although they were not mass produced until the First World War and were thus a treasured item in the armoury of the opposing forces in the Mexican Revolution.
Their impact could well have been decisive but for the equalising weapon of the dynamite bomb, the favourite device of guerrilla revolutionaries. Although Hollywood movies anachronistically show dynamite in use in Juarezs wars with the French, the development of this unique high explosive was a feature of the lat 1860s. One of the amazing stories in the history of technology was the discovery that, by adding nitric acid, cotton-wool could become explosive gun-cotton, and that an emollient cosmetic liquid, glycerine, could become nitroglycerine, a heavy, oily-looking liquid which explodes with tremendous violence. It is more destructive than gun-cotton, and can be exploded by a fuse containing fulminating powder, fired from a distance by electricity. Ten times as powerful as gunpowder (gun-cotton six times), it became the favourite blasting agent for miners. It was first used in liquid form as blasting oil, but because of the dangers of handling it, it was later mixed with a powdered substance (itself without action and merely a vehicle for containing the nitroglycerine), and this became known as dynamite. The art of detonation became more nuanced: if one wanted to blast an object to smithereens, one used high explosive or dynamite; if one wanted to blast, say, large granite blocks to make building stone, or a coal seam to yield lumps of coal, one used low explosive or gunpowder.
There were many nineteenth-century developments in dynamite, notably the use of chlorate of potassium instead of nitrate as the oxygen-supplying material. The great name in the history of dynamite is Alfred Nobel. Although Sobrero had discovered nitroglycerine in laboratory experiments, several grave accidents in the late 1860s seemed to put a question mark against blasting oil. Nitroglycerine was perceived to be so dangerous that Britain prohibited its import in a liquid state; it had to be pre-processed into dynamite. The breakthrough came when Nobel discovered a detonation method, enabling nitroglycerine to be absorbed by an inert porous material, a silicaceous earth of which one part would absorb three times its weight in nitroglycerine. Later, other substances were used for absorbing the liquid, and in the end there were two types of dynamite: one with inert absorbents and the other with absorbents that were themselves combustible or explosive, such as charcoal, nitrate, chlorate and even gunpowder, gun-cotton and nitro-mixtures. But the first significant use of dynamite in bomb form was in the Mexican Revolution.
--- Villa and Zapata: A History of the Mexican Revolution, Frank McLynn, Carroll & Graf Publishers, New York, 2002, pp. 100-101.