EXPLOITATION OF MINES.

Otago Witness, Issue 1418, 25 January 1879, Page 5

EXPLOITATION OF MINES.

Translated from Le Charban. The following is made up from the exhibits, etc , appearing at the International Exhibition at Pans for 1878. In the working even of mineral veins marked progress has been made, owing to a more extensive exploitation, characterised by a better choice of methods, and their perfection for the most part. In the coal mines, S particularly at the time of the great price of coal, they attacked neglected beds or tho3e hitherto insufficiently worked. In the little beds they accomplished a complete removal with the least possible deterioration of the matter to be extracted, owing to the fact that the worked out parts of the mine were filled in, settling and caving, as well as explosions wero avoided, and all the precautions could be taken for the security of the men and the purity of the product obtained. This more thorough exploitation of the mineral riohes has produced an amelioration of all the details of subterranean transport. Everywhere have been adopted cars better studied, often of iron to augment their cap acity, with given exterior dimensions, and of ways established with stronger rails, often joined with fishplates (eclisses) fixed upon larger cross ties. In short, in all the coal mines have been established steam or compressed air engines for working interior shafts, inclines and horizontal roadways by cables or chains, by means of which the cars are drawn from these interior shafts to the coal bins often very diatant. At the mines of Oessons, they have introduced small looomotives in the mines, and at Blanzy they are about to construct a locomotive run by compressed air, which will not vitiate the air of the works. Tbe hoisting machines have become more strongly built of late, to fulfil the greater duty demanded of them, owing to the further development of the mines, which has greatly increased their depth. The system of expansion was adopted for the powerful hoisting machines at Blanzy for the first time ; since which the system has extended itsdf, and ingenious mechanisms have besn invented to perfect it. At the mines of Epinac they have substituted for the ordinary hoisting arrangement, with cable and drum, the system called atmospheric. In this system the guides are replaced by a tube of largo diameter, reaching like it from top to bottom of the shaft, and in the interior of which moves a piston, carrying at its bottom the charge to le raised. A vacuum is made above tbe piston, and the atmospheric pressure from below raises the charge. This system applied to a shaft of 650 metors in depth (2132 feet) offers the advantage over the hoisting with cables of being independent of the depth. But it is necessary that it should be tried some time before pro nouncing upon its value. The hoisting machinery taken albogether shows the advances that have been made, dictated by the concentration of the production to a few shafts, from which have often been extracted from a depth of more than 500 meters (1640 feet) 600 to 800 tons in 10 hours. The flat cable? are often of steel ; their strands havo been increased to give a great suppleness with tbe strength necessary for tho charges to be r&i3ed. The cages have several stages to receive several cars, and are often of steel to reduce tho suspended weight. The appliances for safety, parachutes, corrugated wheeLi, signals, &c, have deen multiplied and simplified to make their working certain in spite of the rapid working in vc-Jiie in the shafts at present The guides have been attended to with increasing care, and rigid ones of wood or of iron replacing thosa of round rope, par ticularly where the hoisting of workmen in the cage necessitates an emcrcious parachute. The raiaiDg and lowering of workmen in the hoisting cages is in all caßes the rule in mines deeper than 300 or 400 meters (984 fco 1312 feet), the special apparatus, oscillating timbers or columns (iiges ostihlanles) not being necessary, the maximum depth of Bbaits in France not being afc present greater than 650 meter** (2132 feet). In tho large perinanenent pumping machinery it has been attempted to augment the power of the apparatus by increasing the number of strokes of the piston per minute. This increase is obtained by work, ing tho pumps with compound engines, orbetter still, by rotating engines with a con tinuous motion and a fly wheel On the other hand it has been aimed to simplify the apparatus of the pumps and to augment the free space in the shaft by adopting a single pump rod of a working length of 200 meters (650 feet), or, better still, by installing at the bottom a rotating pump, which forces the water directly to the surface by a column of pipe occupying only an insignificant space iv the shaft. In all the machines of great power, the condensation and the expansions are pushed os far as possible. Considerable progress has been made in ventilating the worksby the mechanical apparatus of ventilat : on. Centrifugal ventilators as well as thoKe of Lemville are widely used, and of late have been made often of considerable dimensions, to ssnd an augmented volume of air through a careful system of conduits to every part of the mine. Numerous improvements have been made in the lighting of mines. The mineral oils are generally employed for the fixed lamps, and the mode of enclosing safety lamps lias been improved, and at the same time the degree of safety given by them has bicn increased by some modifications of detail. The electric Jight has remained the grcafc

exception, even in the works where the screening and sorting is done, except in the open air, where it seem* likuly to render aome servicU The apparatus for safety have been increased, owing to the simplifications _added to the primitive arrangements exhibited in 1867. The signals have been usually limited to the ancient hammer worked by a metallic cam, in spite of the happy efforts made in ! some mines fco replace it by electricity. The aparatus for separating and concentrating the ore extracted have made great progress, above all from the point of view of cost occasioned by the apparatus, of the re* duction of the manual labour necessary, and of the less amount of slack occasioned by screening. la this connection might be mentioaed the screening by concussion of Commentary, and the endless webs or cloth sheets {toilet sans fin) of the mines of Lens. In the washing of coal tbe power of the apparatus has been increased without reducing its effectiveness. In the washing of mineral ores the general use of the screens continued, to small Bizas, and the filtering screens of the Hartz Mountains have transformed the mechanical preparation in giving it a rapidity unknown before, and in reducing the loss by washing it has also pushed still further the the washing of fine matter. > The industry of the agglomeration of coat {agglomeres de honille) is a notable develop ment of Prauce since 1867, and the use of dry pitch as a cement is almost entirely substituted for liquid pitch, it giving a more solid mass, and burning with less odour and smoke. Great perfection has been reached m the apparatus for the agglomeration, especially for the grinding, for which entirely new' designs have been invented. In the carbonization of coal the augmentation of value of the fine coal has led to the adoption of coke ovens better adapted to large production, a-'.d consequently to the abandoning nearly always of those admitting air directly, and substituting for tha ovens fours a carnattx, and sometimes even ovens completely olosed, permitting the collection of the products of distillation, the ammoniacal liquor and the tar. The relative purity of fat coals has led to the carbonization of s'mi-bituminous coals,' or to the mixing with the fat coals a considerable amount of lean ooal } this result oannot be attained except by grinding them more finely and mixing them most intimately, and also by decreasing greatly the s ; za of tha [ oven?, bo as to largely increase the heated surface in order to promote more perfect carbonization^ In short, the constant' augmentation of the dimensions of Bhaff furnaces, which prevents the use of any but the most solid coke, has increased very much the hight of the coke oven, leading to the use of those which are straight and high, prolonging often the duration of the carbon* izing. i