Plots of shear stress versus time, logged over an extended period in a campaign of experiments to measure the wall friction properties of limestone, were indicative of stick slip friction and were affected by the method of filling the trough of the annular cell. Results are presented for three limestones with different geological origins. These were an algal Oligocene limestone containing small amounts of quartz and mica, an Oligocene sandy coquina, and an Ordovician marble containing small amounts of mica; the size distributions of each were similar. The influence of filling method and the effect of normal load is discussed.