156 Scientific Intelligence. 



rays. The author describes certain experiments which support 

 this view, and maintains that one thus obtains a photog ,l \>hic 

 image of chemical processes and has, to a certain measure Ja dis- 

 tance working of chemical processes. The author suspects that 

 an active material is present in the H 2 O a to which the radiation 

 is due. — Ann. tier Physik, No. 13, 1902, pp. 1100-1110. j. t. 



9. Photography of the Ultra-Red Iron Spectrum. — The pho- 

 tography of the ultra-violet spectra of alkali and alkali earths 

 demands a standard of iron lines. Hans Lehmann seeks to sup- 

 ply this need, and gives a table of wave-lengths extending from 

 A.=6811*34 to A.=8690-98. The author refers to the remark of 

 Abney that no lines of certain metals were found in the region 

 of the extreme ultra-red which he photographed with his sensi- 

 tive plates, and to his conclusion that there is an upper limit to 

 their spectra. Lehmann believes that this supposition is more or 

 less confirmed by his observations. — Ann. der Physik, No. 13, 

 1902, pp. 1330-1333. j.T. 



10. JSxcited Radio-activity and its Transmission. — Professor 

 E. Rutherford has made an exhaustive study of this subject, and 

 the conclusions from his prolonged investigations are as follows : 



(1) Excited radio-activity produced by thorium and radium 

 compounds is due to the deposits of radio-active matter, which is 

 derived from the emanation given out by these bodies. 



(2) Excited radio-activity is transmitted by positively charged 

 carriers, produced from the emanation, which travel in an electric 

 field with about the same velocity as the positive ions produced 

 in air by the Rontgen rays. This velocity (about l-3 cm per sec. 

 for 1 volt per cm.) is about the same for the carriers of thorium 

 and radium excited activity. 



(3) These positively charged carriers are due to the expulsion 

 of a negatively charged body from the molecule of the emana- 

 tion. 



(4) Evidence is adduced for the view that the easily absorbed 

 and apparently non-deviable rays of radio-active substances are 

 due to the expulsion of charged bodies at a high velocity. The 

 rays are thus analogous to the Canal Strahlen of Goldstein, which 

 Wien has shown to be positively charged bodies projected at a 

 great speed. In the case of the emanations the expelled particles 

 are for the most part negative in sign. 



(5) In the case of radium about 5 per cent, of the carriers of 

 excited activity are distributed on the anode in a strong electric 

 field. 



(6) The excited radiations from thorium due to a short exposure 

 in the presence of the emanations increase, in the course of sev- 

 eral hours after removal, to three or four times their initial value. 



(7) The emanations and the matter which gives rise to excited 

 activity are the result of a succession of chemical changes occur- 

 ring in radio-active matter. In thorium there is evidence of at 

 least four distinct chemical changes. — Phil. Mag., Jan. 1903, pp. 

 95-117. J. t. 



