‘The Transit [of Venus] was more than just an astronomical curio, it was the key to a wealth of information about the universe, information that would be seized upon by the intensely curious men of science who characterised the age’. Vanessa Collingridge, Captain Cook, The Life, Death and Legacy of History’s Greatest Explorer, Random House, 2003

1663 – England: In 1663 during the reign of King Charles II (1660-1685) a collection of ‘intensely curious men of science’ – the ‘Invisible College’ – morphed into the Royal Society.

A century later, the Society flowered under the patronage of King George III (1720-1820), to become one of the world’s most celebrated scientific institutions.

In 1767 with the Transit of Venus in the offing – 3 June 1769 – its second appearance that decade – the Society petitioned King George III for financial support to send observers to report on the phenomenon.

‘That the passage of the Planet Venus over the Disc of the Sun, which will happen on the 3rd of June in the year 1769, is a Phaenomenon (sic) that must, if the same be accurately observed in proper places, contribute greatly to the improvement of Astronomy on which Navigation so much depends.

 As the [Fellows] are in no condition to defray this Expense about £4,000 pounds, exclusive of the Expense of the Ships…with all humility and submit the same to your Majesty’s Royal consideration’. Cited, H.C. Cameron, Sir Joseph Banks, Angus and Robertson, Sydney, 1968

1768 – February: To that end James Douglas 14th Earl of Morton, then President of the Royal Society, on 15 February 1768 penned a Memorial requesting the Monarch’s financial support.

Royal money was forthcoming for it was clear accurate and reliable ‘Navigation on which so much depends’ equated with domination over the world’s oceans. Domination would expedite expansion of territory and trade and with strategically placed ‘bases’ more likely assure victory in time of conflict.

‘And the sum of £4,000 pounds clear of fees, [was] to be placed at the disposal of the Society…On March 5th of the next year, 1768, the Navy Board was instructed by the Admiralty to purchase a suitable vessel for the great voyage to the South Seas’. Cameron, Sir Joseph Banks, Angus and Robertson, 1968

1768 – 5 March: Admiralty settled on the Earl of Pembroke. Renamed Endeavour she was a typical coal carriercat-built bark’ of 368 tons ‘stoutly built, flatly bottomed of shallow draught’.

 ‘In the all important question of the command of the expedition there was at first a difficulty….The Royal Society had accepted the recommendation of the Astronomer Royal [Nevil Maskelyne] that the well-known hydrographer Mr Dalrymple…should be chosen as ‘a proper person to be sent to the South Seas’ in the capacity of Chief Observer’. Cameron. ibid.

But the Admiralty in what was seen as a stunning reversal of protocol selected James Cook a mere Warrant Officer of the Royal Navy.

Cook then aged thirty-eight (38), was not only to captain HMS Endeavour he was given overall ‘management’ of the expedition.

It would be an understatement to say Cook’s appointment disturbed many illustrious members of the Royal Society. Dalrymple son of a wealthy well-connected Scottish family, had spent over a decade attached to the powerful joint-stock trading company, the British East India Company.

Dalrymple, obsessed by the wealth and romance of India, was intrigued by the south seas and the fabled land-mass Terra Australis Incognita. He was devastated by the Admiralty’s rebuff; ‘he would not make the voyage at all…on any footing than that of having management of the ship’.

Even though the Society pressed he retain the role of Chief Observer Dalrymple refused; ‘I can give no thoughts of undertaking the voyage as a passenger going out to make the observation’. Cameron. ibid.

Cameron says Dalrymple failed to appreciate that his demand; ‘having management of the ship [was] entirely repugnant to the regulations of the Navy’. 

 ‘The Admiralty based its refusal on the unfortunate results which had followed when the astronomer Edmund Halley had been placed in command of the war-sloop Paramour Pink.

 Halley had sailed in 1698 on a voyage to study the variations of the compass but was forced to return because of the mutinous conduct of the crew’. Cameron ibid.

 Now in 1768 the Navy, having supplied HMS Endeavour paid her captain and crew, was not about to give over another king’s ship to a hot-headed civilian whose arrogance was sure to get up the nose of professional seamen.

But the Admiralty’s rejection was to have the most  serious consequences. For the decision also reflected on Astronomer Royal Nevil Maskelyne who had championed Dalrymple’s cause.

When Endeavour departed Plymouth for Tahiti on 26 August 1768 and later, to satisfy the Admiralty’s ‘secret mission’ in search of the Great South Land she sailed without John Harrison’s marine chronometer the H-4.

‘John Harrison had perfected the chronometer some years before but it is the character that authorities who, for a great many years had withheld half of the prize for his achievement, should also decline to make an instrument available to Cook’. A.W. Beasley, Fellowship of Three. John Hunter Surgeon, James Cook Navigator, Joseph Banks Naturalist, Kangaroo Press, Sydney, 1993

Although it is known and, perhaps to muddy the waters, Maskelyne did provide Cook with a ‘astronomical clock’ but it was not Harrison’s accurate H-4.

‘H-4 [was] bolted to a window seat in the Observatory’. Dava Sobel, Longitude, Fourth Estate, London, 1998

It is arguable that if Cook had known the precise position of his ship while in vast uncharted waters he may not have had to spend so much time at sea and many lives could have been saved.

As it was, at Batavia homeward bound, Cook lost one half of Endeavour’s debilitated crew to malaria and dysentery. Among them Charles Green the astronomer who had represented the Royal Society as Official Observer. See: Cook, Harrison, Green – Three Yorkshire Men Walked Into A Bar – Nevil Maskelyne 

Joseph Banks, the celebrated botanist and Fellow of the Royal Society, had gathered a party of prominent naturalists and artists to accompany him on the Endeavour voyage and record their findings.  Of its ten (10) men only four (4) – including Banks himself – survived.


Dava Sobel has dissected forensically the Astronomers Royal of that time at Greenwich Observatory and in particular Maskelyne and his relentless persecution of John Harrison and his sea-going ‘pocket watch’.

Admiral Shovell’s disastrous multiship wreck off the Scilly Isles after the turn of the eighteenth century [1707 had] intensified the pressure to solve the longitude problem’.

In 1714, following the Scilly disaster off the Cornwell coast Parliament passed the Longitude Act. A Board of Longitude was established charged with solving the ‘longitude problem’.

From its inception the Board was dominated by Britain’s Astronomer Royals – John Flamsteed 1675-1719, Edmond Halley 1720-1742, William Bradley 1742-1762, Nathaniel Bliss 1762-1764 and Nevil Maskelyne 1765 -1811.

Dava Sobel has paid particular attention to Reverend Nevil Maskelyne. Smarting from the Admiralty’s rejection of Alexander Dalrymple he was responsible for with-holding H-4 from Lieutenant James Cook RN.  See: Captain Cook Caught Short

In 1768 however not all Royal Society’s Fellows were upset by Cook’s selection.  Among them James Douglas 14th Earl Morton the Society’s President. He has been described as; ‘a man of the thesis and the telescope rather than of blood and the sword’.

Cook had ,between 1762 and 1764 following Britain’s defeat of France in the Seven Years War, spent his summers surveying and charting the coastline of Newfoundland. His published maps received critical acclaim.

In 1766 Cook submitted the Royal Society a meticulous report on his observation of the eclipse of the sun made that year in Newfoundland. The report and Cook’s maps convinced Earl Morton that, although still a lowly warrant officer, Cook was eminently suitable for the task as leader of the Tahiti expedition and Chief Observer of the Transit of Venus.

‘Thereafter the Admiralty and the Royal Society worked amicably together in a vast amount of necessary preparation’. Cited, Cameron. ibid.

First Lieutenant James Cook RN was commissioned on 25 May 1768 and received his ‘Secret [Admiralty] Instructions’. After observing the Transit Cook was to sail further south in search of the fabled Great South Land.

It was thought logical that such a land-mass should exist. If found Cook was to assess if it was ripe for invasion?

‘You [Cook] are also to be careful to observe the nature of the soil and the products thereof, the beasts and fowls that inhabit or frequent it; the fishes that are to be found in the rivers or upon the coast, and in what plenty, and in case you find any mines, mineral or valuable stones, you are to bring home specimens of each.

 You are likewise to observe the genius, temper, disposition and number of the Natives.’ Public Records Office Admiralty 2/1132, issued July 30, 1768, cited Cameron.

Following the Admiralty’s refusal to accept Dalrymple the Royal Society looked to Greenwich Observatory for a skilled astronomer and engaged Charles Green to act as Cook’s Assistant Observer.

Green, born in 1734, was like Cook from Yorkshire. An excellent choice he served as chief assistant to three (3) Astronomer Royals – Rev. James Bradley, Rev. Nathaniel Bliss and briefly under Rev. Nevil Maskelyne.

These three (3) highly educated gifted mathematicians and astronomers were, unlike Green, wedded to old technology. Celestial navigation based solely on the movement of heavenly bodies – moon and stars. At Greenwich these had been set down in Luna Tables and Star Catalogue by Reverend John Flamsteed Britain’s first Astronomer Royal 1675-1719.

Nicholas Copernicus had been born in Poland in 1514. As a young man he moved to Bologna to study cannon law and found the wondrous world of astronomy.

De Revolutionilus Orbioum Caelestium’ his opus on the revolution of heavily bodies was published shortly before his death in May 1543. His work described a model of the solar system that placed the sun not the earth at its centre.

Then came Italy’s Galeileo Galilei the ‘father of observational astronomy’ 1564 -1642 and Johannes Keppler his German contemporary 1571-1630 who introduced an improved telescope.

In England Jeremiah Horrocks 1618-1641 was the first person to demonstrate the moon’s elliptical orbit. In 1639 amidst the horror and chaos of England’s Civil Wars Horrocks observed the Transit of Venus and recorded the phenomena in his Treatise ‘Venus in sole visa’.

‘On the day before reliable time-keeping, the skies were used as a giant clock’. Vanessa Collingridge. Ibid

No doubt Luna Tables were well suited to static land-based platforms such observatories in France, Germany, Italy, Russia and Britain. However, in pitching seas under dense cloud on dark and stormy nights, the required complicated calculations were ‘difficult to execute’ taking four (4) men to complete.

During Edmond Halley’s tenure at Greenwich 1720-1742 however a revolution in time-keeping was taking place. John Harrison’s marine chronometer H-I, had shown as early as 1736-7, on a timed voyage from England to Lisbon Portugal, aboard HMS Centurian, his sea-going ‘watch’ was found to be a ‘reliable time-keeping’.

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

However in the mid 1760s the Astronomer Royals of Greenwich Observatory had not moved on. They continued to argue vehemently for the efficacy of Lunar Tables.

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

Edmond Halley died in 1742 and Rev. James Bradley who succeeded him held the post of Astronomer Royal for twenty (20) years. While Bradley remained wedded to the ‘heavenly bodies’ his chief assistant Charles Green, a young mathematician and astronomer, dared to be different, He celebrated the certainty of the ‘Watch’.

On Bradley’s death in 1762 Rev. Nathaniel Bliss succeeded as Astronomer Royal. His two (2) year tenure was dogged by ill-health so much so, apart from visiting Greenwich, he did not take residence at the Observatory and died in Oxford in 1764. During this time Charles Green functioned as surrogate Astronomer Royal. 

Green believed time was the essential ingredient in establishing longitude at sea. However the argument over the reliability of Harrison’s ‘watch’ was still raging and The Longitude Board requested another time-trial.

1761 – November: William, John Harrison’s son, boarded HMS Deptford with H-4 for a voyage from Portsmouth to Jamaica. Not long after departure it was discovered much of Deptford’s food was rotten. Even more disastrous the grog had gone off; ‘with all the Beer gonethe People were obliged to drink water’.

With all haste Dudley Digges, Deptford’s captain, made for Madeira. Dava Sobel’s Longitude tells it best.

‘William [Harrison] promised a speedy end to the distress, as he reckoned with H-4 that the Deptford would make Madeira within a day. Digges argued that the Watch was way off, as was the island, and offered to lay odds on the bet.

Sceptical as to H-4’s accuracy Digges took a bet with William Lyttleton who was on his way to Jamaica to take up position of Governor.

Regardless the next morning brought Madeira into sight – and fresh barrels of wine into the hold. At this junction Digges made Harrison a new offer: he would buy the first longitude timekeeper that William and his father put up for sale, the moment it was available.

 While still in Madeira, Digges wrote to John Harrison: “Dear Sir, I have just time to acquaint you…of the great perfection of your watch in making the island on the Meridian.

According to our Log we were 1 degree 27 minutes to the Eastward, this I made by a French map which lays down the longitude of Teneriffe, therefore I think your watch must be right’. Cited in Sobel. ibid.

 But nothing would be good enough for the Board of Longitude or Bliss  who; ‘like Bradley before him was all for lunars’.

‘He insisted that the Watch’s so-called accuracy was a mere chance occurrence, and he did not predict a precision performance on the next trial’. Sobel. ibid.

1764 – March: The next trial came two (2) years later. In March of 1764 William Harrison, John’s son with a friend Thomas Wyatt, boarded HMS Tarter and sailed with H-4 to Barbados.

By this time Bliss was close to death. Greenwich Observatory sent Charles Green to accompany Nevil Maskelyne, representing The Board of Longitude, to evaluate H-4’s performance.

‘The Tartar’s captain, Sir John Lindsay, oversaw this first phase of this trial, and monitored the handling of the Watch on the way to the West Indies.

 After HMS Tarter arrived on May 15, Lindsay compared notes with the board-appointed astronomers who had preceded him to the island aboard the Princess Louisa, William [Harrison] found a familiar face.

There at the observatory, standing ready to judge the performance of the Watch, was Nathaniel Bliss’s hand picked henchman, none other than the Reverend Nevil Maskelyne.

En-route to Barbados, [Maskelyne] boasted he was sure he’d clinched the case and secured the prize.

When William heard word of these claims, he and Captain Lindsay challenged Maskelyne’s fitness to judge H-4 impartially.

Maskelyne was outraged by their accusations.

 He became huffy, then nervous. In his disquieted condition, he botched the astronomical observations – even though all those present recalled there wasn’t a cloud in the sky.’ Sobel. ibid

Like Captain Digges – Jamaica 1761, Charles Green at Barbados in 1764 was left in no doubt of H-4’s efficacy.

‘He [Harrison] wrested the world’s whereabouts from the stars, and locked the secret in a pocket watch’. Sobel. ibid.

It would not be difficult then to imagine Charles Green’s frustration when he joined HMS Endeavour for the voyage to Tahiti and the South Seas to find the Admiralty had not demanded a H-4 chronometer be supplied to Lieutenant James Cook RN.

Nor can it be doubted during Endeavour’s long three (3) year voyage Charles Green convinced Cook that John Harrison’s sea-going ‘pocket-watch’ had solved the knotty question of how to calculate longitude accurately when a ship was beyond sight of land.

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

So why did HMS Endeavour sail without H-4 John Harrison’s now proven sea-going chronometer?


 1765: Nathaniel Bliss died in 1764. After a  hiatus of six (6) months King George III – February 1765 – appointed Rev. Nevil Maskelyne Astronomer Royal. See: Lotto and Longitude

 1765 – 15 March: Green recorded his final observations at Greenwich Observatory on 15 March 1765 shortly before Nevil Maskelyne took up his appointment later in March. Maskelyne would hold the position for nigh on fifty (50) years 1765-1811.

‘Shortly before Cook sailed Maskelyne published his Nautical Almanac’. Lyn Withey, Voyages of Discovery Captain Cook and the Exploration of the Pacific, Century Hutchinson, London, 1987

It is possible to speculate irreconcilable differences, that had their origin on the Barbados trial of H-4  in 1764, were prominent among the reasons Charles Green quit Greenwich Observatory and why H-4 was not aboard HMS Endeavour. See: Charles Green The Third Man

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

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