must be fastened to some thing fixed, and the other to a stick conveyed between the legs, and placed in such a manner, as to be behind the person who choaks the cartridge. The cord is then to be stretched by retiring backwards, and the cartridge must be pinched until there remains only an aperture capable of admitting the piercer. The cord employed for pinching it is then removed, and its place is supplied by a piece of pack-thread, which must be drawn very tight, passing it several times round the cartridge, after which it is secured by means of running knots made one above the other.

Besides the roller, a rod is used, which being employed to load the cartridge, must be somewhat smaller than the roller, in order that it may be easily introduced into the cartridge. The rod is pierced lengthwise, to a sufficient depth to receive the piercer, which must enter into the mould, and unite with it exactly at its lower part. The piercer, which decreases in size, is introduced into the car. tridge through the part where it has been choaked, and serves to preserve a cavity within it. Its length, besides the nipple or button, must be equal to about two-thirds that of the mould. Lastly, if the thickness of the base be a fourth part of the calibre of the mould, the point must be made equal to a sixth of the calibre.

It is evident that there must be at least three rods, pierced in proportion to the diminution of the piercer, in order that the powder which is rammed in by means of a mallet, may be uniformly packed throughout the whole length of the rocket. It may be easily perceived also, that these rods ought to be made of some very hard wood, to resist the strokes of the mallet,

In loading rockets, it is more convenient not to employ a piercer. When loaded on a nipple, without a piercer, by means of one massy rod, they are pierced with a bit and a piercer fitted into the end of a bit-brace. Care however must be taken to make this hole suited to the proportion assigned for the diminution of the piercer. That is to say, the extremity of the hole at the choaked part of the cartridge, ought to be about a fourth of the calibre of the mould; and the extremity of the hole which is in the inside for about twothirds of the length of the rocket ought to be a sixth of the calibre. This hole must pass directly through the middle of the rocket. Ia short, experience and ingenuity will suggest what is most conve nient, and in what manner the method of loading rockets, which we shall here explain, may be varied.

After the cartridge is placed in the mould, pour gradually into it the prepared composition; taking care to pour only two spoonfuls at a time, and to ram it immediately down with the rod, striking it in a perpendicular direction with a mallet of a proper size, and giving an equal number of strokes, for example, 3 or 4, each time that a new quantity of the composition is poured in.

When the cartridge is about half filled, separate with a bodkin the half of the folds of the paper which remains, and having turned them back on the composition, press them down with the rod and a few strokes of the mallet, in order to compress the paper on the composition.

Then pierce three or four holes in the folded paper, by means of a piercer, which must be made to penetrate to the composition of the rocket. These holes serve to form a communication between the body of the rocket and the vacuity at the extremity of the cartridge, or that part which has been left empty.

In small rockets this vacuity is filled with granulated powder, which serves to let them off: they are then covered with paper, and pinched in the same manner as at the other extremity. But in other rockets, the pot containing stars, serpents, and running rockets is adapted to it, as will be shewn hereafter.

It may be sufficient however to make, with a bit or piercer, only one hole, which must be neither too large nor too small, such as a fourth part of the diameter of the rocket, to set fire to the powder, taking care that this hole be as straight as possible, and exactly in the middle of the composition. A little of the composition of the rocket must be put into these holes, that the fire may not fail to be communicated to it.

It now remains to fix the rocket to its rod, which is done in the following manner. When the rocket has been constructed as above described, make fast to it a rod of light wood, such as fir or willow, broad and flat at the end next the rocket, and decreasing to wards the other. It must be as straight and free from knots as possible, and ought to be dressed, if necessary, with a plane. Its length and weight must be proportioned to the rocket; that is to say, it ought to be six, seven, or eight feet long, so as to remain in equilibrium with it, when suspended on the finger, within an inch or an inch and a half of the neck. Before it is fired, place it with the neck downwards, and let it rest on two nails, in a direction perpendicular to the horizon. To make it ascend straighter and to

a greater height, adapt to its summit a pointed cap or top, made of common paper, which will serve to facilitate its passage through the air.

These rockets, in general, are made in a more complex manner, several other things being added to them to render them more agreeable, such for example as a petard, which is a box of tin-plate, filled with fine gunpowder, placed on the summit. The petard is deposited on the composition, at the end where it has been filled; and the remaining paper of the cartridge is folded down over it to keep it firm. The petard produces its effect when the rocket is in the air and the composition is consumed.

Stars, golden rain, serpents, saucissons, and several other amusing things, the composition of which we shall explain here. after, are also added to them. This is done by adjusting to the head of the rocket, an empty pot or cartridge, much larger than the rocket, in order that it may contain serpents, stars, and various other appendages, to render it more beautiful.

Rockets may be made to rise into the air without rods. For this purpose four wings must be attached to them in the form of a cross, and similar to those seen on arrows or darts. In length, these wings must be equal to two-thirds that of the rocket; their breadth towards the bottom should be half their length, and their thickness ought to be equal to that of a card.

But this method of making rockets ascend is less certain, and more inconvenient than that where a rod is used; and for this reason it is rarely employed.

We shall now shew the method of finding the diameters or calibre of rockets, according to their weight; but we must first observe that a pound rocket, is that just capable of admitting a leaden bullet of a pound weight, and so of the rest. The calibre for the different sizes may be found by the two following tables, one of which is calculated for rockets of a pound weight and below; and the other for those from a pound weight to 50 pounds.

I. Table of the calibre of moulds of a pound weight and below.

The use of this table will be understood merely by inspection; , for it is evident that a rocket of 12 ounces ought to be 17 lines in diameter; one of 8 ounces, 15 lines; one of 10 drams, 6 lines; and so of the rest.

On the other hand, if the diameter of the rocket be given, it will be easy to find the weight of the ball corresponding to that calibre. For example, if the diameter be 19 lines, it will be immediately seen, by looking for that number in the column of lines, that it cor responds to a bail of 5 ounces.

II. Table of the calibre of moulds from 1 to 50 pounds ball.

Pounds. Calibre. | Pounds, Calibre. Pounds. Calibre.

The use of the second table is as follows: If the weight of the

ball be given, which we shall suppose to be 24 pounds, seek for

that number in the column of pounds, and opposite to it, in the column of calibres, will be found the number 288. Then say as 100 is to 19, so is 288 to a fourth term, which will be the number of lines of the calibre required; or multiply the number found, that is 288, by 19, and from the product 56.16, cut off the two last figures: the required calibre therefore will be 56.16 lines, or 4 inches 8 lines.

On the other hand, the calibre being given in lines, the weight of the ball may be found with equal ease: if the calibre, for example, be 28 lines, say as 19 is to 28, so is 100 to a fourth term, which will be 143.5, or nearly 144. But in the above table, opposite to 144, in the second column, will be found the number 3 in the first; which shews that a rocket, the diameter or calibre of which is 28 lines, is a rocket of a 3 pounds ball.

CHAP. II.

COMPOSITION OF THE POWDER FOR ROCKETS, AND THE MANNER OF FILLING THEM.

THE composition of the powder for rockets must be different, according to the different sizes; as that proper for small rockets, would be too strong for large ones. This is a fact respecting which almost all the makers of fire-works are agreed. The quantities of the ingredients, which experience has shewn to be the best, are as follows:

For rockets capable of containing one or two ounces of composition.

To one pound of gunpowder, add two ounces of soft charcoal; or to one pound of gunpowder, a pound of the coarse powder used for cannon; or to nine ounces of gunpowder, two ounces of char. coal; or to a pound of gunpowder, an ounce and a half of saltpetre, and as much charcoal.

For rockets of two or three ounces.

To four ounces of gunpowder, add an ounce of charcoal; or to mine ounces of gunpowder, add two ounces of saltpetre.