When Did the Accurate Mechanical Clocks Appear?
In Europe during most of the Middle Ages (roughly 500 to 1500 A.D.), technological advancement was at a virtual standstill. Sundial styles evolved, but not far from ancient principles. Then, in the early-to-mid-14th century, large mechanical clocks began to appear in the towers of several large Italian cities. These clocks those were weight-driven and regulated by a verge-and-foliot escapement. Like water flow, the rate was difficult to regulate.
Another advance was the invention of spring-powered clocks between 1500 and 1510 by Peter Henlein of Nuremberg. They slowed down as the mainspring unwound. The clock was invented part by part. In 1577, Jost Burgi invented the minute hand. Burgi’s invention was part of a clock made for Tycho Brahe, an astronomer who needed an accurate clock for his star-gazing.
In 1656, Christian Huygens, a Dutch Scientist, made the first pendulum clock, regulated by a mechanism with a ‘natural’ period of oscillation. Although Galileo Galilei, sometimes credited with inventing the pendulum, studied its motion as early as 1582, Galileo’s design for a clock was not built before his death. Huygen’s pendulum clock had an error of less than one minute a day, the first time such accuracy had been achieved.
His later refinements reduced the error to less than ten seconds a day. In 1721, George Graham improved the pendulum clock’s accuracy to one second a day by compensating for changes in the pendulum’s length due to heat variations. John Harrison, a carpenter and self taught clock maker, refined Graham’s temperature sation techniques and added new methods of reducing friction.
By 1761, he had built a marine chronometer with a spring and balance wheel. It kept time on board rolling ship to about one-fifth of a second a day, nearly as well as a pendulum clock could do on land, and ten times better than required. One of the most famous, the W. H. Shortt clock, was demonstrated in 1921.
The Shortt clock almost immediately replaced Riefler’s clocks as a supreme time keeper in many observations. This clock consists of two pendulums, one a slave and the other a master. The slave pendulum gives the master pendulum the gentle pushes needed to maintain its motion, and also drives the clock’s hands. This allows the master pendulum to remain free from mechanical tasks that would disturb its regularity.