-An moas rifled canijpu is just bouig (iuislictl at the Furt PUt foundry, Pittsburgh. - Tlio Iongth of the gun is 16 feet ; length of bore 14 feet ; diameter of boro l2 inuhts ; diameter of the gun at the breech 4S iucb.es: diameter at the muaile 2ö iuches. The ball will be'l2" inphpa in diameter, and the weiglit about, G(M pouiids. ïUe rongb casting of . the gun weighs 78,000 pounds. Fiijishcd it will weigh 50,000 pounds. ïhc ehaniber has 21 grooves. This most formidable ve:pon is understood to be prep&red for Portress Monroc.