THE accompanying flow pictures arc selected from those used to illustrate the lecturer's notes in a course dealing with viscous fluids. The use of the pictures saves an astonishing amount of lecture time in those categories of study where the real flow patterns agree reasonably with the classical rationalized concepts. This time is profitably used in those regions of sharp departure of the real pattern from the classical concepts: in boundary layer transition, in leading edge separation with subsequent rejoining, in the mechanism of circulation growth accompanying rapid change of angle of attack, in wake survey for drag determination and in many others.