x PREFACE 



many errors, and helped me most materially in the 

 general chapter on chemistry. 



I have to thank the Editors of several papers for 

 leave to make use of material published, notably 

 the Editors of the Proceedings of the Royal Society, 

 and the Edinburgh Medical Journal y the Annals 

 of Botany, the Journal of the Royal Society of Arts, 

 the Biochemical Journal, and Country Life. The 

 Editor of the Morning Post has kindly allowed me 

 to use the papers on the " National Food Supply," 

 contributed by Mr. Charles W. Fielding. I have to 

 thank that gentleman and Dr. N. L. Watson-Wemyss 

 for the ready permission they gave me to make use 

 of their writings. I have consulted several books 

 in the course of my work, particularly The Geological 

 Survey of Ohio, by Dr. Alfred Dachnowski; The 

 Soil, by Dr. A. D. Hall; Bacteria in Relation to 

 Country Life, by Dr. Jacob G. Lipman ; and Soil Con- 

 ditions and Plant Growth, by Dr. Edward J. Russell. 

 I have also to thank the Editors of those papers 

 which I have quoted in the text for permission to 

 make use of the extracts that have appeared in 

 their columns. 



In typing the manuscript of the book Mrs. 

 Marshall and her staff have very materially assisted 

 me by their promptness and accuracy. 



GORDON D. KNOX. 



u, GARRICK STREET, W., 

 August 9, 1915. 



