David Brewster, 1781 – 1868, an engraving by William Holl.

Occasionally I come across a scientist who suddenly steps off his academic perch and comes up with something totally unexpected. One such man was David Brewster, born in 1781 in Jedburgh Scotland. His range of interests included that of a physicist, mathematician, astronomer, inventor, and writer. He was a scientist who studied light – prisms, polarisation of light, mirrors, stereoscopes, lighthouse lenses, etc., He was a Member of the Royal Society, was showered with medals and awards, and was made a knight of the realm in 1831. He is also credited with having invented the sea thermometer. He was an eminent scientist yet in 1815 he came up with the kaleidoscope, an invention which he patented two years later.

He had originally intended it as a scientific tool. It consisted of a tube with two mirrors at an angle at one end and a translucent disc at the other through which diffused light could pass. In between he placed coloured beads. With two mirrors the beads were shown in multiple reflection, the patterns illuminated against a black background. Introducing a third mirror placed at 60° produced six duplicate objects, with eight if the angle was 45°. The three mirrors meant that the patterns filled the whole field of vision.

Brewster turned to a famous lens developer Philip Carpenter to develop his invention once the patent came through in 1817. It was a sensation, with over 200,000 kaleidoscopes sold within three months in London and Paris alone. Carpenter simply could not keep up with demand and Brewster was forced to seek his permission to bring in other manufacturers. He hoped to make a fortune from the invention, but unfortunately for him a mistake on the patent application meant that others were able to copy it with impunity.

In later years he was to become Principal of St Andrews University (1837 to 1859) and then of Edinburgh University (1859, up to his death nine years later). He was devoutly religious, highly strung and often highly irritable with people who disagreed with his views. His scientific works are sufficiently obscure as to be quite beyond my limited abilities to understand. Suffice to say that Encyclopedia Britannica delivered this obituary after his death in 1868.

“His scientific glory is different in kind from that of Young and Fresnel; but the discoverer of the law of polarization of biaxial crystals, of optical mineralogy, and of double refraction by compression, will always occupy a foremost rank in the intellectual history of the age.”

And the name kaleidoscope? Well for those of us who never woke up in time for Greek lessons it is a combination of three words from ancient Greece meaning ‘tool for observing beautiful shapes.’ In other words, it does what it says on the tin. Thanks Sir David, and many happy returns of the day! (His birthday was on the Eleventh of December).

NB This post echoes my main blog at http://blog.mikerendell.com (go there for up to date posts)