David Brewster

Sir David Brewster (11 December 1781 - 10 February 1868) was a Scottish natural philosopher known for his experimental work on the polarization of light, for the kaleidoscope, and for the lenticular stereoscope, the lens-based viewer that made stereoscopic pictures a mass-market product in the 1850s. Charles Wheatstone had described the first stereoscope, which used mirrors, in 1838. Brewster's contribution was to replace the mirrors with lenses: in 1849 he showed a compact viewer in which two half-lenses, one in front of each eye, merged a pair of pictures into a single image in relief. The Royal Society's archivist has written that Brewster has "a legitimate claim as the inventor of the first portable 3D viewing device".

The lenticular stereoscope puts one lens in front of each eye and a pair of pictures behind them, the same basic arrangement as a lens-based head-mounted display. Brewster's own description of the instrument in 1856 includes a sliding mount to fit viewers whose eyes are "more or less distant", tubes that move to suit "eyes of different focal lengths", and a slot for extra lenses for long-sighted or short-sighted users. He also spent years in a public dispute with Wheatstone over the credit for the stereoscope and over how binocular vision produces depth.

Reviewed 11 October 2026. Checked every cited source (1911 Britannica, Edinburgh and St Andrews university records, Brewster's 1815, 1819, 1844, 1849 and 1856 texts, Wade 2019, Royal Society blog, Stereoscopic Society, FSU, Physics World and LaValle) against all biographical dates, honours, stereoscope history, quotations and DOIs. About review dates.

Early life and education

Brewster was born in Jedburgh, Roxburghshire, where his father, James Brewster, was rector of the grammar school; his mother was Margaret Key. He was sent to the University of Edinburgh at the age of twelve, intended for the ministry. The University of Edinburgh records that he graduated MA in 1800, and the University of St Andrews biographical register lists divinity studies at Edinburgh in 1801-1803 and 1804-1805 and a licence to preach from the Presbytery of Edinburgh. According to the 1911 Encyclopaedia Britannica, his interest in science had been encouraged by James Veitch of Inchbonny, a local maker of telescopes, and although he finished his theological course he never took up the active duties of a minister.

Career

Optics and polarization

Brewster's research was almost entirely in experimental optics. In 1815 the Philosophical Transactions of the Royal Society published his paper "On the laws which regulate the polarisation of light by reflexion from transparent bodies", the work behind the relationship between a material's refractive index and its polarizing angle that is now known as Brewster's law or Brewster's angle. The 1911 Britannica names this law, his discovery of crystals with two axes of double refraction, and the production of double refraction by irregular heating as his most important results. In 1815 he was elected a Fellow of the Royal Society of London and received its Copley Medal, and in 1818 he received the society's Rumford Medal. He later also received the Royal Medal, making him a recipient of all three of the society's principal medals.

The same encyclopedia credits him with describing a dioptric (lens-based) lighthouse apparatus in 1812 and with pressing its adoption in Britain by 1820, while acknowledging that Augustin Fresnel perfected the design independently and put it into service first. Brewster never explicitly adopted the wave theory of light.

The kaleidoscope

In A Treatise on the Kaleidoscope (1819) Brewster wrote that the first idea for the instrument came to him in 1814, during experiments on the polarization of light by successive reflections between inclined plates of glass. He took out a patent, but one of the patent instruments was shown to London opticians and its properties became known before any number could be prepared for sale; he reported an estimate that "no fewer than two hundred thousand instruments have been sold in London and Paris during three months". The patent dates from 1817. The University of Edinburgh notes that a flawed patent application left the design unprotected, so Brewster earned little from it.

Editing and writing

Brewster edited the Edinburgh Encyclopaedia from 1807 (its last part appeared in 1830), co-founded the Edinburgh Philosophical Journal with Robert Jameson in 1819, and ran the Edinburgh Journal of Science from 1824 to 1832. His long article on optics for the Edinburgh Encyclopaedia became the basis of his Treatise on Optics (1831). He contributed articles, among them "Optics" and "Stereoscope", to the seventh and eighth editions of the Encyclopaedia Britannica, and the 1911 Britannica calls his Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton (1855) the most important of his separate works. The 1911 Britannica puts his output at between three and four hundred papers in the transactions of learned societies; the University of Edinburgh gives a figure of about 315 scientific papers.

British Association and university posts

Brewster proposed, in an article in the Quarterly Review, an association of scientists that was realised as the British Association for the Advancement of Science; at its first meeting, at York in 1831, he worked with Charles Babbage and John Herschel on its constitution. He was its president in 1849, the year he was also elected one of the eight foreign associates of the Institute of France. He received the Hanoverian Guelphic Order and was knighted in the early 1830s: the 1911 Britannica places both honours in 1831, while the University of St Andrews register dates the knighthood to 1832.

In 1838 he became Principal of the United College of St Salvator and St Leonard at St Andrews; the university's register dates the appointment to 3 March 1838 and his resignation to 26 November 1859. Edinburgh Town Council then elected him Principal of the University of Edinburgh, the first layman in the post since 1622, and he held it until his death. From 1864 he was also president of the Royal Society of Edinburgh. He died at Allerly, near Melrose, on 10 February 1868.

Stereoscopy

Response to Wheatstone

Wheatstone read his paper on binocular vision and the mirror stereoscope to the Royal Society on 21 June 1838 and showed the instrument at the British Association meeting in Newcastle that August. Brewster first welcomed it, calling it at Newcastle "one of the most valuable optical papers which has been presented to the Section". By 1844 he had changed his view, writing that "these extraordinary results are obviously subversive of the established laws of vision". His own theory explained binocular depth through the retina and a "law of visible direction" carried over from single-eye vision, while Wheatstone argued for central processing of the two eyes' images. Brewster set out his position in a paper to the Royal Society of Edinburgh, "On the law of visible position in single and binocular vision, and on the representation of solid figures by the union of dissimilar plane pictures on the retina", submitted in January 1843 and printed in its Transactions, and followed it in April 1844 with "On the knowledge of distance given by binocular vision". In 1844 he coined the term "ocular equivocation" for the rivalry between conflicting contours that he saw when using Wheatstone's stereoscope.

The lenticular stereoscope

Brewster wrote that during these studies he found the reflecting stereoscope "of little service, and ill fitted, not only for popular use, but for the application of the instrument to various useful purposes". He built several new stereoscopes at St Andrews and Dundee, in sizes down to a pocket version, "but particularly ... the Lenticular Stereoscope". He announced it in a British Association report in 1849, and the first instrument was made in Dundee by the optician George Lowdon (spelled "Loudon" in Brewster's book). The 1911 Britannica stresses that the stereoscope's principle was Wheatstone's, and that what is due to Brewster is "the merit of suggesting the use of lenses for the purpose of uniting the dissimilar pictures".

In his 1856 book Brewster explained the optics. Looking at a picture through the edge of a convex lens displaces its image sideways; if the lens is cut in two and one half placed in front of each picture, the two images are refracted toward each other and seen "united into one ... standing out in beautiful relief". Quarter lenses cut to a round or square shape work the same way. The instrument he described is a pyramidal box, blackened inside, with a lid to let light onto the pictures and two eye tubes on top. The two halves of the top could slide in grooves, adjusted by a jointed parallelogram and screw, "so as to suit different persons whose eyes ... are more or less distant", a mechanical adjustment for interpupillary distance. The tubes moved up and down "to suit eyes of different focal lengths", and a groove below them took extra convex or concave lenses for long-sighted or short-sighted users, a purpose served in modern headsets by prescription lens inserts.

Brewster also designed a binocular camera for taking stereoscopic portraits and copying statues, described in 1849, and at Brewster's request Dr. Adamson of St Andrews made two binocular portraits of himself to show the use of the stereoscope for portraiture.

Commercial success

Brewster could not persuade opticians in London or Birmingham to make the instrument after its 1849 showing. In 1850 he took one of Lowdon's stereoscopes to Paris and showed it to the Abbe Moigno and to the opticians Soleil and Jules Duboscq; Duboscq began making it for sale at once, together with stereoscopic daguerreotypes. Duboscq exhibited a lenticular stereoscope at the Great Exhibition of 1851 in London, where, Brewster wrote, it "attracted the particular attention of the Queen", and Brewster presented a Duboscq stereoscope to Queen Victoria. Orders from England followed, and by 1856 Brewster reported an estimate that "upwards of half a million of these instruments have been sold". The Royal Society notes that the lenticular instrument was more compact than Wheatstone's and that its ease of use meant the "Brewster Stereoscope" gained popularity over Wheatstone's design.

Priority dispute

The two men's disagreement extended to credit. Brewster claimed that Wheatstone had not been interested in using photographs with the stereoscope, and went so far as to suggest that someone else had a prior claim to the whole concept. In The Stereoscope (1856) he argued that James Elliot, an Edinburgh mathematics teacher, had devised an "ocular stereoscope" in 1834. The claim was repeated in an anonymous letter to The Times later in 1856, which drew Wheatstone and Brewster into a public exchange of letters; Elliot himself withdrew the claim in 1862. In 1860 Brewster also argued, without having seen them, that the Chimenti drawings were binocular pictures. Measurements by Edwin Emerson in 1864, later confirmed by others, found a mix of stereoscopic and pseudoscopic differences between the drawings with no systematic depth. Wade concludes that in both the Elliot and Chimenti cases "time has indeed found in Wheatstone's favour".

Legacy

Brewster's lenticular design, not Wheatstone's mirror box, became the popular form of the stereoscope, and by 1856 Brewster described it as "in general use over the whole world". In his Virtual Reality textbook, Steven LaValle notes that the mirrors of the first stereoscope "were replaced by lenses soon afterward", and his history of the field places the stereoscope and the View-Master among the forerunners of VR. LaValle also describes how a virtual reality headset can place a smartphone display close to the eyes and bring it into focus "using one magnifying lens for each eye", with Google Cardboard as an example of a case built around a phone, the same one-lens-per-eye principle Brewster applied to paired photographs.

Selected works

Year	Title	Publication
1815	"On the laws which regulate the polarisation of light by reflexion from transparent bodies"	Philosophical Transactions of the Royal Society, vol. 105
1819	A Treatise on the Kaleidoscope	Archibald Constable, Edinburgh
1831	Treatise on Optics	Book
1844	"On the Law of Visible Position in Single and Binocular Vision, and on the representation of Solid Figures by the union of dissimilar Plane Pictures on the Retina"	Transactions of the Royal Society of Edinburgh, vol. 15
1844	"On the Knowledge of Distance given by Binocular Vision"	Transactions of the Royal Society of Edinburgh, vol. 15
1849	"Account of a binocular camera, and of a method of obtaining drawings of full length or colossal statues, and of living bodies, which can be exhibited as solids by the stereoscope"	Journal of the Franklin Institute, vol. 48
1855	Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton	Book
1856	The Stereoscope: Its History, Theory, and Construction	John Murray, London

See also

• Charles Wheatstone
• Stereoscope
• Stereopsis
• History of virtual reality