132 MILITARY SCIENCES 



the mould, nothing more is required on these subjects here, save a few' 

 words of explanation with respect to the manner of withdrawing the 

 trunnion patterns. In moulding the trunnions, cylinders are at the same 

 time imbedded in the sand layers E and F, at the centre of the trunnion 

 pattern forming the hollows u u. The trunnion patterns have holes, m, with 

 screw threads, one larger, one smaller. If now, after the screws 1 1 are 

 taken out, the chamber pattern is withdrawn, then a plate, t, with a hole in 

 it, is brought in front of the trunnion pattern at E and a spindle o, of which 

 there are two, fitting the large and small screw-thread ; the one now referred 

 to, being the smallest, is thrust through u and the trunnion pattern G, and 

 screwed into the thread in the opposite pattern, F ; the spindle, o, has a 

 screw cut upon its opposite extremity also, on which works a wrench, r ; 

 by turning this wrench the spindle is drawn directly backwards, and thus 

 the pattern F, into which its end is screwed, is drawn out from its mould. 

 In exactly similar manner the other trunnion pattern is withdrawn, and 

 then, in the retouching of the mould, the holes uu are filled up and the 

 stopping-plates, jop, screwed on. The prepared mould is now carried to the 

 pit of the foundry for casting, where it is either rammed in sand, or screwed 

 fast upon a bed for that purpose and held by ties and braces. 



c. The Foundry and the Casting. The casting of cannon is made from 

 the flame or reverberatory furnace, as it is called, whenever gun-metal, a 

 mixture of copper and tin, is employed ; and from the cupola furnace when 

 iron guns are to be cast. In the former cast the metal flows from the tap-hole 

 in the hearth, upon which it was melted by the reverberated flame, into the 

 mould, which is placed perpendicularly in the pit immediately in front of 

 the furnace. In the second case, however, the melted iron is drawn from 

 the furnace in great kettle-shaped ladles and poured into the mould ; yet 

 casting in iron could be practised from blast furnaces adapted for the 

 purpose, or even from peculiarly constructed reverberatory furnaces. Iron 

 guns are cast at iron- works, where all the necessary apparatus for moulding, 

 boring, and turning are already on hand ; for bronze guns, however, a 

 particular casting-house is constructed in the place where the artillery work- 

 shops are located, provided with all the requisite apparatus and the machinery 

 for boring and turning. PI. S9, Jig. 1, is the longitudinal section along the 

 hne XY in the ground-plan (Jig. 2) of a casting-house or cannon foundry, 

 and Jig. 3 is the cross section of the same, through its principal spaces. 

 A is the foundry proper and space for moulding the guns ; B, the room for 

 small mouldings, with a pot furnace for lesser castings. C is a large hearth 

 sloping to the tap-hole ; D, a smaller one, to be used when only one or two 

 guns are to be cast ; if both are used at once, from eight to ten guns can 

 be cast at the same time. E is the pit ; F, a drying oven for loam casting ; 

 G, the platform scales for weighing the metal and the guns when finished ; 

 H, the great crane, turning on a pivot, for moving heavy masses in the 

 moulding process and for setting in the mould ; I, the smithy ; K, pattern 

 room and dwelling of the director ; L, furnace space ; a, steps to the ash- 

 pit ; h h^ b", pipe for leading the air blast to the furnaces ; c, drain to carry 

 off" water from the pit ; d, wells ; e, drain from the moulding-room ; /, drain 

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