A similar arrangement is employed also to carry on water a kind of firework called the spiral machine. This is a cone formed by six light strips of pine, 5 feet long, nailed at one end on a wooden disk 3 inches in diameter and at the other on a disk of wood 2 feet in diameter. The middle of their length is sustained by another disk of intermediate size, to which they are nailed. The cone is finally twisted to make spirals, in which form it is held by another strip of wood, very thin and very flexible, extending from the top to the bottom, which is nailed on the spirals. When the machine is finished it is garnished from top to bottom, following the turnings of the spirals, with small lances fastened on it. It is finished by attaching to the bottom disk a dozen turning suns, arranged in four sections of three jets each, which are discharged together. (PL VIII, fig. 3.)
This piece is placed in the middle of the bowl on an iron rod. The rod is the pivot on which it turns, receiving its movement from jets attached to the bottom disk. The first of these jets gives fire to all the others by a communicating match.