[Illustration: PLATE 4] Of a Projected Regulated Piece of Nine Mutations. A regulated piece, if well executed, is as curious a work as any in fireworks; for it consists of fixed and moveable pieces on one spindle, representing various sorts of figures, which take fire successively one from another, without any assistance after lighting the first mutation; but, for the better explanation of this piece, I shall give a full description of the method of communicating the fire from one mutation to the other, with a figure of each as they stand on the spindle. Regulated pieces are made of many sorts, and of any number of mutations, from two to nine, which is the greatest number I ever knew a piece to consist of, except one of my own making, which was composed of fifteen mutations, all different fires, and figures. But, as an explanation of so large a piece would be very difficult to comprehend, I shall omit it, leaving so many changes to those who have made a great progress in this art, and only teach the manner of making a piece of nine mutations, as shewn in Plate V, fig. 53. As it will be necessary that every mutation should be separately explained, I will first give the name of each, with the colour of fire, and size of the case belonging to it: after which shall proceed, with the proportion of each mutation, together with the nature of the spindle, and manner of placing the leaders. First Mutation Is a hexagon vertical wheel, illuminated in front with small port fires tied on the spokes; this wheel must be cloathed with two ounce cases, filled with black charge; the length of these cases are determined by the size of the wheel, but must burn singly. Second Mutation Is a fixed piece called a golden glory, by reason of the cases being filled with spur-fire; the cases must stand perpendicular to the block on which they are fixed, so that, when they are burning, they may represent a glory of fire; this mutation is generally composed of five, or seven two ounce cases. Third Mutation Is moveable, and is nothing more then an octagon vertical wheel, cloathed with four ounce cases, filled with brilliant charge; two of these cases must burn at a time: in this wheel you may make changes of fire. Fourth Mutation Is a fixed sun of brilliant fire, consisting of twelve four ounce cases; the necks of these cases must be a little larger than those of four ounce wheel cases; in this mutation may be made a change of fire, by filling the cases half with brilliant charge and half with grey. Fifth Mutation Is a fixed piece called the porcupine’s quills; this piece consists of twelve spokes, standing perpendicular to the block in which they are fixed; on each of these spokes, near the end, must be placed a four ounce case of brilliant fire; all these cases must incline either to the right or left, so that they may all play one way. Sixth Mutation