Eighteenth-century eclipse maps by Halley and Whiston

Earlier this month I published a post at the H Word on ‘Halley’s Eclipse’ of 1715. It has been associated with Edmond Halley because, using the best theory and data then available, he made impressively accurate predictions of its timing and path, publicised through a broadsheet map and the Royal Society. As I explain in the post, however, he was not the only one to do so: London was a competitive market for scientific publications and authority.

This post is an appendix, where I can show more of the eclipse maps published than I could on the Guardian’s website. I should add, too, that these were not the first predictions or maps of solar eclipses, and that there were earlier German, Dutch and French maps.

Here, however, is Halley’s first map, from Eclipse Maps, which was published in advance of the event, encouraging observation. It is titled “A Description of the Passage of the Shadow of the Moon over England, In the Total Eclipse of the Sun, on the 22d Day of April 1715 in the Morning”. I am not sure where the original is kept, but it may be the same as that reproduced in black and white in Jay Pasachoff’s article on Halley’s eclipse maps, which is from the Houghton Library. The full text, which is not high enough resolution to read here, has been transcribed by Pasachoff.

Halley's predictive map of the 1715 eclipse, from Eclipse-Maps.com.
Halley’s predictive map of the 1715 eclipse, from Eclipse-Maps.com.

Halley seems to have produced more than one edition of the map before 22 April 1715 (O.S. – the anniversary was celebrated on 3 May N.S.), and also one after the event, showing the path as corrected by observations. This copy of his “A Description of the Passage of the Shadow of the Moon over England as it was Observed in the late Total Eclipse of the Sun April 22d, 1715 Manè” is from the Institute of Astronomy, University of Cambridge, where you can see some superbly high-resolution images.

Halley's map of the 1715 eclipse, produced and corrected after the event. Institute of Astronomy, University of Cambridge
Halley’s map of the 1715 eclipse, produced and corrected after the event. Institute of Astronomy, University of Cambridge

Halley came back to his winning formula when another eclipse rolled along. His map, published in 1723 (annotated November 17123 here), showed both the recomputed path of the 1715 eclipse and the predicted path of 11 May 1724. This image is from the Houghton Library’s Tumblr, where it is available in higher resolution. The text declares that the first map “has had the desired effect” in encouraging observation and uses this one to demonstrate that his predictions had been pretty good in 1715 and were worth acting on again.

Halley's map showing the 1715 and 1724 solar eclipses. Houghton Library (EB7 H1552 715d2b).
Halley’s map showing the 1715 and 1724 solar eclipses. Houghton Library (EB7 H1552 715d2b).

However, as my post discussed, William Whiston was also in the business of predicting eclipses and selling scientific paraphernalia.  Like Halley, he was making predictions based on John Flamsteed’s observations at the Royal Observatory and corrected with Isaac Newton’s theory, and encouraging observations. Whiston made comparison of his observations with Halley’s and his  two eclipse-predicting broadsheets are again from the Cambridge Institute of Astronomy’s Library here and here.

The one I think is the earlier from Whiston was dated 2 April 1715 and titled “A Compleat Account of the great Eclipse of the Sun which will happen Apr. 22 in the Morning”. It is much more text-heavy and technical in content, and the map is a celestial one, showing the positions of the heavenly bodies rather than the path of the shadow on Earth.

Whiston's broadsheet predicting the timing and path of the 1715 comet. Institute of Astronomy, University of Cambridge (AMI/11/B).
Whiston’s broadsheet predicting the timing and path of the 1715 comet. Institute of Astronomy, University of Cambridge (AMI/11/B).

A second broadsheet by Whiston did show the Sun’s shadow on the Earth, but from a global point of view. The title too emphasised that this was not just an English matter: “A Calculation of the Great Eclipse of the Run, April 22d 1715 in ye Morning, from Mr Flamsteed’s Tables; as corrected according to Sr Isaac Newton’s Theory of ye Moon in ye Astronomical Lectures; with its Construction for London Rome and Stockholme”. It also advertised an instrument that could be bought from Whiston.

Whiston's second 1715 eclipse broadsheet. Institute of Astronomy, University of Cambridge (AMI/11/C).
Whiston’s second 1715 eclipse broadsheet. Institute of Astronomy, University of Cambridge (AMI/11/C).

John Westfall and William Sheehan’s new book on observing eclipses, transits and occultations, indicates the Whiston and Halley’s estimates varied by about 25 miles, which perhaps puts the more triumphant claims of accuracy in perspective. I think (correct me below if I am wrong) that Halley’s prediction was the more accurate, but there was an element of luck involved. Above all, his map, showing geographical detail of England beneath the path of totality, was much more persuasive and appealing – this is the main reason that the 1715 eclipse became ‘Halley’s’.

Whiston had learned the importance of the image by 1724. His “The Transit of the Total Shadow of the Moon” this time showed familiar coastal outlines, although again other parts of Europe were included: Paris would be a better observing site than London this time. This version is from the Science & Society Picture Library and belongs to the Royal Astronomical Society.

Whiston's map showing the predicted path of the 1724 eclipse. Science & Society Picture Library/Royal Astronomical Society.
Whiston’s map showing the predicted path of the 1724 eclipse. Science & Society Picture Library/Royal Astronomical Society.

And so the maps continued: there are many to explore in the wonderful albums at Eclipse Maps. It was a flourishing business come eclipses in the 1730s and beyond, especially that of 1764, as many publishers jumped on the opportunity that Halley and Whiston had spotted in 1715. So too, of course, had the person that links all the images shown here: the engraver and cartographer John Senex, who deserves a much fuller biography on Wikipedia than this!


Navigating 18th-century science: Board of Longitude archive digitised

Cross-posted from The H Word blog.

Today [18 July 2013] the complete archive of the Board of Longitude is being launched online, with stories of innovation, exploration and endeavour – and much more than just John Harrison

Design for a marine chair

Design for a marine chair submitted to the Board of Longitude. Source: Cambridge University Library


Today Lord Rees will be launching the digitised archive of the Board of Longitude at Cambridge University Library. Stuffed full of the correspondence and work of those who preceded him as Astronomer Royal, it also contains letters and papers of artisans, inventors, expeditionary astronomers and maritime explorers.

For those not familiar with the story of the 18th-century search for a means to determine longitude at sea, this video, gives an introduction to the project and the story.

The digitisation project is a collaboration between CUL and the National Maritime Museum, funded by JISC, and is closely allied to an AHRC-funded project on the history of the Board of Longitude that brings together researchers from the NMM and History and Philosophy of Science department in Cambridge.

This association has meant that as well as digitising 48,596 pages from the archives and libraries at Cambridge and NMM, the content is supported by links to relevant object records at the Museum, summaries of all and transcriptions of some of the files and essays on key figures, places, institutions, objects and events.

Written by the project researchers, there is enough text there for a couple of PhDs (at least) and a really useful resource for users of the site. I was the laggard who has only contributed one essay so far, on Astronomer Royal Nevil Maskelyne. He was, though, an extremely significant figure both for the longitude story and in this project, which also includes selections from Maskelyne’s archive from the Royal Observatory and his personal papers held now at the NMM.

While historical researchers will undoubtedly find many ways to start digging into the archive, for those newer to the game there are, on top of the summaries and essays, resources for schools and some selected stories lifted from the archive. The content can take the reader to the observatory at Greenwich, meetings at the Admiralty, artisan workshops of London and the South Seas.

William Wales' map of Easter Island, from Cook's Second Voyage

William Wales’ map of Easter Island, from Cook’s Second Voyage. Source: Cambridge University Library

Key Stage 2 pupils will, we hope, learn about Captain Cook’s voyagesand Key Stage 3 will be able to think about inventors and enterprise.

For those who feel they are familiar with the story of longitude, having read about John Harrison and his sea clocks in Dava Sobel’s Longitude, they will find there is much more to explore. As my NMM colleague, Richard Dunn says,

The archive places the familiar story of Harrison in its richer context. He was a crucial figure but the story is much broader. It takes in the development of astronomy, exploration and technological innovation and creativity during the period of the Industrial Revolution, the work of the first government body devoted to scientific matters, and public reactions to a challenge many considered hopeless.

Simon Schaffer, who leads the research project, adds that

The longitude story is a spectacular example of expert disagreement and public participation. As well as attracting the greatest scientific minds of the day, the board enticed people who belong to one of the most important traditions in British society; the extreme eccentric.

Thus while there may be interest in reading the full story of the Board’s dealings with Harrison, eyes are likely to be caught by what were damned by the archive’s 19th-century compilers as “Impractical schemes”. Some of these are real green ink stuff, with perpetual motion and squaring the circle bound into the seemingly intractable problem of finding longitude.

Scheme for dead reckoning

Proposal for finding longitude by determining the ship’s rate of sailing. Source: Cambridge University Library

However, there are many other schemes that, while they did not come to fruition, were based on sound ideas. These included improvements todead reckoning – the educated estimate of position that was not displaced by chronometers until the 20th century – or ways to steady an observer sufficiently to allow them to use Jupiter’s satellites as a celestial timekeeper (the standard means of determining longitude on land).

In its later life, the Board supported the two successful methods of finding longitude at sea – chronometer and lunar distance – and broadened its remit into other fields. Thus those who explore the digital archive will also land on geomagnetic researchpendulum experiments measuring gravity, the search for the North-West Passage and a young Michael Faraday pulled in to investigate ways to improve optical glass.

And much more besides – go on, dive in!

Mr Punch does transits, constellations and coiffures

Punch, or the London Charivari is a wonderful source for history of science. It is impossible to think of a popular magazine today including jokes that span politics, science, the arts, classical reference and what we might call observational comedy. As with the image posted on the Ptak Science Books blog the other day, the editors of Punch had high expectations of their readers’ ability to recognise not just a handful of scientific celebrities but a while range of figures from the scientific community. Those of us who have commented on John’s post are struggling to be sure of the identities of some of those represented, or to explain just what the mathematician is doing with a fish that has so shocked a zero (have a look – and let me know if you can explain!).

In the comments, I pointed to the existence of the SciPer Index, created at the HPS department in Leeds between 1999 and 2007. This indexed short runs of sixteen 19th-century periodicals, creating a online resource and three important books.[1] While the project suffered from being at the head of the game – being superseded in many ways by mass digitisation projects, which cover much longer runs of periodicals with full images – it remains immensely impressive in terms of the added value created by the project members. This is not just a word-searchable set of texts, but a real index, explication and glossary.

For something as visual and complex as Punch, this is exactly what is required. The image on John Ptak’s site is nothing to a search engine until it is described in words. And the SciPer Index not only describes, but identifies and connects. It is not, of course, infallible: the dedicated scholar-indexers occasionally missed or misidentified references, and had to make complicated choices about just what we, or 19th-century writers, define as ‘science’, but it is the only thing I know that really spells out just how prevalent, and how intricate, such references were at this period.

I often come back to Punch, especially as I was lucky enough to inherit a set of bound 19th-century volumes. Because I have recently been thinking about the historic transits of Venus, I was looking today at the 1874 and 1882 volumes, knowing from Jessica Ratcliffe’s The Transit of Venus Enterprise in Victorian Britain (2008), that there are some great illustrations, revealing popular interest and the imperial and nationalistic agendas bound up with the transit expeditions. More of those another time – one will certainly be making its way into the exhibition at the Royal Observatory this spring. What struck me today, leafing through these volumes, is just how many references to science are there each year. Take a look at the SciPer Index for earlier volumes to see what I mean.

I will share just a couple of 1874 astronomical examples (a year that saw a comet and a transit of Venus), otherwise I could be here all night….


I hold, whatever PROCTOR writes,
Out-door observing, these chill nights,
A snare to the unwary

Long though you gaze into the sky
(Not quite, I hope, cigarless),
What chance of seeing meteors fly
Through a heaven that hangs starless?

A blazing fire in bright steel bars
Best observe, after dining;
And study – if you must have stars –
Those ‘neath arched eyebrows shining.

Transit of Venus snugly watch.
With comforts that enhance it:
There is no place like home to catch
Your Venus in her transit.

Let who will, ‘mid Kerguelen’s snows,
Seek freezing-post and thawing-room,
My Venus one short transit knows –
From dining-room to drawing-room.

Let me observe her, by lamp-light,
In chaise longue, soft and lazy,
Her witch-face framed in hair-wreaths bright,
Enough to drive one crazy.

Sweet star of eve, whose beauties blend
With foam of vaporous laces,
That like a cloudy setting lend
A mystery to thy graces,

Heightening the charms they half enwrap –
Sweet star too of the morning,
In muslins fresh, and pretty cap
A prettier head adorning!

Yes, “Vive l’Astronomie,” say I –
But what I add between us is –
While our Home-Heavens can still supply
Observers with their Venuses!

Not the best poetry – though kudos for rhyming “Venuses” with “between us is” – and rather sickly sweet than funny, perhaps. There is little to hint at the strides that women were beginning to make in education and public life at this date. However, this image ‘Constellations and Coiffures’ does something distinctly different:

The joke, of course, is about the fashionable new hairstyle, but it takes its range of astronomical references for granted. A telescopic chignon was, of course, apt for a comet, ‘long-haired’ being the literal meaning, though please note too the telescope earrings. Ether, nebulae and cluster are also thrown into the accompanying poem. At the end, “Berenice’s hair” refers to Coma Berenices, formerly part of Leo and now a constellation in its own right. It was named after Queen Berenice II of Egypt, who swore to sacrifice her long, blond hair to Aphrodite if her husband Ptolemy III Euergetes returned safely from war. He did, and she placed her hair in the temple. It disappeared and, the story goes, the court astronomer, Conon of Samos, appeased the angry king by claiming that the gods were so pleased by the hair that they had taken it and placed it in the heavens.

A source of early feminism Punch is not, but as a source for developing an understanding of the role, meaning and cultural baggage of science among the Victorian middles classes it is, undoubtedly, essential reading.



[1] These were Science in the Nineteenth-Century Periodical: Reading the Magazine of Nature (CUP, 2004), Culture and Science in the Nineteenth-Century Media (Aldershot: Ashgate Publishing, 2004) and Science Serialized: Representations of the Sciences in Nineteenth-Century Periodicals (Cambridge, MA: M.I.T. Press, 2004).