ABSTRACT
Paschen has described some experiments which indicate that the rays from radium supply a large proportion of the total heat emission. It is known that the heating effect of radium when surrounded by an envelope of sufficient thickness to absorb both the rays is about 100 gram calories per hour per gram. In Paschen's experiments, the heating effect was determined in a special Bunsen ice calorimeter, in the central tube of which the radium, surrounded by a lead cylinder about 4 cm. in diameter, was placed. The heating effect was measured by the movement of the xylene column, observed by a telescope with micrometer eye-piece, and the scale was calibrated by a small heating coil of approximately the same dimensions as the radium. According to Paschen's results, the heating with the lead cylinders should have been at least 50 per cent, greater than with the aluminium cylinders.
