seamus dubhghaill

Promoting Irish Culture and History from Little Rock, Arkansas, USA


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Death of Mathematician Sir William Rowan Hamilton

Sir William Rowan Hamilton, Irish mathematician, Andrews Professor of Astronomy at Trinity College, Dublin, and Royal Astronomer of Ireland, who makes important contributions to classical mechanics, optics, and algebra, dies in Dublin on September 2, 1865, following a severe attack of gout.

Hamilton is born in Dublin on August 4, 1805, the fourth of nine children born to Sarah Hutton (1780–1817) and Archibald Hamilton (1778–1819). He is part of a small but well-regarded school of mathematicians associated with Trinity College, Dublin, which he enters at age eighteen. He is said to have shown immense talent at a very early age. Astronomer Bishop Dr. John Brinkley remarks of the 18-year-old Hamilton, “This young man, I do not say will be, but is, the first mathematician of his age.”

Trinity College awards him two Optimes, or off-the-chart grades. He studies both classics and mathematics, and is appointed Professor of Astronomy just prior to his graduation. He then takes up residence at Dunsink Observatory where he spends the rest of his life.

Although Hamilton regards himself as a pure mathematician rather than a physicist, his work is of major importance to physics, particularly his reformulation of Newtonian mechanics, now called Hamiltonian mechanics. This work has proven central to the modern study of classical field theories such as electromagnetism, and to the development of quantum mechanics. In pure mathematics, he is best known as the inventor of quaternions.

Hamilton’s scientific career includes the study of geometrical optics, classical mechanics, adaptation of dynamic methods in optical systems, applying quaternion and vector methods to problems in mechanics and in geometry, development of theories of conjugate algebraic couple functions, solvability of polynomial equations and general quintic polynomial solvable by radicals, the analysis on Fluctuating Functions, linear operators on quaternions and proving a result for linear operators on the space of quaternions, which is a special case of the general theorem which today is known as the Cayley–Hamilton theorem. He also invents Icosian calculus, which he uses to investigate closed edge paths on a dodecahedron that visit each vertex exactly once.

Hamilton retains his faculties unimpaired to the very last, and steadily continues the task of finishing the Elements of Quaternions which occupies the last six years of his life. He dies in Dublin on September 2, 1865, following a severe attack of gout precipitated by excessive drinking and overeating. He is buried in Mount Jerome Cemetery in Dublin.


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Birth of George Francis FitzGerald, Academic & Physicist

Professor George Francis FitzGerald FRS FRSE, Irish academic and physicist, is born at No. 19, Lower Mount Street in Dublin on August 3, 1851. He is known for his work in electromagnetic theory and for the Lorentz–FitzGerald contraction, which becomes an integral part of Albert Einstein‘s special theory of relativity.

FitzGerald is born to the Reverend William FitzGerald and his wife Anne Frances Stoney. He is the nephew of George Johnstone Stoney, the Irish physicist who coins the term “electron.” After the particles are discovered by J. J. Thomson and Walter Kaufmann in 1896, FitzGerald is the one to propose calling them electrons. He is also the nephew of Bindon Blood Stoney, an eminent Irish engineer. His cousin is Edith Anne Stoney, a pioneer female medical physicist.

Professor of Moral Philosophy at Trinity College Dublin and vicar of St. Anne’s, Dawson Street, at the time of his son’s birth, William FitzGerald is consecrated Bishop of Cork, Cloyne and Ross in 1857 and translates to Killaloe and Clonfert in 1862. George returns to Dublin and enters TCD as a student at the age of sixteen, winning a scholarship in 1870 and graduating in 1871 in Mathematics and Experimental Science. He becomes a Fellow of Trinity in 1877 and spends the rest of his career there, serving as Erasmus Smith’s Professor of Natural and Experimental Philosophy from 1881 to 1901.

Along with Oliver Lodge, Oliver Heaviside and Heinrich Hertz, FitzGerald is a leading figure among the group of “Maxwellians” who revise, extend, clarify, and confirm James Clerk Maxwell‘s mathematical theories of the electromagnetic field during the late 1870s and the 1880s.

In 1883, following from Maxwell’s equations, FitzGerald is the first to suggest a device for producing rapidly oscillating electric currents to generate electromagnetic waves, a phenomenon which is first shown to exist experimentally by the German physicist Heinrich Hertz in 1888.

In 1883, FitzGerald is elected Fellow of the Royal Society. In 1899, he is awarded a Royal Medal for his investigations in theoretical physics. In 1900, he is made an honorary fellow of the Royal Society of Edinburgh.

FitzGerald is better known for his conjecture in his short letter to the editor of Science. “The Ether and the Earth’s Atmosphere” explains that if all moving objects were foreshortened in the direction of their motion, it would account for the curious null-results of the Michelson–Morley experiment. He bases this idea in part on the way electromagnetic forces are known to be affected by motion. In particular, he uses some equations that had been derived a short time before by his friend the electrical engineer Oliver Heaviside. The Dutch physicist Hendrik Lorentz hits on a very similar idea in 1892 and develops it more fully into Lorentz transformations, in connection with his theory of electrons.

The Lorentz–FitzGerald contraction hypothesis becomes an essential part of the Special Theory of Relativity, as Albert Einstein publishes it in 1905. He demonstrates the kinematic nature of this effect, by deriving it from the principle of relativity and the constancy of the speed of light.

FitzGerald suffers from many digestive problems for much of his shortened life. He becomes very ill with stomach problems. He dies on February 22, 1901 at his home, 7 Ely Place in Dublin, the day after an operation on a perforated ulcer. He is buried in Mount Jerome Cemetery.

A crater on the far side of the Moon is named after FitzGerald, as is a building at Trinity College Dublin.


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Birth of Sir Joseph Larmor, Physicist & Mathematician

Sir Joseph Larmor FRS FRSE, Irish and British physicist and mathematician who makes breakthroughs in the understanding of electricity, dynamics, thermodynamics, and the electron theory of matter, is born in Magheragall, County Antrim on July 11, 1857. His most influential work is Aether and Matter, a theoretical physics book published in 1900.

Larmor is the son of Hugh Larmor, a Belfast shopkeeper and his wife, Anna Wright. The family moves to Belfast around 1860, and he is educated at the Royal Belfast Academical Institution, and then studies mathematics and experimental science at Queen’s College, Belfast, where one of his teachers is John Purser. He obtains his BA in 1874 and MA in 1875. He subsequently studies at St. John’s College, Cambridge where in 1880 he is Senior Wrangler and Smith’s Prizeman, and obtains his MA in 1883. After teaching physics for a few years at Queen’s College, Galway, he accepts a lectureship in mathematics at Cambridge in 1885. In 1892 he is elected a Fellow of the Royal Society of London, and he serves as one of the Secretaries of the society. He is made an Honorary Fellow of the Royal Society of Edinburgh in 1910.

In 1903 Larmor is appointed Lucasian Professor of Mathematics at Cambridge, a post he retains until his retirement in 1932. He never marries. He is knighted by King Edward VII in 1909.

Motivated by his strong opposition to Home Rule for Ireland, in February 1911 Larmor runs for and is elected as Member of Parliament for Cambridge University (UK Parliament constituency) with the Conservative Party. He remains in parliament until the 1922 general election, at which point the Irish question has been settled. Upon his retirement from Cambridge in 1932 he moves back to County Down in Northern Ireland.

Larmor receives the honorary Doctor of Laws (LLD) from the University of Glasgow in June 1901. He is awarded the Poncelet Prize for 1918 by the French Academy of Sciences. He is a Plenary Speaker in 1920 at the International Congress of Mathematicians (ICM) at Strasbourg and an Invited Speaker at the ICM in 1924 in Toronto and at the ICM in 1928 in Bologna.

Larmor dies in Holywood, County Down, Northern Ireland on May 19, 1942.


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Birth of Robert Boyle, Philosopher, Writer & Chemist

Robert Boyle, Anglo-Irish natural philosopher, theological writer, chemist, physicist, inventor and a preeminent figure of 17th-century intellectual culture, is born on January 25, 1627 at Lismore Castle, in County Waterford.

At age eight, Boyle begins his formal education at Eton College, where his studious nature quickly becomes apparent. In 1639 he and his brother Francis embark on a grand tour of the continent together with their tutor Isaac Marcombes. In 1642, owing to the Irish rebellion, Francis returns home while Robert remains with his tutor in Geneva and pursues further studies.

Boyle returns to England in 1644, where he takes up residence at his hereditary estate of Stalbridge in Dorset. There he begins a literary career writing ethical and devotional tracts, some of which employ stylistic and rhetorical models drawn from French popular literature, especially romance writings. In 1649 he begins investigating nature via scientific experimentation. From 1647 until the mid-1650s, he remains in close contact with a group of natural philosophers and social reformers gathered around the intelligencer Samuel Hartlib. This group, the Hartlib Circle, includes several chemists who heighten his interest in experimental chemistry.

Boyle spends much of 1652–1654 in Ireland overseeing his hereditary lands and performing some anatomic dissections. In 1654 he is invited to Oxford, and he takes up residence at the university until 1668. In Oxford he is exposed to the latest developments in natural philosophy and becomes associated with a group of notable natural philosophers and physicians, including John Wilkins, Christopher Wren, and John Locke. These individuals, together with a few others, form the “Experimental Philosophy Club.” Much of Boyle’s best known work dates from this period.

In 1659 Boyle and Robert Hooke, the clever inventor and subsequent curator of experiments for the Royal Society, complete the construction of their famous air pump and use it to study pneumatics. Their resultant discoveries regarding air pressure and the vacuum appear in Boyle’s first scientific publication, New Experiments Physico-Mechanicall, Touching the Spring of the Air and Its Effects (1660). Boyle and Hooke discover several physical characteristics of air, including its role in combustion, respiration, and the transmission of sound. One of their findings, published in 1662, later becomes known as “Boyle’s law.” This law expresses the inverse relationship that exists between the pressure and volume of a gas, and it is determined by measuring the volume occupied by a constant quantity of air when compressed by differing weights of mercury.

Among Boyle’s most influential writings are The Sceptical Chymist (1661), which assails the then-current Aristotelian and especially Paracelsian notions about the composition of matter and methods of chemical analysis, and the Origine of Formes and Qualities (1666), which uses chemical phenomena to support the corpuscularian hypothesis. He argues so strongly for the need of applying the principles and methods of chemistry to the study of the natural world and to medicine that he later gains the appellation of the “father of chemistry.”

Boyle is a devout and pious Anglican who keenly champions his faith. He sponsors educational and missionary activities and writes a number of theological treatises. He is deeply concerned about the widespread perception that irreligion and atheism are on the rise, and he strives to demonstrate ways in which science and religion are mutually supportive. For Boyle, studying nature as a product of God’s handiwork is an inherently religious duty. He argues that this method of study would, in return, illuminate God’s omnipresence and goodness, thereby enhancing a scientist’s understanding of the divine. The Christian Virtuoso (1690) summarizes these views and may be seen as a manifesto of his own life as the model of a Christian scientist.

In 1668 Boyle leaves Oxford and takes up residence with his sister Katherine Jones, Vicountess Ranelagh, in her house on Pall Mall in London. There he sets up an active laboratory, employs assistants, receives visitors, and publishes at least one book nearly every year. Living in London also provides him the opportunity to participate actively in the Royal Society.

Boyle is a genial man who achieves both national and international renown during his lifetime. He is offered the presidency of the Royal Society and the episcopacy but declines both. Throughout his adult life, he is sickly, suffering from weak eyes and hands, recurring illnesses, and one or more strokes. He dies in London at age 64 on December 31, 1691 after a short illness exacerbated by his grief over Katherine’s death a week earlier. He leaves his papers to the Royal Society and a bequest for establishing a series of lectures in defense of Christianity. These lectures, now known as the Boyle Lectures, continue to this day.


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Birth of John Tyndall, Experimental Physicist

File source: //commons.wikimedia.org/wiki/File:John_Tyndall_(scientist).jpgJohn Tyndall, Irish experimental physicist who, during his long residence in England, is an avid promoter of science in the Victorian era, is born on August 2, 1820 in Leighlinbridge, County Carlow.

Tyndall is born into a poor Protestant Irish family. After a thorough basic education he works as a surveyor in Ireland and England from 1839 to 1847. When his ambitions turns from engineering to science, he spends his savings on gaining a Ph.D. from the University of Marburg in Marburg, Hesse, Germany (1848–1850), but then struggles to find employment.

In 1853 Tyndall is appointed Professor of Natural Philosophy at the Royal Institution, London. There he becomes a friend of the much-admired physicist and chemist Michael Faraday, entertains and instructs fashionable audiences with brilliant lecture demonstrations rivaling the biologist Thomas Henry Huxley in his popular reputation and pursuing his research.

An outstanding experimenter, particularly in atmospheric physics, Tyndall examines the transmission of both radiant heat and light through various gases and vapours. He discovers that water vapor and carbon dioxide absorb much more radiant heat than the gases of the atmosphere and argues the consequent importance of those gases in moderating Earth’s climate, that is, in the natural greenhouse effect. He also studies the diffusion of light by large molecules and dust, known as the Tyndall effect, and he performs experiments demonstrating that the sky’s blue color results from the scattering of the Sun’s rays by molecules in the atmosphere.

Tyndall is passionate and sensitive, quick to feel personal slights and to defend underdogs. Physically tough, he is a daring mountaineer. His greatest fame comes from his activities as an advocate and interpreter of science. In collaboration with his scientific friends in the small, private X Club, he urges greater recognition of both the intellectual authority and practical benefits of science.

Tyndall is accused of materialism and atheism after his presidential address at the 1874 meeting of the British Association for the Advancement of Science, when he claims that cosmological theory belongs to science rather than theology and that matter has the power within itself to produce life. In the ensuing notoriety over this “Belfast Address,” his allusions to the limitations of science and to mysteries beyond human understanding are overlooked. He engages in a number of other controversies such as spontaneous generation, the efficacy of prayer and Home Rule for Ireland.

In his last years Tyndall often takes chloral hydrate to treat his insomnia. When bedridden and ailing, he dies from an accidental overdose of this drug on December 4, 1893 at the age of 73 and was buried at Haslemere, Surrey, England.

Tyndall is commemorated by a memorial, the Tyndalldenkmal, erected at an elevation of 7,680 ft. on the mountain slopes above the village of Belalp, where he had his holiday home, and in sight of the Aletsch Glacier, which he had studied.


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Birth of James Thomson, Engineer & Physicist

james-thomsonJames Thomson, engineer and physicist whose reputation is substantial though overshadowed by that of his younger brother William Thomson (Lord Kelvin), is born in Belfast on February 16, 1822.

Thomson spends much of his youth in Glasgow. His father James is professor of mathematics at the University of Glasgow from 1832 onward. He attends Glasgow University from a young age and graduates in 1839 with high honors in his late teens. After graduation, he serves brief apprenticeships with practical engineers in several domains. He then gives a considerable amount of his time to theoretical and mathematical engineering studies, often in collaboration with his brother, during his twenties in Glasgow. In his late twenties he enters into private practice as a professional engineer with special expertise in water transport. In 1855, he is appointed professor of civil engineering at Queen’s University Belfast. He remains there until 1873, when he accepts the Regius professorship of Civil Engineering and Mechanics at the University of Glasgow in which he is successor to the influential William Rankine. He serves in this position until he resigns with failing eyesight in 1889.

In 1875 Thomson is elected a Fellow of the Royal Society of Edinburgh. His proposers are his younger brother William, Peter Guthrie Tait, Alexander Crum Brown and John Hutton Balfour. He is elected a Fellow of the Royal Society of London in June 1877. He serves as President of the Institution of Engineers and Shipbuilders in Scotland from 1884 to 1886.

Thomson dies of cholera in Glasgow on May 8, 1892. He is buried on the northern slopes of the Glasgow Necropolis overlooking Glasgow Cathedral. One obituary describes Thomson as “a man of singular purity of mind and simplicity of character,” whose “gentle kindness and unfailing courtesy will be long remembered.”

Thomson is known for his work on the improvement of water wheels, water pumps and turbines. He is also known for his innovations in the analysis of regelation, i.e., the effect of pressure on the freezing point of water, and his studies in glaciology including glacial motion, where he extends the work of James David Forbes. He studies the experimental work of his colleague Thomas Andrews concerning the continuity of the liquid and gaseous states of matter, and strengthens understanding of it by applying his strong knowledge of thermodynamics. He derives a simplified form of the Clapeyron equation for the solid-liquid phase boundary. He proposes the term triple point to describe the conditions for which solid, liquid and vapour states are all in equilibrium.

Thomson also makes contributions in the realm of fluid dynamics of rivers. It is claimed that the term torque is introduced into English scientific literature by Thomson in 1884.


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Birth of Henry Dixon, Biologist & Professor

Generated by IIPImageHenry Horatio Dixon, plant biologist and professor at Trinity College, Dublin, is born in Dublin on May 19, 1869. Along with John Joly, he puts forward the cohesion-tension theory of water and mineral movement in plants.

Dixon is the youngest of the seven sons of George Dixon, a soap manufacturer, and Rebecca (née Yeates) Dixon. He is educated at Rathmines School and Trinity College, Dublin. In 1894, after studying in Bonn, Germany, he is appointed assistant and later full Professor of Botany at Trinity. In 1906 he becomes Director of the Botanic gardens and in 1910 of the Herbarium also. He has a close working relationship with physicist John Joly and together they develop the cohesion theory of the ascent of sap.

Dixon’s early research includes work on the cytology of chromosomes and first mitosis in certain plants. Familiarity with work on transpiration and on the tensile strength of columns of sulfuric acid and water leads Dixon and Joly to experiment on transpiration. “On the Ascent of Sap” (1894) presents the hypothesis that the sap or water in the vessels of a woody plant ascends by virtue of its power of resisting tensile stress and its capacity to remain cohesive under the stress of great differences of pressure. Dixon and Joly further demonstrate that water is transported through passive vessels and not living cells.

Dixon writes Transpiration and the Ascent of Sap in Plants (1914), which brings various theories and experimental works together in a coherent argument. He also writes a textbook, Practical Plant Biology (1922).

In 1907 Dixon marries Dorothea Mary, daughter of Sir John H. Franks, with whom he raises three sons. He is the father of biochemist Hal Dixon and grandfather of Adrian Dixon and Joly Dixon.

In 1908 Dixon is elected a Fellow of the Royal Society. In 1916 he is awarded the Boyle Medal of the Royal Dublin Society. He delivers the society’s Croonian Lecture in 1937.

Henry Dixon dies in Dublin on December 20, 1953.

(Pictured: Henry Horatio Dixon, bromide print by Walter Stoneman, 1922, National Portrait Gallery, London)


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Death of Robert Boyle, Philosopher & Writer

robert-boyle

Robert Boyle, Anglo-Irish natural philosopher, theological writer, chemist, physicist, inventor and a preeminent figure of 17th-century intellectual culture, dies on December 31, 1691 in London.

Boyle is born on January 25, 1627 at Lismore Castle, in County Waterford. At age eight, he begins his formal education at Eton College, where his studious nature quickly becomes apparent. In 1639 he and his brother Francis embark on a grand tour of the continent together with their tutor Isaac Marcombes. In 1642, owing to the Irish rebellion, Francis returns home while Robert remains with his tutor in Geneva and pursues further studies.

Boyle returns to England in 1644, where he takes up residence at his hereditary estate of Stalbridge in Dorset. There he begins a literary career writing ethical and devotional tracts, some of which employ stylistic and rhetorical models drawn from French popular literature, especially romance writings. In 1649 he begins investigating nature via scientific experimentation. From 1647 until the mid-1650s, he remains in close contact with a group of natural philosophers and social reformers gathered around the intelligencer Samuel Hartlib. This group, the Hartlib Circle, includes several chemists who heighten his interest in experimental chemistry.

Boyle spends much of 1652–1654 in Ireland overseeing his hereditary lands and performing some anatomic dissections. In 1654 he is invited to Oxford, and he takes up residence at the university until 1668. In Oxford he is exposed to the latest developments in natural philosophy and becomes associated with a group of notable natural philosophers and physicians, including John Wilkins, Christopher Wren, and John Locke. These individuals, together with a few others, form the “Experimental Philosophy Club.” Much of Boyle’s best known work dates from this period.

In 1659 Boyle and Robert Hooke, the clever inventor and subsequent curator of experiments for the Royal Society, complete the construction of their famous air pump and use it to study pneumatics. Their resultant discoveries regarding air pressure and the vacuum appear in Boyle’s first scientific publication, New Experiments Physico-Mechanicall, Touching the Spring of the Air and Its Effects (1660). Boyle and Hooke discover several physical characteristics of air, including its role in combustion, respiration, and the transmission of sound. One of their findings, published in 1662, later becomes known as “Boyle’s law.” This law expresses the inverse relationship that exists between the pressure and volume of a gas, and it is determined by measuring the volume occupied by a constant quantity of air when compressed by differing weights of mercury.

Among Boyle’s most influential writings are The Sceptical Chymist (1661), which assails the then-current Aristotelian and especially Paracelsian notions about the composition of matter and methods of chemical analysis, and the Origine of Formes and Qualities (1666), which uses chemical phenomena to support the corpuscularian hypothesis. He argues so strongly for the need of applying the principles and methods of chemistry to the study of the natural world and to medicine that he later gains the appellation of the “father of chemistry.”

Boyle is a devout and pious Anglican who keenly champions his faith. He sponsors educational and missionary activities and writes a number of theological treatises. He is deeply concerned about the widespread perception that irreligion and atheism are on the rise, and he strives to demonstrate ways in which science and religion are mutually supportive. For Boyle, studying nature as a product of God’s handiwork is an inherently religious duty. He argues that this method of study would, in return, illuminate God’s omnipresence and goodness, thereby enhancing a scientist’s understanding of the divine. The Christian Virtuoso (1690) summarizes these views and may be seen as a manifesto of his own life as the model of a Christian scientist.

In 1668 Boyle leaves Oxford and takes up residence with his sister Katherine Jones, Vicountess Ranelagh, in her house on Pall Mall in London. There he sets up an active laboratory, employs assistants, receives visitors, and publishes at least one book nearly every year. Living in London also provides him the opportunity to participate actively in the Royal Society.

Boyle is a genial man who achieves both national and international renown during his lifetime. He is offered the presidency of the Royal Society and the episcopacy but declines both. Throughout his adult life, he is sickly, suffering from weak eyes and hands, recurring illnesses, and one or more strokes. He dies at age 64 on December 31, 1691 after a short illness exacerbated by his grief over Katherine’s death a week earlier. He leaves his papers to the Royal Society and a bequest for establishing a series of lectures in defense of Christianity. These lectures, now known as the Boyle Lectures, continue to this day.


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Death of Thomas Andrews, Chemist & Physicist

thomas-andrewsThomas Andrews, chemist and physicist who does important work on phase transitions between gases and liquids, dies in Belfast on November 26, 1885. He is a longtime professor of chemistry at Queen’s University Belfast.

Andrews is born in Belfast on December 19, 1813, where his father is a linen merchant. He attends the Belfast Academy and the Royal Belfast Academical Institution, where at the latter of which he studies mathematics under James Thomson. In 1828 he goes to the University of Glasgow to study chemistry under Professor Thomas Thomson, then studies at Trinity College, Dublin, where he gains distinction in classics as well as in science. Finally, at the University of Edinburgh in 1835, he is awarded a doctorate in medicine.

Andrews begins a successful medical practice in his native Belfast in 1835, also giving instruction in chemistry at the Royal Belfast Academical Institution. In 1842, he marries Jane Hardie Walker. They have six children, including the geologist Mary Andrews.

Andrews first becomes known as a scientific investigator with his work on the heat developed in chemical actions, for which the Royal Society awards him a Royal Medal in 1844. Another important investigation, undertaken in collaboration with Peter Guthrie Tait, is devoted to ozone. In 1845 he is appointed vice-president and professor of chemistry of the newly established Queen’s University Belfast. He holds these two offices until his retirement in 1879 at the age of 66.

His reputation mainly rests on his work with liquefaction of gases. In the 1860s he carries out a very complete inquiry into the gas laws — expressing the relations of pressure, temperature, and volume in carbon dioxide. In particular, he establishes the concepts of critical temperature and critical pressure, showing that a substance passes from vapor to liquid state without any breach of continuity.

In Andrews’ experiments on phase transitions, he shows that carbon dioxide may be carried from any of the states we usually call liquid to any of those we usually call gas, without losing homogeneity. The mathematical physicist Josiah Willard Gibbs cites these results in support of the Gibbs free energy equation. They also set off a race among researchers to liquify various other gases. In 1877-78 Louis Paul Cailletet is the first to liquefy oxygen and nitrogen.

Thomas Andrews dies in Belfast on November 26, 1885 and is buried in the city’s Borough Cemetery.


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Birth of Physicist John Joly

John Joly, Irish physicist famous for his development of radiation therapy in the treatment of cancer, is born in Bracknagh, County Offaly, on November 1, 1857. He is also known for developing techniques to accurately estimate the age of a geological period, based on radioactive elements present in minerals.

Joly is a second cousin of Charles Jasper Joly, the astronomer. He enters Trinity College, Dublin in 1876, graduating in Engineering in 1882 in first place with various special certificates in branches of engineering, at the same time obtaining a First-Class Honours in modern literature. He works as a demonstrator in Trinity’s Engineering and Physics departments before succeeding William Johnson Sollas in the Chair of Geology and Mineralogy in 1897, a position which he holds until his death in 1933.

Joly joins the Royal Dublin Society in 1881 while still a student, and is a frequent contributor of papers. During his career he writes over 270 books and scientific papers.

On May 17, 1899 Joly reads his paper “An Estimate of the Geological Age of the Earth” to the Royal Dublin Society. In it, he proposes to calculate the age of the earth from the accumulation of sodium in the waters of the oceans. He calculates the rate at which the oceans should have accumulated sodium from erosion processes, and determines that the oceans are about 80 to 100 million years old. The paper is quickly published, appearing four months later in the Society’s Scientific Transactions. Although this method is later considered inaccurate and is consequently superseded, it radically modifies the results of other methods in use at the time.

In 1903 he publishes an article in Nature in which he discusses the possibility of using radium to date the Earth and goes on to study the radioactive content of the Earth’s crust to formulate a theory of thermal cycles, and examines the radioactive constituents of certain rocks as a means of calculating their age. Working in collaboration with Sir Ernest Rutherford, he uses radioactive decay in minerals to estimate, in 1913, that the beginning of the Devonian period could not be less than 400 million years ago, an estimate which is in line with modern calculations.

Joly serves as President of Section C (Geology) when the British Association for the Advancement of Science meets in Dublin in 1908, during which he presents his paper “Uranium and Geology” in an address to the society. This work describes radioactive materials in rocks and their part in the generation of the Earth’s internal heat.

Along with his friend Henry Horatio Dixon, Joly also puts forward the cohesion-tension theory which is now thought to be the main mechanism for the upward movement of water in plants.

In 1914 Joly develops a method of extracting radium and applies it in the treatment of cancer. As a Governor of Dr. Steevens’ Hospital in Dublin, in collaboration with Walter Stevenson, he devises radiation therapy methods and promotes the establishment by the Royal Dublin Society of the Irish Radium Institute where they pioneer the “Dublin method” of using a hollow needle for deep radiation therapy, a technique that later enters worldwide use. The Radium Institute also supplies capillary tubes containing radon to hospitals for some years for use in the treatment of tumours.

Joly is elected a Fellow of the Royal Society of London in 1892, is awarded the Boyle Medal of the Royal Dublin Society in 1911, the Royal Medal of the Royal Society of London in 1910, and the Murchison Medal of the Geological Society of London in 1923. He is also conferred honorary degrees by the National University of Ireland, the University of Cambridge, and the University of Michigan. After his death in 1933, his friends subscribe the sum of £1,700 to set up a memorial fund which is still used to promote the annual Joly Memorial Lectures at the University of Dublin, which were inaugurated by Sir Ernest Rutherford in 1935. He is also remembered by the Joly Geological Society, a student geological association established in 1960.

In 1973 a crater on Mars is named in Joly’s honour.