On 2 October 1798, Davy joined the Pneumatic Institution at Bristol. It had been established to investigate the medical powers of factitious airs and gases (gases produced experimentally or artificially), and Davy was to superintend the various experiments. The arrangement agreed between Dr Beddoes and Davy was generous, and enabled Davy to give up all claims on his paternal property in favour of his mother. He did not intend to abandon the medical profession and was determined to study and graduate at Edinburgh, but he soon began to fill parts of the institution with voltaic batteries. While living in Bristol, Davy met the Earl of Durham, who was a resident in the institution for his health, and became close friends with Gregory Watt, James Watt, Samuel Taylor Coleridge and Robert Southey, all of whom became regular users of nitrous oxide (laughing gas). The gas was first synthesized in 1772 by the natural philosopher and chemist Joseph Priestley, who called it "phlogisticated nitrous air" (see phlogiston). Priestley described his discovery in the book "Experiments and Observations on Different Kinds of Air (1775)", in which he described how to produce the preparation of "nitrous air diminished", by heating iron filings dampened with nitric acid.