The goals of successive editions of this book remained essentially un¬changed from those stated in the Preface to the First Edition: “… to present the material in the simplest possible language” and “to lead the reader through appropriate phases of the basic sciences of geology, pedol¬ogy, soil physics, and physical chemistry. . .”Geology, pedology and sampling come first because they are the basic, fundamental part of any geotechnical investigation, and by inference or chapter position or postponement it should not be implied that they are an afterthought.New material in this edition includes chapters on elementary soil dy¬namics and on shallow and deep soil stabilization. The calculator revolution is recognized by a reduced reliance on graphs and increased use of equations that may be programmed. The fourth edition also starts a transition to metric SI (Systeme International) units. Both SI and English equivalents are given, and practice problems are given such that they may be solved in either system.