Dr. Henry on the Philosophical Character of Dr. Priestley. 209 



genious artists, from whom the chemical philosopher now 

 derives such valuable aid, had not then been called into 

 existence by the demands of the science. With a very 

 limited knowledge of the general principles of chemistry, 

 and almost without practice in its most common manipula- 

 t'lons; — restricted by a narrow income, and at first with 

 little pecuniary assistance from others ; — compelled, too, to 

 devote a large portion of his time to other pressing occupa- 

 tions, he nevertheless surmounted all obstacles; and in the 

 career of discovery, outstripped many, who had long been ex- 

 clusively devoted to science, and were richly provided with all 

 appliances and means for its advancement. 



It is well known that the accident of living near a public 

 brewery at Leeds, first directed the attention of Dr. Priestley 

 to pneumatic chemistry, by casually presenting to his observa- 

 tion the appearances attending the extinction of lighted chips 

 of wood in the gas which floats over fermenting liquors. He 

 remarked, that the smoke formed distinct clouds floating on the 

 surface of the atmosphere of the vessel, and that this mixture 

 of air and smoke when thrown over the sides of the vat fell 

 to the ground ; from whence he deduced the greater weight of 

 this sort of air than of atmospheric air. He next found that 

 water imbibes the new air, and again abandons it when boiled 

 or frozen. These more obvious properties of fixed air having 

 been ascertained, he extended his inquiries to its other quali- 

 ties and relations ; and was afterwards led by analogy to the 

 discovery of various other gases, and to the investigation of 

 their characteristic properties. 



It would be inconsistent with the scope of this Essay to give 

 a full catalogue of Dr. Priestley's discoveries, or to enumerate 

 more of them than are necessary to a just estimate of his philo- 

 so})hical habits and character. He was the unquestionable 

 author of our first knowledge of oxygen gas, of nitrous oxide, 

 of muriatic, sulphurous, and fluor acid gases, of ammoniacal 

 gas, and of its condensation into a solid form by the acid gases. 

 Hydrogen gas was known before his time ; but he greatly ex- 

 tended our acquaintance with its properties. Nitrous gas, 

 barely discovered by Dr. Hales, was first investigated by 

 Priestley, and applied by him to eudiometry. To the chemi- 

 cal history of the acids derived from nitre, he contributed a 

 vast accession of original and most valuable facts. He seems 

 to have been quite aware that those acids are essentially gaseous 

 sulistances, and that they might be exhibited as such, provided 

 a fluid c(juld be found that is incapable of absorbing or acting 

 upon them *. He obtained and distinctly described f the cu- 

 • Scries I. Vol. ii. p. 175. t Scries II. Vol. i. p. 2 



N.S. Vol. 11. No. 63. March 1832. 2 E 



