In the presence of an enemy increase above charges 50% to allow for contingencies. =House with Moderately Thick Walls.=--Attack portions of walls between the windows, the charges being tamped, and inside the house if possible. Otherwise place outside, or one or two large charges inside untamped. To demolish a building, a sufficient height of wall must be brought down to insure the arches over the doors and windows falling. The length of breach must be equal to this height. With very thick walls cut grooves. =To Cut Down Trees.=--Place charge in an auger-hole bored horizontally into the tree at desired height. If tree be 1½ to 2 feet in diameter, use two holes. With a little care they can be bored so as to meet in the centre, in which case one detonator will suffice to fire the charge; with plenty of detonators it may be better to fire one hole first and then a second hole in the uninjured part of the tree, and so on. The tree may be made to fall in any required direction by attaching a rope to the upper branches, and taking the strain on it before firing. The guncotton may be hung around the tree, but this often fails with trees over 12 inches in diameter. A hole may be dug under the roots. Dig down by the side of the tree and then horizontally under the bottom close to the wood, the hole being just large enough for the cartridge. The rules for felling trees apply to timbers of wooden bridges, the uprights of the piers being the best point to attack. =To Blow Down a Stockade 12″ × 12″.=--Use 3 lbs. of guncotton per running foot. The slabs should be threaded together, so as to be in contact, and hung or laid against the timbers at the required level. If gunpowder be used, a charge of 80 lbs. should be allowed for the same stockade when the charge is not tamped; when tamped by having a few sand-bags piled on top, the charge may be reduced to 60 lbs. This would probably make a breach about 6 feet wide. =To Demolish a Gate.=--Fifty pounds of guncotton hung against the gate by a nail or pickaxe or laid on the ground will suffice. The charge of gunpowder should be 200 lbs., covered with sand-bags if possible. =Destruction of Iron Bridges.=--Place charge on lower girders near an abutment, and at a point where the thickness of the plates is least. If sections are uniform throughout the length of the bridge, place charge at centre of a span between two piers. When the bridge plate is entirely of iron, place charge on top of beams. =Destruction of Railroad Tracks.=--To destroy heavy iron rails, a charge of six 2-ounce disks (including primer) should be used. =To Destroy a Tunnel.=--The crown of the arch or the side-walls should be attacked. The points selected should be some distance inside the tunnel. =To Destroy Field-and Siege-guns.=--Detonate 1½ lbs. of guncotton on the outside near the muzzle. In heavier wrought-iron guns detonate 4 lbs. in the bottom of the bore, tamping with sand.