For demonstrating the effect of capillary action, i.e., relationship between capillary pressure or level of liquid in capillary and the bore diameter of the capillary tube. The apparatus comprises a rectangular sheet-metal frame, the base of which takes the form of a trough for holding water. The upper part of the frame supports six capillary tubes, each of a different bore, in the holed rubber bung with their lower ends resting in the trough underneath. The difference in heights of the resulting columns of water in each capillary tube is readily apparent. Length of capillary tubes about 150mm.