MINES AND MINING, MILITARY. The term military mining is used in two senses. The first refers to the broad subject of the placing and ex plosion of charges of explosive underground with a view to destroying men and material. This includes the ordinary use of mines as an obstacle to the approach of an attacking force. The other and more generally accepted use of the term is to denote one of the stages in a stub born siege. In the discussion of siege and siege works (q.v.) it is shown that when troops are no longer able to advance in the open, prog ress is made by approaches and parallels, in the hope that if the besieged is not first starved, the besieger May advance close enough under the pro tection of his own trenches for the delivery of an assault. occasionally the relative force and skill of the combatants are such that the besieged, by virtue of his heavier fire and skill in handling it, may be able to bring the approach of the besieger by trenches to a standstill. He may accomplish the same result by running under ground tunnels and placing countermines which so threaten an overland advance as to make it impracticable. When this happens, the usual method of advance is by military mining.
From the last advanced open position he has been able to construct, the besieger proceeds Un derground by a system of shafts and galleries. These vary in size. In general the start is made with large galleries gradually ramifying into smaller but more numerous galleries whose heads arc close together. The principal types are great galleries with a height of G feet and width of 7 feet, common galleries with the same height and half the width, half galleries with a height feet and width of 3 feet, and branches with a height of feet and width of feet. The accompanying cut indicates the methods in which these branches develop. The shafts and galleries usually are lined with board casings two to four inches thick, or with heavy frames placed at in tervals and holding in position thin sheeting. For the work of excavating, special tools are pro vided shorter than those used above ground. Pro vision must be made at frequent intervals for ventilating the tunnels sullieiently to permit the miners to work in them. Passage from one level to another is by shafts or by inclined slopes. Great care is taken in the preparation of a map, which is kept correcte41 to date. and shows the position of the various tunnels and branches, and their relations to each other, both in plan and in elevation. A similar system of tunnels is eon
strueted by the besieged. As the two systems approach near to each other, it becomes the •Th ject of each combatant to destroy the system of the other. In doing this the besieger is usually desirous of forming a crater reaehing to the ground above which lie can occupy with his troops, thus obtaining new points of vantage on the surface. For similar reasons the besieged is desirous of effecting his explosions without breaking the surface of the ground.
The explosive used, in all soil.. so far as known, has been gunpowder. Experiment,: have been conducted with g,uncotton and other high explo 1854 and 1855, where the Russians, under the lead of the accomplished engineer. General Todle hen, were aide to withstand the Allies a period of 349 days. :Mining was carried on in the sieges of Vicksburg and Petersburg in the Civil War, sires, but they have not vet been used in mining operations in actual warfare. The quantity of powder to be used depends upon the result de sired. A cOnt mon mine is one in which the erater formed has a di ameter at the sur face approximately twice t he depth. Alines with larger charge- of powder will produce this result are known as erec t. harye (I !nines; with Ili.ss.iis trnd r (-burg/ mines. \‘'heil given a charge so that no crater is produced on the surface, they are Iled Is.
To produce a e0111111011 mine the charge varies considerably with the nature of the soil. The general rule for them in ordinary earth is that the charge most be equal in pounds to onc•tenth the elilie of its distance in feet bellm%. the sur face.
'File last instance of mining operations upon a large sea I. was :I t tilt' siege of Sebastopol in hut was not the predominant feature in either case. In view of the fact that in the past mili tary mining has played 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 adapted to mod ern conditions it may at some time in the future serve to the fate of a war. The subject of siege works and military mining is treated in .1 t tuck of Port Places (New York, 1894). and in the Chatham Monnols, especially part iv. (London. 1883). For submarine mines and torpedo defenses, see TORPEDO.