By the middle 1400's the little popguns that tossed one-or two-pound pellets had grown into enormous bombards. Dulle Griete, the giant bombard of Ghent, had a 25-inch caliber and fired a 700-pound granite ball. It was built in 1382. Edinburgh Castle's famous Mons Meg threw a 19-1/2-inch iron ball some 1,400 yards (a mile is 1,760 yards), or a stone ball twice that far. The Scottish kings used Meg between 1455 and 1513 to reduce the castles of rebellious nobles. A baron's castle was easily knocked to pieces by the prince who owned, or could borrow, a few pieces of heavy ordnance. The towering walls of the old-time strongholds slowly gave way to the earthwork-protected Renaissance fortification, which is typified in the United States by Castillo de San Marcos, in Castillo de San Marcos National Monument, St. Augustine, Fla. Some of the most formidable bombards were those of the Turks, who used exceptionally large cast-bronze guns at the siege of Constantinople in 1453. One of these monsters weighed 19 tons and hurled a 600-pound stone seven times a day. It took some 60 oxen and 200 men to move this piece, and the difficulty of transporting such heavy ordnance greatly reduced its usefulness. The largest caliber gun on record is the Great Mortar of Moscow. Built about 1525, it had a bore of 36 inches, was 18 feet long, and fired a stone projectile weighing a ton. But by this time the big guns were obsolete, although some of the old Turkish ordnance survived the centuries to defend Constantinople against a British squadron in 1807. In that defense a great stone cut the mainmast of the British flagship, and another crushed through the English ranks to kill or wound 60 men. [Illustration: Figure 4--EARLY SMALL BOMBARD (1330). It was made of wrought-iron bars, bound with hoops.] The ponderosity of the large bombards held them to level land, where they were laid on rugged mounts of the heaviest wood, anchored by stakes driven into the ground. A gunner would try to put his bombard 100 yards from the wall he wanted to batter down. One would surmise that the gunner, being so close to a castle wall manned by expert Genoese cross-bowmen, was in a precarious position. He was; but earthworks or a massive wooden shield arranged like a seesaw over his gun gave him fair protection. Lowering the front end of the shield made a barricade behind which he could charge his muzzle loader (see fig. 49).