Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/484

Rh 466 MINING [LEGISLATION. Tin. Tin-bearing rock is crushed by the stone -breaker and then stamped fine. The resulting sand and slime may be concentrated by the repeated use of the round buddle, with the keeve for a final cleaning ; but often the sand only is enriched by the buddle, whilst the very finest particles, constituting an almost impalpable mud (slime] when mixed with water, are treated by frames. When much pyrites is present it is necessary to make a preliminary concentra tion and roast the enriched product (witts) in a furnace. The calcination converts the heavy iron and arsenical pyrites into a light oxide which can be got rid of with the rest of the waste by buddling and framing. The final product from the keeve is clean enough to approach pure cassiterite in the percentage of metal. Alluvial tin ore is concentrated in sluice-boxes, and sometimes by jiggers, after a preliminary treatment in a puddling -machine (GOLD, vol. x. p. 745) if there are balls of clay which have to be broken up. When the alluvial ore occurs as a hard con glomerate (cement), it has to be stamped. Copper. Copper ores are treated by crushing by rolls and some times stamps, sizing by trommels, and then jigging and buddling ; but, as some of the ores are very friable and easily carried away by water, hand-picking is employed to a greater extent than with lead and tin ore, and the enrichment by water is not carried so far on account of the inevitable loss that would ensue. The amount of concentration depends upon the distance from the smelting works, and the mine-owner has to calculate whether it is best to get a low price for a large quantity of ore, after paying the carriage, or a higher price for a smaller lot (parcel] when due allowance has been made for the cost of dressing and loss sustained in that process. Thus, for instance, in Cornwall, the ore containing copper pyrites is dressed so as to contain only from 5 to 8 or 9 per cent, of metal, because it can easily be conveyed to Swansea by sea, and because further reduction in bulk would cause greater loss in value than the saving of freight. Loss in The loss in dressing is very considerable. P. von dressing. Rittinger estimates it at from 30 to 50 per cent., and stubborn facts bear out his conclusions. Heaps of refuse from dressing floors are frequently worked over again with profit; and in the year 1881 no less than 909 tons of &quot; black tin &quot; (i.e., concentrated tin ore fit for the smelter), worth 35,283, were extracted from the muddy water allowed to flow away from the dressing floors of some of the principal Cornish tin mines. The fall in air has been employed instead of the fall in water for concentrating purposes, and several ingenious air-jigs have been constructed and worked upon this principle. Separa- I Q exceptional cases magnetic attraction may be utilized. Mag- tion by netic iron can be separated in this way, and the magnetic process is magnet- applied for treating mixed blende and chalybite, the specific gravities ism. 0* which are too close to render concentration by water practicable. The mixed ore is calcined, and the chalybite is thus converted into magnetic iron, which can be extracted by a magnetic separator, leaving saleable blende. Before concluding this part of the subject we will briefly enumerate the principal improvements that have been made in metal-mining during the last quarter of a century. They are as follows : diamond-drill for prospecting ; machine drills for driving, sinking, and stoping ; use of compressed air for winding underground ; stronger explo sives, especially the nitro-glycerin compounds dynamite and blasting gelatin ; increased use of steel for various purposes ; Blake s stone-breaker and continuous jiggers ; extended application of hydraulic mining ; larger employ ment of electricity both for blasting purposes and for signalling by telegraph and telephone. It may be reason ably hoped that ere long electricity will render increased services to the miner for lighting the workings and for the transmission of power. Recent improve ments. 1 4. Recent Legislation affecting Mines in the United King- Recent dom. 1 In England the person owning the surface of a free- British hold is prima facie entitled to all the minerals underneath, excepting in the case of mines of gold and silver, which be long to the crown. The crown, however, does not claim gold and silver extracted from the ores of the baser metals. The ownership of the minerals can be, and often is, severed from that of the surface, the latter being sold whilst the mineral rights are reserved by the original owner. Local customs, now regulated by Acts of Parliament, are still in force in Derbyshire (High Peak Mining Customs and Mineral Courts Act, 1851, 14 & 15 Viet. c. 94, and the Derbyshire Mining Customs and Mineral Courts Act, 1852, 15 & 16 Viet. c. 43) and in the Forest of Dean (1 & 2 Viet. c. 43, and 24 & 25 Viet. c. 40). The Stannaries Act (32 & 33 Viet. c. 19) regulates the commercial dealings of mining companies in Cornwall and Devon, and provides for their liquidation. The working of mines in the United Kingdom is con trolled by five Acts of Parliament, viz., &quot; The Coal Mines Regulation Act, 1872&quot; (35 & 36 Viet. c. 76), &quot;The Metalliferous Mines Regulation Acts, 1872 and 1877 &quot; (35 & 36 Viet. c. 77, and 38 & 39 Viet c. 39), &quot; The Stratified Ironstone Mines (Gunpowder) Act, 1881 &quot; (44 & 45 Viet. c. 26), and &quot;The Slate Mines (Gunpowder) Act, 1882&quot; (45 Viet. c. 3). The last three Acts simply refer to the annual returns, and exemptions from certain restrictions concerning +he use of gunpowder. The Coal Mines Regulation Act applies to mines of coal, stratified ironstone, shale, and fire-clay. The Metalliferous Mines Regulation Act applies to all mines not included under the Coal Mines Act, and therefore controls not only workings for lead, tin, copper, and iron, commonly known as mines, but also the salt-mines, and under ground quarries worked for stone, slate, or other earthy minerals. The principal provisions of the Coal Mines Regulation Act have been set forth at vol. vi. p. 78 ; those of the Metalliferous Mines Regulation Act are similar, but less strict owing to the almost complete absence of fire-damp. One important difference is that the manager of a mine under the Metalliferous Act need not hold any certificate of competency or service. Other Acts of Parliament are the &quot;Explosives Act, 1875&quot; (38 Viet. c. 17), regulating the manner in which explosives are stored ; the &quot;Elementary Education Acts, 1876 and 1880&quot; (38 & 39 Viet. c. 79, and 43 & 44 Viet. c. 23), regulating the employment of children; the &quot; Factory and Workshop Act, 1878&quot; (41 Viet. c. 16), which applies to the dressing floors of mines under the Metalliferous Mines Regulation Act. The statute of Elizabeth (43 Eliz. c. 2) which was passed for raising money for the relief of the poor mentions coal mines, but omits other mines ; these have been made subject to poor- rates by &quot;The Rating Act, 1874&quot; (37 & 38 Viet. c. 54). The &quot;Employers Liability Act, 1880&quot; (43 & 44 Viet. c. 42), extends and regulates the liability of employers to make compensation for personal injuries suffered by workmen in their service. Finally, if, as sometimes happens, works are put up at a mine for roasting copper ores with common salt in order to extract the metal by the wet way, the provisions of the &quot;Alkali, &c., Works Regulation Act, 1881 &quot; (44 & 45 Viet. c. 37), must be attended to. It is thus very evident that the laws affecting mines have received most important additions during the last few years. 15. Accidents in Mines. Mining is one of the occupa- Accidents. tions that may decidedly be called hazardous. This fact has been thoroughly impressed upon the public mind by explosions of fire-damp in collieries ; but, though accidents of this kind are appalling, owing to the number of victims who perish at one time, fire-damp is by no means the worst enemy with which the miner has to contend. Falls of roof and sides both in collieries and metal mines are far more fatal in their results. With the risks attending the collier s calling we need not deal, as statistics upon 1 For information concerning the laws relating to mines in the United Kingdom, see W. Bainbridge, A Treatise on the Law of Mines at d Minerals, 1878, and Arundel Rogers, The Law relating to Mines, Minerals, and Quarries in Great Britain and Ireland, with a Sum mary of the Laws of Foreign States, 1876.