The official report of General Desvaux on the artesian borings executed in the Desert of Zahara of the province of Constantine, in 1856-7, states, “that a spring affording 4010 quarts of water per minute, was the result of one of the borings, and that others affording 35, 120, and 4,300 quarts respectively were successively completed.” And he goes on to say: “When the shouts of the soldiers announced the gush, the Arabs sprang in crowds to the spot, laving themselves in the welcome abundance, into which mothers dipped their children; while the old Sheik fell upon his knees and wept, returning thanks to Allah and the French. At Oum Thiour a well sunk to the depth of 170 metres and yielding 180 quarts a minute was at once taken as the centre of a settlement by a portion of a previously nomadic tribe.... As soon as the water appeared they began the construction of a village, the plantation of 1,200 date trees, and entirely renounced their wandering existence.”
According to General Desvaux’s report, these artesian wells are likely to have a most important influence on Arab life, and greatly to subdue the roving propensities of many of the tribes.
MINES.
Mines are excavations made in the earth for the purpose of raising the various minerals which exist below its surface, such as coal, rock-salt, and the various ores from which metals are extracted (see “[Smelting]”). Mines consist of those which contain minerals that lie in strata parallel (or nearly so) to the surface of the earth, as coal, rock-salt, or iron-stone, and those containing the ores and minerals which are imbedded in seams or fissures of the primitive rocks, and are nearly perpendicular to the surface. Of the former kind, coal-mines form the chief examples. When indications of coal are discovered, a “boring” is commenced to ascertain its existence, and the depth at which it is placed below the surface. Each piece of earth raised by the boring-tools is placed one beside the other, in the exact order in which they are raised, so as to show the kind of earth being bored through, and the thickness of each strata between the surface of the earth and the seam of coal; and it sometimes happens that the boring is stopped on arriving at certain kinds of rock—the old red sandstone, for example—for it would be useless to continue boring beyond this, no coal ever existing below it.
When coal is found, and its quality and the thickness of the seam ascertained to be such as to warrant further expense, a shaft is dug down of some eight or ten feet diameter, cased with brickwork or wood to prevent the falling-in of its sides, and in some cases powerful machinery has to be erected to pump out the water which flows in. On reaching the coal, galleries—called “gates,” or “bords”—are dug in it in opposite directions, forming one long straight passage, and from this other smaller ones, called “headways,” are dug, at right angles, to the depth of about twenty-four feet, and from these other “gates” are carried parallel with the first, forming a series of roadways joined by short passages, and having squares of coal between them; the height of all these passages is determined by the thickness of the seam of coal, usually from three to ten feet. The great masses of coal forming the squares between these passages are gradually dug away (as far as can be done with safety) and the gates continued onwards, but before long the ventilation becomes impeded, and the air foul and dangerous from “fire-damp” (carburetted hydrogen) or “choke-damp” (carbonic acid), gases which are given off from the fissures in the coal.It is therefore necessary to produce a continuous current of fresh air in every part of the mine, which is done by sinking another shaft at the furthest part of the mine and keeping a large fire burning at its mouth, over which a tall shaft is generally erected, from which a column of light air ascends, drawing fresh air down the other shaft and through every part of the mine, to supply this “up-cast” shaft, as it is called. This supply of fresh air is economised and regulated by doors or valves, so placed that any part requiring extra ventilation can obtain it at any moment by shutting these doors and letting the whole current go through that particular part.
The removal of coal is effected partly by digging with the “pick,” and partly by blasting with gunpowder; a large square mass is cut all round, and a charge of powder fired behind it, so as to bring down at once sixty or eighty tons of coal, which is brought along the gates on “trams” to the bottom of the shaft, where “corves” or baskets filled with it are drawn up to the “pit’s-mouth” by steam machinery, one corve ascending full while another is descending empty.
The mines from which most minerals, such as sulphuret of lead (galena) or of copper, are drawn, belong to the second class, or those whose shafts “cut” the vein of mineral at a very acute angle. When the existence of the required mineral and its “dip” or inclination is ascertained, a shaft is sunk so as to cut its upper surface, and then carried through it, cross-cuts being formed on to the vein, and “levels” or galleries right and left in the direction of the vein. From these levels “winzes” or small shafts are cut at intervals from one level to that below it, thus leaving square portions of the mineral vein to be explored, which is done by digging away the roof or upper part, so that the rubbish and ore falls down, when it is sorted and carried away.