|James Clerk Maxwell|
James Clerk Maxwell (1831–1879)
|Born||13 June 1831
|Died||5 November 1879 (aged 48)
|Fields||Physics and mathematics|
|Institutions||Marischal College, Aberdeen, UK
King's College London, UK
University of Cambridge, UK
|Alma mater||University of Edinburgh, UK
University of Cambridge, UK
|Academic advisors||William Hopkins|
|Notable students||George Chrystal|
|Known for||Maxwell's equations
Maxwell speed distribution
Generalized Maxwell model
|Notable awards||Smith's Prize (1854)
Adams Prize (1857)
Rumford Medal (1860)
James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish theoretical physicist and mathematician. His most important achievement was classical electromagnetic theory, synthesizing all previously unrelated observations, experiments and equations of electricity, magnetism and even optics into a consistent theory. His set of equations—Maxwell's equations—demonstrated that electricity, magnetism and even light are all manifestations of the same phenomenon: the electromagnetic field. From that moment on, all other classic laws or equations of these disciplines became simplified cases of Maxwell's equations. Maxwell's work in electromagnetism has been called the "second great unification in physics", after the first one carried out by Isaac Newton.
Maxwell demonstrated that electric and magnetic fields travel through space in the form of waves, and at the constant speed of light. Finally, in 1864 Maxwell wrote "A dynamical theory of the electromagnetic field", where he first proposed that light was in fact undulations in the same medium that is the cause of electric and magnetic phenomena. His work in producing a unified model of electromagnetism is considered to be one of the greatest advances in physics.
Maxwell also developed the Maxwell distribution, a statistical means of describing aspects of the kinetic theory of gases. These two discoveries helped usher in the era of modern physics, laying the foundation for future work in such fields as special relativity and quantum mechanics.
Maxwell is considered by many physicists to be the 19th-century scientist with 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 Isaac Newton and Albert Einstein. In the end of millennium poll, a survey of the 100 most prominent physicists saw Maxwell voted the third greatest physicist of all time, behind only Newton and Einstein. On the centennial of Maxwell's birthday, Einstein himself described Maxwell's work as the "most profound and the most fruitful that physics has experienced since the time of Newton." Einstein kept a photograph of Maxwell on his study wall, alongside pictures of Michael Faraday and Newton.
James Clerk Maxwell was born on 13 June 1831 at 14 India Street, Edinburgh, to John Clerk Maxwell, an advocate, and Frances Maxwell (née Cay). Maxwell's father was a man of comfortable means, related to the Clerk family of Penicuik, Midlothian, holders of the baronetcy of Clerk of Penicuik; his brother being the 6th Baronet. He had been born John Clerk, adding the surname Maxwell to his own after he inherited a country estate in Middlebie, Kirkcudbrightshire from connections to the Maxwell family, themselves members of the peerage.
Maxwell's parents did not meet and marry until they were well into their thirties, unusual for the times, and Frances Maxwell was nearly 40 when James was born. They had had one earlier child, a daughter, Elizabeth, who died in infancy. They named their only surviving child James, a name that had sufficed not only for his grandfather, but also many of his other ancestors.
The family moved when Maxwell was young to "Glenlair", a house his parents had built on the 1500 acre (6.1 km2) Middlebie estate. All indications suggest that Maxwell had maintained an unquenchable curiosity from an early age. By the age of three, everything that moved, shone, or made a noise drew the question: "what's the go o' that?". In a letter to his sister-in-law Jane Cay in 1834, his father described this innate sense of inquisitiveness:
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 ...
Recognizing the potential of the young boy, his mother Frances took responsibility for James' early education, which in Victorian era was largely the job of the woman of the house. She was however taken ill with abdominal cancer, and after an unsuccessful operation, died in December 1839 when Maxwell was only eight. James' education was then overseen by John Maxwell and his sister-in-law Jane, both of whom played pivotal roles in the life of Maxwell. His formal schooling began unsuccessfully under the guidance of a sixteen-year old hired tutor. Little is known about the young man John Maxwell hired to instruct his son, except that he treated the younger boy harshly, chiding him for being slow and wayward. John Maxwell dismissed the tutor in November 1841, and after considerable thought, sent James to the prestigious Edinburgh Academy. He lodged during term times at the house of his aunt Isabella; while there his passion for drawing was encouraged by his older cousin Jemima, herself a talented artist.
The ten-year old Maxwell, raised in isolation on his father's countryside estate, did not fit in well at school. The first year had been full, obliging him to join the second year with classmates a year his senior. His mannerisms and Galloway accent struck the other boys as rustic, and arriving on his first day at school wearing home-made shoes and tunic earned him the unkind nickname of "Daftie". Maxwell, however, never seemed to have resented the epithet, bearing it without complaint for many years. Any social isolation at the Academy however ended when he met Lewis Campbell and Peter Guthrie Tait, two boys of a similar age, and themselves to become notable scholars. They would remain lifetime friends.
Maxwell was fascinated by geometry at an early age, rediscovering the regular polyhedron before any formal instruction. Much of his talent went unnoticed however, and, despite winning the school's scripture biography prize in his second year, his academic work remained unremarkable, until, at the age of 13, he won the school's mathematical medal, and first prizes for English and poetry.
For his first scientific work, at the age of only 14, Maxwell wrote a paper describing a mechanical means of drawing mathematical curves with a piece of twine, and the properties of ellipses and curves with more than two foci. His work, "Oval Curves", was presented to the Royal Society of Edinburgh by James Forbes, professor of natural philosophy at Edinburgh University, Maxwell deemed too young for the task. The work was not entirely original, Descartes having examined the properties of such multifocal curves in the seventeenth century, though Maxwell had simplified their construction.
Maxwell left the Academy in 1847 at the age of 16 and began attending classes at the University of Edinburgh. Having the opportunity to attend Cambridge after his first term, Maxwell decided instead to complete the full course of his undergraduate studies at Edinburgh. The academic staff of Edinburgh University included some highly regarded names, and Maxwell's first year tutors included Sir William Hamilton, who lectured him on logic and metaphysics, Philip Kelland on mathematics, and James Forbes on natural philosophy. Maxwell did not however find his classes at Edinburgh very demanding, and was able to immerse himself in private study during free time at the university, and particularly when back home at Glenlair. There he would experiment with improvised chemical and electromagnetic apparatus, but his chief preoccupation was the properties of polarized light. He constructed shaped blocks of gelatine, subjecting them to various stresses, and with a pair of polarizing prisms gifted him by the famous scientist William Nicol, would view the coloured fringes developed within the jelly. Maxwell had discovered photoelasticity, a means of determining the stress distribution within physical structures.
In his eighteenth year, Maxwell contributed two papers for the Transactions of the Royal Society of Edinburgh—one of which, "On the equilibrium of elastic solids", laid the foundation for an important discovery of his later life: the temporary double refraction produced in viscous liquids by shear stress. The other was titled "Rolling curves". As with his schoolboy paper "Oval Curves", Maxwell was considered too young to stand at the rostrum and present it himself, and it was delivered to the Royal Society by his tutor Kelland.
In October 1850, already an accomplished mathematician, Maxwell left Scotland for Cambridge University. He initially attended Peterhouse, but before the end of his first term transferred to Trinity College, where he believed it would be easier to obtain a fellowship. At Trinity, he was elected to the elite secret society known as the Cambridge Apostles. In November 1851, Maxwell studied under William Hopkins, whose success in nurturing mathematical genius had earned him the nickname of "senior wrangler-maker". A considerable part of Maxwell's translation of his electromagnetism equations was accomplished during his time in Trinity.
In 1854, Maxwell graduated from Trinity with a degree in mathematics. He scored second highest in the final examination, coming behind Edward Routh, and thereby earning himself the title of Second Wrangler, but was declared equal with Routh in the more exacting ordeal of the Smith's Prize examination. Immediately after taking his degree, Maxwell read to the Cambridge Philosophical Society a novel memoir, "On the transformation of surfaces by bending". This is one of the few purely mathematical papers he published, and it demonstrated Maxwell's growing stature as a mathematician. Maxwell decided to remain at Trinity after graduating and applied for a fellowship, a process that he could expect to take a couple of years. Buoyed by his success as a research student, he would be free, aside from some tutoring and examining duties, to pursue scientific interests at his own leisure.
The nature and perception of colour was one such interest, and had begun at Edinburgh University while he was a student of Forbes. Maxwell took the coloured spinning tops invented by Forbes, and was able to demonstrate that white light would result from a mixture of red, green and blue light. His paper, "Experiments on colour", laid out the principles of colour combination, and was presented to the Royal Society of Edinburgh in March 1855. This time, it would be Maxwell himself who delivered his lecture.
Maxwell was made a fellow of Trinity on 10 October 1855, sooner than was the norm, and was asked to prepare lectures on hydrostatics and optics, and to set examination papers. However, the following February he was informed by Forbes that the Chair of Natural Philosophy at Marischal College, Aberdeen, had become vacant, and urged to apply. 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. Maxwell nevertheless accepted the professorship at Aberdeen, leaving Cambridge in November 1856.
The twenty-five year old Maxwell was a decade and a half younger than any other professor at Marischal, but engaged himself with his new responsibilities as head of department, devising the syllabus and preparing the lectures. He committed himself to lecturing 15 hours a week, including a weekly pro bono lecture to the local working men's college. He lived in Aberdeen during the six months of the academic year, and would spend the summers at Glenlair, which he had inherited from his father.
His mind was focused on a conundrum which had eluded scientists for two hundred years: the nature of Saturn's rings. It was unknown how they could remain stable without breaking up, drifting away or crashing into Saturn. The problem took on a particular resonance at this time as St John's College, Cambridge had chosen it as the topic for the 1857 Adams Prize. Maxwell devoted two years to studying the problem, proving that a regular solid ring could not be stable, and a fluid ring would be forced by wave action to break up into blobs. Neither met with observations, and Maxwell was able to conclude that the rings must comprise numerous small particles he called "brick-bats", each independently orbiting Saturn. Maxwell was awarded the £130 Adams Prize in 1859 for his essay "On the stability of saturn's rings"; he was the only entrant to have made enough headway to submit an entry. 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." It was considered the final word on the issue until direct observations by the Voyager flybys of the 1980s, which confirmed Maxwell's prediction.
Maxwell had in 1857 befriended the Principal of Marischal, the Reverend Daniel Dewar, and through him he was to meet Dewar's daughter, Katherine Mary Dewar. They were engaged in February 1858, marrying in Aberdeen on 2 June 1859. Comparatively little is known of Katherine, seven years Maxwell's senior: Maxwell's biographer and friend Campbell adopted an uncharacteristic reticence on the subject, though describing their married life as "one of unexampled devotion".
In 1860, Marischal College merged with the neighbouring King's College to form the University of Aberdeen. There was no room for two professors of Natural Philosophy, and Maxwell found himself in the extraordinary position for someone of his scientific stature of being laid off. He was unsuccessful applying for Forbes' recently vacated chair at Edinburgh, the post going to Tait, but was granted instead the Chair of Natural Philosophy at King's College London. After recovering from a near-fatal bout of smallpox in the summer of 1860, Maxwell headed south to London with his wife Katherine.
Maxwell's time at King's was probably the most productive of his career. He was awarded the Royal Society's Rumford Medal in 1860 for his work on colour, and elected to the Society itself in 1861. This period of his life would see him display the world's first colour photograph, develop further his ideas on the viscosity of gases, and proposed 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—Faraday was 40 years Maxwell's senior and showing signs of senility—but they maintained a strong respect for each other's talents.
The time is especially known for the advances Maxwell made in electromagnetism. He had examined the nature of electromagnetic fields in his two-part 1861 paper "On physical lines of force", in which he had provided a conceptual model for electromagnetic induction, consisting of tiny spinning cells of magnetic flux. A further two parts to the paper were published early in 1862, in the first of which he discussed the nature of electrostatics and displacement current. The final part dealt with the rotation of the plane of polarization of light in a magnetic field, a phenomenon discovered by Faraday and now known as the Faraday effect.
In 1865, Maxwell resigned the chair at King's College London and returned to Glenlair with Katherine.
He wrote a textbook of the Theory of Heat (1871), and an elementary treatise on Matter and Motion (1876). Maxwell was also the first to make explicit use of dimensional analysis in 1871.
In 1871, he became the first Cavendish Professor of Physics at Cambridge. Maxwell was put in charge of the development of the Cavendish Laboratory. He supervised every step of the progress of the building and of the purchase of the very valuable collection of apparatus paid for by its generous founder, the 7th Duke of Devonshire (chancellor of the university, and one of its most distinguished alumni). One of Maxwell's last great contributions to science was the editing (with copious original notes) of the electrical researches of Henry Cavendish, from which it appeared that Cavendish researched such questions as the mean density of the earth and the composition of water, among other things.
He died in Cambridge of abdominal cancer on 5 November 1879 at the age of 48. Maxwell is buried at Parton Kirk, near Castle Douglas in Galloway, Scotland. The extended biography The Life of James Clerk Maxwell, by his former schoolfellow and lifelong friend Professor Lewis Campbell, was published in 1882 and his collected works, including the series of articles on the properties of matter, such as "Atom", "Attraction", "Capillary action", "Diffusion", "Ether", etc., were issued in two volumes by the Cambridge University Press in 1890.
Ivan Tolstoy, author of one of Maxwell's biographies, remarked at the frequency with which scientists writing short biographies on Maxwell often omit the subject of his Christianity. Maxwell's religious beliefs and related activities have been the focus of several peer-reviewed and well-referenced papers. Attending both Presbyterian and Episcopalian services as a child, Maxwell later underwent an evangelical conversion (April 1853), which committed him to an anti-positivist position.
As a great lover of British poetry, Maxwell memorised poems and wrote his own. 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 immortal opening lines
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 in 1882.
Maxwell had studied and commented on the field of electricity and magnetism as early as 1855/6 when "On Faraday's lines of force" was read to the Cambridge Philosophical Society. The paper presented a simplified model of Faraday's work, and how the two phenomena were related. He reduced all of the current knowledge into a linked set of differential equations with 20 equations in 20 variables. This work was later published as "On physical lines of force" in March 1861.
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, and commented "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."
Working on the problem further, Maxwell showed that the equations predict the existence of waves of 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 310,740,000 m/s. In his 1864 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".
His famous equations, in their modern form of four partial differential equations, first appeared in fully developed form in his textbook A Treatise on Electricity and Magnetism in 1873. 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. Maxwell expressed electromagnetism in the algebra of quaternions and made the electromagnetic potential the centerpiece of his theory. In 1881 Oliver Heaviside replaced Maxwell’s electromagnetic potential field by ‘force fields’ as the centerpiece of electromagnetic theory. Heaviside reduced the complexity of Maxwell’s theory down to four differential equations, known now collectively as Maxwell's Laws or Maxwell's equations. According to Heaviside, the electromagnetic potential field was arbitrary and needed to be "murdered". A few years later there was a great debate between Heaviside and Peter Guthrie Tait 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.
Maxwell was proven correct, and his quantitative connection between light and electromagnetism is considered one of the great accomplishments of 19th century mathematical physics.
Maxwell also introduced the concept of the electromagnetic field in comparison to force lines that Faraday discovered. 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. Over time, the existence of such a medium, permeating all space and yet apparently undetectable by mechanical means, proved more and more difficult to reconcile with experiments such as the Michelson–Morley experiment. 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, and in the process Einstein dispensed with the requirement of a luminiferous aether.
Maxwell contributed to the area of optics and colour vision, and is credited with the discovery that colour photographs could be formed using red, green, and blue filters. In 1861 he presented the world's first colour photograph during a Royal Institution lecture. He had Thomas Sutton, inventor of the single-lens reflex camera, photograph a tartan ribbon three times, each time with a different colour filter over the lens. The three images were reversal developed to form three colour separation transparencies, and then projected onto a screen with three different projectors, each equipped with the same colour filter used to take its image. When brought into focus, the three images formed a full colour image. The three photographic plates now reside in a small museum at 14 India Street, Edinburgh, the house where Maxwell was born.
However, in the strictest sense, this demonstration did not produce a tangible photograph, but a photographic image produced by three carefully aligned projectors. It served as a "proof of concept" of the possibility of colour photography, using the additive principle, where white is produced by the presence of all three additive primaries (red, green and blue).
From 1855 to 1872, he published at intervals a series of valuable investigations connected with the "Perception of colour" and "Colour-blindness", for the earlier of which the Royal Society awarded him the Rumford Medal. The instruments which he devised for these investigations were simple and convenient in use. For example, Maxwell's discs were used to compare a variable mixture of three primary colours with a sample colour by observing the spinning "colour top."
One of Maxwell's major investigations was on the kinetic theory of gases. Originating with Daniel Bernoulli, this theory was advanced by the successive labours of John Herapath, John James Waterston, 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.
In 1866, he formulated statistically, independently of Ludwig Boltzmann, the Maxwell–Boltzmann kinetic theory of gases. His formula, called the Maxwell distribution, gives the fraction of gas molecules moving at a specified velocity at any given temperature. In the kinetic theory, temperatures and heat involve only molecular movement. This approach generalized the previously established laws of thermodynamics and explained existing observations and experiments in a better way than had been achieved previously. Maxwell's work on thermodynamics led him to devise the Gedankenexperiment (thought experiment) that came to be known as Maxwell's demon.
In 1871, he established Maxwell's thermodynamic relations, which are statements of equality among the second derivatives of the thermodynamic potentials with respect to different thermodynamic variables.
Maxwell published a famous paper "On governors" in the Proceedings of Royal Society, vol. 16 (1867–1868). This paper is quite frequently considered a classical paper of the early days of control theory. Here governors refer to the governor or the centrifugal governor used in steam engines.
JAMES CLERK MAXWELL (1831-1879), British physicist, was the last representative of a younger branch of the wellknown Scottish family of Clerk of Penicuik, and was born at Edinburgh on the 13th of November 1831. He was educated at the Edinburgh Academy (r840-1847) and the university of Edinburgh (1847-1850). Entering at Cambridge in 1850, he spent a term or two at Peterhouse, but afterwards migrated to Trinity. In 1854 he took his degree as second wrangler, and was declared equal with the senior wrangler of his year (E. J. Routh, q.v.) in the higher ordeal of the Smith's prize examination. He held the chair of Natural Philosophy in Marischal College, Aberdeen, from 1856 till the fusion of the two colleges there in 1860. For eight years subsequently he held the chair of Physics and Astronomy in King's College, London, but resigned in 1868 and retired to his estate of Glenlair in Kirkcudbrightshire. He was summoned from his seclusion in 1871 to become the first holder of the newly founded professorship of Experimental Physics in Cambridge; and it was under his direction that the plans of the Cavendish Laboratory were prepared. He superintended every step of the progress of the building and of the purchase of the very valuable collection of apparatus with which it was equipped at the expense of its munificent founder the seventh duke of Devonshire (chancellor of the university, and one of its most distinguished alumni). He died at Cambridge on the 5th of November 1879.
For more than half of his brief life he held a prominent position in the very foremost rank of natural philosophers. His contributions to scientific societies began in his fifteenth year, when Professor J. D. Forbes communicated to the Royal Society of Edinburgh a short paper of his on a mechanical method of tracing Cartesian ovals. In his eighteenth year, while still a student in Edinburgh, he contributed two valuable papers to the Transactions of the same society - one of which, " On the Equilibrium of Elastic Solids," is remarkable, not only on account of its intrinsic power and the youth of its author, but also because in it he laid the foundation of one of the most singular discoveries of his later life, the temporary double refraction produced in viscous liquids by shearing stress. Immediately after taking his degree, he read to the Cambridge Philosophical Society a very novel memoir, " On the Transformation of Surfaces by Bending." This is one of the few purely mathematical papers he published, and it exhibited at once to experts the full genius of its author. About the same time appeared his elaborate memoir, " On Faraday's Lines of Force," in which he gave the first indication of some of those extraordinary electrical investigations which culminated in the greatest work of his life. He obtained in 185 9 the Adams prize in Cambridge for a very original and powerful essay, " On the Stability of Saturn's Rings." From 1855 to 1872 he published at intervals a series of valuable investigations connected with the " Perception of Colour " and " Colour-Blindness," for the earlier of which he received the Rumford medal from the Royal Society in 1860. The instruments which he devised for these investigations were simple and convenient, but could not have been thought of for the purpose except by a man whose knowledge was co-extensive with his ingenuity. One of his greatest investigations bore on the " Kinetic Theory of Gases." Originating with D. Bernoulli, this theory was advanced by the successive labours of John Herapath, J. P. Joule, and particularly R. Clausius, to such an extent as to put its general accuracy beyond a doubt; but it received enormous developments from Maxwell, who in this field appeared as an experimenter (on the laws of gaseous friction) as well as a mathematician. He wrote an admirable textbook of the Theory of Heat (1871), and a very excellent elementary treatise on Matter and Motion (1876).
But the great work of his life was devoted to electricity. He began by reading, with the most profound admiration and attention, the whole of Faraday's extraordinary self-revelations, and proceeded to translate the ideas of that master into the succinct and expressive notation of the mathematicians. A considerable part of this translation was accomplished during his career as an undergraduate in Cambridge. The writer had the opportunity of perusing the MS. of " On Faraday's Lines of Force," in a form little different from the final one, a year before Maxwell took his degree. His great object, as it was also the great object of Faraday, was to overturn the idea of action at a distance. The splendid researches of S. D. Poisson and K. F. Gauss had shown how to reduce all the phenomena of statical electricity to mere attractions and repulsions exerted at a distance by particles of an imponderable on one another. Lord Kelvin (Sir W. Thomson) had, in 1846, shown that a totally different assumption, based upon other analogies, led (by its own special mathematical methods) to precisely the same results. He treated the resultant electric force at any point as analogous to the flux of heat from sources distributed in the same manner as the supposed electric particles. This paper of Thomson's, whose ideas Maxwell afterwards developed in an extraordinary manner, seems to have given the first hint that there are at least two perfectly distinct methods of arriving at the known formulae of statical electricity. The step to magnetic phenomena was comparatively simple; but it was otherwise as regards electromagnetic phenomena, where current electricity is essentially involved. An exceedingly ingenious, but highly artificial, theory had been devised by W. E. Weber, which was found capable of explaining all the phenomena investigated by Ampere as well as the induction currents of Faraday. But this was based upon the assumption of a distance-action between electric particles, the intensity of which depended on their relative motion as well as on their position. This was, of course, even more repugnant to Maxwell's mind than the statical distance-action developed by Poisson. The first paper of Maxwell's in which an attempt at an admissible physical theory of electromagnetism was made was communicated to the Royal Society in 1867. But the theory, in a fully developed form, first appeared in 1873 in his great treatise on Electricity and Magnetism. This work was one of the most splendid monuments ever raised by the genius of a single individual. Availing himself of the admirable generalized co-ordinate system of Lagrange, Maxwell showed how to reduce all electric and magnetic phenomena to stresses and motions of a material medium, and, as one preliminary, but excessively severe, test of the truth of his theory, he pointed out that (if the electromagnetic medium be that which is required for the explanation of the phenomena of light) the velocity of light in vacuo should xvii. 30 be numerically the same as the ratio of the electromagnetic and electrostatic units. In fact, the means of the best determinations of each of these quantities separately agree with one another more closely than do the various values of either.
One of Maxwell's last great contributions to science was the editing (with copious original notes) of the Electrical Researches of the Hon. Henry Cavendish, from which it appeared that Cavendish, already famous by many other researches (such as the mean density of the earth, the composition of water, &c.), must be looked on as, in his day, a man of Maxwell's own stamp as a theorist and an experimenter of the very first rank.
In private life Clerk Maxwell was one of the most lovable of men, a sincere and unostentatious Christian. Though perfectly free from any trace of envy or ill-will, he yet showed on fit occasion his contempt for that pseudo-science which seeks for the applause of the ignorant by professing to reduce the whole system of the universe to a fortuitous sequence of uncaused events.
His collected works, including the series of articles on the proper- << " " " << ties of matter, such as tom, Attraction," Capillary Action," " Diffusion," " Ether," &c., which he contributed to the 9th edition of this encyclopaedia, were issued in two volumes by the Cambridge University Press in 1890; and an extended biography, by his former schoolfellow and lifelong friend Professor Lewis Campbell, was published in 1882. (P. G. T.)
Maxwell grew up in a rich religious family. In 1845, when he was only 14, he wrote a paper describing a way of drawing mathematical curves with a piece of string. In 1847 he started studying mathematics at the University of Edinburgh. In 1850 Maxwell changed to Trinity College at the University of Cambridge. He won prizes from the university for his work and was given his degree in 1854. From 1855 to 1872 he did research on colour blindness.
In 1856 Maxwell was made a professor of 'Natural Philosophy' (which is what science was called then) at Marischal College, Aberdeen. He worked there until the two colleges in Aberdeen joined together in 1860 and he lost his job. He then became a professor at King's College London. In 1861, Maxwell was made a member of the Royal Society, a group of important scientists. In 1871, became the first Cavendish Professor of Physics at Cambridge.
Maxwell died in 1879 from cancer.
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