The image on the cover shows the flow between a smooth outer cylinder and an inner rotating cylinder with axisymmetric and axially-periodic topography, in an hourglass shape. The solid lines correspond to streamfunction contours which show that the flow is made up of two counter-rotating toroidal vortices, while the grey background contours correspond to azimuthal velocity which is zero at the smooth nonrotating outer wall and takes on its maximum and minimum values at the rotating inner wall. See the paper in this issue by D. L. Cotrell and A. J. Kearsley for the complete description. Cover arranged by C. Carey.