Ludwig Prandtl, with his fundamental contributions to hydrodynamics, aerodynamics, and gas dynamics, greatly influenced the development of fluid mechanics as a whole, and it was his pioneering research in the first half of the last century that founded modern fluid mechanics. His book Fuhrer durch die Stromungslehre, which appeared in 1942, originated from previous publications in 1913, Lehre von der Fliissigkeit und Gasbewegung, and 1931, Abrifi der Stromungslehre. The title Fuhrer durch die Stromungslehre, or Essentials of Fluid Mechanics, is an indication of PrandtFs intentions to guide the reader on a carefully thought-out path through the different areas of fluid mechanics. On his way, the author advances intuitively to the core of the physical problem, without extensive mathematical derivations. The description of the fundamental physical phenomena and concepts of fluid mechanics that are needed to derive the simplified models has priority over a formal treatment of the methods. This is in keeping with the spirit of Prandtl's research work...