prosecuting his experiments. Lord Shelburne allowed him $200 a year extra to assist in this object. This arrangement continued seven years, when his lordship seems to have got tired of it, and a separation resulted, although it was entirely amicable. Some years afterward his lordship proposed to renew the relation, but Priestley declined.
Dr. Priestley then took up his residence in Birmingham, where he assumed charge of a congregation, and continued for several years engaged in his theological and scientific investigations. His apparatus, by the liberality of his friends, had become excellent, and his income was now so good that he could prosecute his researches with freedom. He here continued his Theological Repository, and published a variety of tracts on his peculiar opinions in religion and upon the history of the primitive Church.
Dr. Priestley had commenced the investigation of gases while living at Leeds, and had there prepared the first volume of his researches upon air. These researches were continued during his residence with Lord Shelburne, and the last three volumes of his experiments on air were printed after he was settled in Birmingham; and while here he also contributed various papers to the Transactions of the Royal Society. No man ever entered upon any undertaking with less apparent means of success than Dr. Priestley did on the investigation of airs. He was unacquainted with chemistry, excepting that he had some years before attended an elementary course delivered by Mr. Turner, of Liverpool. He had no apparatus, and knew nothing of chemical experimenting, and was without means to carry on investigations. These adverse conditions may, however, have been serviceable as he entered upon a new field of chemistry, where apparatus had to be invented, and the arrangement devised by him for the manipulation of gases is unsurpassed in simplicity, and has been in use ever since. The first of his discoveries was nitrous gas, the properties of which he ascertained with much sagacity, and 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. It was while living with Lord Shelburne that he made his grand discovery of oxygen gas, and established the properties of that remarkable body. He showed its power of supporting combustion better, and animal life longer, than the same volume of common air. Lavoisier laid claim to the discovery, but 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, the Swedish chemist, 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 became known to the public.
Dr. Priestley first made known sulphurous acid, fluosilicic acid, and
