Horseshoe to the modern hoof boot. Historians differ on the origin of the horseshoe. Because iron was a valuable commodity, and any worn out items were generally reforged and reused, it is difficult to locate clear archaeological evidence. Although some credit the Druids, there is no hard evidence to support this claim. In 1897 four bronze horseshoes with what are apparently nail holes were found in an Etruscan tomb dated around 400 B.C. The assertion by some historians that the Romans invented the "mule shoes" sometime after 100 BC is supported by a reference by Catullus who died in 54 BC.
Casing (submarine) easily, eliminating any buoyancy contributed by the casing and allowing the submarine to submerge with as little delay as possible. Casings have been eliminated since the end of World War II as the flow of water through the numerous flood-holes creates noise that may be detected by an enemy using passive sonar, as well as causing hydrodynamic drag. Casing (submarine) The casing of a submarine is a light metal structure, usually incorporating a deck, built over the upper surface of the vessel's pressure hull. The pressure hull of a submarine is usually cylindrical and possesses a low freeboard when in