4:72 Scientific Intelligence. 



a combination of the Foucault and the Fizeau methods. Instead 

 of a revolving toothed wheel of Fizeau, he suggests the use of a 

 stationary grating, and by a double reflection of light from sta- 

 tionary and revolving mirrors, and proposes to measure the eclipses 

 the light suffers from the gratings. Figures accompany the original 

 article which make the author's plan clear. He estimates that 

 the velocity of light can be measured to a probable error of only 

 5 kilometers. j. t. 



8. Ultra- Violet of the Mercury Spectrum. — Hans Lehmann and 

 R. Straubel give a table of wave lengths, extending from wave 

 length 221-31 to 193*04. They used the Berolina-Kupferdruck- 

 platten of Gebhard, and developed with glycin. The apparatus 

 consisted of an Abbe spectrometer, with collimator, prism and 

 camera. Quartz fluor spar lenses were employed. The prism was 

 a Cornu right and left quartz. The source of light was a Geissler 

 tube with mercury electrodes. — Ann. der Physik, No. 4, 1902, 

 pp. 909-911. j. t. 



9. A new Peculiarity in the Structure of the Cyanogen Bands. 

 — Arthur Scott King gives a description of a band structure 

 of the carbon arc spectrum, beginning at wave length 3465 and 

 ending at 3274. Another band runs from 3203*84 to 31-28. — Ann. 

 der Physik, No. 4, 1902, pp. 791-800. j. t. 



10. Stationary PJlectric Waves. — The subject of wireless tele- 

 graphy lends great interest to investigations upon the reflection 

 of Hertzian waves from mirrors. K. F. Ltndman has studied 

 the subject under the following heads : 



(1) The dimensions of the mirror were great in comparison 

 with the wave lengths. 



(2) The indicator was a resonator with a therrno element. 



(3) The thermo resonator was rectilinear. 



(4) The thermo resonator was circular. 



(5) The indicator was a resonator with spark gap. 



(6) The dimensions of the mirror were of the order of the 

 wave lengths. An important conclusion is, that the parabolic 

 reflector of the oscillator should not be shorter than the wave 

 length, in case the focal length of the mirror is a quarter wave 

 length. — Ann. der Physik, No. 4, 1902, pp. 824-850. j. t. 



11. Oscillatory Discharges. — H. Andriessen calls attention to 

 the importance of oscillatory discharges in the use of condensers. 

 Such discharges often occasion greater ones than the calculation 

 of tension, capacity, and periodicity would indicate, and there- 

 fore break down insulation which would resist non-oscillatory 

 discharges. — Ann. der Physik, No. 4, 1902, pp. 909-9] 8. j. t. 



12. Meteor ologische Optik,v<m J. M. Pernter, Professor an der 

 Universitat in Wien und Director der Centralanstalt fur Meteor- 

 ologie und Erdmagnetismus. I. Abschnitt : pp. 1-54. Wien 

 und Leipzig, 1902 (Wilhelm Braumiiller). — The aim of this work 

 is to present all that is known concerning the optics of the atmos- 

 phere, and, as no author has attempted the same task hitherto, it 

 promises to be of great value. Part I treats in a clear and inter- 



