David Brewster

11 Dec 1781
10 Feb 1868
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Sir David Brewster KH PRSE FRS FSA(Scot) FSSA MICE (11 December 1781 – 10 February 1868) was a Scottish physicist, mathematician, astronomer, inventor, writer, historian of science and university principal.

Most noted for his contributions to the field of optics, he studied the double refraction by compression and discovered the photoelastic effect, which gave birth to the field of optical mineralogy. For his work, William Whewell dubbed him the “Father of modern experimental optics” and “the Johannes Kepler of Optics.”

He is well-recognized for being the inventor of the kaleidoscope and an improved version of the stereoscope applied to photography. He called it the “lenticular stereoscope”, which was the first portable, 3D viewing device. He also invented the binocular camera, two types of polarimeters, the polyzonal lens and the lighthouse illuminator.

A prominent figure in the popularization of science, he is considered one of the founders of the British Association, of which he would be elected President in 1849. In addition, he was the editor of the 18-volume Edinburgh Encyclopædia.

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; 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, but only preached from the pulpit on one occasion. 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.

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:

The laws of light polarization by reflection and refraction, and other quantitative laws of phenomena;
The discovery of the polarising structure induced by heat and pressure;
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;
The laws of metallic reflection;
Experiments on the absorption of light.
In this line of investigation, the prime importance belongs to the discovery of

the connection between the refractive index and the polarising angle;
biaxial crystals, and
the production of double refraction by irregular heating.
These discoveries were promptly recognised.

As early as 1807 the degree of LL.D. was conferred upon Brewster by Marischal College, Aberdeen; in 1815 he was elected a Fellow of the Royal Society of London, and received the Copley Medal; in 1818 he received the Rumford Medal of the society; and in 1816 the French Institute awarded him one-half of the prize of three thousand francs for the two most important discoveries in physical science made in Europe during the two preceding years. In 1821, he was made a foreign member of the Royal Swedish Academy of Sciences.

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.

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.

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