Joseph Priestley (1773-1804) discovered ‘dephlogisticated air’, subsequently named oxygen, whilst living and working in Leeds. His statue now stands in City Square in Leeds town centre showing him using a magnifying glass to focus the sun on to mercuric oxide to produce some dephlogisticated air, which he correctly identified as being essential for life, but also toxic when breathed to excess. Across the road from the statue is the site of Mill Hill Baptist Church where he was the Minister at the time of his experiments on “Different kinds of air”