Of Illumination and other Lights.
These are very important in all fireworks, as well on account of their intrinsic beauty, and of the variety they afford among other fires, as because of the num ber of uses to which they are applied. As they burn very slowly, they may be made to last a long time by using long cases; or, what is better, by firing different short ones in succession.
One of the chief uses of these lights in fireworks on the large scale, is to illuminate transparencies, as we formerly noticed in treating of this department of py rotechny. When they, are to be used for this purpose, a sufficient number of cases, calculated to burn out the whole duration of the firework, however long that may be, must be arranged on a proper board, well secured, with a leader, passing in succession from the end of the preceding to the beginning of the following one. For such purposes, if it is the front of a piece of architecture that is to be lighted, the cases also should reach from three or four to six or eight inches in diameter. In other works, they are proportioned to the sizes of the pictures, as in illuminated guns, or coats of arms, or crowns, and other emblems commonly used in public exhibitions. For small Chinese transparencies, as lanthorns, dragons, and such like objects, they arc very small.
They are often used to terminate buildings, or other large complicated exhibitions of fireworks, when they may surmount turrets or columns. Thus also they are introduced into a variety of complicated fireworks that will be described hereafter; and, in these cases, they are exposed to view. These are always necessarily of a large size. We have already mentioned their uses in sky rockets, and they may be floated on the water so as to become a kind of water rocket.
Wilh respect to those larger kinds of lights, differ ent compositions are found in books of pyrotechny. But the only three worth preserving are those formed with orpiment, with zinc, and with antimony. Re ceipts for all these will be found in our table of com positions; but we have introduced into this article, for the reader's convenience, those which we think may supersede all other contrivances of this nature, namely, the zinc light and the antimonial one, the former being of a bright white, and the other a beau tiful pale blue. No particular attention is required as
to the cases, as it is sufficient if they are barely thick and strong enough to retain the composition. It is rather an advantage that the case and composition should burn together, as the white of the light is thus better displayed.
The smaller illumination lights, commonly called speckles, are even of more consequence than the large, as no complicated ornamental firework can be made without them. It is by means of these, that crowns, inscriptions, and figures of all kinds are made. By these also, all the architectural lines in a piece of architecture in fireworks are defined. Entablatures and basements, columns, windows, and door-ways, arc produced by lines of these lights, which must be dis posed at distances, varying from six inches to a foot, according to the expense which is admissible, and the effect which it is intended to produce. In the same way spirals are formed, together with cones, globes, pyramids, and other mathematical figures. Thus also they are applied to moving figures, such as revolving cones, or globes, or wheels; the !notions of these being sometimes produced by machinery, at others by means of attached recoiling as formerly mentioned in treating of machinery in fireworks.
In smaller works, these lights may be applied to the central parts of wheels, so as to form concentric circles of light during their revolution; or they may be attached to sky rockets, or to line rockets, as was suggested on former occasions. The mode of manag ing these requires no particular direction; as the same methods of lighting, of disposing, and of connecting them, are applicable to all.