The torsion clock, typically known as a 400-day clock in the U.K and the anniversary clock in the United States, was first developed by Aaron D. Crane in 1841 using a rotary—rather than swinging—pendulum invented by Robert Leslie nearly 50 years earlier. Crane’s clock, which was designed to run for more than a year without winding, was driven by an escapement activated by this style of spinning pendulum, which Crane hung from a slender...Continue Reading