founded an Order for women which never had more than fourteen convents and is now almost extinct, and a third Order (see Tertiary), for persons living in the world. Consult d'Attichy, Histoire générale de l'ordre sacré de Minimes (2 vols., Paris, 1824).
MINIMUM DEVIATION, Angle of. See Light.
MINING. The art of obtaining from the earth the metallic ores and other useful minerals in an economical and profitable manner. The earliest metals employed by man were those found in the native state. Gold is the most widely distributed of these, and has been mined and utilized from very remote times. Meteoric iron was also known and utilized by many ancient peoples, and the native copper of Lake Superior was extensively mined and utilized by the aborigines of America. As, however, the knowledge of metals increased and civilization advanced, the ores, or metals in combination, were recognized and utilized and mining proper began. Reference is made to mining in the Bible, and other ancient records prove that the Phœnicians navigated the seas as far as Cornwall, England, in order to obtain tin ores for the manufacture of bronze. The Romans had extensive mines for iron ore in the island of Elba that are still in operation. They also worked the great copper veins at the Rio Tinto, Spain, and the timbering left by them is still visible. The mines at Laurium, Greece, were famous in ancient times for their yield of silver. From the old mining districts of Cornwall and from the Erzgebirge (Ore Mountains) and the Harz Mountains in Germany miners have gone all over the world, and under their tuition the mining practice of to-day has grown up in all the newer districts.
Problems in mining to-day may be grouped into those relating to: (1) mining geology; (2) mining engineering; (3) mechanical engineering; and (4) metallurgy. The problems of each group overlap to some extent those of the other groups, but the division adopted serves for a general consideration of the subject of mining. In this article particular attention will be devoted to mining as involving the problems of mining engineering and mechanical engineering. These problems embrace the operations of discovering and locating mineral deposits, of opening the earth and excavating the ores, of transporting the ores to the surface, and of handling mechanically the ores during their metallurgical treatment. As, however, the handling of the ores preparatory to and during the processes involved in extracting the metals is of a different nature than mining proper and is frequently done at places far from the mines, these operations are considered in the article on Ore-Dressing and in the section devoted to Metallurgy in the articles on the various metals and the adjunct articles there mentioned.
Prospecting. The search for and location of deposits or veins of metal-bearing ores is called prospecting, and the men who perform this kind of work are called prospectors. The first procedure in prospecting a tract of land suspected to contain mineral wealth is thoroughly to traverse it and to note carefully the familiar indications of the presence of minerals. These indications are often numerous in kind for each mineral and they also vary for different minerals. Generally speaking, coal, gypsum, salt, and similar minerals occur in unaltered deposits, that is, in rocks which have not undergone metamorphism, while the metallic minerals are found in rocks that have undergone more or less metamorphism. These are among the broad indications of the presence or absence of certain minerals. The geological age of the rocks is in respect to certain minerals a pretty certain indication whether these minerals are likely to be found or not. For example, the bulk of the coal deposits of the world has been found in rocks of the Carboniferous age; they exist in rocks of subsequent ages, but almost never in rocks of preceding ages. Referring to specific indications, the prospector for coal will search for traces of smut or coal dust in the streams and water-worn banks, and for the presence of outcropping seams.
The presence of iron is indicated by mineral springs and rust-like stains of earth and rock. The presence or absence of vegetation may also indicate the existence of minerals; for example, a bed of phosphate rock is commonly indicated by a line of luxuriant vegetation and the outcrop of a mineral deposit by a lack of vegetation. Beds of magnetic iron are frequently located by their attraction for the magnetic needle. Placers are fragmental deposits from water in which the heavier minerals have been concentrated in certain portions, usually next the underlying or bed rock. When prospecting for placers the prospector examines the country for the presence of any existing or ancient watercourses in which deposits of placer material are likely to have been formed. Metallic gold and precious stones occur frequently in placers. In prospecting for petroleum, natural gas, and bitumen, the surface indications looked for are springs of petroleum oil and naphtha; porous rocks saturated with bitumen or cracks in slate and other rocks filled with the same material; springs, pools, or creeks showing bubbles of escaping gas or an iridescent coating of oil.
The presence of a mineral deposit having been established, the next procedure is to determine its extent and richness. The richness of the ore is determined by assaying average samples. (See Assaying.) To determine the thickness of the veins or beds and their lateral extent, borings are sunk at more or less close intervals and records taken of the continued presence of the ore vein and of its thickness. These coupled with a geological survey of the region give fairly reliable data as to the quantity of ore and its location with respect to the ground surface. Upon these data the miner estimates the value of the deposit and decides whether it will pay to work it or not.
If the deposit is located on Government land, a ‘claim’ of variable size, according to the laws of the country or district, is staked out, and when this is opened up sufficiently to have necessitated the expenditure of a certain specified sum of money, a permanent title can be obtained. In the Western States of the United States claims usually extend 1500 feet along the vein, and either 150 feet or 300 feet on each side of it. The owner can then follow the vein where it leads him between the vertical planes of his end lines. The outcrop is called the apex. As, however, veins are so irregular and obscure underground, great uncertainty may arise as to title, and expensive
