This thesis is a study of the boundary layer on a flat plate, using a new method of observation. The boundary layer, and in particular, the laminar region, has been examined using a new device, which takes the form of a small vane. This vane is freely hinged and suspended at its leading edge, lies vertically in the xz plane, and its dimensions are of the same order as the wavelengths of the disturbances, to which it is expected to respond. Such an instrument responds only to v fluctuations of velocity and is uninfluenced by those of u and w. The ultimate aim of the research programme is to use the vane in the transition and turbulent regions, and attempt to obtain information on the formation of turbulence. Before the vane can be put in the turbulent region, however, its own performance has to be ascertained, by investigating relatively well known phenomena in the laminar region, and this forms the subject of the thesis.