ABSTRACT
This chapter shows that the production of excited radioactivity is one of the properties of the emanation from thorium and radium. The excited radiation is caused by the deposit on the surface of bodies of radioactive matter, which is transmitted by positively charged carriers travelling through air in an electric field with about the same velocity as the positive ion, produced in air by Rontgen rays. The term excited has been used throughout these investigations rather than induced, which has found favour with many physicists. The emanations from thorium and radium possess very similar properties. They both readily diffuse through glass and porous substances; they both possess the power of ionizing the gas in their neighbourhood and producing excited radioactivity on bodies. It sees that the values of the velocity of the carrier lie between 10 and 15 cm. per sec. for a potential gradient of one volt per centimetre.
