Comparatively little work has been attempted on the subject of the effect of temperature on the conduction of heat through hydrogen. Eucken carried out investigations on the thermal conductivity of hydrogen for a range of temperature between -252·2º and 100º C. A modification of the hot wire method was employed in which his final values were obtained relative to a predetermined value for the thermal conductivity of air, viz., 566 × 10 -7 cal cm -1 sec -1 deg -1 . The values thus determined at various temperatures are given in Table I and compared with those of other observers.