CANNON, a military engine for throwing balls, &c. by the help of Gunpowder.

The invention of brass cannon is by Laney ascribed to J. Owen. He says that they were first known in England in the year 1535; but he yet acknowledges that, in 1346, there were four pieces of cannon in the English army at the battle of Cressy, and that these were the first that were known in France. And Mezeray relates, that by means of five or six pieces of cannon, King Edward struck terror into the French army, it being the first time they had seen any of these thundering machines; though others affirm that cannon were known also in France at the same time, but that the French king, in his hurry to attack, the English, and in confidence of victory, left all his cannon behind him as useless encumbrances. The Germans carry the invention farther back, and attribute it to Albertus Magnus, a Dominican monk, about the year 1250. Vossius rejects all these opinions, and finds cannon in China almost 1700 years ago. According to him, they were invented by the Emperor Kitey in the year of Christ 85. See Artillery and Gunnery. Cannon, the Art of Casting. Formerly the mould for casting cannon was of loam, but now it is usually made of dry sand. Loam for making moulds is a composition consisting principally of an earth that contains a good deal of clay. This earth is passed through sieves, and then mixed, whilst wet, with horse dung, cow’s hair, chopped straw, or tow cut short; the loam being mixed up with one of these substances, they are well beaten up together on a wooden board with an iron bar. By this addition the loam becomes susceptible of being dried rapidly without cracking. The most attenuated loam is used for the surface of the mould that is to come in contact with the metal, to the end that the surface may come oft' smooth. The loam moulders are a particular class of workmen, different from the common sand moulders. The business to which they are bred consists in making, of loam and of dry sand, the moulds for steam-engine cylinders, pipes for conveying water, boilers, guns, and other large articles.

Formerly on a tapering wooden spindle, entwined with straw ropes, a model was made of loam, copied exactly from the pattern gun. This model was painted over with a coat of wood ashes mixed with water. By means of this coat no adhesion took place between the convex model and the loam which was afterwards applied. Over this coat of ashes successive coats of loam were applied, each being dried by fire before the next was laid on; and the whole was bound externally with longitudinal iron bars, and with hoops transversely. Over this carcass of iron a coat of plaster of Paris was applied. This was dried, and then the spindle and its envelope of straw was taken out. The interior convex model being thus deprived of its core and support, fell to pieces and was picked out; and then a hollow mould of the gun remained. In this way the mould for the body of the piece was formed; the moulds for the breech and head were made separately; and these three parts were joined together so as to form a complete mould. This method of moulding guns required the construction of a new convex model for every gun that was moulded; and it was used in the French government founderies of Douai, Ruelle near Paris, and Strasburg, in 1794.

The following method of constructing the loam-mould is an improvement on that just mentioned. A model of wood, or, to prevent change of form by moisture, a model of brass or pewter, is made and formed on the turning lathe, with its exterior surface exactly resembling that of the gun, with its head and the square piece at the cascabel; if the model is of metal, it is made hollow for the sake of lightness. This model is laid with its longitudinal axis horizonal, and one half immersed in a bed of sand. Upon that part of the model which projects above the sand successive coats of loam are applied and pressed on the model. When the first layer is dried by fire, a second layer is applied and dried, and so on till the model is covered with a coat of loam four or five inches thick. Over this an iron carcass is applied, and over the carcass another coat of loam. The mould with the model in it is now turned, so that the half already covered with loam shall be lowermost. The plain surface of the loam which had been in contact with the sand is painted over with a coat of blacking, composed of finely powdered charcoal mixed with clayed water; this prevents the adhesion of the flat surface with the loam that is to be laid on it. A layer of [7:6:85] loam is applied upon the naked half of the model. - This is dried, and several more layers are applied successively. A carcass is put over the loam corresponding to the carcass of the first half, so that these two carcasses can be bound together with bolts and wedge-formed keys, with screw-bolts and nuts, or tied with iron-wire.’ When the loam is dry, the upper half of the mould is lifted off, the model is taken out, and the interior surfaces of both parts of the mould are painted over with blacking; this prevents the loam from being melted, and from adhering to the hot metal. The two halves of the mould are then put together, and the carcasses are firmly connected by their bolts; the whole is thoroughly dried by fire. When dried, the mould is placed vertically in the pit of the casting house, with the breech lowermost; sand is beat round it for support, and the metal is poured in at the top of the head. This method was practised in the Arsenal of Paris in 1794.

The most approved method of constructing the mould of a gun is in dry sand, and this is the method now practised in Britain. Guns cast in loam do not come from the mould with a surface so correctly resembling that of the model as those cast in dry sand; and in order to render the surface correct, and to remedy defects, it was always necessary to subject them to the process of turning. In guns carefully cast in dry sand, the process of turning might be dispensed with; the gun would then be strengthened by the outer skin of metal, which, having cooled more rapidly than the other parts, is the hardest. This outer skin is also less liable to rust than the surface laid bare by turning. The mould of a gun in dry sand, at the same time that it is more accurate, is also sooner made and dried, than a loam-mould. Dry sand moulding is a part of the business of the loam-moulder.

The sand for dry sand mouldings is made by mixing a quantity of sharp refractory sand with water in which clay has been diluted. After the mixture is thoroughly made, if a handful is grasped, and on opening the hand the sand retains the form given it, then the consistence of the mixture is good. The sand should have the following qualities :— ∖ st, It should not be fusible by the heat of melted cast-iron; if it were, it would adhere to the metal, and make the surface of the gun rough. i 2,dly, It must be sharp, and composed of angular particles; if the particles of the sand were round, it would not hold together on taking out the model. 3<√7τ∕, It must not contain too much clay, for in that case it would crack in drying, ⅛thly, It must contain a certain proportion of clay, to retain the form that the model impresses on it.

I. For dry sand moulding, a pattern of wood may be used, turned exactly to the form of the gun; or, to avoid expansion from humidity, the model, or pattern as it is termed in the founderies, may be of metal. Brass or pewter arc preferable to iron for making patterns, as a smooth surface may be more easily given them, so that they may leave a correct impression, and may come out well from the sand. The metallic pattern is hollow, that it may be lighter and more easily handled: it is also in different pieces; and each piece fits into the adjacent piece by a rabbet.

The length of each piece of the model should be a very little greater than the given length of the corresponding part of the gun, because the length of the mould is the length of the gun whilst hot, and this is longer than the length of the gun when it comes to the temperature of the atmosphere, at which temperature the dimensions of the guns are given. It has been estimated that some kinds of cast iron contract six hundredths of an inch in a foot in passing from the liquid state to the temperature of the atmosphere. This contraction is not considerable enough to be taken into consideration in the diameter of the pattern. The shrinking of the sand in drying, though not considerable, tends likewise to make the piece shorter, and is another motive for making the pattern a little longer than the dimensions taken from a gun at the usual temperature. The patterns of the trunions are attached to the pattern of the second reinforce by screws, so as to be unscrewed and separated when the pattern is to be lifted out of the sand.

The gun-box, in which the dry sand mould is to be formed, is of cast iron, and cast in sand. It consists of several portions; each of these portions has flanges, by which it is fixed to the others, and the whole, when connected together, form the gun-box. In the flanges are holes through which bolts are passed; the bolts are secured by wedge-formed keys; thus the different parts of the box are firmly held together. The two portions of the gun-box which contain the brecch-ring and cascabel are single, not being divided longitudinally. Each of the other five transverse portions is divided longitudinally into two. A handle is fixed to each portion of the box, for the purpose of moving it. The upper transverse portion A A contains the gun-head. In each of the two portions BB, which contain the second reinforce, there is a lateral projection for the trunnions. The figure represents the gun-box with the breech lowermost, in the position in which it is placed when the metal is poured in.

To make the mould, the pattern of the breech is first placed on a board, and the corresponding portion of the gun-box is put over it, and sand is rammed between the pattern and the box. The flat exposed surface of the sand is painted over with blacking, which consists of charcoal and clayed water, that there may be no adhesion with the sand of the next portion of the mould. The pattern of the first reinforce is now fitted into the pattern of the breech, and the corresponding portions of the first reinforce box adjusted on the flange of the breech box. Sand is well ramified, in small quantities at a time, between the pattern and the box; and the upper flat surface of the sand is painted over with blacking. The mould is completed by adding the remaining pieces of the model and of the box, one above another, ramming the sand, and painting the transverse surface of the sand at the top of each division of the box with blacking. The sand must be strongly and equably rammed, that every part of its surface may be able to resist the pressure of the liquid metal. Three little wedges are interposed between the two adjacent transverse portions of the box, that the sand may project a little, so that after it is dry it may be flush with the box; if this were not done, there would be an interval between the adjacent surfaces of the sand, through which the metal would pass and form a fin.

When every part is moulded, the box is taken to pieces, and the parts of the pattern are carefully taken out of the sand, for which purpose they are first struck with a wooden mallet. Each part of the mould is then carried separately to the stove to dry. The stove is a room twelve or’ fifteen feet square, with large iron doors on one side; the [7:6:86]fire is made in a large conical grate placed on the middle of the floor; the smoke issues by an aperture in the brick ceiling. The heat in this stove is considerable, but it must not be so great as to make the boxes red hot; for then, by the expansion of the iron, the mould would be injured; the moulds take about fifteen hours to dry in this situation. When the moulds are taken out of the stove, their interior surface is painted over with a coat of blacking, that there may be no adhesion between the mould and the metal.

The pieces of the gun-box containing the mould are then taken to the pit, and being carefully placed the one upon the other by the crane, they are put together, and secured by their bolts. The mould is placed with the breech undermost; the axis of the mould is made perpendicular to the horizon by a plumb-line, that the weight of melted metal may press equably, and not more on one side of the mould than on another. It is not necessary that sand should be rammed round the mould, the box being strong, and its parts firmly bound together, so as to require no additional support. The mould is now in a position for the metal to flow into it through its open end, which is the extremity of the head. Whether the gun is to be of cast iron or brass, the construction of the mould is the same.

The pig-iron from which the gun is to be made is melted in a furnace, called an air-furnace in the iron founderies, and termed by some authors a reverberatory furnace. The flame of pit-coal is carried by a current of, air so as to play upon the pig-iron. The stack of the chimney is forty feet high. By the pressure of the unrarefied external air on the lower part of the rarefied column of air in the furnace and chimney, the current of air through the furnace is produced. The grate G is larger than any other transverse section of the furnace. (See figure next column.) The furnace has three openings, one, C, for introducing the coals; the second, P, which has a sliding brick door, with a counterpoise, serves for introducing the pig-iron. The third, I, is for the purpose of stirring the metal, and taking out the melted iron for small castings by iron ladles coated with clay, and made red hot. This third opening has a door of fire-brick; the joints between the door and the door-frame are luted. In the middle of the door is a hole, through which the state of the melted metal may be seen. There is likewise a smaller opening, T, for letting out the melted metal.

The furnace and stack are of brick. The, interior of the furnace is a coating of fire-brick, nine inches thick, detached and separate from the outer, coat and the other parts of the building, in order that the heat may not melt the common brick of which the outer, parts are composed. The fire-brick is made of refractory clay, which, containing little, iron, and little, or no calcareous, master, burns white, and sustains a great heat without melting. These bricks are made of S,tourbridge clay, or of a light bluish gray stratified clay found in the strata that accompany coal in some of the collieries in Scotland. The clay is first ground, the pieces of ironstone, picked out, and then made into bricks. In making the interior coating of the furnace, the bricks must be built with moistened fire-clay, and not with lime mortar. The quantity of metal put into the furnace should be equal to the weight of the solid unbored gun with, its head, and something more in case of need. It requires a large air-furnace to contain metal enough for one large gun.

The pig-iron for guns should be gray, that kind having most tenacity; white pig-iron is too brittle, and so hard that the head cannot be cut off, nor the gun bored.

A bed of sand, N, is made in the furpace, on which the pig-iron is to be laid. The furnace is heated to a white heat, til the sand is vitrified, which is known to have taken place by touching the surface of the sand with an iron ringard. The brick door is then lifted up, and the pig-iron is laid on the bed of sand. The heat should be applied so as to produce a speedy fusion; for if the iron is long exposed to heaţ before melting, a portion of its carbonaceous matter is burnt, and it passes from the state of gray cast iron to that of white. In situations where pit-coal cannot be had, wood may be used in the air-furnace; but the heat given by wood is not so great as that produced by pit-coal. To obtain the utmost heat that the wood is capable of affording, it should be well dried, cut into small logs, and the logs should be placed with their end upon the grate.

The pig-iron melted by the flame playing on it, flows down into a cavity, L, which has a hole, T, opening outwardly, and stopped with clay. When the hole is forced open by a workman, the metal issues and is conveyed by a gutter formed of sand to the gun-mould, into which the melted metal falls through the open end of the head. The sand forming the gutter should be in a proper state of moisture. If it is too dry, some pieces of it will be carried away tíy the metal. Across the gutter is a dam composed of an iron plate luted, and dipping a little below the surface of the metal to retain the scoriae. This dam is driven down to stop the current of metal when the mould is full. The metal is also skimmed, as it passes along, by a skimmer, composed of a rod of iron, terminated by a flat semi-elliptical piece luted and made red hot. It is sometimes the practice to plunge a piece of green wood for a short time into the head whilst liquid. This is with a view to prevent honeycombs, and its action may be to metallize any oxidated particles of the metal, and that the vapour from the green wood, rising to the surface of the metal, may, carry with it small air bubbles, or other extraneous bodies that would, if they remained, occasion cavities in the metal.

The figure is a transverse section of the air-furnace. C is the opening through which the coals are introduced. P, the opening at which the pig-iron is thrown in. T, the hole through which the metal is let out. The metal flows into the casting-house. 0, the floor of the casting-house. In this floor is the pit in which the moulds of large goods are sunk, that the metal may flow down into them. I, the door, with a hole in it, for seeing the state of the melted metal.

G, the grate. L, the lower part of the cavity of the furnace, into which the metal, as it is melted, flows. S, steps [7:6:87]leading to A, the ash-pit. N, bottom of the furnace, lined with sand. H, chimney; the height of the stack if forty feet from the surface of the ground. Tħe stack is strengthened in different places by iron bars, X. F is the mass of building which forms the foundation built below the surface of the ground to support the weight of the furnace and stack. R, the surface of the ground out of doors. C P N L H is the course that the flame takes.

It is better to cast thg guns from the air-furnace than from the blast-furnace; for in the blast-furnace, where the ironstone is smelted, the quality of the metal is uncertain, and it may vary from one cast to another, by causès either unknown, or not under the cóhtrol of the iron-master. On the other hand, in the air-furnace, pig-iron of a quality proper for making guns is put in, and the quality of the iron is not materially altered by the process of melting.

The head of the gun is like the jet (gate or geet of the workmen) of any other casting. Whilst the whole is liquid, the head is a column of liquid metal that acts by its height, exerting pressure on the metal that forms the body of the gun. The metal subjected to this pressure whilst liquid is less subject to porosity when cooled. The head also furnishes metal to fill up the cavities that occur in the piece by the contraction and crystallization of the metal whilst it is passing to the solid state. All the great contractions and crystallizations are thus transferred to the surface of the head, which is found to be composed of large cavities, sometimes containing cast iron crystallized in a fern-leafed shape. The head also serves to receive any impurities that may have escaped the attention of those appointed to skim the iron as it flows along the gutter.

In ten or twelve hours, the piece is sufficiently cool to be removed. It is then stripped of the mould and taken to the boring-mill, to undergo the operations described under our article Boring of Cannon. Mortars, howitzers, and carronades are moulded, cast, and bored in the same way as long guns.

The English Board of Ordnance is supplied with iron guns by contract. The contractors ärc those iron-masters who offer the guns at the lowest price, and the guns are cast at their works in the country. The guns are sent to Woolwich to be examined in respect to their dimensions, the coincidence of the axis of the bore with that of the piece, the position of the touch-hole, and to undergo a proof by powder. It is also tried whether water can be forced through the substance of the gun. If any cavities called honey-combs be found in the bore, the piece is rejected. The proofs are at the risk of the contractors, who generally examine and prove the guns at their works before sending them to Woolwich. Unserviceable guns are taken to the triangle, where a large mass of cast iron is let fall upon the gun, from a height of forty or fifty feet. The gun is thus broken into pieces of a size fit for being introduced into the air furnace to be re-cast. Some brass guns are cast and bored in the foundery of the Board of Ordnance at Woolwich.

Cast-iron guns have the advantage of not suffering any injurious alteration from the beat.of repeated firing. Brass guns when fired rapidly in succession droop at the muzzle. Cast-iron guns alone are used on board British ships; brass guns are now principally used for field pieces. Brass guns, in strict and precise language, might be called bronze guns, as the word brass is most commonly used to denote a composition of copper and zinc, whereas, in gun-metal, there is generally little zinc, and often none. Copper alone is too soft, so that the guns that have been made of it were cut and furrowed by the ball in firing. Use is made, therefore, of a mixture of copper and tin, this composition being harder than copper. Copper and tin separately are soft and malleable; when combined they form a composition that is hard and brittle; and these two qualities are increased by augmenting the relative quantity of tin. Different proportions have been employed for guns; ten parts by weight, of copper, and one of tin, is a proportion that is found to give the requisite hardness, and not too much, nor too great brittleness. The copper is first melted; and the tin is added. If the tin were melted first, and the copper added, much of the tin would be oxidated before the combination took place; the metal, during the process, is stirred with a rod of green wood.

Bell-metal is a combination of copper and tin in other proportions,. It is made hard by means of tin, in order that it may be sonorous. It contains twenty-five per cent. of tin, and is too brittle and too hard for making guns. In the year 1794 the revolutionary government of France obtained gun-metal by depriving bell-metal of a part of its tin. Bell-metal was heated with the contact of air, and stirréd to oxidate the tin; the bell-metal was thus reduced to the state of a coarse powder; this powder was thrown into another quantity of bell-metal in fusion; the metallic and oxidated copper in the powder melted, and was mixed with the already fused bell-metal; the oxide of tin of the powder remained on the surface. A melted mass was thus obtained, containing a larger proportion of copper than the bell-metal, and fit for making guns.

The mould for brass guns is formed of dry sand, in the same way as the mould for cast-iron guns already described. The furnace for melting brass for guns is a reverberatory furnace, the metal being exposed to the flame. It has no high chimney like the air-furnace for melting iron, the heat required not being so great as that for melting cast iron.

Brass guns are subject to melt at the interior extremity of the touch-hole, by the heaa of quick firing; and the melted parts are driven out by the explosion, so as to render the touch-hole too wide. To prevent this, there is sometimes a bush of copper inserted, and in this bush the toucħ-hole is drilled. The copper being less fusible than the brass, is not melted by the heat of firing the piece. To form the bush, a cylindrical piece of copper is hammered cold, and made into the form of a male screw. A hole is then bored, reaching from the surface of the gun into its bore; the diameter of this cylindrical hole is equal to the diameter of the cylinder of copper measured from the bottom of the threads of the screw. The piece of copper is then screwed into the cylindrical hole, and the touchhole is drilled in it.

The improvements in casting cannon, as in other arts, have been gradual. Formerly cannon were cast with a core, and this was practised in some founderies in Flanders, even in the year 1794; but they are now always cast solid, experience having shown that guns cast solid are stronger, and lefes liable to burst, and the bore is freer from honeycombs, and more likely to haVe. the same axis with the piece. The second of these qualities is still more certainly attained by the practice now in use of making the gun itself revolve whilst boring; in this way, as long as the boring bar remains unmoved, the axis is right; but if the boring bar has a conical motion, then the point of the bit is out of the axis; when the boring bar was made to revolve, the bore might deviate greatly from the axis. The improvements in the casting of cannon have kept pace with the improvements in the manufacture of cast iron.

The art of casting iron was known to the ancients, as appears from a small antique statute of Hercules, of cast iron, dug up at Rome. In China it appears to be practised with a dexterity visible in the Chinese specimens of many other arts. In modern Europe it has grown with [7:6:88]the general advancement of society, and has latterly attained to a high degree of improvement in this island, where individuals having the command of capital, and the power of making advances for the salaries of workmen and the construction of buildings, were induced to form large establishments for the smelting of ironstone, and for the manufacture of cast iron. In France cast iron is little used; many of the articles which in England are of cast iron being there of wrought iron, copper, earthenware, or wood. In the Prussian dominions the art of casting statues and small medals in cast iron is successfully practised. But in none of the other countries of Europe is cast iron so generally used, and nowhere is it manufactured on so large a scale, and with the employment of so much capital, as in Britain.

Pit-coal has been the main instrument in this extensive manufacture. As it gives a better heat for the melting of cast iron, and saves the great extent of ground required for rearing wood, the greater part of the cast iron in Britain is now extracted from the ironstone, and made into castings by pit-coal. Pit-coal began to be used in the smelting of ironstone in 1619. This first operation was performed in Worcestershire by Dudley, who describes his process in a book entitled Metallum Martis. The manufacture of cast iron was not much advanced one hundred years afterwards; for in the first half of the eighteenth century cast-iron goods were imported into some part of Britain from Holland; and the Dutch chimney-backs, with the figure of a parrot, are to be seen in old country houses in Scotland to this day.

Two kinds of mineral are smelted· for iron in Britain. The first is the haematites of Ulverstone and the neighbourhood of Whitehaven, which, as it contains much iron (60 per cent.), is carried by sea to smelting furnaces in different parts of Britain. The second is the argillaceous ironstone, which constitutes some of the strata that accompany pit-coal. This is more generally used than the haematites. And it is in the vicinity of the masses of stratified minerals which yield coal and ironstone that the principal iron-works in Britain arc set down. These strata are found in various parts of the island, and arc portions of that class of depositions called by geologists the coal formation. A stratum of coal or of ironstone of considerable extent is termed by the coal and iron masters a coal field, or an ironstone field.

Pit-coal cannot be employed entire in the blast-furnace; the bituminous part would be conglutinated by the heat, and the furnace would be choked, and the materials would no longer descend gradually as they ought to do. The coal is therefore burnt to drive off its bitumen, and it is then in a state of cinder, and called coak. It requires a larger mass of coak than of charcoal to smelt ironstone. Hence the coak blast-furnaces are large, and the machines employed to blow them are more powerful than the wooden spring bellows invented in Germany in 1620, and which continue to be employed in the charcoal iron furnaces in Germany and France. Bellows connected by leather, and worked by water, were used to blow the blast-furnaces at Carron at the commencement of that establishment in 1760. Some time after, these bellows gave place to blowing machines, composed of pistons working in iron cylinders, constructed by the celebrated Smeaton, and described in his reports. The blowing machines of the blastfurnaces in Britain are now always composed of pistons moving in iron cylinders. The improvements in the steamengine have rendered practicable the working of blastfurnaces in situations where there is no fall of water; and, on the other hand, the manufacture of the various parts of numerous steam-engines has called forth the abilities and ingenuity of the iron founder.

In consequence of the advanced state of the English cast-iron manufacture, several foreign nations have been desirous of introducing the English method, and have procured English workmen for that purpose. In this way iron-works on the English plan were erected in Russia about 1780, in Silesia in 1790; and in France, at Creusot, twelve miles south of Autun, there were three English coak blast-furnaces begun about 1790, under the direction of William Wilkinson.

The strength of guns depends on the strength of the metal of which the gun is composed, and on the quantity of metal and the manner in which it is disposed. This subject will be considered in the article Gunnery. The nature of the subject does not admit of determining with precision the best weight and length that can be given to a gun fitted for exploding a ball of a given weight. Guns of the same caliber are consequently made of different dimensions even in the same country. The four tables that follow contain the weight, length, and other dimensions of British and of French guns.
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(b. b.)