Distinguished authors discuss topics in physical oceano- graphy, transonic aerodynamics, dynamics of vorticity, numerical simulation of turbulent flows, astrophysical jets, strange attractors, human-powered flight, and thefluid mechanics of the Old Faithful geyser and of the Mount St. Helens eruption of 1980. The authors deal with specific problems, but the emphasis is usually on the way that re- search is carried out at the edge of understanding, and often on the role of new techniques, instruments, and re- search strategies.