by Brian Clegg
Quoted in the biography by Campbell and Garnett, Maxwell remarks that his decision to switch from a legal track was made to pursue ‘another kind of laws’. Most undergraduates content themselves with the work programme that the university sets, but Maxwell was already at his best when exploring on his own, continuing his early experiments with some remarkably sophisticated developments – something that comes across particularly in his work on stress and polarised light.
A particular light
Maxwell had been introduced to the topic of polarisation – a variation in the direction of oscillation of waves of light, which can be separated by special materials – while still at school. His mother’s older brother, John Cay, took Maxwell and Lewis Campbell to visit the optical expert William Nicol, who had found a way to produce polarised light at will.
The concept of polarisation dated back to 1669, when Danish natural philosopher Erasmus Bartholin had been the first to explain the workings of an odd crystal known as Iceland spar. This is a form of calcite – crystalline calcium carbonate. If you put a chunk of the transparent crystal on top of, say, a document, you see not one, but two copies of the writing, shifted with respect to each other. The phenomenon itself had been known for centuries – it has even been suggested that the Vikings may have used ‘sunstones’ with a piece of Iceland spar in them as a navigating device to estimate distances. But Bartholin’s insight was to realise that the crystal split two different forms of light that were both present in ordinary sunlight.
When at the start of the nineteenth century Thomas Young demonstrated that light was a wave that rippled from side to side as it moved forward (known as a lateral or transverse wave), the French physicist Augustin Fresnel realised that this provided an explanation for the special ability of Iceland spar. Light waves from a source such as the Sun would be oriented in all directions – some would be rippling side to side while others oscillated up and down – in fact the waving could take place in any direction at right angles to the direction of the light beam’s travel. If the crystal split apart waves rippling in different directions – the direction of the side-to-side ripple being described as its direction of polarisation – then the two images could be the result of the crystal separating rays with two different directions of polarisation.
When Maxwell’s uncle John Cay took him and his friend to visit William Nicol, they were shown prisms made from Iceland spar which had the effect of splitting off just one polarisation of light (for a time these optical devices were known as nicols, after their maker). This seems to have inspired Maxwell while he was at Edinburgh University, with polarised light soon becoming the prime focus of his spare-time experiments. It was known that when such light is passed through ordinary glass there is relatively little effect. However, if the same light is shone through unannealed glass, glass that has been heated until it is glowing and then cooled very quickly, the polarised light produces a coloured pattern, caused by the internal stresses in the glass.
Initially, Maxwell experimented with pieces of window glass, heating them to red heat then rapidly cooling them.‡‡‡ In a letter to Lewis Campbell he wrote:
I cut out triangles, squares, etc., with a diamond, about 8 or 9 of a kind, and take them to the kitchen, and put them on a piece of iron in the fire one by one. When the bit is red hot, I drop it into a plate of iron sparks [filings] to cool, and so on till all are done.
To produce polarised light, he made his own polarisers using a matchbox with pieces of glass set in it to produce reflections (reflected light is partially polarised); he also attempted to make polarisers from crystalline saltpetre (potassium nitrate). Maxwell made watercolour paintings of the brightly coloured patterns that he obtained in his heated and cooled window glass, some of which he sent to William Nicol, who was sufficiently impressed to send Maxwell a pair of his optically precise nicols, producing far better polarised light than Maxwell had been able to obtain with his do-it-yourself matchbox devices.
From an engineering viewpoint, getting an understanding of the stresses inside an object is essential to predict how it will stand up to strain when it is put in use. Maxwell had the insight to see that if, for example, a girder could be made of a transparent material, it would be possible to use polarised light to study the internal stresses as the girder begins to bear a load. Clearly this isn’t possible using an actual iron or steel girder – but if a model of it could be constructed in a suitable transparent material, it could be used to discover how stresses form in the structure and change under load, reducing the risk of structural collapse.
Unfortunately, glass doesn’t respond well to strain, and the clear plastics and resins that would later be used in this ‘photoelastic’ method that Maxwell devised, and which is still used by engineers, weren’t available at the time. Instead, with that same make-do-and-mend approach that had seen him attempt to use beetles as part of his electrical toolkit, he got hold of some gelatine from the Glenlair kitchen and used it to make clear jelly shapes. Maxwell was delighted to discover that his jellified models produced exactly the kinds of stress patterns he hoped for as he put them under strain.
The path to Cambridge
When not doing experiments, Maxwell would be working through numerous physical propositions or ‘props’ as he and his friends called them, often studying the most mundane of objects and trying to deduce something interesting from them. Sometimes these can seem a little bizarre. For example, in a letter written from Glenlair in October 1849 he noted: ‘I have got an observation of the latitude just now with a saucer of treacle, but it is very windy.’
As well as more practical work, Maxwell followed up his pin and string mathematical paper and other topics while still an undergraduate. His most outstanding attempt of the period was to derive a mathematical analysis of the stress patterns he had observed using his photoelastic technique. He confirmed these mathematical formulae, covering different basic 3D shapes such as cylinders and beams, as much as he was able with his experimental work. This was a remarkable achievement for someone with his very limited experience, but he was to discover that it wasn’t enough to perform careful experiments or to produce mathematics that successfully described them. It was also important that you could communicate your scientific findings effectively. He wrote up his work and asked Professor Forbes to present it to the Royal Society of Edinburgh.
Forbes may have been highly impressed with the younger Maxwell’s ventures into mathematics, but this new paper was more directly impinging on his own field, and Maxwell was now nearing adulthood. Forbes did not think much of his writing style in the paper, which was refereed by Maxwell’s mathematics lecturer, Philip Kelland. Forbes commented that Professor Kelland ‘complains of the great obscurity of several parts owing to the abrupt transitions and want of distinction between what is assumed and what is proved in various passages’.
Professor Forbes went on to say: ‘it must be useless to publish a paper for the use of scientific readers generally, the steps of which cannot, in many places, be followed by so expert an algebraist as Prof. Kelland; – if, indeed, they be steps at all …’ This kind of criticism could have been deadly for a beginner who took it personally, but it spurred Maxwell into studying the best of the period’s scientific writing, analysing the wording and structure to see what made it effective and incorporating what he discovered into his own style. While he never became one of the greats of science communication, after this his papers were usually lucid and well written.
There was something about Maxwell’s personality that made him able to adapt well to constructive criticism in this way. He seems to have had the ideal balance of freedom to experiment and try things out, with a network of peers who were prepared to point out his failings and help him overcome them. Like his scientific hero Michael Faraday, Maxwell never gave himself the airs and graces of some of their contemporaries such as Sir Humphry Davy in London or, in later years, Maxwell’s regular correspondent William Thomson, who would become Sir
William and then Lord Kelvin. Maxwell’s religious upbringing, his mixing with the country children on the estate and his down-to-earth humour seem to have protected him from ever having an over-inflated sense of his own importance.
Maxwell’s paper on the mathematics of the stresses observed in his photoelastic experiments was originally submitted to Professor Forbes in December 1849. After Forbes and Kelland’s feedback, Maxwell redrafted it in the spring of 1850 and the revised version, which had large chunks of the original omitted or reworded, appeared in the Transactions of the Royal Society of Edinburgh that year. It was a long piece of work running to 43 pages, which combined some of his own experimental observations with a much wider mathematical analysis.
Although Edinburgh allowed Maxwell considerable freedom in pushing forward his scientific thinking, it was still primarily seen as a track for him to achieve a degree on the way to a career in law. But as he wrote to Lewis Campbell on 22 March 1850:
I have notions of reading the whole of Corpus Juris and Pandects [for his studies of law] in no time at all; but these are getting somewhat dim, as the Cambridge scheme has been howked up from its repose in the regions of abortions, and is as far forward as an inspection of the Cambridge Calendar and a communication with Cantabs.§§§
Maxwell decided that after three years at Edinburgh University, before he had completed his degree, he needed a more thorough scientific and mathematical content to his studies and applied to Peterhouse college, Cambridge, where his friend Peter Tait was already resident. Such a move was not uncommon. Tait had left Edinburgh for Cambridge after just one year and another friend, Allan Stewart, after two years. This change of academic venue required Maxwell’s father’s support, which seems to have been given wholeheartedly. John Clerk Maxwell travelled down to Cambridge with his son on 18 October 1850, as the young scientist started on the next leg of his academic journey.
Notes
1 – The description of travel to the Maxwell estate is from Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 26.
2 – The idea that Maxwell’s father undertook scientific experiments is from Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 4.
3 – John Clerk Maxwell’s paper ‘Outline of a plan for combining machinery with the manual printing-press’ was published in The Edinburgh New Philosophical Journal, 10 (1831): 352–7.
4 – The assertion that the family of Mary Godwin (Shelley) was of ‘a very restricted income’ despite having a governess is from Kathryn Harkup, Making the Monster (London: Bloomsbury Sigma, 2018), p. 11.
5 – The ill treatment of Maxwell by his tutor is recorded in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 43.
6 – Maxwell’s early questions about how things worked are recorded in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 12.
7 – Maxwell’s arriving back with his tunic in rags after his first day is described in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 50.
8 – Descriptions of contemporary English public schools and their limited curricula are from David Turner, BBC History, ‘Georgian and Victorian public schools: Schools of hard knocks’, June 2015, available at https://www.historyextra.com/period/georgian/georgian-and-victorian-public-schools-schools-of-hard-knocks/
9 – Baden Powell’s concern that the higher classes were not gaining scientific knowledge is quoted in Pietro Corsi, Science and Religion: Baden Powell and the Anglican Debate, 1800–1860 (Cambridge: Cambridge University Press, 1988), p. 116.
10 – Maxwell’s first paper at the age of fourteen is in Proceedings of the Royal Society of Edinburgh, Vol. 2 (April 1846) and reproduced in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990) pp. 35–42.
11 – The description of Maxwell’s holiday activities at Glenlair is from Peter Tait, ‘James Clerk Maxwell: Obituary’, Proceedings of the Royal Society of Edinburgh, Vol. 10 (1878–80): 331–9.
12 – Maxwell’s letter to Lewis Campbell detailing his day at university, written from 31 Heriot Row, Edinburgh in November 1847 is reproduced in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990). p. 69.
13 – Maxwell’s maintenance of some odd behaviour at Edinburgh University is described in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 105.
14 – Maxwell’s letter to Lewis Campbell on both the barometer experiment and the devil with two sticks, written from Glenlair on 26 April 1848, is quoted in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 116.
15 – Maxwell’s letter to Lewis Campbell about his home lab, written on 5 July 1848, is in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990), p. 71.
16 – The paper ‘On the Theory of Rolling Curves’ was published in the Trans. Roy. Soc. Edinb., 16 (1849): 519–40 and is reproduced in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990), pp. 74–95.
17 – Maxwell’s change of subject to pursue ‘another kind of laws’ is noted in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 131.
18 – Maxwell’s description of heating shapes of window glass is from a letter to Lewis Campbell, written from Glenlair on 22 September 1848, reproduced in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990), pp. 96–8.
19 – Maxwell’s use of a saucer of treacle to ‘observe the latitude’ is mentioned in a letter to Lewis Campbell, quoted in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 126.
20 – Forbes’ criticism of Maxwell’s writing style is quoted in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990), p. 186.
21 – The draft with revisions of Maxwell’s paper ‘On the Equilibrium of Elastic Solids’ is reproduced in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990), pp. 133–83.
22 – Maxwell’s change of plans from law is from a letter to Lewis Campbell quoted in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 130.
* It’s the demon here – I’ll be handling the footnotes throughout the book. There is something decidedly demonic about footnotes. For those of you not familiar with the English system of titles, a baronet is the only hereditary title that does not make someone a lord – they’re a knight. If buying one sounds a little cheesy, bear in mind the whole idea was dreamed up by James I as a fundraiser.
† Penicuik House has been a shell since being destroyed by fire in 1899, but it was partly restored around 2014 and is now open to visitors.
‡ Strictly speaking, the Victorian era didn’t begin until Maxwell was six, but I am inclined to allow the author some leeway here.
§ In other words, ‘What makes it go?’
¶ Maxwell was not the first great physicist to be brought up in a house with airs and graces beyond its physical reality. Newton’s childhood home, the impressive-sounding Woolsthorpe Manor, was equally nothing more than a large farmhouse. It’s interesting to speculate whether the hands-on life of a farm provides an ideal encouragement to take an interest in the world around us.
|| Unlike the other houses Maxwell lived in throughout his working life, most of which remain in good condition, Glenlair is mostly a ruin since a fire in the 1920s, though the oldest part of the house remain
ed habitable and was renovated in the 1990s.
** This was a distinctly trendy simile from Maxwell’s contemporary at the Edinburgh Academy – Maxwell started school in 1842, only twelve years after the world’s first steam railway, the Liverpool and Manchester, was opened. Presumably, the railway then had the same fascination for schoolchildren as space travel has more recently.
†† Natural Philosophy was the generic term for science until the nineteenth century, as science originally simply meant a topic of knowledge – so, for instance, the favourite subject of us demons, theology, was known as the ‘queen of the sciences’. A practitioner of what we would now call science was known as a natural philosopher. As philosophy became an increasingly specific discipline, the label changed to natural sciences, a term still used by some of the older universities.
‡‡ There were none of your lazy internet searches back then, of course; this was a matter of physically sorting through books and journals. It’s worth thinking that without Maxwell’s work, we might not even have the internet today.
§§ This is typical of the humour of Maxwell’s circle: ‘rude’ here means ‘rough and ready’, but is used to get in a sly reference to Shakespeare, who has Puck speak of ‘rude mechanicals’ in A Midsummer Night’s Dream.
¶¶ Not as exciting as it sounds: nothing more exotic than jam jars.
|||| The bright blue chemical compound, copper sulfate.
*** Confusingly, since the name is reminiscent of the Latin for lead (plumbum), plumbago is in fact naturally occurring carbon – graphite. The ore was frequently confused for lead ore or galena as both are found as shiny black deposits – hence the way we still refer to the graphite in a pencil as its lead.