This book presents the physics of incompressible flow for the benefit of students and others who need to understand fluid motion. In this new edition, much of the material is new or rewritten, but the purpose and style of the first edition are retained. Particular emphasis is given to information obtained by experiment and observation in addition to analysis of the equations of motion. The book's primary concern is to convey a fundamental understanding of the behavior of fluids in motion. Special features include an introductory non-mathematical treatment of three particular flow configurations; extensive consideration of geophysical topics; and detailed coverage of topics that are known primarily through experimental data. Numerous photographs illustrate the phenomena discussed, and a concluding chapter demonstrates the wide applicability of fluid mechanics. New topics in the second edition include double diffusive convection and modern ideas about dynamical chaos. The discussion of instabilities has been restructured and the treatments of separation and of convection in horizontal layers considerably expanded.