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William Thomson, 1st Baron Kelvin, (Lord Kelvin)
(26 June 1824 – 17 December 1907)

He was a British mathematical physicist, engineer, and outstanding leader in the physical sciences of the 19th century. He did important work in the mathematical analysis of electricity and thermodynamics, and did much to unify the emerging discipline of physics in its modern form. He is widely known for developing the Kelvin scale of absolute temperature measurement. The title Baron Kelvin was given in honour of his achievements, and named after the River Kelvin, which flowed past his university in Glasgow, Scotland.

He also had a second career as a telegraph engineer and inventor, a career that propelled him into the public eye and ensured his wealth, fame and honour.


Early life and work


The identity of William Thomson's mother is yet unknown, however Willam was only six years old when she died. William's father was Dr. James Thomson, the son of a Belfast farmer. James received little youthful instruction in Ulster but, when 24 years old, started to study for half the year at the University of Glasgow, Scotland, while working as a teacher back in Belfast for the other half. On graduating, he became a mathematics teacher at the Royal Belfast Academical Institution. He married Margaret Gardner in 1817 and, of their children, four boys and two girls survived infancy.

William and his elder brother James were tutored at home by their father while the younger boys were tutored by their elder sisters. James was intended to benefit from the major share of his father's encouragement, affection and financial support and was prepared for a fashionable career in engineering. However, James was a sickly youth and proved unsuited to a sequence of failed apprenticeships. William soon became his father's favourite.

In 1832, his father was appointed professor of mathematics at Glasgow and the family relocated there in October 1833. The Thomson children were introduced to a broader cosmopolitan experience than their father's rural upbringing, spending the summer of 1839 in London and, the boys, being tutored in French in Paris. The summer of 1840 was spent in Germany and the Netherlands. Language study was given a high priority.


William began study at Glasgow University in 1834 at the age of 10, not out of any precociousness; the University provided many of the facilities of an elementary school for abler pupils and this was a typical starting age. In 1839, John Pringle Nichol, the professor of astronomy, took the chair of natural philosophy. Nichol updated the curriculum, introducing the new mathematical works of Jean Baptiste Joseph Fourier. The mathematical treatment much impressed Thomson.

In the academic year 1839-1840, Thomson won the class prize in astronomy for his Essay on the figure of the Earth which showed an early facility for mathematical analysis and creativity. Throughout his life, he would work on the problems raised in the essay as a coping strategy at times of personal stress.

Thomson became intrigued with Fourier's Théorie analytique de la chaleur and committed himself to study the "Continental" mathematics resisted by a British establishment still working in the shadow of Sir Isaac Newton. Unsurprisingly, Fourier's work had been attacked by domestic mathematicians, Philip Kelland authoring a critical book. The book motivated Thomson to write his first published scientific paper under the pseudonym P.Q.R., defending Fourier, and submitted to the Cambridge Mathematical Journal by his father. A second P.Q.R paper followed almost immediately.

While vacationing with his family in Lamlash in 1841, he wrote a third, more substantial, P.Q.R. paper On the uniform motion of heat in homogeneous solid bodies, and its connection with the mathematical theory of electricity. In the paper he made remarkable connections between the mathematical theories of heat conduction and electrostatics, an analogy that James Clerk Maxwell was ultimately to describe as one of the most valuable science-forming ideas.


William's father was able to make a generous provision for his favourite son's education and, in 1841, installed him, with extensive letters of introduction and ample accommodation, at Peterhouse, Cambridge. In 1845 Thomson graduated as Second Wrangler. However, he won a Smith's Prize, sometimes regarded as a better test of originality than the tripos. Robert Leslie Ellis, one of the examiners, is said to have declared to another examiner You and I are just about fit to mend his pens.

While at Cambridge, Thomson was active in sports and athletics. He won the Silver Sculls, and rowed in the winning boat of the Oxford and Cambridge Boat Race. He also took a lively interest in the classics, music, and literature; but the real love of his intellectual life was the pursuit of science. The study of mathematics, physics, and in particular, of electricity, had captivated his imagination.

In 1845 he gave the first mathematical development of Faraday's idea that electric induction takes place through an intervening medium, or "dielectric", and not by some incomprehensible "action at a distance". He also devised a hypothesis of electrical images, which became a powerful agent in solving problems of electrostatics, or the science which deals with the forces of electricity at rest. It was partly in response to his encouragement that Faraday undertook the research in September of 1845 that led to the discovery of the Faraday effect, which established that light and magnetic (and thus electric) phenomena were related.

On gaining a fellowship at his college, he spent some time in the laboratory of the celebrated Henri Victor Regnault, at Paris; but in 1846 he was appointed to the chair of natural philosophy in the University of Glasgow. At twenty-two he found himself wearing the gown of a learned professor in one of the oldest Universities in the country, and lecturing to the class of which he was a freshman but a few years before.


By 1847, Thomson had already gained a reputation as a precocious and maverick scientist when he attended the British Association for the Advancement of Science annual meeting in Oxford. At that meeting, he heard James Prescott Joule making yet another of his, so far, ineffective attempts to discredit the caloric theory of heat and the theory of the heat engine built upon it by Sadi Carnot and Émile Clapeyron. Joule argued for the mutual convertibility of heat and mechanical work and for their mechanical equivalence.

Thomson was intrigued but skeptical. Though he felt that Joule's results demanded theoretical explanation, he retreated into an even deeper commitment to the Carnot-Clapeyron school. He predicted that the melting point of ice must fall with pressure, otherwise its expansion on freezing could be exploited in a perpetuum mobile. Experimental confirmation in his laboratory did much to bolster his beliefs.

In 1848, he extended the Carnot-Clapeyron theory still further through his dissatisfaction that the gas thermometer provided only an operational definition of temperature. He proposed an absolute temperature scale in which 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, whatever be the number T. Such a scale would be quite independent of the physical properties of any specific substance. By employing such a "waterfall", Thomson postulated that a point would be reached at which no further heat (caloric) could be transferred, the point of absolute zero about which Guillaume Amontons had speculated in 1702. Thomson used data published by Regnault to calibrate his scale against established measurements.

In his publication, Thomson wrote:

... the conversion of heat (or caloric) into mechanical effect is probably impossible, certainly undiscovered

- but a footnote signalled his first doubts about the caloric theory, referring to Joule's very remarkable discoveries. Surprisingly, Thomson did not send Joule a copy of his paper but when Joule eventually read it he wrote to Thomson on 6 October, claiming that his studies had demonstrated conversion of heat into work but that he was planning further experiments. Thomson replied on 27 October, revealing that he was planning his own experiments and hoping for a reconciliation of their two views.

Thomson returned to critique Carnot's original publication and read his analysis to the Royal Society of Edinburgh in January 1849, still convinced that the theory was fundamentally sound. However, though Thomson conducted no new experiments, over the next two years he became increasingly dissatisfied with Carnot's theory and convinced of Joule's. In February 1851 he sat down to articulate his new thinking. However, he was uncertain of how to frame his theory and the paper went through several drafts before he settled on an attempt to reconcile Carnot and Joule. During his rewriting, he seems to have considered ideas that would subsequently give rise to the second law of thermodynamics. In Carnot's theory, lost heat was absolutely lost but Thomson contended that it was "lost to man irrecoverably; but not lost in the material world". Moreover, his theological beliefs led to speculation about the heat death of the universe.

I believe the tendency in the material world is for motion to become diffused, and that as a whole the reverse of concentration is gradually going on - I believe that no physical action can ever restore the heat emitted from the sun, and that this source is not inexhaustible; also that the motions of the earth and other planets are losing vis viva which is converted into heat; and that although some vis viva may be restored for instance to the earth by heat received from the sun, or by other means, that the loss cannot be precisely compensated and I think it probable that it is under compensated.

Compensation would require a creative act or an act possessing similar power.

In final publication, Thomson retreated from a radical departure and declared "the whole theory of the motive power of heat is founded on ... two ... propositions, due respectively to Joule, and to Carnot and Clausius." Thomson went on to state a form of the second law:

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.

In the paper, Thomson supported the theory that heat was a form of motion but admitted that he had been influenced only by the thought of Sir Humphry Davy and the experiments of Joule and Julius Robert von Mayer, maintaining that experimental demonstration of the conversion of heat into work was still outstanding.

As soon as Joule read the paper he wrote to Thomson with his comments and questions. Thus began a fruitful, though largely epistolary, collaboration between the two men, Joule conducting experiments, Thomson analysing the results and suggesting further experiments. The collaboration lasted from 1852 to 1856, its discoveries including the Joule-Thomson effect, sometimes called the Kelvin-Joule effect, and the published results did much to bring about general acceptance of Joule's work and the kinetic theory.

Thomson published more than 600 scientific papers and filed over 70 patents.

Transatlantic cable

Calculations on data-rate

Though now eminent in the academic field, Thomson was obscure to the general public. In September 1852, he married childhood sweetheart Margaret Crum but her health broke down on their honeymoon and, over the next seventeen years, Thomson was distracted by her suffering. On 16 October 1854, George Gabriel Stokes wrote to Thomson to try to re-interest him in work by asking his opinion on some experiments of Michael Faraday on the proposed transatlantic telegraph cable.

To understand the technical issues in which Thomson became involved, see Submarine communications cable: Bandwidth problems

Faraday had demonstrated how the construction of a cable would limit the rate at which messages could be sent — in modern terms, the bandwidth. Thomson jumped at the problem and published his response that month. He expressed his results in terms of the data rate that could be achieved and the economic consequences in terms of the potential revenue of the transatlantic undertaking. In a further 1855 analysis, Thomson stressed the impact that the design of the cable would have on its profitability.

Thomson contended that the speed of a signal through a given core was inversely proportional to the square of the length of the core. Thomson's results were disputed at a meeting of the British Association in 1856 by Wildman Whitehouse, the electrician of the Atlantic Telegraph Company. Whitehouse had possibly misinterpreted the results of his own experiments but was doubtless feeling financial pressure as plans for the cable were already well underway. He believed that Thomson's calculations implied that the cable must be "abandoned as being practically and commercially impossible."

Thomson attacked Whitehouse's contention in a letter to the popular Athenaeum magazine, pitching himself into the public eye. Thomson recommended a larger conductor with a larger cross section of insulation. However, he thought Whitehouse no fool and suspected that he may have the practical skill to make the existing design work. Thomson's work had, however, caught the eye of the project's undertakers and in December 1856, he was elected to the board of directors of the Atlantic Telegraph Company.

Scientist to engineer

Thomson became scientific adviser to a team with Whitehouse as chief electrician and Sir Charles Tilston Bright as chief engineer but Whitehouse had his way with the specification, supported by Faraday and Samuel F. B. Morse.

Thomson sailed on board the cable-laying ship HMSS Agamemnon in August 1857, with Whitehouse confined to land owing to illness, but the voyage ended after just 380 miles when the cable parted. Thomson contributed to the effort by publishing in the Engineer the whole theory of the stresses involved in the laying of a submarine cable, and showed that when the line is running out of the ship, at a constant speed, in a uniform depth of water, it sinks in a slant or straight incline from the point where it enters the water to that where it touches the bottom.

Thomson developed a complete system for operating a submarine telegraph that was capable of sending a character every 3.5 seconds. He patented the key elements of his system, the mirror galvanometer and the siphon recorder, in 1858.

However, Whitehouse still felt able to ignore Thomson's many suggestions and proposals. It was not until Thomson convinced the board that using a purer copper for replacing the lost section of cable would improve data capacity, that he first made a difference to the execution of the project.

The board insisted that Thomson join the 1858 cable-laying expedition, without any financial compensation, and take an active part in the project. In return, Thomson secured a trial for his mirror galvanometer, about which the board had been unenthusiastic, alongside Whitehouse's equipment. However, Thomson found the access he was given unsatisfactory and the Agamemnon had to return home following the disastrous storm of June 1858. Back in London, the board was on the point of abandoning the project and mitigating their losses by selling the cable. Thomson, Cyrus West Field and Curtis M. Lampson argued for another attempt and prevailed, Thomson insisting that the technical problems were tractable. Though employed in an advisory capacity, Thomson had, during the voyages, developed real engineer's instincts and skill at practical problem-solving under pressure, often taking the lead in dealing with emergencies and being unafraid to lend a hand in manual work. A cable was finally completed in August 5.

Disaster and triumph

Thomson's fears were realised and Whitehouse's apparatus proved insufficiently sensitive and had to be replaced by Thomson's mirror galvanometer. Whitehouse continued to maintain that it was his equipment that was providing the service and started to engage in desperate measures to remedy some of the problems. He succeeded only in fatally damaging the cable by applying 2,000 V. When the cable failed completely Whitehouse was dismissed, though Thomson objected and was reprimanded by the board for his interference. Thomson subsequently regretted that he had acquiesced too readily to many of Whitehouse's proposals and had not challenged him with sufficient energy.

A joint committee of inquiry was established by the Board of Trade and the Atlantic Telegraph Company. Most of the blame for the cable's failure was found to rest with Whitehouse. The committee found that, though underwater cables were notorious in their lack of reliability, most of the problems arose from known and avoidable causes. Thomson was appointed one of a five-member committee to recommend a specification for a new cable. The committee reported in October 1863.

In July 1865 Thomson sailed on the cable-laying expedition of the SS Great Eastern but the voyage was again dogged with technical problems. The cable was lost after 1,200 miles had been laid and the expedition had to be abandoned. A further expedition in 1866 managed to lay a new cable in two weeks and then go on to recover and complete the 1865 cable. The enterprise was now feted as a triumph by the public and Thomson enjoyed a large share of the adulation. Thomson, along with the other principals of the project, was knighted on November 10 1866.

To exploit his inventions for signalling on long submarine cables, Thomson now entered into a partnership with C.F. Varley and Fleeming Jenkin. In conjunction with the latter, he also devised an automatic curb sender, a kind of telegraph key for sending messages on a cable.

Later expeditions

Thomson took part in the laying of the French Atlantic submarine communications cable of 1869, and with Jenkin was engineer of the Western and Brazilian and Platino-Brazilian cables, assisted by vacation student James Alfred Ewing. He was present at the laying of the Pará to Pernambuco section of the Brazilian coast cables in 1873.

Thomson's wife had died on 17 June 1870 and he resolved to make changes in his life. Already addicted to seafaring, in September he purchased a 126 ton schooner, the Lalla Rookh and used it as a base for entertaining friends and scientific colleagues. His maritime interests continued in 1871 when he was appointed to the board of enquiry into the sinking of the HMS Captain.

In June 1873, Thomson and Jenkin were onboard the Hooper, bound for Lisbon with 2,500 miles of cable when the cable developed a fault. An unscheduled 16-day stop-over in Madeira followed and Thomson became good friends with Charles R. Blandy and his three daughters. On 2 May 1874 he set sail for Madeira on the Lalla Rookh. As he approached the harbour, he signalled to the Blandy residence Will you marry me? and Fanny signalled back Yes. Thomson married Fanny, 13 years his junior, on 24 June 1874.

Thomson & Tait: Treatise on Natural Philosophy

Over the period 1855 to 1867, Thomson collaborated with Peter Guthrie Tait on a text book that unified the various branches of physical science under the common principle of energy. Published in 1867, the Treatise on Natural Philosophy did much to define the modern discipline of physics.


Thomson was an enthusiastic yachtsman, his interest in all things relating to the sea perhaps arising, or at any rate fostered, from his experiences on the Agamemnon and the Great Eastern.

Thomson introduced a method of deep-sea sounding, in which a steel piano wire replaces the ordinary land line. The wire glides so easily to the bottom that "flying soundings" can be taken while the ship is going at full speed. A pressure gauge to register the depth of the sinker was added by Thomson.

About the same time he revived the Sumner method of finding a ship's place at sea, and calculated a set of tables for its ready application. He also developed a tide predicting machine.

During the 1880s, Thomson worked to perfect the adjustable compass in order to correct errors arising from magnetic deviation owing to the increasing use of iron in naval architecture. Thomson's design was a great improvement on the older instruments, being steadier and less hampered by friction, the deviation due to the ship's own magnetism being corrected by movable masses of iron at the binnacle. Thomson's innovations involved much detailed work to develop principles already identified by George Biddell Airy and others but contributed little in terms of novel physical thinking. Thomson's energetic lobbying and networking proved effective in gaining acceptance of his instrument by The Admiralty.

Scientific biographers of Thomson, if they have paid any attention at all to his compass innovations, have generally taken the matter to be a sorry saga of dim-witted naval administrators resisting marvellous innovations from a superlative scientific mind. Writers sympathetic to the Navy, on the other hand, portray Thomson as a man of undoubted talent and enthusiasm, with some genuine knowledge of the sea, who managed to parlay a handful of modest ideas in compass design into a commercial monopoly for his own manufacturing concern, using his reputation as a bludgeon in the law courts to beat down even small claims of originality from others, and persuading the Admiralty and the law to overlook both the deficiencies of his own design and the virtues of his competitors'.

The truth, inevitably, seems to lie somewhere between the two extremes.

Charles Babbage had been among the first to suggest that a lighthouse might be made to signal a distinctive number by occultations of its light but Thomson pointed out the merits of the Morse code for the purpose, and urged that the signals should consist of short and long flashes of the light to represent the dots and dashes.

Electrical standards

Thomson did more than any other electrician up to his time to introduce accurate methods and apparatus for measuring electricity. As early as 1845 he pointed out that the experimental results of William Snow Harris were in accordance with the laws of Coulomb. In the Memoirs of the Roman Academy of Sciences for 1857 he published a description of his new divided ring electrometer, based on the old electroscope of Johann Gottlieb Friedrich von Bohnenberger and he introduced a chain or series of effective instruments, including the quadrant electrometer, which cover the entire field of electrostatic measurement. He invented the current balance, also known as the Kelvin balance or Ampere balance (sic), for the precise specification of the ampere, the standard unit of electric current.

In 1893, Thomson headed an international commission to decide on the design of the Niagara Falls power station. Despite his previous belief in the superiority of direct current electric power transmission, he was convinced by Nikola Tesla's demonstration of three-phase alternating current power transmission at the Chicago World's Fair of that year and agreed to use Tesla's system. In 1896, Thomson said "Tesla has contributed more to electrical science than any man up to his time."

Geology and theology

Thomson remained a devout believer in Christianity throughout his life: attendance at chapel was part of his daily routine, though he might not identify with fundamentalism if he were alive today. He saw his Christian faith as supporting and informing his scientific work, as is evident from his address to the annual meeting of the Christian Evidence Society, 23 May 1889.

One of the clearest instances of this interaction is in his estimate of the age of the Earth. Given his youthful work on the figure of the Earth and his interest in heat conduction, it is no surprise that he chose to investigate the Earth's cooling and to make historical inferences of the earth's age from his calculations. Thomson believed in an instant of Creation but he was no creationist in the modern sense. He contended that the laws of thermodynamics operated from the birth of the universe and envisaged a dynamic process that saw the organisation and evolution of the solar system and other structures, followed by a gradual "heat death". He developed the view that the Earth had once been too hot to support life and contrasted this view with that of uniformitarianism, that conditions had remained constant since the indefinite past. He contended that "This earth, certainly a moderate number of millions of years ago, was a red-hot globe ... ."

After the publication of Charles Darwin's On the Origin of Species in 1859, Thomson saw evidence of the relatively short habitable age of the Earth as tending to contradict an evolutionary explanation of biological diversity. He noted that the sun could not have possibly existed long enough to allow the slow incremental development by evolution — unless some energy source beyond what he or any other Victorian era person knew of was found. He was soon drawn into public disagreement with Darwin's supporters John Tyndall and T.H. Huxley. In his response to Huxley’s address to the Geological Society of London (1868) he presented his address "Of Geological Dynamics", (1869) which, among his other writings, set back the scientific acceptance that the earth must be of very great age.

Thomson ultimately settled on an estimate that the Earth was 20-40 million years old. Shortly before his death however, Becquerel's discovery of radioactivity and Marie Curie's studies with uranium ores provided the insight into the 'energy source beyond' that would power the sun for the long time-span required by the theory of evolution.

Limits of classical physics

In 1884, Thomson delivered a series of lectures at Johns Hopkins University in the United States in which he attempted to formulate a physical model for the aether, a medium that would support the electromagnetic waves that were becoming increasingly important to the explanation of radiative phenomena. Imaginative as were the "Baltimore lectures", they had little enduring value owing to the imminent demise of the mechanical world view.

In 1900, he gave a lecture titled Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light. The two "dark clouds" he was alluding to were the unsatisfactory explanations that the physics of the time could give for two phenomena: the Michelson-Morley experiment and black body radiation. Two major physical theories were developed during the twentieth century starting from these issues: for the former, the Theory of relativity; for the second, quantum mechanics. Albert Einstein, in 1905, published the so-called "Annus Mirabilis Papers", one of which explained the photoelectric effect and was of the foundation papers of quantum mechanics, another of which described special relativity.

Pronouncements later proven to be false

Like most scientists of his day, he is known for making some embarrassing mistakes in terms of predicting the future of technology.

In 1895, as president of the Royal Society, Kelvin is quoted as saying, "Heavier-than-air flying machines are impossible," proven false a mere eight years later with the flight of Orville and Wilbur Wright's Wright Flyer at Kitty Hawk in 1903. In 1897, he predicted that "Radio has no future;" while the popularity of radio did not appear in his lifetime (it was not until the 1920s and 30s that it attained any degree of popularity), the statement was nevertheless proven false.










This web page was last updated on: 16 December, 2008