John Harrison - Career

Career

Harrison built his first longcase clock in 1713, at the age of 20. The mechanism was made entirely of wood, which was a natural choice of material for a joiner. Three of Harrison's early wooden clocks have survived; the first (1713) is at the Worshipful Company of Clockmakers' Collection in Guildhall; the second (1715), is in the Science Museum and the third (1717) is at Nostell Priory in Yorkshire, the face bearing the inscription "John Harrison Barrow". The Nostell example, in the billiards room of this fine stately home, has a Victorian outer case, which has been thoughtfully provided with small glass windows on each side of the movement so that the wooden workings may be inspected. In the early 1720s Harrison was commissioned to make a new turret clock at Brocklesby Park, North Lincolnshire. The clock still operates and like his previous clocks has a wooden movement, made of oak and lignum vitae. Unlike his early clocks it incorporates some original features to improve timekeeping, for example the grasshopper escapement. Between 1725 and 1728 John and his brother James, also a skilled joiner, made at least three precision pendulum-clocks, again with oak and lignum vitae movements and longcase. The grid-iron pendulum was developed during this phase. These precision pendulum-clocks are thought by some to have been the most accurate clocks in the world at the time, and significantly are the direct link to the sea clocks. No.1, now in a private collection was in the collections of the Time Museum, USA, until that museum closed in 2000 and its collection dispersed at auction in 2004. No. 2 is in the collections of Leeds Museums and Galleries, West Yorkshire, United Kingdom. It is not usually on display but it will form part of a 2012 exhibition at York. No. 3 is in the Worshipful Company of Clockmakers' collection.

He was a man of many skills and used these to systematically improve the performance of pendulum clocks. He invented the gridiron pendulum, consisting of alternating brass and iron rods assembled so that the different expansions and contractions cancel each other out. Another example of his inventive genius was the grasshopper escapement – a control device for the step-by-step release of a clock's driving power. Developed from the anchor escapement, it was almost frictionless, requiring no lubrication because the pallets were made from the wood lignum vitae. This was an important advantage at a time when lubricants and their degradation were little understood. It is not often recognized that in his earlier work on the "Sea clocks" Harrison was continually assisted both financially and in many other ways by George Graham, the watchmaker and instrument maker who lent him a large sum on the basis of trust even after Harrison's first visit to Graham in 1728 to explain how his timekeeper worked. Harrison was introduced to Graham by the Astronomer Royal Edmond Halley who also championed Harrison and his work. This support was important as Harrison is reputed to have found it difficult to communicate his ideas in a coherent manner.