MINING 



Afii-r tin' mineral has been 



t tn tin- shaft linttorn, it 



n!ii>t be hoisted or wound uptntin- 



Miifare. Thf \\i-rk i- |tcrfi. lined liy 



u 11 id i ii- < urines, which are still 



steam-driven, although 



and powerful rli.in. 



winder* have been introduced, and 



air 111 MI, , rssful operation. 



I 'limping ia necessary in moat 

 mines, tinman it is noteworthy 

 i hat the quantity of water met 

 \\itli in deep mines is usually con- 

 .-ideralily less than in shallow ones, 

 A number of different systems of 

 pumping are adopted. Sometimes 

 pumps are placed in the 

 shaft, earh pump having a lift of 

 -e \eial hundred feet when it de- 

 livers water into a cistern, from 

 whieh the pump immediately above 

 it draws its supply, and so on until 

 the water is discharged at the sur- 

 face. In many cases underground 

 electric pumps have been substi- 

 tuted for the above, there being 

 serious objections to a heavy set 

 of pumping spears working in a 

 shaft. Opinions are pretty equally 

 divided between electrically direct- 

 driven, high-speed multi-stage cen- 

 trifugal pumps and three-throw ram 

 pumps driven by suitable gearing 

 from a motor, each type having 

 its advantages and drawbacks. 



Ventilation is necessary in a 

 mine in order to supply the miners 

 with fresh air, to remove the foul 

 air produced by respiration, by the 

 combustion of lamps or candles, 

 and by the gases evolved from 

 explosives ; far more important is 

 the removal of large volumes of gas 

 given off from the deposit itself, or 

 from the adjoining strata. In col- 

 lieries fire-damp is evolved in con- 

 siderable volume, and in certain 

 collieries, as well as in certain metal 

 mines, large volumes of carbonic 

 acid gas are sometimes given off. 

 Ventilation is usually produced by 

 means of a suction fan, modern 

 practice favouring relatively small 

 fans running at high velocity. 

 In extensive coal mines modern 

 practice uses the system known as 

 splitting the air current, each 

 separate district being ventilated 

 independently of the others by a 

 special stream of air split off from 

 the main current, and diverted int( 

 the district in question. 



The subject of explosions in 

 coal mines deserves mention. Such 

 explosions are due to two causes, 

 either to the ignition of a mixture 

 of tiro-damp and air, which forms 

 an explosive mixture that can be 

 fired by a flame or a spark, or to a 

 cloud of finely divided coal dust 

 suspended in air, which also forms 

 an explosive mixture, though lees 

 easily ignited .than the gaseous 

 mixture above referred to. It is 



B437 



generally admitted that, provided 

 the proper precautions are observed, 

 a gas explosion should be practic- 

 ally an impossibility. The problem 

 of dust explosions cannot be con- 

 sidered quite so completely solved 

 as that of gas explosions. It is, 

 however, becoming generally ad- 

 mitted that if coal dust is mixed 

 with 50 p.c. of incombustible dust 

 of a suitable degree of fineness, the 

 mixture is thus rendered incapable 

 of explosion, and modern legisla- 

 tion has adopted this method. 



It is only in very rare instances 

 that a mineral, as it comes from 

 the mine, is directly marketable as 

 such, and it usually requires more 

 or less preparation for the market. 

 All methods of such preparation 

 are generally included under the 

 term of " dressing." 



The amount of dressing required 

 varies within very wide limits ; at 

 the one end of the scale we have 

 those minerals that really require 

 no dressing at all, as when iron ore 

 is loaded direct into railway trucks 

 by means of a steam shovel ; at the 

 other end of the scale there are 

 such extremely complex mineral 

 substances as, say, tin ore, which 

 may consist of vein -stuff containing 

 quartz, felspar, and other non- 

 metallic minerals associated with 

 small quantities of iron pyrites, 

 arsenical pyrites, wolfram, and tin 

 stone, where only the last named, 

 or possibly the last two or three, 

 have any real economic value, and 

 their proportion may not exceed 

 1 p.c. of the total mass treated; 

 such an ore has to undergo a very 

 complex series of operations, includ- 

 ing crushing, washing, calcining, 

 re-washing, magnetic separation. 



The most modern method of 

 separation is that depending upon 

 differences in the surface tensions 

 of minerals brought in contact with 

 an air-water interface. This differ- 

 ence in surface attraction has been 

 made the basis of a number of 

 processes for separating minerals 

 by flotation ; the origin of these 

 processes may be sought in the 

 discovery by C. V. Potter, in 

 1901, that it was possible to float 

 up the zinc blende from finely 

 crushed Broken Hill ores in New 

 South Wales. Since then the method 

 has been extensively developed, 

 and in 1920 no less than 70,000,000 

 tons of mineral were treated by it ; 

 without such a process it would be 

 impossible to treat to advantage 

 a number of low-grade deposits 

 of copper ore which are being so 

 extensively worked in the United 

 States, and which are producing 

 quite a considerable proportion of 

 tne world's supply of copper. The 

 process ia also applicable to the 

 treatment of coal. 



MINISTER 



Bibliography. Elements of Mining 

 and Qimrrvnii.', ('. Le Neve Foster, 

 L'nd f,|. r . v S If. COT. 1910; Ore 

 and stone Mining, C. Le Neve 

 Foster. 7th ed. rev. 8. H. Cox, 1910 ; 

 Practical Coal Mining, <J. L. Ki-rr, 

 nth ed. 1914; Mining and Mm- 

 Ventilation, J. J. Walsh. 1917; 

 Modern Practice in Mining, R. A. 8. 

 Redmayne, 2nd ed. 1920; The Mm 

 ing Industry, Annual, New York ; 

 Transactions of the Institute of 

 Mining and Metallurgy, London, and 

 the Institute of Mining Engineers, 

 Newcastle-on-Tyne. 



Mining and Metallurgy, IN- 

 STITUTION OF. British institution, 

 founded 1892, and incorporated 

 by royal charter in 1915. It devotes 

 attention to both the practical 

 side of mining and to research 

 work. At the monthly meetings 

 from Oct. to May technical papers 

 are read, and afterwards published 

 in Transactions. The institution 

 also issues to members a monthly 

 bulletin. Its offices are at 1, 

 Finsbury Circus, London, B.C. 



Minion. In printing, a type one 

 size larger than nonpareil and one 

 size smaller than brevier. Also 

 known as 7 -point, it runs to about 

 10 lines to an inch in depth. In 

 French it is called mignonne ; in 

 Italian, mignone ; in Spanish, 

 minona ; in German and Dutch, 

 colonel. The type called emerald 

 in Britain, and in size between 

 nonpareil and minion, is known in 

 the U.S.A., as minionette. 



Minister. Latin word meaning 

 originally a servant. It is now used 

 chiefly in two senses : (1) Members 

 of the government are called min- 

 isters and collectively the ministry, 

 because they are in theory the 

 king's servants. The head of the 

 government is the prime, or first, 

 minister, and in the 20th century 

 Great Britain adopted the custom, 

 in existence in France, Canada, 

 Australia, and other countries, of 

 making the word the official title of 

 the heads of certain departments, 

 e.g. the minister of health. A min- 

 ister without portfolio was the 

 designation of a member of the 

 Government who had no depart- 

 mental duties, among such being 

 G. N. Barnes and Dr. C. Addison. 

 Such were appointed to assist the 

 prime minister during the Great 

 War, and afterwards, but in 1921, 

 owing to a widespread protest, such 

 appointments were dropped. It ia 

 also used for those who are sent to 

 represent their country in foreign 

 capitals, e.g. the British minister at 

 Athens. (2) Men ordained for ser- 

 vice in the churches of the various 

 Nonconformist bodies are known 

 usually as ministers, or ministers of 

 religion. The Church of England 

 uses the form clergyman. See 

 Clergy ; Prime Minister. 



