The sea–mine called the 'submarine dragon–king' is made of wrought iron, and carried on a (submerged) wooden board, weighted with stones. The (mine) is enclosed in an ox-bladder. Its subtlety lies in the fact that a thin incense(–stick) is arranged (to float) above the mine in a container. The (burning) of this joss stick determines the time at which the fuse is ignited, but without air its glowing would of course go out, so the container is connected with the mine by a (long) piece of goat's intestine (through which passes the fuse). At the upper end the (joss stick in the container) is kept floating by (an arrangement of) goose and wild–duck feathers, so that it moves up and down with the ripples of the water. On a dark (night) the mine is sent downstream (towards the enemy's ships), and when the joss stick has burnt down to the fuse, there is a great explosion.