30 Philosophical Character of Dr. Priestley. 



They were chiefly, too, the work of his own hands, or were con- 

 structed under his direction by unskilled persons ; for the class of in- 

 genious artists, from whom the chemical philosophers now derives 

 such valuable aid, had not then been called into existence by the de- 

 mands of the science. With a very limited knowledge of the general 

 principles of chemistry, and almost without practice in its most com- 

 mon manipulations ; — 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 occupations, he neverthe- 

 less surmounted all obstacles ; and in the career of discovery, out- 

 stripped many, who had long been exclusively devoted to science, 

 and were richly provided with all appliances and means for its ad- 

 vancement. 



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 observation the appearances 

 attending the extinction of lighted chips of wood, in the gas which 

 floats over fermenting liquors. He remarked, that the smoke form- 

 ed 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 hav- 

 ing been ascertained, he extended his inquiries to its other qualities 

 and relations ; and was afterwards led by analogy to the discovery of 

 various others 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 philosophical habits 

 and character. He was the unquestionable author of our first knowl- 

 edge of oxygen gas, of nitrous oxide, of muriatic, sulphurous, and 

 fluor acid gases, of aramoniacal gas, and of its condensation into a 

 solid form by the acid gases. Hydrogen gas was known before his 

 time ; but he greatly extended 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 chemical 

 history of the acids derived from nitre, he contributed a vast acces- 

 sion of original and most valuable facts. He seems to have been 



