His discoveries in pneumatic chemistry are so numerous, that I must satisfy myself with a bare outline; to enumerate every thing, would be to transcribe his three volumes, into which he digested his discoveries. His first paper was published in 1772, and was on the method of impregnating water with carbonic acid gas; the experiments contained in it were the consequence of his residing near a brewery in Leeds. This pamphlet was immediately translated into French; and, at a meeting of the College of Physicians in London, they addressed the Lords of the Treasury, pointing out the advantage that might result from water impregnated with carbonic acid gas in cases of scurvy at sea. His next essay was published in the Philosophical Transactions, and procured him the Copleyan medal. His different volumes on air were published in succession, while he lived with Lord Shelburne, and while he was settled at Birmingham. They drew the attention of all Europe, and raised the reputation of this country to a great height. The first of his discoveries was _nitrous gas_, now called _deutoxide of azote_, which had, indeed, been formed by Dr. Hales; but that philosopher had not attempted to investigate its properties. Dr. Priestley ascertained its properties with much sagacity, and almost immediately applied it to the analysis of air. It contributed very much to all subsequent investigations in pneumatic chemistry, and may be said to have led to our present knowledge of the constitution of the atmosphere. The next great discovery was _oxygen gas_, which was made by him on the 1st of August, 1774, by heating the red oxide of mercury, and collecting the gaseous matter given out by it. He almost immediately detected the remarkable property which this gas has of supporting combustion better, and animal life longer, than the same volume of common air; and likewise the property which it has of condensing into red fumes when mixed with nitrous gas. Lavoisier, likewise, laid claim to the discovery of oxygen gas; but his claim is entitled to no attention whatever; as Dr. Priestley informs us that he prepared this gas in M. Lavoisier's house, in Paris, and showed him the method of procuring it in the year 1774, which is a considerable time before the date assigned by Lavoisier for his pretended discovery. Scheele, however, actually obtained this gas without any previous knowledge of what Priestley had done; but the book containing this discovery was not published till three years after Priestley's process had become known to the public.