Oxygen is the third most avundant element in the universe after Hydrogen and Helium. One of the first times Oxygen was used was in 1624 when the first ever submarine used containers to 'refresh' the air in the submarine. The isolation of Oxygen is attributed to three chemists, Joseph Priestly, Swede Carl Wilhelm Scheele and Antoine Lavoisier, all of whom independently discovered it . Priestly was the first to publish an account of Oxygen in 1774 generating it by focusing sunlight over mercuric oxide (HgO). He noted that a candle burned brighter in this new 'air' and that a mouse lived longer and appeared more lively. Scheele however produced Oxygen three years earlier in 1771 by heating mercuric oxide (HgO) as well as various nitrates. Scheele submitted an account of his findings in 1775 but it did not appear until 1777. Lavoisier not only discovered Oxygen but also noted the first important characteristics such as being a requirement for burning a flame.