673 



CANNON. 



CANNON. 



674 



the whole is built up. The portions of the jacket are kept slightly 

 apart when making the mould, in order to allow for the contraction 

 when drying. The mould is then dried gradually in a stove ; when 

 dry, the jackets being opened and the model taken out, the portions 

 are taken to the pit, and there carefully put together again in a vertical 

 position. A number of moulds being put up side by side, the inter- 

 vals are filled in with earth or sand, and channels made to a central 

 basin by which the metal is allowed to run in at the top of the dead- 

 head, to this basin another channel is made from the reverberatory 

 furnace. The metal usually employed in England is a mixture of 

 the different sorts usually known as Nos. 2, 3, and 4 of the best cold- 

 blast iron. To arrive at the right qualities for a gun, which are, 

 hardness combined with toughness and strength, is a delicate opera- 

 tion, and requires great judgment and experience in the mixture of the 

 different qualities of iron. The metal is melted in two or three rever- 

 beratory furnaces, according to the number of castings, with the purest 

 description of coal, when the furnaces are tapped, and the metal run 

 into a basin of sand, made close to the moulds, into which, when at the 

 right temperature, it ia allowed to run. The casting, after standing 

 for twenty -four hours in the pit, is taken out, and remains for about 

 the same length of time in the jacket, which is then released, and the 

 mould broken off by a few blows of the hammer. / 



The dead-head is then cut off in a lathe, and the gun taken to the 

 boring bench. If found to be without flaws, and sound, it is then 

 taken to the lathe again, and turned down to its proper dimensions. 

 It is then carefully examined inside and out, and if without faults 

 taken to the machine for turning the trunnions ; after which it is 

 vented and finished off, either by filing or turning. The specific gravity 

 of the iron of which guns are made varies from 7'0 to 7'2. To obtain 

 the best quality of iron for guns, about the following proportions of 

 iron ore are generally mixed in the smelting furnace : Black iron ore, 

 2 ; aluminous clay ore, 14 ; silicious clay ore, 1J. This gives an iron 

 not nearly so soft and crystalline as the quality known as No. 1, nor so 

 hard and brittle as No. 4, but a mean between them, being a mixture 

 combining some of the qualities of each. 



Bronze Ordnance. All the brass or bronze guns used in the British 

 service are cast at Woolwich, in the foundry in the Royal Arsenal. 

 The metal is an alloy of ten or twelve parts of tin to 100 of copper. 

 Copper of itself, though a very ductile, malleable metal, with great 

 tenacity, has not sufficient hardness to resist the wear and tear and 

 chance of external injury to which a gun is exposed. Though it resists 

 the action of gunpowder better than any other metal, shot would soon 

 indent the bore if it were not hardened with some other metal ; and tin, 

 though a softer metal, has the property of hardening it. The specific 

 gravity of bronze gun-metal is from 8'6 to 8'9. Bronze guns, in the 

 same manner as iron ones, are cast solid, and with a large dead-head, by 

 which the whole length of the gun is obtained of sound metal ; the dross 

 and impurities rising to the top, and the column of metal, by its weight, 

 assisting to compress the lower portion and supply the shrinkage. 



Bronze is not so much used in England as abroad for the manu- 

 facture of guns. In France the siege artillery has been formed of 

 bronze on account of its lightness, and perhaps from the difficulty of 

 obtaining good castings with the foreign iron, which, with the exception 

 of Swedish iron, is not adapted for guns. The defect of all iron for 

 gun*, and more particularly foreign iron, except the Swedish, which is 

 the best, is its want of elastic work and small sphere of cohesive force. 

 The want of elastic work prevents the particles of metal, when 

 expanded by the charge of powder, returning to their former state ; 

 and the smallness of the sphere of cohesive force makes the gun liable 

 to burst when at all strained. The tenacity of cast-iron is influenced 

 by the amount of carbon it contains ; and as it is extremely difficult 

 to regulate this quantity, guns, even from the same casting, vary much 

 in their strength. The tenacity of cast iron varies from 6 to 9} tons 

 on the square inch, while that of bronze is 15 tons, and the sphere of 

 cohesive force ig greater; while its principal defects are its want of 

 hardness, which causes the bore of the gun to lose its shape from the 

 mechanical action of the gas and ball if exposed to continued rapid 

 firing, the bore becoming enlarged and indented, and drooping at the 

 muzzle. They are also likely to suffer from the chemical action of the 

 gas, which has a tendency to separate the metals of the alloy, an effect 

 which would be increased by the addition of more tin, which, though 

 it would harden the compound, would decrease its tenacity. 



The method of forming the model employed in the Royal Arsenal at, 

 Woolwich is rather different to that described for iron ordnance. The 

 model is formed on a wooden spindle, of a slightly conical form. This 

 spindle, which is a good deal smaller than the required model, having 

 been well greased to allow of its after withdrawal, is rested in a hori- 

 zontal position between two support*, and has a cross handle attached 

 to one end to turn it by. The portions of the model formed on the 

 spindle extend from the base ring [ORDNANCE] to the muzzle and part 

 of the dead-head, the rest of the dead-head and breach and cascable 

 being formed separately. Plaited straw is now wound round the 

 spindle, bringing the whole nearly to the size and form of the desired 

 model ; the object of the straw is to furnish a key for the model com- 

 position to adhere to. The model composition is now put on by hand 

 in a moist itate ; it consist* of sand, loam, and horse-dung, -the horse- 

 dung being added to make it friable when burned. A modelling board, 

 cut out to the profile, so to speak, of the gun, is placed alongside, at 



the proper distance from the centre of the spindle, which being turned 

 round, the soft composition is cut off to the required shape. Care is 

 taken to ensure a sufficient thickness of composition over the straw, 

 and it is laid on in three coats, each coat being dried by a charcoal fire 

 before the next is put on. The model of the cascable is made in the 

 same manner on an iron spindle, and a wooden patch added at the base 

 ring for the tangent scale. The wooden models of the trunnions are 

 then fixed on by an iron pin, and the vent-patch and dispart, if a 

 howitzer, being added, the model is complete. It is washed over with 

 tan-ash and water, to prevent the adhesion of the mould composition. 

 The mould composition consists of loam, sand, and cow-hair, well mixed 

 together with water ; this, first in a wet and then In a drier state, is 

 laid on in coats, which are strengthened with hemp fibres and iron 

 hoops. The vent and dispart patches are removed after the first coat, 

 and the trunnions when the mouldings are finished. After the three 

 coats have been put on, and the mould strengthened with iron bars, 

 the spindle is knocked out, and the straw carefully removed. A wood 

 fire is then made inside, and the model composition becoming quite 

 brittle is easily extracted. The mould of the cuscable, prepared in the 

 same way, and the remainder of the dead-head, having been added, the 

 mould is raised vertically in the casting-pit, in the same manner as 

 with iron guns. The metal is melted in a reverberating furnace, and if 

 it be a re-casting, a small quantity, about '3 per cent, of tin, is added 

 to replace the waste, the whole being kept well stirred with fir-poles. 

 When at the right temperature, it is allowed to rim into a channel 

 which communicates with the moulds ; and having risen to a certain 

 height (about eight inches), the sluice-gates are opened, and the moulds 

 filled two at a time. After remaining three days in the pit, the 

 moulds are taken up and broken off the casting. From two to three 

 times the quantity of metal actually required for each piece when 

 finished is allowed to make up for dead-head, turning down, &c. The 

 dead-head of a 24-pounder howitzer is about 3J feet long. 



The casting is now taken to the boring department, and the dead- 

 head cut off in a lathe. It is then put in the centering machine, the 

 object of which is to obtain the exact centre or axis of the piece, on 

 which all the other lathe operations depend. The piece is laid hori- 

 zontally on two saddles; each saddle has a system of three slides moving 

 inwards at a uniform rate on screws of the same pitch, two moving 

 horizontally towards each other, the other vertically upwards. As 

 they move at the same rate, the faces of the slides at each saddle are 

 always tangential to the same circle, the centre of which is a drill 

 which is moveable horizontally. When the faces of the slides all 

 touch the outside of the casting, the drills are moved forward, and the 

 centerings are cut. 



The gun is now taken to the second lathe, and being fixed by these 

 centerings, the muzzle and base rings, and two rings, one on each side 

 of the trunnion, are accurately turned. This is an important operation, 

 as on it depends the accuracy of the bore. 



The trunnioning machine is now employed. The gun rests between 

 two cones, which run into the centerings, and are moveable horizon- 

 tally to suit any length of gun, and vertically to raise the gun according 

 to its calibre to the right height for the frames carrying the cutting- 

 tools to work on the trunnions. The frames work in and out opposite 

 to each other, on a bed exactly at right angles to the bed on which the 

 gun rests, and have motion communicated to them by a driving-shaft 

 underneath. When the trunnions have been turned, the portion be- 

 tween the trunnions is removed by a planing-machine, from which the 

 gun is removed to the drilling-frame, where the hole for the tangent 

 scale is drilled, and also that to receive the bushing for the vent. 

 As the bush does not run in vertically to the bore, the gun is tilted 

 up to suit the drill, which acts vertically. The hole thus prepared is 

 tapped, and a bush of pure copper with a vent two-ninths of an inch in 

 diameter is screwed in. Copper is employed in preference to other 

 metals, as it withstands the chemical action of powder best. 



The boring is next performed, the muzzle-ring (accurately turned in 

 the second lathe) resting in a V, and the gun receiving motion from the 

 mandrill of the lathe ; the boring-bits are fixed to the end of a boring- 

 bar, which has a horizontal self-acting motion, or is driven forward by 

 the hand. 



The remaining portions of the outside of the gun having been 

 cleaned off in a turning-lathe, the portions at the shoulders of the 

 trunnions which cannot be touched are removed in the shaping-machine. 

 It is then proved, and the driver sawn off, and the button finished with 

 the hand. 



The foregoing description applies only to the manufacture of guns at 

 present in use. With respect to the newly adopted Sir William 

 Armstrong's gun, the manufacture is kept strictly secret, and no pre- 

 cise details can therefore be given. The following account, extracted 

 from the ' Times ' of May 14th, 1859, is believed to give an accurate 

 general idea : 



"Two hundred guns are to be made this year by Sir William 

 Armstrong, all of them 9, 12, and 18 pounder field guns, a number 

 quite sufficient to supply all our field artillery batteries. Before long, 

 however, we hope to see guns of 50 cwt. which will throw a 90 Ib. or 

 100 Ib. ball a distance of five miles. Each gun is made in about three 

 feet lengths, and on much the same principle as the twisted gun- 

 barrels. Thin bars of the best wrought iron, about two inches broad, 

 are heated to a white heat, and in this state twisted and welded 



