Cutaway drawing of a Huo Tong, from 'Wu Bei Zhi (《武備志》)'.
Huo Tong (火桶, fire barrel), also known as Mai Yao Huo Tong (埋藥火桶, lit. 'Buried gunpowder fire barrel') is a primitive but rather powerful short range naval weapon used by the Ming navies. It is improvised from large wooden barrel filled with five catties of low grade or spoiled gunpowder (deemed unsuitable for cannon charge) and then covered with a layer of dry sand or soil. A bowl filled with embers covered in ash is carefully placed on top of the soil layer just before the barrel is sealed and thrown (or dropped) onto enemy warship. Once the barrel get knock over, it will either explode into a burst of flame or spill burning gunpowder everywhere.
Huo Tong can be used in siege defense as well.
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