Explosive, freezing of, 165 Explosive, noxious gases from, 133, 158 Explosive, relative strength of, 131, 179 Explosive, tamping of, 178-9 Exposed sunken battery, 46 F False frame, 146 Field kitchens and ovens, 114 Field-level, description, 136 Field-level, use, 146, 148, 149 Filtration of water, 117 Fire, musketry, 84 Fire, opening by attack, 76 Fire, opening by defence, 104 Fire, opening from second artillery position, 83 Firing blasts, 178 Firing and loading mines, 161-6 Firing-tubes and needles, 178-9 First artillery position, 75 First parallel, 78 First period of the siege, 65 Flying sap, 20 Flying sap, construction of, 22 Fort Wagner, 86 Form and volume of crater, 121 Fortifying camps, parks, etc., 68 Frames and sheeting compared with cases, 141 Frames and sheeting, use in shafts, 139-45 Frames and sheeting, use in galleries, 145-51 Freezing of high explosives, 165 Full sap, 28 Full sap, driving of, 28 Full sap, breaking out from a parallel, 30 Fuzes, 161, 164, 166 G Galleries, blinded, 156 Galleries, change of direction of, 148, 150, 154 Galleries, change of slopes of, 149, 154 Galleries, definitions and dimensions, 119, 138 Galleries, direction in attack, 171 Galleries, distance apart, 170 Galleries, for breaching, 177 Galleries, inclined, 147-9, 155