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The ‘rayless change’ certainly does not give out α rays, and special experiments showed that no appreciable amount of β rays were present. On the other hand, the second change gives out all three types of rays.

Miss Brooks, Phil. Mag. Sept. 1904.

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

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Rutherford and Soddy, Phil. Mag. April, 1903.

Rutherford, Phil. Trans. A. p. 169, 1904. Curie and Danne, C. R. p. 748, 1904.

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