Thomson, William,Baron Kelvin

• Crosbie Smith

William Thomson,Baron Kelvin (1824–1907)

byLowes Cato Dickinson,1869

Master and Fellows of Peterhouse, Cambridge

Thomson, William,Baron Kelvin (1824–1907),mathematician and physicist, was born on 26 June 1824 at College Square, Belfast, second son among seven children ofJames Thomson (1786–1849), professor of mathematics in the collegiate department of the Belfast Academical Institution, and his wife,Margaret Gardner (c.1790–1830), whose mother wasElizabeth Patison of Kelvin Grove to the west of Glasgow. AfterMargaret's death in 1830James Thomson assumed full responsibility for the education of his children, and two years later took up his appointment to the Glasgow College chair of mathematics. The family lived in the old college off the High Street during the six-month winter sessions but in the summer they moved to rented accommodation at various localities on the Firth of Clyde, most notably Arran. AlthoughWilliam and his elder brotherJames Thomson had attended some school classes at the Academical Institution (and won first and second prizes respectively in 1831), they had received almost no formal schooling. Having attended as listeners their father's junior class in Glasgow, the brothers matriculated in 1834 whenWilliam was just ten.

Making a Cambridge wrangler

For the next six years the brothers were constantly together,James increasingly committed to engineering problems andWilliam to mathematics and natural philosophy. Early in 1835 their older sisterAnna reported that 'James andWilliam are quite delighted just now, having been making an electrical machine. It gives strong shocks' (E. King, 135n.). The following yearWilliam told his eldest sister,Elizabeth, that 'We have not begun the steam-engine, for papa was not wanting us to do it' (E. King, 138). By the end of the year the brothers had each built an electrical machine,James's machine apparently larger and more carefully finished than his younger brother's but the latter was well satisfied with the utility of his production, its power demonstrated by subjecting other members of the family to frequent shocks. In due course the brothers were allocated a room in the college house where they pursued their mechanical and philosophical researches. In college classesWilliam took first prize, his physically less robust elder brother often coming second.

By May 1839 the brothers were eligible for the degree of BA, butThomson did not take the degree because he planned to enter Cambridge University as an undergraduate. A further session (1839–40) saw the brothers attending the senior natural philosophy class which, initially under the ailingWilliam Meikleham, passed to the control ofJohn Pringle Nichol, radical professor of astronomy. At the end of the sessionWilliam won a university medal for an 85-page essay on'The figure of the earth' which drew on advanced texts byLaplace,Poisson, andAiry. In that summer theThomsons and theNichols travelled together to the Rhine. Fired byNichol's enthusiasm forJoseph Fourier,Thomson took with him a library copy ofFourier'sThéorie analytique de la chaleur (1822), and secretly read right through the treatise when he was supposed to be giving his undivided attention to the German language. He nevertheless quickly announced to his incredulous father that the Edinburgh professor of mathematics,Philip Kelland, was mistaken in recent criticisms ofFourier's mathematics. The outcome was the publication ofWilliam Thomson's first paper, under the pseudonym‘P. Q. R.’, in theCambridge Mathematical Journal. He had only just turned sixteen.

Thomson was formally entered at Peterhouse on 6 April 1841 but did not come into residence as an undergraduate until the following October. The connections of the mathematical coach,William Hopkins, with Peterhouse probably influenced the choice of college. In any case, Cambridge offered the best mathematical training available anywhere in Britain, training which could open careers in the church and in the legal profession as well as in the universities.Hopkins himself recognized deficiencies in undergraduates who came to Cambridge by way of the Scottish universities with their emphasis on a broad philosophical education rather than on rigorous mathematical practice: 'men from Glasgow and Edinburgh require a great deal of drilling' (Smith andWise, 55). Only days after arriving in Cambridge,Thomson was singled out as the likely senior wrangler of his year.

Thomson's Cambridge years were lived with characteristic intensity. He quickly made the acquaintance of distinguished Trinity College Scots such asD. F. Gregory (editor of theCambridge Mathematical Journal) andArchibald Smith (senior wrangler in 1836). With one eye on his father's financial imperatives to avoid dissipation and the other on Cambridge's moral strictures designed to shape its wranglers, he attempted to adhere to highly disciplined routines of reading and exercising. His private diary (1843) suggests a different story. Rising at six or seven on February mornings, his days were filled by passionate rather than disciplined involvement in walking, skating, swimming, reading, and, above all, wide-ranging discussions with a large circle of friends extending well into the night. Against the wishes of his father he became increasingly enthusiastic about rowing. By the end of his second year he had joined the college eight and towards the close of 1843 won the Colquhoun silver sculls for single-seater boats. The family too had been won over. As his sisterAnna perceptively observed:

I got your letter today containing all your reasons for having joined the boat races, which has one good effect at least—that of convincing us all that you are a most excellent logician, and that … you possess the excellent talent of being able to defend yourself most eloquently when anything you do is in the least blamed.

Smith and Wise, 78

As an enthusiastic musician and player of the cornet,William also became a founder member of theCambridge University Music Society in the spring of 1844.

From his second undergraduate yearThomson's coaching took the form of constant rehearsals according toHopkins's training methods. In the summer of 1844 he joinedHopkins's reading party, which included his friendsHugh Blackburn (later professor of mathematics at Glasgow) andW. F. L. Fischer (later professor of natural philosophy at St Andrews), at Cromer in the months leading up to the Senate House examinations. In January 1845, twelve mathematical examination papers later,Thomson emerged as second wrangler, afterStephen Parkinson of St John's College. One of the examiners,R. L. Ellis, remarked to a fellow examiner that 'You and I are just about fit to mend his [Thomson's] pens' (Thompson, 97–8) whileWilliam Whewell noted toJ. D. Forbes that 'Thomson of Glasgow is much the greatest mathematical genius: the Senior Wrangler was better drilled' (ibid., 103). The fault lay not withHopkins, however, but withThomson's irrepressible zeal for physical problems that interested him. In the subsequent Smith's prize examination the order was reversed. By June 1845 he had been appointed a fellow of Peterhouse and in the same year took over as editor of theCambridge Mathematical Journal which he soon expanded into theCambridge and Dublin Mathematical Journal.

The mathematical theory of electricity

During his undergraduate yearsThomson had published eleven papers in theJournal which, under the editorship of firstGregory and latterlyEllis, represented the young and reforming generation of Cambridge mathematicians. Whigs both in mathematics and politics, asThomson noted approvingly, the three successive editors regardedFourier as their inspiration (Smith andWise, 174). On the basis ofFourier's treatment of heat conduction,Thomson's'On the uniform motion of heat in homogeneous solid bodies, and its connexion with the mathematical theory of electricity' (1841–2) constructed a mathematical analogy between electrostatic induction and heat conduction. Instead of forces acting at a distance over empty space, he viewed electrical action mathematically as represented by a series of geometrical lines or 'surfaces of equilibrium' intersecting at right angles with the lines of force. These surfaces would later be called equipotential lines or surfaces. At each stage he correlated the mathematical forms in thermal and electrical cases, but avoided any physical inferences about the nature of electricity as an actual contiguous action like fluid flow.

Thomson soon deployed the analogy to reformulate the action-at-a-distance mathematical theory of electricity (developed byPoisson and employed inRobert Murphy's Cambridge textbook on electricity) intoFaraday's theory of contiguous action, though withoutFaraday's quantity–intensity distinction. In the analogy, force at a point was analogous to temperature gradient while specific inductive capacity of a dielectric was analogous to conductivity. Over the next decade or soThomson would search for the mechanism of propagation, perhaps in terms of an elastic-solid model such as that used to explain the wave nature of light, or in terms of a hydrodynamical model which would show not only electricity, magnetism, and heat, but ponderable matter itself, to result from the motions of an all-pervading fluid medium or ether. This quest for a unified field theory acquired special urgency once he adopted a dynamical theory of heat about 1850. However,Thomson also pursued other analogies as problem-solving geometrical techniques, including the method of images (1847) which deployed a simple analogy from geometrical optics to solve complex problems in electrostatics.

By 1850Thomson had contributed more than thirty papers to theCambridge Mathematical Journal; two years later he relinquished its editorship, his strenuous efforts to expand it into a national journal for mathematical sciences having been hampered by what he saw as the stubborn preponderance of contributions from pure mathematicians and correspondingly few papers on physical subjects. With few converts to his own style of electrical science, he especially welcomed in 1854 the enthusiasm of a recent Cambridge graduate and second wrangler,James Clerk Maxwell, for following throughThomson's insights into the mathematical theories of electricity and magnetism.

The Glasgow chair and the motive power of heat

As early as 1843Thomson's father had begun to prepare him as a potential successor to the Glasgow professor of natural philosophy,Meikleham, who had been unable to conduct the class since 1839. In alliance withNichol and the new professor of medicine, anotherWilliam Thomson,James Thomson agreed that a mere mathematician, unskilled in lecture demonstrations, could not command the class. In order to fill this lacuna in his training,Thomson was dispatched to Paris after graduation from Cambridge. His brief was to observe, and if possible to participate in, a full range of experimental practice, from lecture demonstrations by the finest of the French experimentalists to the physical laboratory ofVictor Regnault at the Collège de France.Thomson later acknowledged his principal debt to the Frenchphysicien as 'a faultless technique, a love of precision in all things, and the highest virtue of the experimenter—patience' (Thompson, 1154).

Regnault's accurate measurements on the properties of steam and other gases were being funded by the French government with a view to improving the efficiency of heat engines. A year earlierJames had written fromWilliam Fairbairn's Thames shipbuilding works to his younger brother asking if he knew who it was that had offered an account of the motive power of heat in terms of the mechanical effect (or work done) by the 'fall' of a quantity of heat from a state of intensity (high temperature as in a steam-engine boiler) to a state of diffusion (low temperature as in the condenser), analogous to the fall of a quantity of water from a high to a low level in the case of water-wheels. While in Paris,Thomson locatedEmile Clapeyron's memoir (1834) on the subject but failed to locate a copy ofSadi Carnot's original treatise (1824). At the same time he began to consider solutions to problems in the mathematical theory of electricity (notably that of two electrified spherical conductors, the complexity of which had defiedPoisson's attempts to obtain a general mathematical solution) in terms of mechanical effect given out or taken in, analogous to the work done or absorbed by a water-wheel or heat engine. He therefore recognized that measurements of electrical phenomena and of steam were both to be treated in absolute, mechanical and, above all, engineering terms. The contrast to the action-at-a-distance approach ofLaplace andPoisson, as well as toMichael Faraday's non-mechanical perspective, was striking.

After returning to Cambridge,Thomson bided his time by coaching four or five pupils during the long vacation and then taking on the duties of college lecturer in mathematics from October 1845. The death ofProfessor Meikleham the following May publicly opened the campaign for the succession, a competition which ended with the unanimous election ofThomson to the Glasgow chair on 11 September 1846. Six years later, in September 1852, he married his second cousin,Margaret Crum, daughter of the prosperous cotton manufacturer and calico-printerWalter Crum FRS, of Thornliebank, who had a strong interest in industrial chemistry. TheCrums had always been closely associated with theThomsons and the couple had known each other since childhood. Soon after the marriage, however,Margaret's health broke down and she remained, despite all attempts at finding a cure, an invalid until her death in 1870.

The focal point ofThomson's academic life was the natural philosophy classroom. Filling a chair which had been largely neglected for the seven years since he himself had attended the class as an undergraduate, the 22-year-old professor's most immediate challenge was to fashion his authority over a class of more than 100 students and to establish his credibility within a college still largely ruled by a 75-year-old principal,Duncan Macfarlan, who deployed all his power to oppose academic and political reform. Yet the election had actually tipped the numerical balance of reforming over tory professors within the college, and the reformers therefore gave the young professor a practical vote of confidence when they won financial backing from the college for the rapid replacement of the existing stock of physical apparatus.Thomson immediately embarked on an investment programme which, over the first few years, saw the classroom equipped with the latest and finest electrical, acoustical, and optical apparatus and instruments from prestigious instrument makers such asWatkins andHill in London andPixii in Paris. Travelling to London and Paris in the summer following his first session with the class, he told his brotherJames that he aimed to see for himself the kind of apparatus, 'on the best possible scale for a lecture room', deployed by celebrated natural philosophers such asFaraday (Thompson, 202).

Early in 1847Thomson rediscovered a model air engine, presented to the college classroom in the late 1820s by its designer,Robert Stirling, but long since clogged with dust and oil. Having joined his elder brother as a member of theGlasgow Philosophical Society in December 1846,Thomson addressed the society the following April on issues raised by the engine when considered as a material embodiment of theCarnot–Clapeyron account of the motive power of heat. If, he suggested, the upper part of the engine were maintained at the freezing point of water by a stream of water and if the lower part were held in a basin of water also at the freezing point, the engine could be cranked forward without the expenditure of mechanical effect (other than to overcome friction) because there existed no temperature difference. The result, however, would be the transference of heat from the basin to the stream and the gradual conversion of all the water in the basin into ice. Such considerations raised two fundamental puzzles: on the one hand, the production of seemingly unlimited quantities of ice without work, and on the other hand the seeming 'loss' of work which might have been produced from heat generated at high temperature if that heat were instead used to melt ice. As he explained the second puzzle toJ. D. Forbes:

It seems very mysterious how power can be lost in such a way [by the conduction of heat from hot to cold], but perhaps not more so than that power should be lost in the friction of fluids (a plumb line with the weight in water for instance) by which there does not seem to be any heat generated, nor any physical change effected.

Smith and Wise, 294

At the close of his first Glasgow College sessionThomson attended the Oxford meeting of theBritish Association for the Advancement of Science. He had long been acquainted with these annual spectacles—as long before as 1840 he andJames had played supporting roles during the association's Glasgow meeting. However, 1847 marked his first appearance as a professor of natural philosophy and author of a string of avant-garde articles on electricity. It also marked his first encounter withJames Prescott Joule who had been arguing since 1843 for the mutual convertability of work and heat according to an exact mechanical equivalence.Thomson immediately recognized inJoule's claim for the conversion of work into heat an answer to the puzzle of what happened to the seeming 'loss' of that useful work which might have been done but which was instead 'wasted' in conduction and fluid friction. Unconvinced byJoule's complementary claim that such heat could in principle be converted into work,Thomson remained deeply perplexed by what seemed to him the irrecoverable nature of that heat. Furthermore, he could not acceptJoule's rejection of theCarnot–Clapeyron theory, with its 'fall' of heat from high to low temperature, in favour of mutual convertibility.

With regard to the first puzzle raised by the Stirling engine, however,James Thomson quickly pointed out the implication that, since ice expands on freezing, it could be made to do useful work: in other words, the arrangement would function as a perpetual source of power, long held to be impossible by almost all orthodox engineers and natural philosophers. He therefore concluded that avoidance of this implication would require that the freezing point be lowered with increase of pressure. His prediction, and its subsequent experimental confirmation inWilliam Thomson's laboratory, did much to persuade the brothers of the value of theCarnot–Clapeyron theory.

Within a yearThomson had added another feature to theCarnot–Clapeyron construction, namely, an absolute scale of temperature. In presentations to the Glasgow and Cambridge philosophical societies in 1848 he explained that an air-thermometer scale provided 'an arbitrary series of numbered points of reference sufficiently close for the requirements of practical thermometry'. In an absolute thermometric scale 'a unit of heat descending from a body A at the temperature T° of this scale, to a body B at the temperature (T-1)°, would give out the same mechanical effect [motive power or work], whatever be the number T'. Its absolute character derived from its being 'quite independent of the physical properties of any specific substance' (Thomson, 1.104). In other words, unlike the air-thermometer which depended on a particular gas, he deployed the waterfall analogy to establish a scale of temperature independent of the working substance.

The Glasgow College natural philosophy classroom had long been complemented by an adjacent professor's room and apparatus room for the storage of instruments and the preparation of lecture demonstration apparatus. Having worked with his brotherJames since childhood on mechanical and philosophical apparatus in the college, and having participated himself in the Parisian physical laboratory ofRegnault,Thomson also used these spaces for the production of new scientific knowledge, aided by his classroom assistantRobert Mansell and, increasingly, by enthusiastic students. The location of the college near the heart of a growing industrial city also providedThomson with many material resources for experimental work. Indeed, he later declined the offer of the new Cambridge chair of experimental physics on the grounds that 'the convenience of Glasgow for getting mechanical work done' gave him 'means of action which I could not have in any other place' (Thompson, 563).

Thomson's lectures to the experimental natural philosophy class became increasingly linked to the experimental practices of the ‘apparatus room’. Thus in the 1849/50 session he instructed his class on the skills required for thermometry, insisting that, for instruments of the highest precision, accurate testing of the suitability of the glass tube in the laboratory was necessary before the thermometer was made by the instrument maker. Indeed, such testing, calibration, and standardization soon became another characteristic function of the Glasgow research and teaching programme. The professor and his assistant deployed one such highly sensitive thermometer to investigate the depression of the freezing point of ice under pressure. The results, confirming his brother's prediction of the lowering of the freezing point in accordance withCarnot's theory, were announced to the class and to his opposite number in Edinburgh,J. D. Forbes, prior to being made public at a meeting of theRoyal Society of Edinburgh.

WhenThomson acquired from his colleagueLewis Gordon (professor of civil engineering and mechanics) a copy of the very rareCarnot treatise, he presented an exposition, especially in the light of the issues raised byJoule, to theRoyal Society of Edinburgh. In particular,Thomson readCarnot as claiming that any work obtained from a cyclical process can only derive from transfer of heat from high to low temperature. From this claim, together with a denial of perpetual motion, it followed that no engine could be more efficient than a perfectly reversible engine (Carnot's criterion for a perfect engine). It further followed that the maximum efficiency obtainable from any engine operating between heat reservoirs at different temperatures would be a function of those temperatures (Carnot's function).

The science of energy

Prompted by the competing investigations ofMacquorn Rankine andRudolf Clausius,Thomson finally laid down two propositions in 1851, the first a statement ofJoule's mutual equivalence of work and heat and the second a statement ofCarnot's criterion for a perfect engine. His long-delayed acceptance ofJoule's proposition rested on a resolution of the problem of the irrecoverability of mechanical effect lost as heat. He now believed that work 'islost to man irrecoverably thoughnot lost in the material world'. Thus although:

no destruction of energy can take place in the material world without an act of power possessed only by the supreme ruler, yet transformations take place which remove irrecoverably from the control of man sources of power which … might have been rendered available.

Smith and Wise, 329

In other words, God alone could create or destroy energy (i.e., energy was conserved in total quantity) but human beings could make use of transformations of energy, for example in water-wheels or heat-engines.

In a private draftThomson referred these transformations to a universal statement that 'Everything in the material world is progressive' (Smith andWise, 330). On the one hand, this statement expressed the geological directionalism of Cambridge dons such asHopkins andAdam Sedgwick in opposition to the steady-state uniformitarianism ofCharles Lyell, but on the other it could be read as agreeing with the radical evolutionary doctrines of the subversiveVestiges of Creation (1844). In his published statement,Thomson opted instead for universal dissipation of energy, a doctrine which reflected the presbyterian (Calvinist) views of a transitory visible creation rather than a universe of ever-upwards progression. Work dissipated as heat would be irrecoverable to human beings, for to deny this principle would be to imply that they could produce mechanical effect by cooling the material world with no limit except the total loss of heat from the world.

This reasoning crystallized in what later became the canonical‘Kelvin’ statement of the second law of thermodynamics, first enunciated byThomson in 1851: 'it is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects' (Thomson, 1.179). This statement providedThomson with a new demonstration ofCarnot's criterion of a perfect engine. Having resolved the recoverability issue, he also quickly adopted a dynamical theory of heat, making it the basis ofJoule's proposition of mutual equivalence and abandoning theCarnot–Clapeyron notion of heat as a state function (with the corollary that in any cyclic process the change in heat content is zero).

Thomson's'On a universal tendency in nature to the dissipation of mechanical energy' took the new 'energy' perspective to a wide audience. In this short paper for thePhilosophical Magazine the term 'energy' achieved public prominence for the first time and the dual principles of conservation and dissipation of energy were made explicit: 'As it is most certain that Creative Power alone can either call into existence or annihilate mechanical energy, the “waste” referred to cannot be annihilation, but must be some transformation of energy' (Thomson, 1.511). Now the dynamical theory of heat, and with it a whole programme of dynamical (matter-in-motion) explanation, went unquestioned; and now, too, the universal primacy of the energy laws opened up fresh questions about the origins, progress, and destiny of the solar system and its inhabitants. Two years laterThomson told the Liverpool meeting of theBritish Association thatJoule's discovery of the conversion of work into heat by fluid friction, the experimental foundation of the new energy physics, had 'led to the greatest reform that physical science has experienced since the days ofNewton' (Thomson, 1.34).

From the early 1850s the Glasgow professor and his new ally in engineering science,Macquorn Rankine, began replacing an older language of mechanics with terms such as ‘actual’ (‘kinetic’ from 1862) and ‘potential energy’. Within a few years they had been joined by like-minded scientific reformers, most notably the Scottish natural philosophersJames Clerk Maxwell andPeter Guthrie Tait and the engineerFleeming Jenkin. With strong links to theBritish Association, this informal grouping of ‘North British’ physicists and engineers was primarily responsible for the construction and promotion of the ‘science of energy’, inclusive of nothing less than the whole of physical science [seeNorth British network]. Natural philosophy or physics was thus redefined as the study of energy and its transformations. It was a programme which served a wide range of functions. At the level of the Glasgow classroom, consisting largely of students destined for the ministry of the Scottish kirk,Thomson could represent the new physics as a counter to the seductions of enthusiast biblical revivals on the one hand and of evolutionary materialism on the other at a time of considerable instability in Scottish society. At a national levelThomson and his friends could offer through theBritish Association a powerful rival reform programme to that of the metropolitan scientific naturalists (includingT. H. Huxley andJohn Tyndall) who aimed at a professionalized science free from the perceived shackles of Anglican theology.

To these endsThomson examined the principal source of all the mechanical effect on earth. Arguing that the sun's energy was too great to be supplied by chemical means or by a mere molten mass cooling, he at first suggested that the sun's heat was provided by vast quantities of meteors orbiting round the sun but inside the earth's orbit. Retarded in their orbits by an etherial medium, the meteors would progressively spiral towards the sun's surface in a cosmic vortex analogous toJames's vortex turbines (horizontal water-wheels). As the meteors vaporized by friction, they would generate immense quantities of heat. In the early 1860s, however, he adoptedHermann Helmholtz's version of the sun's heat whereby contraction of the body of the sun released heat over long periods. Either way, the sun's energy was finite and calculable, making possible order-of-magnitude estimates of the limited past and future duration of the sun. In response toCharles Darwin's demand for a much longer time for evolution by natural selection and in opposition toCharles Lyell's uniformitarian geology upon whichDarwin's claims were grounded,Thomson deployedFourier's conduction law to make similar estimates for the earth's age. The limited time-scale of about 100 million years (later reduced) approximated to estimates for the sun's age, but the new cosmogeny was itself evolutionary, offering little or no comfort to strict biblical literalists within the Scottish kirk, especially the recently foundedFree Church of Scotland.

The most celebrated textual embodiment of the 'science of energy' wasThomson andTait'sTreatise on Natural Philosophy (1867). Originally intending to treat all branches of natural philosophy,Thomson andTait in fact produced only the first volume of theTreatise. Taking statics to be derivative from dynamics, they reinterpretedNewton's third law (action–reaction) as conservation of energy, with action viewed as rate of working. Fundamental to the new energy physics was the move here to make extremum conditions, rather than point forces, the theoretical foundation of dynamics. The tendency of an entire system to move from one place to another in the most economical way would determine the forces and motions of the various parts of the system. Variational principles (especially least action) thus played a central role in the new dynamics.

Although never published in treatise form,Thomson's subsequent attempts to produce a unified theory of matter and ether at first centred on the ‘vortex atom’ which also had a powerful practical foundation inJames Thomson's vortex turbines and pumps. From 1867Thomson drew extensively onHermann Helmholtz's mathematical work on vortex motion and onTait's experimental demonstrations of smoke rings. The theory supposed matter to consist of rotating portions of a perfect (that is, frictionless) fluid which continuously filled space. Without internal friction the fluid and everything therein would require a creative act for the production or destruction of rotation and hence of matter. Although the model seemed ideal for simple thermodynamic systems, stability remained a serious problem.

In the wake ofMaxwell's electromagnetic theory of light,Thomson defended an elastic-solid model for light waves and remained for the most part highly sceptical of the work ofMaxwell's scientific heirs. Grounding his criticism upon the practical success of his own telegraph theory, he continually argued against any methodology which dealt in theoretical entities without a basis in direct sensory perception. These views were forcefully expressed in hisBaltimore Lectures, delivered to a distinguished academic audience at Johns Hopkins University in 1884, when he famously asserted: 'I can never satisfy myself until I can make a mechanical model of a thing … and that is why I cannot get the electro-magnetic theory'. For him,Maxwell's 'beautiful theory of electro displacements' had no foundation in such sensory reality (Smith andWise, 470).

Towards a system of electrical standards

Thomson's energy physics had its focal point in the physical laboratory. Ever since his participation inRegnault's laboratory practice in 1845 he had resolved to make physical measurements in absolute or mechanical measures. This commitment derived from a realization that electricity could be measured simply in terms of the work done by the fall of a quantity of electricity through a potential just in the way that work was done by the fall of a mass of water through a height. His absolute scale of temperature utilized the same notion of absolute measurement in the case of heat. His first public commitment to a system of absolute units for electrical measurement coincided both with his reading ofWilhelm Weber's contribution'On the measurement of electric resistance according to an absolute standard' toPoggendorff'sAnnalen (1851) and with his own'Dynamical theory of heat' series. In contrast toWeber's system founded on absolute measures of electromotive forces and intensities,Thomson's approach continued to be grounded on measurements of mechanical effect or work. His 1851 paper on the subject deployedJoule's mechanical equivalent to calculate the heat produced by the work done in an electrical circuit. Further applyingJoule's earlier relationship of heat to current and resistance squared yielded an expression for resistance in absolute measure.

Production of knowledge in this manner, and the establishment of new functions for laboratory work, led to an increasing number of student volunteer assistants whose labour was divided into a range of skills from basic measurement techniques to involvement in the most advanced experimental practice. By the winter session of 1860 the number of such volunteers had risen to about twenty, a large proportion of whom were deployed on telegraphic work which from the mid-1850s formed an integral part of the laboratory. By 1857, after resistance to further territorial expansion had been overcome,Thomson gained official recognition for the ‘physical laboratory’ which was now centred in a converted ground-floor space beneath the classroom but which was expanded by the early 1860s by annexation of the redundant Blackstone examination room, also on the ground floor and beneath the apparatus room. Even the college tower, however, was secured for experiments where a long perpendicular drop was required. Constituting the first university physical laboratory in Britain,Thomson's college spaces were replaced by a new, purpose-built laboratory when the whole University of Glasgow transferred to its Gilmorehill site in 1870.

Laboratory concerns with measurement of physical properties of matter soon connected directly with a matter of national importance. Unforeseen retardation effects upon signalling in long submarine telegraph cables threatened the viability of several ambitious projects aimed at giving rapid communication, and hence physical unity, to the scattered British empire.Faraday's qualitative diagnosis of the problem as one of treating underwater cables as Leyden jars of vast capacity for electric charge inspiredThomson's mathematical analysis, usingFourier's techniques, in 1854. His resulting law of the squares showed the dependence of the retardation effect on resistance and inductive capacity and suggested optimum dimensions for the planned Atlantic telegraph. His approach facilitated a new demand for accurate measurement of electrical quantities and his physical laboratory became a major source for the supply of such data. Employing his 1851 method of determining resistances in absolute measure, for example, he drew attention to the great variation in the resistance of different specimens of supposedly pure copper wire manufactured by different firms for use in telegraph cables. The effects on the commercial transmission of signals over long distances would be to reduce profitability and perhaps even render the project unworkable. Accurate measurement of resistances during manufacture would introduce quality control, and hence greater commercial stability, into the highly volatile telegraph business.

Submarine telegraphy

By 1856Thomson had been made a director of the newly formedAtlantic Telegraph Company. He accompanied the first expedition in 1857 but the parting of the cable after only a fewhundred miles had been laid halted the project. The following year he again joined the cable-laying ships, taking with him a new instrument, the marine mirror galvanometer, which he had recently invented and developed in Glasgow. The company's electrician,Wildman Whitehouse, remained ashore andThomson took charge of the electrical test-room aboard HMSAgamemnon, monitoring the condition of the cable. Soon after completion, however, signals became more and more unreliable, culminating in the total failure of communication. Other long-distance cables of the period suffered similar fates. A jointBoard of Trade/Atlantic Telegraph Company inquiry published its findings in 1861. Given the scientific representation on the committee, it was not surprising thatWhitehouse was portrayed as representing a discredited 'trial-and-error' approach and thus the principal scapegoat for telegraphic failures. The inquiry came down strongly in favour ofThomson's laboratory-centred methods, characterized by accurate measurement and absolute units.

Unable to attend the 1861 Manchester meeting of theBritish Association on account of a broken thigh sustained while curling on ice at Largs,Thomson had nevertheless been working vigorously behind the scenes to secure the appointment of a committee on standards of electrical resistance.Fleeming Jenkin, only recently introduced toThomson, handled on his behalf the delicate negotiations among practical electricians and natural philosophers. The outcome was a committee, already heavily weighted towards scientific men, which eventually included most members of the North British energy group:Thomson,Jenkin,Joule,Balfour Stewart, andMaxwell. Throughout the 1860sThomson played a leading role both in shaping the design of measuring apparatus and in promoting the adoption of an absolute system of physical measurement such that all the units (including resistance) of the system should bear a definite relation to the unit of work, 'the great connecting link between all physical measurements' (Smith andWise, 687).

In 1865 the largest ship in the world,Isambard Kingdom Brunel'sGreat Eastern, had been converted for the laying of a new Atlantic cable. Although the cable parted in mid-ocean, theGreat Eastern laid another new cable the following season before recovering and completing the severed original.Thomson's direct involvement in the two expeditions brought him a knighthood. Meanwhile, he had secured his first joint telegraphic patent withJenkin. By 1865 the partnership included the telegraph engineerCromwell Varley. This pooling of patent property enabled the partners, after protracted legal negotiations, to win favourable financial terms from the Atlantic telegraph companies—£7000 initially to the partners, with a guaranteed£2500 per annum for ten years thereafter. Many other patents followed, including in 1867 that forThomson's ‘siphon recorder’ which, by the automatic recording of telegraph signals on moving paper tape, served to minimize waste of time and improve economy of working.Thomson's involvement with ocean telegraphy continued: in 1869, for example, he andVarley were consulting electricians for the French Atlantic cable project.Thomson indeed later claimed that between 1866 and 1883 all signalling on ocean telegraphs was carried out with his instruments.

The instruments of navigation

With the wealth generated by telegraph patentsThomson purchased the126 ton schooner-rigged yachtLalla Rookh in 1870, a few months after the death of his wife,Margaret. Laid up during the six-month Glasgow session, theLalla Rookh served asThomson's floating laboratory and home throughout the summer as she voyaged among the Western Isles or made much longer cruises to Lisbon (1871), Gibraltar (1872), and Madeira (1874 and 1877). His absences from more familiar workplaces prompted his friendG. G. Stokes to remark that it was 'not easy to say where to find a man who owns a yacht' (Smith andWise, 736). However,Thomson was never idle. By the early 1870s he was testing both a new sounding apparatus (using pianoforte wire) and a new design of dry-card magnetic compass. The original sounding apparatus aided the cable shipHooper in the laying of the Brazilian cable in 1873. As theHooper lay at Madeira for sixteen days,Thomson made the acquaintance of theBlandy family, who lived on the island; he returned aboard theLalla Rookh a year later and proposed toFrances Anna Blandy (c.1838–1916), who became his second wife in June 1874. There were no children from either of his marriages. During a voyage to North America in 1876 aboard theCunard linerRussia,Thomson carried out extensive trials with both sounding machine and compass for navigational purposes. Patents quickly followed and soon he was marketing sounder and compass to the prestigious mail-liner companies of the empire, includingCunard,White Star,P. & O., andBritish India. Thanks to the vigorous support ofJacky Fisher (later first sea lord) theAdmiralty in 1889 adopted as its standard compassThomson's design which retained its naval pre-eminence until theAdmiralty began switching to liquid compasses in the 1900s.

Although the laboratory and theLalla Rookh remained the principal sites for invention, the expansion into manufacturing of telegraphic and navigational instruments required the construction of a separate factory.Thomson's association with the Glasgow instrument makerJames White dated from about 1854 and had developed especially during the peak of telegraphic work in the 1860s. By the 1880s the business had been transformed into a large-scale instrument factory, effectively underThomson's control and devoted to the production of his instruments. By 1900 the firm took the formal title ofKelvin and James White Ltd, with a rigorous division of labour among its 400-strong labour force from drawing office to polishing shop. The firm typically produced some 400 compasses per annum in the 1890s. With the growth of electric lighting and power in the 1880s, the firm added electrical measuring instruments to its production.Thomson, meanwhile, became directly involved in numerous electrical projects which ranged from electric traction for trams and trains to the production of hydroelectric power from Niagara and in the Scottish highlands (especially for the large-scale smelting of aluminium at Foyers by Loch Ness). By the end of his life he had a total of some seventy patents to his credit, either separately or jointly with his business partners.

Politics and peerage

A lifelong Liberal in politics,Thomson split with theLiberal Party at the time ofGladstone's firstHome Rule Bill (1886). As president of theWest of Scotland Liberal Unionist Association between 1886 and 1892, he therefore took an active role in opposing the moves for an Irishparliament. He firmly believed that liberal values of free trade, equality before the law, and freedom of religion were best preserved within a United Kingdom of Great Britain and Ireland and that local rule was a sure guarantee of sectarian strife, fruitless factionalism among parties, and the stifling of free commerce under protectionist legislation. Through his friendship with Liberal Unionist aristocrats such asLord Hartington (eighth duke of Devonshire from 1891) and theduke of Argyll,Thomson was well placed for elevation to the peerage in 1892, the first scientist to be thus honoured. With maternal connections to Kelvin Grove and with the university's location adjacent to the River Kelvin since 1870, it was appropriate thatWilliam Thomson should have becomeBaron Kelvin of Largs. Begun in the 1870s, his country seat, Netherhall, near Largs, provided the new peer with a permanent residence, although in his later years he and his wife would frequently travel to their London home at 15 Eaton Place.

The very high level of national and international credibility whichLord Kelvin had built up through his 53-year reign as Glasgow professor meant that he wielded immense scientific authority, but for the new generation, his views looked increasingly anachronistic. As younger groups of physicists grew more enthusiastic aboutMaxwell's electromagnetic theory of light, for instance, soKelvin's resistance to Maxwellian approaches and his own commitment to elastic-solid models made him appear increasingly conservative. Likewise, his reluctance to abandon his age-of-the-earth estimates (based on secular cooling of an originally molten earth) presented advocates of radioactivity (based on the generation of heat by radioactive elements distributed in the earth's crust) with a serious obstacle to easy acceptance of the new views. Even his representation of his dry-card compass as a majorAdmiralty reform came to be seen as a barrier to the introduction of liquid compasses in the 1900s.

During his life,Lord Kelvin received some twenty-one honorary doctorates from universities around the world (including Princeton, Yale, Toronto, and Heidelberg). He was a member or honorary member of nearly ninety learned societies and academies. Elected fellow of theRoyal Society in 1851, he was awarded its Copley medal in 1883 and served as its president from 1890 until 1895. He was also president of theBritish Association in 1871, president of theSociety of Telegraph Engineers in 1874, and three times president of theRoyal Society of Edinburgh (1873–8, 1886–90, and 1895–1907). In 1881 he was made commander of the French Légion d'honneur, and he became a grand officer eight years later. He was made knight of the Prussian order of merit in 1884. He served onAdmiralty committees in 1871 (for designs of ships of war) and in 1904–5 (for designs of the new dreadnought battleships and battle cruisers). He was appointed to the Order of Merit and was sworn of theprivy council in 1902.Lord Kelvin retired from the Glasgow chair in 1899, but became chancellor of the university in 1904 and continued working right up to his death, from a severe chill, at Netherhall on 17 December 1907. His funeral and burial took place in Westminster Abbey two days before Christmas.

View the article for this person in the Dictionary of National Biography archive edition.

See also

• North British network (act. c. 1845–c. 1890)
• Thomson, James (1786–1849), mathematician
• Thomson, James (1822–1892), mechanical engineer

More on this topic

• Kelvin, 1st Baron cr 1892, (William Thomson) (26 June 1824–17 Dec. 1907) inWho Was Who

External resources

• Bibliography of British and Irish history
• National Portrait Gallery
• National Archives
• English Heritage Blue Plaque
• Westminster Abbey, burials
• Dictionary of Irish Biography
• Dictionary of Ulster Biography
• Hansard