hat level of irearm technology did not occur in Europe until a century or two later. Fundamental knowledge of gunpowder and its potential for use in warfare passed slowly but steadily from China to Europe during the 1100s and early 1200s. One pathway seems to have been verbal accounts by merchants and other travelers who periodically made the long trek over the handful of trade routes linking the two regions. Some evidence also suggests that a few eastern Europeans witnessed the Mongols, a tribal people who conquered China, using gunpowder weapons. Hearing about these devices, European inventors became fascinated and started to experiment. hey found that the main ingredients of gunpowder could be combined in numerous proportions, and it took a while to ind the most efective ones. he famous English scientist Roger Bacon hit on a moderately useful formula in 1267. It mixed the components in fractions of about 29 percent sulfur, 41 percent potassium nitrate, and close to 30 percent charcoal. Bacon found that this combination generated a lash of light and a loud bang, but its detonation produced almost no damage. Only after several more decades did European inventors begin to ind a handful of gunpowder recipes that produced considerable destructive force. Some came fairly close to the modern formula. Meanwhile, by the early 1300s European military engineers had begun to experiment with delivery systems for the gunpowder explosions—that is, the actual irearms. he irst examples were not guns but rather grenade-like devices similar to the Chinese thunderclap bombs, only more destructive. Some of these weapons were relatively small and hand-held, which allowed soldiers to throw or catapult them into enemy camps, castles, or towns. Another version was the irst land mine, a big pot of gunpowder that was inserted into a sap dug beneath a castle wall during a siege. Its explosion directly under a wall could help bring that wall down. Conversely, defenders could use the same device to destroy a sap before it reached a wall. Still another early bomb was the petard (meaning “little fart” in French). It was a large metal container of gunpowder that a soldier hung on the front gate of a castle or fortiied town. After lighting the fuse, he ran for cover, hoping the bomb would not ignite before it was supposed to. If it did, and he suf ered injury or death, it was said that he was “hoisted [lifted into the air] by his own petard.” h at phrase is still used today to denote a person whose scheme somehow backi res.