26.  Watts, Phil. Mag. July, 1903; August, 1904.

27.  Runge, Phil. Mag. December, 1903.

28.  Debierne, C. R. 129, p. 593, 1899; 130, p. 206, 1900.

29.  Giesel, Ber. d. D. Chem. Ges. p. 3608, 1902; p. 342, 1903.

30.  Debierne, C. R. 139, p. 538, 1904. Miss Brooks, Phil. Mag. Sept. 1904. Giesel, Phys. Zeit. 5, p. 822, 1904. Jahrbuch. d. Radioaktivität, no. 4, p. 345, 1904.

31.  Giesel, Ber. d. D. Chem. Ges. 37, p. 1696, 1904; Hartmann, Phys. Zeit. 5, No. 18, p. 570, 1904.

32.  Mme Curie, C. R. 127, p. 175, 1898.

33.  Mme Curie, Thèse, Paris, 1903.

34.  Crookes, Proc. Roy. Soc. May, 1900.

35.  Berndt, Phys. Zeit. 2, p. 180, 1900.