Who Invented the Kaleidoscope? Brewster's 1817 Patent
Updated: 2 days ago
By Rocco (Roi) Ramon - licensed architect, founder of Studio Yabaye
The short answer to "who invented the kaleidoscope" is Sir David Brewster (1781-1868), who patented it in Britain in 1817. The longer answer is a dispute. Within months the instrument was being copied in London and Paris, and critics pointed to older books showing two mirrors joined at an angle. Brewster answered both in print.
This article follows his own account in "The Kaleidoscope: Its History, Theory, and Construction", quoted from the third edition (London, 1870), which follows the chapter structure of the second edition (London, 1858). His first book on the subject was "A Treatise on the Kaleidoscope" (Edinburgh, 1819). For the wider timeline, see the history of the kaleidoscope.
The invention sequence, 1814-1815
Brewster did not set out to build an instrument. The opening section of his book, headed "Introduction - History of the Kaleidoscope", describes experiments in which the kaleidoscope appeared as a side effect.
1814 - polarisation experiments. "The first idea of this instrument presented itself to me in the year 1814", during experiments on the polarisation of light by successive reflections between plates of glass, published in the Philosophical Transactions for 1815. He noticed multiplied images arranged round a centre, but the effect was not regular enough to hold his attention.
7 February 1815 - gold and silver plates. Repeating the reflections between two plates of gold and silver, he observed complementary colours produced by polarised light, and the effects of the kaleidoscope, "though rudely exhibited, were again forced upon my notice".
6 March 1815 - letter to Biot. He described the reflected images to the French physicist Biot.
The glass trough. Later, while repeating Biot's experiments on the action of fluids on polarised light, he held the fluids in a triangular trough made of two glass plates cemented together at an acute angle. Cement pressed through between the plates at the object end appeared, by reflection, "far more regular and symmetrical" than anything he had seen before. This observation started the systematic work.
Three conditions that define the instrument
From the trough, Brewster worked out three conditions. He treats them as the definition of the kaleidoscope; the priority argument rests on them.
Angle. The reflectors must be set at an even or an odd aliquot part of a circle - an angle that divides 360 degrees a whole number of times.
Object position. Of an infinite number of positions for the object, only one gives perfect symmetry: in contact with the ends of the reflectors.
Eye position. Of an infinite number of positions for the eye, only one gives perfect symmetry: as near as possible to the angular point where the mirrors meet.
The geometry is explained in how a kaleidoscope works. The steps from principle to instrument, in Brewster's order:
Fixed objects. Pieces of coloured glass and other irregular objects were fixed permanently across the ends of the reflectors. He showed this version to members of the Royal Society of Edinburgh.
Moving objects. Giving motion to the objects was, in his words, "the great step" towards completion: the coloured pieces were placed loosely in a cell at the end, so the pattern changed as the instrument turned. With the reflectors in a tube, the kaleidoscope "in its simple form, was completed".
Lens and draw tube. A draw tube with a convex lens or an achromatic object-glass formed an image of a distant object at the ends of the reflectors, removing the limit to objects held against the mirrors - "by far the most important step of the invention". It is the ancestor of the modern teleidoscope - see what is a teleidoscope.
The 1817 patent
At this stage Brewster expected two uses: the ornamental arts and a popular instrument of rational amusement. He therefore decided to secure the exclusive property of the instrument by a patent.
The book does not give the patent number or date. Reference sources record it as British patent no. 4136, granted in July 1817, for a new optical instrument called "The Kaleidoscope".
In a footnote Brewster states that the validity of the patent was never questioned by any lawyer or any philosopher acquainted with its theory and construction. The same footnote records that a judge, in a later trial over a different patent, stated that the kaleidoscope patent had been set aside in a court of law. Brewster calls this erroneous: the party prejudiced by it asked him for an affidavit, which was used to contradict the statement in court.
How the design was copied
The loss of control happened before the patent instruments reached the market. Brewster's account is one sentence: one of the patent instruments was exhibited to some London opticians, and the properties of the kaleidoscope became known before any number could be prepared for sale.
A kaleidoscope is easy to imitate in outline: two strips of mirror in a tube with loose coloured fragments at the end produce a multiplied pattern even when the three conditions are ignored. That is what the copyists built. The figures Brewster gives:
No fewer than two hundred thousand instruments were sold in London and Paris during three months.
Of these, "perhaps not one thousand constructed upon scientific principles".
Of the millions who had seen its effects, perhaps not a hundred understood the principles or could tell a spurious instrument from a real one.
The scale of that first year is covered in the kaleidoscope craze of 1817. Reference sources add that the London optician Philip Carpenter became Brewster's licensed maker, marked "sole maker", and that from 1818 other makers were permitted. Later chapters of the book name further makers: Bate (Chapter XI), Dollond and Ruthven (Chapter XII).
The earlier claims and Brewster's reply
Chapter XXIII of the book is titled "History of the combinations of plane mirrors which have been supposed to resemble the kaleidoscope". Its heading names three authors - Porta, Kircher and Bradley - the precedents raised against the patent.
Giambattista della Porta, in the sixteenth century, described multiplied reflection between plane mirrors.
Athanasius Kircher described two mirrors set at an angle in 1646.
Richard Bradley, a botanist, published in 1717 a pair of hinged mirrors to be stood on a drawing as an aid to laying out designs.
Each is a pair of plane mirrors at an angle. None, in Brewster's account, specifies the three conditions: the angle as an aliquot part of the circle, the object at the ends of the reflectors, the eye at the angular point. That is the ground of his reply. The three precedents are described in the kaleidoscope before Brewster.
What the dispute comes down to
The two sides were arguing about different objects.
The critics' definition: two plane mirrors at an angle, multiplying whatever lies between them. By that definition the device is as old as Porta, and older.
Brewster's definition: a specified mirror angle, object plane and eye position, plus loose objects in motion. By that definition nothing before 1814-1815 qualifies.
The test of Brewster's definition is the result. A mirror pair that meets the three conditions produces a pattern in which every sector joins its neighbours without a visible break; a pair that does not produces steps and gaps at the joints. The same test is used today on any mirror system - see mirror alignment and the image seam. Terms such as sector and object cell are defined in the kaleidoscope glossary.
FAQ
Who invented the kaleidoscope?
Sir David Brewster, a Scottish physicist, invented the kaleidoscope between 1814 and 1816 and patented it in Britain in 1817. He arrived at it during experiments on the polarisation of light between glass plates, and defined it by three conditions: mirror angle, object position and eye position.
When was the kaleidoscope patented?
The British patent is recorded as no. 4136, granted in July 1817, for a new optical instrument called "The Kaleidoscope". Brewster's book does not give the number; it states only that he decided to secure the exclusive property of the instrument by a patent once the draw tube and lens were added.
How was the kaleidoscope copied before Brewster could profit?
Brewster writes that one of the patent instruments was exhibited to some London opticians, and its properties became known before a stock could be prepared. By his figure, two hundred thousand instruments were then sold in London and Paris in three months, fewer than one thousand of them built on correct principles.
Was Brewster's patent ever overturned?
By his own account, no. In a footnote Brewster states that the validity of the patent was never questioned by any lawyer or any philosopher who understood the instrument. He reports that a judge later said the patent had been set aside in court, and that an affidavit from him was used to contradict this statement.
Did Kircher or Bradley invent the kaleidoscope first?
Kircher in 1646 and Bradley in 1717 described two plane mirrors at an angle used to multiply an image. Brewster devotes Chapter XXIII of his book to these precedents. His reply rests on the three conditions of symmetry defined in his Introduction - mirror angle, object position, eye position - which the earlier devices did not specify.
What makes Brewster's instrument different from two mirrors at an angle?
Three conditions: the mirror angle must divide the circle a whole number of times, the object must lie at the ends of the reflectors, and the eye must be close to the line where the mirrors meet. Brewster adds loose objects in motion. Earlier mirror pairs did not meet these conditions.
About Studio Yabaye
At Studio Yabaye I build kaleidoscopes and teleidoscopes with front-surface mirror systems in several configurations, in a brass tube, cut, fitted and hand-finished in the studio. Each object wheel is poured and composed by hand, so no two pieces are alike. The studio is based in Israel and ships worldwide. Collecting is covered in kaleidoscope collecting and the Brewster Kaleidoscope Society. The range is at all products; questions go through the contact page.
Related reading: Kaleidoscope craze of 1817 - Miniature kaleidoscopes of 1819 - Charles Bush
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