As to the different compositions, it will be sufficient to remark, that for _wheels_, _fixed cases_, _sun cases_, _gerbes_, _Chinese fire_, _tourbillons_, _water balloons_, _water squibs_, _serpents_, _port-fires_, _cones_, _globes_, _air-balloon fuses_, _fire-pumps_, and many others to be noticed hereafter, the basis of them is either gunpowder or saltpetre, and sulphur and charcoal, with or without additions. With respect to the composition of the stars of different colours, it is to be observed, that the particular colour is given by pulverized cast-iron, steel-filings, camphor, amber, antimony, perchloride of mercury, (corrosive sublimate), ivory-dust, copper, frankincense, &c. To produce _tails of sparks_, pitch or rosin is added. Stars which produce _some_ sparks are usually made by using gum water in mixing the composition. The gum appears to produce a separation of the inflammable substances, and, as it is not combustible, to check, as it were, the rapidity of the combustion. In some preparations, also, isinglass or fish-glue is used in solution. This, no doubt, acts in the same manner, as well as to give firmness to the composition; but its solution is also used as a vehicle. On the same principle also, we learn the use of caustic ley, quicklime, &c. in preparing match-rope. After soaking the cord in a solution of nitre, it is afterwards dipped into ley, which is nothing more than a solution of potash rendered caustic by means of quicklime. The potash evidently checks the combustion. The formulæ for slow match, are, however, various. In the match-wood, also, prepared from the wood or bark of the linden, the wood is usually first soaked in a solution of saltpetre, and afterwards in a solution of acetate or sugar of lead, &c. For the same purpose, nitrate of copper is recommended. For stars of a yellow colour, besides gum arabic, or gum tragacanth, saltpetre, and sulphur, the addition of powdered glass, orpiment, (sulphuret of arsenic), and white amber, are occasionally made. The colour is owing to the amber and the orpiment, which have the property of communicating it to flame. We may observe, generally, that the colours produced by different compositions, is a subject of importance to the pyrotechnist. He should know the properties of each substance, and the effect of each ingredient; and, with respect to their action, be able to foretell the appearance of the flame, and other circumstances connected with the art. As a general example, we may state, that sulphur gives a blue; camphor, a white, or pale colour; saltpetre, a clear white yellow; amber, a colour inclining to yellow; muriate of ammonia, (sal ammoniac), a green; antimony, a reddish; rosin, a copper colour, and Greek pitch, a bronze, or a colour between red and yellow. In using these substances, the following remarks may be useful;--that for producing a white flame, the saltpetre should be the chief part; for blue, the sulphur;