Small petards weighed about 50 pounds; the large ones, around 70 pounds. They had to be heavy enough to be effective, yet light enough for a couple of men to lift up handily and hang on the target. The bucket part was packed full of the powder mixture, then a 2-1/2-inch-thick board was bolted to the rim in order to keep the powder in and the air out. An iron tube fuze was screwed into a small hole in the back or side of the weapon. When all was ready, the petardiers seized the two handles of the petard and carried it to the troublesome door. Here they set a screw, hung the explosive instrument upon it, lit the fuze, and "retired." Petards were used frequently in King William's War of the 1680's to force the gates of small German towns. But on a well-barred, double gate the small petard was useless, and the great petard would break only the fore part of such a gate. Furthermore, as one would guess, hanging a petard was a hazardous occupation; it went out of style in the early 1700's. PROJECTILES There are four different types of artillery projectiles which, in one form or another, have been used since very early times: (1) Battering projectiles (solid shot). (2) Exploding shells. (3) Scatter shot (case or canister, grape, shrapnel). (4) Incendiary and chemical projectiles. SOLID SHOT At Havana, Cuba, in the early days, there was an abundance of round stones lying around, put there by Mother Nature. Artillerists at Havana never lacked projectiles. Stone balls, cheap to manufacture, relatively light and therefore well suited to the feeble construction of early ordnance, were in general use for large caliber cannon in the fourteenth century. There were experiments along other lines such as those at Tournay in the 1330's with long, pointed projectiles. Lead-coated stones were fairly popular, and solid lead balls were used in some small pieces, but the stone ball was more or less standard. Cast-iron shot had been introduced by 1400, and, with the improvement of cannon during that century, iron shot gradually replaced stone. By the end of the 1500's stone survived for use only in the pedreros, murtherers, and other relics of the earlier period. Iron shot for the smoothbore was a solid, round shot, cast in fairly accurate molds; the mold marks that invariably show on all cannonballs were of small importance, for the ball did not fit the bore tightly. After casting, shot were checked with a ring gauge (fig. 41)--a hoop through which each ball had to pass. The Spanish term for this tool is very descriptive: _pasabala_, "ball-passer."