THE bicentenary of the death of John Playfair occurs this week, and that allows me to pay tribute to him and his extended family, who were such towering figures of the Scottish Enlightenment.

Next week I’ll look at the amazing Scotland-changing career of the architect William Henry Playfair and his father James, also an architect, but this week I’ll examine the life of James’s brother John Playfair and his other brother William.

John was a remarkable figure, being a Church of Scotland minister, a Professor of Mathematics and Natural Philosophy (physics), an astronomer and geologist, and he is one of only three Scots with a crater named after him on both Mars and the Moon – the others being the father of geology James Hutton, whose work greatly influenced Playfair, and Sir Charles Lyell, whose pioneering work in geology was in turn influenced by Playfair.

The four Playfair brothers – John, James, Robert and William – were the sons of the Reverend James Playfair, minister of the Church of Scotland at Benvie west of Dundee, and his wife Margaret née Young.

All four brothers were brought up to be “lads o’pairts” with an education at home that was wide-ranging.

John went to St Andrews University in 1762 when he was just 14, studying divinity as it was his intention to follow in his father’s footsteps and become a minister.

His love of mathematics slightly intervened as he studied the subject at Edinburgh University – he was such a mathematical prodigy that he was a candidate for the Chair of Mathematics at Marischal College in Aberdeen at the age of just 18. It was an open contest with the teenager losing but making a huge impression on all who saw and heard him.

John was destined for the Kirk, however, and he graduated from St Andrews in 1769.

He attempted to gain academic posts while living in Edinburgh, where he mixed with the elite of the Enlightenment – Adam Smith, Dugald Stewart, Joseph Black, Robert Adam and James Hutton – before his father died in 1772, John succeeding him the following year as minister for the linked parishes of Liff and Benvie, though he continued to study his various subjects.

In 1774, a fellow churchman, Rev Dr Nevil Maskelyne, asked Playfair to accompany him on what became known as the Schiehallion Experiment in which their observations enabled Maskelyne to calculate the mass of the planet Earth.

It was Maskelyne who encouraged Playfair to interact with London’s scientific elite and in 1779 he submitted his first paper to the Royal Society of London.

It was called On The Arithmetic Of Impossible Quantities, and it immediately propelled him into the upper ranks of British mathematicians.

The philosopher and Enlightenment historian Adam Ferguson of Raith next made a dramatic intervention in Playfair’s life, offering him the well-paid post of tutor to his two sons. The switch enabled Playfair to enter fully into the life of Enlightenment Edinburgh and also advance his own studies – works of genius would soon flow from his pen, while his appointment to the Chair of Mathematics at Edinburgh University confirmed his academic reputation, as did his solving of a problem that had first been raised by the ancient Greek mathematician Euclid. His ingenious solution is known as Playfair’s Axiom.


Back in the day: How Scots have interfered with England’s history

ALL this time, he was spending many hours with Enlightenment fellows, one of whom was his friend James Hutton. After Hutton died in 1797, Playfair published Illustrations Of The Huttonian Theory Of The Earth, in which he greatly simplified Hutton’s complex theories, thereby making Hutton’s reputation as the father of geology.

Hutton travelled widely throughout the British Isles and the Continent, but it was on Edinburgh that he made his greatest impact over the decades, helping to found the Royal Society of Edinburgh and the Astronomical Institution of Edinburgh, before publishing his Outlines Of Natural Philosophy after taking the Chair of Natural Philosophy at Edinburgh. His Elements Of Geometry was another important publication.

In dozens of academic papers and countless lectures, Playfair effectively instituted the methods of scientific analysis that are still used today.

He became ill with the disease strangury, which affected his bladder, and he eventually died of it on July 20, 1819, at the age of 71. His grave in Edinburgh’s Old Calton Burial Ground is marked with a plaque that was erected by his admirers as recently as 2011.

John’s brother William, another eminent figure, became the founder of graphical statistics. You may remember bar charts and pie charts from school – William Playfair devised them, the latter in a book which he published in 1801.

After his father died when he was 13, William as the youngest son was brought up by John Playfair, and it was probably the family’s fame within the Enlightenment circles that enabled William to become draftsman and personal assistant to James Watt, no less, at his Soho foundry in Birmingham.

He could have become an important engineer, but then came an extraordinary period in William’s career. He moved to France, where some say he took part in the Storming of the Bastille in 1789. After the French Revolution, he stayed in France and became a spy.

The British Government feared the spread of France’s revolutionary philosophies so Playfair devised a plan to undermine the revolution by effectively destroying France’s new currency, the Assignat, by flooding the country with counterfeit notes – they were so good, the Assignat lasted just long enough to destroy the French government.

He had a varied career after that, including, most importantly, his pioneering works on statistics, for which he is most remembered. He ended up in prison over a speculative venture that failed, but he took to pamphleteering and journalism before dying in London at the age of 63 on February 11, 1823.