Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/473

Rh CARRIAGE.] MINING 405 Diamond owned by separate individuals or companies, considerably affect the mines. methods of working. This is especially the case with the diamond deposits of South Africa. The diamantiferous rock at the celebrated Kimberley mine (formerly called Colesberg Kopje) occurs in the shape of an elliptical upright mass, the greatest length being about 330 yards and the greatest breadth about 200 yards. The super ficial area is about 9 acres; the mass extends down wards within almost perpendicular walls of shale, and is worked in places to a depth of about 400 feet. The claims are only 31 feet sqiiare, and are more than four hundred in number, and these have in some instances been subdivided into portions as small as the sixteenth of a claim ; but, as at the present time one company may own very many claims, the number of individual holdings is less numerous than formerly when the limit was two claims. The working is carried on vertically downwards, and, as the claims are not all worked at the same rate, those that progress most rapidly are surrounded by perpendicular walls of neighbouring claims. The shale, or reef, enclosing the deposit is constantly falling into the huge open pit, and has to be cut away to a slope, the expense of this work being charged to the claim -holders generally by the mining board. The diamanti ferous rock is extracted by innumerable wire-rope inclines. Evils at- We have already referred to the method of working gold-bearing tending alluvia by the hydraulic process, which has rendered such services hy- in the United States (GoLD, vol. x. p. 746). At the same time one draulic must not be blind to the evils of this method of working, which have raining, at last necessitated legislative interference. Some idea of the extent of the mischievous results of hydraulic mining will be gathered from the statement that one working alone, the Gold Run Ditch and Mining Company, for the last eight years has been discharging 4000 to 5000 cubic yards of sand, gravel, and boulders daily, for a period of five months each year, into a tributary of the Sacramento. As a natural consequence deposits are formed lower down the river, ob structing the navigable channels, rendering overflows more frequent and destructive, and causing valuable land to be destroyed by de posits of sand. The superior court of Sacramento county, California, has recently decided that the hydraulic mining companies must build dams to impound the coarse and heavy debris, or take other efficacious means to prevent their being washed down the rivers. 8. Carriage or Transport of Minerals along the Under ground Roads. After the mineral has been broken down in a deposit it is necessary to pick out any barren rock and then convey to the surface all that is of value. The simplest and oldest method of transport along underground roads is carriage on the back, and this method may still be seen at the present day even in countries where the art of mining is generally highly advanced. Thus, for instance, in the little slate mines near Cochem on the Moselle men and lads carry up all the blocks of slate upon their backs, walking upon steps cut in the rock ; they come up with their hands upon the ground bent almost double under the weight of the block, which rests upon a thick pad. Again, the blocks of slate are still carried on the back from the actual working place to the nearest tram-road, in the slate mines of the Ardennes. In the Sicilian sulphur mines the same method is common, and it is found also in parts of Spain and China, where baskets are used, whilst bags are employed in Mexico and also in Japan. Even in England the system still survives in the Forest of Dean, where boys carry iron ore in wooden trays from the very irregular ore-producing cavities either to the surface or to the nearest shaft. Sledges. Sledges, or sleds, enable greater loads to be transported ; but they are not available unless the conveyance is along roads sloping downwards. They have been largely employed in coal mines, and are still resorted to in some collieries for conveying the coal from the working place to the nearest tram-road. Wheel We next come to wheeled carriages. The simplest is the carriages, wheelbarrow. The barrow used in Cornwall at the present day is not unlike that figured more than three centuries ago by Agricola. The navvy s barrow is more advan tageous, but it requires a wider and higher level. The barrow runs upon the natural floor of the level, upon boards, or upon thin strips of iron. Carts drawn by horses may be used in large underground quarries. Excepting in special cases it is advisable to replace barrows by waggons running upon rails. The oldest form is the German Hund. Under ground trans port. Carriage by workers. It consists of a rectangular wooden body, with four wheels, resting upon two boards as rails, and it is kept on the track by a pin which runs between the boards. Cast-iron tram-plates were introduced in the last century, and were finally succeeded by iron rails, which are now in general use, though steel threatens to displace iron in this as in other departments of mining. Various forms of rail are employed. The simplest is a bar of iron set on its edge in transverse sleepers, or flat iron nailed to longitudinal sleepers. Small T-headed and bridge rails are not uncommon. In the Harz the rails sometimes lie on stone sleepers ; a hole is bored in the stone, plugged with wood, and the rail is nailed on. The gauge varies from 1 4 inches to 3 feet or more ; 20 inches to 22 inches is a common gauge in metal mines. Arrangements of course have to be made for passing from one line to another by points ; but the transference is frequently best effected by putting down flat plates of cast iron, upon the smooth surface of which the waggons can be handled with ease and turned in any direc tion ; raised ledges guide the wheels into any particular track. The form and size of the waggons running upon the rails necessarily vary according to the size of the underground roads and the manner in which the mineral is raised in the shaft. In some mines the practice exists of loading the mineral in the level into an iron bucket (kibble) standing upon a trolley, which is merely a small platform upon wheels. This trolley is pushed (trammed) to the shaft ; the full kibble is hooked on to the winding-rope and drawn up, whilst an empty kibble is placed upon the trolley and trammed back along the level, where it is again loaded from a shoot (mill, pass) or by the shovel. The usual plan, however, is to have a waggon, which is tipped on coming to an enlargement of the shaft (plat, lodge) where the level joins it. These waggons may be made of wood or sheet- iron, and of late years sheet-steel for the body and cast- steel for the wheels have been coming into favour. The most modern system in metal mines is to imitate collieries, and use waggons which are drawn up in cages. Fig. 83 represents the plain but strong waggon of the Van mines, consisting of a rectangular body of sheet-iron resting on an oak frame, and provided with cast-steel wheels. The wheels are loose upon the axles, which them selves run loose in the pedestals. The waggon is emptied by being Fig. 83. run on to a &quot;tippler,&quot; which enables it to be completely over turned with great ease. A commoner plan is to construct the waggon with a hinged door at one end, and the contents are discharged by opening this door and raising the body. The motive power for tramming waggons along the levels of metal mines is generally supplied by men or boys, though, where large quantities have to be extracted, and where the roads are favourable, recourse may be had to ponies and horses and the various kinds of mechanical haulage described in COAL, vol. vi. p. 69. Trains of cars are sometimes drawn along underground railways by locomotives ; they have the great disadvantage of polluting the air with the products of combustion, and consequently they are not available unless the ventilation is very good. A small locomotive of 2 horse-power nominal is used on an 18^-inch track in the adit-level of the Great Laxey mine (Isle of Man), now approaching a mile in length, and full-sized locomotives ply along the adit of the Rio Tinto mines. Locomotives worked by compressed air improve the ventilation instead of injuring it, and are not a source of danger in cases where fire-damp may be present ; but, except in special cases, they cannot be worked so cheaply as engines fired with coal. Con veyance by electric railroads underground has hardly gone beyond the experimental stage, but the results obtained at the Zaukeroda colliery in Saxony 1 show that electricity can be applied with profit in this department of mining. A few instances of transport by boats may still be met with. Boats. The boats used in the underground canal at Klausthal are 31 feet 1 Jahrbuch fur das Berg- und Huttenwesen im Konigreiche Saclisen aufdasJa.hr 1883, p. 50.