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As the performance of rockets depend much upon their moulds, they should be made according to the following proportions:—Taking the diameter of the orifice, its height should be equal to six diameters and two-thirds; the choke, one diameter and one third of this model, will serve for every rocket from four oz. to six lbs.; for instance, suppose the diameter of a rocket of one pound be one and a-half inch, then its length being six diameters and two thirds, the length of the case must be ten inches one-eighth, and the choke two and a quarter inches. Your rammer must have a collar of brass to prevent the wood from splitting.

The principal part of the performance of the rocket depends on the compositions being well mixed; therefore great care must be taken in this part of the work, particularly in the manufacture of rockets.

Rockets are filled hollow, otherwise they would not ascend. The charge of rockets must always be driven above the piercer, and on it must be rammed a thin head of clay, through the middle of which bore a small hole to the composition, that when the charge is burned to the top, it may communicate its fire through the hole to the stars in the head. When you load the heads of your rockets with stars or serpents or any thing else, remember always to put a ladlefull of powder into each head.

The beautiful red fire which is used in the theatres is composed of the following ingredients:—Forty parts of dry nitrate of strontian, thirteen parts of finely powdered sulphur, five parts of chlorate of potash, and four parts of sulphuret of antimony.

Take of flour of sulphur thirteen parts, of nitrate of baryta, seventy-seven, of oxymuriate of potassa, five, of metallic arsenic, two, of charcoal three. The nitrate of baryta should be well dried and powdered.

These cases are made much the same as for serpents, and are filled with a composition of a quarter of an ounce of saltpetre, half an ounce of powder, and one ounce of sulphur.

A very small quantity of charcoal may be added, which will have a sparkling effect.