demand has relegated it to a comparatively minor place.

Of miniature collections one of the very finest is that of J. P. Morgan (Metropolitan Museum of Art, New York). Excellent collections are in the possession of the king of England, the queen of Holland and also at the Louvre, Amsterdam, Berlin, Petrograd, Vienna, Florence, Stockholm and Helsingfors. Private collections of fine quality belong to notable families in England.

Bibliography. Ferrand, Traité de peinture en email et en miniature' (Paris 1732); Mayol, Introduction à la miniature) (Paris 1771); 'Ecole de miniature' (Leipzig 1776); Propert, J. L., History of Miniature Art (London 1887); Bradley, J. W., 'Dictionary of Miniaturists, Calligraphers and Copyists, From the Establishment of Christianity to the 18th Century) (London 1887-89); Williamson, 'Portrait Miniatures from the Time of Holbein 1531, to that of William Ross, 1860) (London 1897); Wharton, A. H., Heirlooms in Miniatures (Philadelphia 1898); Foster, J. J., 'Miniature Painters, British and Foreign, and 'British Miniature Painters and Their Works' (New York 1903); Leichsing, 'Die Sildnis Muniaturmalerei in Osterreich) (Vienna 1905); Heath, D., 'Miniatures) (London 1908); Faust, C., 'Les Miniatures de l'Empire et de la Restauration (Paris 1913). Consult also the catalogues of the various collections.

MINIÉ, mec-nee-ay,

Claude Etienne, French soldier and inventor: b. Paris, 1814; d. 1879. He enlisted in the army as a private when very young and left as a colonel in 1858. He devoted himself to the perfecting of fire-arms and in 1849 invented the Minié rifle and bullet. In 1858 the Khedive of Egypt appointed him director of a small arms factory and musketry school in Cairo.

MINIMITES (Fratres minimi, "least brethren"), a Catholic religious order founded by Saint Francis of Paula (1416-1507). Having become a Franciscan monk Saint Francis went into retreat near Paula, where he was joined by devout companions and, their number increasing, a community life was begun in 1454, when a large monastery and church were built. The rule of life was of extraordinary severity. To express the character of extreme poverty and humility Saint Francis eventually obtained from the Holy See permission to call his order, Minims, "the least of all religious bodies." In 1474 Sixtus IV confirmed the order which_was first known by the title Hermits of Saint Francis. Alexander VI changed it to Minims. Their first definite rule was drawn up by Saint Francis in 1493. It was so austere that all animal products, including butter, cheese, milk and eggs were forbidden, as well as meat. At one time the order numbered 450 monasteries and convents, but to-day only a few remain in Italy. Saint Francis also founded an order for nuns, which never had more than 14 convents, and a third order for persons living in the world. Louis XI summoned Saint Francis to France; and in Paris the order was known as "Bons Hommes," from the fact that it succeeded an older monastery of that name in Vincennes. In Spain the order was called Fathers of Victory, because the recovery of Malaga from the Moors was attributed to their

MINIMUM WAGE, the lowest reward that legislature considers just payment to laborers for their regular work. It is a wage, not only commensurate with the bare cost of living, but, so far as reasonably possible, to supply to every worker the means of procuring health, comfort and happiness in the broadest sense of those words. The minimum is difficult to determine because the cost of food, housing, fuel and clothing differs in different countries and States. Investigations of the conditions of living have to be taken into consideration before the sum can be determined. The minimum wage movement may be defined as a concerted effort on the part of social reformers and workers to wrest from capitalists a fair sum for the workers employed by them. The statutory minimum wage movement is a modern idea. It first appeared in Belgium in 1887 in the form of a minimum wage statute for laborers employed in public work. The first legislative minimum wage applying to private employment was adopted in Victoria, Australia, in 1896, and was soon followed by similar statutes in other Australian provinces and in New Zealand. It has also been in force in England since January 1910. These acts were applied to both male and female laborers. The adoption of a minimum wage in this country, beginning with the Massachusetts act of 1912, was borrowed, as was other labor legislation, from England. See LABOR; Wages.

MINING. Mining is a basic industry, the magnitude of which is indicated by the 6,000,000 men employed in the various mines in the world. Of this number about 3,800,000 men are engaged in coal mining and 2,200,000 in other mining. In addition millions are employed in the allied industries, such as the manufacture of iron and steel, copper wares, coke and chemicals, all of which are directly based upon the mining industry. The mines and quarries of the United States in 1917 employed over 1,127,000 men segregated as follows: Coal mines, 757,000; metal mines and metallurgical works, 280,000; quarries, 90,000.

Geographic Distribution. The mining industry of the United States is roughly geographically distributed as follows: The anthracite coal mines are in northeastern Pennsylvania the bituminous coal mines occupy the western slope of the Appalachian Mountain system from northern Pennsylvania to northern Tennessee, with a large coal field in the vicinity of Birmingham, Ala. The central coal field occupies central and southern Illinois, southwestern Indiana and western Kentucky. The coal fields west of the Mississippi River include southern Iowa, northern and western Missouri, southeastern Kansas and northeastern Oklahoma, with large bituminous and lignite fields in Texas. The coal fields of the Rocky Mountain States are scattered with the principal fields in southern Wyoming, northern Wyoming, western Montana and northeastern

New Mexico and southeastern Colorado. The Pacific Coast States coal fields occupy the northwestern part of Washington with a small area in western Oregon and a small field in California. Alaska has coal fields in the southern portion which are of considerable importance, although not well developed. The United States is the greatest producer of coal, and in normal times the yield is 38 per cent, Great Britain 22 per cent and Germany 20 per cent of the world's output of coal. The metal-mining industry of the United States is distributed approximately as follows: The principal iron mines are in Minnesota, Michigan, northern Wisconsin, northeastern New York and central Alabama. The principal copper mines occur in northern Michigan, western Montana, Utah, Nevada, Arizona and southern Alaska. The lead mines are in southeastern Missouri, the Coeur d'Alene district, Idaho, and in Colorado. The principal zinc mines occur in southwestern Missouri and eastern Oklahoma; Leadville, Colo., and Butte, Mont., are becoming large producers. The gold and silver mines occur in Alaska, California, Colorado and Nevada, while every Rocky Mountain and Coast Range State produces more or less of the precious metals. Phosphate rock occurs in large quantities in Tennessee, Florida and South Carolina; bauxite in Arkansas and Georgia; salt in New York, Michigan and Kansas; petroleum and natural gas in Oklahoma, Texas, California, Pennsylvania, Ohio, West Virginia and Indiana.

The United States is the world's largest producer of copper, iron, lead, zinc and petroleum. About 20 per cent of the world's gold supply comes from the United States; 40 per cent from South Africa and 15 per cent from Australasia. (See article on GOLD MINING). The Central Powers of Europe produce only 0.6 per cent, while the United States and her allies produce 91.3 per cent, and neutrals (1918) produce 8.1 per cent.

Prospecting. Preliminary work in mining operations is known as prospecting, and is often conducted by individuals who work on their own account, spending weeks or months in outlying districts in search of mineral outcrops or rock indicating that valuable minerals may be present. The prospector of the early days is fast disappearing and prospecting is now carried on in a scientific way by large development or exploration companies, whereby a promising mineral field is thoroughly tested by churn drills or core drills as economy may suggest. The core or diamond drill is most important in this particular work in that it obtains a core so that it is possible to know accurately the formation through which the drill has passed together with its thickness, depth and mineral content. The ground is marked out in squares of 100 to 500 feet on a side and at the corners or in the centre of each square a drill hole is sunk, and the core or cutting thoroughly tested. This work is carried on in conjunction with geological studies, in which the character of the various country rock is studied, as, for example, its position and composition, lithological character and other data which may be of interest to the prospector and geologist, and help to point out the places where ore deposits are most likely to occur. Trenches are often cut across mineral zones, and small

shafts sunk to test the character and quality of the mineral.

Development.-After a property has been prospected and it is definitely known that it contains mineral deposits of economic importance the development proper begins by the construction of shafts, entries or slopes, and the blocking out of the ore or coal which is to be taken out at a later date. This work is usually done preliminary to the building of a mill or other reduction works.

Drainage. In the development of mines. one of the important factors to be taken into consideration is the matter of drainage and ventilation. Of course drill holes and preliminary shafts indicate to a certain extent the amount of water that will be encountered, but as the mine workings are extended larger areas are opened for the entrance of ground waters, thus increasing the amount of water which in the small mines would be considered negligible. When a mine is opened on a hillside, the drainage is usually taken care of by an adit and all of the mine workings drained from the lowest level, the upper workings in this case being absolutely without water. Where a mine cannot be thus drained, it is necessary to install large and expensive pumping plants, as frequently the amount of water handled is far in excess of the coal or ore produced.

Ventilation.-The ventilation of mines is also an important item to be considered, especially when mines are opened to a considerable depth. The ventilation of coal mines has been well worked out in the anthracite and bituminous fields by reason of the fact that many of the mines generate noxious or poisonous gases, making it impossible to work without adequate ventilation. The metal mines as a rule do not generate gas, therefore their ventilation has not, in many cases, received proper attention. Natural ventilation in metal mines is usually provided for by surface openings at different elevations which, in most cases, give a very satisfactory distribution of fresh air. Where there is but slight difference in elevation of two or more openings it is necessary to install mechanical ventilation whereby fresh air is supplied by fans. Coal mines, and frequently metal mines, are often opened by a drift-slope tunnel or adit with no outlet at the inner end, so that it is necessary to use a force fan to send in new air to the working face. The fresh air then circulates through the places in the mines where the men are at work; the air thus circulated becomes more or less vitiated as to its oxygen content, and is also burdened with gas and dust, before escaping from the mine. Its escape is often assisted by a suction fan. The circulation of large volumes of air is necessary to make working conditions tolerable in gaseous mines.

SYSTEMS OF MINING.

There are two classes of mines, namely: (a) Open-pit mines, which are operated with or without steam shovels, and (b) underground mines, which are entered by a shaft, drift, entry or slope, and in which the mining is done under cover of rock.

Open-pit Mines.- This class of mines is becoming more and more important since the development of the steam shovel. In the iron mining districts of Minnesota, it is not un

common for mines to be operated where an overburden of 100 or 150 feet is stripped and carried a distance of three or four miles in order that large ore bodies may be exposed. After the overburden has been removed the operation of the steam shovel is continued and the iron ore loaded into railway cars which are provided for it in the bottom of the pit which in many cases is 80 acres, or more, in area. Steam-shovel mining is the principal method of mining ore in Minnesota, and is rapidly coming into favor for mining copper ores in Arizona, Utah and Nevada. The steam shovel is becoming an important factor in coal mining where an overburden of 15 to 50 feet may be removed from a four- or five-foot coal bed, and the coal loaded by steam shovel into railroad cars. The open-pit mines operating without steam shovel are usually small and in this connection the overburden is removed by drag line scrapers, wheel scrapers, as in the case of railway excavations, or by the use of wheel-barrows and hand labor. This work is confined largely to the less important minerals, as barite, small iron-ore deposits, phosphate deposits and to shallow coal beds.

of workings, called stopes, one immediately over the other or vice-versa. (See Fig. 1). A stope is an excavation from which the ore has been extracted, either above or below a level, in a series of steps and is usually applied to highly-inclined or vertical veins, or an open place in a thick ore body. The term is frequently used incorrectly as a synonym of room, which is a wide working-place in a flat mine.

a

WINZE

UNDERHAND STOPE

SHAFT

LEVEL

Placer Mining. Another class of open-pit mines is known as placers or placer mines, where goldbearing sands and gravels are mined for the gold which they contain. In the earliest stages of placer mining the gravel was washed in pans, the gold collecting at the bottom, and saved as metallic gold. This was followed by mechanical devices such as the rocker, long tom and sluice. The sluice consists of a long wooden trough or box, or channels cut in the bed rock, provided with riffles in which the gold collects as the gold-bearing sands are washed through the sluices. Mercury is spread in the bottom of the sluice so as to catch the fine particles of gold, forming a goldmercury-amalgam. The clean-up" takes place at stated intervals when the amalgam is collected and the mercury is driven off by heat and the gold collected. The large placer operations are known as hydraulicing and dredging. Mining by hydraulic methods consists in using water under various pressures from 250 to 400 pounds per square inch, which escapes through a nozzle and is directed at the goldbearing gravel banks; as the water carries the finer gravels and sands to the sluices the gold is collected in the manner described above under sluicing. The latest commercial development in placer mining is dredging, whereby it is possible to recover sands and gravels containing as low as five or six cents in gold per cubic yard. The powerful dredges scoop up the sand and pass it through screens, the finer material being washed through sluice boxes provided with riffles and mercury traps and the gold is recovered by cleaning out the sluice and retorting the amalgam.

Underground Mining.-Stoping.-A method of mining in which the ore is excavated from a vein by driving horizontally upon it a series

Each horizontal working or stope (probably a corruption of step), when a number of them are in progress, assumes the shape of a flight of stairs. When the first stope is begun at a lower corner of the body of ore to be removed, and, after it has advanced a convenient distance, the next is commenced above it, and so on the process is called overhead stoping. When the first stope begins at an upper corner and the succeeding ones are below it, it is underhand stoping. The term stoping is loosely applied to any subterranean extraction of ore except that which is incidentally performed in sinking shafts, driving levels, etc., for the purpose of opening the mine. This method probably originated in the Cornish tin mines and is applicable to vertical or highlyinclined ore bodies; also to massive deposits which may have great thickness.

Room-and-Pillar.-A system of mining in which the distinguishing feature is the winning of 50 per cent or more of the coal in the first working. The coal is mined in rooms separated by narrow ribs or pillars. The coal in the pillars is won by subsequent working which may be likened to top slicing in which the roof is caved in successive blocks. The first working in rooms is an advancing and the winning of the pillar coal a retreating method. Fig. 2). The rooms are driven parallel with one another, and the room faces may be extended parallel with, at right angles, or at an acute angle to the dip. When applied to metal mines, with a good cover, as much as 75 to 85 per cent of the ore is removed, leaving pillars 10 to 20 feet in diameter; wherever possible, pillars

(See

are left in the poorest ore, hence their position is more or less irregular as compared with the pillars left in coal mining. This method is applicable to flat deposits, such as coal, iron ore, lead and zinc, etc., which occur in bedded deposits. Modifications of this method are County of Durham system; Double-entry roomand pillar mining; Double-room system; Double-stall working; Heading and stall; Pillar and stall; Post and stall; Room and stoop; Single-entry room-and-pillar mining; Single

stall working; Square work (South Staffordshire thick seam method); Stall and breasts; and Triple-entry room-and-pillar mining.

Longwall Method.-A system of working a seam of coal or ore in which the whole bed or seam is taken out and no pillars left, excepting the shaft pillars, and sometimes the main-road pillars. Longwall advancing consists in mining the coal outward from the shaft pillar and maintaining roadways through the worked-out portion of the mine. (See Fig. 3, in which the arrows indicate the direction of advance and points to the working face). Longwell retreating, first driving haulage roads and airways to the boundary of a tract of coal and then mining it in a single face without pillars toward the shaft. The longwall method is usually applied to coal mining and occasionally to flat ore deposits, as iron, etc. This system of mining is also known as Longwork, Shropshire method, Combination longwall and Nottingham or Barry system.

Milling-A system of mining originating in the combination of open cut and underground mining, where the ore is mined in open cut (surface workings) and handled underground. It is underhand stoping applied to large deposits, wherein the ore is mined near the mouth of winzes or raises and dropped by gravity to working levels below for transportation to the

surface. Sometimes called "glory-hole” method. (See Fig. 4).

Caving System.-A method of mining in which the support of a great block of ore being removed, it is allowed to cave or fall, and in falling is broken sufficiently to be handled; the overlying strata subsides as the ore is withdrawn. Two important_variations are Top slicing and cover caving; Top slicing combined with ore caving.

Top Slicing and Cover Caving. The important feature in this method is the working of the ore body from the top down in successive horizontal slices that may follow one another sequentially or simultaneously. The whole thickness of the slice is worked and the ore broken by overhead or under hand stoping in each unit. It is a retreating method, as the overburden or cover is caved after mining a unit. The longwall, the pillar robbing in both room-andpillar and bord-and-pillar methods of mining coal are essentially the same in principle as top slicing. The principal difference is that a single slice only is worked in these methods when applied to coal mining. There are two modifications: top slicing by drifts and top slicing by rooms. A timber mat is used as a cover in almost all cases. The method is applicable to thick or massive ore deposits. Other terms used for this system are Caving system; Crosscut method (combined with removal of pillars); Horizontal slicing descending; Mining ore from top_down; Panel slicing; Prop slicing; Removing pillars and allowing roof to cave; Slicing under mats of timber in panels; Square-set slicing; Top slicing and caving; Transverse slicing with caving. Top Slicing Combined with Ore Caving.In this method the ore body is worked from the top down in successive slices. Instead of taking the full height of the slice, only the lower part is taken and the upper part is caved. After removing this portion of the ore, the cover is caved. A timber mat is used in most cases to separate the broken cover from the ore to give safety. Also known as Caving system, Sub-drifting and caving, Sub-slicing, Slicing under ore with back caving in rooms, Sub-level caving and Sub-level slicing.

Explosives. In all methods of mining, explosives are essential. The maximum amount of explosives is used in stoping and room-andpillar methods, while a minimum amount is used in the caving system and its various modifications, due to the fact that much of the ore is loosened by caving of the overburden. The importance of the mining industry is further shown by the fact that 75 per cent of all explosives used in the United States are used in the mining industry (not including quarries). The enormous production from the mines in the United States would not be possible without the use of large amounts of explosives. The total production of explosives in the United States in 1917 was as follows: Black powder, 277,118,525 pounds; dynamite and high explosives other than permissibles, 262,316,080; per

required to carry the above amount of ore would be 151,500 miles, or six times the circumference of the earth. The mine-haulage problem is usually separated into three divisions: (1) Underground haulage, that is, from the working face of the mine to the bottom of the shaft or to the surface in the event that the mine is opened by a tunnel or adit. (2) Hoisting, that is, handling the ore or coal from the mine through either vertical or inclined

missibles, 43,040,722. Of the black powder, 85 per cent was used in coal mining; of high explosives, 10.8 per cent; and of permissibles, 76.5 per cent. Other mining consumed 3.4 per cent of the black powder, 50.4 per cent of high explosives and 14.2 per cent of permissibles. In the production of coal an explosive is required which will not shatter the coal and at the same time not produce too long a flame nor too much heat and thus ignite gas and dust with which it might come in contact. This led to the introduction of so-called safety or shortflame explosives in the coal mines of Pennsylvania at Johnstown in 1902, and since that date their use has increased rapidly. The term "permissible explosives" was coined by Dr. J. A. Holmes in 1908, and in 1909 the Federal Bureau of Mines established a testing station at Pittsburgh to determine the permissibility of explosives that are to be used in coal mines. This work is still being carried on in connection with the investigation of mine explosions to determine the nature and character of an explosive that will meet the needs of the various branches of mining, and especially to increase safety in coal mines. Both the improper use of explosives and the use of improper explosives have resulted in coal-mine disasters. The Federal Bureau of Mines has brought about what is little short of a revolution through the introduction of new types of low-temperature, quick-flame powders, designated as "permissible explosives," for use in the more dangerous coal mines of the country. the bituminous coal mines of the United States the fatality rate per 10,000 men employed has been reduced from 3.39 in 1903 to 0.80 in 1917, largely as a result of the use of permissible explosives. In metal mining a different type of explosive is needed, namely, one which will shatter the hard mineral formation, and for this purpose dynamite of different grades is employed. Black powder, by reason of its slow heaving action, is used to a certain extent in the iron mining districts, where steam-shovel work is carried on, and where it is necessary to loosen large masses of soft or friable ore.

In

Mine Haulage. The transportation problem is one of the most important features in the development of the mining industry with which the mining engineer and mine manager have to deal. (It is seldom given a passing thought by the layman). The quantity of merchantable material handled by the various mines and quarries in the United States during a single year is in excess of 1,000,000,000 tons. The work of the Panama Canal is cited as perhaps the greatest engineering feat in modern times, yet the amount of material handled at the canal each year was but slightly in excess of the amount of iron ore and overburden removed annually in two States, namely, Michigan and Minnesota. The task of moving 1,000,000,000 tons of ore, coal and rock would require 20,000,000 50-ton cars. Reducing this to trains of 40 cars, each would represent 500,000 trains. Assuming the average length of a 50-ton car as 40 feet, the length of train

LONGWALL RETREATING
MAY BE SINGLE OR DOUBLE ENTRY)

FIG. 3.-Long Wall Method of Mining.

shafts to the surface. (3) Surface haulage, which delivers the ore or coal from the mouth of the shaft to ore bins at smelters or coal tipples at railway yards.

Evolution of Mine Haulage.- In the early years of the mining industry the transportation of ore or coal was crude, and even to-day primitive methods prevail in the more remote districts. In China the ore is transported by coolies, and in some of the mining regions of Mexico Indians carry the ore on their backs for perhaps a number of miles. This class of transportation will apply both to surface and underground workings. In Central America Indians carry ore in a box mounted on two small poles, similar to a hospital stretcher, two men working together. In Peru and Bolivia the llama is the beast of burden and occupies the same position as the burro in Mexico. In early years a large percentage of the coal transportation underground in Great Britain was handled by women and children. The coal was loaded into buckets which were mounted on sleds and when these were used in thin coal beds it was necessary for the women or children to creep along the floor on their hands and knees and draw the sled behind them. A laborious task indeed. The next step in underground transportation was the introduction of two-wheel carts and wheelbarrows, followed by small wooden cars operated on wooden tracks. In 1803 the wooden tracks were first covered with strap iron. The motive power in these cases was largely women and children, and this condition existed in Great Britain until prevented by law in 1842. In 1846 ponies were first used in the English mines. The next improvement was the introduction of iron tracks followed by the use of substantial wooden cars and sheet-iron cars with a capacity of about one ton. The cars were enlarged and horses