• Can an astronomical instrument be religious? Wooden quadrants from the Late Ottoman Empire.

    Yasemin Akçagüner, Columbia University, New York
    Recipient of SIS grant 2022


    In 2018, Silke Ackermann posed the following question in an SIS Bulletin article: “Can an astronomical instrument be religious?” [1]. In many museum collections today, scientific instruments from the Middle East and North Africa are placed within Islamic galleries or labeled as Islamic instruments, while instruments from the Western world are largely labeled and exhibited according to the nation-states or polities in which they were crafted or manufactured. Such is the case with a wooden astrolabic quadrant exhibited in the Albukhary Foundation Gallery of the Islamic World at the British Museum (Figure 1), an instrument whose functions and possible use in trade across the Ottoman Empire complicates its straightforward designation as an Islamic instrument used for determining prayer times.

    Figure 1: Wooden quadrant from AD 1891-92 (AH 1307-08).

    Figure 1 shows a wooden quadrant from AD 1891-92 (AH 1307-08), was made in Damascus, Syria and “would have been used by an Ottoman merchant or official. It contains a correspondence table for comparing hijri (the Islamic lunar calendar), Coptic, French Julian and financial calendars, demonstrating the coexistence of different faiths and calendars with the Islamic world,” the display label reads [2]. This particular quadrant points to uses of the instrument beyond timekeeping for the purposes of establishing prayer times and postulates a use for the quadrant in daily affairs of commerce and trade in the late nineteenth century, a claim that would benefit from further exploration.

    Intrigued by the instrument from the British Museum, I have set out to explore others of the same kind, specifically wooden quadrants from the Ottoman Empire. Owing to the Empire’s longevity (from the fourteenth to the twentieth century) and its geographic span (ranging from the Balkans to the Red Sea at its height in the early seventeenth century), it offers an ideal laboratory for studying scientific instruments across the Middle East and North Africa, both in their variety and similarity across time and space. While the history of Islamic astronomical instruments in the medieval period have been studied extensively by David King and Emilie Savage-Smith [3], late Ottoman astronomical instruments are only recently coming into the limelight thanks to the works of Feza Günergun and Gaye Danışan. Feza Günergun’s recent research has shown the role of artisan-scholar collaboration in the making of Ottoman astronomical instruments, and specifically astrolabic quadrants – an instrument largely understood to be used by muwaqqits, or timekeepers of imperial mosques, for the purpose of determining prayer times [4]. Yet the scope of the possible uses of these quadrants and who might benefit from their uses remains to be explored: Beyond timekeeping for the purposes of establishing prayer times, how were these quadrants used?

    To be able to answer that question we first need to know the answers to a number of more basic questions: Who could learn to use the quadrant? And how did they learn it? Was the learning process tactile, textual or in some other form? Is the large number of surviving manuscripts with instructions for the use of this instrument a testament to the instrument’s use by a wider group of lettered people that included not only the timekeepers of mosques, but also seafarers and merchants for instance? Could any lettered person hope to learn how to use the instrument simply by reading through one of these manuals?

    With the support of an SIS grant I am comparing and contrasting the inscriptions on various quadrants as well as manuals for the instruments found in select collections in the UK. These include the Oxford HSM, Cambridge Whipple Museum and the British Museum, alongside a number of manuals, in manuscript form, on the uses of these instruments in the relevant University and British Library collections. One such manuscript is from the British Library Oriental Manuscripts collection (Figure 2).

    Figure 2: British Library, Oriental Manuscripts, MS Oriental 14275.

    British Library, Oriental Manuscripts, MS Oriental 14275 (see figure 2) was copied in the year AH 1268 (1851-52 AD). It describes the parts of the quadrant and provides instructions on how to use the instrument to determine time in two parts. Part one, Terceme-i Gedūsī li’l-Muḳanṭarāt (Translation of Gedusi on the Muqantarat) describes the parts and function of the astrolabic face of the quadrant whereas part two, Terceme-i Gedūsīli’l-Ceyb (Translation of Gedusi on the Ceyb) explains the sine face of the quadrant. The text is a translation from the Arabic original into Ottoman Turkish by the author himself. The first part refers to resm or images that are meant to accompany the text but are missing from this copy. The text relies on the drawings of the quadrant for its explanation, which is perhaps a later phenomenon in the development of such quadrant manuals with earlier copies such as the Risale-i Ceyb (Treatise on the Sine Quadrant) in the sixteenth-century MS Selden Superius 97 (ff 34-59, Bodleian Library, Oxford University) featuring no such images or mentions of images. This points us towards the potential use of technical drawings as tools for the practical teaching of astronomy in the nineteenth-century Ottoman Empire.

    In a follow up article in the SIS-Bulletin I hope to offer a more detailed and comprehensive analysis of the quadrants and manuals found in the above mentioned collections.

    Yasemin Akçagüner is a doctoral candidate in the History department at Columbia University, New York.


    [1] S. Ackermann, ‘Gerard Turner Memorial Lecture: In the Service of Religion? ‘Islamic Science’ in the Museum’, In: Bulletin of the Scientific Instrument Society No. 139, (December, 2018).

    [2] Astrolabic quadrant, 1997, 0210.1, The British Museum. For the curator’s comments see https://www.britishmuseum.org/collection/object/W_1997-0210-1

    [3] King, David A. “Quadrants.” In Islamic Astronomy and Geography, 167–69. London: Routledge, 2022; and Savage-Smith, Emilie, and Andrea P. A. Belloli. Islamicate Celestial Globes, Their History, Construction, and Use. Smithsonian Studies in History and Technology, no. 46. Washington, D.C: Smithsonian Institution Press, 1985.

    [4] Günergun, Feza. “Timekeepers and Sufi Mystics: Technical Knowledge Bearers of the Ottoman Empire.” Technology and Culture 62, no. 2 (2021): 348–72. https://doi.org/10.1353/tech.2021.0063. See also Danışan, Gaye. “Paper Instruments in the History of Ottoman Astronomy.” Scientific Instrument Society Blog (blog), 22 February 2021. https://scientificinstrumentsociety.org/blog/?query-28-page=3.

  • The Russian diplomatic representatives in London and the acquisition process of navigational instruments for Russian navigators at the beginning of the 19th century, by Feliks Gornischeff, Research Fellow, Estonian Maritime Museum


    Vasily Mikhailovich Golovnin, portrait by Orest Kiprensky (c.1816) (copyright: Public Domain).

    The Russian Empire started intensive exploration at the beginning of the 19th century when Adam Johann von Krusenstern, a Russian naval officer from Estonia influenced heavily by the British navigation and exploration, carried out the first Russian circumnavigation. Many Russian naval figures had gained training with the British and had learned about the principles of British navigation and maritime trade. Therefore, it was logical for the Russian explorations at the beginning of the 19th century to acquire most of their navigational instruments in England. Krusenstern’s first Russian circumnavigation in 1803–06 set an example of the use of British instruments. Other Russian voyages, such as Vasily Golovnin’s in 1807–09 and 1817–19 (see adjacent painting), Otto von Kotzebue’s in 1815–18 and Fabian Gottlieb von Bellingshausen’s in 1819–21 used British instruments on board the ships.

    My ongoing research examines the role of Russian diplomatic representatives in Britain in the process of acquiring navigational instruments for Russian expeditions in the first half of the 19th century. Even though it is known roughly which instruments Russian voyages carried, it is still unclear who and how exactly ordered the instruments from well-known makers such as Troughton, Dollond, Arnold, Barraud, or Massey, although it is known that Russian diplomatic representatives played a role in assisting the explorers. British historian Rip Bulkeley has looked into the aspects of acquiring navigational instruments in the case of Fabian Gottlieb von Bellingshausen, but some details remain unclear [1]. Also, Simon Werrett [2] has analysed common aspects of Russian and British navigators, and mentions British instruments as preferred by the Russians, but leaves the question posed here unanswered.

    Russian exploration and diplomatic representatives

    The Guildhall Library (photograph by the author).

    The starting point for this research were the accounts of the Russian expeditions where British instrument makers and instruments were mentioned on several occasions. Also, the diplomatic representatives were mentioned in these accounts which gave me the indication that the diplomatic corps was involved in the acquisition process. The Russian Embassy in London were to become an important link between explorers and instrument makers. They usually had information in advance regarding what to organize in London, but the leaders of the expeditions subsequently stopped over in England themselves to complete the purchases. This allows us to argue that without the Russian diplomatic representatives in England, the preparation of the expeditions would have been much more complicated. But it is vital to add the layer of archival sources to this research.

    During the period of my interest, there were two full time Russian ambassadors in London, Semyon Vorontsov (period in London 1785–1806) and Christoph Heinrich von Lieven (London 1812–34). There were other personnel as well, for example councillor Paul von Nicolay who served in London 1804–08. Regarding the supplies, important role here was played by the network of Russian consuls in Britain. We know that general consuls Samuel Greig, Andrey Dubachevsky and George Benkhausen were involved, but also consul John Hawker in Plymouth. Of course, it is necessary to map the whole Russian diplomatic personnel in Britain to get a clear overview of the main actors.

    Research plan and sources

    The National Maritime Museum, Greenwich (photograph by the author).

    Thanks to the SIS Grant I visited several archives in London to find out what connections the Russian diplomatic representatives had with the British navigational instrument makers. I focused on the personal archive of Russian ambassador Christoph Heinrich von Lieven which is located in the British Library. It was interesting to see these materials to find out if there were any communication between them. Also, I wanted to map Adam Johann von Krusenstern’s connections with London’s navigational instrument makers when he visited London in 1814–15 to purchase inventory for Otto von Kotzebue’s Rurik expedition that took place from 1815–18. Besides the British Library, I visited the Guildhall Library and the London Metropolitan Archives (LMA) where, according to the catalogues some papers of Arnold and Dollond were supposed to be held. Although I managed to find an account book of John Roger Arnold at the LMA (I had information that it is at the Guildhall, but it was transferred some 10 years ago), this was dated to 1796, 1800–02 and 1824–30, which meant there was no information regarding the expeditions of Krusenstern, Golovnin, Kotzebue and Bellingshausen. The archive of the Dollond family is also held at the LMA, but it did not consist of any correspondence or financial records. Therefore, it was necessary to continue looking for Arnold’s and Dollond’s archival sources. I also consulted the collections of Troughton (held at the Borthwick Institute in York) and Massey (formerly at the University of Keele, now at the V&A Wedgwood Archives) but they either did not have material from the early 19th century or anything regarding the sales of instruments to the Russians. However, the unsuccessful visit of the archives opened new aspects of my research. Regarding chronometers, I searched the catalogue of the Royal Museums Greenwich and contacted the staff regarding the entries in the International Chronometer Ledgers. The next step is to search the Royal Greenwich Observatory Archives at the University of Cambridge and the archive of the History of Science Museum at the University of Oxford which contains further material regarding the Dollond family.


    [1] R. Bulkeley, ‘Bellingshausen in Britain: Supplying the Russian Antarctic expedition, 1819’, in: The Mariner’s Mirror, 107:1, pp. 40–53, here p. 43.

    [2] S. Werrett, ‘‘Perfectly Correct’: Russian Navigators and the Royal Navy’, in: R. Dunn, R. Higgitt (edit.), Navigational Enterprises in Europe and its Empires, 1730–1850 (Basingstoke: Palgrave MacMillan, 2016), pp. 111–133.

    This research was funded by a SIS Grant.

  • An early modern portable clock with Islamic calendar, by Artemis Yagou, Research Associate, Deutsches Museum, Munich

    Figure 1. The WLM 1968-195 clock. Copyright © Landesmuseum Württemberg, Stuttgart. Photo by Moritz Paysan, used with permission.

    My research interest in the various forms and manifestations of luxury in early modern south-eastern Europe has led me to the study of clocks and watches made in Europe for the market of the Ottoman Empire. In the eighteenth century, this multinational, multilingual and multi-confessional empire occupied a vast area including most of south-eastern Europe, Asia Minor, the Middle East and North Africa. Thanks to a SIS grant, I had the chance to examine a clock with Ottoman-era numerals (numbers used with the Arabic script) intended for the Ottoman market and now kept in the Collection of Clocks and Scientific Instruments of the Landesmuseum Württemberg in Stuttgart (inventory number WLM 1968-195). It is an oval-shaped, silver and bronze, gold-plated, engraved, rather large portable clock, equipped with verge escapement movement and weighing almost 600 grams (Figure 1).

    The face of the watch is made of gilt bronze covered with openwork silver floral tendrils and includes two dials with iron hands marking the date and hour respectively. The date dial also has a circular aperture under which a rotating disk is located, bearing a red shape with stars. When the underlying disk rotates, different parts of the starred shape are exposed, to indicate the phases of the moon. Additionally, on the left and right of the clock face there are two curved trapezoid apertures, through which we can see two rotating disks with the names of the weekdays and of the twelve months, all in Arabic script. Days and months conform to the Islamic, lunar-based Hijri calendar, the object was therefore clearly intended for Muslim customers, for whom timekeeping was important in relation to the five daily prayers.

    The functional and aesthetic features of the WLM 1968-195 are rather unusual. Nevertheless, it is possible to identify a number of clocks that are quite similar from both stylistic and functional points of view – for example, a large pectoral watch from the Omega collection, probably made by Persian craftsmen working under the direction of European watchmakers in the early part of the seventeenth century, as well as a Swiss-made oval gilt metal astronomical watch with Ottoman-era numerals from the mid-seventeenth century. The WLM 1968-195 also resembles various watches for Western customers, for example one made by Georg Bayr of Friedberg (South Germany) before 1674 and another made by Jacob Mayr of Augsburg around 1680. The documentation of the Landesmuseum Württemberg dates the WLM 1968-195 around 1700 but, given the aforementioned affinities, it could be even older. There is no signature, hallmark or other indication of the object’s origin. Landesmuseum documentation describes the watch as being ‘of South German manufacture’, possibly because of its oval shape, typically associated with watches produced in Nuremberg in mid- to late-sixteenth century. Nevertheless, in the meantime the oval watch style was much more widespread, for example in France, therefore around 1700 the oval shape is insufficient evidence of a South German background.

    Through this object, we have a glimpse into the world of early modern European trade for the Eastern markets. In that time period, a great variety of clocks and watches were exported from Europe to the Ottoman Empire and were quite sought after. Elaborate and precious watches were intended as gifts or bribes for rulers and high-ranking officials; accessible watches appeared only towards the end of the eighteenth century. Given that there is scant information on the origin and date of this watch, we can only speculate about its market trajectory, its sellers, buyers and users. The quality of its craftsmanship and other features suggest that it was intended for a person of some standing, for example a diplomat or a rich merchant. Furthermore, the exploration of its collection history reveals interesting albeit somehow confusing information involving several individuals, including the industrialist Arthur Junghans who donated the object to the Landesmuseum. Many questions remain unanswered about the clock’s provenance and usage; they are open to further research. Arguably, as a portable object to be used ‘on the move’, it illuminates and exemplifies an important feature of the early modern period, namely the evolving mobility patterns and associated novel ways of living, working, communicating and learning.

    Artemis’s research was funded by a SIS Grant.

  • Eliminating errors, automating observation: The Photographic Zenith Tube of the Neuchâtel Observatory in Switzerland, by Julien Gressot

    Figure 1. The PZT at the Neuchâtel Observatory. Copyright image – Bibliothèque de la Ville de La Chaux-de-Fonds, Département audiovisuel, Fonds Fernand Perret, used with permission.

    In the mid-twentieth century, the Neuchâtel Observatory decided to modify its time determination operating chain – the set of scientific instruments, mathematical operations and methods that provide the exact time at the end of the process. The Photographic Zenith Tube (PZT) and quartz clocks were the central elements of this transformation, which began in the 1940s. These technologies had a profound impact on the spatial organisation, the status of the human factor and the practice of time determination at the Observatory.

    Edmond Guyot (1900-1963), the third director of the Observatory, was the protagonist of this transformation. In 1946, he sought to implement the recommendations of the International Astronomical Union (IAU) meeting held in Copenhagen in September 1946, underlining “the great interest in equipping observatories with PZTs”.

    Thereafter, he contacted the Washington Naval Observatory (USNO) and the company Grubb & Parsons, then located in Newcastle upon Tyne, to obtain a PZT. The company had been in discussion since 1943 with the Royal Observatory at Greenwich (ROG) to develop an instrument, which had its origins in developments at the USNO to combine photography with a zenith instrument, the objective being to determine the time to a thousandth of a second by eliminating many of the errors involved in the process (personal equation, collimation, azimuth, flexion errors, …).

    Grubb & Parsons developed three models in parallel, for the Neuchâtel Observatory (1954, Figure 1), for Greenwich Observatory (1955), and for the Mount Stromlo Observatory in Australia (1956). Research visits funded by a SIS grant to the Tyne & Wear Archives, the Cambridge Library, the Archives de l’État de Neuchâtel (AEN), and the Musée international d’horlogerie de La Chaux-de-Fonds (MIH) allowed me to learn more about the process of design, manufacture and the circulation of knowledge leading to the creation of these scientific instruments.

    The Neuchâtel PZT became fully automated in 1959. The work at the Observatory was modified; the human observer was replaced by an operator in charge of preparing the observation cycle of the instrument, which took place at night without human intervention. However, the photographic output led to an increase in the work of reduction and comparison of the resulting photographic plates; the Observatory – with its limited staff – had to outsource these calculations.

    Despite its initial hopes, it was soon found that the PZT also contained sources of error (the gelatin of the plates, refraction of the atmosphere, etc.). Moreover, the PZT came at a moment of paradigmatic breakthrough in time measurement as atomic clocks were developed, which quickly surpassed the precision of astronomical time determination. The use of the PZT for obtaining accurate time therefore lasted only a few years before becoming obsolete.

    The material and archival study of the PZT allows us to better understand the place of an instrument that represents the culmination of the automation of time determination, shortly before astronomy lost its expertise in the field to physics.

    Julien’s research was funded by a 2021 SIS Grant. A longer piece on this subject will feature in a future SIS Bulletin.

  • In Celsius’ footsteps, by Ian Hembrow

    Retracing the route of the 1736-37 Arctic Circle expedition to establish the shape of the Earth

    A daily blog by SIS member and travel grant recipient Ian Hembrow on a research trip to Lapland for his biography of the Swedish astronomer and mathematician Anders Celsius (1701-1744).

    Figure 1. Measuring one degree of latitude in the Arctic Circle, 1736-37.1

    Thursday 5 May 2022

    The thick winter ice is just beginning to break up on the River Torne as it reaches and empties into the Baltic Sea in the Gulf of Bothnia on the border between modern Finland and Sweden. The cracks starting to snake across the surface are a reminder that we live on a dynamic planet – one that’s constantly being shaped and altered by the immense forces of gravity, magnetism, volcanism and climate.

    The river – Europe’s longest free-flowing waterway without locks, dams or any other human-made intervention – is also what brought a small but intrepid band of French and Swedish scientists here in June 1736. Their mission, decreed and bankrolled by France’s young King Louis XV, was to help settle the great scientific debate of the age – the exact shape and form of the Earth.

    The twenty-five-year-old king had already dispatched a similar expedition to Peru a year earlier. The logic was that by precisely measuring the distance of degrees latitude at the equator and as far north as possible then comparing the results, it would be possible to determine whether the planet was a perfect sphere, or as great natural philosophers like Newton and Cassini had theorised, it was slightly deformed. The big question was whether that difference was at the planet’s waistline – squeezing it into an elongated lemon shape, or at the poles making it flatter, more like an orange.

    Figures 2 and 3: Then and now – Tornio Church is little changed today from how it looked in 1736.

    My friend Mark and I arrived in Tornio at the mouth of the river in the late evening, still light of course at this time of year. In case we were in any doubt, the final stage of our journey – a two-hour propeller plane flight north from Helsinki – proved we were entering a very different realm. Far below us, Baltic pack ice stretched into the distance, with the tiny dot of an ice-breaking ship bravely battling to keep open a narrow, navigable channel.

    This is why the eighteenth-century Earth-measuring scientists had to come here in midsummer – arriving just in time to make their first astronomical observations from the elegant, birch-shingled bell-tower of Tornio Church on the longest day of 1736. The adjacent steeple became the southernmost marker on a latticework of observation and triangulation points stretching northwards up the river valley. Their objective was to survey and measure one degree of latitude – roughly 95km along the meridian running through Tornio.

    The expedition was led by the flamboyant French mathematician and royal court-favourite Pierre Louis Moreau de Maupertuis. But we’ve come to focus on another of the party, Anders Celsius – the man whose name still lives on in the one-hundred-point (‘centi-grade’) temperature scale he invented and bequeathed to the post-Enlightenment world.

    Figure 4: Period map of Tornio.

    It was good fortune and coincidence that led to Celsius being part of the study. At the time King Louis was commissioning his expeditions, the thirty-two-year-old Swede had arrived in Paris as part of his Grand Tour of Europe’s great scientific capitals. His mix of astronomical, mathematical and geodesic surveying experience was exactly what De Maupertuis needed to achieve the desired results. Plus of course it was useful that he and another member of the party – one of Celsius’ students, Anders Hellant, spoke Swedish and knew something of their Arctic destination.

    All of this is what brought us to the council chamber on the top floor of Tornio’s modern City Hall, with magnificent views of the icy river and its thickly wooded valley. Ilkka Halmkrona, head of education for the Tornio region spoke with passion and pride about not just the city’s important history, but also its unique status as a cooperative, open-border centre for business, industry, culture and tourism with its Swedish twin settlement Haparanda on the opposite riverbank. In an era of division and conflict it was refreshing to witness such enthusiasm for internationalism and clear evidence of its benefits.

    Figure 5: Early signs of thaw at Tornio – until the eighteenth century, the world’s most northerly town.

    Next we heard from Veli-Markku Korteniemi – an impressively energetic Finnish academic and entrepreneur, Chair of the Maupertuis Foundation and someone with a deeply personal reason to keep the story of the 1736-37 expedition alive. Eight generations ago, his family owned and ran a remote but well-appointed guest house where most of the scientific expedition stayed, working on their calculations during the dark and frozen months of winter.

    Alongside us was Jarno Niskala, an affable and committed social scientist leading a project to commemorate another, even more ambitious scientific enterprise a century later. In 1842, the Torne Valley once again became the focus of international attention as a segment of the Struve Geodetic Arc – a 2,800km line of survey triangles passing through ten countries, from Norway to Ukraine’s Black Sea coast.

    Figures 6 and 7: Eighteenth and twenty-first century technologies meet at Tornio Museum.

    This UNESCO-heritage path and world-changing exercise are now brought to life through an excellent virtual reality exhibit at Tornio Museum, which we visited before heading off to see the real thing. Two hours later, a strenuous march through deep snow and stony outcrops took us to the 189m top of Mt Kaakamavaara – the next point on both the Maupertuis and Struve meridians.

    Figure 8: Jarno and Mark approaching the top of Mt Kaakamavaara.

    While we were still puffing and perspiring from a rugged climb, the incredible physical and logistical achievement of these pioneer scientists came into fresh perspective. With our modern binoculars, it was just possible to see the Tornio Church steeple to the south and another key landmark, Mt Niemivaara, a little bump on the horizon in the opposite direction.

    Maupertuis’s team had to row upstream against a strong current, lug heavy wooden and brass instruments through dense forest up to this point, fell hundreds of trees to clear the summit (all the time plagued by vicious biting mosquitoes and flies), and then be able to accurately measure angles and observe stars. It was an astonishing feat. And more astounding still is that the party – supported by a troop of tough Finnish soldiers and some local Lapps – did this for all eight of the principal measuring points in just 63 days.

    Even with modern access, equipment, machinery and communications this would be a mammoth task. And in itself, the valley route was a hastily-concocted ‘Plan B’. De Maupertuis had originally intended to use a series of islets at the mouth of the river for the survey, but these proved to be much too low and flat for the purpose. So Celsius and his companions had to draw on their collective initiative to adapt and act quickly, before the ice returned.

    Figure 9: Clearing and preparing Mt Niemivaara, with the white wooden summit marker in place.

    Friday 6 May 2022

    Our itinerary took us to two more hilltops – Aavasaksa, where the brightly-painted but crumbling ghost of the Imperial Lodge sits, patiently waiting for a Russian Tsar who never came, and Luppiovaara, overlooking a straight stretch of frozen river. This is where, after waiting for the cold and dark of winter, Celsius led his companions out onto the ice to measure a 14km baseline, from which they could then calculate all the other distances.

    Figure 10: Viewing the site of the 1736-37 baseline with the Maupertuis Foundation’s Tuomo Korteniemi.

    With just a few hours of daylight and the shimmering, ethereal Northern Lights to illuminate their work, the group split into two teams, starting from each end of the line and laying 30-foot-long, birch poles end-to-end to measure the distance. It took them ten, brutal and freezing days, vividly described by the expedition’s leader:

    Judge what it must be to walk in snow two feet deep, with heavy poles in our hands, which we must be continually laying upon the snow and lifting again; in a cold so extreme, that whenever we would take a little brandy, the only thing that could be kept liquid, our tongues and lips froze to the cup and came away bloody.’2

    But the scientists proved their mettle. When the two teams compared their results, they differed by just ten centimetres. It was a prodigious undertaking and outcome in fearsome conditions.

    For this part of our day, we met Tuomo Korteniemi: the younger brother of Veli-Markku and a journalist and publisher who first founded the Maupertuis Foundation. From Luppiovaara on the Swedish side of the river he directed us to the Arctic Circle monument at Juoksengi.

    The exact position of this line (the southern limit of continuous daylight at the summer solstice) constantly wobbles around because of the Earth’s tilt and the influence of the sun, moon and planets. But at roughly 66° 33’ it’s an eerily atmospheric place. A stainless steel depiction of the globe stands surrounded by the flags of the eight Arctic countries – with the Russian pole now conspicuously empty…

    Figures 11 and 12: Mark’s iPhone confirms our location at the Arctic Circle crossing point, Juoksengi, Sweden.
    Figure 13: The massive, heavyweight sector built by George Graham to Celsius’ specifications to observe stars in the Draco constellation and thereby pinpoint the exact latitudes at both ends of the measurement chain. The viewer lay on the bench in the centre looking directly upwards.

    Saturday 7 May 2022

    Over to Finland again to meet Miia Kallioinen and Janne Tolvanen – two young colleagues from the Pello mayor’s office giving up their weekend to act as our guides. They took us first to the ultimate destination of Celsius and his fellow scientists, Mt Kittisvaara, at the northern end of the expedition’s survey chain.

    We crunched through snow as the rocky path wound between slender trees and a dark green carpet of bilberry and lingonberry plants just emerging to greet the spring sunshine. As we rounded a bend, a squat stone pyramid appeared – indicating the place where the scientists built a wooden observatory to house the huge sector and portable zenith custom-built for the trip by London’s master instrument maker George Graham.

    For me too, this felt like an arrival. The culmination of five years’ fascination and study of the modest young Swede with the familiar name who brought his team – and us – to this place. I left the other three and walked away into the trees for a while, listening to the breeze and birdsong. I tried to imagine the experiences and feelings of the expedition members who came here, desperately hoping that the precision of their work would satisfy their own instincts, the scientific establishment and King Louis back in the opulence of Paris.

    I paused at prominent rocks – unmoved since they were deposited by glaciers – and ran my palms across their surfaces, crusted with pink, green and white lichens. And I thought about how Celsius and his fellow scientists had probably done the same.

    Figure 14 and 15: Mark, Miia and Janne at the Maupertuis expedition pyramid on Mt Kittisvaara.
    Figure 16: Korteniemi guest house with the wooden observatory on Mt Kittisvaara top left.

    Back down from the mountain, Miia and Janne took us to two other landmarks – a memorial stone to Celsius’ student Anders Hellant, who was just 20 years old when he returned to this his hometown. He was born where another stone now stands near to the river. It marks the site of the Korteniemi guest house, where Veli-Markku and Tuomo’s ancestors sheltered the exhausted scientists and helped them to recover from their exertions.

    Some remnants of this compound might still be visible if it were not for the terrible destruction wrought by retreating Nazi forces as they left Finland in autumn 1944. In a literal application of ‘scorched earth’ tactics, they burned and obliterated everything in this part of Lapland: homes, barns, forests, bridges and crops, so that nothing remained for the Finnish population.

    The Korteniemi house was just one casualty of these events, and a sadness seemed to hang over the place as I walked down towards the riverbank. A few small buildings now dot the area – not unlike those shown in the drawing from Celsius’ time, with Mt Kittisvaara a silent, sorrowful sentinel above.

    Figures 17 and 18: Site of the Korteniemi house where Celsius stayed, with the frozen River Torne behind.
    Figure 19: Janne explains geodesic measurements – and the delights of a jug of Kalja rye beer.

    But a lovely surprise awaited us at the end of our tour around Pello – a late lunch in the town’s special Maupertuis dining room, where the walls are tastefully decorated with prints of the expedition and reproductions of seminal equations, formulae and graphs. Very tasty too was the traditional homemade dark, malted rye Kalja beer we were served – a kind of non-alcoholic-stout-meets-dandelion-and-burdock, which is almost a meal in itself.

    Sunday 8 May 2022

    A day off from the serious research as we headed further north, the scenery quickly taking on a more remote and blasted feel than any we’d encountered before. We saw our first wild reindeer – a silver- and pewter-coated adolescent grazing peacefully at the side of the road – and several sturdy-looking black-tailed capercaillies scuttling across in front of us.

    We headed for Pajala, about 60km up the valley, where the Torne is joined by the even bigger River Muonio pouring down from the far north on the border with Norway. On the way, we stopped at Kengis Bruk – a dramatic set of cascades and rapids. It’s another place with a strong connection to Celsius.

    Here, four decades before the Maupertuis expedition, Celsius’ maternal grandfather Anders Spole visited and stayed while on his own astronomical and botanical adventure to Lapland. It was partly from hearing and reading about his grandfather’s exploits that Celsius had suggested this region for the 1736 expedition. Today, Kengis is a magnet for salmon fishing, with 20kg-plus monsters more than a metre long often hauled from the dark, peaty pools beneath the waterfalls.

    Figures 20 and 21: Some of the rapids at Kengis Bruk, where Celsius’ grandfather Anders Spole stayed in 1695.

    Monday 9 May 2022

    Our final day of travel and investigation. We drove south, heading off the main highway onto an unmade road that took us many kilometres into the surrounding lakes and forests, to visit Mt Niemivaara.

    More reindeer lifted their heads to gaze at us from the surrounding trees. One walked straight down the track and skipped past with a barely audible clicking of its flattened hooves. There were no signs or marked paths, so when the car could go no further we just stopped and struck out for the top.

    Figure 22: A local resident.

    It was easier going than some of the other ascents, but Niemivaara has its own peculiarities: sheer stone walls cut with deep fissures and promontories that we had to negotiate our way around. And just before the summit a massive boulder field demanded careful steps and a few leaps of faith. We wondered again how Celsius and his companions had managed when this was even rougher and completely unknown territory.

    Figures 23 and 24: Boulders and smooth walls of stone near the summit of Mt Niemivaara.

    At the top of the hill we were rewarded with a stunning view of Lake Ajankijärvi – still frozen from end to end. Once again, De Maupertuis’s eighteenth-century description closely matched what we saw and felt:

    Figure 25: The frozen Lake Ajankijärvi seen from the top of Mt Niemivaara.

    ‘The beautiful lakes that surround this mountain, and the many difficulties we had to overcome in getting thither, gave it the air of an enchanted island in a romance. On one hand you see a grove of trees rise from a plain, smooth and level as the walks of a garden, and on the other you have rocks so perpendicular, so high and so smooth that you would take them for the walls of an unfinished palace rather than for the work of nature. We had been frighted with stories of bears that haunted this place, but saw none. It seemed rather a place of resort for fairies and genii than for bears.’

    Figure 26: Peeling away bark to reveal bright white wood beneath – perfect material for summit markers.

    Stopping by a towering pile of freshly cut pine and birch trunks on our way down, the air was filled with sweet, fragrant resin and sizeable black butterflies suddenly roused into busy flight by the light and warmth. I peeled back the bark of a log to uncover the pure white wood underneath. This was an important part of the expedition’s method of creating summit markers that could be easily seen from far away.

    In an unplanned instant, this simple act connected me once more to the brave and brilliant band of scientists who came here so long ago.

    Tuesday 10 May 2022

    I leave Lapland with a far greater understanding of who the members of the 1736-37 expedition were, and of what they did, why, how and where. Having followed in his footsteps, I feel closer to my subject Anders Celsius. And after standing where he stood and seeing and hearing what he saw and heard, I am even more in awe of his qualities and capabilities – both as a scientist and as a man.

    Before they even departed Finland for France in spring 1737, and years before the few survivors of the Peru expedition returned, De Maupertuis, Celsius and the rest of their team were confident that they had solved the great puzzle about the shape of the Earth.

    Figure 27: The Earth is an orange, not a lemon.

    It took some time and effort to persuade the sceptics, but their painstaking measurements conclusively showed that the planet is a slightly flattened ellipsoid – about 40 kilometres fatter than it is tall.

    The River Torne was our constant companion throughout this trip – a dominant, surging presence always in view, its colour, form and texture changing by the hour. Thanks to Celsius, his colleagues and their adventures in its majestic, snaking valley we know today that our planet is an orange not a lemon.

    [1] This and other drawings taken from Journal D’un Voyage Au Nord, En 1736 & 1737 written by expedition member Abbé Réginald Outhier. Sadly the artists’ names are not recorded.

    [2] Maupertuis P L M de, Clairaut A C, Camus C E L, Le Monnier P C, Outhier R, Celsius A. The figure of the earth, determined from observations made by order of the French king at the Polar Circle, London, 1738

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