The average rate of heat transfer as well as the oscillatory span-widths of the Nusselt number and the Rayleigh number were measured for natural convection in a layer of liquid gallium (Pr = 0.023) heated from below electrically and cooled from above with running water. These quantities were determined by measuring the instantaneous temperature difference between the upper and lower horizontal copper plates. The time-averaged Nusselt number agreed well with the previous data of Rossby for mercury (Pr = 0.025), at comparable values of the Rayleigh number. The oscillations are a consequence of reduced viscous damping for a fluid with low Prandtl number.