Section 190, That the Expulsion of α Particles From the Emanation Must

set the part of the system left behind in rapid motion. A close examination of the mode of transference of the excited activity by actinium and the emanation substance is likely to throw further light on the processes which give rise to the deposit of active matter on the electrodes.

Footnote 269:

M. and Mme. Curie, C. R. 129, p. 714, 1899.

Footnote 270:

Rutherford, Phil. Mag. Jan. and Feb. 1900.

Footnote 271:

As regards date of publication, the priority of the discovery of “excited activity” belongs to M. and Mme. Curie. A short paper on this subject, entitled “Sur la radioactivité provoquée par les rayons de Becquerel,” was communicated by them to the Comptes Rendus, Nov. 6, 1899. A short note was added to the paper by Becquerel in which the phenomena of excited activity were ascribed to a type of phosphorescence. On my part, I had simultaneously discovered the emission of an emanation from thorium compounds and the excited activity produced by it, in July, 1899. I, however, delayed publication in order to work out in some detail the properties of the emanation and of the excited activity and the connection between them. The results were published in two papers in the Philosophical Magazine (Jan. and Feb. 1900) entitled “A radio-active substance emitted from thorium compounds,” and “Radio-activity produced in substances by the action of thorium compounds.”

Footnote 272:

Rutherford, Phil. Mag. Feb. 1900.

Footnote 273:

Rutherford, Phys. Zeit. 3, No. 12, p. 254, 1902. Phil. Mag. Jan. 1903.

Footnote 274:

Miss Brooks, Phil. Mag. Sept. 1904.

Footnote 275:

Rutherford and Miss Brooks, Phil. Mag. July, 1902.

Footnote 276:

Curie and Danne, C. R. 136, p. 364, 1903.

Footnote 277:

Mme Curie, Thèse, Paris, 1903, p. 116.

Footnote 278:

Debierne, C. R. 138, p. 411, 1904.

Footnote 279:

Giesel, Ber. d. D. Chem. Ges. No. 3, p. 775, 1905.

Footnote 280:

Miss Brooks, Phil. Mag. Sept. 1904.

Footnote 281:

Rutherford, Phys. Zeit. 3, No. 12, p. 254, 1902.

Footnote 282:

F. von Lerch, Annal. d. Phys. 12, p. 745, 1903.

Footnote 283:

Pegram, Phys. Review, p. 424, Dec. 1903.

Footnote 284:

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

Footnote 285:

A more complete examination of the effect of temperature on the excited activity of thorium has been made by Miss Slater (section 207).

Footnote 286:

Rutherford, Phil. Mag. Feb. 1900.

Footnote 287:

Henning, Annal. d. Phys. 7, p. 562, 1902.

Footnote 288:

Rutherford, Phil. Mag. Feb. 1900.

Footnote 289:

Curie and Debierne, C. R. 132, p. 768, 1901.

Footnote 290:

Fehrle, Phys. Zeit. 3, No. 7, p. 130, 1902.

Footnote 291:

Rutherford, Phil. Mag. Jan. 1903.

Footnote 292:

Giesel, Ber. d. D. Chem. Ges. 36, p. 342, 1903.

Footnote 293:

Debierne, C. R. 136, pp. 446 and 671, 1903; 138, p. 411, 1904.