6S Scientific Intelligence. 



8. The Normal Element. — The weighty questions in regard to 

 the conditions of stability of the mercuric sulphate do not appear 

 to be solved. At present the silver voltameter is as reliable as 

 the Weston element, and there does not appear any reason why 

 those countries which have adopted the silver voltameter as a 

 standard should give it up for the Weston element. — Physic. 

 Techn., Peichsanstalt, 1904. j. t. 



9. Influence of Character of Excitation upon Structure of 

 Spectral lines. — If a Geissler tube is excited by electric oscilla- 

 tions, the fine spectral lines undergo a marked change, which is 

 probably due to an increase of temperature arising from the 

 electrical oscillations. — Phys. Techn. Heichsanstalt, 1904. j. t. 



10. On the Radio-active Minerals. — In a paper upon this sub- 

 ject in the Proceedings of the Royal Society (A, lxxvi, 88-100) 

 the author, R. J. Strutt, summarizes his results as follows : 



(1) The conclusion, that the amount of radium in a mineral is 

 proportional to the uranium, is confirmed. The investigation of 

 this point has brought to light the existence of uranium in some 

 minerals not previously known to contain it, monazite, for instance. 



(2) It is shown that thorium minerals invariably contain the 

 uranium-radium combination. The observation is difficult to 

 interpret, but it may possibly indicate that thorium is producing 

 uranium. 



(3) Helium never occurs except in very minute quantity unless 

 thorium is present. The helium of minerals, therefore, is proba- 

 bly produced more by thorium than by radium. 



(4) Thorium minerals vary much in emanating power. Some 

 retain nearly all their emanation, others give off large quantities. 



11. On the Absence of excited Radio-activity due to tempo- 

 rary Exposure to y-rays. — This subject is discussed by J. J. 

 Thomson and by H. A. Bumstead in brief articles published in 

 the Proceedings of the Cambridge Philosophical Society, vol. 

 xiii, part 2 (pp. 124, 125-128). Thomson says: 



" Experiments were made to see if the radiation given out by 

 metals could be temporarily increased by exposure to the radia- 

 tion from radium. The method used was to measure the satura- 

 tion current inside a closed metallic vessel, then to place a sealed 

 glass tube containing 30 mg. of radium bromide inside the vessel 

 and leave it there for times varying from one hour to ten days ; 

 the radium was then removed and as soon as possible afterwards 

 the saturation leak again measured ; experiments were made with 

 vessels made of lead, brass, tin, but no increase in the saturation 

 current attributable to exposure to the radium was ever detected. 

 The measurement of the saturation current took at least five 

 minutes after the removal of the radium, so that a very short- 

 lived increase might escape detection by this method." 



The last mentioned point was independently investigated by 

 Bumstead, who experimented with copper, lead, tin and uranium 

 nitrate by a method specially devised for the purpose, but also 

 without positive results. The author remarks : 



