For determining the relative conductivity of thin layers of materials, it consists of cylindrical brass slab of 11cm dia and 10.5mm thickness. On this is connected another 4.5cm deep brass hollow cylinder (steam chest) of the same dia with inlet and outlet tubes for steam. A hole for thermometer is drilled radially in each, and the cylindrical brass slab is fitted with eyelets to enable it to be suspended by three strings from a stout annular ring. The ring is held on a heavy Retort Stand complete as above with accessories but without thermometer.