Attack of Fortified Places. Including Siege-works, Mining, and Demolitions.

Chapter IV: Blasting and Demolitions

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BLASTING.

=94. Blasts= are small mines used generally for breaking up rocks, or masonry in demolitions.

=95.= Holes for placing the charges are drilled usually with _drill-bars_ or _churn-drills_, known also as _jumpers_.

These are steel bars sharpened to a chisel edge. The _drill-bar_ is usually held by one man and struck with a hammer by another; it is turned slightly after each blow in order to make a round hole.

For small holes the driller holds the drill in one hand and strikes with the other.

The _churn-drill_ is a longer bar, generally sharpened at both ends and enlarged in the middle. It is used for drilling vertical holes by raising and dropping it in the holes, turning it slightly after each blow.

=96.= The _charge_ may be gunpowder or high explosive. If the former, it must be thoroughly tamped. If the latter, tamping will greatly increase its effect; but it is in some cases preferable to obtain the desired effect by increasing the charge and saving the time taken in tamping.

=97.= Blasts are fired by electric fuses, Bickford fuse, firing-tubes, needles, etc.

The fuses have been already described.

The _firing-tube_ is a very small iron pipe, which is inserted in the powder charge and the tamping rammed around it.

After the tamping is finished the tube may be filled with fine powder poured in it if the hole is vertical or inclined downward, or straws filled with powder may be inserted if it inclines upward or is horizontal. A “squib” of wet powder is also sometimes placed in the tube and ignited, when it passes down the tube like a rocket and fires the charge.

The _needle_ is a smooth copper wire, longer than the depth of the hole. It has a ring handle, by which it may be turned around and withdrawn. It is inserted in the charge, the tamping is well rammed around it, and it is withdrawn, leaving a pipe in the tamping, through which fire may be communicated, as described for the firing-tube.

=98. Tamping.=--The best and safest tamping is perfectly dry silicious sand, poured in the hole so as to fill it completely, but not rammed. It cannot be used in holes which incline upward nor when the needle is used.

In such cases moist clay, brick-dust, etc., are used. The first layers are pressed in upon the charge, and the subsequent ones thoroughly rammed down with a copper tamping-bar. A hammer is used with the bar, when necessary, in deep holes and hard rock.

_With high explosives no tamping should be used except dry sand or water. Holes which incline upwards should receive an extra charge and be untamped._

=99. Determining the Charge.=--The charge of gunpowder or high explosive required for any particular hole in ordinary blasting can be best estimated by an experienced blaster. If one is not to be obtained, an approximate estimate for the first experiment may be made from the formulas (counting the high explosives about four or five times as strong as gunpowder for ordinary use), and the charges for subsequent blasts may be estimated from the effects of those first fired.

=100. Precautions.=--If a _tamped_ hole misses fire _it should never be cleared out for recharging_. A new hole should be drilled near, but not breaking into it.

Electric fuses or Bickford fuses (with blasting-caps for high explosives) should always be used when they can be obtained.

DEMOLITIONS.

=101. Deliberate Demolitions=, such as the destruction of walls, casemates, etc., in time of peace, or at a distance from the enemy in time of war, should be so made as to economize powder and work. To accomplish this, the mines and blasts should be located where they will produce the best effects attainable, and the charges should be proportioned to the work required from them.

The table previously given (p. 124) will serve as a guide for computing the first charges used, and from the results of these the charges of subsequent ones may be determined.

Judgment must be used in placing the charges, so that, when possible, they will destroy the supports and allow the superstructure to break up by falling.

The charges will usually be placed in chambers under or hollowed out in the masonry. Sometimes they are more advantageously placed in a trench outside and close to the foot of the walls. They should always be well tamped: when in mine-chambers, by methods previously described; when in trenches, or laid along the exterior of walls, by loading them with earth, etc., until the line of least resistance passes through the wall to be destroyed.

=102. Hasty Demolitions= are made when the time available for the work is limited.

The structures usually destroyed are houses, walls, stockades, bridges, tunnels, canal-locks, railroads, rolling-stock, etc., etc.

The time does not usually allow the charge to be placed in the most advantageous position or to be properly tamped. For this reason the high explosives are best suited for this kind of work, and large charges are a necessity.

=103. Houses and Magazines= are best destroyed by placing several charges with connecting trains inside and along the walls, laying strong timbers upon them, with struts from the timbers to the floors and roof above; barricading the doors and windows from within, and firing the powder from a safe distance without.

=104. Walls.=--A wall not exceeding 3 or 4 feet in thickness may be breached by charges of gunpowder placed at intervals along it. Calling the thickness of the wall in feet _t_, the charge in pounds may be 3_t_^3, placed at intervals of 2_t_.

For gun-cotton the Woolwich rule calls for charges in pounds of from ⅓_t_^2 to ½_t_^2 per running foot. Experiments made in New York with dynamite indicate that the charges should be at least ½_t_^2 per running foot, and for very good masonry should exceed this.

A charge of dynamite of ½_t_^2 per running foot will be given by a cylindrical cartridge whose diameter in inches equals the thickness of the wall in feet.[22] The effect of the charge will be very much increased by throwing over it even a very light tamping of earth or sand.

=105. Stockades.=--A strong stockade or palisade may be broken down by charges of from 40 to 60 lbs. of gunpowder placed in contact with it, and preferably covered with sand-bags. 10 or 15 lbs. of high explosive should produce about the same effect.

=106. Bridges.=--Arched bridges are best attacked in the piers if high and thin, or at the haunches and crown of the arch. Two or more charges in the length of the pier, or width of the roadway, will be more effective than the same amount in a single charge at the middle.

The charges should be placed in chambers cut in the piers or down through the roadway to the back of the arch.

The abutments of single-span arches are generally very strong, and the haunches well covered with earth and masonry. In hurried work, therefore, the crown will generally be selected, a trench dug down to it across the roadway, the charge placed in the trench, tamped if possible, and fired.[23]

High explosives, from their shattering effect, are perhaps most advantageously used by suspending them beneath and in contact with the arch at the crown and haunches. The plank or timber upon which they are placed should be as heavy as possible, in order to act as a partial tamping, and should be drawn up so that the explosive will be in actual contact with the soffit of the arch.

Under these circumstances they should produce as great an effect as four or five times their weight of gunpowder.

Iron and wooden truss-bridges should be thrown down by breaking the main braces near the piers, or the chords near the centre, by charges placed in a joint if possible. High explosives are particularly valuable for this purpose.

In wooden bridges they may be placed in auger-holes bored for them, and in iron bridges inside the hollow members, between eye-bars, or in other similar places.

=107. Tunnels, Canal-locks=, and similar constructions must be attacked with large charges, so placed as to temporarily or permanently disable the work, as may be considered necessary. The location of each charge should be determined and its amount computed from these considerations before the destruction is attempted.

A temporary obstruction is frequently all that is necessary or desirable for these works, and the damage done to them should be carefully regulated with a view to their subsequent repair and use.

=108. Railroads.=--Railroads are temporarily disabled by tearing up the track, making hot fires of piles of ties, placing the rails upon them so that they will heat and bend by their own weight; or, better still, twisting the rails while hot by suitably-shaped steel hooks and wooden levers of the kind devised by General Haupt (Pl. XII, Fig. 33). Rails so twisted cannot be again used until re-rolled.

=109. Rolling-stock.=--Railroad cars may be disabled by breaking one or more wheels with sledges, or may be destroyed by burning. Locomotives may be disabled temporarily by carrying away the smaller parts of the mechanism, or permanently by breaking the engine-cylinders with sledges; bursting the boilers or burning out their fire-boxes by drawing out nearly all their water, fastening down the safety-valves, and building a hot fire in the furnaces; or by making a hot fire under them so as to heat and thus bend or warp the reciprocating parts of the machinery.

=110.= In all hasty demolitions with explosives the charges should be well in excess of those computed by the ordinary rules: first, because the explosives will not be so placed as to act to the greatest advantage; and, second, because the demolition should be _immediate_ and _complete_.

INDEX.

PAGE
Additional operations--intrenched camps, 91

Advance from first parallel, 84

Advanced positions, 104

Advantage lies with attack, 176

Ammunition, 44, 57, 101

Angle template, 137, 148

Approaches, 16

Approaches, execution of, 20-3

Approaches, tracing, 18

Approaches, over-ground, 31

Ascending galleries, 148

Armament, 100

Army of observation, 69

Artillery, first position, 75, 104

Artillery, first position opening fire, 67

Artillery, second position, 81

Artillery, second position opening fire, 83

Artillery-fire, opening, by defence, 104

Assault, 4

Assault, defence against, 7

Assault, dispositions for, 5

Assault of breach, 89

Attaching a miner, 177

Attack by mines, 169-171

Attack by sap, 91

Attack, close, 107

Attack, journal of, 97

Attack, plan of, 78

Attack, point of, 73

Attack, successive steps of, 64

Auger, earth, 138

Auxiliary frame, 144

Battery, alternative construction, 50

Battery behind crest of hill, 53

Battery, breaching, 83

Battery, construction of, 48

Battery, constructing centre passage of, 48

Battery, counter, 82

Battery, definitions, 42

Battery, electric, 163-6

Battery, enfilading, 82

Battery, exposed sunken, 46

Battery for field-guns, construction of, 43

Battery for siege-guns and howitzers, 44

Battery for siege-guns, ammunition required, 44

Battery, general requirements of siege, 42

Battery, location of, 9, 75

Battery, mortar, 55

Battery of rifled mortars and howitzers, 83

Battery on sloping ground, 53

Battery, sunken, in a parallel, 51

Battery, tracing the, 47

Belfort, siege of, 71-2, 86, 104

Besieging force, bringing up and posting, 67

Besieging force, strength and composition, 70-2

Blasts, 178

Blasting and demolitions, 178-84

Blindage-frames or blinds, 156

Blinded descents or galleries, 38, 156, 170

Blinded sap, 38

Blinded sap, traverse by, 35

Blinds or screens, 45

Blockade, 1

Bombardment, 8

Bombardment, defence against, 10

Bombardment, defence during, 105

Bomb-proofs and traverses, 25, 170

Branches, 170-72

Breach, capture and crowning of, 89

Breaching batteries, 83

Breaching by mines, 176-7

Breaching galleries, 177

Breaching the scarp and counter-scarp, 88

Breaking out a full sap from a parallel, 30

Breaking out a double sap from a parallel, 33

Bridge, demolition of, 182

Bridge, floating--passage of ditch, 40

Brigade or detachment of sappers, 28

Bringing up and posting the besieging force, 67

Camps, fortifying, 68

Camouflet, 120, 167, 171, 172

Canal locks, demolition of, 183

Capitulation, the, 109

Capture and crowning of breach, 89

Capture and crowning of covered way, 87

Cases, mining, 139-41

Chamber, definition, 119

Chamber, form and location, 160

Changing direction of double sap, 33

Changing direction of galleries, 148, 150, 154

Changing slope of galleries, 149, 155

Charge, definition, 119

Charge, excess to be used in demolitions, 184

Charge for over- or under-charged mines, 125

Charge for blasts, weight determined, 179

Charge for blasts, when tamped, 178-9

Charge for common mines, 122-4

Charge for mines, placing, 165

Charge for mines, preparing, 161

Choice of explosives, 132

Churn-drill, 178

Circular place of arms, 31

Conquered place, occupation of, 93

Common mine defined, 120

Common mine volumes and charges, 120-4

Construction of battery for field-guns, 43

Construction of battery, sunken, 48-50

Construction of central passage, 48

Construction of magazine, 60

Construction of simple trench, 20

Construction of trench by flying sap, 22

Counter-battery, 82

Cover for bomb and splinter proofs, 23-25

Cover for magazines, 58

Covered way, crowning of the, 35

Crater, definitions, 119

Crater, assumed form of, 121

Crater relation between volume and charge, 120-7

Crater radius, definition, 119

Crowning the covered way, 35

Crutch, 154

Dampness, precautions against, 63

Defence, the, 99-111

Defence against assault, 7, 105

Defence against bombardment, 10, 105

Defence against surprise, 4

Defence, ammunition for, 101

Defence, armament for, 100

Defence by mines, 171-2

Defence, council of, 98

Defence during bombardment and assault, 105

Defence during first period, 103

Defence during second period, 106

Defence during third period, 107

Defence, garrison for, 99

Defence, journal of, 110

Defence, opening artillery fire by, 104

Defence, preliminary considerations, 98

Defence, preparations for, 101

Defence, provisions and supplies, 101

Demi-parallels, 86

Demolitions, deliberate, 180

Demolitions, hasty, 181

Descending galleries, 147

Detachment or brigade of sappers, 28

Detonation, 162

Dispositions for an assault, 5

Distribution of fuzes in charge, 161

Distance of line of investment, 70

Ditch, passage of, 37

Double sap, 32

Double sap, breaking out, from a parallel, 33

Double sap, changing direction of, 33

Double sap, execution of, 32

Drainage, 16, 24, 55, 59

Drawings, working, 151

Drill-bars and drills, 178

Dynamite, etc., 132-5

Dynamite, freezing of, 165

Dynamite, tamping, 179

Earth auger, 138

Electric batteries, wires, and lights, 165-6

Elevated and sunken batteries, 44

Elevated magazine, 62

Embrasures, 53

Enfilading batteries, 82

Execution of double sap, 32

Execution of single sap, 28

Experimental mines, 125, 131, 133

Explosion, theory of, 120

Explosive, charge for blasts, 179

Explosive, charge for mines, 122-5

Explosive, choice of, 132-5

Explosive, expenditure of energy, 120

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

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

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

Galleries, listening, 170

Galleries of departure, 150

Galleries, partly lined, 148

Galleries, rate of advance of, 157

Galleries, transverse, 170

Gallery linings, 139-41

Gallery with frames and sheeting, 145-51

Gallery with cases, 153-6

Garrison of place, 99

Gases generated in mines, 133, 158

General requirements of siege batteries, 42

Globe of compression defined, 120

Governor of the place, 98

Guns, field, batteries for, 43

Guns and howitzers, batteries for, 44

Guns, ammunition required, 44-57

Guns for armament, 100

Guns of first artillery position, 76

Guns, positions of, to be changed, 106

Gunpowder, amount per cubic yard, 123, 124, 178

Hasty demolitions, 181

High explosives compared with gunpowder, 131-5

High explosives, freezing of, 165

High explosives, use in blasting, 179-80

Houses and magazines, demolition of, 181

Howitzer batteries, 44

Howitzers for vertical fire, 83

Huts and shelters, 113

Inclined galleries, 47

Infantry trenches, 104

Intrenched camp, attack upon, 91

Investment, 9, 65

Investment, distance of line of, 70-72

Journal of the attack, 97

Journal of the defence, 110

Jumper, 178

Kitchens and ovens, 114

Landings, 150-1

Latrines, sinks, etc., 115

Line of investment, distance of, 70

Line of least resistance = L. L. R., 119

Listening galleries or listeners, 170-72

Loading and firing mines, 161

Location of batteries, 9, 75

Location of magazine, 58

Lodgement, 170

Magazines, 57

Magazines, construction of, 60

Magazines, cover for, 58

Magazines, drainage of, 59

Magazines, elevated, 62

Magazines, execution of the work upon, 61

Magazines, location of, 58

Magazines, mined, 61

Magazines, precautions against dampness, 63

Maps, 151

Masks for batteries, etc., 45

Masks, air-tight, for exploring mines, 160

Maxims, Vauban’s, 94

Mine defined, 119

Mine-chamber, 160

Mine, common, 120-5

Mine, overcharged and undercharged, 120, 125, 131, 171-72

Mines of attack, 169, 171

Mines of defence, 171-2

Mines, organization of, 169

Mine tactics, 172-6

Mined magazine, 61

Mining, military, object of, 119

Miner, attaching a, 177

Miner’s bellows, 137

Miner’s candlestick, 137

Miner’s lamp, 137

Miner’s pick and shovel, 136

Miner’s rule, 122

Miner’s truck or car, 137

Mortar batteries, 55, 83

Mortars, siege, 57, 107

Musketry fire, 84

Observatories, 54

Occupation of conquered place, 93

Opening fire, attack, 76

Opening fire, defence, 104

Opening fire from second artillery position, 83

Opening the first parallel, 80

Organization and duties of brigade of sappers, 28

Organization and tactics of mines, 169-76

Ovens and kitchens, 114

Overcharged and undercharged mines, 120, 125, 171-2

Overground approaches, 31

Parallels, 15

Parallels, demi-, 86

Parallels, execution of, 20-3

Parallel, first, 78

Parallel, first, opening, 80

Parallel, first, advance from, 84

Parallel, second, 85

Parallel, third, etc., 86

Parallel, tracing a, 17

Parks, camps, etc., fortifying, 68

Parks and depots, 111

Partly-lined galleries, 148

Paris, siege of, 71-2

Passage, central, of battery, 48

Passage of the ditch, 37

Period, first, of siege, 65, 103

Period, second, of siege, 75, 106

Period, third, of siege, 86, 107

Pick and shovel, miner’s, 136

Pick, miner’s, distance heard, 170

Placing fuzes in charge, 164

Placing the charge, 165, 176

Plan of attack, 78

Plevna, siege of, 71, 72

Point of attack, 73

Posting besieging force, 67

Posting working parties, 18

Powder-boxes, 58

Powder for siege batteries, 44, 57

Precautions against dampness, 63

Precautions in blasting, 180

Preliminary considerations of defence, 98

Preparations for defence, 101

Preparing the charge, 161

Progress of the siege, 12

Proofs, bomb, 25

Proofs, splinter, 23, 48, 50

Provisions and supplies, 101

Push pick, 136

Radius of explosion, 119

Radius of rupture, 120, 128, 131

Railroads, demolition of, 183

Rate of advance of galleries, 157

Rate of advance of sap, 29

Regular approaches, 12

Requirements, general, of siege batteries, 42

Returns, 150-1

Rifled mortars and howitzers, batteries of, 83

Rolling-stock, demolition of, 184

Sand-bag fork, 13

Sap, attack by, 91

Sap, definition, 27

Sap, blinded, 35

Sap, breaking out from a parallel, 30

Sap, double, 32-3

Sap-fork, 13

Sap, flying, 20, 22

Sap, full, 28-30

Sap, shallow, 31

Sap-shield, 13, 23

Sap, traversed, 33-5

Sap, widening the, 30

Sapping, definitions, etc., 27

Sapping, former methods, 36

Scraper, 13

Screens, 45

Second artillery position, 81

Second artillery position, opening fire from, 83

Second parallel, 85

Shaft, definitions and dimensions, 119, 138

Shaft à la Boule, 156, 172

Shaft intervals, 142

Shaft linings, 139-141

Shaft mines, 172

Shaft, sinking, with cases, 152-4

Shaft, sinking, with frames and sheeting, 141-5

Shaft in a lodgement, 170

Shallow sap, 31

Shelters and huts, 113

Shield for covering ditch, 38-40

Shield for driving gallery, 147

Shovel and pick, miner’s, 136

Siege, definitions, etc., 12, 64

Siege batteries, 42-53

Siege, first period of, 65, 103

Siege, second period of, 75, 106

Siege, third period of, 86, 107

Siege, length of, 71

Siege of Belfort, Fort Wagner, Paris, Plevna,
and Strasburg, 71, 86, 104

Simple trench, 20

Sinking shaft with frames and sheeting, 141-5

Sinking shaft with cases, 152-4

Sinks and latrines, 115

Slope, defined, 119

Slope-block, 137, 148

Slope, change of, 149, 155

Slope, method of fixing, 147

Squibs, 178

Splinter-proofs, 23, 48, 56

Sterilizing water, 117

Stockades, demolition of, 182

Strasburg, siege of, 71, 86

Sunken battery, 45-53

Supplies and provisions, 101

Surprise, 2

Surprise, defence against, 4

Surrender of the place, 109

Tamping blasts, 178-9

Tamping mines, 166

Third period of siege, 86

Todleben’s rules, 173

Tools and appliances, 10, 136

Tracing approaches, 18

Tracing a battery, 47

Tracing lanterns, pickets, tapes, etc., 14

Tracing parallels, 17

Transverse galleries or transversals, 170

Traverse by blinded sap, 35

Traverse, cube, 34

Traverses, length of, 34

Traversed sap, 33

Trenches, 15

Trench cavalier, 36

Trenches, guard of the, 15

Trench, infantry, 104

Trench, simple, 20

Tunnels, demolition of, 183

Underground warfare, 169

Vauban’s maxims, 94

Ventilation of mines, 158-60

Vertical fire, batteries for, 83

Volume and form of craters, 121

Volume and weight of charge, 161, 181

Wagner, Fort, siege of, 86

Walls, demolition of, 181

Water-supply, 116

Weight and volume of charge, 161, 181

Wet ditch, passage of, 38-40

Working drawings, 151

_Plate I._