The rods are covered by a thin coat of wax by immerging them in a recipient containing melted wax. When the container they are attached to is filled with boiling water, after a certain time it is seen that the wax, which melts at about 65°C, melts off the different rods to varying distances from the side of the container. The conductance of the materials of which they are made is greater in the rods on which the distance is greater and are related to each other by the square of such distances.
This is true only if the surfaces of the rods are radiated to the same degree, a condition that can be met by making the surfaces equal only from this viewpoint, for example by silver-plating them and polishing them all to a high shine.
In 1853, Wiedeman and Franz, using this technique, but with a far more sophisticated device, found that by assuming the conductance of silver to be equal to 100, the result was:

Silver CopperGoldZincTin IronLeadPlatinum
100 73,6 53,2 19 14,5 11,9 8,5 8,4