Since the occlusion of hydrogen and carbonic oxide by palladium and iron was first discovered by Graham, many similar effects have been discovered. Prof. Knott has investigated in considerable detail the very peculiar changes in the thermo-electric position and in the electrical resistance of palladium when variously charged with hydrogen. With respect to iron, Dr Monckman has experimented on the resistance of iron occluding carbonic oxide, but, in regard to hydrogen, he came to the conclusion that no change in the thermo-electric properties could be detected.