386 Scientific Intelligence. 



into electrical work, A. Brand determined the electromotive force 

 of ozone. The electromotive force of the O^ and the O3 electrode 

 of a Grove gas cell was measured against a normal mercury ele- 

 ment (mercury covered with mercuric sulphide), in a normal sul- 

 phuric acid( -JH^SO^ g. to the liter). It was found that the electro- 

 motive force with increasing proportion of ozone approached a 

 limit which at 17° was 0*919 ; at 0"", 0-950 volt. — Anii. der 

 Physik, No. 10, 1902, pp. 468-474. j. t. 



9. Influence of Electrification of the Air on Electric Sparks. — 

 The passage of electricity through a gas is such a complicated 

 phenomenon and is influenced by so many conditions that it is 

 difficult to frame a comprehensive theory of it. Ernst Lecher 

 shows that a hitherto unknown condition results from electrifying 

 the air or gas through which the electric spark is discharged. 

 For this experiment two sources of electrification are employed. 

 An induction coil produces the spark and a Holtz machine serves 

 to electrify the dielectric. Many interesting phenomena result 

 from this arrangement. The author believes that the phenomena 

 are due to an ionization of the discharge space. — Ann. der Physik, 

 No. 10, 1902, pp. 442-451. J. T. 



1 0. On a neio Reaction between Electrostatic Tabes and Insulators. 

 — M. W. DE NicoLAiEVE belicves that certain attractions and 

 repulsions due to an electrostatic field set up in the process of 

 electrolysis form a new phenomenon and confirm Professor Poynt- 

 ing's theory of the action of tubes of force. — Phil. Mag., No. 19, 

 July, 1902, pp. 133-138. j. T. 



11. A Magnetic Detector for electrical waves. — In a communica- 

 tion to the Royal Society, of London, Marconi describes his 

 magnetic detector. On a core of thin iron wires is wound a coil 

 consisting of one or two layers of insulated copper wire, and over 

 this and separated from it by insulating material is wound a 

 second and longer coil. The ends of the inner coil are connected 

 to earth and the aerial conductor ; and the ends of the outer coil 

 to a telephone. The iron core is magnetized by a permanent 

 magnet at one end, which is rotated by clockwork so as to cause 

 a continual slow change in the magnetization. The magnetization 

 lays behind the magnetic force, owing to hysteresis ; but when a 

 high frequency current passes through the inner winding there is 

 a decrease in the hysteresis, A sudden variation in the magnetiza- 

 tion of the iron results, and this results in inducing a current in 

 the coil connected to the telephone. This receiver is more sensi- 

 tive than the coherer. Experiments have been carried out between 

 points 135 miles apart. This detector seems to be Rutherford's 

 magnetic detector. — Nature, July 31, 1902, p. 334. j, t. 



12. Radiations from Radioactive S%d)stances. — Prof essor Ruth- 

 erford and Miss Brooks conclude from extended observations 

 that radioactivity is a very complicated phenomenon. Both 

 uranium and radium emit negatively charged particles with high 

 velocities, similar in all respects to cathode rays. Uranium, 

 radium and thorium emit rays which are not deflected by the 



