Abron For determining the relative conductivity of thin layers of material. Consists of cylindrical slab of brass 11 casein diameter and 10.5 mm thick. On this rests a 5 cms. deep hollow cylinder of the same diameter with inlet and outlet tubes for steam. Both the cylinders have radial holes for insertion of thermometers. The material under test is placed between the two cylinders. The apparatus is suspended by strings attached to the lower cylinder. Without thermometers