In the center of each mortar fix a case of spur fire; on the second rail fix four mortars, so as to stand exactly in the middle of the intervals of them on the bottom rail; on the third rail place three mortars; on the fourth two; and on the top of the posts one; the bottom rail must be six feet in length; all the mortars must incline a little forwards, that they may easily discharge themselves, and the spur-fires rammed exactly alike that the mortars may all be fired at the same time, having prepared your pyramid according to the preceeding directions, carry pipes of communication, from one spur-fire to the other. The Illuminated Regulating Piece. Fig. 11, represents one half of this piece; A, A, A, A, are flat wooden spokes, each five feet in length, and at the end of each, place a vertical wheel, ten inches diameter, clothed with six four ounce cases of brilliant fire, these cases must burn but one at a time; on two of the spokes of each wheel, place two port-fires, which must be lighted with the first case of the wheel; on each spoke A, A, &c. behind the wheels place six cases of the same size as them on the wheels; these cases must be tied across the spokes with their mouths all one way, and be made to take fire successively one after the other, so that they may assist the whole pieces to turn round. The diameter of the wheel B, must be two feet six inches, and its fell made of wood, which must be fixed to the large spokes, on this wheel place twenty four cases of the same sort as them on the small wheels, these cases must burn four at a time; in this wheel make three circles with iron wire, and on them place illuminating port-fires, as shewn in the figure; the star points on the large spokes may be made of thin ash hoops, the diameter of these points close to the center wheel must be eleven inches; on these points place port-fires, at three inches and a half distance, one from the other. Fig. 12, represents the blocks of this piece, the diameters of these blocks at A and B, must be eight inches and C and D, four inches and a half, the length of each, of these blocks must be six inches; at the small ends of these blocks fix an iron wheel five inches diameter, which wheels must have teeth, to turn the wheel E, this wheel which is fixed on a small spindle screwed into the large spindle which goes through the two blocks, and on which they run. * * * * *