Halley and longitude

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If you’ve been following this blog about Halley’s voyages, you’re probably aware that 2014 is the 300th anniversary of the Longitude Act, which offered financial rewards for practicable methods of finding longitude at sea to specified degrees of accuracy.

Halley was involved with the quest for longitude throughout his long life: in 1675, aged 18, he was present when Flamsteed and Hooke visited the proposed site of the new observatory in Greenwich, being built by order of Charles II to help find longitude at sea; he was made a commissioner under the 1714 Longitude Act, courtesy of his position as Savilian Professor of Geometry (later also as Astronomer Royal), and around 1730 it was Halley who sent clockmaker John Harrison to see George Graham to discuss his ideas for a marine chronometer.

By the second half of the 18th century, there were two serious contending methods for finding longitude at sea, lunar distances and timekeepers, but in the late 17th and early 18th centuries, a diverse range of schemes was proposed, including finding longitude via magnetic variation.

Magnetic variation (or declination) is the angle between magnetic and true north in a horizontal plane and was well known to the scientifically-minded, as too was the fact that it varied in different locations and also over time. It was thought that if an underlying pattern to the variation could be identified, it might offer a way of finding one’s longitude.

Halley undertook his first two voyages to measure the declination around the Atlantic in order to improve the accuracy of compass measurements, and to ascertain more accurate co-ordinates for the places he visited – but his published magnetic data also offered a means of estimating longitude at sea.

We’ll see Halley’s results in due course but for now we’ll consider one of the key difficulties with the theory, which is best illustrated by comparing data from four ships’ logs. [1]

At the start of Halley’s first voyage, he sailed from the Isle of Wight to Madeira in company with Admiral Benbow’s squadron and four of the five ships’ logs have survived, so we can compare their recorded latitude and longitude over several days:

COMPARISON OF LATITUDES AT NOON

1698 Falmouth Gloucester Lynn Paramore
Dec 2 47°28′ 47°39′ 47°24′ 47°23′
Dec 3… 46.28 46.30 46.13 46.20
Dec 14 32.39 32.36 32.43 32.25
Dec 15 32.22 32.26 32.19 32.15

Here, I’m showing the first and last two days that all four ships recorded data (leaving the English Channel and approaching Madeira) and you can see immediately that the latitudes are very similar – but the reported longitudes present a very different picture (first/last 5 days):

COMPARISON OF LONGITUDES AT NOON

1698 Falmouth Gloucester Lynn Paramore
Dec 2 149.3 8°01′ 2°10′ W 8°00′
Dec 3 60.1 6.59 3.30 9.10
Dec 4 5.53 5.12 10.03
Dec 5 29.9 5.34 6.00 10.09
Dec 6… 51′-5/10 4.27 7.07 11.07
Dec 11 8.41 W 3.00 9.35 12.15
Dec 12 8.55 W 3.00 9.39 12.15
Dec 13 10.50 1.08 11.15 14.09
Dec 14 12.03 0.14 11.42 15.03
Dec 15 13.20 13.11 16.07

This table looks like a confused jumble, demonstrating that this is a problematic coordinate. Looking first at the Paramore, Halley always noted that his longitude position was measured west from London, and on December 15 he described himself as being to the south-east of Madeira, which is 16°55′ west of London, and so 16°07′ seems a respectable figure for his position.

The Gloucester does not specify where its longitude is measured from but apparently starts from the same longitude as the Paramore but then declines in value to zero as it approaches Madeira, and so that ship’s longitude is being measured east from Madeira (or possibly El Hierro in the Canaries, a common zero meridian of the time, in which case the final value is over a degree out).

The Lynn‘s figures increase like the Paramore‘s, but the values are quite different and I think these values are measured from Lizard Point as they depart from the English Channel (it isn’t specified). The later values for the Falmouth are similar to the Lynn‘s but the earlier ones are unlike any others and I’m assuming these positions are only partially calculated and represent the minutes travelled since the previous noon.

So these logs demonstrate one of the problems with longitude: even if you could accurately measure your longitude, where did you measure it from? (The prime meridian at Greenwich wasn’t agreed upon until the 1880s.) And how did this varying data affect the accuracy of the period’s maps and charts?

In other words, Halley didn’t really know where he was (his recorded longitude is often erroneous, sometimes considerably so) or even, strictly, where he was heading as many places were wrongly laid down in maps – and so how useful could a theory be that was founded on wrongly-placed locations?

In spite of this, Halley apparently found all the islands he states he will sail for, even though some are little more than large rocks in a vast ocean. Halley followed the customary practice of parallel sailing (sailing along a coast until you attained the latitude of the place you were aiming for and then sailing east/west until you reached it) but on his “Southern cruise” he was seeking tiny islands (Tristan da Cunha, Martim Vaz) from the middle of the Atlantic ocean – I think he must have had at least one very sharp-sighted crew member on board!

IMG_0165 - Version 2

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[1] References for the logs are: Falmouth NA, ADM 51/341; Gloucester NA, ADM 51/401; Lynn NA, ADM 51/3892; Paramore BL, Add MSS 30398. The figures are (mostly) degrees/minutes but the notation differs in each log (I’ve used the Paramore‘s).

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Halley Redux

I recently completed my MA at Birkbeck, after submitting my (delayed) dissertation on Halley’s maritime science. The dissertation looked at Halley’s work on oceanography and meteorology, navigation and cartography, and diving and salvage, as well as his legacy and reputation in maritime affairs. One of the things I concluded was that while Halley’s maritime activities were well known in the eighteenth century, they became lost from sight in the nineteenth, when the dispute between Newton and Halley (on the one side) and Flamsteed (on the other) dominated the history of science. There was renewed interest among academics during the twentieth century – in his cartography and geomagnetic theories in particular – but these studies were not aimed at the general reader, and so his voyages and important cartographic work remain largely unknown.

This seems regrettable, given that Halley’s voyages have a strong claim to being the first government-funded expeditions for purely scientific purposes, and that they predated the ever-popular Cook voyages by almost 70 years (and Cook’s first voyage was prompted by a paper of Halley’s!). So I’ve decided to continue my own attempts to raise awareness of Halley’s voyages with a repeat run of his logbooks on Twitter.

As on the first run, Halley will tweet his ship’s journals from his account @HalleysLog around 9.00pm London time (though he doesn’t make an entry every day). If you’re not on Twitter, you can still follow the logs via the Twitter widget on the Home page of this blog, and he’ll weigh from Deptford on 20 October (1698). During the first run (2012-2015), I published posts on the blog to elucidate events in the logbooks and these will remain visible throughout the repeat run, but I will set each entry as a featured post on the Home page as it arises in the narrative and Halley will tweet a link to it from his account. I don’t intend to make many changes to the posts, but I will probably revise one or two.

I’m due to start a PhD on Halley in January 2017 (on his social and cultural world), and I’m preparing a new blog to run in tandem with that – but I’ll say more about that project next year. In the meantime, thank you for your interest in Edmond Halley and for reading this blog!

'...Being a Relation of their Perils and Dangers, and of the extraordinary Hazards they undergo in their noble Adventures...' (© National Library of Scotland-Crawford 1399, EBBA ID 33925)

‘Neptune’s Raging Fury’, a broadside ballad about mariners dating from the mid-1690s, ‘Being a Relation of their Perils and Dangers, and of the extraordinary Hazards they undergo in their noble Adventures…’ (© National Library of Scotland-Crawford 1399, EBBA ID 33925)

The end of Halley’s third voyage

Halley arrived back at Deptford on 10 October 1701 and immediately began to prepare his data for publication. He had undertaken the voyage with the aim of identifying a general rule for the complex tides of the Channel, and before he returned he had written to Josiah Burchett, Secretary to the Admiralty, to tell him that he had “discovered, beyond my expectation, the generall rule of the Tides in the Channell; and in many things corrected the Charts therof”.[1]

Halley had observed the tides and depths in the Channel, and surveyed the coastline and hazards, such as sandbanks and shoals. He again chose to publish his data in the form of a chart, and by mid-November he had a draught ready to show to a meeting of the Royal Society. Some time later, the chart was published by Mount & Page under the title, ‘A NEW and CORRECT CHART of the CHANNEL between ENGLAND & FRANCE: with considerable Improvements not extant in any Draughts hitherto Publish’d; shewing the Sands, shoals, depths of Water and Anchorage, with ye flowing of the Tydes, and the setting of the Current’, which left the prospective buyer in little doubt as to what he was purchasing.[2]

Western section of Halley's Channel Chart (© Royal Geographical Society with IBG, Image No S0015918)

Western section of Halley’s Channel Chart (the inset maps appear on the eastern section). The original chart was probably published in 1702, and this version is no earlier than 1710, when Halley received his honorary doctorate (© Royal Geographical Society (with IBG) (£), Image No S0015918)

Halley’s chart resembles a portolan chart with its radiating lines, but it was an improvement on existing maps because Halley surveyed by taking angles from the rising or setting sun, rather than the more usual (but less accurate) magnetic compass. The chart has inset maps of the Isle of Wight and Plymouth Sound, and it records depths in fathoms around the Channel and ‘ye Hour of High-Water, or rather ye End of the Stream that setts to ye Eastward, on ye Day of ye New & Full Moon’ was indicated by roman numerals. Halley gave instructions to seamen on how they could use these figures to estimate the height of tides around the Channel, and he included his customary call to mariners to send him new data that could be added to future editions of the chart. The Admiralty were evidently pleased with Halley’s work as they again paid a bonus of £200 “as a reward to him for his Extraordinary pains and care he lately tooke, in observing and setting down the Ebbing, and Flowing, and setting of the Tydes in the Channell”.[3]

Manuscript version of the inset map of Plymouth Sound. The handwriting isn't Halley's hand, so was presumably made by another under his direction (@ Biblithèque Nationale de France, Image No xx)

Manuscript version of the inset map of Plymouth Sound. The handwriting isn’t Halley’s, so it was presumably drawn by another under Halley’s direction (© Bibliothèque Nationale de France, Image No GESH18PF23DIV5P16D)

The chart was incorporated into pilot books and reprinted many times throughout the eighteenth century, both in England and on the continent (you can view several examples on the BNF’s Gallica website here), although Halley isn’t always credited as the source in later editions. Halley’s performance probably secured him the mission to the Adriatic, where he was sent by Queen Anne to survey the Imperial coast for the purpose of identifying a harbour where English ships could overwinter during the War of the Spanish Succession. Halley made two trips to the area in 1702 and 1703, and not only identified a suitable harbour, but also directed its fortification. Ultimately the Royal Navy did not need to overwinter in the area, but Halley’s work was rewarded by the support of the Secretary of State in the election for the Savilian Professor of Geometry at Oxford, where success brought Halley’s seafaring days to a close.

'Carte de la Manche' by the Chevalier de Beaurain 'd'Après les Observations du Scavant Capitaine Haley', 1778 (© Biblithèque National de France, Image No GESH18PF30P23)

‘Carte de la Manche’ by the Chevalier de Beaurain ‘d’Après les Observations du Scavant Capitaine Haley’, 1778. Beaurain has added a number of insets on astronomical and navigational instruments (© Bibliothèque Nationale de France, Image No GESH18PF30P23)

This final post has been horribly delayed by what Halley would call “Domestick Occasions”, but there’ll be another post with news about the project in mid-October.

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[1] TNA, ADM 1/1872, 13 Sept 1701.

[2] In fact, this may not have been the title when it was first published: I’ve looked at several versions of the chart and they all seem to have a slightly different title and it isn’t clear which one was Halley’s original.

[3] Thrower, Three Voyages of Edmond Halley, p. 345.

Back in the Thames

On 2 October, Halley wrote a short letter to Josiah Burchett, advising that he had arrived back in the Thames and requesting permission to come up to London to give the Lords of the Admiralty a report of his Channel voyage.

In the next post – which will probably appear in November* – we’ll conclude the third voyage by looking at Halley’s results. 

Paramore Pink in Long reach

Octob 2. 1701

Honoured Sr

Finding the season of the year too far lapsed to ride at anchor in the Channell; in persuance of their Lopps orders, I came into the River of Thames last night, and am at present moored in this place, where I waite their Lopps farther pleasure, hoping they please to allow me the Liberty to waite on them to render them an account of my Summers Expedition.

I am

Your Honours most obed:t Serv:t

Edm: Halley

River_Thames_Reaches

C19 image of Thames reaches from the sea to Woolwich (Source: Wikimedia Commons)

* Postscript: In fact, the concluding post for this voyage will probably be delayed until after I’ve finished my dissertation in January as I’m very pressed for time at present.

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[1] Halley to Burchett, 2 Oct 1701, TNA, ADM 1/1872

Halley’s third logbook

I said at the start of this Channel voyage that I wouldn’t be live-tweeting the logbook as I’d done for Halley’s two Atlantic voyages, as I felt the high proportion of technical data would be of little interest to the general reader. That was a pity as the third logbook is the only one handwritten by Halley, and so from that point of view it’s an interesting document.

In fact I did tweet a few entries at the start of the voyage and I’m doing so again now at the end as these entries contain more general information – but to give you a flavour of the main substance of the log, here’s a typical entry in which Halley records soundings and the times and lunar positions of the tides:

[Sat, June 21] about 9h in the Morn I weighd and stood off to Sea, with a gentle gale of ENE wind, and about One after noon came to an anker in 18 fath. the Ness Light baring NNW; and Calis cliff ENE. here the westward tide was done at 5h.35′, or three hours and half before the Moons Southing. whence I concluded the course of the Tides here the same as at the Ness. viz that a II½ Moon ends the Eastern Tide. at 6h I weighd and stood to the eastward with a small gale of SSW wind, and about 9h fell with the West end of the Riprapps which is a narrow rigd of soft sand. I crost it severall times in 9, 8 and 7 fath and the Eastern tide being near done, I came to an anker in that depth the Ness light baring WNW and that of the South Foreland NbE p[er] Compass. here I rode two tides and found the Eastern tide done on a SW or NE Moon nearest. that it flowed about three fath. that it runs half tide here as by the Shore and that the Sett of the Stream is nearest NE and SW.

We’ll consider the purpose of this data when we look at the results of the voyage, but in this post I want to focus on what I like to call The Mystery of Halley’s Clerks.

Now that remark may excite expectations that this post will struggle to satisfy for this is not a tale of clerks going to sea and mysteriously disappearing, but rather a puzzle about what exactly the clerks did on the voyages – why, for example, was the third logbook written up by Halley and not by his clerk?

The clerk on the third voyage was one Richard Pinfold, who was the only person besides Halley to sail on all three voyages. On the two Atlantic voyages Pinfold was listed as captain’s servant, but on the third voyage he was said to have been captain’s clerk, and so I wondered whether he might have been a servant in Halley’s own household and been promoted to clerk as a ‘reward’ for going on the first two voyages, with Halley effectively covering the job himself. However, the manuscript pay and muster books show that Pinfold was actually entered as gunner’s mate and that the post of captain’s clerk was later interposed in the pay book beneath gunner’s mate. Pinfold was paid a salary as both gunner’s mate (£5 8s 6d) and captain’s clerk (£1 12s 11d), and the small wage paid to him as clerk suggests he performed that job for only a short time, and we know he wrote neither the logbook nor Halley’s letters.

The logs of the two Atlantic voyages weren’t written up by Halley, so they must’ve been written up by his clerks… well, possibly, but possibly not. There’s no immediate reason to doubt that the log of the first voyage was written by the clerk, Caleb Harmon, but the log of the second voyage is more of a puzzle. Halley wrote all his own letters to the Admiralty on both voyages, except for two on the second, and you might expect these to have been written by the clerk, William Curtiss, but they are in a different hand from that of the logbook. My first thought was that Curtiss perhaps fell ill with the “Barbadoes desease” at the same time as Halley, and so another crew member wrote them – but the two rogue letters (which are in the same hand) were written on 30 March and 8 July, either side of the period of sickness in late May, and the July letter states specifically that “we are a very healthy ship” at present. Why then did someone else write the letters, more than three months apart, and why did that person not receive extra pay as Pinfold did on the third voyage? Or why did Curtiss write the letters but not then the logbook?

The person who wrote the first logbook isn’t straightforward either. From the start of this project I’d been surprised at how neat and uniform the logs were and wondered whether they’d actually been written during the voyage or after the ship’s return to London, but then found that other logbooks were similarly neat and so thought that clerks might make draft notes and then write them up neatly while at anchor or in calm seas.

The idea of draft notes fits with a comment made by Alexander Dalrymple in an advertisement for his 1773 publication of Halley’s two Atlantic logs that

The Journal of Dr. Halley’s first Voyage is written on sundry scraps of paper, and some parts repeated in different places, and so blended that it was a very difficult matter to make it out intelligibly…

Dalrymple, who borrowed (and seemingly failed to return) these “scraps of paper” from the Board of Longitude, doesn’t mention whether the handwriting on the scraps was Halley’s or someone else’s, which is a pity as that might tell us something about how that logbook was compiled. A further curiosity is that Dalrymple seems to have been unaware of the existence of fair copies of the two logbooks (now in the British Library), and his published version of the second log was evidently compiled from another source, as there are discrepancies between the two. So what was the source for the second log used by Dalrymple, and who wrote it? And when were the fair copies of the two journals written?

These “sundry scraps of paper” also suggest a new spin on the warning given to Halley by Josiah Burchett at the end of the second voyage. Burchett wrote to Halley in Deptford, giving him permission to leave his ship to call on their lordships in London, “only lett mee give you this Caution, To have ye Books in readinesse”. Now I’d previously assumed this warning was intended to help Halley overcome the misgivings felt by some of their lordships about his handling of the prematurely-terminated first voyage* by making sure he was properly prepared when he met them, but now I wonder if it instead implies that Halley had previously displeased their lordships by returning from that voyage with only “scraps of paper” for his journal, and only had it written up on his return.

So while I think the mysteries surrounding Halley’s clerks might not rival And Then There Were None for excitement, they certainly seem to form a Problem at Sea.

* If you didn’t follow the first voyage, click on the tag for Edward Harrison to read about Halley’s problems with Lt Harrison and other officers.

Paramore pink at Spithead

On 13 September 1701, Halley wrote again to Josiah Burchett, Secretary to the Admiralty, advising that he had arrived in Spithead two days earlier to “recruite” new provisions from the Victualling Office at Portsmouth, and claiming with characteristic optimism that he had succeeded in his project “beyond my expectation”.

To_the_right_honorable_the_master,_wardens_&_elder_brethren_of_the_Trinity_House,_this_chart_of_Spithead_is_..._dedicated_(8249820033)

Chart of Spithead by William Heather, 1797; Spithead is the channel north-east of the Isle of Wight (Source: Wikimedia Commons)

Paramore pink at Spithead Sept 13 1701

 Honoured Sr

These may serve to acquaint you that having observed the Course of the Tides in the Western part of the Channell, and my provision being almost spent, I came in here on the 11th Instant to recruite, and yesterday I received a months provision, with which I am going this morning to saile, to observe some particulars, which the circonstances of the Winds would not suffer me to do as I past down. I am in hopes I shall be so fortunate as to please their Lopps in this Summers Expedition, wherin I have discovered, beyond my expectation, the generall rule of the Tides in the Channell; and in many things corrected the Charts therof. Before this Months provision expires the winter season will oblige me to return, hoping from Yr Honour a favourable acceptance of the endeavours of

Honr:d Sr

Your most obedt Servt

Edm. Halley

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[1] Halley to Burchett, 13 Sept 1701, TNA, ADM 1/1872

Halley writes from Dartmouth

On 23 August, Halley followed up his 29 July letter informing Burchett of his activities in the eastern part of the Channel with a report of his work in the western section. We learn that Halley continued to be hampered by the weather, but what I particularly like is that the letter provides another instance of Halley showing concern for his men by noting that the continual weighing of anchor was hard physical labour for an under-manned crew.

The south-east coast of England showing Lizard Point (red pin) and Start Point (purple), with Halley’s location at Dartmouth further along the coast at north-west.

The south-east coast of England showing Lizard Point (red pin) and Start Point (purple), with Halley’s location at Dartmouth further along the coast to the north-west.

Paramore pink at Dartmouth

Aug 23 1701

Honoured Sr

By my last of July 29 from Spitthead I gave you an account that I had carefully observed the Course of the Tides in the Eastern part of the Channell of England; Since then I have lost no opportunity, in order to do the like for the Western part, and I have ankered all along the English Coast in the Offing as far as the Lizard, and from thence inn the midd Channell, and over to Ushant, where I was the last week. The frequent weighing ankers in so deep water has been very hard service to my small company, but the greatest difficulty I find, is from the frequent gales of Wind, which, (especially without the Start) raise the Sea to that degree that there is no riding, and which, in this month of August, have forced me four severall times into Harbour. I waite here for an opportunity of smooth weather, to anker in severall places between the Start and the Sept Isles; wherby I shall be able to compleat the Sett of observations necessary to the description of the Tides in the Offing; of which I cannot find any of our books to give a tollerable account. When I return from the French coast, I entend to putt in to Spitthead, to receive any farther orders their Lopps may think proper for me. With my humble duty to their Lopps I remain

Your Honrs most obed:t servant

Edm. Halley

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[1] Halley to Burchett, 23 Aug 1701, TNA, ADM 1/1872

Instructions for Halley’s third voyage

In a previous post, we read Halley’s letter to the Lords of the Admiralty proposing a new voyage to make “an exact account of the Course of the Tides on and about the Coast of England”, which he claimed would be “a work of generall Use to all Shipping”. Their lordships quickly approved his proposal, and Halley set sail on his third voyage on 14 June 1701 – but what exactly was he doing? Here’re the Admiralty’s instructions:

Whereas his Maj[es]ties Pink the Paramour, is particularly fitted out and Putt under your Command that you may proceed with her, and observe the Course of the Tydes in the Channell of England, and other things remarkable, You are therefore hereby required and directed to proceed with the Said Vessell, and use your utmost care and Diligence in observing the Course of the Tydes accordingly, as well in the Midsea as on both shores; As alsoe the Precise times of High and Low Water of the Sett and Strength of the Flood and Ebb, and how many feet it flows, in as many, and at such certaine places, as may Suffice to describe the whole. And whereas in many places in the Channell there are Irregular and halfe Tydes you are in a particular Manner to be very carefull in observing them.

And you are alsoe to take the true bearings of the Princip[a]l head Lands on the English Coast one from another, and to continue the Meridian as often as conveniently you can from side to side of the Channell, in ord[e]r to lay downe both Coast truly against one another.

And in case dureing your being employed on this Service, any other Matters may Occur unto you, the observing and Publishing whereof may tend towards the Security of the Navigation of the Subjects of his Maj[es]tie or other Princes tradeing into the Channell you are to be very carefull in the takeing notice thereof: And when you Shall have p[er]formed what Service you can, with relation to the particulars before menc[i]o[n]ed, you are to returne with the Ship you Command into the River of Thames, giving Us from time to time an Account of your Proceedings Dated this 12° June 1701 [1]

These instructions can be summarised as:

  • to make observations of the behaviour of the tides in the Channel and along the English and French coasts
  • to take bearings that will allow the French and English coasts to be correctly situated north-south from one another
  • to take note of anything else that might lead to safer navigation in the Channel for traders

The first two points were copied almost verbatim from a letter of Halley’s dated the previous day (11 June), but the third point was added by the Admiralty, and it’s been suggested that it might represent an order for Halley to gather intelligence from French waters as the two countries slid towards war. [2] That idea has been given ballast by a 1693 diary entry made by Hooke, when Halley and business partner Thomas Jett were engaged in a salvage operation, that “Hally and Jed [were] Spys”. [3]

Now I have to admit that I’m far from indifferent to this notion of Halley as a secret agent but, like Alan Cook, I’m not wholly convinced by the idea in respect to his present voyage: the Admiralty instructions clearly refer to publishing Halley’s information and they express a concern with the safety of traders of all nations operating in the Channel.

A philosophical James Bond? (© Royal Society, ID xxx)

A philosophical James Bond? (© Royal Society, Image ID RS.9284)

That said, Halley’s earlier surveying activities do seem rather surprising, for example, he was apparently surveying the Thames approaches in early 1689, during the politically-sensitive aftermath of the so-called Glorious Revolution. I’ve started to trawl through the government archives to see if I can unearth anything that indicates whether he was ever employed on intelligence work, but I’ve encountered nothing as yet – though I’ll be sure to reveal such state secrets here if I do!

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[1] National Archives, ADM 2/27, pp 131-2.

[2] See Cook, Edmond Halley: Charting the Heavens and the Seas (Oxford, 1998) pp 285-6, but note that Cook refers to a published mistranscription of Hooke’s remark.

[3] Hooke, Diary, 24 March 1693, British Library, Sloane MS 4024.