Rockets described in the "Huolongjing" were not all in the shape of standard fire arrows and some had artificial wings attached. An illustration shows that fins were used to increase aerodynamic stability for the flight path of the rocket, which according to Jiao Yu could rise hundreds of feet before landing at the designated enemy target. The "Huolongjing" also describes and illustrates the oldest known multistage rocket; this was the "fire-dragon issuing from the water" (huo long chu shui), which was known to be used by the Chinese navy. It was a two-stage rocket that had carrier or booster rockets that would automatically ignite a number of smaller rocket arrows that were shot out of the front end of the missile, which was shaped like a dragon's head with an open mouth, before eventually burning out. This multistage rocket is considered by some historians to be the ancestor of modern cluster munitions. Needham says that the written material and illustration of this rocket come from the oldest stratum of the "Huolongjing", which can be dated to about 1300-1350 from the book's part 1, chapter 3, page 23. The fire lance or fire tubea combination of a firearm and flamethrowerhad been adapted and changed into several different forms by the time Jiao Yu edited the "Huolongjing". The earliest depiction of a fire lance is dated c. 950, a Chinese painting on a silk banner found at the Buddhist site of Dunhuang. These early fire lances were made of bamboo tubes, but metal barrels had appeared during the 13th century, and shot gunpowder flames along with "coviative" projectiles such as small porcelain shards or metal scraps. The first metal barrels were not designed to withstand high-nitrate gunpowder and a bore-filling projectile; rather, they were designed for the low-nitrate flamethrower fire lance that shot small coviative missiles. This was called the "bandit-striking penetrating gun" (ji zei bian chong). Some of these low–nitrate gunpowder flamethrowers used poisonous mixtures such as arsenious oxide, and would blast a spray of porcelain shards as fragmentation. Another fire lance described in the "Huolongjing" was called the 'lotus bunch' shot arrows accompanied by a fiery blast. In addition to fire lances, the "Huolongjing" also illustrates a tall, vertical, mobile shield used to hide and protect infantry, known as the "mysteriously moving phalanx-breaking fierce-flame sword-shield".