In the preparation of this volume no attempt has been made to treat the subject exhaustively. A few paragraphs have been introduced on the origin and nature of the soil, which seem to be essential to a clear understanding of the effects produced by manure; but it is hoped that these Will serve to whet the appetite for a more thorough treatment of the subject, as given by King, Hilgard, Hopkins, Hall, Van Slyke and Merrill.