and can be lifted or lowered at the lower parts of its corners the frame 34 is provided with inclined guides 35 which cooperate with complementary guides on the clamping devices 27 fig8 shows a cross section of a cell provided with an anode cassette 8 which has an alternatively designed holding and feeding arrangement this example includes a cassette with two guides for the anode carbon blocks 21 instead of using clamping devices as explained above each of the anode carbon blocks 21 has two vertical bores 41 formed therethrough conical spindles 40 having threads 38 at their lower ends are provided and extend through the bores 41 which have complementary threads 39 the spindle 40 are provided with thrust bearings 37 at their upper ends and can be rotated by means of a gear and driving arrangement shown schematically at 50 the anode carbon blocks 21 are held in position by means of the spindles and can be elevated or lowered by rotating the spindles electric current can be supplied wholly or partly through the spindles or through guiding jackets 42 a preferred method of adding new carbon blocks to the top of the anode as they are gradually consumed is illustrated schematically in fig9 as can be seen each of the carbon blocks or elements consist of two halves 43 each of which is provided with two parallel semi circular grooves 44 the halves 43 should be placed on top of the 34 stack 34 of.