The besieged also made underground passages, from the town, under the besiegers' machines, by which they battered the walls, to destroy them, proving that necessity has been the inventress of mines.
The first mines we read of, since the invention of gunpowder, were made in 1487, by the Genoese, at the attack of Serezanella, a town in Florence. These, however, failed, and they were neglected, till Peter Navarro, being then engineer to the Genoese, and afterwards to the Spaniards, in 1503, against the French, at the siege of the castle del Ovo, at Naples, made a mine under the wall, and blew it up; in consequence of which the castle was taken by storm. Valliers says, that the engineer was Francis George, an Italian.
The place where the powder is lodged, is called the chamber of the mine, or fourneau, and the passage leading to the powder, is called the gallery. The line of the least resistance, is the line drawn from the centre of the chamber, perpendicular to the surface of the ground; and the excavation, called the crater, is the pit or hole, made by springing the mine.
Counter-mines are those made by the besieged, whereas mines are generally made by the besiegers. Both mines and counter-mines, are made in the same manner, and for like purposes, viz. to blow up their enemies and their works.
Galleries, made within the fortification, before the place is attacked, and from which several branches are carried to different places, are generally 4 and 41/2 feet wide, and 5 or 51/2 feet high. The earth is supported from falling in, by arches and walls, as they are to remain for a considerable time. But when mines are made to be used in a short time, then the galleries are but 3 or 31/2 feet wide, and 5 feet high, and the earth is supported by wooden frames, or props.
The gallery being carried on to the place, where the powder is to be lodged, the miners make the chambers. This is generally of a cubical form, large enough to hold the wooden box, which contains the powder necessary for the charge. The box is lined with straw and sand bags, to prevent the powder from contracting dampness.
The chamber is sunk rather lower than the gallery, if the soil permits; but where water is to be apprehended, it must be made higher than the gallery; otherwise the besieged will let in the water, and spoil the mine.
The fire is communicated to the mine by a pipe, or hose, made of coarse cloth, whose diameter is about 11/2 inches, called a saucisson, (for the filling of which, near half a pound of powder is allowed to every foot), extending from the chamber to the entrance of the gallery, to the end of which is fixed a match, that the miner who sets fire to it, may have time to retire before it reaches the chamber.
To prevent the powder from contracting any dampness, the saucisson is laid in a small trough, called an auget, made of boards 31/2 inches broad, joined together lengthwise, with straw in it, and round the saucisson, with a wooden cover nailed upon it.