Rutherford, Phil. Mag. January, 1899.

Rutherford and Grier, Phil. Mag. September, 1902.

Becquerel, C. R. 130, pp. 206, 372, 810, 979. 1900.

M. and Mme Curie, C. R. 130, p. 647, 1900.

The activity of the radium preparation was not stated in the paper.

Dorn, Phys. Zeit. 4, No. 18, p. 507, 1903.

Strutt, Phil. Mag. Nov. 1903.

Wien, Phys. Zeit. 4, No. 23, p. 624, 1903.

Dorn, C. R. 130, p. 1129, 1900.

Becquerel, C. R. 130, p. 809, 1900.