Saucissons may either be used in the manner we have mentioned or thrown by hand. According to their size, and the strength of the case, so will be the report. They resemble a thick and short sausage, hence their name.
Fire-pumps are intended for a particular use, which we will describe hereafter. The composition is the following:
| 1. | Saltpetre, | 5 | lbs. | ||
| Sulphur, | 1 | — | |||
| Meal powder, | 1½ | — | |||
| Glass-dust, | 1 | — | |||
| 2. | Saltpetre, | 5 | lbs. | 8 | oz. |
| Sulphur, | 2 | — | |||
| Meal powder, | 1 | — | 8 | — | |
| Glass-dust, | 1 | — | 8 | — |
Cases for fire-pumps are made like those for tourbillons, except that they are pasted, instead of being rolled dry. In charging them, first put in a little meal powder, and then a star; then a ladleful or two of the above composition, which ram tightly; then a little meal powder, on that a star, and then composition again, and so on until the case is filled. Stars for fire-pumps should not be round; but must be made either square, or flat and circular, with a hole through the middle. The quantity of powder for throwing the stars must increase as we come near the top of the case; for, if much powder be put at the bottom, it will burst the case. The stars must differ in size in this manner: Let the star, which is first put in, be about one-fourth less than the caliber of the case; but let the next star be a little larger, and the third star a little larger than the second, and so on for the rest. Let them increase in diameter till within two of the top of the case, which two must fit in tight. As the loading of fire-pumps requires some skill, it will be necessary to make two or three trials before depending on their performance.
When a number of pumps are filled, care must be taken not to put in each an equal quantity of charge between the stars; so that, when they are fired, they may not throw up too many stars together. Cases for fire-pumps should be made very strong, and rolled on four or eight-ounce formers, each ten or twelve inches long. For the composition and preparation of stars, see [stars.]
Sec. XXVII. Of the Volcano of Lemery.
The artificial earthquake, or volcano of Lemery, is formed by mixing into a paste with water, about equal parts of sulphur and steel or iron filings, and burying the mixture in the earth. The composition in a short time, will grow hot, and burst out; the earth will break, and open in several places.
Baumé mixed 100 pounds of iron filings and the same quantity of sulphur together, with water, and rammed the mixture into an iron pot. After ten hours, the mass swelled up and grew warm, aqueous vapours arose, and the mass burst. Ten hours afterwards, the heat, vapours, &c. greatly increased, and a flame issued forth, lasting only from 2 to 3 minutes. Finally, the mass became red-hot, and the burning and heat continued 40 hours longer; but without flame.
We may merely remark, that this effect is produced by the chemical union, which takes place between the sulphur and iron, forming a sulphuret of iron, analogous in composition to the native martial pyrites. The water is at the same time, decomposed, during which the mixture swells, becomes hot, and throws up the earth, producing at the same time a large quantity of sulphuretted hydrogen gas. This gas is formed by the combination of a part of the sulphur with the hydrogen of the water; whilst the oxygen, the other element of the water, goes to oxidize the metal and to acidify the remaining sulphur. Hence sulphate of iron, or green vitriol is produced. The experiment may be made in a common basin.