if desired the upper portion of the cylinder 1 is provided with a guide 1 39 in which a seal 2 is located passing through the seal 2 is a piston generally designated by the reference numeral 3 and being formed of an iron tube 4 which is completely filled with a filler material 5 such as for example concrete the iron tube 4 is provided with an upper end plate 4 39 and a lower end plate 4 34 the thickness of the wall of the iron tube 4 is preferably about or less than one eighth the diameter of the tube the upper part of the piston 3 is rigidly connected to an arm 6 shown only schematically to the end of which a load 7 is attached indicated schematically by an arrow 7 the base plate 1 34 is fastened by means of bolts not shown to a foundation 8 in which there is a central opening 9 for receiving the lower end of the piston 3 by filling the iron tube 4 with concrete good mechanical strength is obtained with regard to the bending moment caused by the arm 6 and load 7 the arrangement shown in fig2 corresponds in part to that of fig1 the iron tube 4 however is filled only partially with the solid filler material 5 39 in the outer zone 10 of the interior of the iron tube 4 or in an annular or tubular form and the inner zone 11 of cylindrical form of the tube 4 is therfore not filled a certain quantity of the solid filler material 5 39 is saved in this way and yet the.