The name trompe is given to an assemblage of several fire pots placed one above another, which are discharged successively in such a manner that the first in throwing out its garniture kindles the slow-burning composition of the second's port fire; then this latter, in discharging, sets fire to the third, while at the same time it drives away the first pot which has ended its functions; similarly as to the various other fire pots. This variety of firework is seldom employed on the ground, but it is often used on water - to vomit forth a marine monster; or to produce other bizarre effects. (PL VII, fig. 2.)
A case having 2 1/2 inches of interior diameter, 20 inches long and 3 lines thick, is first molded. This case is called the sheath of the trompe. It is mounted, like a fire pot, on a base of wood carrying a screw.
Five fire pots, each 3 1/2 inches high and 1 line thick, with a diameter such that it may enter easily into the sheath, are next fashioned.
The fifth of these pots, which is to occupy the bottom of the sheath, should be entirely closed by a choke. But the four others have each a hole of 6 lines at the choke to receive the port fire.
The four cases not choked, having an exterior diameter of 6 lines and a length of 4 inches, are charged with ordinary powder, for the purpose of communicating fire from one pot to another. For this reason they are named port fires. When these have been primed at one end, each in turn is attached by this end to one of the four pots, in the same manner as the pots are fastened to the fuse. At the other end, a powder bag is fastened, and around each port fire the artificer fastens, along with the match, as many serpents as the pot is capable of containing.
When the four garnitures have been thus prepared, that attached to the fourth pot is placed within the fifth pot, on which the fourth pot is set. The garniture carried by the third pot is then placed within the fourth pot, upon which the third sits, and similarly as to the remaining pots. A trompe ends in a jet charged with sparkling fire, or with Chinese fire, which kindles the first pot and the serpent garniture.
The opening of each pot is closed with paper pasted over it, to prevent the fire of one from being communicated to another, and the interval between the pots, which is about a half inch, is covered with a paper band, pasted from one pot to another in such a manner that the five pots appear to make only a single case.
When the trompe is dry, it is set within the sheath, and the top of the sheath is closed with a round of pasteboard, pierced in the middle in order to allow passage to the jet. A surrounding circle is cut in eight sections, and the ends are pressed up and pasted to the jet, in the manner described for the pots a aigrettes. The garniture of the trompe may be diversified by employing stars or other devices in place of serpents.