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.CHAPTER VI.

ARTILLERY MATERIAL.

The term artillery material, includes all carriages and machines used for the service of the pieces, for the transportation of the munitions of war, and for the establishment of the movable bridges necessary on the marches of an army. In the United States' service, the term is more restricted, and does not include the apparatus for bridges, which is placed under charge of the engineers; a special company having been formed during the Mexican war, and kept up ever since.

A gun carriage is the machine on which a piece is mounted for manoeuvering and firing.  Those first in use consisted of blocks of wood or frame structures, upon which the ancient bombardes were fixed, by means of iron work. These machines, made in imitation of the mountings of small-arms, bore the names "fust," "fustage," "house," the first of which seems to be derived from the latin fustis (club, baton), from which the French have derived their term affut, (gun-carriage).

In the next form, Fig. 116, the framework was mounted upon wheels, or rather rollers, by means of which the piece was transported and fired horizontally. When the arm was of small calibre, it was mounted upon a light wooden horse, or placed on a small wheel-barrow, which served to transport and fire it.

When trunnions were first used on guns, the carriages had assumed pretty much the form they now have. And from the time of Louis XI and Charles VIII. (1461), a limber was used with the carriage, and taken away, as now, when the piece was to be fired. The horses were harnessed to it in single file, as in heavy drays of the present day.

Valliere's System .-- The structure of gun carriages in France, has undergone but little modification from the earliest times; and even Valliere's system did not change it. His system regulated simply the calibre of the pieces, and did not extend to the carriages, the forms of which were very variable. Gun and howitzer carriages preserved the old forms. Those for mortars were not so high, and had no wheels. As formerly, the supplies were transported in carts, the horses being still harnessed in single file.

In battle, a pile of balls, one of wads, and a barrel of powder, were placed near each piece. The charge was taken from the barrel and placed in the piece with a kind of long–handled ladle. (Fig. 119.)  This kind of artillery, devoid of all mobility, was more particularly suited for the attack and defense of fortified places.

Gribeauval's System succeeded that of Valliere in 1765, and was the first in which the different parts were perfectly regulated and made uniform, so that the parts of any carriage could be used on any other of the same kind.

A tongue was used and the horses harnessed double, which enabled more rapid movements to be made, and shortened the columns of troops very much. Frown this period, we find established a distinction between siege, garrison, sea-coast, and field artillery; and in the last-named the charges all ready for use were carried in boxes called caissons .

Desirous of giving to his system the greatest possible lightness and mobility, Gribeauval calculated the minimum dimensions which the different parts of his carriage should leave; but, from this results the grave inconvenience of a great multiplicity of kinds, which rendered their replacement in war very difficult.

The mode of harnessing the horses in this system, was especially calculated to preserve them. In the year XI. attempts were made to modify the system, but were not successful except in the bridge equipage, which was made much lighter.

Each piece had a, particular, gun-carriage, and its own sized wheels. The greater part of the wagons also had distinct wheels. The limbers were simplified, and some could be used with several different carriages. Eighteen different hinds of wheels were used. In 1814, there were in France seven kinds of field gun-carriages, six of siege, four of garrison, four of sea-coast, and flour of mortars. These are now reduced to two of the 1st and 2d; four of the garrison and sea-coast, one mountain and four mortar carts.

U. S Carriages .-- The most essential properties of the present artillery material both of France and this country are: its mobility, and the reduction of the different kinds to the smallest possible number. All field-carriages in the U. S. service have the same limber, and the wheels are all of the same form and height, and fit on the same axle-tree. They differ only in strength and weight. There are two numbers: No. 1, the lightest, is used for the 0-pound gun-carriage, the caisson, forge, battery-wagon, and the limbers of all field-carriages; No. 9, the heaviest, for the 24-pound howitzer and 12-pound gun-carriages.

For siege service, all the wheels are the same, and used indiscriminately on all gun-carriages, limbers, and mortar-wagons.  The same limber is used for all siege-carriages.

Gribeauval's carriages were provided with swingle-trees and movable splinter-bars, like a stage, with a view to give the horses all possible liberty of motion. This arrangement made the two parts of the carriage dependent upon each other; allowed but little flexibility; the connection between the two often broke; the smallest obstacle would overturn, or separate the two parts; and the caisson could not turn with sufficient ease. It was difficult to limber and unlimber, the trail being very heavy, and it being necessary previously to lift off from its position on the trail the heavy box which contained the ammunition. Manoeuvering with the prolonge in presence of the enemy became necessary, which rendered the draught extremely difficult, and caused many accidents.

The swingle-tree, being liable to get out of order and break, is now entirely dispensed with. In field-carriages, the end of the tongue is supported by the horses; and the two parts being united at a single point, are perfectly flexible, and can pass over the roughest ground without accident. The separation of the two parts is effected without any difficulty, and the use of the prolonge in the presence of the enemy is now almost entirely abandoned.

The siege-carriages serve not only to fire the pieces from, but also to transport them. Garrison and sea-coast carriages can be used only for the former; though some of them are so made as to be able to transport the piece for very short distances, as from one face of a fortification to another.

The French use bronze for their nave-boxes entirely, as the less friction of the iron axle –tree against it is favorable to the draught. Bronze is used in our siege-carriage wheels, but cast iron in the field-carriages.  The English have a field-carriage similar to our own; but the fore-wheels are smaller than the hind ones; and instead of having one ammunition-box extending all the way across the limber, they have it divided in two, leaving an interval between to enable them to limber the piece, the pintle-hook being very long, and extending up above the bottom line of the boxes.

Instead of a pin for the pintle-hook, a hinged hasp is used, which turns down over the top of the pintle-hook, and has to be raised and turned up in the interval between the two boxes before the piece can be unlimbered. No particular advantage is obtained frown this arrangement; and it has the great disadvantages of lessening the capacity of the box for ammunition, and destroying, or at least impairing very much, its quality as a seat for cannoneers.

By means of the modifications made in the Gribeauval system, the mobility of the carriages is increased. Repairs, always so difficult in war, are made with greater ease, the parts being able to supply each other's places; and the field artillery possesses all the necessary means to seize promptly the favorable occasions to act during a bottle.

Gun-carriages may be divided into movable and stationary carriages. To the former class belong those used in the field and for siege purposes. The conditions which they should fulfill will now be examined.

Movable carriages are used for the transportation of the pieces, as well as for firing them; and are, for these purposes, mounted on large wheels.

In firing, the carriage should yield to the recoil. Were it fixed immovably, it would soon be destroyed, no matter how great its solidity. Its weight should. be proportional to that of the piece. It' too heavy, it would soon be destroyed by the shocks of the piece. If too light, the recoil would be immoderate. The weight should always be less than that of the piece. Too heavy a piece upon too light a carriage will perform better service than the reverse arrangement, since the effort exerted by a piece is a function of its mass into the square omits velocity.

The carriage consists of two cheeks, connected together and with the stock by assembling-bolts. The front parts supports the piece, and rests upon an axle-tree furnished with wheels, the back end of the stock or trail resting on the ground, and forming the third point of support for the system.

The parts of the carriage between which the piece is placed are called the cheeks. In ancient carriages these cheeks extended all the way to the ground, joined to each other by transoms and bolts; but in the new, the cheeks are short, and fastened upon a stock formed of two pieces close together, and terminating in the trail.

The wheel is composed of a nave, into which the axle-tree enters; of a certain number of spokes fastened in the nave; and the circumference of the wheel, which is composed of a number of felloes equal to half the number of spokes.

The wheels are always made with a certain convexity called the dish. The obliquity of the spokes gives elasticity to the wheel, and protects it from shocks which, were the spokes in the same plane, would destroy it. The dish should increase as the ground to be passed over becomes more broken.

The object of the dish is, for the purpose of making the body of the carriage wider; to diminish the length of the axle-tree, thus increasing its strength; to t hrow the mud and water outside the wheels; and to tend, from the effect produced by the decomposition of forces, to keep the wheel close against the carriage, and prevent any tendency to run off the axle.

As the weight of the carriage should not be increased beyond a certain point, it is only by making use of friction, skillfully applied, that the recoil can be diminished. The friction of a wheel is proportional to the ratio between the radii of the wheel and axle. The recoil of the carriage may be diminished by decreasing the diameter of its wheels, or increasing that of its axle. For this reason, certain carriages (as, for example, mortar-beds) have been mounted upon rollers, and others upon wooden axles, with truck wheels.

The weight of the wheels, as it adds to the weight of the carriage, tends to diminish the recoil. If they are too heavy, they strain the axle-tree very much, and tend to bend it. The wheels slide along the ground at first, and commence to turn only after a certain length of time; but once they have acquired a certain velocity, they carry the carriage with them until this velocity is destroyed.

The position of the trunnions exercises some influence over the recoil. The higher they are placed above the axle-tree, the greater is the arm of the lever which tends to force the trail into the ground, the more energetic is this tendency, and the more is the recoil diminished.

For a given angle of fire below the horizon, or for a given length of carriage, the carriage tends to overturn to the rear, raising the wheels. The angle of incidence of the line along which the shock of the piece is transmitted to the ground, has a great influence on the recoil of the carriage.

For siege-guns and howitzers, the ancient carriages were very heavy, as were also the wheels. The axle-tree was of wood, the elasticity of which was necessary to prevent accidents. Though the carriage was very long, which diminished the angle of incidence of the force of recoil, the actual recoil was diminished by the great weight of the carriage and the friction of the axle in the nave.

In the more modern carriage, the axles are of iron, and the nave-boxes of iron or bronze, which decreases the friction. The trunnions are nearer the stock, and the carriage, though lighter, is shorter, and hence the pressure exerted by the trail on the ground is increased, and the recoil kept within proper limits. Pieces, especially those which are light relative to their projectiles, strain their carriages a good deal, particularly when the firing is at angles of elevation. Thus, a Howitzer-carriage which will resist a horizontal fire perfectly, is liable to be broken when fired under a large angle. The only means to obviate this inconvenience is to favor the recoil at first.

Gribeauval's howitzers, which were very light in proportion to their projectiles, and which were mounted upon very heavy carriages with wooden axles, frequently caused accidents when they were fired at long ranges, or under large angles of elevation.

When the space in which a piece is fired is limited, its recoil may be reduced by using a rope, which, acting gradually, does not break the carriage. The rope is tied to the felloes near the highest point of both wheels, leaving a portion slack, which, catching on the stock when the piece recoils, forces the trail into the ground.

Mortars, which are still lighter than howitzers of the old model, and which are habitually fired under large angles, should never be mounted upon wheel-carriages; fort heir recoil being very violent and almost direct, would break and crush the axles. For this reason mortar-carriages are without wheels.

In general, a gun-carriage should be so made as to be easily placed in the direction of an object, and allow the piece different degrees of elevation or depression within the limits recognized as necessary for the kind of service in which it is to be used. It should also be such as to be easily manoeuvred by the smallest possible number of men for any particular calibre, and its recoil should be restrained within proper limits.

Carriages with two wheels, or carts, enjoy some special advantages, but they have the disadvantage of requiring the first horse attached to them to bear a part of the load, which diminishes his draught powers, and the rate of travelling. This fact, recognized from the earliest times, led to the adoption of the fore-wheels in the form of the limber, by which the cart becomes a four-wheeled vehicle, which runs easier, and is more serviceable.

It is apparent that for the proper manoeuvering of the piece, it is of importance that the connection between the gun-carriage and its limber should be as easily and as promptly made as possible.

The gun-carriage and its limber united form a four-wheeled vehicle, which should satisfy the same conditions as other carriages.

In all kinds of carriages. the ease of draught is increased by < enlarging the diameter of the wheels and decreasing those of the axles. There is, however, but little advantage in using wheels more than from 58 to 62 in. high. Those used in our field service are 57 in., and those for siege-carriages, 60 in. high.

Formerly, the greater part of the axletree was made of wood, fitting into nave-boxes of iron, which caused a considerable amount of friction; but the elasticity of these axles was indispensable in preserving certain very heavy carriages, which did not run easy. Gribeauval adopted the use of iron axles for the greater part of field-carriages, with bronze for the nave-boxes. This arrangement allows the axles to be made smaller, diminishes the friction, and favors the draft, and these last objects are farther attained by the use of grease.

Increasing the diameter of the wheel diminishes the draft in soft ground; as the large wheel bearing upon a greater number of points, makes a shallower rut. This is also the case with wide felloes.

The large wheel is also advantageous for surmounting obstacles. One wheel twice the height of another will surmount, other things being equal, an obstacle twice as high as will the small wheel.

On the other hand, as the dimensions of the wheel increase its weight and price become greater, so that beyond 58 inches, the advantages to be gained in a few particular instances are not sufficient to outweigh the objections to a further increase in diameter.

It may be remarked besides, that if the axletree be higher than the breast of the horse, there would be a decomposition in the tractive force, and the carriage would be different to manage in going down even the most gradual descents. In this view, then, there is a limit to the size of the wheel. As the horse acts from the shoulder, the traces ought to be inclined downwards from that point. For an unloaded horse, the most advantageous angle of traction appears to be about 12º; but when he carries a rider, as his shoulders are already loaded the most advantageous angle is reduced to 6º, which is about the angle made by the traces in the carriage now adopted. This limits the height of the wheel to about 58 inches. But as only one of the horses in each couple carries a rider, it results that the most advantageous angle of traction is really comprised between 6º and 12º.

When the carriages are designed to pass over very unequal broken ground, there is an advantage in the wheels of both parts being equal in height; for, were they unequal, the smallest-turning the quickest to get over the same distance-- experience more resistance, and often slide in place of turning; besides which, a small obstacle, as a stone, would suffice to stop them.

When the ground passed over is very undulating, there is an advantage in the two parts of the carriage being connected by a single point, for then they might be on differently  inclined ground without hampering or dragging each other. The force of traction of the limber is then applied to the axletree of the rear carriage, and its action is as direct as possible.

In this hind of carriage, the centre of gravity should be as low as possible, in order that the carriage be less liable to turn over.

The distance between the axletrees of the limber and rear carriage is of great importance. As the carriage should be able to pass over the sharp crest of a hill, it should not be too long; for it might happen that the body would catch on the summit and the wheels be suspended on each side. Taking 30 degrees as the maximum slope accessible to artillery, and we have for the distance between the two axletrees:

For field artillery, 99 inches. It really is 96 inches for the light pieces, and 101.7 inches for the heavy, in field artillery. In field artillery carriage, as the horses bear all the weight of the tongue, it is made as light as possible in order not to be too fatiguing for the rear team.

In siege artillery it can be made much heavier and stronger as it is held up by the trail bearing upon its rear end.  To facilitate manoeuvering, the carriages should have the greatest turning capacity possible.

Two-wheeled carriages are the only ones which can turn on their own ground. Four –wheeled ones always have to describe an are of a circle. In carriages which have all the wheels equal, the necessary turning capacity has been given by reducing as much as possible the width of the middle part of the carriage, employing for that purpose a narrow stock. By this means, the modern carriage has at least as great a turning capacity as Gribeauval's, the fore wheels of which were the smallest.

In four-wheeled carriages, the two parts should be loaded in proportion to the diameter of the wheels. The front wheels, breaking the road and forming the rut, meet with more resistance than the hind wheels, and should not be too heavily loaded. Other things being equal the weight which they carry should be to that on the hind wheels as to 2:3.

The length of the axletree and the dish of the wheel, determine the width of the track, which is the distance between the impression of the wheels on the ground measured from centre to centre. A knowledge of the track of a carriage and the length of its axletree, is indispensable in making reconnoissances of defiles and routes to be passed over by columns of artillery.

The track of all our carriages is 60 inches, and the greatest length of axletree is 81.8 inches (siege); the field axletree being 78.84.

Field-carriages should be able to carry a sufficient quantity of ammunition to prevent the possibility of the pieces being without it, and to seat the cannoneers when it becomes necessary to move at rapid gaits.

All possible liberty should be allowed the horses when harnessed, in order that the action of one may not shackle the others, that accidents may be as rare as possible, and that killed and wounded horses may be replaced easily and promptly.

A draught-horse can draw 1,800 lbs. 23 miles a, day, weight of carriage included, on a, good smooth road, and 3,000 lbs. on a paved road. At a trot, and on good roads, the weight is reduced to 840 lbs. In the French field artillery, each horse has to draw 720 lbs. In our service it varies from 530 to 760 lbs. for the field service, and from 900 to 1,000 lbs. for the siege.

As, upon ordinary roads, a horse can draw about seven times as much as he can carry, and the mule about the same, it follows that military stores and machines should be packed only when they cannot be drawn.  A good pack-horse or mule can carry from 250 to 300 lbs. 20 miles a day.

The quality and degree of mobility of the different kinds of material, should be in keeping with their destination. Hence results its division into different classes, according to the kind of service in which it is used. 1st. Field material. 2d. Mountain. 3d. Siege and garrison. 4th. Sea-coast; and 5th. Bridge equipages.

FIELD MATERIAL.

It is composed of six different carriages, all having the same kind of limber and the same sized wheel, so that any limber or any wheel may be used with any carriage, though if possible the heaviest wheel (No. 2), should be used on the carriages of the three heaviest pieces, 12-pd. gun and 24 and 32-pd. howitzers. The two parts of these carriages are connected by a stock, by means of a pintle hook and lunette. In consequence of this single point of connection, the tongue is not influenced by the movements of the rear part of the carriage, a matter of some importance in regard to fatiguing the horses.

The independence of the two parts requires the weight of the tongue to be supported by the horses, and it is consequently made as light as is consistent with its proper strength.

Thus constituted, these carriages can manoeuvre easily on very rough ground, which they are often required to pass over. The disadvantage of the way in which the horses are harnessed to these carriages, results from the oscillations of the tongue, which is very fatiguing to them, although the improvements introduced in the harness have reduced this defect very much.

The six carriages are:

1. The carriage for the 6-pd. gun and 12-pd. howitzer.

2. The carriage for the 24-pd. howitzer, and formerly for the 9-pd. gun also.

3. The carriage for the 12-pd. gun and 32-pd. howitzer.*

4. Caisson.

5. Battery-wagon; and

6. Travelling-forge.

* The new 12-pdr. gun is mounted on the 24-pdr. howitzer carriage, the cheeks being somewhat shortened and the elevating screw brought forward.

1, 2, and 3, The Gun-carriages , Fig. 120, Pl. 17, consist of two short cheeks of wood, bolted upon a stock and wooden axle-body, in a recess of which fits the iron axle on which the wheels are placed. The stock terminates in a trail and trail plate, which rests on  the ground, and has on the end a strong ring called the lunette, which is placed on the pintle hook when the piece is limbered. In the stock is placed an elevating screw-box of bronze, in which the elevating screw fits.  The limber consists of a similar axle-body,  axle, and two wheels: and on these rests a framework to receive the tongue.

On top of the whole is an ammunition chest, the top of which forms a seat for three cannoneers. To counterbalance the weight of the tongue, the centre of gravity of the chest is placed a little in rear of the centre of the axletree. It should be carried still farther back, as, when the chest is loaded, the weight on the necks of the wheel-horses is so great that without some arrangement for relieving them on the march, the necks are soon galled, and the horses rendered unfit for service. On long marches this defect is soon made manifest, and whilst crossing the prairies in 1861 I had temporary racks constructed on the rear of the chest, in which the men's knapsacks were placed. In rear of the axletree is a pintle hook to receive the lunette of the trail. Connected with the framework in front is a fixed splinter bar with four hooks, to which are attached the traces of the rear team of horses.

At the extremity of the tongue are placed two pole-chains, by which the pole is held up, and a pole-yoke with two movable branches, to prevent as much as possible the pole from oscillating and striking the horses. Each of these branches has on it a freely sliding ring, which is connected by a chain and toggle to the harness of the horse, and allows him greater freedom of motion. The pole-chain is hooked on to a ring on the breast-strap. The traces of each horse of the front teams are hooked on to those of the horse in his rear, just behind the collar, and are suspended by his sides in scabbards. (For dimensions, weights, &c., see Appendix, p.421.)

4. The Caisson , Fig. 121, Pl. 17, is a carriage to transport ammunition, with three ammunition-chests similar to the one on the limber of the piece. All caissons are the same on the exterior. They differ in their interior compartments, which vary according to the nature of the ammunition with which they are loaded.  On the axle-body of the rear part, and in a direction parallel to the stock, are placed three rails, upon which are fastened two ammunition boxes, one behind the other; so that the caisson has three ammunition boxes, which will seat nine cannoneers. A wooden stock and lunette serve, as in the gun-carriages, to connect the two parts together.

In rear of the last box is placed a spare wheel axle of iron, with a chain and toggle at the end of it. On the rear end of the middle rail is placed a carriage hook, similar to a pintle hook, on which the lunette of a gun-carriage whose limber has become disabled, may be placed, and the gun carried off the field. Under the hind axle a spare pole ring is placed, through which an extra pole is run, and sustained in its position under the stock by a key plate and key fixed beneath, near the lunette.

The caisson has the same turning capacity and mobility as the gun-carriage, so that it can follow the piece in all its manoeuvres if necessary.

The object of the caisson is to carry a supply of ammunition, the limber of the gun –carriage carrying the instruments for use with the piece, and such ammunition as may be necessary for its immediate use. The caisson has also slots left in the iron assembling-bars, between and in rear of the boxes, for the reception of an axe and a pick, and at the side and under the boxes, staples and other arrangements for securing a long-handled shovel and a spare handspike. (For dimensions, weight, and equipment, see Appendix, pp. 423 and 432.)

5. The Battery-wagon, Fig. 122, Pl. 18, consists, besides the limber, of a long-bodied cart with a round top, which is connected with the limber in the same way as all other field-carriages. The lid opens on hinges placed at the side; and in rear is fixed a movable forage-rack, for carrying long forage.

One of these battery wagons accompanies each field-battery, for the purpose of transporting carriage-makers' and saddlers' tools, spare parts of car riages, harness, and equipments, and rough materials for replacing different parts.

Both this and the forge are made of equal mobility with the other field-carriages, in order to accompany them wherever they may be required to go.

The cover is made of light pine, tongued and grooved, and covered, after being painted, with canvas. (For dimensions and contents, see Appendix, pp. 436 to 442.)

6. The Forge , Fig. 123, Pl. 18, consists, besides the limber, of a frame-work of three rails and cross-ties, on which is fixed the bellows, fire-place, &c. The stock, held up by a prop, serves as a support for a vice. Behind the bellows is placed a coalbox, which has to be removed before the bellows can be put in position.

In the limber-box are placed the tools for use with the forge, horse-shoes, nails, and spare parts (iron) of carriages, harness, &c. One of these forges accompanies each field-battery, and others are provided, equipped for general service with the army.

The forge should be as light and movable as possible, in order to be able to repair promptly to the assistance of any carriages which may become disabled. (For dimensions, weight, and equipment, see Appendix, pp. 423 to 441.)

Mountain ARTILLERY .-- The material for mountain artillery service consists of, a gun-carriage for the 12-pd. mountain howitzer, without a limber; ammunition-boxes for the supplies and stores, and a portable forge, which is carried in boxes.

The Carriage , Fig. 124, Pl. 19, is formed like the field gun carriage, but much smaller, the cheeks not being formed of pieces, distinct from the stock, but all three made of two pieces bolted together. The axle-tree is of wood, which lessens the recoil, and gives an elasticity to the whole carriage better adapted to resist the shocks of firing. The wheels are but 38 inches high. Ordinarily, over rough ground, the carriage is transported on the backs of mules; but where it is possible to do so, a pair of shafts is attached to the trail in such a way as to keep it from the ground, and the piece is dry on its Carriage by harnessing One Of the pack–mules to it.

The ammunition for the howitzer and the cartridges for small arms are carried in the ammunition-boxes on the backs of mules, two boxes to each mule. The same kind of pack-saddle is used for carrying the piece, carriage, ammunition, and forge. The transom on each side of the saddle has a circular notch cut in it, to receive the trunnions of the piece, Which is carried with the muzzle to the rear.

For the transportation of a single piece, its carriage, and ammunition, three mules are required.

On the 1st is placed the piece, and shafts of the carriage, weighing 251 lbs.

On the 2d is placed the carriage and implements, weighing 295 lbs.

On the 3d is placed two ammunition-chests, weighing about 238 lbs.

To attach the shafts to the trail, the supporting bar is laid on the trail-plate, near the handspike-staple, the projecting knee in rear of the lunette resting on the cross-bar plate; these two pieces having holes through them, by means of which, with a pin, they are keyed together. (For dimensions, weights, &c., see appendix, p. 442.)

The recoil of the carriage being considerable, it is limited as heretofore described (especially when the ground on which the piece is used is very narrow), by attaching a rope to the top parts of the wheels so as to press against the trail when the carriage recoils.

The Prairie Carriage .-- The necessity for a s mall carriage for the mountain howitzer when used on our western prairies, has led to the adoption of a special carriage for that service, with a limber attached as in a field-carriage. This gives a carriage less liable to overturn, and preferable in many ways for that service to the two-wheeled one. The limber is furnished with two ammunition-boxes, placed over the axletree and parallel to it, and just wide enough for one row of shells and their cartridges.

The caisson for this new carriage is a two-wheeled cart with shafts, on which are filed four boxes for ammunition, similar to those on the limber, but placed perpendicular to the axletree, and a fifth box for equipments, &c., in front of the other boxes, perpendicular to them, and resting against their ends.

The Portable Forge is designed for service in a mountainous country, where wheeled vehicles cannot travel, for the purpose of making repairs not only for the artillery, but for all other arms of service taken on such expeditions. Its construction is as followers:

The hearth is of sheet-iron, bent into a hollow form, and rivetted to an iron frame. The back of the hearth is bent under the bottom and rivetted to it. The border of the hearth is bent round the back, and is rivetted to it and to the frame. The back of the fire-place is of sheet-iron, connected with the back of the hearth by two hinges, which are rivetted to each.

The edges of both the back pieces are stiffened by strips of sheet-iron riveted to them. An air back is formed by a piece of sheet-iron, bent hot into a convex shape, and rivetted to the inside of the plate of the fireplace. A button, turning on an axis which is rivetted to the outside of trio back plate, serves to fasten this plate to a stud in the front border of the hearth, when the back is turned down on its hinges.

The frame is supported by three legs, which are connected with it by bolts, so that they can be folded up close to the frame. The front leg is divided into two branches, which are bolted to two eye-pieces which are rivetted to the sides of the frame. The two other legs are connected together by a cross-bar, with a nut at each end. This bar supports also the fork in which the bellows handle works. The legs of the frame have round tenons at the lower ends, with shoulders which rest on three socket plates attached to the side of the forge-chest, for the forge to stand on when set up for use.

The bellows handle is of iron, with a wooden head. It is attached to a fork which fits in a square hole in the cross-bar joining the rear legs of the frame. The lower end of the handle is hooked into a connecting rod. attacked to the rear end of the bellows; it is fastened to this rod by a sliding catch which is secured by a thumb-screw. When the bellows is dismounted, this rod is hooked into an eye on the upper side of the bellows, to keep it closed.

The Bellows .-- The frame consists of an upper, a lower, and a middle plank (walnut), and two ribs (poplar), connected by a cross-head, as in a common smith's bellows. There are valves in the middle and the lower plank.

A bar of iron, attached to the middle plank, terminates in two journals, which support the bellows, fitting in the joints of the rear legs of the frame of the forge.

The nozzle, of sheet-iron, is inserted into the cross-head, above the middle plank. It enters into a cast-iron pipe which is attached to the rear of the forge back by means of a bridle bolted to the back plate of the hearth.

A handle is attached to a plate which is fastened on the upper bellows plank. A leaden weight of one pound is attacked to the inside of the lower plank, by the rivets which hold the eye-plate on the connecting rod.

The bellows leather (calfskin) is fastened to the planks by small bellows-nails. A small anvil accompanies the forge, and is fitted into a block of wood, and fastened with an iron pin.

The forge is made to pack into two boxes similar to the ammunition-boxes, and is like them carried on the back of a mule. Weight, 232 lbs., which includes the weight of the blacksmith's tools and materials necessary for the use of the forge. The carriage-maker's tools, and coal for the forge, are carried in two similar boxes on another mule. Weight, 115 lbs.

As all this material is made to be packed on the backs of mules, it can be carried over the roughest country.

Siege Material .-- The material for service in sieges consists of

1st. Gun-carriages.

2d. Platforms for these carriages.

3d. Mortar-wagons.

4th. Mortar-beds.

5th. Platforms for these beds,-

And some other implements or machines which are used also in the field and in garrison, such as, the Guns (the Siege and Field, the Garrison and the Casemate), Sling Cart, Hand Cart, Lifting Jack, Lever Jack, Truck, Manoeuvering Blocks, &c.

1st. The gun-carriages, Fig. 125, Plate 19, are three in number, as follows:

One for the 12-pound gun.

One for the 18 pound gun.

One for the 24 pound gun and 8-in. howitzer.

They are all constructed in the same manner, differing only in their dimensions. All the limbers and wheels are the same, so that they can be used in common. The gun-carriage is similar in its construction to the field carriage, but is joined to the limber in a different way. Projecting upwards from the limber and in rear of the axletree, is placed a pintle, which enters a hole made in the trail from the under side, and a lashing-chain and hook keep the two parts together when once in position. The weight of the trail resting on the rear end of the tongue keeps this nearly horizontal, and relieves the horses of the weight of it, which, as it must be both long and heavy, is too much for the horses to carry.

The splinter-bar is, as in field-carriages, stationary, but the traces of the next team are attached to a movable bar which is connected with the end of the tongue. The tongue is furnished with pole-chains but no yoke, and the rest of the teams are harnessed as in field artillery.

It is not necessary for siege-carriages to have the same degree of mobility and flexibility that field-carriages have, as they are properly speaking transportation wagons for use on roads, and never intended for manoeuvering with troops.

The axletrees are of iron with axle-bodies of wood; which last, by its elasticity, renders the percussion of the piece less direct and violent.

On the upper surface of the cheeks, near the back ends, are placed two projecting bolts which, with the curve of the cheeks, form resting-places for the trunnions, when the piece is in position for transportation. They are called the travelling trunnion beds. When in this position, the breech of the piece rests upon the bolster, a curved block of wood bolted to the upper side of the stock. On each side of the trail, and perpendicular to it, a strong manoeuvering bolt is placed to serve as places to apply the handspikes in manoeuvering the carriages, or as handles in limbering, unlimbering, &c.

The travelling trunnion-beds are used for the purpose of distributing the load more equally over the carriage. Before the piece is put in the travelling position, the elevating screw is taken out and inserted from beneath in the screw-box, and the piece is run forward to its position on rollers, the carriage being limbered.

The limber consists of--

1 the fork, 2 the splinter-bar, 3 the hounds, 4 the sweep-bar, 5 the tongue, 6 the pintle, 7 the lashing-chain eye, 8 the axletree (iron).

The sweep-bar is of iron, and on it rests the trail which by its weight keeps up the tongue. (For dimensions, see Appendix, p. 422.)

The transportation of a 24-pdr. gun requires ten horses and five drivers; an 18-pdr. Eight horses and four drivers; a battery wagon six horses and three drivers; and spare carriages-at the rate of one for every Five pieces-- require, each, six horses and three drivers.

When the 8-inch howitzer is mounted on the 24-pounder carriage, a quoin is used, instead of the elevating screw; the howitzer being too short to rest on the screw.

Laying.-- To lay this platform, establish the center line of the embrasure, and stretch a cord on this line from the middle of the embrasure to the rear. This is the directrix of the platform.

Lay the two outside sleepers parallel to this direct fix, their outside edges being 54 inches distant from it. The four other sleepers are laid parallel to these, the edge of each 15 ½ inches from the edge of the next. The upper surface of the front ends of these sleepers to be 50 inches, on a vertical line, below the sole of the embrasure.

They are laid with an elevation to the rear of 1 ½  inches to the yard, or 4 ½  inches to their whole length. This elevation may be determined by placing a block 4 ½  inches high on the front end of the sleeper, and laying a straight-edge, with a gunner's level on it, from this block to the rear end, then so arrange the earth as to bring the level true in this position.

The next set of sleepers are laid against and inside of the first, overlapping them three feet, having the rear ends inclined outwards, so that the outer edges of the exterior ones shall each be 54 inches from the directrix, and the spaces between the rear edges of the others, the same as in the first set, viz., 15 ½  inches from the edge of one to the edge of the next, all having the elevation to the rear of 1 ½  inches to the yard, and perfectly level across. The earth is then rammed firmly around these sleepers, and made even with their upper surface.  The fist deck-plank, with a hole through each end for the eye-bolts, is laid in place, perpendicular to the directrix, its holes corresponding with those in the sleepers.  The hurter is placed on it, and the bolts driven through the corresponding holes in these pieces.

The hurter should be so placed as to prevent the wheels from striking against the epaulement when the piece is in battery. If the interior slope has a base of two-sevenths of its height, the inner edge of the hurter should be 2 ½  inches from the foot of the slope. The other planks are then laid, each one forced against the preceding, the last plank having holes for the rear eye-bolts. By drawing out or driving in the outside sleepers, the holes through their rear ends are made to correspond with those in the last deck plank, and the bolts are put in.  Drive stakes in rear of each sleeper, leaving their tops level with the upper surface of the platform. Raise, ram, and level the earth in rear of the platform, so as to have a plain hard surface to support the trail when the recoil is great.

The earth should be raised nearly as high as the platform at the sides, and well rammed, giving it a slight inclination outwards to allow the water to run off.

Another kind of platform, called the ricochet platform, is sometimes used with these carriages when the pieces are used for ricochet firing. The parts then made use of are-

1 Hurter, 8 feet long, 8 inches wide, and 8 inches thick.

3 Sleepers, 9 feet long, 5 ½  inches wide, and 5 ½  inches thick

2 Planks, 10 ft. 8 in. long, 13 in. wide, 2 ¼  inches thick

1 Plank, 7 ft. long, 18 in. wide, 2 ¼  inches thick

1 Plank, 2 ½  ft. long, 13 in. wide, 2 ¼  inches thick

and some stakes, and the platform is constructed in the following manner:

Place the hurter perpendicular to the line of fire, and secure it by four stakes, one at each end and two in front, 31 ½ inches from the middle towards each end; lay the three sleepers parallel to the hurter; the first, 16 inches from the rear edge of the hurter; the second, 43 ½ inches from the rear edge of the first; and the third, 43 ½  inches from the rear edge of the second. Lay the plank 31 ½  inches from the directrix of the platform to the centre of the plank. Place the piece of plank 60 inches from the rear edge of the last sleeper, and bed it in the ground. Place on the last sleeper and this piece of plank the plank (84 inches long), its front end 106 inches from the rear edge of the hurter. This platform will bear firing with charges as high as three pounds.

Platforms of this hind, of larger dimensions, may be used for guns and howitzers in firing at a fixed object with full charges.

3d. Mortar-wagons, Fig. 127, Pl.20.-- This wagon is designed for the transportation of siege-mortars and their beds, or of guns, or large shot and shells.

The limber and the wheels are the same as those of the gun carriage.

The body consists of a platform of rails and transoms resting on an axletree, the two middle rails being prolonged to form the stock, six stakes or standards are inserted in sockets on the sides of this platform, and used in securing the load.

The side-rails are prolonged to the rear, and furnish pivots for a roller placed immediately in rear of the platform. This roller has holes for the insertion of handspikes, and is used in loading the wagon; the guns, mortars, &c., being drawn up on the stock.

A muzzle bolster on the stock near the limber, and. a breech hurter near the hind part of the wagon, are provided and used when long ordnance is transported on it. Mortars are usually carried mounted on their carriages. (For dimensions and weights, see Appendix, p. 423.)

4th. Mortar-beds, Fig. 129, Pl. 21.-- The carriage from which a mortar is fired, is called its bed. It has already been stated that the size of the angle of fire, and the violent reaction in a vertical direction which the mortar-bed experiences, prohibit its being mounted upon wheels. In consequence of this, also, the cheeks cannot be made of wood or bronze, the elasticity of which, being brought into play by the recoil, would cause the bed to bounce on the platform and throw the mortar from its place Ancient carriages, of wood or bronze, were provided with capsquares, to prevent this.

There are four siege mortar-beds:*

The 8-in. mortar-bed,

The 10-in. mortar-bed,

The stone mortar-bed,

The Coehorn mortar-bed,

The first three are alike, differing only in dimensions, and made of cast iron, which has very little elasticity. The bed consists of two cheeks, joined by two transoms, all cast together in the same piece. The manoeuvering bolts, placed on each side, one near each end of the cheeks, are made of wrought iron, and set in the mould when the bed is cast.

* The beds for the new model mortars are to be made of wrought iron.

On the front transom is fastened a wooden bolster, grooved to receive the elevating quoin, which it is prescribed should be put in position in a direction perpendicular to the axis of the piece, but is usually for convenience placed obliquely.

Notches on the under side of the front and rear of the cheeks, give hold to the handspike in throwing the piece to the right or left.

Cap-squares are used with these beds, but probably only for the purpose of preventing the piece from jumping from its place when fired at very small angles of elevation, as, for.instance, in ricochet firing.

The Coehorn Mortar-bed is made of a block of oak wood, in one piece, or two pieces joined together with bolts. A recess, for the trunnions and part of the breech, is made in the top of the bed; and the trunnions are kept in their places by plates of iron bolted down over them. Two iron handles are bolted to the bed on each side, by which four men can carry the bed with the mortar in its place.

The Eprouvette-bed consists of a block of wood, on top of which is countersunk and bolted the bed-plate, which is a heavy circular plate of cast iron, having a rectangular recess, with sloping sides, so as to make it longest at the bottom. Into this recess the sole of the mortar slides. The wooden block is bolted to a stone block of the same size, which is firmly placed in the ground on a masonry foundation. (For dimensions and weights of the beds, see Appendix, p. 423.)

Mortar-platforms are made each of twenty-four pieces, similar to those used for siege-guns. Six of these are laid as sleepers perfectly horizontal, and parallel to the direction in which the piece is to be fired. The other eighteen are laid on top of these and perpendicular to them, the front and rear ones being bolted to each one of the sleepers. Between each pair of the latter (deck-planks), four dowels are placed, to prevent the plank from sliding out. These dowels are short, hard pieces of wood, which are fastened in the edge of each plank, and fit into corresponding holes made in the one next to it.  (For dimensions, &c., see Appendix, p. 428.)

The Hand-cart.-- A. two-wheeled cart, being able to turn on its own ground, is more suitable than any four-wheeled vehicle for service in the trenches and parallels of a siege.

The handcart consists of a light body with shafts, mounted on two wheels, which in the French service are the same as those used on their field-carriages. The shafts are joined together at the ends, and supported just in front of the body by iron legs. The cart is used for the transportation of light stores in siege and garrison service.

The Hand Sling-cart Fig. 130, Pl. 21, is used in siege and garrison service, or, in fact, under any circumstances where light pieces or their carriages, or objects about that weight, have to be transported for short distances. It is made entirely of iron, except the  pole, which is of oak. The axletree is arched, to make it stronger, and connected with the pole by strong wrought-iron straps and braces. In the rear of the axle a projection is  welded to receive the end of a strong hook, the two being fastened together by a bolt. The end of the pole is terminated with an iron strap (through which is passed the handle), and  an eye. The eye is for the purpose of attaching to the cart, when necessary, a limber or a horse, the handle in the last case being held up by hand.

The Field and Siege Gun , Fig. 131, Pl. 21, is used for mounting or handling guns, or other heavy bodies in the field, or in the trenches of a siege. It consists, like all guns, of two legs and a pry-pole of spruce or ash as supporters, a windlass of oak, sheaves, pulleys, and a fall or rope. The two legs are mortised for the reception of three braces, on the ends of which tenons are cut. These pass through the mortises, and are keyed with pins outside.

The top-end of the pry-pole has on it an iron tongue, which fits in between the top of the legs, and all three are joined by a pin; just below which, and held between the legs by a bolt, two sheaves are placed to receive the fall, which is a strong four-inch rope. The legs are fastened together at top by a bolt.

Two and a half feet from the bottom of the pry-pole a round handle is run through it and fastened, and is used in handling or putting up the gun. The feet of the legs and pry-pole are provided with metal points, to prevent slipping when a weight is put upon the fall.

The windlass is provided with journals at the ends, which turn in journal-boxes, the plates of which are fixed to the legs by bolts. No ratchet wheel or pall is used, and the windlass is made fast by allowing a, handspike, inserted in its place, to bear against the lower brace, or another handspike placed across the legs for the purpose. The ends of the windlass are left square, but the middle part is made round for the reception of the fall, which, in raising a weight, is coiled round it. The legs are about 14 ½  feet long, and the height of the gun, standing up, about 12 feet.

To put the gun together, the legs are laid on the ground, the outer sides up, the bevelled ends together, and the windlass put in its place. The assembling-bolt is put in, and the 1st, 2d, and 3d cross-bars inserted in succession and keyed.

To set up the gun, the bottoms of the legs are held in position by two men placing their feet against them, or holding handspike against the lower cross-bar. The tongue of the pry-pole is inserted in its place and keyed. The gun is then raised by carrying up the foot of the pry-pole to its proper position, which is equally distant from the two legs, and 12 feet from the lower cross-bar. The fall may be attached by a man mounting on the third cross-bar; or, if he is too much exposed in that position, it may be done while the gun is lying down.  (For dimensions and weights, see Appendix, p. 428.)

The gun may be equipped with one or several pulleys, according to the weight to be raised—

a greater number being employed than is absolutely necessary, in order not to strain the rope.

With one pulley a 12-pd. siege and garrison gun ca n be raised; with two, an 18-pd.; with

three, a 24-pd., and with five or six, a 32 or 42-pd.

To Sling a Piece .-- A small piece without handles may be slung by a piece of rope, the ends of which are tied together after passing it under the piece in rear of trunnions, then up over the trunnion, under the piece again in front and over the other trunnion, hooking both sides over the pulley-hook. Larger pieces are slung by making use of an endless rope or chain, when double somewhat greater in length than the piece. One end of this is looped round the neck of the cascable, and the other round a handspike or billet of wood inserted in the muzzle. Both strands are hooked in the pulley-hook just in rear of the trunnions, binding the two together, it necessary, with a cord or piece of small rope.

When the gun is put together and raised, that part included between the legs and pry-hole is called the inside; the outside being the part without the legs; the right corresponding to the right hand of a man standing at the middle and outside of the windlass, facing towards it; the left corresponding to his left hand.

Barbette-carriages , Fig. 132, Pl. 21.-- The barbette-carriage belongs to that class which has been denominated immovable. That is to say, it is used simply to fire the piece from, and not to transport it except for very short distances.

The gun-carriages described under the head of siege material, may also be used in a fortification or garrison; and the mortar beds heretofore described, are used either for siege or garrison service. The barbette-carriage, however, is used only in a fixed position in garrison, and is a carriage on which a gun is mounted to fire over a parapet instead of through it, as siege or sea-coast guns usually fire. A, barbette-gun is any gun mounted on   barbette-carriage.

There are but two forms of the barbette-carriage in the United States service.

1st. One for the iron guns and sea-coast howitzers (12, 18, 24, 32, 42-pdr. and 8 and 10-in.); and

2d. One for the columbiads.

1st. This carriage consists of a gun-carriage and a chassis.

The Gun-carriage is formed of two upright pieces of timber, nearly vertical, forming the cheeks. Behind these are placed two inclined braces, mortised into the uprights and designed to receive the force of the recoil. A horizontal piece (the transom and axle-tie) runs from front to rear between these pieces, and the whole is firmly connected and braced by transoms and assembling-bolts, thus forming a triangular framework, which is less liable than any other form, to become deformed from the shocks of the gun. The trunnion-bed is formed at the top of the upright, where it is joined to the brace; and the breech of the gun is supported on an elevating screw, working into a screw box placed in the rear end of the transom and axle-tie, near the front part of the rear transom.

The front transom is just under the gun, and is cut out to receive it. The middle transom is placed between the braces about their middle points, and is notched out to receive the upper side of the transom and axle-tie. The rear transom is at the lower end of the braces, and under the transom and axle-tie, into which it is notched, dowels being placed between the two to prevent sliding; the lower part of this transom is notched to receive the tongue of the chassis on which it slides. Between this transom and the transom and axle-tie, the end of a lunette is placed projecting to the rear and fastened by a bolt, for the purpose of attaching a limber to the carriage.

The feet of the uprights and front end of the transom and axle-tie are joined to an axle-body, in which an iron axle is placed. On the ends of the axle are fitted cast-iron rollers, which rest upon the rails of the chassis and support the front of the carriage. On the outside of the roller is placed an octagonal projection, on which the cast-iron nave of the wheel fits, secured by a washer and linch-pin. The spokes of the wheels are wood, inclosed within heavy iron tires.

Manoeuvering-bolts are inserted in front of the feet of the uprights, and in the carriages for pieces heavier than a 24-pounder in rear of these feet also. These bolts and the spokes of the wheels form the points of application for the handspikes, in manoeuvering the piece. Manoeuvering-staples are placed in front of the feet of the braces, for the purpose of using handspikes to raise the rear of the carriage from the tongue of the chassis in running to and from battery.

The 32-pound gun and 8-inch howitzer, go on the same carriage. All other pieces have separate carriages.

Two sizes of rollers are used, one for the carriages of the 12, 18, and 24-pounders; the other, for the rest of the carriages. The roller part, however, is of the same diameter, and the octagonal projection accurately made, so that a wheel from any carriage will fit on any other. The wheels are all of the same diameter, 43 ½  inches.

No cap-squares are used with these carriages.

Besides serving to assist in maneuvering the gun-carriage, the wheels are also used in transporting the piece on its carriage for short distances; as, for instance, from one front of a fortification to another. To do this, the rear of the chassis is raised until the traverse wheels can be removed, when it is lowered to rest on the prop of the tongue and then on the traverse circle. Planks are then laid, inclining to the rear, to receive the wheels, which are backed on to them. A siege-limber is backed up to the carriage, the lunette placed over the pintle and keyed, and the gun-carriage drawn from the chassis.

The Chassis (the French for frame or framework) consists of two rails and a tongue, joined by three transoms. The tongue is in the middle and projects considerably beyond the rails, to the rear. At each end of the rails, on top, a hard piece of wood is notched in and bolted. They are called hurters and counter hurters, and used to prevent the gun-carriage from running from the chassis.

Rail-plates of iron to protect the wooden rails, are let in to the outside of the rails 0.2 of an inch below their upper surface, bolted at each end with an iron bolt, and fastened along the rails with wooden screws, which probably are less liable to break from the shock of the recoil.

At the rear end of the tongue a swinging prop is placed to support the end of the tongue when the piece is run back or the traverse wheels are removed. The lower side of the end of the tongue is notched out and a manoeuvering-loop fixed the re, with a bolt and screws to assist in handling the chassis.

The same chassis serves for the 12 and 18-pdr. carriages. On the under side of each rail opposite the rear transom a mortise is formed, for the reception of a fork socket of iron which receives the handle of the traverse-wheel fork. Each of these forks receives a traverse-wheel, joined to it by an axle-bolt, and these support the rear end of the chassis. The front end is supported on a pintle-plate of iron; through which, and up into the middle of the front transom, passes a pintle or bolt, which serves as a pivot around which the whole system moves.

In permanent batteries, the pintle is fixed in a block of stone, and the traverse circle is an iron plate set also on stone. For temporary batteries, the pintle is attached to a wooden bolster, which is covered by a circular cast-iron plate, and attached by bolts to a wooden cross, picketed firmly into the ground. A temporary traverse-circle is formed of plank pinned to sleepers and fastened to pickets, or secured to string pieces which connect the traverse-circle with the pintle-cross.

The traverse-wheels and their forks retain their places by the weight of the carriage and gun. The pivot-bolts of the traverse wheels project to the rear, and are acted against by the handspikes in traversing the carriage.

The chassis for the heaviest carriages has, in addition to the three transoms, four iron pipes placed in pairs between the tongue and rails. Through each pair a heavy bolt passes, and is fastened on the outside of the rails with nuts. The chassis slopes towards the front in order to diminish the recoil, and aid in running the piece into battery. (For dimensions and weights of these carriages, see Appendix, pp. 424 and 425.)

2. The Columbiad Carriages Fig. 133, Plate 22, consists of a gun-carriage and chassis. Those for the 8 and 10-inch differ only in dimensions.

The Gun-carriage is a triangular framework, consisting on each side of an upright, a horizontal rail or tie, and a brace, firmly mortised and bolted together, the two sides being joined by a transom and axle-body at each end. These project below the lower surfaces of the ties, and fit in between the rails of the chassis, serving, like the flanges on the rollers in the other barbette carriages, to prevent the gun-carriage from moving sideways off the chassis. The lower side of the ties is shod with a friction-plate. Through the front axle-body and near the front ends of the ties, an iron axletree is placed, working in iron boxes fitted in the ties. On the projecting ends of this axletree (the axis of which is eccentric with the axis of the ends), the rollers or manoeuvering wheels are axed, the extreme ends of the axle being octagonal in shape to fit the wrench of the iron handspike.

These eccentrics are so arranged that when the centres of the wheels are at their lowest points, the surfaces of the wheels bear on the rails of the chassis and raise the gun-carriage tie from it; and when the centres are at their highest points, the surface of the wheels do not touch the chassis rails, and the carriage ties themselves are in contact with the rails.

A similar arrangement is made for the rear part of the carriage, except that the axle does not extend all the way through, but the wheel on each side has a projecting piece of axle which works into a box placed in the end of the tie.

The wheel is thrown into or out of gear, that is, made to bear on the rail of the chassis or relieved from it, by turning the axle with a wrench placed on the octagonal end.

In the direction of the radii of the wheels, but inclined outwards, mortises are placed for the reception of the end of the iron handspikes, by acting on which, while inserted, the wheels are turned and the carriage moved back and forth on the chassis. Ordinarily, when the wheels are thrown into gear, the carriage being back, it will run into battery of itself.

The elevating arrangement on this carriage is different from any other in the service. It consists of, first, an elevating screw which works into a screw bed below the second part, which slides in a vertical box, and carries on the top of it a movable pawl to fit into the notches cut in the breech of the gun. The pawl has a slit in it through which the elevating handspike is passed, and the gun raised by making use of the edge of the elevating box as a fulcrum. This arrangement is placed over the rear transom.

Chassis.-- The chassis for this carriage does not differ much in its construction from those used with the other barbette-carriages, heretofore described, except that it has no tongue.

It consists, like them, of two rails connected by three transoms; but the tops of the rails are shod with iron plates, and the rear hurters are the large heads of heavy bolts which pass all the way through the rails. The front hurters are similar in form, but fixed to the front transom by a heavy plate and bolt.

Traverse wheels are placed under both front and rear transoms, and the chassis is pivotted on a pintle passing through the middle transom. Two of these wheels are placed under each end of the chassis, their axles being kept in place by straps bolted to the transoms. Recesses are cut in the under side of the transom for the wheels to turn in. The radius of the traverse circle being much loss in this case than with the other barbette-carriages, the wheels have to be placed in a much more oblique position in regard to the rail.

The Garrison Gun , Fig. 135, Pl. 23, is made heavier and stronger than the field and siege, as it is used for mounting heavier guns, and has not to be transported like the other with an army in the field. The legs are longer, and of course the gun higher, than the other. The legs have but two braces, which are iron bars bolted and keyed to the legs. When the gun is dismounted