THAT RAUCOUS RITE OF SUMMER—the fireworks display—may have started as a scholarly tradition in ancient China. Before the Chinese got around to inventing paper in the second century A.D., scribes, using a stylus, would etch ideograms on the rounded surface of green bamboo stalks. The medium served as a way for recording transactions and stories. As the stalks dried over the fire, air pockets in the wood would often burst with a loud cracking noise.