Discovery of Oxygen gas

The discovery of Oxygen was credited to Priestley in 1774 AD. However in a paper looking into Alchemy, by Richard Brzezinski, an expert in the history of science and Zbigniew Szydlo, a chemistry lecturer, published in the authoritative magazine History Today credit the discovery of Oxygen to a Polish alchemist called Michael Sendivogius who found that heated saltpeter produced "the elixir of life" and who, in 1604, described his experiments in a book regarded as so authoritative that it found its way into every major scientific library in Europe. They say that Priestley, would surely have had access to it. Cornelis Drebbel a Dutch inventor employed by the King of England James 1 in 1621 used Sendivogius work which was about 150 years before Priestley was credited with the discovery of Oxygen. Drebbel built a submarine which was manned by 12 oarsmen, made of wood and waterproofed by a coat of greases leather. It successfully traveled along the River Thames from Westminster to Greenwich, at a dept of 15 ft. The trip, and the method used to keep the oarsmen alive, was subsequently verified by Robert Boyle.