chemical species (Nicholson, Journal , v. 1, 1801). Priestley rejected Cruickshank's views, but asserted that if there were any discovery it was his. In 1800, when he confessed himself all but alone in his opinions, and appealed somewhat pathetically for a hearing, he published his last book, 'The Doctrine of Phlogiston established,' of which the second edition in 1803 shows no change of view. In his last papers he replied to Noah Webster and Erasmus Darwin [q. v.], attacking the theory of spontaneous generation and of evolution, and defending his former experiments with undiminished clearness and vivacity.
Priestley's eminent discoveries in chemistry were due to an extraordinary quickness and keenness of imagination combined with no mean logical ability and manipulative skill. But, owing mainly to lack of adequate training, he failed to apprehend the full or true value of his great results. Carelessness and haste, not want of critical power, led him, at the outset, to follow the retrograde view of Stahl rather than the method of Boyle, Black, and Cavendish. The modification of the physical properties of bodies by the hypothetical electricity doubtless led him to welcome the theory of a 'phlogiston' which could similarly modify their chemical properties. Priestley was content to assign the same name to bodies with different properties, and to admit that two bodies with precisely the same properties, in other respects differed in composition (Considerations . . . on Phlogiston, 1st edit. p. 17). Though often inaccurate, he was not incapable of performing exact quantitative experiments, but he was careless of their interpretation. The idea of 'composition' in the sense of Lavoisier he hardly realised, except for a brief period between 1783 and 1785. But the enthusiasm roused in him by opposition made him keen to the last to see weak points in his opponent's theory: he failed to see its strength. Priestley is unjust to himself in attributing most of his discoveries to chance ; his researches offer admirable examples of scientific induction (e.g. the researches on the action of plants on air). He has been called by Cuvier a 'father of modern chemistry . . . who would never acknowledge his daughter.'
Priestley's scientific works, which have never been collected, were: 1. 'The History and Present State of Electricity, with original Experiments,' 1767, 4to; 2nd edit. 1769, to ; 3rd edit. 1775, 8vo ; 5th edit. 1794, 4to. 2. 'A Familiar Introduction to the Study of Electricity,' &c., 1768, 4to; 4th edit. 1786. 3. 'A Familiar Introduction to the Theory and Practice of Perspective,' &c., 1770, 8vo ; 2nd edit. 1780, 8vo. 4. 'Directions for impregnating Water with Fixed Air,' &c., 1772, 8vo. 5. 'The History of the Present State of Discoveries relating to Vision, Light, and Colours,' &c., 1772, 4to, 2 vols. ; translated into German, Leipzig, 1775-6, 4to. 6. 'Experiments and Observations on Different Kinds of Air,' &c.,vol. i. 1774, 8vo, 2nd edit. 1775, 3rd edit. 1781 ; vol. ii. 1775, 2nd edit. 1784, 8vo ; vol. iii. 1777, 8vo ; vol. iv. 1779, 8vo ; vol. v. 1780, 8vo [containing an ana- lysis of his researches up to this time] ; vol. vi. 1786, 8vo [the last three volumes are entitled 'Experiments and Observations relating to ... Natural Philosophy, with a continuation of the Observations on Air'] ; new edit., abridged and methodised, with many additions, Birmingham, 1790, 8vo, 3 vols. 7. 'Philosophical Empiricism,' &c., 1775, 8vo, in reply to Bryan Higgins, M.D. [q. v.], who accused him of plagiarising his experiments on air. 8. 'Experiments on the Generation of Air from Water,' &c., 1793, 8vo. 9. 'Heads of Lectures on ... Experimental Philosophy,' &c., 1794, 8vo, 10. ' Experiments and Observations relating to the Analysis of Atmospherical Air,' &c., Philadelphia and London, 1796, 8vo. 11. 'Considerations on the Doctrine of Phlogiston and the Decomposition of Water,' 1st edit. Philadelphia, 1796. 12. 'The Doctrine of Phlogiston established, and that of the Composition of Water refuted,' &c., Northumberland, 1800, 8vo ; 2nd edit. Philadelphia, 1803, 8vo. Many of Priestley's earlier books were translated soon after publication.
The following is a list of Priestley's scientific memoirs, many of which appeared in more than one periodical, and most of which are repeated or summarised in his books (the dates given are those of publication but the dates of actual discovery are often specified in the papers) : In the 'Philosophical Transactions' of the Royal Society : '[On] Rings, consisting of ... Prismatic Colours, made by Electrical Explosions on ... Surfaces of . . . Metal,' 1768; 'On the Lateral Force of Electrical Explosions,' 1769; '. . .On the Force of Explosions,' 1769 ; '[On] the Lateral Explosion,' &c., 1770 ; 'Experiments ... on Charcoal,' 1770 ; 'On Different Kinds of Air,' 1772 ; 'On a new Electrometer, by William Henley,' 1772 ; 'On the Noxious Quality of Putrid Marshes,' 1774 ; 'Further Discoveries on Air,' 1775 ; 'On Respiration and the Use of the Blood,' 1776 ; 'Experiments relating to Phlogiston and the seeming Conversion of Water into Air,' 1783; 'Experiments relating to Air and Water,' 1785 ; 'On the Principle of Acidity, the Com-