Michael Sendivogius, the Polish alchemist who may have 'discovered' oxygen in 1601, 170 years before Scheele and Priestley, by warming nitre (saltpetre). He thought of the gas given off as 'the elixir of life'.

Cornelius Drebbel, a Dutch alchemist and inventor, was a protege of Michael Sendivogius, and inventor to the court of James I of Britain. In 1621, his submarine, the world's first, made an underwater voyage down the Thames from Westminster to Greenwich, a distance of 10 miles, watched by the King and thousands of his subjects. Drebbel apparently 'refreshed' the air by removing the lid from a barrel of 'liquor' or gas, presumably oxygen -- made by warming nitre as Sendivogius had done.

Cornelius Drebbel is usually pictured with a voluptuous maiden-student, invariably in a state of semi-deshabile -- not the kind of tutorial that would be approved of in today's educational ethos. But then he was an alchemist -- and judging from the sun and moon necklace, which is full of alchemical symbolism, we're not supposed to take the image literally. No doubt she's just a metaphor. And they wonder why the alchemists got a bad name.

Joseph Priestley, looking a bit glum. He was a political radical as well as a great chemist, who ended his days in the land of the free -- America -- which treated him better than England ever did. But the quest for knowlege seems to have lost some of its fun since Drebbel's day.

Meanwhile, over in Paris, here is Antoine Lavoisier, often rightly called the 'father of modern chemistry', with his remarkable wife Marie Anne. Years later, after Lavoisier had lost his head to the guillotine in the French Revolution, Marie re-married, to Count Rumford, another chemist. She later threw him out after a furious domestic quarrel with the warning never to return.

Carl Scheele, who is credited, correctly, by the Swedes, for the discovery of oxygen in 1771 (if we don't cede precedence to Sendivogius). He was certainly a couple of years ahead of Priestley, but failed to publish his results after relying too heavily on aristocratic patronage. He also wrote to Lavoisier - a letter Lavoisier maintained he never received (and it's possible the letter was hidden by Marie for reasons best known to herself).

Scheele's spartan laboratory and workshop, in which he discovered seven new elements (including oxygen) as well as other new compounds such as glycerol, hydrogen sulphide and citric acid..