‘Tripping the Light Fantastic’:
Henry Talbot and David Brewster
Research Associate, National Museums Scotland
Both Henry Talbot (1800-77) and David Brewster (1781-1868) were involved with photography from its invention until their respective deaths; and because of their friendship and shared involvement in the public arena of the European scientific field of optics, it is worth examining the background of their investigations into the nature of light and colour which formed the firm basis to the astonishing discoveries of the late 1830s . Brewster, of course, is known as the personally difficult but brilliant and eminent scientist based at the University of St Andrews who introduced the Scots to the new art through his correspondence with Talbot in Wiltshire . Talbot, that shy English gentleman, had the wide interests of most men of his class and time, but pursed them all with genuine scholarship, rather than the more predictable butterfly attention of the dilettante . Here, an attempt will be made to place the photographic into the broader context of the optical pursuits of both Brewster and Talbot: firstly, those of Brewster, the Evangelical Scot, the elder of the two, born almost twenty years before the quiet Englishman, Talbot; and subsequently, after the significant events of the 1840s, how their lives continued to mesh optically, photographically and personally.
‘My father’s connexion with photography and photographers might well furnish a chapter of his life in competent hands,’ wrote David Brewster’s first biographer, his daughter Margaret Maria Gordon. She continued: ‘A large correspondence was kept up with Mr Fox Talbot, M. Claudet, Mr Buckle, Paul Pretsch, Messrs Ross and Thomson, and other eminent photographers. He made many experiments in the art, though not able to give sufficient time to master its difficulties … A new photograph was to the last a joy to him, and he was peculiarly pleased with the receipt of a medal from the Photographic Society of Paris in 1865.’ 
This retrospective was given by a close member of his family, who expressed the pious wish in her Preface that ‘the scientific memoirs of Sir David Brewster … it is hoped, may soon be undertaken by competent writers.’ However, this was not to be, principally because Brewster’s views on the nature of light had not moved since his youth, and he died in 1868 at the advanced age of 86, still a convinced Newtonian, possibly the last survivor clinging to a redundant world-view. History has not been entirely kind to Brewster’s memory, for the raw ingredients for such a scientific biography as expressed by Mrs Gordon, gathered carefully by his relatives and kept at the family home near Kingussie, were destroyed in a fire in 1903, long before interest could be rekindled by a later generation in such a project . Not until 1966 do we find the first historian of science becoming interested in Brewster’s role as a correspondent, or an enabler, and finding that his early scientific work in measuring the optical properties of literally hundreds of substances had laid the foundations for nineteenth-century investigations into the nature of light . This was unglamorous donkey work, it rapidly entered the literature, and it was subsequently forgotten to whom the credit was due. It should not be forgotten, either, that Brewster was himself an historian of science, writing the standard biography of Sir Isaac Newton, which was regarded as a classic and not superseded until the 1980s .
So, who was David Brewster? (Fig.1 Dr John Adamson, Sir David Brewster, c.1855, albumen print, NMS.T.19220.127.116.11) He was born in Jedburgh, in the Scottish Borders, the third child of the Rector of Jedburgh Grammar School in 1781 . He spent his childhood surrounded by intelligent and amusing contemporaries, according to his daughter, and these included the slightly older self-taught astronomer and ploughwright James Veitch, who taught him how to construct reflecting telescopes, and encouraged his astronomical pursuits . In 1793, aged twelve, Brewster went to the University of Edinburgh, and, as was usual in those days, would walk the forty-five miles there within the day. There, he was taught by some of the great teachers of the Scottish Enlightenment, among them John Playfair (mathematics), John Robison (natural philosophy, or what we call physics), and Dugald Stewart (moral philosophy): indeed, Brewster fulfils that old Scots stereotype, ‘the lad o’pairts’. Destined for a career in the established church, Brewster obtained his master’s degree in the arts curriculum (the sole one on offer) in 1800, at the age of nineteen. By this time he was already writing regularly for the Edinburgh Magazine (which subsequently became the Scots Magazine – still going strong today), a periodical then combining science and literature, and in 1800 he became its editor. 
Brewster had no independent means and was obliged to find a career to support himself, particularly as he now realised that the Church would not suit him. Although deeply religious, he apparently suffered from nervous faintness when preaching; and of course, such a handicap effectively closed a teaching career as well; despite this, for a few years he supported himself as a private tutor. He was also mooted as a candidate for the Chair in Mathematics at both Edinburgh in 1805 and Aberdeen in 1807, but was ultimately unsuccessful. In 1808 he became editor of a new venture, the Edinburgh Encyclopaedia, seen to be a worthy rival of Britannica (which at this stage was also produced in Edinburgh; indeed, Brewster would contribute a number of articles to the fourth edition of 1810, the fifth edition of 1817, and the sixth edition of 1824). However, his daughter wrote: that ‘it was not until 1809 that he felt himself free to follow the career so manifestly opening before him’: that of scientific journalism . By this time he had already received a number of honorary degrees and had been elected a Fellow of the Royal Society of Edinburgh. In 1810 he married Juliet Macpherson, daughter of the poet James ‘Ossian’ Macpherson, and soon he had to support a growing family which ultimately comprised four sons and a daughter. The first five years of his marriage seem to have been dominated by the affairs of the Encyclopaedia – which was not completed until 1830. ‘The dilatory conduct’ of the contributors, the burdensome correspondence, the rupturing of friendships – all who have been editors will sympathise with Brewster.
His daughter points out that ‘One bright circumstance shines like a sunbeam through the gloom connected with this literary undertaking. A request from Dr Brewster to the Rev Thomas Chalmers of Kilmany, to write the article CHRISTIANITY, turned the mind of the young and careless, though brilliant, divine, to study the truths of which he had then but a superficial knowledge, and ultimately proved the means of leading him to grasp them as a life-reality, with a force and power without which he could not have been the blessing to his country which he proved in after years. This was the beginning of a long and cordial friendship which only terminated with the death of Chalmers in 1847.’  Chalmers became the first Moderator of the Free Church of Scotland after the Disruption in 1843, and as the central figure in D.O. Hill’s painting of that event, played no small part as a subject of early Scottish photographic history. Brewster’s scientific work – as opposed to his scientific journalism – was also being taken notice of in appropriate circles, and in 1813 his first paper ‘On some properties of Light’ was published in the Philosophical Transactions of the Royal Society of London, the same year that he published his first substantial book, a Treatise on New Philosophical Instruments. This volume is devoted to what today we would call scientific instruments – most of which were optical in their nature – and the determinations of the refractive and dispersive powers of nearly 200 substances made during his attempts to improve achromatic telescopes. News of similar work on the Continent towards the end of the Napoleonic Wars – he was able to visit Paris in 1814 – moved Brewster’s interest back to optical theory, but the improvement of optical instrumentation remained a lifelong fascination. 
In 1815, Brewster became a Fellow of the Royal Society of London, and published a series of papers on the polarisation of light. For the next fifteen to twenty years he energetically pursued four related fields of research in this area. First, he followed the line that successive polarisation by refraction by a pile of glass plates, which he concluded was a constant, ought to allow the investigation not only of the form and structure of crystals, but indeed of the nature of light itself. Second, he searched for a general law of polarisation – the law which now bears his name, Brewster’s Law – finding that the index of refraction of the reflecting medium is the tangent of the angle of polarisation. Third, he studied metallic reflection, concluding that light was elliptically polarised, and deduced laws that predicted quantities and angles of polarisation of light. His fourth research area created the new disciplines of optical mineralogy and photoeleasticity. His experiments in 1813 on the structure of topaz led to the unexpected discovery of its two optical axes, and by 1819 Brewster had classified hundreds of minerals and crystals into their optical categories by painstaking experiment. While undertaking this project, he also discovered that heat and pressure could alter the doubly refracting structures of minerals and crystals, and again he deduced the general laws which enabled these phenomena to be predicted.
Still searching for ways to improve instrumentation, Brewster undertook an extensive investigation of absorption spectroscopy. Adding a further 1600 dark lines to Joseph von Fraunhofer’s 354, these researches led him to reinterpret the colours of the spectrum, disagreeing with Newton’s deductions, yet reaffirming an emission theory of light. He never fully accepted the undulatory theory of light, because he felt that it did not explain all the phenomena.
In the 1830s his intensive and energetic youthful investigations changed direction, and he devoted more research time to applications of optics and the physiology of vision. His experiments on the structure of the eye helped to lay the foundations of modern biophysics, while in his work on subjective visual phenomena he made important discoveries, but these were subsequently overshadowed . Brewster was very much an experimentalist rather than a theorist. He deplored the lack of state patronage in supporting scientific research; but on a number of occasions he successfully persuaded societies and universities to supply him with the equipment with which he could do his work. Because he never fully accepted the wave theory of light and because he outlived most of his scientific contemporaries, Brewster found his ground-breaking experimental work marginalised towards the end of his life. Much of the valuable work he had done was not attributed to him, something he would have found hard to take.
A by-product of this serious work was Brewster’s invention of the kaleidoscope in 1816, and his ineffective patenting of the device the following year. The kaleidoscope (Fig.2 Telescopic kaleidoscope, designed by David Brewster and retailed by John Ruthven, Edinburgh, c.1820. NMS.T.1985.20) is primarily a toy which uses simple principles of reflection noticed by Brewster when experimenting; but it was observed even by his contemporaries that these principles had been known since antiquity. In a manner which was to become something of a pattern, Brewster defended his brain-child in print, then mustered supporters to his aid: a series of articles appeared over the years in encyclopaedias and journals, summarised by the grand Treatise on the Kaleidoscope of 1858. In this case, he had rashly gone to the expense of obtaining a patent for protecting the manufacture of the kaleidoscope, which was negated when the enthusiasm of the London instrument maker to whom he had entrusted the prototype led to the principles of the device becoming known. Instantly, the simply-produced brass tube was copied, and from London he wrote to his wife in Edinburgh: ‘… had I managed my patent rightly, I would have made one hundred thousand pounds by it!’ It appears to have been the first instance of a national fashionable craze, and an indication that consumers could create new markets overnight in a newly industrialised society.
‘You can form no conception of the effect which the instrument excited in London’, Brewster continued. ‘All that you have heard falls infinitely short of the reality. No book and no instrument in the memory of man ever produced such a singular effect. They are exhibited publicly on the streets for a penny, and I had the pleasure of paying this sum yesterday; these are about two feet long and a foot wide. Infants are seen carrying them in their hands, the coachmen on their boxes are busy using them, and thousands of poor people make their bread by making and selling them.’ 
Meanwhile, in another part of the country – specifically, in Wiltshire – our second protagonist was growing towards maturity. Henry Talbot’s life and upbringing were far removed from that of his future scientific mentor: his mother was an earl’s daughter, and after a somewhat sticky financial start to life, Henry (Fig.3. John Moffat, William Henry Fox Talbot, 1864, carte-de-visite. NMS.T.1937.93) eventually grew into his role of relatively well-off country gentleman, fulfilling with a marked lack of enthusiasm but grittily held sense of duty, his responsibilities as such, to the extent that he took his seat (briefly) in the reforming House of Commons in 1833 as a Liberal. His father had died when the young Henry was five months old, and had left debts of over £30,000, which his relatives had more or less sorted out by the time he came of age. His mother, Lady Elisabeth, had remarried; but she encouraged her son in all his pursuits, and he was clearly devoted to his step-father and half-sisters, and they to him.  In his schoolboy and undergraduate letters, there is more of the self-confidence of youth, and none of the diffidence and retiring nature so evident in later years. He wrote to his mother in 1818 from Cambridge: ‘It is ludicrous to see how many people here are making or getting made for themselves Calleidoscopes [sic], as they are pompously denominated. From the profoundest mathematician to his unlettered Jip [college servant], all are eager for them. When I have more leisure, I will make one upon better principles, which shall be so contrived, that the Star may be changed to one with more or fewer points, at pleasure, by only setting an Index. This is very easy. And I will make another, which instead of exhibiting stars shall produce straight patterns like the borders for paper: which I flatter myself will be found of more practical use than the other in supplying with designs of genuine novelty, the paper hanger, to whom nature has too sparingly given the powers of invention.’ 
Talbot graduated from Cambridge in 1821 as twelfth wrangler (that is, he was placed twelfth in the first class in the mathematical tripos). His interests after university encompassed mathematics (obviously), oriental languages, botany and poetry. But his great love already appeared to be the various branches of optical science, and by 1826 he had been put in touch with the editor of the Edinburgh Journal of Science by the Secretary of the Royal Society of London, John Herschel.  This editor was that selfsame inventor of the ‘pompously denominated’ kaleidoscope, David Brewster. Talbot’s paper was entitled ‘Some experiments on coloured flames’, and was one of his many contributions to the emerging science of spectroscopy.  The discovery of the dark lines in the solar spectrum is usually ascribed to the Bavarian optical worker Joseph von Frauhofer, after whom the lines were named. In fact, Fraunhofer was motivated by the practical concern of locating a reference point in the spectrum which could be used for accurately measuring refractive indices in optical prisms.  ‘In the work of Brewster, and of W.H. Fox Talbot’, Jim Bennett has written, ‘we see anticipations of a method of chemical analysis.’  Brewster later described ‘the principal object of my enquiries [was] the discovery of a general principle of chemical analysis, in which simple and compound bodies might be characterised by their action on definite parts of the spectrum.’  Meanwhile, Talbot was investigating the analysis of chemicals through flame analysis.  Bearing in mind that the spectroscope – the instrument which specifically investigates spectra – was not devised until 1860, Brewster, always short of cash for apparatus, had borrowed all sorts of bits and pieces for these studies, including ‘a fine plate glass prism, executed by Fraunhofer, … which I owe to the kindness of Mr Talbot.’ 
Further kindness was forthcoming when Brewster first visited Lacock Abbey, (Fig 4. W.H.F. Talbot, Lacock Abbey in Wiltshire, c.1845, salt print from a calotype negative. NMS.T.1937.92.15) Talbot’s family home, in 1836, when Talbot invited him to stay along with a number of other intellectuals (including William Whewell, Charles Babbage, Charles Wheatstone, Peter Roget and William Snow Harris) for the nearby annual meeting of the British Association for the Advancement of Science, held that year in Bristol.  Talbot’s wife Constance wrote to Lady Elisabeth: ‘You are perfectly right in supposing Sir D.B. to pass his time pleasantly here. He wants nothing beyond the pleasure of conversing with Henry discussing their respective discoveries & various subjects connected with science. I am quite amazed to find that scarcely a momentary pause occurs in their discourse. Henry seems to possess new life … when I see the effect produced in Henry by Sir D.B.’s society I feel most acutely how dull must our ordinary way of life be to a mind like his! And yet he shuts himself up from choice …’. 
Not only had the two minds in common the nascent science of spectroscopy; both men were intensely interested in the nature of light and colour, and work done by Talbot (dated – by my former colleague Dr Allen Simpson – to the mid-1820s but only published in 1834 in the Philosophical Magazine, another journal co-edited by David Brewster) resulted in an extraordinary device, assembled by the London instrument makers W. & S. Jones at the request of an American collector of scientific demonstration apparatus.  It is identified along the ivory plaque under the doors as ‘H.F. TALBOT’S Revolving Photometer or MEASURER of the Intensity of LIGHT & COLOUR’, and the hand-turned spiral is identical with one illustrated in the 1834 paper (Fig. 5. Optical photometer designed by W.H.F. Talbot, constructed by W.& S. Jones, c.1830. NMS.T.1995.31). Simpson speculates that this particular device may have been made under Talbot’s direct supervision as the publication was too succinct to allow the detailed construction of such a piece from it. Colour mixing of this nature was later to be investigated by James Clerk Maxwell and Hermann Helmholtz.
Brewster and Talbot were both fascinated by crystals – their formation, and the optical characteristics of individual compounds. Talbot published several important papers in this area during the 1830s, and in 1837 was awarded the Bakerian Prize by the Royal Society of London for this work.  He was already using his microscope for crystal examination, and included polarising devices to work out where their optical axes were. He also went on to make calotypes showing this phenomena. Brewster deeply admired the pioneering work that Talbot was doing, both optically and with the microscope, to the extent that his own Treatise on the Microscope of 1837, originally published as an article in the seventh edition of the Encyclopaedia Britannica, was dedicated by him to Talbot.  Besides some important early photographic equipment (Fig. 6. Camera, printing frame, iron and balance, used by W.H.F. Talbot in the calotype process, 1840s. NMS.T.1936.21, 22, 95 and 96) and images, a number of Talbot’s microscopes, as well as his prisms, have come to the collections of the National Museums of Scotland. Briefly, these are his simple microscope for botanical work (Fig.7. Simple microscope, with a box of simple lenses, made and signed by Andrew Ross, and used by W.H.F. Talbot, c. 1840. NMS.1936.91), made by the eminent London optician, Andrew Ross (he had another, of the same type) ; his cutting-edge (technologically-speaking) bespoke reflecting microscope (Fig.8. Reflecting microscope purchased by W.H.F. Talbot, signed and made by Giovanni-Battista Amici, Modena, 1822.  NMS.T.1936.114), ordered from the Italian botanist and optician, Giovanni-Battista Amici of Modena in 1822; and both simple and Nicol prisms.  Brewster, a poorer man, was forced to rely on less elegant kit. As described by his daughter, ‘Much of his apparatus to unlearned eyes appeared a mass of bits of broken glass, odds and ends of brass, tin, wire, old bottles, burned corks, and broken instruments. Yet it was kaleidoscopic in its nature, and all resulted in effective and beautiful work. Experiments in the midst of this dusty medley formed the chosen and delightful occupation of his life.’ 
Having met, Brewster and Talbot corresponded, although today only Brewster’s replies have survived. By the mid-1830s, Talbot was confiding in Brewster about his new experiments of capturing images on chemically prepared paper, and this has been extensively discussed many times before: I shall trip lightly (even fantastically) over the busy and crucial years of invention, discovery and publication, and the role played by Brewster in introducing the Edinburgh artist D.O. Hill to the young calotypist from St Andrews, Robert Adamson, in May 1843.  The previous year, Brewster had again been visiting Lacock, and a negative believed to be of Brewster, taken by Talbot, is inscribed on the reverse ‘July 1842’. The microscope shown on the table belonged to Talbot, and is now in the Fox Talbot Museum; perhaps this is not the best image of Talbot, if it is indeed him, but it is satisfying to think that it was taken by his scientific protégé. 
There appear to be remarkably few photographs of Talbot, and many more of Brewster. However, it is not entirely clear whether Brewster himself actually took photographs, or whether – being too busy – he merely developed prints from negatives made by others. Talbot, one imagines, was not too frequently in front of the camera lens because he was all too often behind it. His apologia, contained in the Introductory remarks to The Pencil of Nature explains that the calotype prints ‘are impressed by Nature’s hand … [and] when we have learnt more, by experience, respecting the formation of such pictures, they will doubtless be brought much nearer perfection.’ Talbot continued to experiment intermittently with photography for the rest of his life.
In late 1844 Talbot toured the Scottish Borders, Edinburgh and the Perthshire Trossachs (Fig. 9. W.H.F. Talbot, Wooden bridge over a river, possibly in Scotland, c.1845. NMS.T.1937.91.3), and published the following year his second photographically illustrated book, Sun Pictures in Scotland, which was recognisably a tribute to Sir Walter Scott and his works: indeed, two of Talbot’s three daughters shared the names of Scott heroines. There was then a lull in his practical involvement in taking photographs, although he was remarkably busy in other areas which interested him. As H.J.P. Arnold writes, ‘The pattern of the 1840s and 1850s for the family was [of] … Henry Talbot joining them for very brief periods interspersed with long periods of work in London and at Lacock Abbey as well as occasional trips to Europe. … [By 1855] began the pattern of a decade – several months spent in the Lake District followed by an entire winter in Edinburgh. Talbot as a young man had found Edinburgh a delightful city, and as his contacts with Scotland’s capital city grew so did his regard for Scottish scientists and universities.’ In 1859, Talbot’s youngest daughter Matilda – the only one of his children to marry – announced her engagement to an Edinburgh lawyer named John Gilchrist-Clark.
Talbot’s experiments concerning attempts to turn photographs into practical printing (Fig. 10. W.H.F. Talbot, Fern, photoglyphic engraving, 1852-55. NMS.T.1937.90.6) are not so well covered in the literature of the history of photography, for no readily discernable reason. The significance of Talbot’s work in this later area has been summarised by Eugene Ostroff thus: ‘The system devised by Talbot, linking the negative-positive photographic image to the photomechanical technique (patented by him in 1852 and 1858) inaugurated a vast new field offering rapid, mass visual communication of graphic information … within 25 years various photomechanical approaches began to gain acceptance in the printing industry, eventually proving adaptable to large-scale, high-speed production techniques’. It concluded the vision anticipated by Talbot in his idea of photography, first envisaged at Lake Como and subsequently expressed in The Pencil of Nature. Much of Talbot’s later experimental work in photography was undertaken in Edinburgh.
In 1851, Talbot had been involved in early experiments with flash photography at the Royal Institution in London, and although the photographs from this do not apparently survive, he can be credited with the first images taken with electric flash. These experiments were based on ideas which he had discussed with John Herschel as early as 1833, well before the invention of photography. Subsequently, photography using artificial light was undertaken by means of magnesium wire or ribbon, first pioneered in Manchester. In March 1864, at a meeting of the Photographic Society of Scotland, some magnesium was made available, and letters and papers were read describing the new process: Chris Howe believes this was because of the intention of the Astronomer Royal for Scotland, Charles Piazzi Smyth, to go to Egypt later that year and photograph the inside as well as the outside of the Great Pyramid at Giza. However, present at the meeting were David Brewster, by now Principal of the University of Edinburgh, and his guest, Henry Talbot. A local photographer, John Moffat, persuaded the pair to be photographed by magnesium light, which is perhaps a fitting way to conclude this paper, with both protagonists tripping the light fantastic, almost to the end.
As ever, my thanks go to Dr Sara Stevenson for the ‘conspiracy’ of friendship which keeps those difficult questions coming; to Professor Larry Schaaf, who generously supplies Talbot facts on request; and to the Scottish Society of Photography committee which invited me to give this paper at the 2002 Conference, ‘The Artful Use of Light’, to celebrate the Bicentenary of the birth of D.O. Hill, forcing me to re-evaluate the background to early Scottish photography, thus generating much heat and light.
 There is a considerable literature concerning debates over the nature of light and optics during the early nineteenth century, See, in particular, Paul D. Sherman, Colour Vision in the Nineteenth Century: the Young-Helmholtz-Maxwell Theory (Bristol, 1981), and G.N. Cantor, Optics after Newton: Theories of Light in Britain and Ireland 1704-1840 (Manchester, 1983). These were both drawn upon by Alison Morrison-Low and Allen Simpson, ‘A New Dimension: a Context for Photography before 1860’, in Sara Stevenson (ed.), Light from the Dark Room: a Celebration of Scottish Photography, a Scottish-Canadian Collaboration (Edinburgh, 1995), pp.15-28.
 For Brewster’s role in early photography, see David Thomas, The First Negatives (London, 1964); A.D. Morrison-Low, ‘Dr John and Robert Adamson: An Early Photographic Partnership’, Photographic Collector, 4 (1983), pp. 199-214, updated as ‘Brewster, Talbot and the Adamsons: the Arrival of Photography in St Andrews’, History of Photography, 25 (2001), pp.130-141; A.D. Morrison-Low, ‘Sir David Brewster and Photography’, Review of Scottish Culture, 4 (1988), pp.63-73; Graham Smith, Disciples of Light: Photographs in the Brewster Album (Malibu, 1990). See also Sara Stevenson and A.D. Morrison-Low, Scottish Photography: the First Thirty Years (Edinburgh, 2015).
 Much of the background information concerning Talbot is derived from H.J.P. Arnold, William Henry Fox Talbot: Pioneer of Photography and Man of Science (London, 1977), still an excellent and readable biography despite being more then forty years old. Subsequent work, particularly by Larry Schaaf, especially his Out of the Shadows: Herschel, Talbot and the Invention of Photography (New Haven and London, 1992), contains much invaluable information as does M. Brusius et al. (eds.), William Henry Fox Talbot: Beyond Photography (New Haven and London, 2013).
 M.M. Gordon, The Home Life of Sir David Brewster (Edinburgh, 1869), pp.162-163.
 Ibid., Preface.
 Ibid., p.414; also A.D. Morrison-Low and J.R.R. Christie (eds.), ‘Martyr of Science’: Sir David Brewster 1781-1868 (Edinburgh, 1984), pp.82, 105; John Gifford, Highlands and Islands (The Buildings of Scotland) (Harmondsworth, 1992), p.81; http://portal.historicenvironment.scot/designation/LB1652 accessed 15 April 2020.
 John G. Burke, Origins of the Science of Crystals (Berkeley, 1966), pp. 108, 142-145.
 J.R.R. Christie, ‘Sir David Brewster as an Historian of Science’, in Morrison-Low and Christie, op. cit. (6), pp.53-56. The acclaimed 1980s biography was Richard S. Westfall, Never at Rest: A Biography of Sir Isaac Newton (Cambridge, 1980).
 Much of what follows comes from my entry for Brewster, David, in the Oxford Dictionary of National Biography published 2004; online at: http://www.oxforddnb.com/view/article/3371 accessed 15 April 2020.
 See ‘James Veitch of Inchbonny’ in T.N. Clarke, A.D. Morrison-Low and A.D.C. Simpson, Brass & Glass: Scientific Instrument Making Workshops in Scotland (Edinburgh, 1989), pp.16-24.
 See W.H. Brock, ‘Brewster as a Scientific Journalist’, in Morrison-Low and Christie, op. cit. (6), pp.37-42.
 Gordon, op. cit. (4), p.67.
 Ibid., p.77.
 A.D. Morrison-Low, ‘Brewster and Scientific Instruments’ in Morrison-Low and Christie, op. cit. (6), pp.59-65.
 George Duncan, ‘Brewster’s Contributions to the Study of the Lens of the Eye: an Experimental Foundation for Modern Biophysics’, in Morrison-Low and Christie, op. cit. (6), pp.101-103; Nicholas Wade (ed.), Brewster and Wheatstone on Vision (London, 1983).
 Gordon, op. cit. (4), p.97. See also A.D. Morrison-Low, ‘The Gentle Art of Persuasion: Advertising Instruments during Britain’s Industrial Revolution’, in A.D. Morrison-Low, Sara J. Schechner and Paolo Brenni (eds.), How Scientific Instruments have Changed Hands (Leiden, 2017), pp.43-56.
 Gordon, op. cit. (4), p.97.
 Arnold, op.cit (3), pp.17-96.
 Letter, Henry Talbot to Lady Elisabeth Feilding, 23 April 1818: Talbot Correspondence Project Doc no 795: British Library, London, Manuscripts – Fox Talbot Collection. My thanks to Larry Schaaf for this reference; see http://foxtalbot.dmu.ac.uk/letters/transcripts accessed 15 April 2020.
 Larry Schaaf tells me that John Herschel and Henry Talbot met each other for the first time in Munich in 1824: my thanks to him for this: and see Larry J. Schaaf, ‘The First Fifty Years of British Photography, 1794-1844’ in Michael Pritchard (ed.), Technology and Art: The Birth and Early Years of Photography (Bath, 1990), p.10.
 Henry Talbot, ‘Some experiments on coloured flames’, Edinburgh Journal of Science 5:1 (1826), pp.77-81.
 See Myles W. Jackson, Spectrum of Belief: Joseph von Fraunhofer and the Craft of Precision Optics (Cambridge, MA, 2000).
 J.A. Bennett, The Celebrated Phaenomena of Colours: the Early History of the Spectroscope (Cambridge, 1984), p.3.
 David Brewster, ‘Observations on the Lines of the Solar Spectrum …’, Transactions of the Royal Society of Edinburgh 12 (1834), pp.519-30, quote p.519.
 See Frank A.J.L. James, ‘The Creation of a Victorian Myth: The Historiography of Spectroscopy’, History of Science 23 (1985), pp.1-24.
 Brewster, op.cit. (24), quoted in Bennett, op.cit (23), p.3.
 Gordon, op.cit (4), p.161.
 Letter, Constance Talbot to Lady Elisabeth Feilding, [‘Monday’] 1836; now in London, The British Library, Archive of William Henry Fox Talbot and the Talbot Family: Add MS 88942/2/188: Letters to Lady Elisabeth Feilding, NTA: 32576. Previously LA38-58, also partly quoted in Arnold, op.cit. (3), p.80. My thanks to Larry Schaaf for this reference.
 H.F. Talbot, ‘Experiments on Light’, London and Edinburgh Philosophical Magazine and Journal of Science, third series, 5 (1834), pp.321-34. On the collection of Charles N. Bancker, see A.D.C. Simpson, ‘“La plus brilliante collection qui existe au monde”: a Lost American Collection of the Nineteenth Century’, Journal of the History of Collections, 7 (1995), pp.187-196; and for the item itself, see Morrison-Low and Simpson, op.cit (1), pp.20-21, and A.D.C. Simpson, ‘Talbot’s Photometer: or, Developments before Photography’, Studies in Photography, 1996, pp.8-10.
 Especially for his ‘On the Optical Phenomena of Certain Crystals’, published in the Philosophical Magazine, series 3, 9 (1836), pp.288-291, and subsequently by the Royal Society in their Philosophical Transactions (1837), pp.25-27; see Arnold, op.cit. (3), pp.75-76.
 The text of this dedication reads: ‘TO HENRY FOX TALBOT, Esq., F.R.S., &c. MY DEAR SIR, HAVING been requested to draw up a short and Popular Treatise on the MICROSCOPE, for the ENCYCLOPAEDIA BRITANNICA, I have endeavoured to give an account of the most important modern improvements upon that valuable instrument, and of the most interesting observations which have been recently made with it. I could have wished to have enriched it with some account of the very curious discoveries which you have made with the Polarizing microscope, and which I had the advantage of seeing when enjoying your hospitality at Lacock Abbey; but as these required to be illustrated with finely coloured drawings, I trust that you will speedily communicate them to the public in a separate form. In placing your name at the head of this little volume, I express very imperfectly the admiration which I feel for your scientific acquirements, and for the zeal with which you devote your fortune and talents to the noblest purposes to which they can be applied. I am, MY DEAR SIR, Ever most faithfully yours, D. BREWSTER, ALLERLY, Nov. 1837.’ My thanks to Dr R.H. Nuttall, who supplied me with this reference. There is, however, more to the history of the polarising microscope; and the role of the pioneering Scottish lapidary, William Nicol, was considerably downplayed by Brewster: see A.D. Morrison-Low, ‘William Nicol, FRSE, c.1771-1851: Lecturer, Scientist and Collector’, Book of the Old Edinburgh Club, new series, 2 (1992), pp.123-31.
 NMS.T.1936.90 and NMS.T.1936.91.c
 NMS.T.1936.114: discussed in Graham Smith, ‘Talbot and Amici: Early Paper Photography in Florence’, History of Photography, 15 (1991), pp.188-193.
 NMS.T.1936.103, 104, 105 (simple prisms); T.1936.106, 107 and 108 (Nicol prisms). The history and fate of much of Talbot’s apparatus is recounted in Larry J. Schaaf, ‘“Do not burn my history”: the physical evidence of Henry Fox Talbot’s creative mind’ in Bernard Finn (ed.), Presenting Pictures (London, 2004), pp.129-145. The provenance of the material now at the National Museums of Scotland (formerly the Royal Scottish Museum) is discussed by A.D. Morrison-Low, ‘Scientific Apparatus associated with Sir David Brewster’ in Morrison-Low and Christie, op. cit. (6), p.87; and A.D. Morrison-Low, Photography: A Victorian Sensation (Edinburgh, 2015), p.5.
 Gordon, op.cit. (4), pp.307-308.
 There is an extensive literature on the meeting of Hill and Adamson. This includes Thomas, op.cit (2); Morrison-Low, ‘Dr John and Robert Adamson’, op.cit.(2); and Stevenson and Morrison-Low, op.cit (2) pp.45-47. Also Sara Stevenson, David Octavius Hill and Robert Adamson: Catalogue of their Calotypes taken between 1843 and 1847 in the Collection of the Scottish National Portrait Gallery (Edinburgh, 1981); John Ward and Sara Stevenson, Printed Light: The Scientific Art of William Henry Fox Talbot and David Octavius Hill with Robert Adamson (Edinburgh, 1986); Sara Stevenson, Hill and Adamson: The Fishermen and Women of the Firth of Forth (Edinburgh, 1991); and Sara Stevenson, The Personal Art of D.O. Hill (New Haven and London, 2002).
 Text by Larry J. Schaaf, Catalogue Nine Sun Pictures: William Henry Fox Talbot, Friends and Relations [Hans P. Kraus, Jr.] (New York, 1999), pp.30-31; the positive image also reproduced by Andre Jammes, William H. Fox Talbot, Inventor of the Negative-Positive Process (New York, 1973), Plate 26.
 As Monica Thorp has pointed out to me, these were also family names, and perhaps I am stretching coincidence too far. For Talbot’s Sun Pictures in Scotland, see Graham Smith, ‘William Henry Fox Talbot’s Calotype Views of Loch Katrine’, Bulletin of the University of Michigan Museum of Art and Archaeology, 7 (1984-85), pp.49-77; Graham Smith, ‘H. Fox Talbot’s “Scotch Views” for Sun Pictures in Scotland (1845)’, in Patritzia di Bello, Colette Wilson and Shamoon Zamir (eds.), The Photobook: From Talbot to Ruscha and Beyond (London, 2012), pp.17-34; Stevenson and Morrison-Low, op.cit. (2), pp.99-100.
 Arnold, op.cit.(3), p.245; for Talbot in Edinburgh, see Monica Thorp, ‘William Henry Fox Talbot and the Edinburgh connection, 1855-1872’, Studies in Photography (2005), pp. 24-33.
 Her story is told briefly by one of her daughters, Matilda Talbot (formerly Gilchrist-Clark), My Life and Lacock Abbey (London, 1956). Miss Talbot gave large parts of her grandfather’s work – in order to ensure its survival – to the nation in 1936 and 1937: see Roger Taylor and Larry J. Schaaf, ‘The Talbot Collection at Bradford’, in Mike Weaver (ed.), Henry Fox Talbot: selected Texts and Bibliography (Oxford, 1992), pp.131-133; and see (34) above.
 Eugene Ostroff, ‘Photography and Photogravure: History of Photomechanical Reproduction’, Journal of Photographic Science, no 17 (1969), pp.101-115, abridged in Weaver, op.cit. (4), pp.125-130. See also Arthur Gill, ‘Fox Talbot’s photoglyphic engraving process’, History of Photography, 2 (1978), p.134; Larry J. Schaaf, Catalogue Twelve Sun Pictures: William Henry Fox Talbot and Photogravure [Hans P. Kraus, Jr.] (New York, 2003); and Larry J. Schaaf, ‘“The Caxton of Photography”: Talbot’s Etchings of Light’, in Brusius et al. (3), pp. 161-189.
 Chris Howe, To Photograph Darkness: the History of Underground and Flash Photography (Gloucester, 1989), p.266.
 Michael Hallett, ‘Early Magnesium Light Portraits’, History of Photography, 10 (1986), pp.299-301.
 Graham Smith, ‘Magnesium Light Portraits’, History of Photography, 12 (1988), pp.88-89; Howes, op.cit. (42), pp.18-47. For Charles Piazzi Smyth and photography, see Larry J. Schaaf, ‘Charles Piazzi Smyth’s 1865 Conquest of the Great Pyramid’, History of Photography, 3 (1979), pp. 331-354; Schaaf, ‘Piazzi Smyth at Tenerife: Part I , The Expedition and the Resulting Book’, ibid., 4 (1980), pp. 290-294; Schaaf, ‘Piazzi Smyth at Tenerife: Part 2 , Photography and the Disciples of Constable and Harding’, ibid., 5 (1981), pp.27-50; H.A. and M.T. Brück, The Peripatetic Astronomer: The Life of Charles Piazzi Smyth (Bristol and Philadelphia, 1988), pp.95-115; Stevenson and Morrison-Low, op.cit.(2), pp.149-151, 216-217, 253-255, 282-287, 301-302; and Sara Stevenson, ‘The Eyes’ Intelligence’, Studies in Photography (Winter 2019), pp.30-39.
 I had been particularly bothered by my title, which had come as inspiration months before the conference, when (as usual) a title and abstract were demanded. No dictionary of quotations revealed the source, until after the event, while turning this talk into a publishable text. It comes from no less an authority than John Milton’s L’Allegro:
Haste thee, nymph, and bring with thee
Jest and youthful Jollity …
Sport that wrinkled Care derides,
And laughter holding both his sides.
Come, and trip it as ye go
On the light fantastic toe.