Miss Gates, Phys. Rev. p. 300, 1903.

Miss Brooks, Nature, July 21, 1904.

Rutherford, Phil. Mag. Nov. 1904. Nature, p. 341, Feb. 9, 1905.

Rutherford, Nature, p. 341, Feb. 9, 1905.

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.

Meyer and Schweidler, Wien Ber. Dec. 1, 1904.

Rutherford, Phil. Trans. A. p. 169, 1904.

Hofmann, Gonder and Wölfl, Annal. d. Phys. 15, p. 615, 1904.

Phil. Trans. A. p. 25, 1901.

P. Curie and Laborde, C. R. 136, p. 673, 1903.

Runge and Precht, Sitz. Ak. Wiss. Berlin, No. 38, 1903.

P. Curie, Société de Physique, 1903.

Rutherford and Barnes, Nature, Oct. 29, 1903. Phil. Mag. Feb. 1904.

Paschen, Phys. Zeit. Sept. 15, 1904.

Rutherford and Barnes, Nature, Dec. 18, 1904; Phil. Mag. May, 1905.