During this time he finished his books History which was published in 1772 and his other book Present State of Electricity which was published in 1767. After he founded the Leeds Library. He then began researching the properties of gases and became the “father of the soft drinks industry”. He invented “soda water” which is also known as Carbonated water.
While he was in his service of the Earl of Shelburne he discovered Oxygen. During one of his many experiments he used a heating lens to heat up mercuric acid and made an observation that a remarkable gas was made. He described and referred to the gas with the words.. "this air is of exalted nature, a candle burned in this air with an amazing strength of flame; and a bit of red hot wood crackled and burned with a prodigious rapidity, exhibiting an appearance something like that of iron glowing with a white heat, and throwing sparks in all directions. But to complete the proof of the superior quality of this air, I introduced a mouse into it; and in a quantity in which, had it been common air, it would have died in about a quarter of an hour; it lived at two different times, a whole hour, and was taken out quite