106 BLACK. that of the atmosphere, under various modifications. These experiments, at the same time opened to the view of ob- servers, the transition of elastic fluids to a concrete state, by uniting to different bodies, and the change from a solid to an elastic form on their extrication; and as these elastie fluids were probably of many species, it was begun to be considered that aeriform bodies might possess aflinities, and have as great a share in the composition of bodies as acids, alkalies, &c, of which, the first instances had been shewn by the above paper of Dr. Black. This celebrated professor in his lectures, afterwards shewed that the inflammable air was totally different from fixed air; but never having published those experiments, he has never enjoyed the honour of the discovery of this elastic inflammable fluid. The first offspring of these discoveries was, Browprigg's experiments on the air of Pyrmont water, in which was shewn the existence of the fixed air discovered by Dr. Black. These were succeeded by, the accurate and pro- found experiments of Mr. Cavendish on fixed and inflam- mable air, with an excellent description of the apparatus for chemical experiments on aeriforn bodies. Dr. Priestley next extended the knowledge of pneumatic chemistry; and the investigation into this branch of chemical philo- sophy, soon after began in Sweden, Germany, and France. In this latter country, the knowledge resulting from the investigation of the properties of aeriform bodies, suggested the new system of chemistry, so sublimely simple in its theory; and the fountain from which it sprung was the above set of experiments by Dr. Black. To return, however, from this digression, in which the pursuit of the history of the science has led us away from that of the indiyidual.In 1755, Dr. Cullen was removed from the chemical chair at Glasgow, to a professorship at Edinburgh; and the abilities which Black had displayed in the assistance be had afforded to that great man, together with his recent and splendid discoveries, pointed him out
