shews the use of a burning lens in pneumatic experiments, he relates the discovery and properties of marine acid air; he adds much to the little of what had been heretofore known of the airs generated by putrefactive processes, and by vegetable fermentations, and he determines many facts relating to the diminution and deterioration of air, by the combustion of Charcoal, and the calcination of metals. [50] Honestly referring to Dr. Hales and Mr. Cavendish for any idea that might have remotely led to this discovery (See Obs. on air 1st ed. v. 1 p. 108) the discovery however was completely his own. Dr. Priestley seems always to have thought nitrous air as convenient a substance for eudiometrical experiments as any of the later substitutes, viz. the liquid sulphurets and the combustion of phosphorus. The foundation of Mr. Davy’s substitute, muriat or sulphat of iron saturated with nitrous air, was as Mr. Davy acknowledges first discovered by Dr. Priestley himself. See Nich. Journ. for Jan. 1802 p. 41. The different states of the solutions of iron in vitriolic acid have been ingeniously applied to the analysis of mixed gasses by Humboldt and Vauquelin. Soon after this, in confirmation of Sir John Pringle’s theory of intermittents and low fevers being generally owing to moist miasma when people are exposed to its influence, he ascertained by means of his nitrous test that the air of marshes was inferior in purity to the common air of the atmosphere.[51] He had obtained very good air from saltpetre in 1771, but his full discovery of dephlogisticated air, seems not to have been made until June or July, 1774,[52] when he procured it from precipitate per se, and from red lead. This was publicly mentioned by him at the table of Mr. and Madame Lavoisier, at Paris, in October 1774, to whom the phenomena were until then unknown. The experiments on the production of dephlogisticated air, he made before the scientific chemists at Paris about the same time, at Mr. Trudaine’s. This hitherto secret source of animal life and animal heat, of which Mayow had but a faint and conjectural glimpse, was certainly first exhibited by Dr. Priestley, and about the same time, (unknown to each other) by Mr. Scheele of Sweden. For the honour of science, it were much to be wished that the pretensions of Mr. Lavoisier were equally well founded. He has done sufficient and been praised sufficiently for what he has done, to satisfy a mind the most avaricious of fame; he is deservedly placed in the first rank among the philosophers of his day, and he ought not to have thrown a shade over his well earned reputation, by claiming for himself the honour of those discoveries which he had learned from another. [51] Phil. trans. v. 54 p. 92. [52] See Doctrine of Phlog. established p. 119.