The Longitude Act of 1714
If legislators believed that success was imminent, they were encouraged in that view by lobbyists and scientific experts. Their call for a British scheme to echo the Spanish and Dutch was answered on 9 July 1714, when Parliament passed ‘An Act for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea’. It provided
That the First Author or Authors, Discoverer or Discoverers of any such Method ... shall be Entitled to ... a Reward, or Sum of ten thousand Pounds, if it Determines the said Longitude to One Degree of a great Circle, or Sixty Geographical Miles; to fifteen thousand Pounds, if it Determines the same to Two Thirds of that Distance; and to Twenty thousand Pounds, if it Determines the same to One half of the same Distance ...4
The value of this reward, in today’s terms, depends on the yardstick. £20,000 in 1710 can be calculated as worth over £1.5 million early in the twenty-first century, or as a sum that would have paid the annual wages of more than 600 craftsmen in the building trade or bought nearly 5000 cows.5 By any measure it was a large amount of money but the Act asked for a great deal: the successful method was to be ‘Tried and found Practicable and Useful at Sea’.
The emphasis on practical utility was underlined by the provision that half of the reward could be given to a method that ensured ‘the Security of Ships within Eighty Geographical Miles of the Shores, which are the Places of the greatest Danger’. However, the full reward was dependent on a successful long-distance sea trial:
Fig. 1 – The opening of ‘An Act for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea’ (the Longitude Act, 1714)
{Parliamentary Archives, London}
Fig. 2 – Isaac Newton, by Charles Jervas, 1717
{The Royal Society}
when a Ship by the Appointment of the said Commissioners, or the major part of them, shall thereby actually Sail over the Ocean, from Great Britain to any such Port in the West-Indies, as those Commissioners, or the major part of them, shall Choose or Nominate for the Experiment, without Losing their Longitude beyond the Limits before mentioned.
The Act also allowed for the advancement of sums up to £2000 ‘to make Experiment’ of promising schemes. This appears to have meant costs associated with the trial but was later interpreted more broadly by the Commissioners. It was also possible to give rewards to schemes that failed to achieve the desired accuracy, but were nevertheless thought to be ‘of considerable Use to the Publick’.
Perhaps most importantly, the Act appointed the Commissioners of Longitude. They were the Lord High Admiral, or First Commissioner of the Admiralty; the Speaker of the House of Commons; the First Commissioner of the Navy; the First Commissioner of Trade; the Admirals of the Red, White and Blue Squadrons of the Navy; the Master of Trinity House; the President of the Royal Society; the Astronomer Royal; the Savilian, Lucasian and Plumian Professors of Mathematics (the first at Oxford University, the other two at Cambridge); and ten named Members of Parliament. They were not yet a standing body or a ‘Board’, but the Act was significant in creating a group, mostly selected because they held another relevant office, that combined political, navigational and scientific interests. While the President of the Royal Society and university professors had previously acted as advisors, this Act brought philosophers and mathematicians directly into a process of allocating government funds.
When action was being considered in June 1714, it was one of the future Commissioners, Isaac Newton, who presented evidence to a Committee of the House of Commons. He was then President of the Royal Society and, as such, an unofficial advisor to politicians on matters scientific (Fig. 2). He was also working directly on the mathematical and astronomical theories that had potential to help solve the problem. Newton’s written statement noted, in a phrase echoed in the legislation, that ‘there have been several Projects, true in theory but difficult to execute’. He provided a succinct summary of the methods and the problems still surrounding them:
One is by a Watch to keep Time exactly. But, by reason of the motion of a ship, the variation of heat & cold, & the difference of gravity in different Latitudes, such a Watch hath not yet been made.
Another is by the Eclipses of Jupiter’s Satellites. But by reason of the length of Telescopes requisite to observe them & the motion of a ship at sea, those Eclipses cannot yet be there observed.
A third is by the place of the Moon. But her Theory is not yet exact enough for this purpose. It is exact enough to determine her Longitude within two or three degrees, but not within a degree.
A Fourth is Mr Ditton’s project. And this is rather for keeping an account of the Longitude at sea than for finding it if at any time it should be lost, as it may easily be in cloudy weather ...6
The first three methods on this list were, to Newton, the most promising. All were a means of carrying or finding a reference time against which to compare observations of local time on board ship. If practicable, they would allow difference in longitude to be established anywhere in the world. The last method, ‘Mr Ditton’s project’, as Newton said, targeted particular circumstances rather than being a universal solution to the problem. It is, however, of particular interest to the story, being the cause of parliamentary interest in the issue of longitude in 1713.
‘Mr Ditton’s project’
The Mr Ditton to whom Newton referred was Humphry Ditton (1675–1715), Master of the Royal Mathematical School at Christ’s Hospital. In reality, it was Mr Ditton’s and Mr Whiston’s project, but the latter was an individual with whom Newton, once close, had now broken ties. Perhaps Newton could not quite bring himself to write the name, despite the presence of William Whiston (1667–1752, Fig. 3) at the parliamentary committee. Whiston had been Newton’s chosen successor as Lucasian Professor of Mathematics at Cambridge in 1702, but was expelled from the university in 1710 for his unorthodox theological views. Those views were largely shared by Newton but he was anxious to avoid a public accusation of heresy. Whiston blamed their rupture on Newton’s ‘fearful, cautious, and suspicious Temper’.7
After 1710, Whiston made his living as a scientific and theological lecturer, author and, he hoped, longitude projector – that is, someone who sought backing for a scheme, or project, intended to solve the longitude problem. He had lectured with Ditton from at least 1712 and they were promoting their longitude scheme the following year, through newspaper advertisements and letters drumming up English support by asking questions about foreign longitude rewards. In 1714, two petitions to Parliament appeared: one in April from Whiston and Ditton, and another in May recorded as being from ‘several Captains of her Majesty’s Ships, Merchants of London, and Commanders of Merchant-men’. The latter petition suggested that public ‘Encouragement’ would aid the search for a longitude solution.8 It was this, in which Whiston may also have had a hand, that instigated the parliamentary committee at which Newton presented his evidence. Prominent Whig politicians, whose patronage Whiston enjoyed, were to steer the new legislation.
Claiming inspiration from the extraordinary display of fireworks on the Thames that celebrated the end of the War of the Spanish Succession in 1713, Whiston and Ditton proposed that vessels moored at known locations could fire shells vertically to 6440 feet at set times. Navigators would keep a look out for the lights and gauge their bearing and distance relative to the moored vessel by compass and by timing the difference between the