Ten inch balloons of three charges.
| oz. | dr. | |
| Meal-powder, | 3 | 0 |
| Corn-powder, | 3 | 2 |
| Powder for the mortar, | 13 | 0 |
Length of the fuse composition, 1 inch: the shell must be loaded with 2 oz. cases, driven with star composition 1/4th of an inch, and on that one diameter of gold-fire, then bounced three diameters; or with 2 oz. cases, first filled one diameter with gold fire, then one and one-fourth diameters of brilliant fire. These cases must be well secured at top of the charge, lest they should take fire at both ends: but their necks must be larger than the common proportion. For the manner of forming balloon cases of paper, consult the article on that subject, in a preceding chapter.
Balloons, the bombs of some, may be formed of different sizes, and made proportionably strong.
Bombs may be formed of wood by turning it round, and hollow, of a sufficient thickness, and in two parts, which fit each other like a common snuff box. The inferior or lower part must be made thicker than the upper, as it rests upon the powder; and for the same reason, that iron bombs are cast thicker at their bottom. One-twelfth of the diameter is considered a sufficient thickness for the under part, and one-fifteenth for the upper part, which is pierced with a hole to receive the fuse. This hole is called the eye of the bomb.
When balloons, or bombs, are to be charged, the decorations may be varied in the same manner as for sky-rockets. Stars, golden rain, and meteors, are considered the best, as they produce the most brilliant effect.
After the addition of the furniture or decorations, we finish the charge by putting in coarse grain powder, which is introduced through the eye. The fuse is then driven in. It is glued, in order to secure it. The bomb is now covered with three or four turns of canvass, and over this some paper, to secure it. In this state, it ought not to be more than 1/11th of an inch smaller than the caliber of the mortar. This leaves what is denominated the windage.
When the bombs are well dried, the fuse is primed with a double match, and priming paste. A cup, made with two turns of paper, is then attached to the fuse, which receives the double match.
The bomb, thus prepared, is then placed in a cone made of pasteboard, which contains the powder of the charge, or that required for its ascension, and is put into the mortar. One of the matches above described, communicates the fire to the fuse, and the other at the same time to the powder in the cone. The match, it is to be observed, comes out of the mouth of the mortar, and serves to fire it. This mode of discharging the mortar, differs from the one we have previously given.
The following table exhibits the calibers for bombs, the length of the fuse for each caliber, and the weight of the powder required for the charge.