As to the length of sky-rockets, it is regulated by the length of the piercer, if they are pierced in the charging. One-third more than this length is allowed for the _choak_, and the rest, of course, for the composition. With respect to other cases, Morel remarks, that the cases for turning pieces are usually six inches in length, and, for fixed pieces, seven and eight inches. The cases of _Roman candles_, are of the same thickness as those of rockets. In length they are, as well as the _Mosaic candle_, fifteen inches. They are choaked and cut. Those of _serpents_ are made with one or two cards, which are rolled upon a former of wood, or metal, 1/4th of an inch in diameter, and four inches in length. When made, the case measures three inches. Dry rolling is considered sufficient for these cases. The _fixed stars_ are made of common pasteboard, 3-1/2 inches long, on a mandril, 1/2 an inch in diameter. They are pasted with ordinary paste, but mixed with clay, and choaked, and bound as usual. _Sec. VIII. Of Tourbillon Cases._ This kind of case is generally made 8 diameters long; but, if very large, seven will be sufficient. From four ounces to two pounds, will succeed perfectly, but, when larger, there is no certainty. They are best rolled wet with paste, and the last sheet must have a straight edge, so that the case may be all of a thickness. After rolling them in the same manner as wheel cases, pinch them close at one end; then, with a rammer, drive the ends down flat, and, afterwards, ram in about one-third of a diameter of dried clay. The diameter of the former for these cases, must be the same as for sky-rockets. Tourbillons are to be rammed in moulds, without a nipple, or in a mould without its foot. (_Ency. Brit._) _Sec. IX. Of Balloon Cases, or Paper Shells._ First, prepare an oval former, turned out of smooth wood; then paste a quantity of brown, or cartridge paper, and let it lie until the paste is quite soaked through. This being done, rub the former with soap or grease, to prevent the paper from sticking to it. Next, lay the paper on in small slips, until you have made it one-third the thickness of the shell intended. Having this done, set it to dry; and when dry, cut it round the middle, and the two halves will easily come off: but, observe, when you cut, to leave about one inch not cut, which will make the halves join much better than if quite separated. When you have some ready to join, place the halves even together, and paste a slip of paper round the opening, to hold them together, and let them dry. Then lay on paper, all over as before, every where equally, excepting that end which goes downward in the mortar, which may be a little thicker than the rest; for that part, which receives the blow from the pounder in the chamber of the mortar, consequently requires the greatest strength.