involved in the Construction of Artillery. 235 



by abandoning altogether the use of "loam," or "dry sand," or any badly con- 

 ducting moulds for bronze guns, and casting them in massive moulds formed of 

 cast-iron, bored out internally to the exact figure of the gun, with a very small 

 allowance for turning externally, — the iron mould being put together in pieces, 

 separable not only horizontally into frusta, but vertically in a plane passing 

 through the axis, so as to admit of the withdrawal of the gun when cast. Should 

 the main object be found gained, of securing a perfectly homogeneous casting, 

 without deterioration of the properties of the metal in any way that could not 

 be met by suitable variation in its constituents, or in manipulation, then several 

 important subsidiary ends would be gained also : such as greatly reduced cost 

 and saving of time, and hence, increased production, by rendering needless the 

 present system of loam moulding by skilled labour ; absolute identity and per- 

 fection of form of the exterior of the gun when cast, — objects very ill attained, 

 indeed, under the present methods, even in the best hands ; great economy in 

 the subsequent processes of finishing the gim, so far as turning its exterior is con- 

 cerned; considerable economy in the amountof waste metal now cut ofFin turning. 



Besides this, the casting in iron moulds would admit of an almost unlimited 

 increase of statical pressure upon the head of metal, would facilitate the deli- 

 cate process of casting bronze guns hollow, upon slender " loam cores ;" would 

 admit of the fluid metal being introduced into the mould at the bottom instead 

 of at the top, with an ease and safety impossible with " loam moulds ;" and lastly, 

 would allow of the whole vertical mould and fluid metal within it bein" ^iven 

 a rapid motion of rotation round the axis of the gun during the process of cool- 

 ing (if deemed desirable), by which a complete mixture and homogeneity of 

 the included metal might be secured during the short interval that would 

 elapse between the mould being full and the consolidation of the metal. The 

 experience of brass-founders, in connexion with civil works, of late years, has 

 largely extended the use of iron moulds, and shown their extreme utihty and 

 economy ; they do not wear out or burn away, and once properly made and 

 prepared, stand an almost indefinite number of castings. 



It may be said, however, that if it be also a fact that small portions of oxygen, 

 or other gases, are evolved from gun-metal at the moment of consolidation, such 

 rapid cooling would result in the entanglement of the air vesicles so produced 

 in the mass of the metal, rendering it porous and undurable. 



