A grandfather clock (also a longcase clock, tall-case clock, grandfather's clock, or floor clock) is a tall, freestanding, weight-driven pendulum clock with the pendulum held inside the tower or waist of the case. Clocks of this style are commonly 1.8–2.4 metres (6–8 feet) tall with an enclosed pendulum and weights suspended by either cables or chains which have to be calibrated occasionally to keep the proper time. The case often features elaborately carved ornamentation on the hood (or bonnet), which surrounds and frames the dial, or clock face. The English clockmaker William Clement is credited with the development of this form in 1670. Until the early 20th century, pendulum clocks were the world's most accurate timekeeping technology, and longcase clocks, due to their superior accuracy, served as time standards for households and businesses. Today they are kept mainly for their decorative and antique value, having been widely replaced by both analog and digital timekeeping. Naming The Oxford English Dictionary states that the popular 1876 song My Grandfather's Clock is responsible for the common name "grandfather clock" being applied to the longcase clock. The song was composed by an American songwriter by the name of Henry Clay Work who discovered a longcase clock in The George Hotel in Piercebridge, in County Durham in England. When he asked about the clock, he was informed that it had two owners. After the first owner died the clock became inaccurate and when the second owner died, the clock stopped working altogether. The story inspired Henry to create the song. Grandfather clocks are of a certain height, usually at least 1.9 metres (6 feet - 3 inches). There are also "grandmother" and "granddaughter" clocks, which are slightly shorter in height. Origin The advent of the longcase clock is due to the invention of the anchor escapement mechanism by Robert Hooke around 1658. Prior to the adoption of the anchor mechanism, pendulum clock movements used an older verge escapement mechanism, which required very wide pendulum swings of about 80–100°. Long pendulums with such wide swings could not be fitted within a case, so most freestanding clocks had short pendulums. The anchor mechanism reduced the pendulum's swing to around 4° to 6°, allowing clockmakers to use longer pendulums, which had slower "beats". These consumed less power allowing clocks to run longer between windings, caused less friction and wear in the movement, and were more accurate. Almost all