‘But by reason of the motion of the Ship, the Variation of Heat and Cold, Wet and Dry, and the Difference of Gravity in different Latitudes, such a watch hath not yet been made”. And not likely to be, either, he implied’.  Isaac Newton cited, Dava Sobel, Longitude, Fourth Estate, London, 1998

‘Not likely’ however in 1736-7 on a timed voyage, England to Lisbon aboard HMS Centurian, H-1 an early model of John Harrison’s  marine watch – proved to be a reliable time-keeper.

‘He [Harrison] succeeded, against all odds, in using the fourth – temporal – dimension to link points on the three-dimensional globe’. Sobel. ibid.

Accurate time-keeping was essential for the calculation of longitude at sea and John Harrison a Yorkshire carpenter solved that problem  with his sea-going ‘pocket watch’ that gave a ship’s precise position when beyond sight of land.

‘John Harrison, the man who solved longitude in 1759’. Peter Ackroyd, Revolution, Macmillan, London, 2016

Maritime disasters were common-place throughout the centuries. One of England’s worst recorded disasters occurred during the reign of Queen Anne in the middle of the War of Spanish Succession (1701-1714) .

1707 – 29 September: At the end of September 1707 a fleet of twenty-one (21) English ships led by HMS Association flagship of Admiral Cloudesley Shovell, overall Commander of British fleets set sail from Gibraltar, captured in 1704 from Spain, for Portsmouth England their home base.

Shovell’s vessels were battered by fierce gales. As they neared England dense sea-mist thrown up by recurring storms proved a nightmare for ships’ navigators making it all but impossible to plot a safe course.

1707 – 22 October: To add to their woes, when off the coast of Cornwall heavy cloud obscured moon and stars, celestial navigation became impossible. In the darkness some sailing masters lost their bearings and failed to recognise their proximity to the Isles of Scilly.

Four (4) vessels including HMS Association crashed onto rocks and sank with all hands including Admiral Shovell. Two (2) more ships capsized, overall mortality was reckoned at 1500 souls.

 ‘The 1707 incident, so close to the shipping centres of England, catapulted the longitude question into the forefront of national affairs [and] underscored the folly of ocean navigation without a means for finding longitude’. Dava Sobel. ibid.

A lengthy investigation into the Cloudesley Shovell disaster concluded, due to prevailing weather conditions, ships’ navigators had been unable to determine their true position in relation to the Cornish coast.

‘The souls of Sir Cloudesley’s lost sailors – another thousand martyrs to the cause precipitated the famed Longitude Act of 1714, in which Parliament promised a prize of £20,000 for a solution to the longitude problem’. Sobel. ibid.

So why then by 1740, nearly a half-century after Parliament passed the Longitude Act,  did a second naval disaster of similar magnitude occur yet  its prize, £20,000 reckoned now at more than £400 millions, had not been awarded?

Worse still; ‘ when John Harrison arrived in London in the summer of 1730, the Board of Longitude was nowhere to be found. Although that august body had been in existence for more than fifteen years, it occupied no official headquarters in fact, it had never met’. Sobel. ibid.

By 1740 Harrison had built three (3) versions of his mechanical ‘watch’ but persistent hounding by the commissars – Astronomer Royals – of Greenwich Observatory meant that when disaster overtook Admiral Anson;‘the longitude clock stood on terra firma in Harrison’s home at Red Lion Square’. Sobel. ibid.

On the days before reliable time-keeping, the skies were used as a giant clock’.Vanessa Collingridge, Captain Cook, The Life, Death and Legacy of History Greatest Explorer, Random House, London, 2003

1740 – September: Although H-2 and H-3, improved models of Harrison’s chronometer, were available Commodore George Anson in HMS Centurion, took a squadron of six (6) warships to sea ‘the old fashioned way’.

‘Anson’s squadron took the Atlantic the old-fashioned way, on the strength of latitude readings, dead reckoning and good seamanship’. Sobel. ibid.

1741 – March: Anson’s ships rounded Cape Horn in early March 1741 only to be caught by gales so intense navigators had no idea where the squadron stood in relation to the land. As Dava Sobel has it; ‘a grand tragedy unfolded, founded on the loss of their longitude at sea’.

The squadron had been at sea longer than intended. Many crew developed scurvy ‘killing 6 to 10 men every day’. As time went on, there was never enough man-power to repair sails shredded by ‘winds [that] carried rain, sleet and snow’. 

Finally, the ship’s reached Juan Fernandez where Admiral ‘Anson helped carry the hammocks of sick sailors ashore, then watched helplessly as the scourge picked off his men one by one…until more than half of the original five hundred were dead and gone’.  Sobel. ibid.

‘The old fashioned way’ celestial navigation used complex Lunar Tables devised a century earlier by Rev. John Flamsteed during his tenure as Britain’s first Astronomer Royal. Appointed by King Charles II in 1675 he held the post until his death in 1719.

Flamsteed’s Luna Tables and Star Catalogues may have been well suited to static land-based platforms. But much less so on a pitching deck in churning seas when dense cloud and black starless nights magnified a navigator’s problems.

In such circumstances ‘tedious’ complicated ‘difficult to execute’ calculations required four  (4) men with hand-held instruments, the reason many a seaman lost an eye.

Flamsteed himself had, like Harrison, felt the cruel lash of duplicity.

With the connivance of Isaac Newton, Edmond Halley of comet fame,  purloined, plagiarised and, during the Flamsteed’s lifetime, published his work without permission or attribution. In 1720, following Flamsteed’s death, Halley was appointed Astronomer Royal.

Meantime in 1740 Admiral Anson’s martyrs were added to Sir Cloudesley’s lost souls and this, in part at least, because £20,000 up for grabs, had unintended consequences.

‘The Board of Longitude was top-heavy with astronomers, mathematicians and navigators’. Sobel. ibid.

The vast sum proved a heady brew when thrown amidst the warlocks of Greenwich Observatory whose intransigence was without doubt responsible for the loss of countless lives.

‘John Harrison, the man who solved longitude in 1759’. Peter Ackroyd, Revolution, Macmillan, 2016

In the mid 1760s battle-lines were drawn between moon and machine. The Observatory’s Rev. Nevil Maskelyne, Britain’s fifth Astronomer Royal, clung to outmoded 17th century thinking and old technology – Luna Tables versus the mechanical sea-going clock. ‘See: Moon Versus Machine 

1765:  Maskelyne published the first edition of his major work The Nautical Almanac’ one hundred (100) years after King Charles II founded Greenwich Observatory.

Maskelyne was certain theNautical Almanac’, based on the relationship between Sun, Moon and Stars as a means of calculating longitude on the high seas, would deliver him the ‘king’s ransom’ £20,000.

John Harrison died in March 1776 aged ‘exactly eighty-three years’. Dava Sobel covers fully the extraordinary story of the Yorkshire carpenter whose invention of the marine chronometer solved the problem of longitude at sea. See: Cook, Harrison, Green – Three Yorkshire Men Walked Into A Bar – Maskelyne

‘A true-life thriller, jam-packed with political intrigue, international warfare, personal feuds and financial skullduggery’. Francis Wheen, Daily Mail.

Longitude tells of Harrison’s painstaking efforts to perfect his ‘watch’ and of unending frustrations as he butted heads with the dictators of the Longitude Board.

Sobel catalogues the merciless persecution of Harrison by a succession of Astronomer Royals, James Bradley, Nathaniel Bliss and finally Rev. Nevil Maskelyne who held the position from 1765 to 1811. See: Malicious Maskelyne

‘Rarely have I enjoyed a book as much as Dava Sobel’s Longitude. She has an extraordinary gift of making difficult ideas clear’. Patrick O’Brien, Daily Telegraph (London).

For more details on Dava Sobel’s book, Longitude see:


‘In January 1772 William [Harrison] wrote the king [George III] a poignant letter covering the history of his father’s hardships with the Board of Longitude and the Royal Observatory…the king is reported to have muttered under his breath “These people have been cruelly treated”. Sobel. ibid.

And where a mere three (3) years earlier, in 1769, was Harrison’s chronometer when Lieutenant James Cook RN sailed HMS Endeavour deep into the South Seas in search of the fabled Great South Land?

‘[H-4 [was] bolted to a window seat in the [Greenwich] Observatory’. Sobel. ibid. See: Captain Cook Caught Short



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