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HINTS ON HOUSE DEFENCE, BLOCKHOUSES, AND REDOUBTS.
THE object of these notes is to point out simple ways of adapting to purposes of defence, the material usually readiest at hand in homesteads and detached dwellings.
The requirements for defence are, mainly, four: viz.-- facility of fire and clean range on all sides,--as perfect flanking fire as possible,--protection to defenders from bullets,---and security from surprise.
SECTION I.
FORTIFIED HOUSES (PLATE I.)
[N.B. No plates or figures found in this Auckland Museum copy]
The first step in fortifying a house is to loophole it. Let the loopholes be, in the exterior wall planks, 3 inches wide and 6 high,--in the interior planking 6 to 9 inches wide and about 9 inches high,--in order to give range to your rifles.
To prevent any one closing with the loopholes they should be not less than 5 feet from the exterior ground.
Whatever the height of the loopholes, standing places, "banquettes"--to use them from, must be provided,--four feet below the lower edge of the loophole, inside. Beds, boxes, casks, woolbales, hay trusses are available for this use;--a broad plank, on two caskends or on rough trestles, makes the best of all banquettes. (See figure 5.)
Figures 1 to 3 are plans of fortified houses. Nos. 1 and 2 are simple square buildings; No. 3 has an outline made available for defence.
The thick black line shows the original outline of the
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house; the shaded parts are the additions of parapet for flanking defence. Where there is wood, of course, it may he more convenient to make these additions of stockade work. (See figure 13.)
In figure 1 the entrance and every side of the house is perfectly flanked; the greater part of it, indeed, is concealed from outside view. Figure 2 with less labour gives very powerful flank defence. Figure 3 is not fully flanked; but considerable strength is given by the single addition to its original outline.
Figure 4 is a section of the parapet;--figure 13 of the stockade suitable to flank defences. Parapets can be built with either turfsods, or layers of fern and earth alternately; they should be given an outside slope of a quarter their height.
Stockade work is strongest when nailed; where nails are not procurable it can be tied (as in figure 13) with flax, &c. Care should be taken in a double palisade to alternate the inside and outside posts as seen in the figure.
There are three main ways of making the wall of a house bullet-proof.
(A.) By removing a few shingles from the roof above the eaves, and pouring in between the outer and inner boarding pebbles with clay,--ramming these into a solid mass. But the ramming must be very carefully done and no interstices left, for loose gravel does not stop bullets. A neater and safer plan in the case of building a new house would be to adopt the picturesque half-timbered style,--introduced by the Flemings,--and so frequent in Kent and Sussex homesteads to this day,-- the walls of the house being skeleton chequers or chessboards of timber, the openings in which are filled in with panels of brickwork. No earthquake could hurt a building of this kind much, if properly constructed, and if the brickwork be well secured.
In cases where the partition in walls is not wide enough to be made shot proof, a light stockading of branches placed close together may be put up (5 inches outside the wall, and the interval filled in with gravel. (See figure 14.)
(B.) By building up, around and against the exterior
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walls, sod or fern work "revetment," or bank to, and up between the loop-holes. This lean-to bank should be of the dimensions of the parapet in figure 4. (See figure 6.)
(C.) By removing the flooring, and excavating the interior for the defenders, throwing up the earth against the walls, thus forming a banquette and screen.
This mode of obtaining protection is comfortless of course, and injures the house. Its great recommendation is that it can be had report to in a beleagured house during the progress of its defence, (see figure 7.)
Ditches around a house are positively objectionable, unless they can be fully seen in every part and fired into from the interior. This rarely happens unless a position is very skilfully and perfectly flanked.
PENETRATION OF A RIFLE BULLET AT POINT BLANK RANGE.
Brickwork... .... .... ... 2 inches
Seasoned Oak .... .... .... 3 inches.
Deal... ... .... .... 4 to 5 inches
Sun dried brick and rammed clay concrete ... .... ... 5 inches
Ordinary compact earth... .... 9 inches
Fresh heaped loose earth... .... 18 inches
The above table is on the safe side of penetrations, and may be taken as a guide in combining different materials. At Wereroa bullets went through 2 inches of deal and 6 of loose poor gravel; but 2 inches of seasoned deal and four of well rammed concrete will stop any rifle ballet.
To prevent surprise the ordinary entrance should be discontinued at night, and a couple of ladders used over the parapet of the flanking defences--the outer ladder removeable at night.
Double-storied houses are good positions, giving as they do a commanding view, and affording a double row of loop holes. The roof too, being more out of reach is not so easily set on fire.
In these the lower story should be cased with clay and pebbles, as described; and if the upper story is not strong enough to hear the weight of this on it, it should
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be protected to 4 or 5 feet from the floor by every means available. Spare planks might here be used, being nailed on to the lining boards. Any corrugated iron or tin sheeting at hand should be used to face the exterior, and especially the lower part of it. It would not be easy to set on fire a house thus protected even for 5 or 6 feet only from the ground.
As water is the greatest necessity, so is fire the great danger to men whose lot it is to defend wooden buildings. Too much precaution can never betaken to guard against it.
To protect cattle and stock (see figure 8) run out a couple of straight sod bank walls in such directions from the house that both sides of them can be thence seen and fired into. These walls should not terminate abruptly, let them narrow and run down to nothing in the last 10 feet. Join the walls where they begin to decline by a post and rail fence, or, better still, a wire fence. This side of the enclosure, whatever it is made of, must be open and give no cover.
Begin from a line some 20 feet within this fence, excavate a broad shallow ditch of the size required for shelter to the stock, and throw the earth towards the fence, forming a mound, the outer slope of which should he so gentle that its surface can be ranged from the loopholes of the house; a three foot ditch with the mound in front of it, would probably be ample shelter. The ditch of course would require a drain.
Figures 9 to 11 are examples of connecting two or three houses together with lines of parapet, giving the greatest possible flank defence.
In figure 10 and 11 an entrance is left, protected by a traverse or covering breastwork to screen the interior of the enclosure from the outside. The want of one caused casualties at the attack on Turu-turu-mokai.
A gate, and moveable bridge where there is a ditch, should be added.
Figure 12 is a drawing of a barricade gate, useful against surprise. The lower three planks should always be left in, and the whole closed at night.
For general precautions clear away all cover round the house; fill up holes; cut down trees; pull down detached
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buildings. Above all leave no dry wood about outside, and look after the water supply;--keep every vessel in the house constantly full.
SECTION II.
BLOCKHOUSES.
The original American blockhouse is made of squared pine timbers placed on end side by side, the loop holes being slashed out of the sides of the logs. On the roof, which is strong, is heaped earth to two or three feet deep. There is a ditch outside, from which a stout bank slopes up to the sills of the loop holes. (See figure 1, plate II.)
In other countries, where straight woods are scarce, blockhouses are more conveniently constructed of sawn timbers.
A perfect blockhouse should be fully flanked and bullet proof, with a strong door, and a roof protected from fire. It should contain a well or reservoir of water, a magazine and a store room. Lastly, it should be approachable from the main post or town in the rear upon which it is dependent by an open road well clear from bush, otherwise it is liable to become isolated, and difficult to relieve in case of necessity.
An ordinary well-built house is convertible into a blockhouse. The usual outline is a square or a cross. For a blockhouse with overhanging upper storey the square shape is best, since it gives the most internal space, and the trap holes in the upper story compensate for the want of other flanking defence. (Figs 2 and 3) A blockhouse of this nature should be twenty feet broad, nine feet high in each story, and thirty feet or more in length, according to the garrison. The upper story overhangs the lower two feet. The walls should be six inches loose gravel between three of seasoned timber.
A chain of blockhouses has lately been put up across the coast belt, ten miles north of Wanganui. Their dimensions are 14 feet by 12. Each story is 8 feet high.
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The upper story does not project. They have a corrugated iron roof, and iron door opening into the lower room. The wall thickness is two and a half inches of wood incasing six of gravel. There are four loop holes of a side in each story. The building is surrounded by a small ditch, and "glacis" or sloping bank beyond the ditch, and a sod bank is run up at a gentle inclination from the bottom of the ditch to the sills of the lower loop holes.
These blockhouses cost by contract £88 a piece--were cut out in town, and sent to their destination in pieces ready to he put together. They are three or four miles apart. Their garrison is supposed to be twenty men.
These buildings are by no means so strong as they might have been made. Still they are cheap, simple in construction, and will probably answer very well their purpose of giving night security to the neighbouring settlers.
Two storied blockhouses require heavy timber, good carpentry, time and money. They are not likely to be constructed often by private people, and a farther detailed description is not required here.
In ordinary cases the single roomed blockhouse is the cheapest and easiest built. For these the cross-shaped is the better form, as giving good flanking defence. (Fig. 4.) The pointed cross form (Fig. 5) is best of all, the flanking being perfect. They should not be less than 9 feet high, and 20 feet broad for health sake, and for air during heavy firing. Smaller buildings get choked very soon with smoke, and unbearable in action. Where tin roofing is procurable it may be used. But a safer and stronger protection is an earth covered roof. For the latter stout beams must be laid across from wall to wall--planks on these--and, above all, the earth, which should be beaten down firm.--three feet thick at the centre, sloping off to two feet at the sides. Where the roof beams are weak they should be propped by a row of central posts. A thin paling or brushwood fence, with wicket to it, would be a safety to the sentry, as preventing a sudden night rush. (See fig. 2, plate II.)
A rough blockhouse may be built in the following way. (See figs, (6, 7, 8, plate II.):--
Select a commanding piece of level ground, on dry soil.
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Mark out (Fig. 6) a space 20 feet by 30, and, four feet within this, another, which will be of course 12 feet by 22. Excavate within the latter space to 3 feet depth, throwing the earth clear of the outer rectangle, which will be the site of your blockhouse. Set up at one end, twenty feet apart, the corner posts.--strong limbs, with a fork left at the top. They should be put three feet into the ground, and be six feet from the ground to the fork. Put up a similar centre post, six inches longer than, and midway between the corner posts. Lay a couple of 12 feet logs across these three posts, nailing them there, or lashing them with flax. Having thus completed the first frame, plant a second, and so on, at two or three feet distance, according to the strength of the roof timber, (remembering its future load of earth.) When two or three frames are up, lash a layer of stout branches across from frame to frame; upon these strew fern branches, and on this bed begin to throw earth, beating it firm. Let it be three feel thick at centre, sloping to two feet at sides. Keep the framework square by lashing diagonals to it here and there. Now, the wall may be commenced, of stout turf sods, built neatly, breaking the joints of the layers, round the wall-posts and up to the eaves, tightly jamming in the upper layer of sods under the eaves. Loopholes must of course be left four feet apart, and four feet from the ground, and the wall must be not less than two feet thick anywhere,--its base should be from four to five feet thick. A door should be constructed similar to that in figure 12, plate I. Loopholes, be it noted, should never be kept open at night. Wooden ones should have slides inside. Where they are, as in this case, earthen, a few firm sods should be kept inside to close them up with. This blockhouse when finished will be 30 feet by 20, and nine feet nigh. The four foot belt of ground left inside serves for a bed for the guard and a banquette to the loop holes. The advantage of "half sinking," as this mode of construction is called, is, that cover is got in the very quickest way. You are obtaining protection at once from the first spade-full dug,--the first turf sod cut and added to the wall.
It will be observed that in the above directions no material is mentioned that is not commonly obtainable by
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labour anywhere.
If there are planks to spare they should be used in making the upper two or three feet of the walls and the loopholes. The blockhouse, of course, is much more comfortable if it can be lined inside with planks or wattle hurdles.
The dimensions here given of blockhouses are not intended as more than indications. They must of course vary according to the garrisons, the rules for calculating which are hereafter explained.
SECTION III.
REDOUBTS.
Redoubts are enclosed field works--squared ring fences in short--of parapet, made to shelter from 25 to 200 men.
The redoubt military, (See figure 9, plate II.), is a square work, surrounded by a ditch, which last is swept by "caponiers," (blockhouses, in fact), in its opposite angles. These caponiers communicate with the interior by tunnels through the parapet, very tedious to construct. This work, however, when complete, is very strong, and perfectly flanked.
Field guns are sometimes placed at the angles, on a platform so high as to let the piece sweep the country over the parapet. A single gun, of course, is placed at the angle most likely to be attacked, or the weakest one. But it is a good plan to make the platforms for it at every corner. Then, it can be used wherever wanted.
Figure 10 represents the usual New Zealand redoubt; not so good a tracing as the last for two reasons: (1) because the faces of the corner turrets are not flanked at all; (2) because the flanking is not reciprocal and cannot be fully concentrated on any menaced point. For example, if the point B be attacked, there is no flanking fire from C.
Figure 11, a strong tracing, is the square redoubt, with
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flanking turrets, (in the drawing, blockhouses), at the opposite corners.
The entrance, be it noted, is in the least accessible face, that adjoining the cliff.
The side of a redoubt should not be longer than 40 yards. Where a larger work is required, the bestioned-fort tracing should be used. Figure 12 is a bastioned fort. To construct it describe a square on the ground; bisect each side with a perpendicular inwards one-eighth of the length of the side.
From the corners draw lines through the extremity of the perpendicular, from which cut off, for the faces of the bastions one-third of the exterior side, and from the extremity of these faces let fall perpendiculars for the flanks of the bastions to the line producing the adjoining faces. Join the inner ends of the flanks with a "curtain" or connecting wall, and the trace is complete.
The entrance to enclosed works should be closed by a gate, or a traverse (as in figure 11, plate II). The traverse should be at the same distance from the outer parapet as the entrance is wide. It should be provided like the rest of the parapet, with a banquette.
For convenience of construction, a few feet of the ditch should be left till last undug, opposite the entrance; and for the same reason a "berm" or ledge of ground some two feet wide, should remain outside the parapet and between it and the ditch, to enable the workmen thereon standing more easily to hand up turf sods, and build the exterior of the parapet.
In Field Fortification a berm is intended solely for the above temporary purpose. It should be shaved away as the work is completed, for it is then useless, and although often left permanently by ignorant people, its effect is to weaken the work by neutralizing the depth of the ditch, leaving a step lor the enemy to aid him over the parapet.
For a bridge a single plank will generally suffice. A draw-bridge, however, is safer, and saves the trouble of making a traverse or gate. In this case the bridge (see figure 1, plate III.) is pinned down at its inner extremity, the other end being raised when the bridge is required to serve as a gate.
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REDOUBTS.
In these cases the redoubt is generally the first built, the blockhouse being an afterthought.
The two are sometimes placed apart, within mutual range, but isolated from one another. This is a serious error, and should be avoided. The blockhouse should invariably form part of, or lie within, the redoubt, otherwise the capture of one of the two positions places the enemy on equal terms with the defenders,--while the whole advantage of the blockhouse as a citadel to the redoubt is lost.
The attack on the Weraroa redoubt (12th Nov., 1868,) proves this. Here the Maoris crept up to the half-finished blockhouse, 30 yards outside the redoubt, took cover in it, and eventually set it on fire.
When a redoubt has a blockhouse in one corner, the faces of the redoubt not adjoining the blockhouse should be given a parapet sloping so gently outwards as to be swept from the upper loopholes of the blockhouse,--upon the principle of the ditch in Fig. 8, plate I.
Thus the redoubt can be left safely vacant, and fully defended by a few men in the blockhouse.
DEFENCE OF TOWNS.
Where towns are built, as in Europe, of stone and brick, they are, in themselves, irregularly fortified positions; and, with barricades across the principal streets they can be easily defended. Every house being musket proof can be disputed in turn. Every public building is a natural citadel.
The weakness of wooden towns is very evident. Scattered over a large extent of ground--inflammable--affording little cover from bullets--they are everywhere assailable--every where burnable.
To be rendered secure they require to be surrounded by a wall, parapet or stockade.
Figure 13, plate II., represents a town so protected. The shaded part represents a portion of the centre of the place--the wall completely encircling it, and barricades
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being formed at the entrances. The suburban portions can be protected, as there is time, by additional walls.
The ways of entrance, shown by dotted lines, should be left somewhat tortuous if possible, to increase the difficulty of rushing the place.
Figure 14, plate II., represents a plan and section of the manner of erecting the defences along the roads, without interfering with private property. Stockading is more convenient, as it needs no ditch, and does not cut up the roads. Here, an earthen parapet is represented, 7 feet high, 3 feet broad at the top, with a banquette and a shallow (two feet) ditch. The small flanking angles should be at intervals of not more than forty yards apart; the entrances should be somewhat retired, and well flanked
Figure 2, plate III., represents the town of Wanganui as an example of the use of natural features in protecting a position. The bend of the river, and the two long ridges of hill, on which stand the two stockades, A and B, render the place easy to fortify.
By connecting the extremities of the ridges with the river bank, and blocking up the entrance of the valley between them, 600 yards of stockading would cover the main part of the town.
LINES OF BLOCKHOUSES.
This mode of protecting the country is cheap and effectual, provided (1) that the blockhouses be not more than 1 1/2 or 2 miles apart; and (2) that the communication to their rear be perfectly open.
Otherwise, the blockhouses fail in their purpose of protecting all in their rear, and they are moreover in great danger of becoming isolated.
SECTION IV.
STRENGTH OF GARRISONS.
In European warfare there are two rules about garrisons:
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1. A work should have two men per running yard of its parapet.
2. There should be fifteen square feet of internal space per man.
Very few works will meet the exact requirements of both these rules; but in determining a garrison the mean between them is taken.
Take, for example, a rectangular work 30 feet by 20: By the first rule it would need for its 100 feet of outline 67 men. But this number could hardly move--certainly not lie down, inside; and, containing as it does only 600 square feet internal space, it should accommodate by the second rule but forty men.
This first rule, in fact, applies to large works, and the second to small ones. Neither are suitable to blockhouses and redoubts in the bush, where the defenders have no artillery to fear. For such posts, with breechloaders at any rate, one man to every four feet is sufficient garrison. And this furnishes an easy rule to remember, viz.:--That in a square work the garrison should be one man per foot to one side; a redoubt 50 feet square, for example, should be manned by fifty men.
In a rectangular work the number of the garrison will be of course by the same rule, half the sum of the adjacent sides. A redoubt 20 feet by 40, for instance, will be held by half 20 added to 40, that is, by 30 men.
With reference to the above rule, a redoubt of the ordinary size (50 feet) will shelter about three times the number of its garrison; and larger works more in proportion.
TRACING OF FIELD WORKS.
To lay out a redoubt or other work:--
Proceed to the proposed site provided with about 50 nine inch pickets, a mallet or short tomahawk to drive them in with, and a sheaf of flax or some string. (White tape is best for night working.)
Select the position which has most command of roads and view of neighbouring posts, freedom from surrounding bush, facility of access, and means of obtaining water. Sites for redoubts are often chosen, like some of the ancient pas of New Zealand, with reference, principally,
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to the first of these advantages, neglecting the others--positions formidable in themselves, but quite off any road, difficult of access, and waterless.
Works for local protection--to be garrisoned by settlers, and to which in a night alarm terror-stricken women and children may easily find their way,--should be constructed near to the main road (and to an inn if possible.) They should of course have some elevation or natural strength to recommend them.
If it so happens that they are commanded by a hill, a little judicious labour will generally make them tenable, by neutralizing this in the following ways:--
Lay out an oblong work, with its long face towards the side from which it is commanded. Raise the parapet on that side a few feet. If the hill can still be seen from the interior after this, standing under the raised parapet, step back until you can distinctly see the hill over the parapet. Put down a picket at your feet, and step back from another point, and so on until you have a line of pickets across the interior from side to side.
Here erect a seven or eight foot parapet, taking the earth for it from the ground, inside the work, most commanded from the hill. An entrance, of course, must be left between the two divisions of the Field Work.
This digression is merely to show how easy it is to neutralize, by "defilading" as it is called, an evil of this kind in a position selected as otherwise suitable;--
And these remarks apply only to ordinary cases of a commanded position. None but madmen would construct, or hope to defend, a work at the base of a cliff, for instance.
To proceed with the redoubt. Set your working party to gathering fern or brushwood, and two or three to tying flax strips into rope.
Having previously fixed your outline, proportioned to the strength of the garrison, drive in a picket at one of the proposed corners, and pace out roughly the shape of the work, adapting it to the form of the elevation on which it is to rest, with a view to making the least amount of labour, by letting the ditches run where nature has already given them.
Let the angles point down the most difficult approaches
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and the faces oppose the flatter ground--the longest faces, where they are unequal, being directed against the easiest approaches.
Determine the positions of the flanking angles. These, the ordinary posts for sentries, should give the most extensive view, should overhang and sweep the valleys below the work.
Return to the corner picket, and take the angle from it with a prismatic compass or other instrument. Not having these a right angle can always be taken with three lengths of string, 3, 4, and 5 yards; carefully measured. (3² + 4² = 5².)
Having got the direction, measure off the lengths of the sides, and going to the other corners complete the tracing. The line should, most conveniently, represent the base of the interior crest of the parapet, or "master line" from which other measurements are taken.
Next, define the flanking angles, which should project from 8 to 10 feet,--for a 50 foot redoubt, say 8 feet
From the corner peg lay off 8 feet on each side, drive in pickets, and from these points, outwards, erect perpendiculars to the sides, of the same length, (8ft.) From the outer extremity of the perpendicular carry on the faces parallel to the redoubt sides, as in fig. 11, plate II., or better still a little thrown forward, that they may be flanked, as in the bastion tracing fig. 12.
In fact, where more than two flanking angles are contemplated, it is proper to lay them out bastion-fashion as has been previously described, and is show n in fig. 12.
The main line being completed, lay down the interior line of the banquette, and the exterior lines for thickness of parapet and width of ditch. Fig. 3, plate ill., gives fair dimensions for these. The ditch opposite the flanking angles is better deeper, and less wide, than the rest of ditch,--so that lodgement therein may be difficult.
PROFILE OF FIELD WORKS.
The determining of a profile is dependent entirely on the material at hand for construction.
Where logs, sand bags, or fascines can be got, the
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parapet need only be six feet high, the logs, &c., laid along the top, raising the shelter another foot.
When the parapet is to be entirely of earth, it must be built up to the full height, 7 feet, as given in fig. 3, plate III., where dimensions are given.
It must he remembered that a redoubt, owing to the trace of the work, and the internal support of the banquette, seldom falls inwards. When it gives, it is always in the direction of the ditch.
The slope of the parapet therefore should be nearly all outside. According to tenacity of soil it ought to slope from one-eighth to one-sixth, that is to say, it should be, allowing for outside and inside slopes, 3 to 4 inches broader at base for every foot of elevation.
This rule applies to stiff soil only,--as sod work, or earth strengthened with fern or brushwood in layers (the thick ends inside.)
A much greater slope is often required. Drift sand, for instance, stands only at 45°, that is, on a base equal to its height.
The slope of a parapet must therefore be left, in the main, to the judgment of the constructor, according to the soil he works with.
SECTION V.
GABIONS
Ara cylindrical baskets, made of twigs, open at both ends, 2 feet in diameter, and 2 feet 9 inches high.
When filled with earth they are bullet-proof. They are used to support the interior slope of the parapet in bad soil (fig. 7, plate III.) or to sap with (figures 6 and 7)
Fig. 4, plate III. shows the method of construction. Draw on hard dry ground a circle 21 inches in diameter. Drive in 10 or 12 pickets, 3 feet long, at equal intervals 3 inches into the ground on the circumference. Place 3 withes, as shewn in fig. 4, weave them over and over, inside one picket and outside two. Add fresh withes
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when near the ends of the first ones. Weave the topmost and lowest webs in and out. Bind with gags, as shown in fig. 4. Thrust both ends of the gad through the gabion, and secure it inside, the adjacent gads overlapping. Cut off the picket ends, and the gabion is finished.
Two men can make a gabion in an hour. The materials required are 1 mallet, 1 handsaw, 1 billhook, 2 knives, and l measuring rod, with brushwood and 3 foot stakes.
FASCINES
Are long faggots of brushwood, 18 feet long and 9 inches in diameter. They are bullet-proof and are used to support the interior slope of a parapet, or to lay along the top of it, giving head protection and forming rough loopholes. Fig. 5 shows the method of construction. Place trestles, crossing 2 feet 6 inches from the ground, in a row 4 feet apart. Five of these in a row make a "fascine horse." See by measurement that the trestles cross at the same height. Tie a stout cord to two levers with knots on the cord 28 inches apart. This is the "choker." Lay on the trestles the brushwood; choke it until the knots meet, beginning at 3 inches from the end. Bind at this point with a "gad," and continue to choke and bind with a gad at every 15 inches until the fascine is completed.
FLYING SAP
Is used for making a lodgement and shot proof cover in the quickest possible way. It is constructed at night. The workmen are marched up to the line carrying two gabions, a spade and a pickaxe each (Fig. 6). Arrived on the line they place their gabions in line close together, 2 feet beyond the tracing, and lie down behind them until the signal for excavation is given. The gabions can be filled in 15 minutes, and afford bullet proof shelter. This work might be useful to cover the supports and the advance of stormers, if put up the night before the storm of a pa or other work.
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SINGLE SAP.
Sapping is an art more suited to regular warfare--ut even in bush fighting it is occasionally possible to apply it with advantage. Where, for instance, a short advance has to be made over a peculiarly exposed piece of ground, a night's sapping might turn the day in the morning.
Fig. 7, plate III., shows the quickest method of sap. The workmen are divided into parties of 4, who relieve each other at the work. A sap roller, or large gabion 6 feet long, 4 feet wide, well stuffed with pickets of wood, must first be provided, as also 10 or 12 gabions of the ordinary dimensions and similarly stuffed, and the same number of "sap faggots" or three-foot lengths of fascine with a sharp picket driven through their centre, and projecting so that they can be stuck up on end. Placing themselves in file at 4 feet apart behind the sap roller, the squad drop on their knees and commence work. No. 1 places the gabions, and between each a sap faggot, and eighteen inches within the line of gabions digs a trench eighteen inches square throwing the earth beyond the gabions. No. 2 follows and widens the trench 18 inches. No. 3 deepens No. 2's work eighteen inches. No. 4, who can work standing, widens the whole trench 10 inches. Other workmen follow, widening and deepening, and as sufficient cover is obtained the hinder gabions and sap faggots are removed and passed on to the front.
It is better of course, where there is time to get gabions enough for the whole trench, to place them empty, and fill them with earth. The above mentioned method is only given as a way of working where gabions are not plentiful.
Advance is made, according to the soil, from 4 to 7 yards an hour.
STONE FOUGASS.
A very formidable auxiliary to defence is the stone fougass,--placed, for instance, in front of a weak angle, or opposite a line that the enemy must traverse in approaching.
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It consists of an excavation 5 or 6 feet deep, the axis of which, shown by the arrow in Fig. 8, makes an angle of 45° with the horizon.
A charge of powder is placed at the bottom, and covered with a strong shield of wood at right angles to the axis. It is then filled up with stones, and turfed over. The thick black line shows the powder hose communicating with the interior.
Twenty-five pounds of powder will project two cubic yards of stone over a square 60 yards wide--the stones beginning to fall at about 50 yards from the mouth of the fougass.
DESTRUCTION OF STOCKADING.
To effect an entrance, or to make a diversion during the storm of wooden works, it is sometimes required to blow in a portion (Figure 9, plate III.)
During the earlier Indian wars the Maharatta forts were often taken in this way. Bags of powder were nailed to a gate, the fuse was lit, and the bag left hanging. Gate after gate was thus carried. To destroy stockading the charge must be placed at the foot of the stockade, and half-a-dozen sand bags or a dozen heavy sods thrown upon it. 30 to 40 lbs. of powder will blow in from 12 to 30 feet of the heaviest timber work.
ATTACK OF STOCKADES OR PAS.
It occasionally happens that a work of this description is erected on level ground, over which a cart might be driven close up to it. Where carts are at hand, as they always are in a camp, they should be collected, and a rough stockading, 12 to 14 feet wide and 7 feet high should be lashed across their rear. (See fig. 10, plate in). Let the carts then be placed in line,--or wedge fashion, if flanking fire is to be suspected,--and with eight or ten men at the shafts of each let them advance covering the head of the storming party (fig. 11).
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BRIDGES.
Simple bridges can often be readily constructed in the field.
Figure 12 shows a "single lever" bridge. Four stout spars are required, and four transoms, or cross pieces. Lash two transoms to each pair of spars, the spars being wider apart at base than at top. When these two frames are completed, strengthen them with diagonals (not shown to avoid complication), and attach preventer guys (or ropes, to steady them, fastened to trees, &c., on the banks),--lower them over each bank, and let them lock in the middle. Then lash them and add the flooring, &c.
Figure 13 represents a "double lever" bridge, made on exactly the same principle, with a third frame locking in between the other two.
WELLINGTON:
PRINTED BY THOMAS W. M'KENZIE, GHUZNEE STREET, AT HIS STEAM PRINTING OFFICE, WILLIS STREET.
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