SULPHUR Vivum.—This is the sulphuret of lime which remains alter the ordinary purifications of sul phur by inciting. It will scarcely burn at all alone, and very imperfectly with nitre : whence it is easy to conjecture what results are to be expected from the numerous compositions into which it enters.
IsiNGLAss.—T his is used or recommended to make up the composition for stars into balls ; but it is infe rior for these purposes to gum, which is therefore here recommended. If too much gum be used, the ready ascension of the stars is impeded. If flour paste be used, the quantity of carbonaceous matter is so great, that they sometimes will not burn at all unless the quantity of charcoal in them is reduced.
LAPIS CALANINAILIS.—This is recommended as pro ducing what is called a dead lire." On the same principle as clay, it would not only deaden but extin guish any fire, and is, if not injurious, a nugatory in gredient.
SAW DUST.—There is no advantage in saw dust which is not to be obtained by charcoal. In the very large cases it may burn in sparks, but not better than that substance does ; and in the small ones it is much more likely to extinguish than to maintain the fire.
ANBEn.—This is one of the useless substances re commended in all the books. It is only calculated to make a bad flame in large cases, and smoke in small ones. It may be safely rescinded from the catalogue of necessaries altogether.
CLAY.—This is a necessary ingredient for the pur pose of stopping up various fireworks. It is indispens
able in tourbillons and simple wheels, or in all cases of fire that are to burn at the sides instead of the ends. In the cases which are choked, for the purposes of burn ing the iron more effectually, it is also useful, as it may be rammed down in the vent, and being after wards perforated, it serves to protect the paper about the choke from burning, and thus preserves the aper ture of the same size. In the military iron rockets it is indispensable, to prevent the plate which contains the vent from being destroyed by the torrent of fire ; and it ought always to be used in the larger paper rock ets, for preserving the dimensions of the hole during the burning. Clay for these purposes ought always to be freed from sand, to prevent all risk of accidents in driving. This the artificer must do for himself, as it is not to be procured thus pure. To effect this, it is in f,,,,larprl iron a cask with water, through which plug holes may be made towards the middle and the top. The water and clay being then stirred up, and suffered to stand for a few seconds, the sand subsides to the bottom. If then the muddy water he drawn off in succession through the holes, the finer clays will be suspended in two degrees of tenuity, should that be thought necessary. After it has subsided, and the water is drawn off, it is to be dried and powdered, and thus reserved for use.