including an outer shell 11 insulation 12 and carbon lining 13 defining a space for containing a pad of molten aluminum 14 and molten bath constituents 15 also included in cell 10 is anode 16 and cathode voltage supply bus 17 each connected to a current source not shown in one embodiment of the invention the cathode element comprises an elongated hollow body 18 the lower end of which is affixed to or embedded in the carbon lining 13 hollow body 18 extends upwardly through the aluminum pad 14 into the cryolite layer 15 and is provided with a cap element 26 having a cathodically active surface 21 confronting the under surface 20 of anode 16 and provided on its underside with at least one downwardly depending member 27 which extends into the interior of hollow body 18 and is in contact with a body of molten aluminum 28 confined within hollow body 18 thus providing an electrically conductive path from the cathode voltage supply bus 17 embedded in carbon lining 13 to the cathodically active surface 21 of cap 26 the dimensions of cap 26 and its mode of engagement with hollow body 18 may vary considerably so long as the cap fits sufficiently snug so as not to allow entrance of bath material into the interior of hollow body 18 for example as shown in fig1 the periphery of cap 26 is formed as a downwardly depending annular flange which engages the outer periphery of the upper end of hollow body 18 when the cap is in place to assure accurate placement of the cap and to prevent lateral movement of the cap with respect to.