MINES AND MINING. 546 is dosiioiis (if clVcctinj; his ixplosions without breaking the surface of the ground. The ex]ph)sive used, in all soils, so far as known, has been ginipowder. Experiments have been conducted with guncotton and other high explo- MINE WORKERS OF AMERICA. 1854 and ISJj, where the Itussinns. under the lead of the aocomplislied engineer. General Todle- ben, were able to withstand the Allies a period of 349 days. ]Iining was carried on in the siegea of Vicksburg and I'etersburg in the Civil War, BESIEGERS GALLERIES j^j^^jj^^j^^ MINES I.ILm.IV.V_ COUNTERMINE GALLERIES " PERMANENT GALLERIES IN OUTLINE PARTS DESTROYED SHADED. UUflNO 0PERATI0S3 AT ORAUDENZ, 1862. MINES ITOH. sives, but they have not yet been used in mining operations in ac- tual warfare. The <|iiantityof powder to be used depends upon the result de- sired. A common mine is one in which the crater formed has a di- ameter at the sur- face approximately twi<'e the depth. Mines with larger charges of powder than will produce this result are known as orcT- r h (I (■ (/ '" (/ mines; with less, as under- (■ h (I r II r <l mines. W hen given a charge so small that no crater is produced on the surface, they are called rtimouflcts. To produce a connnon mine the charge varies eonsiih'rably with the nature of the soil. The general rule f(jr them in ordinary earth is that the charge nuist be equal in pounds to one-tenth the cube of its distance in feet below the sur- face. The last instance of mining operntions upon a large scale was at the siege of Sebastopol in HBAPT-LlillXO. but was not the predominant feature in either case. In view of the fact that in the i)ast mili- tary mining has jdaycd such an important part at critical times, the subject is studied by mili- tary engineers, and it is quite within the range of possibility that in a form adajited to mod- ern conditions it may at some time in the future serve to decide the fate of a war. The subject of siege works and military mining is treated in Mercur, Attack of Forti/u'd I'laces (New York, 1894), and in the Chatham Maniiali, especially part iv. (London, 188.S). For submarine mines and torpedo defenses, see ToRPF.no. MINETTE, min<"t' (Fr., diminutive of mine, mine, whence llhcnish C.er. M incite, iron ore). An igneous rock of granular or porphyrilic tex- ture, composed essentially of orthoclase feldspar and biotite. In contrast'with the granites, syen- ites, and dioritcs. to which it is related, it is rich in fcrro-magnesian minerals, and hence has a darker color. Minettes generally occur in dykes, and are (|uitc siisccptible to weathering agencies. MINE WORKERS OF AMERICA, The I'NiTEn. The largest American labor union, whose declared object is "to unite ninc employees that produce or handle coal or coke in or around the mines, and ameliorate their condition by means of conciliation, arbitration, or strikes." The officers consist of a president, vice-president, and secretary-treasurer, who, together with one delegate from each of the 2.") districts into which the jurisdiction of the United Mine Workers is dividid, constitute the National Executive Board, which has the power to levy assessments and to order general strikes by a two-thirds vote. The I
