Engineering geology is an interdisciplinary subject concerned with the application of geological science to engineering practice, and it is therefore important for the engineering geologist to recognize the boundary between engineering application and purely scientific enquiry. Much research in applied clay science results from imperfectly understood engineering behaviour. Engineering geology is most closely allied to the geotechnical and materials areas of civil engineering. The scope of the present book is limited to the influence of clay but because clay is almost ubiquitous in earth materials the subject still remains broad. In soil and rock, clay is the smallest size fraction, but it is that very fact which often determines its major influences on engineering behaviour.In this book the author reviews the importance of clay in engineering geology and summarizes present knowledge in this field. The plan of the book has remained unchanged since the first edition was published in 1968 but the text, diagrams and reference lists have all been extensively updated. The first 5 chapters review the classification, origin, composition, fabric and physical chemistry of clays. Behavioural aspects, covered in the following 4 chapters, include moisture interaction, strength and rheology, soil stabilization and the use of clays as materials. The final 3 chapters describe methods of analysis of clays and soils.Clay in Engineering Geology contains material drawn from a wide variety of sources and, together with its literature review and indexes, will provide much of value to geologists, mineralogists, civil and geotechnical engineers concerned with applied clay science.