Category Archives: History of Optics

Vision, Seeing Better, Seeing Further

In the normal blog post rotation, a book review should be due today. However, instead today’s post is a literature review, listing and describing books on the histories of the theories of vision, spectacles, and telescopes, with the latter coming first as they are the actual main theme of the review. I announced my intention to do this is response to a regular readers request, so long ago I’ve forgotten when, and I was recently reminded of that announcement when someone on Twitter asked me if one of the history of the telescope books, which I own is any good; it is as I will explain later.

The classical standard text on the early history of the telescope is Albert van Helden’s The Invention of the Telescope, which was first published as a paper in the Transactions of the American Philosophical Society in 1977 but has long been available as a monograph, the second edition appearing in 2008 to celebrate the 400thanniversary of the invention of the telescope. 

Van Helden presents and analyses all of the early literature related to the emergence of the telescope in the first decade of the seventeenth century, as well as earlier descriptions of instruments similar to the telescope that proceeded it His text contains full quotes from the original literature in their source languages followed by English translations. It is justifiably called a classic and is a must read for anybody seriously studying the history of the telescope.

Van Helden’s text includes the historical references to Zacharias Janssen (1585–before 1632), as one of the candidates for the invention of the telescope. In 2008, there was a big conference in Middelburg, in the Netherlands, where the telescope first emerged, to celebrate that 400th anniversary; I was there! In the conference proceedings, The origins of the telescope (edited by Albert van Helden, Sven Dupré, Rob van Gent, Huib Zuidervaart, and published by KNAW Press, Amsterdam, 2010) there is a paper by Huib J. Zuidervaart, The ‘true inventor’ of the telescopeA survey of 400 years of debatewhich clearly shows that Zacharias Janssen was not an inventor of the telescope.

The entire proceedings contain an amazing collection of papers on all possible aspects of the history of the telescope by an all star cast of the world’s best historians of optics. It is available as a printed book but is also available as an open access e-book online.

The two books I’ve described so far only really deal with the origins of the telescope; we now turn our attention to books that delve further into the history of the telescope. A classic that is substantially older than van Helden’s The Invention of the Telescope is Henry King’s The History of the Telescope, which was originally published by Charles Griffin & Co. Ltd. In 1955 and then republished by Dover in 1979. 

It opens with a short chapter on the beginning of astronomical observation that is followed by an even shorter chapter on the history of lenses and optics that ends with Lipperhey and his invention of the refracting telescope, with the rival claims of Metius and Jansen. There follows chapter for chapter a chronological history of telescopes and their user and uses beginning with Galileo and ending around 1950 with the construction of the Jodrell Bank radio telescope. Despite the fact that it is dated, it is well researched and well written and can still be read with profit.

More up to date is Fred Watson’s Stargazer the life and times of the Telescope (Da Capo Press, 2005).

As with King, Watson opens with the pre-telescopic era and the various reports of things that might have been telescope but probably weren’t prior to 1608 and Lipperhey.

He then takes his reader on an episodic journey through the history of the telescope down to the present day, ending with plans and discussion of a new generation of super telescopes. A well-researched and well written book, which I found a pleasure to read and highly informative. 

I managed an absolute classic in Middelburg in 2008. I got into a conversation with another participant at the conference and during the exchange started to talk about something from Watson’s book blithely unaware that my conversation partner was the man himself! Mildly embarrassing but also somewhat amusing.

For those readers, who are interested but don’t want to plough their way through a dense academic tome on the history of the telescope but would prefer something more digestible, I heartily recommend Richard Dunn’s The Telescope: A Short History (National Maritime Museum, 2009, Conway, 2011).

Dunn was then curator at the National Maritime Museum in Greenwich, which has its own excellent collection of telescopes, and is now Keeper of Technologies and Engineering at the Science Museum. The chapters of his book are more topic orientated rather than purely chronological. Beautifully illustrated, it is a comparatively light introduction to the history of the telescope, as I said ideal for those interested but not necessarily prepared to take a deep dive into the subject. This was the book I got asked about recently on Twitter. 

Of a somewhat different nature is Marvin Bolt’s Telescopes Though the Looking Glass (Adler Planetarium, 2009).

This is actually a catalogue of an exhibition that Bolt curated at the Adler upon his return from the 2008 conference in Middelburg. I will quote Bolt’s brief description of the exhibition in full because it captures the general concept of all of the history of the telescope texts:

The exhibition and catalogue address four themed zones. The first, the pretelescope zone, addresses ways in which people have looked at the sky and tried to make sense of it, using their surrounding landscapes or relatively simple tools to develop an understanding or model of the Universe. Zone two presents the invention of the telescope, the challenges it brought to the Earth-centered Universe, and the beautiful craftsmanship and ornamentation of some of the earliest surviving examples in the world. In zone three, the technical challenges of improving telescopes led to variations in design and materials; the telescopes also became popular devices with brand-name recognition. Zone four displays the culmination of the refracting telescope and the emergence of spectroscopy, leading to the marvels of modern telescopes: some see wavelengths beyond the optical realm, others detect invisible particles, a few compensate for atmospheric turbulence, while still others travel beyond the Earth’s atmosphere into space.

Each exhibit is illustrated with a description on the facing page. If you can find a copy, it’s a great introduction to the history of the telescope. 

The ‘if you can find a copy’, illustrates a major problem with this bibliography. Because they only have a limited appeal and target readership, many of the books I am describing are out of print and you have to hunt around to find second-hand copies. Several of mine were bought second-hand.

Galileo, of course, gets a whole telescope bibliography to himself. I’ll start with Eileen Reeves’ excellent Galileo’s Glassworks (Harvard University Press, 2008).

There was a significant gap between Galileo first hearing about the new invention from the Netherlands and the manufacture of his own first telescope. In her book Reeves argues convincingly that Galileo at first thought that the new instrument was somehow based on mirrors and spent substantial time and effort trying to work out how. Reeves backs this up with a detailed account of the history of (magical) mirrors that allowed their owners to see great distances.

The book also contains much information on the critical period before and during the early period of telescope manufacture. A fascinating, thoroughly researched, and beautifully book.

Galileo’s TelescopesA European Story (Harvard University Press, 2015) by Massimo Bucciantini, Michele Camerota, and Franco Giudice and translated by Catherine Bolton describes in great detail the spread of the influence of Galileo’s publications on his telescopic discoveries and the distribution of the instruments that he manufactured throughout Europe and the influence that he exercised thereby.

An important contribution to the literature on the early telescope and its influence, well researched and excellently presented.

The same phenomenon, Galileo’s telescopes and their influence, is treated from a different angle by Mario Biagioli in his Galileo’s Instruments of CreditTelescopes, Images, Secrecy (University of Chicago Press, 2007).

This can be read alone but is much better read as a sequel, which it was, to Biagioli’s Galileo CourtierThe Practice of Science in The Culture of Absolutism (University of Chicago Press, 1993). 

In the earlier book Biagioli basically presents Galileo as a social climber, who uses his scientific career to win status within the political climate of Northern and Middle Italy at the beginning of the seventeenth century. Hustling for status and favour, Biagioli argues, I think correctly, that Galileo’s downfall was largely a product of the mechanisms of absolutist politics. Having raised Galileo up as a favourite at his papal court, Maffeo Barberini, Pope Urban VIII, then cast him down as a demonstration of his absolute power during a period of political crisis. This treatment of court favourites was quite common in absolutist regimes throughout Europe.

In his second volume, Biagioli shows how Galileo, having become the telescope man throughout Europe, through the publication of his Sidereus Nuncius in 1610, manufactured telescopes together with his instrument maker, who usually gets left out of the story, and distributed them as favours throughout Europe.

However, he did not give them to other mathematicians and astronomers, who could have used them to confirm Galileo’s discoveries or made new ones of their own, but to powerful figures within the Catholic Church and political potentates, in order to raise his own social status. In his defence it should be pointed out Galileo was not alone in doing this. It was common practice for Renaissance mathematici to design and manufacture high class scientific instruments as gifts for potential aristocratic patrons.

Both of Biagioli’s books are excellent and highly recommended for anybody interested in Galileo, his telescopes, his telescopic discoveries, and his use of them within a socio-politic context rather than a scientific one.

Having looked briefly at the social, political, and cultural contexts of the telescope and Galileo’s use of the instrument and his discoveries, it should be obvious that the advent of the telescope and its impact was not just scientific. Two further books by Eileen Reeves investigate the impact of the new culture of visual awareness in two non-scientific areas.

Her Painting the HeavensArt and Science in the Age of Galileo (Princeton University Press, 1997) explores the impact that the new telescopic astronomical discoveries had on the work of a group of leading contemporary artists.

Her Evening NewsOptics, Astronomy, and Journalism in Early Modern Europe(University of Pennsylvania Press, 2014).

The weekly newssheets began to emerge in Early Modern Europe almost simultaneously with the invention of the telescope and the publication of Galileo’s Sidereus Nuncius. To quote the publishers blurb:

Early modern news writers and consumers often understood journalistic texts in terms of recent developments in optics and astronomy, Reeves demonstrates, even as many of the first discussions of telescopic phenomena such as planetary satellites, lunar craters, sunspots, and comets were conditioned by accounts of current events. She charts how the deployment of particular technologies of vision—the telescope and the camera obscura—were adapted to comply with evolving notions of objectivity, censorship, and civic awareness. Detailing the differences between various types of printed and manuscript news and the importance of regional, national, and religious distinctions, Evening News emphasizes the ways in which information moved between high and low genres and across geographical and confessional boundaries in the first decades of the seventeenth century.

Changing direction, the man who is credited with being the first to publicly present a working telescope Hans Lipperhey (c. 1570–1619) in Middelburg in 1608, was a professional spectacle maker. This is in no way surprising as spectacle makers were the artisans, who worked with lenses. This means if one wants to understand the invention of the telescope, one must also take a look at the history of spectacles. Above all one needs to answer the questions, how did spectacle come to be invented and given that spectacles first emerged in the late thirteenth century, why did it take more than two hundred years before somebody invented the telescope? 

There are two books that answer these questions in great detail of which the first is Rolf Willach’s magisterial Long Route to the Invention of the TelescopeA Life of Influence and Exile (American Philosophical Society, 2008), like van Helden’s The Invention of the Telescope, published in English both as a journal article in the society’s transactions and as a separate monograph.

It also appears in English in the volume The origins of the telescope described above. His essay was originally published in German in Der Meister und die FernrohreDas Wechselspiel zwischen Astronomie und Optik in der GeschichteFestschrift zum 85. Geburtstag von Rolf Riekher[1] herausgeben von Jürgen Hamel und Inge Keil, Acta Historica Astronomia Vol. 33, Verlag Harri Deutsch, 2007. 

For those of my readers who can read German this volume contains a large collection of excellent papers on the history of the telescope. A couple of them are even in English.

The number of different publications of Willach’s essay signify its ground-breaking status in the histories of spectacles and telescopes. Based on his very extensive empirical investigations he hypothesises that the invention of spectacles was made by monks working in medieval cloisters, cutting and polishing gemstones to decorate reliquaries, the containers for holy relics. At the other end of the two hundred years, he showed that the clue to constructing a successful telescope lay in stopping down the eyepiece lens with a mask. This is because early lenses were inaccurately ground, and the outer edges of the lens distorted the image. By masking off the outer edges, the image became comparatively sharp and usable. 

Equally impressive is Vincent Ilardi’s Renaissance Vision from Spectacles to Telescopes (Memoires of the American Philosophical Society, Band 259, 2007).

This is the definitive account of the Early Modern history of spectacles. Ilardi was a diplomatic historian, who studied a vast convolute of trade documents and correspondence in order to reconstruct the history of spectacles in the first two centuries of their existence. I have read this book twice but do not own a copy as it is prohibitively expensive, thank God for libraries. Iladi should have held a lecture in Middelburg in September 2008 but he was already dying of prostate cancer, which deprived the world of his excellence in January 2009. 

The histories of spectacles and telescopes are, of course, just integral parts of the much wider history of optics. Optics was originally the theory of vision, how do we see? How do our eyes perceive the world around us bringing information of everything within our field of vision into our brain for processing. 

The absolute classic, which outlines the various theories developed from the ancient Greeks down to Johannes Kepler at the beginning of the seventeenth century and the advent of the telescope is David C. Lindberg’s Theories of Vision from Al-Kindi to Kepler (University of Chicago Press, 1976).

Popular wisdom claims that the ancient Greeks believed that we see with a fire that the eyes emit to touch and illuminate the objects seen. This is in simplistic form the extramission theory of vision of Plato. Lindberg explains that this was only one of several extramission and intromission (rays entering the eyes) theories of vision held by different individuals and schools of philosophy in ancient Greece. He also presents the geometric opticians–Euclid, Ptolemaeus, Heron–who propagated a mathematical extramission theory. 

Moving on he shows how these theories were assimilated by Islamic scholars and how al-Kindi supported a Euclidian extramission theory but also developed his punctiform theory of reflection, which states that light is reflected from every point on an object in every direction. Enter al-Haytham, who produced a synthesis of an intromission theory, geometrical optics, and al-Kindi’s punctiform theory of reflection, which when translated into Latin in the thirteenth century became the so-called perspectivist theory, which led the field in Europe right down to Kepler. Lindberg sees Kepler as the last of the perspectivists. The book is a historical tour de force. If you are really interested, Lindberg has a long list of excellent academic papers investigating individual topics in medieval optics.

Even an absolute classic can be surpassed, and this has happened to Lindberg’s masterpiece. A. Mark Smith was a doctoral student of Lindberg’s and followed in his master’s footsteps becoming a brilliant historian of optics. His synthesis is From Sight to Light (University of Chicago Press, 2015).

His narrative follows that of Lindberg, but in greater detail and including many figure that Lindberg did not feature. The biggest difference come at the end, unlike Lindberg, he does not consider Kepler the last of the perspectivists but rather the first of a new direction in the optics. He argues his case very convincingly and I think he in probably correct.

If I were to recommend just one of the two, then it would have to be Smith and that despite the fact that the Lindberg was one of those turning point books in my own development. Of course, I think you should read both of them! Smith, like his mentor, has a very long list of papers and book on optics, all of which are recommended reading.

Both Lindberg and Smith stop at the beginning of the seventeenth century, although Smith has a short capital at the end sketching the further developments during the century. If you want to follow the story further then I recommend Oliver Darrigol’s A History of OpticsFrom Greek Antiquity to the Nineteenth Century (OUP, 2012).

Darrigol deals with the passage from the Greeks to Kepler in the first thirty-six pages of his books and devotes the rest to developing the story from there down to the end of the nineteenth century with Stoke, Poincare et al. 

As I noted above when talking about Galileo and his telescopic discoveries, the new possibilities revealed by the new instruments and the new theories of optics went well beyond the boundaries of science touching on other areas such as culture, politics and society. They literally changed people’s perceptions of the world in which they lived. I will briefly mention three books which deal with this, a by no means exhaustive list. 

The first one that I read was Svetlana Alpers’ The Art of DescribingDutch Art in the Seventeenth Century(University of Chicago Press, 1984).

As we have already seen with Eileen Revees’ Painting the HeavensArt and Science in the Age ofGalileo art visually reflected the new developments in optics. To quote a review of Alpers’ book: 

“The art historian after Erwin Panofsky and Ernst Gombrich is not only participating in an activity of great intellectual excitement; he is raising and exploring issues which lie very much at the centre of psychology, of the sciences and of history itself. Svetlana Alpers’s study of 17th-century Dutch painting is a splendid example of this excitement and of the centrality of art history among current disciples. Professor Alpers puts forward a vividly argued thesis. There is, she says, a truly fundamental dichotomy between the art of the Italian Renaissance and that of the Dutch masters. . . . Italian art is the primary expression of a ‘textual culture,’ this is to say of a culture which seeks emblematic, allegorical or philosophical meanings in a serious painting. Alberti, Vasari and the many other theoreticians of the Italian Renaissance teach us to ‘read’ a painting, and to read it in depth so as to elicit and construe its several levels of signification. The world of Dutch art, by the contrast, arises from and enacts a truly ‘visual culture.’ It serves and energises a system of values in which meaning is not ‘read’ but ‘seen,’ in which new knowledge is visually recorded.”—George Steiner, Sunday Times

My second book is Stuart Clark’s Vanities of the EyeVision in Early Modern European Culture (OUP, 2007).

Once again to quote the back cover blurb:

Vanities of the Eye investigates the cultural history of the senses in early modern Europe, a time in which the nature and reliability of human vision was the focus of much debate. In medicine, art theory, science, religion, and philosophy, sight came to be characterized as uncertain or paradoxical-mental images no longer resembled the external world. Was seeing really believing? Stuart Clark explores the controversial debates of the time-from the fantasies and hallucinations of melancholia, to the illusions of magic, art, demonic deceptions, and witchcraft. The truth and function of religious images and the authenticity of miracles and visions were also questioned with new vigor, affecting such contemporary works as Macbeth- a play deeply concerned with the dangers of visual illusion. Clark also contends that there was a close connection between these debates and the ways in which philosophers such as Descartes and Hobbes developed new theories on the relationship between the real and virtual. Original, highly accessible, and a major contribution to our understanding of European culture, Vanities of the Eye will be of great interest to a wide range of historians and anyone interested in the true nature of seeing.

The Last of my three is Laura J Snyder’s Eye of the BeholderJohannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing (W. W. Norton, 2015):

Once again resorting to publisher’s blurb:

By the early 17th century the Scientific Revolution was well under way. Philosophers and scientists were throwing off the yoke of ancient authority to peer at nature and the cosmos through microscopes and telescopes. 

In October 1632, in the small town of Delft in the Dutch Republic, two geniuses were born who would bring about a seismic shift in the idea of what it meant to see the world. One was Johannes Vermeer, whose experiments with lenses and a camera obscura taught him how we see under different conditions of light and helped him create the most luminous works of art ever beheld. The other was Antoni van Leeuwenhoek, whose work with microscopes revealed a previously unimagined realm of minuscule creatures. 

By intertwining the biographies of these two men, Laura Snyder tells the story of a historical moment in both art and science that revolutionized how we see the world today.

I’m going to close this overlong literature review with two books that I don’t think you’ll be able to get hold of, but you might get lucky. Peter Louwman is a rich Dutchman, who has a very impressive automobile museum in De Haag. The museum also houses a massive historical collection of telescopes and binoculars.

For the 400th anniversary conference in Middelburg Louwman produced a wonderful annotated edition of the French newsletter reporting on the visit of the Ambassador of Siam to Den Haag in September 1608, which contains a description of Lipperhey’s demonstration of his telescope to the assembled delegates of the peace conference taking place there.

This special edition contains an explanatory introduction, a facsimile of the newsletter,

a French transcription, and an English as well as a Dutch translation.

First every report of a public demonstration of a telescope pp. 9-11

Every participant in the conference received a copy and I think it’s the best goody that I’ve every received at a conference. I think for a time it was on sale in the museum shop but that no longer appears to be the case.

Another Louwman publication is a wonderful catalogue of the Louwman Collection of Historic Telescopes, A Certain Instrument for Seeing Far by P.J.K. Louwman and H. J. Zuidervaart (2013), which definitely used to be sold by the museum, because I bought one, but no longer seems to be available.

One of hundreds of beautiful illustration in the book

I’m not trying to impress my readers with all the books that I’ve read on the history of optics and the telescopic but trying to make clear that if you truly want to understand that history, the road that led up to the invention of the telescope, its impact as a scientific instrument, and its impact outside of the direct field of science then you have to extend your scope and dig deep. 

[1] Rolf Riekher was a leading German optician and historian of optics, who bought me a cup of tea and a piece of cake on a sunny afternoon in Middelburg in 2008.


Filed under History of Astronomy, History of Optics, History of Technology

The Wizard Earl’s mathematici 

In my recent post on the Oxford mathematician and astrologer Thomas Allen, I mentioned his association with Henry Percy, 9th Earl of Northumberland, who because of his strong interest in the sciences was known as the Wizard Earl.

HENRY PERCY, 9TH EARL OF NORTHUMBERLAND (1564-1632) by Sir Anthony Van Dyck (1599-1641). The ‘Wizard Earl’ was painted posthumously as a philosopher, hung in Square Room at Petworth. This is NT owned. via Wikimedia Commons

As already explained there Percy actively supported four mathematici, or to use the English term mathematical practitioners, Thomas Harriot (c. 1560–1621), Robert Hues (1553–1632), Walter Warner (1563–1643), and Nathaniel Torporley (1564–1632). Today, I’m going to take a closer look at them.

Thomas Harriot is, of course, the most well-known of the four; I have already written a post about him in the past, so I will only brief account of the salient point here.

Portrait often claimed to be Thomas Harriot (1602), which hangs in Oriel College, Oxford. Source: Wikimedia Commons

He graduatied from Oxford in 1580 and entered the service of Sir Walter Raleigh (1552–1618) in 1583. At Raleigh’s instigation he set up a school to teach Raleigh’s marine captains the newest methods of navigation and cartography, writing a manual on mathematical navigation, which contained the correct mathematical method for the construction of the Mercator projection. This manual was never published but we can assume he used it in his teaching. He was also directly involved in Raleigh’s voyages to establish the colony of Roanoke Island.

Sir Walter Ralegh in 1588 artist unknown. Source: Wikimedia Commons

In 1590, he left Raleigh’s service and became a pensioner of Henry Percy, with a very generous pension, the title to some land in the North of England, and a house on Percy’s estate, Syon House, in Middlesex.[1] Here, Harriot lived out his years as a research scientist with no obligations.

Syon House Attributed to Robert Griffier

After Harriot, the most significant of the Wizard Earl’s mathematici was Robert Hues. Like Harriot, Hues attended St Mary’s Hall in Oxford, graduating a couple of years ahead of him in 1578. Being interested in geography and mathematics, he was one of those who studied navigation under Harriot in the school set up by Raleigh, having been introduced to Raleigh by Richard Hakluyt (1553–1616), another student of Thomas Allen and a big promoter of English colonisation of North America.  

Hakluyt depicted in stained glass in the west window of the south transept of Bristol Cathedral – Charles Eamer Kempe, c. 1905. Source: Wikimedia Commons

Hues went on to become an experienced mariner. During a trip to Newfoundland, he came to doubt the published values for magnetic declination, the difference between magnetic north and true north, which varies from place to place.

In 1586, he joined with Thomas Cavendish (1560–1592), a privateer and another graduate of the Harriot school of navigation, who set out to raid Spanish shipping and undertake a circumnavigation of the globe, leaving Plymouth with three ships on 21 July. After the usual collection of adventures, they returned to Plymouth with just one ship on 9 September 1588, as the third ever ship to complete the circumnavigation after Magellan and Drake. Like Drake, Cavendish was knighted by Queen Elizabeth for his endeavours.

Thomas Cavendish An engraving from Henry Holland’s Herōologia Anglica (1620). Animum fortuna sequatur is Latin for “May fortune follow courage.” Source: Wikimedia Commons

Hues undertook astronomical observations throughout the journey and determined the latitudes of the places they visited. In 1589, he served with the mathematicus Edward Wright (1561–1615), who like Harriot worked out the correct mathematical method for the construction of the Mercator projection, but unlike Harriot published it in his Certaine Errors in Navigation in 1599.

Source: Wikimedia Commons

In August 1591, he set out once again with Cavendish on another attempted circumnavigation, also accompanied by the navigator John Davis (c. 1550–1605), another associate of Raleigh’s, known for his attempts to discover the North-West passage and his discovery of the Falkland Islands.

Miniature engraved portrait of navigator John Davis (c. 1550-1605), detail from the title page of Samuel Purchas’s Hakluytus Posthumus or Purchas his Pilgrimes (1624). Source: Wikimedia Commons

Cavendish died on route in 1592 and Hues returned to England with Davis in 1683. On this voyage Hues continued his astronomical observations in the South Atlantic and made determinations of compass declinations at various latitudes and the equator. 

Back in England, Hues published the results of his astronomical and navigational research in his Tractatus de globis et eorum usu (Treatise on Globes and Their Use, 1594), which was dedicated to Raleigh.

The book was a guide to the use of the terrestrial and celestial globes that Emery Molyneux (died 1598) had published in 1592 or 1593.

Molyneux CEltial Globe Middle Temple Library
A terrestrial globe by Emery Molyneux (d.1598-1599) is dated 1592 and is the earliest such English globe in existence. It is weighted with sand and made from layers of paper with a surface coat of plaster engraved with elaborate cartouches, fanciful sea-monsters and other nautical decoration by the Fleming Jodocus Hondius (1563-1611). There is a wooden horizon circle and brass meridian rings.

Molyneux belong to the same circle of mariners and mathematici, counting Hues, Wright, Cavendish, Davis, Raleigh, and Francis Drake (c. 1540–1596) amongst his acquaintances. In fact, he took part in Drake’s circumnavigation 1577–1580. These were the first globes made in England apparently at the suggestion of John Davis to his patron the wealthy London merchant William Sanderson (?1548–1638), who financed the construction of Molyneux’s globes to the tune of £1,000. Sanderson had sponsored Davis’ voyages and for a time was Raleigh’s financial manager. He named his first three sons Raleigh, Cavendish, and Drake.

Molyneux’s terrestrial globe was his own work incorporating information from his mariner friends and with the assistance of Edward Wright in plotting the coast lines. The circumnavigations of Drake and Cavendish were marked on the globe in red and blue line respectively. His celestial globe was a copy of the 1571 globe of Gerard Mercator (1512–1594), which itself was based on the 1537 globe of Gemma Frisius (1508–1555), on which Mercator had served his apprenticeship as globe maker. Molyneux’s globes were engraved by Jodocus Hondius (1563–1612), who lived in London between 1584 and 1593, and who would upon his return to the Netherlands would found one of the two biggest cartographical publishing houses of the seventeenth century.

Hues’ Tractatus de globis et eorum usu was one of four publications on the use of the globes. Molyneux wrote one himself, The Globes Celestial and Terrestrial Set Forth in Plano, published by Sanderson in 1592, of which none have survived. The London public lecturer on mathematics Thomas Hood published his The Vse of Both the Globes, Celestiall and Terrestriall in 1592, and finally Thomas Blundeville (c. 1522–c. 1606) in his Exercises containing six treatises including Cosmography, Astronomy, Geography and Navigation in 1594.

Hues’ Tractatus de globis has five sections the first of which deals with a basic description of and use of Molyneux’s globes. The second is concerned with matters celestial, plants, stars, and constellations. The third describes the lands, and seas displayed on the terrestrial globe, the circumference of the earth and degrees of a great circle. Part four contains the meat of the book and explains how mariners can use the globes to determine the sun’s position, latitude, course and distance, amplitudes and azimuths, and time and declination. The final section is a treatise, inspired by Harriot’s work on rhumb lines, on the use of the nautical triangle for dead reckoning. Difference of latitude and departure (or longitude) are two legs of a right triangle, the distance travelled is the hypotenuse, and the angle between difference of latitude and distance is the course. If any two elements are known, the other two can be determined by plotting or calculation using trigonometry.

The book was a success going through numerous editions in various languages. The original in Latin in 1593, Dutch in 1597, an enlarged and corrected Latin edition in 1611, Dutch again in 1613, enlarged once again in Latin in 1617, French in 1618, another Dutch edition in 1622, Latin again in 1627, English in 1638, Latin in 1659, another English edition also in 1659, and finally the third enlarged Latin edition reprinted in 1663. There were others.

The title page of Robert Hues (1634) Tractatvs de Globis Coelesti et Terrestri eorvmqve vsv in the collection of the Biblioteca Nacional de Portugal via Wikimedia Commons

Hues continued his acquaintance with Raleigh in the 1590s and was one of the executors of Raleigh’s will. He became a servant of Thomas Grey, 15th Baron Gray de Wilton (died 1614) and when Grey was imprisoned in the Tower of London for his involvement in a Catholic plot against James I & VI in 1604, Hues was granted permission to visit and even to stay with him in the Tower. From 1605 to 1621, Northumberland was also incarcerated in the Tower because of his family’s involvement in the Gunpowder Plot. Following Grey’s death Hues transferred his Tower visits to Northumberland, who paid him a yearly pension of £40 until his death in 1632.

He withdrew to Oxford University and tutored Henry Percy’s oldest son Algernon, the future 10th Earl of Northumberland, in mathematics when he matriculated at Christ’s Church in 1617.

Algernon Percy, 10th Earl of Northumberland, as Lord High Admiral of England, by Anthony van Dyck. Source: Wikimedia Commons

In 1622-23 he would also tutor the younger son Henry.

Oil painting on canvas, Henry Percy, Baron Percy of Alnwick (1605-1659) by Anthony Van Dyck Source: Wikimedia Commons

During this period, he probably visited both Petworth and Syon, Northumberland’s southern estates. He in known to have had discussion with Walter Warner on reflection. He remained in Oxford discussing mathematics with like minded fellows until his death.

Compared to the nautical adventures of Harriot and Hues, both Warner and Torporley led quiet lives. Walter Warner was born in Leicestershire and educated at Merton College Oxford graduating BA in 1579, the year between Hues and Harriot. According to John Aubrey in his Brief Lives, Warner was born with only one hand. It is almost certain that Hues, Warner, and Harriot met each other attending the mathematics lectures of Thomas Allen at Oxford. Originally a protégé of Robert Dudley, 1st Earl of Leicester, (1532–1588), he entered Northumberland’s household as a gentleman servitor in 1590 and became a pensioner in 1617. Although a servant, Warner dined with the family and was treated as a companion by the Earl. In Syon house, he was responsible for purchasing the Earl’s books, Northumberland had one of the largest libraries in England, and scientific instruments. He accompanied the Earl on his military mission to the Netherlands in 1600-01, acting as his confidential courier.       

Like Harriot, Warner was a true polymath, researching and writing on a very wide range of topics–logic, psychology, animal locomotion, atomism, time and space, the nature of heat and light, bullion and exchange, hydrostatics, chemistry, and the circulation of the blood, which he claimed to have discovered before William Harvey. However, like Harriot he published almost nothing, although, like Harriot, he was well-known in scholarly circles. Some of his work on optics was published posthumously by Marin Mersenne (1588–1648) in his Universæ geometriæ (1646).

Source: Google Books

It seems that following Harriot’s death Warner left Syon house, living in Charing Cross and at Cranbourne Lodge in Windsor the home of Sir Thomas Aylesbury, 1st Baronet (!576–1657), who had also been a student of Thomas Allen, and who had served both as Surveyor of the Navy and Master of the Mint. Aylesbury became Warner’s patron.

This painting by William Dobson probably represents Sir Thomas Aylesbury, 1st Baronet. 
Source: Wikimedia Commons

Aylesbury had inherited Harriot’s papers and encouraged Warner in the work of editing them for publication (of which more later), together with the young mathematician John Pell (1611–1685), asking Northumberland for financial assistance in the endeavour.

Northumberland died in 1632 and Algernon Percy the 10th Earl discontinued Warner’s pension. In 1635, Warner tried to win the patronage of Sir Charles Cavendish and his brother William Cavendish, enthusiastic supporters of the new scientific developments, in particular Keplerian astronomy. Charles Cavendish’s wife was the notorious female philosopher, Margaret Cavendish. Warner sent Cavendish a tract on the construction of telescopes and lenses for which he was rewarded with £20. However, Thomas Hobbes, another member of the Cavendish circle, managed to get Warner expelled from Cavendish’s patronage. Despite Aylesbury’s support Warner died in poverty. 

Nathaniel Torporley was born in Shropshire of unknow parentage and educated at Shrewsbury Grammar Scholl before matriculating at Christ Church Oxford in 1581. He graduated BA in 1584 and then travelled to France where he served as amanuensis to the French mathematician François Viète (1540–1603).

François Viète Source: Wikimedia Commons

He is thought to have supplied Harriot with a copy of Viète’s Isagoge, making Harriot the first English mathematician to have read it.


Torporley returned to Oxford in 1587 or 1588 and graduated MA from Brasenose College in 1591. 

He entered holy orders and was appointed rector of Salwarpe in Worcestershire, a living he retained until 1622. From 1611 he was also rector of Liddington in Wiltshire. His interest in mathematics, astronomy and astrology attracted the attention of Northumberland and he probably received a pension from him but there is only evidence of one payment in 1627. He was investigated in 1605, shortly before the Gunpowder Plot for having cast a nativity of the king. At some point he published a pamphlet, under the name Poulterey, attacking Viète. In 1632, he died at Sion College, on London Wall and in a will written in the year of his death he left all of his books, papers, and scientific instrument to the Sion College library.

Although his papers in the Sion College library contain several unpublished mathematical texts, still extant today, he only published one book his Diclides Coelometricae; seu Valuae Astronomicae universales, omnia artis totius munera Psephophoretica in sat modicis Finibus Duarum Tabularum methodo Nova, generali et facillima continentes, (containing a preface, Directionis accuratae consummata Doctrina, Astrologis hactenus plurimum desiderata and the Tabula praemissilis ad Declinationes et coeli meditations) in London in 1602.


This is a book on how to calculate astrological directions, a method for determining the time of major incidents in the life of a subject including their point of death, which was a very popular astrological method in the Renaissance. This requires spherical trigonometry, and the book is interesting for containing new simplified methods of solving right spherical triangles of any sort, methods that are normally attributed to John Napier (1550–1617) in a later publication. The book is, however, extremely cryptic and obscure, and almost unreadable. Despite this the surviving copies would suggest that it was widely distributed in Europe.

Our three mathematici came together as executors of Harriot’s will. Hues was charged with pricing Harriot’s books and other items for sale to the Bodleian Library. Hues and Torporley were charged with assisting Warner with the publication of Harriot’s mathematical manuscripts, a task that the three of them managed to bungle. In the end they only managed to publish one single book, Harriot’s algebra Artis Analyticae Praxis in 1631 and this text they castrated.


Harriot’s manuscript was the most advanced text on the topic written at the time and included full solutions of algebraic equations including negative and complex solutions. Either Warner et al did not understand Harriot’s work or they got cold feet in the face of his revolutionary new methods, whichever, they removed all of the innovative parts of the book making it basically irrelevant and depriving Harriot of the glory that was due to him.

For myself the main lesson to be learned from taking a closer look at the lives of this group of mathematici is that it shows that those interested in mathematics, astronomy, cartography, and navigation in England the late sixteenth and early seventeenth centuries were intricately linked in a complex network of relationships, which contains hubs one of which was initially Harriot and Raleigh and then later Harriot and Northumberland. 

[1] For those who don’t know, Middlesex was a small English county bordering London, in the South-West corner of Essex, squeezed between Hertfordshire to the north and Surry in the South, which now no longer exists having been largely absorbed into Greater London. 


Filed under Early Scientific Publishing, History of Astrology, History of Astronomy, History of Cartography, History of Mathematics, History of Navigation, History of Optics, History of science, Renaissance Science

Renaissance science – XXIX

In theory the undergraduate course of study at medieval universities was based on the seven liberal arts, the trivium–grammar, rhetoric, logic–and the quadrivium–arithmetic, geometry, music, and astronomy. What was actually taught at individual universities often deviated from this curriculum. One of the changes that took place was that other subjects were often added to the quadrivium. 


One subject that became very much a standard part of the quadrivium was the study of optics. This came about largely as a result of the influence of the work of Robert Grosseteste (1168–1253), who, drawing on the theory of radiation propagated by the Arabic polymath al-Kindi (C. 801–873) in his De radiis stellarum, “that everything in the world … emits rays in every direction, which fill the whole world”, made optics a central part of his cosmogony, believing light to be the first form of all things, the source of all generation and motion. Following Grosseteste, Roger Bacon (c.1220–c. 1292) also made optics a central part of his work drawing heavily on the Kitab al-Manazir (Book of Optics) of Ibn al-Haytham (c.965–1040), which had been translated into Latin by an unknown translator in the late twelfth or early thirteenth century, under the title De aspectibus.Ibn al-Haytham produced a synthesis of an intromission theory of vision with the geometrical optics of Euclid, Hero of Alexandria and Ptolemaeus. Vision is a result of light reflected from external objects entering the eyes. A very modern theory, whose only fault was that he believed that the image was formed in the lens of the eye. Both John Peckham (c.1230–1292), a later Archbishop of Canterbury, and Witelo (c. 1230–1280) produced works on optics based on Bacon’s transmission of al-Haytham, Peckham Perspectiva communis and Witelo Perspectiva around 1270, and these became the standard university textbooks.

Page from a manuscript of Witelo’s Perspectiva with a miniature of the author Source: Wikimedia Commons

This became known as Perspectivist theory, and there was very little change in this situation in the universities down to the sixteenth centuries. For example, when Regiomontanus (1436–1476) finally got awarded his MA, i.e., his permission to teach, at the age of 21, the first lecture course he held was on optics.

Source: Wikimedia Commons

An interesting phenomenon is that around the same time as Bacon et al were creating the Perspectivist theory of optics, Eyeglasses were invented in Italy but there was no known connection between the two creations. The currently accepted theory, formulated by the Swiss historian of optics, Rolf Willach, is that medieval monks grinding and polishing precious stones to decorate the reliquaries made to hold saints’ relics, realised that these could be used to magnify texts.

Reliquary chasse of in the form of a miniature simplified church building, between circa 1200 and circa 1250 Source: Wikimedia Commons Note the lens shaped precious stones along the top

So, they ground pieces of quartz, and later glass, to the same size and shape to aid colleagues in the scriptorium, who suffered from presbyopia, age-related farsightedness, and so the pair of glasses was born. Willach undertook extensive optical measurements of both early eyeglasses and the precious stones on shrines to support his thesis. The development of eyeglasses continued, over time, independently of any optical theory taught at the universities and by the middle of the fifteenth century eyeglasses were available for all three of the common eye disorders. 

Oldest surviving depiction of someone wearing glasses: Detail of a portrait of the Dominican Cardinal and renowned biblical scholar Hugh of Saint-Cher painted by Tommaso da Modena in 1352 Source: Wikimedia Commons

The next major development in optics was the invention of linear perspective at the beginning of the fifteenth century. Many sources claim, incorrectly, that this derives from al-Haytham’s theory of vision. However, linear perspective utilises Euclid’s geometrical optics and Alberti (1406–1472) states quite clearly in the first written account of linear perspective, his De pictura (1435), that for the theory it is irrelevant whether one holds an intromission, rays entering the eye, or extramission, rays projected out of the eye, theory of vision. 

Alberti De pictura Source

It was first in the sixteenth century that things began to gradually change in the field of optics, driven by three principal factors, Firstly, the increased interest in astronomical observations, secondly the invention of the printed book, and lastly the Renaissance developments in the discipline of medical anatomy. 

Astronomical observations are by their very nature optical and observational astronomers already became aware in antiquity of the problem of atmospheric refraction i.e., the light rays coming from outer space are refracted, bent, by the Earth’s atmosphere.

Atmospheric refraction

This is what prompted Ptolemaeus (fl. c. 150 CE) to write his Optica, an extensive investigation of a very wide range of optical phenomena and considered one of the three most important works on optics, alongside al-Haytham’s De aspectibus and Kepler’s Astronomia Pars Optica(1604), (about which much more later) before Huygens, Newton et al. Ptolemaeus apparently ignored atmospheric refraction in his Mathēmatikē Syntaxis but discusses it quite extensively in his Optica, which was written later. The reason Ptolemaeus gave for not calculating atmospheric refraction was that he didn’t know how deep the atmosphere was. The eleventh century Muslim mathematician Ibn Mu’adh (989–1079) did calculate the depth of the atmosphere based on his estimate how low below the horizon the Sun was when the light coming from it still was brighter than that coming from the opposite direction. Taking 19° as his value he calculated the atmosphere to be 86.3 km deep. A surprisingly accurate figure. Al-Haytham’s account of atmospheric refraction, in his De aspectibus, closely follows that of Ptolemaeus. 

In the early modern period the question of atmospheric refraction, the law that governs it and how to measure or determine it became more important, as astronomers turned once again to making their own extensive observations. Copernicus, who was not really an observational astronomer, and took nearly all of his observed values from others, simply ignored the problem. However, for Tycho Brahe, a fanatic for accuracy, correcting for atmospheric refraction was an important issue. He conducted a long sequence of measurements based on a series of assumptions, for both the Sun and the fixed stars and achieved excellent results.

Tycho Brahe’s values for atmospheric refraction compared tom modern data

Determining the law of refraction became a pressing issue for many mathematicians and astronomers around the beginning of the seventeenth century. Strangely, Thomas Harriot carried out an extensive correspondence with Johannes Kepler on the issue without once revealing that he had in fact found the correct law.

We now turn our attention to the affect that the invention of movable type printing had on the debate about optics in the sixteenth century. John Peckham’s Perspectiva communis, a comparatively simple optics textbook, was published in Milan already in 1482/3 and went through nine separate editions before the end of the sixteenth century. 

John Peckham’s Perspectiva communis edition from 1580 Source

The first printed edition of Witelo’s Perspectiva, edited by Georg Tannstetter and Peter Apian, a much more advanced text that Peckham’s was issued by Johannes Petreius in 1535.

Vitellionis Mathematici doctissimi Peri optikēs… title page Source: Christie’s

This was obviously well received as a second edition followed in 1551. The interest in optics was obviously growing as Friedrich Risner (c. 1533–1580), who was a pupil of Petrus Ramus and the first professor of mathematics on the Collège Royal de France in 1576, published his majestic Opticae thesaurus: Alhazeni Arabis libri septem, nuncprimum editi; Eiusdem liber De Crepusculis et nubium ascensionibus, Item Vitellonis Thuringopoloni libri X, (Optical Treasury) which as the title states contains both al-Haytham’s De aspectibus, printed for the first time, and the third edition of Witelo’s Perspectiva

Friedrich Risner edition Opticae Thesaurus (Basel, 1572) Title Page Source

As I outlined in the XVIII and XIX episodes of this series there was a gradual development in the study of medical anatomy, which had its beginnings in the High Middle Ages and accelerated with the publication of Vesalius’ De Humani Corporis Fabrica in 1543.

A portrait of Vesalius from his De Humani Corporis Fabrica (1543) Source: Wikimedia Commons

This was followed by the work of other North Italian anatomists such as, Gabrielle Falloppio (1523–1562) and Matteo Realdo Colombo (c. 1515–1559). Vesalius (1514–1564) produced the first accurate description of the eye, based on dissection since Galen (129–c. 216 CE).

Vesalius’s first cross-sectional image of the eye, from Andreas Vesalius, De humani corporis fabrica (On the Fabric of the Human Body), 1543. The Huntington Library, Art Collections, and Botanical Gardens. Photo by Kate Lain.

Al-Haytham used Galen in his work, and this was the model and concept that was adopted and propagated by the European perspectivists. In 1583, the Swiss physician Felix Platter (1536–1614), professor for medicine at the University of Basel,


published a short text, De corporis humani structua et usu … libri III, aimed at popularizing, correcting, and supplementing the work of Vesalius, Colombo, and Falloppio, which consisted of fifty plates and text.


In his description of the eye, he declared the lens of the eye to be simply that, a lens, which collects the incoming rays and spreads them over the retina or retiform nerve. This stand into contradiction to the perspectivist view that the image in formed in the lens.

The Mediate Eye represented in Platter’s 1583 De Corporis. Table 49.

The three streams that I have described, the problem of atmospheric refraction, the publication of printed versions of the main perspectivist texts, and Platter’s new view of how the eye functions came together in the work of Johannes Kepler (1571–1630), who created a new theory of vision, whilst also bringing together the theoretical concepts of the perspectivists and the work of the craftsmen, who manufactured the eyeglasses. 

Kepler’s journey to his new theories of optics began, when he became Tycho Brahe’s assistant in Prague and first confronted the problem of atmospheric refraction, which was so central to Tycho’s work. Motivate by this astronomical problem Kepler made an extensive and deep study of Risner’s Optical Treasury, and also read Platter’s De corporis humani structua. The result was his Ad Vitellionem paralipomena, quibus astronomiae pars optica traditur; potissimum de artificiosa obseruatione et aestimatione diametrorum deliquiorumque solis & lunae. Cum exemplis insignium eclipsium. Habes hoc libro, lector, inter alia multa noua, tractatum luculentum de modo visionis& humorum oculi vsu, contra opticos & anatomicos, authore Ioanne Keplero, to give it its full title, published in Frankfurt in 1604 and commonly referred to as Astronomiae pars optica, or simply Pars Optica, although the beginning of the title Ad Vitellionem paralipomena translates as Addition to Witelo

Astronomiae pars optica. Ad Vitellionem Paralipomena  Source: University of Reading

Weighing in at almost five hundred pages it is as long as the text to which it is supposedly additions. Kepler’s volume is one of the most important publications in the history of optics and either, spells the end of the perspectivist era, according to David C. Lindberg, or the start of the modern era of optics, according to A. Mark Smith. I’ll be catholic and say it probably does both. 

Kepler’s work is far too extensive to deal with in detail here, so I’ll just sketch some of the greatest hits. Firstly, it contains a new theory of vision in which all the light rays entering the eye are focused by the lens, which creates an image on the retina. The eye function like a camera obscura, a term that Kepler coined, with a lens. The image in then transmitted to the brain along the optic nerve. This differs substantially from al-Haytham, who argued that only light rays which met the lens perpendicularly contributed to the image which was created in the lens itself. Kepler was aware that this would mean that the retinal image was inverted. He speculated, correctly, that the brain using its tactile knowledge of the real world would re-invert the image. The Jesuit mathematician, Christoph Scheiner (1573–1650), extended Kepler’s work, confirming the existence of the retinal image by peeling off the back of a bull’s pupil, publishing his results in his Oculus hoc est: Fundamentum opticum in 1619.


Kepler made an extensive analysis of the properties of lenses and gave the first published account of how the various lenes combined with the eye corrected short-sightedness and long-sightedness, bringing together optical theory and artisanal practice. This analysis would stand Kepler in good stead following the invention of the telescope.

Kepler solved the so-called pinhole camera problem in which the image of the moon, for example, created by a camera obscura is larger than it should be. He solved the problem using a method taken from Dürer’s descriptions of how to create linear perspective. Kepler drilled a hole in his desk and then suspended a book above to hole and using strings to replicate the light rays, the idea he took from Dürer, he demonstrated that what one had was not one image but a series of overlapping images, thus creating an image that was too large. 

Dürer from Underweysung der Messung, mit dem Zirckel und Richtscheyt, in Linien, Ebenen unnd gantzen corporen 1525 Source: Wikimedia Commons

Another very important discovery in the Pars optica, is the inverse square law governing the intensity of light. This is often credited with being the first mathematical law in modern physics. Later Ismael Boulliau (1605–1694) argued by analogy that if there was a force emanating from the Sun, which drove the planets around their orbits, as Kepler had argued in his Astronomia Nova (1609), then it would also be governed by an inverse square law. This was the first instance of the law of gravity, which however, Boulliau, himself, rejected. 

What is notably missing from the Pars Optica is, of course the law of refraction. As noted above in the first decade of the seventeenth century there was an intensive correspondence between Kepler and Thomas Harriot (c. 1560–1621) on optics and refraction in general, in which Harriot never mentioned that he had already discovered the law of refraction. This exchange shows that Kepler was not some sort of lone genius rewriting the book on optics, but others were interested in updating and improving the perspectivist canon. As we have seen Scheiner was, but his work came slightly later, largely inspired by Kepler’s work. Harriot’s work was independent of Kepler, but as with everything else he did, Harriot never published, so his pioneering efforts remained unknown and had no influence.

However, there were in the later part of the sixteenth century others who produced interesting work in optics before Kepler. As well as his Optical Treasury, Risner wrote his Opticae libri quator, a concise and clear presentation of the perspectivist optical theories, co-authored with his teacher and mentor Petrus Ramus (1515–1572), which was first published posthumously in 1606. 


 It influenced the work of Willebrord Snell. More interesting was the work of Francesco Maurolico (1494–1575). Already in the 1520s he wrote a book on refraction, Photismi de lumine et umbra, which anticipated much of Kepler’s work on lenses and the eye and explained how spectacles work.


This work was, however, first published posthumously in 1611, so Kepler gets the credit for priority. Lastly the Italian polymath, Giambattista della Porta (1535–1615), who included quite a lot of optics in his monumental Magia Naturalis, which went from one volume in 1558 to twenty volumes in 1589. He also published a separate work on refraction, De refraction optices in 1589, which is a rather poor work in traditional perspectivist optics but regarded the eye, like Kepler, as a miniature camera obscura. However, although he did much to popularise the camera obscura with lens in his Magia Naturalis, he, unlike Kepler, did not draw the conclusion the eye lens focuses the incoming light rays but still thought that the image was created by the lens. Kepler had read the Magia Naturalis but complained that he couldn’t acquire a copy of della Porta’s De refraction optices. Interestingly della Porta has a description, in his Magia Naturalis of a small instrument that has the same lens configuration as the Dutch or Galilean telescope but appears to be a magnifying eyeglass rather than a telescope.

With a concave you shall see small things afar off, very clearly; with a convex, things neerer to be greater, but more obscurely: if you know how to fit them both together, you shall see both things afar off, and things neer hand, both greater and clearly.

He provided a primitive sketch in a letter to Prince Cesi in 1609.

Kepler, however, attributed the invention of the telescope to della Porta, arguing that the information had somehow reached the spectacle makers in Holland.

One of the ironies of the history of optics is that although both Maurolico and Kepler had combined the practical artisan knowledge of the lens makers with the theoretical knowledge of the scholar, it was the artisan spectacle maker Hans Lipperhey (c. 1570–1619), who invented the most important optical instrument of the Early Modern Period, the telescope, in 1608

Source: Wikimedia Commons

However, when people questioned how the telescope functioned and if one could trust the images it produced, it was Kepler building on the work on lenses that he had already produced in his Pars optica, who quickly explained the function of the telescope in his Dioptrice published in 1611, which it should be noted Galileo dismissed as unreadable. 

Source: Wikimedia Comms

The seventeenth century saw the development of the modern science of optics in the hands of Scheiner, Snell, Descartes, Huygens, Hooke, and Newton amongst others. All of them building on the work of Kepler, although Risner’s Optical Treasury remained an important textbook for most of the century. 


Filed under History of Optics, Renaissance Science


I really shouldn’t but the HISTSCI_HULK is twisting my arm and muttering dark threats, so here goes. A week ago, we took apart Vedang Sati’s post 10 Discoveries By Newton That Changed The World. When I copied it to my blog, I removed the links that Sati had built into his post. I then made the mistake of following his link to his post on Kepler, so here we go again. 

Johannes Kepler Source: Wikimedia Commons

7 Ways In Which Johannes Kepler Changed Astronomy

Johannes Kepler was a German astronomer who discovered the three laws of planetary motion. Apart from his contributions to astronomy, he is also known to have pioneered the field of optics. In this post, let’s read some amazing facts about Kepler and his work. 

He obviously doesn’t rate Kepler as highly as he rates Newton, so the introduction is less hagiographic this time. However, it does contain one quite extraordinary claim, when he writes, “he is also known to have pioneered the field of optics.” Optics as a scientific discipline was pioneered by Euclid, who lived in the fourth century BCE, so about two thousand years before Kepler. There were also quite a few people active in the field in the two millennia in between.

Early Affliction

He suffered from small pox at a very early age. The disease left him with weak eyesight. Isn’t  it wonderful then how he went on to invent eyeglasses for near-eye and far-eye sightedness.

Kepler did indeed suffer from smallpox sometime around the age of four, which almost cost him his life and did indeed leave him with damaged eyesight. However, Kepler did not invent spectacles of any type whatsoever. The first spectacles for presbyopia, far-sightedness occurring in old age, began to appear in the last decades of the thirteenth century CE. Spectacles for myopia, short-sightedness, were widely available by the early fifteenth century. What Kepler actually did was to publish the first scientific explanation of how lenses function to correct defects in eyesight in his Astronomiae Pars Optica (The Optical Part of Astronomy), in 1604. Francesco Maurolico (1494–1574) actually gave the correct explanation earlier than Kepler in his Photismi de lumine et umbra but this was only published posthumously in 1611, so the credit for priority goes to Kepler

Astronomiae Pars Optica Source: Wikimedia Commons

Introduction to Astronomy

Kepler’s childhood was worsened by his family’s financial troubles. At the age of 6, Johannes had to drop out of school so to earn money for the family. He worked as a waiter in an inn.

As Kepler first entered school at the age of seven, it would have been difficult for his schooling to have been interrupted when he was six. His primary schooling was in fact often interrupted both by illness and the financial fortunes of the family. 

In the same year, his mother took him out at night to show him the Great Comet of 1577 which aroused his life-long interest in science and astronomy. 

Yes, she did!

Copernican Supporter

At a time when everyone was against the heliocentric model of the universe, Kepler became its outspoken supporter. He was the first person to defend the Copernican theory from a scientific and a religious perspective.

Not everyone was opposed to the heliocentric model of the universe, just the majority. Poor old Georg Joachim Rheticus (1514–1574), as the professor of mathematics, who persuaded Copernicus to publish De revolutionibus, he would be deeply insulted by the claim that Kepler was the “first person to defend the Copernican theory from a scientific and a religious perspective.” Rheticus, of course, did both, long before Kepler was even born, although his religious defence remained unpublished and was only rediscovered in the twentieth century. Rheticus was not the only supporter of Copernicus, who preceded Kepler there were others, most notably, in this case, Michael Mästlin (1550–1631), who taught Kepler the Copernican heliocentrism. 

Contemporary of Galileo

Galileo was not a great supporter of Kepler’s work especially when Kepler had proposed that the Moon had an influence over the water (tides). It would take an understanding many decades later which would prove Kepler correct and Galileo wrong.

It is indeed very true that Galileo rejected Kepler’s theory of the tides, when promoting his own highly defective theory, but that is mild compared to his conscious ignoring of Kepler’s laws of planetary motion, which were at the time the most significant evidence for a heliocentric cosmos.

Pioneer of Optics

Kepler made ground-breaking contributions to optics including the formulation of inverse-square law governing the intensity of light; inventing an improved refracting telescope; and correctly explaining the function of the human eye.

Kepler’s contributions to the science of optics were indeed highly significant and represent a major turning point in the development of the discipline. His Astronomiae Pars Optica does indeed contain the inverse square law of light intensity and the first statement that the image is created in the eye on the retina and not in the crystal lens.

However, that he invented an improved telescope is more than a little problematic. When Galileo published his Sidereus Nuncius in 1610, the first published account of astronomical, telescopic discoveries, there was no explanation how a telescope actually functions, so people were justifiably sceptical. Having written the book on how lenses function with his Astronomiae Pars Optica in 1604, Kepler now delivered a scientific explanation how the telescope functioned with his Dioptrice in 1611. 

Kepler Dioptrice Source: Wikimedia Commons

This contained not just a theoretical explanation of the optics of a Dutch or Galilean telescope, with a convex objective and a concave eyepiece, but also of a telescope with convex objective and convex eyepiece, which produces an inverted image, now known as a Keplerian or astronomical telescope, also one with three convex lenses, the third lens to right the inverted image, now known as a field telescope, and lastly, difficult to believe, the telephoto lens. Kepler’s work remained strictly theoretical, and he never constructed any of these telescopes, so is he really the inventor? The first astronomical telescope was constructed by Christoph Grienberger (1561–1636) for Christoph Scheiner (c. 1573–1650) as his heliotropic telescope, for his sunspot studies. 

Heliotropic telescope on the left. On the right Scheiner’s acknowledgement that Grienberger was the inventor

Is the astronomical telescope an improved telescope, in comparison with the Dutch telescope? It is very much a question of horses for courses. If you go to the theatre or the opera then your opera glasses, actually a Dutch telescope, will be much more help in distinguishing the figure on the stage than an astronomical telescope. Naturally, the astronomical telescope, with its wider fields of vision, is, as its name implies, much better for astronomical observations than the Dutch telescope once you get past the problem of the inverted image. This problem was solved with the invention of the multiple lens eyepiece by Anton Maria Schyrleus de Rheita (1604–1660), announced in Oculus Enoch et Eliae published in 1645, although he had already been manufacturing them together with Johann Wiesel (1583–1662) since 1643.

Helped Newton

His planetary laws went on to help Sir Isaac Newton derive the inverse square law of gravity. Newton had famously acknowledged Kepler’s role, in a quote: “If I have seen further, it is by standing on the shoulders of giant(s).

Sati is not alone in failing to give credit to Kepler for his laws of planetary motion in their own right, but instead regarding them merely as a stepping-stone for Newton and the law of gravity. Kepler’s laws of planetary motion, in particular his third law, are the most significant evidence for a heliocentric model of the cosmos between the publication of De revolutionibus in 1543 and Principia in 1687 and deserve to be acknowledged and honoured in their own right! 

Newton’s famous quote, actually a much-used phrase in one form or another in the Early Modern period, originated with Bernard of Chartres (died after 1124) in the twelfth century. Newton used it in a letter to Robert Hooke on 5 February 1675, so twelve years before the publication of his Principia and definitively not referencing Kepler:

What Des-Cartes [sic] did was a good step. You have added much several ways, & especially in taking the colours of thin plates into philosophical consideration. If I have seen further it is by standing on the sholders [sic] of Giants.

Kepler’s Legacy

There is a mountain range in New Zealand named after the famous astronomer. A crater on the Moon is called Kepler’s crater. NASA paid tribute to the scientist by naming their exo-planet telescope, Kepler.

Given the vast number of things named after Kepler, particularly in Germany, Sati’s selection is rather bizarre, in particular because it is a mountain hiking trail in New Zealand that is named after Kepler and not the mountain range itself.

Once again, we are confronted with a collection of half facts and straight falsehoods on this website, whose author, as I stated last time has nearly 190,000 followers on Facebook. 

Me: I told you that we couldn’t stop the tide coming in

HS_H: You’re not trying hard enough. You’ve gotta really STOMP EM!

Me: #histsigh


Filed under History of Astronomy, History of Optics, Myths of Science

The astronomical librarian 

I’m continuing my look at the French mathematician astronomers of the seventeenth century with some of those, who were both members of Nicolas-Claude Fabri de Peiresc’s group of telescopic, astronomical observers, as well as Marin Mersenne’s informal Academia Parisiensis, starting with Ismael Boulliau (1605–1694), who like Peiresc and Mersenne was also a prominent member of the Republic of Letters with about 5000 surviving letters. 

Ismael Boulliau Source: Wikimedia Commons

Boulliau was born in Loudun, France the second son of Ismael Boulliau a notary and amateur astronomer and Susanne Motet on 28 September 1605. The first son had been born a year earlier and was also named Ismael, but he died and so the name was transferred to their second son. Both of his parents were Calvinists. His father introduced him to astronomy and in his Astronomia philolaica (1645) Ismael junior tells us that his father observed both Halley’s comet in 1607 and the great comet of 1618. The later was when Boulliau was thirteen years old, and one can assume that he observed together with his father. 

Probably following in his father’s footsteps, he studied law but at the age of twenty-one he converted to Catholicism and in 1631, aged twenty-six, he was ordained a priest. In 1632 he moved to Paris and began to work for Pierre Dupuy (1582–1651) and his brother Jacques (1591–1656), who were keepers of the Bibliothèque du Roi, today the Bibliothèque nationale de France. Boulliau held this position until the death of the Dupuy brothers and during that time travelled widely in Europe collecting books and manuscripts for the library. 

Pierre Dupuy Source: Wikimedia Commons

Boulliau also enjoyed the patronage of the powerful and influential de Trou family, who were closely connected with the library and who financed his book collecting travels. Following the death of the Dupuy brothers he became employed by the French ambassador to the United Provinces, a member of the de Trou family, a secretary and librarian. In 1666, following a dispute with his employer, he became librarian at the Collège de Laon in Paris. For the last five years of his live he returned to the priesthood in the Abbey St Victor near Paris where he died aged 89. Although Boulliau was an active member of Mersenne’s Academia Parisiensis he never became a member of the Académie des sciences, but he was elected one of the first foreign associates of the Royal Society on 4 April 1667. 

Abbey of St. Victor, 1655 Source: Wikimedia Commons

 Like Peiresc, Boulliau was a polymath with extensive knowledge of a wide range of humanities topics, which was useful in his work as a librarian, but, as with Peiresc, it is scientific activities that are of interest here. He continued to make astronomical observations throughout his life, which were of a high level of accuracy. In his Principia, Newton puts him on a level with Kepler for his determination of the planetary orbits. In Book 3 Phenomenon 4 of Principia Newton writes: 

But of all astronomers, Kepler and Boulliau have determined the magnitude of the orbits from observations with the most diligence. 

Boulliau’s first significant scientific publication was, however, not in astronomy but in optics, his De natura lucis (On the Nature of Light) (1638) based on the discussions he was having with Gassendi on the topic. This work is not particular important in the history of optics but it does contain his discussion of Kepler’s inverse square law for the propagation of light.

Source: Wikimedia Commons

His first astronomical work Philolaus (1639), which places him firmly in the Copernican heliocentric camp but not, yet a Keplerian was next. 

He now changed tack once again with a historical mathematical work. In 1644, he translated and published the first printed edition of Theon of Smyrna’s Expositio rerum mathematicarum ad legendum Platonem utilium a general handbook for students of mathematics of no real significance. Continuing with his mathematical publications. In 1657, he published De lineis spiralibus (On Spirals) related to the work of Archimedes and Pappus on the topic.

Source: Wikimedia Commons

Much later in 1682, he published Opus novum ad arithmeticam infinitorum, which he claimed clarified the Arithmetica infinitorum(1656) of John Wallis (1616–1703).

Source: Wikimedia Commons

All of Boulliau’s work was old fashioned and geometrical. He rejected the new developments in analytical mathematics and never acknowledged Descartes’ analytical geometry. As we shall see, his astronomy was also strictly geometrical. He even criticised Kepler for being a bad geometer. 

Boulliau’s most important publication was his second astronomical text Astronomia philolaica (1645).

Source: Wikimedia Commons

In this highly influential work, he fully accepted Kepler’s elliptical orbits but rejects almost all of the rest of Kepler’s theories. As stated above his planetary hypothesis is strictly geometrical and centres round his conical hypothesis:

“The Planets, according to that astronomer [Boulliau], always revolve in circles; for that being the most perfect figure, it is impossible they should revolve in any other. No one of them, however, continues to move in any one circle, but is perpetually passing from one to another, through an infinite number of circles, in the course of each revolution; for an ellipse, said he, is an oblique section of a cone, and in a cone, betwixt the vertices of the ellipse there is an infinite number of circles, out of the infinitely small portions of which the elliptical line is compounded. The Planet, therefore, which moves in this line, is, in every point of it, moving in an infinitely small portion of a certain circle. The motion of each Planet, too, according to him, was necessarily, for the same reason, perfectly equable. An equable motion being the most perfect of all motions. It was not, however, in the elliptical line, that it was equable, but in any one of the circles that were parallel to the base of that cone, by whose section this elliptical line had been formed: for, if a ray was extended from the Planet to any one of those circles, and carried along by its periodical motion, it would cut off equal portions of that circle in equal times; another most fantastical equalizing circle, supported by no other foundation besides the frivolous connection betwixt a cone and an ellipse, and recommended by nothing but the natural passion for circular orbits and equable motions,” (Adam Smith, History of Astronomy, IV.55-57).

Boulliau’s Conical Hypothesis [RA Hatch] Source: Wikimedia Commons

Boulliau’s theory replaces Kepler’s second law, and this led to the Boulliau-Ward debate on the topic with the English astronomer Seth Ward (1617–1689), the Savilian Professor of astronomy at Oxford University.

Bishop Seth Ward, portrait by John Greenhill Source: Wikimedia Commons

Ward criticised Boulliau’s theory in his In Ismaelis Bullialdi astro-nomiae philolaicae fundamenta inquisitio brevis (1653), also pointing out mathematical errors in Boulliau’s work. 

Boulliau responded to Ward’s criticisms in 1657, acknowledging the errors and correcting but in turn criticising Ward’s model in his De lineis spiralibus. A year earlier Ward had published his own version of Keplerian astronomy in his Astronomia geometrica (1656).

Source: Wikimedia Commons

This exchange failed to find a resolution but this very public debate between two of Europe’s leading astronomers very much raised awareness of Kepler’s work and was factor in its eventual acceptance of Kepler’s elliptical heliocentric astronomy. 

It was in his Astronomia philolaica that Boulliau was the first to form an inverse squared theory of attraction between the sun and the planets. 

As for the power by which the Sun seizes or holds the planets, and which, being corporeal, functions in the manner of hands, it is emitted in straight lines throughout the whole extent of the world, and like the species of the Sun, it turns with the body of the Sun; now, seeing that it is corporeal, it becomes weaker and attenuated at a greater distance or interval, and the ratio of its decrease in strength is the same as in the case of light, namely, the duplicate proportion, but inversely, of the distances that is, 1/d2 ​.

Here we see the influence of Kepler’s theory of light propagation, which as noted Boulliau discussed in his De natura lucis. However, having set up this hypothesis Boulliau goes on to reject it. 

… I say that the Sun is moved by its own form around its axis, by which form it was ignited and made light, indeed I say that no kind of motion presses upon the remaining planets … indeed [I say] that the individual planets are driven round by individual forms with which they were provided …

Despite Boulliau’s rejection of his own hypothesis, during Newton’s dispute with Hooke over who should get credit for the theory of gravity, he gives Boulliau the credit in a letter to Edmond Halley.

…so Bullialdus [i.e., Boulliau] wrote that all force respecting ye Sun as its center & depending on matter must be reciprocally in a duplicate ratio of ye distance from ye center, & used that very argument for it by wch you, Sr, in the last Transactions have proved this ratio in gravity. Now if Mr Hook from this general Proposition in Bullialdus might learn ye proportion in gravity, why must this proportion here go for his invention?

In 1667, Boulliau published a final astronomy book, Ad astronomos monita duo in which he was the first to establish the periodicity of the variable star, Mira Ceti.


His estimate of the period 333 days was only out by a one day. Mira had first been recognised as a variable star by David Fabricius beginning 3 August 1596.

Apart from his publications Boulliau kept Mersenne’s correspondence network alive for another thirty years after Mersenne’s death, communicating with Leopoldo de’ Medici (1617–1675) in Italy, Johannes Hevelius (1611–1687) in Danzig and Christiaan Huygens (1629–1695). Huygens first imparted his discovery of the rings of Saturn to Boulliau and Boulliau distributed Huygens’ System sarturnium (1658) in Paris. Boulliau also distributed Pascal’s Letters D’Amos Dettonville (1658–1659) to English and Dutch mathematicians, his challenge on the mathematics of the cycloid, an important publication in the development of calculus.

Ismael Boulliau is a prime example of a scholar, who didn’t make any major discoveries or develop any major theories himself but still had a very significant influence on the development of science.

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Filed under History of Astronomy, History of Mathematics, History of Optics, History of science, The Paris Provencal Connection

Musical, mathematical Minim, Marin Mersenne 

In the seventeenth century, Marin Mersenne (1588–1648) was a very central and highly influential figure in the European intellectual and scientific communities; a man, who almost literally knew everybody and was known by everybody in those communities. Today, in the big names, big events, popular versions of the history of science he remains only known to specialist historian of science and also mathematicians, who have heard of Mersenne Primes, although most of those mathematicians probably have no idea, who this Mersenne guy actually was. So, who was Marin Mersenne and why does he deserve to be better known than he is?

Marin Mersenne Source: Wikimedia Commons

Mersenne was born 8 September 1588, the son of Julien Mersenne and his wife Jeanne, simple peasants, in Moulière near Oizé, a small commune in the Pays de la Loire in North-Western France. He was first educated at the at the nearby College du Mans and then from 1604 to 1609 at the newly founded Jesuit Collège Henri-IV de La Flèche. The latter is important as in La Flèche he would have received the mathematical programme created by Christoph Clavius for the Jesuit schools and colleges, the best mathematical education available in Europe at the time. A fellow student at La Flèche was René Descartes (1596–1650) with whom he would become later in life close friends.

René Descartes at work Source: Wikimedia Commons

However, it is unlikely that they became friends then as Mersenne was eight years older. Leaving La Flèche he continued his education in Greek, Hebrew, and theology at the Collège Royal and the Sorbonne in Paris. In 1611 he became a Minim friar and a year later was ordained as a priest. The Minims are a mendicant order founded in Italy in the fifteenth century. From 1614 to 1618 he taught philosophy and theology at Nevers but was recalled to Paris in 1619 to the newly established house on the Place Royal (now Place des Vosges), where he remained, apart from travels through France, to Holland, and to Italy, until his death. 

View map of an area of Paris near Place Royale, now Place des Vosges, showing the Minim convent where Mersenne lived and the Rue des Minimes, not far from the Bastille, undated, but before 1789 ( Source: Linda Hall Library

In Paris he was introduced to the intellectual elite by Nicolas-Claude Fabri de Pereisc (1580–1637)–wealthy astronomer, antiquarian, and patron of science–whom he had got to know in 1616. 

Nicolas-Claude Fabri de Peiresc by Louis Finson Source: Wikimedia Commons

Settled in Paris, Mersenne began a career as a prolific author, both editing and publishing new editions of classical works and producing original volumes. In the 1620s his emphasis was on promoting and defending the Thomist, Aristotelian philosophy and theology in which he’d been educated. In his first book, Questiones celeberrimae in Genesim (1623), 

he attacked those he saw as opponents of the true Catholic religion, Platonist, cabbalistic and hermetic authors such as Telesio, Pomponazzi, Bruno and Robert Fludd. His second book, L’impiété des déistes, athées, et libertins de ce temps (1624), continued his attacks on the propagators of magic and the occult. His third book, La Vérité des sciences (1625), attacks alchemists and sceptics and includes a compendium of texts over ancient and recent achievements in the mathematical sciences that he saw as in conformity with his Christian belief. The latter drew the attention of Pierre Gassendi (1592–1655), who became his closest friend. I shall return to their joint activities in Paris later but now turn to Mersenne’s own direct scientific contributions, which began to replace the earlier concentration on theology and philosophy.

Pierre Gassendi Source: Wikimedia Commons

Mersenne’s scientific interests lay in mathematics and in particular what Aristotle, who was not a fan of mathematics, claiming it did not apply to the real world, called the mixed sciences or mixed mathematics i.e., astronomy, optics, statics, etc. Here he compiled to collections of treatises on mixed mathematics, his Synopsis Mathematica (1626) and Universae geometriae synopsis (1644). In his Traité de l’Harmonie Universelle (1627), to which we will return, Mersenne gives a general introduction to his concept of the mathematical disciplines:

Geometry looks at continuous quantity, pure and deprived from matter and from everything which falls upon the senses; arithmetic contemplates discrete quantities, i.e. numbers; music concerns har- monic numbers, i.e. those numbers which are useful to the sound; cosmography contemplates the continuous quantity of the whole world; optics looks at it jointly with light rays; chronology talks about successive continuous quantity, i.e. past time; and mechanics concerns that quantity which is useful to machines, to the making of instruments and to anything that belongs to our works. Some also adds judiciary astrology. However, proofs of this discipline are borrowed either from astronomy (that I have comprised under cosmology) or from other sciences. 

In optics he addressed the problem of spherical aberration in lenses and mirrors and suggested a series of twin mirror reflecting telescopes, which remained purely hypothetical and were never realised.

Source: Fred Watson, “Stargazer: The Life and Times of the Telescope”, Da Capo Press, 2004, p. 115

This is because they were heavily and falsely criticised by Descartes, who didn’t really understand them. It was Mersenne, who pushed Descartes to his solution of the refraction problem and the discovery of the sine law. He wrote three books on optics, De Natura lucis (1623); Opticae (1644); L’Optique et la catoptrique (1651). Although his theoretical reflecting telescopes were published in his Harmonie universelle (1636), see below.

Mersenne also wrote and published collections of essays on other areas of mixed mathematics, mechanics, pneumatics, hydro- statics, navigation, and weights and measures, Cogitata physico-mathematica (1644); Novarum observationum physico- mathematicarum tomus III (1647). 

Mersenne dabbled a bit in mathematics itself but unlike many of his friends did not contribute much to pure mathematics except from the Mersenne prime numbers those which can be written in the form Mn = 2n − 1 for some integer n. This was his contribution to a long search by mathematicians for some form of law that consistently generates prime numbers. Mersenne’s law whilst generating some primes doesn’t consistently generate primes but it has been developed into its own small branch of mathematics. 

It was, however, in the field of music, as the title quoted above would suggest, which had been considered as a branch of mathematics in the quadrivium since antiquity, and acoustics that Mersenne made his biggest contribution. This has led to him being labelled the “father of acoustics”, a label that long term readers of this blog will know that I reject, but one that does to some extent encapsulate his foundational contributions to the discipline. He wrote and published five books on the subject over a period of twenty years–Traité de l’harmonie universelle (1627); Questions harmoniques (1634); Les preludes de l’harmonie universelle (1634); Harmonie universelle (1636); Harmonicorum libri XII (1648)–of which his monumental (800 page) Harmonie universelle was the most important and most influential.

Title page of Harmonie universelle Source: Wikimedia Commons

In this work Mersenne covers the full spectrum including the nature of sounds, movements, consonance, dissonance, genres, modes of composition, voice, singing, and all kinds of harmonic instruments. Of note is the fact that he looks at the articulation of sound by the human voice and not just the tones produced by instruments. He also twice tried to determine the speed of sound. The first time directly by measuring the elapse of time between observing the muzzle flash of a cannon and hearing the sound of the shot being fired. The value he determined 448 m/s was higher than the actual value of 342 m/s. In the second attempt, recorded in the Harmonie universelle (1636), he measured the time for the sound to echo back off a wall at a predetermined distance and recorded the value of 316 m/s. So, despite the primitive form of his experiment his values were certainly in the right range. 

Mersenne also determined the correct formular for determining the frequency of a vibrating string, something that Galileo’s father Vincenzo (1520–1591) had worked on. This is now known as Mersenne’s Law and states that the frequency is inversely proportional to the length of the string, proportional to the square root of the stretching force, and inversely proportional to the square root of the mass per unit length.

The formula for the lowest frequency is f=\frac{1}{2L}\sqrt{\frac{F}{\mu}},

where f is the frequency [Hz], L is the length [m], F is the force [N] and μ is the mass per unit length [kg/m].

Source: Wikipedia

Vincenzo Galileo was also involved in a major debate about the correct size of the intervals on the musical scale, which was rumbling on in the late sixteenth and early seventeenth centuries. It was once again Mersenne, who produced the solution that we still use today.

Although Mersenne is certainly credited and honoured by acoustic researchers and music theorists for his discoveries in these areas, perhaps his most important contribution to the development of the sciences in the seventeenth century was as a networker and science communicator in a time when scientific journals didn’t exist yet. 

Together with Gassendi he began to hold weekly meetings in his humble cell with other natural philosophers, mathematicians, and other intellectuals in Paris. Sometime after 1633 these meetings became weekly and took place in rotation in the houses of the participants and acquired the name Academia Parisiensis. The list of participants reads like an intellectual who’s who of seventeenth century Europe and included René Descartes, Étienne Pascal and his son Blaise, Gilles de Roberville, Nicolas-Claude Fabri de Pereisc, Pierre de Fermat, Claude Mydorge, the English contigent, Thomas Hobbes, Kenhelm Digby, and the Cavendishes, and for those not living in or near Paris such as Isaac Beeckman, Jan Baptist van Helmont, Constantijn Huygens and his son Christiaan, and not least Galileo Galilei by correspondence. When he died approximately six hundred letters were found in his cell from seventy-nine different correspondents. In total 193 scholars and literati have been identified as participants. Here it should be noted that although he tended to reject the new emerging sciences in his earlier defence of Thomist philosophy, he now embraced it as compatible with his teology and began to promote it.

This academy filled a similar function to the Gresham College group and Hartlib Circle in England, as well as other groups in other lands, as precursors to the more formal scientific academies such as the Académie des sciences in Paris and the Royal Society in London. There is evidence that Jean-Baptist Colbert (1619–1683), the French Minister of State, modelled his Académie des sciences on the Academia Parisiensis. Like its formal successors the Academia Parisiensis served as a forum for scholars to exchange views and theories and discuss each other’s work. Mersenne’s aim in establishing this forum was to stimulate cooperation between the participants believing science to be best followed as a collective enterprise.

Mersenne’s role was not restricted to that of convener, but he functioned as a sort of agent provocateur deliberately stimulating participants to take up research programmes that he inaugurated. For example, he brought Torricelli’s primitive barometer to Paris and introduced it to the Pascals. It is thought that he initiated the idea to send Blaise Pascal’s brother-in-law up the Puy de Dôme to measure the decreasing atmospheric pressure.

Blaise Pascal, unknown; a copy of the painting of François II Quesnel, which was made for Gérard Edelinck in 1691. Source: Wikimedia Commons

Although they never met and only corresponded, he introduced Christiaan Huygens to the concept of using a pendulum to measure time, leading to Huygens’ invention of the pendulum clock.

Portrait of Christiaan Huygens (1629-1695) C.Netscher / 1671 Source: Wikimedia Commons

It was Mersenne, who brought the still very young Blaise Pascal together with René Descartes, with the hope that the brilliant mathematicians would cooperate, in this case he failed. In fact, the two later became opponents divided by their conflicting religious views. Mersenne also expended a lot of effort promoting the work of Galileo to others in his group, even offering to translate and publish Galileo’s work in French, an offer that the Tuscan mathematician declined. He did, however, publish an unpublished text by Galileo on mechanics, Les Mechaniques de Galilée.

Although not the author of a big theory or big idea, or the instigators of a big event, Mersenne actually contributed with his activities at least as much, if not more, to the development of science in the seventeenth century as any of the more famous big names. If we really want to understand how science develops then we need to pay more attention to figures like Mersenne and turn down the volume on the big names. 


Filed under History of Mathematics, History of Optics, History of science, The Paris Provencal Connection

I do wish people wouldn’t post things like this

I stumbled across the following image on Facebook, being reposted by people who should know better, and it awoke my inner HISTSCI_HULK:

I shall only be commenting on the first three images, if anybody has any criticism of the other ones, they’re welcome to add them in the comments.

To what extent Galileo developed his own telescope is debateable. He made a Dutch, telescope a model that had first been made public by Hans Lipperhey in September 1608. By using lenses of different focal lengths, he managed to increase the magnification, but then so did several others both at the same time and even before him.

Galileo was not the first to point the telescope skywards! As I have pointed out on several occasions, during that first demonstration by Lipperhey in Den Hague, the telescope was definitely pointed skywards:

The said glasses are very useful at sieges & in similar affairs, because one can distinguish from a mile’s distance & beyond several objects very well, as if they are very near & even the stars which normally are not visible for us, because of the scanty proportion and feeble sight of our eyes, can be seen with this instrument[1]

Even amongst natural philosophers and astronomers, Galileo was not the first. We know that Thomas Harriot preceded him in making astronomical observations. It is not clear, but Simon Marius might have begun his telescopic astronomical observations before Galileo. Also, the astronomers of the Collegio Romano began telescopic observations before Galileo went public with his Sidereus Nuncius and who was earliest they or Galileo is not determinable.

I wrote a whole very detailed article about the fact that Newton definitively did not invent the reflecting telescope that you can read here.

By the standards of the day William Herschel’s 20-foot telescope, built in 1782 seven years before the 40-foot telescope, was already a gigantic telescope, so the 40-footer was not the first. Worse than this is the fact that the image if of one of his normal ‘small’ telescopes and not the 40-footer. 

Herschel’s 40-foot telescope Source: Wikimedia Commons

People spew out these supposedly informative/educational or whatever images/articles, which are sloppily researched or not at all and are full of avoidable error. To put it bluntly it really pisses me off!

[1] Embassies of the King of Siam Sent to His Excellency Prince Maurits Arrived in The Hague on 10 September 1608, Transcribed from the French original, translated into English and Dutch, introduced by Henk Zoomers and edited by Huib Zuidervaart after a copy in the Louwman Collection of Historic Telescopes, Wassenaar, 2008 pp. 48-49 (original pagination: 9-11)


Filed under History of Optics, History of science, History of Technology

Christmas Trilogy 2020 Part 2: Charles brightens up the theatre

There is a strong tendency in the present to view Charles Babbage as a one trick pony i.e., Babbage the computer pioneer. In reality he was a true polymath whose intellectual activities covered a very wide spectrum.

Already as a student at Cambridge, he agitated for major curriculum reform in the mathematics taught and practiced in Britain. He also produced some first class cutting edge mathematics, much of which for some reason he never published. His interest in automation stretched way beyond his computing engines and after extensive research on automations in industry, both throughout Europe and in Britain, he wrote and published a book on the organisation of industrial production, On the Economy of Machinery and Manufactures (1832), which became a highly influential bestseller, influencing the work of both John Stuart Mill and Karl Marx. He was a leader in a campaign to improve the standard of science research in Britain, largely aimed at what he saw as the moribund Royal society, which resulted in his Reflections on the Decline of Science and some of its Causes (1830). As part of this campaign, he was a leading figure in the establishment of the British Association for the Advancement of Science (BAAS).


Engraving of Charles Babbage dated 1833 Source: Wikimedia Commons 

His achievements were not confined to purely intellectual activities, he was also an assiduous inventor of mechanical devices and improvement, well outside of his proto computers. For example, he designed and had constructed a four wheeled light carriage for one of his extensive tours of Europe. It was so designed that he could sleep on board and had drawers large enough to stow frock coats and technical plans without folding, as well as a small on board kitchen. However, it is his activities in practical optics that interest me here, in particular his foray into early theatre lighting, which I found fascinating, having, for several years in my youth, been a lighting technician both in theatre and live music.  

An ophthalmoscope is a medical instrument designed to make it possible to observe the interior of the eye by means of a beam of light. The invention of the ophthalmoscope is traditionally attributed to Hermann von Helmholtz in 1851. However, it would appear that Babbage preceded him by four years.

Charles Babbage, the mathematic genius and inventor of what many consider to be the forerunner of today’s computer, his analytical machine, was the first to construct an instrument for looking into the eye. He did this in 1847 but when showing it to the eminent ophthalmologist Thomas Wharton Jones he was unable to obtain an image with it and, thus discouraged, did not proceed further. Little did he know that his instrument would have worked if a minus lens of about 4 or 5 dioptres had been inserted between the observer’s eye and the back of the plano mirror from which two or three holes had been scraped. Some seven years later it was his design and not that of Helmholtz which had been adopted.


The image shows a reconstruction of Babbage’s ophthalmoscope, c. 1847. No actual example survives but this replica was made for the Science Museum in 2003, based upon Wharton Jones’ written description.

Dr. Helmholtz, of Konigsberg, has the merit of specially inventing the ophthalmoscope. It is but justice that I should here state, however, that seven years ago Mr. Babbage showed me the model of an instrument which he had contrived for the purpose of looking into the interior of the eye. It consisted of a bit of plain mirror, with the silvering scraped off at two or three small spots in the middle, fixed within a tube at such an angle that the rays of light falling on it through an opening in the side of the tube, were reflected into the eye to be observed, and to which the one end of the tube was directed. The observer looked through the clear spots of the mirror from the other end. This ophthalmoscope of Mr Babbage, we shall see, is in principle essentially the same as those of Epkens and Donders, of Coccius and of Meyerstein, which themselves are modifications of Helmhotlz’s.

         Wharton-Jones, T., 1854, ‘Report on the Ophthalmoscope’, Chronicle of Medical Science (October 1854).

Around the same time as he built his ophthalmoscope, Babbage designed and built a mechanical, clockwork, programmable, self-occulting, signalling lamp to aid ship to ship and ship to shore communications. He was disappointed that the British marine fleets showed no interest in his invention, but the Russian navy used it against the British during the Crimean War. During the Great Exhibition of 1851, in which Babbage played a central role, he set his signal lamp in the window of his house in the evenings and people passing by would drop in their visiting card with the signalled number written on them. Babbage’s occulting lights were later used in lighthouses in various parts of the world starting in the USA.


Babbage’s mechanical, clockwork, programmable, self-occulting, signalling lamp mechanism

Babbage was a theatre goer and during his phase of light experiments and invention he undertook an interesting project in theatre lighting. During the Renaissance, theatres, such as Shakespeare’s Globe, were open air arenas and performances took place in daylight. Later closed theatre and opera house were lit with chandeliers with the cut glass or crystal prisms dispersing the candlelight in all directions. Of course, the large number of candles needed caused much smoke and the dripping wax was a real problem. By the early nineteenth century theatres were illuminated with gas lamps.

One day during a theatre visit, Babbage noticed that during a moonlit scene the white bonnet of his companion had a pink taint and wondered about the possibility of using coloured light in theatre. He began a serious of interesting experiments with the then comparatively new limelight.

Limelight is an intense illumination created when an oxyhydrogen flame is directed at a cylinder of quicklime (calcium oxide). Quicklime can be heated to 2,572°C before melting and the light is produced by a combination of incandescence (the emission of electromagnetic radiation such as visible light e.g., red hot steel) and candoluminescence a form of radiation first observed and investigated in the early nineteenth century.


Diagram of a limelight burner Source: Wikimedia Commons

As with many inventions the oxyhydrogen blowpipe has many fathers and was first developed in the late eighteenth and early nineteenth centuries by Jean-Baptiste-Gaspard Bochart de Saron (1730–1794), Edward Daniel Clarke (1769–1822) and Robert Hare (1781–1858) all of whose work followed out of the pneumatic discoveries of Carl Wilhelm Scheele (1742–1786), Joseph Priestly (1733–1804), who both discovered oxygen, and Henry Cavendish (1731–1810), who discovered hydrogen.


Nineteenth century bellows-operated oxy-hydrogen blowpipe, including two different types of flashback arrestor John Griffen – A Practical Treatise on the Use of the Blowpipe, 1827 Source: Wikimedia Commons

The first to discover and experiment with limelight was the English chemist Goldsworthy Gurney (1792–1875)


Goldsworthy Gurney Source: Wikimedia Commons

but it was the Scottish engineer Thomas Drummond (1797–1840) who, having seen it demonstrated by Michael Faraday (1791–1867),  first exploited its potential as a light source. Drummond built a practical working light in 1826, which he then used as a signal lamp in trigonometrical surveying. The light was bright enough to be seen at a distance of 68 miles by sunlight. Drummond’s application was so successful that limelight was also known as Drummond light and he was falsely credited with its discovery, instead of Gurney.


Thomas Drummond by Henry William Pickersgill. The original picture is in the National gallery of Ireland Source: Wikimedia Commons

The earliest know public performance illuminated with limelight was an outdoor juggling performance by the magician Ching Lau Lauro (real name unknown) Herne Bay Pier in Kent in 1836. It was first used in theatre lighting in Covent Garden Theatre in 1837. By the 1860s and 1870s limelight was used worldwide in theatres and operas, used to highlight solo performers in the same way as modern spotlights, hence the expression, standing in the limelight. By the end of the nineteenth century, it had been largely replaced by electrical, carbon arc lighting.

 Babbage wanted to take the process one step further and use limelight not just as a very bright white light, but to introduce colour into theatre lighting. Babbage began to experiment with glass cells constructed out of two parallel sheets of glass and filled with solutions of various metal salts, such as chrome and copper. His experiment proved very successful and he developed coloured, limelight spots. Babbage now developed a dance scenario to display his new invention. He proposed replacing the stage footlights with four limelight projectors in the colours red, blue, yellow and purple. His imagined piece had four groups of dancers dressed in white, each of which entered the stage dancing in one of the four pools of light. Dancers springing from one pool of light into another would change colour. Gradually the apertures would widen with the lights crossing each other producing a rainbow of colours through which the dancers would circle. Babbage went on to develop a dramaturgy with dioramas telling an allegorical story.

Babbage discussed his project with Benjamin Lumley, the manager of the Italian Opera House (now Her Majesty’s Theatre) and arranged a demonstration of his new lights. The demonstration took place in the theatre with a smaller group of dancers, and it was apparently a great success. However, because of the fire risk he had two fire engines and their crews on standby during his demonstration and although impressed, Lumley declined a real performance with an audience because of the fire risk. Babbage didn’t develop the idea further.


Portrait of Benjamin Lumley by D’Orsay Source: Wikimedia Commons

As a onetime theatre lighting technician and a historian of science, I would would quite like the idea of staging a modern version of Babbage’s little dance fantasy. I would also like to draw this episode in his life to the attention of all the Ada Lovelace acolytes, who are firmly of the opinion that Babbage was only capable of thinking about mathematics and therefore the imaginative flights of fancy in the Analytical Engine memoir notes must be entirely the work of Lady King.

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Filed under History of Optics, History of Technology

The emergence of modern astronomy – a complex mosaic: Part L


By the end of the eighteenth century, Newton’s version of the heliocentric theory was firmly established as the accepted model of the solar system. Whilst not yet totally accurate, a reasonable figure for the distance between the Earth and the Sun, the astronomical unit, had been measured and with it the absolute, rather than relative, sizes of the orbits of the known planets had been calculated. This also applied to Uranus, the then new planet discovered by the amateur astronomer, William Herschel (1738–1822), in 1781; the first planet discovered since antiquity. However, one major problem still existed, which needed to be solved to complete the knowledge of the then known cosmos. Astronomers and cosmologists still didn’t know the distance to the stars. It had long been accepted that the stars were spread out throughout deep space and not on a fixed sphere as believed by the early astronomer in ancient Greece. It was also accepted that because all attempts to measure any stellar parallax down the centuries had failed, the nearest stars must actually be at an unbelievably far distance from the Earth.

Here we meet a relatively common phenomenon in the history of science, almost simultaneous, independent, multiple discoveries of the same fact. After literally two millennia of failures to detect any signs of stellar parallax, three astronomers each succeeded in measuring the parallax of three different stars in the 1830s. This finally was confirmation of the Earth’s annual orbit around, independent of stellar aberration and gave a yardstick for the distance of the stars from the Earth.

The first of our three astronomers was the Scotsman, Thomas Henderson (1798–1844).


Thomas Henderson Source: Wikimedia Commons

Henderson was born in Dundee where he also went to school. He trained as a lawyer but was a keen amateur astronomer. He came to the attention of Thomas Young (1773-1829), the superintendent of the HM Nautical Almanac Office, after he devised a new method for determining longitude using lunar occultation, that is when a star disappears behind the Moon. Young brought him into the world of astronomy and upon his death recommended Henderson as his successor.


Copy of a portrait of Thomas Young by Henry Briggs Source: Wikimedia Commons

Henderson didn’t receive to post but was appointed director of the Royal Observatory at the Cape of Good Hope. The observatory had only opened in 1828 after several years delay in its construction. The first director Fearon Fallows (1788–1831), who had overseen the construction of the observatory had died of scarlet fever in 1831 and Henderson was appointed as his successor, arriving in 1832.


The Royal Observatory Cape of Good Hope in 1857 Illustrated London News, 21 March 1857/Ian Glass Source: Wikimedia Commons

The Cape played a major role in British observational astronomy. In the eighteenth century, it was here that Charles Mason (1728–1786) and Jeremiah Dixon (1733–1779), having been delayed in their journey to their designated observational post in Sumatra, observed the transit of Venus of 1761. John Herschel (1792–1871), the son and nephew of the astronomers William and Caroline Herschel, arrived at the Cape in 1834 and carried extensive astronomical observation there with his own 21-foot reflecting telescope. cooperating with Henderson successor Thomas Maclear. In 1847, Herschel published his Results of Astronomical Observations made at the Cape of Good Hope, which earned him the Copley Medal of the Royal Society.

Manuel John Johnson (1805–1859), director of the observatory on St Helena, drew Henderson’s attention to the fact that Alpha Centauri displayed a high proper motion.


Ladder Hill Observatory St Helena Source

Proper motion is the perceived motion of a star relative to the other stars. Although the position of the stars relative to each other appears not to change over long periods of time they do. There had been speculation about the possibility of this since antiquity, but it was first Edmund Halley, who in 1718 proved its existence by comparing the measured positions of prominent stars from the historical record with their current positions. A high proper motion is an indication that a star is closer to the Earth.

Aimed with this information Henderson began to try to determine the stellar parallax of Alpha Centauri. However, Henderson hated South Africa and he resigned his position at the observatory in 1833 and returned to Britain. In his luggage he had nineteen very accurate determinations of the position of Alpha Centauri. Back in Britain Henderson was appointed the first Astronomer Royal for Scotland in 1834 and professor for astronomy at the University of Edinburgh, position he held until his death.

Initially Henderson did not try to determine the parallax of Alpha Centauri from his observational data. He thought that he had too few observations and was worried that he would join the ranks of many of his predecessors, who had made false claims to having discovered stellar parallax; Henderson preferred to wait until he had received more observational data from his assistant William Meadows (?–?). This decision meant that Henderson, whose data did in fact demonstrate stellar parallax for Alpha Centauri, who had actually won the race to be the first to determine stellar parallax, by not calculating and publishing, lost the race to the German astronomer Friedrich Wilhelm Bessel (1784–1846).


Portrait of the German mathematician Friedrich Wilhelm Bessel by the Danish portrait painter Christian Albrecht Jensen Source: Wikimedia Commons

Like Henderson, Bessel was a self-taught mathematician and astronomer. Born in Minden as the son of a minor civil servant, at the age of fourteen he started a seven-year apprenticeship as a clerk to an import-export company in Bremen. Bessel became interested in the navigation on which the company’s ships were dependent and began to teach himself navigation, and the mathematics and astronomy on which it depended. As an exercise he recalculated the orbit of Halley’s Comet, which he showed to the astronomer Heinrich Wilhelm Olbers (1758–1840), who also lived in Bremen.


Portrait of the german astronomer Heinrich Wilhelm Matthias Olbers (lithography by Rudolf Suhrlandt Source: Wikimedia Commons

Impressed by the young man’s obvious abilities, Olbers became his mentor helping him to get his work on Halley’s Comet published and guiding his astronomical education. In 1806, Olbers obtained a position for Bessel, as assistant to Johann Hieronymus Schröter (1745–1816) in Lilienthal.


Johann Hieronymus Schröter Source: Wikimedia Commons

Here Bessel served his apprenticeship as an observational astronomer and established an excellent reputation.


Schröter’s telescope in Lilienthal on which Bessel served his apprenticeship as an observational astronomer

Part of that reputation was built up through his extensive correspondence with other astronomers throughout Europe, including Johann Carl Fried Gauss (1777–1855). It was probably through Gauss’ influence that in 1809 Bessel, at the age of 25, was appointed director of the planned state observatory in Königsberg, by Friedrich Wilhelm III, King of Prussia.


Königsberg Observatory in 1830. It was destroyed by bombing in the Second World War. Source: Wikimedia Commons

Bessel oversaw the planning, building and equipping of the new observatory, which would be his home and his workplace for the rest of his life. From the beginning he planned to greatly increase the accuracy of astronomical observations and calculation. He started by recalculated the positions of the stars in John Flamsteed’s stellar catalogue, greatly increasing the accuracy of the stellar positions. Bessel also decided to try and solve the problem of determining stellar parallax, although it would be some time before he could undertake that task.

One of the astronomers with whom Bessel took up contact was Friedrich Georg Wilhelm von Struve (1793–1864), who became a good friend and his rival in the search for stellar parallax, although the rivalry was always good natured. Struve was born the son of Jacob Struve (1755–1841), a schoolteacher and mathematician, in Altona then in the Duchy of Holstein, then part of the Denmark–Norway Kingdom and a Danish citizen.


Friedrich Georg Wilhelm von Struve Source: Wikimedia Commons

Whilst he was still a youth, his father sent him to live in Dorpat (nowadays Tartu) in Estonia with his elder brother, to avoid being drafted into the Napoleonic army. In Dorpat he registered as a student at the university to study, at the wish of his father, philosophy and philology but also registered for a course in astronomy. He financed his studies by working as a private tutor to the children of a wealthy family. He graduated with a degree in philology in 1811 and instead of becoming a history teacher, as his father wished, he took up the formal study of astronomy. The university’s only astronomer, Johann Sigismund Gottfried Huth (1763–1818), was a competent scholar but was an invalid, so Struve basically taught himself and had free run of the university’s observatory whilst still a student, installing the Dolland transit telescope that was still packed in the crates it was delivered in. In 1813 he graduated PhD and was, at the age of just twenty, appointed to the faculty of the university. He immediately began his life’s work, the systematic study of double stars.


The old observatory building in Dorpat (Tartu) Source: Wikimedia Commons

Like Bessel, Struve was determined to increase the accuracy of observational astronomy. In 1820 whilst in München, to pick up another piece of observational equipment, he visited Europe’s then greatest optical instrument maker, Joseph Fraunhofer (1787–1826), who was putting the finishing touches to his greatest telescopic creation, a refractor with a 9.5-inch lens.


Joseph Fraunhofer Source: Wikimedia Commons

Struve had found his telescope. He succeeded in persuading the university to purchase the telescope, known as the ‘Great Refractor’ and began his search for observational perfection.


Frauenhofer’s Great Refractor Source: Wikimedia Commons

Like Struve, Bessel turned to Fraunhofer for the telescope of his dreams. However, unlike Struve, whose telescope was a general-purpose instrument, Bessel desired a special purpose-built heliometer, a telescope with a split objective lens, especially conceived to accurately measure the distance between two observed objects. The first  really practical heliometer was created by John Dolland (1706–1761) to measure the variations in the diameter of the Sun, hence the name. Bessel needed this instrument to fulfil his dream of becoming the first astronomer to accurately measure stellar parallax. Bessel got his Fraunhofer in 1829.


Königsberger Heliometer Source: Wikimedia Commons

One can get a very strong impression of Bessel’s obsession with accuracy in that he devoted five years to erecting, testing, correcting and controlling his new telescope. In 1834 he was finally ready to take up the task he had set himself. However, other matters that he had to attend to prevented him from starting on his quest.

The Italian astronomer Giuseppe Piazzi (1746–1826), famous for discovering the first asteroid, Ceres, had previously determined that the star 61 Cygni had a very high proper motion, meaning it was probably relatively close to the Earth and this was Bessel’s intended target for his attempt to measure stellar parallax.


Giuseppe Piazzi pointing at the asteroid Ceres Painting by Giuseppe Velasco (1750–1826). Source: Wikimedia Commons

It was also Struve’s favoured object for his attempt but, unfortunately, he was unable in Dorpat with his telescope to view both 61 Cygni and a reference star against which to measure any observable parallax, so he turned his attention to Vega instead. In 1837, Bessel was more than somewhat surprised when he received a letter from Struve containing seventeen preliminary parallax observations of Vega. Struve admitted that they were not yet adequate to actually determine Vega’s parallax, but it was obvious that he was on his way. Whether Struve’s letter triggered Bessel’s ambition is not known but he relatively soon began a year of very intensive observations of 61 Cygni. In 1838 having checked and rechecked his calculations, and dismantled and thoroughly examined his telescope for any possible malfunctions, he went public with the news that he had finally observed a measurable parallax of 61 Cygni. He sent a copy of his report to John Herschel, President of the Royal Astronomical Society in London. After Herschel had carefully studied the report and after Bessel had answered all of his queries to his satisfaction. Herschel announced to the world that stellar parallax had finally been observed. For his work Bessel was awarded the Gold Medal of the Royal Astronomical Society. Just two months later, Henderson, who had in the meantime done the necessary calculations, published his measurement of the stellar parallax of Alpha Centauri. In 1839 Struve announced his for Vega. Bessel did not rest on his laurels but reassembling his helioscope he spent another year remeasuring 61 Cygni’s parallax correcting his original figures. 

All three measurements were accepted by the astronomical community and both Henderson and Struve were happy to acknowledge Bessel’s priority. There was no sense of rivalry between them and the three men remained good friends. Modern measurements have shown that Bessel’s figures were within 90% of the correct value, Henderson’s with in 75%, but Struve’s were only within 50%. The last is not surprising as Vega is much further from the Earth than either Alpha Centauri or Cygni 61 making it parallax angle much, much smaller and thus considerably more difficult to measure.

In the sixteenth century Tycho Brahe rejected heliocentricity because the failure to detect stellar parallax combined with his fallacious big star argument meant that in a heliocentric system the stars were for him inconceivably far away. I wonder what he would think about the fact that Earth’s nearest stellar neighbour Proxima Centauri is 4.224 lightyears away, that is 3. 995904 x 1013 kilometres!



Filed under History of Astronomy, History of Optics, History of science, History of Technology

Microscopes & Submarines

The development of #histSTM in the early decades of the Dutch Republic, or Republic of the Seven United Netherlands, to give it its correct name, was quite extraordinary. Alongside the development of cartography and globe making, the most advanced in the whole of Europe, there were important figures such as the engineer, mathematician and physicist, Simon Stevin, the inventors of the telescope Hans Lipperhey and Jacob Metius, the mathematical father and son Rudolph and Willebrord Snel van Royan and Isaac Beeckman one of the founders of the mechanical philosophy in physics amongst others. However, one of the most strange and wonderful figures in the Netherlands during this period was, without doubt, the engineer, inventor, (al)chemist, optician and showman Cornelis Jacobszoon Drebbel (1571–1631).


Source: Wikimedia Commons

Drebbel is one of those larger than life historical figures, where it becomes difficult to separate the legends and the myths from the known facts, but I will try to keep to the latter. He was born to Jacob Drebbel an Anabaptist in Alkmaar in the province of North Holland. He seems not to have received much formal education but in about 1587 he started attending the Academy of the printmaker, draftsman and painter Hendrick Goltzius (1558–1617) in Haarlem also in North Holland.


Hendrick Goltzius – Self-Portrait, c. 1593-1594 – Google Art Project Source: Wikimedia Commons

Goltzius was regarded as the leading engraver in the Netherlands during the period and he was also an active alchemist. Drebbel became a skilled engraver under Goltzius’ instruction and also acquired an interest in alchemy. In 1595 he married Sophia Jansdochter Goltzius, Hendrick’s younger sister. They had at least six children of which four survived into adulthood. The legend says that Sophia’s prodigal life style drove Drebbel’s continual need to find better sources for earning money.


Drebbel’s town plan of Alkmaar 1597 Source: Wikimedia Commons

Drebbel initially worked as an engraver, cartographer and painter but somewhere down the line he began to work as an inventor and engineer.


Astronomy [from the series The Seven Liberal Arts]. Engraving by Drebbel Source: Wikimedia Commons

Not surprisingly, for a Netherlander, he a turned to hydraulic engineering receiving a patent for a water supply system in 1598. In 1600 he built a fountain at the Noorderpoort in Middelburg and at the end of his life living in England he was involved in a plan to drain the Fens. At some point, possibly when he was living in Middelburg, he learnt the craft of lens grinding, which would play a central roll in his life.

Also in 1598 he acquired a patent for Perpetuum mobile but which he, however, had not invented. The so-called Perpetuum mobile was a sort of clock, which was in reality powered in changes by the air temperature and air pressure had actually been invented by Jakob Dircksz de Graeff (1571–1638), an influential politician and natural philosopher, who was a friend of both Constantijn Huygens and René Descartes, and Dr Pieter Jansz Hooft (1574/5–1636) a politician, physician and schoolteacher.


Jakob Dircksz de Graeff Source: Wikimedia Commons


Pieter Jansz Hooft (1619), Attributed to Michiel van Mierevelt Source: Wikimedia Commons

Drebbel not only patented the Perpetuum mobile but also claimed to have invented it. His increasing reputation driven by this wonder machine earned his an invitation to the court of King James VI &I in London as the guest of the crown prince Henry in 1604. When on the court in London the Queen accidentally broke the Perpetuum mobile, Drebbel was unable to repair it.


The barometric clock of Cornelis Drebbel patented in 1598 and then known as “perpetuum mobile”. Print by Hiesserle von Choda (1557-1665) Source: Wikimedia Commons

At the court in London he was responsible for staging masques, a type of play with poetry, music, dance, and songs that was popular in the sixteenth and seventeenth centuries. He designed and built the stage sets and wonderful machines to enchant the audiences. Drebbel was by no means the only scientist-engineer to be employed to stage such entertainments during the Early Modern Period but he appears to have been very good at it. It was almost certainly Drebbel, who through his contacts imported from the Netherlands the first ever telescope to be seen in England, which was presented to James at the high point of a masque in 1609. He also built a magic lantern and a camera obscura with which he also entertained the members of the court.

Drebbel’s reputation grew to the point where he received an invitation to the court of the Holly Roman Empire, Rudolf II, in Prague in October 1610. Rudolf liked to surround himself with what might be termed wonder workers. Amongst those who had served in this capacity in Prague were Tycho Brahe, John Dee, Edward Kelley, Johannes Kepler and Jost Bürgi. There are no reports of any interactions between Drebbel and either Kepler or Bürgi, who were all on the court of Rudolf at the same time. In Prague he once again functioned as a court entertainer or showman.


AACHEN, Hans von – Portrait of Emperor Rudolf II Source: Wikimedia Commons

Rudolf was deposed by his brother Archduke Mathias in 1611and Drebbel was imprisoned for about a year. Following the death of Rudolf in 1612, Drebbel was released from prison and returned to London. Here, however, his situation was not as good as previously because Henry, his patron, had died in 1612. He kept his head above water as a lens grinder and instrument maker.

As a chemist Drebbel published his best-known written work Een kort Tractaet van de Natuere der Elemente (A short treatise of the nature of the elements) (Haarlem, 1621).


He was supposedly involved in the invention of the explosive mercury fulminate, Hg(CNO)2, but this is disputed. He also developed other explosive mixtures. He invented a chicken incubator with a mercury thermostat to keep it at a constant, stable temperature. This is one of the earliest feedback controlled devices ever created. He also developed and demonstrated a functioning air conditioning system.


Error-controlled regulator using negative feedback, depicting Cornelius Drebbel’s thermostat-controlled incubator of circa 1600. Source: Wikimedia Commons

He didn’t himself exploit one of his most successful discoveries, one that he made purely by accident. He dropped a flask of aqua regia (a mixture of nitric and hydrochloric acid, normally used to dissolve gold) onto a tin windowsill and discovered that stannous chloride (SnCl2) makes the colour of carmine (the red dye obtained from the cochineal insect) much brighter and more durable. Although Drebbel didn’t exploit this discovery his daughters Anna and Catherina and their husbands the brothers, Abraham and Johannes Sibertus Kuffler (a German inventor and chemist) did, setting up dye works originally in Leiden and then later in Bow in London. The colour was known as Colour Kuffler of Bow Dye and was very successful. Kuffler later continued his father-in-law’s development of self-regulating ovens that he demonstrated to the Royal Society.

In the early 1620s Constantijn Huygens, the father of Christiaan, came to London on a diplomatic mission. He made the acquaintance of Drebbel, who demonstrated his magic lantern and his camera obscura for the Dutch diplomat. Huygens was much impressed by his landsman and for a time became his pupil learning how to grind lenses, a skill that he might have passed onto his sons.


Constantijn Huygens (1596-1687), by Michiel Jansz van Mierevelt. Source: Wikimedia Commons

It is not known, who actually invented the microscope and it’s more than likely that the principle of the microscope was discovered by several people, all around the same time, who like Galileo looked through their Galilean or Dutch telescope the wrong way round. What, however, seems to be certain is that Drebbel is the first person known to have constructed a Keplerian telescope, that is with two convex lenses rather than a concave and a convex lens. As with all of his other optical instruments, Drebbel put on microscope demonstration introducing people to the microscopic world, as always the inventor as showman.

Drebbel’s most famous invention was without doubt his submarine. This is claimed to be the first-ever navigable submarine but has become the stuff of legends, how much of story is fact is difficult to assess. His submarine consisted of a wooden frame covered in leather, and one assumes waterproofed in someway; it was powered by oar.


Artistic representation of Drebbel’s submarine, artist unknown Source: Wikimedia Commons

It had bladders inside that were filled with water to enable the submarine to submerge; the bladders were emptied when the vessel was required to surface. In total between 1620 and 1624 Drebbel built three different vessels increasing in size. The final submarine had six oars and could carry up to sixteen passengers. Drebbel gave public demonstrations with this vessel on the river Thames. According to reports the vessel dived to a depth of four to five metres and remained submerged for three hours traveling from Westminster and Greenwich and back again. Assuming the reports to be true, there has been much speculation as to how fresh air was supplied inside the closed vessel. These speculations include a mechanical solution with some form of snorkel as well as chemical solutions with some sort of chemical apparatus to generate oxygen. It is also reported that Drebbel took King James on a dive under the Thames. Despite all of this Drebbel failed to find anybody, who would be prepared to finance a serious use of his submarine.

In the later 1620s Drebbel served the Duke of Buckingham as a military advisor but his various suggestions for weapons proved impractical and failed, the British blaming  the inventor and Drebbel blaming the English soldiers, finally ruining whatever reputation he still had. As already stated above towards the end of his life he was supposedly involved in a scheme to drain the Fens but the exact nature of his involvement remains obscure. Drebbel died in financial straights in 1633 in London, where he was scraping a living running a tavern on the banks of the Thames.

















Filed under History of Alchemy, History of Cartography, History of Chemistry, History of Optics, History of Technology, Renaissance Science