19Henning, Annal. d. Phys. 7, p. 562, 1902.20Rutherford, Phil. Mag. Feb. 1900.21Curie and Debierne, C. R. 132, p. 768, 1901.22Fehrle, Phys. Zeit. 3, No. 7, p. 130, 1902.23Rutherford, Phil. Mag. Jan. 1903.24Giesel, Ber. d. D. Chem. Ges. 36, p. 342, 1903.25Debierne, C. R. 136, pp. 446 and 671, 1903; 138, p. 411, 1904.CHAPTER IX. THEORY OF SUCCESSIVE CHANGES.1Ramsay, Proc. Roy. Soc. p. 470, June, 1904; C. R. 138, June 6, 1904.