Velocities inside large drops suspended in a fluid flowing upward in a tapered glass tube were measured by darkfield particle trace photography. Drop Reynolds numbers were between 3.76 and 19. There was a slow decay of internal velocity and a change in circulatory pattern with the accumulation of minute amounts of colloidal impurities at the interface. The evidence indicates that streamlines leave the interface over the entire rear hemisphere of the drop as circulation is damped.

Methods of photographing bubbles and drops moving in a liquid field are described. Shape, size, terminal velocity, local semi‐vectorial velocities, size distribution and high speed phenomena such as coalescence and breakup can be advantageously investigated by photographic methods. Recommended combinations of lights, reflectors, diffusers, screens, films, and f‐stop values are given. Applications of particle trace and interrupted particle trace photography are described.

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