FABRICATION OF ARTILLERY. 129 



interior surface of the bore thus obtained was always of a somewhat spongy- 

 texture, never exactly straight and cylindrical ; and finally that the piece 

 itself was injured by the iron anchor of the core rod, which remained 

 imbedded in the breech. Meanwhile the methods of working in metal had 

 improved, particularly the art of boring ; the plan of hollow casting for 

 guns was, therefore, entirely laid aside, all guns were cast solid and after- 

 wards bored out to the proper calibre, whereby not only was the best 

 metal brought into the region of the bore, but a piece was obtained which 

 shot more trul)^ and lasted longer. In the moulding itself two methods 

 were followed : the loam moulding and the dry sand moulding, the last of 

 which is more and more used. The metal of which guns are cast is either 

 bronze, a mixture of 10 parts copper and 1 part tin, or refined and repeat- 

 edly melted iron. 



a. Loam Moulding. This is so called because a mixture of loam and 

 horse-dung is used to form the mould. For each mould the pattern must 

 first be produced. This is done by laying a core stafT on two trestles and 

 winding it round with tow and old rope, keeping it all the while revolving, 

 until the overlaying has nearly the shape and dimensions of the gun, which 

 is judged of by a pattern board, laid before the workman, in which the pro- 

 file of the gun is cut out. Then a layer of mould stuff is put on and dried, 

 and so a succession of layers, which, however, are made finer and finer, 

 until at last they consist purely of washed clay and water, wherewith a 

 mould board, plated with iron, is used, in order to get the mouldings and 

 other parts exact and true by turning them off against them. Each layer 

 must be perfectly dry, wherefore a moderate coal fire is kept constantly 

 going under the cylinder. The last layer is coated with a paste of loam, 

 and over this a coat of wax dissolved in oil of turpentine is laid, and the 

 pattern turned. Then the trunnions and dolphins, mounted in wax, are put 

 on and the pattern is complete. Upon this the mould proper is made, the 

 first layer of washed loam and clay and coarser stuff being employed by 

 degrees. Fl, 39, fig. 26, shows the art and manner of forming the pattern 

 mould for a 50-pound mortar which corresponds with the above described, 

 with the distinction only, that they are formed standing, and that instead of 

 the woolded core the rough mould is built up. That is, a circular hearth, 

 q, is built, in the centre of which is the bed, e, for the mould spindle, and 

 then the rough form of the pattern is begun with a round layer of bricks, u, 

 in which air-holes are left ; on this a cupola-shaped structure, p, having nearly 

 the form of the mortar when standing on its muzzle, is erected of tiles 

 cemented with loam. On the top is a tube, p, for the core spindle. The 

 whole stands near a wall, to which the turning apparatus is attached. This 

 consists of horizontal arms, c, which are fastened to the wall by means of 

 ties,/', and run together in the middle, b. An oblique tie, d, also fastened 

 to the wall at /, runs likewise to the point of junction, which thus forms 

 the vertex of an immovable triangle. From this point to the bed, e, in the 

 hearth runs the spindle, a, whose upper end {fig. 27) lies in the collar, b, 

 and is regulated by the fly-screw, g. About this spindle the mould board, 

 k k, is turned, being suspended from the frame, h, which is attached to the 



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