‘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’ – not so – as early as 1736, on a timed voyage, England to Lisbon aboard HMS Centurian, H-1 a marine clock had shown itself 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 to the calculation of longitude that gave a ship’s precise position at sea when beyond sight of land.

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

Harrison was the carpenter from Yorkshire whose invention, the sea-going watch, solved the problem of longitude.

On the day 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, 2003

Throughout the centuries maritime disasters were common-place. One of England’s worst recorded disasters occurred in the first decade of the 18th century in the middle of the War of Spanish Succession (1701-1714) during the reign of Queen Anne.

 1704: England had captured Gibraltar from Spain in 1704.

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 for Portsmouth their home base.

Nearing England Shovell’s vessels were battered by fierce gales. Dense sea-mist thrown up by recurring storms proved a nightmare for ships’ navigators as they attempted to plot a safe course.

 1707 – 22 October: Off the coast of Cornwall celestial navigation became impossible when a run of dark nights with heavy cloud obscured moon and stars.

Sailing masters lost their bearings and failed to recognise their proximity to the Isles of Scilly.

Four (4) vessels including HMS Association crashed into those rocky isles 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, Longitude, Fourth Estate, 1998

 A lengthy investigation into the 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 by 1740 when a second naval disaster of similar magnitude occurred and, nearly a half-century after Parliament passed the Longitude Act of 1714 authorising a prize of £20,000 reckoned now at more than £400 million, had the prize not been awarded to John Harrison?

As the result of persistent hounding by the commissars of Greenwich Observatory; ‘the longitude clock stood on terra firma in Harrison’s home at Red Lion Square’. Sobel. ibid

 1740 – September: Commodore George Anson in HMS Centurion led a squadron of six (6) warships to sea in 1740;‘the old fashioned way’ that is without benefit of a Harrison chronometer although improved models H-2 and H-3 were available.

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

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.

Lunar Tables ‘the old fashioned way’ had been devised a century earlier by John Flamsteed during his tenure as Britain’s first Astronomer Royal from 1675 to 1719.

 Flamsteed’s Luna Tables and Star Catalogues were well suited to static land-based platforms but not so on a pitching deck in churning seas under dense cloud on starless nights.

In such circumstances, complicated calculations made with hand-held instruments, were ‘difficult to execute’ and there-in lay the reason many a seaman lost an eye.

Flamsteed himself felt the cruel lash of duplicity. Halley of comet fame had purloined, plagiarised and published Flamsteed’s work without the author’s permission.

In 1720, following Flamsteed’s death, Halley was appointed Astronomer Royal.

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

Admiral Anson’s martyrs were added to Sir Cloudesley’s lost souls in part at least because The Longitude Prize of £20,000 had unintended consequences.

This 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 however battle-lines were drawn between moon and machine. The Observatory’s Rev. Nevil Maskelyne clung to outmoded 17th century thinking and old technology – Luna Tables versus the sea-going clock.

See: Moon Versus Machine 

1765:  Maskelyne, Britain’s fifth Astronomer Royal, one hundred (100) years after King Charles II founded Greenwich Observatory in 1675, published the first edition of his work The Nautical Almanac’.

Maskelyne was certain theNautical Almanac’, based exclusively 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.

 ‘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.

Dava Sobel covers fully the extraordinary story of Mr. John Harrison the Yorkshire carpenter who invented the marine chronometer and solved the problem of longitude.

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

 Longitude tells of John Harrison’s painstaking efforts to perfect his ‘watch’ and 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 then the Rev. Nevil Maskelyne who held the position of Britain’s fifth Astronomer Royal between 1765 and 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:


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

Why then a decade later, in 1769, did Lieutenant James Cook RN sail Endeavour deep into the South Seas in search of the Great South Land without Harrison’s chronometer?

‘[H-4 [was] bolted to a window seat in the [Greenwich] Observatory’. Sobel. ibid.

See: Captain Cook Caught Short



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