the bottom excepted; which, as already said, must be of wood. The chamber for the powder must be pierced obliquely, with a small gimblet; so that the aperture corresponding to the aperture of the metal mortal, the fire applied to the latter may be communi. cated to the powder which is at the bottom of the chamber, imme. diately below the globe. By these means the globe will catch fire, and make an agreeable noise as it rises into the air; but it would not succeed so well, if any vacuity were left between the powder and the globe.

A profile or perpendicular section of such a globe is represented by the right-angled parallelogram, the breadth of which is nearly equal to the height. The thickness of the wood, towards the two sides, is equal, as above said, to the twelfth part of the diameter of the globe; and the thickness of the cover is double the preceding, or equal to a sixth part of the diameter. The height of the chamber, where the match is applied, and which is terminated by a semicircle, is equal to the fourth part of the breadth; and its breadth is equal to the sixth part.

We must here observe that it is dangerous to put wooden covers on aërial balloons or globes; for these covers may be so heavy, as to wound those on whom they happen to fall. It will be sufficient to place turf or hay above the globe, in order that the powder may experience some resistance.

The globe must be filled with several pieces of cane or common reed, equal in length to the interior height of the globe, and charged with a slow composition, made of three ounces of pounded gun. powder, an ounce of sulphur moistened with a small quantity of petroleum oil, and two ounces of charcoal; and in order that these reeds or canes may catch fire sooner, and with more facility, they must be charged at the lower ends, which rest on the bottom of the globe, with pulverised gunpowder moistened in the same manner with petroleum oil, or well besprinkled with brandy, and then dried.

The bottom of the globe ought to be covered with a little gunpowder half pulverised and half grained; which, when set on fire, by means of a match applied to the end of the chamber, will set fire to the lower part of the reed. But care must have been taken to fill the chamber with a composition similar to that in the reeds, or with another slow composition, made of eight ounces of gun

powder, four ounces of saltpetre, two ounces of sulphur, and one ounce of charcoal: the whole must be well pounded and mixed.

Instead of reeds, the globe may be charged with running rockets, or paper petards, and a quantity of fiery stars or sparks mixed with pulverised gunpowder, placed without any order above these pe. tards, which must be choaked at unequal heights, that they may perform their effect at different times.

These globes may be constructed in various other ways, which it would be tedious here to enumerate. We shall only observe, that when loaded, they must be well covered at the top; they must be wrapped up in a piece of cloth dipped in glue, and a piece of woollen cloth must be tied round them, so as to cover the hole which contains the match.

CHAP. VIII.

JETS OF FIRE.

JETS of fire are a kind of fixed rockets, the effect of which is to throw up into the air jets of fire, similar to jets of water. They serve also to represent cascades; for if a series of such rockets be placed horizontally on the same line, it may be easily seen that the fire they emit, will resemble a sheet of water. When arranged in a circular form, like the radii of a circle, they form what is called a fixed sun.

To form jets of this kind, the cartridge for brilliant fires must, in thickness, be equal to a fourth part of the diameter, and for Chinese fire, only to a sixth part.

The cartridge is loaded on a nipple, having a point equal in length to the same diameter, and in thickness to a fourth part of it; but as it generally happens that the mouth of the jet becomes larger than is necessary for the effect of the fire, you must begin to charge the cartridge, as the Chinese do, by filling it to a height equal to a fourth part of the diameter with clay, which must be rammed down as if it were gunpowder. By these means the jet will ascend much higher. When the charge is completed with the composi

tion you have made choice of, the cartridge must be closed with a tompion of wood, above which it must be choaked.

The train or match must be of the same composition as that employed for loading; otherwise the dilatation of the air contained in the hole made by the piercer, would cause the jet to burst.

Clayed rockets may be pierced with two holes near the neck, in order to have three jets in the same plane.

If a kind of top, pierced with a number of holes, be added to them, they will imitate a bubbling fountain.

Jets intended for representing sheets of fire ought not to be choaked. They must be placed in a horizontal position, or in. clined a little downwards.

It appears to us that they might be choaked so as to form a kind of slit, and be pierced in the same manner; which would contribute to extend the sheet of fire still farther. A kind of long narrow mouth might even be provided for this particular purpose.

PRINCIPAL COMPOSITIONS FOR JETS OF FIRE.

1st. Jets of five lines or less, of interior diameter. Chinese fire.-Saltpetre 1 pound, pulverised gunpowder 1 pound, sulphur, 8 ounces, charcoal 2 ounces.

White fire.-Saltpetre 1 pound, pulverised gunpowder 8 ounces, sulphur 3 ounces, charcoal 2 ounces, iron sand of the first order 8 ounces.

2d. Jets of from ten to twelve lines in diameter. Brilliant fire.-Pulverised gunpowder 1 pound, iron-filings of a mean size, 5 ounces.

White fire.-Saltpetre 1 pound, pulverised gunpowder 1 pound, sulphur 8 ounces, charcoal 2 ounces.

Chinese fire.-Saltpetre 1 pound 4 ounces, sulphur 5 ounces, sand of the third order 12 ounces.

3d. Jets of fifteen or eighteen lines in diameter.

Chinese fire.-Saltpetre 1 pound 4 ounces, sulphur 7 ounces, charcoal 5 ounces, of the six different kinds of sand mixed 12

ounces.

Pere d'Incarville, in his memoirs on this subject, gives various other proportions for the composition of these jets; but we must

confine ourselves to what has been here said, and refer the reader to the author's memoirs, which will be found in the Manuel de l'Artificier.

The saltpetre, pulverised gunpowder, and charcoal, are three times sifted through a hair sieve. The iron sand is besprinkled with sulphur, after being moistened with a little brandy, that the sulphur may adhere to it; and they are then mixed together: the sulphured sand is then spread over the first mixture, and the whole is mixed with a ladle only; for if a sieve were employed, it would separate the sand from the other materials. When sand larger than that of the second order is used, the composition is moistened with brandy, so that it forms itself into balls, and the jets are then Foaded if there were too much moisture, the sand would not perform its effect.

SECTION I.

Of Fires of different Colours.

It is much to be wished that, for the sake of variety, different cofours could be given to these fireworks at pleasure; but though we are acquainted with several materials which communicate to flame various colours, it has hitherto been possible to introduce only a very few colours into that of inflamed gunpowder.

To make white fire, the gunpowder must be mixed with iron or rather steel filings.

To make red fire, iron sand of the first order must be employed in the same manner.

As copper filings, when thrown into a flame, render it green, it might be concluded, that if mixed with gunpowder, it would produce a green flame; but this experiment does not succeed. It is supposed that the flame is too ardent, and consumes the inflammable part of the copper too soon. But it is probable that a suffi cient number of trials have not yet been made; for is it not possible to lessen the force of gunpowder in a considerable degree, by increasing the dose of the charcoal?

However, the following are a few of those materials which, in books on pyrotechny, are said to possess the property of communicating various colours to fireworks.

Camphor mixed with the composition, makes the flame to appear of a pale white colour

Raspings of ivory give a clear flame of a silver colour, inclining a little to that of lead; or rather a white dazzling flame.

Greek pitch produces a reddish flame, of a bronze colour. Black pitch, a dusky flame, like a thick smoke, which obscures the atmosphere.

Sulphur, mixed in a moderate quantity, makes the flame appear blueish.

Sal ammoniac and verdigris give a greenish flame.

Raspings of yellow amber communicate to the flame a lemon colour.

Crude antimony gives a russet colour.

Borax ought to produce a blue flame; for spirit of wine, inwhich sedative salt, one of the component parts of borax, is dissolved by the means of heat, burns with a beautiful green flame,

Much, however, still remains to be done in regard to this sub. ject; but it would add to the beauty of artificial fireworks, if they could be varied by giving them different colours: this would be creating for the eyes a new pleasure.

SECTION II.

Composition of a Paste proper for representing Animals, and other Devices in Fire.

IT is to the Chinese also that we are indebted for this method of representing figures with fire. For this purpose, take sulphur reduced to an impalpable powder, and having formed it into a paste with starch, cover with it the figure you are desirous of representing on fire it is here to be observed, that the figure must first be coated over with clay, to prevent it from being burnt.

When the figure has been covered with this paste, besprinkle it while still moist with pulverised gunpowder; and when the whole is perfectly dry, arrange some small matches on the principal parts of it, that the fire may be speedily communicated to it on all sides.

The same paste may be employed on figures of clay, to form de. vices and various designs. Thus, for example, festoons, garlands, and other ornaments, the flowers of which might be imitated by fire of different colours, could be formed on the frieze of a piece of ar. chitecture covered with plaster. The Chinese imitate grapes ex