John Farrell: The Clock and the Camshaft
Although nailing a bent strip of iron to a horse’s hoof dates to Roman times, widespread use of horseshoes arose only at the end of the 800s. Horseshoes provided better traction and boosted draft horses’ endurance, helping foster greater agricultural productivity, John Farrell reports in The Clock and the Camshaft and Other Medieval Inventions We Still Can’t Live Without.