Rockets which go under the denomination of swarmers, are those from two ounces downards. These small rockets are fired sometimes, in flights, and in large water-works, &c. Swarmers of one and two ounces, are bored, and made in the same manner as large rockets, except when headed, their heads must be put on without a collar; the number of strokes, for driving one ounce rockets, must be eight; and for two ounce rockets, twelve.
All rockets under one ounce, are not bored, but must be filled to the usual height, with composition, which is generally composed, of fine meal prowder four ounces, and charcoal or steel dust two drams; the number of strokes for ramming these small swarmers, is not very material, so as they are rammed true, and moderately hard. The necks of unbored rockets, must be in the same proportion, as in common cases.
Of the cause of sky Rockets rising.
Having promised in the second section, to prove that the effect of sky rockets, and proportion of their charge, depends on the size of the cavity in the composition; I shall here endeavour to give a mathematical demonstration thereof.
Let ABC be the hollow cone for the fire, AYCZB, the superficies of that cone, all the lines OZ at right angles with BC, all the lines OY at right angles with AC: now all the angles ZOY being towards R, whether the angles ZOY are obtuse or acute, but the more acute the better. The rays of fire ZO and YO issuing from the sides of the cone BC and AC, and continually acting with the greater force one upon another at O, forcing the whole BCA upward from the point R; and the wider the cone is, (so as not to exceed one third at bottom, and one sixth at top, of the exterior diameter of the rocket,) the greater velocity will the rocket rise with.
Of Stands for Sky Rockets.
Care must be taken, in placing the rockets, when they are to be fired, in order to give them a vertical direction at their first setting out; which may be managed thus. Have two rails of wood, of any length, supported, at each end, by a perpendicular leg, so that the rails be horizontal, and let the distance from one to the other, be almost equal to the length of the sticks of the rockets, intended to be fired; then in the front of the top rail, drive square hooks at eight inches distance from one another, with their points turning sideways, so that when the rockets are hung on them, the points will be before the sticks, and keep them from falling, or being blown off by the wind; in the front of the rail at bottom, must be staples, drove perpendicular under the hooks at top; through these staples, put the small ends of the rocket sticks. Rockets are fired by applying a lighted port fire, to their mouths.
N. B. When sky rockets are made to perfection, and fired, they will stand two or three seconds on the hook before they rise, and then mount up briskly, with a steady motion, carrying a large tail from the ground all the way up, and just as they turn, break and disperse the stars.