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Sebastian A. Molina

Dr. Richard Hirsh

History 3715

October 22, 2013

The £20,000 clock that changed the history

With the start of exploration voyages in the fifteenth century, a system to determine

the longitude at sea in an accurate form became very important. The relevance of the

longitude problem relied on the economic needs of merchants and the safety of seamen in

case of sea storms and possible shipwrecks.1 To fulfill this need, the Board of Longitude

offered a £20,000 prize for anyone who can develop a practical method to precisely

calculate the longitude on a ship.2 The amount of the prize caught the attention of a young

carpenter and clockmaker from Lincolnshire called John Harrison. He began to develop the

very first precision timekeeper, the basis of today’s watches.

John Harrison made a breakthrough with his first major project in which he changed

the conventional anchor escapement with an invention of his own, the grasshopper

escapement. This escapement allowed the clock to have a system that avoids the friction

caused by oil and the deterioration of oil-based mechanisms by incorporating bearings that

used rolling contact instead of sliding contact.3

The first prototype, called H1, implemented the grasshopper escapement, an

oscillator and the gridiron system used in Harrison’s previous clocks.4 The oscillator

1 Jonathan Betts, Time Restored: The Harrison Timekeepers and R.T. Gould, the man who knew (almost) everything (New York: Oxford University Press Inc., 2006), 83.

2 Jonathan Betts, “John Harrison: inventor of the precision timekeeper,” Endeavour, 1993, 160.3 Rupert T. Gould, The marine chronometer; its history and development [by] Lt. Commander

Rupert T. Gould. With a foreword by Sir Frank W. Dyson. (London: Holland Press, 1923), 41.4 Rupert T. Gould, The marine chronometer; its history and development [by] Lt. Commander

Rupert T. Gould. With a foreword by Sir Frank W. Dyson. (London: Holland Press, 1923), 41.

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consists in two bar-balances link to each other and connected with balance springs which

allows the clock to have its own gravity so that every motion affecting one balance is

counteracted by the other balance. In order to manage the temperature changes Harrison

used the gridiron system, a compensated pendulum that uses a grid of bras and steel wires,

which he developed previously.

The H2 had a simplified design of the gridiron system and include a remontoir.5 The

remontoir device consists in a small spring that controls the main train to avoid time

variations. The H3 had just improvements and redesigning on previous mechanisms but the

H4 was made from a completely new approach.

Made as a large watch, the H4 had a higher frequency oscillation and a bimetallic

strip6 to compensate the temperature changes. It also had a verge escapement, similar to

common watches but unfortunately it requires oil on its bearings. The last timekeeper called

H5 showed improvements on H4 design and a simplified appearance.

The impact of the marine timekeeper relies on the solution of the longitude problem

and the strengthening of the Royal British and merchant navies by keeping them out of

shipwrecks and giving them economic and trading power.7 Also, the Harrison’s designing

concepts made England the leader on marine timekeepers and precision watches production

until the nineteenth century.8

Word count:432

5Jonathan Betts, “John Harrison: inventor of the precision timekeeper,” Endeavour, 1993, 163. 6Jonathan Betts, Time Restored: The Harrison Timekeepers and R.T. Gould, the man who knew

(almost) everything (New York: Oxford University Press Inc., 2006), 97. 7Jonathan Betts, Time Restored: The Harrison Timekeepers and R.T. Gould, the man who knew

(almost) everything (New York: Oxford University Press Inc., 2006), 86. 8Jonathan Betts, “John Harrison: inventor of the precision timekeeper,” Endeavour, 1993, 167.

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Bibliography

Betts, Jonathan. 1993. "John Harrison: inventor of the precision timekeeper." Endeavour 17 (4): 160-167.

—. 2006. Time Restored: The Harrison timekeepers and R.T. Gould, the man who knew (almost) everything. New York: Oxford University Press Inc.

Gould, Rupert T. 1923. The marine chronometer; its history and development [by] Lt. Commander Rupert T. Gould. With a foreword by Sir Frank W. Dyson. London: Holland Press.

Harrison, John. 1767. The principles of Mr. Harrison's time-keeper. London: Commissioners of Longitude.

2010. The Clock That Changed the World. Directed by Paul Bader. Produced by Paul Bader. Performed by Adam Hart-Davis.

May, W. E., and H. D. Howse. 1976. "How the chronometer went to sea." Vistas in Astronomy 20 (1): 135-136.