These fire pots have the same form, and are made in the same manner, as the pots a aigrettes; with this difference, that a counterbalance is attached underneath as for the barrils de trompes, and that they are smeared with tallow.
The fire pots are garnished with genouillferes, with divers and with other pieces designed for water display. A bag of powder, placed at the bottom of the pot to which a jet communicates fire at the finish, throws them into the air, whence they fall back to writhe along the surface of the water.
The genouilleres are arranged upright in the pot, reaching to the rim in a circle, with the throats on the bag of powder and the sheaths outside of the pot. The space left in the middle is garnished with stars. The pot is next covered with a pasteboard disk, through which a jet passes. But, since this cover does not rest on the rim of the pot, by reason of the interposition of the sheaths of the genouilleres, among which there is a space to be closed, these openings are sealed with paper bands, fastened at one end on the pot and at the other on the cover, and the joints also are covered in such a manner that water can not penetrate.
When it is desired to throw forth balloons, the jet is fastened on the exterior of the pot, and on finishing it gives fire to the charge by a communicating match, which passes through a hole pierced in the bottom of the pot.
The balloons are made of wood, or of pasteboard, similar to those for use on land. They are filled with pieces suitable for display on the water, and are smeared over with tallow. Since they should not explode, for their best effect, except on the water after they fall, care must be taken that they are not thrown above a medium height, and they are made lighter in weight than an equal volume of water, in order that they shall not sink. Several may be fired at the same time in a cask made of stout staves, banded with iron hoops, by arranging them in the manner that has been described in connection with grenades to be fired from a barrel.