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Sir David Brewster
Born 11 December 1781
Canongate, Jedburgh, Roxburghshire
Died 10 February 1868(1868-02-10) (aged 86)
Allerly House, Gattonside, Roxburghshire
Citizenship Great Britain
Nationality Scottish
Fields Physics, mathematics, astronomy
Alma mater Edinburgh University
Known for Physical optics, Brewster's angle, photoelasticity, stereoscope, kaleidoscope
Influences Isaac Newton, Étienne-Louis Malus
Influenced James David Forbes
Notable awards Copley Medal (1815)
Rumford Medal (1818)
Keith Prize (1827–9, 1829–31)
Royal Medal (1830)
Founding Director of the Scottish Society of Arts (1821)
Principal of St Andrews University (1837–59)
Principal of Edinburgh University (1859–68)

Sir David Brewster KH PRSE FRS FSA(Scot) FSSA MICE (11 December 1781 – 10 February 1868) was a Scottish scientist, inventor, author, and academic administrator. In science he is principally remembered for his experimental work in physical optics, mostly concerned with the study of the polarization of light and including the discovery of Brewster's angle. He studied the birefringence of crystals under compression and discovered photoelasticity, thereby creating the field of optical mineralogy. For this work, William Whewell dubbed him the "father of modern experimental optics" and "the Johannes Kepler of optics."

A pioneer in photography, Brewster invented an improved stereoscope, which he called "lenticular stereoscope" and which became the first portable 3D-viewing device. He also invented the binocular camera, two types of polarimeters, the polyzonal lens, the lighthouse illuminator, and the kaleidoscope.

Brewster was a Presbyterian and walked arm in arm with his brother on the Disruption procession which formed the Free Church of Scotland.

As a historian of science, Brewster focused on the life and work of his hero, Isaac Newton. Brewster published a detailed biography of Newton in 1831 and later became the first scientific historian to examine many of the papers in Newton's Nachlass.

Brewster also wrote numerous works of popular science, and was one of the founders of the British Science Association, of which he was elected President in 1849. He became the public face of higher education in Scotland, serving as Principal of the University of St Andrews (1837–59) and later of the University of Edinburgh (1859–68). Brewster also edited the 18-volume Edinburgh Encyclopædia.

Early life

David Brewster was born at the Canongate in Jedburgh, Roxburghshire, to Margaret Key (1753–1790) and James Brewster (c. 1735–1815), the rector of Jedburgh Grammar School and a teacher of high reputation. David was the third of six children, two daughters and four sons: James (1777–1847), minister at Craig, Ferryden; David; George (1784–1855), minister at Scoonie, Fife; and Patrick (1788–1859), minister at the abbey church, Paisley.

At the age of 12, David was sent to the University of Edinburgh (graduating MA in 1800), being intended for the clergy. He was licensed a minister of the Church of Scotland, and preached around Edinburgh on several occasions. He had already shown a strong inclination for natural science, and this had been fostered by his intimacy with a "self-taught philosopher, astronomer and mathematician", as Sir Walter Scott called him, of great local fame, James Veitch of Inchbonny, a man who was particularly skilful in making telescopes.


Work on optics

The view in a kaleidoscope

Though Brewster duly finished his theological studies and was licensed to preach, his other interests distracted him from the duties of his profession. In 1799 fellow-student Henry Brougham persuaded him to study the diffraction of light. The results of his investigations were communicated from time to time in papers to the Philosophical Transactions of London and other scientific journals. The fact that other scientists – notably Étienne-Louis Malus and Augustin Fresnel – were pursuing the same investigations contemporaneously in France does not invalidate Brewster's claim to independent discovery, even though in one or two cases the priority must be assigned to others. A lesser-known classmate of his, Thomas Dick, also went on to become a popular astronomical writer.

The most important subjects of his inquiries can be enumerated under the following five headings:

  1. The laws of light polarization by reflection and refraction, and other quantitative laws of phenomena;
  2. The discovery of the polarising structure induced by heat and pressure;
  3. The discovery of crystals with two axes of double refraction, and many of the laws of their phenomena, including the connection between optical structure and crystalline forms;
  4. The laws of metallic reflection;
  5. Experiments on the absorption of light.

In this line of investigation, the prime importance belongs to the discovery of

  1. the connection between the refractive index and the polarizing angle;
  2. biaxial crystals, and
  3. the production of double refraction by irregular heating.
Brewster cigar box
Inner picture of a cigar box from the early 1900s with a portrait of Brewster.

Among the non-scientific public, his fame spread more effectually by his invention in about 1815 of the kaleidoscope, for which there was a great demand in both the United Kingdom, France, and the United States.

As a reflection of this fame, Brewster portrait was later printed in some cigar boxes. Brewster chose renowned achromatic lens developer Philip Carpenter as the sole manufacturer of the kaleidoscope in 1817. Although Brewster patented the kaleidoscope in 1817 (GB 4136), a copy of the prototype was shown to London opticians and copied before the patent was granted. As a consequence, the kaleidoscope became produced in large numbers, but yielded no direct financial benefits to Brewster. It proved to be a massive success with two hundred thousand kaleidoscopes sold in London and Paris in just three months.

PSM V21 D055 The brewster stereoscope 1849
The Brewster stereoscope, 1849.

An instrument of more significance, the stereoscope, which – though of much later date (1849) – along with the kaleidoscope did more than anything else to popularise his name, was not as has often been asserted the invention of Brewster. Sir Charles Wheatstone discovered its principle and applied it as early as 1838 to the construction of a cumbersome but effective instrument, in which the binocular pictures were made to combine by means of mirrors. A dogged rival of Wheatstone's, Brewster was unwilling to credit him with the invention, however, and proposed that the true author of the stereoscope was a Mr. Elliot, a "Teacher of Mathematics" from Edinburgh, who, according to Brewster, had conceived of the principles as early as 1823 and had constructed a lensless and mirrorless prototype in 1839, through which one could view drawn landscape transparencies, since photography had yet to be invented. Brewster's personal contribution was the suggestion to use prisms for uniting the dissimilar pictures; and accordingly the lenticular stereoscope may fairly be said to be his invention.

A much more valuable and practical result of Brewster's optical researches was the improvement of the British lighthouse system. Although Fresnel, who had also the satisfaction of being the first to put it into operation, perfected the dioptric apparatus independently, Brewster was active earlier in the field than Fresnel, describing the dioptric apparatus in 1812. Brewster pressed its adoption on those in authority at least as early as 1820, two years before Fresnel suggested it, and it was finally introduced into lighthouses mainly through Brewster's persistent efforts.


David brewster group
Calvert Jones, Lady Brewster (Jane Kirk Purnell), Mrs. Jones, David Brewster and Miss Parnell (seated)

Brewster married twice. His first wife, Juliet Macpherson (c. 1776–1850), was a daughter of James Macpherson (1736–1796), a probable translator of Ossian poems. They married on 31 July 1810 in Edinburgh and had four sons and a daughter:

  • James (1812–)
  • Charles Macpherson (1813–1828), drowned.
  • David Edward Brewster (17 August 1815 –) became a military officer (Lieutenant Colonel) serving in India.
  • Henry Craigie (1816–1905) became a military officer and photographer.
  • Margaret Maria Gordon (1823–1907) wrote a book on Brewster, which is considered the most comprehensive description of his life.

Brewster married a second time in Nice, on 26 (or 27) March 1857, to Jane Kirk Purnell (b. 1827), the second daughter of Thomas Purnell of Scarborough. Lady Brewster famously fainted at the Oxford evolution debate of 30 June 1860. Brewster died in 1868, and was buried at Melrose Abbey, next to his first wife and second son. The physics building at Heriot-Watt University is named in his honour.

Recognition and modern references

Street sign in Kings Buildings, Edinburgh to the memory of David Brewster
Street sign in Kings Buildings, Edinburgh to the memory of David Brewster

A bust of Brewster is in the Hall of Heroes of the National Wallace Monument in Stirling.

A street within the Kings Buildings complex (science buildings linked to Edinburgh University) was named in his memory in 2015.

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