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

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

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

123.  Strutt, Phil. Mag. Nov. 1903.

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

125.  Dorn, C. R. 130, p. 1129, 1900.

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

127.  Kaufmann, Phys. Zeit. 4, No. 1 b, p. 54, 1902.

128.  Abraham, Phys. Zeit. 4, No. 1 b, p. 57, 1902.

129.  Kaufmann, Nachrichten d. Ges. d. Wiss. zu Gött., Nov. 8, 1901.

130.  Simon, Annal. d. Phys. p. 589, 1899.

131.  Kaufmann, Phys. Zeit. 4, No. 1 b, p. 54, 1902.

132.  Paschen, Annal. d. Phys. 14, p. 389, 1904.

133.  Meyer and Schweidler, Phys. Zeit. pp. 90, 113, 209, 1900.

134.  Lenard, Annal. d. Phys. 56, p. 275, 1895.

135.  Strutt, Nature, p. 539, 1900.

136.  Seitz, Phys. Zeit. 5, No. 14, p. 395, 1904.

137.  It is presumed that the results were corrected, if necessary, for the discharging action due to the ionized gas, although no direct mention of this is made in the paper by Seitz.

138.  Strutt, Phil. Trans. A, p. 507, 1901.

139.  Crookes, Proc. Roy. Soc. 1902. Chem. News, 85, p. 109, 1902.

140.  Mme Curie, C. R. 130, p. 76, 1900.

141.  Rutherford, Phil. Mag. Feb. 1903. Phys. Zeit. 4, p. 235, 1902.

142.  Becquerel, C. R. 136, p. 199, 1903.

143.  Becquerel, C. R. 136, p. 431, 1903.

144.  Des Coudres, Phys. Zeit. 4, No. 17, p. 483, 1903.

145.  Becquerel, C. R. 136, p. 1517, 1903.

146.  Bragg, Phil. Mag. Dec. 1904; Bragg and Kleeman, Phil. Mag. Dec. 1904.

147.  Further experimental results bearing on this important question are given in an Appendix to this book.

148.  Bakerian Lecture, Phil. Trans. A, p. 169, 1904.

149.  Strutt, Phil. Mag. Aug. 1904.

150.  J. J. Thomson, Proc. Camb. Phil. Soc. 13, Pt. I. p. 39, 1905. Nature, Dec. 15, 1904.

151.  Rutherford, Nature, March 2, 1905. J. J. Thomson, Nature, March 9, 1905.

152.  Crookes, Proc. Roy. Soc. 81, p. 405, 1903.

153.  Elster and Geitel, Phys. Zeit. No. 15, p. 437, 1903.

154.  Glew, Arch. Röntgen Ray, June 1904.

155.  Becquerel, C. R. 137, Oct. 27, 1903.

156.  Tommasina, C. R. 137, Nov. 9, 1903.

157.  An interesting side-light is thrown on this question by the experiments described in Appendix A of this book.

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

159.  In order to obtain a thin layer, the compound to be tested is ground to a fine powder and then sifted through a fine gauge uniformly over the area, so that the plate is only partially covered.

160.  Rutherford, Phil. Mag. Jan. 1899.

161.  Owens, Phil. Mag. Oct. 1899.

162.  Rutherford and Miss Brooks, Phil. Mag. July, 1900.

163.  Since the ionization at any point above the plate is the resultant effect of the α particles coming from all points of the large radio-active layer, λ is not the same as the coefficient of absorption of the rays from a point source. It will however be proportional to it. For this reason λ is called the “absorption constant.”

164.  Townsend, Phil. Mag. Feb. 1901.

165.  Durack, Phil. Mag. July 1902, May 1903.

166.  Bragg and Bragg and Kleeman, Phil. Mag. Dec. 1904.

167.  Villard, C. R. 130, pp. 1010, 1178, 1900.

168.  Becquerel, C. R. 130, p. 1154, 1900.

169.  Rutherford, Phys. Zeit. 3, p. 517, 1902.

170.  McClelland, Phil. Mag. July 1904.

171.  Paschen, Phys. Zeit. 5, No. 18, p. 563, 1904.

172.  A. S. Eve, Phil. Mag. Nov. 1904.

173.  Paschen, Annal. d. Physik, 14, p. 114, 1904; 14, 2, p. 389, 1904. Phys. Zeit. 5, No. 18, p. 563, 1904.

174.  Paschen, Phys. Zeit. 5, No. 18, p. 563, 1904.

175.  Rutherford and Barnes, Phil. Mag. May 1905. Nature, p. 151, Dec. 15, 1904.

176.  Barkla, Nature, March 17, 1904.

177.  Becquerel, C.R. 132, pp. 371, 734, 1286. 1901.

178.  Mme Curie, Thèse présentée à la Faculté des Sciences, Paris 1903, p. 85.

179.  A. S. Eve, Phil. Mag. Dec. 1904.

180.  In a recent paper (Phil. Mag. Feb. 1905), McClelland has, in the main, confirmed the experimental results obtained by Eve. An electrometer was used instead of an electroscope. He finds, in addition, that the amount of secondary radiation depends on the angle of incidence of the primary rays, and is greatest for an angle of 45°. In a letter to Nature (Feb. 23, p. 390, 1905), he states that more recent experiments have shown that the amount of secondary radiation from different substances is a function of their atomic weights rather than of their densities. In every case examined, the amount of secondary radiation increases with the atomic weight, but is not proportional to it.

181.  Rutherford and McClung, Phil. Trans. A. p. 25, 1901.

182.  Meyer and Schweidler, Wien Ber. 113, July, 1904.

183.  Rutherford and Grier, Phil. Mag. Sept. 1902.

184.  Becquerel, C. R. 129, p. 912, 1899.

185.  Bary, C. R. 130, p. 776, 1900.

186.  Kunz and Baskerville, Amer. Journ. Science XVI. p. 335, 1903.

187.  See Nature, p. 523, March 31, 1904.

188.  Crookes, Proc. Roy. Soc. 74, p. 47, 1904.

189.  Kunz and Baskerville, Science XVIII, p. 769, Dec. 18, 1903.

190.  Beilby in a recent communication to the Royal Society (Feb. 9 and 23, 1905) has examined in some detail the production of phosphorescence by the β and γ rays of radium and has put forward a theory to account for the different actions observed.

191.  Huggins, Proc. Roy. Soc. 72, pp. 196 and 409, 1903.

192.  The spark spectrum of the radium bromide showed the H and K lines of calcium and also faintly some of the strong lines of barium. The characteristic lines of radium of wave-lengths 3814·59, 3649·7, 4340·6 and 2708·6, as shown by Demarçay and others are clearly shown in the figure. The strong line of wave-length about 2814 is due to radium.

193.  Giesel, Ber. d. D. Chem. Ges. 37, p. 1696, 1904.

194.  Hartmann, Phys. Zeit. 5, No. 18, p. 570, 1904.

195.  In a recent paper, Giesel (Ber. d. D. Chem. Ges. No. 3, p. 775, 1905) has shown that the bright lines are due to didymium, which is present as an impurity. Exposure of didymium to the radium rays also causes the appearance of the lines.

196.  Wiedemann and Schmidt, Wied. Annal. 59, p. 604, 1895.

197.  Wiedemann, Phys. Zeit. 2, p. 269, 1901.

198.  Elster and Geitel, Annal. d. Phys. 69, p. 673, 1899.

199.  Willons and Peck (Phil. Mag. March, 1905) found that under some conditions, especially for long sparks, the rays of radium hindered the passage of the spark.

200.  Hemptinne, C. R. 133, p. 934, 1901.

201.  Himstedt, Phys. Zeit. p. 476, 1900.

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

203.  Kohlrausch and Henning, Verh. Deutsch. Phys. Ges. 6, p. 144, 1904.

204.  Kohlrausch, Verh. Deutsch. Phys. Ges. 5, p. 261, 1904.

205.  P. Curie, C. R. 134, p. 420, 1902.

206.  Becquerel, C. R. 136, p. 1173, 1903.

207.  Becquerel, C. R. 133, p. 199, 1901.

208.  P. Curie, Société de Physique, March 2, 1900.

209.  Joly, Phil. Mag. March, 1904.

210.  S. and P. Curie, C. R. 129, p. 823, 1899.

211.  Giesel, Verhandlg. d. D. Phys. Ges. Jan. 5, 1900.

212.  Salomonsen and Dreyer, C. R. 139, p. 533, 1904.

213.  Elster and Geitel, Phys. Zeit. p. 113, No. 3, 1902.

214.  Becquerel, C. R. 133, p. 709, 1901.

215.  Hardy and Miss Wilcock, Proc. Roy. Soc. 72, p. 200, 1903.

216.  Hardy, Proc. Physiolog. Soc. May 16, 1903.

217.  Whetham, Phil. Mag. Nov. 1899; Theory of Solution, Camb. 1902, p. 396.

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

219.  Giesel, Ber. D. d. Chem. Ges. 35, p. 3605, 1902.

220.  Ramsay and Soddy, Proc. Roy. Soc. 72, p. 204, 1903.

221.  Danysz, C. R. 136, p. 461, 1903.

222.  Aschkinass and Caspari, Arch. d. Ges. Physiologie, 86, p. 603, 1901.

223.  Himstedt and Nagel, Drude’s Annal. 4, p. 537, 1901.

224.  Hardy and Anderson, Proc. Roy. Soc. 72, p. 393, 1903.

225.  Crookes, Proc. Roy. Soc. 66, p. 409, 1900.

226.  Becquerel, C. R. 131, p. 137, 1900; 133, p. 977, 1901.

227.  Rutherford and Soddy, Phil. Mag. Sept. and Nov. 1902. Trans. Chem. Soc. 81, pp. 321 and 837, 1902.

228.  Rutherford and Soddy, Phil. Mag. Sept. 1902.

229.  The general method of regarding the subject would be unchanged, even if it were proved that the radio-activity of thorium is not due to thorium at all but to a small constant amount of a radio-active impurity mixed with it.

230.  Rutherford and Soddy, Phil. Mag. Sept. 1902.

231.  Owens, Phil. Mag. p. 360, Oct. 1899.

232.  Rutherford, Phil. Mag. p. 1, Jan. 1900.

233.  Rossignol and Gimingham, Phil. Mag. July, 1904.

234.  Bronson, Amer. Journ. Science, Feb. 1905.

235.  Phil. Mag. April, 1904.

236.  Dorn, Abh. der. Naturforsch. Ges. für Halle-a-S., 1900.

237.  P. Curie, C. R. 135, p. 857, 1902.

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

239.  P. Curie, C. R. 136, p. 223, 1903.

240.  Debierne, C. R. 136, p. 146, 1903.

241.  Giesel, Ber. D. deutsch. Chem. Ges. p. 3608, 1902.

242.  Curie and Debierne, C. R. 132, pp. 548 and 768, 1901.

243.  Curie and Debierne, C. R. 133, p. 931, 1901.

244.  Rutherford and Soddy, Trans. Chem. Soc. p. 321, 1902. Phil. Mag. Sept. 1902.

245.  Rutherford, Phys. Zeit. 2, p. 429, 1901.

246.  Rutherford and Soddy, Phil. Mag. Nov. 1902.

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

248.  Rutherford and Soddy, Phil. Mag. Nov. 1902.

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

250.  Curie and Debierne, C. R. 133, p. 931, 1901.

251.  Rutherford and Soddy, Phil. Mag. Nov. 1902.

252.  Ramsay and Soddy, Proc. Roy. Soc. 72, p. 204, 1903.

253.  Rutherford and Miss Brooks, Trans. Roy. Soc. Canada 1901, Chem. News 1902.

254.  Loschmidt, Sitzungsber. d. Wien. Akad. 61, II. p. 367, 1871.

255.  See Stefan, Sitzungsber. d. Wien. Akad. 63, II. p. 82, 1871.

256.  P. Curie and Danne, C. R. 136, p. 1314, 1903.

257.  Bumstead and Wheeler, Amer. Jour. Science, Feb. 1904.

258.  Makower, Phil. Mag. Jan. 1905.

259.  Wallstabe, Phys. Zeit. 4, p. 721, 1903.

260.  Stefan, Wien. Ber. 2, p. 371, 1878.

261.  Rutherford and Soddy, Phil. Mag. Nov. 1902.

262.  Phil. Mag. May, 1903.

263.  P. Curie, Société de Physique, 1903.

264.  Rutherford and Soddy, Phil. Mag. May, 1903.

265.  Nature, Aug. 20, 1903.

266.  Proc. Roy. Soc. 73, No. 494, p. 346, 1904.

267.  Proc. Roy. Soc. 73, No. 495, p. 470, 1904.

268.  Pickering, Astrophys. Journ. Vol. 14, p. 368, 1901.

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

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

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.”

272.  Rutherford, Phil. Mag. Feb. 1900.

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

274.  Miss Brooks, Phil. Mag. Sept. 1904.

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

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

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

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

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

280.  Miss Brooks, Phil. Mag. Sept. 1904.

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

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