Joseph Priestly apparently had attention deficit disorder - and it served him well. Well, it may not have been ADD; he was an enlightened man with leisure time, interested in the free flow of information across many disciplines. And in his era (he lived from 1733 to 1804) it was not apparently not without precedent. He and his peers participated in chemistry, physics, education, religion. As Priestly involved himself in all this, he discovered oxygen and established the foundation for environmental science.
Steven Johnson's book, The Invention of Air, is not necessarily a biography of Priestly, whom he points out is a "footnote in most popular accounts of the revolutionary generation"; rather it is a dissertation on the man's ideas and how they affected the founders of the United States and how his activities are important today. Like Priestly, who didn't restrain himself to just one scientific pursuit, the book touches on many subjects.
Admittedly knowing very little about Priestly at all, and having just a vague outline of the American revolutionary period and its players, I was keen to find out more. Johnson's book did provide some insights that I appreciated. It reveals his friendships with Thomas Jefferson and John Adams and Ben Franklin. By including excerpts of his correspondence with these men, we're able to see how they were affected by him and we gain insight into Priestly's mild attitude.
He went to London in 1765 and met the Honest Whigs (a coffeehouse society of freethinkers) to discuss with them theories of electricity. It was after this that he moved on to his experiments with air and writings about Christianity and political scandal.
I will have to admit that I either didn't know or did not recall (how Reagan-esque) that Joseph Priestly is credited with the discovery of oxygen, though there are footnotes to that discovery. He found out about it, but adhered to an old theory about an airy ingredient called phlogiston, which allowed things to burn and which was very wrong.