‘He [John Harrison] wrested the world’s whereabouts from the stars, and locked the secret in a pocket watch’. Dava Sobel, Longitude, Fourth Estate, London, 1998

Harrison H-4 Chronometer

Since earliest times Europe’s sea-faring nations England, Portugal, France, Spain the Netherlands vied with each other to solve – the Holy Grail of Navigation – longitude – calculating with precision a ship’s position at sea while beyond sight of land.

Cornwell – 1707:  In heavy weather six (6) of Admiral Clowdisley Shovell’s ships lost their bearings off the Cornish coast and dashed to pieces against the Scilly Isles with the loss of 1500 lives

1714  – Westminster: An enquiry into England’s first recorded 18th century maritime disaster resulted in legislation- The Act of Longitude 1714.

A Board of Longitude was established under the Act. Its task to invite and evaluate submissions and award a prize of £20,000 to whom-so-ever solved the problem of determining longitude at sea.

The contest,  to the detriment of the world’s seafarers, developed into a naked grab for cash. A king’s ransom, reckoned now at more than £400,000,000, did much to delay recognition of the solution at the cost of countless lives.  See: Lotto and Longitude

‘John Harrison, the man who solved longitude in 1759’. Peter Ackroyd, Revolution, Macmillan, London, 2016 See: Lieutenant William Dawes & ‘The Eternal Flame’

There had only two (2) viable contenders for the Longitude Prize. Astronomer Royal Rev. Nevil Maskelyne’s Nautical Almanac , a system of  Luna Tables  and Star Cataglog favoured by a succession of Astronomer Royals and a sea-going ‘pocket-watch’ the invention of John Harrison a Yorkshire carpenter.

‘The Board of Longitude was top-heavy with astronomers, mathematicians and navigators…the Reverend Nevil Maskelyne the fifth astronomer royal, who contested his [Harrison’s] claim to the [Longitude] prize money and whose tactics at certain junctions can only be described as foul-play’. Dava Sobel. ibid.

‘As early as 1514, the German astronomer Johannes Werner struck on a way to use the motion of the moon as a location finder. The moon travels a distance roughly equal to its own width ever hour’. Dava Sobel. ibid.

Greenwich Observatory: A succession of Astronomer Royals were wedded to Luna Tables.  Understandably so with Rev. John Flamsteed the first to hold the post.  Appointed in 1676 by King Charles 11 Luna Tables were his life’s work.

On Flamsteed’s death in 1719 Edmond Halley of comet fame became Britain’s second Astronomer Royal.  Halley died in 1742.  Then came James Bradley who held the position for twenty (20 years until his demise in 1762.

Next Nathaniel Bliss (1762-1764) sickness however cut his reign short. Although he visited the Observatory once or twice Bliss did not take up residence.

During this period and, until  Rev. Nevil Maskeltyne the fifth appointee took up his tenure in 1765, Charles Green acted as surrogate Astronomer Royal.

In 1765 Maskelyne began his long tenure (1765 -1811) during which period he held a strangle-hold over everything but the moon and stars. See: Moon Versus Machine.

‘The Almanac represents Maskelyne’s enduring contribution to navigation – and the perfect task for him too, as it embodied an abundance of excruciating detail’. Sobel. ibid.


Portugal:  In 1736-7 in HMS Centurian John Harrison had taken H-1 on a supervised time-trial voyage London to Lisbon. It performed within the guidelines required by the Board of Longitude.

. …a banner week for Harrison, because on the 30th [June 1737] the commissioners of the Board of Longitude convened for the very first time – twenty-three years after the board was created – citing his marvellous machine [H-1] as the occasion’. Sobel. ibid.

The might of one commissioner, Nevil Maskelyne however, was brought to bear on Harrison personally and against his ‘marvellous machine’ the ‘pocket-watch‘.  The prize money did not find its way to Harrison’s pocket.


Shortly before Cook sailed [for Tahiti]’ Maskelyne published his Nautical Almanac. See: Moon Versus Machine

Tahiti – 1769: When in 1769 Yorkshire-man Lieutenant James Cook RN, after observing the Transit of Venus at Tahiti sailed Endeavour, under ‘Secret Admiralty Instructions’,  to search for the fabled Great South Land.

He had with him Maskelyne’s ‘tedious’ celestial Almanac but not Harrison’s ‘never-failing pocket-watch’. See: Captain Cook Caught Short

‘[It] was bolted to a window-seat at the Observatory’. Dava Sobel. ibid.

Cook did however have the invaluable service of Charles Green a fellow Yorkshire-man. Green, an accomplished astronomer, had served as official Assistant to two (2) Astronomer Royals. Firstly under Rev. James BradIey who succeeded Edmond Halley in 1742.

Bradley held the post for twenty (20) years until his death in 1762. Nathaniel Bliss followed Bradley in 1762 but ill-health marked his short tenure.

Bliss remained at Oxford University and did not take up residence at Greenwich. He died in 1764. During Bliss’ absence, until a fifth Astronomer Royal was appointed in 1765, Charles Green acted as surrogate Astronomer Royal.

Barbados – 1764:  With Bliss too ill to travel, Green acting as official representative of the Board of Longitude, travelled to Barbados with the Rev. Nevil Maskelyne, to assess yet again the accuracy of H- 4, John Harrison’s improved ‘pocketwatch’.

Green found H-4 ‘the perfect timekeeper‘. It satisfied all that was required. Maskelyne however took the opposing view. See: The Third Man – Charles Green

‘At the heart of Dava Sobel’s fascinating brief history of astronomy, navigation, and horology stands the figure of John Harrison and his forty-year obsession with building the perfect timekeeper’. Sobel, Longitude, Cited Cover Paperback Edition


Greenwich – 1765: At the beginning of 1765 King George III announced Reverend Maskelyne ‘s appointment as Britain’s fifth Astronomer Royal.

On the 15th of March 1765 Green logged his final Observations and left the Observatory soon afterwards.

Nevil Maskelyne, after negotiating a much more than satisfactory salary, assumed his active role as Astronomer Royal in mid March 1765. He held the post until his death in 1811. See: The Third Green, Charles Green


Tags: , , , , , , , ,

Leave a Reply