Mme Curie also found that bismuth was made active by solution with a radium compound, and succeeded in fractionating the above bismuth in the same way as polonium. In this way bismuth was obtained 2000 times as active as uranium, but the activity, like that of polonium separated from pitchblende, decreased with the time. In the light of the experiments on the transformation products of radium, it is seen that these early experiments of Mme Curie add additional confirmation to the view that the product (radium F) separated from radium itself is identical with the polonium obtained directly from pitchblende. Footnote 314: Rutherford and Soddy, _Phil. Mag._ April, 1903. Footnote 315: Rutherford, _Phil. Trans._ A. p. 169, 1904. Curie and Danne, _C. R._ p. 748, 1904. Footnote 316: P. Curie and Danne, _Comptes Rendus_, 138, p. 748, 1904. Footnote 317: Miss Gates, _Phys. Rev._ p. 300, 1903. Footnote 318: Miss Brooks, _Nature_, July 21, 1904. Footnote 319: Rutherford, _Phil. Mag._ Nov. 1904. _Nature_, p. 341, Feb. 9, 1905. Footnote 320: Rutherford, _Nature_, p. 341, Feb. 9, 1905. Footnote 321: Marckwald (_Ber. d. D. Chem. Ges._ p. 591, 1905) has recently found that the activity of his radio-tellurium falls to half value in 139 days. Footnote 322: Meyer and Schweidler, _Wien Ber._ Dec. 1, 1904. Footnote 323: Rutherford, _Phil. Trans._ A. p. 169, 1904. Footnote 324: Hofmann, Gonder and Wölfl, _Annal. d. Phys._ 15, p. 615, 1904. CHAPTER XII. RATE OF EMISSION OF ENERGY. =243.= It was early recognised that a considerable amount of energy is emitted by the radio-active bodies in the form of their characteristic radiations. Most of the early estimates of the amount of this energy were based on the number and energy of the expelled particles, and were much too small. It has been pointed out (section 114) that the greater part of the energy emitted from the radio-active bodies in the form of ionizing radiations is due to the α rays, and that the β rays in comparison supply only a very small fraction.