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 string casing might be described as 9-5/8" 53.5# P-110 LT&C Rg 3: specifying OD, weight per foot (53.5 lbm/ft thus 0.545-inch wall thickness and 8.535-inch inside diameter), steel strength (110,000 psi yield strength), end finish ("Long Threaded and Coupled"), and approximate length ("Range 3" usually runs between 40 and 42 feet). Casing is run to protect or isolate formations adjacent to the wellbore. It is generally not possible to drill a well through all of the formations from surface (or the seabed) to the target depth in one hole-size section. For example, fresh-water-bearing zones (usually found only near the surface) must