It may not be improper, in this place, to give the manner of forming paper mortars. These mortars are necessary for a variety of exhibitions, as will appear hereafter.
Mortars are made of stout paper; or several sheets are pasted together, and made into pasteboard, in the manner before described. (See [Pasteboard.]) The preparations are various according to the size required. For a coehorn mortar, which is 4 inches and 2/5ths in diameter, roll the pasteboard on the former, on which it is made, 1/6th of its diameter thick, and, when dry, cut one end smooth and even; then nail and glue it on the upper part of the foot. Afterwards cut off the pasteboard at the top, allowing for the length of the mortar, two and a half diameters from the mouth of the powder chamber.
The mortar is then bound round with a strong cord, wetted with glue. The bottom of the foot, it being turned out of elm, is one diameter and two thirds broad, and one diameter high, and the part which goes into the mortar is two-thirds of its diameter in height. The copper chamber for the powder, which is separate from this, is made in a conical form, and is one-third of the diameter wide, and one and a half of its own diameter long. In the centre of the bottom of this chamber, make a small hole, a short distance down the foot; this hole must be met by another of the same size, made in the side of the foot. If these holes are made true, and a copper pipe fitted into both, the mortar, when loaded, will prime itself; for the powder will naturally fall to the bottom of the first hole. By putting a piece of quick match to the side, it will be prepared for firing.
When mortars of a larger size than ten inches in diameter are required, it is better to have them made of brass. See further observations on this subject in section seventh of this chapter, in the article on [fire-pots.]
Sec. III. Of Mortars to throw Aigrettes, &c.
Shells are filled with a variety of pyro-preparations, as stars, rains, serpents, &c. These are put in first, and then the blowing powder, as it is called; but the shells must not be quite filled. They must be introduced into the shells through the fuse hole. Some substances, however, as marrons, being too large to go through the fuse hole, must be put in before the shell is closed. When the shells are loaded, glue and drive in the fuses very tight. With respect to the diameter of the fuse hole; for a coehorn balloon, let the diameter be seven-eighths of an inch; for a balloon, five and a half inches in diameter, make the fuse hole one inch and one-sixth in diameter; for an eight-inch balloon, one inch and three-eighths; and for a ten-inch balloon, one inch and five-eighths.
Air-balloons are divided, according to the substances they contain, or the effect they are to produce, and are usually of four kinds; namely, 1. Illuminated air-balloons, 2. Balloons of serpents, 3. Balloons of reports, marrons, and crackers, 4. Compound balloons. Balloons and shells, in fire-works, are the same.
In the following view of the different balloons, we have given the number and quantity of each article for the different shells, designating their kind and character:
Coehorn balloon Illuminated.
| Meal-powder, | 1½ | oz. |
| Grain, do. | ½ | — |
| Powder for the mortar, | 2 | — |