390 Scientific t Intelligen ce. 



fusively reflected from metal surfaces connected to the earth. 

 With aluminum, zinc, iron, and copper, the maximum of intensity 

 of the reflected rays was displaced toward the mirror. While 

 with platinum, silver, and gold, the reflection was strongest 

 in a direction between that of the incidence ray and the normal to 

 the metal surface. In the case of the first class of metals the 

 reflection increases with the angle of incident ; and with the last 

 class diminishes. At perpendicular incidence the reflective 

 power increases with the atomic weight. Zinc departs slightly 

 from this law. The absorption of cathode rays in thin plates is 

 independent of the tension. The absorption-coefficient increases 

 with the thickness of the window through which the rays pass. 

 Lenard's law that thin plates of different metals, having equal 

 masses per unit of surface, absorb the same fraction of the inci- 

 dent rays, is only a first approximation. The increase of the 

 absorption-coefficient, with the thickness of the window, cannot 

 be explained by the assumption that the electrons lose their 

 velocity by friction with the molecules and are then absorbed, 

 for no difference is observed between the magnetic and electric 

 deflection of the rays in the case where they pass direct from 

 the cathode, or in the case where they have passed through an 

 aluminum window. Moreover, the rays emerging obliquely from 

 the window behave in the same manner as those emerging along 

 the normal to the window. The following values were obtained: 



v = 0*703 . 10 10 ; -- = 0-645 . 10\— Ann. der PhysiTc, No. 9, 1901, 

 m 



pp. 1-33. J. T. 



9. Photography of the Infra-Red Spectra of the Alkali-metals. 

 — H. Lehmann describes the method of sensitizing plates for the 

 red portion of the spectra, and adopted Burbanks' sensitizing 

 bath, which is constituted as follows : 



Distilled water ._.___ 160 cm 



Cyanine solution (Burbanks) ..-._. l cm 



Ammonia (sp. gr. 0-91) _ l cm 



Silver nitrate (1 : 40) ... . 5 drops 



This enabled the author to photograph the spectra of glowing 

 metallic paper as far as 1000 //yx. The arrangement of spectrum 

 apparatus is fully described. Five new lines of rubidium and 

 nine of cassium were discovered. — Ann. der Physih i No. 7, pp. 

 633-658. J. T. 



10. Ether and Gravitational Matter through Infinite Space. — 

 In the course of an article on this- subject, Lord Kelvin thus 

 remarks upon the old hypothesis that if we could see far enough 

 into space the whole sky would be seen occupied with discs of 

 stars all of perhaps the same brightness as our own sun, and that 

 the reason why the whole of the night sky and day sky is not as 

 bright as the sun's disc, is that light suffers absorption in travel- 

 ing through space. 



