62 Scientific Intelligence. 



light effects. Professors Nichols and Mr. G. F. Hull obtain 

 P = 1-05X1 Cr 4 dynes ; theory demanded P — 1 "34 X 1 -4 dynes. 

 They believe that the observations show the existence of the 

 phenomenon. Lebedew gives complete details of the construc- 

 tion of his vanes, which were of many forms, and of the method 

 of exhausting his vessel. He used the most modern form of 

 vacuum pump, shunning as far as possible complications due to 

 greased joints. After as complete an exhaustion as possible, a 

 globule of mercury in the vessel which contained the vanes was 

 heated and after a renewal of the exhausting process the vessel 

 was cooled. The value obtained for the pressure of light on an 

 absolutely black body was P == 0*0000258 dynes. This pressure 

 is directly proportional to the quantity of the incident energy 

 and independent of the color of the light. Lebedew considers 

 that the existence of the Maxwell-Bartoli pressure of light has 

 been proved. — Ann. der JPhysik, No. 11, pp. 433-458. j. t. 



8. On some Chemical Effects produced by Radium Radia- 

 tions. — In the Comptes Rendus of Nov. 4 Henri Becquerel 

 states* that the radium radiation consists of a part capable of 

 deviation in the magnetic field, identical with the cathode rays, 

 and a part non-deviable, a fraction of which is absorbable and 

 the remainder extremely penetrating. Observations are brought 

 forward to show the action of the rays on glass, the transforma- 

 tion of yellow into red phosphorus, the reduction of mercury 

 perchloride in the presence of oxalic acid and the effect upon 

 seeds. It is found that prolonged exposure to the radium radia- 

 tions had the effect of destroying the power of germinating in 

 the seed. — Nature, Nov. 14, 1901. j. t. 



9. On the Induction Coil. — Lord Rayleigh reviews the recent 

 papers of Oberbeck, Walter, Mizuno, Beattie, and Klingelfuss, 

 and considers that the subject is by no means exhausted. The 

 author maintains that highly magnetized iron cannot be regarded 

 as a store of energy, and that the energy expended in producing 

 the magnetization is recoverable to a very small extent. The 

 available energy of a highly magnetized closed circuit of iron is 

 insignificant. The question of the desirability of a condenser in 

 the primary circuit is next discussed, and shows that with a very 

 quick break the condenser only does harm. He details experi- 

 ments to produce such a break ; among these experiments are 

 interesting ones with a rifle bullet. The experiments supported 

 the view that the only use of a condenser in conjunction with an 

 ordinary break is to quicken it by impeding the development of 

 an arc. If a sufficient rapidity of break can be obtained by 

 other means, the condenser is deleterious, operating in the 

 reverse direction and prolonging the period of decay of the cur- 

 rent. The author does not refer to the Wehnelt interrupter and 

 other forms of electrolytic breaks, which accomplish the object 

 which he desires. — Phil. Mag., Dec. 1901, pp. 581-594. j. t. 



10. Resistance in High Vacua ; by William Rollins. (Com- 

 municated.) — The statement is frequently made that the resistance 



*See also p. 59. 



