A battery, in respect to its profile, may be either elevated, half sunken, or sunken; and it is usually reveted with gabions, fascines, sand-bags, &c.
An elevated batteryhas its whole parapet raised above the natural surface of the ground, and, to procure the mass of earth required, a ditch is usually dug directly in front of the parapet.
A half-sunken batteryhas its interior space, or terreplein, sunk some inches below the natural surface, and its parapet is composed of the earth thus obtained, and of that taken from a narrow ditch in front.
A sunken batteryhas the whole of the earth taken from the interior space to form the parapet; and it must therefore be lowered from 2 feet to 3 feet 6 inches, according to the height of the gun carriages to be used.
The half-sunken batteryis constructed the quickest, as the diggers can work both in front and rear, at the same time. In a sunken battery, the diggers are as much crowded as in an elevated one, but, since the mass of parapet to be raised is smaller, it may be completed in much less time.
Casemates, or vaulted batteries, are made bomb-proof, and the embrazures are cut through the revetment.
Barbet batterieshave no embrazures, the guns being placed on traversing platforms to enable them to fire over the parapet.
A direct firefrom a battery is when the line of fire is perpendicular to the parapet, and anoblique firewhen it is oblique. The direct fire being preferable, the battery should be placed parallel to the object against which the fire is to be directed.
The line of fireis an imaginary line drawn through the centre of an embrazure, in the direction of the object against which a battery is constructed.
Embrazuresare openings cut through parapets, flanks of bastions, &c., for guns to fire through.
The neck of the embrazureis the inward, or narrowest part of it.
The mouth of the embrazureis the outward, or widest part of it.
The sole of the embrazureis the bottom, or space, between the cheeks or sides.
The sillis the front of the sole.
The genouillereis that part of the parapet which is immediately beneath the embrazures.
The merlonis the portion of the parapet contained between two embrazures.
The following dimensions are requisite to be proof,
Note.—A 6-pounder shot, with a charge of one pound, will penetrate amass of iceto the depth of 4½ feet, at the distance of twenty-one yards.
GENERAL DIMENSIONS OF AN ELEVATED GUN BATTERY,
DIRECTIONS FOR TRACING A BATTERY.
Batteries at sieges are generally traced in the dusk of the evening.
Detail of men, and tools required:
Tracers.—1 non-commissioned officer, and 2 privates.
Tools.—1 ground-square. 1 measuring tape.
1 white tracing-line. 2 ten-feet rods. 1 bundle of pickets. 1 mallet.
Directions.—The tracing-pickets, and mallet, are carried in a sand-bag, and a few long pickets are necessary to mark the embrazures. A line should be stretched about 40 feet in the direction of the objectagainst which the battery is to be erected; this will showthe line of fire. By means of a ground-square, a line may be laid down at right angles to the former, touching the first placed picket. This will be the interior base line. Another line must be placed parallel to this, at a distance equal to the sum of the breadth of the base of the parapet, breadth of the berm (if any), and breadth of the slope of the ditch (viz., about 27 feet), which line will represent the reverse slope of the ditch. A picket is then driven in on the interior base line, where it is intended to have one extremity of the battery, and as many long pickets (18 feet apart), measuring from this end, as there are guns, which will mark the centre of the embrazures. Then one more picket, 18 feet distant from the last, will show the other extremity. For the embrazures, drive in a picket at the distance of one foot on each side of the centre of the embrazures, for the width of the neck. Set off, and drive in pickets 3 feet 6 inches on each side of, and perpendicular to the line of fire, for the width of the mouth.
WORKING PARTY; TOOLS; AND MATERIALS REQUIRED
for each gun; mortar; traverse; or epaulment; in an elevated fascine battery.
2 sappers, with 6 assistants, to revet the work.
12 infantry, to excavate the ditch, and form the parapet.
9 pickaxes, 15 shovels, or spades, 14 fascines, 18 feet long, 1 bundle of 50 pickets to 6 fascines, 3 mauls, 3 rammers, 1 sawto every two guns,1 hatchetper gun,1 bill-hook, 1 field-service level, 1 six-feet rod, 1 bundle of matchesto every three guns,1 lantern, do., 1 lb.of candles, do.,1 bundle of gadsto each gun,1 tape of 50 feet in lengthper battery.
A battery will seldom be completed in less than 24 hours, when executed by inexperienced workmen; but by those inured to hard labour, and with proper reliefs, in about 10 hours. In light soil, that can be easily dug without the aid of a pickaxe, a man can, in 8 hours, load from 19 to 20 cubic yards of earth on barrows. If a pickaxe be required, 2 men will do the same quantity of work. A man can wheel 20 cubic yards of earth per day to a distance of 30 yards on level ground, or 20 yards on a ramp. Twenty cubic yards of earth will fill 500 wheelbarrows. When near the surface, in soil requiring but little the use of the pickaxe, an excavation of 6 cubic yards in a day of 8 hours would be a fair task for a soldier, who in general is little accustomed to working with the pickaxe and shovel.
SHELTER FROM AN ENEMY’S FIRE.[36]
The following method of sheltering the workmen from the enemy’s fire was used with great success during the construction of the batteries. It was towards the end of the siege that Lieutenant Néandre received orders to construct a battery 130 paces from thecounterscarp, the covered way being strongly occupied by the enemy. Foreseeing the difficulties that would occur, Lieutenant Néandre provided 120 common platform planks, and, when the gabions were in their places, arranged the planks outside them, in such a manner as to present an inclined plane, (one end of the plank being supported on the gabion, and the other end resting on the ground towards the enemy): the gabions were then half filled with earth, and the pickets driven in. At this moment the enemy threw some fire balls, and fired a few shot, all of which went over. Soon after, the workmen were assailed with a well-sustained fire of musketry; but, on the balls striking the epaulment,they ricocheted andpassed over the workmen, so that not a single man was hit. The battery was finished in a few hours, when the planks were drawn in, and used for the platforms.
A portable framework might be rapidly made, and used instead of the gabions, to obtain immediate cover from musketry fire; and, for sapping, the framework, with the planks fixed thereon, might be readily moved on trucks, as a substitute for the present sap roller.
EPAULMENTS.
Batteries at sieges are generally secured on one flank at least, by a parapet called an epaulment, forming an obtuse angle with that of the battery. Their use is to secure the reverse of the terreplein from any flanking fire, and they are not in general made so thick as the parapet, being seldom subject to a direct fire.
ELEVATED SAND-BAG BATTERIES.
The base of the interior slope of a battery reveted with sand-bags is rather broader than that of one reveted with fascines, being about one-third the height of the parapet.Bushel sand-bagsare now the only kind in use, andwhen filled are of the following dimensions:
Sand-bagsare laidheader, andstretcher, as in masonry; the ends which are tied being always hid. As the sand-bags near the neck of the embrazure would be destroyed after a few hours’ firing, and constantly require repairing, gabions, or casks should be substituted for them.
Howitzer batteriesare similar to those for guns, except that the interior openings of the embrazures are 2 feet 6 inches, and the soles are raised, towards the front, about 10°, in order to cover the gunners as much as possible.
Mortar batteriesare constructed with the same dimensions as gun batteries (the parapet being generally 8 feet high, and from 18 to 22feet thick), but, as they have not embrazures, the ditch of elevated batteries is made two feet deeper to obtain the requisite quantity of earth. A preference would in general be given to the sunken, or half-sunken profile for a mortar battery, on account of its requiring less time for its construction, and it being of no consequence whether the platforms are sunken, or otherwise. Mortars are placed at the distance of 15 feet from centre to centre of each other, where no traverses intervene; and the parapet has the same profile as a gun, or howitzer battery.
HALF-SUNKEN BATTERIES.
The sill is about half its total height above the natural surface of the ground; the most convenient depth to which the terreplein may be sunk is 2 feet. The height of a sill for a travelling carriage will be 18 inches, and for a garrison carriage one foot above the natural level. The profile of the parapet isthe same as inan elevated battery.
In forming the epaulment of a half-sunken battery, the earth is taken from a ditch in front, six feet wide, and about five feet deep.
SUNKEN GUN BATTERIES.
The soles of the embrazures are on a level with the natural ground, therefore the terreplein is sunk a sufficient depth for the solid, and, the merlons are formed of the excavated earth. The height of the solid depends on the nature of gun carriage to be used. The first operation is to trace out the embrazures. The profile is the same as in the elevated battery. Should there be traverses, all the earth excavated from the interior will be required; if not, the overplus may be scattered in the rear.
RICOCHET BATTERIES.
Ricochet firingis the art of projecting shot, or shell, with a certain velocity, and in such a direction as to ensure its striking the ground at any spot that may be required; afterwards making several grazes upon the earth, and destroying, or striking all that may oppose its progress. The piece of ordnance is loaded with a diminished charge of powder, and the elevation is from 3° to 10°, which causes the shot to bound or hop along the ground. The smaller the angle under which the shot is made to ricochet, the longer it will preserve its force, and have effect, as it will sink in the same proportion so muchless into the ground on which it bounds. In the ricochet of a fortress, or field work, the elevation should seldom exceed 10° to throw the shot over the crest of the parapet; but in the field, the objects to be fired at being principally infantry, and cavalry, the guns need seldom be elevated above 3°; as, under greater angles, the shot would be apt to bound too high, thereby defeating its intended purpose.
Ricochet batteriesshould, if possible, be at a distance of 400 yards, or not exceeding 600 yards; as, from the uncertainty of the fire at a greater distance, at least two-thirds of the ammunition might be expended without producing any good effect.
The best elevation to enfilade a workbeing from 6° to 9° measured above the parapet, the charge should be regulated accordingly, which varies from one-half, to one-tenth the service charge.
Ricochet firingis very efficacious in dismounting the guns on the faces, or flanks of bastions, &c., the batteries for this purpose being erected on the prolongation of these works, and as nearly as possible perpendicular thereto, by which their whole length will be exposed to the effects of plunging, and destructive ricochet fire.
Vide Tables of Ricochet practice,pages 73,79,80.
FASCINES.
Fascinesare bundles of wood of various lengths, according to the purposes to which they are to be applied.
Fascinesfor a revetment should be strong, and well bound. When small brushwood is used,they are made 6 feet long, and 7 inches in diameter, and are firmly bound with four or five withes, or gads.
The gadsare made of tough twigs, first twisted until the fibres separate, the smaller end is then turned round, so as to form a loop, or noose. To make a fascine 6 feet long, the workmen set up three fascine horses on the same level, and in a right line.
(A fascine horseis formed with two pickets, each 5 feet long, driven about 1 foot obliquely into the ground, so as to cross each other at right angles 2 feet above the surface of the earth; and they are fastened together at their point of meeting, with cord, three or four-thread spun yarn, or gads.) The brushwood, stripped of all its leaves and smaller branches, and which should be from half to one inch in diameter, and 5 or 6 feet long, is then laid on the fascine horses, the thick ends being placed alternately at each end. The large stuff must be used to form the exterior, and the smaller twigs the interior of the fascine. Before binding the fascine, it must be compressed with afascine choaker, which consists of a cord, or chain, equal in length to one and a half times the circumference of the fascine, fastened at one end to a lever 5 feet long and 2½ inches in diameter, with a loop at the other end, into which, after passing the chain round the fascine near the part to be bound, a lever, similar to the one already described, is inserted, and the brushwood is squeezed tightly together until the gad is tied. The fascine must be compressedin a similar manner before each gad is fastened.The weight of the fascineis about 33 lb.Three men can make a 6 feet fascine in twenty minutes.Two of the workmen place the brushwood, while the third prepares the gads. If large brushwood can be procured, the fascines should be 18 feet long, the strength of the revetment being materially increased by diminishing the number of joints.When the fascines are 18 feet long, they are made nine inches in diameter, and the gads are placed 18 inches apart, the fascine horses being one yard apart.This fascine weighsabout 2 cwt.Four men can make an 18 feet fascine in two hours, or, if the wood be cut and brought to them, they can make four fascines in that time.They require 3 bill-hooks, 1 saw, 1 fascine choaker (each lever about 6 feet long), and 6 fascine horses.Three men prepare the brushwood, and lay it on the horses, while the fourth makes the gads.
The revetment is formed in proportion as the parapet is raised, the first fascine being half buried in the banquette, with three pickets driven vertically through it, each picket being from 3 to 4 feet long, and from 1¼ to 1½ inches in diameter at the thickest end. The second row of fascines is then laid a little in front of the first, so as to form the required slope, and three pickets are driven through each fascine; the extreme pickets through the fascine previously laid in the direction of the slope, the other perpendicular to the slope.
The joints of the different rows of fascinesshould be so broken, that no two adjoining joints may be in the same line, and the ends of the fascines at the angles should alternately be flush with, and be inserted in the parapet; care being taken to lay the fascines so that the ties of the gads may be concealed in the parapets. Six rows of large fascines are sufficient to form the revetment of a parapet, the upper row being covered with a layer of sods, the grass upwards. When fascines of seven inches in diameter are used, eight rows are required.
GABIONS.
Gabionsare cylindrical baskets open at both ends, and are very commonly used to revet parapets. For the interior of parapets they should be3 feet in height, and diameter.The common gabions are 2 feet in diameter, and 2 feet 9 inches high.
To make them.—A directing circle consisting of two hoops, kept apart by bits of wood, to which both the hoops are secured with packthread, is first made. The diameter of the hoops must be such as to permit of the pickets for the gabion being driven between the exterior of the one, and the interior of the other. The directing circle is then laid on a level piece of ground, and from seven to twelve pickets are driven at equal distances apart, between the hoops; the number of pickets depending on the size of the rods, or brushwood with which the basket-work is to be made. The circle is then raised, and fastened to the middle of the pickets, and the web is made above it, two or three rods being used at the same time; the workman twisting them round each other while he interlaces them with the pickets, striking down the web from time to time with a stick. Theranding, orbasket-work, is continued to near the top of the pickets, where it is secured with four gads, each one passed round one of the pickets and four or five of the rods, which should be from 8 to 10 feet long, and not more than half an inch in diameter. The gabion is then pulled up, the finished end is placed on the ground, and the directing circle being removed, the remainder of the web is completed and secured as before described.
Two men can make a gabionin three quarters of an hour, using about 80 rods for each gabion.
In forming the revetment, the gabions are placed touching each other with a slope of one quarter the height; the first row is surmounted with two rows of fascines side by side, and a second row of gabions rests on them.
SOD, OR TURF.
A revetment is sometimes made with sods of unequal sizes, calledheaders, andstretchers.
The headers are 1 foot 6 inches long, 1 foot wide, and about 4½ inches thick.
The stretchers are 1 foot wide, and long, and about 4½ inches thick.
Sometimes the sods are first cut all of the same dimensions—viz., 1½ foot long and 1 foot wide; this sod is then cut diagonally, across, so as to form two, and they are then all laid as headers. This saves nearly half the turf, and labour. The sods should be cut from good meadow land, previously mown, and watered; but the sods should not be laid or built when wet, because they would shrink in dry weather, and all the joints would open. The sod-work is laid with the grass downwards, either alternately headers, and stretchers, or two stretchers to one header; care being taken that the joints of no two rows fall immediately over one another, which is termed breaking joint. If the layers of sods are laid perpendicular to the slope, they will answer better than if laid horizontally. Each sod should have two or three pegs driven through it, to secure it to the work beneath. When the revetment is completed, the whole should be cut off smooth to the proper slope; a pair of hedge-clippers, or a cutting knife, will answer well for this purpose.
One man can lay 19 square yards of sod-work in eight hours, when the sods are brought to the spot, and require no previous trimming.
PLATFORMS.
To facilitate the working of a gun, it must be placed on a platform of stone, or timber and plank: but, as a temporary measure, when required to fire only in one direction, timbers to take the wheels will suffice. The usual inclination given to platforms, from the rear to the front, is half an inch per foot. Platforms on barbettes should be perfectly level, and their dimensions must depend on the extent of the lateral range which may be required.
In laying a gun platform, the first thing to be done is to fix thehurter, which may be a piece of timber 7 or 8 feet long, and 7 inchessquare, or a strong fascine 9 feet in length may be advantageously used. The hurter is intended to take the wheels, or trucks of the carriage when the gun is run out, and to prevent their damaging the interior slope of the parapet. The position of the hurter necessarily depends therefore on the steepness of the interior slope. The hurter should be placed perpendicular to the axis, or central line of the embrazure. Three, four, or five sleepers of from 6 to 8 inches square, are then laid, their upper surface on a level with the bottom of the hurter, and they are covered with two-inch planks, nailed down when three sleepers are used; but if there be four or five sleepers, the planks may be confined by tworibbands(which are pieces of wood of the same length, but weaker scantling than the sleepers) and the platform racked down withrack lashingsat the proper intervals.
A rack lashingconsists of a piece of 2-inch rope about 9 feet long, which is fastened to a stick 15 inches long, 2 inches wide at the head, with a hole in it to receive the lashing, and tapering to a blunt point: it is passed round the timber, and sleeper beneath, then twice round itself. The end of the stick is then put into the loose gromet so formed, and twisted round until the whole is firmly secured, when the stick is turned flat on the upper piece of scantling.
The gun, and mortar platforms for sieges are now made rectangular: the dimensions of the former are 15 feet long by 10 feet 6 inches broad; those of a mortar platform are 7 feet 6 inches long by 6 feet 6 inches broad. Mortar platforms are laid exactly horizontal, the front part being placed 5 feet within the foot of the interior slope of the parapet.
Madras platformsconsist of two stout planks about 12 feet long; they are supported on two sleepers, having a transom in front. The planks are secured with a moveable bolt, or pivot to the front transom, slide freely on the sleepers, and are connected together in rear by two cross pieces parallel to the rear sleeper, one in front, and the other in rear of it. To the centre of these two cross pieces is bolted another 12-feet plank, called the trail-piece, of a width equal to the distance between the cheeks of a siege-carriage, which is supported on a sleeper in the rear. When the gun is to be traversed, the whole platform is moved on the sleepers on the pivots in front. These platforms are chiefly intended for a direct fire. Two wedges are required for this platform to form inclined planes for the wheels, in running the gun on, or off the platform. Each wedge is of elm, 3 inches thick, 2½ feet long, and 1 foot wide, with a block to give the requisite height, the block being 12 inches long, 4 thick, and 7 in extreme height.
Alderson’s platform.
The platform invented by Colonel Alderson, R.E., is 15 feet long, by 9 feet wide; and is composed of 46 similar pieces of timber (baulks) each measuring 9 feet × 5 inches × 3½ inches. Of these, ten are used as sleepers, and the remainder as planking. The weightof the platform (when 15 feet long and 9 feet wide) for guns is 15 cwt. 2 qrs. 14 lb. By addition of the small beams, this platform may easily be extended from 15 to 18 feet.