A scientist, nonconformist minister and political radical. Conducted important experiments leading to the discovery of oxygen. Backed by Birmingham’s Lunar Men but forced to flee after a loyalist mob torched his home.

On 8 April 1794 Joseph Priestley set sail for America. London had become too dangerous a place for this leading radical philosopher and scientist. He would never return.

In The Invention of Air, Steven Johnson tells of Priestley’s odyssey. What schoolchild could fail to be impressed by the tale of Priestley inventing soda water after studying the bubbles in a brewers’ vat?

I blogged about my reflections on the book, including Priestley’s trip to Paris where he met Antoine Lavoisier, and in November 2009, thanks to the power of Twitter, we welcomed Steven to Leeds. On a rainy night, only nine people turned up, but they were the best nine people.

The Priestley Society is a charity dedicated to spreading information about this important scientist, political theorist and clergyman.

Among the younger generation of British radicals that Priestley left behind was John Thelwall.