Mathematician John Playfair

John Playfair (1748-1819), Fellow of the Royal Society of Edinburgh and Fellow of the Royal Society was a professor of natural history at the University of Edinburgh.  His name lives on most prominently in "Playfair's Axiom" an axiom equivalent to Euclid's Fifth Postulate but simpler to state and grasp.  The fact that his name is attached to it is odd, since this axiom had been around since the time of Proclus and was used by others, particularly William Ludlum, whom Playfair did credit in his writings.  

Playfair's nephew was the famous architect William Henry Playfair, and it was he who built the above monument to John Playfair, which can be found on Calton Hill just in front of the City Observatory, which William also designed.

John Playfair is buried just across the way from Calton Hill, in Old Calton Burial Ground, which is one of the places I was most hoping to see while in Edinburgh, but when I found the gate closed and all these "no access" signs posted :-(  (It seems they are quite serious about not letting people in right now!)

I find that many cemeteries here have a board posting the "celebrities" who are buried inside, so I was able to get a picture of his name on that board just beside the gate.

Here is a view looking down into Old Calton Burial Ground from Calton Hill.  The round monument is to philosopher David Hume.  (Aside - the unusual dome just left of center on the skyline is that of St. Giles' Cathedral.)