Excerpt of John Harrison's early work from the AHS journal 1976. Re-produced with the kind permission of the Antiquarian Horological Society with updated images from David Penney

John Harrison (April 3, 1693 - March 24, 1776) was an English horologist, born in Foulby, Yorkshire, England. He invented the first accurate marine chronometer, enabling navigators to calculate their longitude accurately at sea.

Harrison was brought up as a carpenter and his understanding of wood can be seen in the execution of wheels in some of his early clocks that were made in a combination of oak and the pinions using lignum vitae (a hard wood with a naturally greasy surface).

To ensure the teeth remained strong enough to resist the pressure transmitted through the train they were cut systematically along the strongest direction of the grain of the wood. Then each section was slotted into the central disc and glued in position.

The assembled wheel and pinion below pivot on the cross-over section between two brass wheels to reduce friction, replacing a conventional pivot and circular bearing.

Re-produced with the kind permission of

the Antiquarian Horological Society and David Penney