MINING. The use of the metals, and con sequently some process for the extraction and separation of them, may be traced to the most remote antiquity. In respect to our own country, mines were worked in Britain by the Romans ; but during the Saxon period they were much neglected; and subsequently to this period they were chiefly worked by Jews. In the reign of Elizabeth the art of mining had fallen into so much decay that an impor tation of foreign skill was found necessary to revive them ; and the Germans, long and justly celebrated as skilful miners, received every encouragement to settle in this country and turn their attention to them. In the 17th century the use of gunpowder in mines was introduced ; and early in the next century the rich copper mines of Cornwall were first worked. The invention of the steam-engine was early rendered applicable to mining in this country, and contributed to the present perfect state of the art. After the invention by Savery and Newcomen, the steam engine became a most useful auxiliary in the hands of the miner ; and the improvements of Watt were still more beneficial. The Cornish steam engines are now among the most powerful in the world. The use of iron pumps instead of wooden in the shafts, and the laying down of tramroads in the galleries of a mine, were two other great improvements. Great improve ments, too, have been made in the mechanical treatment of the ores after they have been extracted.
There are four principal classes into which mineral deposits may be divided ; veins, beds, masses, and fragmentary deposits. Veins- are generally long, narrow, and irregular fissures, traversing the rocky crust of the globe, which they penetrate to an unknown depth, and at a high angle of inclination. They are for the most part filled with sparry and stony sub stances called the veinstone,' or the ' gangue,' of the vein, but contain here and there irregular masses or ' bunches' of the metallic ores, often of immense size and value, and which it is the principal business of the miner to discover and extract. Most of the metals are of common occurrence in veins. Beds are layers of mineral substances interposed between the strata of solid rock, which, except in their containing valuable matter, they very much resemble. Several of the metals, especially lead, are occasionally found in beds ; coal, clay-ironstone, and rock-salt, exclusively so.
Masses or Pipe-Veins, are irregular branching cavities descending either vertically or obliquely into the rock, and filled up with metalliferous matter. They usually contain copper, lead, or oxides of iron. Fragmentary Deposits occur associated with many of the loose superficial beds of sand and gravel which occur in the valleys of mineral districts, con sisting of the detritus of the neighbouring mountains, which has been washed down from thence at remote geological epochs. Tin and gold are the chief metals found in this form. Each kind of metallic ore is found to prevail in some one geological formation rather than others.
Most metals are found in the state of Ores, that is, chemically combined with certain mineralizing substances. The most important of these mineralizing bodies are oxygen and sulphur; the next in rank are chlorine, and the sulphuric, carbonic, and phosphoric acids. These elements require to he separated by the processes of metallurgy ; but there are also other mechanical impurities scarcely less im portant, which require to be partially separated in the mine, and which therefore fall entirely within the province of the miner. It frequently happens too that ores of a worthless character are mixed up with the more valuable ones ; .hus copper and lead are very generally accom panied by iron pyrites and blende, both of vhich must be regarded as impurities, and lterefore separated as far as possible previous 0 any process in the furnace.
Veins or beds are seldom visible at the surface of the ground, being generally con cealed by the soil. As the deposits usually present no trace of their existence at the surface, certain general indications must be had recourse to for their discovery ; the number of indications which guide the miner is con siderable, and increases as science and experience advances. When a new vein or mineral deposit has been by any process dis covered, the most usual step, after obtaining the consent of the proprietor, is the formation of a company ; for companies are generally found to work mines better than individuals. The company agree with the proprietor as to the extent of ground within which operations may be carried on, the proportion of the gross mineral produce or its equivalent in money which the owner is to receive free of all expense in raising and making it marketable, and other matters.