A System of Pyrotechny / Comprehending the theory and practice, with the application of chemistry; designed for exhibition and for war. - James Cutbush

Sec. I. Of the Caliber and Proportion of Rockets.

Sky-rockets are generally made of seven calibers, from half an inch to three inches. Different opinions have been entertained respecting the proper proportions. Some contend that the height should be always regulated by their exterior diameter. On this subject, several experiments, it seems, have been made by an experienced artist, M. Morel, not only to determine the length, which is best calculated to produce the maximum of ascension, but also with respect to the length compared with the caliber of the case.

The following tables are necessary in the formation of rockets. The first shows the size of the caliber of the mould, for rockets of a pound weight, and below; and the second points out the size required for the caliber of moulds, from one pound to fifty pounds. A lb. rocket, it must be observed, is that which is just capable of admitting a leaden bullet of a pound weight, and so of the rest.

TABLE I. Size of the caliber of moulds of a pound weight, and below to an ounce.

Weight of Rockets in ounces.	Diameters in lines.
16	19½
12	17
8	15
7	14¾
6	14¼
5	13
4	12⅓
3	11½
2	9¹/₆
1	6½

Here, it is evident, that the mould of a rocket of twelve ounces in weight, ought to be seventeen lines (12 lines to the inch) in diameter; and one of five ounces, will require a mould of thirteen lines in diameter. Hence, we derive an easy method of finding the size, when the weights are given: and, if the diameter of the rocket be given, it will be equally easy to find the weight of the ball, corresponding to the weight of that caliber.

TABLE II. Size of the caliber of moulds, of from one to fifty pound ball.

Pounds	Caliber	Pounds	Caliber	Pounds	Caliber	Pounds	Caliber
1	100	14	241	27	300	40	341
2	126	15	247	28	304	41	344
3	144	16	252	29	307	42	347
4	158	17	257	30	310	43	350
5	171	18	262	31	314	44	353
6	181	19	267	32	317	45	355
7	191	20	271	33	320	46	358
8	200	21	275	34	323	47	361
9	208	22	280	35	326	48	363
10	215	23	284	36	330	49	366
11	222	24	288	37	333	50	368
12	228	25	292	38	336
13	235	26	296	39	339

By this second table, if the weight of the ball be given, the size of the mould may be found: suppose it be eighteen pounds; opposite to it is the number 262. Then we say, by the rule of proportion, (as 19¹/₂, see [Table 1], is supposed to be divided into a hundred parts) 100 : 19¹/₂ : : 262 to the fourth term sought, viz. 51.09; which gives for the required caliber 52 lines nearly, or four inches and four lines. But if the caliber be given in lines, the weight of the ball may be found: suppose the given caliber be 36 lines, then as 19¹/₂ : 100 : : 36 : 184. The nearest number in the table to this is 181, which shows that the weight of the ball will be rather more than 6 lbs; or, in other words, that a rocket, the diameter or caliber of which is thirty-six lines, is a rocket of a 6 lb. ball. See [Congreve Rocket.]