It is also his pleasing duty to thank his friends Dr Bernard Dyer, Hon Secretary of the Society of Public Analysts, Dr A. P. Aitken, Chemist to the Highland and Agricultural Society of Scotland; Professor Douglas Gilchrist of Bangor; Mr F. J. Cooke, late of Flitcham; Mr Hermann Voss of London; and Professor Wright of Glasgow, for having assisted him in the revision of proof-sheets. ANALYTICAL LABORATORY, 128 WELLINGTON STREET, GLASGOW, _January_ 1894. CONTENTS. PART I.--HISTORICAL INTRODUCTION. PAGE Beginning of agricultural chemistry 4 Early theories regarding plant-growth 4 Van Helmont 4 Digby 6 Duhamel and Stephen Hales 8 Jethro Tull 9 Charles Bonnet's discovery of source of plants' carbon 11 Researches of Priestley, Ingenhousz, Senebier, on assimilation of carbon 11-12 Publication of first English treatise by Earl Dundonald 13 Publication of Theodore de Saussure, 'Chemical Researches on Vegetation,' 1804 14 Theories on source of plant-nitrogen 15 Early experiments on this subject 16 Sir Humphry Davy's lectures (1802-1812) 17 State of agricultural chemistry in 1812 17 Beginning of Boussingault's researches (1834) 21 Publication of Liebig's first report to the British Association 24 Refutation of "humus" theory 26 Liebig's mineral theory 26 Liebig's theory of source of plants' nitrogen 27 Publication of Liebig's second report to British Association 30 Liebig's services to agricultural chemistry 31 Development of agricultural research in Germany 32 The Rothamsted Experiment Station 33 Sir J. B. Lawes and Sir J. H. Gilbert, the nature and value of their experiments 33 Review of the present state of our knowledge of plant-growth 36 Proximate composition of the plant 36 Fixation of carbon by plants 37 Action of light on plant-growth, Dr Siemens' experiments 38 Source of oxygen and hydrogen in the plant 39-40