The _mosaic candle_ owes its effect, in a great measure, to the rocket composition. Using alternately, composition, meal-powder, and a star, ramming the composition sufficiently, but not so as to break the stars, a case is formed, the effect of which is brilliant and striking. Besides the rapid combustion of the composition, the stars, when the fire comes to the meal-powder, are thrown out by it in succession, and to the height of one hundred and more feet. We have also, in this instance, the effect of the rocket composition, and that of gunpowder; the last of which, acting in the case in the same manner as powder in a musket on a ball, throws the stars to a great height. Hence the _effect_ is varied according to the manner of loading the case; and by employing alternately the substances we have mentioned, the effects follow in regular succession. The use of gunpowder in this manner, is strikingly shown in many other fire-works. When, for instance, stars, serpents, &c. forming the furniture of a rocket, are to be dispersed, gunpowder is put in the head or conical cap of the rocket, and fire is communicated to it at the moment the rocket has arrived at its extreme elevation. In the bursting of paper shells, the same effect ensues, and the different substances contained in the shell are dispersed in every direction. Balloons are nothing more than shells made either of paper, or wood turned hollow. These balloons are discharged from mortars, or fire-pots, sometimes called pots of ordnance. They are merely cylinders of various diameters, made of paper and very thick, or of metal, and are furnished at their bottom with a conical cavity lined with copper, designed to hold the charge of powder. When the balloon is filled, (see _Balloons_), it is introduced into the mortar over the charge, and being furnished with a fuse as in other shells, takes fire the moment the powder is inflamed. According to the quantity of powder made use of, so will be the height of ascension. By determining the ascension, and the time required for the fuse to burn, and communicate fire to the shell, we may fix the precise moment for its explosion. The powder contained in the shell is sufficient only to burst it, and disperse its contents. (See _Mortars_, _Fire-pots_, and _pots of Aigrette_.) A balloon will contain more stars, serpents, &c. than the head of an ordinary rocket, and the effect which they produce, must of course be more striking. The Congreve rocket, calculated as it is to convey carcass composition, balls, grenades, &c. if furnished with stars, crackers, &c. would produce an effect equal, if not superior to the balloon.