Water with a controllable amount of swirl was admitted to a long Perspex tube which could be held at any angle. At tappings along the tube, the wall pressure and the air core diameter were measured, colour bands were inserted at various radii, and total-head traverses across the stream were made. From these observations the distribution was determined of the axial and tangential components of velocity, which were about 10 to 15 ft./s. Experiments were made when the outlet was partly blocked, causing a jump to form, and also when it was unobstructed as in a 'vortex drop'. For both states the inviscid theory of the motion is derived; but agreement with the experiments is not close because, as in swirling flow through a nozzle, the shearing action in the stream was intense. The core sometimes assumed a helical shape of its own accord, and always took this form after the stream had been forced round a bend. Observations of these effects are compared with theoretical analysis.