Mine

in a military sense, implies a subterraneous pa age dug under the wall or rampart of a fortification, for the purpose of blowing it up by gunpowder. The excavation formed by the blowing up of a mine is found by experiment to be nearly a paraboloid. It was formerly supposed that the diameter of the entonnoir, or excavation, was always equal to only double the line of least resistance; but experiments have proved, that the diameter of the excavation may be increased to six times the line of least resistance; and that the diameter of the globe of compre ion may be increased to eight times that line; this is called the maximum of a mine, or the greatest effect In any mine intended to produce an effect within this extent, the effects will be nearly as the charges. The globes are to each other as the cubes of their radii. Their radii are the hypothenuse of right angled triangles, of which the line of least resistance, and the semi-diameter of the excavation, are the other two sides. Therefore, to find the charge to produce any required diameter of the excavation, the following will be the rule, the radius being found as above: As the cube of the radius of the globe of compre ion in the following table, (having the same line of least resistance as the required globe,) Is to the cube of the radius of the required globe; So is the charge corresponding in the following table, To the charge required. Table for the Charges of Mines, according to Valliere. | Line of least Resistance. | Charge for the Mine. | Line of least Resistance. | Charge for the Mine. | | Feet. | lbs. | oz. | Feet. | lbs. | oz. | | 1 | 0 | 2 | 21 | 868 | 3 | | 2 | 0 | 12 | 22 | 998 | 4 | | 3 | 2 | 8 | 23 | 1140 | 10 | | 4 | 6 | — | 24 | 1296 | — | | 5 | 11 | 11 | 25 | 1558 | 9 | | 6 | 20 | 4 | 26 | 1647 | 12 | | 7 | 32 | 2 | 27 | 1815 | 4 | | 8 | 48 | — | 28 | 2053 | — | | 9 | 68 | 5 | 29 | 2286 | 7 | | 10 | 93 | 12 | 30 | 2530 | 4 | | 11 | 124 | 12 | 31 | 2792 | 4 | | 12 | 162 | — | 32 | 3072 | — | | 13 | 205 | 15 | 33 | 3369 | 1 | | 14 | 257 | 4 | 34 | 3680 | 12 | | 15 | 316 | 4 | 35 | 4019 | 8 | | 16 | 384 | — | 36 | 4374 | — | | 17 | 460 | 9 | 37 | 4748 | 11 | | 18 | 546 | 12 | 38 | 5144 | 4 | | 19 | 643 | — | 39 | 5561 | 2 | | 20 | 750 | — | 40 | 6000 | — | This table is calculated upon a supposition that the excavation of the mine is a paraboloid, having a base double the line of resistance; and that 10 lbs. 10 oz. of powder is sufficient for raising one cubic fathom of earth. By the rule above given may be found the charge for any mine, that shall only shake the ground, without making any excavation, by making the line of least resistance of the required globe only equal to the radius of the globe of compre ion. The charges thus found by means of this table, being only for one nature of soil; viz. , light earth and sand, (that for which the table is calculated) must be augmented according to the following table of Vauban’s, by one, four, five, seven, or nine elevenths of the charge found. Table of the quantity of powder required to raise a cubic fathom, according to the soil. | 1 | Light earth, mixed with sand | 11 | pounds. | | 2 | Common earth | 12 | | 3 | Strong sand | 15 | | 4 | Clay, or fat earth | 16 | | 5 | Old and good masonry | 18 | | 9 | Rock | 20 | The following rule is however laid down by Belidor, and generally adopted, if it be intended that the mine shall produce its maximum or greatest effect: multiply the line of least resistance, expre ed in feet, by 300, the product will be the charge in pounds. In making mines of any kind, the following remarks may be of service. The best form for the chamber would be spherical; but from the difficulty of its construction, it is always made a cube, of one inch larger dimensions than the box to contain the powder. The chamber must not be made in the prolongation of the branch of the mine, but at one side, and lower than the level of the branch, if the soil be dry; but higher if it be wet. One cubic foot will contain 75 lbs of powder; upon which principle the size of the case to contain the powder must be regulated. The auget is generally one inch square interior dimensions, and the end of it must reach the centre of the chamber; where the sauci on must be fastened, to prevent its being easily pulled out. The branch of the mine to be sprung must be closed in the strongest manner by doors well secured by props, and must be stopped with earth or rubbish to a distance, taken in a straight line, equal to 1¹⁄₂ times the line of least resistance. In proportioning the length of sauci on, in order that any number of mines may be fired at the same instant, a return of a right angle is generally reckoned equal to 4 inches in a right line. The first step in making a mine, whether for attack or defence, is to sink a shaft to the depth of the bottom of the gallery, having two of its sides in the direction of the sides of the gallery. These shafts should be where the galleries are to cro each other, or in the centre of the length of gallery to be made. These shafts should never be further apart than 40 or 50 fathoms; for it is found, that the air is not fit for respiration in the larger galleries at a greater distance from the shaft than 25 fathoms; at 20 fathoms in those of medium dimensions; and at 15 in the smallest. The rectangular frames used in sinking a shaft are commonly placed 4 feet asunder; and in the galleries they are only 3 feet. A gallery intended to be lined with masonry, must be 7 feet high and 6 feet wide, in order that it may be when finished, 6 feet high and 3 feet wide. Temporary galleries are only made 4¹⁄₂ feet high, and 2¹⁄₂ or 3 feet wide. The branches, at the ends of which the chambers are to be placed, are only made 2¹⁄₂ or 3 feet high, and 2 feet, or 2 feet 3 inches wide. The first of these is dug on the knees; the second sitting or lying. The miners are divided into squads of 4 each; and the rate of the work for each squad is 3 feet of the temporary gallery in 4 hours. The first squad is relieved by a second, after having worked 4 hours, or laid one frame; which second squad is again relieved by the first, at the expiration of the same time. In the most easy ground to work, a miner may be heard to the distance of 14 or 15 fathoms under ground; and the noise made by fixing the frames of the galleries may often be heard as far as 20 or 25 fathoms. A drum braced, standing on the ground, with a few peas or other round substances on the head, will be very sensibly affected by an approaching miner. It is of the most e ential consequence to place the entrances to the countermines beyond the reach of any surprise from the enemy. To prevent an enemy gaining po e ion of the galleries of the countermines they should be well secured by strong doors, at every 15 fathoms. These should be musquet proof. A glacis, properly countermined, and every advantage taken of it to retard the besiegers, may, with proper management, prolong a siege at least 2 months; and if the rest of the works are also countermined, and properly defended, they may add another month to the siege. Every system of countermines must depend upon the system of fortification to which they are to be adapted; the general principle for their regulation is, that the galleries should occupy situations, from which branches can be most readily run out under the most probable points of the besieger’s batteries and approaches. The general system of countermines commonly used in a place prepared before hand, is as follows: the principal or magistral gallery runs all round the work, under the banquette of the covert way, and acro the places of arms, having the entrances at the re-entering places of arms. Nearly parallel to this at 20, 25 or 30 fathoms distance is another gallery, called the envellope . These two galleries are connected by galleries of communication , under the gutters of the re-entering parts of the glacis, and under the ridges of the salient parts. From the envellope are run out about 15 or 16 fathoms, galleries in directions parallel to the capitals of the works, and at 23 fathoms distance from each other. These are called listeners . Sometimes, shafts are sunk from the end of these listeners, and by connecting these shafts, a second envellope formed. Behind the escarps of the different works, galleries are likewise made, about the level of the bottom of the ditch; from whence branches may be run out into or under the foundations of the walls; and if the ditch be dry, galleries of communication may be made from these to the magistral gallery; and from which communications branches may be run out for chambers to annoy the besiegers in their pa age of the ditch. The entrances to the escarp galleries are by means of posterns, which descend from behind the interior slope of the rampart. If a place be not countermined before hand, a great deal may be done even after the investment of the place, to prolong the siege by countermines. In this case, the first thing to be done immediately that the place is invested, is to sink a shaft in each of the places of arms of the covert way; one in each branch of the covert way opposite that part of the bastion where the breach will most probably be made; and one in the flanked angle of each bastion. Those on the covert way will be on the banquette, and sunk to about 18 inches below the bottom of the ditch. Those in the bastions to about 12 feet below the bottom of the ditch. Thus prepared, the moment the side on which the attack is to be made can be ascertained, galleries must be carried on from these shafts on the side attacked along the capitals, in the form of trefles, or double T; and advanced as far into the country as the time will admit. Communication galleries may likewise be driven between these different works on the covert way, and from them to the work in the bastion; which will prevent the enemy gaining po e ion of their entrances. All these works may be carried on after the investment of the place; and be in sufficient forwardne by the time the enemy gains the third parallel. The following rules are given by Vauban for fouga es, or small mines, having the diameter of the excavation equal to double the line of least resistance. The side of the chamber must be exactly a sixth part of the depth of the shaft. The side of the box to hold the powder exactly a ninth part of the depth of the shaft. These remarks respecting mines are principally extracted from the General E ay on Fortification before mentioned, written in French and published at Berlin, 1799. 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 the like purposes, viz. to blow up their enemies and their works; only the principal galleries and mines of the besieged, are usually made before the town is besieged, and frequently at the same time the fortification is built, to save expence. Eventer la Mine , Fr. to spring a mine. When used figuratively, this expre ion signifies to discover a plot, or make it known. It is likewise used to expre the failure of any expedition or undertaking. Definitions of Mines . A mine is a subterraneous cavity made according to the rules of art, in which a certain quantity of powder is lodged, which by its explosion blows up the earth above it. It has been found by experiments, that paraboloid , and that the centre of the powder, or charge, occupies the focus . The place where the powder is lodged is called the chamber of the mine, or fourneau . The pa age leading to the powder is called the gallery . The line drawn from the centre of the chamber, perpendicular to the nearest surface of the ground, is called the line of least resistance. The pit or hole, made by springing the mine, is called the excavation . The fire is communicated to the mines by a pipe or hose, made of coarse cloth, whose diameter is about one and a half inch, called a sauci on , (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 dampne , the sauci on is laid in a small trough, called an auget made of boards, three and a half inch broad, joined together, lengthwise, with straw in it, and round the sauci on, with a wooden cover nailed upon it. Foyer , Fr. Focus or centre of the chamber , some authors call the end of the sauci on that comes within the work, and which is to be set fire to, the foyer, or focus: but by most people, this is generally understood to be the centre of the chamber. Galleries and chambers of Mines . Galleries made within the fortification, before the place is attacked, and from which several branches are carried to different places, are generally 4 or 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 chamber. This is generally of a cubical form, large enough to hold the wooden box, which contains the powder nece ary for the charge: the box is lined with straw and sand-bags, to prevent the powder from contracting dampne . The chamber is sunk something 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. Quantities of powder to charge , Mines . Before any calculation can be made of the proper charge for a mine, the density and tenacity of the soil in which it is to be made, must be ascertained, either by experiment, or otherwise; for, in soils of the same density, that which has the greatest tenacity, will require the greatest force to separate its parts. The density is determined by weighing a cubic foot (or any certain quantity) of the soil; but the tenacity can only be determined by making a mine. The following table contains experiments in 6 different soils, which may be of some a istance to form a judgment of the nature of the soil, when an actual experiment cannot be had. | Nature of the soil. | Density. | Tenacity. | | Weight of 1 cubic foot. | Quantity of power to raise 1 cubic fathom. | | 1. | Loose earth or sand | 95 | pds. | 8 | | pds. | | 2. | Common light soil | 124 | | 10 | | | 3. | Loam, or strong soil | 127 | | 12 | ¹⁄₄ | | | 4. | Potter’s clay, or stiff soil | 135 | | 13 | ¹⁄₂ | | | 5. | Clay, mixed with stones | 160 | | 16 | | | 6. | Masonry | 205 | | 21 | ¹⁄₂ | | All the requisites in mining may be determined by the following problems, which admit of 4 cases; for any 3 of the articles below being given, the 4th may thence be found. 1. The nature of the soil, 2. The diameter of the excavation, 3. The line of least resistance, 4. The charge.