Mine

(min.) [Fr.; L. mina.] A cavity under ground, formed for the purpose of obtaining minerals, and often very deep and extensive. The descent into it is by a pit, called ash aft, and the excavations which follow the minerals sought are called the workings. The art of mining includes the scientific knowledge requisite for opening and working mines, as well as preparing ores for use. The latter consists, in the first place, in breaking in pieces the larger ma es, and then freeing them, by means of water, from the earth which adheres to them; in the separation of the coarser substances from the finer, by means of a sieve that moves up and down in water; in the breaking of the ore in stamping-mills, and in the separation of the finely interspersed metal from the stone or earth with which it is surrounded, . It also includes the final purification of the ore, by means of acids, by amalgamation, by fusion, & c. (Mil.) A subterranean pa age under a wall or fortification, for the purpose of blowing it up. The gunpowder in the M. is ignited by means of a pipe or hose, made of coarse cloth, called a sauci on, extending from the chamber to the entrance of the gallery; to the end of it is fixed a match, that the miner who lights it may have time to retire before the fire reaches the chamber, or place where the powder is lodged. But galvanism affords a safe and certain means of exploding M. at any moment, however distant they may be. The conducting wire from a galvanic battery is made to pa through the powder, within which is a portion of wire so thin as to become red-hot, or even to ignite when the electric current is transmitted through it. This explodes the M.- The M. of a fortre are called counter mines, the gallery of which runs under the covered way along the [s. 603]