The origin, dispersal, deposition and burial of natural sediment grains is the central concern of sedimentology. The subject is truly inter­ disciplinary, commands the attention of Earth scientists, is of consider­ able interest to fluid dynamicists and civil engineers, and it finds widespread practical applications in industry. Sedimentology may be approached from two viewpoints: a descrip­ tive approach, as exemplified by traditional petrography and facies analysis, and a quantitative approach through the physical and chemical sciences. Both approaches are complementary and must be used in tandem if the recent remarkable progress in the field is to be sustained. This text aims to introduce such a combined approach to senior undergraduate students, graduate students and to interested professional Earth scientists. Thus the many descriptive diagrams in the text are counterbalanced by the use of basic physical and chemical reasoning through equations. I have tried to construct a text that follows logically on from the origin of sediment grains through fluid flow, transport, deposition and diagenesis (the change from sediment to rock). The text has been written assuming that some basic previous instruction has been given in the Earth sciences and in general physics and chemistry. Certain important derivations are given in appendices. I have avoided advanced mathematical treatment since it is my opinion that recogni­ tion of the basic physical or chemical basis to a problem is more important to the student than the formal mathematical reduction of poorly gathered data. As T. H.