For demonstrating the transmissibility of fluid pressure. The apparatus comprises two metal cylinders 19 and 38 mm diameters respectively, fitted with pistons and connected by metal tube. The pistons are provided with rods terminating in the circular platform each 75 mm diameter for loading, masses are required. The complete apparatus is mounted on moulded plastic base of size 20 x 12.5 cm and the overall height with both pistons at the bottom of their cylinders is 24 cm.