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tons per 1200 metres. Stassart {loc. cit. p. 465) considers the heavier waste falls and is discharged at a lower level, that they should be used in preference to flat steel wire or through a valve at the bottom of the machine. The ropes down to 1500 metres. The new large engine of the larger or “ nut ” sizes, from ^ inch upwards, are washed Anzi Company, to lift a gross load of 15 tons from 750 on plain sieve plates, but for finer-grained duff the sieve metres, is also fitted with flat ropes. These are 3 inches is covered with a bed of broken felspar lumps about 3 thick and 22|- inches broad at the drum end, weigh inches thick, forming a kind of filter, through which the 18 tons each, and coil upon a diameter increasing from fine dirt passes to the bottom of the hutch. The cleaned 14 to 2 6'3 feet. coal is carried by a stream of water to a bucket elevator The continuous change in direction experienced by the and delivered to the storage bunkers, or both water and rope between the head-gear pulley and the drum in coiling coal may be lifted by a centrifugal pump into a large on or off (the so-called “ angling ” of the rope) is a source of cylindrical tank, where the water drains away, leaving the wear when the depth becomes considerable. This is to coal sufficiently dry for use. Modern screening and washsome extent diminished by placing the engine at some ing plants, especially when the small coal forms a condistance from the pit, up to 50 or 60 yards; but a complete siderable proportion of the output, are large and costly, remedy has been proposed by Mr W. Morgan, who uses requiring machinery of a capacity of 100 to 150 tons per a winding engine upon a frame carried upon two lines of hour, which absorbs 350 to 400 horse-power. In this, as railway, which is shifted laterally though a distance equal in many other cases, electric motors supplied from a central to the thickness of the rope at each revolution of the station are now preferred to separate steam-engines. drum, so that the end of the coil is always in the same In addition to its use as fuel, there are two principal vertical plane with the guide pulley and the cage. The first outlets for small coal, namely, as briquettes, or patent engine of this class has just been erected at Dolcoath tin fuel, and coke, the former being adopted for mine in Cornwall, at a shaft which is to be carried down non-caking and the latter for caking coals. -povBri9uettes‘ to 3000 feet in depth. briquettes the small coal, if previously washed, is dried to In the United Kingdom the drawing of coal is generally reduce the moisture to at most 4 per cent., and, if necesconfined to the day shift of eight or ten hours, with an sary, crushed in a disintegrator and incorporated in a pug output of 100 to 150 tons per hour, according to the mill with from 8 to 10 per cent, of gas pitch, softened by depth, capacity of coal tubs, and facilities for landing and heating to between 70° and 90° C. to a plastic mass, which changing tubs. With Fowler’s hydraulic arrangement is then moulded into blocks and compacted by a pressure 2000 tons are raised 600 yards in eight hours. In the 'of ^ to 2 tons per square inch in a machine with a rotating deeper German pits, where great thicknesses of water- die plate somewhat like that used in making semi-plastic bearing strata have to be traversed, the first establishment clay bricks. When cold, the briquettes, usually weighing expenses are so great that in order to increase output the from 7 to 20 fi) each, although smaller sizes are made shaft is sometimes provided with a complete double equip- for domestic use, become quite hard, and can be handled ment of cages and engines. In such cases the engines with less breakage than the original coal. Their principal may be placed in line on opposite sides of the pit, or at use is as fuel for marine and locomotive boilers, the right angles to each other. According to Kohne, the evaporative value being about the same or somewhat more output of single shafts has been raised by this method to than that of coal. The principal seat of the manufacture 3500 and 4500 tons in the double shift of sixteen hours. in Great Britain is in South Wales, Avhere the dust and It is particularly well suited to mines where groups of smalls resulting from the handling of the best steam coals seams at different depths are worked simultaneously. Some (which are very brittle) is obtainable in large quantities characteristic figures of the yield for British collieries in and finds no other use. Some varieties of lignite, when 1898 are given below :— crushed and pressed at a steam heat, soften sufficiently to Albion Colliery, South,000 tons in a year for one shaft furnish compact briquettes without requiring any cementing material. These are now made to a very large extent from Wales . . . ./ and one engine. Silksworth Colliery, North-) 535,000 tons in a year for shaft 580 the tertiary lignites in the vicinity of Cologne, and are umberland . . ,j yards deep, two engines. used mainly for house fuel on the Lower Bhine and in Bolsover Colliery, Derby . 598,798 tons in 279 days, shaft 365 Holland. yards deep. The principal novelty of interest in connexion with cokeDenaby Main Colliery, 629,947 tons in 281 days, maximum makiug is the development of the so-called by-product Yorkshire . . ./ per day 2673 tons. ovens, where, in addition to the carbonized fuel, Coal as raised from the pit is now generally subjected to volatile products, such as tar, benzol, and am- taking some final process of classification and cleaning before being monia, are recovered by condensation from the despatched to the consumer. The nature and gases evolved in the oven before the latter are burnt to ex en arrange^ ^ these operations vary with the character supply the necessary heat for the coking process. The meats. of the coal, which if hard and free from shale part- first successful application of this principle was made by Mr ings may be finished by simple screening into Carves at Besseges, in France, and it was introduced into large and nut sizes and smaller slack or duff, with a final Great Britain, with some modifications in details, by the late hand-picking to remove shale and dust from the larger sizes. Mr H. Simon, under the name of the Simon-Carves system. But when there is much small duff, with intermixed shale, Other and subsequent developments were those of Semetmore elaborate sizing and washing plant becomes necessary. Solvay and Hiissener. The whole of these have a common Where hand-picking is done, the larger-sized coal, separated feature in the narrow Q-shaped oven, which is heated by a by 3-inch bar screens, is spread out on a travelling band, series of parallel horizontal flues in the side walls, while in which may be 300 feet long and from 3 to 5 wide, and the Otto-Hoffmann system, which has been most largely carried past a line of pickers stationed along one side, who adopted, the Coppee oven with vertical heating flues is take out and remove the waste as it passes by, leaving the used. The condensing arrangements, which are generally clean coal on the belt. The smaller duff is separated by similar for all the systems, resemble those of an ordinary vibrating or rotating screens into a great number of sizes, gas-works, somewhat simplified. The gas given off by the which are cleaned by washing in continuous-current or coal is led by one or two openings in the roof, through pulsating jigging machines, where the lighter coal rises to water-sealed dip pipes, to a collecting main leading to a the surface and is removed by a stream of water, while system of atmospheric condensers, pipes cooled by exposure S. III. —16
