Steven Johnson's "The Invention of Air" tells Joseph Priestley's story of discovery

"The Invention of Air: A Story of Science, Faith, Revolution and the Birth of America"

by Steven Johnson

Riverhead, 254 pp., $25.95

Next time you open a can of pop, give a thought to the sprightly Englishman Joseph Priestley, the inventor of soda water — and also a political radical, religious heretic and scientific pioneer.

In 1771, Priestley was the first to discover that green plants create good air. He had used up the "good air" in an inverted jar by burning a candle in it, and then grown a sprig of mint in the unwholesome air. After 10 days, he tried the candle again and it burned brightly.

The mint had restored the good air, which would later be named oxygen.

Priestley wrote of his discovery to his American friend, Benjamin Franklin. Already it was known that animals used up good air. "That the vegetable creation should restore the air which is spoiled by the animal part of it," Franklin wrote, "looks like a rational system."

That is one of the "aha!" moments in "The Invention of Air" — a premonition, two centuries early, of ecosystem theory.

"The Invention of Air" is not just about Priestley. Author Steven Johnson uses the life of Priestley, a kitchen-sink experimenter, to sketch the connections between science, politics and religion. Priestley was a radical in all of them.

In politics he was a disloyal fellow who supported the American Revolution. In theology he was a heretic who proclaimed the new Unitarian idea that Jesus was a man, not a god. Priestley believed firmly in God, and found it "lamentable" that Franklin did not, but, writes Johnson, Priestley "considered half of modern Christianity to be a bunch of Pagan hocus-pocus." When he said so in a 1782 book, "The History of the Corruptions of Christianity," it so excited the English public that a mob burned down his house.

Priestley fled with his family to America, becoming "the first great scientist-in-exile to seek safe harbor in America after being persecuted for his religious and political beliefs at home."

Johnson also sketches the sociology of English science in those days. Priestley was not employed by a government office, as his French counterpart, Antoine Lavoisier, was, nor by a large corporation. Priestley was supported by individual patrons, much of the time by the new industrialists, who tended also to political liberalism and religious dissent. He shared his ideas with his friends, using two new networks of the time: the coffeehouse and the postal system. Of course science was simpler in those days, and Johnson notes that Priestley's brand of it was the yes-no experiment. "The plant lived; the mouse died; the flame went out."

It was a revolutionary age from which the radicals saw a sunlit future. At his book's end, Johnson laments that "the radical's default temperament today is precisely the opposite of Priestley's: bleak and dystopian, filled with gloomy predictions of imminent catastrophe."

"The Invention of Air" is much like Johnson's 2006 work, "The Ghost Map," which was about the unraveling of the secret of cholera. Both are about a moment in science that illuminates how science comes about and what it means for human society. Highly recommended.