{{Short description|Scottish physicist and mathematician (1831–1879)}}
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{{Use British English|date=March 2026}}
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{{Infobox scientist
| name              = James Clerk Maxwell
| honorific_suffix  = {{post-nominals|size=100%|FRS|FRSE|country=GBR}}
| image             = James-Clerk-Maxwell-1831-1879.jpg
| caption           = Maxwell, {{circa|1870s}}
| birth_date        = {{birth date|df=yes|1831|6|13}}
| birth_place       = [[Edinburgh]], Scotland
| death_date        = {{death date and age|df=yes|1879|11|5|1831|6|13}}
| death_place       = [[Cambridge]], England
| resting_place     = [[Parton, Dumfries and Galloway]]
| resting_place_coordinates = {{coord|55.006693|-4.039210|type:landmark|display=inline}}
| education         = {{ubl|[[University of Edinburgh]]|[[Peterhouse, Cambridge]]|[[Trinity College, Cambridge]]}}
| known_for         = {{collapsible list|title={{nobold|''See list''}}|{{ubl|[[Maxwell's equations]]|[[Statistical mechanics]]|[[Displacement current]]|[[Maxwell relations]]|[[Betti's theorem|Maxwell–Betti theorem]]|[[Maxwell–Boltzmann distribution]]|[[Maxwell–Boltzmann statistics]]|[[Maxwell–Stefan diffusion]]|[[Maxwell's demon]]|[[Maxwell construction]]|[[Kinematic coupling#Maxwell coupling|Maxwell coupling]]|[[Kinetic theory of gases]]|[[Maxwell's discs]]|[[Maxwell speed distribution]]|[[Stress functions#Maxwell stress functions|Maxwell stress functions]]|[[Maxwell's theorem]]|[[Maxwell's theorem (geometry)]]|[[Maxwell material]]|[[von Mises yield criterion|Maxwell–Huber–Hencky–von Mises theory]]|[[Maxwell–Wagner–Sillars polarization]]|[[Maxwell bridge]]|[[Maxwell coil]]|[[Luneburg lens#Maxwell's fish-eye lens|Maxwell's fish-eye lens]]|[[Fovea centralis#Entoptic effects in the fovea|Maxwell's spot]]|[[Additive color|Maxwell's wheel]]|[[Maxwell's thermodynamic surface]]|[[Rings of Saturn]]|[[Control theory]]|[[Coherence (units of measurement)|Coherent system of units]]|[[Chaos theory]]|[[Dimensional analysis]]|[[Generalized conic]]|[[Singularity (system theory)|Singularity]]|[[Structural rigidity]]}}}}
| spouse            = {{marriage|[[Katherine Clerk Maxwell|Katherine Dewar]]|1858}}
| awards            = {{ubl|[[Smith's Prize]] (1854) |[[Adams Prize]] (1857) |[[Rumford Medal]] (1860)|[[Fellow of the Royal Society|FRS]] (1861)|[[Royal Society Bakerian Medal|Bakerian Medal]] (1866)|[[Keith Medal]] (1869–1871)}} [[The William Hopkins Prize]] (1870)
| fields            = [[Physics]]<br />[[Mathematics]]
| workplaces        = {{ubl|[[Marischal College]], [[University of Aberdeen]]|[[King's College, London]]|[[University of Cambridge]]}}
| academic_advisors = [[William Hopkins]]
| notable_students  = {{ubl|[[George Chrystal]]| [[Horace Lamb]]| [[John Henry Poynting]]}}
| module            = {{Infobox officeholder
| embed             = yes
| office            = Cavendish Professor of Physics
| order             = 1st
| term_start        = 1871
| term_end          = 1879
| successor         = [[John William Strutt, 3rd Baron Rayleigh|Lord Rayleigh]]
}}
| signature         = James Clerk Maxwell sig.svg
}}
'''James Clerk Maxwell''' {{Post-nominals|FRS|FRSE|country=GBR}} (13 June 1831&nbsp;– 5 November 1879) was a Scottish physicist and mathematician<ref>{{cite web|url=http://www-history.mcs.st-and.ac.uk/HistTopics/Knots_and_physics.html |title=Topology and Scottish mathematical physics |publisher=University of St Andrews |access-date=9 September 2013 |url-status=live |archive-url=https://web.archive.org/web/20130912050227/http://www-history.mcs.st-and.ac.uk/HistTopics/Knots_and_physics.html |archive-date=12 September 2013 }}</ref> who was responsible for the [[classical theory]] of [[electromagnetic radiation]], which was the first theory to describe electricity, [[magnetism]] and light as different manifestations of the same phenomenon. [[Maxwell's equations]] for electromagnetism achieved the [[Unification (physics)#Unification of magnetism, electricity, light and related radiation|second great unification in physics]],<ref>{{cite journal |doi=10.1109/6.123329 |author=Nahin, P.J. |journal=IEEE Spectrum |volume =29 |issue =3 |year=1992 |page=45 |title=Maxwell's grand unification|bibcode=1992IEEES..29c..45N |s2cid=28991366 }}</ref> where [[Unification of theories in physics#Unification of gravity on Earth with astronomical behaviors|the first one]] had been realised by [[Isaac Newton]]. Maxwell was also key in the creation of [[statistical mechanics]].

Maxwell graduated from [[Trinity College, Cambridge]], in 1854, where he earned distinction in mathematics and the [[Smith's Prize|Smith's Prize]]. He remained at Cambridge briefly, publishing early mathematical work and investigations into [[optics]], particularly the principles of colour combination and colour-blindness. He later held the Chair of Natural Philosophy at [[Marischal College]] in [[Aberdeen]], where he studied the [[rings of Saturn]] and correctly proposed that they were composed of numerous small particles,<ref>{{Cite journal |last=Bittanti |first=Sergio |date=2 December 2015 |title=James Clerk Maxwell, a precursor of system identification and control science |url=http://www.tandfonline.com/doi/full/10.1080/00207179.2015.1098783 |journal=International Journal of Control |language=en |volume=88 |issue=12 |pages=2427–2432 |bibcode=2015IJC....88.2427B |doi=10.1080/00207179.2015.1098783 |hdl=11311/983132 |issn=0020-7179 |hdl-access=free}}</ref> work that earned him the [[Adams Prize]] in 1859. During this time he married [[Katherine Clerk Maxwell|Katherine Mary Dewar]], who assisted him in his laboratory work. From 1860 to 1865, he served as the Professor of Natural Philosophy at [[King's College London|King's College London]], where he developed his theory of electromagnetic fields. His publication of "''[[A Dynamical Theory of the Electromagnetic Field]]''" in 1865 demonstrated that [[electric force|electric]] and [[magnetic field]]s travel through space as [[wave]]s moving at the [[speed of light]], proposing that light is an undulation in the same medium that is the cause of electric and magnetic phenomena.<ref name="ADTEF">{{cite journal|last=Maxwell |first=James Clerk |title=A dynamical theory of the electromagnetic field |url=http://upload.wikimedia.org/wikipedia/commons/1/19/A_Dynamical_Theory_of_the_Electromagnetic_Field.pdf |journal=Philosophical Transactions of the Royal Society of London |volume=155 |pages=459–512 |year=1865 |bibcode=1865RSPT..155..459M |doi=10.1098/rstl.1865.0008 |s2cid=186207827 |url-status=live |archive-url=https://web.archive.org/web/20110728140123/http://upload.wikimedia.org/wikipedia/commons/1/19/A_Dynamical_Theory_of_the_Electromagnetic_Field.pdf |archive-date=28 July 2011 }} (This article accompanied an 8 December 1864 presentation by Maxwell to the Royal Society. His statement that "light and magnetism are affections of the same substance" is at page 499.)</ref> His unification of light and electrical phenomena led to his prediction of the existence of [[Radio wave|radio waves]]. 

Maxwell was the first to derive the [[Maxwell–Boltzmann distribution]], a statistical means of describing aspects of the [[kinetic theory of gases]], which he worked on sporadically throughout his career.<ref name=":1">{{Cite web |last=Johnson |first=Kevin |title=Kinetic Theory of Gases |url=https://mathshistory.st-andrews.ac.uk/Projects/Johnson/chapter-6/ |access-date=7 November 2023 |website=Maths History |language=en}}</ref> He presented the first durable [[colour photograph]] in 1861, and showed that any colour can be produced with a mixture of any three primary colours, those being red, green, and blue, the basis for [[Color television|colour television]].<ref name=":5" /> He worked on analysing the rigidity of rod-and-joint frameworks ([[Truss|trusses]]) like those in many bridges. He devised modern [[dimensional analysis]] and helped to establish the [[Centimetre–gram–second system of units|CGS system]] of measurement. He was the first to recognize [[Chaos theory|chaos]], and the first to emphasize the [[butterfly effect]]. His 1863 paper ''On Governors'' serves as an important foundation for [[control theory]] and [[cybernetics]], and was also the earliest mathematical analysis on [[Control system|control systems]].<ref>{{Cite journal |last=Bittanti |first=Sergio |date=2 December 2015 |title=James Clerk Maxwell, a precursor of system identification and control science |url=http://www.tandfonline.com/doi/full/10.1080/00207179.2015.1098783 |journal=International Journal of Control |language=en |volume=88 |issue=12 |pages=2427–2432 |bibcode=2015IJC....88.2427B |doi=10.1080/00207179.2015.1098783 |hdl=11311/983132 |issn=0020-7179 |hdl-access=free}}</ref>{{Sfn|Mahon|2003|pp=2–3, 140}} In 1867, he proposed the thought experiment known as [[Maxwell's demon]], which challenges how information affects entropy in thermodynamics. In his seminal 1867 paper ''On the Dynamical Theory of Gases'' he introduced the [[Maxwell model]] for describing the behavior of a [[Viscoelasticity|viscoelastic]] material and originated the [[Relativistic heat conduction#Hyperbolic model (relativistic)|Maxwell-Cattaneo equation]] for describing the transport of heat in a medium.

In 1871, Maxwell returned to Cambridge as the first [[Cavendish Professor of Physics]], overseeing the construction of the [[Cavendish Laboratory]]. As a result of his work he is regarded as a founder of the modern field of [[electrical engineering]].<ref name=":5">{{Cite book |last1=Sarkar |first1=Tapan K. |author-link=Tapan Sarkar |last2=Salazar-Palma |first2=Magdalena|author2-link=Magdalena Salazar Palma |last3=Sengupta |first3=Dipak L. |chapter=James Clerk Maxwell: The Founder of Electrical Engineering |date=2010 |title=2010 Second Region 8 IEEE Conference on the History of Communications |pages=1–7 |doi=10.1109/HISTELCON.2010.5735323 |isbn=978-1-4244-7450-9 |s2cid=42295662 |via=IEEE}}</ref> His discoveries helped usher in the era of modern physics, laying the foundations for such fields as [[Theory of relativity|relativity]], also being the one to introduce the term into physics,<ref name=":2">{{Cite web |last=Everett |first=Francis |date=1 December 2006 |title=James Clerk Maxwell: a force for physics |url=https://physicsworld.com/a/james-clerk-maxwell-a-force-for-physics/ |access-date=7 November 2023 |website=Physics World |language=en-GB}}</ref> and [[quantum mechanics]].{{Sfn|Mahon|2003|p=2}}<ref>{{Cite journal |last1=Qadir |first1=Asghar |last2=Mason |first2=D. P. |date=2015 |title=Sesquicentennial of the presentation by James Clerk Maxwell of his paper "A Dynamical Theory of the Electromagnetic Field" to the Royal Society of London |journal=International Journal of Modern Physics: Conference Series |language=en |volume=38 |page=1560070 |doi=10.1142/S2010194515600708 |bibcode=2015IJMPS..3860070Q |issn=2010-1945|doi-access=free }}</ref>

==Life==
===Early life, 1831–1839===
[[File:James Clerk Maxwell's birthplace at 14 India Street.jpg|thumb|upright|Clerk Maxwell's birthplace at 14 India Street in Edinburgh is now the home of the [[James Clerk Maxwell Foundation]].]]

James Clerk Maxwell was born on 13 June 1831<ref>{{cite web|title=Early day motion 2048 |url=http://www.parliament.uk/edm/2005-06/2048 |access-date=22 April 2013 |publisher=UK Parliament |url-status=live |archive-url=https://web.archive.org/web/20130530165850/http://www.parliament.uk/edm/2005-06/2048 |archive-date=30 May 2013 }}</ref> at 14 India Street, [[Edinburgh]], to [[John Clerk Maxwell of Middlebie]], an advocate, and Frances Cay,<ref name="oxford_506">{{harvnb|Harman|2004|p=506}}</ref><ref name="Waterston">{{harvnb|Waterston|Macmillan Shearer|2006|page=633}}</ref> daughter of [[Robert Hodshon Cay]] and sister of [[John Cay]]. (His birthplace now houses a museum operated by the [[James Clerk Maxwell Foundation]].) His father was a man of comfortable means<ref>{{cite book|url=https://books.google.com/books?id=MwTNCEoGsfYC&pg=PA49 |page=49 |title=Energy and the Unexpected |last=Laidler |first=Keith James |publisher=Oxford University Press |year=2002 |isbn=978-0-19-852516-5 |url-status=live |archive-url=https://web.archive.org/web/20160424071517/https://books.google.com/books?id=MwTNCEoGsfYC&pg=PA49 |archive-date=24 April 2016 }}</ref> of the Clerk family of [[Penicuik]], holders of the [[baronetcy]] of [[Clerk baronets|Clerk of Penicuik]]. His father's brother was the [[Sir George Clerk, 6th Baronet|6th baronet]].<ref name="preface">{{cite book |chapter-url=https://books.google.com/books?id=Jrzq_7NhGRkC&pg=PR90BARONET |chapter=Preface |title=The Scientific Papers of James Clerk Maxwell |isbn=978-1-108-01225-6 |last1=Maxwell |first1=James Clerk |year=2011 |publisher=Cambridge University Press |access-date=5 September 2020 |archive-date=16 December 2020 |archive-url=https://web.archive.org/web/20201216132606/https://books.google.com/books?id=Jrzq_7NhGRkC&pg=PR90baronet |url-status=live }}</ref> He had been born "John Clerk", adding "Maxwell" to his own after he inherited (as an infant in 1793) the Middlebie estate, a  Maxwell property in [[Dumfriesshire]].<ref name="oxford_506"/> James was a first cousin of both the artist [[Jemima Blackburn]]<ref>{{cite web|url=http://www.scottish-places.info/scotgaz/people/famousfirst2374.html |title=Jemima Blackburn |publisher=Gazetteer for Scotland |access-date=27 August 2013 |url-status=live |archive-url=https://web.archive.org/web/20131112214008/http://www.scottish-places.info/scotgaz/people/famousfirst2374.html |archive-date=12 November 2013 }}</ref> (the daughter of his father's sister) and the civil engineer [[William Dyce Cay]] (the son of his mother's brother). Cay and Maxwell were close friends and Cay acted as his best man when Maxwell married.<ref>{{cite web|url=http://www.scottisharchitects.org.uk/architect_full.php?id=404238 |title=William Dyce Cay |work=scottisharchitects.org.uk |url-status=live |archive-url=https://web.archive.org/web/20150925234918/http://www.scottisharchitects.org.uk/architect_full.php?id=404238 |archive-date=25 September 2015 }}</ref>

Maxwell's parents met and married when they were well into their thirties;<ref>{{Cite book|title=James Clerk Maxwell: a biography|last=Tolstoy|first=Ivan|publisher=University of Chicago Press|year=1981|isbn=0-226-80785-1|location=Chicago|page=11|oclc=8688302}}</ref> his mother was nearly 40 when he was born. They had had one earlier child, a daughter named Elizabeth, who died in infancy.<ref>{{harvnb|Campbell|1882|p=1}}</ref>

When Maxwell was young his family moved to [[Glenlair House|Glenlair]], in Kirkcudbrightshire, which his parents had built on the estate which comprised {{convert|1500|acre|ha}}.<ref>{{harvnb|Mahon|2003|pp=186–187}}</ref> All indications suggest that Maxwell had maintained an unquenchable curiosity from an early age.<ref>{{Cite book|title=James Clerk Maxwell: a biography|last=Tolstoy|first=Ivan|publisher=University of Chicago Press|year=1981|isbn=0-226-80785-1|location=Chicago|page=13|oclc=8688302}}</ref> By the age of three, everything that moved, shone, or made a noise drew the question: "what's the go o' that?".<ref>{{harvnb|Mahon|2003|p=3}}</ref> In a passage added to a letter from his father to his sister-in-law Jane Cay in 1834, his mother described this innate sense of inquisitiveness:
{{Blockquote|He is a very happy man, and has improved much since the weather got moderate; he has great work with doors, locks, keys, etc., and "show me how it doos" is never out of his mouth. He also investigates the hidden course of streams and bell-wires, the way the water gets from the pond through the wall....<ref name="Campbell_p 27">{{harvnb|Campbell|1882|p=27}}</ref>}}

===Education, 1839–1847===
Recognising the boy's potential, Maxwell's mother Frances took responsibility for his early education, which in the [[Victorian times|Victorian era]] was largely the job of the woman of the house.<ref name=":0" /> At eight he could recite long passages of [[John Milton]] and the whole of the [[Psalm 119|119th psalm]] (176 verses). Indeed, his knowledge of [[Religious text|scripture]] was already detailed; he could give chapter and verse for almost any quotation from the Psalms. His mother was taken ill with [[abdominal cancer]] and, after an unsuccessful operation, died in December 1839 when he was eight years old. His education was then overseen by his father and his father's sister-in-law Jane, both of whom played pivotal roles in his life.<ref name=":0">{{Cite book|title=James Clerk Maxwell: a biography|last=Tolstoy|first=Ivan|publisher=University of Chicago Press|year=1981|isbn=0-226-80785-1|location=Chicago|pages=15–16|oclc=8688302}}</ref> His formal schooling began unsuccessfully under the guidance of a 16-year-old hired tutor. Little is known about the young man hired to instruct Maxwell, except that he treated the younger boy harshly, chiding him for being slow and wayward.<ref name=":0" /> The tutor was dismissed in November 1841. James' father took him to [[Robert Davidson (inventor)|Robert Davidson]]'s demonstration of electric propulsion and magnetic force on 12 February 1842, an experience with profound implications for the boy.<ref>Anthony F. Anderson (11 June 1981) [https://books.google.com/books?id=ONm4--sv5mcC&pg=PA712 Forces of Inspiration] {{Webarchive|url=https://web.archive.org/web/20211202072916/https://books.google.ca/books?lr=&id=ONm4--sv5mcC&pg=PA712 |date=2 December 2021 }}, [[The New Scientist]], pages 712,3 via [[Google Books]]</ref>

In 1841, at age ten, Maxwell was sent to the prestigious [[Edinburgh Academy]].<ref>{{harvnb|Campbell|1882|pp=19–21}}</ref> He lodged during term times at the house of his aunt Isabella. During this time his passion for drawing was encouraged by his older cousin Jemima.<ref name="mahon_p 12-14">{{harvnb|Mahon|2003|pp=12–14}}</ref> The young Maxwell, having been raised in isolation on his father's countryside estate, did not fit in well at school.<ref name="mahon_p 10">{{harvnb|Mahon|2003|p=10}}</ref> The first year had been full, obliging him to join the second year with classmates a year his senior.<ref name="mahon_p 10"/> His mannerisms and [[Galloway]] accent struck the other boys as rustic. Having arrived on his first day of school wearing a pair of homemade shoes and a tunic, he earned the unkind nickname of "[[wikt:daft|Daftie]]".<ref>{{harvnb|Mahon|2003|p=4}}</ref> He never seemed to resent the epithet, bearing it without complaint for many years.<ref>{{harvnb|Campbell|1882|pp=23–24}}</ref> Social isolation at the Academy ended when he met [[Lewis Campbell (classicist)|Lewis Campbell]] and [[Peter Guthrie Tait]], two boys of a similar age who were to become notable scholars later in life. They remained lifelong friends.<ref name="oxford_506"/>

Maxwell was fascinated by [[geometry]] at an early age, rediscovering the [[regular polyhedra]] before he received any formal instruction.<ref name="mahon_p 12-14"/> Despite his winning the school's scripture biography prize in his second year, his academic work remained unnoticed<ref name="mahon_p 12-14"/> until, at the age of 13, he won the school's mathematical medal and first prize for both English and poetry.<ref name="Campbell, p 43">{{harvnb|Campbell|1882|p=43}}</ref>

Maxwell's interests ranged far beyond the school syllabus and he did not pay particular attention to examination performance.<ref name="Campbell, p 43"/> He wrote his first [[scientific paper]] at the age of 14. In it, he described a mechanical means of drawing [[Curve|mathematical curves]] with a piece of twine, and the properties of [[ellipse]]s, [[Cartesian ovals]], and related curves with more than two [[Focus (geometry)|foci]]. The work,<ref name="oxford_506"/><ref name="gardner"/> of 1846, "On the description of oval curves and those having a plurality of foci"<ref>{{cite web |title=Key dates in the life of James Clerk Maxwell |url=http://www.clerkmaxwellfoundation.org/html/key_facts_about_maxwell.html |website=[[James Clerk Maxwell Foundation]] |publisher=www.clerkmaxwellfoundation.org/ |access-date=8 December 2023|archive-date=5 March 2020 |archive-url=https://web.archive.org/web/20200305045153/http://www.clerkmaxwellfoundation.org/html/key_facts_about_maxwell.html |url-status=live }}</ref> was presented to the [[Royal Society of Edinburgh]] by [[James David Forbes|James Forbes]], a professor of [[natural philosophy]] at the [[University of Edinburgh]],<ref name="oxford_506"/><ref name="gardner">{{harvnb|Gardner|2007|pp=46–49}}</ref> because Maxwell was deemed too young to present the work himself.<ref name="Mahon_2003_p_16">{{harvnb|Mahon|2003|p=16}}</ref> The work was not entirely original, since [[René Descartes]] had also examined the properties of such [[multifocal ellipse]]s in the 17th century, but Maxwell had simplified their construction.<ref name="Mahon_2003_p_16"/>

===University of Edinburgh, 1847–1850===
[[File:Edinburgh University 1827.jpg|thumb|Old College, University of Edinburgh]]

Maxwell left the Academy in 1847 at age 16 and began attending classes at the [[University of Edinburgh]].<ref name="Harman_p 662">{{harvnb|Harman|2004|p=662}}</ref> He had the opportunity to attend the [[University of Cambridge]], but decided, after his first term, to complete the full course of his undergraduate studies at Edinburgh. The academic staff of the university included some highly regarded names; his first-year tutors included [[Sir William Hamilton, 9th Baronet|Sir William Hamilton]], who lectured him on [[logic]] and [[metaphysics]], [[Philip Kelland]] on mathematics, and [[James David Forbes|James Forbes]] on [[natural philosophy]].<ref name="oxford_506"/> He did not find his classes demanding,<ref>{{harvnb|Tolstoy|1982|p=46}}</ref> and was, therefore, able to immerse himself in private study during free time at the university and particularly when back home at Glenlair.<ref>{{harvnb|Campbell|1882|p=64}}</ref> There he would experiment with improvised chemical, electric, and magnetic apparatus; however, his chief concerns regarded the properties of [[polarized light|polarised light]].<ref>{{harvnb|Mahon|2003|pp=30–31}}</ref> He constructed shaped blocks of [[gelatine]], subjected them to various [[stress (physics)|stresses]], and with a pair of [[Nicol prism|polarising prisms]] given to him by [[William Nicol (inventor)|William Nicol]], viewed the coloured fringes that had developed within the jelly.<ref>{{harvnb|Timoshenko|1983|p=58}}</ref> Through this practice he discovered [[photoelasticity]], which is a means of determining the stress distribution within physical structures.<ref>{{harvnb|Russo|1996|p=73}}</ref>

At age 18, Maxwell contributed two papers for the [[Royal Society of Edinburgh|Transactions of the Royal Society of Edinburgh]]. One of these, "On the Equilibrium of Elastic Solids", laid the foundation for an important discovery later in his life, which was the temporary [[double refraction]] produced in [[viscosity|viscous]] liquids by [[shear stress]].<ref>{{harvnb|Timoshenko|1983|pp=268–278}}</ref> His other paper was "Rolling Curves" and, just as with the paper "Oval Curves" that he had written at the Edinburgh Academy, he was again considered too young to stand at the rostrum to present it himself. The paper was delivered to the Royal Society by his tutor Kelland instead.<ref>{{harvnb|Glazebrook|1896|p=23}}</ref>

===University of Cambridge, 1850–1856===
[[File:YoungJamesClerkMaxwell.jpg|thumb|right|upright|A young Maxwell at [[Trinity College, Cambridge]], holding one of his [[colour wheel]]s]]

In October 1850, already an accomplished mathematician, Maxwell left Scotland for the [[University of Cambridge]]. He initially attended [[Peterhouse, Cambridge|Peterhouse]], but before the end of his first term transferred to [[Trinity College, Cambridge|Trinity]], where he believed it would be easier to obtain a [[fellow]]ship.<ref>{{harvnb|Glazebrook|1896|p=28}}</ref> At Trinity he was elected to the elite secret society known as the [[Cambridge Apostles]].<ref>{{harvnb|Glazebrook|1896|p=30}}</ref> Maxwell's intellectual understanding of his Christian faith and of science grew rapidly during his Cambridge years. He joined the "Apostles", an exclusive debating society of the intellectual elite, where through his essays he sought to work out this understanding.

{{blockquote|Now my great plan, which was conceived of old, ... is to let nothing be wilfully left unexamined. Nothing is to be holy ground consecrated to Stationary Faith, whether positive or negative. All fallow land is to be ploughed up and a regular system of rotation followed. ... Never hide anything, be it weed or no, nor seem to wish it hidden. ... Again I assert the Right of Trespass on any plot of Holy Ground which any man has set apart. ... Now I am convinced that no one but a Christian can actually purge his land of these holy spots. ... I do not say that no Christians have enclosed places of this sort. Many have a great deal, and every one has some. But there are extensive and important tracts in the territory of the Scoffer, the Pantheist, the Quietist, Formalist, Dogmatist, Sensualist, and the rest, which are openly and solemnly Tabooed. ..."

Christianity—that is, the religion of the Bible—is the only scheme or form of belief which disavows any possessions on such a tenure. Here alone all is free. You may fly to the ends of the world and find no God but the Author of Salvation. You may search the Scriptures and not find a text to stop you in your explorations. ...

The Old Testament and the Mosaic Law and Judaism are commonly supposed to be "Tabooed" by the orthodox. Sceptics pretend to have read them and have found certain witty objections ... which too many of the orthodox unread admit, and shut up the subject as haunted. But a Candle is coming to drive out all Ghosts and Bugbears. Let us follow the light.<ref name="MIT IAP Seminar">{{cite web|url=http://silas.psfc.mit.edu/maxwell |title=James Clerk Maxwell and the Christian Proposition |publisher=MIT IAP Seminar |access-date=13 October 2014 |url-status=live |archive-url=https://web.archive.org/web/20141025173206/http://silas.psfc.mit.edu/maxwell/ |archive-date=25 October 2014 }}</ref>}}

In the summer of his third year, Maxwell spent some time at the [[Otley, Suffolk|Suffolk]] home of the Rev. [[Charles Benjamin Tayler|C. B. Tayler]], the uncle of a classmate, G. W. H. Tayler. The love of God shown by the family impressed Maxwell, particularly after he was nursed back from ill health by the minister and his wife.<ref>{{harvnb|Campbell|1882|pp=[https://books.google.com/books?id=8_iS-4ec9wwC&pg=PA170 169–170]}}</ref>

On his return to Cambridge, Maxwell writes to his recent host a chatty and affectionate letter including the following testimony,<ref name="MIT IAP Seminar"/>

{{blockquote|... I have the capacity of being more wicked than any example that man could set me, and ... if I escape, it is only by God's grace helping me to get rid of myself, partially in science, more completely in society, —but not perfectly except by committing myself to God ...}}

In November 1851, Maxwell studied under [[William Hopkins]], whose success in nurturing mathematical genius had earned him the nickname of "[[Senior Wrangler (University of Cambridge)|senior wrangler]]-maker".<ref>{{harvnb|Warwick|2003|pp=84–85}}</ref>

In 1854, Maxwell graduated from Trinity with a degree in mathematics. He scored second highest in the final examination, coming behind [[Edward Routh]] and earning himself the title of Second Wrangler. He was later declared equal with Routh in the more exacting ordeal of the [[Smith's Prize]] examination.<ref name="Tolstoy_p 62">{{harvnb|Tolstoy|1982|p=62}}</ref> Immediately after earning his degree, Maxwell read his paper "On the Transformation of Surfaces by Bending" to the [[Cambridge Philosophical Society]].<ref>{{harvnb|Harman|1998|p=3}}</ref> This is one of the few purely mathematical papers he had written, demonstrating his growing stature as a mathematician.<ref>{{harvnb|Tolstoy|1982|p=61}}</ref> Maxwell decided to remain at Trinity after graduating and applied for a fellowship, which was a process that he could expect to take a couple of years.<ref name="Mahon_p 47-48">{{harvnb|Mahon|2003|pp=47–48}}</ref> Buoyed by his success as a research student, he would be free, apart from some tutoring and examining duties, to pursue scientific interests at his own leisure.<ref name="Mahon_p 47-48"/>

The nature and perception of colour was one such interest which he had begun at the University of Edinburgh while he was a student of Forbes.<ref name="Mahon_p 51">{{harvnb|Mahon|2003|p=51}}</ref> With the coloured [[spinning top]]s invented by Forbes, Maxwell was able to demonstrate that white light would result from a mixture of red, green, and blue light.<ref name="Mahon_p 51"/> His paper "Experiments on Colour" laid out the principles of colour combination and was presented to the Royal Society of Edinburgh in March 1855.<ref name="Tolstoy_p 64-65">{{harvnb|Tolstoy|1982|pp=64–65. The full title of Maxwell's paper was "Experiments on colour, as perceived by the eye, with remarks on colour-blindness".}}</ref> Maxwell was this time able to deliver it himself.<ref name="Tolstoy_p 64-65"/>

Maxwell was made a fellow of Trinity on 10 October 1855, sooner than was the norm,<ref name="Tolstoy_p 64-65"/> and was asked to prepare lectures on [[hydrostatics]] and [[optics]] and to set examination papers.<ref name="Glazebrook_p 43-46">{{harvnb|Glazebrook|1896|pp=43–46}}</ref> The following February he was urged by Forbes to apply for the newly vacant [[chair (academic)|Chair]] of Natural Philosophy at [[Marischal College]], [[Aberdeen]].<ref>{{cite web |title=James Clerk Maxwell |url=http://www.sciencemuseum.org.uk/onlinestuff/People/James%20Clerk%20Maxwell%20183179.aspx |access-date=22 April 2013 |publisher=The Science Museum, London |archive-url=https://web.archive.org/web/20130531131420/http://www.sciencemuseum.org.uk/onlinestuff/People/James%20Clerk%20Maxwell%20183179.aspx |archive-date=31 May 2013 }}</ref><ref name="Campbell p 126">{{harvnb|Campbell|1882|p=126}}</ref> His father assisted him in the task of preparing the necessary references, but died on 2 April at Glenlair before either knew the result of Maxwell's candidacy.<ref name="Campbell p 126"/> He accepted the professorship at Aberdeen, leaving Cambridge in November 1856.<ref name="Glazebrook_p 43-46"/>

===Marischal College, Aberdeen, 1856–1860===
[[File:Saturn HST 2004-03-22.jpg|thumb|Maxwell proved that the [[rings of Saturn]] were made of numerous small particles.]]
The 25-year-old Maxwell was a good 15 years younger than any other professor at Marischal. He engaged himself with his new responsibilities as head of a department, devising the syllabus and preparing lectures.<ref name="Mahon_p 69-71">{{harvnb|Mahon|2003|pp=69–71}}</ref> He committed himself to lecturing 15 hours a week, including a weekly ''[[pro bono]]'' lecture to the local working men's college.<ref name="Mahon_p 69-71"/> He lived in Aberdeen with his cousin [[William Dyce Cay]], a Scottish civil engineer, during the six months of the academic year and spent the summers at Glenlair, which he had inherited from his father.<ref name="preface"/>

Later, his former student described Maxwell as follows:
<blockquote>In the late 1850s shortly before 9 am any winter's morning you might well have seen the young James Clerk Maxwell, in his mid to late 20s, a man of middling height, with frame strongly knit, and a certain spring and elasticity in his gait; dressed for comfortable ease rather than elegance; a face expressive at once of sagacity and good humour, but overlaid with a deep shade of thoughtfulness; features boldly put pleasingly marked; eyes dark and glowing; hair and beard perfectly black, and forming a strong contrast to the pallor of his complexion.<ref>{{cite web |last1=Reid |first1=John S. |title=James Clerk Maxwell plaque – 129 Union Street |url=https://studylib.net/doc/18046724/james-clerk-maxwell-plaque-%E2%80%93-129-union-street |publisher=The Scientific Tourist: Aberdeen}}</ref></blockquote>

[[File:James Clark Maxwell and his wife by Jemima Blackburn.jpg|thumb|upright|James Clerk Maxwell and his wife, painted by [[Jemima Blackburn]]]]
He focused his attention on a problem that had eluded scientists for 200 years: the nature of [[Rings of Saturn|Saturn's rings]]. It was unknown how they could remain stable without breaking up, drifting away or crashing into Saturn.<ref>{{harvnb|Harman|1998|pp=48–53}}</ref> The problem took on a particular resonance at that time because [[St John's College, Cambridge]], had chosen it as the topic for the 1857 [[Adams Prize]].<ref name="oxford_508">{{harvnb|Harman|2004|p=508}}</ref> Maxwell devoted two years to studying the problem, proving that a regular solid ring could not be stable, while a fluid ring would be forced by wave action to break up into blobs. Since neither was observed, he concluded that the rings must be composed of numerous small particles he called "brick-bats", each independently orbiting Saturn.<ref name="oxford_508"/> Maxwell was awarded the £130 Adams Prize in 1859 for his essay "On the stability of the motion of Saturn's rings";<ref>{{cite web|url=https://archive.org/details/onstabilityofmot00maxw |title=On the stability of the motion of Saturn's rings |access-date=24 March 2014 |url-status=live |archive-url=https://web.archive.org/web/20150616221114/https://archive.org/details/onstabilityofmot00maxw |archive-date=16 June 2015 }}</ref> he was the only entrant to have made enough headway to submit an entry.<ref>{{harvnb|Mahon|2003|p=75}}</ref> His work was so detailed and convincing that when [[George Biddell Airy]] read it he commented, "It is one of the most remarkable applications of mathematics to physics that I have ever seen."<ref name="mactutor">{{cite web |last1=O'Connor |first1=J.J. |last2=Robertson |first2=E.F. |date=November 1997 |title=James Clerk Maxwell |url=https://mathshistory.st-andrews.ac.uk/Biographies/Maxwell/ |url-status=live |archive-url=https://web.archive.org/web/20211105081645/https://mathshistory.st-andrews.ac.uk/Biographies/Maxwell/ |archive-date=5 November 2021 |access-date=19 June 2021 |publisher=School of Mathematical and Computational Sciences University of St Andrews}}</ref> It was considered the final word on the issue until direct observations by the ''[[Voyager program|Voyager]]'' flybys of the 1980s confirmed Maxwell's prediction that the rings were composed of particles.<ref>{{cite web|url=http://digital.nls.uk/scientists/biographies/james-clerk-maxwell/index.html |title=James Clerk Maxwell (1831–1879) |publisher=National Library of Scotland |access-date=27 August 2013 |url-status=live |archive-url=https://web.archive.org/web/20131006063943/http://digital.nls.uk/scientists/biographies/james-clerk-maxwell/index.html |archive-date=6 October 2013 }}</ref>  It is now understood, however, that the rings' particles are not totally stable, being pulled by gravity onto Saturn.  The rings are expected to vanish entirely over the next 300 million years.<ref>{{cite web |url=https://earthsky.org/space/saturns-rings-disappearing-ring-rain-video |title=Goodbye to Saturn's Rings |date=19 December 2018 |publisher=EarthSky |access-date=20 February 2019 |archive-date=21 February 2019 |archive-url=https://web.archive.org/web/20190221113238/https://earthsky.org/space/saturns-rings-disappearing-ring-rain-video |url-status=live }}</ref>

In 1857 Maxwell befriended the Reverend [[Daniel Dewar]], who was then the Principal of Marischal.<ref>{{cite web |url=http://www.stanford.edu/group/auden/cgi-bin/auden/individual.php?pid=I20494&ged=auden-bicknell.ged |title=Very Rev. Daniel Dewar DD (I20494) |publisher=Stanford University |access-date=27 August 2013|archive-url=https://web.archive.org/web/20150518064846/http://www.stanford.edu/group/auden/cgi-bin/auden/individual.php?pid=I20494&ged=auden-bicknell.ged|archive-date=2015-05-18}}</ref> Through him Maxwell met Dewar's daughter, [[Katherine Clerk Maxwell|Katherine Mary Dewar]]. They were engaged in February 1858 and married in Aberdeen on 2 June 1858. On the marriage record, Maxwell is listed as Professor of Natural Philosophy in Marischal College, Aberdeen.<ref>James Clerk Maxwell and Katherine Mary Dewar marriage certificate, Family History Library film #280176, district 168/2 (Old Machar, Aberdeen), page 83, certificate No. 65.</ref> Katherine was seven years Maxwell's senior. Comparatively little is known of her, although it is known that she helped in his lab and worked on experiments in [[viscosity]].<ref>{{harvnb|Maxwell|2001|p=351}}</ref> Maxwell's biographer and friend, Lewis Campbell, adopted an uncharacteristic reticence on the subject of Katherine, though describing their married life as "one of unexampled devotion".<ref>{{harvnb|Tolstoy|1982|pp=88–91}}</ref>

In 1860 Marischal College merged with the neighbouring [[King's College, Aberdeen|King's College]] to form the [[University of Aberdeen]]. There was no room for two professors of Natural Philosophy, so Maxwell, despite his scientific reputation, found himself laid off. He was unsuccessful in applying for Forbes's recently vacated chair at Edinburgh, the post instead going to [[Peter Tait (physicist)|Tait]]. Maxwell was granted the Chair of Natural Philosophy at [[King's College, London]], instead.<ref name="Glazebrook_p 54">{{harvnb|Glazebrook|1896|p=54}}</ref> After recovering from a near-fatal bout of [[smallpox]] in 1860, he moved to London with his wife.<ref>{{harvnb|Tolstoy|1982|p=98}}</ref>

===King's College, London, 1860–1865===
[[File:Maxwell IEEE Plaque KCL.jpg|thumb|upright=1.3|Commemoration of Maxwell's equations at King's College. Two identical [[Institute of Electrical and Electronics Engineers|IEEE]] Milestone Plaques are at Maxwell's birthplace in Edinburgh and the family home at Glenlair.<ref>{{cite web|url=http://www.clerkmaxwellfoundation.org/JCMF_brochure_v2.pdf |title=James Clerk Maxwell Foundation |publisher=James Clerk Maxwell Foundation |access-date=28 May 2015 |url-status=live |archive-url=https://web.archive.org/web/20150819023911/http://clerkmaxwellfoundation.org/JCMF_brochure_v2.pdf |archive-date=19 August 2015 }}</ref>]]

Maxwell's time at King's was probably the most productive of his career. He was awarded the [[Royal Society|Royal Society's]] [[Rumford Medal]] in 1860 for his work on colour and was later elected to the Society in 1861.<ref name="Tolstoy_p 103-104">{{harvnb|Tolstoy|1982|p=103}}</ref> This period of his life would see him display the world's first light-fast colour photograph, further develop his ideas on the [[viscosity]] of gases, and propose a system of defining physical quantities—now known as [[dimensional analysis]]. Maxwell would often attend lectures at the [[Royal Institution]], where he came into regular contact with [[Michael Faraday]]. The relationship between the two men could not be described as close, because Faraday was 40&nbsp;years Maxwell's senior and showed signs of [[senility]]. They nevertheless maintained a strong respect for each other's talents.<ref>{{harvnb|Tolstoy|1982|pp=100–101}}</ref>

This time is especially noteworthy for the advances Maxwell made in the fields of electricity and magnetism. He examined the nature of both electric and magnetic fields in his two-part paper "[[On Physical Lines of Force]]", which was published in 1861. In it, he provided a conceptual model for [[electromagnetic induction]], consisting of tiny spinning cells of [[magnetic flux]]. Two more parts were later added to and published in that same paper in early 1862. In the first additional part, he discussed the nature of [[electrostatics]] and [[displacement current]]. In the second additional part, he dealt with the rotation of the plane of the [[Polarization (waves)|polarisation of light]] in a magnetic field, a phenomenon that had been discovered by Faraday and is now known as the [[Faraday effect]].<ref>{{harvnb|Mahon|2003|p=109}}</ref>

===Later years, 1865–1879===
In 1865 Maxwell resigned the chair at King's College, London, and returned to Glenlair with Katherine. In his paper "On governors" (1868) he mathematically described the behaviour of [[governor (device)|governors]]—devices that control the speed of steam engines—thereby establishing the theoretical basis of control engineering.<ref>Maxwell, J.C. (1868), "On governors", from the proceedings of the Royal Society, No. 100</ref> In his paper "On reciprocal figures, frames and diagrams of forces" (1870) he discussed the rigidity of various designs of lattice.<ref>{{cite journal|url=http://digital.nls.uk/scientists/pageturner.cfm?id=74629052 |doi=10.1017/S0080456800026351 |title=I.—On Reciprocal Figures, Frames, and Diagrams of Forces |year=2013 |last1=Maxwell |first1=J. Clerk |journal=Transactions of the Royal Society of Edinburgh |volume=26 |issue=1 |pages=1–40 |s2cid=123687168 |url-status=live |archive-url=https://web.archive.org/web/20140512223948/http://digital.nls.uk/scientists/pageturner.cfm?id=74629052 |archive-date=12 May 2014 }}</ref><ref>{{cite journal|url=http://www.iri.upc.edu/people/ros/StructuralTopology/ST1/st1-06-a3-ocr.pdf |title=Structural rigidity |last=Crapo |first=Henry |journal=Structural Topology |year=1979 |issue=1 |pages=26–45 |url-status=live |archive-url=https://web.archive.org/web/20141023180547/http://www.iri.upc.edu/people/ros/StructuralTopology/ST1/st1-06-a3-ocr.pdf |archive-date=23 October 2014 }}</ref> He wrote the textbook ''Theory of Heat'' (1871) and the treatise ''Matter and Motion'' (1876). Maxwell was also the first to make explicit use of [[dimensional analysis]], in 1871,<ref>{{cite book|url=https://archive.org/details/creativepowerofc0000lest |url-access=registration |pages=[https://archive.org/details/creativepowerofc0000lest/page/20 20]–21 |title=The Creative Power of Chance |publisher=University of Illinois Press |isbn=978-0-252-06686-3 |last=Lestienne |first=Rémy |year=1998 }}</ref><ref name=":2" /><ref name=":8">{{Cite journal |last=Bramwell |first=Steven T. |date=2 August 2017 |title=The invention of dimension |url=https://www.nature.com/articles/nphys4229 |journal=Nature Physics |language=en |volume=13 |issue=8 |page=820 |bibcode=2017NatPh..13..820B |doi=10.1038/nphys4229 |issn=1745-2481 |s2cid=125401842 |url-access=subscription}}</ref> and helped to establish the [[Centimetre–gram–second system of units|CGS system]] of measurement.<ref name=":7">{{Cite book |url=https://physics.nist.gov/cuu/pdf/sp330.pdf |title=The International System of Units (SI) |publisher=[[National Institute of Standards and Technology]] |editor-last=Taylor |editor-first=Barry N. |edition=7th |publication-date=2001 |page=2 |language=en}}</ref>

Maxwell has been credited as being the first to grasp the concept of [[Chaos theory|chaos]], as he acknowledged the significance of systems that exhibit "sensitive dependence on initial conditions."<ref name=":4">{{Cite journal |last1=Hunt |first1=Brian R. |last2=Yorke |first2=James A. |date=1993 |title=Maxwell on Chaos |url=https://yorke.umd.edu/Yorke_papers_most_cited_and_post2000/1993_04_Hunt_%20Nonlin-Science-Today%20_Maxwell%20on%20Chaos.PDF |url-status=dead |journal=Nonlinear Science Today |volume=3 |issue=1 |archive-url=https://web.archive.org/web/20231103150943/https://yorke.umd.edu/Yorke_papers_most_cited_and_post2000/1993_04_Hunt_%20Nonlin-Science-Today%20_Maxwell%20on%20Chaos.PDF |archive-date=3 November 2023 |access-date=3 November 2023}}</ref> He was also the first to emphasize the "[[butterfly effect]]" in the 1870s in two discussions.<ref name=":2" /><ref>{{Cite journal |last1=Gardini |first1=Laura |last2=Grebogi |first2=Celso |last3=Lenci |first3=Stefano |date=1 October 2020 |title=Chaos theory and applications: a retrospective on lessons learned and missed or new opportunities |journal=Nonlinear Dynamics |language=en |volume=102 |issue=2 |pages=643–644 |bibcode=2020NonDy.102..643G |doi=10.1007/s11071-020-05903-0 |issn=1573-269X |doi-access=free |hdl-access=free |hdl=2164/17003}}</ref>

In 1871 he returned to Cambridge to become the first [[Cavendish Professor of Physics]].<ref>{{cite web|url=http://www.phy.cam.ac.uk/history/cavprof.php |title=The Cavendish Professorship of Physics |publisher=University of Cambridge, Department of Physics |access-date=27 March 2013 |url-status=live |archive-url=https://web.archive.org/web/20130703172354/http://www.phy.cam.ac.uk/history/cavprof.php |archive-date=3 July 2013 }}</ref> Maxwell was put in charge of the development of the [[Cavendish Laboratory]], supervising every step in the progress of the building and of the purchase of the collection of apparatus.<ref>{{cite web|url=http://www.phy.cam.ac.uk/history/old_maxwell.php |title=The Old Cavendish – "The First Ten Years" |publisher=University of Cambridge Department of Physics |author=Moralee, Dennis |access-date=30 June 2013 |archive-url=https://web.archive.org/web/20130915013523/http://www.phy.cam.ac.uk/history/old_maxwell.php |archive-date=15 September 2013 }}</ref> One of Maxwell's last great contributions to science was the editing (with copious original notes) of the research of [[Henry Cavendish]], from which it appeared that Cavendish researched, amongst other things, such questions as the [[density]] of the Earth and the composition of water.<ref>{{cite book|url=https://books.google.com/books?id=46Rx1U5x70QC&pg=PA40 |page=40 |title=What's Who?: A Dictionary of Things Named After People and the People They are Named After |isbn=978-1-84876-047-9 |last=Jones |first=Roger |year=2009 |publisher=Troubador Publishing |url-status=live |archive-url=https://web.archive.org/web/20160520064247/https://books.google.com/books?id=46Rx1U5x70QC&pg=PA40 |archive-date=20 May 2016 }}</ref> He was elected as a member to the [[American Philosophical Society]] in 1876.<ref>{{Cite web|title=APS Member History|url=https://search.amphilsoc.org/memhist/search?creator=&title=&subject=&subdiv=&mem=&year=1875&year-max=&dead=&keyword=&smode=advanced|access-date=5 May 2021|website=search.amphilsoc.org|archive-date=5 May 2021|archive-url=https://web.archive.org/web/20210505132641/https://search.amphilsoc.org/memhist/search?creator=&title=&subject=&subdiv=&mem=&year=1875&year-max=&dead=&keyword=&smode=advanced|url-status=live}}</ref>

===Death===
[[File:JCM Grave-1.jpg|thumb|upright|The gravestone at Parton Kirk (Galloway) of James Clerk Maxwell, his parents and his wife]]
In April 1879 Maxwell began to have difficulty in swallowing, the first symptom of his fatal illness.<ref>{{cite book|author=Campbell, Lewis|title=The life of James Clerk Maxwell|location=London|publisher=Macmillan|page=411|year=1882|url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015059009939&view=1up&seq=453|access-date=1 February 2020|archive-date=21 March 2020|archive-url=https://web.archive.org/web/20200321182711/https://babel.hathitrust.org/cgi/pt?id=mdp.39015059009939&view=1up&seq=453|url-status=live}}</ref>

Maxwell died in Cambridge of abdominal cancer on 5 November 1879 at the age of 48.<ref name="Harman_p 662"/> His mother had died at the same age of the same type of cancer.<ref>{{cite web|url=http://www.clerkmaxwellfoundation.org/JCMF_brochure_v2.pdf |title=James Clerk Maxwell Foundation |access-date=30 June 2013 |url-status=live |archive-url=https://web.archive.org/web/20130827222612/http://clerkmaxwellfoundation.org/JCMF_brochure_v2.pdf |archive-date=27 August 2013 }}</ref> The minister who regularly visited him in his last weeks was astonished at his lucidity and the immense power and scope of his memory, but comments more particularly,

{{blockquote|... his illness drew out the whole heart and soul and spirit of the man: his firm and undoubting faith in the Incarnation and all its results; in the full sufficiency of the Atonement; in the work of the Holy Spirit. He had gauged and fathomed all the schemes and systems of philosophy, and had found them utterly empty and unsatisfying—"unworkable" was his own word about them—and he turned with simple faith to the Gospel of the Saviour.}}

As death approached Maxwell told a Cambridge colleague,<ref name="MIT IAP Seminar"/>

{{blockquote|I have been thinking how very gently I have always been dealt with. I have never had a violent shove all my life. The only desire which I can have is like David to serve my own generation by the will of God, and then fall asleep.}}

Maxwell is buried at [[Parton, Dumfries and Galloway|Parton]] Kirk, near [[Castle Douglas]] in Galloway close to where he grew up.<ref>{{cite web|url=http://www.clerkmaxwellfoundation.org/html/parton.html |title=Parton & Sam Callander |publisher=James Clerk Maxwell Foundation |access-date=30 June 2013 |url-status=live |archive-url=https://web.archive.org/web/20130602221421/http://www.clerkmaxwellfoundation.org/html/parton.html |archive-date=2 June 2013 }}</ref> The extended biography ''The Life of James Clerk Maxwell'', by his former schoolfellow and lifelong friend Professor [[Lewis Campbell (classicist)|Lewis Campbell]], was published in 1882.<ref>{{cite book|url=https://books.google.com/books?id=8_iS-4ec9wwC |title=The Life of James Clerk Maxwell: With a Selection from His Correspondence and Occasional Writings and a Sketch of His Contributions to Science |isbn=978-1-108-01370-3 |last=Campbell |first=Lewis |year=2010 |publisher=Cambridge University Press |url-status=live |archive-url=https://web.archive.org/web/20160529034539/https://books.google.com/books?id=8_iS-4ec9wwC |archive-date=29 May 2016 }}</ref><ref>{{Cite book|last=Campbell |first=Lewis |year=1882 |title=The Life of James Clerk Maxwell: With a Selection from His Correspondence and Occasional Writings and a Sketch of His Contributions to Science |publisher=Macmillan |place=London |edition=1 |url=https://archive.org/details/lifejamesclerkm01garngoog |access-date=16 June 2014 |url-status=live |archive-url=https://web.archive.org/web/20140905095353/https://archive.org/details/lifejamesclerkm01garngoog |archive-date=5 September 2014 }}</ref> His collected works were issued in two volumes by the [[Cambridge University Press]] in 1890.<ref>{{cite book|url=https://books.google.com/books?id=Jrzq_7NhGRkC |title=The Scientific Papers of James Clerk Maxwell |isbn=978-1-108-01225-6 |last1=Maxwell |first1=James Clerk |year=2011 |publisher=Cambridge University Press |url-status=live |archive-url=https://web.archive.org/web/20160502054439/https://books.google.com/books?id=Jrzq_7NhGRkC |archive-date=2 May 2016 }}</ref>

The executors of Maxwell's estate were his physician [[George Edward Paget]], [[G. G. Stokes]], and Colin Mackenzie, who was Maxwell's cousin. Overburdened with work, Stokes passed Maxwell's papers to [[William Garnett (professor)|William Garnett]], who had effective custody of the papers until about 1884.<ref>{{cite book|url = https://books.google.com/books?id=zfM8AAAAIAAJ&pg=PR18|title = The Scientific Letters and Papers of James Clerk Maxwell: 1846–1862|page = xviii|isbn = 978-0-521-25625-4|editor = Harman, P. M.|last1 = Maxwell|first1 = James Clerk|year = 1990| publisher=CUP Archive |access-date = 1 February 2020|archive-date = 12 March 2020|archive-url = https://web.archive.org/web/20200312120659/https://books.google.com/books?id=zfM8AAAAIAAJ&pg=PR18|url-status = live}}</ref>

There is a memorial inscription to him near the choir screen at [[Westminster Abbey]].<ref>'The Abbey Scientists' Hall, A.R. p58: London; Roger & Robert Nicholson; 1966</ref>

===Personal life===
[[File:James Clark Maxwell by Jemima Blackburn.jpg|thumb|upright|James Clerk Maxwell, painted by [[Jemima Blackburn]]]]
As a great lover of [[Scottish poetry]], Maxwell memorised poems and wrote his own.<ref>{{cite web|url=http://www.amphilsoc.org/sites/default/files/Seitz.pdf |title=James Clerk Maxwell (1831–1879); Member APS 1875 |last=Seitz |first=Frederick |publisher=[[The American Philosophical Society]] |access-date=20 May 2011 |location=Philadelphia |archive-url=https://web.archive.org/web/20111018052416/http://www.amphilsoc.org/sites/default/files/Seitz.pdf |archive-date=18 October 2011 }}</ref> The best known is ''Rigid Body Sings'', closely based on "[[Comin' Through the Rye]]" by [[Robert Burns]], which he apparently used to sing while accompanying himself on a guitar. It has the opening lines<ref>{{cite web|title=Rigid Body Sings |publisher=Haverford College |url=http://www.haverford.edu/physics-astro/songs/rigid.htm |access-date=26 March 2013 |url-status=live |archive-url=https://web.archive.org/web/20130404194532/http://www.haverford.edu/physics-astro/songs/rigid.htm |archive-date=4 April 2013 }}</ref>

{{poemquote|Gin a body meet a body
Flyin' through the air.
Gin a body hit a body,
Will it fly? And where?}}
A collection of his poems was published by his friend [[Lewis Campbell (classicist)|Lewis Campbell]] in 1882.<ref>{{cite web |url=https://tspace.library.utoronto.ca/html/1807/4350/poet400.html |title=Selected Poetry of James Clerk Maxwell (1831–1879) |publisher=University of Toronto Libraries |access-date=27 August 2013 |archive-date=7 May 2016 |archive-url=https://web.archive.org/web/20160507035146/https://tspace.library.utoronto.ca/html/1807/4350/poet400.html |url-status=live }}</ref>

Descriptions of Maxwell remark upon his remarkable intellectual qualities being matched by social awkwardness.<ref>{{cite book|url=https://books.google.com/books?id=w0o5Ld53wAEC&pg=PT88 |page=88 |title=The Power Makers: Steam, Electricity, and the Men Who Invented Modern America |isbn=978-1-59691-834-4 |last=Klein |first=Maury |year=2010 |publisher=Bloomsbury Publishing USA |url-status=live |archive-url=https://web.archive.org/web/20160508170756/https://books.google.com/books?id=w0o5Ld53wAEC&pg=PT88 |archive-date=8 May 2016 }}</ref>

Maxwell wrote the following aphorism for his own conduct as a scientist: <blockquote>He that would enjoy life and act with freedom must have the work of the day continually before his eyes. Not yesterday's work, lest he fall into despair, not to-morrow's, lest he become a visionary—not that which ends with the day, which is a worldly work, nor yet that only which remains to eternity, for by it he cannot shape his action. Happy is the man who can recognize in the work of to-day a connected portion of the work of life, and an embodiment of the work of eternity. The foundations of his confidence are unchangeable, for he has been made a partaker of Infinity. He strenuously works out his daily enterprises, because the present is given him for a possession.<ref>{{cite book|url=https://archive.org/details/lecturesontenbri00macfrich/page/12/mode/2up?view=theater |page=13 |title=Lectures on ten British physicists of the nineteenth century|isbn= |last=Macfarlane |first=Alexander |year=1919 |publisher=John Wiley, New York |url-status=live |archive-url=https://archive.org/details/lecturesontenbri00macfrich/page/12/mode/2up |archive-date=14 Dec 2006 }}</ref></blockquote>

Maxwell was an evangelical [[Presbyterianism|Presbyterian]] and in his later years became an [[Elder of the Church of Scotland|Elder]] of the [[Church of Scotland]].<ref name="The Aberdeen University Press">{{cite journal|year=1916 |journal=The Aberdeen University Review |publisher=The Aberdeen University Press |volume=III |url=https://archive.org/stream/aberdeenuniversi03univuoft/aberdeenuniversi03univuoft_djvu.txt |title=The Aberdeen university review |url-status=live |archive-url=https://web.archive.org/web/20120625055930/http://www.archive.org/stream/aberdeenuniversi03univuoft/aberdeenuniversi03univuoft_djvu.txt |archive-date=25 June 2012 }}</ref> Maxwell's religious beliefs and related activities have been the focus of a number of papers.<ref>{{cite web |url=http://www.asa3.org/ASA/PSCF/2004/PSCF9-04McNatt.pdf |title=James Clerk Maxwell's Refusal to Join the Victoria Institute |last1=Jerrold |first1=L. McNatt |date=3 September 2004 |publisher=American Scientific Affiliation |access-date=25 March 2013 |archive-url=https://web.archive.org/web/20120707132916/http://www.asa3.org/ASA/PSCF/2004/PSCF9-04McNatt.pdf |archive-date=7 July 2012 }}</ref><ref name="Rel00">{{cite journal |title=Maxwell and creation: Acceptance, criticism, and his anonymous publication |journal=American Journal of Physics |year=2007 |first=Philip L. |last=Marston |volume=75 |issue=8 |pages=731–740 |doi= 10.1119/1.2735631 |bibcode=2007AmJPh..75..731M }}</ref><ref name="Rel1">{{cite journal |last1=Theerman |first1=Paul |year=1986 |title=James Clerk Maxwell and religion |journal=American Journal of Physics |volume=54 |issue=4 |pages=312–317 |doi=10.1119/1.14636|bibcode = 1986AmJPh..54..312T }}</ref><ref>{{cite web |url=http://silas.psfc.mit.edu/maxwell/ |last=Hutchinson |first=Ian |title=James Clerk Maxwell and the Christian Proposition |orig-date=January 1998 |year=2006 |access-date=26 March 2013 |archive-url=https://web.archive.org/web/20121231001816/http://silas.psfc.mit.edu/maxwell/ |archive-date=31 December 2012 }}</ref> Attending both Church of Scotland (his father's denomination) and [[Scottish Episcopal Church|Episcopalian]] (his mother's denomination) services as a child, Maxwell underwent an [[Evangelicalism|evangelical]] conversion in April 1853.  One facet of this conversion may have aligned him with an [[Antipositivism|antipositivist]] position.<ref name="Rel1"/>

==Scientific legacy==
===Recognition===
In a survey of the 100 most prominent physicists conducted by ''[[Physics World]]'', Maxwell was voted the third greatest physicist of all time, behind only [[Isaac Newton]] and [[Albert Einstein]].<ref>{{cite news |date=29 November 1999 |title=Einstein the greatest |url=https://news.bbc.co.uk/2/hi/science/nature/541840.stm |url-status=live |archive-url=https://web.archive.org/web/20090111155707/http://news.bbc.co.uk/1/hi/sci/tech/541840.stm |archive-date=11 January 2009 |access-date=2 April 2010 |work=BBC News |publisher=BBC}}</ref> Another survey of rank-and-file physicists by ''PhysicsWeb'' also voted him third.<ref>{{Cite web |last= |first= |date=29 November 1999 |title=Newton tops PhysicsWeb poll |url=https://physicsworld.com/a/newton-tops-physicsweb-poll/ |access-date=23 November 2024 |website=Physics World |language=en-GB}}</ref>

Many physicists regard Maxwell as the 19th-century scientist having the greatest influence on 20th-century physics. His contributions to the science are considered by many to be of the same magnitude as those of Newton and Einstein.<ref>{{Cite book |last=Tolstoy |first=Ivan |title=James Clerk Maxwell: a biography |publisher=University of Chicago Press |year=1981 |isbn=0-226-80785-1 |location=Chicago |page=2 |oclc=8688302}}</ref> On the centenary of Maxwell's birthday, his work was described by Einstein as the "most profound and the most fruitful that physics has experienced since the time of Newton".<ref>{{cite web |last1=McFall |first1=Patrick |date=23 April 2006 |title=Brainy young James wasn't so daft after all |url=http://www.maxwellyear2006.org/html/press_coverage.html#Press5 |url-status=live |archive-url=https://web.archive.org/web/20130620031659/http://www.maxwellyear2006.org/html/press_coverage.html |archive-date=20 June 2013 |access-date=29 March 2013 |work=The Sunday Post |publisher=maxwellyear2006.org}}</ref> When Einstein visited the [[University of Cambridge]] in 1922, he was told by his host that he had done great things because he stood on Newton's shoulders; Einstein replied: "No I don't. I stand on the shoulders of Maxwell."<ref>Mary Shine Thompson, 2009, The Fire l' the Flint, p. 103; Four Courts</ref> Tom Siegfried described Maxwell as "one of those once-in-a-century geniuses who perceived the physical world with sharper senses than those around him".<ref>{{Cite book |last=Siegfried |first=Tom |url=https://archive.org/details/beautifulmathjoh0000sieg/page/134/mode/2up |title=A Beautiful Math: John Nash, Game Theory, and the Modern Quest for a Code of Nature |publisher=Joseph Henry Press |year=2006 |isbn=978-0-309-10192-9 |pages=135 |language=en}}</ref>

===Electromagnetism===
{{main|Maxwell's equations|Electromagnetism}}
[[File:Postcard-from-Maxwell-to-Tait.jpg|thumb|A postcard from Maxwell to [[Peter Guthrie Tait|Peter Tait]]]]
Maxwell had studied and commented on electricity and magnetism as early as 1855 when his paper "On Faraday's lines of force" was read to the [[Cambridge Philosophical Society]].<ref>{{cite web|url=https://www.scribd.com/doc/39568221/maxwell-on-faraday-s-lines-of-force |title=On Faraday's Lines of Force |last1=Maxwell |first1=James Clerk |year=1855 |work=Transactions of the Cambridge Philosophical Society |publisher=blazelabs.com |access-date=27 March 2013 |url-status=live |archive-url=https://web.archive.org/web/20140317170056/http://www.scribd.com/doc/39568221/maxwell-on-faraday-s-lines-of-force |archive-date=17 March 2014 }}</ref> The paper presented a simplified model of Faraday's work and how electricity and magnetism are related. He reduced all of the current knowledge into a linked set of [[differential equation]]s with 20 equations in 20 variables. This work was later published as "[[On Physical Lines of Force]]" in March 1861.<ref>{{cite web|url=http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx |title=1861: James Clerk Maxwell's greatest year |date=18 April 2011 |publisher=King's College London |access-date=28 March 2013 |url-status=live |archive-url=https://web.archive.org/web/20130622095747/http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx |archive-date=22 June 2013 }}</ref>

Around 1862, while lecturing at King's College, Maxwell calculated that the speed of propagation of an electromagnetic field is approximately that of the [[speed of light]]. He considered this to be more than just a coincidence, commenting, "We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena.<ref name="mactutor"/>

Working on the problem further, Maxwell showed that the [[Electromagnetic wave equation|equations]] predict the existence of waves of [[electromagnetic radiation|oscillating electric and magnetic fields]] that travel through empty space at a speed that could be predicted from simple electrical experiments; using the data available at the time, Maxwell obtained a velocity of {{convert|310740000|m/s}}.<ref>{{cite web |url=http://ecee.colorado.edu/~ecen3410/ECEN3410-FirstClass.pdf |title=ECEN3410 Electromagnetic Waves |publisher=University of Colorado |access-date=30 June 2013 |archive-url=https://web.archive.org/web/20140317170802/http://ecee.colorado.edu/~ecen3410/ECEN3410-FirstClass.pdf |archive-date=17 March 2014 }}</ref> In his 1865 paper "[[A Dynamical Theory of the Electromagnetic Field]]", Maxwell wrote, "The agreement of the results seems to show that light and magnetism are affections of the same substance, and that light is an electromagnetic disturbance propagated through the field according to electromagnetic laws".<ref name=ADTEF/>

His famous twenty equations, in their modern form of [[partial differential equation]]s, first appeared in fully developed form in his textbook ''[[A Treatise on Electricity and Magnetism]]'' in 1873.<ref>{{cite web|url=http://libraries.mit.edu/150books/2011/01/19/1873/ |title=Year 13 – 1873: A Treatise on Electricity and Magnetism by James Clerk Maxwell |publisher=MIT Libraries |access-date=30 June 2013 |url-status=live |archive-url=https://web.archive.org/web/20130707121529/http://libraries.mit.edu/150books/2011/01/19/1873/ |archive-date=7 July 2013 }}</ref> Most of this work was done by Maxwell at Glenlair during the period between holding his London post and his taking up the Cavendish chair.<ref name=mactutor/> [[Oliver Heaviside]] reduced the complexity of Maxwell's theory down to four [[partial differential equation]]s,<ref>{{Cite book|last=Nahin|first=Paul J.|url=https://books.google.com/books?id=e9wEntQmA0IC|title=Oliver Heaviside: The Life, Work, and Times of an Electrical Genius of the Victorian Age|date=13 November 2002|publisher=JHU Press|isbn=978-0-8018-6909-9|page=109|language=en|access-date=27 March 2020|archive-date=27 July 2020|archive-url=https://web.archive.org/web/20200727165123/https://books.google.com/books?id=e9wEntQmA0IC|url-status=live}}</ref> known now collectively as Maxwell's Laws or [[Maxwell's equations]]. Although potentials became much less popular in the nineteenth century,<ref>B.J. Hunt (1991) ''[[The Maxwellians]]'', pages 165,6, Cornell University Press 
{{ISBN|0801482348}}</ref> the use of scalar and vector potentials is now standard in the solution of Maxwell's equations.<ref>{{harvnb|Eyges|1972|p=section 11.6.}}</ref> His work achieved the [[Unification of theories in physics#Unification of magnetism, electricity, light and related radiation|second great unification in physics]].<ref name=":15">{{cite book |author=Klaus Mainzer |url=https://books.google.com/books?id=QekhAAAAQBAJ&pg=PA8 |title=Symmetries of Nature: A Handbook for Philosophy of Nature and Science |date=2 December 2013 |publisher=Walter de Gruyter |isbn=978-3-11-088693-1 |page=8}}</ref>

As Barrett and Grimes (1995) describe:<ref>{{harvnb|Barrett|Grimes|1995|pp=7–8}}</ref>
<blockquote>Maxwell expressed electromagnetism in the algebra of [[quaternions]] and made the electromagnetic potential the centerpiece of his theory. In 1881 Heaviside replaced the electromagnetic potential field by force fields as the centerpiece of electromagnetic theory. According to Heaviside, the electromagnetic potential field was arbitrary and needed to be "assassinated". (''sic'') A few years later there was a debate between Heaviside and [[Peter Guthrie Tait|[Peter Guthrie] Tate]] (''sic'') about the relative merits of [[vector analysis]] and [[quaternions]]. The result was the realization that there was no need for the greater physical insights provided by [[quaternions]] if the theory was purely local, and vector analysis became commonplace. </blockquote>

Maxwell was proved correct, and his quantitative connection between light and electromagnetism is considered one of the great accomplishments of 19th-century [[mathematical physics]].<ref>{{cite book|url=https://books.google.com/books?id=B6shu_hAiGkC&pg=PA86 |page=86 |title=Dot-Dash to Dot.Com: How Modern Telecommunications Evolved from the Telegraph to the Internet |isbn=978-1-4419-6760-2 |last=Wheen |first=Andrew |year=2010 |publisher=Springer |url-status=live |archive-url=https://web.archive.org/web/20160617122830/https://books.google.com/books?id=B6shu_hAiGkC&pg=PA86 |archive-date=17 June 2016 }}</ref>

Maxwell also introduced the concept of the ''electromagnetic field'' in comparison to force lines that Faraday described.<ref name="tef">{{cite web|url=http://www-history.mcs.st-and.ac.uk/Projects/Johnson/Chapters/Ch4_4.html |title=The Electromagnetic Field |publisher=University of St Andrews |access-date=30 June 2013 |author=Johnson, Kevin |date=May 2002 |archive-url=https://web.archive.org/web/20110827131533/http://www-history.mcs.st-and.ac.uk/Projects/Johnson/Chapters/Ch4_4.html |archive-date=27 August 2011 }}</ref> By understanding the propagation of electromagnetism as a field emitted by active particles, Maxwell could advance his work on light. At that time, Maxwell believed that the propagation of light required a medium for the waves, dubbed the [[luminiferous aether]].<ref name="tef"/> Over time, the existence of such a medium, permeating all space and yet apparently undetectable by mechanical means, proved impossible to reconcile with experiments such as the [[Michelson–Morley experiment]].<ref>{{Cite journal |last1=Michelson |first1=Albert Abraham |last2=Morley |first2=Edward Williams |title=On the Relative Motion of the Earth and the Luminiferous Ether |journal=American Journal of Science |volume=34 |year=1887 |pages=333–345 |doi=10.2475/ajs.s3-34.203.333 |issue=203 |url=https://zenodo.org/record/1450060 |bibcode=1887AmJS...34..333M |s2cid=124333204 |access-date=13 September 2019 |archive-date=1 August 2020 |archive-url=https://web.archive.org/web/20200801231624/https://zenodo.org/record/1450060 |url-status=live }}</ref> Moreover, it seemed to require an absolute [[frame of reference]] in which the equations were valid, with the distasteful result that the equations changed form for a moving observer. These difficulties inspired Albert Einstein to formulate the theory of [[special relativity]]; in the process, Einstein dispensed with the  luminiferous aether as "superfluous".<ref>{{cite web|url=http://www-history.mcs.st-and.ac.uk/Extras/Einstein_ether.html |title=Ether and the Theory of Relativity |last=Einstein |first=Albert |access-date=19 December 2013 |url-status=live |archive-url=https://web.archive.org/web/20131121211828/http://www-history.mcs.st-and.ac.uk/Extras/Einstein_ether.html |archive-date=21 November 2013 }}</ref>

Einstein acknowledged the groundbreaking work of Maxwell, stating that:<ref name=":3">{{Cite web |title=Who was James Clerk Maxwell? |url=https://clerkmaxwellfoundation.org/html/about_maxwell.html |access-date=24 December 2024 |website=clerkmaxwellfoundation.org}}</ref>{{blockquote|One scientific epoch ended and another began with James Clerk Maxwell.}}He also acknowledged the influence that his work had on his relativity theory:<ref name=":3" />{{blockquote|The special theory of relativity owes its origins to Maxwell's equations of the electromagnetic field.}}

===Colour vision===
[[File:Tartan Ribbon.jpg|thumb|First durable colour photographic image, demonstrated by Maxwell in an 1861 lecture]]

Along with most physicists of the time, Maxwell had a strong interest in psychology. Following in the steps of Isaac Newton and [[Thomas Young (scientist)|Thomas Young]], he was particularly interested in the study of [[colour vision]]. From 1855 to 1872, Maxwell published at intervals a series of investigations concerning the perception of colour, [[colour-blindness]], and colour theory, and was awarded the [[Rumford Medal]] for "On the Theory of Colour Vision".<ref>{{cite web|url=http://www-history.mcs.st-and.ac.uk/Projects/Johnson/Chapters/Ch4_2.html |title=Colour Vision |publisher=University of St Andrews |author=Johnson, Kevin |date=May 2012 |access-date=20 May 2013 |url-status=live |archive-url=https://web.archive.org/web/20121111044045/http://www-history.mcs.st-and.ac.uk/Projects/Johnson/Chapters/Ch4_2.html |archive-date=11 November 2012 }}</ref>

Newton had demonstrated, using prisms, that white light, such as [[sunlight]], is composed of a number of [[Spectral color|monochromatic components]] which could then be recombined into white light.<ref>{{cite book|last=Newton |first=Isaac |date=1704 |title=Opticks: or a treatise of the reflexions, refractions, inflexions and colours of light |url=https://archive.org/details/opticksortreatisnewt |location=London |publisher=Printed for Sam. Smith, and Benj. Walford, Printers to the Royal Society, at the Prince's Arms in St. Paul's Church-yard |url-status=live |archive-url=https://web.archive.org/web/20151224071454/https://archive.org/details/opticksortreatisnewt |archive-date=24 December 2015 }}</ref> Newton also showed that an orange paint made of yellow and red could look exactly like a monochromatic orange light, although being composed of two monochromatic yellow and red lights. Hence the paradox that puzzled physicists of the time: two complex lights (composed of more than one monochromatic light) could look alike but be physically different, called ''[[Metamerism (color)|metameres]]''. Thomas Young later proposed that this paradox could be explained by colours being perceived through a limited number of channels in the eyes, which he proposed to be threefold,<ref>{{cite journal|last=Young |first=Thomas |title=Bakerian Lecture: Experiments and calculations relative to physical optics |journal=Philosophical Transactions of the Royal Society |year=1804 |volume=94 |pages=1–16 |url=https://books.google.com/books?id=7AZGAAAAMAAJ&pg=PA1 |bibcode=1804RSPT...94....1Y |doi=10.1098/rstl.1804.0001 |s2cid=110408369 |url-status=live |archive-url=https://web.archive.org/web/20160427130034/https://books.google.com/books?id=7AZGAAAAMAAJ&pg=PA1 |archive-date=27 April 2016 |doi-access=free }}</ref> the ''[[Young–Helmholtz theory|trichromatic colour theory]]''. Maxwell used the recently developed [[linear algebra]] to prove Young's theory. Any monochromatic light stimulating three receptors should be able to be equally stimulated by a set of three different monochromatic lights (in fact, by any set of three different lights). He demonstrated that to be the case,<ref>{{cite journal |last=Maxwell |first=James Clerk |date=1857 |title=XVIII.—Experiments on Colour, as perceived by the Eye, with Remarks on Colour-Blindness |journal=Transactions of the Royal Society of Edinburgh |publisher=Royal Society of Edinburgh |volume=21 |issue=2 |pages=275–298 |doi=10.1017/S0080456800032117 |s2cid=123930770 |url=https://zenodo.org/record/2041790 |access-date=10 March 2020 |archive-date=1 August 2020 |archive-url=https://web.archive.org/web/20200801221025/https://zenodo.org/record/2041790 |url-status=live }}</ref> inventing colour matching experiments and [[Colourimetry]].

Maxwell was also interested in applying his theory of colour perception, namely in [[colour photography]]. Stemming directly from his psychological work on colour perception: if a sum of any three lights could reproduce any perceivable colour, then colour photographs could be produced with a set of three coloured filters. In the course of his 1855 paper, Maxwell proposed that, if three black-and-white photographs of a scene were taken through [[RGB color model|red, green, and blue]] [[filter (optics)|filters]], and transparent prints of the images were projected onto a screen using three projectors equipped with similar filters, when superimposed on the screen the result would be perceived by the human eye as a complete reproduction of all the colours in the scene.<ref>{{cite journal |last1=Maxwell |first1=James Clerk |year=1855 |title=Experiments on Colour, as Perceived by the Eye, with Remarks on Colour-Blindness |journal=Transactions of the Royal Society of Edinburgh |volume=21 |issue=2 |pages=275–298 |doi=10.1017/S0080456800032117 |s2cid=123930770 |url=https://zenodo.org/record/2041790 |access-date=10 March 2020 |archive-date=1 August 2020 |archive-url=https://web.archive.org/web/20200801221025/https://zenodo.org/record/2041790 |url-status=live }} (This thought-experiment is described on pages 283–284. The short-wavelength filter is specified as "violet", but during the 19th century "violet" could be used to describe a deep violet-blue such as the colour of cobalt glass.)</ref>

During an 1861 Royal Institution lecture on colour theory, Maxwell presented the world's first demonstration of colour photography by this principle of three-colour analysis and synthesis. [[Thomas Sutton (photographer)|Thomas Sutton]], inventor of the [[single-lens reflex camera]], took the picture. He photographed a [[tartan]] ribbon three times, through red, green, and blue filters, also making a fourth photograph through a yellow filter, which, according to Maxwell's account, was not used in the demonstration. Because Sutton's [[photographic plate]]s were insensitive to red and barely sensitive to green, the results of this pioneering experiment were far from perfect. It was remarked in the published account of the lecture that "if the red and green images had been as fully photographed as the blue", it "would have been a truly-coloured image of the riband. By finding photographic materials more sensitive to the less refrangible rays, the representation of the colours of objects might be greatly improved."<ref name="Tolstoy_p 103-104"/><ref>{{cite book|chapter-url=http://notesonphotographs.org/index.php?title=Maxwell,_J._Clerk._%22On_the_Theory_of_Three_Primary_Colours.%22|author=Maxwell, J. Clerk|chapter=On the Theory of Three Primary Colours|pages=445–450|year=2011|orig-date=1890|title=The Scientific Papers of James Clerk Maxwell|volume=1|publisher=Cambridge University Press|isbn=978-0-511-69809-5|access-date=28 March 2013|archive-url=https://web.archive.org/web/20110823104203/http://notesonphotographs.org/index.php?title=Maxwell%2C_J._Clerk._%22On_the_Theory_of_Three_Primary_Colours.%22|archive-date=23 August 2011}}</ref><ref>{{cite journal|url=http://notesonphotographs.org/index.php?title=%22The_Theory_of_the_Primary_Colours.%22_The_British_Journal_of_Photography,_August_9,_1861|title=The Theory of the Primary Colours|journal=The British Journal of Photography|author=Maxwell, J. Clerk|year=1861|access-date=28 March 2013|archive-url=https://web.archive.org/web/20130612071037/http://notesonphotographs.org/index.php?title=%22The_Theory_of_the_Primary_Colours.%22_The_British_Journal_of_Photography,_August_9,_1861|archive-date=12 June 2013}}</ref> Researchers in 1961 concluded that the seemingly impossible partial success of the red-filtered exposure was due to [[ultraviolet]] light, which is strongly reflected by some red dyes, not entirely blocked by the red filter used, and within the range of sensitivity of the [[Collodion process|wet collodion process]] Sutton employed.<ref>{{cite journal |last1=Evans |first1=R. |date=November 1961 |title=Maxwell's Color Photography |journal=Scientific American |volume=205 |issue= 5|pages=117–128 |doi=10.1038/scientificamerican1161-118|bibcode=1961SciAm.205e.118E }}</ref>

===Kinetic theory and thermodynamics===
{{main|Maxwell–Boltzmann distribution}}

[[File:Maxwell's demon.svg|thumb|right|[[Maxwell's demon]], a thought experiment where entropy decreases]]
Maxwell also investigated the [[kinetic theory of gases|kinetic theory]] of gases. He was key in the creation of statistical mechanics.<ref name=":9">{{Cite book |last=Keithley |first=Joseph F. |url=https://books.google.com/books?id=uwgNAtqSHuQC&pg=PA180 |title=The Story of Electrical and Magnetic Measurements: From 500 BC to the 1940s |date=1999 |publisher=IEEE Press |isbn=978-0-7803-1193-0 |location=New York |page=180}}</ref>{{Sfn|Mahon|2003|pp=82–83, 164}} Originating with [[Daniel Bernoulli]], this theory was advanced by the successive labours of [[John Herapath]], [[John James Waterston]], [[James Prescott Joule|James Joule]], and particularly [[Rudolf Clausius]], to such an extent as to put its general accuracy beyond a doubt; but it received enormous development from Maxwell, who in this field appeared as an experimenter (on the laws of gaseous friction) as well as a mathematician.<ref>{{cite web|url=http://www.theiet.org/resources/library/archives/biographies/maxwell.cfm |title=Archives Biographies: James Clerk Maxwell |publisher=The Institution of Engineering and Technology |access-date=1 July 2013 |url-status=live |archive-url=https://web.archive.org/web/20130627090441/http://www.theiet.org/resources/library/archives/biographies/maxwell.cfm |archive-date=27 June 2013 }}</ref>

Between 1859 and 1866, he developed the theory of the distributions of velocities in particles of a gas, work later generalised by [[Ludwig Boltzmann]].<ref>{{cite web|url=http://users.ece.gatech.edu/~alan/ECE6451/Lectures/StudentLectures/Hill_5p4_MaxwellBoltzmannDistribution.pdf |title=The Maxwell–Boltzmann distribution |publisher=Georgia Institute of Technology |last=Hill |first=Melanie |access-date=28 August 2013 |url-status=live |archive-url=https://web.archive.org/web/20140103232904/http://users.ece.gatech.edu/~alan/ECE6451/Lectures/StudentLectures/Hill_5p4_MaxwellBoltzmannDistribution.pdf |archive-date=3 January 2014 }}</ref><ref>{{cite book|url=https://books.google.com/books?id=DWRkfjIFdOIC&pg=PA51 |page=51 |title=The Corresponding-States Principle and its Practice: Thermodynamic, Transport and Surface Properties of Fluids |isbn=978-0-08-045904-2 |last1=Xiang |first1=Hong Wei |year=2005 |publisher=Elsevier |url-status=live |archive-url=https://web.archive.org/web/20160512213205/https://books.google.com/books?id=DWRkfjIFdOIC&pg=PA51 |archive-date=12 May 2016 }}</ref> The formula, called the [[Maxwell–Boltzmann distribution]], gives the fraction of gas molecules moving at a specified velocity at any given temperature. In the [[kinetic theory of gases|kinetic theory]], temperatures and heat involve only molecular movement. This approach generalised the previously established laws of thermodynamics and explained existing observations and experiments in a better way than had been achieved previously. His work on [[thermodynamics]] led him to devise the [[thought experiment]] that came to be known as [[Maxwell's demon]], where the [[second law of thermodynamics]] is violated by an imaginary being capable of sorting particles by energy.<ref>{{cite news|last1=Merali|first1=Zeeya|title=Demonic device converts information to energy|url=http://www.nature.com/news/2010/101114/full/news.2010.606.html|work=Nature News|date=14 November 2010|language=en|doi=10.1038/news.2010.606|access-date=5 August 2017|archive-date=19 August 2017|archive-url=https://web.archive.org/web/20170819040059/http://www.nature.com/news/2010/101114/full/news.2010.606.html|url-status=live}}</ref><ref name=":10">{{Cite book |last1=Hemmo |first1=Meir |url=https://academic.oup.com/edited-volume/42642/chapter/358144458 |title=Maxwell's Demon |last2=Shenker |first2=Orly |date=7 March 2016 |publisher=Oxford University Press |doi=10.1093/oxfordhb/9780199935314.013.63}}</ref>

In 1871, he established [[Maxwell relations|Maxwell's thermodynamic relations]], which are statements of equality among the second derivatives of the [[thermodynamic potentials]] with respect to different thermodynamic variables. In 1874, he constructed a [[Maxwell's thermodynamic surface|plaster thermodynamic visualisation]] as a way of exploring phase transitions, based on the American scientist [[Josiah Willard Gibbs]]'s graphical [[thermodynamics]] papers.<ref>{{cite journal |author=West, Thomas G. |title=Images and reversals: James Clerk Maxwell, working in wet clay |journal=ACM SIGGRAPH Computer Graphics |url=http://www.siggraph.org/publications/newsletter/v33n1/columns/west.html |volume=33 |issue=1 |date=February 1999 |pages=15–17 |doi=10.1145/563666.563671 |s2cid=13968486 |access-date=1 July 2013 |archive-date=19 April 2021 |archive-url=https://web.archive.org/web/20210419091357/http://www.siggraph.org/publications/newsletter/v33n1/columns/west.html |url-status=live }}</ref><ref>{{cite book|url=https://books.google.com/books?id=UqbxZpELwHYC |page=118 |title=Great Physicists: The Life and Times of Leading Physicists from Galileo to Hawking |isbn=978-0-19-517324-6 |last=Cropper |first=William H. |publisher=Oxford University Press |year=2004 |url-status=live |archive-url=https://web.archive.org/web/20161203175602/https://books.google.com/books?id=UqbxZpELwHYC |archive-date=3 December 2016 }}</ref>

In his 1867 paper ''On the Dynamical Theory of Gases'' he introduced the [[Maxwell model]] for describing the behavior of a [[Viscoelasticity|viscoelastic]] material and originated the [[Relativistic heat conduction#Hyperbolic model (relativistic)|Maxwell-Cattaneo equation]] for describing the transport of heat in a medium.<ref name=":6">{{Cite web |last1=Christov |first1=Ivan C. |last2=Jordan |first2=Pedro M. |date=21 September 2015 |title=Maxwell's "other" equations |url=https://royalsociety.org/blog/2015/09/maxwells-other-equations/ |access-date=2 March 2025 |website=royalsociety.org |language=en}}</ref>

[[Peter Guthrie Tait]] called Maxwell the "leading molecular scientist" of his time.<ref name=":1" /> Another person added after Maxwell's death that "only one man lived who could understand Gibbs's papers. That was Maxwell, and now he is dead."<ref>{{Cite book |last=Rukeyser |first=Muriel |url=https://archive.org/details/willardgibbs0000muri/page/n4/mode/1up |title=Willard Gibbs |publisher=[[Doubleday (publisher)|Doubleday]] |year=1942 |page=251 |language=en}}</ref>

===Control theory===
{{main|Control theory}}

Maxwell published the paper "On governors" in the ''Proceedings of the Royal Society'', vol. 16 (1867–1868).<ref name="Maxwell1867">{{cite journal |author=Maxwell, James Clerk |year=1868 |title=On Governors |journal=Proceedings of the Royal Society of London |volume=16 |pages=270–283 |doi=10.1098/rspl.1867.0055 |jstor=112510|doi-access=free }}</ref> This paper is considered a central paper of the early days of [[control theory]].<ref>{{cite journal |last=Mayr |first=Otto | author-link= Otto Mayr |title=Maxwell and the Origins of Cybernetics |journal=Isis |volume=62 |issue=4 |year=1971 |pages=424–444 |doi=10.1086/350788|s2cid=144250314 }}</ref> Here "governors" refers to the [[governor (device)|governor]] or the [[centrifugal governor]] used to regulate [[steam engine]]s.

==Honours==
[[File:James Clerk Maxwell statue in George Street, Edinburgh.jpg|thumb|upright|The James Clerk Maxwell Monument in Edinburgh, by [[Alexander Stoddart]]. Commissioned by The Royal Society of Edinburgh; unveiled in 2008]]
{{Main|List of things named after James Clerk Maxwell}}

==Publications==
* {{Citation | last1=Maxwell | first1=James Clerk | title=A treatise on electricity and magnetism Vol I | url=https://archive.org/details/electricandmagne01maxwrich | publisher=Clarendon Press |location=Oxford | year = 1873}}
* {{Citation | last1=Maxwell | first1=James Clerk | title=A treatise on electricity and magnetism Vol II | url=https://archive.org/details/electricandmag02maxwrich | publisher=Clarendon Press |location=Oxford  | year = 1873}}
* {{Citation | last1=Maxwell | first1=James Clerk | title=Matter and Motion | url=https://books.google.com/books?id=3jMKAAAAIAAJ&pg=PR1 | place= London and New York  |publisher= Society for Promoting Christian Knowledge and Pott, Young & Co.| year = 1876}}
* {{Citation | last1=Maxwell | first1=James Clerk | title=An Elementary treatise on electricity | url=https://archive.org/details/elementarytreati00maxwrich | publisher=Clarendon Press |location=Oxford  | year = 1881}}
* {{Citation | last1=Maxwell | first1=James Clerk | title=The scientific papers of James Clerk Maxwell Vol I | url=https://archive.org/details/scientificpapers01maxw | publisher=Dover Publication | year = 1890}}
* {{Citation | last1=Maxwell | first1=James Clerk | title=The scientific papers of James Clerk Maxwell Vol II | url=https://archive.org/details/scientificpapers02maxwuoft | publisher= Cambridge, University Press | year = 1890}}
* {{Citation | last1=Maxwell | first1=James Clerk | title=Theory of heat | url=https://archive.org/details/theoryofheat00maxwrich | publisher=Longmans Green Co. | year = 1908 }}<ref>See also: {{cite book| last = Maxwell| first = James Clerk| title = Theory of Heat| url = https://books.google.com/books?id=qE50pbHfQtgC| edition = 9th| year = 2001| publisher = Courier Dover Publications| isbn = 978-0-486-41735-6| access-date = 5 September 2020| archive-date = 6 June 2020| archive-url = https://web.archive.org/web/20200606100814/https://books.google.com/books?id=qE50pbHfQtgC| url-status = live}}</ref>
* Three of Maxwell's contributions to ''Encyclopædia Britannica'' appeared in the Ninth Edition (1878): ''Atom'',<ref>{{cite EB9 |wstitle = Atom |volume= III | page=36 |short=1 }}</ref> ''Attraction'',<ref>{{cite EB9 |wstitle = Attraction |volume= III | page=63 |short=1 }}</ref> and ''Ether'';<ref>{{cite EB9 |wstitle = Ether |volume= VIII | page= |short=1 }}</ref> and three in the Eleventh Edition (1911): ''Capillary Action'',<ref>{{cite EB1911|wstitle=Capillary_Action |volume=05 |short=x}}</ref> ''Diagram'',<ref>{{cite EB1911|wstitle=Diagram |volume=08 |short=x}}</ref> and ''Faraday, Michael''<ref>{{cite EB1911|wstitle=Faraday, Michael |volume=10 |short=x}}</ref>
{{clear}}

==Notes==
{{reflist}}

==References==
* {{cite book| last1 = Barrett| first1 = Terence William| last2 = Grimes| first2 = Dale Mills| title = Advanced Electromagnetism: Foundations, Theory and Applications| url = https://books.google.com/books?id=lA8tgLMRu2kC| year = 1995| publisher = World Scientific| isbn = 978-981-02-2095-2}}
* {{Cite book| author-link=Pierre Duhem | publisher = Springer | isbn = 978-3-319-18515-6| doi = 10.1007/978-3-319-18515-6 | volume = 314| last = Duhem| first = Pierre Maurice Marie |translator-first = Alan |translator-last = Aversa | title = The Electric Theories of J. Clerk Maxwell | series = Boston Studies in the Philosophy and History of Science| access-date = 8 July 2015| date = 2015| url = https://isidore.co/calibre/browse/book/4976}}
* {{cite book |first=Lewis |last=Campbell |author2=Garnett, William |title=The Life of James Clerk Maxwell |publisher=MacMillan |location=Edinburgh |year=1882 |url=http://www.sonnetsoftware.com/bio/maxbio.pdf |oclc=2472869 }}
* {{cite book| last = Eyges| first = Leonard| title = The Classical Electromagnetic Field| url = https://books.google.com/books?id=4U_2KXNi5pgC| year = 1972| publisher = Dover | location = New York| isbn = 978-0-486-63947-5}}
* {{cite book| last = Gardner| first = Martin| author-link = Martin Gardner| title = The Last Recreations: Hydras, Eggs, and Other Mathematical Mystifications| url = https://archive.org/details/lastrecreationsh00gard_0| url-access = registration| year = 2007| publisher = Springer-Verlag| isbn = 978-0-387-25827-0}}
* {{cite book| last = Glazebrook| first = R.T.| author-link=Richard Glazebrook | title = James Clerk Maxwell and Modern Physics| url = https://archive.org/stream/jamesclerkmaxwel00glaziala#page/n7/mode/2up| year = 1896| publisher =811951455|  oclc = 811951455}}
* {{cite book| last = Harman| first = Peter M.| title = The Natural Philosophy of James Clerk Maxwell| url = https://books.google.com/books?id=v4xjVtszqssC| year = 1998| publisher = Cambridge University Press| isbn = 0-521-00585-X}}
* {{cite ODNB|id=5624|title=Maxwell, James|year=2004|last=Harman|first=Peter M.}}
* {{cite book| last = Mahon| first = Basil| title = The Man Who Changed Everything – the Life of James Clerk Maxwell| url = https://books.google.com/books?id=mGo_jtHwL0sC| year = 2003| publisher = Wiley | isbn = 0-470-86171-1}}
* {{cite book| last = Russo| first = Remigio| title = Mathematical Problems in Elasticity| url = https://books.google.com/books?id=qe05dx_hpVsC| year = 1996| publisher = World Scientific| isbn = 981-02-2576-8}}
* {{cite EB1911|wstitle=Maxwell, James Clerk |last= Tait|first= Peter Guthrie |volume= 17 }}
* {{cite book| last = Timoshenko|first= Stephen |author-link=Stephen Timoshenko |year=1983|title=History of Strength of Materials|publisher= Courier Dover |isbn=978-0-486-61187-7}}
* {{cite book| last = Tolstoy| first = Ivan| title = James Clerk Maxwell: A Biography| year = 1982| publisher = University of Chicago Press| isbn = 0-226-80787-8| oclc = 8688302}}
* {{cite book| last = Warwick| first = Andrew| title = Masters of Theory: Cambridge and the Rise of Mathematical Physics| url = https://archive.org/details/mastersoftheoryc0000warw| url-access = registration| year = 2003| publisher = University of Chicago Press| isbn = 0-226-87374-9}}
* {{cite book |last1=Waterston |first1=Charles D |last2=Macmillan Shearer |first2=A. |title=Former Fellows of the Royal Society of Edinburgh 1783–2002: Biographical Index |url=http://www.rse.org.uk/cms/files/fellows/biographical_index/fells_indexp2.pdf |volume=II |date=July 2006 |publisher=[[The Royal Society of Edinburgh]] |location=Edinburgh |archive-url=https://web.archive.org/web/20150509130414/http://www.rse.org.uk/cms/files/fellows/biographical_index/fells_indexp2.pdf |archive-date=2015-05-09 |isbn=978-0-902198-84-5}}
* {{cite book| last = Wilczek| first = Frank| author-link = Frank Wilczek| title = A Beautiful Question: Finding Nature's Deep Design |chapter=Maxwell I: God's Esthetics. II: The Doors of Perception |pages=117–164 |chapter-url=https://books.google.com/books?id=Oh3ICAAAQBAJ&pg=PT107 | year = 2015| publisher = Allen Lane| isbn = 978-0-7181-9946-3 }}

==External links==
{{Commons}}
{{wikiquote}}
{{wikisource|works=or}}
*{{NPG name}}
* {{Gutenberg author |id=1586| name=James Clerk Maxwell}}
* {{Internet Archive author |sname=James Clerk Maxwell}}
* {{Librivox author |id=736}}
* {{MacTutor Biography|id=Maxwell}}
* {{cite web |url=http://www.numericana.com/arms/maxwell.htm |title=Genealogy and Coat of Arms of James Clerk Maxwell (1831–1879) |publisher=Numericana}}
* {{cite web |url=http://www.clerkmaxwellfoundation.org/ |title=The James Clerk Maxwell Foundation}}
* {{cite web |url=http://www.scotlandspeople.gov.uk/content/help/index.aspx?r=546&1145 |title=Maxwell, James Clerk (Maxwell's last will and testament) |date=31 May 2013 |publisher=scotlandspeople.gov.uk |access-date=25 November 2008 |archive-date=30 December 2006 |archive-url=https://web.archive.org/web/20061230185305/http://www.scotlandspeople.gov.uk/content/help/index.aspx?r=546&1145 }}
* {{cite web |url=http://www.clerkmaxwellfoundation.org/PUBLISHED_SCIENTIFIC_PAPERS.pdf |title=The Published Scientific Papers and Books of James Clerk Maxwell |publisher=Clerk Maxwell Foundation}}
* {{cite web |url=http://www.clerkmaxwellfoundation.org/Bibliography.pdf |title=Bibliography |publisher=Clerk Maxwell Foundation}}
* James Clerk Maxwell, [http://lhldigital.lindahall.org/cdm/ref/collection/color/id/29023 "Experiments on colour as perceived by the Eye, with remarks on colour-blindness"]. ''Proceedings of the Royal Society of Edinburgh'', vol. 3, no. 45, pp.&nbsp;299–301. (digital facsimile from the [[Linda Hall Library]])
* [https://www.bbc.co.uk/programmes/p005491g Maxwell], BBC Radio 4 discussion with Simon Schaffer, Peter Harman & Joanna Haigh (''In Our Time'', 2 October 2003)
* [https://www.bbc.co.uk/programmes/b06rd56j Scotland's Einstein: James Clerk Maxwell – The Man Who Changed the World], BBC Two documentary 2015.

{{Scientists whose names are used as non SI units}}

{{Authority control}}

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