=16.= For use in overcharged mines designed to break in the enemy’s galleries, the high explosives, from the violent character of their explosion and from the phenomena exhibited in submarine mining, promise to give relatively greater radii of rupture than gunpowder; but sufficient data are not available to state this positively.[12] =17.= Beside the considerations above stated, which refer to the effects produced by the explosive when fired, there are others equally important relating to the safety and facility with which the explosive may be transported, handled, and placed in the mines. The latter will frequently have greater weight than the former in determining the explosive to be used in any particular case which may arise in the practical operations of mining. Of the latter considerations some of the most important in deciding whether to use gunpowder or high explosives are the following, viz.: Gunpowder is easily obtained, and most enlisted men are more or less familiar with its properties. It explodes when ignited by fire. It does not ordinarily explode when struck by a bullet. It is injured by moisture and destroyed by thorough wetting. It is not affected by ordinary changes of temperature. It requires thorough tamping to produce good effects. Many high explosives are not injured by moisture, and some are unaffected by total immersion in water. They generally burn without detonation if ignited by flame. Some of them do not explode when struck by a bullet. The more sensitive ones do. The properties of some of them are materially changed by freezing. On account of their greater strength, the same effects may be produced by smaller charges, requiring smaller chambers and cases. By reason of the violence of their action they produce good results even if imperfectly tamped. The last two considerations, together with the possibility of using them in wet places without protection against moisture, lessen greatly the time required to excavate, charge, and tamp a mine, and may frequently enable the one using them to anticipate an enemy using gunpowder and thus secure success, when the use of gunpowder would reverse the situation. In mining operations and in expert hands the high explosives, upon the whole, seem to cause fewer accidents than gunpowder. CHAPTER II. PRACTICAL OPERATIONS AND DETAILS. =18. Tools and Appliances.=--The different operations of mining are carried on by the use of picks, shovels, bars, saws, axes, hammers (large and small), chisels, wheel and hand barrows, windlasses, ropes, wooden or leather buckets, gauge-sticks, mason’s levels (Pl. XI, Fig. 4), plumb-lines, candles, closed lanterns, tin pipes, rubber and canvas hose, canvas, nails, etc., etc., of the kinds in common use; and the following special tools and appliances, viz.: The _Miner’s Pick_. Smaller and lighter than the common pick. Neither its head nor its handle exceeds 2 feet in length.