Chapter XI 167 Priestley as a man of science—His characteristics as a philosopher—_Experiments and Observations on Different Kinds of Air_—His discovery of the influence of vegetation on vitiated air—Atmospheric air not elementary—His researches on nitric oxide—Eudiometry—Nitrous oxide—Discovers hydrogen chloride—Prepares oxygen from nitre (1771)—Isolates ammonia gas—Discovers sulphur dioxide—Dephlogisticated air (oxygen)—Discovers silicon fluoride—Intra-diffusion of gases—Respiration—Priestley’s opinions of the value of experimental science in education—Discovers nitrosulphuric acid—Notes the constancy of composition of the atmosphere—Prepares chlorine—Sound in “air”—Experiments relating to phlogiston—The seeming conversion of water into air—Watt and the compound nature of water—Discovers sulphuretted hydrogen—Priestley’s confession of faith in phlogiston. Index 225 LIST OF ILLUSTRATIONS Joseph Priestley, from the portrait in Dr Williams’ Library by Artaud (_Photogravure_) _Frontispiece_ Birthplace of Priestley, from a drawing by J. A. Symington after a photograph _page_ 5 The Pillaging of Priestley’s House during the Birmingham Riots _facing page_ 120 Joseph Priestley CHAPTER I Birth—Parentage—Home Life—Early Education “If,” says Mr Frederic Harrison, “we choose one man as a type of the intellectual energy of the eighteenth century we could hardly find a better than Joseph Priestley, though his was not the greatest mind of the century. His versatility, eagerness, activity and humanity; the immense range of his curiosity in all things, physical, moral or social; his place in science, in theology, in philosophy and in politics; his peculiar relation to the Revolution, and the pathetic story of his unmerited sufferings, may make him the hero of the eighteenth century.” In these few lines Mr Harrison has indicated, in terms sufficiently precise, the leading features in the character and life-history of one of the most remarkable men of the eighteenth century. To what extent he may be regarded as a hero and as a type of the intellectual energy of that century it is the purpose of the following pages to make clear. Joseph Priestley was born at Fieldhead, in the parish of Birstall, near Leeds, on March 13 (Old Style), 1733.[1] He was named after his paternal grandfather, “an eminent tradesman, as much famed for his heavenly conduct as his grandson (Joseph) has since been for natural abilities.”