Studies were made of the depression caused by subsonic jet streams impinging on the surface of various liquids. For nozzle distance-nozzle dia. ratios greater than 20, the fluid dynamics of the stream at its axis of symmetry, derived from the depth and diameter of depression on the surface, is found to be in accordance with theory. The kinematic eddy viscosity computed from these measurements agrees well with the previous data on free circular turbulent jets. Depending on the nature of the liquid, beyond a certain critical axial impact pressure, depression on the liquid surface becomes unstable and liquid droplets are ejected. This critical impact pressure is shown to increase. with increasing surface tension of the liquid. THEORETICAL THE PIONEERING work on the fluid dynamics of jet streams is due primarily to TOLLMIEN [l] and GOERTLER [2] for turbulent jet streams and to SCHLICHTING [3] and BICKLEY [4] for laminar jets. The general applicability of these theoretical analyses, underlying the basic concepts of fluid dynamics of jets, to systems of experimental interest was also demonstrated by the outstanding work of ZIMM [5], RULIEN [6], FOERTHMANN [7], and RBICHARDT [8]. The fundamentals of such flow systems are described adequately in textbooks, e.g. SCHLICHTING [9], PAI [IO], and HINZE [l l] ; therefore, they need not be discussed here in detail.