486 /Scientific Intelligence. 



b. They are not regularly reflected by known bodies. 



c. They are not polarized by ordinary means. 



d. Their absorption depends only on the factor of thickness of 

 absorbing layer. 



According to the author, the absence of observed reflection 

 could be due to a wave-length extremely small in comparison 

 with the inequalities of even highly polished surfaces. The 

 absence of polarization can also be explained by similar reason- 

 ing ; b and c are thus explained. The behavior of the new rays 

 toward metals and other substances is compared with the 

 behavior of certain solutions like fuchsin, and aniline toward 

 ordinary light. In the case of fuchsin solutions the absorbtion 

 is proportional to the concentration. If we compare Rontgen's 

 results on the effect of thickness of layers on the rays, with the 

 absorption of fuchsin, one is led to believe that the thickness 

 of bodies plays the role with X-rays of the concentration of 

 fuchsin solutions for ordinary light. Prisms filled with fuchsin 

 solutions give anomalous refraction and dispersion, is it not possi- 

 ble that the bodies investigated by Rontgen exhibit anomalous 

 dispersion? By means of anomalous refraction and dispersion 

 a and d can thus be explained. With rays of extremely short 

 wave-length, the absorption fitness of bodies may be mainly 

 determined by their thickness. It is possible that the X-rays are 

 present in the arc spectrum of platinum or lead. — Ann. der Physik 

 und Chemie, No. 4, 1896, pp. 635-638. J. t. 



8. Recent work with Rontgen Rays. — Nature, April 30,1 896, has 

 a resume of this work. Dr. A. Winkelmann and Dr. R. Straubel 

 (Jena) have investigated the refraction of the Rontgen rays and 

 by using prisms of various metals obtained in each case a value of 

 about 1 : 0-0038 referred to air. Professor Rhigi and Drs. A. 

 Fontana and A. Umani (Rome) find that the radiation from a 

 Crookes tube does not effect the radiometer in any way. Various 

 observers have determined the relative opacity of different sub- 

 stances. Professor E. Doelter of Graz finds (1) that the opacity 

 of minerals does not always increase with the density, although 

 minerals having a specific gravity greater than 5 are relatively 

 opaque ; (2) that the complexity of the chemical constitution of 

 a mineral effects its opacity, but no general law of relationship 

 can be enunciated; (3) dimorphous minerals exhibit but slight 

 differences in their behavior with regard to the rays in their 

 different forms ; (4) in most crystals, the amount of absorption 

 does not depend sensibly on the direction of the incident rays ; 

 (5) all minerals naturally fall into about eight well-defined 

 groups, corundum, talc, quartz, rock salt, Iceland spar, etc. The 

 diamond is ten times as transparent as corundum and 200 times 

 as transparent as tin foil. Dr. Filippo Campanile and Dr. Emilio 

 Stromei (Naples) have succeeded in obtaining Rontgen rays from 

 ordinary Geissler tubes. A variety of new forms of Crookes tubes 

 have been invented. Professor Elihu Thomson has devised a 

 double focus tube for use with a Thomson or Tesla coil. Both 



