In the sixteenth century the heavy guns were very varied in calibre and length of barrel, and had divers curious names. The sharp metz, the carronade, culverin and nightingale, the singer, the falcon and the falconet, the field serpent and serpentine, with balls from one hundred pounds down to one pound, besides the organ,[2] mortars large and small, rifle-barrelled guns and rifles. But in the beginning of the Thirty years' war the forms were already simplified; they cast forty-eight, and twenty-four pounders, twelve and six pounders, with forty-two, twenty-four, twelve and six pound balls;[3] the first were fortress and siege guns, the last were field guns; besides these, disproportionately long culverins and falconets, also chamber pieces for throwing shells, or bomb mortars which were soon called howitzers, smaller mortars for throwing fire-balls, stinkpots, &c.; and in the beginning of the war bombarders, which fired pieces of iron, lead, small shot, and stones. Lastly from forged pieces they fired half-ounce bullets, double, single, and half-hooks, or grappling irons. But the length of the barrels of the guns was too long for balls; the powder was bad, and the aim consequently uncertain. Gustavus Adolphus introduced shorter and lighter guns; his leather cannon, made of copper cylinders with thick hemp and leather coverings[4] held together by iron hoops, soon ceased to be used, probably because they were not sufficiently durable, but his short four-pounders, two of which were given to every regiment, and which worked best with grape shot, lasted over the war. These field pieces fired not only from position but were moved with tolerable rapidity during action, but the bombardes and petards were unwieldy; the last were twisted round with ropes more like a sort of cannon than our bombs and grenades, but were of uncertain effect because the locks were badly prepared and they did not measure the time for the explosion. The old disposition of the Germans to give life to the inanimate had already in earlier times bestowed especial names on favourite guns, and the custom remained, even after pieces of the same calibre were cast in greater numbers; then particular guns, for example, were called after the planets, months, and signs of the zodiac, like a high sounding alphabet,[5] and in this case indicated by single letters. There was always a new name given according to the calibre, which in spite of all the simplification was still very varied. The progress of artillery and its influence on the conduct of war was impeded in the last half of the war by the want of experienced master gunners, the greater portion of them were infantry commanders; the loss of an artillery officer of capacity was difficult to replace.