392 Scientific Intelligence. 



are discussed. It was found that the secondary excitation of 

 cathode rays is not due to a splitting up of the molecule in an 

 electrolytic sense. The question is discussed whether the bearers of 

 electricity are bound to the material gas particles, and whether the 

 light electric phenomena are due to double layers on material in 

 air which subsist for a long time in a vacuum. — Ann. der PhysiJc., 

 No. 11, 1903, pp. 450-490. j. t. 



11. Discharge of Electricity from Hot Platinum, — Harold A. 

 Wilson, of Trinity College, Cambridge, finds that the presence 

 of traces of hydrogen in platinum wire enormously increases the 

 leak of negative electricity from it. The presence also of traces 

 of phosphoric pentoxide greatly increased this leak. The varia- 

 tion of the negative leak with air pressure and potential differ- 

 ence is due to the ionization of the air by collisions of air mole- 

 cules with the negative ions leaving the wire. — Roy. Soc.^ June 

 18, 1903 ; Nature, July 16, 1903. j. t. 



12. Penetrating Radiation from the EartKs Surface. — Mr. H. 

 Lester Cooke of McGill University, Montreal, working under 

 the direction of Prof. Rutherford, gives as the results of his inves- 

 tigation : 



" (1) The proof of the existence of a very penetrating radia- 

 tion, present everywhere under ordinary conditions. This radia- 

 tion is similar in properties to the radiation from radium, and is 

 comparable to it in penetrating power. This radiation is account- 

 able for between 30 and 33 per cent of the natural ionization 

 observed in ordinary testing vessels, 33 percent being the greatest 

 reduction obtained by the use of massive lead screens. This 

 penetrating radiation may have its origin in the radio-active 

 matter which is distributed throughout the earth and atmosphere. 

 It was not found possible to obtain sufficient excited activity on 

 a wire charged negatively in the open air to show the presence of 

 a very penetrating radiation due to it. The effect observed is 

 too large to be accounted for by the excited activity distributed 

 on the walls of the laboratory. 



(2) That all substances examined give forth a radiation of a 

 not very penetrating character: that this is probably the cause 

 of all the residual ionization in the electroscope when surrounded 

 by heavy metal screens ; and that this activity varies with dif- 

 ferent substances, being very low in the case of brass. 



(3) The reduction by the experimental arrangements of the 

 number of ions produced per c.c. per second in air under atmos- 

 pheric pressure from 14 to 5." — Phil. Mag., Oct., 1903, pp. 403- 

 411. J. T. 



13. Mathematical Papers of the late George Green. xii-f336 

 pp. Paris, 1903 (A. Hermann). — This is a fac-simile reprint by 

 photographic process of Ferrers' edition of Green's Papers and 

 is to be welcomed as increasing their accessibility to students of 

 mathematical physics. There is no better introduction to the 

 theory of electrostatics and the Newtonian potential in general 

 than the celebrated paper of 1828 in which the name potential 



