The balloon itself is made of wood or pasteboard. Those of wood are composed of two hemispheres, which close by fitting into each other. A greater thickness is given to the lower side of the globe, which has to receive the impulsion of the powder. This is called the base. .
The eye of the balloon is pierced either in the base or in the upper portion, according to the position which is required when it is placed in the mortar - that is to say, so that, if it is fired by hand, the eye will be in the upper part of the balloon, but, if fire is to be communicated from the driving charge, the eye will be in the base.
Balloons of pasteboard are made in three different methods.
For the first, use is made of a wooden ball having a diameter equal that to be given to the interior of the balloon. This ball is well rubbed with soap, and is then covered with a pulp of paper to a thickness proportionate to its diameter. It is pressed with a sponge to draw off the humidity, and also to give it form. When it is dry, the globe thus made from pulp is severed around the middle, so that, on being detached from the ball, it forms two hollow hemispheres, which, on being filled with the necessary materials and reunited, form the balloon.
The pulp is made from clippings of paper or pasteboard. These are placed in water, and manipulated from time to time until thoroughly softened. A little flour paste is added to the pulp, to give it the proper degree of consistency.
In the second method, a ball of string is made by winding it on the end of a small stick, to which one end of the string has been fastened. This stick has a diameter equal to that intended for the eye of the balloon, which is to be formed by it. The ball, after being brought almost to its full size, is completed by winding over it a covering of thread, in order to make it smoother. It is next rubbed with soap, and bits of paper are pasted over it to a thickness forming one-twentieth of the ball's diameter for the lower half, and one-twenty-fourth of its diameter for the upper portion. After the ball has taken on some degree of consistence, in drying, the stick is withdrawn, and by it the string also is pulled out through the hole until the case is left entirely empty. (Pl. VII, figs. 5 and 6.)
In the third method, the case is molded from pasteboard as are rocket pots. They have a size sufficient to permit their being choked, and the height is equal to the diameter. The portion that is to receive the impulsion of the driving charge is fortified by means of paper pasted over it. (PL V, fig. 2.)
Balloons, whether of wood or of pasteboard, are garnished with a mixture of different pieces, such as serpents, saucis-sons, stars, and the like. Among these, after the balloon has been filled, is scattered some of the composition used for charging fire pots. The quantity should be sufficient to cause the bursting of the case.
The fuse is placed in the eye of the balloon, to set fire to the garniture. When the balloon is of wood, care must be taken to have the fuse thicker at one end than at the other, in order to prevent any risk of its being driven through into the balloon by the pressure of the burning powder of the driving charge; and, also, glue should be used to hold it fast in position.
It is necessary for experimental purposes to set off balloons loaded with dirt, for guidance in regulating the duration of the fuse, which should give fire to the garniture only when the balloon has mounted to its greatest height. Such experiments, moreover, serve to show the exact quantity of powder required to hurl the balloon to the greatest possible distance without risking destruction of the case by the force of the discharge.
The duration of the fuse is regulated by cutting it longer or shorter, or by making the paste in which it is soaked livelier or slower. It is usually impregnated with the composition given for serpents of one card.
After the match has been placed in the balloon the whole is covered over with canvas, which is glued on, or the balloon is wound about with a string of suitable weight. It is then finally coated with a paste made from iron scalings and glue. These scalings are to be found in blacksmiths' shops, where they may be picked up around the anvil. They are the bits of metal detached from iron when it is being forged. This paste mixture of glue and scalings fills up the interstices of the string, and gives the balloon a solidity in its outer surface almost equal to that of iron. The balloon is now rolled on dry scalings, which adhere to it, and give it the color of the metal, so that the final appearance is exactly that of a bomb.
Mortars of pasteboard, used for throwing balloons, have the form of pots a aigrettes. There is no difference except in the base of wood upon which they are mounted. This base for the mortars should have such a thickness that the worker may hollow out in its center a cavity of sufficient size to place within it a chamber of cast copper in the form of a funnel. The powder is placed within this chamber. The end of the funnel reaches to the exterior center of the mortar bottom, and thus forms a channel through which a fuse runs. (Pl. V, fig. 3.)
The chamber contains a quantity of powder equal to one-thirty-second part of the balloon's weight. This charge is inclosed in paper cases, which also are funnel-shaped. The fuse passes from the charge through the neck of this paper funnel, and then extends on into the neck of the copper funnel, through a hole in the bottom of the mortar.
After the charge has been placed within the chamber, the paper containing it is pierced with a number of pinholes, A little powder is then spread over the top. The balloon is next placed in the mortar, with its fuse resting on the driving charge by which it is to be kindled. Bits of torn paper are wadded between the balloon and the walls of the mortar, which serve to offer resistance to the action of the powder, and thus to increase its effect. They also aid in preventing any shifting of the balloon's position within the mortar.
Balloons under 6 inches may be discharged from an ordinary pot a aigrette. A rounded piece of board on which the pot is mounted should be pierced in the middle by a hole of 2 or 3 lines in diameter, communicating with a groove on the underside, extending from the circumference of the board to its center. The pot is loaded with a bag of powder to which a match is fastened. The match is passed through the hole in the baseboard, and its length is laid along the groove on the underside of the board, so that it reaches to the rim. Paper is then pasted over the groove and hole.
The charge should weigh one-twenty-fourth the weight of the balloon itself, when the balloon's diameter is 5 inches. For a diameter of 4 inches, the weight of the charge should be one-sixteenth that of the balloon. Thus, the weight of the charge increases its proportionate relation to the weight of the balloon as the size of the balloon decreases.
Mortars and pots made of pasteboard, when they are to be used for projecting balloons, should always be covered throughout the length of their cylinders by winding them with strong cord, fastened with glue. Without this precaution, the cases would not be strong enough to withstand the action of the powder.