The heaviest of our up-to-date ordnance is of moderate calibre, the largest breech-loaders being 12-inch, 10-inch, and 9.2-inch guns. But the elaborateness of its manufacture is such that one big gun takes nearly as long to “build up” as the ship for which it is destined. Each weapon has to pass through about sixteen different processes:-- (1) The solid (or hollow) ingot is _forged_. (2) _Annealed_, to get rid of strains. (3) It is placed horizontally on a lathe and _rough-turned_. (4) _Rough-bored_ in a lathe. (5) _Hardened._ Heated to a high temperature and plunged, while hot, into a bath of rape oil kept cold by a water-bath. It cools slowly for seven to eight hours, being moved about at intervals by a crane. This makes the steel more elastic and tenacious. (6) _Annealed_, _i.e._ reheated to 900° Fahr. and slowly cooled. Siemens’ pyrometer is used in these operations. (7) _Tested_ by pieces cut off. (8) _Turned_ and _bored_ for the second time. (9) Carefully turned again for _shrinkage_. Outer coil expanded till large enough to fit easily over inner. Inside, set up vertically in a pit, has outside lowered on to it, water and gas being applied to make all shrink evenly. Other projections, hoops, rings, &c., also shrunk on. (10) Finish--_bored_ and _chambered_. (11) _Broached_, or very fine bored, perhaps _lapped_ with lead and emery. (12) _Rifled_ horizontally in a machine. (13) Prepared for breech fittings. (14) Taken to the Proof Butts for trial. (15) Drilled for sockets, sights, &c. Lined and engraved. Breech fittings, locks, electric firing gear, &c., added. Small adjustments made by filing. (16) _Browned_ or _painted_. When worn the bore can be lined with a new steel tube. These lengthy operations completed, our gun has still to be _mounted_ upon its field-carriage, naval cone, or disappearing mounting, any of which are complicated and delicately-adjusted pieces of mechanism, the product of much time and labour, which we have no space here to describe. Some account of the principal parts of these guns has already been given, but the method by which the breech is closed remains to be dealt with.