When the shell is perfectly dry, burn a vent at the top, with an iron, large enough for the fuse. This method will answer for balloons from 4 inches 2/5ths, to 8 inches in diameter; but, if they are larger, or required to be thrown to a great height, let the first shell be turned of elm, instead of being made of paper. For balloons 4 inches 2/5ths, let the former be 3 inches 1/8th, in diameter, and 5-1/2 inches long. For a balloon of 5-1/2 inches, the diameter of the former must be 4 inches, and 8 inches long. For a balloon of 8 inches, let the diameter of the form be 5 inches and 15/16ths, and 11 inches 7/8ths long. For a 10 inch balloon, let the form be 7 inches 3/16ths, in diameter, and 14-1/2 inches long. The thickness of a shell for a balloon of 4 inches 2/5ths, must be 1/2 an inch. For a balloon of 5-1/2 inches, let the thickness of the paper be 5/8ths, of an inch; for an 8 inch balloon, 7/8ths, of an inch; and for a ten inch balloon, 1 inch and 1/8th of an inch. Shells, that are designed for stars only, may be made quite round, and the thinner they are at the opening, the better; for if they are too strong, the stars are apt to break at the busting of the shell. When making the shell, employ a pair of callipers, or a round gage; so that you may not lay the paper thicker in one place than other, and also that you may be able to know, when the shell is of a proper thickness. Balloons must always be made to go easy into the mortars. (See _Encycl. Brit. Art. Balloon cases_.) _Sect. X. Of Cases for Illumination Port-fires._ These must be made very thin, of paper, and rolled on formers; from 2 to 3/8ths of an inch in diameter, and from 2 to 6 inches long: they are pinched close at one end, and left open at the other. When they are to be filled, put in but a little composition at a time, and ram it lightly, so as not to break the case. Three or four rounds of paper, with the last round pasted, will be sufficiently strong for these cases. (_Ibid._) _Sect. XI. Of Cases and Moulds for Common Port-fires._ Common port-fires, are intended purposely to fire the works, their fire being very slow, and the heat of the flame so intense, that, if applied to rockets, leaders, &c. it will fire them immediately. When used, they are held in copper sockets, fixed in the end of a long stick. These sockets are made like port-crayons, only with a screw instead of a ring. Port-fires, or _lances of service of the French_, may be made of any length, but are seldom more than 21 inches long.